JP5621251B2 - UV curable inkjet ink and printed matter - Google Patents

Description

  The present invention relates to an ultraviolet curable inkjet ink and printed matter excellent in ejection property, curability and flexibility.

  Conventionally, active energy ray curable inks have been supplied and used for offset, silk screen, topcoat, etc. Solvent inks have the advantage of reducing costs and simplifying the drying process, and reducing solvent volatilization as an environmental response. In recent years, the amount of use has increased due to the replacement of. Water-based and solvent-based inks are often used as ink-jet inks, and their uses are properly used according to their characteristics. However, for industrial use, there are limitations on the printing substrate, water resistance is relatively poor, There are problems such as large drying energy and adhesion of ink components to the head due to drying, and replacement with ultraviolet curable ink having relatively low volatility is expected.

  However, the cured film of the conventional ultraviolet curable ink is often hard but fragile, and has a defect such as a crack in the printed part when the printed material is processed after printing. When the crosslink density of the cured film is lowered to give flexibility to the cured film, the curability of the ink is lowered, so it is essential to print at a lower speed, resulting in lower productivity and practical use. The actual situation was that we could not get enough speed.

  Patent Documents 1 and 2 exemplify ultraviolet curable inkjet inks containing N-vinylcaprolactam and a monomer having a Tg of less than 20 ° C. However, since none of them contained dipropylene glycol diacrylate, the dischargeability was insufficient, and it was not suitable for practical use.

JP 2006-169419 JP JP 2007-262177 A

  An object of this invention is to provide the ultraviolet curable inkjet ink excellent in discharge property, sclerosis | hardenability, and flexibility, and printed matter.

That is, the present invention provides an inkjet ink comprising at least (A) dipropylene glycol diacrylate, (B) N-vinylcaprolactam, and (C) a monofunctional acrylic monomer having a Tg of less than 20 ° C., (A), (B) , (C) The total amount of (C) is 60 to 90% by weight of all ink components, and the amount of monofunctional acrylic monomer having a Tg of 20 ° C. or higher is less than 10% by weight. About.
The present invention also relates to the above ultraviolet curable inkjet ink, wherein the blending amount of each component satisfies (A) + (B) :( C) = 2: 1 to 4: 1.

The present invention also relates to the above ultraviolet curable ink-jet ink, wherein (C) the monofunctional acrylic monomer having a Tg of less than 20 ° C. is a monomer selected from lauryl acrylate, ethoxyethoxyethyl acrylate, and phenoxyethyl acrylate.
Furthermore, this invention relates to the printed matter formed by printing on the printing base material with the said ultraviolet curable inkjet ink.

  According to the present invention, it was possible to provide an ultraviolet curable ink jet ink excellent in ejection property, curability and flexibility. As a result, the production speed of the printed matter can be increased, the construction period can be shortened, and the printed matter having no problem in practical use can be provided.

  The ultraviolet curable inkjet ink according to the present invention refers to a composition containing a monomer and a photopolymerization initiator and curable by ultraviolet rays. Moreover, the ultraviolet curable inkjet ink of this invention can use a pigment, a pigment dispersant, a polymerization inhibitor, a leveling agent, and other additives suitably by a use.

  In the present invention, by containing 60 to 90% by weight of a monofunctional acrylic monomer having dipropylene glycol diacrylate, N-vinylcaprolactam, and Tg of less than 20 ° C., an ink composition excellent in ejection property, curability and flexibility is obtained. providing.

  Dipropylene glycol diacrylate and N-vinylcaprolactam are excellent in ejectability and curability, so if they are mixed in a large amount in the ink, the printing speed can be increased and the productivity of the printed matter can be increased, but the obtained printed matter is hard and brittle. Therefore, it is not suitable for practical use. Therefore, by adding together a monofunctional acrylic monomer having a Tg of less than 20 ° C., flexibility is imparted, and a printed matter having practically sufficient flexibility can be provided. In order to obtain sufficient dischargeability and curability, each of these monomers is preferably contained in an amount of 10% by weight or more, more preferably 20-40% by weight. In addition, when 10% or more of a monomer having a Tg of 20 ° C. or higher is blended, flexibility is lowered and it is not suitable for practical use. It is preferable that no monomer having a Tg of 20 ° C. or higher is contained.

  However, many monofunctional acrylic monomers having a Tg of less than 20 ° C. are generally poor in reactivity, and if mixed in a large amount, the curability may be lowered. For this reason, it is desirable to mix 1/2 to 1/4 with respect to the total content of dipropylene glycol diacrylate and N-vinylcaprolactam.

Specific examples of monofunctional acrylic monomers having a Tg of less than 20 ° C include isooctyl acrylate, lauryl acrylate, ethoxylated (2 mol) ethylhexyl acrylate, tetrahydrofurfuryl acrylate, ethoxyethoxyethyl acrylate, phenoxyethyl acrylate, ethoxylated (4 mol) ) Nonylphenyl acrylate may be mentioned, but is not limited thereto.
Of these, lauryl acrylate, ethoxyethoxyethyl acrylate, and phenoxyethyl acrylate are preferably used from the viewpoint of curability.

  In the present invention, a polyfunctional monomer other than dipropylene glycol diacrylate can be blended at an arbitrary ratio. Specifically, dimethylol tricyclodecane diacrylate, (ethoxy (or propoxy)) bisphenol A diacrylate, cyclohexane dimethanol diacrylate, (poly) ethylene glycol diacrylate, (ethoxy (or propoxy)) 1,6 -Hexanediol diacrylate, (ethoxy (or propoxy)) neopentyl glycol diacrylate, hydroxypivalate neopentyl glycol diacrylate, tripropylene glycol diacrylate, pentaerythritol tri (or tetra) acrylate, trimethylolpropane tri (or Tetra) acrylate, tetramethylol methane tri (or tetra) acrylate, dipentaerythritol hexaacrylate, ethoxylated isocyanuric acid tri (or di) acrylate Relate can be mentioned but not limited thereto.

  The polyfunctional monomer used in the present invention is preferably a bifunctional and / or trifunctional monomer, and those having more functional groups than this may cause the cured film to be too hard, making the printed material unsuitable for practical use.

  As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is preferably used. Specific examples include 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1 -(4-Methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, oligo (2-hydroxy-2 -Methyl-1- (4- (1-methylvinyl) phenyl) propanone), 2-hydroxy-1- (4- (4- (2-hydroxy-2-methyl-propionyl) -benzyl) -phenyl) -2 -Methyl-propan-1-one and the like are preferably used, and other molecular cleavage types include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-Isopropylphenyl -2-hydroxy-2-methylpropan-1-one may be used in combination, and hydrogen abstraction type photopolymerization initiators, such as benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'- Methyl-diphenyl sulfide can be used in combination.

  For the photo radical polymerization initiator, as sensitizers, for example, trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, An amine such as N-dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone can also be used in combination. The above radical photopolymerization initiator and sensitizer are preferably selected from those that are excellent in solubility in an ultraviolet curable compound and that do not impair ultraviolet transparency.

  In recent years, high-speed printing is also required for ink jet printing. In order to realize this, it is preferable to use two or more kinds of initiators, one having an absorption maximum wavelength on the long wavelength side and one having on the short wavelength side. By using a plurality of initiators, the energy emitted from the light source can be used efficiently, and the curability can be improved.

2,4,6-trimethylbenzoyldiphenylphosphine oxide or bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and 2-methyl-1- (4-methylthiophenyl) -2-morphol It is particularly preferred to use a combination of linopropan-1-one or 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one.
The radical photopolymerization initiator and the sensitizer are preferably used in a range of 5 to 20% with respect to 100% of the monomer.

  When the coloring component is contained in the ultraviolet curable ink-jet ink according to the present invention, a dye or a pigment can be used, but the pigment can be more preferably used from the viewpoint of the durability of the printed matter. As pigments, pigments that are generally used for printing and paint inks such as cyan, magenta, yellow, black, and white can be used, and should be selected according to the required application such as color development and light resistance. Can do. In addition, it is preferable to mix | blend the ratio with respect to the whole ink of a pigment in arbitrary ratios 1-25% with respect to 100% of ink. In addition, a pigment dispersant can be used to stably disperse the pigment in the ink.

  In the present invention, a polymerization inhibitor such as hydroquinone, p-methoxyphenol, t-butylcatechol, and di-t-butylhydroxytoluene is added to 100% of the ink in order to enhance the storage stability of the ink and the stability in the recording apparatus. Therefore, it is preferable to blend at an arbitrary ratio of 0.01 to 5%.

  In the ultraviolet curable inkjet ink of the present invention, additives such as an ultraviolet absorber and an antioxidant can be used as necessary in order to enhance printability and printed matter resistance.

  In order to use the ultraviolet curable ink-jet ink of the present invention, the ink-jet ink is first supplied to the printer head of an ink-jet recording printer, discharged from the printer head onto a substrate, and then irradiated with ultraviolet light. This quickly cures the composition on the print medium.

  The timing of irradiating ultraviolet rays is preferably within 10 seconds after the ink has landed on the substrate, preferably within 30 milliseconds to 1 second. If the timing of irradiation is too late, the droplets mix with each other and the image blurs. On the other hand, if the timing is too early, the droplets do not spread, resulting in a noticeable grainy image.

  The printing equipment used in the present invention is not particularly limited, but plastic substrates such as polycarbonate, hard vinyl chloride, soft vinyl chloride, polystyrene, polystyrene foam, PMMA, polypropylene, polyethylene, PET, and the mixed or modified products thereof, and glass, Examples thereof include metal substrates such as stainless steel and wood.

  When the ultraviolet curable inkjet ink of the present invention is mounted on an inkjet printer and used, it can be used as an ink set in which a plurality of colors are combined as necessary. There are no particular restrictions on the combination, but four colors can be used in combination of cyan, magenta, yellow, and black.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not particularly limited to the examples. Absent. In the examples, “part” represents “part by weight”.

The raw materials used in the present invention are as shown below.
・ LIONOL BLUE FG-7400G (Cyan pigment manufactured by Toyo Ink Co., Ltd.)
・ CINQUASIA Magenta B RT-343-D (Magenta pigment manufactured by Ciba Specialty Chemicals)
・ LIONOGEN YELLOW ID250 (Yellow pigment manufactured by Toyo Ink Co., Ltd.)
・ Special BLACK 350 (Black pigment manufactured by Evonik Degussa)
・ Solsperse 32000 (Abisia pigment dispersant)
Photomer 4226 (Dipropylene glycol diacrylate manufactured by Cognis)
・ VCAP / RC (N-vinylcaprolactam manufactured by ISP)
・ Biscoat 192 (Phenoxyethyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ Biscoat 190 (Ethoxyethoxyethyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)
SR335 (Sartomer lauryl acrylate)
SR440 (Isooctyl acrylate manufactured by Sartomer)
・ Biscoat 150 (Tetrahydrofurfuryl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ SR257 (Sartomer Stearyl Acrylate)
・ IBXA (Isobornyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ TPGDA (Tripropylene glycol triacrylate manufactured by Daicel Cytec)
・ Light acrylate DCP-A (Kyoeisha dimethylol tricyclodecane diacrylate)
・ Irgacure369 (2-Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one manufactured by Ciba Specialty Chemicals)
・ Irgacure819 (Biba (2,4,6-trimethylbenzoyl) -phenylphosphine oxide manufactured by Ciba Specialty Chemicals)
・ Kayacure BMS (Nippon Kayaku Co., Ltd. 4-Benzoyl-4'-methyl-diphenyl sulfide)
・ Kayacure EPA (Nippon Kayaku Co., Ltd. ethyl p-dimethylaminobenzoate)
・ BYK UV3510 (polyether-modified polydimethylsiloxane manufactured by BYK Cheme)

First, Pigment Dispersion A was prepared with the following composition. A dispersion was prepared by adding a pigment and a dispersant to a monomer, stirring the mixture with a high speed mixer or the like until uniform, and then dispersing the obtained mill base with a horizontal sand mill.
・ LIONOL BLUE FG-7400G 15 parts ・ Solce 32000 5 parts ・ Photomer 4226 80 parts

In addition, Pigment Dispersion B was prepared with the following composition. The production method of the dispersion was prepared by the same production method as that of Dispersion A.
・ CINQUASIA Magenta B RT-343-D 25 parts ・ Solsperse 32000 10 parts ・ Photomer 4226 65 parts

In addition, Pigment Dispersion C was prepared with the following composition. The production method of the dispersion was prepared by the same production method as that of Dispersion A.
・ LIONOGEN YELLOW ID250 20 parts ・ Solsparse 32000 15 parts ・ Photomer 4226 65 parts

Also, Pigment Dispersion D was prepared with the following composition. The production method of the dispersion was prepared by the same production method as that of Dispersion A.
・ Special BLACK 350 15 copies ・ Solsparse 32000 5 copies ・ Photomer 4226 80 copies

Example 1
The raw materials shown in Table 1 were added sequentially from the top of the table with stirring. After stirring for 2 hours, it was confirmed that there was no undissolved residue, and filtration was performed with a membrane filter to remove coarse particles causing the clogging of the head, thereby preparing an ink. Using this ink, the evaluation of dischargeability, curability and flexibility was performed.

Examples 2-12
In the same manner as in Example 1, inks were prepared as shown in Table 1, printed and cured to produce printed matter, and evaluation was performed.

Comparative Examples 1-12
Ink was prepared as described in Table 2 in the same manner as in Example 1, and printing and curing were carried out to produce a printed material for evaluation.

Evaluation Method for Ejectability Evaluation ink was ejected with an inkjet head KJ4A manufactured by Kyocera Corporation, and evaluation was performed from the droplet flying state and ejection stability at that time. As for the droplet flying state, when the ink droplet was ejected, the ink droplet in which no satellite or mist was generated was passed, and the ink droplet was disqualified. As for the discharge stability, continuous printing was performed for 30 minutes, and the nozzles with no missing nozzles were passed, and some were disqualified. The evaluation criteria are as follows.
◎: Both droplet flying state and ejection stability passed ○: Only droplet flying state passed ×: Droplet flying state disqualified

Curability evaluation method The evaluation ink was discharged onto a vinyl chloride sheet by an inkjet discharge device, and immediately after that, the curability was evaluated from the conveyor speed when cured by irradiating with a metal halide lamp 120 W / cm manufactured by Toshiba Lighting & Technology. The evaluation criteria are as follows.
◎: 40m / min or more ○: 20-40m / min
×: 20m / min or less

Flexibility Evaluation Method Evaluation ink is discharged onto a vinyl chloride sheet with an inkjet discharge device so as to have a film thickness of 5 μm, and immediately after that, it is cured with a metal halide lamp manufactured by Toshiba Lighting & Technology Corp. to obtain a printed matter. The printed surface of this printed matter was bent outward at 180 °, and at that time, the case where no crack occurred in the cured film was judged as “◯”, and the case where it occurred was judged as “X”.

  In the examples, dipropylene glycol, N-vinylcaprolactam, and a monofunctional monomer having a Tg of less than 20 ° C. were blended in an amount of 60 to 80%, and it was shown that the ink was excellent in ejection property, curability, and flexibility. . In Examples 7 and 8, the dischargeability could be improved by adjusting the monomer mixing ratio. In Examples 1 and 2, curability could be improved by selecting a monomer having a Tg of less than 20 ° C. In Examples 5, 6, and 9 to 12, inks that sufficiently satisfy all physical properties are obtained.

In Comparative Examples 1 to 4, dipropylene glycol, N-vinylcaprolactam, and Tg have no monofunctional acrylic monomer having a temperature of less than 20 ° C. In Comparative Examples 4 to 8, dipropylene glycol, N-vinylcaprolactam, and Tg are 20 ° C. Less than 60% acrylic monomer, but the blending amount is less than 60%, so the physical properties cannot be satisfied. In Comparative Examples 9-12, since it has a monofunctional acrylic monomer having a Tg of 20 ° C. or higher, the flexibility is poor.

Claims (3)

In an inkjet ink comprising a monofunctional acrylic monomer having a Tg of less than 20 ° C selected from at least (A) dipropylene glycol diacrylate, (B) N-vinylcaprolactam, (C) at least lauryl acrylate, and ethoxyethoxyethyl acrylate ( A), (B), and (C) are combined in a total amount of 60 to 90% by weight of all ink components, and the amount of monofunctional acrylic monomer having a Tg of 20 ° C. or higher is less than 10% by weight. UV curable inkjet ink. 2. The ultraviolet curable inkjet ink according to claim 1, wherein the blending amount (weight ratio) of each component satisfies (A) + (B) :( C) = 2: 1 to 4: 1. A printed matter obtained by printing on a printing substrate with the ultraviolet curable inkjet ink according to claim 1 or 2 .