JP2011195649A - Photocurable ink composition, inkjet recording method, and recorded matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable ink composition which can reduce initial coloring derived from a thioxanthone-based photopolymerization initiator of an image recorded on a recording medium and which is excellent in curability and light stability of the image.SOLUTION: The photocurable ink composition includes at least a polymerizable compound and the thioxanthone-based photopolymerization initiator. The photocurable ink composition includes ≥0.5 mass% and ≤5 mass% of the thioxanthone-based polymerization initiator. When a total mass of the thioxanthone-based photopolymerization initiator included in the photocurable ink composition is 100 pts.mass, the thioxanthone-based photopolymerization initiator includes ≥90 pts.mass of 2-isopropyl thioxanthone. When there are residues other than 2-isopropyl thioxanthone in the thioxanthone-based photopolymerization initiator, the initiator includes 4-isopropyl thioxanthone as a major component of the residues.

Description

  The present invention relates to a photocurable ink composition, and an ink jet recording method and a recorded matter using the same.

  In recent years, development of photocurable inks that are cured by ultraviolet rays, electron beams, or other radiation has been promoted. Such a photo-curable ink realizes a recording which is quick-drying and prevents bleeding of ink in a recording on a non-absorbing medium which does not absorb or hardly absorbs an ink such as plastic, glass and coated paper. Can do. Such a photocurable ink is composed of a polymerizable compound, a photopolymerization initiator, other additives, and the like.

  Conventionally, several photocurable inks containing a specific polymerizable compound and a thioxanthone-based photopolymerization initiator have been proposed from the viewpoint of improving the curability and abrasion resistance of recorded images, adhesion to a recording medium, and the like. (For example, see Patent Documents 1 to 4).

JP 2008-280427 A JP 2008-280428 A JP 2009-185157 A JP 2009-227968 A

  However, the image recorded using the photocurable ink as described above has an initial yellow or brown color derived from the thioxanthone photopolymerization initiator, and sunlight or outside air (ozone, nitrogen oxide, sulfur oxidation) There was a tendency to further color by being exposed to the object.

  Some aspects of the present invention can reduce the initial coloration derived from the thioxanthone-based photopolymerization initiator of an image recorded on a recording medium by solving the above-mentioned problems, and also provide the curability and light resistance of the image. The present invention provides a photocurable ink composition excellent in the above.

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

[Application Example 1]
One aspect of the photocurable ink composition according to the present invention is:
A photocurable ink composition containing at least a polymerizable compound and a thioxanthone photopolymerization initiator,
The photocurable ink composition contains the thioxanthone photopolymerization initiator in an amount of 0.5% by mass to 5% by mass,
When the total mass of the thioxanthone photopolymerization initiator contained in the photocurable ink composition is 100 parts by mass, the thioxanthone photopolymerization initiator contains 90 parts by mass or more of 2-isopropylthioxanthone,
When the thioxanthone photopolymerization initiator has a remainder other than 2-isopropylthioxanthone, 4-isopropylthioxanthone is contained as a main component of the remainder.

  According to the photocurable ink composition described in Application Example 1, it is possible to reduce initial coloring derived from a thioxanthone photopolymerization initiator and to record an image having excellent curability and light resistance on a recording medium. Can do.

[Application Example 2]
In application example 1,
As said polymeric compound, 10 mass% or more and 50 mass% or less of phenoxyethyl acrylate can be contained.

[Application Example 3]
In application example 1 or application example 2,
As the polymerizable compound, a monofunctional acrylate having an alicyclic structure can be contained in an amount of 25% by mass to 40% by mass.

[Application Example 4]
In application example 3,
The monofunctional acrylate having the alicyclic structure may be at least one selected from dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, and azobonyl acrylate.

[Application Example 5]
In any one of Application Examples 1 to 4,
An amino acrylate can be contained as the polymerizable compound.

[Application Example 6]
In any one of Application Examples 1 to 5,
Furthermore, a benzoate photopolymerization initiator having an amino group can be contained.

[Application Example 7]
In any one of Application Examples 1 to 6,
Furthermore, a pigment can be contained.

[Application Example 8]
In any one of Application Examples 1 to 7,
The viscosity at a measurement temperature of 20 ° C. may be from 8 mPa · s to 40 mPa · s, and the surface tension at a measurement temperature of 20 ° C. may be from 20 mN / m to 30 mN / m.

[Application Example 9]
One aspect of the inkjet recording method according to the present invention is:
(A) discharging the photocurable ink composition according to any one of Application Example 1 to Application Example 8 onto a recording medium;
(B) irradiating the discharged photocurable ink composition with light having an emission peak wavelength in a range of 350 nm to 430 nm from a light source;
It is characterized by including.

[Application Example 10]
The recorded matter according to the present invention is:
It is recorded by the ink jet recording method described in Application Example 9.

1 is a perspective view of an ink jet recording apparatus that can be used in an ink jet recording method according to the present embodiment. The front view of the light irradiation apparatus shown in FIG. FIG. 3 is an AA arrow view of FIG. 2.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Photocurable ink composition A photocurable ink composition according to an embodiment of the present invention is a photocurable ink composition containing at least a polymerizable compound and a thioxanthone-based photopolymerization initiator, and the photocurable ink composition. The ink composition contains 0.5% by mass or more and 5% by mass or less of the thioxanthone photopolymerization initiator, and the total mass of the thioxanthone photopolymerization initiator contained in the photocurable ink composition is 100% by mass. Part, when the thioxanthone photopolymerization initiator contains 90 parts by mass or more of 2-isopropylthioxanthone and the thioxanthone photopolymerization initiator has a remainder other than 2-isopropylthioxanthone, It contains 4-isopropylthioxanthone as a component.

  In the present invention, “image” indicates a print pattern formed from a group of dots, and includes text printing and solid printing. Hereinafter, each component used for this Embodiment is demonstrated in detail.

1.1. Polymerizable compound The photocurable ink composition according to the present embodiment contains a polymerizable compound. Although it does not restrict | limit especially as a polymeric compound, Monofunctional (meth) acrylate, a bifunctional (meth) acrylate, a trifunctional (meth) acrylate, a urethane type oligomer, an epoxy (meth) acrylate oligomer, amino which are illustrated below, etc. (Meth) acrylate, N-vinyl compound and the like can be mentioned. In addition, in this specification, (meth) acrylate shows an acrylate or a methacrylate.

  The monofunctional (meth) acrylate is not particularly limited. For example, (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl (meth) acrylate, (2-methyl-2-isobutyl-1) , 3-Dioxolan-4-yl) methyl (meth) acrylate, phenoxyethyl (meth) acrylate, methoxydiethylene glycol mono (meth) acrylate, (meth) acryloylmorpholine, trimethylolpropane formal mono (meth) acrylate, adamantyl (meth) Examples include acrylate and oxetane (meth) acrylate.

  Among the monofunctional (meth) acrylates exemplified above, it is preferable to use phenoxyethyl (meth) acrylate. This is because phenoxyethyl (meth) acrylate has good curability and functions as a good solvent for the polymerization initiator. Further, since the viscosity is low, there is an advantage that the viscosity of the photocurable ink composition can be easily adjusted to a low value (20 ° C./8 mPa · s or more and 40 mPa · s or less) suitable for the ink jet recording method. The content of phenoxyethyl (meth) acrylate is preferably 10% by mass or more and 50% by mass or less with respect to the total mass of the photocurable ink composition.

  Moreover, as monofunctional (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 3,3,5-trimethylcyclohexane (meth) acrylate, It is preferable to use a monofunctional acrylate having an alicyclic structure such as isobornyl (meth) acrylate. A monofunctional acrylate having such an alicyclic structure can impart toughness to an image recorded on a recording medium by having a bulky alicyclic structure, and thereby the image has an abrasion resistance. It is because it can improve. Further, since the viscosity is low, there is an advantage that the viscosity of the photocurable ink composition can be easily adjusted to a low value (20 ° C./8 mPa · s or more and 40 mPa · s or less) suitable for the ink jet recording method. The content of the monofunctional acrylate having an alicyclic structure is preferably 25% by mass or more and 40% by mass or less with respect to the total mass of the photocurable ink composition.

  These monofunctional acrylates can be used alone or in combination of two or more.

  The bifunctional acrylate is not particularly limited, and examples thereof include alkylene glycol di (meth) acrylate and di (meth) acrylate having an alicyclic structure. Examples of the alkylene glycol di (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, and 1,9-nonanediol. Di (meth) acrylate, polyethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 2-hydroxy-1, Examples include 3-di (meth) acryloxypropane. Examples of the di (meth) acrylate having an alicyclic structure include dioxane glycol di (meth) acrylate, isocyanuric acid EO-modified di (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, 1,3- And adamantanediol di (meth) acrylate. These bifunctional acrylates can be used alone or in combination of two or more.

  In addition, when phenoxyethyl (meth) acrylate is used as the polymerizable compound, it is more preferable to use at least one selected from alkylene glycol diacrylate and diacrylate having an alicyclic structure. The alkylene glycol diacrylate and the diacrylate having an alicyclic structure function as a cross-linking agent, and can improve the film strength of an image recorded on a recording medium. In particular, since diacrylate having an alicyclic structure has a bulky molecular structure, the film strength of an image can be more effectively improved.

  Although it does not restrict | limit especially as trifunctional acrylate, For example, a trimethylol propane tri (meth) acrylate, a trimethylol propane EO modified tri (meth) acrylate, a trimethylol propane PO modified tri (meth) acrylate, glycerin PO modified tri (meth) Examples thereof include acrylate and isocyanuric acid EO-modified tri (meth) acrylate. These trifunctional acrylates can be used alone or in combination of two or more.

  Examples of the urethane oligomer include oligomers produced by an addition reaction between a polyol and a polyisocyanate and a polyhydroxy compound. A urethane-based oligomer has at least one urethane bond and radically polymerizable unsaturated double bond in the molecule, and is substantially or conceptually from a molecule having a small relative molecular mass (synonymous with molecular weight). A molecule having a medium relative molecular mass having a repeating structure of a small number of units, typically about 2 to 20 times. Commercially available CN963J75, CN964, CN965, CN966J75 (all available from SARTOMER), etc. can be used as the urethane oligomer.

  Examples of the epoxy acrylate oligomer include an epoxy acrylate oligomer based on a bifunctional bisphenol A. The oligomer is a small number of units substantially or conceptually obtained from a molecule having a small relative molecular mass (synonymous with molecular weight), generally about 2 to 20 times, like the urethane-based oligomer. Molecules with a medium relative molecular mass with a degree of repetitive structure. As an epoxy acrylate oligomer, commercially available CN120 (available from SARTOMER) or the like can be used.

  Although it does not specifically limit as aminoacrylate, Commercially available CN371, CN373, CN384, CN386, CN501, CN549, CN550, CN551 (available from SARTOMER), EBECRYL7100 (available from Daicel-Cytec), etc. are used. be able to.

  The content of amino (meth) acrylate is preferably 1% by mass or more and 5% by mass or less with respect to the total mass of the photocurable ink composition. When the content of amino (meth) acrylate is in the above range, the curing reaction can proceed smoothly and the curability of the image recorded on the recording medium can be improved.

  Examples of the N-vinyl compound include N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam, and derivatives thereof.

  The content of the polymerizable compound is preferably 20% by mass or more, and more preferably 20% by mass or more and 95% by mass or less with respect to the total mass of the photocurable ink composition. When the content of the polymerizable compound is 20% by mass or more, the curability of the image recorded on the recording medium is improved. On the other hand, when the content of the polymerizable compound is less than 20% by mass, the curability of the image recorded on the recording medium may be insufficient.

1.2. Thioxanthone photopolymerization initiator The photocurable ink composition according to the present embodiment contains a thioxanthone photopolymerization initiator. The thioxanthone photopolymerization initiator acts as an energy transfer type sensitizer that gives energy from the triplet excited state to another photopolymerization initiator. Further, by extracting hydrogen from a hydrogen donor pair such as an amine, free radicals can be generated and the photopolymerization reactivity can be increased.

  The thioxanthone photopolymerization initiator that can be used in the present embodiment contains 90 parts by mass or more of 2-isopropylthioxanthone when the total mass is 100 parts by mass. When the content of 2-isopropylthioxanthone is 90 parts by mass or more, initial color derived from a thioxanthone photopolymerization initiator of an image recorded on a recording medium can be reduced, and the light resistance of the image can be improved. it can. If the content of 2-isopropylthioxanthone is less than 90 parts by mass, yellow or brown initial coloring derived from the thioxanthone photopolymerization initiator may be seen, and the curability of the image tends to be lowered.

  Moreover, when the thioxanthone type photoinitiator which can be used by this Embodiment sets the total mass to 100 mass parts, except the case where 100 mass parts of 2-isopropyl thioxanthone is contained, a remainder will be produced. In such a case, the thioxanthone photopolymerization initiator that can be used in the present embodiment includes 4-isopropylthioxanthone as the remaining main component. The “main component of the balance” means a component having the largest content part by mass in the balance. That is, the remainder is substantially composed of 4-isopropylthioxanthone, and thioxanthone and thioxanthone derivatives other than 2-isopropylthioxanthone and 4-isopropylthioxanthone which are inevitably mixed in the process of producing a thioxanthone-based photopolymerization initiator. In addition, impurities such as components derived from the reaction solution may be included.

  The content of the thioxanthone photopolymerization initiator described above is 0.5% by mass or more and 5% by mass or less, preferably 1% by mass or more and 4% by mass or less, with respect to the total mass of the photocurable ink composition. is there. When the content of the thioxanthone photopolymerization initiator is within the above range, it is possible to reduce the initial coloring derived from the thioxanthone photopolymerization initiator of the image recorded on the recording medium and to improve the light resistance of the image. it can. Further, the curability of the image is good. When the content of the thioxanthone photopolymerization initiator is less than the above range, the curability of the image recorded on the recording medium may be impaired. On the other hand, when the content of the thioxanthone-based photopolymerization initiator exceeds the above range, the photopolymerization initiator may remain undissolved depending on the amount ratio with the polymerizable compound, which is not preferable for the product.

1.3. Other Additives The photocurable ink composition according to the present embodiment may include a photopolymerization initiator other than a thioxanthone photopolymerization initiator, a pigment, a dispersant, a slip agent, a photosensitizer, and a polymerization as necessary. You may contain additives, such as an inhibitor.

  The photocurable ink composition according to this embodiment is preferably a solventless photocurable ink composition that does not contain an organic solvent.

  The photocurable ink composition according to the present embodiment may contain a photopolymerization initiator other than the thioxanthone photopolymerization initiator. Such photopolymerization initiator is not particularly limited, but includes alkylphenone photopolymerization initiators, acylphosphine oxide photopolymerization initiators, titanocene photopolymerization initiators, benzoate photopolymerization initiators having amino groups, and the like. A well-known photoinitiator is mentioned.

  Among these, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide excellent in compatibility with the polymerizable compound described above, bis (2,4,6-trimethylbenzoyl) -phenyl having a wide range of light absorption characteristics It is preferable to use a molecular cleavage type acyl phosphine oxide photopolymerization initiator such as phosphine oxide in combination. The reason why acylphosphine oxide photopolymerization initiators are preferable is that the structure of the chromophore changes greatly before and after photocleavage, so the change in absorption is large, and a decrease in absorption called photobleaching (photobleaching) is observed. It is. Moreover, it is because yellowing hardly occurs despite the absorption ranging from the UV region to the VL region, and is excellent in internal curing. For this reason, it is particularly preferable for a transparent thick film or a pigmented coating film having a large hiding power.

  In addition, the photocurable ink composition according to the present embodiment has an amino group-containing benzoate photopolymerization in that the effect of promoting the photopolymerization reactivity can be obtained by using in combination with a thioxanthone photopolymerization initiator. It is preferable to further contain an initiator. Examples of the benzoate photopolymerization initiator having an amino group include SPEEDCURE EDB (manufactured by Lambson).

  The content of the photopolymerization initiator other than the thioxanthone photopolymerization initiator is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass with respect to the total mass of the photocurable ink composition. % Or less.

  The photocurable ink composition according to the present embodiment can function as a so-called clear ink as it is, but may further contain a pigment. Although it does not restrict | limit especially as a pigment which can be used in this Embodiment, An inorganic pigment and an organic pigment are mentioned. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. On the other hand, organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinofullerone pigments, etc.) Nitro pigments, nitroso pigments, aniline black, and the like can be used.

  Among specific examples of pigments that can be used in the present embodiment, carbon black includes C.I. I. Pigment black 7, for example, No. available from Mitsubishi Chemical Corporation. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. Raven5750, 5250, 5000, 3500, 1255, 700, etc. available from Columbia Chemical Company 2200B, etc. Also, Regal400R, 330R, 660R, MoguL, available from Cabot 700, Monarch 800, 880, 900, 1000, 1100, 1300, 1400, etc. are further available from Degussa, such as ColorBlack FW1, FW2, FW2V, FW18, FW200, ColorBlackS150, S160. , S170, Printex35, U, V, 140U, Special Black6, 5, 4A, 4 and the like.

  Examples of pigments that can be used when the photocurable ink composition according to the present embodiment is yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213 and the like.

  Examples of pigments that can be used when the photocurable ink composition according to the present embodiment is magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209, C.I. I. Pigment violet 19 and the like.

  Examples of pigments that can be used when the photocurable ink composition according to the present embodiment is cyan ink include C.I. I. Pigment blue 1, 2, 3, 15: 3, 15: 4, 16, 22, 60, and the like.

  Examples of pigments that can be used when the photocurable ink composition according to the present embodiment is a green ink include C.I. I. Pigment green 7, 8, 36, and the like.

  Examples of pigments that can be used when the photocurable ink composition according to this embodiment is an orange ink include C.I. I. Pigment orange 51, 66 and the like.

  Examples of pigments that can be used when the photocurable ink composition according to this embodiment is white ink include basic lead carbonate, zinc oxide, titanium oxide, and strontium titanate.

  The average particle diameter of the pigment that can be used in the present embodiment is preferably in the range of 10 nm to 200 nm, more preferably in the range of 50 nm to 150 nm.

  The addition amount of the pigment that can be added to the photocurable ink composition according to the present embodiment is preferably 0.1% by mass or more and 25% by mass or less with respect to the total mass of the photocurable ink composition. More preferably, it is 0.5 mass% or more and 15 mass% or less.

  In the photocurable ink composition according to the present embodiment, a dispersant may be added for the purpose of improving the dispersibility of the pigment described above. Dispersants that can be used in the present embodiment include Solsperse 3000, 5000, 9000, 12000, 13240, 17000, 24000, 26000, 28000, 36000 (above, manufactured by Lubrizol), DISCOL N-503, N-506. , N-509, N-512, N-515, N-518, N-520 (above, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and the like.

  A slip agent may be added to the photocurable ink composition according to the present embodiment. The slip agent that can be used in the present embodiment is preferably a silicone-based surfactant, more preferably a polyester-modified silicone or a polyether-modified silicone. Specifically, examples of the polyester-modified silicone include BYK-347, 348, BYK-UV3500, 3510, 3530 (above, manufactured by BYK Chemie Japan Co., Ltd.), and the polyether-modified silicone includes BYK. -3570 (made by Big Chemie Japan Co., Ltd.) and the like.

  A photosensitizer may be added to the photocurable ink composition according to the present embodiment. Photosensitizers usable in the present embodiment include amine compounds (aliphatic amines, amines containing aromatic groups, piperidine, reaction products of epoxy resins and amines, triethanolamine triacrylate, etc.), urea compounds (Allylthiourea, o-tolylthiourea, etc.), sulfur compounds (sodium diethyldithiophosphate, soluble salts of aromatic sulfinic acid, etc.), nitrile compounds (N, N-diethyl-p-aminobenzonitrile, etc.), phosphorus compounds ( Tri-n-butylphosphine, sodium diethyldithiophosphide, etc.), nitrogen compounds (Michler ketone, N-nitrisohydroxylamine derivative, oxazolidine compound, tetrahydro-1,3-oxazine compound, formaldehyde or a condensate of acetaldehyde and diamine) ), Chlorine compounds (carbon tetrachloride, hexachloroethane, etc.) and the like.

  A polymerization inhibitor may be added to the photocurable ink composition according to the present embodiment. Examples of the polymerization inhibitor that can be used in the present embodiment include hydroquinone, benzoquinone, p-methoxyphenol, and the like.

1.4. Physical Properties The viscosity at 20 ° C. of the photocurable ink composition according to the present embodiment is preferably 8 to 40 mPa · s, more preferably 10 to 25 mPa · s. When the viscosity at 20 ° C. of the photocurable ink composition is in the above range, an appropriate amount of the photocurable ink composition is ejected from the nozzle, and the flight bending and scattering of the photocurable ink composition can be further reduced. The ink jet recording apparatus can be suitably used. The viscosity is measured by using a viscoelasticity tester MCR-300 (manufactured by Pysica), increasing the Shear Rate to 10 to 1000 in an environment of 20 ° C., and reading the viscosity at Shear Rate 200. Can be measured.

  The surface tension at 20 ° C. of the photocurable ink composition according to the present embodiment is preferably 20 mN / m or more and 30 mN / m or less. When the surface tension at 20 ° C. of the photocurable ink composition is in the above range, the photocurable ink composition is difficult to get wet with the nozzle subjected to the liquid repellent treatment. As a result, an appropriate amount of the photocurable ink composition is ejected from the nozzle, and the flight bend and scattering of the photocurable ink composition can be further reduced. Therefore, the photocurable ink composition can be suitably used for an ink jet recording apparatus. The surface tension is measured by using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) by confirming the surface tension when the platinum plate is wetted with ink in an environment of 20 ° C. be able to.

2. Inkjet Recording Method An inkjet recording method according to an embodiment of the present invention includes: (a) a step of discharging the above-described photocurable ink composition onto a recording medium; and (b) a discharged photocurable ink composition. And a step of irradiating light having an emission peak wavelength in a range of 350 nm to 430 nm from the light source.

  Hereinafter, the ink jet recording method according to the present embodiment will be described for each step.

2.1. Step (a)
This step is a step of discharging the above-described photocurable ink composition onto the recording medium.

  Since the photocurable ink composition is as described above, detailed description thereof is omitted.

  The recording medium is not particularly limited, and examples thereof include plastics such as polyvinyl chloride, polyethylene terephthalate, polypropylene, polyethylene, and polycarbonate, those whose surfaces are processed, glass, coated paper, and the like.

  As a means for discharging the photocurable ink composition, for example, an ink jet recording apparatus described below can be used.

  FIG. 1 is a perspective view of an ink jet recording apparatus that can be used in the ink jet recording method according to the present embodiment.

  The ink jet recording apparatus 20 shown in FIG. 1 has a motor 30 for feeding the recording medium P in the sub-scanning direction SS, a platen 40, and a photocurable ink composition having a very small particle size and ejected from the head nozzle to record the recording medium P. A print head 52 serving as a recording head for discharging the ink, a carriage 50 on which the print head 52 is mounted, a carriage motor 60 for moving the carriage 50 in the main scanning direction MS, and the print head 52 discharging a photocurable ink composition. And a pair of light irradiation devices 90A and 90B for irradiating light onto the ink adhesion surface on the recording medium P.

  The carriage 50 is pulled by a pulling belt 62 driven by a carriage motor 60 and moves along a guide rail 64.

  The print head 52 shown in FIG. 1 is a serial head for full color printing that ejects ink of three or more colors, and is provided with a large number of head nozzles for each color. In addition to the print head 52, the carriage 50 on which the print head 52 is mounted is supplied to the print head 52 and a black cartridge 54 as a black ink container that contains black ink supplied to the print head 52. A color ink cartridge 56 is mounted as color ink containing color ink. The ink stored in each of the cartridges 54 and 56 is the above-described photocurable ink composition.

  A capping device 80 for sealing the nozzle surface of the print head 52 when stopped is provided at the home position of the carriage 50 (the position on the right side in FIG. 1). When the print job ends and the carriage 50 reaches above the capping device 80, the capping device 80 is automatically raised by a mechanism (not shown) to seal the nozzle surface of the print head 52. This capping prevents the ink in the nozzles from drying out. The positioning control of the carriage 50 is performed to accurately position the carriage 50 at the position of the capping device 80, for example.

  By using such an ink jet recording apparatus 20, a photocurable ink composition can be discharged onto a recording medium. In addition, according to the inkjet recording apparatus 20, the process (a) and the process (b) can be continuously performed by one apparatus without performing the process (a) and the process (b) by separate apparatuses. It becomes possible.

2.2. Step (b)
This step is a step of irradiating the ejected photocurable ink composition with light having an emission peak wavelength in a range of 350 nm to 430 nm from the light source. According to this step, by irradiating the photocurable ink composition ejected onto the recording medium with light of a specific wavelength, the photocurable ink composition is cured and an image is recorded on the recording medium. be able to.

  Hereinafter, the case where a process (b) is performed using the inkjet recording device 20 mentioned above is demonstrated in detail.

  2 is a front view of the light irradiation device 90A (corresponding to 190A in FIG. 2) and 90B (corresponding to 190B in FIG. 2) shown in FIG. FIG. 3 is an AA arrow view of FIG.

  As shown in FIGS. 1 to 3, the light irradiation devices 190 </ b> A and 190 </ b> B are respectively attached to both side ends along the moving direction of the carriage 50.

  As shown in FIG. 2, the light irradiation device 190A mounted on the left side of the print head 52 ejects onto the recording medium P during the right scanning when the carriage 50 moves in the right direction (the direction of arrow B in FIG. 2). The applied ink layer 196 is irradiated with light. On the other hand, the light irradiation device 190B attached to the right side of the print head 52 has an ink layer 196 ejected onto the recording medium P during left scanning in which the carriage 50 moves leftward (in the direction of arrow C in FIG. 2). Is irradiated with light.

  Each of the light irradiation devices 190A and 190B includes a housing 194 that is attached to the carriage 50 and supports the light sources 192 one by one, and a light source control circuit (not shown) that controls light emission and extinction of the light sources 192. ing. As shown in FIGS. 2 and 3, the light irradiation devices 190A and 190B are each provided with one light source 192, but two or more light sources 192 may be provided. As the light source 192, it is preferable to use either LED or LD. Thereby, compared with the case where a mercury lamp lamp, a metal halide lamp, and other lamps are used as a light source, it is possible to avoid an increase in the size of the light source due to the provision of a filter or the like. In addition, the light intensity emitted by absorption by the filter does not decrease, and the photocurable ink composition can be efficiently cured.

  In addition, each light source 192 may have the same wavelength or different wavelengths. When an LED or LD is used as the light source 192, the emission peak wavelength of the emitted light may be any one in the range of about 350 to 430 nm.

  According to the light irradiation apparatuses 190A and 190B described above, as shown in FIG. 2, the recording medium in the vicinity of the print head 52 with respect to the ink layer 196 deposited on the recording medium P by ejection from the print head 52. Light 192a is irradiated by the light source 192 that irradiates P, and the surface and the inside of the ink layer 196 can be cured.

Since the illuminance of light varies depending on the thickness of the ink layer 196 attached on the recording medium P, it cannot be strictly specified, and preferable conditions are selected as appropriate, but the above-described photocurable ink composition is used. Therefore, it can be sufficiently cured with an illuminance of about 10 to 2000 mW / cm ² .

  According to the inkjet recording apparatus 20, a plurality of photocurable ink compositions ejected onto the recording medium P even during full color printing where the viscosity of the photocurable ink composition is low and the film thickness of the ink layer is relatively thin. Can be cured well without causing problems such as bleeding or color mixing.

  Note that the configuration of the inkjet recording apparatus 20 is not limited to the configuration of the recording head, carriage, light source, and the like described above, and various configurations are adopted based on the gist of the inkjet recording method according to the present embodiment. Can do.

3. Recorded matter A recorded matter according to an embodiment of the present invention is recorded by the ink jet recording method described above. Since the image recorded on the recording medium is formed using the above-described photocurable ink composition, it is possible to reduce initial coloration derived from the thioxanthone photopolymerization initiator and to improve curability and light resistance. Is also excellent.

  The use of the recorded matter according to the present embodiment is not particularly limited, and can be used as an image recorded on the recording medium described above. Since such an image can reduce initial coloration derived from a thioxanthone photopolymerization initiator, the original hue of the pigment can be reproduced. In addition, since the image is excellent in light resistance, it is difficult to discolor not only indoors but also outdoors.

4). Examples Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

4.1. Preparation of Pigment Dispersion Solution Cyan pigment (manufactured by Ciba Japan Co., Ltd., trade name “IRGALITE BLUE GLVO”) 16 parts by mass as a colorant, Solsperse 36000 (manufactured by LUBRIZOL) as a dispersant, 7.2 parts by mass, phenoxyethyl acrylate ( Osaka Organic Chemical Industry Co., Ltd., trade name “V # 192”) was added to make 100 parts by mass, and the mixture was stirred to obtain a mixture. This mixture was subjected to a dispersion treatment for 6 hours together with zirconia beads (diameter 1.5 mm) using a sand mill (manufactured by Yaskawa Seisakusho Co., Ltd.). Then, the cyan pigment dispersion liquid was obtained by isolate | separating a zirconia bead with a separator.

4.2. Preparation of Photocurable Ink Composition After mixing a polymerizable compound, a photopolymerization initiator, and a slip agent so as to have the composition shown in Table 1, they were mixed and stirred at room temperature for 1 hour, and further 5 μm. The photocurable clear ink compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were obtained.

  In addition, a polymerizable compound, a photopolymerization initiator, and a slip agent were mixed and completely dissolved so that the composition described in Table 1 was obtained, and then the cyan pigment dispersion was mixed with the cyan pigment concentration in Table 1. The solution was added dropwise with stirring to the stated concentration. After completion of the dropwise addition, the mixture was stirred at room temperature for 1 hour and further filtered through a 5 μm membrane filter to obtain photocurable cyan ink compositions of Examples 4 to 6 and Comparative Example 4.

In addition, the component used in the table | surface is as follows.
・ Phenoxyethyl acrylate (Osaka Organic Chemical Industry Co., Ltd., trade name “V # 192”)
・ Dicyclopentenyl acrylate (manufactured by Hitachi Chemical Co., Ltd., trade name “FA511AS”)
・ Dicyclopentenyloxyethyl acrylate (manufactured by Hitachi Chemical Co., Ltd., trade name “FA512AS”)
・ Dipropylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “APG-100”)
・ Tripropylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “APG-200”)
・ Dimethylol tricyclodecane diacrylate (Daicel Cytec Co., Ltd., trade name “EBECRYL IRR214K”)
Amino acrylate (Daicel Cytec Co., Ltd., trade name “EBECRYL 7100”)
・ Epoxy acrylate oligomer (SARTOMER, trade name “CN120”)
IRGACURE 819 (Ciba Japan Co., Ltd., bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, photopolymerization initiator)
DAROCUR TPO (Ciba Japan Co., Ltd., 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, photopolymerization initiator)
SPEEDCURE EDB (manufactured by Lambson, benzoate photopolymerization initiator having an amino group)
・ KAYACURE DETX (Nippon Kayaku Co., Ltd., 2,4-diethylthioxanthone)
-BYK-UV3500 (by Big Chemie Japan Co., Ltd., polydimethylsiloxane having a polyether-modified acrylic group, slip agent)
・ 2-Isopropylthioxanthone (Sigma Aldrich, photopolymerization initiator)
・ 4-Isopropylthioxanthone (manufactured by Sigma-Aldrich, photopolymerization initiator)
・ IRGALITE BLUE GLVO (Ciba Japan Co., Ltd., cyan pigment)
・ Solsperse 36000 (manufactured by LUBRIZOL, dispersant)

4.3. Preparation of Recorded matter Using an ink jet printer PX-G5000 (manufactured by Seiko Epson Corporation), the photocurable ink composition was filled in each nozzle row. On the PVC film (trade name “PVC80M”, manufactured by Lintec Corporation) at room temperature and normal pressure, a solid pattern image is printed so that the dot diameter of the ink is medium and the film thickness of the printed material is 10 μm. The solid pattern image was cured by irradiating ultraviolet rays of 365 nm and 395 nm with irradiation intensity of 60 mW / cm ² from the UV-LED in the ultraviolet irradiation device mounted on the side. As described above, a recorded matter in which a solid pattern image was printed on a PVC film was produced.

4.4. Evaluation Test The following evaluation test was performed on the obtained recorded matter. The following evaluation tests were all performed in a room temperature environment.

4.4.1. Evaluation of Curability A recorded matter in which a solid pattern image was printed on a PVC film was produced in the same manner as in “4.3. Production of recorded matter”. The accumulated light amount required until the surface of the recorded material was tack-free was determined, and the curability was evaluated. Judgment as to whether or not it is in a tack-free state was made by rubbing the surface of the recorded material with a cotton swab, and when there was no scratch mark on both the surface and the deep part of the recorded material, it was determined that the state was tack-free. The classification of evaluation criteria is as follows.
“◯”: Integrated light quantity was less than 200 mJ / cm ² .
"△": cumulative amount of light is less than 200mJ / cm ² or more 250mJ / cm ^2.
“×”: The accumulated light amount was 250 mJ / cm ² or more.

4.4.2. Evaluation of initial coloring Evaluation of initial coloring was carried out only for the photocurable clear ink compositions of Examples 1 to 3 and Comparative Examples 1 to 3 containing no pigment. Wherein the L ^* a ^* b ^* values of PVC film before recorded matter prepared L ^* a ^* b ^* values of the recording material obtained in "4.3. Preparation of recorded article" Gretag Macbeth Co. Each measurement was performed using a colorimeter “Spectrolino”, and the difference ΔE was obtained. The classification of evaluation criteria is as follows.
“◯”: ΔE was 0 or more and less than 3.0.
“X”: ΔE was 3.0 or more.

4.4.3. Evaluation of light resistance The recorded matter obtained in “4.3. Production of recorded matter” was measured with an Xe fade meter (trade name “XL75”, manufactured by Suga Test Instruments Co., Ltd.) and an environment with a light illuminance of 50 W / m ² . Left for 160 hours. The change (ΔE) of the value of L ^* a ^* b ^* before and after being left was determined using a colorimeter “Spectrolino” manufactured by Gretag Macbeth. The classification of evaluation criteria is as follows.
“◯”: ΔE was 0 or more and less than 1.0.
“Δ”: ΔE was 1.0 or more and less than 2.0.
“×”: ΔE was 2.0 or more.

4.5. Evaluation results The results of the above evaluation tests are also shown in Table 1.

  According to the photocurable clear ink compositions of Examples 1 to 3, almost no initial coloring was observed in any recorded matter, and an image having good curability and light resistance could be recorded on the PVC film. It was. However, in Example 2, the content of the thioxanthone-based photopolymerization initiator was a small amount of 0.5% by mass, so that the image was cured more than in the case of Example 1 or Example 3. It was found that energy was required and the curability decreased.

  According to the photocurable cyan ink compositions of Examples 4 to 6, images having good curability and light resistance could be recorded on the PVC film. However, in Example 6, since the content of the thioxanthone-based photopolymerization initiator was as large as 5% by mass, it was found that the light resistance was lowered as compared with Examples 4 and 5. .

  According to the photocurable clear ink composition of Comparative Example 1, since the content of 2-isopropylthioxanthone is less than 90 parts by mass when the thioxanthone photopolymerization initiator is 100 parts by mass, the initial coloring of the recorded matter is It was observed that the curability and light resistance were reduced.

  According to the photocurable clear ink composition of Comparative Example 2, when 1% by weight of “KAYACURE DETX” (2,4-diethylthioxanthone) is contained, initial coloration of the recorded matter is recognized and curability is lowered. Furthermore, it was found that the light resistance is remarkably lowered.

  According to the photocurable clear ink composition of Comparative Example 3, when the content of the thioxanthone-based photopolymerization initiator is 0.3% by mass, the light resistance is lowered, and the curability is significantly lowered. I understood.

  According to the photocurable cyan ink composition of Comparative Example 4, it was found that when the content of the thioxanthone photopolymerization initiator was 5.5% by mass, the photopolymerization initiator remained undissolved. Therefore, the photocurable ink composition of Comparative Example 4 was not applicable because it was not in the category of non-defective products.

  The determination as to whether or not the photopolymerization initiator remains undissolved was made by referring to “4.2. Preparation of photocurable ink composition”, when the photopolymerization initiator was filtered on a filter paper when filtered through a 5 μm membrane filter. It was carried out by visually checking whether there was any undissolved residue.

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

DESCRIPTION OF SYMBOLS 20 ... Inkjet recording device 30 ... Motor, 40 ... Platen, 50 ... Carriage, 52 ... Print head (recording head), 54 ... Black ink cartridge, 56 ... Color ink cartridge, 60 ... Carriage motor, 62 ... Traction belt, 64 ... guide rail, 80 ... capping device, 90A (190A), 90B (190B) ... light irradiation device, 192 ... light source, 192a ... light, 194 ... housing, 196 ... ink layer, P ... recording medium

Claims (10)

A photocurable ink composition containing at least a polymerizable compound and a thioxanthone photopolymerization initiator,
The photocurable ink composition contains the thioxanthone photopolymerization initiator in an amount of 0.5% by mass to 5% by mass,
When the total mass of the thioxanthone photopolymerization initiator contained in the photocurable ink composition is 100 parts by mass, the thioxanthone photopolymerization initiator contains 90 parts by mass or more of 2-isopropylthioxanthone,
When the thioxanthone photopolymerization initiator has a remainder other than 2-isopropylthioxanthone, a photocurable ink composition containing 4-isopropylthioxanthone as a main component of the remainder. In claim 1,
A photocurable ink composition comprising 10% by mass or more and 50% by mass or less of phenoxyethyl acrylate as the polymerizable compound. In claim 1 or claim 2,
A photocurable ink composition containing, as the polymerizable compound, a monofunctional acrylate having an alicyclic structure in an amount of 25% by mass to 40% by mass. In claim 3,
The photocurable ink composition, wherein the monofunctional acrylate having an alicyclic structure is at least one selected from dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, and isobornyl acrylate . In any one of Claims 1 thru | or 4,
A photocurable ink composition containing aminoacrylate as the polymerizable compound. In any one of Claims 1 thru | or 5,
Furthermore, the photocurable ink composition containing the benzoate type photoinitiator which has an amino group. In any one of Claims 1 thru | or 6,
Furthermore, the photocurable ink composition containing a pigment. In any one of Claims 1 thru | or 7,
A photocurable ink composition having a viscosity at a measurement temperature of 20 ° C. of 8 mPa · s to 40 mPa · s and a surface tension at a measurement temperature of 20 ° C. of 20 mN / m to 30 mN / m. (A) discharging the photocurable ink composition according to any one of claims 1 to 8 onto a recording medium;
(B) irradiating the discharged photocurable ink composition with light having an emission peak wavelength in a range of 350 nm to 430 nm from a light source;
An ink jet recording method comprising:   A recorded matter recorded by the ink jet recording method according to claim 9.

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