JP7665359B2 - Oil-based ink composition for writing instruments, water-based ink composition for writing instruments, ballpoint pen - Google Patents

Description

The present invention relates to an oil-based ink composition for a writing instrument, a water-based ink composition for a writing instrument, and a ballpoint pen.

In recent years, there has been a rapid increase in user demand for writing instruments (especially ballpoint pens) that differ in ink and function, such as writing feel, writing start (initial writing performance), and stable and continuous writing. Ballpoint pens can be broadly classified into oil-based ballpoint pens, water-based ballpoint pens, gel ink ballpoint pens, etc.
Oil-based inks come in a variety of colors, including black, red, blue, pink, green, and orange, and are usually produced by dissolving or dispersing a colorant in an organic solvent. In order to further improve writing performance, resins, surfactants, additives, and other ingredients are added depending on the application.
Dyes, pigments, and mixtures thereof are used as colorants contained in oil-based inks. For example, oil-based inks using pigments have excellent fastness of handwriting, but the pigments tend to aggregate and settle in the ink, which can cause problems in handwriting. In contrast, oil-based inks using dyes have the characteristic that the dyes are easily dissolved in solvents, so they are less likely to aggregate or settle compared to pigments, but they tend to have inferior water resistance and weather resistance.
As dyes, various dyes such as acid dyes, basic dyes, and processed dyes such as salt-forming dyes are known. For example, inks using triphenylmethane dyes as colorants (Patent Document 1) and inks using a mixture of dyes and pigments (Patent Document 2) have been reported.
On the other hand, in the case of water-based ink, in addition to water-soluble dyes, pigments and oil-based dyes are dispersed as colorants.
In recent years, cellulose nanofibers, which can be obtained by chemically or mechanically defibrating plant fibers, have been attracting attention and active research into their application in various fields has been conducted, with examples of cellulose nanofibers being used in writing instruments being reported (Patent Documents 3 and 4).In addition, a method of encapsulating a colorant by emulsion polymerization of a monomer has been reported (Patent Documents 5 and 6).

JP 2015-193682 A JP 2003-113339 A JP 2017-105907 A JP 2017-125135 A JP2016-196623Publication JP2019-112561Publication

The dyes described in Patent Documents 1 and 2 tend to aggregate, and when the ink solvent at the tip of the ball tip evaporates, the ink thickens, and there are cases where smearing occurs when starting to write. In addition, triphenylmethane dyes in particular have low solubility stability, so depending on the usage environment, there are problems in that a good writing feel (handwriting density does not change and handwriting continues to be produced stably) cannot be obtained, and handwriting fastness is also low.
Since the dye has low compatibility with the carrier (resin or cellulose nanofiber), the dye, resin, and cellulose nanofiber each aggregate, which causes the resin and cellulose nanofiber to be non-uniformly dyed with the dye. In addition, ink compositions containing resins or cellulose nanofibers in such a non-uniformly dyed state have a problem of poor storage stability. On the other hand, even with the method of incorporating a colorant by polymerization, there is a problem of poor handwriting fastness.

The present invention relates to a medium containing an alcohol or a glycol ether;
a resin that dissolves in the medium; and a colorant containing a compound represented by the following general formula (1):

［式（１）中、Ｒ₁及びＲ₂は、各々独立して、置換基を有するフェニル基又は無置換のフェニル基を表し、Ｒ₃及びＲ₄は、各々独立して、炭素数２以上１２以下の置換基を有するアルキル基若しくは無置換のアルキル基、シアノ基、トリフルオロメチル基、又はハロゲン原子を表し、Ｒ₅及びＲ₆は、各々独立して、水素原子又はアルキル基を表し、
Ｒ₇は、下記式（２）または（３）で示される構造を表し、

[In formula (1), R ₁ and R ₂ each independently represent a substituted phenyl group or an unsubstituted phenyl group; R ₃ and R ₄ each independently represent an alkyl group having a substituent and having 2 to 12 carbon atoms or an unsubstituted alkyl group, a cyano group, a trifluoromethyl group, or a halogen atom; R ₅ and R ₆ each independently represent a hydrogen atom or an alkyl group;
R ₇ represents a structure represented by the following formula (2) or (3):

式（２）中、Ｒ₈は、－ＳＯ₃ ^-基、アルコキシスルホニル基、スルホン酸アミド基、ハロゲン原子、パーフルオロアルキル基、又はニトロ基を表し、Ｒ₉は、水素原子又はハロゲン原子を表し、
式（３）中、Ｒ₁₀～Ｒ₁₂は、各々独立して、水素原子、アルキル基、又は置換基を有するアリール基若しくは無置換のアリール基を表し、
Ｘ^-は、陰イオンを表し、分子内に少なくとも１つのアニオン性置換基を持つ場合はなくてもよい。］
を含むことを特徴とする筆記具用油性インキ組成物、及び当該インキ組成物を用いたボールペンに関する。
また、本発明は、水性媒体に分散されている、上記一般式（１）を担持しているキャリアを含有することを特徴とする筆記具用水性インキ組成物、及び当該インキ組成物を用いたボールペンに関する。

In formula (2), R ₈ represents a —SO ₃ ^— group, an alkoxysulfonyl group, a sulfonamide group, a halogen atom, a perfluoroalkyl group, or a nitro group; R ₉ represents a hydrogen atom or a halogen atom;
In formula (3), R ₁₀ to R ₁₂ each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group;
X ⁻ represents an anion, and may be absent when there is at least one anionic substituent in the molecule.
The present invention relates to an oil-based ink composition for a writing instrument, comprising:
The present invention also relates to an aqueous ink composition for a writing instrument, characterized in that it contains a carrier carrying the above general formula (1) dispersed in an aqueous medium, and a ballpoint pen using said ink composition.

According to the present invention, the oil-based ink composition for writing instruments has high dissolution stability because the aggregation of the colorant in the ink composition is suppressed even under low and high temperature conditions. Furthermore, by using the oil-based ink composition for writing instruments, it is possible to provide a ballpoint pen that suppresses the phenomenon of smearing at the start of writing, has a good writing feel without line skipping or smearing in the handwriting (handwriting density does not change and handwriting continues to be stably produced) and has high handwriting fastness.
In addition, the aqueous ink composition for writing instruments has high dispersion stability in an aqueous medium of the carrier carrying the general formula (1). That is, this indicates that when the carrier is prepared by a polymerization method, polymerization inhibition with the general formula (1) does not occur, and when cellulose nanofibers are used, compatibility with the general formula (1) is high. Furthermore, by using the aqueous ink composition for writing instruments, it is possible to provide a ballpoint pen that suppresses the phenomenon of blurring at the beginning of writing, has a good writing feel without line skipping or blurring in the handwriting (the handwriting density does not change and the handwriting continues to be stably produced) and has high handwriting fastness.

The following describes in detail the embodiments of the present invention.

[Coloring agent]
First, the compound represented by formula (1) used as a colorant will be described.

［式（１）中、Ｒ₁及びＲ₂は、各々独立して、置換基を有するフェニル基又は無置換のフェニル基を表し、Ｒ₃及びＲ₄は、各々独立して、炭素数２以上１２以下の置換基を有するアルキル基若しくは無置換のアルキル基、シアノ基、トリフルオロメチル基、又はハロゲン原子を表し、Ｒ₅及びＲ₆は、各々独立して、水素原子又はアルキル基を表し、
Ｒ₇は、式（２）または（３）で示される構造を表し、

[In formula (1), R ₁ and R ₂ each independently represent a substituted phenyl group or an unsubstituted phenyl group; R ₃ and R ₄ each independently represent an alkyl group having a substituent and having 2 to 12 carbon atoms or an unsubstituted alkyl group, a cyano group, a trifluoromethyl group, or a halogen atom; R ₅ and R ₆ each independently represent a hydrogen atom or an alkyl group;
R ₇ represents a structure represented by formula (2) or (3);

式（２）中、Ｒ₈は、－ＳＯ₃ ^-基、アルコキシスルホニル基、スルホン酸アミド基、ハロゲン原子、パーフルオロアルキル基、又はニトロ基を表し、Ｒ₉は、水素原子又はハロゲン原子を表し、
式（３）中、Ｒ₁₀～Ｒ₁₂は、各々独立して、水素原子、アルキル基、又は置換基を有するアリール基若しくは無置換のアリール基を表し、
Ｘ^-は、陰イオンを表し、分子内に少なくとも１つのアニオン性置換基を持つ場合はなくてもよい。］

In formula (2), R ₈ represents a —SO ₃ ^— group, an alkoxysulfonyl group, a sulfonamide group, a halogen atom, a perfluoroalkyl group, or a nitro group; R ₉ represents a hydrogen atom or a halogen atom;
In formula (3), R ₁₀ to R ₁₂ each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group;
X ⁻ represents an anion, and may be absent when there is at least one anionic substituent in the molecule.

Even if they have a similar structure to that of general formula (1), their properties differ greatly depending on the delicate balance of the electron donating groups and electron donating groups of the substituents. It has been revealed by the comparative examples described below that when the substituents are other than R ₁ to R ₄ in general formula (1) of the present invention, the solubility of the compound in the solvent decreases, and aggregation of the colorant is promoted in the ink composition under low and high temperature conditions, resulting in low solubility stability.

In contrast, the compound of the present invention solves the problem. That is, _R1 and _R2 each independently represent a phenyl group having a substituent or an unsubstituted phenyl group, _R3 and _R4 each independently represent an alkyl group having a substituent with 2 to 12 carbon atoms or an unsubstituted alkyl group, a cyano group, a trifluoromethyl group, or a halogen atom, and one methylene group is present between the nitrogen atom and _R3 and between the nitrogen atom and _R4 .

When _R1 and _R3 , and _R2 and _R4 are asymmetric and bulky structures, the three substituents substituted at the N-position form a three-dimensional twisted structure. Therefore, it is speculated that the interaction between compounds within or between molecules is suppressed, and the aggregation of the colorant in the ink composition is suppressed even under low and high temperature conditions, resulting in high dissolution stability. In addition, when _R1 and _R2 are substituted phenyl groups or unsubstituted phenyl groups directly bonded to the nitrogen atom, the charge is delocalized and stable. As a result, it is speculated that a ballpoint pen with high handwriting fastness can be provided.

The aqueous ink composition for writing instruments has high dispersion stability in an aqueous medium of a carrier carrying general formula (1).

Conventionally, the compatibility of compounds which are substituents other than R ₁ to R ₄ in the general formula (1) of the present invention with cellulose nanofibers was low. As a result, dye molecules or cellulose nanofibers were strongly aggregated together. The compound represented by the following general formula (1) of the present invention has high compatibility with cellulose nanofibers because intramolecular or intermolecular interactions between compounds are suppressed, and therefore intramolecular or intermolecular interactions between compounds are suppressed, making it possible to control aggregation. As a result, an aqueous ink composition for writing instruments containing cellulose nanofibers that are nearly uniformly colored and have excellent storage stability is obtained.

On the other hand, when a polymerization method is carried out by mixing a monomer and a colorant (particularly a dye), the colorant causes polymerization inhibition, and there are problems such as failure to polymerize, failure to uniformly disperse the colorant (particularly a dye), and failure to incorporate the colorant. In the case of substituents other than R ₁ to R ₄ in the general formula (1) of the present invention, polymerization inhibition occurs. However, when preparing the carrier of the present invention, it has been found that the general formula (1) does not cause polymerization inhibition because the interaction between compounds within or between molecules is suppressed.

First, we will explain the compound represented by the above general formula (1).

In formula (1), the substituent of the "substituted phenyl group" in _R1 and _R2 is not particularly limited, and examples thereof include the following: a linear, branched, or cyclic alkyl group having from 1 to 20 carbon atoms, an alkoxy group, a cyano group, a halogen atom, a sulfo group ( _-SO3H ), a sulfonate ester group, a sulfonamide group, a sulfonate salt group, a benzenesulfonyl group, a trifluoromethanesulfonyl group, and the like.

In formula (1), the alkyl group substituted on the phenyl group in _R1 and _R2 is not particularly limited, but examples thereof include the following: methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, tert-butyl group, n-hexyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, decyl group, dodecyl group, etc.

Among these, methyl, n-butyl, n-hexyl, 2-ethylhexyl, octyl, and decyl groups are preferred because they suppress aggregation of the colorant in the ink composition and increase the dissolution stability even under low and high temperature conditions.

In formula (1), the alkoxy group substituting the phenyl group in _R1 and _R2 is not particularly limited, but includes the following: methoxy group, ethoxy group, propoxy group, n-butoxy group, t-butoxy group, hexyloxy group, 2-ethylhexyloxy group, octyloxy group, decyloxy group, dodecyloxy group, etc.

Among these, n-butoxy, hexyloxy, 2-ethylhexyloxy, octyloxy, and decyloxy groups are preferred because they suppress aggregation of the colorant in the ink composition and increase dissolution stability even under low and high temperature conditions.

In formula (1), the halogen atom substituted on the phenyl group in _R1 and _R2 is not particularly limited, but examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom or a chlorine atom is preferred because it suppresses aggregation of the colorant in the ink composition even under low and high temperature conditions, thereby increasing the dissolution stability.

In formula (1), the sulfonate ester group substituted on the phenyl group in _R1 and _R2 is not particularly limited, but examples thereof include the following: methyl sulfonate group, ethyl sulfonate group, propyl sulfonate group, butyl sulfonate group, hexyl sulfonate group, octyl sulfonate group, etc. Among these, butyl sulfonate group and hexyl sulfonate group are preferred because they suppress aggregation of the colorant in the ink composition even under low and high temperature conditions, thereby increasing the dissolution stability.

In formula (1), the sulfonamide group substituting the phenyl group in R ₁ and R ₂ is not particularly limited, and examples thereof include the following: N-methylsulfonamide group, N,N-dimethylsulfonamide group, N-ethylsulfonamide group, N,N-diethylsulfonamide group, N-propylsulfonamide group, N,N-dipropylsulfonamide group, N-butylsulfonamide group, N,N-dibutylsulfonamide group, N-pentylsulfonamide group, N,N-dipentylsulfonamide group, N-hexylsulfonamide group, N,N-dihexylsulfonamide group, N-octylsulfonamide group, N,N-dioctylsulfonamide group, N-(2-ethyl N,N-bis(2-ethylhexyl)sulfonamide group, N-(1-methylhexyl)sulfonamide group, N-(1-methylheptyl)sulfonamide group, N-methyl-N-butylsulfonamide group, N-methyl-N-pentylsulfonamide group, N-methyl-N-hexylsulfonamide group, N-methyl-N-octylsulfonamide group, N-phenylsulfonamide group, N-(p-methylphenyl)sulfonamide group, N-pyrrolidylsulfonyl group, N-piperidylsulfonyl group, and the like.

Among these, the following are preferred because they suppress aggregation of the colorant in the ink composition and increase dissolution stability even under low and high temperature conditions: N,N-dibutylsulfonamide group, N,N-dipentylsulfonamide group, N,N-dihexylsulfonamide group, N,N-dioctylsulfonamide group, and N,N-bis(2-ethylhexyl)sulfonamide group.

In the formula (1), the sulfonate group substituted on the phenyl group in R ₁ and R ₂ is not particularly limited, but examples thereof include lithium sulfonate, sodium sulfonate, and potassium sulfonate.

In formula (1), the unsubstituted alkyl groups for _R3 and _R4 are not particularly limited, but the following are preferred because they result in compounds that suppress aggregation of the colorant in the ink composition and increase the dissolution stability even under low and high temperature conditions: ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, tert-butyl group, n-hexyl group, cyclohexyl group, 2-ethylhexyl group, heptyl group, octyl group, decyl group, dodecyl group, etc.

In formula (1), the substituent of the alkyl group having a substituent of _R3 and _R4 is not particularly limited, but a methoxy group, a bromine atom, a chlorine atom, a fluorine atom, a cyano group, a trifluoromethyl group, etc. are preferred because they result in a compound that suppresses aggregation of the colorant in the ink composition and increases the dissolution stability even under low and high temperature conditions.

In formula (1), the halogen atoms of _R3 and _R4 are not particularly limited, but examples thereof include a bromine atom, a chlorine atom, a fluorine atom, and an iodine atom. Among these, a chlorine atom and a fluorine atom are preferred because they suppress aggregation of the colorant in the ink composition even under low-temperature and high-temperature conditions, and provide a compound with high dissolution stability.

In formula (1), the alkyl group of _R5 and _R6 is not particularly limited, but examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, etc. Among these, a methyl group or an ethyl group is preferred because it results in a compound in which aggregation of the colorant in the ink composition is suppressed even under low-temperature and high-temperature conditions, and the compound has high dissolution stability.

In formula (1), _R7 has a structure represented by the following formula (2) or (3): When the compound has these structures, the compound has excellent light resistance and storage stability.

In formula (2), R ₈ represents a --SO ₃ ^-- group, an alkoxysulfonyl group (--SO ₃ R group), a sulfonamide group (--SO ₂ NRR group), a halogen atom, a perfluoroalkyl group, or a nitro group, and R ₉ represents a hydrogen atom or a halogen atom.

In formula (2), the halogen atom in _R8 and _R9 is not particularly limited, but may be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. The perfluoroalkyl group in _R8 is not particularly limited, but may be a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, or the like.

In formula (3), R ₁₀ to R ₁₂ each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group.

In formula (3), examples of the alkyl group in R ₁₀ to R ₁₂ include the same substituents as those exemplified as the alkyl groups in R ₁ and R ₂ in formula (1) above.

In formula (3), the substituted or unsubstituted aryl group in R _to R ₁₂ is not particularly limited, but may be a phenyl group. The substituent on the aryl group is not particularly limited, but may be a methyl group, an ethyl group, a methoxy group, a cyano group, etc.

It is more preferable that R ₇ in formula (1) has a structure represented by the following formula (4) in which R ₈ in formula (2) is an --SO ₃ ^-- group and R ₉ is a hydrogen atom.

Preferred examples of the compound represented by formula (1) include compounds (A1) to (A92) shown below, but are not limited to the compounds shown below.

Among these, the compounds represented by the formula (A2), (A3), (A4), (A5), (A6), (A8), (A9), (A10), (A18), (A19), (A22), (A23), (A24), (A25), (A26), (A27), (A28), (A29), (A30), (A31), (A40), (A41), (A42), (A43), (A44), (A45), (A46), (A47), (A48), (A49), (A59), (A60), (A64), (A65), (A66), (A67), (A68), (A76), (A77), (A78), (A79), (A80), (A83), (A87), (A88), (A89), (A90), and (A91) are preferred.

Among them, (A2), (A4), (A5), (A6), (A8), (A18), (A19), (A24), (A25), (A26), (A27), (A28), (A40), (A45), (A46), (A64), (A65), (A84), (A88), (A89), (A90), (A91), and (A92) are particularly preferred.

In the compound represented by formula (1), the cation is delocalized, and the cationic site may be present at any position in the molecule, and any of them is within the scope of the present invention. For example, in the case of compound (A1) having an anionic substituent in the molecule, ^X- in formula (1) does not exist, and the structure changes as follows.

On the other hand, in the case of compound (A74) that does not have an anionic substituent in the molecule, the structure changes as shown below.

The compound represented by the above general formula (1) may be used alone or in combination with two or more kinds to adjust the color tone, etc., depending on the application. Furthermore, it may be used in combination with a known pigment or dye. The known pigment or dye to be combined may be two or more kinds.

The oil-based ink composition for writing instruments and the water-based ink composition for writing instruments containing the compound represented by the above general formula (1) can be suitably used in ballpoint pens, felt-tip pens, marking pens, etc.

The amount of the compound represented by general formula (1) is appropriately selected depending on the application, but is preferably 1% by mass or more and 50% by mass or less of the total amount of the ink composition. More preferably, it is 2% by mass or more and 45% by mass or less, and even more preferably, it is 5% by mass or more and 40% by mass or less.

In addition, the compound represented by general formula (1) may be used alone as a colorant, but other known colorants may also be used in combination.

The colorants (dyes, pigments) that can be used in combination are determined according to the purpose and application of the ink, taking into consideration factors such as hue, printing sensitivity, light resistance, storage stability, and solubility with the resin.

Known dyes that can be used in combination are not particularly limited, but examples include acid dyes, basic dyes, metal complex dyes, salt-forming dyes, azine dyes, condensed azo compounds, azo metal complexes, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, perylene compounds, methine compounds, allylamide compounds, phthalocyanine dyes, triphenylmethane dyes, basic dye lake compounds, oxazine compounds, thiazine compounds, xanthene compounds, etc.

Specific examples include NIGROSIN BASE EX-BP, NUBIAN BLACKPA-2800, VALIFAST BLACK 1805, VALIFAST BLACK 1807, VALIFAST BLACK 1815, VALIFAST BLACK 1821, Oil Blue 613, VALIFAST RED 1308, VALIFAST RED 1320, VALIFAST RED 1355, VALIFAST RED 1360, VALIFAST BLUE 1601, VALIFAST BLUE 1605, VALIFAST BLUE 1621, VALIFAST YELLOW 1101, VALIFAST YELLOW 1151 (all manufactured by Orient Chemical Industry Co., Ltd.), Aizen Spilon Blue 2BNH, Aizen Spilon Red C-GH, Aizen Spilon Red C-BH, Aizen Spilon Yellow C-GHN new, Aizen Spilon Yellow GRLH special, Aizen S.P.T. Blue-121 (all manufactured by Hodogaya Chemical Co., Ltd.), etc.

The amount of the dye of the present invention is selected in the range of 1% by mass or more and 50% by mass or less based on the total amount of the ink composition.

Known pigments that can be used in combination are not particularly limited, but examples include carbon black, aniline black, titanium dioxide pigments, phthalocyanine, quinacridone, diketopyrrole, azo, dioxane, quinophthalone, triphenylmethane, perylene, perinone, metallic pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments.

Specific examples include FUJI FAST RED 8800 (C.I. Pigment Red 254) and FUJI FAST RED 2200 (C.I. Pigment Red 170) (both manufactured by Fuji Pigment Co., Ltd.).

It is preferable that the pigment has an average particle size of 30 nm or more and 700 nm or less after dispersion in the medium.

The amount of pigment to be blended may be in the range of 0.5% to 25% by mass, preferably 0.5% to 20% by mass, based on the total amount of the ink composition, as required.

The colorant, including the compound represented by formula (1) and the dyes and pigments that can be used in combination, is appropriately selected depending on the application, but is preferably blended in the range of 1% by mass or more and 50% by mass or less based on the total amount of the ink composition.

<Oil-based ink composition for writing instruments>
Next, the oil-based ink composition for a writing instrument according to the present invention will be described.

The oil-based ink composition for writing instruments of the present invention contains, in addition to a colorant containing a compound represented by general formula (1), a medium containing alcohol, and a resin that dissolves in the medium.

In addition to the above components, additives may be added as appropriate to the extent that they do not impair the properties for various applications. The additives will be described later.

[Media]
The "medium" in the present invention is alcohol or glycol ether. The medium is selected according to the purpose and use of the ink, and is not particularly limited, and one or more kinds may be used.

The following are some suitable alcohols:

For example, alkyl monoalcohols having no substituents, such as ethanol, isopropanol, n-butanol, isobutanol, tert-butanol, sec-butanol, 2-methyl-2-butanol, 3-pentanol, octanol, and cyclohexanol; alkyl monoalcohols having substituents, such as 2-phenoxyethanol and 3-methyl-3-methoxy-1-butanol; and aromatic alcohols, such as benzyl alcohol. Examples of the substituents in alkyl monoalcohols having a substituent include alkoxy groups and aryloxy groups.

Other examples include alkyl polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 3-methyl-1,3-butanediol, and 1,3-butanediol.

Further examples include glycol ether alcohols such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, and triethylene glycol monobutyl ether.

In particular, 3-methyl-3-methoxy-1-butanol, 1,3-butanediol, propylene glycol monomethyl ether, etc. are preferably used.

Glycol ethers can also be used. Glycol ethers include monoalcohol monoethers, but these are described as alcohols. Examples of diethers include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol, ethylene glycol diethyl ether, diethylene glycol diethyl ether, and diethylene glycol dipropyl ether.

In addition to alcohol and glycol ether, the medium may also contain water; ester solvents such as 3-methyl-3-methoxybutyl acetate, butyl acetate, and methyl propionate.

The amount of the medium used in the present invention varies depending on the type of writing instrument, such as a ballpoint pen, a felt tip pen, or a marking pen, but is preferably from 1% by mass to 70% by mass, more preferably from 3% by mass to 60% by mass, and particularly preferably from 5% by mass to 30% by mass, based on the total amount of the ink composition.

[resin]
The oil-based ink composition for writing instruments of the present invention contains a resin that dissolves in the above-mentioned medium in order to adjust the viscosity of the ink and improve the scratch resistance.

The resin is determined according to the purpose and use of the ink, and is not particularly limited, but examples include butyral resin, ketone resin, polyvinylpyrrolidone resin, styrene resin, styrene-acrylic resin, styrene-maleic acid resin, terpene resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, terpene phenol resin, rosin modified maleic resin, rosin phenol resin, maleic acid resin, phenol resin, xylene resin, urea resin, polyamide resin, phenoxy resin, cellulose-based resin, etc. These resins may be used alone, or two or more types may be used in combination as necessary.

In the present invention, butyral resins and ketone resins are preferably used to provide a writing feel that does not cause smearing.

Examples of butyral resins include low polymerization types such as S-LEC BL-1, BL-2, and BL-10, and high polymerization types such as BH-3, BH-6, BX-1, BX-5, and BH-S (all manufactured by Sekisui Chemical Co., Ltd.).

Examples of ketone resins include Ketone Resin K-90 (manufactured by Arakawa Chemical Industries, Ltd.), Hilac 901, Hilac 110H, and Hilac 111 (all manufactured by Hitachi Chemical Co., Ltd.).

An example of a polyvinylpyrrolidone resin is Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.).

The amount of resin is preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 30% by mass or less, and particularly preferably 5% by mass or more and 25% by mass or less, based on the total amount of the ink composition. Within the above range, viscosity adjustment is easy, wear on the pen tip can be prevented, and a stable and good writing feel can be obtained. Furthermore, since film-forming properties can be appropriately suppressed, solidification of the ink can be suppressed even if the pen tip is left exposed for a long period of time, and the "blurring phenomenon" when starting to write can be suppressed.

[Additives]
Furthermore, if necessary, additives may be added within a range that does not adversely affect the ink, such as rust inhibitors, surfactants, lubricants, wetting agents, UV absorbers, defoamers, antioxidants, pH adjusters, leveling agents, preservatives, and cellulose nanofibers.

Anti-rust agents include, but are not limited to, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, ethylenediaminetetraacetic acid, metal salt compounds, and phosphate ester compounds.

The surfactant is not particularly limited, but examples thereof include cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, silicone-based surfactants, and fluorine-based surfactants.

The lubricant is not particularly limited, but examples thereof include higher fatty acids, silicone oils, glycerin fatty acid esters, castor oil, phosphate esters and their metal salts, ammonium salts, etc., and are effective in preventing wear of the ball receiving seat of the ball tip of a ballpoint pen. These lubricants may be used alone or in combination of two or more kinds. Furthermore, fine particles such as silica fine particles and alumina fine particles may be added to improve lubricity.

Humectants include, but are not limited to, glycerin, sorbitan compounds, polysaccharides, urea, etc.

Examples of ultraviolet absorbers include, but are not limited to, 2-(2'-hydroxy-3'-t-butyl-5'-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and p-benzoic acid-2-hydroxybenzophenone.

Antifoaming agents include, but are not limited to, silicone compounds such as dimethylpolysiloxane, mineral oils, and fluorine-based compounds.

Antioxidants include, but are not limited to, dibutylhydroxytoluene, nordihydroxytoluene, flavonoids, butylhydroxyanisole, ascorbic acid derivatives, α-tocopherol, and catechins.

Examples of pH adjusters include, but are not limited to, alkalizing agents such as sodium hydroxide, alkanolamines, oxyethylene alkylamines, polyoxyethylene alkylamines, laurylamine, N,N-dimethylstearinamine, N,N-dimethylstearylamine, N,N-dimethyloctylamine, and ammonium, and acidic compounds such as alkylbenzenesulfonic acid, methanesulfonic acid, dialkylsulfosuccinic acid, naphthalenesulfonic acid, oleic acid, and naphthalenesulfonic acid-formaldehyde condensates.

Leveling agents are not particularly limited, but examples include acetylene glycol, acetylene alcohol, and silicone surfactants.

[Production method]
The oil-based ink composition for a writing instrument can be produced by a known method.

For example, the medium, the compound represented by formula (1), the resin, and, if necessary, other colorants and additives are mixed at an appropriate temperature range, and the mixture is stirred and mixed using a mixer, roll, homogenizer, disperser, or the like. In addition, a media-type dispersing machine such as a rotary shear homogenizer, ball mill, sand mill, or attritor, and a high-pressure counter-collision type dispersing machine can also be used.

The oil-based ink composition for writing instruments of the present invention must have a certain amount of solids content. If the solids content is too low, the ink will have a low viscosity, which can lead to ink dripping.

That is, the viscosity of the oil-based ink composition for writing instruments of the present invention is in the range of 100 to 3000 mPa·s at a shear rate of 38.30 (1/s) in an atmosphere of 24.5 to 25.5°C.

The oil-based ink composition for writing instruments produced in this manner is filled into ballpoint pens, felt tip pens, and marking pens.

For example, let's explain about ballpoint pens.

The structure and shape of the ballpoint pen are not particularly limited. For example, there is a ballpoint pen having an ink reservoir tube with a ball tip attached to a ball receiving seat at the tip, which is connected to the tip, housed inside the barrel, and the tip protruding from the tip of the barrel. After the oil-based ballpoint pen ink composition is filled from the opening of the ink reservoir tube through the base end, the opening at the base end is closed with a backflow prevention plug or backflow prevention body.

As the ball rolls over the writing medium, the ink composition for the oil-based ballpoint pen is supplied to the surface of the ball through the gap between the ball tip and the ball, soaking into the writing medium and forming a handwritten mark.

<Water-based ink composition for writing instruments>
Next, the water-based ink composition for a writing instrument according to the present invention will be described.

The aqueous ink composition for writing instruments of the present invention is characterized by containing a carrier carrying general formula (1) dispersed in an aqueous medium.

[Career]
The carrier carrying the general formula (1) in the present invention means a state in which the compound represented by the general formula (1) is dispersed in the carrier, a state in which the compound represented by the general formula (1) is encapsulated in the carrier, or a state in which the carrier is colored with the compound represented by the general formula (1), etc.

The carrier is not particularly limited, but examples include binder resins, cellulose nanofibers, microcapsules, etc.

The method for producing resin particles containing coloring material is not particularly limited, but examples include a bulk resin grinding method, a suspension polymerization method, an emulsion polymerization method, a mini-emulsion polymerization method, and a phase inversion emulsification method.

The lump resin crushing method is a method in which a lump resin obtained by polymerizing in advance so as to contain the compound represented by general formula (1) is physically crushed using a crusher or the like.

The suspension polymerization method is a method in which a polymerizable monomer in which a compound represented by general formula (1) is dissolved is suspended in a liquid state in an aqueous medium in the presence of a dispersant, and the droplets are polymerized in this state.

The emulsion polymerization method is a method in which a polymerizable monomer is polymerized in an aqueous medium in the presence of a compound represented by general formula (1).

The mini-emulsion polymerization method is a method in which a polymerizable monomer is dissolved or dispersed in a compound represented by general formula (1) and vigorously stirred in an aqueous medium in the presence of a surfactant to form resin particles.

The transfer emulsification method involves dissolving the compound represented by general formula (1) and a resin in a solvent, vigorously stirring the mixture in an aqueous medium in the presence of a surfactant to form resin particles, and then distilling off the solvent.

Examples of methods for bonding the compound represented by general formula (1) to the surface of resin particles that have been produced in advance include a physical dyeing method in which the compound represented by general formula (1) is attached to the surface of the resin particles, and a chemical swelling method in which the resin particles are swollen with an organic solvent and mixed with the compound represented by general formula (1), allowing the compound represented by general formula (1) to penetrate into the interior of the resin.

Among the above, emulsion polymerization, mini-emulsion polymerization, phase inversion emulsification, etc. are preferred from the viewpoint of being able to sufficiently reduce the particle size of the resin particles and obtain a resin with a high degree of coloration in order to solve the problems of the present invention.

The aqueous ink composition for writing instruments of the present invention can be obtained by mixing a dispersion of a carrier carrying general formula (1) in an aqueous medium, and, if necessary, other colorants and additives, at an appropriate temperature range, and stirring and mixing with a mixer, roll, homogenizer, disperser, etc. It can also be prepared using a media-type disperser such as a rotary shear homogenizer, ball mill, sand mill, or attritor, and a high-pressure counter-collision type disperser.

The aqueous ink composition for writing instruments of the present invention can have a pen tip that is suitable for the application. Examples include ballpoint pen tips, felt tips, fiber tips, fiber cores, plastic tips, porous cores, etc.

The aqueous ink composition for writing instruments of the present invention is preferably in a state in which the compound represented by general formula (1) is dispersed in the carrier, or in a state in which the compound represented by general formula (1) is encapsulated in the carrier.

To incorporate such a compound represented by general formula (1) into a carrier, it can be produced, for example, by polymerizing the compound represented by general formula (1) using a hydrophobic monomer in which the compound is dissolved, or by polymerizing the compound represented by general formula (1) using a hydrophobic monomer adsorbed on the surface of the compound.

The content of the compound represented by general formula (1) is preferably 0.4 to 20 times the mass ratio of the carrier content. If the content of the compound represented by general formula (1) is less than 0.4 times the mass ratio of the resin content, there is a tendency for skipped lines and smudges to occur in the handwriting. On the other hand, if the content of the compound represented by general formula (1) is more than 20 times the mass ratio of the resin content, aggregation is promoted, and there is a tendency for the tip of the lead to become clogged.

When an oil-based dye is used as a coloring material, the polymerization can be performed using a hydrophobic monomer in which the oil-based dye is dissolved. A detailed study of this polymerization method is reported in Colloid and Polymer Science, December 2003, Vol. 282, pp. 119-126. A specific example of a method of polymerization using a hydrophobic monomer adsorbed on the coloring material surface is a method of mixing a dispersion of a coloring material and a dispersion of a hydrophobic monomer that have been separately prepared, and then polymerizing the mixture. A detailed study of this method is reported in "Encapsulation of Carbon Black by Miniemulsion Polymerization", Macromolecular Chemistry and Physics, January 2001, Vol. 202, pp. 51-60, and this was used as a reference.

The binder resin of the carrier carrying the general formula (1) in the aqueous medium of the aqueous ink composition for writing instruments of the present invention is selected according to the application, but for example, a binder resin obtained by copolymerizing a hydrophilic polymerizable monomer such as acrylic acid, methacrylic acid, N-(2-hydroxyethyl)acrylamide, N-vinylpyrrolidone, or a polymerizable monomer having an ammonium salt with a lipophilic polymerizable monomer such as an acrylic acid ester, a methacrylic acid ester, vinyl acetate, styrene, or N-vinylcarbazole in an appropriate mixing ratio by a known method can be used.

Specific examples include homopolymers or copolymers (vinyl resins) of esters having vinyl groups, such as meryl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, isobornyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

Monofunctional acrylates such as polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, phenoxyethyl acrylate, and phenoxyethyl methacrylate; polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, trimethylolethane triacrylate, trimethylolethane trimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, pentaerythritol dimethacrylate, and polyfunctional acrylates and methacrylates such as trimethylolpropane triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, trimethylolpropane tri(acryloyloxypropyl)ether, tri(acryloyloxyethyl)isocyanurate, tri(acryloyloxyethyl)cyanurate, triallyl isocyanurate, glycerin triacrylate, and glycerin trimethacrylate; and polyfunctional acrylates and polyfunctional methacrylates obtained by adding ethylene oxide or propylene oxide to a polyfunctional alcohol such as trimethylolpropane or glycerin, followed by acrylate or methacrylate. In addition, urethane acrylates, polyester acrylates, and polyfunctional epoxy acrylates or epoxy methacrylates, which are reaction products of epoxy resins and acrylic acid or methacrylic acid, can also be used.

Examples of such copolymers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-t-butylstyrene, 4-methoxystyrene, and 4-chlorostyrene. In other words, the above-mentioned (meth)acrylic acid ester copolymer is preferably a styrene-(meth)acrylic acid copolymer having a styrene monomer.

Among the above polymerizable monomers, it is preferable to use cyclohexyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, and triallyl isocyanurate. The above polymerizable monomers may be used alone or in combination of two or more types as necessary.

Multifunctional polymerizable monomers can also be used as crosslinking agents.

As the polymerization initiator used in the polymerization of the polymerizable monomers used in the present invention, an oil-soluble initiator and/or a water-soluble initiator can be used.

Examples of oil-soluble initiators include, but are not limited to, azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile; and peroxide initiators such as acetylcyclohexylsulfonyl peroxide, diisopropyl peroxycarbonate, decanonyl peroxide, lauroyl peroxide, stearoyl peroxide, propionyl peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxyisobutyrate, cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and cumene hydroperoxide.

Water-soluble initiators include, but are not limited to, ammonium persulfate, potassium persulfate, 2,2'-azobis(N,N'-dimethyleneisobutyromidine) hydrochloride, 2,2'-azobis(2-aminodinopropane) hydrochloride, azobis(isobutylamidine) hydrochloride, 2,2'-azobisisobutyronitrile sodium sulfonate, ferrous sulfate, or hydrogen peroxide.

The concentration of the polymerization initiator is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.03% by mass or more and 5% by mass or less, based on the total mass of the monomer components including the hydrophobic monomer.

The emulsifier used in the polymerization of the polymerizable monomer used in the present invention is not particularly limited, and may be a cationic surfactant, an anionic surfactant, a nonionic surfactant, or the like.

Specific examples of cationic surfactants include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, and hexadecyl trimethyl ammonium bromide.

Anionic surfactants include fatty acid soaps such as sodium stearate and sodium dodecanoate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium lauryl sulfate.

Further examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, nonylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, monodecanoyl sucrose, and lauric acid monoglyceride (manufactured by Taiyo Kagaku Co., Ltd.).

The content of the binder resin in the carrier is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less, relative to the mass (total solids) of the aqueous ink composition for writing instruments according to the present invention. By making the content 5% by mass or more and 50% by mass or less, it is possible to further improve the sensitivity to light exposure and the strength of the drawing paper, and the adhesion of the aqueous ink composition for writing instruments is also improved.

The binder resin of the carrier of the present invention may contain a photopolymerization initiator. Examples of photopolymerization initiators include vicinal polyketoaldonyl compounds, α-carbonyl compounds, acionoin ethers, polyquinone compounds, combinations of triaryl imidazole dimer and p-aminophenyl ketone, trioxadiazole compounds, etc. Among these, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (product name: Irgacure 369, manufactured by BASF) is preferred.

In addition, a photoacid generator may be added to the binder resin of the carrier of the present invention as necessary. As the photoacid generator, known photoacid generators such as salts of onium ions, such as sulfonium, iodonium, selenium, ammonium, and phosphonium, and anions can be used.

Examples of the sulfonium ions include triphenylsulfonium, tri-p-tolylsulfonium, tri-o-tolylsulfonium, tris(4-methoxyphenyl)sulfonium, 1-naphthyldiphenylsulfonium, diphenylphenacylsulfonium, phenylmethylbenzylsulfonium, 4-hydroxyphenylmethylbenzylsulfonium, dimethylphenacylsulfonium, and phenacyltetrahydrothiophenium.

Examples of the iodonium ions include diphenyliodonium, di-p-tolyliodonium, bis(4-dodecylphenyl)iodonium, bis(4-methoxyphenyl)iodonium, and (4-octyloxyphenyl)phenyliodonium.

The above selenium ions include triarylseleniums such as triphenylselenium, tri-p-tolylselenium, tri-o-tolylselenium, tris(4-methoxyphenyl)selenium, 1-naphthyldiphenylselenium, tris(4-fluorophenyl)selenium, tri-1-naphthylselenium, and tri-2-naphthylselenium.

The above ammonium ions include tetraalkylammonium such as tetramethylammonium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium, tetraethylammonium, trimethyl-n-propylammonium, trimethylisopropylammonium, trimethyl-n-butylammonium, and trimethylisobutylammonium.

The above phosphonium ions include tetraphenylphosphonium, tetra-p-tolylphosphonium, tetrakis(2-methoxyphenyl)phosphonium, triphenylbenzylphosphonium, triphenylphenacylphosphonium, triphenylmethylphosphonium, triethylbenzylphosphonium, and tetraethylphosphonium.

_{Examples of the} anion include perhalogen acid ions such as _ClO4- ^and _BrO4- ^; halogenated sulfonate ions such as _{FSO3- and} ^{ClSO3- ;} sulfate ions such as _CH3SO4- ^, _CF3SO4- ^and _HSO4- ^; carbonate ions such _{as HCO3-} ^and _CH3CO3- ; aluminate ions such as _AlCl4- ^and _{AlF4- ; hexafluorobismuthate ion , carboxylate} ^ions _{such as CH3COO- ,} ^{CF3COO- , C6H5COO-} _, ^CH3C6H4COO- _{, C6F5COO- and} ^CF3C6H4COO- _{; B (} ^C6H5 _{) 4- and} ^{CH3CH2CH2CH2B} ₍ ^C6H5 ₎ aryl borates such ^{as 3-} _; thiocyanate, and nitrate.

The cellulose nanofibers that serve as carriers carrying general formula (1) in the aqueous medium of the aqueous ink composition for writing instruments of the present invention are selected according to the intended use, but are, for example, ultrafine fibers that are obtained by subjecting plant fibers to chemical and/or mechanical fiber defibration treatment and have an average width of several nm to 20 nm and an average length of 0.5 μm to several μm.

Materials that contain cellulose fibers include plants such as wood, bamboo, kenaf, hemp, jute, wood pulp, waste paper, crystalline cellulose, agricultural waste, and recycled pulp, animals such as sea squirts, algae, and microorganisms.

Equipment used for defibration processing includes rotary shear homogenizers, high-pressure homogenizers, high-pressure homogenizers, ball mills, sand mills, attritors, high-pressure opposed collision type dispersers, grinders, conical refiners, etc.

Cellulose nanofibers are commercially available and can be used. Examples of commercially available products include Leocrysta I-2AX, CNF 03, and CNF 04 (manufactured by Daiichi Chemical Industry Co., Ltd.), ELLEX-S (manufactured by Daio Paper Co., Ltd.), and nanoforest-S (manufactured by Chuetsu Pulp Industry Co., Ltd.).

The size (fiber diameter) of these cellulose nanofibers varies depending on the type of cellulose nanofiber. In addition, a fiber diameter is selected that is in a suitable range in terms of thickening effect, stability over time, color development, etc., within a range that does not impair the characteristics in various applications.

The amount of cellulose nanofibers is preferably 0.001 parts by mass or more and 40 parts by mass or less, more preferably 0.01 parts by mass or more and 10 parts by mass or less, and even more preferably 0.05 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the aqueous medium contained in the aqueous ink composition for writing instruments.

In addition, in the aqueous ink composition for writing instruments, the aqueous medium in which the compound represented by general formula (1) is dispersed can be water or a mixture of water and a water-soluble organic solvent.

The method of dyeing cellulose nanofibers using a compound represented by general formula (1) is not particularly limited. For example, cellulose nanofibers are contacted with a compound represented by general formula (1) in an aqueous medium, and then heated or oxidized as necessary, and the medium is then distilled off to obtain dyed cellulose nanofibers. When contacting, a pH adjuster, a color developer, a dispersant, etc. may be added.

The aqueous coloring liquid may be the same system used when dyeing the cellulose nanofibers, or it may be a liquid in which the colored cellulose nanofibers are extracted by drying and then dispersed again in an aqueous medium.

[Media]
When preparing an aqueous ink composition for writing instruments, it is preferable to use a mixture of water and a water-soluble organic solvent as the aqueous medium. Examples of the water-soluble organic solvent to be contained in the aqueous medium include alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, and sulfur-containing polar solvent. Specific examples include ethylene glycol, diethylene glycol, triethylene glycol, 3-methyl-1,3-butanediol, 1,3-butanediol, polyethylene glycol, glycerin, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. These water-soluble organic solvents contribute to maintaining the moisture retention of the ink for writing instruments, improving the solubility of coloring materials, and effectively penetrating the ink for writing instruments into recording paper. In the aqueous medium in the ink for writing instruments, the ratio of water to the water-soluble organic solvent (based on mass) is preferably water/water-soluble organic solvent=9/1 to 1/9. More preferably, it is 8/2 to 2/8, and even more preferably 7/3 to 3/7. In this way, the dispersibility or solubility of the colorant containing the compound represented by general formula (1) in the ink can be improved.

The aqueous ink composition for writing instruments can be suitably used in aqueous ballpoint pens, gel inks, inks for aqueous ballpoint pens, felt tip pens, marking pens, etc., and additives such as dispersants, lubricants, pH adjusters, rust inhibitors, preservatives, or antibacterial agents may be added as appropriate within the limits that do not impair the properties in various applications. The additives will be described later.

[Additives]
The lubricant is not particularly limited, but examples thereof include nonionic lubricants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, and alkyl phosphate esters; anionic lubricants such as alkyl sulfonates and alkyl aryl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols, fluorine-based surfactants, and polyether-modified silicones.

The pH adjuster is not particularly limited, but examples include sodium hydroxide, urea, monoethanolamine, diethanolamine, triethanolamine, sodium tripolyphosphate, sodium carbonate, and alkali metal salts of phosphoric acid. For example, from the viewpoints of usability, safety, and the stability of the ink itself, it is preferable to adjust the pH to 4 to 11, and more preferably 5 to 10.

Anti-rust agents include, but are not limited to, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, and phosphate ester compounds.

Preservatives or antibacterial agents are not particularly limited, but examples include phenol, sodium benzoate, benzimidazole compounds, sodium omadine, sodium pentachlorophenol, sodium sorbate, and 1,2-benzisothiazolin-3-one.

[Production method]
The aqueous ink composition for a writing instrument can be produced by a known method.

For example, the aqueous ink composition for writing instruments of the present invention and, if necessary, other colorants and additives are mixed at an appropriate temperature range, and the mixture is stirred and mixed using a mixer, roll, homogenizer, disperser, etc. Alternatively, a media-type dispersing machine such as a rotary shear homogenizer, ball mill, sand mill, or attritor, and a high-pressure counter-collision type dispersing machine can also be used.

The water-based ink composition for writing instruments may contain other pigments, water-soluble solvents, etc.

The pigments that can be used in combination are not particularly limited, but can be selected from inorganic and organic pigments that are conventionally used in writing instruments such as water-based ballpoint pens.

Examples of inorganic pigments include carbon black and metal powder.

Examples of organic pigments include azo pigments, phthalocyanine pigments, perylene pigments, and quinacridone pigments. The content is from 0.1 to 50 parts by mass, and preferably from 0.5 to 30 parts by mass, per 100 parts by mass of the aqueous medium.

When a pigment is used in combination, it is preferable to use a dispersant. As a dispersant, ionic surfactants, nonionic surfactants, polymeric surfactants, water-soluble resins, etc. can be used as long as they do not impair the characteristics of the application.

The oil-based ink composition for writing instruments produced in this manner is filled into ballpoint pens, felt tip pens, and marking pens.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the text, "parts" and "%" refer to "parts by mass" and "% by mass" unless otherwise specified.

The compound represented by general formula (1) was synthesized by a known method, and was identified using a ^1H nuclear magnetic resonance spectroscopy ( ^1H -NMR) apparatus (ECA-400, manufactured by JEOL Ltd.) and an LC/TOF MS apparatus (LC/MSD TOF, manufactured by Agilent Technologies).

<Production of Oil-Based Ink Composition for Writing Instruments>
[Examples 1 to 22 and Comparative Examples 1 to 13]
The constituent materials shown in Tables 1-1 and 1-2 were used. The compounds of general formula (1) are the compounds (A1) to (A92) listed above. First, a resin was added to a medium, which was then heated to 70°C to dissolve it, and then cooled to room temperature. A colorant and other constituent materials were added, and the mixture was dispersed for 3 hours using an attritor (manufactured by Mitsui Mining Co., Ltd.) to produce an oil-based ink composition for a writing instrument.

The comparative colorant compounds (B1) to (B4) in Table 1-2 are the following compounds.

[Evaluation of dissolution stability]
20 mL of each of the oil-based ink compositions for writing instruments obtained above was added to a 50 mL sample bottle, which was then sealed and left for one month under low temperature (0°C) and high temperature (60°C) conditions to evaluate the dissolution stability of the ink composition. The presence or absence of aggregates in the ink composition was visually observed using a phase contrast microscope (BX53, manufactured by Olympus Corporation). The fewer aggregates present, the better the dissolution stability was judged to be.
A: The ink composition is good and free of agglomerates.
B: A small amount of agglomerates were generated in the ink composition.
C: Coagulation occurred in the ink composition.

[Evaluation of blurring (initial writing ability) when writing]
Each of the oil-based ink compositions for writing instruments obtained above was filled into an ink reservoir made of polypropylene tube having an inner diameter of 1.2 mm and a length of 140 mm. A ballpoint pen for evaluation test was prepared by using this ink reservoir and a phosphor bronze tip (ball diameter 0.7 mm).

The cap was removed from the test ballpoint pen and it was left for 1 hour under low temperature (0°C) and high temperature (60°C) conditions with a humidity of 65%, after which a circle was handwritten on it using JIS P3201 writing paper.

The smearing at the beginning of writing was evaluated according to the following criteria. The less smearing occurred, the better the initial writing performance was judged to be.
A: No smearing occurred under both low temperature (0° C.) and high temperature (60° C.) conditions.
B: Blurring occurred under either the low temperature (0° C.) or high temperature (60° C.) condition.
C: Significant smearing occurred under either the low temperature (0° C.) or high temperature (60° C.) condition.

[Writing feel evaluation]
Following the evaluation of initial writing performance, the writing feel was evaluated. The writing feel was evaluated based on the following criteria: whether the handwriting continued to be stable without skipping or smearing, and without any change in the writing density. The writing feel was judged to be good if the handwriting continued to be stable without skipping or smearing, and without any change in the writing density.
A: Under both low temperature (0° C.) and high temperature (60° C.) conditions, there is no skipping or smearing of lines in the handwriting, and there is no change in the density of the handwriting.
B: Under at least one of the low temperature (0° C.) and high temperature (60° C.) conditions, slight skipping or smearing of lines in handwriting occurred, or slight change in handwriting density occurred.
C: At least one of the low temperature (0° C.) and high temperature (60° C.) conditions caused skipping or smearing of lines in handwriting, and changes in handwriting density occurred.

[Evaluation of handwriting robustness]
The handwriting fastness was evaluated. For the handwriting fastness evaluation, the ballpoint pen was used to write 20 cm at a constant writing pressure to create a sample. The sample was placed in a xenon test device (Atlas Weatherometer Ci4000, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and exposed for 10 hours under the conditions of (illuminance: 0.28 W/m ² at 340 nm, black panel temperature: 40° C., relative humidity: 50%). The spectra before and after exposure were read with a scanner, and the initial optical density was defined as OD ₀ , and the O.D. after 5 hours of exposure was defined as OD _5. The O.D. residual rate was defined as follows.
O. D. Survival rate (%) = (OD ₅ /OD ₀ ) x 100

The evaluation criteria are as follows:
A: 85≦O.D. remaining rate (%) and handwriting fastness is very sufficient.
B: 70≦O.D. remaining rate (%)<85, and handwriting fastness is sufficient.
C: O.D. remaining rate (%) is <70, and writing fastness is insufficient.

The results of the above evaluation are shown in Table 2.

As described above, the oil-based ink composition for writing instruments of the present invention, compared to the comparative oil-based ink composition, suppresses aggregation of the colorant within the ink composition and has high dissolution stability even under low and high temperature conditions, and by using this oil-based ink composition for writing instruments, it is possible to provide a ballpoint pen that suppresses the smearing phenomenon at the start of writing, has a good writing feel without skipped lines or smearing, and has high handwriting durability.

<Production of Water-Based Ink Composition for Writing Instruments>
Example 23
5 parts of compound A-2, 1 part of methanol, and 0.5 parts of cellulose nanofiber (LEOCRYSTA I-2AX) were added, and then 99 parts of ion-exchanged water was added. The internal temperature was heated to 80°C, and the mixture was stirred for 2 hours while removing methanol. After cooling to room temperature, the mixture was dispersed with a homogenizer for 5 minutes to prepare an aqueous ink composition (23) for writing instruments containing cellulose nanofiber dyed with compound A-2.

[Examples 24 to 42, Comparative Examples 14 to 27]
Water-based ink compositions for writing instruments (24) to (42) containing cellulose nanofibers dyed with compounds and comparative water-based ink compositions for writing instruments (14) to (27) were prepared in the same manner as in Example 23, except that the compounds and cellulose nanofibers were changed to those shown in Table 3. The cellulose nanofibers are available from Rheocrysta I-2AX, CNF 03, CNF 04 (Dai-ichi Kogyo Seiyaku Co., Ltd.), ELLEX-S (Daioh Paper Co., Ltd.), and nanoforest-S (Chuetsu Pulp Industry Co., Ltd.).

Comparative compounds (B1) to (B4) are the same as above.

Example 43
10 g of cyclohexyl methchlorate, 8 g of n-butyl methacrylate, 2 g of triallyl isocyanurate, and 0.5 g of 2,2'-azobis-(2-methylbutyronitrile) were mixed and stirred at 100 rpm for 1 hour. The mixture obtained was added dropwise to 70 g of an aqueous solution (concentration 0.3%) of 0.05 g of lauric acid monoglyceride (manufactured by Taiyo Kagaku Co., Ltd.), and stirred at 300 rpm for 1 hour. The mixture was dispersed with a homogenizer for 1 hour (Dispersion A).

10 g of compound (A-2) was added to 110 g of an aqueous solution of lauric acid monoglyceride (concentration 2.7%), stirred at 300 rpm for 2 hours, and then dispersed with a homogenizer for 1 hour (dispersion liquid B).

20 g of dispersion A and 80 g of dispersion B were mixed and stirred at 300 rpm for 1 hour. The mixture was then dispersed with a homogenizer for 5 minutes and stirred for 1 hour. After further dispersing with a homogenizer for 5 minutes, the mixture was polymerized at 70°C for 8 hours in a nitrogen atmosphere. The mixture was filtered through a 5.0 μm filter to obtain an aqueous ink composition for writing instruments (43). The average particle size of the resin particles in the resulting aqueous ink composition for writing instruments was 58 nm.

[Examples 44 to 48, Comparative Examples 28 to 32]
Water-based ink compositions for writing instruments (44) to (48) in which the compound represented by general formula (1) was dispersed or encapsulated in a carrier, and comparative water-based ink compositions for writing instruments (28) to (32) were prepared in the same manner as in Example 43, except that the materials used were changed to those shown in Table 4. Note that in all of Comparative Examples 28 to 32, polymerization inhibition occurred, making it impossible to prepare water-based ink compositions for writing instruments, and evaluation was not possible.

[Evaluation of dissolution stability]
20 mL of each of the aqueous ink compositions for writing instruments obtained above was added to a 50 mL sample bottle, which was then sealed and left for one month under low temperature (0°C) and high temperature (60°C) conditions to evaluate the dissolution stability of the ink composition. The presence or absence of aggregates in the ink composition was visually observed using a phase contrast microscope (BX53, manufactured by Olympus Corporation). The fewer aggregates there were, the more excellent the dispersion stability in the aqueous medium was judged to be.
A: The ink composition is good and free of agglomerates.
B: A small amount of agglomerates were generated in the ink composition.
C: Coagulation occurred in the ink composition.

[Evaluation of blurring (initial writing ability) when writing]
Each of the water-based ink compositions for writing instruments obtained above was filled into an ink reservoir made of polypropylene tube having an inner diameter of 1.2 mm and a length of 140 mm. A ballpoint pen for evaluation test was prepared by using this ink reservoir and a phosphor bronze tip (ball diameter: 0.7 mm).

The cap was removed from the test ballpoint pen and it was left for 1 hour under low temperature (0°C) and high temperature (60°C) conditions with a humidity of 65%, after which a circle was handwritten on it using JIS P3201 writing paper.

The smearing at the beginning of writing was evaluated according to the following criteria. The less smearing occurred, the better the initial writing performance was judged to be.
A: No smearing occurred under both low temperature (0° C.) and high temperature (60° C.) conditions.
B: Blurring occurred under either the low temperature (0° C.) or high temperature (60° C.) condition.
C: Significant smearing occurred under either the low temperature (0° C.) or high temperature (60° C.) condition.

[Writing feel evaluation]
Following the evaluation of initial writing performance, the writing feel was evaluated. The writing feel was evaluated based on the following criteria: whether the handwriting continued to be stable without skipping or smearing, and without any change in the writing density. The writing feel was judged to be good if the handwriting continued to be stable without skipping or smearing, and without any change in the writing density.
A: Under both low temperature (0° C.) and high temperature (60° C.) conditions, there is no skipping or smearing of lines in the handwriting, and there is no change in the density of the handwriting.
B: Under at least one of the low temperature (0° C.) and high temperature (60° C.) conditions, slight skipping or smearing of lines in handwriting occurred, or slight change in handwriting density occurred.
C: At least one of the low temperature (0° C.) and high temperature (60° C.) conditions caused skipping or smearing of lines in handwriting, and changes in handwriting density occurred.

[Evaluation of handwriting robustness]
The handwriting fastness was evaluated. For the handwriting fastness evaluation, the ballpoint pen was used to write 20 cm at a constant writing pressure to create a sample. The sample was placed in a xenon test device (Atlas Weatherometer Ci4000, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and exposed for 10 hours under the conditions of (illuminance: 0.28 W/m ² at 340 nm, black panel temperature: 40° C., relative humidity: 50%). The spectra before and after exposure were read with a scanner, and the initial optical density was defined as OD ₀ , and the O.D. after 5 hours of exposure was defined as OD _5. The O.D. residual rate was defined as follows.
O. D. Survival rate (%) = (OD ₅ /OD ₀ ) x 100

The evaluation criteria are as follows:
A: 85≦O.D. remaining rate (%) and handwriting fastness is very sufficient.
B: 70≦O.D. remaining rate (%)<85, and handwriting fastness is sufficient.
C: O.D. remaining rate (%) is <70, and writing fastness is insufficient.

The results of the above evaluation are shown in Tables 5 and 6.

From the above, the aqueous ink composition for writing instruments of the present invention has a higher dispersion stability in an aqueous medium of the carrier carrying general formula (1) than the comparative ink composition. In other words, this indicates that when the carrier is prepared by polymerization, polymerization inhibition with general formula (1) does not occur, and when cellulose nanofiber is used, compatibility with general formula (1) is high. Furthermore, by using the aqueous ink composition for writing instruments of the present invention, the phenomenon of smearing at the start of writing is suppressed, and a ballpoint pen with a good writing feel without skipped lines or smearing in the handwriting and high handwriting robustness can be provided.

The oil-based ink composition for writing instruments of the present invention suppresses aggregation of the colorant within the ink composition even under low and high temperature conditions, and has high dissolution stability. Furthermore, by using the oil-based ink composition for writing instruments, it is possible to provide ballpoint pens, felt-tip pens, marking pens, etc. that suppress the phenomenon of smearing at the start of writing, have a good writing feel without line skipping or smearing in the handwriting (the handwriting density does not change and the handwriting continues to be stable) and have high handwriting fastness.

The aqueous ink composition for writing instruments of the present invention also has high dispersion stability in an aqueous medium of the carrier carrying general formula (1). Furthermore, by using the aqueous ink composition for writing instruments, it is possible to provide ballpoint pens, felt-tip pens, marking pens, and the like that suppress the phenomenon of smearing at the start of writing, provide a good writing feel without skipping or smearing in the handwriting (the handwriting density does not change and the handwriting continues to be stable) and have high handwriting fastness.

Claims (10)

a medium containing an alcohol or a glycol ether;
a resin that dissolves in the medium; and a colorant containing a compound represented by the following general formula (1):

[In formula (1), _R1 and _R2 each independently represent a substituted phenyl group or an unsubstituted phenyl group, _R3 and _R4 each independently represent an alkyl group having a substituent and having from 2 to 12 carbon atoms or an unsubstituted alkyl group, a cyano group, a trifluoromethyl group, or a halogen atom, _R5 and _R6 each independently represent a hydrogen atom or an alkyl group, and _R7 represents a structure represented by the following formula (2) or (3):

In formula (2), R ₈ represents a —SO ₃ ^— group, an alkoxysulfonyl group, a sulfonamide group, a halogen atom, a perfluoroalkyl group, or a nitro group; R ₉ represents a hydrogen atom or a halogen atom;
In formula (3), R ₁₀ to R ₁₂ each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group;
X ⁻ represents an anion, and may be absent when there is at least one anionic substituent in the molecule.
1. An oil-based ink composition for a writing instrument, comprising: 2. The oil-based ink composition for writing instruments according to claim 1, wherein in formula (1), R ₁ and R ₂ are phenyl groups having the same substituent or unsubstituted phenyl groups. 3. The oil-based ink composition for a writing instrument according to claim 1, wherein the formula (2) is a structure represented by the following formula (4):

The oil-based ink composition for writing instruments according to any one of claims 1 to 3, wherein the resin contains at least one resin selected from the group consisting of butyral resins and ketone resins. A ballpoint pen using the oil-based ink composition for a writing instrument according to any one of claims 1 to 4. 1. An aqueous ink composition for a writing instrument, comprising a carrier carrying a compound represented by the following general formula (1) dispersed in an aqueous medium:

[In formula (1), _R1 and _R2 each independently represent a substituted phenyl group or an unsubstituted phenyl group, _R3 and _R4 each independently represent an alkyl group having a substituent and having from 2 to 12 carbon atoms or an unsubstituted alkyl group, a cyano group, a trifluoromethyl group, or a halogen atom, _R5 and _R6 each independently represent a hydrogen atom or an alkyl group, and _R7 represents a structure represented by the following formula (2) or (3):

In formula (2), R ₈ represents a —SO ₃ ^— group, an alkoxysulfonyl group, a sulfonamide group, a halogen atom, a perfluoroalkyl group, or a nitro group; R ₉ represents a hydrogen atom or a halogen atom;
In formula (3), R ₁₀ to R ₁₂ each independently represent a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group;
X ⁻ represents an anion, and may be absent when there is at least one anionic substituent in the molecule. 7. The water-based ink composition for writing instruments according to claim 6, wherein in formula (1), R ₁ and R ₂ are phenyl groups having the same substituent or unsubstituted phenyl groups. The aqueous ink composition for a writing instrument according to claim 6 or 7, wherein the formula (2) is a structure represented by the following formula (4):

The aqueous ink composition for writing instruments according to any one of claims 6 to 8, wherein the carrier is a binder resin or cellulose nanofiber. A ballpoint pen using the aqueous ink composition for a writing instrument according to any one of claims 6 to 9.