JP7175850B2 - silver ink composition - Google Patents

Description

The present invention relates to silver ink compositions.

The inkjet printing method does not require platemaking during printing, and is therefore suitable for producing a wide variety of printed matter. However, in the inkjet printing method, it is difficult to express a highly glossy (light-reflecting) silver color on a printing object. One of the reasons for this is that the ink jet printing method requires a very small amount of ink to be ejected from the print head. This is because there are significant restrictions on bright pigments such as silver.

As an ink capable of solving such problems, a silver ink composition containing an organic silver compound instead of a bright pigment has been disclosed (see Patent Document 1). When this silver ink composition is used for printing by an inkjet printing method, the organic silver compound is decomposed by heating to form metallic silver on the object to be printed, resulting in a highly glossy silver color. of printing patterns can be formed.

However, when this silver ink composition is used, it is desirable to heat-treat the silver ink composition at a temperature of 100° C. or higher in order to form metallic silver with high glossiness. There is a problem that the constituent materials of the object are limited to those having heat resistance.

On the other hand, there is disclosed a silver ink composition capable of forming a highly glossy silver-containing material without heat treatment (see Patent Document 2). This silver ink composition contains an ultraviolet curable resin and a silver compound, and can form a cured product of the ultraviolet curable resin and a silver-containing material containing metallic silver by ultraviolet irradiation treatment.

JP 2018-59058 A Japanese Patent Application Publication No. 2018-518399

However, the silver ink composition disclosed in Patent Document 2 is said to be applicable to various printing methods without being limited to the inkjet printing method. is not. And when this silver ink composition is actually applied to the inkjet printing method, it may be difficult to handle due to the poor handling property, and it may be difficult to form a silver-containing material. There is a problem that the formation aptitude of the object is not sufficient.

The present invention has been made in view of the above circumstances, and provides a silver ink composition that is applicable to inkjet printing and capable of forming a highly glossy silver-containing material without heat treatment. is the subject.

The present invention is a silver ink composition, wherein the silver ink composition contains silver nitrate, an energy ray-curable compound, and a solvent, and the total amount of the silver ink composition in the silver ink composition is C1 is the ratio of the content of silver in the silver nitrate to the mass, and _C2 is the ratio of the content of the energy ray _- curable compound to the total mass of the silver ink composition in the silver ink composition. Then, a silver ink composition is provided in which C ₁ is 8 mass % or more and less than 12 mass % and C ₁ /C ₂ is 0.3 or more and less than 1.4.
The silver ink composition of the present invention preferably contains an alcohol as the solvent. The silver ink composition of the present invention further contains a photopolymerization initiator. A content ratio _C4 of the photopolymerization initiator with respect to the total mass may be 9% by mass or more.

ADVANTAGE OF THE INVENTION According to this invention, the silver ink composition which is applicable to the inkjet printing method and can form a highly glossy silver-containing material without heat-processing is provided.

<<Silver Ink Composition>>
A silver ink composition according to one embodiment of the present invention contains silver nitrate, an energy ray-curable compound, and a solvent, and the ratio of silver nitrate to the total mass of the silver ink composition in the silver ink composition C ₁ is the content ratio of silver in the silver ink composition, and C ₂ is the content ratio of the energy ray _- curable compound with respect to the total mass of the silver ink composition in the silver ink composition. is 8% by mass or more and less than 12% by mass, and C ₁ /C ₂ is 0.3 or more and less than 1.4.
Since the silver ink composition of the present embodiment has C ₁ and C ₁ /C ₂ within the specified ranges, it can be applied to an inkjet printing method, and in this case, the glossiness can be improved without heat treatment. It is possible to form silver inclusions with high properties.

The silver ink composition of this embodiment is configured to be suitable for application to an inkjet printing method. However, the silver ink composition of the present embodiment can also be applied to printing methods other than the inkjet printing method, if necessary.
By performing printing using the silver ink composition of the present embodiment, a printed layer (in other words, a silver ink composition layer) can be formed on an object to be printed. This printed layer forms a silver-containing material by irradiating an energy beam without heat treatment. At this time, metallic silver is formed from silver nitrate in the silver ink composition, and a cured product is formed from the energy ray-curable compound in the silver ink composition by energy ray curing. That is, the silver-containing material contains at least metallic silver and the cured product.

<Silver nitrate>
In the silver ink composition of the present embodiment, silver nitrate (AgNO ₃ ) is a metallic silver-forming material capable of forming metallic silver by its reaction.
When the silver ink composition (silver ink composition layer, printing layer) is irradiated with an energy beam, the energy beam-curable compound is cured as described above. When the silver ink composition is used, electron transfer occurs between some of the radicals generated in the curing process and the silver ions (Ag ⁺ ) generated from silver nitrate, thereby converting metallic silver into presumed to be formed.

In the silver ink composition, the content ratio C1 of silver (Ag) in the silver nitrate with respect to the total mass of the silver ink composition is 8% by mass or more and less than 12% by mass ( ₈ % by _mass≤C1 < 12% by mass). When C1 is within such a range, a highly glossy silver _- containing material can be formed without heat treatment when the silver ink composition is applied to an inkjet printing method. More specifically, when C1 is ₈ % by mass or more, a sufficient amount of metallic silver can be formed. On the other hand, when C1 is less than 12% by mass, an excessive amount of silver nitrate in the silver ink composition is avoided, and precipitation of silver nitrate in the silver _- containing substance is suppressed when the silver-containing substance is formed. Finally, contamination of silver nitrate and silver nitrate-derived impurities into the silver-containing material is suppressed.

In the silver ink composition, the total amount (parts by mass) of silver in silver nitrate is synonymous with the total amount (parts by mass) of silver in silver nitrate blended (added) during production of the silver ink composition.

C ₁ is preferably 8.4% by mass or more, more preferably 8.8% by mass or more, for example, 9.2% by mass or more, and 9 .6% by mass or more.

In terms of enhancing the above effects, C ₁ is preferably 11.8% by mass or less, more preferably 11.2% by mass or less, and further preferably 10.6% by mass or less. It is preferably 10.0% by mass or less, particularly preferably 10.0% by mass or less, and may be, for example, 9.4% by mass or less.

C1 can be appropriately adjusted within _a range set by arbitrarily combining any of the lower limits and any of the upper limits described above.
For example, in one embodiment, C ₁ is 8.4 wt% to less than 12 wt%, 8.8 wt% to less than 12 wt%, 9.2 wt% to less than 12 wt%, and 9.6 wt% It may be any of less than 12% by mass, 8 to 11.8% by mass, 8 to 11.2% by mass, 8 to 10.6% by mass, 8 to 10.0% by mass, and 8 to It may be either 9.4% by mass, 8.4 to 11.8% by mass, 8.8 to 11.2% by mass, 9.2 to 10.6% by mass, and 9.6 to Any of 10.0 mass % may be sufficient. However, these are examples of _C1 .

<Energy ray-curable compound>
In the present embodiment, the energy ray-curable compound is a compound having the property of being cured by irradiation with energy rays, and may be, for example, any of monomers, oligomers and polymers.
As used herein, the term "monomer" means a basic unit that constitutes a polymer. "Polymer" means a polymer of monomers, and those having a molecular weight of 1000 or less are called "oligomers".

Examples of the energy rays include ultraviolet rays such as far ultraviolet rays, ultraviolet rays and near ultraviolet rays; infrared rays; electromagnetic radiation such as X-rays and gamma rays; particle radiation such as electron beams, proton beams and neutron beams.

The cured product of the energy ray-curable compound has a function as a binder that binds the metallic silver particles together in the silver-containing material. It also has a function of taking in by-products derived from the components contained in and a function of suppressing the precipitation of silver nitrate in the silver-containing material during the formation of the silver-containing material.
The energy ray-curable compound has a function of suppressing precipitation of its constituent components during printing, particularly in the silver ink composition during ejection in inkjet printing.

The energy ray-curable compound preferably does not have an anion or an anionic group. As used herein, the term "anionic group" means a group capable of forming an anion, an example of which is a carboxyl group ( ^- C(=O)-OH), but not limited to.
Anions are likely to interact with silver ions (Ag ⁺ ) and may inhibit the action of silver ions in the composition. On the other hand, since the energy ray-curable compound having no anion or anionic group hardly interacts with silver ions, when a silver ink composition containing such an energy ray-curable compound is used, increases the amount of metallic silver formed from silver nitrate.

Examples of the energy ray-curable compound include
Ethylene glycol di(meth)acrylate (alias: 1,2-ethanediol di(meth)acrylate), Propylene glycol di(meth)acrylate (alias: 1,2-propanediol di(meth)acrylate), 1,3- alkanediol di(meth)acrylates such as butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate;
Structural units derived from alkylene oxides such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate (e.g. a structural unit represented by the formula “—CH ₂ CH _{(CH 3 )} O—”), and the number of said structural units per molecule is ₂ or di(meth)acrylates of glycols that are 3;
Polyalkylene glycol di (meth) acrylate such as polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate (in other words, having the above structural unit derived from alkylene oxide, the number of the above structural units per molecule di(meth)acrylates of glycols whose number is 4 or more);
ethoxylated bisphenol A diacrylate;
3 per molecule, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, etc. Poly(meth)acrylates of compounds having one or more hydroxyl groups;
N-hydroxyalkyl (meth)acrylamides such as N-(2-hydroxyethyl) (meth)acrylamide;
Examples include N,N-dialkyl(meth)acrylamides such as N,N-diethyl(meth)acrylamide.

In addition, in this specification, "(meth)acrylate" is a concept that includes both "acrylate" and "methacrylate". The same applies to terms similar to (meth)acrylate, for example, "(meth)acrylic acid" is a concept that includes both "acrylic acid" and "methacrylic acid", and "(meth)acryloyl group " is a concept that includes both "acryloyl group" and "methacryloyl group".

The energy ray-curable compound contained in the silver ink composition may be of only one kind, or may be of two or more kinds. can be adjusted to

For example, commercially available polyethylene glycol diacrylates include polyethylene glycol #200 diacrylate and polyethylene glycol #400, which are mixtures of two or more types of polyethylene glycol diacrylates corresponding to the number of structural units derived from ethylene oxide. diacrylate, polyethylene glycol #600 diacrylate, polyethylene glycol #1000 diacrylate, and the like. These are described in different formats, for example, "polyethylene glycol #200 diacrylate" is described as "polyethylene glycol (200) diacrylate" or "polyethylene glycol 200 diacrylate". sometimes

The energy ray-curable compound is preferably water-soluble. The silver ink composition contains silver nitrate, and in order to facilitate the formation of metallic silver, it is preferable that the silver ink composition contains water, in which silver nitrate is highly soluble, as a solvent, which will be described later. . Correspondingly, when the energy ray-curable compound has water solubility, the uniformity of the silver ink composition becomes higher, and a larger amount of metallic silver can be formed.
As used herein, a compound being "water-soluble" means that the compound is completely soluble in any amount of water at room temperature.
In the present specification, the term "ordinary temperature" means a temperature that is not particularly cooled or heated, that is, a normal temperature.

The energy ray-curable compound is one or more selected from the group consisting of polyalkylene glycol di(meth)acrylates, N-hydroxyalkyl(meth)acrylamides and N,N-dialkyl(meth)acrylamides. preferably one or more selected from the group consisting of polyethylene glycol di(meth)acrylate, N-(2-hydroxyethyl)(meth)acrylamide and N,N-diethyl(meth)acrylamide is more preferable, and may be, for example, one or more selected from the group consisting of polyethylene glycol diacrylate, N-(2-hydroxyethyl)acrylamide and N,N-diethylacrylamide. Silver ink compositions containing such energy ray-curable compounds are particularly advantageous in that they are more uniform and can form greater amounts of metallic silver.

In the silver ink composition, the content ratio _C2 of the energy ray-curable compound with respect to the total mass of the silver ink composition is not particularly limited as long as the above condition of C1 _{/ C2} is satisfied.
For example, if _C2 is too large, the amount of the energy ray-curable compound in the silver ink composition is too large relative to the amount of silver, and the energy ray-curable compound cannot be sufficiently cured. , the energy beam dose required to form a sufficient amount of metallic silver is excessively high. In this case, the quality of an object to be printed with the silver ink composition (in other words, an object to be formed with a silver-containing material, such as a substrate to be described later) may be impaired by the irradiation of the energy beam. _C2 is preferably, for example, less than 50% by mass, for example, 45% by mass or less, 35 Any one of 25% by mass or less, and 15% by mass or less may be used.

On the other hand, if _C2 is too small, the amount of the energy ray-curable compound in the silver ink composition is too small relative to the amount of silver, and the amount of cured product of the energy ray-curable compound formed becomes excessively low. In this case, the energy ray-curable compound and its cured product have the functions described above (function as a binder, function to incorporate the by-product when forming the silver-containing material, and suppression of precipitation of silver nitrate when forming the silver-containing material. and the function of suppressing precipitation of the contained components in the silver ink composition) cannot be sufficiently exhibited. In terms of making it easy for the energy ray-curable compound and its cured product to sufficiently exhibit these functions, C ₂ is, for example, 9% by mass or more and 10.5% by mass or more. good too.

_C2 can be appropriately adjusted within a range set by arbitrarily combining any of the lower limits and any of the upper limits described above.
For example, in one embodiment, _C2 may be either 9 wt% or more and less than 50 wt%, and 10.5 wt% or more and less than 50 wt%, or 9 to 45 wt%, 9 to 35 wt%, % by mass, 9 to 25% by mass, and 9 to 15% by mass, or 10.5 to 45% by mass, 10.5 to 35% by mass, 10.5 to 25% by mass, and It may be anywhere from 10.5 to 15% by mass. However, these are examples of _C2 .

In the silver ink composition, C ₁ /C ₂ is 0.3 or more and less than 1.4 (0.3≦C ₁ /C ₂ <1.4). When C ₁ /C ₂ is within such a range, a highly glossy silver-containing material can be formed without heat treatment when the silver ink composition is applied to an inkjet printing method. More specifically, it is as follows.
That is, C ₁ /C ₂ is 0.3 or more, and the relative value of C ₁ to C ₂ is a certain value or more (in other words, the relative value of C ₂ to C ₁ is a certain value or less) This makes it possible to reduce the energy ray irradiation dose required to sufficiently cure the energy ray-curable compound and form a sufficient amount of metallic silver. Therefore, a sufficient amount of metallic silver can be formed without impairing the quality of a printing object (for example, a substrate to be described later) by irradiation with energy rays.
On the other hand, C ₁ /C ₂ is less than 1.4, and the relative value of C ₁ to C ₂ is less than a certain value (in other words, the relative value of C ₂ to C ₁ is greater than a certain value) As a result, the energy ray-curable compound and its cured product have the functions described above (function as a binder, function to incorporate the by-products when forming the silver-containing material, and suppression of precipitation of silver nitrate when forming the silver-containing material. and the function of suppressing precipitation of the contained components in the silver ink composition).

C ₁ /C ₂ may be, for example, 0.4 or more, 0.5 or more, and 0.6 or more, in that the above-mentioned effect by specifying the lower limit value becomes higher. .

C ₁ /C ₂ is preferably 1.3 or less, more preferably 1.1 or less, and 0.9 or less in terms of increasing the effect of defining the upper limit described above. is more preferable, and may be, for example, 0.7 or less, or 0.5 or less.

C ₁ /C ₂ can be appropriately adjusted within a range set by arbitrarily combining any of the lower limits and any of the upper limits described above.
For example, in one embodiment, C ₁ /C ₂ may be any of 0.4 or more and less than 1.4, 0.5 or more and less than 1.4, and 0.6 or more and less than 1.4. , 0.3 to 1.3, 0.3 to 1.1, 0.3 to 0.9, 0.3 to 0.7, and 0.3 to 0.5. , 0.4-1.3, 0.5-1.1, and 0.6-0.9. However, these are examples of C1 _{/ C2} .

In the silver ink composition, it is preferable that C ₁ is in any of the above numerical ranges and C ₁ /C ₂ is in any of the above numerical ranges.
That is, preferred examples of the silver ink composition include C ₁ of 8% by mass or more, 8.4% by mass or more, 8.8% by mass or more, 9.2% by mass or more, and 9.6% by mass. % or more and less than 12% by mass, 11.8% by mass or less, 11.2% by mass or less, 10.6% by mass or less, 10.0% by mass or less, and 9.4% by mass or less and C ₁ /C ₂ is any of 0.3 or more, 0.4 or more, 0.5 or more, and 0.6 or more, and less than 1.4, 1 .3 or less, 1.1 or less, 0.9 or less, 0.7 or less, and 0.5 or less (provided that C ₁ is 8% by mass or more and less than 12% by mass, and C ₁ / _C2 is 0.3 or more and less than 1.4).
_In addition, preferred examples of the silver ink composition include: Less than, 9.6% by mass or more and less than 12% by mass, 8 to 11.8% by mass, 8 to 11.2% by mass, 8 to 10.6% by mass, 8 to 10.0% by mass, 8 to 9.4 % by mass, 8.4 to 11.8% by mass, 8.8 to 11.2% by mass, 9.2 to 10.6% by mass, and 9.6 to 10.0% by mass, and , C ₁ /C ₂ is 0.4 or more and less than 1.4, 0.5 or more and less than 1.4, 0.6 or more and less than 1.4, 0.3 to 1.3, 0.3 to 1.1 , 0.3-0.9, 0.3-0.7, 0.3-0.5, 0.4-1.3, 0.5-1.1, and 0.6-0.9 Any one is mentioned.

<Solvent>
In this embodiment, the solvent is a component for dissolving or dispersing components other than the solvent of the silver ink composition, such as silver nitrate and energy ray-curable compounds.

Examples of the solvent include water and organic solvents.

The silver ink composition preferably contains water, in which silver nitrate is highly soluble, as a solvent in order to facilitate the formation of the silver-containing material (metallic silver).

The organic solvent may be liquid at normal temperature and normal pressure.
The organic solvent preferably has a hydrophilic group such as a hydroxyl group (--OH), and may be hydrophilic.
As used herein, a liquid being “hydrophilic” means that the liquid is uniformly miscible with any amount of water at room temperature.

Examples of preferable organic solvents include alcohols. That is, the silver ink composition preferably contains alcohol as the solvent. Silver ink compositions containing alcohols are highly suitable for inkjet printing due to their low surface tension. In addition, the alcohol-containing silver ink composition can easily contain components other than the solvent that are insoluble in water or have low solubility in water (in particular, the photopolymerization initiator described later). and favors the formation of silver inclusions.

The alcohol may be a monohydric alcohol having only one hydroxyl group per molecule, or a polyhydric alcohol having two or more hydroxyl groups per molecule (e.g., dihydric alcohol, trihydric alcohol, etc.) good too.
Examples of the alcohol include those having 1 to 6 carbon atoms.

Examples of the monohydric alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol (also known as isobutyl alcohol), 2-methyl-2-propanol. (alias: tert-butyl alcohol), 1-pentanol, 2-pentanol, 1-hexanol, 2-hexanol and the like.
Examples of the polyhydric alcohol include ethylene glycol (also known as 1,2-ethanediol), propylene glycol (also known as 1,2-propanediol), 1,2-butanediol, 1,3-butanediol, 1 ,5-pentanediol, 1,2-hexanediol and the like.

Preferably, the alcohol is an aliphatic alcohol.

The alcohol preferably has 1 to 4 carbon atoms, more preferably an aliphatic alcohol having 1 to 4 carbon atoms, from the viewpoint of enhancing the ink jet printability of the silver ink composition. Preferred alcohols include, for example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, propylene glycol and the like. mentioned.

The solvent contained in the silver ink composition may be of one type, or may be of two or more types. When two or more types are used, the combination and ratio thereof can be arbitrarily adjusted.

More preferred solvents include a combination of water and alcohol. That is, the silver ink composition more preferably contains both water and alcohol as the solvent.
In the silver ink composition containing water and alcohol, silver nitrate, which is highly soluble in water, is easily dissolved, and components other than silver nitrate that are either insoluble in water or have low solubility in water are used. However, since it dissolves easily, the uniformity of the silver ink composition is higher. When a component other than silver nitrate is soluble in both water and alcohol, a mixed solvent of water and alcohol can be used to obtain a silver ink composition with even higher uniformity. Furthermore, by using a combination of water and a hydrophilic alcohol, a silver ink composition with higher uniformity can be obtained.

In the silver ink composition, the mass ratio between the water content (parts by mass) and the alcohol content (parts by mass) is appropriately selected according to the type of components other than the solvent contained in the silver ink composition. There is no particular limitation.
Usually, in the silver ink composition, the [water content (parts by mass)]:[alcohol content (parts by mass)] mass ratio is preferably from 20:80 to 96:4. :65 to 95:5, more preferably 50:50 to 94:6, for example, either 50:50 to 75:25 or 50:50 to 65:35. or any of 78:22-94:6 and 86:14-94:6.

The content of the solvent in the silver ink composition is not particularly limited, and may be appropriately adjusted so that properties such as viscosity and uniformity of the silver ink composition are suitable for printing.
In the silver ink composition, the content ratio C3 of the solvent with respect to the total weight of the silver ink composition may be, for example, either ₃₅ to 90% by mass or 50 to 75% by mass. .

<Other ingredients>
The silver ink composition may contain other components other than silver nitrate, the energy ray-curable compound, and the solvent, as long as the effects of the present invention are not impaired.
The type of the other component can be arbitrarily selected according to the purpose, and is not particularly limited.

The other components contained in the silver ink composition may be of only one kind, or may be of two or more kinds. can.

Preferred other components include, for example, photopolymerization initiators and surfactants.

[Photoinitiator]
The photopolymerization initiator is a component for reducing the irradiation dose of energy rays required for energy ray curing of the energy ray-curable compound. By reducing the irradiation dose of the energy ray, the energy ray-curable compound can be sufficiently cured by the irradiation with the energy ray without impairing the quality of the print target (for example, the base material described later).
In order to obtain such effects, the silver ink composition preferably further contains a photopolymerization initiator.

The photopolymerization initiator may be a known one and is not particularly limited.
Examples of the photopolymerization initiator include 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (trade name “Omnirad 2959”) and 1-hydroxycyclohexylphenyl ketone. (alias: phenyl (1-hydroxycyclohexyl) methanone), trade name “Omnirad 184”), 2-hydroxy-2-methyl-1-phenylpropanone (trade name “Omnirad 1173”), 1,1′-(methylene -di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (alias: -hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl) )-2-methylpropan-1-one, trade name "Omnirad 127") and other hydroxyalkylphenones;
2-dimethylamino-1-(4-morpholinophenyl)-2-benzyl-1-butanone (trade name "Omnirad 369"), 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholino Phenyl)-1-butanone (trade name “Omnirad 379EG”), 2-[4-(methylthio)benzoyl]-2-(4-morpholinyl)propane (alias: 2-methyl-1-[4-(methylthio)phenyl ]-α-aminoalkylphenones such as 2-morpholinopropan-1-one, trade name “Omnirad 907”);
Acylphosphine oxides such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name “Omnirad 819”) and 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide (trade name “Omnirad TPO-L”) ;
benzyl diketals such as 2,2-dimethoxy-2-phenylacetophenone (trade name “Omnirad 651”);
metallocenes such as bis(2,4-cyclopentadienyl)bis[2,6-difluoro-3-(1-pyryl)phenyl)titanium (IV) (trade name “Omnirad 784”);
"FAI-101L" manufactured by Fujifilm;
benzaldehyde derivatives; benzophenone; benzophenone derivatives; thioxanthone; thioxanthone derivatives and the like.

In this specification, when a structure in which one or more hydrogen atoms are substituted with a group other than a hydrogen atom is assumed in a certain compound, the compound having such a substituted structure is referred to as the above-mentioned are referred to as "derivatives" of certain compounds of In addition, in the present specification, unless otherwise specified, the term "group" includes not only an atomic group formed by bonding a plurality of atoms, but also a single atom.

The photopolymerization initiator contained in the silver ink composition may be of only one type, or may be of two or more types. Adjustable.

The photopolymerization initiator preferably has a hydrophilic group, and may have water solubility. The silver ink composition containing such a photoinitiator, especially when containing water as a solvent, is more uniform and can form a greater amount of metallic silver.

Examples of the hydrophilic group include a hydroxyl group (--OH) and a dimethylamino group (--N(CH ₃ ) ₂ ).

Preferred examples of the photopolymerization initiator include the hydroxyalkylphenone, the α-aminoalkylphenone, and the like, in that the above effects can be obtained at low cost.

When the photopolymerization initiator is used, in the silver ink composition, the content ratio _C4 of the photopolymerization initiator with respect to the total weight of the silver ink composition is, for example, 0.2% by mass or more. However, it is preferably 9% by mass or more from the viewpoint of enhancing the above-mentioned effects of using the photopolymerization initiator.
That is, an example of a preferable silver ink composition further contains a photopolymerization initiator, and the content ratio _C4 of the photopolymerization initiator in the silver ink composition with respect to the total mass of the silver ink composition is 9. % by mass or more.

When using the photopolymerization initiator, the upper limit of _C4 is not particularly limited. For example, _C4 is preferably 15% by mass or less, more preferably 12% by mass or less, in order to avoid excessive use of the photopolymerization initiator. The smaller _C4 is, the higher the effect of suppressing unintended energy ray curing of the energy ray-curable compound during storage of the silver ink composition.

When the photopolymerization initiator is used, _C4 can be appropriately adjusted within a range set by arbitrarily combining any of the above lower limits and upper limits.
For example, in one embodiment, _C4 can be anywhere from 0.2 to 15 wt%, and from 9 to 15 wt%, or from 0.2 to 12 wt%, or from 9 It may be up to 12% by mass. However, these are examples of _C4 .

So far, the case where the photopolymerization _initiator is used has been described. is more effective in suppressing In order to improve the storage stability of the silver ink composition and form a sufficient amount of metallic silver, for example, no photopolymerization initiator is used, or the amount of the photopolymerization initiator used is reduced to A very small amount is preferred.
To that end, C ₄ is preferably 0-5% by weight, and may be, for example, either 0-3% by weight, and 0-1% by weight.

[Surfactant]
The surfactant is a component for reducing the surface tension of the silver ink composition. Silver ink compositions containing surfactants are highly inkjet printable due to their low surface tension.
In order to obtain such effects, the silver ink composition preferably further contains a surfactant.

The surfactant may be a known one and is not particularly limited.
The surfactant is preferably nonionic. Surfactants with such properties suppress interaction with silver ions (Ag ⁺ ), so that the amount of metallic silver formed from silver nitrate increases.

Examples of commercially available nonionic surfactants include "Surflon S-241" (water-soluble fluorosurfactant, manufactured by AGC Seimi Chemical Co., Ltd.), "Futergent 710FL", "Futergent 710FM", and "Futergent 710FS", "Futergent 730FL", "Futergent 730LM", "Futergent 610FM", "Futergent 683" (fluorine-hydrophilic group-containing surfactants, manufactured by Neos), "Olfine EXP.4001" (water-soluble acetylenic surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) and the like. However, these are examples of nonionic surfactants. Here, "fluorine-based" means having a fluorine atom, and "acetylenic" means having a triple bond between carbon atoms.

The surfactant contained in the silver ink composition may be of only one type, or may be of two or more types. can.

In the case of using the surfactant, the above-described effect due to the use of the surfactant is enhanced. In the silver ink composition, the content of the surfactant with respect to the total mass of the silver ink composition The ratio _C5 of may be, for example, 0.1% by mass or more and 0.6% by mass or more.

_When using the surfactant, the upper limit of C5 is not particularly limited. For example, C5 may be ₂ wt% or less in that excessive use of surfactant is avoided.

_When the surfactant is used, C5 can be appropriately adjusted within a range set by arbitrarily combining any of the above lower limits and upper limits.
For example, in one embodiment, C ₅ can be either 0.1-2 wt% and 0.6-2 wt%. However, these are examples of _C5 .

The viscosity of the silver ink composition is not particularly limited as long as the silver ink composition can be used for its intended purpose.
When the silver ink composition is applied to an inkjet printing method, the viscosity of the silver ink composition measured using an ultrasonic vibration viscometer at room temperature (20 to 25° C.) is usually 2 to 13 mPa·. It is preferably 3 to 10 mPa·s, more preferably 3 to 10 mPa·s, and may be, for example, 3 to 7 mPa·s. When the viscosity of the silver ink composition is equal to or higher than the lower limit, it is possible to suppress the unintended leakage of the silver ink composition from the inkjet head at the time of printing, so that the printing can be performed more stably. When the viscosity of the silver ink composition is equal to or less than the upper limit, the ejection of the silver ink composition during printing becomes easier.

Since the silver ink composition contains silver nitrate having photosensitivity, it is preferable to store and handle it under light-shielding conditions.

In terms of being able to moderately reduce the irradiation dose of the energy ray and also form a sufficient amount of metallic silver during the energy ray curing of the energy ray-curable compound, more preferable silver ink compositions include, for example: , silver nitrate, the energy ray-curable compound, and the solvent, and may further contain the photopolymerization initiator, C ₁ is 8.8 to 11.2% by mass, and C ₁ /C ₂ is 0.5 to 1.1 (hereinafter sometimes referred to as “silver ink composition (I)”).
An example of the silver ink composition (I) having a higher effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] in a mass ratio of 50:50 to 94:6.
An example of the silver ink composition (I) having the above effects is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 94:6, and the energy ray-curable compound is polyalkylene glycol di(meth)acrylate, N-hydroxyalkyl(meth)acrylamide and N,N-dialkyl One or two or more selected from the group consisting of (meth)acrylamide.
An example of the silver ink composition (I) having the above effects is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 94:6, and the photopolymerization initiator is the hydroxyalkylphenone.
An example of the silver ink composition (I) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [content of water (parts by mass)]: [content of the alcohol ( parts by mass)] is 50:50 to 94:6, and the energy ray-curable compound is polyalkylene glycol di(meth)acrylate, N-hydroxyalkyl(meth)acrylamide and N,N-dialkyl One or two or more selected from the group consisting of (meth)acrylamide, and the photopolymerization initiator is the hydroxyalkylphenone.
An example of the silver ink composition (I) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 94:6, the alcohol is 2-propanol, and the energy ray-curable compound is polyethylene glycol diacrylate and N-(2-hydroxyethyl)acrylamide. and N,N-diethylacrylamide, and the photopolymerization initiator is 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl -1-propanone.

From the viewpoint that the storage stability of the silver ink composition is high and a sufficient amount of metallic silver can also be formed, a more preferable silver ink composition includes, for example, silver nitrate, the energy ray-curable compound, It contains the solvent and may further contain the photopolymerization initiator, C ₁ is 9.2% by mass or more and less than 12% by mass, and C ₁ /C ₂ is 0.3 or more and 1. less than ₄ and 0 to 5% by mass of C4 (hereinafter sometimes referred to as “silver ink composition (II)”).
An example of the silver ink composition (II) having a higher effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] in a mass ratio of 78:22 to 94:6.
An example of the silver ink composition (II) having a higher effect is, for example, containing water and the alcohol as the solvent, [content of water (parts by mass)]: [content of the alcohol ( parts by mass)] is from 78:22 to 94:6, and the energy ray-curable compound is polyalkylene glycol di(meth)acrylate.
An example of the silver ink composition (II) having a higher effect is, for example, containing water and the alcohol as the solvent, [content of water (parts by mass)]: [content of the alcohol ( parts by mass)] is from 78:22 to 94:6, and when the photopolymerization initiator is contained, the photopolymerization initiator is the hydroxyalkylphenone.
An example of the silver ink composition (II) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is from 78:22 to 94:6, the energy ray-curable compound is polyalkylene glycol di(meth)acrylate, and contains the photopolymerization initiator, the Examples thereof include those in which the photopolymerization initiator is the above hydroxyalkylphenone.
An example of the silver ink composition (II) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 78:22 to 94:6, the alcohol is 2-propanol, the energy ray-curable compound is polyethylene glycol diacrylate, and the photopolymerization initiator is contained. In some cases, the photoinitiator is 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone.

In terms of being able to remarkably reduce the irradiation dose of the energy ray and also form a sufficient amount of metallic silver when the energy ray-curable compound is cured with the energy ray, more preferable silver ink compositions include, for example: , silver nitrate, the energy ray-curable compound, the solvent, and the photopolymerization initiator, C ₁ is 8 to 9.4% by mass, and C ₁ /C ₂ is 0.3 or more and less than 1.4 and _C4 is 9 to 15% by mass (hereinafter sometimes referred to as "silver ink composition (III)").
An example of the silver ink composition (III) having a higher effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] in a mass ratio of 50:50 to 75:25.
An example of the silver ink composition (III) having the above effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 75:25, and the energy ray-curable compound is polyalkylene glycol di(meth)acrylate, N-hydroxyalkyl(meth)acrylamide and N,N-dialkyl One or two or more selected from the group consisting of (meth)acrylamide.
An example of the silver ink composition (III) having the above effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is from 50:50 to 75:25, and the photopolymerization initiator is the hydroxyalkylphenone.
An example of the silver ink composition (III) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 75:25, and the energy ray-curable compound is polyalkylene glycol di(meth)acrylate, N-hydroxyalkyl(meth)acrylamide and N,N-dialkyl One or two or more selected from the group consisting of (meth)acrylamide, and the photopolymerization initiator is the hydroxyalkylphenone.
An example of the silver ink composition (III) having a particularly high effect is, for example, containing water and the alcohol as the solvent, [water content (parts by mass)]: [alcohol content ( parts by mass)] is 50:50 to 75:25, the alcohol is 2-propanol, and the energy ray-curable compound is polyethylene glycol diacrylate and N-(2-hydroxyethyl)acrylamide. and N,N-diethylacrylamide, and the photopolymerization initiator is 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl -1-propanone.

<<Method for producing silver ink composition>>
The silver ink composition of this embodiment is obtained by blending silver nitrate, an energy ray-curable compound, a solvent, and, if necessary, the other components. After blending the respective components, the obtained blend may be used as the silver ink composition as it is, or a purified product obtained by subsequently performing a known purification operation as necessary may be used as the silver ink composition. .
Since silver nitrate has photosensitivity, the production of the silver ink composition is preferably carried out under light-shielding conditions.

The order in which each component is added is not particularly limited.
When blending each component, the resulting mixture may be mixed after all the components are added, or the resulting mixture may be mixed while sequentially adding some of the components. The results of the additions may be mixed while adding all the ingredients in sequence.

When each component is blended, any of the above-described components (silver nitrate, energy ray-curable compound, solvent, other components) may be partially or entirely combined with any remaining component or partially, They may be premixed to form a mixture, and this mixture may be compounded.

For example, among the four categories of silver nitrate, energy ray-curable compound, solvent, and other components, components in different categories may be mixed in advance to form a mixture, and this mixture may be added to the object. . Such a technique may be particularly useful, for example, when a component that is solid at ambient temperature is used in advance with a component that is liquid at ambient temperature. To give a more specific example, silver nitrate, which is in the form of powder at room temperature, may be added to an object as it is in the form of powder without being premixed with any other ingredients. is used, the silver ink composition can be produced with more stable quality by mixing with water in advance to form an aqueous solution of silver nitrate and adding this aqueous solution of silver nitrate to the object.

Further, for example, among the energy ray-curable compound, the solvent and the other components, in the same category, when two or more components are blended, all of these two or more components may be combined with any other component. It may be added alone to the object without being premixed with the ingredients, or two or more of these components may be partially or entirely mixed with each other in advance to form a mixture, and this mixture is added to the object. Alternatively, some or all of these two or more components may be pre-mixed with other components of different categories to form a mixture, and this mixture may be added to the object. To give a more specific example, when water and alcohol are used as the solvent, the water and alcohol are combined with silver nitrate, the energy ray-curable compound, the solvent other than water and alcohol, and the other components. It may be added alone to the object without being mixed in advance, or water and alcohol may be mixed with each other in advance to form a mixture (i.e., a mixed solvent), and this mixture may be added to the object, Either one or both of water and alcohol may be pre-mixed with any of silver nitrate, energy ray-curable compound, and other components to form a mixture, and this mixture may be added to the object.

The method of mixing each component is not particularly limited, and a method of mixing by rotating a stirrer or a stirring blade; a method of mixing using a mixer, three-roll, kneader, bead mill, etc.; It may be appropriately selected from known methods such as methods.

The temperature at which each component is blended is not particularly limited as long as each component does not deteriorate, but it is preferably -5 to 60°C. The temperature at the time of blending may be appropriately adjusted according to the types and amounts of the components to be blended so that the mixture obtained by blending has a viscosity that is easy to stir.
Also, the blending time is not particularly limited as long as each blended component does not deteriorate, but it is preferably 10 minutes to 36 hours.

<<Method for Using Silver Ink Composition (Method for Producing Silver-Containing Material)>>
The silver ink composition of the present embodiment can be applied to printing by various printing methods, and particularly excellent effects are exhibited when applied to inkjet printing.
When attempting to form a silver-containing material with high glossiness (light reflectivity) on a printing object by an inkjet printing method, the conventional silver ink composition requires heat treatment, and the constituent material of the printing object is required. was limited to those having heat resistance (see Patent Document 1). There are also silver ink compositions that can form highly glossy silver-containing materials by UV irradiation without heat treatment. When applied to a printing method, the suitability for use and the suitability for forming a silver-containing material were not sufficient (see Patent Document 2).
In contrast, the silver ink composition of the present embodiment is applicable to the inkjet printing method, and can form a highly glossy silver-containing material by irradiation with energy rays without heat treatment. Moreover, the silver ink composition of the present embodiment can similarly form a highly glossy silver-containing material even when applied to a printing method other than the inkjet printing method.

In the method for producing a silver-containing material using the silver ink composition of the present embodiment, a printed layer (in other words, a silver ink A step of forming a composition layer) on an object to be printed (in this specification, may be referred to as a “printing step”), and by irradiating the printed layer with an energy ray, the and a step of forming a silver-containing substance (which may be referred to herein as a “silver-containing substance forming step”). Each of the above steps will be described below.

<Printing process>
As described above, the printing method applied in the printing step is preferably an inkjet printing method in that the characteristics of the silver ink composition of the present embodiment are most strongly exhibited, but other printing methods are also applicable. It is possible.
The formation of the printed layer by the printing method can be performed by a known method in any printing method.

The print target includes all substrates that can be used in the printing method.
Preferred printing objects include sheet-like and film-like objects.

Examples of the constituent material of the object to be printed (base material) include paper, resin, ceramics, composite materials using these (paper, resin, ceramics) in combination, and the like.

Examples of the paper include Kent paper, coated paper, paperboard, high-quality paper, art paper, cast-coated paper, resin-coated paper, and synthetic paper.

Examples of the resin include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polymethylpentene (PMP), polycycloolefin, polystyrene (PS), and polyvinyl acetate. (PVAc), acrylic resin such as polymethyl methacrylate (PMMA), AS resin, ABS resin, polyamide (PA), polyimide, polyamideimide (PAI), polyacetal, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), Polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyphenylene sulfide (PPS), polysulfone (PSF), polyethersulfone (PES), polyetherketone (PEK), poly Synthetic resins such as ether ether ketone (PEEK), polycarbonate (PC), polyurethane, polyphenylene ether (PPE), modified polyphenylene ether (m-PPE), polyarylate, epoxy resin, melamine resin, phenol resin, and urea resin. .

Examples of the ceramics include glass and silicon.

Examples of the composite material include glass epoxy resin and the like.

The constituent materials of the object to be printed may be of one type or two or more types, and when two or more types are used, their combination and ratio can be arbitrarily adjusted.
For example, one of the resins may be used alone, two or more of them may be used in combination as a polymer alloy, or may be used in combination with other than the resin.

The object to be printed may consist of one layer (single layer) or may consist of multiple layers of two or more layers. When the object to be printed consists of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited. For example, as a print target consisting of two or more layers, an ink-receiving layer for forming a print or an image by absorbing an ink such as the silver ink composition is provided on a paper sheet. What was done is mentioned.

In this specification, not only in the case of the printing object, "multiple layers may be the same or different" means "all the layers may be the same, or all the layers may be It may be different, or only a part of the layers may be the same.” Further, “multiple layers are different from each other” means that “at least one of the constituent material and thickness of each layer is different from each other. ” means.

The shape of the printed layer (printed pattern) can be arbitrarily selected according to the purpose, and is not particularly limited. For example, the shape of the printed layer may be linear (linear, curved, linear with a mixture of straight and curved lines), or a shape in which a specific range of areas is filled (in this specification, "filled may be referred to as a "shape"), or a shape in which lines and filled areas are mixed.
Also, the printed layer may form characters such as letters, numbers, etc., may form graphics or the shape of some object, or may form other shapes that do not correspond to any of these. may

The thickness of the object to be printed may be appropriately selected depending on the purpose, and is not particularly limited.
When the object to be printed is sheet-like or film-like, its thickness may be, for example, 10 to 5000 μm.
When the object to be printed consists of multiple layers, the total thickness of each layer should be the thickness of the object to be printed.

The thickness of the printed layer formed in the printing step can be arbitrarily selected according to the use of the silver-containing material to be finally formed, and is not particularly limited.
The thickness of the printed layer can be adjusted, for example, by adjusting the printing conditions of the silver ink composition according to the printing method.

<Silver-containing material forming step>
In the silver-containing substance forming step, the energy beams with which the printed layer is irradiated are the same as those described above as the energy beams with which the energy beam-curable compound is irradiated.

In the silver-containing substance forming step, the printed layer may be continuously irradiated with the energy beam without stopping the irradiation of the energy beam, or by repeating irradiation and stopping of the energy beam, You may irradiate an energy beam intermittently.

By the end of the formation of the silver-containing material, the lower limit of the dose of the energy beam irradiated to the printed layer (irradiation dose, in other words, the integrated dose) is such that a sufficient amount of silver-containing material can be formed from the printed layer (in other words, Then, as long as a sufficient amount of metallic silver can be formed from silver nitrate, there is no particular limitation. For example, the dose may be either 0.8 J/cm ² or more and 1 J/cm ² or more.

The dose of the energy beam irradiated to the printed layer is preferably 9 J/cm ² or less, for example, 5 J/cm ² or less, 3.5 J/cm ² or less, and 2 J/cm ² or less. When the dose is equal to or less than the upper limit, deterioration in quality of an object (for example, the base material) on which the silver-containing material is formed is suppressed during energy beam irradiation. Generally, the smaller the dose, the lower the risk of impairing the quality of the object on which the silver-containing material is to be formed during irradiation with the energy beam.

In the silver inclusion forming step, the printed layer may be heated at a temperature of, for example, 40° C. or higher. However, since the silver ink composition (printing layer) can form a silver-containing material only by irradiation with energy rays, it is preferable not to heat the printing layer. good too. By not heating the printing layer, for example, it is not necessary to limit the constituent materials of the printing object to those having heat resistance, and a wide range of printing objects can be used.

In the printed layer being irradiated with energy rays, the curing of the energy ray-curable compound and the formation of metallic silver from silver nitrate proceed, and the removal of the solvent also proceeds. Therefore, as the energy beam irradiation time elapses, the color of the printed layer changes, the amount of solvent in the printed layer decreases, and the mass of the printed layer decreases. state is changing. Finally, the color change and mass reduction of the printed layer stop, the surface state of the printed layer stops changing, and a silver-containing material having a silvery appearance and high glossiness is formed. When the obtained silver-containing material is in the form of a film (in this specification, the film-like silver-containing material is sometimes referred to as a "silver-containing film"), the surface of the silver-containing film is glossy. has a high specularity.
The formed silver-containing material contains at least the cured product of the energy ray-curable compound, but the content of other impurities is small, and the amount of metallic silver formed is sufficiently large, so the silver-containing material has high glossiness. It is assumed that you will get something.

The shape of the formed silver-containing material (silver-containing material pattern) is determined by the shape of the printed layer (printed pattern) described above, and is usually the same as the shape of the printed layer.

The thickness of the silver-containing material formed on the object to be printed is not particularly limited, and can be arbitrarily set according to the purpose. For example, the thickness of the silver inclusions may be 0.1-30 μm. When the thickness of the silver-containing material is equal to or greater than the lower limit, the effect of forming the silver-containing material is enhanced. When the thickness of the silver-containing material is equal to or less than the upper limit, excessive thickness of the silver-containing material can be avoided.
The thickness of the silver inclusions can be adjusted, for example, by adjusting the thickness of the printing layer.

The manufacturing method may include other steps that are neither the printing step nor the silver-containing material forming step. The other steps are not particularly limited as long as they do not impair the effects of the present invention, and can be arbitrarily selected according to the purpose. The timing of performing the other process can be arbitrarily selected according to the type of the other process.

A silver-containing material formed using the silver ink composition of the present embodiment has high glossiness. In particular, a silver-containing material formed by forming a printed layer by an inkjet printing method without heating the printed layer has a higher gloss than a silver-containing material formed by a similar method using a conventional silver ink composition. remarkably high. Therefore, the silver ink composition of the present embodiment is particularly useful as a raw material for forming a highly glossy silver-containing material by an inkjet printing method.

Regarding a film-like silver-containing material (silver-containing film) formed using the silver ink composition of the present embodiment, when the 20° specular glossiness was measured in accordance with JIS Z 8741: 1997, the specular surface The glossiness may be, for example, 700 or more and 850 or more.

The present invention will be described in more detail below with reference to specific examples. However, the present invention is by no means limited to the examples shown below.

Raw materials used in Examples or Comparative Examples and their abbreviations used as necessary are shown below.
・ 50% by mass aqueous solution of silver nitrate (manufactured by Kojima Chemicals Co., Ltd.)
・Energy ray-curable compound (a)-1: Polyethylene glycol #400 diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
(a)-2: N-(2-hydroxyethyl)acrylamide (manufactured by KJ Chemicals)
(a)-3: N,N-diethylacrylamide (manufactured by KJ Chemicals)
- Photopolymerization initiator (b)-1: 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone ("Omnirad 2959" manufactured by IGM RESINS B.V.)
(b)-2: "FAI-101L" manufactured by Fuji Film Co., Ltd.
(b)-3: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide ("Omnirad 819" manufactured by IGM RESINS B.V.)
Surfactant (c)-1: Nonionic surfactant ("Olfine EXP.4001" manufactured by Nissin Chemical Industry Co., Ltd.)

[Example 1]
<<Production of silver ink composition>>
In a dark room, under the conditions of room temperature (20 to 23° C.), 50% by mass silver nitrate aqueous solution (3.14 parts by mass), energy ray-curable compound (a)-1 (3 parts by mass), photopolymerization initiator ( b)-1 (0.03 parts by mass), surfactant (c)-1 (0.11 parts by mass), 2-propanol (IPA, 0.53 parts by mass) and water (3.33 parts by mass) A silver ink composition was obtained by mixing and stirring for 30 minutes.
Table 1 shows the content ratio (% by mass) of each component in the silver ink composition with respect to the total mass of the silver ink composition.

<<Evaluation of Silver Ink Composition>>
<Measurement of viscosity>
The viscosity of the silver ink composition obtained above was measured at room temperature (20 to 25° C.) using an ultrasonic vibration viscometer. Table 1 shows the results.

<<Formation of silver-containing film>>
Using an inkjet printer and the silver ink composition obtained above, inkjet printing was performed on one side of a base material ("Yupojet VJFN160" manufactured by Yupo Corporation) whose main component is synthetic paper. . The printing at this time was carried out by filling in a rectangle with a resolution of 600 dpi and a size of 50 mm×150 mm on the substrate. The silver ink composition immediately after printing was a colorless and transparent liquid.

Immediately thereafter, the base material after printing was placed on a conveyor and transported directly under a high-pressure mercury lamp, and the printed layer of this base material was irradiated with ultraviolet rays using the high-pressure mercury lamp. At this time, the irradiation dose of ultraviolet rays having a wavelength of 365 nm was 190 mJ/cm ² . Then, the substrate after the irradiation was transported from directly under the high-pressure mercury lamp to the outside.
By repeating this series of operations, the printed layer of the substrate was repeatedly irradiated with ultraviolet rays with the upper limit of the integrated dose set to 8.9 J/cm ² . During this time, the color of the printed layer (silver ink composition) on the substrate changed from colorless and transparent to yellow, then to brown, and finally to silver.

As described above, a silver-containing film (thickness of about 2 μm) was formed from the printed layer on the substrate. The irradiation dose of ultraviolet rays required to complete the formation of the silver-containing film (that is, the cumulative dose) was 8.55 J/cm ² . At this time, it was judged that the formation of the silver-containing film was completed when the color of the printed layer under UV irradiation became silver and no change in the surface condition was observed. The irradiation dose of ultraviolet rays is shown in the column of "required irradiation dose of ultraviolet rays" in Table 1. In addition, the appearance of the obtained silver-containing film was visually observed. Table 1 shows the results.

<<Production and Evaluation of Silver Ink Composition, Formation of Silver-Containing Film>>
[Examples 2 to 6, Comparative Examples 1 to 5]
At the time of manufacturing the silver ink composition, by changing either one or both of the types and amounts of the ingredients, the ratio of the content of each component to the total mass of the silver ink composition in the silver ink composition ( %) was changed as shown in Table 1 or Table 2, a silver ink composition was produced and evaluated in the same manner as in Example 1, and an attempt was made to form a silver-containing film. However, in Comparative Examples 2 to 5, the viscosity of the silver ink composition was not measured.
The results are shown in Table 1 or Table 2.

In Tables 1 and 2, "-" in the "Contained component (% by mass)" column means that the component is not contained.
In addition, the description of "-" in the "viscosity (mPa·s)" column means that the viscosity has not been measured.
In addition, the description of "-" in the column of "necessary UV irradiation dose (J/cm ² )" means that the required irradiation dose was not determined.

As is clear from the above results, in Examples 1 to 6, a silver-containing film having silver luster and specularity could be formed.
In the silver ink compositions of Examples 1-6, C ₁ was 9.0-9.9 mass % and C ₁ /C ₂ was 0.33-0.77.
Further, the viscosities of the silver ink compositions of Examples 1 to 6 were 3.1 to 8.3 mPa·s.
In Examples 1 to 6, the irradiation dose of ultraviolet rays required to complete the formation of the silver-containing film was 1.14 to 8.55 J/cm ² .

The 20° specular glossiness of the silver-containing films obtained in Examples 1 and 2 was measured according to JIS Z 8741:1997. .

On the other hand, in Comparative Examples 1 and 2, although a silver-containing film could be formed, the content of impurities was large, and the silver-containing film was yellow and did not have silver luster, and naturally had specular properties. I didn't. In Comparative Examples 1 and 2, the cumulative dose of irradiated ultraviolet rays reached the upper limit without forming the desired silver-containing film.
In the silver ink compositions of Comparative Examples 1 and 2, C ₁ is 7.4% by mass or less (2.0 to 7.4% by mass), and in the silver ink composition of Comparative Example 1, C ₁ / _C2 was 0.03.
In Comparative Examples 1 and 2, the amount of silver nitrate in the silver ink composition was too small, and thus the amount of silver in the silver nitrate was too small, resulting in insufficient formation of metallic silver. presumed to have a strong tendency

In Comparative Examples 3 and 4, a silver-containing film having silver luster could be formed, but the appearance of the silver-containing film was matte and did not have specularity.
In the silver ink compositions of Comparative Examples 3 and 4, C ₁ was 12.9 mass % or more (12.9 to 14.9 mass %).
In Comparative Examples 3 and 4, the amount of silver nitrate in the silver ink composition was too large, and when the silver-containing film was formed, silver nitrate precipitated in the silver-containing film, and silver nitrate or silver nitrate-derived silver nitrate was deposited in the silver-containing film. It was presumed that the silver-containing film having specularity could not be formed due to contamination of impurities.

In Comparative Example 5, a silver-containing film having silver luster could be formed, but the appearance of the silver-containing film was matte and did not have specularity. contained.
In the silver ink composition of Comparative Example ₅ , C1/ _C2 was 1.42.
In Comparative Example 5, the amount of energy ray-curable compound in the silver ink composition was relatively too less than the amount of silver in the silver nitrate in the silver ink composition, resulting in by-products in the silver-containing film. It was presumed that the uptake amount of substances increased, and as a result, a silver-containing film having specular properties could not be formed, and the silver-containing film contained brown precipitates.

INDUSTRIAL APPLICABILITY The present invention can be used as a raw material for producing a highly glossy silver-containing material. In particular, a printed layer is formed by an inkjet printing method, and a highly glossy silver-containing material is formed without heating the printed layer. It is particularly useful as a raw material when

Claims (3)

A silver ink composition comprising:
The silver ink composition contains silver nitrate, an energy ray-curable compound, and a solvent,
C1 is the ratio of the content of silver in the silver nitrate to the _total mass of the silver ink composition in the silver ink composition, and the ratio of the silver content in the silver ink composition to the total mass of the silver ink composition is A silver ink in which C1 is 8% by mass or more and less than 12% by mass, and C1 _{/ C2} is 0.3 or more and less than _1.4 , where _C2 is the content ratio of the energy ray-curable compound. Composition. 2. The silver ink composition according to claim 1, wherein said silver ink composition contains alcohol as said solvent. The silver ink composition further contains a photopolymerization initiator,
3. The silver ink composition according to claim 1, wherein a content ratio _C4 of the photopolymerization initiator in the silver ink composition with respect to the total mass of the silver ink composition is 9% by mass or more. .