JP2016156006A - Inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet ink which contains a metallic pigment excellent in brightness, and also in water proofness, chemical resistance, and weatherproofness, with little color change or color fading under high temperature and high pressure, and durable at outdoor use for a long period of time, and which is insusceptible to electric charge from a pressure element of an inkjet head.SOLUTION: The inkjet ink is provided which includes a nonconductive metal pigment having an average particle size of 0.4 to less than 0.95 μm, a resin, and a solvent, and in which the surface of the nonconductive metal pigment is coated with an alkoxide containing an organoalkoxysilane having a structure represented by formula (2a) and formula (2b) and a coating film has a crosslinked structure. R-Si-(OR)... (2a) (Ris a monovalent group having a (meth)acryl group, Ris a monovalent C1-4 alkyl group). R-Si-(OR).... (2b) (Ris a glycidoxy group, or a monovalent group having a C5-6 epoxycycloalkyl group functional group, and Ris a monovalent C1-4 alkyl group).SELECTED DRAWING: None

Description

  The present embodiment relates to an ink used for an ink jet recording apparatus, particularly an ink containing a metal pigment that can be suitably used for an apparatus employing a piezo method.

2. Description of the Related Art As an ink jet head of an ink jet recording apparatus, those employing various ejection methods are known. For example, in a piezo ink jet head, ink is ejected by electrical vibration of a piezoelectric element in an ink chamber.
In the piezo method, the electric charge necessary for ink ejection is given to the piezoelectric element. Therefore, an ink containing a highly conductive pigment such as a metal powder represented by metallic ink is affected by the electric charge, and the ink is normal. In some cases, the piezoelectric element itself cannot be ejected or the piezoelectric element itself is destroyed by energizing the ink.

  On the other hand, brightness is required for a pigment made of a metal blended in a metallic ink or the like. However, for example, a pigment made of a metal mainly composed of aluminum has a drawback in that it easily reacts with moisture in the atmosphere, resulting in a decrease in metallic luster, discoloration, and generation of hydrogen gas. As a solution to this drawback, there is known a surface-coated aluminum pigment having water resistance and the like while maintaining the luminance by coating the aluminum surface with a coating containing alkoxysilane as a main component.

Japanese Patent No. 4358897

  In view of the above-mentioned problems of the prior art, the object of the present invention is excellent in brightness, excellent in water resistance, chemical resistance, weather resistance, etc., has little discoloration / discoloration even under high temperature and high pressure, and is used outdoors for a long time. In addition to providing an ink containing a metal pigment that can withstand the above, an ink for inkjet including a metal pigment that is not affected by the electric charge of the pressure element of the inkjet head is provided.

  As a result of intensive studies in view of the above-mentioned problems, the inventors of the present invention coat the surface of a pigment made of metal (hereinafter referred to as “metal pigment”) with a dense continuous film containing alkoxide containing Si as a main component. Thus, it has been found that the conductivity of the metal pigment can be significantly reduced while maintaining the metallic luster, and the present invention has been completed.

That is, the ink-jet ink of the present embodiment includes a non-conductive metal pigment having an average particle size of 0.4 μm or more and less than 0.95 μm, a resin, and a solvent. It is coated with an alkoxide containing an organoalkoxysilane having a structure represented by the formula (2a) and an organoalkoxysilane having a structure represented by the following general formula (2b), and the film has a crosslinked structure, and is obtained by printing. The glossiness of printing at an incident angle of 20 ° with respect to a medium is 352 or more and 435 or less, the average number of print missing at ± 2 V is 0.2 or more and 2 or less, and the fixing property of printing is partially printed in the friction fastness test. It is characterized by disappearing.

  The ink-jet ink of the present embodiment is characterized in that the alkoxide includes a metal alkoxide represented by the following general formula (3).

Hereinafter, the configuration of the inkjet ink according to the present embodiment will be described in detail.
The ink-jet ink according to this embodiment is an ink containing a non-conductive metal pigment, a resin, and a solvent, and a film having a crosslinked structure is formed on the surface of the non-conductive metal pigment by an alkoxide containing alkoxysilane. ing. The metal pigment applied to the ink according to the present embodiment is particularly useful for a metal pigment that has poor environmental resistance such as water resistance and easily lowers the metallic luster.

In general, alkoxysilane is modified by a chemical reaction with a compound having active hydrogen. Since the alkoxysilane is stable in a solution that does not have active hydrogen, the alkoxysilane is selectively adsorbed on the metal surface, and the hydroxyl group and adsorbed water bonded directly to the metal atom on the metal surface are used as a starting point for mild dealcoholization. It is considered that the reaction proceeds, the alkoxysilane reacts with the metal surface, the reaction product repeats three-dimensional crosslinking, and the obtained three-dimensional crosslinked product forms a dense and uniform film on the metal pigment surface.
Therefore, it is considered that the metal pigment on which the coating film is formed is less likely to reduce the original luminance of the metal pigment and can reduce the surface activity.

[Non-conductive metal pigment]
The non-conductive metal pigment according to the present embodiment has an organic surface having at least an alkoxysilane represented by the general formula (1) or an organoalkoxysilane represented by the general formula (2) on the surface of the metal pigment. It can be obtained by treatment in a treatment solution containing a solvent and a dealcoholization catalyst as essential components.

  In this embodiment, an aluminum pigment mainly composed of aluminum is used as the metal pigment. The aluminum pigment to be used is not particularly limited, but it covers aluminum fine powder that has been spread by a known method to form a flaky shape, or a vapor-deposited aluminum foil that has been crushed into a flaky shape. When the subsequent pigment is powdered to make it fine, it breaks in the direction of thinner thickness, which is preferable because the decrease in coverage can be suppressed as much as possible. In particular, the vapor-deposited aluminum foil flakes are preferable because the surface is smooth and high brightness can be obtained, and the thickness is as very thin as 0.1 μm or less.

As such an aluminum pigment, for example, a paste having a solid content of 10 to 80% by mass with a hydrocarbon solvent such as mineral spirit or xylene or an ester solvent such as ethyl acetate or isopropyl acetate is used. can do. Examples of commercially available products include aluminum paste 5660NS (manufactured by Toyo Aluminum Co., Ltd .; trade name), METASHEEN 71-0010 (manufactured by Ciba Japan; trade name), and SILVERSHINE P-4100 (manufactured by Big Chemie Japan Co., Ltd .; trade name). Can do.
In addition, when it is set as the ink containing a metal pigment, it is difficult to grind | pulverize the average particle diameter of a metal pigment to 0.4 micrometer or less. In the present embodiment, the average particle diameter of the metal pigment is preferably in the range of 0.4 μm to 1.5 μm.

(Compound represented by the general formula (1))
Examples of the alkoxysilane represented by the following general formula (1) used in the present embodiment include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and condensates thereof (n is 2 or more). be able to. These can be used alone or in admixture of two or more. In addition, although a compound having 5 or more carbon atoms in the alkyl group (R) in the general formula (1) is also known, a compound having 5 or more carbon atoms has a slow condensation reaction on the surface of the metal pigment and is not practical.

（式中、Ｒは炭素数１〜４のアルキル基を、ｎは１〜２０の数を表す。）

(In the formula, R represents an alkyl group having 1 to 4 carbon atoms, and n represents a number of 1 to 20).

(Compound represented by the general formula (2))
The organoalkoxysilane represented by the following general formula (2) used in the present embodiment co-condenses with the alkoxysilane represented by the general formula (1) on the surface of the metal pigment, and becomes a constituent component of the coating layer. When various resin (binder) is mix | blended as ink, adhesiveness with resin (binder) can be improved with the organic functional group contained. Further, the organoalkoxysilane represented by the general formula (2) may be used alone.

（式中、Ｒ^１は水素原子、アルキル基、アルケニル基、グリシドキシ基、炭素数５または６のエポキシシクロアルキル基、（メタ）アクリル基、アミノ基、メルカプト基およびイソシアネート基から選ばれる官能基を有する１価の基を、Ｒ^２は、炭素数１〜４のアルキル基およびフェニル基から選ばれる基を、Ｒ^３は１価の炭素数１〜４のアルキル基を、ａは０、１または２を表す。）

(Wherein R ¹ represents a functional group selected from a hydrogen atom, an alkyl group, an alkenyl group, a glycidoxy group, an epoxycycloalkyl group having 5 or 6 carbon atoms, a (meth) acryl group, an amino group, a mercapto group, and an isocyanate group). R ² is a group selected from an alkyl group having 1 to 4 carbon atoms and a phenyl group, R ³ is a monovalent alkyl group having 1 to 4 carbon atoms, and a is 0, 1 or 2)

  For this reason, the organoalkoxysilane represented by the general formula (2) may be appropriately selected depending on the resin (binder) to be used and is not particularly limited. Ethoxysilane, tripropoxysilane, methyldimethoxysilane, methyldiethoxysilane, dimethylmethoxysilane, dimethylethoxysilane, dimethylpropoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, hexyltripropoxysilane, vinyltrimethoxysilane, vinyltri Ethoxysilane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, allyldimethylmethoxysilane, allyldimethylethoxysilane 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, 2- (3,4-epoxycyclohexyl) Ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryl Roxypropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- Aminopropyl Examples thereof include triethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane. These can be used alone or in admixture of two or more.

（式中、ＭはＴｉ、ＺｒまたはＡｌの原子を、Ｒ^４は炭素数１〜１０のアルキル基を、ｂは０または１を、ｎは１〜２０の数を表す。） (Compound of general formula (3))
The metal alkoxide represented by the following general formula (3) used in the present embodiment is copolymerized with the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2), or Ternary co-condensation with the alkoxysilane represented by the formula (1) and the organoalkoxysilane represented by the general formula (2), and the resulting metal pigments have improved environmental resistance such as weather resistance, acid resistance, alkali resistance, and salt water resistance. Is added for the purpose.

(In the formula, M represents an atom of Ti, Zr or Al, R ⁴ represents an alkyl group having 1 to 10 carbon atoms, b represents 0 or 1, and n represents a number of 1 to 20).

  Depending on the amount of the metal alkoxide represented by the general formula (3), the hue of the metal pigment is changed. Accordingly, the metal alkoxide represented by the general formula (3) can be used for the purpose of coloring at the same time as the coating of the metal pigment. Furthermore, the metal alkoxide represented by the general formula (3) has high activity and acts as a condensation catalyst (dealcoholization catalyst) for the alkoxysilane represented by the general formula (1) and the organoalkoxysilane represented by the general formula (2). To do. The condensation catalyst (dealcoholization catalyst) will be described later.

  Specific examples of the metal alkoxide represented by the general formula (3) include aluminum triisopropylate, aluminum triethylate, aluminum tributyrate, monobutoxyaluminum diisopropylate, titanium tetraisopropoxide, and titanium tetrabutoxide. , Titanium butoxide dimer, titanium tetra-2-ethylhexoxide, zirconium tetrapropoxide, zirconium tetrabutoxide and the like.

(Organic solvent without active hydrogen)
The surface coating in this embodiment is preferably performed in a state where the metal pigment is diluted with an organic solvent, stirred, and dispersed. When organic solvents with active hydrogen such as water, alcohols, primary amines, secondary amines, thiols, and carboxylic acids are used as the solvent to be diluted, surface corrosion of metal pigments and coating components Since it reacts with the alkoxides represented by the general formulas (1), (2) and (3), the dealcohol condensation reaction is inhibited, and the reaction rate is remarkably reduced.

  Therefore, it is necessary to use an organic solvent having no active hydrogen as the organic solvent used in this embodiment. Specific examples include aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, organic acid esters, ethers, ketones, and the like. Are preferred.

  Examples of organic acid esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate, 3- Acetic esters such as methyl-3-methoxybutyl acetate are easily available and suitable. Among these, water-soluble esters such as propylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate are preferable because the reaction mixture can be immediately used for both oil-based inks and water-based inks.

(Dealcoholation catalyst)
The dealcoholization condensation reaction of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2) proceeds even without a catalyst, but the reaction is usually slow and not practical. The dealcoholization catalyst used in the present embodiment is added to accelerate the dealcoholization condensation reaction of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2). .

  Examples of the dealcoholization catalyst include metal salts of carboxylic acids such as alkyl titanates and tin octylates, amine salts such as dimethylamine acetate, quaternary ammonium salts such as tetraamine ammonium acetate, and tetramethylpentamine. Amines, amine-based silane coupling agents such as N-β-aminoethyl-γ-aminopropyltrimethoxysilane, acids such as p-toluenesulfonic acid, aluminum alkoxides such as aluminum ethoxide, aluminum ethyl acetoacetate diisopropyl Aluminum chelates such as rate, titanium alkoxides such as titanium tetrapropoxide, titanium chelates such as titanium diisopropoxybis (acetylacetonate), zirconies such as zirconium tetrapropoxide And zirconium chelates such as um alkoxide and zirconium tetraacetylacetonate.

  Among these, since the catalyst itself becomes a component of the coating layer (coating) of the metal pigment after the reaction is completed, aluminum alkoxide such as aluminum ethoxide, aluminum chelate such as aluminum ethyl acetoacetate diisopropylate, titanium tetrapropoxy, etc. Metal compounds such as titanium alkoxides such as titanium, titanium chelates such as titanium diisopropoxybis (acetylacetonate), zirconium alkoxides such as zirconium tetrapropoxide, and zirconium chelates such as zirconium tetraacetylacetonate are preferred. In particular, aluminum alkoxides, titanium alkoxides, and zirconium alkoxides, which are metal alkoxides represented by the general formula (3), are preferable because they act as a condensation catalyst and can impart acid resistance, alkali resistance, and the like to the coating.

[Surface coating treatment]
The surface coating treatment includes the above-described components, that is, a metal pigment, an alkoxysilane represented by the general formula (1) or an organoalkoxysilane represented by the general formula (2), an organic solvent having no active hydrogen, Mix with alcohol catalyst. The method of mixing is not particularly limited. For example, a treatment solution is first prepared, and a metal pigment is added to the solution, followed by stirring and mixing to perform a reaction as a reaction mixture.

  The concentration of the metal pigment in the reaction mixture is usually preferably 1 to 40% by mass. If the concentration is too low, it is uneconomical, and if the concentration is too high, the uniformity of the reaction may decrease. The amount of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2) is preferably 5 to 50 parts by mass per 100 parts by mass of the metal pigment. If the amount of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2) is too small, the coating of the metal pigment may be insufficient. On the other hand, if the amount used is too large, it is uneconomical and the brightness of the product obtained may be reduced.

  When the alkoxysilane represented by the general formula (1) and the alkoxysilane represented by the general formula (2) are used in combination, the total amount used is 5 to 50 parts by mass per 100 parts by mass of the metal pigment as described above. . The compounding ratio of the alkoxysilane represented by the general formula (1) and the organoalkoxysilane represented by the general formula (2) is represented by the general formula (2) per 100 parts by mass of the alkoxysilane represented by the general formula (1). When the organoalkoxysilane is in the range of 5 to 200 parts by mass and the amount of the organoalkoxysilane represented by the general formula (2) is too small, the adhesion with the resin (binder) is not remarkable, and on the other hand, when the amount is too large. The strength of the coating is reduced, and the water resistance and chemical resistance of the metal pigment are insufficient.

  Moreover, in addition to the alkoxysilane represented by the general formula (1) and the organoalkoxysilane represented by the general formula (2), the metal alkoxide represented by the general formula (3) is used in combination, thereby providing chemical resistance, particularly acid resistance. The effect of improving alkali resistance can be obtained. By using a metal alkoxide represented by the general formula (3) in combination, an alkoxysilane represented by the general formula (1) or a cocondensate with an organoalkoxysilane represented by the general formula (2), or the general formula (1) A metal pigment coated with a ternary cocondensate with an alkoxysilane represented by the general formula (2) and an organoalkoxysilane represented by the general formula (2) is obtained.

  The alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2), or the alkoxysilane represented by the general formula (1) and the organoalkoxysilane represented by the general formula (2) and the general formula ( When the metal alkoxide represented by 3) is used in combination, the total amount used is 5 to 50 parts by mass per 100 parts by mass of the metal pigment as described above. The compounding ratio of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2) and the metal alkoxide represented by the general formula (3) is the alkoxysilane represented by the general formula (1) or the general When the amount of the metal alkoxide represented by the general formula (3) is too small in the range of 1 to 50 parts by mass per 100 parts by mass of the organoalkoxysilane represented by the formula (2), the above effect is not remarkable. If the amount is too large, the film formation reaction becomes non-uniform.

  The used amount of the dealcoholization catalyst is preferably 0.1 to 5 parts by mass per 100 parts by mass of the alkoxysilane represented by the general formula (1) or the organoalkoxysilane represented by the general formula (2). If the amount of the dealcoholization catalyst is too small, it takes a long time for the reaction, which is uneconomical. On the other hand, if the amount is too large, the reaction is not particularly advantageous. The reaction temperature is preferably 40 ° C to 90 ° C. If the reaction temperature is too low, it takes a long time for the reaction, which is uneconomical. There is.

  The coating reaction of this embodiment is generally slow and usually 4 to 8 hours, although it varies depending on the reaction temperature. If the reaction time is too short, the condensation reaction of the alkoxide may be insufficient, and the durability of the resulting coating may be insufficient. On the other hand, if the reaction time is too long, it is uneconomical. These reactions can be performed at normal pressure in an air atmosphere or an inert gas atmosphere such as nitrogen gas. In order to complete the reaction and to obtain a dense and uniform film, it is preferable to age for 7 to 30 days after completion of the reaction at an arbitrary temperature, preferably 15 to 30 ° C.

  Further, after completion of the reaction, preferably after aging, the reaction mixture is filtered off and stored in the state of the paste as it is, and it is preferable to use it as an ink component. It may be dried after washing with a low boiling point solvent.

  By performing such a coating treatment, the metal pigment can be converted into an alkoxysilane represented by the general formula (1) or a condensate of an organoalkoxysilane represented by the general formula (2), an alkoxysilane represented by the general formula (1), and Cocondensate with organoalkoxysilane represented by general formula (2), alkoxysilane represented by general formula (1) or organoalkoxysilane represented by general formula (2) and metal alkoxide represented by general formula (3) Or a ternary cocondensate of an alkoxysilane represented by general formula (1), an organoalkoxysilane represented by general formula (2) and a metal alkoxide represented by general formula (3) Is coated. These coatings are not just aggregates of silica fine particles, but are transparent (co) condensates of the above-mentioned dense compounds, so that the resulting metal pigment has excellent brightness and chemical resistance such as water resistance, acid resistance, and alkali resistance. In addition to being excellent in properties, it is less likely to discolor or fade even at high temperatures and high humidity, can withstand long-term outdoor use, and is useful as a raw material for metallic inks that require metallic luster. Further, since the electrical conductivity of the metal pigment can be greatly reduced by coating with the above film, it is particularly useful as a raw material for piezo ink jet ink.

[Preparation of inkjet ink]
The ink-jet ink according to this embodiment can be prepared by adding a solvent to the metal pigment that has been subjected to the above-described surface treatment, stirring, adding a resin, and stirring. In addition, you may add a dispersing agent as needed.

(solvent)
The non-conductive metal pigment according to the present embodiment is resistant to corrosion of the surface of the metal pigment in the ink and has good stability over time. Therefore, the solvent used in the inkjet ink is not particularly limited, but may cause corrosion. It is preferred to use a solvent without any. Examples of such a solvent include a solvent having no active hydrogen, and specific examples include aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, organic acid esters, ethers, and ketones. Although organic acid esters are preferable from the viewpoints of safety and solubility such as alkoxysilane, specifically, for example, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol mono Acetic esters such as ethyl ether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate, and 3-methyl-3-methoxybutyl acetate are easily available and suitable. Furthermore, water-soluble esters such as propylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate are preferable because the reaction mixture can be used immediately for any of oil-based paints and inks and water-based paints and inks.

(Resin (polymer))
The resin used for the ink-jet ink of the present embodiment is not particularly limited as long as it is dissolved or dispersed in the solvent mixed in the ink. Specific examples include acrylic resin, polyester resin, phenol resin, polyamide, polyvinyl butyral, cellulose acetate butyrate, nitrocellulose resin, polyurethane, and vinyl chloride-vinyl acetate copolymer. These can be used alone or in admixture of two or more. The type of resin may be selected depending on the type of medium.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, of course, this invention is not limited to the following Example. In the following, “parts” and “%” are based on mass unless otherwise specified.

[Example of surface coated aluminum pigment (non-conductive metal pigment)]
In a 500 ml round bottom flask equipped with a stirrer and a condenser, 100 parts of aluminum paste (METASHEEN 71-0010), 100 parts of propylene glycol monomethyl ether acetate, and 2 parts of 3-glycidoxypropyltrimethoxysilane were stirred and mixed. Tetrabutoxide 0.1 part was added, and it stirred at 60 degreeC for 5 hours with the hot water bath. After cooling to room temperature, the solution was transferred to a glass bottle, sealed, and allowed to stand for 20 days to obtain a surface-coated aluminum pigment paste having an aluminum concentration of 5%. A part of the obtained paste was taken, dried at 150 ° C. for 2 hours, and observed with an electron microscope. The surface of the aluminum pigment particles was coated with a transparent condensate of 3-glycidoxypropyltrimethoxysilane and was uniformly flat. there were.
In addition, about the average particle diameter of the obtained pigment, it measured by laser diffraction type particle size distribution measurement (SALD-7000 by Shimadzu Corp.).
(Conductivity measurement test)
A 1% aluminum slurry MIBK solution was prepared using an aluminum pigment surface-coated in accordance with the above preparation example, spray-coated on an acrylic plate (100 × 100 mm), and the surface resistance after drying (Mitsubishi Chemical Analytech Co., Ltd .; Hiresta- up MCP-HT450; Measurement range 10 ⁴ to 10 ¹³ Ω). The measurement results are shown in Table 1.

As shown in Table 1, it can be seen that the electrical conductivity of the aluminum pigment coated on the aluminum surface with a continuous coating containing an alkoxide containing alkoxysilane as a component is as low as 1 × 10 ⁻¹³ (Ω · cm) ⁻¹ .

[Examples 1 to 3, Reference Examples 1 to 17]
After applying the coating treatment to the aluminum pigment by changing the addition amount and type of alkoxysilane by the method shown in the above preparation example, after adding an organic solvent and an appropriate amount of dispersant and stirring, further adding resin and stirring. Inkjet inks of Examples 1 to 3 and Reference Examples 1 to 17 were prepared. The blending ratio of each component of Examples 1 to 3 and Reference Examples 1 to 17 is shown in Tables 2 to 4 below.
[Comparative Examples 1 and 2]
Ink jet inks of Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that an aluminum pigment not subjected to coating treatment was used. The blending ratio of each component of Comparative Example 1 and Comparative Example 2 is shown in Table 4 below.

[Evaluation of inkjet ink]
Evaluation with an ink jet recording apparatus was carried out as follows, paying attention to the relationship between the type of alkoxysilane used in the surface-coated aluminum pigment, the image quality on the media obtained by printing, and the glossiness.

Glossiness and fixability on the print media (glossy paper manufactured by Mitsubishi Paper Industries) printed using the inks of Examples 1 to 3, Reference Examples 1 to 17, Comparative Examples 1 and 2 prepared above. In addition, the number of missing prints was evaluated. Tables 2 to 4 show the evaluation results of the organoalkoxysilanes by R1 functional group. The evaluation test is as follows.
(Glossiness measurement)
The glossiness at an incident angle of 20 ° was measured using a PG-1M glossiness meter (manufactured by Nippon Denshoku Industries Co., Ltd.).

(Measurement of fixability)
A frictional fastness tester (manufactured by Daiei Chemical Seiki Co., Ltd .; NR-100 type Rubbing Tester) subjected to a load of 500 g was reciprocated five times to observe printing defects. The friction material used was a Pita pad manufactured by Daitanic. The judgment criteria are as follows.
1; The printed part of the rubbed part disappears completely 3; The printed part disappears partially 5; The printed part does not disappear at all

(Number of missing prints)
Average number at ± 2V:
Measure the print omission when applying 5 levels of voltage: a voltage for discharging 42 pl of ink (predetermined voltage), a voltage set to ± 2 V for the predetermined voltage, and a voltage set to ± 1 V for the predetermined voltage, The average number was calculated.
Average number of 10 continuous prints of 0V:
The printing failure of 10 consecutive sheets when a voltage (predetermined voltage) for ejecting 42 pl of ink was applied was measured, and the average number was calculated.

［備考］
＊１：アルミニウム顔料表面を被覆する最小量を１とした場合の倍数値

[Remarks]
* 1: Multiple value when the minimum amount covering the aluminum pigment surface is 1.

［備考］
＊１：アルミニウム顔料表面を被覆する最小量を１とした場合の倍数値

[Remarks]
* 1: Multiple value when the minimum amount covering the aluminum pigment surface is 1.

［備考］
＊１：アルミニウム顔料表面を被覆する最小値を１とした場合の倍数値

[Remarks]
* 1: Multiple value when the minimum value covering the surface of the aluminum pigment is 1.

  From the evaluation results of Tables 2 to 4, in Examples 1 to 3 and Reference Examples 1 to 17 using the surface-coated aluminum pigment according to this embodiment, printing by the ink jet recording apparatus is possible. On the other hand, it can be seen that Comparative Example 1 and Comparative Example 2 using an aluminum pigment with no surface coating are affected by the charge of the pressure element of the ink jet head and cannot be printed by the ink jet recording apparatus.

  Further, in the examples, when the average particle size of the pigment is larger than 1.5 μm, printing omission tends to increase and glossiness tends to decrease, but it can sufficiently withstand printing by the ink jet recording apparatus. there were.

  In addition, in comparison with the examples in which diethylene glycol monomethyl ether was formulated as a solvent, the examples in which 2- [2- (2-ethylhexyloxy) ethoxy] ethanol, propylene glycol monomethyl ether acetate and diethyl diglycol were formulated were fixed. It was good. Further, in the examples in which 2- [2- (2-ethylhexyloxy) ethoxy] ethanol, propylene glycol monomethyl ether acetate, and diethyl diglycol were formulated, the fixing property was improved as the amount of the polymer added was increased.

In addition, when the R ¹ functional group of the organoalkoxysilane was an acrylic, epoxy, or acrylic / epoxy combination, good results with few missing prints were obtained. Furthermore, the R ¹ functional group of the organoalkoxysilane is preferably used in combination with acrylic or acrylic / epoxy, and the amount of alkoxysilane added to the aluminum pigment is 1.2, which is better than 2.

Claims (8)

A non-conductive metal pigment having an average particle size of 0.4 μm or more and less than 0.95 μm, a resin, and a solvent;
The surface of the nonconductive metal pigment is coated with an alkoxide containing an organoalkoxysilane having a structure represented by the following general formula (2a) and an organoalkoxysilane having a structure represented by the following general formula (2b). Has a cross-linked structure,
The gloss of the print at an incident angle of 20 ° with respect to the media obtained by printing is 352 or more and 435 or less, the average number of print missing at ± 2 V is 0.2 or more and 2 or less, and the fixability of the print is in the friction fastness test. An ink-jet ink characterized in that the printing is partially erased.

The inkjet ink according to claim 1, wherein the alkoxide further includes a metal alkoxide represented by the following general formula (3).

(In the formula, M represents an atom of Ti, Zr or Al, R ⁴ represents an alkyl group having 1 to 10 carbon atoms, b represents 0 or 1, and n represents a number of 1 to 20). 2. The ink-jet ink according to claim 1, wherein the non-conductive metal pigment has a conductivity of 10 ⁻¹³ (Ω · cm) ⁻¹ or less.   2. The inkjet ink according to claim 1, wherein the addition amount of the alkoxide is 1 to 3 times when the minimum amount covering the surface of the metal pigment is 1.   The solvent is an organic solvent having no active hydrogen, and is at least one organic solvent selected from aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, organic acid esters, ethers, and ketones. Item 10. The inkjet ink according to Item 1.   The resin is at least one selected from acrylic resin, polyester resin, phenol resin, polyamide, polyvinyl butyral, cellulose acetate butyrate, nitrocellulose resin, polyurethane, vinyl chloride-vinyl acetate copolymer, and resin emulsion thereof. The inkjet ink according to claim 1.   The inkjet ink according to claim 1, wherein the non-conductive metal pigment is a metal mainly composed of aluminum.   The inkjet ink according to claim 1, wherein the non-conductive metal pigment has a scale shape.