JP2011213931A - Photocuring ink composition for inkjet recording - Google Patents

Abstract

Provided is a photocurable ink composition for ink jet recording which is excellent in scratch resistance and elasticity in a cured layer of an ink.
A photocurable ink composition for ink-jet recording comprising a photoradically polymerizable compound, a photopolymerization initiator, and hollow silica.
[Selection figure] None

Description

  The present invention relates to a photocurable ink composition for inkjet recording.

  Conventionally, various methods are used as an image recording method for forming an image on a recording medium such as paper based on an image data signal. Among these, the ink jet system is an inexpensive apparatus, and ink is ejected only to a required image portion to form an image directly on a recording medium. Therefore, the ink can be used efficiently, and the running cost is low. Furthermore, the inkjet method is excellent as an image recording method because of its low noise.

  In recent years, photocurable ink compositions for ink jet recording that are cured when irradiated with light such as ultraviolet rays have been used to form images with excellent water resistance, solvent resistance, scratch resistance, etc. on the surface of the recording medium. ing. However, this photocurable ink composition for ink jet recording is inferior in adhesion to a recording medium. Therefore, attempts have been made to improve adhesion.

  For example, Patent Document 1 discloses an ink composition containing a polymerizable compound, a photocationic polymerization initiator, a pigment, and colloidal silica for the purpose of improving scratch resistance and adhesion.

JP 2009-7462 A

  However, the cured layer (coating film) obtained by curing the photocurable ink composition for ink jet recording described in Patent Document 1 has a problem of causing cracks due to poor elasticity. Therefore, a photocurable ink composition for ink jet recording that does not have such a problem is desired.

  Accordingly, an object of the present invention is to provide a photocurable ink composition for ink-jet recording which has excellent scratch resistance and elasticity in a cured layer of ink.

  The inventors of the present application have made extensive studies to solve the above problems. As a result, the photocurable ink composition for ink jet recording (hereinafter, also simply referred to as “ink composition”) contains hollow silica, so that it has excellent scratch resistance and adhesion in the cured layer of the ink, and also has elasticity. The present invention has been completed.

That is, the present invention is as follows.
[1]
A photocurable ink composition for inkjet recording, comprising a photoradical polymerizable compound, a photopolymerization initiator, and hollow silica.
[2]
The photocurable ink composition for ink jet recording according to [1], wherein the content of the hollow silica is 0.5 to 30% by mass with respect to the total amount of the ink composition.
[3]
The photo-radical polymerizable compound according to [1] or [2], wherein the photo-radically polymerizable compound includes at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate.
[4]
The photo-radical polymerizable compound according to [3], wherein the photo-radically polymerizable compound further contains N-vinylcaprolactam.
[5]
The photo-radical polymerizable compound according to [3] or [4], wherein the photo-radical polymerizable compound further comprises a (meth) acrylate oligomer.
[6]
The photocurable ink composition for inkjet recording according to [5], wherein the (meth) acrylate oligomer includes a urethane (meth) acrylate oligomer.
[7]
The photocurable ink composition for ink jet recording according to any one of [1] to [6], further comprising at least one colorant of a pigment and a dye.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not restrict | limited to the following embodiment, A various deformation | transformation can be implemented within the range of the summary.

In the present specification, “(meth) acrylate” means acrylate and its corresponding methacrylate, and “(meth) acryl” means acryl and its corresponding methacryl.
The “oligomer” in the present specification is synthesized by the reaction of about 2 to several tens of monomers, has a relatively small number of repeating units, and has one or more photopolymerizable groups. Means a molecule.

[Photocurable ink composition for inkjet recording]
One embodiment of the present invention relates to a photocurable ink composition for inkjet recording. The photocurable ink composition for ink jet recording contains a photoradical polymerizable compound, a photopolymerization initiator, and hollow silica.

  Hereinafter, each component contained in the ink composition will be described in detail.

[Hollow silica]
By including hollow silica, the ink composition of the present embodiment is excellent in scratch resistance and elasticity in the cured layer of the ink. “Hollow silica” can be said to be hollow silica fine particles. Since the hollow silica has a balloon structure and has a function of creating a void in the coating film of the ink composition, the cured ink layer has excellent elasticity. Further, since the hollow silica exhibits a function as a filler in the ink composition, the strength of the ink cured layer is increased and the scratch resistance is excellent.

Examples of the silica material include silicon dioxide (SiO ₂ ) and silicate, and amorphous, crystalline, anhydrous, hydrated, and hydroxides thereof. Among these, the silica material preferably contains silicon dioxide as a main component. A silica material may be used individually by 1 type, and may use 2 or more types together.

  Examples of commercially available hollow silica include Silinax (registered trademark) (manufactured by Nittetsu Mining CO., Ltd.), ELECOM V-8209 (manufactured by JGC Catalysts & Chemicals Co., Ltd.), and the like. Moreover, as a manufacturing method of such a hollow silica, the manufacturing method disclosed by Unexamined-Japanese-Patent No. 7-133105 and Unexamined-Japanese-Patent No. 2008-74645 is mentioned, for example.

  The content of the hollow silica is preferably 0.5 to 30% by mass, more preferably 1.5 to 15% by mass, and more preferably 1.5 to 5% by mass with respect to the total amount of the ink composition. When the content is within the above range, flexibility is improved and an increase in viscosity is also suppressed.

The lower limit of the average particle size of the hollow silica is preferably 10 nm, more preferably 40 nm, and even more preferably 50 nm. When the lower limit is within the above range, the elasticity of the ink cured layer is further improved. Here, when the colored ink composition contains hollow silica, 80 nm or more is even more preferable. On the other hand, the upper limit of the average particle diameter of the hollow silica is preferably 200 nm, more preferably 130 nm, and even more preferably 100 nm. When the upper limit is within the above range, the refractive index of light is increased, so that the transparency and gloss are excellent.
In addition, the average particle diameter in this specification is the value obtained by the method of measuring from the electron micrograph by a scanning electron microscope (SEM). In addition, measurement by using a dynamic light scattering method, a static light scattering method, or the like is possible.

  The shape of the hollow silica is not particularly limited as long as the ejection stability of the ink is not hindered, and examples thereof include a spherical shape, a long shape, and a needle shape. Among these, spherical shape is preferable.

[Photoradical polymerizable compound]
The radical photopolymerizable compound contained in the ink composition of the present embodiment is polymerized at the time of light irradiation by the action of a photopolymerization initiator described later, and can cure the printed ink. As the photo-radical polymerizable compound, conventionally known various monomers and oligomers such as monofunctional, bifunctional, and trifunctional or more polyfunctional can be used. Examples of monomers include unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid, their salts or esters, urethanes, amides and anhydrides thereof, acrylonitrile, styrene, various types Unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated urethanes, and lactams. Moreover, as an oligomer, the oligomer formed from said monomers, such as a linear acrylic oligomer, epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate are mentioned, for example.

  Among those listed above, esters of (meth) acrylic acid, that is, (meth) acrylates are preferred.

  Among the (meth) acrylates, monofunctional (meth) acrylates include, for example, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, and isomyristyl. (Meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meta ) Acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate Tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone modified flexibility Examples include (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and isobornyl (meth) acrylate. .

  Among the (meth) acrylates, examples of the bifunctional (meth) acrylate include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and tripropylene glycol di (meta). ) Acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol Di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, EO (ethylene oxide) adduct of bisphenol A di (meth) acrylate, PO of bisphenol A (propylene oxide) Adduct di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, and polytetramethylene glycol di (meth) acrylate.

  Among the (meth) acrylates, trifunctional or higher polyfunctional (meth) acrylates include, for example, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) acrylate, pentaerythritol ethoxy Examples include tetra (meth) acrylate and caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  Among these, it is preferable that a radical photopolymerizable compound contains a monofunctional (meth) acrylate. In this case, the ink composition has a low viscosity, is excellent in solubility of additives such as a photopolymerization initiator, and is easy to obtain ejection stability during ink jet recording. Furthermore, it is more preferable to use a monofunctional (meth) acrylate and a bifunctional (meth) acrylate in combination from the viewpoint of increasing toughness (abrasion resistance), heat resistance, and chemical resistance of the ink cured layer.

  Furthermore, the monofunctional (meth) acrylate preferably has one or more skeletons selected from the group consisting of an aromatic ring skeleton, a saturated alicyclic skeleton, and an unsaturated alicyclic skeleton. When the radical photopolymerizable compound is a monofunctional (meth) acrylate having the skeleton, the viscosity of the ink composition can be reduced.

  Examples of the monofunctional (meth) acrylate having an aromatic ring skeleton include phenoxyethyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate. Examples of the monofunctional (meth) acrylate having a saturated alicyclic skeleton include isobornyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Examples of the monofunctional (meth) acrylate having an unsaturated alicyclic skeleton include dicyclopentenyloxyethyl (meth) acrylate. Among these, from the viewpoint of low viscosity and low odor, at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate is preferable. More preferred is phenoxyethyl acrylate.

  The content of at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total amount of the ink composition. When the content is within the above range, advantageous effects such as low viscosity and high reactivity of the ink can be obtained.

  The radical photopolymerizable compound preferably contains lactams in addition to at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate. Although it does not specifically limit as lactams, For example, N-vinyl pyrrolidone, N-vinyl caprolactam (N-vinyl- (epsilon) -caprolactam), (epsilon) -caprolactam, and (omega) -laurolactam are mentioned. Among these, N-vinylcaprolactam is preferable because more advantageous effects can be obtained from the viewpoint of improving adhesion and safety of materials.

  When the radical photopolymerizable compound further contains N-vinylcaprolactam, the content of N-vinylcaprolactam is preferably 1 to 15% by mass, more preferably 3 to 10% by mass, based on the total amount of the ink composition. is there. When the content is within the above range, adhesion can be secured and deterioration of storage stability can be prevented.

  Moreover, it is also preferable that a radical photopolymerizable compound further contains a (meth) acrylate oligomer in addition to at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate. When the radical photopolymerizable compound contains the (meth) acrylate oligomer, the (meth) acrylate oligomer functions as a binder for the recording medium. Therefore, the adhesion of the ink cured layer to the recording medium can be further improved.

  When the radical photopolymerizable compound further contains a (meth) acrylate oligomer, the content of the (meth) acrylate oligomer is preferably 1 to 10% by mass, more preferably 1.5 to the total amount of the ink composition. 5% by mass. When the content is within the above range, adhesion and coating strength can be improved while maintaining low viscosity.

  Although it does not specifically limit as a (meth) acrylate oligomer, For example, the above-mentioned urethane (meth) acrylate, epoxy (meth) acrylate, and polyester (meth) acrylate are mentioned. Among these, urethane (meth) acrylate is preferable because adhesion and elasticity in the ink cured layer can be further improved. Although it does not specifically limit as urethane (meth) acrylate, For example, aliphatic urethane (meth) acrylate and aromatic urethane (meth) acrylate are mentioned. The average number of functional groups of each oligomer may be larger than 2. The average molecular weight of each oligomer is about 400 to 20,000.

  The content of urethane (meth) acrylate is preferably 1 to 10% by mass, more preferably 1.5 to 5% by mass, based on the total amount of the ink composition. When the content is within the above range, it is possible to improve adhesion and film strength while maintaining low viscosity.

  Said radical photopolymerizable compound may be used individually by 1 type, and may use 2 or more types together.

(Photopolymerization initiator)
The photopolymerization initiator contained in the ink composition of the present embodiment is used for forming an image by curing ink present on the surface of a recording medium by photopolymerization by light irradiation. Here, examples of the light source include γ rays, β rays, electron beams, ultraviolet rays (UV), visible rays, and infrared rays. Among these, ultraviolet rays are preferable from the viewpoint of safety and the cost of the light source lamp. As the photopolymerization initiator, a known polymerization initiator such as a photoradical polymerization initiator or a photocationic polymerization initiator can be used. Among them, a photoradical polymerization initiator is used because a photoradical polymerizable compound is used. It is preferable.

  The radical photopolymerization initiator is not particularly limited, and examples thereof include aromatic ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, and ketoxime ester compounds. , Borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon halogen bond, and alkylamine compounds.

  Specific examples of the photo radical polymerization initiator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine. , Carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) ) -2-Hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethyl Oxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, bis (2,4,6-trimethylbenzoyl) -phenyl Examples include phosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4-diethylthioxanthone and bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide. It is done.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone), DAROCUR 1173. (2-hydroxy-2-methyl-1-phenyl-propan-1-one), IRGACURE 2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one), IRGACURE 127 (2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl] -2-methyl-propan-1-one}, IRGACURE 907 (2-Methyl-1- (4-methylthiophenyl) -2-morphol Linopropan-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4- Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide), IRGACURE 784 (bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-) Yl) -phenyl) titanium), IRGACURE OXE 01 (1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]), IRGACURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRGACURE 754 (oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (Mixture of (2-hydroxyethoxy) ethyl ester) (Ciba Japan KK), KAYACURE DETX-S (2,4-diethylthioxanthone) (Nippon Kayaku Co., Ltd. .)), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF), and Ubekrill P3 (Manufactured by UCB), and the like.

  Said photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type. The photopolymerization initiator is preferably 2 to 20% by mass, more preferably 5 to 15% by mass, based on the total amount of the ink composition. When the content is within the above range, the photocuring rate is sufficiently large, and the photopolymerization initiator is hardly dissolved and there is almost no color derived from the photopolymerization initiator.

[Color material]
The ink composition of the present embodiment may further include a color material. The color material is at least one of a pigment and a dye.

(Pigment)
In this embodiment, the light resistance of the ink composition can be improved by using a pigment as the color material. As the pigment, both inorganic pigments and organic pigments can be used.

  As the inorganic pigment, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Polycyclic pigments, dye chelates (for example, basic dye chelates, acid dye chelates, etc.), dye rakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daytime A photofluorescent pigment is mentioned. The said pigment may be used individually by 1 type, and may use 2 or more types together.

  Further, any pigment not described in the color index can be used as long as it is insoluble in water.

(dye)
In the present embodiment, by using a dye as the color material, it is easier to lower the viscosity of the ink, and it is possible to prevent ejection failure due to the adhesion of pigment or a decrease in dispersibility. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9, 45, 249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive black 3, 4, and 35 are mentioned.
The above color materials may be used alone or in combination of two or more.

[Other ingredients]
The ink composition of this embodiment may contain components other than the components listed above. Such components are not particularly limited, and may include, for example, conventionally known solvents, dispersants, polymerization accelerators, polymerization inhibitors, slip agents, and other additives. Examples of the other additives include conventionally known penetration enhancers, wetting agents (humectants), fixing agents, antifungal agents, antiseptics, antioxidants, ultraviolet absorbers, chelating agents, pH adjusting agents, and A thickener is mentioned.

[Physical properties of photocurable ink composition for inkjet recording]
According to JIS K5600-5-6, the adhesion of the recorded matter on which an image was formed from the ink composition of the present embodiment was cross-cut on the surface of the ink cured layer. The content is preferably 0 to 15%, more preferably 0 to 5%. Here, the adhesion in the present specification is measured by the method performed in the section of Examples described later.

  Here, the JIS K5600-5-6 test will be described. JIS K5600-5-6 corresponds to ISO2409. The outline of the JIS K5600-5-6 test is to evaluate the resistance of the ink cured layer to peeling from the substrate when a rectangular grid pattern having 25 squares is cut into the ink cured layer and penetrates to the substrate. There is. As a tool used for the test, a multi-blade or single-blade cutting tool is used. A multi-blade cutting tool is used for a thick ink curing layer exceeding 120 μm or a hard ink curing layer, and a single blade cutting tool is used for the other ink curing layers. In addition, when using single blades, such as a commercially available cutter, the guide for cutting at equal intervals is needed. A transparent adhesive tape having a width of 25 ± 1 mm is also used. Subsequently, in the test procedure, first, cutting is performed by applying a blade so as to be perpendicular to the ink cured layer. Next, after the six cuts are made, the six cuts are performed in a straight line by changing the 90 ° direction. Next, the tape is taken out to a length of about 75 mm. Next, the tape is affixed to the cut portion of the grid of the ink cured layer, and the tape is firmly rubbed with fingers so that the ink cured layer can be seen through. Next, it is surely pulled apart in 0.5 to 1.0 seconds at an angle close to 60 ° within 5 minutes. Here, the test results in the present embodiment are the four stages AA to C, depending on the ratio of the lattice in which the peeling occurs with respect to the total number of the lattice eyes in the lattice-like ink cured layer surface (hereinafter referred to as “the peeling rate”). Evaluate with. The above test results are described in detail in the [Example] section below.

  Further, the elasticity of a recorded matter in which an image is formed from the ink composition of the present embodiment is measured by the method carried out in the Examples section below according to JIS K5600-5-1.

  Here, the JIS K5600-5-1 test will be described. JIS K5600-5-1 corresponds to ISO1519. The JIS K5600-5-1 test is also referred to as a flex resistance test (cylindrical mandrel method). The outline is a test for confirming resistance to cracking of the coating film and peeling from the substrate when it is bent by a cylindrical mandrel. Select the size of the mandrel, check the crack and peeling of the coating film when bent, and conduct a pass / fail test to see if the conditions required for the test are cleared. Alternatively, the minimum diameter of the mandrel that begins to crack or peel off from the test substrate is determined.

[Recording medium]
The recording medium on which the ink cured layer of the ink composition of the present embodiment is formed may be absorbent or non-absorbable, but more effectively improves the scratch resistance and elasticity. From the viewpoint, a non-absorbable recording medium is preferable. The non-absorbable recording medium is not particularly limited, and for example, resin materials such as polyethylene terephthalate (PET), vinyl chloride resin (PVC), polypropylene, and polyethylene can be used. Moreover, you may have a process layer (coat layer) etc. on the surface of these base materials.

  As described above, according to this embodiment, it is possible to provide a photocurable ink composition for ink jet recording excellent in scratch resistance, elasticity, and flexibility resulting from this elasticity in a cured layer of ink.

  Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples.

1. Examples 1-9, Comparative Examples 1-3
[Use ingredients]
The components used in Examples 1 to 9 and Comparative Examples 1 to 3 are as follows.
[Photopolymerizable compound]
(Monofunctional monomer)
-Phenoxyethyl acrylate biscoat # 192 (manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD., Abbreviated as PEA in Table 1)
Isobornyl acrylate IBXA (Osaka Organic Chemical Co., Ltd., abbreviated as IBXA in Table 1)
Dicyclopentenyloxyethyl acrylate FA-512AS (manufactured by Hitachi Chemical Co., Ltd., abbreviated as DCPOEA in Table 1)
Dicyclopentenyl acrylate FA-511AS (manufactured by Hitachi Chemical Co., Ltd., abbreviated as DCPA in Table 1)
N-vinylcaprolactam (manufactured by BASF, trade name “N-vinylcaprolactam”), abbreviated as NVC in Table 1. )
(Bifunctional monomer)
Dimethylol-tricyclodecane diacrylate EBECRYL IRR214K (manufactured by DAICEL-CYTEC Company LTD., Abbreviated as DMTCDA in Table 1)
(Oligomer)
Urethane acrylate oligomer EBECRYL 8301 (manufactured by Daicel-Cytec, abbreviated as UA in Table 1)
[Polymerization accelerator]
Aminoacrylate EBECRYL7100 (manufactured by Daicel-Cytec, abbreviated as EB7100 in Table 1)
(Photopolymerization initiator)
IRGACURE 819 (Ciba Japan, abbreviated as 819 in Table 1)
DAROCUR TPO (Ciba Japan, abbreviated as TPO in Table 1)
KAYACURE DETX-S (Nippon Kayaku Co., Ltd., abbreviated as DETX in Table 1)
〔silica〕
・ Hollow silica (Sirinax (registered trademark), manufactured by Nippon Steel Mining Co., Ltd.)
Colloidal silica (Snowtex, manufactured by Nissan Chemical Industries, Ltd.)
[Thermal polymerization inhibitor]
P-methoxyphenol (KANTO CHEMICAL CO., INC, abbreviated as MP in Table 1)
[Pigment]
IRGALITE BLUE GLVO (Cyan pigment, manufactured by Ciba Japan, abbreviated as BLUE GLVO in Table 1)
[Dispersant]
Solsperse 36000 (manufactured by LUBRIZOL, abbreviated as SOL36000 in Table 1)

[Measurement and evaluation method]
[Preparation of ink composition]
The components shown in Table 1 below were added so as to have the composition (unit: mass%) shown in Table 1, and this was stirred with a high-speed water-cooled stirrer, whereby a cyan UV curable ink composition was obtained. Got.

(1. Dispersion stability)
Ink dispersion stability was evaluated as follows.
The sample was placed in a transparent glass bottle and stored at 60 ° C. for 1 week. The sedimentation state of the ink was visually observed and evaluated according to the following evaluation criteria.
A: No hollow silica particles or silica particle precipitates are observed.
-B: Although a very small amount of hollow silica particles or silica particle precipitates are observed, they are recovered immediately when the glass bottle is shaken.
C: Precipitation of hollow silica particles or silica particles is clearly observed, and the precipitate does not disappear even if the glass bottle is shaken.

[Preparation of recorded matter using ink composition]
The ink compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 3 below are filled in an ink jet recording apparatus equipped with a piezo ink jet nozzle, and printed on a PVC sheet (Frontlit Glossy 120 g, manufactured by Cooley). Various images were obtained. The ink discharge amount was adjusted so that the film thickness of each recorded matter was 10 μm. Each of the above ink compositions had good ejection properties, and various good images (recorded materials) were obtained. The obtained image (recorded material) was cured with a metahalide lamp under irradiation conditions of 250 mJ / cm ² per PASS, and after adding the PASS number until there was no surface tack, the following evaluation was performed.

(2. Scratch resistance)
After producing a coating film with a thickness of 10 μm on a glass substrate, a pencil scratch test (pencil hardness) is evaluated according to JIS K5600-5-4, and the obtained result is obtained. By classifying into the following ranks AA to D, it was set as an index of scratch resistance.
-AA: 3H or more-A: 2H
・ B: H
・ C: F
・ D: Below HB

(3. Adhesiveness)
According to JIS K 5600-5-6, the ink cured layer surface was cross-cut, and the adhesion was evaluated based on the following ranks AA to D from the results of a peel test using a cellophane tape. Each rank value is obtained by rounding off the first decimal place of the value obtained by calculating the peeling rate. The evaluation results are shown in Table 2 below.
・ AA: Hagaret rate 0-5%
・ A: Hagaret rate 6-15%
・ B: Hagaret rate 16-35%
・ C: 36-65% peel rate
・ D: Haggare rate 66-100%

(4. Elasticity)
The cured composition is printed on synthetic paper (synthetic paper YUPO FGS manufactured by YUPO Corporation) to a film thickness of 40 μm, and a hot cathode tube (NIPPO ELECTRIC CO., LTD.) (Manufactured) Using a 200 W power source, a light amount of 180 mW / cm ² was irradiated 0.1 seconds after landing to obtain a cured product. According to the method of bending resistance evaluation of JIS K 5600-5-1, the resulting cured film was evaluated for the occurrence of cracks. The evaluation results are shown in Table 2 below.
-AA: No cracks occurred.
A: There was a slight crack, but it was at a level where there was no problem in use.
-B: There was a crack and it was a practical limit level.
C: Cracks occurred frequently and it was difficult to use.

As shown in Table 2, when Examples 1-4 and Comparative Examples 1-3 are compared, when silica other than hollow silica is blended by blending hollow silica into the ink composition, silica is blended. It was found that the ink was excellent in scratch resistance, adhesion, elasticity, and dispersion stability (precipitation) in the cured layer of the ink as compared with the case where it was not present.
Further, as shown in Table 2, when Examples 1-4 and Examples 5-9 are compared, by blending a predetermined amount or more of hollow silica and urethane acrylate oligomer into the ink composition, in the cured layer of the ink It has been found that the scratch resistance, adhesion and elasticity are further improved.

Claims (7)

  A photocurable ink composition for inkjet recording, comprising a photoradical polymerizable compound, a photopolymerization initiator, and hollow silica.   The photocurable ink composition for inkjet recording according to claim 1, wherein the content of the hollow silica is 0.5 to 30% by mass with respect to the total amount of the ink composition.   The photocurable ink composition for ink jet recording according to claim 1, wherein the photoradical polymerizable compound contains at least one of phenoxyethyl (meth) acrylate and isobornyl (meth) acrylate.   The photocurable ink composition for inkjet recording according to claim 3, wherein the photoradically polymerizable compound further comprises N-vinylcaprolactam.   The photocurable ink composition for inkjet recording according to claim 3 or 4, wherein the photoradical polymerizable compound further comprises a (meth) acrylate oligomer.   The photocurable ink composition for inkjet recording according to claim 5, wherein the (meth) acrylate oligomer comprises a urethane (meth) acrylate oligomer.   The photocurable ink composition for inkjet recording according to any one of claims 1 to 6, further comprising at least one colorant of a pigment and a dye.