JP4722462B2 - Water-based pigment ink composition - Google Patents

Description

  The present invention relates to a water-based pigment ink composition, and specifically relates to a water-based pigment ink composition that can be suitably used for, for example, a writing instrument or ink jet printing.

  Aqueous pigment ink compositions are already used in writing instruments such as sign pens, ballpoint pens, and plotter pens, and inkjet printers in inkjet printing, but achromatic and chromatic colors compared to ink compositions that use dyes as colorants. In any case, color development on absorbent paper, especially white paper, that is, recorded matter on absorbent white paper by the ink composition, that is, by handwriting or ink jet printing when writing with a writing instrument There was a problem that the obtained inkjet image was inferior in color density.

  In the aqueous pigment ink composition for writing instruments, in addition to the dispersion stability of the pigment, for example, the property of maintaining excellent writing properties even when a writing instrument such as a sign pen is left for a long period of time, that is, storage Satisfies the function as a writing instrument such as stability and the ability to maintain excellent writing properties even after leaving the cap removed from the writing instrument such as a sign pen for a long period of time. It was an important issue. Moreover, also in the ink composition for inkjet printers, the dispersion stability of the pigment in the ink composition has been an important issue. Therefore, the color density of an image obtained by inkjet printing on an absorptive surface, such as ordinary paper, with respect to an aqueous pigment ink composition for a writing instrument and an aqueous pigment ink composition used for an inkjet printer. Has not been fully considered.

  In more detail, the water-based pigment ink for writing instruments is absorbed by the paper when written on ordinary absorbent paper, so that it is difficult to obtain a handwriting having the original concentration of the ink. When written on paper, the handwriting is grayish because of the above properties. In order to cope with such a problem, in Japanese Patent No. 3108541 (Patent Document 1), in a water-based ink composition, a certain resin emulsion and a saccharide are used in combination, whereby coloration due to a difference in paper quality is caused. It is proposed to eliminate the density difference. However, when a resin emulsion and a saccharide are used together in this way, an undesirable effect is exerted on the dispersion stability of the pigment, and as a result, for example, such an ink composition is used for a sign pen and the pen tip is placed downward. If writing is performed after being left for a long time in the state of being directed, there is a problem in that handwriting tends to be drawn and, therefore, the storage stability is poor.

  Similarly, in an aqueous pigment ink composition for an ink jet printer, in order to obtain dispersion stability of the pigment, for example, JP 2000-212486 (Patent Document 2) and International Publication WO 99/05230 (Patent Document 3). ), A certain water-soluble resin is used as a dispersant, and a pigment is dispersed in water to prepare an aqueous pigment dispersion, which is used for the production of an ink composition. In such an aqueous pigment ink composition for an ink jet printer, although the dispersion stability of the pigment is improved, an image obtained by using the black ink composition for ink jet printing on a white recording paper is obtained. Is greyish as well. In addition, even when a chromatic ink composition is used for ink jet printing on white recording paper, the obtained image is inferior in color density and exhibits a dull color. In order to cope with such problems, it may be one measure to increase the concentration of the pigment in the ink composition. However, when the concentration of the pigment is increased, the dispersion stability of the pigment in the ink composition is increased. In addition to the risk of damage, there is a problem of clogging in the nozzles for ink ejection of the ink jet printer.

Japanese Patent No. 3108541 JP 2000-212486 A International Publication No. WO99 / 05230

  The present invention has been made to solve the above-mentioned problems in conventional aqueous pigment ink compositions, and is sufficiently high when written on an absorbent surface such as ordinary paper or inkjet printed. A water-based pigment ink composition which gives a recorded matter having a color density, that is, a handwriting or an inkjet image, and has excellent storage stability when incorporated in a writing instrument or an inkjet printer, together with the dispersion stability of the pigment in the ink composition. The purpose is to provide.

  According to the present invention, the O / W of at least one water-insoluble resin selected from the group consisting of water, a pigment, a water-soluble resin, a surfactant composed of a phosphate ester, and an acrylic resin, a styrene resin, and a styrene-acrylic resin. A water-based pigment ink composition comprising a type emulsion, wherein the water-insoluble resin particles in the emulsion have an average particle diameter in the range of 50 to 200 nm, and the emulsion has a minimum film-forming temperature of 50 ° C. or higher. Provided.

  Such an aqueous pigment ink composition according to the present invention has excellent pigment dispersion stability and storage stability when incorporated in a writing instrument or an ink jet printer, and when used in a writing instrument, the ink composition In order not to damage the writing property by drying with the pen tip of the writing instrument, and when used in an ink jet printer, it is further dried so as not to precipitate the pigment by the nozzle tip of the printer. The polyhydric alcohol is preferably contained in the range of 5 to 25% by weight. In particular, according to the present invention, the polyhydric alcohol contains at least one selected from the group consisting of dihydric alcohols and trihydric alcohols, particularly at least one selected from the group consisting of glycerin and diethylene glycol. It is preferable.

  In addition, the aqueous pigment ink composition according to the present invention is further improved so that the writing instrument filled therewith has excellent cap-off properties, and an ink jet printer using the same also prevents urea from drying at the nozzle. Or it is preferable to contain the derivative | guide_body in the range of 2 to 20 weight%.

  Such a water-based pigment ink composition according to the present invention is excellent in coloration on an absorptive surface such as normal paper, whether it is black, chromatic, or highly concentrated handwriting or inkjet. It gives an image and is excellent in dispersion stability of the pigment and storage stability in use.

  The aqueous pigment ink composition according to the present invention is at least selected from the group consisting of water, a pigment, a water-soluble resin, a surfactant composed of a phosphate ester, a (meth) acrylic resin, a styrene resin, and a styrene- (meth) acrylic resin. It contains an O / W type emulsion of one kind of water-insoluble resin, the resin particles in this emulsion have an average particle size in the range of 50 to 200 nm, and this emulsion has a minimum film-forming temperature of 50 ° C. or higher. is there.

  The pigment used in the present invention includes various organic pigments and inorganic pigments, and is not particularly limited. Examples of the organic pigment include monoazo pigments derived from β-naphthol derivatives and the like, β-oxynaphthoic acid, and the like. Water-insoluble azo pigment, disazo pigment, condensed azo pigment, phthalocyanine pigment, quinacridone pigment, dioxazine pigment, perylene pigment, perinone pigment, thioindigo pigment, isoindoline pigment, isoindolinone pigment, anthraquinone pigment And diketopyrrolopyrrole pigments, quinophthalone pigments, indanthrene pigments, lake pigments obtained by lake-forming basic dyes such as triarylmethane dyes, and metal complex pigments.

  Specific examples of such organic pigments include, for example, Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 42, Pigment Yellow 74, Pigment Yellow 83, Pigment Yellow 106, Pigment Yellow 117, Pigment Yellow Yellow 126, Pigment Yellow 183, Pigment Orange 5, Pigment Orange 16, Pigment Red 3, Pigment Red 48: 1, Pigment Red 48: 4, Pigment Red 101, Pigment Red 112, Pigment Red 122, Pigment Red 267, Pigment Violet 23, Pigment Violet 27, Pigment Blue 1, Pigment Blue 15: 1, Pigment Blue 15: 3, Pigment Bu Over 61, Pigment Green 7, mention may be made of Pigment Green 36, and the like.

  Representative examples of inorganic pigments include, for example, iron oxide, ferricyanide, sulfur-containing sodium aluminum silicate, titanium dioxide, carbon black and the like. Specific examples of such inorganic pigments include, for example, Pigment Yellow 42, Pigment White 6, Pigment Blue 27, Pigment Blue 29, Pigment Black 7, and the like.

  In the present invention, the average particle size of the organic and inorganic pigments is usually in the range of 50 to 200 nm, preferably in the range of 60 to 150 nm, and particularly preferably in the range of 70 to 120 nm. When the pigment has an average particle diameter in such a range, the pigment can be stably dispersed in the solvent without impairing the storage stability. Here, in order to disperse the pigment in the solvent, an appropriate means may be used. For example, a conventionally known general means such as a bead mill or a roll mill may be used. In addition, after dispersing the pigment in the solvent using such a dispersing means, coarse particles are removed from the dispersion by a method such as centrifugation or filter filtration, so that the pen tip of the writing instrument or the inkjet It is possible to prevent clogging at the nozzles of the printer head. However, the coarse particles mixed in the pigment may be performed after the preparation of the ink composition. In the present invention, the above-described pigments may be used alone or in combination of two or more.

  The aqueous pigment ink composition according to the present invention usually contains the above-described pigment in the range of 0.2 to 15% by weight, and preferably in the range of 0.5 to 12% by weight. In particular, according to the present invention, in the case of an ink composition for a writing instrument, the aqueous pigment ink composition comprises 1 to 15% by weight of the pigment described above, preferably 3 to 12% by weight, most preferably In the case of an ink composition for an ink jet printer, it is contained in a range of 0.2 to 10% by weight, preferably in a range of 0.5 to 9% by weight. Contained.

   In general, when the content of the pigment in the aqueous pigment ink composition is less than 0.2% by weight, the density of the handwriting or the ink jet image is small and lacks practicality. On the other hand, when it exceeds 15% by weight, the storage stability of the ink composition tends to deteriorate, and in an extreme case, the viscosity of the ink composition increases with time, the fluidity decreases, and the writing instrument. When used in the printer, it does not flow out of the pen tip, and when used in an ink jet printer, it may not fly from the nozzle to the recording paper.

  However, according to the present invention, in particular, when an aqueous pigment ink composition for a writing instrument that gives handwriting with a pastel color tone without using a white inorganic pigment or white resin particles is obtained, the aqueous pigment ink composition Contains 0.5 to 7% by weight, preferably 1 to 5% by weight of the pigment. When the amount is less than 0.5% by weight, the handwriting becomes thin. On the other hand, when the amount exceeds 7% by weight, a pastel color cannot be obtained.

On the other hand, according to the present invention, when carbon black is used as a pigment in an aqueous pigment ink composition for an ink jet printer, an aqueous pigment ink composition for an ink jet printer having a high black density can be obtained. It is preferably 150 m ² / g or more.

The water-based pigment ink composition according to the present invention contains a water-soluble resin, and the water-soluble resin has a role as a dispersant for the pigment in the ink composition, and is also used on a paper handwriting or a recording paper having an absorbent surface. It also serves as a binder for attaching the inkjet image to such an absorbent surface. According to the present invention, for example, an unsaturated carboxylic acid copolymer resin is preferably used as the water-soluble resin. Specific examples of such unsaturated carboxylic acid copolymer resins, for example, styrene - (meth) acrylic acid copolymer, (meth) acrylic acid - (meth) acrylic acid ester copolymer, styrene - ( Mention may be made of (meth) acrylic acid- (meth) acrylic acid ester copolymers, styrene-α-methylstyrene- (meth) acrylic acid copolymers, styrene-maleic acid copolymers, and the like. Here, (meth) acrylic acid means acrylic acid or methacrylic acid. In the present invention, these water-soluble resins may be used alone or in combination of two or more.

  In the present invention, such a water-soluble resin usually has a weight average molecular weight of about 3000 to 30000, preferably about 5000 to 15000. When the weight average molecular weight of the water-soluble resin is too large, the resulting aqueous pigment ink composition has a high viscosity, which is not suitable for use as an ink composition for writing instruments and inkjet printers, and on the other hand, when it is too small Since the effect as a pigment dispersant is poor, the resulting ink composition is poor in pigment dispersion stability.

  The water-based pigment ink composition according to the present invention generally contains such a water-soluble resin in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight, depending on the kind and amount of the pigment described above. Contains in a range. When the content of the water-soluble resin in the aqueous pigment ink composition is less than 0.5% by weight, the dispersion stability of the pigment in the ink composition is deteriorated, and the pigment tends to aggregate. On the other hand, when the content of the water-soluble resin in the water-based pigment ink composition is more than 10% by weight, the dispersion stability of the pigment in the ink composition is deteriorated, and the viscosity of the ink composition becomes too high. Since the properties are reduced, it is not suitable for writing instruments and inkjet printers.

  The water-based pigment ink composition according to the present invention is not particularly limited in its production method, but the water-soluble resin is usually dissolved in water in advance and mixed with other components as an aqueous solution. Are preferably used. In this case, when the water-soluble resin described above is dissolved in water, for example, the unsaturated carboxylic acid copolymer resin with a basic substance such as dimethylethanolamine, triethanolamine, morpholine, aqueous ammonia, or sodium hydroxide. It is better to neutralize. The amount of the basic substance used may be optimally determined according to the acid value of the water-soluble resin to be used, and it is generally good that the resin is neutralized using an equivalent amount. The alkaline substance to be used may be appropriately selected according to required properties such as the handwriting and the drying speed of the inkjet image. Further, when the water-soluble resin is dissolved in water, diethylene glycol, isopropanol, ethylene glycol monobutyl ether or the like may be used as a dissolution aid.

  The water-based pigment ink composition according to the present invention has, as one important feature, an O / W of at least one water-insoluble resin selected from the group consisting of (meth) acrylic resins, styrene resins, and styrene- (meth) acrylic resins. Contains type emulsion. Examples of the (meth) acrylic resin include, for example, homopolymers or copolymers of (meth) acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and the like. Can do. Therefore, examples of the styrene- (meth) acrylic resin include a copolymer of the (meth) acrylic acid ester and styrene. Examples of the styrene resin include a styrene and α-methylstyrene homopolymer or copolymer, a copolymer of styrene and butadiene (SBR), a copolymer of styrene and acrylonitrile (AS resin), and styrene. Examples thereof include a copolymer of acrylonitrile and butadiene (ABS resin). Here, (meth) acrylic resin means acrylic resin or methacrylic resin, and (meth) acrylic acid means acrylic acid or methacrylic acid as described above.

  According to the present invention, the emulsion has an average particle diameter of the resin particles contained in the range of 50 to 200 nm and a minimum film-forming temperature of 50 ° C. or more. The average particle diameter of the resin particles is in the range of 50 to 150 nm, and the minimum film forming temperature is preferably 60 ° C. or higher. The solid content concentration of the emulsion to be used is not particularly limited, but is usually in the range of 20 to 60% by weight, and preferably in the range of 30 to 50% by weight.

  When the average particle diameter of the resin particles contained in the emulsion is smaller than 50 nm, it is difficult for the resulting ink composition to form a high-concentration handwriting or inkjet image on the absorbent surface. On the other hand, when the average particle diameter of the resin particles contained in the emulsion is larger than 200 nm, the resin particles easily settle in the ink composition. For example, an aqueous pigment ink composition prepared using such an emulsion is used as a sign pen. In particular, when a writing instrument such as the above is filled, the ink composition is clogged at the nib and the handwriting is liable to be drowned, especially when the pen nib is left facing down for a long time. When used in the printer, clogging tends to occur at the nozzles of the printer. In addition, when the minimum film-forming temperature of the emulsion is lower than 50 ° C., when used for a writing instrument, for example, when the pen tip is dried, writing may be impossible. Ink jet printing may become impossible when the temperature of the printer becomes high. Moreover, although the upper limit of the minimum film forming temperature of an emulsion is not specifically limited, Usually, it is about 300 degreeC.

  According to the present invention, the aqueous pigment ink composition contains such an emulsion in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight in terms of solid content (resin content). . In the water-based pigment ink composition, when the content of the emulsion exceeds 10% by weight in terms of solid content, the obtained water-based ink composition is reduced in storage stability, and on the other hand, 0.5% by weight When the amount is less than that, a handwriting or an ink jet image having a high color density is not formed on the absorbent surface.

Furthermore, the water-based pigment ink composition according to the present invention has an important feature in that it contains a surfactant composed of a phosphate ester as another important feature. In the present invention, the surfactant comprising such a phosphate ester is preferably represented by the general formula (I)

Where X is a hydrogen atom or general formula (II)

R is an alkyl group having 8 to 30 carbon atoms or an alkylphenyl group having such an alkyl group, and n is a number in the range of 0 to 15 on average. . At least one of X is the monovalent group. That is, the surfactant comprising a phosphate ester that can be preferably used in the present invention is at least one phosphate ester selected from the group consisting of mono-, di-, and triesters represented by the above general formula.

  Accordingly, specific examples of surfactants comprising phosphate esters that can be preferably used in the present invention include, for example, phosphate esters of polyoxyethylene alkyl ether and phosphate esters of polyoxyethylene alkyl phenyl ether. Can do. As described above, these phosphate esters are at least one selected from the group consisting of mono-, di-, and triesters.

  In the present invention, the reason for this is not clear by using a surfactant comprising such a phosphate ester, but without impairing the dispersion stability of the pigment and the O / W emulsion, and on the absorbent surface. Improve the storage stability of the resulting ink composition in the use of writing instruments and inkjet printers without adversely affecting the color density of the handwriting or inkjet image, and without adversely affecting the water resistance of the handwriting or inkjet image be able to. When using a surfactant other than the above-mentioned surfactants composed of phosphate esters, the resulting ink composition is not improved in storage stability, while the ink surface tension tends to increase significantly. In the handwriting or ink jet image on the absorbent surface, the effect of using the above-mentioned emulsion is not sufficiently exhibited, the color density may be lowered, the water resistance is also lowered, and the handwriting or the ink jet image is blurred. It tends to occur.

  The water-based pigment ink composition according to the present invention has excellent dispersion stability of the pigment, and when used in a writing instrument, the ink composition does not dry with the nib and is used in an ink jet printer. Furthermore, it is preferable to further contain a polyhydric alcohol in the range of 5 to 25% by weight as the first humectant so as not to dry with the nozzle, in particular in the range of 5 to 20% by weight. It is preferable to contain. According to the present invention, it is preferable that the polyhydric alcohol contains at least one polyhydric alcohol selected from the group consisting of dihydric alcohols and trihydric alcohols.

  Examples of the dihydric alcohol include ethylene glycol, propylene glycol, and diethylene glycol. Examples of the trihydric or higher alcohol include glycerin and sorbitol. These polyhydric alcohols may be used alone or in combination of two or more. When the content of the polyhydric alcohol in the water-based pigment ink composition is less than 5% by weight, although depending on the form of the writing instrument, the nib tends to dry, particularly under high temperature environmental conditions. Even under such conditions, drowning is likely to occur. Even when used in an ink jet printer, the ink composition tends to dry at the nozzles of the printer, particularly under high-temperature environmental conditions, thereby hindering smooth ink jet printing. On the contrary, when the content of the polyhydric alcohol in the aqueous pigment ink composition exceeds 25% by weight, the drying speed of the handwriting or the ink jet image is slow, which is not preferable from the viewpoint of practicality.

  In particular, according to the present invention, as the polyhydric alcohol, at least one selected from the group consisting of diethylene glycol and glycerin is blended in the range of 5 to 15% by weight, thereby lowering the pen tip of a writing instrument such as a sign. It is possible to improve the storage stability in the state of being directed to. In the aqueous pigment ink composition, when the amount of at least one selected from the group consisting of diethylene glycol and glycerin is less than 5% by weight, the above effect is poor, and when it exceeds 15% by weight, the drying speed of the handwriting is low. May be significantly slower.

  In particular, the aqueous pigment ink composition according to the present invention contains 2 to 20% by weight of urea or a derivative thereof as a second humectant in order to better prevent drying of the nib when left in a cap-off state. It is preferable to contain in the range, especially 5 to 15 weight%. Examples of urea derivatives include ethylene urea, propylene urea, thiourea, and the like. Urea and its derivatives may be used alone or in combination of two or more. In particular, according to the present invention, in combination with the aforementioned O / W emulsion or the first humectant, drying at the pen tip when left in a state where the cap of a writing instrument such as a sign pen is removed, Moreover, it has the high effect which prevents the drying with the nozzle of an inkjet printer.

  When the amount of urea and its derivative in the aqueous pigment ink composition is less than 2% by weight, the above effect as a humectant cannot be obtained sufficiently. On the other hand, when it exceeds 20% by weight, there is a drawback that the drying speed of the handwriting and the inkjet image becomes slow, and when the writing instrument is left with the cap removed, crystals are deposited on the pen tip. There is also a possibility that crystals are deposited at the nozzle of the printer. In particular, according to the present invention, drying of the ink composition can be more effectively prevented by using the first and second humectants in combination as a humectant.

  In the aqueous pigment ink composition of the present invention, the balance other than the above-mentioned components is made of water, and therefore the amount of water may be adjusted so that the above-mentioned components are contained in the above-described proportions. However, the water-based pigment ink composition according to the present invention, as long as it does not impair the above-described characteristics of the water-based pigment ink composition of the present invention, if necessary, components other than the above-described components, such as preservatives and antifungal agents. Further, it may contain a pH adjuster, a rust inhibitor, a surfactant and the like.

EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.
≪Example of ink composition for writing instruments≫
The color density of each of the aqueous pigment ink compositions obtained in the following Examples and Comparative Examples, the storage stability and the cap-off property when using a writing instrument filled with the ink composition were examined as follows.

(Color density of handwriting)
A water-based pigment ink composition is filled into a sign pen (writing line width: 0.6 mm), which is a kind of writing instrument provided with an ink storage body composed of fiber bundle chips, and white PPC (plain paper copier) is used therewith. Written on a sheet of paper, ie, a normal copy sheet, the black aqueous ink composition was defined as “good” when the handwriting was dark black and “bad” when it was a grayish color. In addition, regarding the chromatic water-based ink composition, when the handwriting had a high density and was vivid, it was judged as “good”, and when it was dull, it was judged as “bad”.

(Storage stability of ink composition)
The sign pen filled with the ink composition was set up vertically so that the pen tip faced downward, left at a temperature of 50 ° C. for 1 month, and then 10 circles having a diameter of 15 mm were drawn continuously. “5” indicates that writing was successful while drawing the first circle, and “4” was writing when writing correctly while drawing the second circle. “3” when writing normally until or while drawing a circle, “2” when writing normally until or while drawing the 10th circle, 10 “1” was given when the handwriting was drowning while drawing the eye circle.

(Cap-off property)
After removing the cap from the sign pen filled with the ink composition and leaving it for 5 hours under an environmental condition of a temperature of 20 ° C. and a relative humidity of 65%, 10 circles having a diameter of 15 mm were drawn continuously. “5” indicates that writing was successful while drawing the first circle, and “4” was writing when writing correctly while drawing the second circle. “3” when writing normally until or while drawing a circle, “2” when writing normally until or while drawing the 10th circle, 10 “1” was given when drowning occurred while drawing the eye circle.

Moreover, the aqueous pigment dispersion used in the following Examples and Comparative Examples was prepared as follows.
Aqueous black pigment dispersion A
An aqueous resin solution was prepared by mixing and stirring 20% by weight of a water-soluble resin (manufactured by Johnson Polymer, Jonkrill 683), 2% by weight of sodium hydroxide and 78% by weight of ion-exchanged water. 25% by weight of this resin aqueous solution, 25% by weight of carbon black (Cabot Monarch 800), 20% by weight of ethylene glycol, and 30% by weight of ion-exchanged water are stirred and mixed, and dispersed using a bead mill to disperse an aqueous black pigment. Body A was obtained.

・ Aqueous pink pigment dispersion B
20% by weight of water-soluble resin (Johnson polymer styrene-acrylic acid resin, acid value 160, molecular weight 8000, Joncryl 683), 2% by weight of sodium hydroxide and 78% by weight of ion-exchanged water are mixed and stirred under heating. An aqueous resin solution was prepared. 25% by weight of this resin aqueous solution, 25% by weight of quinacridone pigment (Chromophthal Pink PT manufactured by Ciba Specialty Chemicals), 20% by weight of ethylene glycol and 30% by weight of ion-exchanged water are mixed and dispersed using a bead mill. An aqueous black pigment dispersion B was obtained.

Example 1
Aqueous black pigment dispersion A 36% by weight, acrylic resin emulsion (Nicarbazole A-19 manufactured by Nippon Carbide Corporation, minimum film forming temperature 75 ° C., solid content 46% by weight, average particle size 99 nm) 6% by weight, phosphate ester interface Activator (Phosphanol PE-510, manufactured by Toho Chemical Co., Ltd., polyoxyethylene alkylphenyl ether monophosphate ester, diphosphate ester and trace amount of triphosphate ester) 0.6% by weight, glycerin 10% by weight, urea 15 % By weight, ion-exchanged water 32.2% by weight, antifungal agent (Coatside H manufactured by Takeda Pharmaceutical Co., Ltd.) 0.1% by weight, antiseptic (Avicia Co., Ltd. Proxel XL-2) 0.1% by weight %, And after stirring and mixing, coarse particles were removed by centrifugation to obtain an aqueous black pigment ink composition.
The color density of the handwriting by this ink composition was “good”, and the storage stability and cap-off property during use were both “5”.

Example 2
36% by weight of aqueous black pigment dispersion A, 6% by weight of styrene-acrylic resin emulsion (Polysol AP-6730, Showa Polymer Co., Ltd., minimum film forming temperature 78 ° C., solid content 45% by weight, average particle size 108 nm), phosphorus Acid ester surfactant (Phosphanol PE-510 manufactured by Toho Chemical Co., Ltd.) 0.8% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 32.0% by weight, antifungal agent (Takeda Pharmaceutical Co., Ltd. ( Coat side H) 0.1% by weight and preservative (Avicia Proxel XL-2) 0.1% by weight were added, stirred and mixed, then centrifuged to remove coarse particles. An aqueous black pigment ink composition was obtained. The color density of the handwriting by this ink composition was “good”, and the storage stability and cap-off property during use were both “5”.

Example 3
Aqueous black pigment dispersion A 36% by weight, acrylic resin emulsion (Clariant polymer mobile 790, minimum film forming temperature 220 ° C., solid content 40% by weight, average particle size 83 nm) 7% by weight, phosphate ester surfactant (Toho Chemical) Phosphanol PE-510 manufactured by Co., Ltd. 1.0% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 30.8% by weight, antifungal agent (Takeda Pharmaceutical Co., Ltd., Coatside H) Add 0.1 wt% and preservative (Avicia Co., Proxel XL-2) 0.1 wt%, stir and mix, then centrifuge to remove coarse particles, water black pigment ink composition I got a thing. The color density of the handwriting by this ink composition was “good”, and the storage stability and cap-off property during use were both “5”.

Example 4
Aqueous pink pigment dispersion B 32% by weight, acrylic resin emulsion (Nicarbazole A-19 manufactured by Nippon Carbide Corporation, minimum film forming temperature 75 ° C., solid content 46% by weight, average particle size 99 nm) 6% by weight, phosphate ester interface Activator (Toho Chemical Co., Ltd., Phosphanol PE-510) 0.6% by weight, glycerin 10% by weight, urea 10% by weight, ion-exchanged water 41.2% by weight, antifungal agent (Takeda Pharmaceutical Co., Ltd.) Coatside H) 0.1% by weight and preservative (Avicia Co., Proxel XL-2) 0.1% by weight were added, stirred and mixed, then centrifuged to remove coarse particles. An aqueous pink pigment ink composition was obtained. The saturation of the handwriting by this ink composition was “good”, and the storage stability and cap-off property during use were both “5”.

Example 5
In Example 3, an aqueous black pigment ink composition was obtained in the same manner except that ethylene glycol was used instead of glycerin. The color density of the handwriting by this ink composition was “good”, and the storage stability and cap-off property during use were both “4”.

Example 6
An aqueous black pigment ink composition was obtained in the same manner as in Example 3, except that urea was replaced with ion-exchanged water. The color density of the handwriting by this ink composition was “good”, the storage stability during use was “4”, and the cap-off property was “1”.

Comparative Example 1
Aqueous Pigment Dispersion A 44% by weight, phosphate ester surfactant (manufactured by Toho Chemical Co., Ltd., Phosphanol PE-510) 0.6% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 30.2% by weight %, 0.1% by weight of an antifungal agent (Takeda Pharmaceutical Co., Ltd., Coatside H) and 0.1% by weight of an antiseptic (Avicia Co., Ltd., Proxel XL-2) were added, mixed and stirred. Thereafter, the mixture was centrifuged to remove coarse particles to obtain an aqueous pigment ink composition. The color density of the handwriting by this ink composition was “poor”, the storage stability during use was “1”, and the cap-off property was “5”.

Comparative Example 2
Aqueous black pigment dispersion A 36% by weight, styrene-acrylic resin emulsion (Nicarbazole RX-3006E manufactured by Nippon Carbide Co., Ltd., minimum film forming temperature 70 ° C., solid content 39% by weight, average particle size 210 nm) 8% by weight, phosphoric acid Ester surfactant (Phosphanol PE-510 manufactured by Toho Chemical Co., Ltd.) 0.6% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 30.2% by weight, antifungal agent (Takeda Pharmaceutical Co., Ltd.) ) Coatside H) 0.1 wt% and preservative (Avicia Proxel XL-2) 0.1 wt% were added, stirred and mixed, then centrifuged to remove coarse particles, A black pigment ink composition was obtained. The color density of the handwriting by this ink composition was “good”, the storage stability during use was “2”, and the cap-off property was “5”.

Comparative Example 3
In Example 3, an aqueous black pigment ink composition was obtained in the same manner except that dioctylsulfosuccinic acid (Sanmoline OT-70 manufactured by Sanyo Chemical Industries, Ltd.) was used instead of the phosphate ester surfactant. . The color density of the handwriting by this ink composition was “good”, the storage stability during use was “2”, and the cap-off property was “5”.

Comparative Example 4
Aqueous pink pigment dispersion B 40% by weight, phosphate ester surfactant (Phosphanol PE-510 manufactured by Toho Chemical Co., Ltd.) 0.6% by weight, glycerin 10% by weight, urea 10% by weight, ion-exchanged water 39.2% by weight %, 0.1% by weight of antifungal agent (Takeda Pharmaceutical Co., Ltd. Coatside H) and 0.1% by weight of antiseptic (Avicia Proxel XL-2), and after stirring and mixing, Centrifugation was performed to remove coarse particles to obtain an aqueous pink pigment ink composition. The color density of the handwriting by this ink composition was “good”, the storage stability during use was “3”, and the cap-off property was “5”.

  The water-based pigment ink composition according to the present invention contains an O / W emulsion and a surfactant composed of a phosphate ester. When used in a writing instrument, the water-based pigment ink composition provides handwriting with a high color density and excellent storage stability. ing. Furthermore, according to the present invention, an aqueous pigment ink composition having excellent cap-off properties can be obtained by using a polyhydric alcohol or urea or a derivative thereof.

  The aqueous pigment ink composition according to the present invention is suitable, for example, as an aqueous pigment ink composition for writing instruments such as marking pens and ballpoint pens having fiber bundles as ink reservoirs, recorders, printing, stamps, etc. Can be used.

≪Examples of ink compositions for inkjet printers≫
Each ink composition obtained in the following examples and comparative examples was applied on white paper using an applicator to prepare a test sample, and a color difference meter CR-241 manufactured by Minolta Co., Ltd. was used. The color density, ie L * value, was measured. According to this test, the smaller the L * value, the higher the color density, while the larger the L * value, the lower the color density. As another test, the color density was visually evaluated. When the color was dark, it was set as “good”, when the color was a little light, “somewhat bad”, and when the color was light, it was set as “bad”. Furthermore, as an evaluation of color developability, as an ink jet recording paper, art paper (non-absorbent surface) and plain paper (absorbent surface) were ink jet printed, and the obtained ink jet images were compared with each other, and the above recording paper It was examined visually whether there was a difference in color density. When there is no difference in the color density of the inkjet image between the above art paper and plain paper, “No difference” is indicated, and when the color density is slightly inferior on plain paper, “Slight difference” is indicated. When the density was inferior, it was considered “difference”.

Resin aqueous solutions and aqueous pigment dispersions used in the following Examples and Comparative Examples were prepared as follows.
Preparation of aqueous resin solution While stirring 76.5 parts by weight of ion-exchanged water, 20.0 parts by weight of a water-soluble resin (John Crill 683 manufactured by Johnson Polymer) was added thereto, and then 3% by weight of ammonia water having a concentration of 28% by weight. 5 parts by weight were added. Next, the mixture was heated to around 60 ° C. to dissolve the resin, and then cooled to room temperature with stirring to obtain an aqueous resin solution.

-Preparation of aqueous black pigment dispersion C 25.0 parts by weight of the above aqueous resin solution, 25.0 parts by weight of black pigment (carbon black, Monarch 800 manufactured by Cabot Corporation), 20.0 parts by weight of ethylene glycol, and 30.0 parts of ion-exchanged water. A part by weight was stirred and mixed, defoamed, and then dispersed using a bead mill to obtain an aqueous black pigment dispersion C.

-Preparation of aqueous blue pigment dispersion D 25.0 parts by weight of the aqueous resin solution, 25.0 parts by weight of blue pigment (Fastgen Blue TGR manufactured by Dainippon Ink & Chemicals, Inc.), 20.0 parts by weight of ethylene glycol and ions Aqueous blue pigment dispersion D was obtained by stirring and mixing 30.0 parts by weight of the exchanged water, defoaming, and then dispersing using a bead mill.

-Preparation of aqueous red pigment dispersion E 25.0 parts by weight of the resin aqueous solution and 25.0 parts by weight of red pigment (Fastgen Super Magenta RG manufactured by Dainippon Ink & Chemicals, Inc.), 20.0 parts by weight of ethylene glycol, and Aqueous red pigment dispersion E was obtained by stirring and mixing 30.0 parts by weight of ion-exchanged water, defoaming, and then dispersing using a bead mill.

-Preparation of aqueous yellow pigment dispersion F 25.0 parts by weight of the resin liquid, 25.0 parts by weight of yellow pigment (Pigment Yellow IRC manufactured by Sanyo Dyeing Co., Ltd.), 20.0 parts by weight of ethylene glycol, and 30. After stirring 0 parts by weight, the mixture was defoamed and then dispersed using a bead mill to obtain an aqueous yellow pigment dispersion F.

Example 7
36% by weight of aqueous black pigment dispersion C, acrylic resin emulsion (Clariant polymer mobile 790, minimum film forming temperature 220 ° C., solid content 40% by weight, average particle size 83 nm) 6% by weight, phosphate ester surfactant (Toho Chemical) Phosphanol PE-510 manufactured by Co., Ltd. 0.6% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 32.2% by weight, antifungal agent (Takeda Pharmaceutical Co., Ltd. Coatside H) 0 0.1% by weight and 0.1% by weight of a preservative (Proxel XL-2 manufactured by Avicia Co., Ltd.) were added, stirred and mixed, and then coarse particles were removed by centrifugation to obtain an aqueous black pigment ink. The color density of this ink composition was 29.0 in terms of L * value, the color density visually was “good”, and the coloration was “no difference”.

Example 8
In Example 7, instead of the acrylic resin emulsion (Clariant Polymer mobile 790, minimum film-forming temperature 220 ° C., solid content 40% by weight, average particle size 83 nm), the acrylic resin emulsion (Nicarbazole A-manufactured by Nippon Carbide Corporation) was used. 19, an aqueous black pigment ink was obtained in the same manner except that 6 wt% (solid content 46 wt%, average particle size 99 nm) was used. The color density of this ink composition was 28.0 in terms of L * value, the visual color density was “good”, and the coloration was “no difference”. In addition, the possibility of clogging of the printer head was “small”.

Example 9
An aqueous pigment ink was obtained in the same manner as in Example 7 except that the aqueous blue pigment dispersion D was used in place of the aqueous black pigment dispersion C. The color density of this ink composition was 53.0 in terms of L * value, the color density by visual observation was “good”, and the color developability was “no difference”.

Example 10
An aqueous pigment ink was obtained in the same manner as in Example 7, except that the aqueous red pigment dispersion E was used instead of the aqueous black pigment dispersion C. The color density of this ink composition was 56.0 as an L * value, the color density visually was “good”, and the coloration was “no difference”.

Example 11
An aqueous pigment ink was obtained in the same manner as in Example 7, except that the aqueous yellow pigment dispersion F was used in place of the aqueous black pigment dispersion C. The color density of this ink composition was 85.0 in terms of L * value, the color density visually was “good”, and the coloration was “no difference”.

Comparative Example 5
Aqueous black pigment dispersion C 44% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 30.2% by weight, antifungal agent (Coatside H, Takeda Pharmaceutical Co., Ltd.) 0.1% by weight, antiseptic 0.1 wt% of an agent (Avicia Co., Ltd. Proxel XL-2) was added, stirred and mixed, and then coarse particles were removed by centrifugation to obtain an aqueous pigment ink. The color density of this ink composition was 30.0 in terms of L * value, the color density visually was “slightly bad”, and the coloration was “slightly different”.

Comparative Example 6
Aqueous black pigment dispersion C 36% by weight, glycerin 10% by weight, urea 15% by weight, ion-exchanged water 38.2% by weight, antifungal agent (Coatside H, Takeda Pharmaceutical Co., Ltd.) 0.1% by weight, antiseptic 0.1 wt% of an agent (Avicia Co., Ltd. Proxel XL-2) was added, stirred and mixed, and then coarse particles were removed by centrifugation to obtain an aqueous black pigment ink. The color density of this ink composition was 35.0 in terms of L * value, the color density visually was “bad”, and the coloration was “difference”.

Comparative Example 7
In Comparative Example 6, an aqueous pigment ink was obtained in the same manner except that the aqueous blue pigment dispersion D was used instead of the aqueous black pigment dispersion C. The color density of this ink composition was 56.0 in terms of L * value, the color density visually was “bad”, and the coloration was “difference”.

Comparative Example 8
In Comparative Example 6, an aqueous pigment ink was obtained in the same manner except that the aqueous red pigment dispersion E was used instead of the aqueous black pigment dispersion C. The color density of this ink composition was 60.0 in terms of L * value, the color density visually was “slightly bad”, and the coloration was “difference”.

Comparative Example 9
In Comparative Example 6, an aqueous pigment ink was obtained in the same manner except that the aqueous yellow pigment dispersion F was used in place of the aqueous black pigment dispersion C. The color density of this ink composition was 88.0 as an L * value, the color density visually was “bad”, and the coloration was “difference”.

As can be seen from the above results, the water-based pigment ink composition according to the present invention gives an ink-jet image having a high color density to the absorptive surface, particularly when using an ink-jet printer. In particular, the ink jet image produced by is not only low in color density by visual observation, but also has a significant difference in coloration due to paper quality.

Claims (7)

O / W type emulsion of at least one water-insoluble resin selected from the group consisting of water, pigment, water-soluble resin, surfactant composed of phosphate ester, and (meth) acrylic resin and styrene- (meth) acrylic resin It is contained in the range of 0.5 to 10% by weight in solid content, and the resin particles in the emulsion have an average particle diameter in the range of 50 to 200 nm, and the emulsion has a minimum film-forming temperature of 50 ° C. or higher. Monodea is, further urea or writing instrument for aqueous pigment ink composition containing the derivative in the range of 2 to 20 wt%. A surfactant comprising a phosphate ester is represented by the general formula (I)
Where X is a hydrogen atom or general formula (II)
R is an alkyl group having 8 to 30 carbon atoms or an alkylphenyl group having such an alkyl group, and n is a number in the range of 0 to 15 on average. of the X, at least one writing instrument for aqueous pigment ink composition according to claim 1 is made of a phosphoric acid ester is the above monovalent group. Further writing instrument for aqueous pigment ink composition according to claim 1 or 2 containing a polyhydric alcohol with 5 to 25 wt% range. Writing instrument for aqueous pigment ink composition according to with which of claims 1 to 3 containing at least one polyhydric alcohol from 5 to 15 wt% of the range selected from diethylene glycol and the group consisting of glycerin. Writing instrument for aqueous pigment ink composition according to any one of claims 1 to 4 containing the pigment at 0.2 to 15 wt% range. Writing instrument for aqueous pigment ink composition according to any one of claims 1 to 5 containing a pigment within a range of 1-15 wt%. Water-soluble resin is styrene- (meth) acrylic acid copolymer, (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene The writing instrument according to claim 1, which is at least one unsaturated carboxylic acid copolymer resin selected from the group consisting of -α-methylstyrene- (meth) acrylic acid copolymer and styrene-maleic acid copolymer . Water-based pigment ink composition.