JP4923523B2 - Active energy ray curable ink for ink jet - Google Patents

Description

  The present invention relates to an ink having excellent processability with respect to an active energy ray-curable ink for ink jet. The ink of the present invention is suitable for interior and exterior printing applications that require cosmetics by processing, printing applications for CDs, DVDs, etc., and printing on non-permeable substrates such as printing on flexible substrates. Is suitable.

  Conventionally, active energy ray curable inks have been supplied and used for offsets, silk screens, top coats, etc., but from the merits such as cost reduction by simplifying the drying process and reduction of solvent volatilization as an environmental response. The amount used has increased in recent years. Among them, water-based and solvent-based inks are often used as ink-jet inks, and the use is properly used according to each feature, but for industrial use, there are limitations on the receiving substrate, relatively poor water resistance, There are problems such as high ink drying energy and adhesion of ink components to the head due to drying, and replacement with active energy ray-curable ink with relatively low volatility is expected.

However, cured films using conventional active energy ray curable inks often exhibit hard but brittle properties. In addition, a cured film in which Tg is simply lowered to room temperature or lower is excellent in flexibility such as bending, but on the other hand, the scratch resistance and friction resistance due to extremely reduced hardness are reduced. It becomes difficult to use as the above handling or as the quality of the product itself. All active energy ray cured films are greatly inferior to conventional solvent-based inks in terms of stretch processing characteristics. As a result, in high quality applications that require molding, significant changes are not made, although alternatives are expected. is the current situation. This situation is also the same with the current active energy ray-curable ink jet ink. However, in order to stably discharge with the ink jet, it is necessary to suppress the viscosity to about several tens of cps at the highest, and to reduce the head member. Since it is necessary to selectively use a monomer that does not erode, the actual compounded monomer is very limited. As a result, no ink that satisfies many required properties has been put on the market.
In addition, as described in Comparative Examples of the present invention, conventionally, the crosslink density and ductility are correlated, and the curability of the ink designed for low crosslinking is deteriorated, and stickiness after curing occurs. In addition, a cured film with low crosslink density may cause delamination due to the low strength of the cured film itself even if it is in close contact with the base material, and there is a trade-off between ductility, stickiness, and cured film strength. Either of the above performances had to be prioritized.

  In order to solve such problems, the present invention makes it possible to provide an ink or printed matter that breaks the conventional relationship between crosslink density and ductility. Moreover, this invention was able to express more effectively by controlling the molecular weight between ethylenic double bonds. In addition, with respect to the monofunctional monomer, it is possible to further enhance the effect by selectively using a monomer having excellent ductility.

  As a solvent-free active energy ray-curable ink jet ink, Patent Document 1 discloses a dye and 50 to 95% polymerizable monomer, a maximum of 70% by weight of a monofunctional monomer, a maximum of 70% by weight of a bifunctional monomer, 0 Disclosed is a 10% by weight monomer-based ink jet ink having a functionality of 3 or more. The composition of the monofunctional monomer up to 70% by weight means that it contains 30% by weight or more of the polyfunctional monomer and uses many polyfunctional monomers having a large cure shrinkage, so that the adhesiveness to the polycarbonate or polyester substrate is poor and suitable for practical use. It was not.

  Patent Document 2 discloses an ink composition composed of monomers having an alkoxylated component and a non-aromatic heterocyclic component as adhesive components. Although this ink had good adhesion to the polycarbonate substrate and good flexibility, the substrate adhesion of the coating film was deteriorated in the weather resistance test. This is presumably because the alkoxylation component absorbed water and caused floating at the coating film / substrate interface. This phenomenon is particularly noticeable with lower alkoxy groups.

Patent Document 3 discloses an ink composition composed of a monofunctional or higher polyester urethane oligomer having a polycaprolactone ester component and a hydroxyl component and a reactive diluent in order to alleviate shrinkage during curing. This ink has adhesion and flexibility with urethane oligomer components, and the viscosity is adjusted to a predetermined range with a reactive diluent, but the viscosity is high and the temperature temperature dependence is relatively large, and there is a problem with ink jet suitability. Remains.
Further, since a necessary amount of the oligomer component is added, it is necessary to select a low-viscosity reactive diluent such as tetrahydrofurfuryl acrylate, and there are many problems such as the use period of the head is shortened due to the erosion of the head peripheral member and the cost is increased. In general, when an inert resin such as a urethane resin or an oligomer is contained as a constituent element, the ductility is often improved.

Patent Document 4 presents an ultraviolet curable ink excellent in adhesion to polycarbonate and processability, but this ink has a high viscosity because it uses a polyurethane-based oligomer, and it is very ejected by an ink jet. Can not. In addition, even when the viscosity is lowered to a level that allows ejection, the phenomenon of ink stringing due to the high molecular weight component of the polyurethane-based oligomer appears during ink ejection, causing stains. Cannot be used above. In addition, the polycaprotactic urethane acrylate synthesized by the method described in this document becomes a bifunctional oligomer because hydroxyacrylate can be added to the —NCO groups attached to both ends of urethane prepared in advance. In this document, post-processability is imparted by the flexibility and adhesiveness of urethane, but as a result of adding a large amount of bifunctional monomer, it is possible to cope with slight stretching. The stretch workability as large as described in the invention cannot be obtained.
In addition, as an important matter clarified in this study, using an inert resin having no reactivity, an oligomer having a relatively high molecular weight, etc. simply reduces the crosslink density of the cured film, It turns out that it only improves the ductility. In other words, using an inert resin or an oligomer to obtain a desired ductility depends on the classification of the conventional invention described in the present invention, and if the ductility is obtained, the coating film becomes sticky, the reactivity becomes worse, the curing Problems such as a decrease in film strength have occurred.

Japanese Patent Laid-Open No. 5-214280 JP-T-2004-518787 JP-A-6-184484

  An object of the present invention is to provide an active energy ray-curable ink for an ink jet, which can obtain a printed matter having ductility or curing performance, which has not been obtained in the past, for applications requiring processability.

That is, the present invention is an active energy ray-curable ink for an ink jet containing a polymerizable monomer, and an ink cured film formed on a polycarbonate substrate having a thickness of 500 μm has a strain rate of 2 / The present invention relates to an active energy ray-curable ink characterized by exhibiting elongation at break satisfying [Equation 1] when stretched at min.
[Formula 1]
( ^Breaking elongation at 190 ° C., strain rate 2 / min)> 1.83 × (molecular weight between cross-linking points) ^0.437

  In addition, the present invention relates to the active energy ray-curable ink as described above, wherein the polymerizable monomer contains a polyfunctional monomer having an ethylenic double bond molecular weight of 250 or more.

  Further, the present invention relates to the active energy ray-curable ink as described above, wherein the polymerizable monomer contains a monofunctional monomer in an amount of 50% by weight or more based on the whole monomer.

  In addition, the present invention relates to the above active energy ray-curable ink, wherein a part of the monomer contained in the monofunctional monomer is phenoxyethyl acrylate and isobornyl acrylate.

  Further, in the polymerizable monomer, the active energy ray-curable ink as described above, wherein phenoxyethyl acrylate is 30% by weight to 90% by weight and isobornyl acrylate is 10% by weight to 40% by weight. .

  Moreover, it is related with the printed matter formed by printing on the printing base material with the above-mentioned active energy ray curable ink.

  When the active energy ray-curable ink for ink jet of the present invention has the conventional stretch processability, it is possible to provide a printed material that exceeds the curability and strength of the conventional coating film, and the conventional curing is possible. As for printed matter having the properties and coating film hardness, it is possible to provide a printed matter having high stretch processability. The effect shows that the performance of the area | region which is not before is expressed, as shown in [FIG. 1] described in this invention. As a specific application, in printing which requires an application for performing deformation processing after ink jet printing, it is possible to solve the tack remaining after the conventional curing and the adhesion failure due to peeling of the ink in the cured layer. This effect has made it possible to reduce the post-printing processes such as overexposure of active energy rays after printing and heat treatment, and to realize a significant cost reduction by shortening the lead time.

  In the active energy ray-curable ink according to the present invention, it was found that the ductility specified in Formula 1 in the cured coating film after ink jet discharge onto various substrates is a ductility that has not been obtained conventionally. It can be expected that the ductility is not improved, or that the curability is improved and the strength of the cured film is improved when ductility is imparted to the same level as before.

Specifically, (breaking elongation at 190 ° C., strain rate 2 / min)> 1.83 × (molecular weight between cross-linking points) ^0.437
When exceeding the said formula, it turned out that it is a coating film beyond the relationship between the molecular weight between crosslinking points and ductility by a prior art.
This suggests how important the molecular weight between cross-linking points is in ductility in the present invention, and it can be generally said that a highly crosslinked cured film has low ductility. is there.
The elongation at break described in the present invention indicates the ductility at the time when the surface of the coating film is broken when tensile drawing is performed. As a calculation method, [Calculation Formula 1] represented by the following formula is used. In other words, 100% is assumed to be the same length as the initial length.
[Calculation Formula 1]
Elongation at break (%) = (actually extended length + initial length) / initial length × 100
Moreover, the molecular weight between crosslinking points described in the present invention is described by the following [Calculation Formula 2].
[Calculation Formula 2]
Molecular weight between cross-linking points = average molecular weight x molar ratio of monofunctional monomer x 2 / average number of functional groups of polyfunctional monomer average molecular weight = Σ
Monofunctional monomer molar ratio = (Σ (weight of each compound / molecular weight of each monomer))
/ Σ (Each blended weight% / Molecular weight of each polyfunctional monomer)
Average number of functional groups of polyfunctional monomer = Σ (number of functional groups of each polyfunctional monomer
× (Mixed weight% of each polyfunctional monomer / Molecular weight of each polyfunctional monomer)
/ Σ (Mixed weight% of each polyfunctional monomer / Molecular weight of each polyfunctional monomer))
The molecular weight between crosslinking points shown here indicates the average molecular weight sandwiched between one double bond at one end of the polyfunctional monomer and the other double bond. Although the actual molecular weight between crosslinks may be different, the versatility of this formula is as shown in the examples of the present invention. In addition, this formula is not only applied to a system containing only a monomer having a polymerizable double bond, but is calculated as a monofunctional monomer component when an inert resin having no polymerizable reactive group is used. This is enough to adapt. The pigment, dispersant, initiator, additive, and the like contained in the ink are irrelevant to the above formula.
In addition to the conditions described in the claims, for example, when the evaluation is performed on a substrate on which adhesion is not significantly obtained, when the temperature and strain rate are stretched under different conditions, or when the curing conditions are changed And the like are not considered to be the same conditions because they may deviate from the conditions described in the claims. Since the present invention relates to an ink that can exhibit ductility different from the conventional one or a printed matter when stretched under the conditions described in the claims, the actual application includes a base material, stretching conditions, and processing conditions. It is not intended to limit.
The curing described in the present invention refers to the surface of a cured film made of ink by irradiating an active energy ray, for example, ultraviolet rays after the ink is applied on a substrate by a coating method such as an ink jet or a bar coater. The case where tack is lost from is shown. Tack can be judged by finger touch evaluation. For example, when a conveyor type ultraviolet irradiation device is used, a cured film in which the number of irradiation passes is repeated and the tack does not change even if the number of passes is repeated is shown. Depending on the type of ink, the tack may remain without disappearing. In this case, if the number of passes does not change, the cured film is determined. Further, the curing method and the curing conditions are not limited to this.

In order to more effectively escape from the conventional relationship between the conventional ductility and the molecular weight between cross-linking points, the polyfunctional monomer has a structure in which the number of molecules for ethylenic double bonds is 250 or more. It was important to incorporate the monomer.
The molecular weight between ethylenic double bonds described in the present invention indicates the molecular weight between the double bond and the double bond in the molecule of the polyfunctional monomer. For example, if the structure is a known bifunctional monomer, the molecular weight existing between the double bonds can be calculated. In the case of a monomer having a functional group number of 3 or more, it can be calculated by the following [Calculation Formula 3].
[Calculation Formula 3]
Molecular weight between ethylenic double bonds = molecular weight other than double bonds x 2 / number of double bonds in molecule In addition, when the structure of the newly polymerized monomer is not limited, NMR, GPC, GC / MS analysis, etc. It is also possible to specify and use the structure. In addition, in the case of a monomer having a structure in which a double bond is not coordinated to the molecular end, by calculating the distance between the double bonds specifically, and when the distance between the double bonds is not constant, the average two The molecular weight between heavy bonds is defined as the present invention.
In any case, the molecular weight between the ethylenic double bonds described in the present invention is calculated by excluding the molecular weight of the ethylene moiety. Further, the calculation is performed without including the case where hydrogen in the ethylene portion is substituted with a methyl group or the like.
More specifically, the molecular weight other than the double bond in the above [Calculation Formula 3] refers to a value obtained by subtracting 54 from the molecular weight of the monomer, assuming 27 as one double bond.
According to the present invention, when the molecular weight between the ethylenic double bonds is smaller than 250, sufficient ductility cannot be obtained or the coating strength is lowered.
When cured with active energy rays, the cured film is uniformly cross-linked when viewed macroscopically in the plane direction, but due to an increase in the viscosity of the ink that occurs during the descent, that is, polymerization that occurs at the initial stage of curing, It is called heterogeneous crosslinking when viewed microscopically due to a decrease in molecular mobility due to a crosslinking reaction. If the molecular weight between the ethylenic double bonds is still large, the cross-linking points become microscopically or locally close to a uniform structure, and as a result, the molecular weight between the cross-linking points of the cured film becomes uniform, thereby improving ductility. It seems to do. In addition, when the molecular weight between the ethylenic double bonds is small, the cross-linking points are partially non-uniform, and when deformation such as stretching is performed, stress is concentrated on the short cross-linking points and breakage is considered to occur. Further, this non-uniformity of the crosslinking points is considered to cause a decrease in the strength of the cured film.
Further, a monomer having an ethylenic double bond molecular weight of 300 or more can be used more suitably because it can obtain higher ductility and cured film strength.
However, a relatively high molecular weight polyfunctional monomer having a molecular weight between ethylenic double bonds of 1000 or more needs to be blended in a large amount in order to obtain a desired molecular weight between cross-linking points. Since it may become impossible to discharge with a jet printer, it is not preferable.

  As described above, the elongation at break generally depends largely on the molecular weight between cross-linking points, so the ductility of the ink containing a large amount of polyfunctional monomer is low, but a certain degree of effect can be desired by the present invention. It is. Furthermore, in an ink containing 50% by weight or more of a monofunctional monomer, the effect of the present invention is sufficiently exhibited, and a remarkable effect on ductility and coating strength can be expected.

  In particular, an ink using phenoxyethyl acrylate and isobornyl acrylate as a monofunctional monomer showed high ductility. The reason is not clear, but phenoxyethyl acrylate and isobornyl acrylate have good repeatability of polymerization, resulting in a high molecular weight of the cured film, leading to reduction of voids generated from molecular ends that cause breakage during stretching. Analogy.

As a specific use amount, phenoxyethyl acrylate has a high curing reactivity with active energy rays, and therefore, when the content is less than 30% by weight, the curing rate decreases. Moreover, when it contains 90 weight% or more, Tg of a cured film falls and it becomes a cured film with low hardness although it is flexible. In addition, isobornyl acrylate is often used as a reactive diluent because of its low viscosity, but when blended in excess of 40% by weight, the polymerizability is not as good as phenoxyethyl acrylate. Odor may remain on the film, and in some cases, it may cause poor curing, resulting in deterioration of productivity. Moreover, when mix | blending in less than 10 weight%, the effect of the ductility improvement by interaction with phenoxyethyl acrylate becomes difficult to be observed.
In order to obtain higher ductility and curing speed, a more suitable coating film can be obtained by using 45% to 80% by weight of phenoxyethyl acrylate and 10% to 25% by weight of isobornyl acrylate. Can do.

Moreover, a general polymerizable monomer can be used for the polymerizable monomer used in the ink.
Specific examples of the monofunctional monomer include cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, methylphenoxyethyl acrylate, 4-t-butylcyclohexyl acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, tribromophenyl acrylate, ethoxylated tribromophenyl Acrylate, 2-phenoxyethyl acrylate ethylene oxide and / or propylene oxide addition monomer, acryloylmorpholine, phenoxydiethylene glycol acrylate, vinyl caprolactam, vinyl pyrrolidone, 2-hydroxy-3-phenoxypropyl acrylate 1,4-cyclohexanedimethanol monoacrylate, 2 -Hydroxyethyl acrylate, 2-hydride Roxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, 3-methoxybutyl acrylate, ethoxyethoxyethyl acrylate , Butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, dipropylene glycol acrylate, β-carboxyl ethyl acrylate, ethyl diglycol acrylate, trimethylolpropane formal monoacrylate, imide acrylate, isoamyl acrylate, ethoxylated succinic acid acrylate, Trifluoro Chill acrylate, .omega.-carboxypolycaprolactone monoacrylate, there may be mentioned N- vinylformamide, but not limited thereto.
Specific examples of the polyfunctional monomer include dimethylol-tricyclodecane diacrylate, propoxylated bisphenol A di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, di Methylol dicyclopentane diacrylate, ethoxylated isocyanuric acid triacrylate, tri (2-hydroxyethyl isocyanurate) triacrylate, tri (meth) allyl isocyanurate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, ethoxylated 1,6-hexanediol diacrylate, neopentyl Coal di (meth) acrylate, polypropylene glycol diacrylate, 1,4-butanediol di (meth) acrylate, 1,9-nonanediol diacrylate, tetraethylene glycol diacrylate, 2-n-butyl-2-ethyl-1, 3-propanediol diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane triacrylate, hydroxypivalic acid trimethylolpropane triacrylate, ethoxylated phosphoric acid triacrylate, Ethoxylated tripropylene glycol diacrylate, neopentyl glycol modified trimethylolpropane diacrylate, stearic acid modified pentaerythritol diacrylate , Pentaerythritol triacrylate, tetramethylolpropane triacrylate, tetramethylol methane triacrylate, pentaerythritol tetraacrylate, caprolactone-modified trimethylolpropane triacrylate, propoxylate glyceryl triacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, ditri Methylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, caprolactone-modified dipentaerythritol hexaacrylate, dipentaerythritol hydroxypentaacrylate, neopentyl glycol oligoacrylate, 1,4-butanediol oligo Acrylate, 1,6-hexanediol oligoacrylate, trimethylolpropane oligoacrylate, pentaerythritol oligoacrylate, ethoxylated neopentyl glycol di (meth) acrylate, propoxylated neopentyl glycol di (meth) acrylate, tripropylene glycol di (meth) ) Acrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, and the like, but are not limited thereto. These monofunctional and polyfunctional monomers may be used alone or in combination of two or more as required.
Furthermore, in order to obtain a cured film having excellent ductility and strength, the amount of the polyfunctional monomer having an ethylenic double bond molecular weight of 250 or more is preferably 50% by weight or more in the polyfunctional monomer used. .
Also, the higher the molecular weight between the ethylenic double bonds, the better the ductility tends to be obtained. It becomes difficult.

  The active energy ray described in the present invention affects an electron orbit of an irradiated object such as an electron beam, an ultraviolet ray, and an infrared ray, and indicates an energy ray that can trigger a polymerization reaction such as a radical, a cation, and an anion. The energy ray is not limited to this as long as it induces a polymerization reaction.

The ink shown by this invention shows the liquid printed or applied to the base-material surface.
When this ink does not contain a coloring component, it can be used as a coating application, and it can also be used as a single coating layer or laminated coating with an ink containing a colorant described below. Various fillers and resin components can also be added to impart durability such as hardness and scratch resistance of the cured film, moldability, and design properties such as gloss control. Examples of the filler include extender pigments such as calcium carbonate, barium sulfate, spherical silica, and hollow silica, and resin beads. The resin component is not particularly limited as long as the resin is inactive to active energy rays. , Polyurethane resin, vinyl chloride resin (eg, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer), polyester resin, poly (meth) acrylic resin, polyketone resin, polyvinyl resin (For example, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl pyrrolidone resin), cellulose resin (for example, CAB resin, CAP resin) and the like can be mentioned. When these fillers and resin components are added, it is preferable to consider the type and composition in consideration of ink jet aptitude, but other printing methods such as silk screen printing, gravure printing, offset printing, or spray coating. You may perform the coating by. In addition, in the multi-layer coating with the ink containing the colorant, the coating material used in general printing applications other than the ink of the present invention, for example, silk screen printing, gravure printing, offset printing, etc. includes the colorant of the present invention. Lamination may be performed on the ink layer, or a separately molded coating layer (such as a film) may be transferred by lamination, or lamination using a spray coating material or the like may be performed.
On the other hand, when the ink of the present invention contains a coloring component, it can be used as a material for displaying graphics, characters, photographs and the like. Conventionally, dyes and pigments have been widely used as the coloring component, but pigments are often used particularly in terms of weather resistance. Among the pigment components, specific examples of carbon black include “Special Black 350, 250, 100, 550, 5, 4, 4A, 6” “Printex U, V, 140 U, 140 V, 95, 90, 85, manufactured by Degussa. 80, 75, 55, 45, 40, P, 60, L6, L, 300, 30, 3, 35, 25, A, G ”,“ REGAL 400R, 660R, 330R, 250R ”“ MOGUL E, L ”manufactured by Cabot Corporation “MA7, 8, 11, 77, 100, 100R, 100S, 220, 230” manufactured by Mitsubishi Chemical Corporation “# 2700, # 2650, # 2600, # 200, # 2350, # 2300, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 900, # 850, # 750, # 650, # 52, # 50, # 4 , # 45, # 45L, # 44, # 40, # 33, # 332, # 30, # 25, # 20, # 10, # 5, CF9, # 95, and the like # 260 ". In the present invention, in yellow, magenta, cyan ink, or other colors such as white, pigments used in inks for general printing applications and paint applications can be used, such as color developability and light resistance. From this point, it can be selected as necessary.
The ratio of the pigment to the whole ink is 0.2 to 15 parts by weight for organic pigments such as yellow, magenta, cyan, and black with respect to 100 parts by weight of ink. In the case, it is preferable to mix in an arbitrary ratio of 5 to 40 parts by weight.

Further, the ink of the present invention can use a dispersant for stabilizing the dispersion of the filler and pigment, and other additives for imparting each function.
As the dispersing agent, there are various kinds of dispersing agents such as a high molecular weight dispersing agent and a low molecular weight dispersing agent, which can be selected according to the dispersibility. A pigment derivative can be used as a dispersion aid.
Moreover, as an additive, the conventionally used wettability adjusting agent, surface tension adjusting agent, antifoaming agent, slipping agent, antiblocking agent, ultraviolet ray preventing agent and the like can be used.
Any dispersant, dispersion aid, and additive can be selected according to the intended application, and none of them is limited in the present invention.

  Moreover, when ultraviolet rays are used as active energy rays, a photopolymerization initiator is contained in the ink. The photopolymerization initiator can be freely selected depending on the curing speed, the cured coating film properties, and the coloring material. Specifically, as the radical photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the present invention. Specific examples include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- (4- Morpholinophenyl) -butan-1-one, bis (2,4,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 1,2-octanedione, 1- (4- (phenylthio) -2,2- (O-benzoyloxime)) and the like are preferably used, and other molecular cleavage types include 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2 -Methyl-1-phenylpropane-1-o 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one Moreover, benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide, etc., which are hydrogen abstraction type photopolymerization initiators, can also 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 that does not cause an addition reaction with the polymerizable component, such as N-dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the radical photopolymerization initiator and the sensitizer, which are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.

  In the present invention, a polymerization inhibitor such as hydroquinone, p-methoxyphenol, t-butylcatechol, pyrogallol, and butylhydroxytoluene is used in order to increase the stability of the ink over time and the stability in the printing apparatus. It is preferable to blend 0.01 to 5% by weight in the ink.

The active energy ray-curable inkjet ink of the present invention uses one or more additives such as a plasticizer, a surface conditioner, an ultraviolet light inhibitor, a light stabilizer, and an antioxidant such as dibutylhydroxytoluene as necessary. Can do.

  Moreover, when using an electron beam as an active energy ray, it can adjust as an electron beam hardening ink by mix | blending except the said initiator and a sensitizer.

  The ink of the present invention can be used as a set of inks having different pigments, for example, 4, 5, 6, 7, etc. For example, in the case of four types, yellow, magenta, cyan, black, yellow, magenta, cyan, white, etc. can be exemplified.

The ink of the present invention can be used by printing on a printing substrate with an ink jet discharge device. There are no particular limitations on the printing substrate, but plastic substrates such as polycarbonate, hard vinyl chloride, soft vinyl chloride, polystyrene, foamed polystyrene, PMMA, polypropylene, polyethylene, PET, and mixed or modified products thereof, and glass, stainless steel, etc. Examples include metal substrates and wood.
Moreover, when processing after printing on the said base material, processing conditions, such as the processing temperature, can be set as needed.

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

First, Pigment Dispersion A was prepared with the following composition. Hereinafter, 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 for about 1 hour.
・ Solspers 32000 (pigment dispersant manufactured by Lubrizol) 9 parts ・ Phenoxyethyl acrylate 61 parts

Also, Pigment Dispersion B was prepared with the following composition. The method for producing the dispersion was prepared by the same production method as that for Dispersion A.
・ Novoperm Yellow P-HG (Clariant Benzimidazolone Pigment) 35 parts ・ Solspers 24000 (Lubrisol Pigment Dispersant) 7 parts ・ Phenoxyethyl acrylate 58 parts

In addition, Pigment Dispersion C was prepared with the following composition. The method for producing the dispersion was prepared by the same production method as that for Dispersion A.
Hostaperm Red E5B02 (Clariant quinacridone pigment) 20 parts Solspers 24000 (Lubrisol pigment dispersant) 6 parts Phenoxyethyl acrylate 74 parts In addition, Pigment Dispersion D was prepared with the following composition. The method for producing the dispersion was prepared by the same production method as that for Dispersion A.
・ Special Black 350 (Degussa carbon black pigment) 30 parts ・ Solspers 32000 (Lubrisol pigment dispersion) 6 parts ・ Phenoxyethyl acrylate 64 parts

Also, Pigment Dispersion E was prepared with the following composition. The method for producing the dispersion was prepared by the same production method as that for Dispersion A.
-Taihke PF740 (Ishihara Sangyo Co., Ltd. Silica-treated 1.0%, Alumina-treated 2.0% white pigment) 40 parts-Azisper PB821 (Ajinomoto Fine Techno Co., Ltd. pigment dispersant) 2 parts-Phenoxyethyl acrylate 58 parts

Example 1
The raw materials in Table 1 were added 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. This ink was discharged onto a polycarbonate plate by an ink jet discharge device so as to have a film thickness of 10 μm. Immediately after the ejection, 120 W / cm from Harrison Toshiba Lighting, one high-pressure mercury lamp, an irradiation distance of 10 cm, a conveyor speed of 5 m / min, and 1 Pass, UV-cured, and after confirming the surface coins, a cured film was obtained.

Example 2 to Example 8
As in Example 1, ink was prepared as shown in Table 1, printed and cured to obtain a cured film.

Comparative Examples 1 to 7
As in Example 1, ink was prepared as shown in Table 2, printed and cured to obtain a cured film.

  The cured film after leaving the cured film at room temperature for 24 hours is punched into a dumbbell shape with a base material using a punching machine (manufactured by Dumbbell), and the obtained test piece is Tensilon (UCT-1T: manufactured by ORIENTEC) Was heated to 190 ° C., and the tensile test was performed together with the base material. Since it was difficult to grasp the breaking point of the cured film from the change in tension obtained from the load cell, the elongation at the time when the fracture of the cured film surface was confirmed visually was expressed in terms of%.

The curing rate was measured separately.
After coating using a bar coater # 8 (manufactured by Tester Sangyo Co., Ltd.) on a polycarbonate plate so that the film thickness is 10 μm, 120 W / cm from Harrison Toshiba Lighting Co., Ltd., 1 high pressure mercury lamp, irradiation distance 10 cm, conveyor speed The number of passes at which UV curing was performed at 20 m / min and the tack of the cured film stopped changing was evaluated as the curing speed.

The composition of each formulation and the evaluation results are shown in Table 1, Table 2, and FIG. FIG. 1 shows the results of plotting the molecular weight between crosslinks and the elongation at break so that the effect of the present invention can be understood more clearly.
In the first place, the important point of the present invention is that the cured film cured with active energy rays has poor ductility, and tackling to solve problems such as occurrence of tack when emphasizing ductility. During the study of the present invention, it is understood that physical properties that are difficult to quantify such as tack are expressed as specific numerical values of molecular weight between cross-linking points, and the cured film that remains tack has a molecular weight between cross-linking points of The cured film with a large tack and a small tack showed a small molecular weight between crosslinking points. In addition, using this concept of molecular weight between cross-linking points, it has been understood that the ductility of a conventional cured film is uniquely determined by the molecular weight between cross-linking points, leading to the present invention that breaks this trade-off relationship. It was. That is, FIG. 3 shows the molecular weight between crosslinks and the elongation at break, but intends the relationship between tack and ductility.
A real 1 and a ratio 1 in FIG. 1 indicate Example 1 and Comparative Example 1, respectively. Moreover, it described similarly of the other result.

Examples 1 to 10 are shown in Table 1, comparative examples are shown in Table 2, and FIG. From this result, Examples 1-10 show high ductility compared with the result of the conventional cured film of Comparative Examples 1-8, and exist in the area | region prescribed | regulated to this invention. This result is also influenced by the large molecular weight between the double bonds. In Example 5, the amount of isobornyl acrylate added was small, and in Examples 6 and 8, the amount of phenoxyethyl acrylate added was small, so the curing rate was slightly reduced.
Comparative Examples 1-8 used a monomer having a small molecular weight between double bonds, indicating that the ductility is within the conventional range. Further, in Comparative Examples 2 and 7, as a result of blending a small amount of phenoxyethyl acrylate, the curing rate was significantly reduced. Further, in Comparative Example 2, since there was no blending of isobornyl acrylate, the ductility showed a lower value.

    Furthermore, when a multilayer coating was performed on the printed matter printed using any of the inks described in Examples 1 to 6 using the ink not containing the coloring component described in Example 7 or 8, all the printed matter exhibited high ductility, In addition, a sufficiently practical printed matter with no tack remaining was obtained.

  The active energy ray-curable ink for ink jet of the present invention is excellent in processability and excellent in curability, and as a result, UV printing, which is considered to be difficult to process in the past, especially ink jets with strict regulations on the monomers used. In printing, the application was greatly expanded. In particular, it is suitable for interior and exterior printing applications that require cosmetics by processing, printing applications for CDs, DVDs, etc., and printing on non-permeable substrates such as printing on flexible substrates.

The graph which shows the relationship between the molecular weight between the crosslinking points of the cured film of the ink obtained in each example, and elongation at break

Claims (3)

A monofunctional monomer having an acrylic group or a vinyl group as a polymerizable monomer is 50% by weight or more with respect to the whole polymerizable monomer, and a polyfunctional monomer having an ethylenic double bond molecular weight of 250 or more is 2 with respect to the whole monomer. wherein .6 wt% or more 26.0% by weight and a polyfunctional monomer in 50% by weight or more, and an ink jet activity, wherein the content of the photopolymerization initiator is less than 20% by weight of the monofunctional monomer When the ink cured film formed on a polycarbonate substrate having a thickness of 500 μm is stretched at a strain rate of 2 / min in an environment of 190 ° C., the elongation at break satisfying [Equation 1] is obtained. An active energy ray-curable ink, characterized in that:
[Formula 1]
( ^Breaking elongation at 190 ° C., strain rate 2 / min)> 1.83 × (molecular weight between cross-linking points) ^0.437
The elongation at break indicates the ductility at the time when the surface of the coating film is broken when tensile stretching is performed. As a calculation method, [Calculation Formula 1] represented by the following formula is used.
[Calculation Formula 1]
Elongation at break (%) = (actually extended length + initial length) / initial length × 100
Moreover, the molecular weight between crosslinking points is described by the following [Calculation Formula 2].
[Calculation Formula 2]
Molecular weight between cross-linking points = average molecular weight × molar ratio of monofunctional monomer × 2 / polyfunctional monomer average functional group number average molecular weight = Σ (molecular weight of each monomer × each blending weight%)
Monofunctional monomer molar ratio = (Σ (weight of each compound / molecular weight of each monomer))
/ Σ (Each blended weight% / Molecular weight of each polyfunctional monomer)
Average number of functional groups of the polyfunctional monomer = Σ (number of functional groups of each polyfunctional monomer × (mixing weight% of each polyfunctional monomer / molecular weight of each polyfunctional monomer)
/ Σ (Mixed weight% of each polyfunctional monomer / Molecular weight of each polyfunctional monomer))
The molecular weight between crosslinking points shown here indicates the average molecular weight sandwiched between one double bond at one end of the polyfunctional monomer and the other double bond.
Furthermore, the molecular weight between ethylenic double bonds indicates the molecular weight between the double bond and the double bond in the molecule of the polyfunctional monomer. In the case of a monomer having a functional group number of 3 or more, it can be calculated by the following [Calculation Formula 3].
[Calculation Formula 3]
Molecular weight between ethylenic double bonds = molecular weight other than double bond × 2 / number of double bonds in molecule However, the molecular weight of the ethylene part is excluded. In addition, the calculation is performed without including the case where hydrogen in the ethylene portion is substituted with a methyl group or the like. 2. The active energy ray curable ink according to claim 1, wherein the monofunctional monomer contains phenoxyethyl acrylate and isobornyl acrylate. A printed matter obtained by printing on a printing substrate with the active energy ray-curable ink according to claim 1 or 2.

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