JP7152205B2 - Water-based ink composition for writing instrument, and writing instrument using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aqueous ink composition for writing instruments and a writing instrument using the same.

The writing instrument has a structure in which a pen tip is attached to the end of a barrel through an appropriate ink flow rate adjusting body for adjusting the ink flow rate, and an ink reservoir containing an ink composition is provided in the barrel. There is In this type of writing instrument, when the pen tip is turned upward or horizontally to write, the ink composition contained in the ink reservoir flows along the inner wall of the ink reservoir, and the pen is drawn into the pen. By flowing down in the forward direction, writing becomes possible. (This flow down of the ink composition is referred to as ink mobility.)
However, even when the pen tip is directed downward, the wettability of the ink composition to the ink reservoir is insufficient, and the ink composition does not flow down and stays in the original position, or the ink in the ink reservoir foams, and the bubbles occur. As a result, the ink composition is not sufficiently supplied to the pen tip, such as the ink not flowing smoothly in the direction of the pen tip, and the handwriting becomes blurred, and in the worst case, it becomes impossible to write. ing.

In order to solve the above problems, it is generally considered to lower the surface tension of the ink composition and improve the wettability to the ink reservoir.
Therefore, it is conceivable to add additives such as surfactants. Sometimes we can't reach a solution.
In addition, since surface tension plays an important role as a resistance force against movement of the ink composition due to gravity, atmospheric pressure, and impact, attempts have been made to reduce the surface tension of the ink composition to improve ink mobility within the ink reservoir. In such a case, the above-mentioned drag will be insufficient, and even when not writing, the ink may drip when the pen tip is pointed downward. , ink overflowed, and a new problem of ink leakage occurred.

Therefore, water-based ink compositions have been proposed in which an additive such as maltosylcyclodextrin is added to improve the mobility of the ink in the ink reservoir without lowering the surface tension. (Patent Document 1)
However, when the maltosylcyclodextrin or the like is added to the ink composition to such an extent that good ink mobility is obtained, the ink viscosity increases, the ink followability decreases, and it is difficult to obtain good handwriting. In addition, because of its low solubility in water, it has problems such as affecting the dry-up resistance of the nib.

As described above, in the conventional ink composition, when the wettability to the ink reservoir is improved by lowering the surface tension in order to improve the ink mobility in the ink reservoir, the resistance is insufficient and the ink cannot be retained. Ink leakage occurs. On the other hand, if the surface tension of the ink composition is increased to some extent in order to suppress ink leakage, sufficient ink mobility within the ink reservoir cannot be obtained. In addition, when the above problems are attempted to be solved without adjusting the surface tension of the ink composition, problems arise in the writing performance and the resulting handwriting, such as the handwriting becoming faint and being unable to write better than the first time. The performance as a composition was not fully satisfied.

Therefore, there is a demand for an aqueous ink composition that simultaneously solves the two problems of improving ink mobility in an ink reservoir and suppressing leakage of ink, and that can provide good handwriting without bleeding or strike-through. In particular, a writing instrument having a structure in which a pen tip is attached to the end of a barrel through an appropriate ink flow rate regulator for adjusting the ink flow rate, and an ink reservoir containing an ink composition is provided in the barrel. With the low-viscosity ink composition that is preferably used, it is even more difficult to solve the above problems, which has been a major problem.

JP-A-5-140498

The present invention provides a water-based ink composition for writing utensils, which has excellent leakage resistance and ink transferability in an ink reservoir, and writing utensils using the same.

The water-based ink composition for writing instruments according to the present invention comprises water, a coloring agent, and a surfactant, and is measured by the Loss-Miles test method of a 0.1% by mass aqueous solution of the surfactant at 25°C. A water-based ink composition for writing utensils characterized by having a foaming power (Amm) and a foam stability (Bmm) of A>3 and A>1.5B.

Moreover, the writing instrument according to the present invention is characterized by containing the water-based ink composition for writing instruments.

According to the present invention, it is possible to sufficiently suppress the phenomenon of ink leakage from the nib, to have excellent ink mobility in the ink reservoir, and to provide good handwriting with less bleeding and strike-through. It is possible to provide a water-based ink composition for writing instruments and a writing instrument using the same.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In this specification, "parts", "%", "ratios" and the like indicating formulations are based on mass unless otherwise specified, and the content rate refers to the constituent components based on the mass of the ink composition. is the mass % of

A water-based ink composition for writing instruments according to the present invention (hereinafter sometimes referred to as an ink composition) comprises water, a colorant, and a surfactant, and 0.1 mass of the surfactant is % aqueous solution at 25 ° C. The foaming power (A mm) and foam stability (B mm) measured by the Ross-Miles test method are characterized by A > 3 and A > 1.5B. be.
Each component used in the present invention will be described in detail below.

<Surfactant>
The surfactant used in the ink composition of the present invention has a foaming power (Amm) and foam stability (Bmm) measured by the Ross-Miles test method of a 0.1% by mass aqueous solution at 25° C. >3 and A>1.5B.
Surfactants such as those described above provide the ink composition with a certain level of foamability and excellent foam breakability.
Therefore, in the ink composition containing the surfactant, although bubbles are generated in the ink, the bubbles tend to disappear quickly, so that problems due to residual bubbles in the ink can be suppressed.
Therefore, even if the ink in the ink reservoir foams, the writing instrument using the ink composition of the present invention is excellent in defoaming. At that time, the generated bubbles allow the ink to smoothly flow down along the wall surface in the direction of the nib without remaining in its original position.
In addition, since bubbles are less likely to remain in the ink, the ink flow rate regulator is not hindered by residual bubbles in the ink, and its function can be fully exerted. Therefore, the ink does not leak out from the pen tip, and the ink ejection property from the pen tip can be maintained satisfactorily, so that a good handwriting can be left.
In particular, when the ink composition of the present invention is used in a writing instrument having a comb tooth-shaped ink retaining member as an ink flow rate adjusting body, as will be described later, the remaining bubbles hinder the inflow of ink into the ink retaining member. Since the ink flows in smoothly, the function of the ink flow rate regulator can be fully utilized, and leakage of ink from the nib of the pen can be effectively suppressed.

Furthermore, the present inventors have found that by using a surfactant having a specific relationship between foaming power and foam stability, as described above, the surface tension of the ink composition at rest can be extremely lowered. It is possible to impart good wettability to the writing instrument parts, and furthermore, to have a certain foaming property, so that even when the ink moves, the wettability to the writing instrument parts does not deteriorate. It was found that the
The reason for this is not clear, but in ink compositions containing surfactants, movement of the ink usually disrupts the arrangement of the surfactant present at the air-liquid interface of the ink, increasing the surface tension of the ink. It tends to increase and the wettability to writing instrument parts tends to decrease. However, by using a surfactant with a certain degree of foamability as described above, even if the ink moves, the increase in the surface tension of the ink is suppressed, and good wettability to the writing instrument parts is maintained. think it can be done.
Therefore, the writing instrument using the ink composition of the present invention can change the pen tip from an upward or horizontal position to a downward pen tip for writing, and even if the ink in the ink reservoir moves, The wettability to the ink reservoir is maintained well without a large increase in surface tension. Therefore, the ink composition in the ink reservoir can immediately flow down along the wall surface, exhibiting excellent ink transfer performance. In addition, since the surface tension of the ink composition of the present invention at rest does not decrease significantly, the ink does not jump out of the pen tip due to slight impact or vibration even when not writing, and the ink composition has excellent leakage resistance. In addition, it exhibits good ink jettability, and furthermore, can maintain proper permeability to the paper surface, so that good handwriting that is less likely to bleed or strike through can be produced.

As described above, the ink composition of the present invention suppresses residual bubbles in the ink and is effective against writing instrument parts when the ink moves due to the surfactant that exhibits a specific relationship between the foaming power and the stability of the bubbles. The dual approach of suppressing the deterioration of wettability makes it possible to obtain the contradictory performance of excellent ink transfer performance and excellent leakage resistance performance, and also to leave excellent handwriting with less bleeding and strike-through. be.

The surfactant can impart the above effects to the ink composition even in a very small amount. Therefore, excellent ink transferability and excellent anti-leakage performance can be provided without adversely affecting the performance and physical properties of the ink composition such as discoloration of the ink.
The content of the surfactant is preferably 0.001 to 1% by mass based on the total mass of the ink composition. If the content of the surfactant is within the above numerical range, the ink will not leak from the pen tip even when the pen tip is pointing downward when not writing, and it is possible to adjust the wettability to the parts of the writing instrument well. At the same time, it is possible to achieve a sufficient effect of suppressing a decrease in wettability with respect to writing instrument parts when movement of ink occurs. For this reason, it is possible to obtain a good balance between the performance of ink movement in the ink reservoir and the performance of anti-leakage performance, and it is possible to suppress bleeding and strike-through of handwriting. Further, considering the improvement of problems caused by residual bubbles in the ink composition, it is more preferably 0.001 to 0.5% by mass.
Furthermore, considering the improvement of the above effect, it is particularly preferable that the content is 0.01 to 0.1% by mass.

In the present invention, the foaming power by the Ross-Miles test at 25 ° C. can be measured according to JIS K3362, and the surfactant prepared using ion-exchanged water as the device and test liquid specified by this JIS. is a value obtained by visually measuring the height of foam immediately after all the test liquid has flowed out in a test using a 0.1% aqueous solution of .
The stability of foam in the present invention is a value obtained by visually measuring the height of foam 5 minutes after all the test liquids have flowed out in the Ross-Miles test.

The value of A, which indicates the foaming power of the surfactant used in the present invention, is preferably A>10, more preferably A>50.
A surfactant having a value of A, which indicates foaming power, of a certain value or more as described above can further improve the ink transfer performance of the ink composition.
This is because a surfactant having a value of A above a certain value is particularly excellent in foaming power, and by including the surfactant in the ink composition, even if movement occurs in the ink, , the surface tension of the ink tends to be more likely to be suppressed when the arrangement of the surfactant is broken and the surface tension of the ink is more likely to increase.
In particular, in a writing instrument having an ink reservoir made of a resin material, the ink tends to lack wettability to the ink reservoir, and it is necessary to consider ink migration performance. Therefore, in this case, it is effective to use a surfactant having a value of A equal to or higher than the above constant value, since excellent ink transferability can be easily obtained.
Furthermore, considering the improvement of the above effect, it is more preferable to use a surfactant with A>80.
In addition, considering the improvement of productivity by suppressing foaming of the ink during production and the improvement of the absorbability of the ink into the ink reservoir as described later, the value of A is preferably A<120. More preferably, A<110.

Further, the value of B, which indicates the foam stability of the surfactant used in the present invention, is preferably B<100, more preferably B<80, and even more preferably B<60. .
Surfactants having a value of B, which indicates the stability of foam, that is equal to or less than the above-mentioned constant value have poor foam stability, and thus tend to suppress defects caused by residual foam in the ink composition. This is because it is possible to further improve ink transfer performance and leakage resistance performance in the ink reservoir. In addition, from the viewpoint of preventing a decrease in productivity due to bubbles during ink production, it is preferable to use an ink having a certain degree or less of stability of bubbles as described above.

In addition, the surfactant used in the present invention has a foaming power (Amm) and foam stability (Bmm) measured by the Ross-Miles test method of a 0.1% by mass aqueous solution at 25 ° C. is A > 3. And if A > 1.5B is established, there is no particular limitation, and examples include ionic surfactants such as anionic surfactants, cationic surfactants, and amphoteric surfactants, and nonionic surfactants. be done.

In the present invention, it is more preferable to use a nonionic surfactant in consideration of compatibility with other components in the ink and in consideration of sufficiently obtaining the effect of the surfactant.
Moreover, as will be described later, when the ink composition is stored in a glass ink container, it is necessary to consider the suppression of the generation of precipitates due to reaction with metal ions. In the present invention, it is preferable to use a nonionic surfactant also from the viewpoint of suppressing the generation of this precipitate.

Examples of nonionic surfactants include ether-type, ether-ester-type, ester-type, and nitrogen-containing-type surfactants, and examples thereof include the following compounds.
(1) Ether type nonionic surfactant Polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene aryl ether, polyoxyethylene polyoxypropylene alkyl aryl ether, polyoxyethylene alkyl ether, polyoxyethylene aryl ether , polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl aryl ethers and polyoxyethylene tristyrylphenyl ethers, polyoxyalkylene glycols such as polyoxyalkylene aryl ethers, polyoxyalkylene alkyl aryl ethers, and polyoxyethylene polyoxypropylene glycols .
(2) Ether ester type nonionic surfactants Polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene tristyrylphenyl phosphate diesters, polyoxyethylene polyoxypropylene tristyrylphenyl phosphate diesters , fatty acid alcohol polyglycol ether and the like.
(3) Ester-type nonionic surfactants Polyoxyalkylene vegetable oils such as polyoxyethylene castor oil, polyoxyalkylene hydrogenated vegetable oils such as polyoxyethylene hydrogenated castor oil, polyoxyethylenes such as polyoxyethylene polyoxypropylene castor oil Polyoxypropylene vegetable oils, polyoxyethylene fatty acid esters, sorbitan fatty acid esters such as sorbitan monostearate and sorbitan tristearate, glycerin fatty acid esters, fatty acid esters of polyoxyethylene polyoxypropylene block polymers, and the like.

Furthermore, in the present invention, it is preferable to use an ether-type nonionic surfactant, and among them, it is preferable to use a polyoxyalkylene alkyl ether or a polyoxyalkylene glycol.

Among polyoxyalkylene alkyl ethers, it is preferable to use polyoxyalkylene branched decyl ether and polyoxyalkylene tridecyl ether. Furthermore, polyoxyethylene isodecyl ether and polyoxyethylene polyoxypropylene tridecyl ether are preferably used, and polyoxyethylene isodecyl ether is preferably used in consideration of obtaining handwritings with suppressed bleeding and strike-through. is more preferred.

Among polyoxyalkylene glycols, polyoxyethylene polyoxypropylene glycol is preferably used.
Among polyoxyethylene-polyoxypropylene glycols, it is more preferable to use polyoxyethylene-polyoxypropylene block polymers represented by formula (1).

式（１）中、ｘ、ｙ、ｚは正数である。

In formula (1), x, y, and z are positive numbers.

Furthermore, in the present invention, considering the improvement of ink transfer performance and leakage resistance performance, and obtaining good handwriting with less bleeding and strike-through, the polyoxyethylene polyoxypropylene block represented by the above formula (1) The polymer preferably has a weight average molecular weight of 1000 or more, more preferably 1200 or more. In the polyoxyethylene polyoxypropylene block polymer represented by formula (1), the weight average molecular weight is preferably 10,000 or less, preferably 8,000 or less, and more preferably 5,000 or less. , 3000 or less.
Moreover, in the polyoxyethylene-polyoxypropylene block polymer represented by formula (1), the content of ethylene oxide is more preferably 5% or more and 60% or less.

Specific examples of the polyoxyalkylene alkyl ether include Noigen LF series (polyoxyalkylene branched decyl ether, Daiichi Kogyo Seiyaku Co., Ltd.), Noigen SD series (polyoxyethylene isodecyl ether, Daiichi Kogyo Seiyaku ( Co., Ltd.)), Neugen TDX series (polyoxyalkylene tridecyl ether, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Neugen XL series (polyoxyalkylene branched decyl ether, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)), Noigen TDS series (polyoxyethylene tridecyl ether, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and the like.
Specific examples of the polyoxyalkylene glycol include Epan series (polyoxyethylene polyoxypropylene block polymer, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

<Colorant>
Colorants that can be used in the present invention include any dyes or pigments, and are not particularly limited.

The dyes are not particularly limited, but examples include acid dyes, basic dyes, direct dyes, disperse dyes, oil-soluble dyes, reactive dyes, metallized dyes, food dyes and various salt-forming type dyes. is mentioned.
These dyes may be used alone, or two or more dyes may be used.

Specifically, as the acid dye, C.I. I. Acid Red 18, C.I. I. Acid Red 51, C.I. I. Acid Red 52, C.I. I. Acid Red 87, C.I. I. Acid Red 92, C.I. I. Acid Red 289, C.I. I. Acid Orange 10, C.I. I. Acid Yellow 3, C.I. I. Acid Yellow 7, C.I. I. Acid Yellow 23, C.I. I. Acid Yellow 42, C.I. I. acid green 3, C.I. I. Acid Green 16, C.I. I. acid blue 1, C.I. I. Acid Blue 9, C.I. I. Acid Blue 22, C.I. I. Acid Blue 90, C.I. I. Acid Blue 239, C.I. I. Acid Blue 248, C.I. I. Acid Violet 15, C.I. I. Acid Violet 49, C.I. I. Acid Black 1, C.I. I. Acid Black 2 and basic dyes such as C.I. I. Basic Orange 2, C.I. I. Basic Orange 14, C.I. I. Basic Green 4, C.I. I. Basic Blue 9, C.I. I. Basic Blue 26, C.I. I. Basic Violet 1, C.I. I. Basic Violet 3, C.I. I. Basic Violet 10, and as a direct dye, C.I. I. Direct Red 28, C.I. I. Direct Yellow 44, C.I. I. Direct Blue 86, C.I. I. Direct Blue 87, C.I. I. Direct Violet 51, C.I. I. Direct Black 19 and disperse dyes such as C.I. I. Disperse Yellow 82, C.I. I. Disperse Yellow 3, C.I. I. Disperse Yellow 54, C.I. I. disperse thread 191, C.I. I. disperse thread 60, C.I. I. Disperse Violet 57, food coloring such as C.I. I. Food Yellow 3, C.I. I. Food Black 2 and the like.

Moreover, the pigment that can be used in the present invention is not particularly limited. Examples include inorganic pigments, organic pigments, and processed pigments. Specifically, carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, quinophthalone-based, threne-based, triphenylmethane-based, perinone-based, perylene-based, gioxazine-based, Examples include aluminum pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, complementary color pigments, and the like. In addition, colored resin particles such as resin particles colored with a dye or the like, or colored bodies obtained by dispersing a coloring material in a medium are encapsulated in a shell made of a resin wall film-forming substance by a known microencapsulation method or the like. A solid-soluted microcapsule pigment may also be used.

In the ink composition of the present invention containing a surfactant that exhibits a specific relationship between foaming power and foam stability, dyes are preferably used, and among these, acid dyes and basic dyes are preferably used. It is particularly preferred to use acid dyes. Furthermore, when xanthene-based or azo-based dyes are used, the effect of surfactants that show the relationship between specific foaming power and foam stability, and the effect of suppressing residual bubbles of surfactants and the effect of ink movement on writing instruments The effect of suppressing a decrease in wettability can be easily obtained, and the ink tends to improve the mobility of the ink in the ink reservoir and the anti-leakage performance.

As the colorant, the above pigments and dyes may be used singly or in combination of two or more.
The content of the colorant in the ink composition of the present invention is preferably 0.1 to 10% by mass based on the total mass of the ink composition. If the content of the colorant is within the above numerical range, it is possible to obtain a sufficient effect of the surfactant while preventing the deterioration of the ink jettability, and it is possible to obtain good handwriting with excellent color development. .

<Water>
Water is not particularly limited, and for example, tap water, ion-exchanged water, ultrafiltered water, distilled water, or the like can be used.

<Other additives>
The ink composition of the present invention can contain optional additives as needed. Additives that can be used are described below.

Amines are preferably used in the ink composition of the present invention. Examples of amines include alkylamines, alkanolamines, heterocyclic amines, etc. Among them, it is more preferable to use alkanolamines.
Alkanolamine has been conventionally used as a pH adjuster. It tends to improve ink mobility in the reservoir and anti-leakage performance.
The reason for this is not clear, but by using it in combination with alkanolamine, the dissolution stability of the surfactant used in the present invention is sufficiently maintained, and the effect of suppressing residual bubbles and the movement of the ink are reduced. It is thought that this is because the effect of suppressing the decrease in wettability can be sufficiently obtained.

Alkanolamine is a compound having a hydroxyl group and an amino group in the alkane skeleton, and in the present invention, it is preferable to use alkanolamine represented by the following formula (2).

式（２）中、Ｒ_１ はエチレン基、トリメチレン基又はプロピレン基を示し、Ｒ_２ 及びＲ_３ はそれぞれ独立に水素原子、メチル基、エチル基又は －Ｒ_１－ＯＨ 基を示す。

In formula (2), R ₁ represents an ethylene group, a trimethylene group or a propylene group, and R ₂ and R ₃ each independently represents a hydrogen atom, a methyl group, an ethyl group or a --R ₁ --OH group.

Specific examples of such alkanolamine include methylethanolamine, monoisopropanolamine, diethylethanolamine, monoethanolamine, propanolamine, methyldiethanolamine, diethanolamine, and triethanolamine.
In the present invention, considering the compatibility with surfactants that show the relationship between specific foaming power and foam stability, and the stability of the ink composition over time, among the above alkanolamines, triethanol, which is weakly basic It is preferable to use an amine, and the effect of suppressing the decrease in wettability to the ink reservoir and the ink flow rate regulator when the ink composition is moved, and the effect of suppressing the remaining foam of the ink composition are excellent. It is possible to stably obtain ink transfer performance in the ink reservoir and excellent leakage resistance performance over time.
In addition, since triethanolamine has excellent hygroscopicity, it tends to improve the dry-up resistance of the ink composition. For this reason, the use of triethanolamine in the present invention is effective because it tends to improve the ink mobility in the ink reservoir and the resistance to leaking out, as well as the writing performance during dry-up.

The alkanolamine content in the ink composition of the present invention is preferably 0.1 to 10% by mass based on the total mass of the ink composition. If the content of alkanolamine is within the above numerical range, the effect of the surfactant described above can be efficiently brought about to the ink composition over a long period of time, and further excellent leakage resistance and ink movement within the ink reservoir can be obtained. performance can be obtained. Furthermore, considering the improvement of dry-up resistance and the color development of handwriting, the content is more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 3% by mass.

Also, the ink composition according to the present invention preferably comprises a chelating agent for sequestering metals present in the ink composition.
Since the ink composition of the present invention is excellent in defoaming, when a user fills the ink reservoir with the ink, it tends to be easily filled without being hindered by generated bubbles. For this reason, the ink composition of the present invention is used by repeatedly replenishing the ink reservoir by the user, and the ink is stored in a glass ink container such as a glass bottle. is assumed.
Glass bottles are easy to mold, are readily available at a low cost, and are easy to obtain the desired strength. If so, there is a high possibility that the alkaline component in the glass will be eluted into the ink composition, and the eluted alkaline component may react with the components of the ink composition to form a deposit.
Therefore, in the present invention, the use of a chelating agent is effective, and when stored in a glass-made ink container, it captures the eluted alkali component, and the alkali component reacts with the components in the ink composition. It is effective because it prevents the formation of water-insoluble precipitates and prevents the ink flow paths from being clogged by the generated precipitates, etc. is.

Chelating agents include aminocarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol etherdiaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), Dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA) and their alkali metal salts, ammonium salts or amine salts.
Considering the fact that the alkali component can be sufficiently supplemented, the physical properties of the ink composition before and after blending the chelating agent tend not to be greatly affected, and the compatibility of the surfactant used in the present invention, etc. Among the chelating agents, aminocarboxylic acids are preferably used, and ethylenediaminetetraacetic acid (EDTA) and salts thereof are particularly preferably used.

The content of the chelating agent in the ink composition of the present invention is preferably 0.01 to 1% by mass based on the total mass of the ink composition. If the content is 1% by mass or less, the performance and physical properties of the ink composition, such as discoloration of the ink, are not adversely affected. Moreover, if it is 0.01% by mass or more, it is possible to capture the alkaline component eluted from the glass and suppress the generation of precipitates.

The ink composition of the present invention further contains additives such as a water-soluble organic solvent, a pH adjuster, a rust preventive, an antiseptic, a moisturizer, a penetrant, and a lubricant for the purpose of improving the physical properties and functions of the ink. may contain.

Water-soluble organic solvents include (i) glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, or glycerin, (ii) methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t - alcohols such as butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate and other higher alcohols, and (iii) ethylene glycol monomethyl ether, ethylene glycol mono Glycol ethers such as ethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol are included.
Among them, the surfactant used in the present invention, which shows the relationship between the specific foaming power and the stability of the foam, has good compatibility and can be stably present, and the effect of the surfactant to suppress residual foam and the ink. It is preferable to use diethylene glycol, ethylene glycol, glycerin, or the like, which can sufficiently obtain the effect of suppressing the decrease in wettability to the writing instrument member when movement occurs.
The content of the water-soluble organic solvent in the ink composition is preferably 0.1 to 10% by mass based on the total mass of the ink composition.

Examples of pH adjusters include inorganic salts such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide and sodium acetate, basic organic compounds, lactic acid and citric acid. A mixture of the above may be used.

Rust inhibitors include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, dialkylthiourea, and the like.

Preservatives include phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, 2-pyridinethiol-1- sodium oxide, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one and the like.

Moisturizing agents include polyhydric alcohol solvents, urea or sorbitol, and N,N,N-trialkylamino acids such as trimethylglycine, triethylglycine and tripropylglycine.

Further, in the present invention, the foaming power (Amm) and foam stability (Bmm) measured by the Ross-Miles test method of a 0.1% by mass aqueous solution at 25° C. are A>3 and A>1. Various surfactants other than surfactants satisfying 5B may also be included. Specific examples include nonionic, anionic and cationic surfactants, surfactants having an acetylene bond in the structure, silicone surfactants, fluorine surfactants and the like.

The ink composition of the present invention preferably has a surface tension of 30 to 70 mN/m at 20°C. If the surface tension of the ink composition is within the above numerical range, the leakage of ink from the nib of the pen when not writing is suppressed, and the wettability to the ink flow rate regulator is properly maintained. While excellent in ink ejection from the tip, it is easy to suppress bleeding and strike-through of handwriting, and excellent handwriting can be obtained. Furthermore, considering the improvement of the above effect, it is more preferable to be 35 to 60 mN/m.
Furthermore, when the ink composition of the present invention is used in a writing instrument having a comb tooth-shaped ink retaining member as an ink flow rate regulator, it is preferably 35 to 60 mN/m, more preferably 40 to 55 mN/m. is more preferable, and excellent ink transfer performance and anti-leakage performance can be obtained, and good handwriting with less bleeding and strike-through can be obtained.
The surface tension is measured by the vertical plate method using a platinum plate using a surface tension measuring instrument (DY-200) manufactured by Kyowa Interface Science Co., Ltd. in an environment of 20°C.

The ink composition according to the present invention preferably has an ink viscosity of 50 mPa·s or less, more preferably 10 mPa·s or less, measured at 60 rpm and 20° C. using a B-type rotational viscometer. Preferably. If the viscosity of the ink composition is within the above numerical range, it is possible to improve the ink jettability from the nib and the ink transferability within the ink reservoir.
As will be described later, when the ink composition of the present invention is used in a writing instrument in which a comb tooth-shaped ink reservoir member is arranged as an ink flow rate regulator, ink smoothly flows into the ink reservoir member when pressure changes. Ink leakage from the pen tip can be effectively suppressed by holding the pen tip. The ink composition of the present invention can be suitably used for the above writing instrument. In this case, considering leakage resistance and ink ejection from the nib, the ink viscosity should be 3 mPa·s or less. It is preferably 2 mPa·s or less, and more preferably 2 mPa·s or less. The viscosity can be measured using a B-type rotational viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd.).

The pH of the ink composition of the present invention is preferably 6-11, more preferably 7-10. If the pH of the ink composition is within the above numerical range, it is preferable because each component in the ink composition can be stably present, and furthermore, corrosion of metal parts of writing instruments such as pen tips that come into contact with the ink composition can be prevented. can do. In the present invention, the pH value can be measured at 20° C. using, for example, an HM-30R type pH meter (manufactured by Toa DKK Co., Ltd.).

The defoaming rate of the ink composition of the present invention is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more, and 80% or more. Especially preferred. When the defoaming rate is at least the above constant value, residual bubbles in the ink composition are suppressed, and the leakage resistance and ink transferability of the ink composition can be improved.
In the present invention, the defoaming rate is measured by putting 50 ml of the ink composition into a 100 ml capped graduated cylinder, shaking the graduated cylinder up and down 100 times (30 seconds) at room temperature (25°C), and then standing still. Place, measure the height of the foam after 5 seconds and the height of the foam after 6 minutes, and measure the height of the foam after 5 seconds (C mm) and the height of the foam after 6 minutes (D mm) , was calculated using the following formula (3).
Defoaming rate (%) = (CD) / C × 100 (Formula 3)

<Method for producing ink composition>
The ink composition according to the present invention can be produced by any conventionally known method. Specifically, the necessary amount of each of the above components is blended and mixed with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, and various dispersers such as a bead mill.

<Writing implements>
The ink composition of the present invention can be used in various writing instruments such as marking pens and ballpoint pens with a writing tip such as a fiber tip, felt tip, plastic tip or ballpoint tip, and fountain pens with a metal writing tip.

In addition, the ink composition of the present invention can be used in a configuration in which the ink composition is directly charged, or in a device provided with an ink reservoir capable of being filled with the ink composition.

The ink composition of the present invention is an ink reservoir (ink cartridge) in which the ink reservoir can be detachably replaced with a writing instrument main body, or ink can be directly supplied from an ink container such as an ink bottle into the ink reservoir. It can be suitably used for a writing instrument provided with an ink reservoir (ink inhaler) having a function of being able to inhale.
Since the ink reservoir as described above may be provided in the barrel of the writing instrument, the inner diameter of the ink reservoir is likely to be restricted. Therefore, it is difficult for the ink composition to flow within the ink reservoir, and particular consideration must be given to ink mobility within the ink reservoir. The ink composition of the present invention can suppress a decrease in wettability with respect to the ink reservoir when the ink moves, has excellent foam breakability, and has excellent ink mobility in the ink reservoir. Therefore, it can be suitably used for a writing instrument provided with the ink reservoir as described above.
In particular, when the material of the ink reservoir is molded from a resin material, the ink reservoir tends to have poor wettability with the ink composition, and it is particularly necessary to consider ink mobility within the ink reservoir. . Since the ink composition of the present invention can suppress a decrease in wettability when the ink moves on a resin material, it can be suitably used for a writing instrument having a resin ink reservoir. .

Further, it is desired that the ink reservoir is made of a material having translucency or transparency so that the remaining amount of ink can be known. Examples of such materials include thermoplastic resins such as polyethylene, polypropylene, polymethylpentene, polyethylene terephthalate, polycyclohexane terephthalate, polycarbonate, and nylon.
In addition, since the ink composition is stored for a long period of time, it is preferable to use a crystalline resin having excellent chemical resistance for the ink reservoir. is more preferred.
The ink composition of the present invention can bring good ink transfer performance even to the ink reservoir using the resin material as described above. When it is set to m, it is easy to get wet with the above resin, and it is easy to improve the ink transfer performance.
In addition, among the above resins, polymethylpentene has excellent chemical resistance, has particularly excellent transparency, and has moderate flexibility. A freely replaceable ink reservoir (ink cartridge) or an ink reservoir (ink inhaler) having a function of directly inhaling ink from an ink container such as an ink bottle into the ink reservoir. It is preferably used.
However, polymethylpentene has a low surface tension, and the ink tends to lack wettability to polymethylpentene. For this reason, it is necessary to particularly consider ink mobility in a writing instrument using an ink reservoir using polymethylpentene. However, since the ink composition of the present invention exhibits excellent wettability even with an ink reservoir using polymethylpentene, it is possible to obtain excellent ink transfer performance. Therefore, the ink composition of the present invention can be suitably used for ink reservoirs using polymethyl pen. Furthermore, when the surface tension of the ink composition is 35 mN/m to 50 mN/m, it is easy to obtain good wettability with respect to polymethylpentene, and it is easy to improve the ink transfer performance, which is effective. preferable.

Further, in a writing instrument provided with an ink reservoir (ink inhaler) having a function of directly inhaling ink from an ink reservoir such as an ink bottle, the conventional ink composition is In addition to the problem of ink mobility in the ink reservoir, there is also the problem that the ink foams when inhaled, and the generated bubbles make it difficult to fill the ink reservoir (ink inhaler) with ink. . However, as described above, although the ink composition of the present invention foams, it is excellent in defoaming and has excellent foam breakability, so that it is easy to fill the ink inhaler with ink. Therefore, from the above points as well, it can be said that the ink composition of the present invention can be suitably used for a writing instrument equipped with an ink inhaler as an ink reservoir.

Further, in the ink inhaler, there is provided a weight for easily moving the ink in the ink inhaler to the pen tip side, or a weight for holding the ink sucked up from the ink bottle at the time of inhaling the ink in the inhaler. As the plug, there is a type in which a moving body that can move forward and backward within the ink inhaler is arranged.
In such an ink inhaler in which a movable body is arranged, the movement of ink inside the ink inhaler may be deteriorated depending on the material of the movable body.
In particular, when the moving body is made of a resin material, the wettability of the ink composition to the moving body tends to be poor, and the ink mobility tends to be suppressed. However, the ink composition of the present invention exhibits excellent wettability even with respect to the movable body made of the resin material, and can suppress the deterioration of the ink mobility. Therefore, the ink composition of the present invention can be suitably used for a writing instrument provided with an ink inhaler in which a mobile body, particularly a mobile body made of a resin material, is disposed.

Writing instruments to which the ink composition of the present invention can be applied include, in addition to the cap-type having a cap that covers the writing tip, knock-type, rotating-type, and sliding-type writing instruments that can accommodate the writing tip in the barrel. can be a formula. In particular, in retractable writing instruments, the prevention of leakage of ink from the nib is more important, so the ink composition of the present invention, which is excellent in leakage resistance, can be suitably used for retractable writing instruments.

The ink supply mechanism of the writing instrument to which the ink composition of the present invention can be applied is not particularly limited. (Mechanism 2) Mechanism for supplying ink composition to the pen tip, (Mechanism 2) Mechanism provided with a comb tooth-shaped ink retention member as an ink flow controller, (Mechanism 3) Valve mechanism and (Mechanism 4) a mechanism for supplying the ink composition directly to the pen tip without an ink flow rate adjuster.

Above all, a writing instrument equipped with an ink flow rate adjusting body maintains proper wettability with respect to the ink flow rate adjusting body, and maintains good ink ejection from the pen tip, while obtaining good handwriting with less bleeding and strike-through. Therefore, it is necessary to keep the surface tension of the ink composition within an appropriate range.
The ink composition of the present invention, which uses a surfactant having a specific relationship between foaming power and foam stability, has an appropriate wettability to the ink flow rate regulator without extremely lowering the surface tension. Since it can be adjusted, it can be suitably used for a writing instrument having an ink flow rate adjusting body such as the above (Mechanism 1), (Mechanism 2), and (Mechanism 3).

Further, when the ink composition of the present invention is used as an ink flow rate regulator in a writing instrument having a comb tooth-shaped ink retaining member, it can remarkably exhibit excellent anti-leakage performance.
A writing instrument having a comb-shaped ink retaining member as described above as an ink flow rate adjusting body basically utilizes capillary action to eject ink. There is a high possibility that the ink will spurt out from the nib and cause ink leakage. However, if the comb tooth-shaped ink retaining member is arranged, the surplus ink is taken into the comb tooth structure and held therein, thereby suppressing ink leakage. However, in order to effectively use the comb-shaped ink retaining member, the ink must have good wettability to the comb-shaped ink retaining member.
However, when the surface tension of the ink is simply lowered to improve the wettability, the resistance of the ink due to the surface tension becomes insufficient, and the ink cannot be retained in the comb-shaped structure, resulting in the ink being transferred to the pen. It leaks out from the front. Conversely, if the wettability is insufficient, the ink cannot smoothly flow into the comb-shaped structure. leak out.
As described above, the ink composition of the present invention exhibits an appropriate surface tension without an extreme decrease in surface tension at rest, and exhibits excellent wettability with respect to parts of writing instruments. It is thought that even when movement occurs, the surface tension does not increase significantly, and excellent wettability with respect to writing instrument parts can be maintained. Therefore, even if the internal pressure of the ink reservoir rises and excess ink is pushed out, the excess ink flows into the comb-shaped ink reservoir member because it exhibits good wettability with respect to the ink flow rate regulator. Furthermore, the ink is held tightly in the comb-shaped retaining member. Therefore, the ink composition of the present invention can sufficiently exert the function of the comb tooth-shaped ink flow rate regulator, and can effectively suppress leakage of ink from the nib.
As described above, the ink composition of the present invention can be suitably used for a writing instrument using a comb-like ink retaining member.

In addition, when a resin material is used for the ink flow controller, the hydrophobicity becomes stronger due to the influence of the resin type and additives such as mold lubricants used during molding, and the wettability with the ink composition should be considered. may be necessary. In this case, since the surface of the ink flow controller is modified by the surface modifier, stable performance of the ink flow controller can be obtained, and the leakage resistance and ink ejection property can be improved. can be done. Examples of the surface modifier include resins and surfactants, and specific examples include copolymers containing vinyl acetate and acrylic acid esters, surfactants having acetylene bonds, succinic surfactants, It is preferred to use a surfactant such as a silicone surfactant. Therefore, when the ink composition of the present invention is used in a writing instrument provided with such a surface-modified ink flow rate regulator, the leakage resistance and ink ejection properties are further improved, and good handwriting is achieved. can be achieved and significant effects can be obtained.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
A base liquid was obtained by mixing raw materials other than the colorant with propeller agitation using the following raw materials and blending amounts. Thereafter, a coloring agent was added to the base liquid and mixed by propeller stirring to obtain an aqueous ink composition for writing instruments.
The viscosity of the resulting ink composition was measured with a B-type rotational viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd., sample volume: 20 ml). Specifically, the viscosity at 20° C. and a rotational speed of 60 rpm was 1.3 mPa·s.
Further, the surface tension of the obtained ink composition was measured with a surface tension measuring instrument DY-200 (at 20° C., platinum plate, vertical plate method, manufactured by Kyowa Interface Science Co., Ltd.) and found to be 46.7 mN/m. Met. Furthermore, the pH of the ink composition was measured at 20° C. using a HM-30R type pH meter (manufactured by DKK Toa Co., Ltd.) and found to be 9.3.
Furthermore, the defoaming rate of the resulting ink composition was measured using a 100 ml capped graduated cylinder (JIS R 3505 standard product, manufactured by Shibata Science Co., Ltd., outer diameter φ32 mm, total height 250 mm), and the result was 5 seconds. The foam height (C mm) after 6 minutes was 113 mm, the foam height (D mm) after 6 minutes was 11 mm, and the defoaming rate was 90%.

・Surfactant A 0.05% by mass
(Foam power (A mm) = 106 mm, foam stability (B mm) = 51 mm, polyoxyethylene polyoxypropylene block polymer)
・ Coloring agent 1.0% by mass
(C.I. Acid Red 289)
・ Coloring agent 0.5% by mass
(C.I. Acid Red 52)
・ Coloring agent 0.5% by mass
(C.I. Acid Yellow 42)
・Amines 1.0% by mass
(triethanolamine)
・Chelating agent 0.05% by mass
(trisodium ethylenediaminetetraacetate)
・Water-soluble organic solvent 2.0% by mass
(diethylene glycol)
・Preservative 0.2% by mass
(1,2-benzisothiazolin-3-one)
・Remaining water

<Examples 2 to 5, Comparative Examples 1 to 5>
Ink compositions of Examples 2 to 5 and Comparative Examples 1 to 5 were prepared by changing the types and amounts of the components to be blended from Example 1 as shown in Tables 1 and 2. Obtained.

Also, 1% aqueous solutions of the surfactants used in Examples 1 to 5 and Comparative Examples 1 to 4 were prepared, and the states of these aqueous solutions were visually observed. The 1% aqueous solutions of surfactants used in Examples 1 to 5 and Comparative Examples 1 and 2 are transparent, whereas the 1% aqueous solutions of surfactants used in Comparative Examples 3 and 4 are cloudy. It was confirmed that the surfactants used in Comparative Examples 3 and 4 were not sufficiently dissolved in water. From this, the surfactants used in Comparative Examples 3 and 4 have lower solubility in water than other surfactants, and the ink compositions of Comparative Examples 3 and 4 have lower water solubility than other ink compositions. However, it was determined that the ink composition was not suitable as a water-based ink composition for writing instruments because of concerns about the stability over time.
Based on these results, the ink compositions of Comparative Examples 3 and 4 were not prepared and tested in the following test writing instruments.

<Production of writing instruments for testing>
The ink compositions of Examples 1 to 5 and Comparative Examples 1, 2, and 5 were applied to an ink inhaler made of polymethylpentene (an ink inhaler in which a resin-made moving body capable of moving back and forth was arranged. ) was injected with the ink inhaler opening facing upward so that the moving body was completely immersed in the ink composition. This ink inhaler is a knock-type ink inhaler having a fountain-pen-shaped nib with a comb tooth-shaped ink retention member (surface-modified by a copolymer containing vinyl acetate and acrylic acid ester) arranged as an ink flow control body. A retractable writing instrument (fountain pen, FCN-1MR-BM, manufactured by Pilot Corporation) was attached with the nib facing upward. Let this writing instrument be a writing instrument for test.

<Ink mobility test in ink reservoir>
Ten test writing instruments filled with each ink composition were prepared. When the test writing instruments with the nib facing upward were gently turned with the nib facing downward, the ink composition was applied to the ink within 10 seconds. A state of flowing down to the pen tip side in the reservoir was visually confirmed, and the ink transfer performance in the ink reservoir was evaluated according to the following criteria. The obtained evaluation results are summarized in Tables 1 and 2.
A: 10 pieces B: 8 to 9 pieces
C: 6 to 7 D: 5 or less

<Writing performance test>
The pen point of the test writing instrument used in the ink transfer test in the ink reservoir was turned downward for a while, and the filled ink composition was allowed to flow up to the pen point to make it ready for writing. In this state, the letter "V" was continuously written on the surface of the writing test paper, the handwriting was confirmed, and the writing performance was evaluated according to the following criteria. The obtained evaluation results are summarized in Tables 1 and 2. JIS P3201 writing paper A was used as the writing test paper for the evaluation.
A: Good handwriting was obtained without blurring, blurring, or strike-through.
B: Bleeding, fading, and strike-through were observed in the handwriting, but the level was practically non-problematic.
C: Bleeding, blurring, strike-through, etc. were observed in handwriting.

<Leakage resistance performance test>
The test writing instrument used in the writing performance test was placed in a decompression desiccator with the tip facing downward. In this state, the inside of the desiccator was evacuated to 70 mmHg in 5 minutes, and then the test writing instrument was allowed to stand in the desiccator for another 5 minutes while maintaining the reduced pressure of 70 mmHg. At this time, the state of the nib of the test writing instrument and the presence or absence of ink leakage were confirmed, and the leakage resistance performance was evaluated according to the following criteria. The obtained evaluation results are summarized in Tables 1 and 2.
A: No leakage of ink occurred.
B: When the pressure in the desiccator was reduced to 70 mmHg in 5 minutes, no ink leaked out, but a small amount of the ink composition was blown out from the pen tip during the 5 minutes in which the reduced pressure state of 70 mmHg was maintained. Some ink leaked out. However, it was at a level that poses no practical problem.
C: When the pressure inside the desiccator was reduced to 70 mmHg in 5 minutes, ink leaked out.

As shown in Table 1, the ink compositions of Examples 1 to 5 were of good levels in all of the ink transfer performance in the ink reservoir, the writing performance, and the leakage resistance performance.

On the other hand, as shown in Table 2, the ink compositions of Comparative Examples 1, 2, and 5 had a foaming power (Amm) measured by the Ross-Miles test method of a 0.1% by mass aqueous solution at 25°C and a Ink that satisfies all of the ink transfer performance in the ink reservoir, the writing performance, and the leakage resistance performance, because no surfactant having a stability (Bmm) of A > 3 and A > 1.5B is used. It was not composition.

From the above, the foaming power (A mm) and foam stability (B mm) measured by the Ross-Miles test method of water, a coloring agent, and a 0.1% by mass aqueous solution at 25 ° C. are A > 3 and A >1.5B, the water-based ink composition for writing instruments has excellent ink transfer performance in the ink reservoir, stably supplies ink to the pen tip, and has good ink ejection from the pen tip. It was found that the ink had excellent resistance to leakage, such as excellent handwriting without bleeding, strike-through, and blurring, and no leakage of ink was observed even when the pressure was abruptly changed.
Therefore, the water-based ink composition for writing instruments of the present invention can leave good handwriting while being excellent in ink transfer performance in the ink reservoir and leakage resistance performance. The writing instrument was found to be excellent as a writing instrument.

The ink composition of the present invention can be used as a water-based ink composition for various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens, and marking pens. In particular, since ink movement performance and leakage resistance performance within the ink reservoir are improved, it can be suitably used in a writing instrument provided with an ink reservoir and an ink supply mechanism with an ink flow rate regulator. Furthermore, it can be effectively used as an ink flow rate adjusting body in a writing instrument, especially a fountain pen, in which a comb tooth-shaped ink retaining member is arranged.

Claims (5)

A resin comb-shaped ink reservoir member is arranged as an ink flow rate adjusting body for adjusting the ink flow rate, and a resin ink reservoir is provided in the shaft cylinder, and the ink stored in the ink reservoir. to the tip of the writing instrument, wherein the aqueous ink composition for writing instrument comprises water, a coloring agent, and a surfactant, and the surfactant The foaming power (A mm) and foam stability (B mm) measured by the Ross-Miles test method at 25 ° C. of a 0.1% by mass aqueous solution of 110>A> 80 and B < 60 and A> 1.5B, the surfactant is a polyoxyalkylene alkyl ether or polyoxyalkylene glycol, and the surface tension at 20° C. of the water-based ink composition for writing instruments is 35 to 60 mN/m. A water-based ink composition for writing instruments, characterized in that: 2. The ink composition according to claim 1, wherein the ink composition has a defoaming rate of 40% or more. 3. The ink composition according to claim 1, wherein the ink reservoir is an ink reservoir using a crystalline olefin resin. The ink composition according to any one of claims 1 to 3, wherein the ink reservoir is an ink reservoir having a function of directly sucking ink into the ink reservoir. A writing utensil containing the ink composition according to any one of claims 1 to 4.