JP2012062415A - Printing ink for plastic label and plastic label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide printing ink for plastic labels that contains titanium oxide in high concentration, has high white density, is excellent in printability and storage stability, and also is excellent in adhesion to a substrate (especially a polyester-based film).SOLUTION: The printing ink for plastic labels is printing ink containing a urethane acrylic resin (A) having a structural unit derived from polyester polyol, an acrylic resin (B), and titanium oxide (C), wherein a content of a structural unit derived from a monomer having a (meth)acryloyl group in the urethane acrylic resin (A) is 1-40 wt.%, an acid value of the acrylic resin (B) is 1-40 mgKOH/g, a weight ratio in a nonvolatile component of the printing ink, [(a content of the acrylic resin (B)):(a content of the urethane acrylic resin (A))], is 50:50 to 99:1, and a content of the titanium oxide (C) in the nonvolatile component of the printing ink is 70-81 wt.%.

Description

  The present invention relates to a printing ink for plastic labels. More specifically, the present invention relates to a printing ink for plastic labels, which contains titanium oxide at a high concentration and has excellent printability, storage stability, and adhesion (adhesiveness) to a substrate. The present invention also relates to a plastic label having a printing layer formed from the printing ink.

  Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as containers for beverages such as tea and soft drinks. These containers are often equipped with plastic labels to give display, decoration, and functionality. For example, because of the merits of decoration, workability (followability to containers), wide display area, etc., shrink Labels are widely used. As such a plastic label, a label in which a printing layer formed from a printing ink is provided on a plastic film substrate is widely used.

  As the plastic film as the base material, a polyester film made of a polyester resin (polyethylene terephthalate (PET), etc.), a polyolefin film made of a polyolefin resin, or a polystyrene made of a polystyrene resin, depending on required characteristics and applications. System films are used. Therefore, as the printing ink, a highly versatile printing ink (also referred to as dual-purpose ink) that can be printed on any of these plastic films is desirable.

  However, among the above-mentioned base materials, particularly polyester-based films are inferior in printing ink adhesion, and in particular in the case of printing inks containing titanium oxide, which is a white pigment, there is a problem that the adhesion to the base material is lowered. It was. Along with this, in the manufacturing process of plastic labels and the mounting process to containers, there is a problem that the printing layer on the label surface is scraped and white powder adheres to rolls, so-called “powder blowing” is likely to occur. It was.

  In order to solve the above problems, as a printing ink having improved adhesion to a substrate, for example, a printing ink using a specific acrylic resin and a specific polyurethane / urea resin is known (see Patent Document 1). ). Moreover, the printing ink using an acrylic resin and nitrocellulose is known (refer patent document 2). However, when the printing ink contains titanium oxide at a high concentration, there is a problem that printability deteriorates. Furthermore, a printing ink using an acrylic resin and an esterified cellulose resin is known (see Patent Document 3). However, the printing ink also has a problem in that the adhesion to the substrate is lowered when the concentration of titanium oxide is very high.

  As described above, the printing ink containing a high concentration of titanium oxide and having a high white density has excellent printability and excellent adhesion to a substrate (particularly adhesion to a polyester film). However, at present, excellent printing ink with high versatility has not been obtained.

  Furthermore, the printing ink containing titanium oxide at a high concentration has a problem that titanium oxide as a pigment is easily aggregated and inferior in storage stability (aggregation inhibiting property of pigment).

JP 2006-219670 A JP 2004-175858 A JP 2008-163215 A

  That is, the object of the present invention is to contain a high concentration of titanium oxide, a high white concentration, excellent printability and storage stability (inhibition of pigment aggregation), and adhesion to a plastic film substrate (especially polyester). It is to provide a printing ink for a plastic label that is excellent in adhesion to a base film.

  As a result of intensive studies to achieve the above object, the inventors of the present invention contain a high concentration of titanium oxide by blending a specific structure urethane acrylic resin and a specific acid value acrylic resin at a specific ratio. Even in this case, the present inventors have found that a printing ink having excellent printability and storage stability and excellent adhesion to a plastic film substrate, particularly a polyester film substrate, can be obtained. did.

  That is, the present invention is a printing ink containing a urethane acrylic resin (A) having a structural unit derived from a polyester polyol, an acrylic resin (B), and titanium oxide (C), and the urethane acrylic resin (A ), The content of the structural unit derived from the monomer having a (meth) acryloyl group is 1 to 40% by weight, the acid value of the acrylic resin (B) is 1 to 40 mgKOH / g, Ratio of content of acrylic resin (B) and content of urethane acrylic resin (A) in nonvolatile content [(content of acrylic resin (B)): (content of urethane acrylic resin (A) Quantity)] (weight ratio) is 50:50 to 99: 1, and the content of titanium oxide (C) in the non-volatile content of the printing ink is 70 to 81% by weight. To provide Le for printing ink.

  Moreover, this invention provides the plastic label which has the printing layer formed from the said printing ink for plastic labels on the at least single side | surface of a plastic film.

  Since the printing ink for plastic labels of the present invention contains titanium oxide, which is a white pigment, at a high concentration, the white concentration is high. In addition, because it contains urethane acrylic resin with a specific structure and acrylic resin with a specific acid value in a specific blending ratio, it has printability and storage stability even though it contains a high concentration of titanium oxide. Excellent adhesion (inhibition of aggregation of titanium oxide) and adhesion to plastic films (especially polyester films). For this reason, it is useful as a highly versatile white printing ink that can be used for various types of plastic film substrates.

[Printing ink for plastic labels]
The printing ink for plastic labels of the present invention (sometimes referred to as “printing ink of the present invention”) is a urethane acrylic resin (A) or acrylic resin (B) having a structural unit (constituent unit) derived from polyester polyol. ) And titanium oxide (C) as essential components. The printing ink of the present invention preferably contains a solvent, and may further contain other additives. In this specification, “urethane acrylic resin (A) having a structural unit derived from polyester polyol” may be referred to as “urethane acrylic resin (A)” or “component (A)”. (B) ”may be referred to as“ component (B) ”, and“ titanium oxide (C) ”may be referred to as“ component (C) ”.

(Urethane acrylic resin (A))
Although the said urethane acrylic resin (A) is not specifically limited, It is a polymer (copolymer) comprised by making a urethane component and an acrylic component into essential structural components. In other words, the urethane acrylic resin (A) is a polymer containing a urethane component part having a urethane bond and an acrylic component part containing a structural unit derived from a monomer having a (meth) acryloyl group in the molecule. The urethane acrylic resin (A) is a resin component that plays a role of improving the adhesion of the printing ink of the present invention to the plastic film (base material). The “(meth) acryloyl group” represents “acryloyl group [CH ₂ ═CHCO—]” and / or “methacryloyl group [CH ₂ ═C (CH ₃ ) CO—]”. A monomer having a (meth) acryloyl group has a structure of [CH ₂ ═CHCO—] and / or [CH ₂ ═C (CH ₃ ) CO—] in the molecule. “(Meth) acryl” means “acryl” and / or “methacryl” (any one or both of acryl and methacryl).

  The acrylic component in the urethane acrylic resin (A) includes a monomer (monomer) having a (meth) acryloyl group as an essential monomer component. That is, the acrylic component and the urethane acrylic resin (A) have at least a structural unit derived from a monomer having a (meth) acryloyl group. The monomer component constituting the acrylic component may contain a monomer component other than the monomer having a (meth) acryloyl group, but the monomer component constituting the acrylic component consists only of a monomer having a (meth) acryloyl group. It is preferable.

Examples of the monomer having the (meth) acryloyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, ( Isobutyl acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl ester having a linear or branched alkyl group such as isononyl acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate [preferably C _1-12 alkyl (meth) acrylate Esters etc.]; (Meth) acrylic acid; carboxyl groups such as carboxyethyl acrylate (Meth) acrylic acid ester; 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meta) ) Hydroxyl group-containing (meth) acrylic acid ester such as acrylate, diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate [preferably (meth) acrylic acid hydroxy C _1-8 alkyl ester etc.]; (Meth) acrylic acid cycloalkyl esters such as cyclohexyl acrylate; N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-di (Meth) acrylic acid amide derivatives such as til (meth) acrylamide; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dipropylamino And (meth) acrylic acid dialkylaminoalkyl esters such as propyl (meth) acrylate. Among these, as a monomer having a (meth) acryloyl group, from the viewpoint of compatibility with the acrylic resin (B), a (meth) acrylic acid alkyl ester having a linear or branched alkyl group [among others, (Meth) acrylic acid C _1-12 alkyl ester] and (meth) acrylic acid are preferable, and methyl methacrylate (MMA) and butyl methacrylate (BMA) are more preferable.

  The monomer component constituting the acrylic component other than the monomer having the (meth) acryloyl group is not particularly limited. For example, a carboxyl group-containing polymerizable unsaturated compound such as crotonic acid, itaconic acid, fumaric acid, maleic acid or the like Its anhydrides; Styrene compounds such as styrene, vinyltoluene and α-methylstyrene; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl halides such as vinyl chloride; Vinyl ethers such as methyl vinyl ether; (Meth) acrylonitrile And cyano group-containing vinyl compounds such as ethylene and propylene.

  Content of monomer having (meth) acryloyl group in the total amount of monomer component constituting the acrylic component, that is, (meth) in acrylic component (total acrylic component) (100% by weight) in urethane acrylic resin (A) The content of the structural unit derived from the monomer having an acryloyl group is not particularly limited, but is preferably 80% by weight or more (80 to 100% by weight), more preferably from the viewpoint of compatibility with the acrylic resin (B). Is 90% by weight or more (90 to 100% by weight).

  Although the urethane component in the said urethane acrylic resin (A) is not specifically limited, For example, a polyisocyanate compound and a polyol compound are comprised as a raw material component. That is, the urethane component has a structural unit derived from a polyisocyanate compound and a structural unit derived from a polyol compound. Especially, the said urethane component is comprised as an essential raw material component as a polyol compound from a viewpoint of an adhesive improvement with a polyester-type film (base material). That is, the urethane component and the urethane acrylic resin (A) have at least a structural unit derived from a polyester polyol.

  Examples of the polyisocyanate compound include known diisocyanates such as aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate. Examples of the diisocyanates include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, and isophorone diisocyanate. The above diisocyanates can be used alone or in combination of two or more. If necessary, trifunctional or higher functional polyisocyanates and polyisocyanate adducts can be used in combination with the diisocyanates. Of these, isophorone diisocyanate (IPDI) and tolylene diisocyanate (TDI) are preferable from the viewpoint of improving the adhesion to the polyester film (base material).

  The polyester polyol is a polyester compound having two or more hydroxyl groups in the molecule (in one molecule), and among them, a polyester diol having two hydroxyl groups in the molecule is preferable. The polyester polyol is not particularly limited, but is preferably a polymer composed of a dicarboxylic acid component and a diol component as essential components. That is, the polyester polyol preferably has at least a structural unit derived from dicarboxylic acid and a structural unit derived from diol.

  Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, 2,5-dimethylterephthalic acid, 5-t-butylisophthalic acid, 4,4′-biphenyldicarboxylic acid, trans-3,3′-stilbene dicarboxylic acid, Trans-4,4′-stilbene dicarboxylic acid, 4,4′-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalene Dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid 1,2-diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether dicarboxylic acid, 2,5-ant Aromatic dicarboxylic acids such as sendicarboxylic acid, 2,5-pyridinedicarboxylic acid, and substituted products thereof; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid , Undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, docosanedioic acid, 1,12-dodecanedioic acid, and Aliphatic dicarboxylic acids such as these substitutes; 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid , Trans-1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedi Carboxylic acid, and include alicyclic dicarboxylic acids such as substituted versions thereof. Of these, aromatic dicarboxylic acids are preferable, and terephthalic acid (TPA) and isophthalic acid (IPA) are more preferable. The said dicarboxylic acid can be used individually or in combination of 2 or more.

  Examples of the diol include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2 -Dimethyl-1,3-propanediol (neopentyl glycol), 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2,4-dimethyl-1,3-hexanediol, 1,10-decanediol, polyethylene glycol, polypropylene Aliphatic diols such as glycol; 1,2-cyclohexanedimethanol, 1,3-cyclohexane Cycloaliphatic diols such as sandimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 2,2-bis (4-β-hydroxyethoxyphenyl) propane And ethylene oxide adducts of bisphenol compounds such as bis (4-β-hydroxyethoxyphenyl) sulfone, and aromatic diols such as xylene glycol. Of these, aliphatic diols are preferable, and neopentyl glycol (NPG) and ethylene glycol (EG) are more preferable. The above diols can be used alone or in combination of two or more.

  In addition to the above, the polyester polyol includes oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; polyvalent carboxylic acids such as trimellitic acid; It may contain structural units derived from monohydric alcohols such as polyalkylene glycol monomethyl ether; polyhydric alcohols such as glycerin, pentaerythritol and trimethylolpropane.

  The polyester polyol (preferably polyester diol) contains an aromatic dicarboxylic acid (particularly, terephthalic acid or isophthalic acid) as a dicarboxylic acid component, particularly from the viewpoint of improving adhesion to an aromatic polyester film (PET film or the like). It is preferable. Furthermore, the diol component preferably includes neopentyl glycol (NPG) or ethylene glycol (EG), which is a diol having a relatively short chain length between carbon atoms to which a hydroxyl group is bonded. By using NPG or EG, it is presumed that the density of the aromatic ring can be made relatively high, especially when copolymerized with an aromatic dicarboxylic acid, but the adhesion with the aromatic polyester film is further improved. . Therefore, the polyester polyol includes a structural unit derived from an aromatic dicarboxylic acid (particularly, terephthalic acid and / or isophthalic acid), and a structural unit derived from neopentyl glycol (NPG) and / or ethylene glycol (EG). The polyester polyol (particularly polyester diol) is particularly preferable.

  The polyol compound in the urethane component may contain a polyol compound other than the polyester polyol. Although it does not specifically limit as polyol compounds other than said polyester polyol, For example, ethylene glycol, diethylene glycol, 1,3-propanediol, propylene glycol (1,2-propanediol), butanediol (1,3-butanediol) , 1,4-butanediol, etc.), 1,6-hexanediol, low molecular weight glycols such as cyclohexanedimethanol; known diols such as polyether diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, A trifunctional or higher functional polyol compound (such as a polyether polyol) may be used.

  The content of the polyester polyol in the polyol compound in the urethane component, that is, the structural unit derived from the polyester polyol in the structural unit (100% by weight) derived from the polyol (total polyol) in the urethane acrylic resin (A). Although content is not specifically limited, From a viewpoint of adhesive improvement (especially adhesive improvement with a polyester-type film), 80 weight% or more (80-100 weight%) is preferable, More preferably, it is 90 weight% or more (90 ~ 100 wt%).

  The ratio of the content of the acrylic component to the content of the urethane component in the urethane acrylic resin (A) [(content of acrylic component) / (content of urethane component)] (weight ratio) is not particularly limited, 0.01-0.67 is preferable, More preferably, it is 0.05-0.45. When [(acrylic component content) / (urethane component content)] is less than 0.01 and the acrylic component is small, the affinity (compatibility) with the acrylic resin (B) is reduced, and printing is performed. Insufficient dispersion in ink may cause problems such as poor printability, pigment aggregation, and poor adhesion to plastic film (base material). In some cases, the adhesion to the substrate may be reduced.

  Content of the structural unit derived from the monomer having the (meth) acryloyl group in the urethane acrylic resin (A) (100% by weight) is 1 to 40% by weight, preferably 5 to 30% by weight. More preferably, it is 10 to 25% by weight. If the content is less than 1% by weight, the acrylic component in the urethane acrylic resin (A) is small, the affinity (compatibility) with the acrylic resin (B) is reduced, and poor dispersion occurs in the printing ink. Problems such as a decrease in printability, agglomeration of pigment, and a decrease in adhesion to a plastic film (base material) occur. On the other hand, when the content exceeds 40% by weight, the urethane component in the urethane acrylic resin (A) is small, and the adhesiveness with a plastic film (particularly a polyester film) as a substrate is lowered.

  The analysis and measurement of the structural unit constituting the urethane acrylic resin (A) and the content of the structural unit are not particularly limited. For example, by nuclear magnetic resonance (NMR), gas chromatograph mass spectrometer (GCMS), etc. It can be carried out.

  As for the weight average molecular weight (Mw) of the said urethane acrylic resin (A), 10000-50000 are preferable, More preferably, it is 15000-45000. If the weight average molecular weight (Mw) is less than 10,000, the adhesion may be reduced, and if it exceeds 50,000, the printability may be deteriorated. In the present specification, Mw can be measured, for example, by gel permeation chromatography (GPC).

  The glass transition temperature (Tg) of the urethane acrylic resin (A) is −30 to 100 ° C. from the viewpoint of improving scratch resistance, heat resistance and ink cracking resistance of the printing layer formed from the printing ink of the present invention. Is preferable, and more preferably 0 to 70 ° C. In the present specification, Tg can be measured by, for example, DSC (differential scanning calorimetry). The DSC measurement is not particularly limited. For example, the DSC measurement can be performed using a differential scanning calorimeter “DSC6200” manufactured by Seiko Instruments Inc. under a temperature rising rate of 10 ° C./min.

  The acid value of the urethane acrylic resin (A) is preferably from 0 to 5 mgKOH / g, more preferably from 0.3 to 3 mgKOH / g, from the viewpoint of storage stability (aggregation inhibiting property of pigment).

  The urethane acrylic resin (A) is available from, for example, Nippon Kaiko Paint Co., Ltd.

(Acrylic resin (B))
The acrylic resin (B) is not particularly limited, and may be selected and used from known or commonly used acrylic resins for printing ink so that the acid value described later is 1 to 40 mgKOH / g. it can. Examples of the acrylic resin (B) include a polymer (polymer) having at least a structural unit derived from a monomer having a (meth) acryloyl group. The monomer component constituting the acrylic resin (B) may contain a monomer component other than the monomer having a (meth) acryloyl group, but the monomer component constituting the acrylic resin (B) is (meth). It preferably consists of only a monomer having an acryloyl group. The acrylic resin (B) does not include a urethane acrylic resin.

Examples of the monomer having the (meth) acryloyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, ( Isobutyl acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl ester having a linear or branched alkyl group such as isononyl acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate [preferably C _1-12 alkyl (meth) acrylate Esters etc.]; (Meth) acrylic acid; carboxyl groups such as carboxyethyl acrylate (Meth) acrylic acid ester; 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meta) ) Hydroxyl group-containing (meth) acrylic acid ester such as acrylate, diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate [preferably (meth) acrylic acid hydroxy C _1-8 alkyl ester etc.]; (Meth) acrylic acid cycloalkyl esters such as cyclohexyl acrylate; N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-di (Meth) acrylic acid amide derivatives such as til (meth) acrylamide; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dipropylamino And (meth) acrylic acid dialkylaminoalkyl esters such as propyl (meth) acrylate.

  Although it does not specifically limit as a monomer component which comprises acrylic resin (B) other than the monomer which has the said (meth) acryloyl group, For example, carboxyl group containing polymeric properties, such as crotonic acid, itaconic acid, fumaric acid, and maleic acid Unsaturated compounds or anhydrides thereof; styrenic compounds such as styrene, vinyltoluene, and α-methylstyrene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl halides such as vinyl chloride; vinyl ethers such as methyl vinyl ether; Examples include cyano group-containing vinyl compounds such as (meth) acrylonitrile; ethylene, propylene and the like.

  Content of monomer having (meth) acryloyl group in total amount of monomer component constituting acrylic resin (B), that is, monomer having (meth) acryloyl group in acrylic resin (B) (100% by weight) The content of the structural unit derived from is not particularly limited, but is preferably 80% by weight or more (80 to 100% by weight), more preferably 90% by weight, from the viewpoint of adhesion to a plastic film (particularly polyester film). That is the above (90 to 100% by weight).

  Analysis / measurement of the structural unit constituting the acrylic resin (B) and the content of the structural unit is not particularly limited, and is performed by, for example, nuclear magnetic resonance (NMR), gas chromatograph mass spectrometer (GCMS), or the like. be able to.

  The acid value of the acrylic resin (B) is 1 to 40 mgKOH / g from the viewpoint of enhancing affinity with titanium oxide, suppressing aggregation of titanium oxide in the printing ink, and improving storage stability. Preferably it is 2-20 mgKOH / g. When the acid value is less than 1 mg KOH / g or more than 40 mg KOH / g, the titanium oxide in the printing ink tends to aggregate and the storage stability of the printing ink is lowered. In addition, in this specification, an acid value is calculated | required based on JISK5601-2-1 (titration method). Moreover, when two or more types of acrylic resins (B) are contained in the printing ink of the present invention, the “acid value of the acrylic resin (B)” is the value of all acrylic resins ( B) Acid value of (mixture).

  The weight average molecular weight (Mw) of the acrylic resin (B) is preferably 30,000 to 70,000, and more preferably 30,000 to 50,000. If the weight average molecular weight (Mw) is less than 30,000, the adhesion may be lowered, and if it exceeds 70,000, the printability may be deteriorated.

  The glass transition temperature (Tg) of the acrylic resin (B) is preferably 40 to 75 ° C. from the viewpoint of improving scratch resistance, heat resistance and ink cracking resistance of a printing layer formed from the printing ink of the present invention. More preferably, it is 45-55 degreeC.

  A commercial item can also be used for the said acrylic resin (B). For example, “Dainal BR-113 (acid value 3.5 mgKOH / g)”, “Dianal BR-116 (acid value 7.0 mgKOH / g)” manufactured by Mitsubishi Rayon Co., Ltd. and the like are available on the market.

(Titanium oxide (C))
As said titanium oxide (C), the well-known thru | or usual titanium oxide (titanium dioxide) used for printing ink can be used. Examples of the titanium oxide (C) include rutile type (tetragonal high temperature type), anatase type (tetragonal low temperature type), and brookite type (orthorhombic type) titanium oxide.

  The average particle diameter of the titanium oxide (C) (in the case where an aggregate is formed, the particle diameter of the aggregate, so-called secondary particle diameter) is not particularly limited, but is preferably 0.1 to 1 μm, for example. More preferably, it is 0.1-0.5 micrometer, More preferably, it is 0.2-0.5 micrometer. If the average particle size is less than 0.1 μm, the dispersion state is poor, the white density is insufficient, or the so-called “plate fogging” (due to poor ink scraping of portions other than the image area on the plate) during gravure printing. Printing defects) may occur, and if it exceeds 1 μm, the decorativeness may be insufficient.

  Commercially available products can be used as the titanium oxide (C). For example, a titanium oxide “JR series (JR-809, JR-708, JR-707, etc.)” manufactured by Teika Corporation is available.

(Printing ink)
The printing ink of the present invention contains the urethane acrylic resin (A), acrylic resin (B) and titanium oxide (C) as essential components. Further, it preferably contains a solvent, and may contain other additives (among others, wax and resin beads are preferred).

  Ratio of content of acrylic resin (B) and content of urethane acrylic resin (A) in nonvolatile content of printing ink of the present invention [(content of acrylic resin (B)): (urethane acrylic type) Resin (A) content)] (weight ratio) is 50:50 to 99: 1, preferably 80:20 to 95, from the viewpoint of achieving both printability and adhesion to a plastic film (substrate). : 5. That is, the acrylic resin (B) with respect to the total content (total content) of the urethane acrylic resin (A) content and the acrylic resin (B) content in the nonvolatile content of the printing ink of the present invention. Content ratio [(content of acrylic resin (B)) / {(content of urethane acrylic resin (A)) + (content of acrylic resin (B))} × 100] (weight ratio) Is 50 to 99% by weight, preferably 80 to 95% by weight.

  When the above ratio [(content of component (B)) :( content of component (A))] is less than 99: 1, the content of component (A) is smaller than the above ratio [(component (B ) Content) / {(content of component (A)) + (content of component (B))} × 100] exceeds 99% by weight), plastic film (especially polyester film) and The adhesiveness of is reduced. On the other hand, when the ratio [(content of component (B)) :( content of component (A))] is higher than 50:50 (ie, the ratio [(component When (B) content) / {(component (A) content) + (component (B) content)} × 100] is less than 50% by weight), the printability of the printing ink is reduced. When printing, “plate fog” (printing failure due to defective ink scraping of parts other than the image line area of the plate), “doctor streaks” (ink streaks away from the ink without being scraped off by the doctor to form a striped pattern) However, in the blank portion that should not be transferred to the film, linear stains are generated), and the printed layer is rubbed (scratched) or uneven (uneven).

  The total content (total content) of the urethane acrylic resin (A) content and the acrylic resin (B) content in the non-volatile content (100% by weight) of the printing ink of the present invention is not particularly limited. From the viewpoint of improving the adhesion of the printing ink and improving the white density, the content is preferably 14 to 30% by weight, and more preferably 15 to 26% by weight.

  The content of titanium oxide (C) in the non-volatile content (100% by weight) of the printing ink of the present invention is 70 to 81% by weight, preferably 74, from the viewpoint of improving the adhesion and white density of the printing ink. It is -81 weight%, More preferably, it is 76-81 weight%. When the content is less than 70% by weight, the white density of the printing ink is insufficient. On the other hand, when it exceeds 81% by weight, the adhesiveness is lowered.

  As the solvent (solvent), an organic solvent or the like usually used for printing ink used for gravure printing, flexographic printing or the like can be used. Examples of the solvent include acetates such as ethyl acetate, propyl acetate, and butyl acetate; alcohols such as methanol, ethanol, isopropyl alcohol (IPA), propanol, and butanol; ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone. Aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; glycols such as ethylene glycol and propylene glycol; ethylene glycol mono Glycol ethers such as propyl ether, propylene glycol monomethyl ether and propylene glycol monobutyl ether; glycol ethers such as propylene glycol monomethyl ether acetate Such as glycol ester compounds and the like. Among these, acetates, ketones, and alcohols are preferable from the viewpoints of solubility and safety. The said solvent can be used individually or in mixture of 2 or more types. The solvent can be removed by drying after applying the printing ink to the substrate. The solvent (solvent) includes the meaning of “dispersion medium”.

  In the printing ink (100% by weight) of the present invention, the content of the solvent is not particularly limited, but is preferably 25 to 45% by weight, more preferably from the viewpoint of improving the printability of the printing ink, viscosity, and white density. 26 to 35% by weight. The non-volatile content concentration of the printing ink of the present invention (the non-volatile content concentration in the printing ink) is not particularly limited, but is preferably 55 to 75% by weight from the viewpoints of improving the printability of the printing ink, viscosity, and white concentration. Preferably it is 65 to 74% by weight. In the present specification, “nonvolatile content” means a nonvolatile component (nonvolatile material). Specifically, the nonvolatile content is, for example, a residue (nonvolatile residue) when 1 g (1 g ± 0.1 g) of a sample (for example, printing ink) is heated at 150 ° C. for 2 hours. In addition, except for said heating conditions (150 degreeC x 2 hours) and sample amount (1g), it is a method (an apparatus, an instrument, a weighing method, a drying method, etc.) based on JISK5601-1-2, and the said non-volatile residue. It is preferable to obtain (heating residue).

  In addition to the above essential components [component (A), component (B) and component (C)] and the solvent, the printing ink of the present invention may contain other additives, if necessary, to impair the effects of the present invention. You may contain in the range which is not. The other additives are not particularly limited, but resins other than the component (A) and the component (B) (sometimes referred to as “other resins”) and pigments other than the component (C) (“other pigments”). ), Plasticizer, lubricant (wax, resin beads, etc.), anti-settling agent, dispersant, stabilizer, curing agent, antifoaming agent, filler, antioxidant, ultraviolet absorber, antistatic Agents, color separation preventing agents, fragrances, deodorants and the like. Among the above, wax and resin beads are preferable.

  Examples of the lubricant include polyolefin waxes such as polyethylene wax and polyethylene oxide wax, various waxes (waxes) such as fatty acid amide, fatty acid ester, paraffin wax, polytetrafluoroethylene (PTFE) wax, carnauba wax, and the like. A resin bead is mentioned. The content of the lubricant (especially wax) in the printing ink (100% by weight) of the present invention is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 2 to 7% by weight. .

  For example, the printing ink of the present invention is a mixture of the urethane acrylic resin (A), the acrylic resin (B), and the titanium oxide (C), a solvent, and, if necessary, other additives. Manufactured by. The component (A) and the component (B) may be previously dissolved in a solvent and then mixed with other components. Mixing can be performed by a known and common mixing method, and is not particularly limited. , Sand mills, ball mills, bead mills, line mills, kneaders and the like are used. The mixing time (retention time) during mixing is not particularly limited, but is preferably 10 to 120 minutes.

  The viscosity (23 ± 2 ° C.) of the printing ink of the present invention is not particularly limited. For example, when applied by gravure printing, it is preferably 10 to 1000 mPa · s, more preferably 20 to 500 mPa · s. is there. When the viscosity exceeds 1000 mPa · s, for example, the gravure printability is lowered, and “blur”, “plate fog”, etc. may occur, and printing may not be performed as desired. In addition, when the viscosity is less than 10 mPa · s, the storage stability is lowered, for example, pigments and additives are likely to settle, or “crossing” occurs, resulting in uneven printing, and printing according to the desired design. May not be possible. The viscosity of the printing ink can be controlled by the nonvolatile content concentration, the weight average molecular weight of the component (A) or the component (B), the thickener, the thinning agent, and the like. In the present specification, “viscosity” is JIS Z 8803 under the conditions of 23 ± 2 ° C. and cylinder rotation speed of 50 rpm using an E-type viscometer (conical flat plate rotational viscometer) unless otherwise specified. The value measured according to.

  The printing ink of the present invention is a printing ink for plastic labels used for plastic label applications (plastic label production applications). Specifically, it is used as a printing ink for forming a printing layer in a plastic label. The printing ink of the present invention is particularly preferably used for plastic labels based on polyester films among plastic labels. Furthermore, shrink label applications are preferred.

In the printing ink of the present invention, the acid value of the acrylic resin (B), which is the main resin component, is controlled within a specific range having good affinity with titanium oxide (C). For this reason, despite containing titanium oxide (C) at a high concentration, the titanium oxide (C) has high aggregation deterrence and excellent storage stability.
In addition, by blending urethane acrylic resin (A) at a specific ratio, excellent printability and excellent plastic film (especially polyester film) despite containing titanium oxide (C) at a high concentration. It has both good adhesion. The urethane acrylic resin (A) contains a specific amount of acrylic component and has good affinity (compatibility) with the main resin component acrylic resin (B). Can maintain aptitude. Furthermore, the adhesiveness between the printing ink of the present invention and the plastic film is improved by the urethane component of the urethane acrylic resin (A). In particular, since the urethane acrylic resin (A) is a polyester polyol-based urethane component in which the urethane component is a polyester polyol, the printing ink of the present invention is also particularly suitable for a polyester-based film whose adhesiveness tends to decrease. Can exhibit excellent adhesion.
As described above, the printing ink of the present invention has good printability and storage stability despite containing titanium oxide (C) at a high concentration, and also has an excellent plastic film substrate. Adhesion can be demonstrated. For this reason, it can be preferably used as a printing ink capable of forming a printing layer having a high white density.

  Furthermore, by making the polyester polyol in the urethane component of the urethane acrylic resin (A) an aromatic polyester polyol made of an aromatic dicarboxylic acid, the adhesion to an aromatic polyester film (for example, a PET film) is further enhanced. It is preferable because it improves.

[Plastic label]
By providing a printing layer formed from the printing ink for plastic labels of the present invention on at least one side of the plastic film (base material), a plastic label (formed from the printing ink for plastic labels of the present invention on at least one side of the plastic film) A plastic label having a printed layer). In the present specification, the above-mentioned “plastic label having a printing layer formed from the printing ink for plastic label of the present invention on at least one surface of the plastic film” may be referred to as “plastic label of the present invention”. Further, the “print layer formed from the printing ink for plastic labels of the present invention” may be referred to as “print layer of the present invention”.

(Plastic film (base material))
The plastic film, which is a base material in the above-described plastic label of the present invention, becomes a carrier (support) for the printing layer, and has a main influence on the strength, rigidity and shrinkage characteristics of the label. The type of the plastic film can be appropriately selected according to the type of the plastic label and is not particularly limited. For example, when the plastic label is a shrink label (heat-shrinkable label), the plastic film Is a shrink film (heat-shrinkable film).

  The type of resin forming the plastic film can be appropriately selected according to the required physical properties, application, cost, etc., and is not particularly limited. For example, polyester resin, polyolefin resin, polystyrene resin, Examples of the resin include polyvinyl chloride resin, polyamide resin, aramid resin, polyimide resin, polyphenylene sulfide resin, and acrylic resin. These resins may be used alone or in combination of two or more. Furthermore, the same kind or different kinds of resins may be laminated to be used as a laminated film. Of these, polyester resins, polyolefin resins, and polystyrene resins are preferable. That is, the plastic film is a polyester film made of a polyester resin, a polystyrene film made of a polystyrene resin, a polyolefin film made of a polyolefin resin, a polyester resin as an outer layer, and a polyolefin resin or a polystyrene resin as an inner layer. The heterogeneous laminated film is preferred. Among the above, a polyester film is particularly preferable from the viewpoint of transparency. The printing ink of the present invention exhibits excellent adhesion even with respect to a polyester film substrate whose adhesion tends to be lowered with respect to general printing inks. Examples of the polyester-based resin, polyolefin-based resin, and polystyrene-based resin include, for example, JP-A-2008-170822, JP-A-2008-170697, JP-A-2008-163215, and JP-A-2008-163231. The polyester resins, polyolefin resins, polystyrene resins, and the like described can be used.

  As the polyester resin used for the polyester film, polyethylene terephthalate (PET) resin, poly (ethylene-2,6-naphthalenedicarboxylate) (PEN), polylactic acid (PLA), and the like can be used. Among them, polyethylene terephthalate (PET) resin is preferable. As the PET resin, polyethylene terephthalate (PET) using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the diol component; terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component, Copolyester (CHDM copolymerized PET) using 4-cyclohexanedimethanol (CHDM) as a copolymerization component, terephthalic acid as a dicarboxylic acid component, ethylene glycol as a main component as a diol component, neopentyl glycol (NPG) as a main component Copolyester (NPG copolymerized PET) used as copolymer component, terephthalic acid as dicarboxylic acid component, ethylene glycol as main component as diol component, diethylene glycol as copolymer component Diol-modified PET, such as copolymerized polyester; (in the dicarboxylic acid component, modified terephthalic acid as a main component with isophthalic acid and / or adipic acid) the dicarboxylic acid-modified PET, and the like.

  As a polystyrene-type resin used for the said polystyrene-type film, as a constituent monomer, for example, styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, pt- Examples thereof include resins containing one or more styrene monomers such as butyl styrene and chloromethyl styrene. Specific examples include general polystyrene, styrene-butadiene copolymer (SBS), styrene-butadiene-isoprene copolymer (SBIS), and styrene-acrylic acid ester copolymer.

  Polyolefin resins used for the polyolefin film include polyethylene resins such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and metallocene catalyst LLDPE (mLLDPE), polypropylene, and propylene-α-olefin. Examples include polypropylene resins such as copolymers, ethylene-vinyl acetate copolymers, and cyclic olefin resins. In particular, the polyolefin film is preferably one having a cyclic olefin resin as an outer layer. For example, it is preferable to use a cyclic olefin resin as an outer layer and a polyethylene resin or a polypropylene resin as an inner layer (center layer).

  The plastic film (base material) may have a single layer structure or a laminated structure. That is, the plastic film may be a single-layer film or a laminated film in which a plurality of film layers are laminated according to required physical properties, applications, and the like. In the case of a laminated film, film layers made of the same kind of resin may be laminated, or film layers made of different resins may be laminated. In the case of a laminated film, a laminated film having a polyester resin as an outer layer and a polyolefin resin or polystyrene resin as an inner layer is preferable.

  The plastic film may be a non-oriented film or an oriented film. Especially, when a plastic film is a shrink film, it is preferable that it is a film orientated uniaxially, biaxially or multiaxially from the viewpoint of exhibiting shrinkage characteristics (heat shrinkage characteristics). When the shrink film is a laminated film, it is preferable that at least one film layer in the laminated film is oriented. When all the film layers are non-oriented, sufficient shrink characteristics may not be exhibited. The plastic film (especially shrink film) is preferably a uniaxial or biaxially oriented film, and more preferably a film (substantially uniaxially stretched) that is strongly oriented in the uniaxial direction of the film. In particular, a film uniaxially stretched in the width direction is preferable.

  The plastic film can be produced by a conventional method such as melt film formation or solution film formation. A commercially available plastic film (such as a shrink film) can also be used. The surface of the plastic film may be subjected to conventional surface treatment such as corona discharge treatment or primer treatment, if necessary. When producing a laminated plastic film, a conventional method such as a co-extrusion method or a dry laminating method can be used as a laminating method. Examples of methods for orienting the plastic film include 2 in the longitudinal direction (film production line direction; also referred to as the longitudinal direction or MD direction) and the width direction (direction orthogonal to the longitudinal direction; also referred to as lateral direction or TD direction). Axial stretching, uniaxial stretching in the longitudinal direction or width direction, and the like can be used. As the stretching method, for example, a roll method, a tenter method, a tube method, or the like can be used. For example, the stretching treatment of the film substantially uniaxially stretched in the width direction is performed at a temperature of about 70 to 100 ° C., if necessary, 1.01 to 1.5 times in the longitudinal direction, preferably 1.05 to After stretching to about 1.3 times, it can be carried out by stretching in the width direction 3 to 6 times, preferably about 4 to 5.5 times.

  When the plastic film is a shrink film, the heat shrinkage rate in the main orientation direction of the shrink film at 90 ° C. for 10 seconds (sometimes referred to as “heat shrinkage rate (90 ° C., 10 seconds)”) is particularly limited. Although not, 15 to 90% is preferable, and more preferably 20 to 85%. The thermal contraction rate (90 ° C., 10 seconds) in the direction orthogonal to the main alignment direction is not particularly limited, but is preferably −3 to 15%. The above-mentioned “main orientation direction” is a direction mainly subjected to a stretching process (a direction having the largest thermal shrinkage), and is generally a longitudinal direction or a width direction, for example, substantially in the width direction. In the case of a uniaxially stretched film, it is the width direction.

  When the plastic film is a transparent film, the haze value (%) of the plastic film (based on JIS K 7105) is preferably less than 10%, more preferably less than 5.0%, and still more preferably less than 2.0%. . When the haze (haze) value is 10% or more, when printing is shown through a plastic film, the printing may become cloudy and the decorativeness may be lowered.

  Although the thickness of the said plastic film (base material) is not specifically limited, From a puncture resistance and a viewpoint of abrasion resistance, 10-100 micrometers is preferable, More preferably, it is 12-80 micrometers, More preferably, it is 15-60 micrometers.

  A commercial item can also be used for the plastic film (for example, shrink film). For example, commercially available shrink films include “Space Clean S7042” and “SV-808” manufactured by Toyobo Co., Ltd., “LX-10S” and “LX-61S” manufactured by Mitsubishi Plastics, Inc. Film); “Bonset” manufactured by CI Kasei Co., Ltd. “GMLS” manufactured by Gunze Co., Ltd. (hereinafter, polystyrene film); “FL” manufactured by Gunze Co., Ltd. (polyolefin film); manufactured by Mitsubishi Plastics, Inc. “Ecology” (polylactic acid film); “DL” manufactured by Mitsubishi Plastics, Inc. “HGS” manufactured by Gunze Co., Ltd. (Laminated film with polyester resin on the surface and polystyrene resin on the center) It is done.

(Plastic label structure, physical properties, manufacturing method, etc.)
As described above, the plastic label of the present invention has the printing layer of the present invention (printing layer formed from the printing ink of the present invention) on at least one side of the plastic film (base material). The printed layer of the present invention is not necessarily provided on the entire surface of the label, and can be provided only on a part of the plastic film (base material). Even if the printed layer of the present invention is directly provided on the plastic film without any other layer such as an anchor coat layer, sufficient adhesion can be exhibited. For this reason, it is advantageous in terms of productivity and cost. In addition, the printing layer of this invention may be provided on the plastic film through the anchor coat layer as needed.

  Although the thickness of the printing layer of this invention is not specifically limited, From an adhesive viewpoint, 0.5-5 micrometers is preferable, More preferably, it is 1-3 micrometers.

  In addition to the plastic film (base material) and the printed layer of the present invention, the plastic label of the present invention includes an adhesive layer, an ultraviolet ray preventing layer, an anchor coat layer, a primer coat layer, and a printed layer other than the printed layer of the present invention. You may provide layers, such as a printing layer (it may call an "other printing layer"), a nonwoven fabric, paper, as needed.

  In the plastic label of the present invention, the transmission density of the printed layer of the present invention is preferably 0.22 or more, more preferably 0.24 or more, and still more preferably 0.27 or more, from the viewpoint of white density. If the transmission density is less than 0.22, the white density may be insufficient. The transmission density can be measured using, for example, a transmission density meter “Ihac-T5” manufactured by Ihara Denshi Kogyo Co., Ltd. The transmission density of the printing layer of the present invention can be determined, for example, by subtracting the transmission density of the substrate from the transmission density of the plastic label of the present invention (configuration of the printing layer / substrate of the present invention).

  The plastic label of the present invention can be produced, for example, by applying the printing ink of the present invention on the surface of a plastic film (base material) and drying to provide the printed layer of the present invention. The above coating and drying processes may be performed during the plastic film manufacturing process (film forming process) (in-line coating), or may be performed after film forming (off-line coating). From the viewpoint of properties, off-line coating is preferred. Moreover, you may provide layers other than the printing layer of this invention as needed.

  As a method for applying the printing ink, a gravure printing method, a flexographic printing method, and a letterpress printing method are preferable from the viewpoints of cost, productivity, printing decoration, and the like, and a gravure printing method is particularly preferable. Moreover, when drying the applied printing ink layer (application layer) by heating or the like, a general heating device capable of heating on the printing device can be preferably used. From the viewpoint of safety, a hot air heater or the like can be preferably used.

  Although it does not specifically limit as a plastic label of this invention, For example, a stretch label, a shrink label, a stretch shrink label, an in-mold label, a tack label, a roll label (a label with a wrapping type glue), a heat-sensitive adhesive label, etc. are mentioned. . Among these, a shrink label is particularly preferable. Although the said shrink label is not specifically limited, such as a cylindrical label and a winding label, A cylindrical shrink label (cylindrical shrink label) is preferable.

  The plastic label of the present invention is attached to a container and can be used as a labeled container. Examples of the container include soft drink bottles such as PET bottles, milk containers for home delivery, food containers such as seasonings, alcoholic beverage bottles, pharmaceutical containers, containers for chemical products such as detergents and sprays, cup noodle containers Etc. are included. The material of the container is not particularly limited, and examples of the container include a plastic container such as PET, a glass container, and a metal container. In addition, the plastic label of this invention may be used for adherends other than a container.

  EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Tables 1 to 4 show the composition (blending amount) of the printing ink, the content of titanium oxide in the non-volatile content of the printing ink, and the [(acrylic resin Content): (Content of urethane acrylic resin)] (weight ratio), acid value of acrylic resin, evaluation results of printing ink and plastic label, and the like are shown.
The blending composition of the above printing ink was indicated by the blending amount (parts by weight) based on weight. “Nonvolatile content” means the amount of titanium oxide, acrylic resin, acrylic resin solution, urethane acrylic resin solution, urethane resin solution and WAX (wax: lubricant) in terms of nonvolatile content (parts by weight). It showed in. The “solvent” is the total amount of the solvent contained in the acrylic resin solution, the solvent contained in the urethane acrylic resin solution, the solvent contained in the urethane resin solution, and the added solvent (organic solvent) ( Parts by weight).

  Tables 5 and 6 show the types and structures of the resins (urethane acrylic resins or urethane resins) contained in each solution in the urethane acrylic resin solutions and urethane resin solutions used in Examples and Comparative Examples. Unit (the compound from which each structural unit is derived) and the content of each structural unit (content in the resin)], acid value and weight average molecular weight, and “(meth) acryloyl group in the resin” "Content of structural unit derived from monomer" (acrylic component content). Moreover, the solvent composition (type and content ratio of the solvent) and nonvolatile content concentration of each solution are shown.

  Table 7 shows structural units of the acrylic resin (or acrylic resin contained in the acrylic resin solution) used in the examples and comparative examples [shown the compounds (constituent monomers) from which each structural unit is derived] and each The content (% by weight) of the structural unit in the resin, and the acid value and the weight average molecular weight of the acrylic resin are shown. The acrylic resin (b1), the acrylic resin (b3), and the acrylic resin (b4) are acrylic resins having a nonvolatile content concentration of 100% by weight. The acrylic resin solution (b2) is an acrylic resin solution (containing a nonvolatile content of 45% by weight, ethyl acetate of 22% by weight and isopropanol of 33% by weight). The acrylic resin solution (b5) is an acrylic resin solution (containing 25.2% by weight of nonvolatile content, 45.4% by weight of ethyl acetate, and 29.4% by weight of isopropanol).

Example 1
(Printing ink)
As the urethane acrylic resin, 1.9 parts by weight of urethane acrylic resin solution (a1) [nonvolatile content concentration: 41.5% by weight] (0.8 parts by weight as urethane acrylic resin) was used. In addition, as shown in Table 5, the urethane acrylic resin solution (a1) has a structural unit derived from neopentyl glycol of 39.4% by weight, a structural unit derived from terephthalic acid of 13.3% by weight, and isophthalic acid. 13.3% by weight of structural units derived from 11.2% by weight, structural units derived from isophorone diisocyanate (above, urethane component), and 22.8% by weight of structural units derived from butyl methacrylate (acrylic component) An ethyl acetate solution (nonvolatile content concentration: 41.5% by weight) of a urethane acrylic resin of an aromatic polyester polyol type having a weight average molecular weight of 42000 and an acid value of 3.0 mgKOH / g.
As the acrylic resin, 10.2 parts by weight of acrylic resin (b1) [acid value: 13 mg KOH / g, nonvolatile content concentration: 100 wt%] was used. As shown in Table 7, the acrylic resin (b1) is derived from 72.7% by weight of structural units derived from methyl methacrylate, 3.2% by weight of structural units derived from ethyl methacrylate, and derived from n-butyl methacrylate. This is an acrylic resin having a weight average molecular weight of 33,000, containing 14.5% by weight of structural units and 9.6% by weight of structural units derived from butyl acrylate.
In the urethane acrylic resin solution (a1) and the acrylic resin (b1), titanium oxide [manufactured by Taika Co., Ltd., trade name “JR-707”, nonvolatile content concentration: 100 wt%] 55.7 parts by weight, Add 3 parts by weight of wax [trade name “SPRAY105”, manufactured by Sasol, nonvolatile concentration: 100% by weight], 13.9 parts by weight of ethyl acetate, and 15.3 parts by weight of n-propyl acetate, and stir and mix with a homodisper. And printing ink (100 parts by weight) was prepared.

(Plastic label (shrink label))
Using the above printing ink, a gravure plate with an engraving of 60 lines / inch and a plate depth of 30 μm on one side of a polyester (PET) shrink film (manufactured by Toyobo Co., Ltd., “S7042”: thickness 45 μm), the process speed Full surface gravure printing was performed at 300 m / min, and drying was performed at 50 ° C. using a hot air dryer to form a printed layer, whereby a plastic label (shrink label) was obtained. The thickness of the printed layer after drying was about 3 μm.

Example 2 and Comparative Example 1
As shown in Table 1, printing inks and plastic labels were produced in the same manner as in Example 1 except that the type of urethane acrylic resin was changed.
The urethane acrylic resin contained in each of the urethane acrylic resin solution (a1), the urethane acrylic resin solution (a2), and the urethane acrylic resin solution (a3) is a structural unit derived from a polyester polyol. It is a urethane acrylic resin.

Comparative Examples 2-5
As shown in Table 1, printing inks and plastic labels were produced in the same manner as in Example 1 by changing the urethane acrylic resin to a urethane resin.

Examples 3-8, Comparative Examples 6-9
As shown in Table 2, printing inks and plastic labels were produced in the same manner as in Example 1 except that the amount of titanium oxide was changed.

Examples 9-15, Comparative Examples 10-12
As shown in Table 3, printing inks and plastic labels were produced in the same manner as in Example 1 by changing the blending amount of the urethane acrylic resin and the acrylic resin.

Examples 16-18, Comparative Examples 13, 14
As shown in Table 4, printing inks and plastic labels were produced in the same manner as in Example 1 except that the type of acrylic resin was changed.

(Evaluation)
The following evaluation was performed about the printing ink and plastic label (shrink label) which were obtained by the Example and the comparative example. The evaluation results are shown in Tables 1 to 4.

(1) Printability In the examples and comparative examples, the formation state of the printing layer, the plate surface of the gravure plate, and the ink pan were visually observed during the production of the plastic label (1 hour immediately after the start of production). The printability was judged according to the following criteria from the presence or absence of blurring and unevenness as the state of formation of the plate fog, doctor lines and printing layer.
○ (Good printability): There is no blurring or unevenness in the formation state of the plate cover, doctor streaks, and print layer.
Δ (usable): No streaking or unevenness in the formation of doctor lines and printed layers. There is a plate cover.
X (Poor printability): The doctor streaks or the formation state of the print layer has blur or unevenness.

(2) Adhesion (adhesion) (tape peeling test)
The test was conducted in accordance with JIS K 5600-5-6 except that no cross cuts were made on the grid. An adhesive tape (manufactured by Nichiban Co., Ltd., trade name “Cerotape (registered trademark)”, width 18 mm) is pasted on the surface of the printed layer of the plastic label obtained in Examples and Comparative Examples. Peeled in the direction.
In the area of 50 mm (longitudinal direction: production line direction) × 18 mm (width direction) in the surface of the printed layer on which the adhesive tape has been applied, the remaining area (ratio) of the printed layer is visually observed, according to the following criteria: It was judged.
The remaining area of the printed layer is 99% or more. : Good adhesion (○)
The remaining area of the printed layer is 90% or more and less than 99%. : Adhesiveness is slightly poor but usable level (△)
The remaining area of the printed layer is less than 90%. : Adhesion failure (×)

(3) Print layer transmission density (white density)
The plastic labels obtained in the examples and comparative examples were cut into a size of 5 cm (longitudinal direction) × 5 cm (width direction) to obtain a measurement sample.
The transmission density of the measurement sample was measured using a black and white transmission densitometer “Ihac-T5” manufactured by Ihara Denshi Kogyo Co., Ltd. Furthermore, the polyester (PET) shrink film (“Toyobo Co., Ltd.,“ S7042 ”: thickness 45 μm), which is a base material, was measured in the same manner, and the transmission density of the base material was measured.
The “transmission density of the printing layer” was determined by subtracting the transmission density of the substrate from the transmission density of the measurement sample.
For example, when the transmission density of the printing layer is 0.22 or more, it can be determined that the white density of the printing layer is high (high white density). The transmission density of the print layer is more preferably 0.24 or more, and still more preferably 0.27 or more.

(4) Aggregation inhibiting property of pigment (titanium oxide) After weighing 100 g of the printing inks obtained in Examples and Comparative Examples into polypropylene bottles, they were allowed to stand at room temperature (23 ° C.) for 24 hours. Thereafter, the observation results of scooping the bottom of the bottle with a spatula were evaluated according to the following criteria.
There is almost no precipitate. : Good aggregation suppression of pigment (titanium oxide) (○)
Precipitate is present. : Poor aggregation inhibition of pigment (titanium oxide) (×)

As can be seen from the above, the printing ink of the present invention contained titanium oxide at a high concentration, and was excellent in printability and storage stability (agglomeration inhibition property of pigment). Moreover, the printing layer formed from the printing ink of this invention had high white density, and also was excellent in adhesiveness with a base material (Example).
On the other hand, when the content of the structural unit derived from the monomer having a (meth) acryloyl group in the urethane acrylic resin exceeds the specified range of the present invention (the proportion of the acrylic component is too large), Adhesion was reduced (Comparative Example 1). Moreover, when a urethane resin was used instead of the urethane acrylic resin, printability was lowered, and adhesion and storage stability were sometimes lowered (Comparative Examples 2 to 5).
Moreover, when content of the titanium oxide in the non volatile matter of printing ink exceeded the regulation range of this invention, adhesiveness and storage stability fell (Comparative Examples 6 and 7). Furthermore, when the content of titanium oxide in the non-volatile content of the printing ink was too small, the transmission density (white density) of the printing layer was reduced (Comparative Examples 8 and 9).
Furthermore, when the content ratio of the acrylic resin in the non-volatile content of the printing ink was too large, the adhesion to the substrate and the printability were reduced (Comparative Example 10). Moreover, when there was too much ratio of content of the urethane acrylic resin in the non volatile matter of printing ink, printability fell (Comparative Examples 11 and 12).
Furthermore, when the acid value of the acrylic resin was outside the specified range of the present invention, the storage stability was lowered (Comparative Examples 13 and 14).

Claims (2)

A printing ink containing urethane acrylic resin (A) having a structural unit derived from polyester polyol (A), acrylic resin (B) and titanium oxide (C),
The content of the structural unit derived from the monomer having a (meth) acryloyl group in the urethane acrylic resin (A) is 1 to 40% by weight,
The acid value of the acrylic resin (B) is 1 to 40 mgKOH / g,
Ratio of content of acrylic resin (B) and content of urethane acrylic resin (A) in nonvolatile content of printing ink [(content of acrylic resin (B)): (urethane acrylic resin (A ) Content))] (weight ratio) is 50:50 to 99: 1,
A printing ink for plastic labels, wherein the content of titanium oxide (C) in the non-volatile content of the printing ink is 70 to 81% by weight.   The plastic label which has the printing layer formed from the printing ink for plastic labels of Claim 1 on the at least single side | surface of a plastic film.