Ink composition for active energy ray-curable offset printing

Abstract

To provide an active energy ray-curable offset ink composition which exhibits good characteristics similar to an ink composition containing trimethylolpropane triacrylate (TMPTA) while containing no TMPTA.SOLUTION: An ink composition for active energy ray-curable offset printing containing a compound having an ethylenically unsaturated bond and a photopolymerization initiator contains at least one selected from the group consisting of a diallyl phthalate resin, polyfunctional polyester acrylate and a rosin-modified alkyd resin having an sp value of 9.0-11.0 (cal / cm3)1 / 2, and is prepared using an EO-modified TMPTA having 1 or more and 9 or less ethylene oxide (EO) units in the molecule as a monomer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an active energy ray-curable ink composition for offset printing. [Background technology]

[0002] Offset printing is a printing method that utilizes the water-repellent property of an oil-based ink composition for offset printing (hereinafter, abbreviated as "ink composition" or "ink"), and is characterized by using a printing plate without unevenness that has lipophilic image areas and hydrophilic non-image areas, unlike letterpress printing methods that use printing plates with unevenness. When printing is performed using this printing plate, first, dampening water is brought into contact with the printing plate to form a water film on the surface of the non-image areas, and then the ink composition is supplied to the printing plate. Then, the supplied ink composition repels and does not adhere to the non-image areas where the water film has been formed, but adheres only to the lipophilic image areas. In this way, an image is formed by the ink composition on the surface of the printing plate, and then the image is transferred successively to the blanket and paper, thereby performing printing.

[0003] In addition to the offset printing using dampening water as described above, a waterless offset printing method using a printing plate on which non-image areas are formed by silicone resin has also been put to practical use. In this printing method, the dampening water does not repel the ink composition to form non-image areas, but the silicone resin repels the ink composition to form non-image areas. Apart from this point, waterless offset printing is also a printing method common to offset printing using dampening water. Therefore, in this specification, the term "offset printing" is used as a concept that includes not only printing methods using dampening water but also waterless printing methods.

[0004] If the ink composition adhering to the surface of the printed matter obtained by offset printing is not sufficiently dried, the ink will be transferred to the back when the printed matter is stacked, or the ink will be attached to the printed matter when the printed matter is touched with a finger, and therefore the printed matter cannot be sent to a later process or distributed as a product. Therefore, after offset printing, a process of drying the ink composition adhering to the surface of the printed matter is required. In order to perform such a process in a short time, printing using an active energy ray curable ink composition has become popular in recent years. This type of ink composition contains a polymerizable compound such as a monomer or oligomer, and a polymerization initiator that polymerizes the polymerizable compound when irradiated with active energy rays such as ultraviolet rays or electron beams. Therefore, when the surface of a printed matter in an undried state printed using this ink composition is irradiated with active energy rays, the polymerizable compounds contained therein are polymerized with each other and become high molecular weight. As a result, the ink composition present on the surface of the printed matter is instantly changed into a non-sticky (i.e., dried) film. Various ink compositions employing such a drying method have been proposed (see, for example, Patent Documents 1 and 2). The active energy rays used in this step include ultraviolet rays and electron beams, but ultraviolet rays are often chosen in view of the cost and ease of handling of the equipment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-102217 A [Patent Document 2] Patent No. 4649952 Summary of the Invention [Problem to be solved by the invention]

[0006] In this type of ink composition, trimethylolpropane triacrylate (hereinafter, also referred to as TMPTA) is often used as one of the polymerizable compounds. TMPTA is a trifunctional acrylate monomer and has good properties. It is also used as a low-viscosity reactive solvent to dissolve the resin components constituting the ink composition to make a varnish, or to adjust the viscosity of the ink composition, and has been widely used in this type of ink composition. However, in recent years, TMPTA has been suspected to be harmful, and it has come to be included in the Negative List (NL) defined by the Japan Printing Ink Makers Association. This Negative List lists ingredients that should be avoided in ink compositions, and each ink manufacturer produces ink compositions under voluntary restrictions that do not use ingredients listed on this list. Products based on this voluntary restrictions are marked with the "NL mark," which serves as an indicator for users when selecting ink compositions. This voluntary restriction by the Japan Printing Ink Makers Association is called the NL restriction.

[0007] As described above, as a result of TMPTA being included in the negative list, it cannot be used under the voluntary restrictions imposed by the Japan Printing Ink Makers Association. The present invention has been made in view of such circumstances, and aims to provide an active energy ray-curable offset printing ink composition that does not contain TMPTA but exhibits properties as good as those of ink compositions containing TMPTA. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to solve the above problems, it has been discovered that an active energy ray-curable offset printing ink composition containing a compound having an ethylenically unsaturated bond and a photopolymerization initiator contains a diallyl phthalate resin, a multifunctional polyester acrylate, and an sp value of 9.0 to 11.0 (cal / cm 3 ) 1 / 2It has been found that by incorporating at least one selected from the group consisting of rosin-modified alkyd resins, which are ethylene oxide (EO)-modified TMPTA having 1 to 9 EO units in the molecule as a monomer, it is possible to obtain curing properties and printability that are comparable to those of ink compositions using normal non-EO-modified TMPTA as a monomer. The present invention is based on this finding and provides the following.

[0009] The present invention relates to an active energy ray-curable offset printing ink composition that contains a compound having an ethylenically unsaturated bond and a photopolymerization initiator, and is characterized in that the ink composition contains a diallyl phthalate resin, a multifunctional polyester acrylate, and a cellulose acetate having an sp value of 9.0 to 11.0 (cal / cm 3 ) 1 / 2 and, as at least a part of the compound having an ethylenically unsaturated bond, containing EO-modified trimethylolpropane triacrylate (TMPTA) containing from 1 to 9 EO units in the molecule, and is substantially free of TMPTA that is not EO-modified.

[0010] The polyfunctional polyester acrylate is preferably tetrafunctional to hexafunctional.

[0011] The number of EO units in the EO-modified TMPTA is preferably 3 or more and 9 or less.

[0012] The rosin-modified alkyd resin preferably has an acid value of 1 to 50 mgKOH / g. Effect of the Invention

[0013] According to the present invention, there is provided an active energy ray-curable ink composition for offset printing which, although it does not contain TMPTA, exhibits properties as good as those of ink compositions which contain TMPTA. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, one embodiment of the active energy ray-curable ink composition for offset printing of the present invention will be described. Note that the present invention is not limited to the following embodiment, and can be practiced by making appropriate modifications within the scope of the present invention.

[0015] The active energy ray-curable ink composition for offset printing of the present invention is an ink composition that is applied to offset lithographic printing, and has the ability to be cured by irradiation with active energy rays such as ultraviolet rays and electron beams. As described below, the ink composition of the present invention contains a compound (monomer, oligomer, etc.) having an ethylenically unsaturated bond and a photopolymerization initiator, and is cured by the radicals generated from the photopolymerization initiator when irradiated with active energy rays, which polymerize the compound having an ethylenically unsaturated bond. Therefore, when the ink composition that is sticky on the surface of a printed matter immediately after printing is irradiated with active energy rays, the ink composition instantly cures to form a film and becomes dry (tack-free).

[0016] The active energy rays used to cure the ink composition of the present invention may be any rays that cleave the chemical bonds in the photopolymerization initiator described below to generate radicals. Examples of such active energy rays include ultraviolet rays and electron beams. Among these, ultraviolet rays are preferred as active energy rays from the viewpoint of the cost and ease of handling of the device. When ultraviolet rays are used as active energy rays, the wavelength may be appropriately determined according to the absorption wavelength of the photopolymerization initiator used, and may be 400 nm or less. Examples of ultraviolet ray irradiation devices that generate such ultraviolet rays include metal halide lamps, high pressure mercury lamps, excimer lamps containing rare gases, and ultraviolet light emitting diodes (LEDs).

[0017] The ink composition of the present invention contains a compound having an ethylenically unsaturated bond and a photopolymerization initiator, and further contains a diallyl phthalate resin, a multifunctional polyester acrylate, and a fluororesin having an sp value of 9.0 to 11.0 (cal / cm 3 )1 / 2 The ink composition of the present invention is characterized in that it contains at least one selected from the group consisting of rosin-modified alkyd resins having 1 to 9 ethylene oxide (EO) units in the molecule as at least a part of the compound having an ethylenically unsaturated bond, and does not substantially contain TMPTA that is not EO-modified. The ink composition of the present invention may also contain a coloring component (in the present invention, a component that imparts a white or metallic color to the ink composition is also included in the coloring component). When the ink composition of the present invention contains a coloring component, the ink composition can be used for printing applications such as images and characters, and when the ink composition of the present invention does not contain a coloring component, the ink composition can be used for applications such as coating. The ink composition of the present invention is suitable for various printing applications brought about by offset printing, such as package printing, as well as for ordinary printed matter intended to transmit information or be an object of appreciation. Each component will be described below.

[0018] [Compounds with ethylenically unsaturated bonds] The compound having an ethylenically unsaturated bond is a component that is polymerized by radicals generated by a photopolymerization initiator described later to obtain a high molecular weight, and is a component called a monomer, oligomer, etc. In addition, various polymers having an ethylenically unsaturated bond and having a higher molecular weight than oligomers are commercially available. Such polymers can also be crosslinked by the above-mentioned monomers or oligomers, or by the polymers themselves to obtain a high molecular weight. Therefore, such polymers may be used as a compound having an ethylenically unsaturated bond together with the above-mentioned monomers or oligomers.

[0019] The monomer is a component that has an ethylenically unsaturated bond and is polymerized to a high molecular weight as described above, but is often a liquid component with a relatively low molecular weight before polymerization, and is used as a solvent when dissolving a resin component to make a varnish, or for the purpose of adjusting the viscosity of the ink composition. The ink composition of the present invention contains, as at least a part of such a monomer, i.e., a compound having an ethylenically unsaturated bond, an EO-modified TMPTA containing 1 to 9 ethylene oxide (EO) units in the molecule, and is substantially free of TMPTA that is not EO-modified.

[0020] As shown in the chemical formula below, TMPTA is a compound in which trimethylolpropane and three molecules of acrylic acid form an ester, and has three acryloyl groups with ethylenic unsaturated bonds. As shown in the chemical formula below, EO-modified TMPTA has an EO unit (-CH 2 CH 2 O-).

[0021] [ka]

[0022] In the present invention, an EO-modified TMPTA containing 1 to 9 ethylene oxide units in the molecule is used, so that x, y, and z in the above chemical formula are all integers of 0 or more, and x+y+z is 1 to 9. Trimethylolpropane has three hydroxyl groups, and as long as the condition that x+y+z is 1 to 9 is satisfied, the EO units may be bonded to these three hydroxyl groups in any manner, and may be bonded in a biased manner such that the EO units are concentrated and bonded to one or two hydroxyl groups, while the EO units are not bonded to the remaining hydroxyl groups, or may be bonded in a balanced manner to each hydroxyl group. If the number of EO units in the EO-modified TMPTA (i.e., x+y+z in the above chemical formula) exceeds 9, the abrasion resistance of the ink film after the ink composition is cured is reduced. It is preferable that the number of EO units in the EO-modified TMPTA (i.e., x+y+z in the above chemical formula) is 3 to 9. In the present invention, the number of EO units contained in a molecule is the average value of the number of EO units contained in each molecule. The content of the EO-modified TMPTA in the ink composition is preferably 20 to 70% by mass, more preferably 20 to 50% by mass, and even more preferably 30 to 50% by mass.

[0023] The ink composition of the present invention contains EO-modified TMPTA as described above, but is substantially free of non-EO-modified TMPTA. "Substantially free" means that TMPTA is not intentionally added as part of the components. For example, if EO-modified TMPTA contains non-EO-modified TMPTA as an impurity and this is used as a raw material, non-EO-modified TMPTA will be unintentionally contained in the ink composition. Even in this case, the ink composition is deemed to be substantially free of non-EO-modified TMPTA.

[0024] The ink composition of the present invention may contain a monomer in addition to the EO-modified TMPTA. Examples of such monomers include monofunctional monomers having one ethylenically unsaturated bond in the molecule and difunctional or higher monomers having two or more ethylenically unsaturated bonds in the molecule. Difunctional or higher monomers can crosslink molecules when the ink composition is cured, and therefore contribute to accelerating the curing speed and forming a strong film. Monofunctional monomers do not have the above-mentioned crosslinking ability, but contribute to reducing the curing shrinkage associated with crosslinking. Various types of these monomers can be used in combination as necessary.

[0025] Examples of monofunctional monomers include alkyl acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, and dodecyl (meth)acrylate, (meth)acrylic acid, (meth)acrylates of ethylene oxide adducts, (meth)acrylates of propylene oxide adducts, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, tricyclodecane monomethylol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxy-3-butoxypropyl (meth)acrylate. Examples of the monofunctional monomer include 2-hydroxy-3-methoxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, glycerin mono(meth)acrylate, acryloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, β-carboxyethyl (meth)acrylate, (meth)acrylic acid dimer, ω-carboxypolycaprolactone mono(meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, N-vinylpyrrolidone, N-vinylformamide, (meth)acryloylmorpholine, vinylmethyloxaziridinone, etc. These monofunctional monomers can be used alone or in combination of two or more. In this specification, "(meth)acrylate" means "acrylate and / or methacrylate", and "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0026] Examples of difunctional or higher functional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, pentyl glycol di(meth)acrylate, and neopentyl glycol. Di(meth)acrylate, hydroxypivalyl hydroxypivalate di(meth)acrylate, hydroxypivalyl hydroxypivalate dicaprolactonate di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,2-octanediol di(meth)acrylate , 1,9-nonanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,2-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,2-hexadecanediol di(meth)acrylate, 2-Methyl-2,4-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-2-propyl-1,3-propanediol di(meth)acrylate, 2,4-dimethyl-2,4-pentanediol di(meth)acrylate, 2,2-diethyl-1,3-propanediol di(meth)acrylate, 2,2,4-trimethyl-1,3-pentanediol di(meth)acrylate, dimethylol octane di(meth)acrylate, 2-ethyl-1,3-hexanediol di(meth)acrylate,2,5-dimethyl-2,5-hexanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate meth)acrylate, 1,2-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,2-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol Di(meth)acrylate, 1,2-hexadecanediol di(meth)acrylate, 2-methyl-2,4-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-2-propyl-1,3-propanediol di(meth)acrylate, 2,4-dimethyl-2,4-pentanediol di(meth)acrylate, 2,2-diethyl-1,3-propanediol di(meth)acrylate, 2,2,4-trimethyl-1,3-pentanediol di(meth)acrylate, dimethylol ester butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, tricyclodecane dimethylol di(meth)acrylate, tricyclodecane dimethylol dicaprolactonate di(meth)acrylate, bisphenol A tetraethylene oxide adduct di(meth)acrylate,Bifunctional monomers such as bisphenol F tetraethylene oxide adduct di(meth)acrylate, bisphenol S tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol A tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol F tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol A di(meth)acrylate, hydrogenated bisphenol F di(meth)acrylate, bisphenol A tetraethylene oxide adduct dicaprolactonate di(meth)acrylate, bisphenol F tetraethylene oxide adduct dicaprolactonate di(meth)acrylate; trifunctional monomers such as glycerin tri(meth)acrylate, trimethylolpropane tricaprolactonate tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; trimethylolpropane tri(meth)acrylate, ... Pan tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tetracaprolactonate tetra(meth)acrylate, diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactonate tetra(meth)acrylate, ditrimethylolethane tetra(meth)acrylate, ditrimethylolbutane tetra(meth)acrylate, ditrimethylolhexane tetra(meth)acrylate Examples of the monomers include tetrafunctional or higher monomers such as dipentaerythritol tetra(meth)acrylate, ditrimethylol octane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, and tripentaerythritol polyalkylene oxide hepta(meth)acrylate. Among these, ditrimethylol propane tetraacrylate (DITMPTA; tetrafunctional), dipentaerythritol hexaacrylate (DPHA; hexafunctional),Preferred examples of the monomer include glycerol propoxy triacrylate (GPTA; trifunctional), hexanediol diacrylate (HDDA; bifunctional), etc. These monomers having two or more functionalities may be used alone or in combination of two or more kinds.

[0027] Another type of monomer is epoxidized vegetable oil acrylate, which is obtained by modifying epoxidized vegetable oil with acrylic. This is a compound in which (meth)acrylic acid is added to the epoxy group of epoxidized vegetable oil, which is obtained by epoxidizing the double bonds of unsaturated vegetable oil with an oxidizing agent such as peracetic acid or perbenzoic acid, through ring-opening addition. The unsaturated vegetable oil is a triglyceride in which at least one fatty acid has at least one carbon-carbon unsaturated bond, and examples thereof include hemp seed oil, linseed oil, perilla oil, oiticica oil, olive oil, cacao oil, kapok oil, kaya oil, mustard oil, apricot kernel oil, tung oil, kukui oil, walnut oil, poppy seed oil, sesame oil, safflower oil, radish seed oil, soybean oil, tallow oil, camellia oil, corn oil, rapeseed oil, niger oil, rice bran oil, palm oil, castor oil, sunflower oil, grape seed oil, almond oil, tall oil, pine seed oil, cottonseed oil, coconut oil, peanut oil, dehydrated castor oil, etc. This type of monomer is derived from vegetable oil, and therefore is useful for increasing the amount of biomass components in the ink composition. Various types of epoxidized vegetable oil acrylates are commercially available, so they may be used.

[0028] As described above, the oligomer is a component that polymerizes to a high molecular weight, but since it is originally a relatively high molecular weight component, it is also used for the purpose of imparting suitable viscosity and elasticity to the ink composition. Examples of the oligomer include epoxy-modified (meth)acrylates, exemplified by esters of hydroxyl groups and (meth)acrylic acid generated after ring-opening of epoxy groups contained in epoxy compounds such as epoxy resins with an acid or base; rosin-modified epoxy acrylates; polyester (meth)acrylates, for example, prepared from polyhydric alcohols, polycarboxylic acids, and acrylic acid or methacrylic acid, having ester bonds in the main chain and acryloyl or methacryloyl groups at the ends; polyether-modified (meth)acrylates, exemplified by esters of terminal hydroxyl groups of polyether compounds and (meth)acrylic acid; and urethane-modified (meth)acrylates, exemplified by esters of terminal hydroxyl groups and (meth)acrylic acid in condensates of polyisocyanate compounds and polyol compounds. Such oligomers are commercially available and can be obtained under trade names such as Ebecryl series manufactured by Daicel-Cytec Co., Ltd., CN and SR series manufactured by Sartomer Co., Ltd., Aronix M-6000 series, 7000 series, 8000 series, Aronix M-1100, Aronix M-1200, and Aronix M-1600 manufactured by Toagosei Co., Ltd., NK Oligo manufactured by Shin-Nakamura Chemical Co., Ltd., and Miramer series manufactured by Miwon Specialty Chemical Co., Ltd. These oligomers can be used alone or in combination of two or more kinds.

[0029] The polymer having an ethylenically unsaturated bond is a component that increases in molecular weight together with the above-mentioned monomers and oligomers, and has a large molecular weight before being irradiated with active energy rays, so it is a component that is useful for improving the viscoelasticity of the ink composition. Such a polymer is used, for example, in a state dissolved or dispersed in a monomer that is a low-viscosity liquid. Examples of the polymer having an ethylenically unsaturated bond include polydiallyl phthalate, an acrylic resin having an unreacted unsaturated group, and an acrylic-modified phenolic resin. Among these, polydiallyl phthalate is preferably used because it has particularly excellent compatibility with the above-mentioned monomers and oligomers.

[0030] The content of the compound having an ethylenically unsaturated bond in the ink composition is preferably 20 to 70% by mass, more preferably 30 to 60% by mass. By having the content of the compound having an ethylenically unsaturated bond in the above range, both good curability and good printability can be achieved. Furthermore, among the compounds having an ethylenically unsaturated bond, the content of the polymer having an ethylenically unsaturated bond is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, and even more preferably 0 to 20% by mass. By having the content of the polymer in the above range, it is possible to impart appropriate viscoelasticity to the ink composition to suppress the occurrence of misting and the like, and it is also possible to ensure good curability of the ink composition, which is preferable.

[0031] The ink composition of the present invention comprises the diallyl phthalate resin, a polyfunctional polyester acrylate among the polyester acrylates, and a polyester having an sp value of 9.0 to 11.0 (cal / cm 3 ) 1 / 2 The resin composition further comprises at least one selected from the group consisting of rosin-modified alkyd resins,

[0032] The diallyl phthalate resin has already been described in the section on the polymer having an ethylenically unsaturated bond, and therefore a description thereof will be omitted here.

[0033] The polyfunctional polyester acrylate is one having a plurality of acryloyl groups among the polyester acrylates described in the section on oligomers having ethylenic unsaturated bonds. Among such polyfunctional polyester acrylates, from the viewpoint of selecting sufficient reactivity, those having 4 to 6 functional groups are preferred, and those having 6 functional groups are more preferred. The polyester acrylate refers to a polymer or oligomer having an ester bond in the main chain and an acryloyl group at the end of the main chain or branched chain, and may be prepared from any raw material as long as it is a compound having such a structure.

[0034] SP value is 9.0 to 11.0 (cal / cm 3 ) 1 / 2 As the rosin-modified alkyd resin, for example, one described in JP 2020-15888 A can be used. The sp value in the present invention is the solubility parameter determined by the turbidity point titration method described in JP 2020-15888 A. As described above, the ink composition of the present invention contains monomers and oligomers as components, and these components exhibit relatively high sp values. On the other hand, as described above, the rosin-modified alkyd resin used in the present invention has a solubility of 9.0 to 11.0 (cal / cm 3 ) 1 / 2 This rosin-modified alkyd resin has a high sp value for this type of material. Therefore, this rosin-modified alkyd resin exhibits good compatibility with monomers and oligomers, and therefore the ink composition of the present invention has good compatibility. The sp value of the rosin-modified alkyd resin is 9.3 to 10.0 (cal / cm 3 ) 1 / 2 More preferably, 9.5 to 10.0 (cal / cm 3 ) 1 / 2 Although the rosin-modified alkyd resin is not a compound having an ethylenically unsaturated bond, it will be described here for convenience of explanation.

[0035] The acid value of the rosin-modified alkyd resin is preferably 1 to 50 mgKOH / g. The acid value of 50 mgKOH or less is preferable because it can suppress the occurrence of problems such as abnormal emulsification in an offset printing ink composition to which the rosin-modified alkyd resin is applied. The acid value is preferably 1 to 25 mgKOH, and more preferably 1 to 10 mgKOH.

[0036] The weight average molecular weight of the rosin-modified alkyd resin is preferably 1000 to 70000. A weight average molecular weight of 1000 or more is preferable because it provides excellent pigment dispersibility and can impart good viscoelasticity to the ink composition, and a weight average molecular weight of 70000 or less is preferable because it provides good solubility and excellent handleability.

[0037] The content of the rosin-modified alkyd resin in the ink composition is preferably from 5 to 40% by mass, more preferably from 10 to 40% by mass, and even more preferably from 15 to 30% by mass.

[0038] [Photopolymerization initiator] The photopolymerization initiator is a component that generates radicals when irradiated with active energy rays, and the generated radicals polymerize the compound having the ethylenically unsaturated bond, thereby curing the ink composition. The photopolymerization initiator is not particularly limited as long as it generates radicals when irradiated with active energy rays.

[0039] Photopolymerization initiators include benzophenone, diethylthioxanthone, 2-methyl-1-(4-methylthio)phenyl-2-morpholinopropan-1-one, 4-benzoyl-4'-methyldiphenyl sulfide, 1-chloro-4-propoxythioxanthone, isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and bis-2,6-dimethoxybenzoyl-2,4,4-trimethylpentylphosphine. Examples of such photopolymerization initiators include 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2,2-dimethyl-2-hydroxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzyl-diphenylphosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2-benzyl-2-dimethylamino-1-(morpholinophenyl)-butan-1-one. Such photopolymerization initiators are commercially available, and can be obtained, for example, from BASF under the trade names Irgacure 907, Irgacure 369, Irgacure 184, Irgacure 379, Irgacure 819, and TPO, and from Lamberti under the trade name DETX. These photopolymerization initiators can be used alone or in combination of two or more.

[0040] The content of the photopolymerization initiator in the ink composition is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 13% by mass. By having the content of the photopolymerization initiator in the ink composition within the above range, it is preferable because sufficient curability of the ink composition can be achieved at the same time as good internal curability and cost.

[0041] [Coloring ingredients] A coloring component can be added to the ink composition of the present invention as necessary. The coloring component is a component added to impart coloring power, hiding power, etc. to the ink composition, and examples of the coloring component include color pigments, white pigments, metal powders, etc. Examples of such coloring components include organic and / or inorganic pigments that have been used in ink compositions in the past, without any particular limitation. When the ink composition of the present invention does not contain a coloring component, it is preferably used for coating applications, etc.

[0042] Examples of coloring components include yellow pigments such as disazo yellow (pigment yellow 12, pigment yellow 13, pigment yellow 14, pigment yellow 17, pigment yellow 1) and Hansa yellow, magenta pigments such as brilliant carmine 6B, lake red C, and watching red, cyan pigments such as phthalocyanine blue, phthalocyanine green, and alkali blue, black pigments such as carbon black, white pigments such as titanium oxide, and metal powders such as aluminum paste and bronze powder.

[0043] The content of the coloring component is, for example, about 1 to 30 mass % based on the total amount of the ink composition, but is not particularly limited. When preparing a colored ink composition, it is possible to use a coloring component of another color as a complementary color, or to add an ink composition of another color.

[0044] [Other ingredients] In addition to the above-mentioned components, other components may be added to the ink composition of the present invention as necessary, such as extender pigments, resin components, polymerization inhibitors, dispersants, salts such as phosphates, waxes such as polyethylene wax, olefin wax, and Fischer-Tropsch wax, and alcohols.

[0045] The extender pigment is a component for imparting suitable printability, viscoelasticity, and other properties to the ink composition, and various types of extender pigments that are commonly used in the preparation of ink compositions can be used. Examples of such extender pigments include clay, kaolinite (kaolin), barium sulfate, magnesium sulfate, calcium carbonate, silicon oxide (silica), bentonite, talc, mica, and titanium oxide. The amount of such extender pigments to be added is, for example, about 0 to 33% by mass based on the total ink composition, but is not particularly limited.

[0046] The resin component is a component that contributes to imparting suitable printability, viscoelasticity, and other properties to the ink composition. Examples of such a resin component include various resins that have been conventionally used in printing ink compositions, and are preferably those that are compatible with the above-mentioned monomers and oligomers, such as styrene-acrylic resins, acrylic resins, alkyd resins, rosin-modified phenolic resins, rosin-modified maleic acid resins, rosin-modified petroleum resins, rosin ester resins, petroleum resin-modified phenolic resins, vegetable oil-modified alkyd resins, and petroleum resins.

[0047] When a resin component is added to the ink composition, the content thereof in the ink composition is preferably 1 to 30% by mass, more preferably 1 to 20% by mass, and even more preferably 1 to 10% by mass. By having the content of the resin component in the above range, it is possible to impart appropriate viscoelasticity to the ink composition, suppress the occurrence of misting, etc., and also to ensure good curability of the ink composition, which is preferable.

[0048] Preferred examples of the polymerization inhibitor include phenolic compounds such as butylhydroxytoluene, tocopherol acetate, nitrosamines, benzotriazole, and hindered amines, among which butylhydroxytoluene is more preferred. By adding such a polymerization inhibitor to the ink composition, it is possible to suppress the ink composition from thickening due to the progress of a polymerization reaction during storage. The content of the polymerization inhibitor in the ink composition is, for example, about 0.01 to 1 mass%.

[0049] Dispersants are used to disperse the coloring components and extender pigments contained in the ink composition in a good state. Various types of dispersants are commercially available, such as the DISPERBYK (trade name) series manufactured by BYK Japan Co., Ltd.

[0050] To produce the ink composition of the present invention using the above components, a conventionally known method can be applied. An example of such a method is to mix the above components, grind them in a bead mill or a triple roll mill, etc. to disperse the pigment (i.e., the coloring component and the extender pigment), add additives (polymerization inhibitors, alcohols, waxes, etc.) as necessary, and further add the above monomer components and oil components to adjust the viscosity. The viscosity of the ink composition is, for example, 10 to 70 Pa·s at 25°C measured with a Raleigh viscometer, but is not particularly limited. EXAMPLES

[0051] The present invention will be described in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0052] Ink compositions of Examples 1 to 7, Reference Example 1, and Comparative Examples 1 to 4 were prepared according to the formulations shown in Tables 1 and 2. The formulation amounts in Tables 1 and 2 are in parts by mass. In preparing the ink compositions, the materials shown in the "Resin" and "Monomer 1" columns of Tables 1 and 2 were mixed in predetermined parts by mass, and heated at 100°C for 60 minutes to form a varnish, and then the remaining materials were mixed in predetermined parts by mass with the varnish, and kneaded in a three-roll mill to form an ink composition.

[0053] The explanation of each material listed in Tables 1 and 2 is as follows. "Carmine 6B": Brilliant Carmine 6B (Pigment red 57:1) "Rosin modified alkyd resin A": Rosin modified alkyd resin with sp value of 9.7 "Rosin modified alkyd resin B": Rosin modified alkyd resin with sp value of 8.8 "Diallyl phthalate resin": A-DAP, manufactured by Osaka Soda Co., Ltd. "Polyester acrylate": EBECRYL870 (hexafunctional polyester acrylate) manufactured by Daicel-Allnex Corporation "Petroleum resin": ENEOS Corporation, Nippon Oil Neopolymer 120 "3EO-TMPTA": TMPTA with 3 EO units in one molecule "6EO-TMPTA": TMPTA with 6 EO units in one molecule "9EO-TMPTA": TMPTA with 9 EO units in one molecule "12EO-TMPTA": TMPTA with 12 EO units in one molecule "3PO-TMPTA": Three propylene oxide units (PO; chemical formula -CH) in one molecule. 2 -CH(CH 3 TMPTA having a -O- unit "DPHA": Dipentaerythritol hexaacrylate (hexafunctional monomer) "Photopolymerization initiator 1": 2,4,6-trimethylbenzyl-diphenylphosphine oxide "Photopolymerization initiator 2": 4,4'-bis(diethylamino)benzophenone

[0054] As described above, each ink composition was prepared, but in Comparative Example 2, compatibility was insufficient and a varnish could not be prepared, so an ink composition could not be obtained. Therefore, the following evaluations were not performed for Comparative Example 2.

[0055] [Friction resistance evaluation] Using an RI-2 type color developer with two divided rolls (manufactured by Akebono Seisakusho), the ink compositions of the Examples, Reference Examples and Comparative Examples were each measured at a rate of 0.1 mL / 204 cm 2The ink composition was applied to art paper (Mitsubishi Toku Art 110K) to prepare a test piece, and then the test piece was irradiated with ultraviolet light using a 160 W / cm metal halide lamp (focal length 13 cm, converging type, 1 lamp; manufactured by Heraeus) to harden the ink composition and make it tack-free. After leaving each test piece at room temperature for 24 hours, the abrasion resistance of each test piece was evaluated using a Gakushin-type abrasion fastness tester. The abrasion resistance evaluation conditions were 10 round trips of friction with a 1 kg weight, and art paper was used as the backing paper. The evaluation criteria were as follows, and the results are shown in the "Abrasion Resistance" column in Tables 1 and 2. ◎: The coated surface did not come off even after 10 round trips of friction 〇: The coating surface was removed after 5 to 9 round trips of friction. △: The coating surface was removed after 2 to 4 round trips of friction. ×: The coating surface was removed after one round trip of friction.

[0056] [Misting rating] 2.62 cc of the ink composition of each Example, Reference Example and Comparative Example was applied to a Toyo Seiki Incometer, and art paper (Mitsubishi Toku Art 110K) was placed under the machine and rotated at 1200 rpm for 3 minutes. After that, misting was visually evaluated based on the amount of ink composition scattered on the placed paper. The evaluation criteria were as follows, and the results are shown in the "Misting" column of Tables 1 and 2. ◎: Scattering of ink composition is observed, but is small. ◯: Some scattering of the ink composition was observed, but it was not enough to affect the quality. ×: A considerable amount of ink composition was scattered, causing quality problems.

[0057] [Metastatic evaluation] Using an RI-2 type color developer with two divided rolls (manufactured by Akebono Seisakusho), the ink compositions of the Examples, Reference Examples and Comparative Examples were each measured at a rate of 0.1 mL / 204 cm 2 The ink composition was applied to art paper (Mitsubishi Toku Art 110K). The mass of the art paper was measured before and after application, and the amount of the ink composition transferred to the art paper was calculated to examine the transferability. The evaluation criteria were as follows, with Reference Example 1 as the standard, and the results are shown in the "Transferability" column in Tables 1 and 2. ◎: The amount of ink composition transferred was 120% or more compared to Reference Example 1. ○: The amount of ink composition transferred was 110% or more and less than 120% compared to Reference Example 1. △: The amount of ink composition transferred was 90% or more and less than 110% of that in Reference Example 1. ×: The amount of ink composition transferred was less than 90% of that in Reference Example 1.

[0058] [Dot Gain Evaluation] The ink compositions of each of the Examples, Reference Examples, and Comparative Examples were printed on art paper (Mitsubishi Toku Art 110K) at a printing speed of 1200 copies / hour using a printing machine (Komori Corporation, Komori LITHRONE LS-426) and a lithographic CTP plate XPF (Fujifilm Corporation). The dampening water used was KG-502 (1.5% by volume in dampening water) manufactured by Komori Corporation. The dot gain of the printed matter obtained by this printing at a position where the halftone dot area was 50% was measured and evaluated using a densitometer (PDC-LITE2) installed in the printing machine under the condition of Status T (without a polarizing filter). The evaluation criteria were as follows, and the results are shown in the "dot gain" column in Tables 1 and 2. ○: Dot gain was within the range of 14±3% ×: Dot gain was outside the range of 14±3%.

[0059] [Evaluation of initial print density and steady-state density] During printing for the above dot gain evaluation, the density of the 10th and 200th prints from the start of printing was measured using a densitometer (PDC-LITE2) attached to the printing press, with the former being the initial density and the latter being the steady density. The conditions for density measurement were Status T (no polarizing filter) and white backing. The results are shown in the "Initial Density" and "Steady Density" columns in Tables 1 and 2, respectively.

[0060] [Table 1]

[0061] [Table 2]

[0062] It can be seen that the ink composition of the present invention provides well-balanced results for each evaluation item. The ink composition of Comparative Example 1 using 12EO-TMPTA also provided a relatively good result in terms of printability, but had poor abrasion resistance and was not suitable for practical use. The ink composition of Example 5 was rated △ for transferability, which means that the result was almost the same as that of Reference Example 1 using TMPTA. From the above results, it can be seen that the ink composition of the present invention provides an ink composition that does not contain TMPTA but has properties equal to or better than those containing TMPTA.

Claims

1. An active energy ray-curable offset printing ink composition comprising a compound having an ethylenically unsaturated bond and a photopolymerization initiator, Diallyl phthalate resin, multifunctional polyester acrylate, and a polyimide having an sp value of 9.0 to 11.0 (cal / cm ３ ) １／２ The resin is at least one selected from the group consisting of rosin-modified alkyd resins, The active energy ray-curable offset printing ink composition is characterized in that it contains, as at least a part of the compound having an ethylenically unsaturated bond, EO-modified trimethylolpropane triacrylate (TMPTA) containing 1 to 9 EO units in the molecule, and is substantially free of non-EO-modified TMPTA.

2. 2. The active energy ray-curable ink composition for offset printing according to claim 1, wherein the polyfunctional polyester acrylate has 4 to 6 functional groups.

3. 3. The active energy ray-curable ink composition for offset printing according to claim 1, wherein the number of EO units in the EO-modified TMPTA is 3 or more and 9 or less.

4. 4. The active energy ray-curable offset printing ink composition according to claim 1, wherein the rosin-modified alkyd resin has an acid value of 1 to 50 mgKOH / g.

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