JP6115701B2 - Water-resistant metal pigment dispersion and water-based ink composition - Google Patents

Description

  The present invention relates to a water resistant metal pigment dispersion and an aqueous ink composition.

  Conventionally, as a method of forming a coating film having a metallic luster on printed matter, printing ink using a metal powder made from brass, aluminum fine particles, etc. as a pigment, foil press printing using a metal foil, thermal transfer using a metal foil Methods have been used.

  In recent years, there have been many examples of application to inkjet in printing, and one of them is metallic printing, and development of an ink capable of forming an image having a metallic luster is in progress. For example, Patent Document 1 discloses an aluminum pigment dispersion based on an organic solvent such as alkylene glycol and a non-aqueous ink composition containing the same.

  On the other hand, from the viewpoints of the global environment and the safety to the human body, the actual situation that development of an ink composition containing water as a solvent is desired rather than a non-aqueous ink composition based on an organic solvent. is there. However, when the metal pigment is dispersed in water, the surface of the metal pigment may be altered or consumed due to reaction with water, and the metallic luster may be impaired.

  In order to solve such problems, for example, Patent Document 2 discloses a water-resistant aluminum pigment dispersion obtained by dispersing a water-resistant aluminum pigment whose surface is coated with a silica film in an aqueous surfactant solution. It is disclosed. In particular, Patent Document 2 discloses that a water-resistant aluminum pigment satisfies a specific parameter (coverage) based on XPS (X-ray photoelectron spectroscopy), thereby providing excellent water resistance and whitening even when dispersed in water. It is described not to.

JP 2008-174712 A JP 2011-132483 A

  However, the water-resistant aluminum pigment as disclosed in the above-mentioned Patent Document 2 is sufficiently resistant to corrosion due to contact with water (for example, whitening due to oxidation) even if the specific parameter based on XPS is satisfied. In some cases, it could not be suppressed and the storage stability was not excellent.

  One of the objects according to some embodiments of the present invention is to suppress corrosion when blended with a paint or ink containing water, to have excellent water dispersibility and metallic luster, and particularly to storage stability. An object is to provide an excellent water-resistant metal pigment dispersion and an ink composition containing the same.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the water resistant metal pigment dispersion according to the present invention is:
A water-resistant metal pigment dispersion in which a water-resistant metal pigment whose surface is coated with a film containing an inorganic oxide is dispersed in an aqueous medium,
The metal pigment has an average thickness of 1 nm or more and less than 100 nm, and a 50% average particle diameter of 0.5 μm or more and 3 μm or less,
The shape of the pigment particles constituting the metal pigment is a flat plate shape,
When a mapping image of the water-resistant metal pigment was obtained for the elements constituting the inorganic oxide by a transmission electron microscope,
The number of pinholes observed from the mapping image is 1 or less per pigment particle,
The pH is 5.0 or more and 8.5 or less.

  The water-resistant metal pigment dispersion of Application Example 1 can suppress corrosion when blended with a paint or ink containing water, has excellent water dispersibility and metallic luster, and is particularly excellent in storage stability.

[Application Example 2]
In application example 1,
The average thickness of the film containing the inorganic oxide may be 3 nm or more and 20 nm or less.

[Application Example 3]
In application example 1 or application example 2,
The metal pigment may be an aluminum pigment,
The inorganic oxide may be silicon oxide.

[Application Example 4]
In application example 3,
The water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, the atomic concentration of Al and O is calculated using energy dispersive X-ray spectroscopy, and the atomic concentration of _Al (M1 _Al ) and the ratio of the O of atomic concentration (M1 _O) a _(M1 O / _{M1 Al)} in case of the R1,
R1 may be 1.2 or less.

[Application Example 5]
In application example 4,
After heating the water-resistant metal pigment at a temperature of 70 ° C. for 6 days, the heated water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, and Al is dispersed using energy dispersive X-ray spectroscopy. and to calculate the atomic number density of O, when a ratio of the atomic concentration of Al _{(M2 Al)} and O of atomic concentration (M2 _O) a _{(M2 O / M2 Al) R2} ,
The ratio of R1 to R2 (R2 / R1) may be 3.0 or less.

[Application Example 6]
In application example 5,
A difference (R2−R1) between R1 and R2 may be 1.5 or less.

[Application Example 7]
In any one of Application Examples 3 to 6,
The water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, the atomic concentration of Al and Si is calculated using energy dispersive X-ray spectroscopy, and the atomic concentration of _Al (M3 _Al ) and the ratio of the atomic concentration of Si _{(M3 Si)} to _(M3 Si / M3 _Al) in case of the R3,
R3 can be more than 0.1 and 0.5 or less.

[Application Example 8]
In any one of Application Examples 1 to 7,
The film containing the inorganic oxide may be formed using tetraethoxysilane.

[Application Example 9]
One aspect of the water-based ink composition according to the present invention is:
The water-resistant metal pigment dispersion described in any one of Application Examples 1 to 8 is included.

  Since the water-based ink described in Application Example 9 contains the above water-resistant metal pigment dispersion, the water-based ink has excellent water dispersibility and metal gloss, and particularly excellent storage stability.

The mapping image obtained based on Si of the water resistant aluminum pigment which concerns on Example 1. FIG. The mapping image obtained based on Si of the water-resistant aluminum pigment which concerns on Example 2. FIG. The mapping image obtained based on Si of the water resistant aluminum pigment which concerns on the comparative example 2. FIG. The mapping image obtained based on Si or O of the water resistant aluminum pigment which concerns on the comparative example 3. FIG.

  Hereinafter, preferred embodiments of the present invention will be described. Embodiment described below demonstrates an example of this invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described in the following embodiments are indispensable constituent requirements of the present invention.

  Hereinafter, the water-resistant metal pigment dispersion, the method for producing the water-resistant metal pigment dispersion, and the water-based ink composition will be described in this order.

1. Water-Resistant Metal Pigment Dispersion Solution A water-resistant metal pigment dispersion according to an embodiment of the present invention is a water-resistant metal pigment dispersion in which a water-resistant metal pigment whose surface is coated with a film containing an inorganic oxide is dispersed in an aqueous medium. The metal pigment dispersion, wherein the metal pigment has an average thickness of 1 nm to less than 100 nm and a 50% average particle size of 0.5 μm to 3 μm, and constitutes the metal pigment The shape of the particles is flat, and the number of pinholes observed from the mapping image when a mapping image of the water-resistant metal pigment is obtained for the elements constituting the inorganic oxide by a transmission electron microscope. Is 1 or less per pigment particle, and the pH is 5.0 or more and 8.5 or less.

1.1. Components Hereinafter, the components contained in the water-resistant metal pigment dispersion according to this embodiment will be described in detail.

1.1.1. Water-Resistant Metal Pigment The water-resistant metal pigment contained in the water-resistant metal pigment dispersion according to this embodiment is obtained by coating the surface of the metal pigment with a film containing an inorganic oxide (hereinafter also referred to as “coating film”). It is.

In the present invention, the pigment refers to an aggregate of pigment particles composed of a plurality of pigment particles.

  The pigment particles constituting the metal pigment have a flat plate shape. It is preferable that the pigment particles constituting the metal pigment have a flat plate shape in that good metal gloss can be easily obtained.

  The metal pigment has a 50% average particle diameter R50 (hereinafter also simply referred to as “R50”) of the equivalent circle diameter determined from the area of the projected image of the pigment particles obtained by the particle image analyzer, and is 0.5 μm or more and 3 μm or less. And has a thickness (Z) of 1 nm or more and less than 100 nm. When the R50 and thickness (Z) of the metal pigment are within the above ranges, the metallic gloss and the printing stability are improved.

  The “equivalent circle diameter” is the diameter of the circle when assuming a circle having the same area as the area of the projected image of the pigment particles obtained using the particle image analyzer. For example, when the projected image of the pigment particles is a polygon, the diameter of the circle obtained by converting the projected image into a circle is referred to as the equivalent circle diameter of the pigment particle.

  As a preferable aspect of R50 of the metal pigment which concerns on this embodiment, they are 0.5 micrometer or more and 1.5 micrometers or less. When R50 is within the above range, the recording stability may be further improved.

  The area of the projected image of the pigment particles constituting the metal pigment and the equivalent circle diameter can be measured using a particle image analyzer. Examples of the particle image analyzer include a flow particle image analyzer FPIA-2100, FPIA-3000, and FPIA-3000S (manufactured by Sysmex Corporation). The average particle diameter of the equivalent circle diameter is a number-based particle diameter.

Further, the particle size distribution (CV value) of the pigment particles constituting the metal pigment can be obtained from the following formula (1).
CV value = standard deviation of particle size distribution / average value of particle diameter × 100 (1)

  Here, the CV value obtained is preferably 60 or less, more preferably 50 or less, and particularly preferably 40 or less. By selecting a metal pigment having a CV value of 60 or less, an effect of excellent recording stability can be obtained.

  Moreover, it is preferable that the maximum particle diameter of the equivalent circle diameter calculated | required from the area of the projection image of the pigment particle which comprises a metal pigment is 3 micrometers or less. When a metal pigment having a maximum particle size of 3 μm or less is used, clogging in the nozzle opening and the ink channel can be effectively suppressed when used in an ink jet recording apparatus.

  A preferred aspect of the thickness (Z) of the metal pigment according to the present embodiment is 10 nm or more and 50 nm or less, and more preferably 10 nm or more and 30 nm or less. When the thickness (Z) is within the above range, even when a coating film containing an inorganic oxide is formed on the surface of the metal pigment, the metal gloss tends to be good without being impaired.

  The thickness (Z) can be measured, for example, by observing a cross section of the pigment particle using an electron microscope. The electron microscope includes a transmission electron microscope (TEM, JEOL JEM-2000EX), a field emission scanning electron microscope (FE-SEM, Hitachi S-4700), a scanning transmission electron microscope (STEM, “HD” manufactured by Hitachi High-Technologies Corporation). -2000 ") or the like. The thickness (Z) means an average thickness, and specifically, an arithmetic average value of thicknesses when 10 pigment particles constituting a metal pigment are selected and individually measured. Say.

  The thickness of the coating film is preferably 3 nm or more and 20 nm, more preferably 3 nm or more and 10 nm or less, and particularly preferably 1 nm or more and 9 nm or less. If the thickness of the coating film is within the above range, particularly the lower limit value or more, the water resistance of the metal pigment is good.If the thickness is not more than the lower limit value, the water resistance is good while suppressing a decrease in metal gloss. can do.

  The thickness of the coating film refers to the thickness of the coating film formed on one surface of the metal pigment in the thickness direction of the metal pigment. Moreover, the thickness of a coating film can be measured by observing the cross section of a water-resistant metal pigment using an electron microscope (for example, TEM, STEM, SEM, FE-SEM).

  The metal pigment is not particularly limited as long as it can exhibit metallic luster when attached to a medium. For example, aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, and One or two or more alloys selected from the group consisting of copper are included. Among these, it is preferable that it is aluminum or aluminum alloy from a viewpoint of ensuring metal glossiness, and a viewpoint of cost.

  Moreover, as a material for forming the film | membrane (coating film | membrane) containing an inorganic oxide, the alkoxysilane (for example, tetraethoxysilane) which has a silicon atom in a structure, a polysilazane etc. are mentioned, for example. Among these, alkoxysilane is preferably used from the viewpoint that a uniform and flat film can be formed on the surface of the metal pigment. In particular, when an aluminum pigment made of aluminum or an aluminum alloy is used, it is more preferable to use tetraethoxysilane because a silica film having excellent adhesion to the aluminum pigment can be formed.

  The concentration of the water-resistant metal pigment in the water-resistant metal pigment dispersion may be appropriately set so as to facilitate the handling of the water-resistant metal pigment dispersion, and is not particularly limited.

1.1.2. Aqueous medium The water-resistant metal pigment dispersion according to this embodiment contains an aqueous medium.

  The aqueous medium should just be a medium which has water as a main component. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltered water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be suppressed over a long period of time.

  The content of the aqueous medium is, for example, preferably from 1% to 99%, more preferably from 10% to 70%, still more preferably from 20% to 60%, based on the total mass of the water resistant metal pigment dispersion. Can be: When the content of the aqueous medium is within the above range, particularly 20% or more, it is preferable from the viewpoint that the environmental load is reduced and the viscosity can be set in a range that is easy to handle. Moreover, generation | occurrence | production of the gas by reaction of a water-resistant metal pigment and water, corrosion of a water-resistant metal pigment, etc. may be reduced because content of an aqueous medium is the said range, especially 60% or less.

1.1.3. Other ingredients <Organic solvent>
The water-resistant metal pigment dispersion according to this embodiment may contain an organic solvent.

The organic solvent is preferably a polar organic solvent from the viewpoint of compatibility with an aqueous medium. Examples of polar organic solvents include alcohols (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, fluorinated alcohol, etc.), ketones (acetone, methyl ethyl ketone, cyclohexanone, etc.), carboxylic acid esters (methyl acetate, Ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.), ethers (diethyl ether, dipropyl ether, tetrahydrofuran, dioxane, etc.), polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, polyethylene) Glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol Le, glycerin, trimethylol ethane, trimethylol propane, etc.), alkylene glycol monoethers, such as glycol ether solvents (triethylene glycol monobutyl ether, alkylene glycol diethers such as diethylene glycol diethyl ether, etc.) and the like.

  Among these, when an aluminum pigment is used as the metal pigment, it is preferable to use at least one of polyhydric alcohols and glycol ethers from the viewpoint of excellent dispersion stability of the aluminum pigment.

  When the organic solvent is contained, the content thereof is preferably 1% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 90% by mass or less, with respect to the total mass of the water resistant metal pigment dispersion. More preferably, it is 40 mass% or more and 80 mass% or less. When the content of the organic solvent is within the above range, particularly 40% by mass or more, generation of gas due to the reaction between the water-resistant metal pigment and water, corrosion of the water-resistant metal pigment, or the like may be reduced. Moreover, it is preferable from viewpoints, such as reduction of an environmental load, that content of an organic solvent is in the said range, especially 80 mass% or less.

<Basic catalyst>
The water-resistant metal pigment dispersion according to this embodiment may contain a basic catalyst. A basic catalyst can be added at the time of reaction with the material (for example, TEOS) for forming the film | membrane containing a metal pigment (for example, aluminum pigment) and an inorganic oxide.

  Examples of the basic catalyst include ammonia, trialkylamine, ethanolamine, sodium hydroxide, potassium hydroxide, urea, choline, tetraalkylammonium hydroxide, and the like.

<Surfactant>
The water-resistant metal pigment dispersion according to this embodiment may contain a surfactant. In some cases, the dispersibility of the water-resistant metal pigment can be improved by adding a surfactant.

  As the surfactant, any known surfactant such as an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, and a polymer surfactant can be used.

<Tertiary amine>
The water-resistant metal pigment dispersion according to this embodiment may contain a tertiary amine. The tertiary amine may be able to improve the dispersibility of the water resistant metal pigment due to the steric hindrance effect or the pH adjusting action.

Examples of the tertiary amine include hydroxylamines such as triethanolamine, tripropanolamine, tributanolamine, N, N-dimethyl-2-aminoethanol, N, N-diethyl-2-aminoethanol and the like. Among these, triethanolamine and tripropanolamine are preferable in terms of further improving water dispersibility, and triethanolamine is more preferable in terms of improving storage stability in addition to water dispersibility.

<Buffer solution>
The water-resistant metal pigment dispersion according to this embodiment may contain a buffer solution. By containing the buffer solution, the fluctuation range of the pH of the dispersion is reduced, and the pH can be maintained in a desired range. Thereby, it may be possible to suppress problems caused by the pH of the dispersion, such as the generation of gas accompanying the reaction between the metal pigment and the aqueous medium and the elution of the water-resistant metal pigment.

  As the buffer solution, any conventionally known buffer solution can be used as long as the pH of the water-resistant metal pigment dispersion can be maintained in the range of 5.0 to 8.5. -(2-hydroxyethyl) -1-piperazineethanesulfonic acid (HEPES), morpholinoethanesulfonic acid (MES), carbamoylmethyliminobisacetic acid (ADA), piperazine-1,4-bis (2-ethanesulfonic acid) ( PIPES), N- (2-acetamido) -2-aminoethanesulfonic acid (ACES), collamine hydrochloride, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid (BES), N-tris ( Hydroxymethyl) methyl-2-aminoethanesulfonic acid (TES), acetamide glycine, tricine, glycinamide, bicine, etc. Buffer, phosphate buffer, Tris buffer, and the like.

1.2. Properties of Water-Resistant Metal Pigment Dispersion Next, properties of the water-resistant metal pigment dispersion according to this embodiment will be described in detail.

1.2.1. The number of pinholes is 1 or less The water-resistant metal pigment contained in the water-resistant metal pigment dispersion according to this embodiment is a pigment in which the number of pinholes observed under specific conditions constitutes the water-resistant metal pigment. It is 1 or less (preferably 0) per particle. When the pinhole is 1 or less, the water-resistant metal pigment dispersion can suppress corrosion when blended with a paint or ink containing water, and has excellent water dispersibility and metallic luster, and particularly storage stability. Excellent. The present invention is not limited to the case where all the pigment particles in the water resistant metal pigment dispersion have a pinhole number of 1 or less.

  In the present invention, the “pinhole” means that when using a transmission electron microscope (TEM) having a line resolution of 0.10 nm or more to obtain a mapping image of a water resistant metal pigment for an element constituting an inorganic oxide, A portion in which an image is not formed in an image corresponding to a water-resistant metal pigment, and a portion in which an image is not formed has a diameter of 0.05 μm or more. Here, in the image corresponding to the water-resistant metal pigment is the outermost side where the element to be measured (element constituting the inorganic oxide) exists when mapping is performed from the plane perpendicular direction of the water-resistant metal pigment. This is the area where An image corresponding to a water-resistant metal pigment includes both a region containing a metal pigment and no inorganic oxide, and a region containing no metal pigment and an inorganic oxide.

  In addition, the diameter of a pinhole means the equivalent circle diameter calculated | required based on the area of the pinhole observed from a mapping image.

  As a transmission electron microscope used for pinhole measurement, a transmission electron microscope (hereinafter also referred to as “EF-TEM”) provided with an energy filter or a scanning transmission electron microscope (hereinafter also referred to as “STEM”) is used. Can do. Among these, EF-TEM can be preferably used in that a clear mapping image can be obtained as compared with STEM. As the EF-TEM, for example, “Tecnai G2 F30” (trade name, manufactured by FEI) or the like can be used.

  Here, the relationship between the performance of the water-resistant metal pigment dispersion and the pinhole was verified as follows.

  JP2011-132483A describes that by satisfying specific parameters based on XPS (X-ray electron spectroscopy), it has excellent water resistance and does not whiten even when dispersed in water. .

  However, even when the water resistant aluminum pigment dispersion described in JP2011-132483A satisfies specific parameters based on XPS, it cannot be said that the water resistance is sufficient and the storage stability is insufficient. The reason for this is that although XPS measurement is excellent for analyzing the vicinity of the surface of the sample, it uses X-ray irradiation, so the position resolution (spatial resolution) is insufficient. It is thought that one reason was that it was not detected sufficiently.

  Therefore, the inventor selected TEM (Transmission Electron Microscope) as a means capable of analyzing with higher resolution than XPS, and the water-resistant aluminum pigment dispersion described in JP2011-132483A has the above water resistance. And the reason why it is not excellent in storage stability (long-term storage stability).

  TEM can irradiate an electron beam in the thickness direction of the pigment particle and form an image of the electron beam that has passed through the pigment particle on a screen using a magnetic lens, enabling high-resolution observation and elemental analysis. . In particular, a TEM equipped with an energy filter (hereinafter also referred to as “EF-TEM”) is capable of spectroscopically analyzing electrons transmitted through a sample and selecting electrons having specific energy to form a mapping image. Analysis of elemental composition with high resolution (nm order) and a clear mapping image can be obtained.

  Specifically, pigment particles constituting the water-resistant aluminum pigment described in JP2011-132483A are individually taken out and used as a sample, and mapping is performed based on the energy loss due to silicon in the sample by EF-TEM. The image was observed. As a result, the inventor found that the pinhole described above exists.

  Thus, when pinholes occur in the coating film, corrosion of the surface of the pigment particles progresses around the pinholes, and the metallic gloss of the water-resistant metal pigment dispersion decreases or the storage stability decreases. Resulting in.

  In particular, when the number of pinholes of the water-resistant metal pigment observed under the above specific conditions is 2 or more per pigment particle constituting the water-resistant metal pigment, the storage stability of the water-resistant aluminum pigment dispersion is stable. It turned out that there exists a tendency for a property to fall remarkably.

  As described above, it has been clarified that performances such as water resistance and storage stability of the water-resistant metal pigment dispersion are closely related to pinholes.

  Although the detailed reason has not been clarified, when the pinhole is present at the end of the pigment particle, the corrosion of the pigment particle is difficult to proceed around the pinhole, and the pinhole is in the central region of the pigment particle. It was found that the pigment particles, especially pinholes, tend to corrode easily. For these reasons, the pinhole in the present invention does not include those present at the ends of the pigment particles.

1.2.2. PH of water resistant metal pigment dispersion
The water-resistant metal pigment dispersion according to this embodiment has a pH of 5.0 or more and 8.5 or less. When the pH of the water-resistant metal pigment dispersion is within the above range, the reaction between the water-resistant metal pigment and the aqueous medium can be suppressed, and the elution of the coating film and the metal pigment can be suppressed. Thereby, the water resistance of the water resistant metal pigment dispersion can be improved, and the storage stability can be improved.

  In particular, when the metal pigment is made of aluminum, when the pH of the water-resistant metal pigment dispersion is too acidic or alkaline (when the pH is not in the range of 5.0 or more and 8.5 or less), the aluminum is eluted, Generation of hydrogen gas, deterioration of water resistance, etc. may occur.

  Also, when the coating film is made of silica, when the pH of the water-resistant metal pigment dispersion is too acidic (when the pH is less than 5.0), silica is eluted and water resistance is lowered. There is.

  As a preferable aspect of the pH of the water-resistant metal pigment dispersion according to this embodiment, the pH is 6.0 or more and 8.5 or less, and the pH is particularly preferably 7.0 or more and 8.5 or less.

1.2.3. Parameters obtained by SEM-EDX The water-resistant metal pigment dispersion according to this embodiment is a water-resistant aluminum pigment dispersion in which a water-resistant aluminum pigment obtained by coating an aluminum pigment with silica (silicon oxide) is dispersed in the aqueous medium. It is preferable that

  The water-resistant aluminum pigment dispersion according to this embodiment is characterized by energy dispersive X-ray spectroscopy (hereinafter also referred to as “EDX”) using a scanning electron microscope (hereinafter also referred to as “SEM”). Can be identified.

  Specifically, the water-resistant metal pigment is irradiated with an electron beam using SEM, the emitted X-ray is detected by EDX, and the water-resistant aluminum pigment is configured based on the X-ray spectrum detected by EDX. The atomic concentration of elements (Al, O, Si, etc.) can be calculated. In calculating the atomic number concentration, for example, an overlap factor method can be used as the peak separation method, and a standardless ZAF method can be used as the quantitative correction method.

Based on the atomic concentration of each element thus obtained, the ratio (M1 _O / M1 _Al ) between the atomic concentration (M1 _Al ) of _Al and the atomic concentration (M1 _O ) of _{O was} defined as R1. In this case, R1 is preferably 1.2 or less, more preferably 0.1 or more and 1.0 or less, and particularly preferably 0.1 or more and 0.7 or less.

  When the R1 is 1.2 or less, the water resistant aluminum pigment can be prevented from being oxidized over time, so that the whitening of the water resistant aluminum pigment due to oxidation is difficult to proceed, and the metallic luster of the water resistant aluminum pigment dispersion is increased. It becomes difficult to deteriorate. When R1 is 0.1 or more, the water resistance of the water resistant aluminum pigment dispersion tends to be good.

Also, after the water-resistant aluminum pigment dispersion was heated for 6 days at a temperature of 70 ° C., the ratio of the atomic concentration of Al after heating _{(M2 Al)} O of atomic concentration _{(M2 O) (M2 O /} M2 Al ) Is R2, the ratio of R1 to R2 (R2 / R1) is preferably 3.0 or less, more preferably 1.0 or more and 2.5 or less, and 1.0 It is especially preferable that it is above 2.1.

  When R1 is 0.7 or less and the ratio (R2 / R1) is 3.0 or less, oxidation of the water-resistant aluminum pigment over time is further suppressed. The metal gloss becomes more difficult to decrease.

Furthermore, while R1 and the ratio (R2 / R1) satisfy the above values, the difference between R1 and R2 (R2
When -R1) is 1.5 or less (preferably 1.0 or less), the oxidation of the water resistant aluminum pigment over time is remarkably suppressed, so that the metallic gloss of the water resistant aluminum pigment dispersion is further reduced. It becomes difficult.

  R2 is preferably 0.1 or more and 1.2 or less, and more preferably 0.1 or more and 0.7 or less. When R2 is within the above range, the storage stability and metallic gloss can be maintained at a good level.

Further, based on the atomic concentration of each element, the ratio of the atomic concentration _{(M3 Al)} and Si atomic concentration of Al _{(M3 Si)} to _(M3 Si / M3 _Al) in case of the R3, the R3 Is more than 0.1 and preferably 0.5 or less, more preferably 0.1 or more and 0.4 or less, and particularly preferably 0.1 or more and 0.3 or less.

  If R3 is in the above range, particularly exceeding 0.1, the surface of the aluminum pigment is satisfactorily covered with the silica film, so that the water resistance of the water-resistant aluminum pigment dispersion becomes good. Further, if R3 is within the above range, particularly 0.5 or less, a silica film is formed to such an extent that the metallic gloss of the aluminum pigment is not deteriorated, so that the metallic gloss of the water resistant aluminum pigment dispersion is secured. The water resistance is excellent.

  In particular, the water-resistant aluminum pigment dispersion has extremely high metallic gloss due to the synergistic action of the above-described effects when R1 and R3 are within the above range.

  In the present specification, R1, R2, R3, R2 / R1, R2-R1 calculated based on the analysis result obtained by EDX using the above SEM is referred to as “parameter obtained by SEM-EDX”. There is a case.

  Since the scanning electron microscope can perform elemental analysis by irradiating an accelerated electron beam, the thickness of the sample is larger than that of the composition analysis using XPS in which the chemical state of the outermost surface of the sample is analyzed by X-ray irradiation. It is suitable for deriving the abundance ratio of elements by averaging more with respect to the direction. That is, if a scanning electron microscope is used, the composition ratio of the elements averaged in the thickness direction of the water resistant aluminum pigment can be obtained rather than XPS.

  Examples of the scanning electron microscope (hereinafter also referred to as “SEM”) include FE-SEM S-4700 manufactured by Hitachi High-Technologies Corporation.

  The X-ray extraction angle by EDX refers to the angle formed by the sample surface and the EDX detector, and is preferably set to 10 ° to 45 °. Thereby, the detection efficiency of the X-rays emitted from the sample can be improved, and a more detailed analysis is possible.

  Moreover, the incident angle of the electron beam by SEM refers to the angle formed by the sample surface and the incident electron beam, and is preferably set to 60 ° or more and 90 ° or less. Thereby, elemental analysis may become easier.

2. Method for Producing Water-Resistant Metal Pigment Dispersion The water-resistant metal pigment dispersion according to this embodiment can be obtained, for example, by the following production method.

Hereinafter, as an example of a method for producing a water-resistant metal pigment dispersion according to the present embodiment, a water-resistant aluminum pigment using an aluminum pigment as a metal pigment and tetraethoxysilane as a material for forming a film containing an inorganic oxide. The method for producing the dispersion will be described in detail. In addition, the manufacturing method of the water-resistant metal pigment dispersion which concerns on this embodiment is not limited to the following examples.

  The method for producing a water-resistant aluminum pigment dispersion according to this embodiment includes a step (a) of preparing an aluminum pigment dispersion in which an aluminum pigment is dispersed in an organic solvent, and the aluminum pigment 1 in the aluminum dispersion. Step (b) of adding 0.5 parts by mass or more and 2.5 parts by mass or less of TEOS to mass parts, and reacting the aluminum pigment and TEOS within a period of 10 days or more and 60 days or less, and at least the organic solvent A step (c) for removing a part and a step (d) for adding an aqueous medium are included.

  Hereinafter, each step will be described in detail.

2.1. Step (a)
Step (a) is a step of preparing an aluminum pigment dispersion in which an aluminum pigment is dispersed in an organic solvent.

  First, a composite pigment base material having a structure in which a release resin layer and a metal layer are sequentially laminated on a sheet-like substrate surface is prepared.

  Although it does not restrict | limit especially as a sheet-like base material, Polytetrafluoroethylene, polyethylene, polypropylene, Polyester films, such as a polyethylene terephthalate, Polyamide films, such as nylon 66 and nylon 6, Polycarbonate films, a triacetate film, a polyimide film, etc. A functional film. Of these, polyethylene terephthalate or a copolymer thereof is preferable.

  The thickness of the sheet-like substrate is not particularly limited, but is preferably 10 μm or more and 150 μm or less. If it is 10 μm or more, there is no problem in handleability in the process or the like, and if it is 150 μm or less, it is rich in flexibility and there is no problem in roll formation / peeling.

  The release resin layer is an undercoat layer of a metal layer, and is a peelable layer for improving the peelability from the sheet-like substrate surface. As the resin used for the release resin layer, for example, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, cellulose derivative, acrylic acid polymer, or modified nylon resin is preferable.

  The resin layer for peeling can be formed by applying a solution of one or two or more of the resins exemplified above to a sheet-like substrate and drying it. After coating, additives such as a viscosity modifier can be added.

  For the application of the release resin layer, commonly used techniques such as gravure coating, roll coating, blade coating, extrusion coating, dip coating, and spin coating can be used. After coating and drying, the surface can be smoothed by calendaring if necessary.

  The thickness of the release resin layer is not particularly limited, but is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 10 μm or less. If it is less than 0.5 μm, the amount as a dispersion resin is insufficient, and if it exceeds 50 μm, when it is rolled, it tends to peel off at the interface with the pigment layer.

  As means for laminating the metal layer, it is preferable to apply vacuum deposition, ion plating or sputtering.

  The metal layer may be sandwiched between protective layers as exemplified in JP-A-2005-68250. Examples of the protective layer include a silicon oxide layer and a protective resin layer.

  The silicon oxide layer is not particularly limited as long as it is a layer containing silicon oxide, but is preferably formed from a silicon alkoxide such as tetraalkoxysilane or a polymer thereof by a sol-gel method. A coating film of a silicon oxide layer can be formed by applying an alcohol solution in which silicon alkoxide or a polymer thereof is dissolved, followed by heating and baking.

  The protective resin layer is not particularly limited as long as it is a resin that does not dissolve in the dispersion medium, and examples thereof include polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, and cellulose derivatives. Of these, it is preferably formed from polyvinyl alcohol or a cellulose derivative. A protective resin layer can be formed by applying and drying an aqueous solution of one or more of the above exemplified resins. Additives such as a viscosity modifier can be further added to the coating solution. The silicon oxide and the resin are applied by the same method as the application of the release resin layer.

  The thickness of the protective layer is not particularly limited, but is preferably in the range of 50 nm to 150 nm. If it is less than 50 nm, the mechanical strength is insufficient, and if it exceeds 150 nm, the strength becomes too high, so that pulverization / dispersion becomes difficult, and peeling may occur at the interface with the metal layer.

  Moreover, as illustrated in US Pat. No. 7,303,619, the composite pigment base may have a color material layer between the protective layer and the metal layer.

  The color material layer is introduced to obtain an arbitrary colored composite pigment, and in addition to the metallic luster, glitter, and background hiding properties of the aluminum pigment used in the present embodiment, a color that can impart an arbitrary color tone and hue. There is no particular limitation as long as the material can be contained. As the color material used for this color material layer, either a dye or a pigment may be used. Moreover, as a dye and a pigment, a well-known thing can be used suitably.

  In such a case, the “pigment” used in the color material layer means a natural pigment, a synthetic organic pigment, a synthetic inorganic pigment or the like defined in the general engineering field.

  The method for forming the color material layer is not particularly limited, but is preferably formed by coating. Further, when the color material used in the color material layer is a pigment, it is preferable to further include a color material dispersion resin. Examples of the color material dispersion resin include a pigment, a color material dispersion resin, and other materials as necessary. It is preferable that the additive is dispersed or dissolved in a solvent to form a uniform liquid film by spin coating as a solution and then dried to produce a resin thin film. In the production of the composite pigment raw material, it is preferable in terms of work efficiency that both the colorant layer and the protective layer are formed by coating.

  As the composite pigment base material, a layer structure having a plurality of sequential laminated structures of a release resin layer and a metal layer is also possible. At that time, the total thickness of the laminated structure composed of a plurality of metal layers, that is, excluding the sheet-like base material and the release resin layer immediately above the metal layer—the release resin layer—the metal layer or the release resin layer— The thickness of the metal layer is preferably 5000 nm or less. When it is 5000 nm or less, even when the composite pigment base material is rolled up, it is difficult to cause cracking and peeling and is excellent in storage stability. Moreover, it is excellent also in the metal glossiness when it is pigmented. Moreover, although the structure where the peeling resin layer and the metal layer were laminated | stacked one by one on both surfaces of the sheet-like base material surface is mentioned, it is not restrict | limited to these.

  Next, the composite pigment base material is peeled from the composite pigment base material in an organic solvent at the interface between the sheet base surface of the composite pigment base material and the release resin layer as a boundary, and then pulverized or refined. By processing, a dispersion containing coarse particles is obtained. Furthermore, the obtained dispersion liquid is filtered to remove coarse particles, whereby a dispersion liquid in which an aluminum pigment composed of flat pigment particles is dispersed in an organic solvent can be obtained.

  As the organic solvent, those mentioned in the above “1.1.3. Other components” can be used.

  The peeling treatment method from the sheet-like substrate is not particularly limited, but is a method that is performed by immersing the composite pigment raw material in a liquid, or the ultrasonic treatment is performed at the same time as the immersion in the liquid. A method of pulverizing the composite pigment thus obtained is preferred.

  The aluminum pigment composed of the flat pigment particles obtained as described above has a release resin layer serving as a protective colloid, and a stable dispersion can be obtained simply by performing a dispersion treatment in an organic solvent. It is possible to obtain.

  The pigment particles constituting the aluminum pigment in the dispersion obtained by the above process have a flat plate shape. It is preferable that the pigment particles constituting the aluminum pigment have a flat plate shape because particularly good metallic luster is easily obtained.

  Here, the “flat pigment particle” means a substantially flat surface (XY plane) when the major axis on the plane of the pigment particle is X, the minor axis is Y, and the thickness is Z. , Refers to particles having a substantially uniform thickness (Z). Moreover, flat form is a concept including shapes, such as scale shape, leaf shape, flat plate shape, for example.

  The aluminum pigment obtained by the above process has an R50 of 0.5 μm or more and 3 μm or less, and a thickness (Z) of 1 nm or more and less than 100 nm. When the R50 and thickness (Z) of the aluminum pigment are within the above ranges, the metallic gloss and the printing stability are improved.

  In addition, you may provide separately the process of wash | cleaning the aluminum pigment contained in the aluminum pigment dispersion liquid obtained by said process. The organic solvent mentioned above can be used for washing | cleaning of an aluminum pigment.

  The aluminum pigment dispersion obtained by the above process may contain the aforementioned release resin layer, or the release resin layer may adhere to the aluminum pigment. The component contained in the release resin layer may inhibit the reaction between TEOS and an aluminum pigment, which will be described later. Therefore, by washing the aluminum pigment, the components of the peeling resin layer can be removed, and the reactivity between TEOS and the aluminum pigment, which will be described later, can be improved.

  Although it does not specifically limit as a washing | cleaning method of an aluminum pigment, For example, it can carry out by the following methods.

  First, at least a part of the organic solvent is removed from the aluminum pigment dispersion. For removing the organic solvent, the organic solvent and the aluminum pigment are separated by an operation such as filtration, centrifugal sedimentation, or centrifugal separation to remove the organic solvent contained in the aluminum pigment dispersion.

  Next, an organic solvent for washing is added to the aluminum pigment to disperse the aluminum pigment in the organic solvent, and then the organic solvent for washing is removed. The operation of dispersing the aluminum pigment in the cleaning organic solvent and removing the cleaning organic solvent may be performed a plurality of times.

  Thereafter, an aluminum pigment dispersion containing the washed aluminum pigment can be obtained by adding and dispersing the above-described organic solvent to the aluminum pigment.

2.2. Step (b)
In the step (b), 0.5 to 2.5 parts by mass of TEOS is added to 1 part by mass of the aluminum pigment in the aluminum dispersion, and the aluminum pigment and TEOS are added to 10 to 60 days. It is the process made to react within the period. By adding TEOS and stirring sufficiently, the hydroxyl groups present on the surface of the aluminum pigment and the silanol groups of TEOS are hydrolyzed and condensed to form a silica film on the surface of the aluminum pigment. By forming a silica film on the surface of the aluminum pigment, it is possible to prevent the aluminum pigment and water from coming into direct contact with each other, so that water resistance can be imparted to the aluminum pigment. In the present specification, an aluminum pigment having a silica film formed on the surface is also referred to as a “waterproof aluminum pigment”.

  The reaction temperature in the hydrolysis condensation is preferably 10 ° C. or higher and 150 ° C. or lower, more preferably 20 ° C. or higher and 130 ° C. or lower. If the reaction temperature is in the above range, particularly the lower limit value or more, the reaction rate of the hydrolysis condensation is good without slowing too much, and if it is not more than the upper limit value, it can be reacted easily without safety problems. .

  Here, as one method for reducing the number of pinholes in the water resistant metal pigment to 1 or less, for example, the addition ratio of the material for forming a film containing the metal pigment and the inorganic oxide and the reaction time are controlled. To do.

  For example, when a water-resistant aluminum pigment is used as an example of a water-resistant metal pigment, 0.5 to 2.5 parts by mass of TEOS is added to 1 part by mass of the aluminum pigment, and hydrolysis is performed. By setting the reaction time in the condensation to 10 days or more and 60 days or less, the number of pinholes can be made 1 or less.

  In terms of reducing pinholes, the TEOS addition amount is more preferably 0.8 parts by mass or more and 2.0 parts by mass or less, particularly preferably 0.8 parts by mass or more and 1.6 parts by mass or less. It is.

  In terms of reducing pinholes, a more preferable embodiment of the reaction time in the hydrolysis condensation is 12 days or more and 45 days or less, and particularly preferably 14 days or more and 30 days or less.

  Moreover, as one method for satisfying the parameter obtained by SEM-EDX mentioned above, for example, the addition ratio of aluminum pigment and TEOS and the reaction time can be controlled.

  For example, with respect to 1 part by mass of the aluminum pigment, TEOS is added in an amount of 0.4 parts by mass to 1.6 parts by mass, and the reaction time in the hydrolysis condensation is 1 day to 30 days, as described above. At least one of parameters obtained by SEM-EDX can be satisfied.

  In terms of satisfying parameters obtained by SEM-EDX, a more preferable embodiment of the addition amount of TEOS is 0.6 parts by mass or more and 1.6 parts by mass or less, and particularly preferably 0.8 parts by mass or more and 1. 6 parts by mass or less.

  In terms of satisfying the parameters obtained by SEM-EDX, the reaction time in the hydrolysis condensation is more preferably 7 days or more and 30 days or less, and particularly preferably 14 days or more and 30 days or less.

  The water-resistant aluminum pigment dispersion has excellent storage stability and excellent metallic luster by setting conditions that satisfy the parameters that can be obtained by SEM-EDX while satisfying the conditions that can reduce the pinhole number to 1 or less. It will be excellent. In order to satisfy both conditions, 0.5 mass part or more and 1.6 mass parts or less (preferably 0.8 mass part or more and 1.6 mass parts or less) of TEOS is added, and the reaction time in the hydrolytic condensation is increased. It may be 10 days or more and 30 days or less (preferably 14 days or more and 30 days or less).

  In step (b), after addition of TEOS, a basic catalyst may be further added to promote hydrolysis and condensation. As the basic catalyst, those mentioned above in “1.1.3. Other components” can be used. Among these, ammonia is particularly preferable.

  The addition amount of the basic catalyst is preferably 1 part by mass or less, more preferably 0.1 part by mass or less, with respect to 10 parts by mass of the aluminum pigment. If the addition amount of the basic catalyst exceeds the above range, the viscosity of the aluminum pigment dispersion may increase, or the aluminum pigment in the aluminum pigment dispersion may aggregate and the metallic luster may not be maintained.

2.3. Step (c)
Step (c) is a step of removing at least a part of the organic solvent.

  The means for removing at least a part of the organic solvent is not particularly limited, and can be carried out by operations such as filtration, centrifugal sedimentation, and centrifugal separation. Specifically, at least a part of the organic solvent is removed by separating the water-resistant aluminum pigment obtained in the step (b) and the other components (mainly organic solvent) by the above operation. Can do.

2.4. Step (d)
Step (d) is a step of adding an aqueous medium. As a result, a water resistant aluminum pigment dispersion in which the water resistant aluminum pigment is dispersed in an aqueous medium is obtained.

  In the step (d), the surfactant, tertiary amine, buffer solution and the like mentioned in “1.1.3. Other components” may be added. These components may be added in advance in an aqueous medium, or may be added individually before and after the addition of the aqueous medium.

2.5. Other Steps The method for producing a water resistant aluminum pigment dispersion according to the present embodiment may include an aging step after the step (d).

  Aging refers to heating the obtained water resistant aluminum pigment dispersion at a temperature of 30 ° C. to 80 ° C. for a period of 1 day to 14 days.

  When the water-resistant aluminum pigment dispersion is aged, the portion of the surface of the water-resistant aluminum pigment where no silica film is formed is oxidized. Thereby, although the metallic luster of the water resistant aluminum pigment dispersion may be slightly lowered, the oxidized portion becomes a protective film, and the water resistance over time of the water resistant aluminum pigment dispersion can be suppressed. There is a case. This may improve the storage stability of the water resistant aluminum pigment dispersion.

The aging period is preferably 2 days or more and 12 days or less, and more preferably 3 days or more and 7 days or less.

  The aging temperature is preferably 35 ° C. or higher and 75 ° C. or lower, and more preferably 40 ° C. or higher and 70 ° C. or lower.

  The water-resistant aluminum pigment dispersion obtained through the above steps has a pinhole of 1 or less in the water-resistant aluminum pigment contained therein, and therefore, when it is blended in water-containing paints or inks, it is resistant to corrosion. It can be suppressed, has excellent water dispersibility and metallic luster, and is particularly excellent in storage stability.

3. Water-based ink composition The water-based ink composition according to this embodiment is characterized by containing the aforementioned water-resistant metal pigment.

  The water-based ink composition according to this embodiment contains a water-resistant metal pigment dispersion that has excellent water dispersibility and metallic luster, and particularly excellent storage stability. Therefore, the water-based ink composition according to the present embodiment has the properties of being excellent in water dispersibility, metallic gloss and storage stability, like the water resistant metal pigment dispersion.

  Further, since the water-based ink composition according to this embodiment contains a water-resistant metal pigment having excellent water dispersibility, nozzle clogging due to aggregation of water-resistant aluminum pigments even when applied to an ink jet printer. Is suppressed. As a result, ink ejection stability is improved.

  In the present invention, the “aqueous ink composition” means an ink composition containing 20% by mass or more, preferably 40% by mass or more of water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltered water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be suppressed over a long period of time.

  The concentration of the water-resistant metal pigment in the water-based ink composition is preferably 0.1 to 5.0% by weight, more preferably 0.1 to 3.0% by weight, based on the total weight of the water-based ink composition. More preferably, it is 0.25-2.5 mass%, Most preferably, it is 0.5-2.0 mass%.

  The aqueous ink composition according to the present embodiment may contain a tertiary amine, resins, surfactant, alkanediol, polyhydric alcohol, pyrrolidone derivative, pH adjuster, buffer solution, and the like.

  The tertiary amine has a function of improving the water dispersibility and storage stability of the water resistant metal pigment. As the tertiary amine, those similar to those mentioned in the above “1.1.3. Other components” can be used.

  The resins have a function of firmly fixing the water-resistant aluminum pigment on the recording medium. Examples of the resins include acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinyl pyrrolidone, vinyl pyridine, vinyl Examples thereof include carbazole, vinylimidazole, vinylidene chloride homopolymer or copolymer, urethane resin, fluororesin, and natural resin. In addition, said copolymer can be used with any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer.

As the surfactant, it is preferable to contain an acetylene glycol surfactant or a polysiloxane surfactant. The acetylene glycol surfactant and the polysiloxane surfactant can improve the wettability of the recording surface of the recording medium or the like to increase the ink permeability. Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, Examples include 5-dimethyl-1-hexyn-3-ol, 2,4-dimethyl-5-hexyn-3-ol, and the like. Moreover, a commercial item can also be utilized for acetylene glycol-type surfactant, for example, Olphine E1010, STG, Y (above, Nissin Chemical Industry Co., Ltd. product), Surfynol 104, 82, 465, 485, TG (End of Air
Products and Chemicals Inc. Manufactured). Commercially available products can be used as the polysiloxane surfactant, and examples thereof include BYK-347, BYK-348 (above, manufactured by Big Chemie Japan Co., Ltd.) and the like. Further, the aqueous ink composition may contain other surfactants such as an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  Alkanediol can enhance the wettability of a recording surface such as a recording medium and improve the ink permeability. Examples of the alkanediol include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, etc. , 2-alkanediol is preferred. Among these, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol having 6 to 8 carbon atoms are more preferable because of their particularly high permeability to recording media.

  For example, when the aqueous ink composition is applied to an inkjet recording apparatus, the polyhydric alcohol can suppress drying of the aqueous ink composition and prevent clogging of the aqueous ink composition in the inkjet recording head portion. As a polyhydric alcohol, the thing similar to what was mentioned by said "1.1.3. Other components" can be used.

  Examples of the pyrrolidone derivative include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone, 5-methyl-2-pyrrolidone and the like.

  Examples of the pH adjuster include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, Examples thereof include sodium hydrogen carbonate.

  The buffer solution can reduce the pH fluctuation range of the aqueous ink composition, and can maintain the pH in a desired range. As the buffer solution, the same buffer solution as described in “1.1.3. Other components” can be used.

  Water-based ink compositions include additives such as fixing agents such as water-soluble rosin, antifungal agents and preservatives such as sodium benzoate, antioxidants such as allophanates and ultraviolet absorbers, chelating agents, and oxygen absorbers. Can be contained. These additives can be used alone or in combination of two or more.

The content of the organic solvent contained in the aqueous ink composition is preferably 50% by mass or more and more preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the water-based ink composition. When the content of the organic solvent is 50% by mass or more, generation of gas due to the reaction between the water-resistant metal pigment and water, corrosion of the water-resistant metal pigment, or the like may be reduced. Moreover, it is preferable from viewpoints of reduction of an environmental load etc. that content of an organic solvent is 80 mass% or less. Here, examples of the organic solvent include the above alkanediols, pyrrolidone derivatives and the like in addition to the organic solvents mentioned in the above-mentioned "1.1.3. Other components".

  The viscosity of the water-based ink composition at 20 ° C. is preferably 2 mPa · s or more and 10 mPa · s or less, and more preferably 3 mPa · s or more and 5 mPa · s or less. When the viscosity of the aqueous ink composition at 20 ° C. is within the above range, an appropriate amount of the aqueous ink composition is ejected from the nozzle, and the flight bending and scattering of the aqueous ink composition can be further reduced. It can be preferably used.

  The pH of the aqueous ink composition is preferably 5.0 or more and 8.5 or less, more preferably 6.0 or more and 8.5 or less, and particularly preferably 7.0 or more and 8.5 or less. preferable. When the pH of the aqueous ink composition is within the above range, the reaction between the water-resistant metal pigment and the aqueous medium can be suppressed, and the elution of the coating film and the metal pigment can be suppressed. Thereby, the water resistance of the water-based ink composition can be improved, and the storage stability can be improved.

  The use of the water-based ink composition is not particularly limited, and can be applied to, for example, a writing instrument, a stamp, a recorder, a pen plotter, and an ink jet recording apparatus.

4). EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

4.1. Water resistant aluminum pigment dispersion 4.1.1. Example 1
<Process (a)>
Resin comprising cellulose acetate butyrate (butylation rate of 35 to 39%, manufactured by Kanto Chemical Co., Ltd.) 3.0 mass% and propylene glycol (manufactured by Sankyo Chemical Co., Ltd.) 97 mass% on a PET film having a thickness of 100 μm. The layer coating solution was uniformly applied by a bar coating method and dried at 60 ° C. for 10 minutes to form a resin layer thin film on the PET film. Subsequently, an aluminum vapor deposition layer having an average film thickness of 20 nm was formed on the resin layer using a vacuum vapor deposition device (“VE-1010 type vacuum vapor deposition device”, manufactured by Vacuum Device Co., Ltd.). Next, the laminate formed by the above method is simultaneously peeled, refined, and dispersed in propylene glycol using a VS-150 ultrasonic disperser (manufactured by ASONE Co., Ltd.), and integrated ultrasonic dispersion treatment. An aluminum pigment dispersion having a time of 12 hours was prepared. The obtained aluminum pigment dispersion was filtered through a SUS mesh filter having an opening of 5 μm to remove coarse particles. The filtrate was then placed in a round bottom flask and propylene glycol was distilled off using a rotary evaporator. Thereby, the aluminum pigment dispersion was concentrated, and then the concentration of the aluminum pigment dispersion was adjusted to obtain a 5.0 mass% aluminum pigment dispersion.

<Step (b)>
Next, 20 parts by mass of the obtained aluminum pigment dispersion (containing 1 part by mass of aluminum pigment) was put into a beaker, and 2 parts by mass of tetraethoxysilane (TEOS) and 1 mol / L aqueous ammonia as a basic catalyst were added thereto. 0.4 parts by mass was added and hydrolytic condensation was carried out by stirring at room temperature for 30 days. Thus, an aluminum pigment dispersion containing an aluminum pigment (water resistant aluminum pigment) having a silica film formed on the surface thereof was obtained.

<Step (c)>
Subsequently, it was centrifuged (10,000 rpm, 60 minutes), and a part of the propylene glycol contained in the aluminum pigment dispersion which was the supernatant was removed.

<Step (d)>
Subsequently, ion-exchanged water and a surfactant (trade name “DISPERBYK-192”, manufactured by Big Chemie Japan Co., Ltd.) are added and stirred at room temperature for 1 day, whereby the water-resistant aluminum pigment dispersion according to Example 1 is obtained. Obtained. The ion-exchanged water and the surfactant are such that the composition of the water-resistant aluminum pigment dispersion is 5% by mass of the water-resistant aluminum pigment, 50% by mass of propylene glycol, 44% by mass of water, and 1% by mass of the surfactant. Added.

4.1.2. Examples 2-5, Comparative Examples 1-7
The water resistant aluminum pigment dispersions of Examples 2 to 5 and Comparative Examples 1 to 7 are described in Table 1 with the addition components, addition amount, and reaction time (synthesis period) in step (b) of Example 1. It was obtained in the same manner as in Example 1 except that the procedure was as described above.

  The water-resistant aluminum pigment dispersion according to Example 5 was obtained by performing aging (70 ° C., 3 days) of the water-resistant aluminum pigment dispersion after the step (d).

  Moreover, pH value of the water-resistant aluminum pigment dispersion liquid of Examples 1-5 and Comparative Examples 1-7 was prepared by adding a pH adjuster, and a pH meter (trade name “Portable PH Meter D-52S”, Measured using HORIBA, Ltd.

  The “polysilazane raw material” used in Comparative Example 3 is a trade name “AQUAMICA NN110” (monomer molecular weight 45) manufactured by Clariant.

4.1.3. Evaluation of properties <Particle size and thickness of aluminum pigment>
The particle diameter and thickness of the aluminum pigment contained in the aluminum pigment dispersion obtained in the step (a) were measured.

  Specifically, the particle diameter of the aluminum pigment is 50% average particle diameter of the equivalent circle diameter determined from the area of the projected image of the aluminum pigment particles using a flow particle image analyzer (FPIA-3000S manufactured by Sysmex Corporation). It was obtained by measuring R50. Moreover, the thickness of the aluminum pigment measured the average thickness Z by observing the cross section of a pigment particle using a scanning transmission electron microscope (STEM, Hitachi HD Technology Co., Ltd. "HD-2000").

  As a result of measurement as described above, all of the aluminum pigments used in Examples and Comparative Examples had a 50% average particle diameter R50 of 1.0 μm and an average thickness Z of 20 nm.

  In addition, due to the nature of aluminum, a natural oxide film may be formed on the surface. Therefore, the average thickness Z of the aluminum pigment includes the thickness of the natural oxide film.

<Thickness of coating film>
The thickness of the coating film (silica film) was measured by observing the cross section of the water-resistant aluminum pigment particles using a transmission electron microscope Tecnai G2f30 (manufactured by Philips). The thickness of the coating film is also shown in Table 1.

<Pinhole>
About the water resistant aluminum pigment contained in the obtained water resistant aluminum pigment dispersion, the number of pinholes was measured as follows.

  First, 0.1 g of the water resistant aluminum pigment contained in the obtained water resistant aluminum pigment dispersion was taken out and diluted to 1/2000 with 200 g of a mixed solvent of acetone and water (acetone: water = 1: 1), A water-resistant aluminum pigment was collected on a grid mesh with a support film and vacuum-dried. Then, using a transmission electron microscope equipped with an energy filter (trade name “Tecnai G2 F30”, manufactured by FEI, acceleration voltage 300 keV), water resistance of elements (Si and O) constituting the coating film (silica film) A mapping image (EELS map image) of an aluminum fluoride pigment was obtained. Based on the mapping image thus obtained, the number of pinholes having a diameter of 0.05 μm or more was counted.

The evaluation criteria for the number of pinholes in the water-resistant aluminum pigment are as follows. The evaluation results are also shown in Table 1.
“A”: 0 pinholes
“B”: 1 pinhole
"C": Number of pinholes is 2 or more

  Representative examples of the obtained mapping images are shown in FIGS. FIG. 1 is a mapping image of a water-resistant aluminum pigment according to Example 1, and is an image corresponding to the k edge of Si. FIG. 2 is a mapping image of the water-resistant aluminum pigment according to Example 2, and is an image corresponding to the k edge of Si. FIG. 3 is a mapping image of the water-resistant aluminum pigment according to Comparative Example 2, and is an image corresponding to the k edge of Si. FIG. 4 is a mapping image of a water-resistant aluminum pigment according to Comparative Example 3, an image corresponding to the k edge of O (FIG. 4A) and an image corresponding to the k edge of Si (FIG. 4B). ).

  Here, it may be difficult to determine the surface state with only the image corresponding to the k edge of Si. In such a case, the number of pinholes can be counted using an image corresponding to the k edge of O. This is because the silica film is made of Si and O, so that if the image corresponding to Si or O can be obtained, the surface state of the water-resistant aluminum pigment can be sufficiently judged.

<Parameters obtained by SEM-EDX>
About each obtained water-resistant aluminum pigment dispersion liquid, the parameter obtained by SEM-EDX was calculated | required as follows.

  First, any one of the obtained water-resistant aluminum pigment dispersions was dropped and applied to a PET film and vacuum-dried. Then, using an FE-SEM (trade name “FE-SEM S-4700”, manufactured by Hitachi High-Tech), an electron beam (acceleration voltage 15 kV, acceleration current 10 μA) is scanned on the surface of the sample to make secondary electrons. While obtaining a scanned image based on the selected area, a place where the water-resistant aluminum pigment was present over 1 μm square was selected, and X-rays emitted from the place were detected by EDX. The electron beam incident angle was 90 ° with respect to the sample surface, and the X-ray extraction angle was 35 °.

  In this way, the atomic number concentration of the elements (Al, O, Si) constituting the water resistant aluminum pigment was calculated based on the spectrum obtained from the X-ray intensity detected by EDX. In calculating the atomic number concentration, the overlap factor method was used for the peak separation method, and the standardless ZAF method was used for the quantitative correction method.

  R1, R2, R3, R2 / R1, and R2-R1 were calculated based on the atomic number concentration of each element thus obtained. Each value is shown together in Table 1.

4.1.4. Evaluation test <Evaluation of glossiness>
Any one of the obtained water-resistant aluminum pigment dispersions was dropped and applied to photographic paper ("PM photographic paper (glossy) model number: KA450PSK", manufactured by Seiko Epson Corporation) and dried at room temperature for 1 day. . The gloss of the water-resistant aluminum pigment was evaluated by visually observing the obtained sample. The evaluation criteria for the glossiness of the water-resistant aluminum pigment are as follows. The glossiness evaluation results are also shown in Table 1.
“A”: Good gloss (excellent metal gloss and specular gloss)
“B” —Slightly good gloss (excellent metal gloss but slightly matte)
“C”: poor gloss (not metallic gloss, blackish gray)

<Evaluation of dispersibility>
The water dispersibility was evaluated based on how much the water-resistant aluminum pigment dispersion liquid obtained above passed through a 10 μm filter (MITEX MEMBRANE FILTERS (model number: LCWPO4700) manufactured by MILIPORE). The evaluation criteria for dispersibility are as follows. The results of the dispersibility evaluation test are also shown in Table 1.
"A" ... Filter passage amount is 50mL or more "B" ... Filter passage amount is 30mL or more and less than 50mL "C" ... Filter passage amount is 10mL or more but less than 30mL "D" ... Filter passage is less than 10mL

<Evaluation of storage stability>
10 mL of the water-resistant aluminum pigment dispersion obtained above was added to the sample bottle, sealed, and allowed to stand at a constant temperature of 25 ° C. The storage stability of the water-resistant aluminum pigment dispersion was evaluated by visually observing the change with time. The evaluation criteria for storage stability are as follows. The results of the water resistance evaluation test are also shown in Table 1.
“AA” —no whitening and separation after 150 days “A” —no whitening and separation after 100 days “B” —whitening and separation after 30 days "C" ... Whitening or separation in less than 30 days

4.1.5. Evaluation results According to the results in Table 1, the water-resistant aluminum of Examples 1 to 5 having a pinhole containing a water-resistant aluminum pigment of 1 or less and having a pH in the range of 5.0 to 8.5. It was shown that the pigment dispersion is excellent in glossiness and water dispersibility, and particularly excellent in storage stability.

  On the other hand, since the water resistant aluminum pigment dispersions of Comparative Examples 1 to 3 and Comparative Example 5 had two or more pinholes, it was shown that storage stability was particularly lowered.

  Moreover, since the water-resistant aluminum pigment dispersion liquid of Comparative Example 4 used an aluminum pigment that did not form a coating film, it was shown that all of glossiness, water dispersibility, and storage stability were significantly reduced.

  It was shown that the storage stability of the water-resistant aluminum pigment dispersions of Comparative Examples 6 and 7 was significantly reduced because the pH was not in the range of 5.0 to 8.5. It is considered that the coating film or the metal pigment eluted with time due to the influence of pH.

4.2. Aqueous ink composition 4.2.1. Preparation of water-based ink composition Water-resistant aluminum pigment dispersion, 1,2-hexanediol, urethane resin (trade name “Rezamin D1060”, manufactured by Dainichi Seika Kogyo Co., Ltd.), propylene glycol, 2-Pyrrolidone, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant), triethanolamine, and ion-exchanged water were mixed and stirred.

<Composition of water-based ink composition>
Water resistant aluminum pigment dispersion (solid content) 1.5% by mass
1,2-hexanediol 5% by mass
Urethane resin 0.1% by mass
Propylene glycol 40% by mass
2-pyrrolidone 5% by mass
Olfin E1010 1% by mass
Triethanolamine 0.4% by mass
Ion exchange water Total remaining 100% by mass

  As the water resistant aluminum pigment dispersion, the water resistant aluminum pigment dispersion of Example 2 obtained above was used.

4.2.2. Evaluation Test An ink cartridge in which the above-described aqueous ink composition was filled in a dedicated cartridge of an inkjet printer PX-G930 (manufactured by Seiko Epson Corporation) was produced. Next, the obtained ink cartridge was attached to the black row of the inkjet printer PX-G930, and a commercially available ink cartridge was attached to the other nozzles. A commercially available cartridge mounted in a place other than the black row is used as a dummy and is not used in the evaluation of this embodiment, and thus does not contribute to the effects of the present invention.

  Next, the above-described aqueous ink composition mounted in a black row was discharged using the above-described printer, and the discharge stability was evaluated by visually checking the discharge state.

4.2.3. Evaluation Results It was confirmed that the above water-based ink composition can be ejected from the printer nozzles without any problem.

4.3. Reference Evaluation As described above, in JP2011-132483A, surface analysis (elemental analysis) of a water-resistant aluminum pigment using XPS is performed. Therefore, in the reference evaluation, it was verified whether or not the change in the quality of the coating film due to the difference in the amount of TEOS charged could be judged by elemental analysis using XPS.

  Specifically, silica polymer A obtained by hydrolytic condensation of 1 g of TEOS, silica polymer B obtained by hydrolytic condensation of 4 g of TEOS, and obtained by hydrolytic condensation of 8 g of TEOS. A silica polymer C was prepared. Next, each silica polymer was fixed on an In foil to obtain a measurement sample. The obtained measurement sample was fixed to a sample stage of an X-ray photoelectron spectrometer (trade name “Quantum 2000”, manufactured by ULVAC-PHI), and elemental analysis of each silica polymer was performed under the following measurement conditions.

<XPS measurement conditions>
-X-ray light source: Monochromatic Al-Kα ray-X-ray irradiation angle: 90 °
・ Measurement elements: C1s, O1s, Si2p

  Table 2 shows the element concentrations of the elements (C, O, Si) contained in the silica polymers A to C thus obtained.

  As a result of Table 2, there was almost no difference in the composition ratio of the elements constituting the silica polymer between the silica polymers. From this, it can be said that the difference in film properties (for example, the presence or absence of pinholes, etc.) cannot be detected even if elemental analysis by XPS is performed.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (8)

A water-resistant metal pigment dispersion in which a water-resistant metal pigment whose surface is coated with a film containing an inorganic oxide is dispersed in an aqueous medium,
The metal pigment has an average thickness of 10 nm or more and less than 50 nm, and a 50% average particle size of 0.5 μm or more and 3 μm or less,
The shape of the pigment particles constituting the metal pigment is a flat plate shape,
When a mapping image of the water-resistant metal pigment was obtained for the elements constituting the inorganic oxide by a transmission electron microscope,
The number of pinholes observed from the mapping image is 1 or less per pigment particle,
pH is 5.0 or 8.5 Ri der below,
The metal pigment is an aluminum pigment,
The water-resistant metal pigment dispersion liquid , wherein the inorganic oxide is silicon oxide . In claim 1,
The average thickness of the film containing the inorganic oxide is a water resistant metal pigment dispersion having a thickness of 3 nm to 20 nm. In claim 1 or claim 2 ,
The water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, the atomic concentration of Al and O is calculated using energy dispersive X-ray spectroscopy, and the atomic concentration of _Al (M1 _Al ) and the ratio of the O of atomic concentration (M1 _O) a _(M1 O / _{M1 Al)} in case of the R1,
The water-resistant metal pigment dispersion, wherein R1 is 1.2 or less. In claim 3 ,
After heating the water-resistant metal pigment at a temperature of 70 ° C. for 6 days, the heated water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, and Al is dispersed using energy dispersive X-ray spectroscopy. and to calculate the atomic concentration of O, when the ratio of the atomic concentration of Al _{(M2 Al)} and O of atomic concentration (M2 _O) a _{(M2 O / M2 Al) R2} ,
A water resistant metal pigment dispersion, wherein the ratio of R1 to R2 (R2 / R1) is 3.0 or less. In claim 4 ,
The water-resistant metal pigment dispersion, wherein the difference between R1 and R2 (R2-R1) is 1.5 or less. In any one of Claims 1 thru | or 5 ,
The water-resistant metal pigment is irradiated with an electron beam using a scanning electron microscope, the atomic concentration of Al and Si is calculated using energy dispersive X-ray spectroscopy, and the atomic concentration of _Al (M3 _Al ) and the ratio of the atomic concentration of Si _{(M3 Si)} to _(M3 Si / M3 _Al) in case of the R3,
A water-resistant metal pigment dispersion in which R3 is more than 0.1 and 0.5 or less. In any one of Claims 1 thru | or 6 ,
The film containing an inorganic oxide is a water resistant metal pigment dispersion formed by using tetraethoxysilane in an amount of 0.8 parts by mass or more based on 1 part by mass of the aluminum pigment . An aqueous ink composition comprising the water-resistant metal pigment dispersion according to any one of claims 1 to 7 .