WO2022070517A1

WO2022070517A1 - Inkjet ink and image recording method

Info

Publication number: WO2022070517A1
Application number: PCT/JP2021/022076
Authority: WO
Inventors: 健次郎荒木
Original assignee: 富士フイルム株式会社
Priority date: 2020-09-29
Filing date: 2021-06-10
Publication date: 2022-04-07
Also published as: JPWO2022070517A1; JP7443552B2

Abstract

An inkjet ink and an image recording method, wherein the inkjet ink contains a radical polymerizable monomer and silica particles, the silica particles have an average primary particle size of not less than 22 nm but less than 100 nm, and has a hydrophobicity degree of 50 or more.

Description

Inkjet ink and image recording method

This disclosure relates to inkjet inks and image recording methods.

As a kind of image recording method, an image recording method is known in which ink is applied onto a recording medium and the applied ink is irradiated with active energy rays such as ultraviolet rays to cure the ink to obtain an image. There is.

For example, Japanese Patent Application Laid-Open No. 2018-024757 contains a photopolymerizable compound, a photopolymerization initiator, and an inorganic filler having an average particle size of 1 nm to 200 nm in an amount of 0.05% by mass to 5.0% by mass in the composition. A clear ink composition for photocurable ink jet printing having a visible light transmittance of 30% or more is described.

Further, Japanese Patent Application Laid-Open No. 2019-162742 describes an active energy ray-curable composition containing fine particles having an average primary particle size of 100 nm to 200 nm.

Further, Japanese Patent Application Laid-Open No. 2020-62758 contains an ultraviolet curable ink containing 1% by mass to 10% by mass of silica particles having an average primary particle size of 7 nm to 16 nm whose surface is surface-modified with dimethylsilyl or dimethylpolysiloxane. Have been described.

By the way, images recorded using active energy ray-curable ink may have strong gloss. Due to the strong gloss, the above image may have a relief feeling or may be conspicuous. Therefore, from the viewpoint of reducing the relief feeling of the image, making the image inconspicuous, and the like, it may be required that the gloss is suppressed as the quality of the image recorded by using the active energy ray-curable ink. .. However, if the ink contains a gloss suppressing component in order to suppress the gloss, the ejection property may be deteriorated when the ink is ejected by the inkjet recording method.

According to one embodiment of the present invention, there are provided an inkjet ink capable of recording an image having excellent ejection properties and suppressed gloss, and an image recording method using the inkjet ink.

The disclosure includes the following aspects:
<1> An inkjet ink containing a radically polymerizable monomer and silica particles, wherein the silica particles have an average primary particle size of 22 nm or more and less than 100 nm, and a degree of hydrophobicity of 50 or more.
<2> The inkjet ink according to <1>, wherein the silica particles have an average secondary particle size of 200 nm to 800 nm.
<3> The silica particles are described in <1> or <2>, wherein the product of the average primary particle size when the unit is nm and the specific surface area when the unit is m ² / g is 2400 or less. Inkjet ink.
<4> The inkjet ink according to any one of <1> to <3>, wherein the silica particles have a degree of hydrophobicity of 70 or more.
<5> The inkjet ink according to any one of <1> to <4>, wherein the content of the silica particles is 1% by mass to 10% by mass with respect to the total amount of the inkjet ink.
<6> The radically polymerizable monomer contains at least one of a monofunctional radically polymerizable monomer and a bifunctional radically polymerizable monomer, and the total content of the monofunctional radically polymerizable monomer and the bifunctional radically polymerizable monomer is the amount of the inkjet ink. The inkjet ink according to any one of <1> to <5>, which is 50% by mass or more with respect to the total amount.
<7> The inkjet ink according to any one of <1> to <6>, wherein the radically polymerizable monomer contains a radically polymerizable monomer having a ClogP value of 2 or more.
<8> The inkjet ink according to <7>, wherein the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles is 6 to 50.
<9> The inkjet ink according to any one of <1> to <8>, wherein the radically polymerizable monomer contains an N-vinyl compound.
<10> The inkjet ink according to <9>, wherein the mass ratio of the content of the N-vinyl compound to the content of the silica particles is 1 to 8.
<11> The inkjet ink according to any one of <1> to <10>, wherein the radically polymerizable monomer contains a vinyl ether compound.
<12> A step of applying the inkjet ink according to any one of <1> to <11> onto a recording medium by an inkjet recording method to obtain an ink film, and irradiating the ink film with active energy rays. Process and
Image recording method including.
<13> The image recording method according to <12>, wherein the step of irradiating the ink film with the active energy ray includes a step of irradiating the ink film with the active energy ray in an atmosphere having an oxygen concentration of 5% by volume or less.

Hereinafter, the inkjet ink and the image recording method according to the present disclosure will be described in detail.

In the present disclosure, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
In the present disclosure, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. do.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Further, it may be replaced with the value shown in the embodiment.
In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.
In the present disclosure, the combination of preferred embodiments is a more preferred embodiment.
In the present disclosure, "light" is a concept including active energy rays such as γ-rays, β-rays, electron rays, ultraviolet rays, and visible rays.
In the present disclosure, ultraviolet rays may be referred to as "UV (Ultra Violet) light".
In the present disclosure, "(meth) acrylate" is a concept including both acrylate and methacrylate, and "(meth) acryloyl group" is a concept including both acryloyl group and methacrylic acid group, and "(meth) acrylate" is included. "Acrylic acid" is a concept that includes both acrylic acid and methacrylic acid.

In the present disclosure, the "image" means the entire film formed by using ink, and the "image recording" means the formation of an image (that is, a film).
The concept of "image" in the present disclosure also includes a solid image.

[Inkjet ink]
The inkjet ink of the present disclosure (hereinafter, simply referred to as “ink”) contains a radically polymerizable monomer and silica particles, and the silica particles have an average primary particle size of 22 nm or more and less than 100 nm, and have a degree of hydrophobicity of 50. That is all.

According to the ink of the present disclosure, it is possible to record an image having excellent ejection properties and suppressed gloss. The reason why the above effect is achieved is presumed as follows.

In general, in image recording using an ink containing a radically polymerizable monomer, ink is applied onto a recording medium, and active energy rays are applied to the ink applied onto the recording medium (hereinafter, also referred to as “ink film”). It is done by irradiating. In this image recording, when the ink film is irradiated with active energy rays, the radically polymerizable monomers in the ink film are polymerized and the ink film is cured. As a result, an image that is a cured ink film is obtained. The ink of the present disclosure can be said to be an active energy ray irradiation type ink.

In the ink of the present disclosure, the degree of hydrophobicity of silica particles is 50 or more. Therefore, the silica particles tend to be present on the surface of the ink film. Further, the average primary particle size of the silica particles is 22 nm or more and less than 100 nm. When silica particles of such a size gather on the surface of the ink film, it is considered that the aggregated silica particles function as a matting agent. It is considered that the gloss of the image is suppressed by curing the ink film with the silica particles gathered on the surface of the ink film.

Further, when the average primary particle size of the silica particles is 22 nm or more, the increase in the viscosity of the ink is suppressed without increasing the surface area of the silica particles. As a result, the ink of the present disclosure is considered to be excellent in ejection property. On the other hand, when the average primary particle size of the silica particles is less than 100 nm, the silica particles are less likely to settle, so that the ink of the present disclosure is considered to have excellent ejection properties.

On the other hand, Japanese Patent Application Laid-Open No. 2018-024757 discloses an ink containing silica particles having an average particle size of 20 nm. This average particle size means a dispersed particle size, and the primary particle size is considered to be 20 nm or less. Further, Japanese Patent Application Laid-Open No. 2020-62758 contains an ultraviolet curable ink containing 1% by mass to 10% by mass of silica particles having an average primary particle size of 7 nm to 16 nm whose surface is surface-modified with dimethylsilyl or dimethylpolysiloxane. Have been described. In the inks disclosed in JP-A-2018-024757 and JP-A-2020-626758, since the average primary particle size of the silica particles is small, the ink has a high viscosity, and as a result, good ejection properties cannot be obtained. it is conceivable that. Further, it is considered that the silica particles do not function as a matting agent because the average primary particle size is not in an appropriate range. Therefore, it is considered that the inks disclosed in JP-A-2018-024757 and JP-A-2020-062758 do not have the effect of suppressing gloss.

Further, Japanese Patent Application Laid-Open No. 2019-162742 describes an active energy ray-curable composition containing silica particles having an average primary particle size of 100 nm to 200 nm. In the composition disclosed in JP-A-2019-162742, it is considered that since the average primary particle size of the silica particles is large, it is easy to settle and good ejection property cannot be obtained. Further, it is considered that the silica particles do not function as a matting agent because the average primary particle size is not in an appropriate range. Therefore, it is considered that the composition disclosed in JP-A-2019-162742 does not have the effect of suppressing gloss.

Hereinafter, each component contained in the ink of the present disclosure will be described.

<Silica particles>
The ink of the present disclosure contains at least one type of silica particles.

The degree of hydrophobicity of the silica particles contained in the ink of the present disclosure is 50 or more. That is, the silica particles contained in the ink of the present disclosure are hydrophobic silica particles. Silica particles having a degree of hydrophobicity of 50 or more are likely to be present on the surface of the ink film, so that the gloss of the image is suppressed. Further, the silica particles having a degree of hydrophobicity of 50 or more act as a surfactant in the ink and reduce the surface tension of the ink. When the surface tension of the ink is small, the drip interference is suppressed and the image quality (particularly the graininess) is improved.

The degree of hydrophobicity of the silica particles is more preferably 70 or more from the viewpoint of further suppressing the gloss of the obtained image and further improving the image quality. The upper limit of the degree of hydrophobicity of the silica particles is not particularly limited, and is, for example, 99. The degree of hydrophobicity of the silica particles is measured by the following method.

First, centrifuge the ink to extract silica particles. Next, 50 mL of ion-exchanged water and 0.2 g of extracted silica particles are placed in a beaker, and methanol is added dropwise from the burette while stirring with a magnetic stirrer. As the concentration of methanol in the beaker increases, the silica particles gradually settle. When the entire amount of silica particles has subsided, the dropping of methanol is terminated. The mass fraction (%) of methanol in the mixed solution of methanol and water at the end of dropping is defined as the degree of hydrophobicity.

The average primary particle size of the silica particles contained in the ink of the present disclosure is 22 nm or more and less than 100 nm. When the average primary particle size of the silica particles is 22 nm or more, the increase in the viscosity of the ink is suppressed without increasing the surface area of the silica particles. As a result, the ink of the present disclosure is excellent in ejection property. On the other hand, when the average primary particle size of the silica particles is less than 100 nm, the silica particles are less likely to settle, so that the ink of the present disclosure is excellent in ejection property. Further, when the average primary particle size of the silica particles is 22 nm or more and less than 100 nm, the silica particles collected on the surface of the ink film function as a matting agent, and the gloss of the image is suppressed.

The average primary particle size of the silica particles is preferably 40 nm to 80 nm, more preferably 50 nm to 80 nm, from the viewpoint of further suppressing the gloss of the obtained image and further improving the ejection property.

In the present disclosure, the average primary particle size of silica particles is a value measured using a transmission electron microscope (TEM). The average primary particle size of the silica particles can be measured, for example, using a transmission electron microscope (product name "1200EX") manufactured by JEOL Ltd. The specific measurement method is as follows.

Ink diluted 1,000 times was dropped onto a Cu200 mesh (manufactured by JEOL Ltd.) to which a carbon film was attached and dried. Then, from the image magnified 100,000 times by TEM, the equivalent circle diameter of 300 independent particles that do not overlap is measured. The average value of the equivalent circle diameter obtained by the measurement is defined as the average primary particle size.

The average secondary particle size of the silica particles contained in the ink of the present disclosure is preferably 200 nm to 800 nm, and more preferably 400 nm to 800 nm. When the average secondary particle size of the silica particles is 200 nm to 800 nm, the presence of the silica particles on the surface of the ink film has a high effect of suppressing the gloss of the image.

In the present disclosure, the secondary particle size means the size of the silica particles dispersed in the ink, and can be said to be the dispersed particle size. The silica particles may exist in the state of primary particles in the ink, or may exist in a state in which a plurality of primary particles are aggregated and aggregated. In the former case, the primary particle size and the secondary particle size have almost the same value.

The average secondary particle size of the silica particles is a value measured using a particle size distribution measuring device. The average secondary particle size of the silica particles can be measured, for example, by using a particle size distribution measuring device (product name “LUMiSizer”) manufactured by LUM. The specific measurement method is as follows.

Centrifugation is performed for 16 hours under the condition of a rotation speed of 3000 using a particle size distribution measuring device (product name "LUMiSizer") manufactured by LUM. The average value of the dispersed particle size obtained by the measurement is defined as the average secondary particle size.

The silica particles contained in the ink of the present disclosure preferably have a product of the average primary particle size when the unit is nm and the specific surface area when the unit is m ² / g is 2400 or less, and preferably 1800 or less. Is more preferable. The lower limit of the product is not particularly limited, and is, for example, 1000.

Normally, the smaller the average primary particle size, the higher the specific surface area. Further, when the primary particles are agglomerated with each other, the higher the degree of agglomeration, the lower the specific surface area. Therefore, the fact that the product of the average primary particle size and the specific surface area is 2400 or less means that the primary particles aggregate to some extent to form secondary particles. Therefore, when the product of the average primary particle size and the specific surface area of the silica particles is 2400 or less, the gloss of the image is suppressed.

The specific surface area of the silica particles is a value measured by the BET method. The specific surface area of the silica particles can be measured, for example, using a rapid BET specific surface area measuring device (product name "BELSORP MR1") manufactured by Microtrac MRB. The specific measurement method is as follows.

First, centrifuge the ink to extract silica particles. Next, the extracted silica particles are washed with propylene glycol monomethyl ether and dried. The specific surface area of the obtained silica particles is calculated from the filling amount of nitrogen gas using a rapid BET specific surface area measuring device.

The silica particles may be fumed silica or colloidal silica as long as the average primary particle size is 22 nm or more and less than 100 nm. In general, colloidal silica is monodisperse and does not easily aggregate. That is, the average primary particle size and the average secondary particle size tend to be almost the same value. On the other hand, in fumed silica, primary particles tend to be loosely aggregated to form secondary particles. In the ink of the present disclosure, the average secondary particle size of the silica particles is preferably 200 nm to 800 nm from the viewpoint of suppressing the gloss of the image. Therefore, the silica particles are preferably fumed silica.

The surface structure of the silica particles is not particularly limited, but from the viewpoint of making the degree of hydrophobicity 50 or more, the silica particles preferably have a polydimethylsiloxane structure or an alkyl group, and preferably have a polydimethylsiloxane structure.

The surface structure of the silica particles can be analyzed using a pyrolysis gas chromatograph, for example, QP2010 Ultra manufactured by Shimadzu Corporation.

Silica particles may be commercially available products. Commercially available products include, for example, VP RY 40S, VP RX 40S (above, manufactured by Ebonic), Aerosil RY50, Aerosil RY51, Aerosil NY50, Aerosil RX50, Aerosil RX50, Aerosil NAX50, Aerosil ASilASilA Examples include Aerosil NX90S, Aerosil NX90G (above, manufactured by Ebonic), and Leolosil PM-09 (manufactured by Tokuyama).

The content of the silica particles is not particularly limited, but is preferably 0.5% by mass to 15% by mass, more preferably 1% by mass to 10% by mass, and 2.5% by mass with respect to the total amount of the ink. It is more preferably% to 8% by mass. When the content of the silica particles is 0.5% by mass or more, the gloss of the image is further suppressed. On the other hand, when the content of the silica particles is 15% by mass or less, the ejection property is further improved.

<Radical polymerizable monomer>
The ink of the present disclosure contains at least one radically polymerizable monomer.

The radically polymerizable monomer means a monomer having at least one radically polymerizable group in one molecule. The radically polymerizable group is preferably an ethylenically unsaturated group from the viewpoint of curability.

The molecular weight of the radically polymerizable monomer is preferably 100 to 400. The molecular weight of the radically polymerizable monomer can be calculated based on the type and number of atoms constituting the radically polymerizable monomer.

The radically polymerizable monomer includes a monofunctional radically polymerizable monomer (hereinafter referred to as "monofunctional monomer"), a bifunctional radically polymerizable monomer (hereinafter referred to as "bifunctional monomer"), and a trifunctional or higher functional radically polymerizable monomer (hereinafter referred to as "bifunctional monomer"). Hereinafter, it may be any of (referred to as "monomer having trifunctionality or higher"). Further, the radically polymerizable monomer may be a combination containing two or more of a monofunctional monomer, a bifunctional monomer, and a trifunctional or higher functional monomer.

The radically polymerizable monomer contained in the ink of the present disclosure preferably contains at least one of a monofunctional monomer and a bifunctional monomer. In this case, the total content of the monofunctional monomer and the bifunctional monomer is preferably 50% by mass or more, more preferably 55% by mass or more, and more preferably 60% by mass or more with respect to the total amount of the ink. Is even more preferable. The upper limit of the total content of the monofunctional monomer and the bifunctional monomer is not particularly limited, but is, for example, 80% by mass.

Among them, the radically polymerizable monomer preferably contains a bifunctional monomer, and more preferably contains a monofunctional monomer and a bifunctional monomer. When the ink contains a bifunctional monomer, silica particles are easily extruded onto the surface of the ink film during polymerization, so that the gloss of the obtained image is further suppressed.

From the viewpoint of further suppressing the gloss of the obtained image, the content of the bifunctional monomer is preferably 5% by mass to 80% by mass, and preferably 10% by mass to 80% by mass, based on the total amount of the ink. More preferably, it is more preferably 20% by mass to 80% by mass.

Further, from the viewpoint of further suppressing the gloss of the obtained image, the mass ratio of the content of the bifunctional monomer to the content of the silica particles is preferably 1 to 100, more preferably 3 to 50. It is more preferably 4 to 20.

From the viewpoint of reducing the viscosity of the ink, the content of the radically polymerizable monomer is preferably 50% by mass or more, more preferably 60% by mass or more, and 65% by mass or more with respect to the total amount of the ink. It is more preferable that the amount is 70% by mass or more, and it is particularly preferable that the amount is 70% by mass or more. The upper limit of the content of the radically polymerizable monomer is not particularly limited, but is, for example, 80% by mass.

-Monofunctional monomer-
Examples of the monofunctional monomer include monofunctional (meth) acrylate, monofunctional (meth) acrylamide, monofunctional aromatic vinyl compound, monofunctional vinyl ether, and monofunctional N-vinyl compound.

Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) Acrylate, 4-n-butylcyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, norbornyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, 2 -Ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyanoethyl (meth) acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate , 3-methoxybutyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, ethylcarbitol (meth) acrylate, 2,2 2-Tetrafluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (Meta) acrylate, 4-chlorophenyl (meth) acrylate, 2-phenoxymethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) ) Acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (Meta) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybuty Lu (meth) acrylate, cyclic trimethylolpropaneformal (meth) acrylate, phenylglycidyl ether (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) Meta) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol ( Meta) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropylphthalate, butoxydiethylene glycol (meth) acrylate, Trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene oxide-modified (hereinafter referred to as EO-modified) phenol (meth) acrylate, EO-modified cresol (hereinafter referred to as EO-modified). Meta) acrylate, EO-modified nonylphenol (meth) acrylate, propylene oxide-modified (hereinafter referred to as PO-modified) nonylphenol (meth) acrylate, EO-modified -2-ethylhexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclo Examples thereof include pentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (3-ethyl-3-oxetanylmethyl) (meth) acrylate, and phenoxyethylene glycol (meth) acrylate.

Examples of the monofunctional (meth) acrylamide include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and Nn-butyl (meth) acrylamide. Nt-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl Examples include (meth) acrylamide and (meth) acryloylmorpholin.

Examples of the monofunctional aromatic vinyl compound include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, and 3-methyl. Styrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene,3-octyl Styrene, 4-octyl styrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene, isopropenyl styrene, butenyl styrene, octenyl styrene, 4-t-butoxycarbonyl styrene, and 4 -T-butoxystyrene can be mentioned.

Examples of the monofunctional vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether and 4-methyl. Cyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydro Full frill vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chlorethyl vinyl ether, chlorbutyl vinyl ether, chlorethoxyethyl vinyl ether , Phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether.

Examples of the monofunctional N-vinyl compound include N-vinylcaprolactam, N-vinylpyrrolidone, N-vinyloxazolidinone, and N-vinyl-5-methyloxazolidinone.

-2 Functional monomer-
Examples of the bifunctional monomer include a bifunctional (meth) acrylate, a bifunctional vinyl ether, and a bifunctional monomer containing a vinyl ether group and a (meth) acryloyl group.

Examples of the bifunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and dipropylene glycol di (meth). Acrylic, Tripropylene Glycol Di (Meta) Acrylic, Polyethylene Glycol Di (Meta) Acrylic, Polypropylene Glycol Di (Meta) Acrylic, Butylene Glycol Di (Meta) Acrylate, Tetraethylene Glycol Di (Meta) Acrylic, Neopentyl Glycol Di (Meta) ) Acrylate, 3-Methyl-1,5-pentanediol di (meth) acrylate, hexanediol di (meth) acrylate, heptanediol di (meth) acrylate, EO-modified neopentyl glycol di (meth) acrylate, PO-modified neopentyl Glycol di (meth) acrylate, EO-modified hexanediol di (meth) acrylate, PO-modified hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, decanediol di (meth) acrylate , Dodecanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl Examples thereof include ether di (meth) acrylate and tricyclodecanedimethanol di (meth) acrylate.

Examples of the bifunctional vinyl ether include 1,4-butanediol divinyl ether (ClogP value: 1.32), ethylene glycol divinyl ether (ClogP value: 0.66), and diethylene glycol divinyl ether (ClogP value: 0.47). Triethylene glycol divinyl ether (ClogP value: 0.29), polyethylene glycol divinyl ether (ClogP value: 0.29 or less), propylene glycol divinyl ether (ClogP value: 0.97), butylene glycol divinyl ether (ClogP value: 1). .32), hexanediol divinyl ether (ClogP value: 2.38), 1,4-cyclohexanedimethanol divinyl ether (ClogP value: 1.66), bisphenol A alkylene oxide divinyl ether (eg, bisphenol A ethylene oxide divinyl ether). In the case of bisphenol F alkylene oxide divinyl ether (for example, in the case of bisphenol F ethylene oxide divinyl ether, Clog P value: 4.55).

Examples of the bifunctional monomer containing a vinyl ether group and a (meth) acryloyl group include 2- (2-vinyloxyethoxy) ethyl (meth) acrylate.

-3 Sensual or higher monomer-
Examples of the trifunctional or higher functional monomer include trifunctional or higher functional (meth) acrylates and trifunctional or higher functional vinyl ethers.

Examples of the trifunctional or higher functional (meth) acrylate include trimethylolethanetri (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, and PO-modified trimethylolpropane tri (meth) acrylate. ) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) Included are acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, and tris (2-acryloyloxyethyl) isocyanurate.

Examples of the trifunctional or higher functional vinyl ether include trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, trimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, and EO. Modified trimethylolpropane trivinyl ether, PO-modified trimethylolpropane trivinyl ether, EO-modified dimethylolpropane tetravinyl ether, PO-modified dimethylolpropane tetravinyl ether, EO-modified pentaerythritol tetravinyl ether, PO-modified pentaerythritol tetravinyl ether, EO-modified dipentaerythritol Hexavinyl ether and PO-modified dipentaerythritol hexavinyl ether can be mentioned.

-Urethane (meth) acrylate-
Examples of the bifunctional monomer and the trifunctional or higher functional monomer include urethane (meth) acrylate.

Examples of the urethane (meth) acrylate include urethane (meth) acrylate, which is a reaction product of a bifunctional isocyanate compound and a hydroxyl group-containing (meth) acrylate.

Examples of the bifunctional isocyanate compound include methylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dipropylether diisocyanate, 2,2-dimethylpentane diisocyanate, and 3-methoxyhexanediisocyanis. , Octamethylene diisocyanate, 2,2,4-trimethylpentane diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 3-butoxyhexane diisocyanate, 1,4-butylene glycol dipropyl ether diisocyanate, thiodihexyl diisocyanate and other aliphatic diisocyanis;
m-phenylene diisocyanate, p-phenylenedi isocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, dimethylbenzene diisocyanate, ethylbenzene diisocyanate, isopropylbenzene diisocyanate, trizine diisocyanate, 1,4-naphthalenedi isocyanate, 1,5 -Aromatic diisocyanates such as naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 2,7-naphthalene diisocyanate, metaxylylene diisocyanate, paraxylylene diisocyanate, tetramethylxylylene diisocyanate;
Alicyclic diisocyanates such as hydrogenated xylylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate;
And so on.
Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxy. Examples thereof include butyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, phenylglycidyl ether (meth) acrylate, pentaerythritol (meth) triacrylate, and dipentaerythritol penta (meth) acrylate.

-Epoxy (meth) acrylate-
Examples of the bifunctional monomer and the trifunctional or higher functional monomer include epoxy (meth) acrylate.

Examples of the epoxy (meth) acrylate include a reaction product of (meth) acrylic acid and an epoxy resin.

Examples of the epoxy resin include bisphenol A type epoxy resin and cresol novolac type epoxy resin.

The radically polymerizable monomer preferably contains a radically polymerizable monomer having a ClogP value of 2 or more. When the ink contains two or more kinds of radically polymerizable monomers, it is preferable that at least one of the two or more kinds of radically polymerizable monomers is a radically polymerizable monomer having a LogP value of 2 or more. When the ink contains a radically polymerizable monomer having a LogP value of 2 or more, hydrophobic interaction is likely to work with silica particles having a degree of hydrophobicity of 50 or more. As a result, the viscosity of the ink is lowered and the ejection property is improved.

From the viewpoint of further suppressing the gloss of the obtained image and further improving the ejection property, the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles is 5 to 100. It is preferably 6 to 50, more preferably 7 to 30, and even more preferably 7 to 30.

Examples of the radically polymerizable monomer having a ClogP value of 2 or more include dipropylene glycol diacrylate (ClogP value: 2.04), tripropylene glycol diacrylate (ClogP value: 2.17), and phenoxyethyl acrylate (ClogP value: 2.04). 2.56), 3-methylpentanediol diacrylate (ClogP value: 2.89), isobornyl acrylate (ClogP value: 4.66), tricyclodecanedimethanol diacrylate (ClogP value: 4.66), Examples thereof include nonanediol diacrylate (ClogP value: 4.66) and lauryl acrylate (ClogP value: 6.62).

In the present disclosure, the ClogP value is calculated using the fragment method. Examples of the calculation software using the fragment method include ChemDrawProfessional16.

The radically polymerizable monomer preferably contains an N-vinyl compound. The N-vinyl compound has an action of pushing silica particles onto the surface of the ink film. Therefore, when the ink contains an N-vinyl compound, silica particles gather on the surface of the ink film, and the gloss of the obtained image is further suppressed.

From the viewpoint of further suppressing the gloss of the obtained image and further improving the ejection property, the mass ratio of the content of the N-vinyl compound to the content of the silica particles is preferably 1 to 15 and 1 to 15. It is more preferably 10 and even more preferably 1 to 8, and particularly preferably 1 to 7.

Further, the radically polymerizable monomer preferably contains a vinyl ether compound. The vinyl ether compound has a slow polymerization rate and is extruded together with the silica particles onto the surface of the ink film. Therefore, when the ink contains a vinyl ether compound, silica particles gather on the surface of the ink film, and the gloss of the obtained image is further suppressed. In addition, the vinyl ether compound is generally highly polar and aggregates silica particles, further suppressing the gloss of the obtained image.

In particular, the polyfunctional vinyl ether compound has a high effect of pushing silica particles onto the surface of the ink film during polymerization. Therefore, the vinyl ether compound is preferably a polyfunctional vinyl ether compound. Further, from the viewpoint that the viscosity of the ink does not become too high and the ejection property is improved, the polyfunctional vinyl ether compound is preferably a bifunctional vinyl ether compound, and more preferably polyethylene glycol divinyl ether.

Further, the ClogP value of the vinyl ether compound is preferably less than 1.0, more preferably 0.5 or less. When the ClogP value of the vinyl ether compound is less than 1.0, the effect of agglomerating the silica particles and suppressing the gloss of the image is high.

The content of the vinyl ether compound is preferably 0.5% by mass to 10% by mass, more preferably 2% by mass to 8% by mass, based on the total amount of the ink.

<Dispersant>
The ink of the present disclosure preferably contains at least one dispersant. When the ink contains a dispersant, the dispersibility of the silica particles in the ink is improved. As a result, the ink ejection property is further improved.

The type of dispersant is not particularly limited, but from the viewpoint of improving the dispersibility of silica particles having a degree of hydrophobicity of 50 or more, the dispersant is a polymer having a structural unit derived from a hydrophobic monomer having a ClogP value of 2 to 10. Is preferable. A polymer having a structural unit derived from a hydrophobic monomer having a ClogP value of 2 to 10 has a high adsorptivity to the surface of silica particles having a degree of hydrophobicity of 50 or more, so that the dispersibility of the silica particles is improved. As a result, the ink ejection property is further improved.

Hydrophobic monomers having a ClogP value of 2 to 10 include, for example, styrene, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, and Examples include stearyl (meth) acrylate.

Further, the dispersant is preferably a basic dispersant. The basic groups contained in the dispersant are adsorbed on the silanol groups present on the surface of the silica particles, so that the dispersibility of the silica particles is improved. As a result, the ink ejection property is further improved.

The dispersant may be a commercially available product. As commercially available products, for example, SOLSparse series (manufactured by Noveon) such as SOLSERSE 13940, 17000, 20000, 24000, 26000, 28000, 32000, 35000, 36000, 39000, etc.
DISPERBYK-108, 109, 161, 162, 163, 164, 167, 168, 180, 182, 184, 185, 2000, 2001, 2008, 2009, 2012, 2013, 2022, 2025, 2026, 2050, 2055, 2150, DISPERBYK series (manufactured by BYK Chemie) such as 2155, 2163, 2164, 9076, 9077, DISPERBYK-9076;
BYKJET series (manufactured by BYK) such as BYKJET-9150, 9151, 9152;
Efka series (manufactured by BASF) such as Efka PX4701, Efka PX4703, Efka PX4733, Efka PU4063;
Diskex Ultra PX 4575 (manufactured by BASF) can be mentioned.

The mass ratio of the content of the dispersant to the content of the silica particles is preferably 0.05 to 0.5, preferably 0.08 to 0.2, from the viewpoint of stably dispersing the silica particles. More preferred.

<Radical polymerization initiator>
The ink of the present disclosure preferably contains at least one radical polymerization initiator.

Examples of the radical polymerization initiator include alkylphenone compounds, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketooxime ester compounds, borate compounds, azinium compounds, metallocene compounds, and activities. Examples thereof include ester compounds, compounds having a carbon halogen bond, and alkylamine compounds.

Above all, the radical polymerization initiator is preferably an acylphosphine compound.

Examples of the acylphosphine oxide compound include a monoacylphosphine oxide compound and a bisacylphosphine oxide compound.

Examples of the monoacylphosphine oxide compound include isobutyryldiphenylphosphine oxide, 2-ethylhexanoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and (2,4,6-trimethylbenzoyl) ethoxyphenyl. Phosphine oxide, o-toluyldiphenylphosphine oxide, pt-butylbenzoyldiphenylphosphine oxide, 3-pyridylcarbonyldiphenylphosphine oxide, acryloyldiphenylphosphine oxide, benzoyldiphenylphosphine oxide, pivaloylphenylphosphine acid vinyl ester, adipoil bis Diphenylphosphine oxide, pivaloyldiphenylphosphine oxide, p-toluyldiphenylphosphine oxide, 4- (t-butyl) benzoyldiphenylphosphine oxide, terephthaloylbisdiphenylphosphine oxide, 2-methylbenzoyldiphenylphosphine oxide, versatoyldiphenylphosphine Examples thereof include oxide, 2-methyl-2-ethylhexanoyldiphenylphosphine oxide, 1-methyl-cyclohexanoyldiphenylphosphine oxide, pivaloylphenylphosphine acid methyl ester and pivaloylphenylphosphine acid isopropyl ester.

Examples of the bisacylphosphine oxide compound include bis (2,6-dichlorobenzoyl) phenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,5-dimethylphenylphosphine oxide, and bis (2,6-dichlorobenzoyl). ) -4-ethoxyphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-propylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2-naphthylphosphine oxide, bis (2,6-dichlorobenzoyl) ) -1-naphthylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-chlorophenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,4-dimethoxyphenylphosphine oxide, bis (2,6-dichloro) Benzoyl) decylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-octylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl)- 2,5-dimethylphenylphosphine oxide, bis (2,6-dichloro-3,4,5-trimethoxybenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dichloro-3,4,5 -Trimethoxybenzoyl) -4-ethoxyphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -4-ethoxyphenylphosphine oxide , Bis (2-methyl-1-naphthoyl) -2-naphthylphosphine oxide, bis (2-methyl-1-naphthoyl) -4-propylphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5 -Dimethylphenylphosphine oxide, bis (2-methoxy-1-naphthoyl) -4-ethoxyphenylphosphine oxide, bis (2-chloro-1-naphthoyl) -2,5-dimethylphenylphosphine oxide and bis (2,6-- Dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide can be mentioned.

Among them, the acylphosphine oxide compounds are bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (product name "Omnirad 819", manufactured by IGM Resins VV), 2,4,6-trimethylbenzoyldiphenylphosphine. Oxide (product name "Omnirad TPO H", manufactured by IGM Resins B.V.) or (2,4,6-trimethylbenzoyl) ethoxyphenylphosphine oxide (product name "Omnirad TPO-L", IGM Resins B.V.) (Manufactured by the company) is preferable.

The content of the radical polymerization initiator is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 8% by mass, based on the total mass of the ink.

<Sensitizer>
When the ink of the present disclosure contains a radical polymerization initiator, the ink of the present disclosure may contain a sensitizer together with the radical polymerization initiator. When the ink contains a sensitizer, the curability is improved, and particularly when an LED light source is used, the curability is improved.

Examples of the sensitizer include polynuclear aromatic compounds, xanthene compounds, cyanine compounds, merocyanine compounds, thiazine compounds, aclysine compounds, anthraquinones (for example, anthraquinones), squalium compounds, coumarin compounds, and thioxanthones. Examples thereof include system compounds and thiochromanone compounds. Above all, the sensitizer is preferably a thioxanthone-based compound from the viewpoint of improving the image quality of the obtained image.

Examples of the thioxanthone compound include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1 -Methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3- (2-methoxyethoxycarbonyl) thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxy Carbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfylthioxanthone, 3,4-di [2- (2-methoxy) Ethoxy) ethoxycarbonyl] thioxanthone, 1-ethoxycarbonyl-3- (1-methyl-1-morpholinoethyl) thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6- (1,1-dimethoxybenzyl) Thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboxyimide, n-octylthioxanthone-3,4-dicarboxyimide, N- (1,1) , 3,3-Tetramethylbutyl) thioxanthone-3,4-dicarboxyimide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-ethoxycarbonyl-2-methylthioxanthone, thioxanthone-2-polyethylene glycol Examples include esters and 2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy) -N, N, N-trimethyl-1-propaneaminium chloride.

Among them, the thioxanthone-based compound is preferably 2,4-diethylthioxanthone, 2-isopropylthioxanthone, or 4-isopropylthioxanthone from the viewpoint of availability and improvement of image quality.

The thioxanthone-based compound may be a commercially available product. Examples of commercially available products include SPEEDCURE series manufactured by Rambson (for example, SPEEDCURE 7010, SPEEDCURE CPTX, and SPEEDCURE ITX).

The content of the sensitizer is preferably 1% by mass to 10% by mass, more preferably 1.5% by mass to 5% by mass, based on the total amount of the ink.

<Polymerization inhibitor>
The ink according to the present disclosure preferably contains at least one polymerization inhibitor.

Examples of the polymerization inhibitor include hydroquinone compounds, phenothiazines, catechols, alkylphenols, alkylbisphenols, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionic acid ester, and mercaptobenzimidazole. , Phosphites, nitrosoamine compounds, hinderedamine compounds, and nitroxyl radicals.

Among them, the polymerization inhibitor is preferably at least one selected from the group consisting of a nitrosamine compound, a hindered amine compound, a hydroquinone compound, and a nitroxyl radical, and more preferably a nitrosamine compound.

Examples of the nitrosamine compound include N-nitroso-N-phenylhydroxylamine aluminum salt and N-nitroso-N-phenylhydroxylamine. Above all, the nitrosamine compound is preferably an N-nitrosamine-N-phenylhydroxylamine aluminum salt.

The content of the polymerization inhibitor is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, based on the total amount of the ink, from the viewpoint of improving the stability of the ink over time. The upper limit of the content of the polymerization inhibitor is not particularly limited, but is preferably 1% by mass from the viewpoint of polymerizability.

<Color material>
The ink of the present disclosure may contain at least one kind of coloring material.

The type of coloring material is not particularly limited and may be either a pigment or a dye. From the viewpoint of light resistance, the coloring material is preferably a pigment.

When a pigment is used as a coloring material, the pigment can be contained in the ink as a pigment dispersion liquid. The pigment dispersion liquid is a liquid obtained by dispersing a pigment in a liquid medium using a pigment dispersant, and contains at least a pigment, a pigment dispersant, and a liquid medium.

Examples of the pigment dispersant include the same dispersants as those described above (that is, dispersants for the purpose of dispersing silica particles).

Examples of the liquid medium include organic solvents. Further, the liquid medium may be the above-mentioned radically polymerizable monomer contained in the ink.

The pigment may be either an organic pigment or an inorganic pigment that is usually commercially available. Further, the pigment may be an invisible pigment having infrared absorption.

When the ink of the present disclosure contains a coloring material, the content of the coloring material is preferably 1% by mass to 20% by mass, more preferably 2% by mass to 10% by mass, based on the total amount of the ink. preferable.

When the ink of the present disclosure is a clear ink for recording a clear image, the ink of the present disclosure does not have to contain substantially a coloring material. In this case, the content of the coloring material may be less than 1% by mass, less than 0.1% by mass, or 0% by mass with respect to the total amount of the ink. The clear image means an image having a transmittance of 80% or more at a wavelength of 400 nm to 700 nm.

<Other ingredients>
The ink of the present disclosure may contain other components other than the above components, if necessary. Other components include, for example, surfactants, co-sensitizers, UV absorbers, antioxidants, anti-fading agents, conductive salts, water, solvents, and basic compounds.

<Physical characteristics>
The pH of the ink is preferably 7 to 10, and more preferably 7.5 to 9.5, from the viewpoint of improving the ejection property when the ink is applied by using an inkjet recording method. The pH is measured at 25 ° C. using a pH meter, and is measured, for example, using a pH meter (model number "HM-31") manufactured by Toa DKK Corporation.

The viscosity of the ink is preferably 0.5 mPa · s to 30 mPa · s, more preferably 2 mPa · s to 20 mPa · s, preferably 2 mPa · s to 15 mPa · s, and 3 mPa · s. It is more preferably about 10 mPa · s. The viscosity is measured at 25 ° C. using a viscometer, and is measured, for example, using a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.

The surface tension of the ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension is measured at 25 ° C. using a surface tension meter, and is measured by a plate method using, for example, an automatic surface tension meter (product name “CBVP-Z”) manufactured by Kyowa Surface Science Co., Ltd.

[Image recording method]
The image recording method of the present disclosure includes a step of applying the above ink on a recording medium by an inkjet recording method to obtain an ink film (hereinafter, also referred to as "first application step"), and an active energy ray on the ink film. It includes a step of irradiating (hereinafter, also referred to as “first irradiation step”).

The image recording method of the present disclosure may include other steps, if necessary.

As described above, the image recording method of the present disclosure uses the ink of the present disclosure. Therefore, according to the image recording method of the present disclosure, the same effect as that of the ink of the present disclosure is obtained.

<First granting process>
The first applying step is a step of applying the ink to the recording medium by an inkjet recording method to obtain an ink film.

The type of recording medium is not particularly limited, and is, for example, paper, paper laminated with plastic (for example, polyethylene, polypropylene, polystyrene, etc.), metal plate (for example, metal plate such as aluminum, zinc, copper, etc.), plastic. Film (for example, Polyvinyl Chloride (PVC) resin, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate (PET: Polyethylene Terephthalate), polyethylene (PE:: Polyethylene), polystyrene (PS: Polystyrene), polypropylene (PP: Polypropylene), polycarbonate (PC: Polycarbonate), polyvinyl acetal, acrylic resin and other films), paper on which the above-mentioned metals are laminated or vapor-deposited, and the above-mentioned. Examples include plastic films on which metal is laminated or vapor-deposited.

The inkjet recording method is not particularly limited as long as it can record an image, and a known method can be used. Inkjet recording methods include, for example, a charge control method that uses electrostatic attraction to eject ink, a drop-on-demand method that uses the vibration pressure of a piezo element (pressure pulse method), and ink that converts electrical signals into acoustic beams. An acoustic inkjet method in which ink is ejected by irradiating the ink with radiation pressure, and a thermal inkjet (bubble jet (registered trademark)) method in which the ink is heated to form bubbles and the generated pressure is used. ..

As the inkjet head used in the inkjet recording method, a short serial head is used, and a shuttle method in which recording is performed while scanning the head in the width direction of the base material and a recording element are arranged corresponding to the entire area of one side of the base material. A line method using a line head that has been used can be mentioned.

In the line method, a pattern can be formed on the entire surface of the base material by scanning the base material in a direction intersecting the arrangement direction of the recording elements, and a transport system such as a carriage that scans a short head becomes unnecessary. Further, in the line method, the movement of the carriage and the complicated scanning control with the base material are not required, and only the base material moves, so that the recording speed can be increased as compared with the shuttle method.

The amount of ink ejected from the inkjet head is preferably 1 pL (picolitre) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

<First irradiation step>
In the first irradiation step, the ink film obtained in the first application step is irradiated with active energy rays.

In the first irradiation step, the ink film is irradiated with active energy rays to polymerize at least a part of the radically polymerizable monomer in the ink film to obtain an image.

In the first irradiation step, when only a part of the radically polymerizable monomer in the ink film is polymerized, the active energy ray is compared with the case where substantially all of the radically polymerizable monomer in the ink film is polymerized. Reduce the irradiation energy of.

In the present disclosure, polymerizing only a part of the radically polymerizable monomer in the ink film is also referred to as "temporary curing", and irradiation with active energy rays for temporary curing is also referred to as "pinning exposure".
In the present disclosure, polymerizing substantially all of the radically polymerizable monomers in the ink film is also referred to as "main curing", and irradiation with active energy rays for main curing is also referred to as "main exposure".

The first irradiation step may be a step of applying pinning exposure (that is, temporary curing) to the ink film, or may be a step of applying main exposure (that is, main curing) to the ink film. death,
It may be a step of applying the pinning exposure and the main exposure to the ink film in this order.

When the first irradiation step is a step of applying pinning exposure (that is, temporary curing) to the ink film, an image of the temporarily cured ink film is obtained by the first irradiation step. When the first irradiation step is a step of applying main exposure (that is, main curing) to the ink film, or a step of applying pinning exposure and main exposure to the ink film in this order, the first irradiation step is performed. An image that is the main cured ink film can be obtained.

When the first irradiation step is a step of applying pinning exposure (that is, temporary curing), it is preferable that the image recording method further includes a second applying step and a second irradiation step described later.

The reaction rate of the ink film after pinning exposure (that is, temporary curing) is preferably 10% to 80%.

Here, the reaction rate of the ink film means the polymerization rate of the radically polymerizable monomer in the ink film obtained by high performance liquid chromatography.

When the reaction rate of the ink film is 10% or more, insufficient spread of dots of the ink (for example, the second ink described later) applied on the ink film is suppressed. As a result, the graininess of the finally obtained image (for example, a multi-order color image described later) is improved. That is, the graininess of the image is reduced.

Further, when the reaction rate of the ink film is 80% or less, the spread of the ink applied on the ink film (for example, the second ink described later) is suppressed to be excessive, and the dots of the ink are suppressed. Drip interference between each other is suppressed. As a result, the image quality of the finally obtained image is improved.

The reaction rate of the ink film is preferably 15% or more from the viewpoint of further improving the graininess of the finally obtained image.

The reaction rate of the ink film is preferably 75% or less, more preferably 50% or less, still more preferably 40% or less, from the viewpoint of further improving the image quality of the finally obtained image. , 30% or less, and particularly preferably 25% or less.

The reaction rate of the ink film after the main exposure is preferably more than 80% and 100% or less, more preferably 85% to 100%, and even more preferably 90% to 100%. When the reaction rate is more than 80%, the adhesion of the image is further improved.

The reaction rate of the ink film is calculated using the following method.

Prepare a recording medium that has been operated until the end of irradiation of the ink film on the recording medium with active energy rays, and prepare a sample piece having a size of 20 mm × 50 mm from the region where the ink film of the recording medium exists. (Hereinafter referred to as a sample piece after irradiation) is cut out, and the cut out sample piece after irradiation is immersed in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain an eluate from which the ink is eluted. With respect to the obtained eluate, the amount of radically polymerizable monomer (hereinafter referred to as "amount of monomer after irradiation X1") is determined by high performance liquid chromatography.

Separately, the same operation as above is performed except that the ink film on the recording medium is not irradiated with the active energy rays, and the amount of the radically polymerizable monomer (hereinafter referred to as “non-irradiated monomer amount X1”) is determined. demand.

Based on the amount of monomer after irradiation X1 and the amount of monomer without irradiation X1, the reaction rate (%) of the ink is determined by the following formula.
Ink reaction rate (%) = ((non-irradiated monomer amount X1-post-irradiated monomer amount X1) / unirradiated monomer amount X1) × 100

The active energy ray in the irradiation step (that is, the active energy ray for pinning exposure and / or the main exposure; the same applies hereinafter) is preferably UV light (that is, ultraviolet light) in the wavelength range of 385 nm to 410 nm. It is more preferable that the UV light has the highest illuminance.

As the UV light source (that is, the light source of UV light), a known UV light source in which at least one of the illuminance and the irradiation time is variable can be used.
The UV light source is preferably an LED (Light Emitting Diode) light source.

Irradiation of the active energy ray in the irradiation step may be performed in an environment where the oxygen concentration is 20% by volume or less (more preferably less than 20% by volume, still more preferably 5% by volume or less). As a result, polymerization inhibition due to oxygen is suppressed, and an excellent image can be obtained due to the adhesion to the recording medium.

In an environment where the oxygen concentration is less than 20% by volume, the presence of an inert gas (for example, nitrogen gas, argon gas, and helium gas) is suitable.

The illuminance of the active energy ray for the pinning exposure is preferably 0.10 W / cm ² to 0.50 W / cm ² from the viewpoint of more easily achieving the reaction rate of the above-mentioned ink, and is more preferably 0.20 W / cm. It is more preferably cm ² to 0.50 W / cm ² , and even more preferably 0.20 W / cm ² to 0.45 W / cm ² .

The irradiation energy of the active energy rays for pinning exposure (hereinafter, also referred to as “exposure amount”) may be 2 mJ / cm ² to 20 mJ / cm ² from the viewpoint of more easily achieving the above-mentioned ink reaction rate. It is preferably 4 mJ / cm ² to 15 mJ / cm ² , more preferably.

The illuminance of the active energy ray for the main exposure is preferably 1.0 W / cm ^{2 or more, and 2.0 W / cm 2} ^or more, from the viewpoint of further improving the adhesion between the recording medium and the image. More preferably, it is more preferably 4.0 W / cm ² or more.

The upper limit of the illuminance of the active energy ray for the main exposure is not particularly limited, but is, for example, 10 W / cm ² .

The exposure amount of the active energy ray for the main exposure is preferably 20 mJ / cm ² or more, and more preferably 80 mJ / cm ² or more, from the viewpoint of further improving the adhesion between the recording medium and the image. preferable.

The upper limit of the exposure amount of the active energy ray for the main exposure is not particularly limited, and is, for example, 240 mJ / cm ² .

<Second granting process>
In the image recording method of the present disclosure, a second ink is applied onto an ink film (hereinafter, also referred to as "first ink film") irradiated with active energy rays in the first irradiation step, and the first ink film is coated with the second ink. It may include a second application step of obtaining a second ink film in contact with the ink film.

The second ink is preferably an ink containing a radically polymerizable monomer and a radical polymerization initiator, and more preferably the ink of the present disclosure.

When the second ink is the ink of the present disclosure, the content of silica particles in the second ink is preferably higher than the content of silica particles in the first ink. Since the silica particles function as a surfactant, the higher the content of the silica particles, the lower the surface tension of the ink. That is, when the content of the silica particles contained in the second ink is larger than the content of the silica particles contained in the first ink, the surface tension of the second ink is lower than the surface tension of the first ink. As a result, when the second ink is applied onto the first ink film, the drip interference is suppressed. As a result, the image quality of the obtained image is improved.

It is preferable that the ink of the present disclosure (hereinafter, also referred to as the first ink) applied in the first application step and the second ink have different hues.

When the hues of the first ink and the second ink are different, a secondary color image can be recorded.

In the second application step, the second ink may be applied across the first ink film and the non-recording medium on which the first ink film is not formed.

Further, in the second application step, the second ink may be applied on at least a part of the first ink film, and does not necessarily have to be applied on the entire first ink film.

The method of applying the second ink is the same as the method of applying the first ink, and the preferred embodiment is also the same.

According to the image recording method of the present disclosure of the embodiment including the second addition step, it is possible to record a secondary color image in which gloss is suppressed.

<Second irradiation step>
The image recording method of the present disclosure including the second application step may further include a second irradiation step of irradiating the entire first ink film and the second ink film with the second active energy ray. ..

The second irradiation step may be a step of applying a pinning exposure to the entire first ink film and the second ink film, or a main exposure to the entire first ink film and the second ink film. It may be a step, or it may be a step of applying pinning exposure and main exposure to the entire first ink film and the second ink film in this order.

The preferred embodiment of the second active energy ray and its irradiation conditions is the same as the preferred embodiment of the active energy ray and its irradiation conditions in the first irradiation step.
For example, the preferred irradiation conditions for the pinning exposure and the main exposure in the second irradiation step are the same as the preferable irradiation conditions for the pinning exposure and the main exposure in the first irradiation step.

<Other processes>
In the image recording method of the present disclosure, after the second irradiation step, the step of applying the ink of the present disclosure and the step of irradiating with active energy rays may be repeated.

When the ink of the present disclosure is applied a plurality of times, the content of the silica particles in the ink to be applied later is the content of the silica particles in the ink to be applied first from the viewpoint of improving the image quality of the obtained image. Preferably more than.

If the hue of the ink applied first and the ink applied later are different, an image of multiple colors can be recorded.

For example, when black ink, cyan ink, magenta ink, and yellow ink are applied, first, black ink is applied on the recording medium to obtain a black ink film, and then cyan is applied on the black ink film. It is preferable to apply ink, apply magenta ink on the cyan ink film, and apply yellow ink on the magenta ink film.

Assuming that black ink, cyan ink, magenta ink, and yellow ink are applied to the recording medium in this order, the content of the silica particles contained in the cyan ink is higher than the content of the silica particles contained in the black ink. In many cases, the content of silica particles contained in magenta ink is higher than the content of silica particles contained in cyan ink, and the content of silica particles contained in yellow ink is the content of silica particles contained in magenta ink. Preferably more than. The content of silica particles means the content with respect to the total amount of each ink.

Hereinafter, examples of the present disclosure will be shown, but the present disclosure is not limited to the following examples.

<Example 1 to Example 45, Comparative Example 1 to Comparative Example 10>
First, a magenta pigment dispersion was prepared.

-Preparation of magenta pigment dispersion-
30 parts by mass of magenta pigment, 50 parts by mass of "SR341", and 20 parts by mass of "SOLSPERSE 32000" were put into a disperser motor mill M50 (manufactured by Eiger), and a peripheral speed was used using zirconia beads having a diameter of 0.65 mm. The dispersion treatment was carried out at 9 m / s for 8 hours to obtain a magenta pigment dispersion.

Next, each component contains the prepared magenta pigment dispersion and the silica particles, radically polymerizable monomers, radical polymerization initiators, sensitizers, polymerization inhibitors, and dispersants shown in Tables 2 to 7 below. The mixture was mixed so as to have the content (% by mass) shown in Tables 2 to 7. The mixture was stirred for 20 minutes at 25 ° C. under the condition of 5000 rpm using a mixer (product name “L4R”, manufactured by Silberson) to obtain ink.

In Tables 2 to 7, the unit of the average primary particle size and the average secondary particle size of the silica particles is "nm", and the unit of the surface area is "m ² / g". "Monomer / silica particles having a ClogP value of 2 or more" means the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles. "N-vinyl compound / silica particles" means the mass ratio of the content of the N-vinyl compound to the content of the silica particles.

In addition, FLORSTAB UV-12 (manufactured by Kromachem) was used for the preparation of the ink. FLORSTAB UV12 is a mixture of N-nitroso-N-phenylhydroxylamine aluminum salt and PEA, and the mixing ratio is 1: 9. Since the N-nitroso-N-phenylhydroxylamine aluminum salt is a polymerization inhibitor and PEA is a radically polymerizable monomer, the polymerization inhibitor and the radically polymerizable monomer will be described below separately. For example, when the content of FLORSTAB UV-12 contained in the ink was 0.5% by mass, PEA was 0.45% by mass and N-nitroso-N-phenylhydroxylamine aluminum salt was 0.05% by mass.

The details of each component listed in Tables 2 to 7 are as follows.

<Radical polymerizable monomer (referred to as "polymerizable monomer" in the table)>
-4-HBA: 4-Hydroxybutyl acrylate (product name "4-HBA", manufactured by Osaka Organic Chemical Industry Co., Ltd.)
-VMOX: 5-Methyl-3-vinyloxazolidine-2-one (product name "VMOX", manufactured by BASF)
-TEGDA: Triethylene glycol diacrylate (product name "SR268", manufactured by Sartomer)
-NVC: N-vinylcaprolactam (product name "NVC", manufactured by BASF)
-OXEA: (3-ethyloxetane-3-yl) methyl acrylate (product name "Oxe-10", manufactured by Osaka Organic Chemical Co., Ltd.)
-GTA: Glycerin triacrylate (product name "Aronix M930", manufactured by Sartomer)
-DPGDA: Dipropylene glycol diacrylate (product name "SR508", manufactured by Sartomer)
-PEA: Phenoxyethyl acrylate (product name "FLORSTAB UV12", manufactured by Kromachem, 90% by mass)
3MPDDA: 3-Methyl-1,5-pentanediol diacrylate (product name "SR341", manufactured by Sartomer)
-IBOA: Isobornyl acrylate (product name "SR506", manufactured by Sartomer)
NDDA: Nonanediol diacrylate (product name "SR578", manufactured by Sartomer)
-LA: Lauryl acrylate (product name "SR335", manufactured by Sartomer)
-DVE-3: Triethylene glycol divinyl ether (product name "Rapi-Curetm DVE-3", manufactured by Ashland)

<Radical polymerization initiator (referred to as "polymerization initiator" in the table)>
Ominirad 819: Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (manufactured by IGM Resins B.V.)
TPO-L: (2,4,6-trimethylbenzoyl) ethoxyphenylphosphine oxide (product name "Omnirad TPO-L", manufactured by IGM Resins BV)

<Sensitizer>
-ITX: 2-isopropylthioxanthone (product name "SPEEDCURE ITX", manufactured by Rambson)

<Polymerization inhibitor>
-Nitrosamine compound: Tris (N-nitrosamine-N-phenylhydroxylamine) aluminum salt (product name "FLORSTAB UV12", manufactured by Kromachem, 10% by mass)
<Dispersant>
-BYKJET9151: Styrene polymer (manufactured by BYK)
DISPERBYK-2013: Styrene-based polymer (manufactured by BYK)
SOLPERSE32000: Polyethyleneimine-based polymer (manufactured by Lubrizol)

<Color material>
-Magenta pigment: Product name "Cinquasia (registered trademark) Magenta L 4540" (manufactured by BASF)

[Preparation of image recording device]
A transport system for transporting the recording medium, a black ink head, a UV (Ultraviolet) light source, a cyan ink head, a UV light source, and a magenta ink head, which are sequentially arranged from the upstream side in the transport direction of the recorded medium. An image recording device (specifically, an inkjet recording device) including a UV light source, a head for yellow ink, a UV light source, a head for white ink, and a nitrogen purge UV exposure machine was prepared. The transport system was a single-pass type sheet-fed printing press.

The black ink head, cyan ink head, magenta ink head, and yellow ink head are each equipped with an inkjet nozzle (hereinafter, also simply referred to as “nozzle”) as a piezo type inkjet head (specifically, a line head). ). From each nozzle, 1 pL to 60 pL multi-size dots can be ejected at a resolution of 1,200 × 1,200 dpi. Here, dpi represents the number of dots per 2.54 cm.

The ink supply system of this inkjet recording device is composed of a former tank, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and an inkjet head. In the image recording in this embodiment, the portion of the ink supply system from the ink supply tank to the inkjet head was heat-insulated and heated. Further, temperature sensors were provided near the nozzles of the ink supply tank and the inkjet head, respectively, and the temperature was controlled so that the nozzle portion was always 70 ° C. ± 2 ° C.

The original tank connected to the magenta ink head contained one of the inks for each embodiment and the inks for each comparative example.

As the UV light source immediately after each inkjet head and the UV light source in the nitrogen purge UV exposure machine, an LED (Light Emitting Diode) lamp (manufactured by Kyocera) capable of irradiating UV light having the highest illuminance in the wavelength range of 385 nm to 410 nm, respectively. 4 cm width, G4B, maximum illuminance 10 W) was used.

Each of these UV light sources is a UV light source whose illuminance and irradiation time of UV light can be changed. In the image recording in this embodiment, the recording medium is so that the irradiation of UV light to the landed ink is started 0.1 seconds after the ink ejected from each head lands on the recording medium. The transport speed was adjusted.

[Image recording]
Using the above-mentioned image recording device, ink is applied to the recording medium in a solid shape so that the halftone dot area ratio is 100%, and the applied ink has an illuminance of 0.40 W / cm ² . An image (specifically, a solid image) is obtained by irradiating UV light for 0.024 seconds (pinning exposure) and then irradiating UV light for 0.024 seconds (main exposure) with an illuminance of 5.0 W / cm ² . Obtained an image recording in which was recorded.

Here, the pinning exposure was carried out in an atmosphere (oxygen concentration 20%) with a UV light source immediately after the magenta ink head.

This exposure was carried out by a nitrogen purge UV exposure machine in an atmosphere with an oxygen concentration of 1% and a nitrogen concentration of 99%.

The obtained image recording material was used to suppress the gloss of the image and the image quality was evaluated, and the ink was used to evaluate the ejection property. The evaluation method is as follows. The evaluation results are shown in Tables 2 to 7.

(Suppression of image gloss)
The glossiness of the recording medium before the above image is recorded and the glossiness of the image recorded in the obtained image recording material are measured by a gloss meter (product name "high gloss gloss checker IG-410", respectively. , Manufactured by HORIBA, Ltd.) under 60 ° gloss conditions.
Based on the obtained results, the value obtained by subtracting the glossiness of the recorded medium (that is, the glossiness of the recorded medium before the image is recorded) from the glossiness of the image (hereinafter, "gloss difference [image-recorded"). Medium] ”) was calculated. The gloss suppression of the image was evaluated based on the gloss difference. The evaluation criteria are as follows. The rank in which the gloss of the image is most suppressed is "5".

5: The gloss difference [image-recording medium] was less than 20.
4: The gloss difference [image-recording medium] was 20 or more and less than 25.
3: The gloss difference [image-recording medium] was 25 or more and less than 30.
2: The gloss difference [image-recorded medium] was 30 or more and less than 40.
1: The gloss difference [image-recorded medium] was 40 or more.

(Dischargeability)
An ejection test was conducted in which the ink was continuously ejected from the magenta ink head of the image recording device in a mode of 1,200 dpi for 5 minutes. After the ejection was completed, the number of nozzles missing was counted. This ejection test was performed 6 times, and the ejection property of the ink was evaluated based on the number of nozzles missing. In addition, nozzle omission means that "the nozzle cannot be ejected and becomes a streak". The evaluation criteria are as follows. The rank with the best ink ejection property is "5".
Nozzle omission did not occur in all 5: 6 ejection tests.
Only one nozzle was missing in one of the 4: 6 ejection tests, and no nozzle was missing in the five ejection tests.
Only one nozzle was missing in two of the 3: 6 ejection tests, and no nozzle was missing in the four ejection tests.
Only one nozzle was missing in three of the 2: 6 discharge tests, and no nozzle was missing in the three discharge tests.
Only one nozzle omission occurred in four or more ejection tests out of 1: 6 ejection tests, and two or more nozzle omissions occurred in at least one ejection test out of six ejection tests. At least one of the things was true.

(image quality)
The obtained image recording material was visually observed, and the image quality (specifically, graininess) of the image was evaluated. The evaluation criteria are as follows. The rank with the best graininess is "5".
5: No roughness was observed in the entire image and the image was uniform.
4: There was a slight graininess in the image, but it was almost uniform as a whole.
3: There is a slight graininess in the image, but it was at a level that was not a problem in practical use.
2: The image was rough and conspicuous even visually, which was a problem in practical use.
1: The image had a lot of roughness with strong shading, and it was a level that could not be said to be uniform.

As shown in Tables 2 to 7, the inks of Examples 1 to 45 contain a radically polymerizable monomer and silica particles, and the silica particles have an average primary particle size of 22 nm or more and less than 100 nm, and the silica particles have an average primary particle size of 22 nm or more and less than 100 nm. It was possible to record an image having a degree of hydrophobicity of 50 or more, excellent ejection properties, and suppressed gloss.

On the other hand, in Comparative Example 1, it was found that the average primary particle size of the silica particles was as small as 18 nm, so that the ink ejection property was inferior.

In Comparative Example 2, Comparative Example 6, and Comparative Example 7, it was found that since the degree of hydrophobicity of the silica particles was 0, an image in which the ink ejection property was inferior and the gloss was suppressed could not be obtained.

In Comparative Examples 3 to 5, since the average primary particle diameters of the silica particles were as small as 20 nm, 13 nm, and 15 nm, respectively, it was found that the ink ejection property was inferior and the image with suppressed gloss could not be obtained. rice field.

In Comparative Example 8, it was found that an image with suppressed gloss could not be obtained because the average primary particle size of the silica particles was as large as 110 nm.

In Comparative Example 9 and Comparative Example 10, it was found that the average primary particle size of the silica particles was as large as 400 nm and 500 nm, respectively, and therefore the ink ejection property was inferior.

It was found that in Example 26, the average secondary particle size of the silica particles was 200 nm to 800 nm, and an image with more suppressed gloss was obtained as compared with Example 42.

In Example 26, the product of the average primary particle size of the silica particles and the specific surface area was 2400 or less, and it was found that an image with more suppressed gloss was obtained as compared with Example 42.

It was found that in Examples 28 to 31, since the degree of hydrophobicity of the silica particles was 70 or more, images with more suppressed gloss were obtained as compared with Examples 36 and 37.

In Example 4, since the content of the silica particles is 1% by mass to 10% by mass, the graininess is excellent and the gloss is higher than that of Example 1 in which the content of the silica particles is less than 1% by mass. It was found that a more suppressed image was obtained.

In Example 4, since the content of the silica particles is 1% by mass to 10% by mass, the ink ejection property is excellent as compared with Example 7 in which the content of the silica particles is more than 10% by mass. It was found that an image with less gloss was obtained.

In Example 12, since the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles is 6 to 50, the mass ratio is less than 6, as compared with Example 11. It was found that an image having excellent ink ejection properties and less gloss was obtained.

In Example 4, since the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles is 6 to 50, the mass ratio is more than 50, as compared with Example 2. It was found that an image having excellent graininess and less gloss was obtained.

In Example 13, since the ink contains the N-vinyl compound, the graininess is excellent and the gloss is further suppressed as compared with Example 17 in which the ink does not contain the N-vinyl compound. It turned out that an image was obtained.

In Example 19, since the mass ratio of the content of the N-vinyl compound to the content of the silica particles is 1 to 8, the graininess is excellent as compared with Example 21 in which the mass ratio is more than 8. It was found that an image with less gloss was obtained.

In Example 4, since the mass ratio of the content of the N-vinyl compound to the content of the silica particles is 1 to 8, the ink ejection property is excellent as compared with Example 7 in which the mass ratio is less than 1. Moreover, it was found that an image with more suppressed gloss can be obtained.

In Example 45, since the ink contained a vinyl ether compound, it was found that an image having more suppressed gloss was obtained as compared with Example 23, which did not contain the vinyl ether compound.

[Examples 46 to 53]
In addition to the magenta pigment dispersion, a cyan pigment dispersion, a yellow pigment dispersion, and a black pigment dispersion were prepared for recording a multi-order color image. The cyan pigment dispersion, the yellow pigment dispersion, and the black pigment dispersion were prepared by the same method as the magenta pigment dispersion by changing the magenta pigment to a cyan pigment, a yellow pigment, and a black pigment, respectively.

<Color material>
-Magenta pigment: Product name "Cinquasia (registered trademark) Magenta L 4540" (manufactured by BASF)
-Cyan pigment: PB15: 4, product name "Heliogen (registered trademark) Blue D 7110 F" (manufactured by BASF)
-Yellow pigment: P. Y. 120, Product name "Novoperm Yellow H2G" (manufactured by Clariant)
-Black pigment: carbon black, product name "Special Black 250" (Orion Engineered Carbons)

Next, each component of each of the prepared pigment dispersions and the silica particles, radically polymerizable monomers, radical polymerization initiators, sensitizers, polymerization inhibitors, and dispersants shown in Table 8 below is shown in Table 8. The mixture was mixed so as to have the stated content (% by mass). The mixture was stirred for 20 minutes at 25 ° C. under the condition of 5000 rpm using a mixer (product name “L4R”, manufactured by Silberson) to obtain ink.

[Preparation of image recording device]
An image recording device was prepared in the same manner as in Example 1. Example 46 The ink of Example 46 is stored in the original tank connected to the black ink head, the ink of Example 47 is stored in the original tank connected to the cyan ink head, and the original tank connected to the magenta ink head is used. Forty-eight inks were stored, and the ink of Example 49 was stored in the original tank connected to the yellow ink head. After the image recording is completed, each original tank is washed, the ink of Example 50 is stored in the original tank connected to the black ink head, and the ink of Example 51 is stored in the original tank connected to the cyan ink head. The original tank connected to the magenta ink head contained the ink of Example 52, and the original tank connected to the yellow ink head contained the ink of Example 53.

[Image recording]
In Example 46, using the above-mentioned image recording apparatus, the ink (black ink) of Example 46 is applied to the recording medium in a solid shape so that the halftone dot area ratio is 100%, and the black ink is applied. The ink is irradiated with UV light at an illuminance of 0.40 W / cm ² for 0.024 seconds (pinning exposure), and then irradiated with UV light at an illuminance of 5.0 W / cm ² for 0.024 seconds (main exposure). ), An image recording material in which an image (specifically, a solid image) was recorded was obtained.

Here, the pinning exposure was carried out in an atmosphere (oxygen concentration 20%) with a UV light source immediately after the black ink head.

In Example 47, using the above-mentioned image recording apparatus, the ink (black ink) of Example 46 is applied to the recording medium in a solid shape so that the halftone dot area ratio is 100%, and the black ink is applied. The ink was irradiated with UV light for 0.024 seconds at an illuminance of 0.40 W / cm ² (pinning exposure). The ink (cyan ink) of Example 47 was applied solidly on the semi-cured black ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied cyan ink. UV light was irradiated for 0.024 seconds at the illuminance of. (Pinning exposure). Then, by irradiating (main exposure) with UV light for 0.024 seconds at an illuminance of 5.0 W / cm ² , an image recording material in which an image (specifically, a solid image) was recorded was obtained.

Here, the pinning exposure was carried out in an atmosphere (oxygen concentration 20%) by a UV light source immediately after the black ink head and the cyan ink head.

In Example 48, using the above-mentioned image recording apparatus, the ink (black ink) of Example 46 is applied to the recording medium in a solid shape so as to have a halftone dot area ratio of 100%, and the black ink is applied. The ink was irradiated with UV light for 0.024 seconds at an illuminance of 0.40 W / cm ² . (Pinning exposure). The ink (cyan ink) of Example 47 was applied solidly on the semi-cured black ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied cyan ink. UV light was irradiated for 0.024 seconds at the illuminance of (pinning exposure). The ink of Example 48 (magenta ink) was applied solidly on the semi-cured cyan ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied magenta ink. UV light was irradiated for 0.024 seconds at the illuminance of (pinning exposure). Then, by irradiating (main exposure) with UV light for 0.024 seconds at an illuminance of 5.0 W / cm ² , an image recording material in which an image (specifically, a solid image) was recorded was obtained.

Here, the pinning exposure was carried out in an atmosphere (oxygen concentration 20%) by a UV light source immediately after the black ink head, the cyan ink head, and the magenta ink head.

In Example 49, using the above-mentioned image recording apparatus, the ink (black ink) of Example 46 is applied to the recording medium in a solid shape so as to have a halftone dot area ratio of 100%, and the black ink is applied. The ink was irradiated with UV light for 0.024 seconds at an illuminance of 0.40 W / cm ² . (Pinning exposure). The ink (cyan ink) of Example 47 was applied solidly on the semi-cured black ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied cyan ink. UV light was irradiated for 0.024 seconds at the illuminance of (pinning exposure). The ink of Example 48 (magenta ink) was applied solidly on the semi-cured cyan ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied magenta ink. UV light was irradiated for 0.024 seconds at the illuminance of (pinning exposure). The ink of Example 49 (yellow ink) was applied solidly on the semi-cured magenta ink film so that the halftone dot area ratio was 100%, and 0.40 W / cm ² was applied to the applied yellow ink. UV light was irradiated for 0.024 seconds at the illuminance of (pinning exposure). Then, by irradiating (main exposure) with UV light for 0.024 seconds at an illuminance of 5.0 W / cm ² , an image recording material in which an image (specifically, a solid image) was recorded was obtained.

Here, the pinning exposure was carried out in an atmosphere (oxygen concentration 20%) by a UV light source immediately after the black ink head, the cyan ink head, the magenta ink head, and the yellow ink head.

For Examples 50 to 53, image recording was performed in the same manner as in Examples 46 to 49.

The obtained image recording material was used to suppress the gloss of the image and the image quality was evaluated, and the ink was used to evaluate the ejection property. Specifically, in Example 46, gloss suppression and image quality evaluation were performed on the black image recorded on the recording medium using the ink of Example 46. In Example 47, gloss suppression and image quality evaluation were performed on the cyan image recorded on the black image using the ink of Example 47. In Example 48, gloss suppression and image quality evaluation were performed on the magenta image recorded on the cyan image using the ink of Example 48. In Example 49, gloss suppression and image quality evaluation were performed on the yellow image recorded on the magenta image using the ink of Example 49. Also in Examples 50 to 53, gloss suppression and image quality evaluation were performed in the same manner as in Examples 46 to 49. The evaluation method is the same as the evaluation for Example 1. The evaluation results are shown in Table 8.

As shown in Table 8, in Examples 51 to 53, the content of the silica particles in the ink applied later is higher than the content of the silica particles in the ink applied earlier, and the examples thereof. It was found that an image having excellent graininess could be obtained as compared with 47 to 49.

<Reference example 1>
Each ink tank provided in an inkjet recording device (product name "Jet Press 540WV", manufactured by FUJIFILM Corporation) was individually filled with ink of each color. As an undercoat composition, UV curable ink (product name "Uvijet MK702", manufactured by FUJIFILM Corporation) and UV curable ink (product name "Uvijet MK703", manufactured by FUJIFILM Corporation) were mixed at a mass ratio of 85:15. A mixed solution was used. Further, as the white ink, a UV curable ink (product name "Uvijet MK021", manufactured by FUJIFILM Corporation) was used. As the black ink, UV curable ink (product name "Uvijet MKA04", manufactured by FUJIFILM Corporation) was used. As the cyan ink, a UV curable ink (product name "Uvijet MK215", manufactured by FUJIFILM Corporation) was used. As magenta ink, UV curable ink (product name "Uvijet MK867", manufactured by FUJIFILM Corporation) was used. As the yellow ink, UV curable ink (product name "Uvijet MKA52", manufactured by FUJIFILM Corporation) was used.
As a recording medium, a biaxially stretched polyester film (product name "Emblet PTM-12", manufactured by Unitika Ltd., film thickness 12 μm) was used.
First, the undercoat composition was applied onto the recording medium. After applying the undercoat composition, pinning exposure was performed at an illuminance of 750 mW / cm ² to form an undercoat layer. Next, a solid image was recorded with white ink on the obtained undercoat layer, and black ink, cyan ink, magenta ink, and yellow ink were ejected on the obtained solid image in this order. Even after each ink was ejected, pinning exposure was performed at an illuminance of 750 mW / cm ² in the same manner as after the undercoat composition was applied. After the final pinning exposure, the main exposure was performed from the upper part of the recording medium (that is, the side where the image is recorded) under a nitrogen atmosphere having an oxygen concentration of less than 0.1% by volume at an illuminance of 3000 mW / cm ² . .. The nitrogen purge was performed using the nitrogen generator attached to the inkjet recording device. Next, under an atmospheric atmosphere, the main exposure was performed from the lower part of the recording medium (that is, the side on which the image was not recorded) at an illuminance of 3000 mW / cm ² to obtain an image recorded object.
The transport speed of the recording medium was set to 50 m / min.

<Reference example 2>
An image recording was obtained in the same manner as in Reference Example 1 except that the undercoat composition was not applied.

<Reference example 3>
Add 0.8 g of a silicon-based surfactant (product name "BYK-307", manufactured by BYK) to 1 liter of UV curable ink (product name "Uvijet MK021", manufactured by Fujifilm) and stir well. As a result, white ink was prepared. An image recording was obtained by the same method as in Reference Example 2 except that the prepared white ink was used instead of the UV curable ink (product name "Uvijet MK021", manufactured by FUJIFILM Corporation).

It was confirmed that in each of Reference Example 1 to Reference Example 3, the adhesion between the recording medium and the image was good, and the image quality was good.

The disclosure of Japanese Patent Application No. 2020-163387 filed on September 29, 2020 is incorporated herein by reference in its entirety. Also, all documents, patent applications and technical standards described herein are to the same extent as if the individual documents, patent applications and technical standards were specifically and individually stated to be incorporated by reference. , Incorporated by reference herein.

Claims

Contains radically polymerizable monomers and silica particles,
The silica particles are inkjet inks having an average primary particle size of 22 nm or more and less than 100 nm and a degree of hydrophobicity of 50 or more.
The inkjet ink according to claim 1, wherein the silica particles have an average secondary particle size of 200 nm to 800 nm.
The inkjet according to claim 1 or 2, wherein the silica particles have a product of an average primary particle size when the unit is nm and a specific surface area when the unit is m 2 / g is 2400 or less. ink.
The inkjet ink according to any one of claims 1 to 3, wherein the silica particles have a degree of hydrophobicity of 70 or more.
The inkjet ink according to any one of claims 1 to 4, wherein the content of the silica particles is 1% by mass to 10% by mass with respect to the total amount of the inkjet ink.
The radically polymerizable monomer contains at least one of a monofunctional radically polymerizable monomer and a bifunctional radically polymerizable monomer.
The method according to any one of claims 1 to 5, wherein the total content of the monofunctional radically polymerizable monomer and the bifunctional radically polymerizable monomer is 50% by mass or more with respect to the total amount of the inkjet ink. Radical ink.
The inkjet ink according to any one of claims 1 to 6, wherein the radically polymerizable monomer contains a radically polymerizable monomer having a ClogP value of 2 or more.
The inkjet ink according to claim 7, wherein the mass ratio of the content of the radically polymerizable monomer having a ClogP value of 2 or more to the content of the silica particles is 6 to 50.
The inkjet ink according to any one of claims 1 to 8, wherein the radically polymerizable monomer contains an N-vinyl compound.
The inkjet ink according to claim 9, wherein the mass ratio of the content of the N-vinyl compound to the content of the silica particles is 1 to 8.
The inkjet ink according to any one of claims 1 to 10, wherein the radically polymerizable monomer contains a vinyl ether compound.
A step of applying the inkjet ink according to any one of claims 1 to 11 onto a recording medium by an inkjet recording method to obtain an ink film.
The step of irradiating the ink film with active energy rays and
Image recording method including.
The image recording method according to claim 12, wherein the step of irradiating the active energy ray includes a step of irradiating the ink film with the active energy ray in an atmosphere having an oxygen concentration of 5% by volume or less.