JP2002226747A - Pigment ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment ink composition capable of inhibiting bleeding without imparting pseudoplasticity to an ink, even though the composition exhibits Newtonian viscosity behavior or similar physical properties. SOLUTION: The pigment ink composition comprises at least a pigment and a dispersant and contains as a main solvent a mixed solvent comprising at least three solvents of different polarity, which mixed solvent comprises two solvent components which do not each dissolve the dispersant when used alone and are not compatible with each other but form a homogeneous mixed solvent when a third solvent component is added thereto to turn to a solvent for the dispersant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writing instrument including a felt-tip pen, a ball-point pen and the like, a desk table, a vermilion table, a desk-top product including a penetrating mark using an open-cell material, and an office supply such as an ink jet and an ink ribbon. The present invention relates to a pigment ink composition used for related products.

[0002]

2. Description of the Related Art As means for suppressing bleeding of ink transferred onto paper or the like, conventionally, a pseudoplasticity imparting agent such as fine particle silica or bentonite is added to an ink composition to make the ink itself difficult to fluidize. And the method of suppressing the ink discharge amount. However, the deterioration of the fluidity of the ink deteriorates the follow-up property at the time of ink discharge, the drying property on paper is deteriorated, and the color density is reduced by suppressing the discharge amount, and various physical properties are impaired. become. There is also a means of suppressing bleeding by increasing the viscosity. However, not only the fluidity of the ink is deteriorated, but also the stability of the ink is deteriorated because the solid content in the ink composition is increased.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems and the like, and is intended to solve such a problem. It is an object of the present invention to provide a pigment ink composition that suppresses bleeding on the paper surface even when the viscosity is a viscosity (even when the shear rate is changed and the viscosity is not affected by the shear rate and shows a constant value) or close to this. Aim.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned conventional problems and the like. As a result, the pigment ink composition does not dissolve the dispersing agent alone, so that three or more types which have not been used conventionally have been used. It has been found that the pigment ink composition of the above object can be obtained by using the specific mixed solvent as the main solvent, and the present invention has been completed.

That is, the pigment ink composition of the present invention comprises:
Two components that contain at least a pigment and a dispersant, and that do not dissolve the dispersant in each single component and that are not mixed with each other,
A pigment ink composition comprising, as a main solvent, at least three kinds of mixed solvents having different polarities, which are capable of dissolving a dispersant as a homogeneous mixed solvent by adding a third component.

[0006] The above three or more mixed solvents include the following A
The pigment ink composition according to claim 1, which is selected from a group, a group B, and a group C. Group A: a solvent in which the solubility of the dispersant is 0.5 wt% or less and which is more polar than the solvent group in the polar range in which the dispersant can be dissolved. A solvent having a polarity lower than that of a solvent group having a polar range in which the dispersant can be dissolved and which is not uniformly mixed with the solvent selected from the group A; a group C used; a mixture selected from the group A and the group B used; A solvent that becomes a uniform mixed solvent when added to a solvent.

In the above-mentioned pigment ink composition of the present invention, it is most preferable that the dispersant and the solvents of Group A, Group B and Group C comprise the following combinations. Dispersant: polyvinyl butyral group A; · ethylene glycol · polyethylene glycol having an ethylene oxide number of 2 to 15 · propylene glycol · monoester or diester of a triol solvent such as glycerin group B; · polypropylene glycol having a molecular weight of more than 800 and not more than 4000 -Among ethylene oxide propylene copolymerized diols, those having a butyral resin solubility of 0.5 wt% or less Group C;-Polypropylene glycol having a molecular weight of 200 or more and 800 or less-Ethylene oxide propylene oxide copolymerized diols-Propylene Esters having a hydroxyl group such as glycol monolysylate Further, the pigment ink composition of the present invention has a Newtonian viscosity or a viscosity close thereto, and has good fluidity and is easy to use. It is preferred.

[0008]

Embodiments of the present invention will be described below in detail. First, the mixed solvents having different polarities used in the present invention will be described. In general, it is known that when a certain substance (here, a dispersant) is dissolved in a solvent, the two substances are easily dissolved if their polarities are close to each other. In the present invention, this solvent having good solubility (close to the polarity of the dispersant) is not used. A mixture of a solvent having a higher polarity, a solvent having a lower polarity and not dissolving with the former, and a solvent dissolving with these two solvents to form a uniform mixed solvent. I do. A substance having a high polarity is a substance having a large electron bias in the substance molecule, and a substance having a hydroxyl functional group, an amino group, a nitro group, a nitrile group, or the like as a polar functional group generally has a high polarity.
Specific examples include water, glycerin, glycol and the like.

Conversely, a substance having a low polarity is a substance having a small electron bias in a molecule, such as a linear hydrocarbon compound. Substances containing large alkyl groups generally have low polarity. However, in the present invention, the content that the polarity is high or low is a relative one. That is, a solvent capable of dissolving the dispersant (a solvent group having a certain polarity range) is not used, and a solvent having a higher polarity than the solvent (solvent group) and a solvent having a lower polarity are used. In addition, a solvent that does not mix uniformly with the solvent used in Group A (Group B) and a solvent that dissolves uniformly with the solvent selected from Group A and Group B to be used (Group C) are used. It forms a uniform mixed solvent of at least three types.

Here, the dispersant is dissolved as a uniform mixed solvent by adding the group C, while the group A and the group B alone do not dissolve the dispersant, and the groups A and B alone do not mix.
The reason why the ink can be used is considered as follows. Usually, the dispersant contains a pigment-friendly functional group for adsorbing pigment and a solvent-friendly functional group for dissolution in a solvent. Conceptually, the dispersant acts as a bridge between the pigment and the solvent. Therefore, a highly polar functional group and a low functional group are present in the dispersant molecule. In this case, the solvent A group alone acts on the highly polar functional group in the dispersant molecule, The low-polarity functional groups in the molecule of the dispersant are aggregated and cannot be uniformly dissolved. Conversely, even if only the solvent B group acts on a low-polarity functional group in the molecule of the dispersant, the high-polarity functional groups in the molecule of the dispersant aggregate and cannot be uniformly dissolved. .

However, in the case of the mixed solvent comprising the groups A and B of the present invention, the group A acts on the highly polar functional group in the molecule of the dispersant, and the group B acts on the less polar functional group. The dispersant dissolves uniformly. However, if the solvents of Group A and Group B are not compatible, the dispersing agent can only exist at the liquid-liquid interface of Group A and Group B and eventually precipitates out. A third solvent having a role as an activator (C
Group) is an absolute condition. With these three types of mixed solvents, a system in which the dispersant is uniformly dissolved can be obtained. When the pigment enters the system in which the dispersant is uniformly dissolved, the solvent acting on the pigment palatability functional group in the dispersant is removed, and the dispersant (the pigment palatability functional group) becomes a pigment. Exchanged and adsorbed, and stabilized as a pigment ink.

Therefore, in the present invention, these groups A, B and C are always used in combination, but two or more of groups A, B and C may be used in combination. The conditions for determining the solubility (0.5 wt% or more / less than or equal to 0.5 wt%) of the dispersant for the groups A and B in the present invention are as follows. At a temperature of 60 ° C., the solvent is 99.5.
0.5% by mass of a dispersing agent is added to the
After stirring for an hour, leave at room temperature for one day. After standing, the dissolution state of the dispersant is visually checked. -When the solution is transparent; solubility exceeds 0.5 wt% (good solvent)
・ When the solution is cloudy or there are undissolved substances; solubility: 0.5
wt% or less (poor solvent).

Here, the solvent of Group A used in the present invention may have a solubility of 0.5 wt.
% Or less (poor solvent) and has a higher polarity than the solvent group in the polar range in which the dispersant to be used can be dissolved. Examples include diols having two or more hydroxyl groups, polyols, and derivatives thereof. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, glycerin, glyceryl monoacetate,
Glyceryl diacetate, glyceryl monobutyrate,
1,2,6-hexanetriol and the like. These are selected according to the type of dispersant used. In particular, when butyral resin is used as the dispersant, diethylene glycol, triethylene glycol, glyceryl monoacetate, and the like are preferable.

The solvent of Group B alone has a solubility of the dispersant used of 0.5% by weight or less, and is lower in polarity than the solvent group in the polar range in which the dispersant used can be dissolved. It is not compatible with one or more solvents selected from Group A. For example, polypropylene glycols, ethylene oxide / propylene oxide copolymerized diols, fatty acids such as myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, n-butanol, 1-pentanol, n
Alcohols such as hexanol, benzyl alcohol, n-octanol, n-decanol, cyclohexanol,

Methyl oleate, isobutyl oleate, lauryl oleate, isopropyl myristate,
Butyl stearate, isopropyl isostearate,
Examples thereof include fatty acid esters such as ethyl benzoate, propyl benzoate, diisobutyl adipate, dibutyl oxalate, and dioctyl maleate. These are selected according to the type of dispersant used. In particular, when butyral resin is used as the dispersant, polypropylene glycol having a molecular weight of more than 800 and 4000 or less, ethylene oxide-propylene oxide copolymerized diols, isostearin Acid, oleic acid and the like can be suitably used.

The group C solvent can be made into a uniform mixed solvent by adding it to the mixed solvent selected from the group A and the group B, and has a role as a surfactant. The solubility of the dispersant used in the group C solvent is not limited, and both a good solvent and a poor solvent can be used. The solvent selected here generally has an intermediate polarity between Group A and Group B, and can be a uniform solvent when combined with Group A and Group B. Examples thereof include polypropylene glycol having a molecular weight of 200 or more and 800 or less, ethylene oxide-propylene oxide copolymerized diols, and esters having a hydroxyl group such as propylene glycol monolithate.

A group which satisfies the above conditions used in the present invention,
The amount of the solvent (main solvent) used in the groups B and C is 50 wt% or more of the entire solvent (in the total amount of the solvent), preferably 80 to 1
When the content is less than 50 wt%, the effect of suppressing bleeding is very poor. Further, in the solvent ratio (mass% ratio) of the group A, the group B, and the group C, the group A and the group B both have 1 to 99%.
wt%, group C is in the range of 0.01 to 90 wt%,
It is appropriately determined depending on the selected solvent and dispersant. A
When the solvent ratio of the group or the group B is less than 1 wt%, the effect of suppressing bleeding is not sufficiently exhibited, and when it exceeds 99 wt%, the dispersion stability of the ink becomes poor. When the content of the group C is less than 0.01 wt%, it is difficult to make the mixed solvent composed of the group A and the group B uniform, so that the stability of the ink cannot be obtained. Not enough.

In addition, it is possible to add a solvent (good solvent) that dissolves the dispersant used in an amount of 0.5 wt% or more as a secondary solvent. The amount is preferably set to 20% by weight or less of the total amount of the solvent. However, group A, B
It is limited to those that are compatible with the mixed solvent consisting of Group C and Group C. Further, in the present invention, the total content of the solvents including the groups A, B and C varies depending on the dispersant, pigment and solvent used, and is 30 to 9 with respect to the total amount of the ink composition.
9 wt%, preferably 50 to 90 wt%. When the total content of the solvent is less than 30 wt% with respect to the total amount of the ink composition, the fluidity of the ink becomes poor, and when it exceeds 99 wt%, the pigment (colorant), dispersant (resin) and other additives The ratio is undesirably reduced, and greatly affects the quality performance of the product such as color density and fixability.

The colorant used in the present invention is a pigment such as an organic pigment, an inorganic pigment, or a colored resin particle.
Those which are hardly soluble in the solvent containing the group, the group B, and the group C and have an average particle diameter after dispersion by a dispersant of 30 nm to 700 nm are preferable. Specific examples include titanium oxide, carbon black, phthalocyanine, azo, dipyrrolopyrrole, anthraquinone, isoindoline, and quinacdrine. These may be used as they are, or their pigments may be surface-modified with a resin, a surfactant or the like.

The coloring agent of the present invention may be used alone or in combination of two or more. The content of the pigment is based on the total amount of the ink composition.
It is 0.5 to 30 wt%, preferably 5 to 20 wt%. The pigment content is 0.5 wt% based on the total weight of the ink composition.
%, The color density becomes low as a product, and if it exceeds 30 wt%, it becomes difficult to secure the stability of the ink. Further, a dye can be added if necessary, but it has a bad influence on bleeding, so that it is necessary to keep a small amount.

The dispersant used in the present invention is not particularly limited as long as it can disperse the pigment. Specific examples include synthetic resins such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl butyral, polyvinyl ether, styrene-maleic acid copolymer, ketone resin, hydroxyethyl cellulose and derivatives thereof, and styrene-acrylic acid copolymer. Particularly preferred is polyvinyl butyral, which is suitable as an oily dispersant. The content of the dispersant is 0.1 to 20 w with respect to the total amount of the ink composition.
t%, preferably 0.2 to 10 wt%. If the content of the dispersant is less than 0.1 wt%, the dispersion stability of the ink will be poor, and if it exceeds 20 wt%, the fluidity of the ink will be poor.

In addition, one or more resins can be added for the purpose of improving the adhesion to paper and adjusting the viscosity. The type and amount of resin used are appropriately used according to the purpose,
There is no particular limitation as long as the stability of the pigment ink is not impaired. In addition, as long as the stability of the pigment ink is not impaired, rust inhibitors, preservatives, fungicides, surfactants, lubricants, wetting agents, etc. can be added as necessary. If it does not impair the properties, it can also contain an auxiliary solvent in terms of product performance, and furthermore, as a drying suppression aid, a non-volatile solvent that is compatible with the main solvent within a range that does not adversely affect the product characteristics. Can be contained.

As the preservative or fungicide, for example,
Phenol, sodium omazine, sodium pentachlorophenol, 1,2-benzisothiazoline 3-one, 2,3,5,6-tetrachloro-4 (methylsulfonyl) pyridine, benzoic acid such as sodium benzoate, sorbitanic acid and dehydro Examples thereof include an alkali metal salt of acetic acid and a benzimidazole compound.

Examples of the rust preventive include benzotriazole, dicyclohexylammonium-nitrite,
Examples include diisopropylammonium nitrite and tolyltriazole. As lubricants and wetting agents,
For example, polyether-modified silicones such as polyethylene glycol adduct of dimethylpolysiloxane and the like can be mentioned. Further, other additives that are commonly used for writing instruments and the like can be pigmented within a range that does not adversely affect the effects of the pigment ink composition of the present invention.

The viscosity of the pigment ink composition of the present invention varies depending on the product to be used. For a writing instrument using a low-viscosity ink, the viscosity is 1 to 100 mPa.s. s, 100 to 3 for writing instruments that use other viscosity ranges
00,000 mPa. s (25 ° C., using an E-type viscometer). The same viscosity range can be used for desk products as long as the product performance can be exhibited.

For producing the pigment ink composition of the present invention, various conventionally known methods can be employed. For example,
Compounding each of the above components, using a stirrer such as a dissolver,
It can be easily obtained by mixing and stirring, or after mixing and grinding by a ball mill, a roll mill, a bead mill, a sand mill or the like, and then removing the coarse particles of the pigment, undissolved matter, and contaminated solid matter by centrifugation or filtration.

In the pigment ink composition of the present invention constituted as described above, the Newtonian viscosity (even when the shear rate is changed, the shear rate is reduced even if the shear rate is changed) is not required to reduce the fluidity by adding pseudoplasticity to the ink. It is possible to suppress bleeding in a state where the viscosity is not affected and the viscosity shows a constant value) or in a state close to this. As a simple method of measuring the Newtonian viscosity, a viscosity is measured at different rotational speeds (shear speeds) using a rotational viscometer, and when the ratio (TI value) is taken, naturally, if it is 1, a new viscosity is used. It's Tonian. In the technical field of the present invention, an ink having Newtonian viscosity has an advantage of being easy to use because of its good fluidity.

In addition, even when compared to ink using a solvent that dissolves a dispersant, the ink has an effect of clearly suppressing bleeding.
It is not clear why such an effect is exhibited, but it has been found that the larger the difference in solvent polarity between the groups A and B used, the greater the bleeding-suppressing effect. Although stable, the difference in solvent diffusion due to wetting on the transferred paper surface causes the solvent balance of the ink to collapse, causing the ink to become rapidly unstable and causing the solid content to rapidly agglomerate on the paper surface. It is presumed that the effect of suppressing bleeding is thereby exhibited.

In the pigment ink composition of the present invention thus constituted, three or more kinds of solvents which are not conventionally used are used as main solvents with respect to the conventional pigment ink used for writing implements and desk products. By having long-term storage stability, it is possible to suppress various phenomena such as sedimentation of pigment, separation of main solvent and dispersion, extreme increase in viscosity, increase in average particle size, etc. it can.

The pigment ink composition of the present invention has various properties such as sedimentation of the pigment, separation of the main solvent and the dispersion, extreme increase in viscosity, increase in average particle size, etc.
Undesired phenomena can be suppressed, so that writing instruments including stamp pens, ballpoint pens and the like, stamp tables, vermilion tables, desk products including penetrating marks using open-cell materials, and OA ribbons, ink jet printers, etc. It can be suitably used for office supply-related products, and in particular, because it can effectively exhibit long-term storage stability of pigments, it is suitable for pigment ink compositions for writing instruments and pigment ink compositions for inkjet printers. Can be used for

[0031]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples. The following "wt%" is% by mass. The pigment ink composition prepared in each of the following examples was filled in a vermilion stand container, and the following test contents were evaluated.

(1) Viscosity Measurement is carried out with an E-type viscometer under the following conditions. Temperature: 25 ° C., number of revolutions: 10 rpm, (2) rheological characteristics (TI value) E-type viscometer similar to the item (1), number of revolutions: 2.5 rpm
The viscosity is measured at m and 10 rpm, and pseudoplasticity is evaluated from the value obtained by the following calculation formula. TI value = Viscosity at 2.5 rpm / 10 Viscosity at 10 rpm When the TI value is close to 1, it is Newtonian, and as it increases from 1, the ink becomes pseudoplastic. (3) Bleeding property Printed on a commercial tracing paper, 25 ° C, humidity 6
After storage for one week under the condition of 0%, the degree of bleeding is visually evaluated according to the following criteria.・ Bleeding degree: (excellent) ◎>>□>△> × (poor)

Example 1 Solvent (Group A) Triethylene glycol 16.4 wt% (Group B) Polypropylene glycol 41.0 wt% (Uniol D-1000: manufactured by NOF Corporation) (Group C) Ethylene oxide / propylene oxide copolymerized diol ( Pronon 104: Nippon Yushi) 24.6 wt% Dispersant polyvinyl butyral 4.0 wt% (Eslec B BM-1: Sekisui Chemical) Pigment (Irgadine DPP Scarlet EK: Ciba-Geigy) 14.0 wt%

Example 2 Solvent (Group A) 8.2% by weight of triethylene glycol (Group B) 32.8% by weight of polypropylene glycol (Uniol D-1000: manufactured by NOF Corporation) (Group C) 41.0% by weight of polypropylene glycol (Uniol) D-700: Nippon Yushi) Dispersant Polyvinyl butyral 4.0 wt% (Eslek B BM-1: Sekisui Chemical) Pigment (Irgazine DPP Scarlet EK: Ciba-Geigy) 14.0 wt%

Example 3 Solvent (group A) polyethylene glycol (PEG # 400) 8.2 wt% (group B) polypropylene glycol 49.2 wt% (Uniol D-1000: manufactured by NOF Corporation) (group C) propylene glycol monolith Rate 24.6 wt% (PGMR: manufactured by Ito Oil) Dispersant polyvinyl butyral 4.0 wt% (Eslek B BM-1: manufactured by Sekisui Chemical) Pigment (Irgadine DPP Scarlet EK: manufactured by Ciba Geigy) 14.0 wt%

Example 4 Solvent (Group A) 8.2% by weight of tetraethylene glycol (Group B) 49.2% by weight of polypropylene glycol (Uniol D-1000: manufactured by NOF Corporation) (Group C) 24.6% of propylene glycol monolysylate % (PGMR: made by Ito Oil Co., Ltd.) Dispersant polyvinyl butyral 4 wt% (Eslec B BM-1: made by Sekisui Chemical) Pigment (Irgazine DPP Scarlet EK: made by Ciba Geigy) 14 wt%

Comparative Example 1 Solvent (good solvent) Polypropylene glycol 85 wt% (Uniol D-400: manufactured by NOF Corporation) Dispersant polyvinyl butyral 5 wt% (Eslek B BM-1: manufactured by Sekisui Chemical) Pigment (Irgazine DPP Scarlet EK: Ciba Geigy) 10 wt%

Comparative Example 2 Solvent (Good Solvent) Polypropylene Glycol 85.0 wt% (Uniol D-400: manufactured by NOF Corporation) Dispersant polyvinyl butyral 5.0 wt% (ESLEC B BM-1: manufactured by Sekisui Chemical) Pigment (Fujifast) Red # 1010: Fuji dye) 10.0 wt%

Comparative Example 3 Solvent (Good Solvent) Propylene Glycol Monolysylate 82.0 wt% (PGMR: manufactured by Ito Oil) Dispersant Polyvinyl Butyral 4.0 wt% (Eslek B BM-1: manufactured by Sekisui Chemical) Pigment (Irgazine DPP) (Scarlet EK: Ciba-Geigy) 14.0wt%

Comparative Example 4 Solvent (good solvent) polypropylene glycol 65.0 wt% (Uniol D-400: manufactured by NOF) (poor solvent) polyethylene glycol) 20.0 wt% (PEG # 200: manufactured by NOF) Dispersant polyvinyl Butyral 5.0 wt% (Eslek B BM-1: Sekisui Chemical) Pigment (Fuji Fast Red # 1010: Fuji dye) 10.0 wt%

Comparative Example 5 Solvent (Good Solvent) Polypropylene Glycol 45.0 wt% (Uniol D-400: Nippon Yushi) (Poor Solvent) Polypropylene Glycol 40.0 wt% (Uniol D-1000: Nippon Yushi) Dispersant Polyvinyl Butyral 5.0 wt% (Eslek B BM-1: Sekisui Chemical) Pigment (Irgazine DPP Scarlet EK: Ciba-Geigy) 10.0 wt%

Comparative Example 6 Solvent (Good Solvent) 85.0 wt% of Polypropylene Glycol (Uniol D-400: manufactured by NOF Corporation) Dispersant Polyvinyl butyral 3.0 wt% (ESREC B BM-1: manufactured by Sekisui Chemical) Pigment (Fujifast) Red # 1010: Fuji dye) 10.0 wt% Pseudoplasticity imparting agent (Aerosil # 380: Nippon Aerosil) 2.0 wt%

Comparative Example 7 Solvent (Group A) Triethylene glycol 20.0 wt% (Group B) Polypropylene glycol 62.0 wt% (Uniol D-1000: manufactured by NOF CORPORATION) Dispersant polyvinyl butyral 4.0 wt% (Eslec B BM -1: Sekisui Chemical Co., Ltd.) Pigment (Irgazine DPP Scarlet EK: Ciba Geigy) 14.0 wt%

Comparative Example 8 Solvent (Group A) 8.2% by weight of triethylene glycol (Group B) 73.8% by weight of polypropylene glycol (Uniol D-1000: manufactured by NOF Corporation) Dispersant Polyvinyl butyral 4.0% by weight (ESLEC B BM -1: Sekisui Chemical Co., Ltd.) Pigment (Irgazine DPP Scarlet EK: Ciba Geigy) 14.0 wt%

A pigment ink composition was obtained by dispersing the composition of Examples 1 to 4 and Comparative Examples 1 to 8 using a roll mill. However, in Comparative Examples 7 and 8, if only the solvent (Group A) and the solvent (Group B) were mixed and there was no solvent (Group C), gelation or coagulated sediment was generated, and the stability of the ink was poor. There was nothing at all, and "inking was impossible". Table 1 shows the results of measuring the viscosity, rheological properties (TI value), and bleeding property of each of the tests other than Comparative Examples 7 and 8 using the test contents described above. In addition, Table 1 shows the bleeding state of imprints obtained by filling each pigment ink composition into a vermilion container and stamping it with [Mitsubishi] three times using a commercially available seal.

[0046]

[Table 1]

As shown in Table 1, in Examples 1 to 4, there was almost no bleeding even in a state close to the Newtonian viscosity, whereas in Comparative Examples 1 to 5, it was equal to or more than the example. Even if the viscosity is high, bleeding is large. In Comparative Example 6, there was almost no bleeding, which is due to the pseudoplasticity of the ink. As described above, in Examples 1 to 4, there was almost no bleeding even in a state close to the Newtonian viscosity, whereas in Comparative Examples 1 to 6, bleeding was large, or finally, by giving pseudoplasticity. It can suppress bleeding, and is clearly inferior to the examples.

[0048]

According to the present invention, with respect to pigment inks used for desk products such as writing implements and seal products, pseudo-dispersing agents can be simulated by mixing three or more solvents of different polarities each having a poor solubility in a dispersant. Provided is a pigment ink composition which can suppress bleeding on paper with a viscosity close to Newtonian without imparting plasticity. In addition, it has long-term storage stability by suppressing undesired phenomena such as sedimentation of pigment, separation of main solvent and dispersion, and extreme increase in viscosity. It can be suitably used for desk-top products including a perfume stamp using a vermicelli, a continuous foam material, and office supply-related products such as OA ribbons and inkjet printers.

Continued on front page F-term (reference) 2C056 EA05 FC01 FC02 2H086 BA52 BA55 BA59 BA61 4J039 AD07 BC07 BC10 BC11 BC19 BC24 BE01 BE12 CA07 EA44 EA47 GA07 GA24 GA26 GA27 GA29

Claims (4)

[Claims] 1. A composition comprising at least a pigment and a dispersant, and
Each single component does not dissolve the dispersant and is not mixed with each other. At least three types of mixed solvents having different polarities that lead to dissolution of the dispersant as a homogeneous mixed solvent by adding the third component are used as the main solvent. A pigment ink composition characterized by containing as a pigment. 2. The pigment ink composition according to claim 1, wherein the three or more mixed solvents are selected from each of the following groups A, B, and C. Group A: a solvent in which the solubility of the dispersant is 0.5 wt% or less and which is more polar than the solvent group in the polar range in which the dispersant can be dissolved. A solvent having a polarity lower than that of a solvent group having a polar range in which the dispersant can be dissolved and which is not uniformly mixed with the solvent selected from the group A; a group C used; a mixture selected from the group A and the group B used; A solvent that becomes a uniform mixed solvent when added to a solvent. 3. The pigment ink composition according to claim 1, wherein the dispersant and the solvents of Group A, Group B and Group C are as follows. Dispersant: solvent of polyvinyl butyral group A; ・ ethylene glycol ・ polyethylene glycol having 2 to 15 ethylene oxides ・ propylene glycol ・ monoester or diester of triol solvent such as glycerin solvent of group B; ・ molecular weight exceeding 800 and 4000 Among the following polypropylene glycols / ethylene oxide propylene copolymerized diols, those having a butyral resin solubility of 0.5% by weight or less: Group C solvents; polypropylene glycol having a molecular weight of 200 or more and 800 or less; ethylene oxide / propylene oxide copolymerization Diols ・ Esters having hydroxyl group such as propylene glycol monolysate 4. The pigment ink composition according to claim 1, which has a Newtonian viscosity or a viscosity close thereto.