JP2019155869A - Printing sheet - Google Patents

Abstract

To provide a printing sheet having suitability for thermal transfer printing, and letter press printing and flexographic printing using ultraviolet-curable ink.SOLUTION: A printing sheet has: a base material; and a printing coat layer that is laminated on one side of the base material and contains polyester, a resin containing an ultraviolet polymerizable functional group, and a crosslinker. The printing coat layer has a surface free energy of 45 mJ/mor more and 73 mJ/mor less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing sheet.

Plastic sheets are used as substrates for printing sheets used for various printing. Generally, when the substrate of the printing sheet is a plastic sheet, a printing coat layer is provided on the surface of the substrate sheet in order to improve the adhesion with ink. In recent years, the demand for flexographic printing has increased in the printing industry. In addition, as a flexographic ink, UV (ultraviolet curable) ink is mainly used. However, flexographic printing has a larger amount of ink than ordinary offset printing, and therefore, when flexographic printing is performed using UV ink, there is a problem that ink drops off due to curing shrinkage of the ink. Accordingly, there is a need for a printing film or printing pressure-sensitive adhesive sheet that can follow the shrinkage of the UV ink even when flexographic printing is performed using the UV ink and has excellent adhesion to the UV ink.
Such ultraviolet curable inks are also widely used in letter press printing.

  In addition, there is a demand for a coating layer for printing that is not specialized for ultraviolet curable ink but is excellent in thermal transfer printing.

  It has a base film made of a polyester-based resin that is excellent in adhesion and printability of UV-curable inks and is useful for labels that involve printing, and a surface layer provided on at least one side of the base film A polyester-based laminated film, in which the surface layer contains a copolymerized polyester resin (A) containing a branched glycol as a constituent component, and a resin containing a blocked isocyanate group containing bisulfite as a blocking agent (B) A polyester-based laminated film composed of a resin composition containing as a main component is disclosed (see Patent Document 1).

  A curable resin having a pencil hardness according to JIS K 5600-5-4 having an ink adhesion in a printed matter of ultraviolet curable ink and having scratch resistance of the printed matter, and an olefin resin Furthermore, a thermoplastic resin film having a coating layer containing protrusions derived from an olefin resin on the outer surface of the thermoplastic resin film on at least one surface is disclosed (see Patent Document 2).

  As described above, various printing sheets have been disclosed. However, a printing sheet having excellent adhesion and printing suitability for ultraviolet curable ink with one printing coat layer, and also excellent thermal transfer printing suitability has been found. The actual situation is not.

Japanese Patent No. 3300909 Japanese Patent Application Laid-Open No. 2005-89736

  An object of the present invention is to provide a printing sheet having suitability for thermal transfer printing and letter press printing and flexographic printing using an ultraviolet curable ink.

Such an object is achieved by the present invention described in the following (1) to (5).
(1) a base material;
Laminated on one surface side of the substrate, comprising a polyester, a resin having an ultraviolet polymerizable functional group, and a coating layer for printing containing a crosslinking agent,
The printing sheet has a surface free energy of 45 mJ / m ² or more and 73 mJ / m ² or less.

  (2) The printing sheet according to (1), wherein the polyester is urethane-modified polyester.

  (3) The printing sheet according to (1) or (2), wherein the content of the polyester in the coating layer for printing is 50 wt% or more and 95 wt% or less.

  (4) The printing sheet according to any one of (1) to (3), wherein the resin having an ultraviolet polymerizable functional group has an acrylate group.

  (5) The printing sheet according to (4), wherein the content of the resin having the ultraviolet polymerizable functional group in the coating layer for printing is 2 wt% or more and 20 wt% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the sheet | seat for printing which has an aptitude for the thermal transfer printing and the letter press printing and the flexographic printing using an ultraviolet curable ink can be provided.

It is a typical longitudinal section showing a suitable embodiment of a printing sheet of the present invention. It is a typical longitudinal section showing other suitable embodiments of a printing sheet of the present invention. It is a typical longitudinal section showing other suitable embodiments of a printing sheet of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.
[Printing sheet]
First, the printing sheet of the present invention will be described.
FIG. 1 is a schematic longitudinal sectional view showing a preferred embodiment of the printing sheet of the present invention.

The printing sheet 1A (1) of the present invention is printed on a base material 10, laminated on one surface side of the base material 10, and includes polyester, a resin having an ultraviolet polymerizable functional group, and a crosslinking agent. And the coating layer 11 for printing has a surface free energy of 45 mJ / m ² or more and 73 mJ / m ² or less.

  The printing sheet 1 of the present invention has good adhesion to the ultraviolet curable ink because the printing coat layer 11 contains a resin having an ultraviolet polymerizable functional group, and letter press printing using the ultraviolet curable ink and Applicable to flexographic printing.

In addition, the printing sheet 1 of the present invention has a surface free energy of 45 mJ / m ² or more and 73 mJ / m ² or less because the printing coat layer 11 has a good affinity with the thermal transfer ribbon, and thermal transfer printing. It has aptitude for.

  In addition, since the printing coat layer 11 includes a crosslinking agent, the bonding force (cohesive force) of the printing coat layer 11 itself is increased, and the destruction of the printing coat layer 11 is prevented. It is possible to prevent peeling from the base material 10.

  As described above, the printing sheet 1 of the present invention has good suitability for both thermal transfer printing using a heat transferable ink and letter press printing and flexographic printing using an ultraviolet curable ink.

<Base material>
The substrate 10 serves as a support that supports the printing coat layer 11.

  As the substrate 10, films made of various resin materials can be used. Specific examples of the material constituting the substrate 10 include, for example, polyolefin resins such as polyethylene resin and polypropylene resin, polyester resins such as polyethylene terephthalate resin, polyethylene naphthalate resin and polybutylene terephthalate resin, polyvinyl chloride resin, polystyrene resin, Acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyurethane resin, polycarbonate resin, polyamide resin, polyimide resin, poly (meth) acrylate, polybutene resin, polybutadiene resin, polymethylpentene resin, acrylic urethane resin, ionomer Various synthetic resin films such as resins, thermoplastic elastomer resins, fluororesins, and mixtures of two or more of these, or a laminate of two or more layers of the same or different types Irumu, synthetic paper.

  As the base material 10, a film made of a polyester resin or a polyolefin resin is preferable, and a base material 10 made of a polyethylene terephthalate resin, a polypropylene resin or a polyethylene resin is more preferable.

  Although the thickness of the base material 10 is not specifically limited, 5 micrometers or more and 350 micrometers or less are preferable, 10 micrometers or more and 300 micrometers or less are more preferable, 15 micrometers or more and 250 micrometers or less are more preferable.

<Coat layer for printing>
The printing coat layer 11 is an ink receiving layer to which ink is applied and fixed when printing is performed on the printing sheet 1.

  The printing coat layer 11 includes polyester, a resin having an ultraviolet polymerizable functional group, and a crosslinking agent.

In the printing sheet 1, the printing coat layer 11 preferably has a surface free energy of 45 mJ / m ² or more and 73 mJ / m ² or less, more preferably 46 mJ / m ² or more and 73 mJ / m ² or less, and 47.5 mJ. / M ² or more and 73 mJ / m ² or less is more preferable.

  The surface free energy of the coating layer 11 for printing mainly relates to the suitability for thermal transfer printing on the printing sheet 1.

  If the surface free energy is smaller than the lower limit, the affinity between the printing coat layer 11 and the heat transferable ink is lowered, transfer unevenness tends to occur, or image reproducibility tends to be inferior, and sufficient thermal transfer printability is obtained. It becomes difficult. On the other hand, if it is larger than the above upper limit value, it is difficult to select the material constituting the coating layer 11 for printing. When the surface free energy of the coating layer 11 for printing is in the above range, the material can be selected more easily and has sufficient thermal transfer printing suitability.

  In this specification, the surface free energy of the coating layer 11 for printing is the Kitasaki / Hata method (Nayaki Kitasaki, et al., Journal of Japan Adhesion Association, Vol. 8, No. 3, 1972, pp. 131-141). Reference).

  A specific method for measuring the surface free energy of the printing coat layer 11 will be described in Examples described later.

  The method for adjusting the surface free energy of the printing coat layer 11 to the above range is not particularly limited, and examples thereof include a method of adjusting either or both of the types and amounts of the components contained in the printing coat layer 11.

  The surface free energy can also be adjusted by subjecting the printing coat layer 11 to surface treatment such as corona treatment or plasma treatment. Among these surface treatments, corona treatment is preferable from the viewpoint of easy treatment and less damage to the printing coat layer 11.

The amount of discharge when the corona treatment is performed is preferably 150 W · min / m ² or more and 1000 W · min / m ² or less, and more preferably 250 W · min / m ² or more and 600 W · min / m ² or less. . Thereby, surface free energy can be adjusted suitably, suppressing the unintentional damage with respect to the surface of the coating layer 11 for printing.

(Polyester resin)
Examples of the polyester resin (polyester) include polyester resins and urethane-modified polyester resins.

  The polyester resin is preferably a polyester copolymer resin obtained by copolymerizing a dicarboxylic acid and a glycol compound.

  Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, sulfoterephthalic acid, and 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as oxalic acid, sebacic acid, succinic acid, and adipic acid. Acid, 1,3-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids Is preferably used.

  Examples of the glycol compound include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, p-xylene glycol, triethylene glycol and the like are preferably used.

  Examples of the urethane-modified polyester resin include those having a urethane bond in the polyester resin. The urethane-modified polyester resin can be obtained, for example, by reacting a polyester resin having two or more functional groups such as hydroxyl groups in one molecule with a polyisocyanate compound.

  As a polyisocyanate compound, the thing similar to the polyisocyanate compound as a crosslinking agent mentioned later can be used. The polyisocyanate compound used for urethane modification of the polyester resin can be used alone or in combination of two or more.

  The polyester resin is preferably a urethane-modified polyester resin, and more preferably a urethane-modified polyester resin having a basic structure of an aromatic polyester. The basic structure of the aromatic polyester is one having a repeating unit derived from an aromatic compound in the main chain polyester structure, for example, one or both of a dicarboxylic acid and a glycol compound of a part or all of a copolymer raw material. Is obtained when is an aromatic compound.

  Polyester resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  The number average molecular weight of the polyester resin is preferably from 5,000 to 100,000, and more preferably from 10,000 to 60,000.

  The hydroxyl value of the polyester resin is preferably 1 mgKOH / g or more and 50 mgKOH / g or less, more preferably 1 mgKOH / g or more and 25 mgKOH / g or less, and further preferably 1.5 mgKOH / g or more and 20 mgKOH / g or less.

  The acid value of the polyester resin is preferably from 0 mgKOH / g to 40 mgKOH / g, and more preferably from 0 mgKOH / g to 30 mgKOH / g.

  The glass transition temperature of the polyester resin is preferably −50 ° C. or higher and 120 ° C. or lower, more preferably −40 ° C. or higher and 100 ° C. or lower, and further preferably −30 ° C. or higher and 90 ° C. or lower.

  When the number average molecular weight, the hydroxyl value, the acid value, and the glass transition temperature of the polyester resin are within the preferable ranges, the effects of the present invention can be further exhibited.

  The content of the polyester resin in the coating layer 11 for printing is preferably 50 wt% or more and 95 wt% or less, more preferably 55 wt% or more and 85 wt% or less, and further preferably 59 wt% or more and 70 wt% or less. preferable.

  If the content of the polyester resin is less than the lower limit, the thermal transfer printing suitability is lowered. On the other hand, if the upper limit is exceeded, the printability of the ultraviolet curable ink is deteriorated.

  By setting the content of the polyester-based resin in the coating layer 11 for printing in the above range, it has good suitability for both thermal transfer printing, letter press printing using ultraviolet curable ink, and flexographic printing.

(resin)
The resin refers to a polymerizable compound that has an ultraviolet polymerizable functional group and is crosslinked and cured by irradiation with ultraviolet rays when a polymerization initiator is present. The ultraviolet polymerizable functional group is preferably an acrylate group.

  Examples of this resin include an ultraviolet polymerizable prepolymer and / or an ultraviolet polymerizable monomer.

Examples of the ultraviolet polymerizable prepolymer include polyester acrylate, epoxy acrylate, urethane acrylate, polyol acrylate, and the like. Here, as the polyester acrylate-based prepolymer, for example, by esterifying the hydroxyl group of a polyester oligomer having a hydroxyl group at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid, or It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a polyvalent carboxylic acid with (meth) acrylic acid.
(Meth) acrylic acid refers to acrylic acid and / or methacrylic acid.

  The epoxy acrylate prepolymer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. The urethane acrylate-based prepolymer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of polyether polyol or polyester polyol and polyisocyanate with (meth) acrylic acid. Furthermore, the polyol acrylate-based prepolymer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid. One of these ultraviolet polymerizable prepolymers may be used alone, or two or more thereof may be used in combination.

Examples of the ultraviolet polymerizable monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di (meth). Acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified di (meth) acrylate phosphate, allylated cyclohexyldi ( (Meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol pentaacrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaeryth Litol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol Examples thereof include polyfunctional acrylates such as hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate. These ultraviolet polymerizable monomers may be used individually by 1 type, may be used in combination of 2 or more type, and may be used together with the said ultraviolet polymerizable prepolymer.
(Meth) acrylate refers to acrylate and / or methacrylate.

  The content of the resin having an ultraviolet polymerizable functional group in the printing coat layer 11 is preferably 2 wt% or more and 20 wt% or less, more preferably 5 wt% or more and 10 wt% or less, and more preferably 5 wt% or more and 7 wt% or less. More preferably.

  Even if the content of the resin having an ultraviolet polymerizable functional group is less than the lower limit value or exceeds the upper limit value, printability by the ultraviolet curable ink is deteriorated.

(Photopolymerization initiator)
For the curing of the resin having an ultraviolet polymerizable functional group, a photopolymerization initiator can be used as necessary.

  Examples of this photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2 (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone Dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4 -Diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamine benzoate and the like. These may be used singly or in combination of two or more, and the blending amount thereof is 100 parts by weight of the UV polymerizable prepolymer and / or UV polymerizable monomer. Usually, it is selected in a range of 0.2 parts by mass or more and 10 parts by mass or less. Such a photopolymerization initiator may be contained in the printing coat layer 11 or may be contained in the ink dropped onto the printing coat layer 11.

(Crosslinking agent)
The coating layer 11 for printing contains a crosslinking agent together with the polyester.

  As the crosslinking agent, an isocyanate compound is preferable. As the isocyanate compound as the crosslinking agent, various isocyanate compounds can be used as long as they react with a functional group such as a hydroxyl group of the polyester resin to form a crosslinked structure.

  The isocyanate compound is preferably a polyisocyanate compound having two or more isocyanate groups per molecule.

  Examples of the polyisocyanate compound include diisocyanate compounds, triisocyanate compounds, tetraisocyanate compounds, pentaisocyanate compounds, hexaisocyanate compounds, and more specifically, aromatics such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate. Polyisocyanate; Alicyclic isocyanate compounds such as dicyclohexylmethane-4,4-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, hydrogenated xylylene diisocyanate; pentamethylene diisocyanate, hexa Methylene diisocyanate, heptamethylene diisocyanate Trimethylhexamethylene diisocyanate, aliphatic isocyanate compounds such as lysine diisocyanate.

  Further, modified products such as biurets and isocyanurates of these compounds and adducts which are the reaction products of these compounds with non-aromatic low-molecular active hydrogen-containing compounds such as ethylene glycol, trimethylolpropane and castor oil Can also be used.

  Of these isocyanate compounds, aliphatic isocyanate compounds are preferable, aliphatic diisocyanate compounds are more preferable, and pentamethylene diisocyanate, hexamethylene diisocyanate, and heptamethylene diisocyanate are more preferable.

  An isocyanate type compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  The coating layer 11 for printing may contain a specific metal crosslinking accelerator together with the isocyanate compound as the crosslinking agent.

  Examples of the metal crosslinking accelerator include bismuth crosslinking accelerator, titanium crosslinking accelerator, vanadium crosslinking accelerator, zirconium crosslinking accelerator, aluminum crosslinking accelerator, nickel crosslinking accelerator, and the like. In this, a bismuth type crosslinking accelerator is preferably used.

  Bismuth crosslinking accelerator, titanium crosslinking accelerator, vanadium crosslinking accelerator, zirconium crosslinking accelerator, aluminum crosslinking accelerator, or nickel crosslinking accelerator are bismuth, titanium, vanadium, zirconium, aluminum, Or an organometallic compound of nickel, which is a compound having a structure such as alkoxide, carboxylate, or chelate, and preferably includes an acetylacetone complex, acetylacetonate, octylic acid compound, or naphthenic acid compound of these metals. .

  Specific examples of the metal acetylacetone complex include acetylacetone titanium, acetylacetone vanadium, acetylacetone zirconium, acetylacetone aluminum, and acetylacetone nickel.

  Specific examples of acetylacetonate include bismuth acetylacetonate, titanium acetylacetonate, vanadium acetylacetonate, zirconium acetylacetonate, aluminum acetylacetonate, nickel acetylacetonate and the like.

  Specific examples of the octyl acid compound include bismuth 2-ethylhexylate, nickel 2-ethylhexylate, zirconium 2-ethylhexylate and the like.

  Specific examples of the naphthenic acid compound include bismuth naphthenate, nickel naphthenate, zirconium naphthenate, and the like.

  In addition, a tin-based compound having a butyl group such as tributyltin laurylate or dibutyltin dilaurate can also be used as the metal-based crosslinking accelerator.

  The said metal type crosslinking accelerator may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the coating layer 11 for printing, the content ratio of the polyester-based resin and the isocyanate-based compound as the crosslinking agent is 1 to 30 parts by mass of the isocyanate-based compound as the crosslinking agent with respect to 100 parts by mass of the polyester-based resin in solid ratio. Part by mass or less, preferably 2 parts by mass or more and 20 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less.

  Moreover, in the coating layer 11 for printing, the content rate of the isocyanate type compound as a crosslinking agent and the said metal type crosslinking accelerator is 0.001 in conversion of a metal amount in the said metal type crosslinking accelerator with respect to 100 mass parts of isocyanate compounds. 001 mass parts or more and 5 mass parts or less are preferable, 0.005 mass parts or more and 2 mass parts or less are more preferable, and 0.01 mass parts or more and 1 mass parts or less are more preferable.

(Other ingredients)
The coating layer 11 for printing can contain a diluent medium in addition to polyester, a resin having an ultraviolet polymerizable functional group, and a crosslinking agent. Examples of the dilution medium include an organic dilution medium and an aqueous dilution medium.

  Examples of the organic dilution medium include aromatic hydrocarbons such as toluene and xylene, aliphatic ketones such as methyl ethyl ketone and diethyl ketone, and organic solvents such as alicyclic ketones such as cyclohexanone. Can be used in combination.

  In the printing coat layer 11, the content of resin solids such as polyester, resin having an ultraviolet polymerizable functional group, and isocyanate compound as a crosslinking agent is preferably 0.5% by mass or more and 10% by mass or less. More preferably, it is 1 mass% or more and 7 mass% or less.

  The printing coat layer 11 can be blended with various fillers such as an organic filler and an inorganic filler in order to improve the slipperiness and obtain a matte feeling.

  Examples of the organic filler include polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polycarbonate resin, acrylic resin such as methyl methacrylate, or resin powder such as a mixture thereof.

  Examples of the inorganic filler include inorganic oxides such as silica and alumina, and metal powders such as gold powder and silver powder.

  The blending amount of the filler is preferably 0.1 parts by mass or more and 20 parts by mass or less and more preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the total amount of the resin component and the crosslinking agent in the coating layer 11 for printing. preferable.

  The thickness of the coating layer 11 for printing is not particularly limited, but is preferably 10 nm or more and 600 nm or less, more preferably 20 nm or more and 400 nm or less, and further preferably 30 nm or more and 200 nm or less.

  When the thickness of the coating layer 11 for printing is less than the lower limit value, printability is deteriorated. On the other hand, when the upper limit is exceeded, blocking resistance is lowered. By setting the thickness of the printing coat layer 11 within the above range, the coating layer 11 has blocking resistance and excellent printability.

[Preparation of printing sheet]
Next, a method for producing the printing sheet 1 of the present invention will be described.

  In the printing sheet 1 of the present invention, the above-mentioned printing coat layer 11 is provided on one surface of the substrate 10, and in order to form this printing coat layer 11, first, for printing A coating layer forming coating solution is prepared.

<Coating liquid for coating layer formation for printing>
As a coating liquid for forming a coating layer for printing for forming the coating layer 11 for printing, the above-described polyester, a resin having an ultraviolet polymerizable functional group, a crosslinking agent, and a necessary agent are used in an appropriate solvent. Coating solutions prepared by dissolving or dispersing photopolymerization initiators and various additives used accordingly, such as organic or inorganic pigments, colorants, plasticizers, antioxidants, light stabilizers, dispersants, leveling agents, etc. Can be used.

(solvent)
The solvent used in the coating liquid for forming a coating layer for printing is not particularly limited. For example, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone, toluene, Examples thereof include aromatic hydrocarbon solvents such as xylene.

  The solid content concentration in the coating liquid for forming a coating layer for printing is not particularly limited as long as it is a concentration that allows coating, but is usually about 1% by mass to 10% by mass, preferably 2% by mass to 5%. It is below mass%.

  In preparing the coating liquid for forming a coating layer for printing, the surface free energy of the printing coating layer 11 to be formed is adjusted to the above range by adjusting either or both of the kind and amount of the component. Can do.

<Formation of coating layer for printing>
First, the printing coat layer forming coating solution prepared as described above is applied to one surface of the substrate 10 and dried to provide the printing coat layer 11.

  The amount of the coating solution for forming a coating layer for printing applied to the substrate 10 is usually such that the thickness of the coating layer for printing 11 after drying is preferably in the range of 10 nm to 600 nm, more preferably 20 nm to 400 nm. The amount is within the range, more preferably within the range of 30 nm to 200 nm.

  Examples of methods for applying the coating liquid for forming a coating layer for printing onto the substrate 10 include conventionally known methods such as a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method. Is mentioned.

  The drying is usually preferably performed at 60 ° C. or higher and 130 ° C. or lower, and more preferably 80 ° C. or higher and 120 ° C. or lower. The drying time is not particularly limited, but usually 10 seconds or more and 5 minutes or less is sufficient.

  Moreover, surface free energy can be adjusted to the said range also by performing surface treatments, such as a corona treatment and a plasma treatment, with respect to the formed coating layer 11 for printing. Of these, corona treatment is preferred.

  In order to improve the adhesion between the printing coat layer 11 and the substrate 10, an anchor coat layer (not shown) is provided on the surface of the substrate 10 as necessary, and printing is performed on the surface of the anchor coat layer. A coat layer 11 can be provided.

  Examples of the anchor coat layer include a polyurethane anchor coat layer and a polyester anchor coat layer.

  The printing sheet 1 of the present invention thus produced has characteristics such as excellent adhesion and printability of ultraviolet curable ink, and further excellent thermal transfer printability.

[label]
As shown in FIG. 2, the printing sheet 1 </ b> B (1) of the present invention has an adhesive layer 12 on the other surface of the substrate 10 (the surface opposite to the side on which the printing coat layer 11 is formed). By providing, it can be used as an adhesive label.

  The other surface of the substrate 10 may be subjected to an easy adhesion treatment in order to further increase the adhesion with the pressure-sensitive adhesive layer 12. Although it does not specifically limit as an easily bonding process, For example, a corona treatment etc. are mentioned.

  As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer 12, various pressure-sensitive adhesives can be used. Specific examples of the pressure-sensitive adhesive include natural rubber-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, acrylic resin-based pressure-sensitive adhesives, polyvinyl ether resin-based pressure-sensitive adhesives, urethane resin-based pressure-sensitive adhesives, and silicone resin-based pressure-sensitive adhesives. Preferred are acrylic resin adhesives, rubber adhesives, silicone resin adhesives, and the like. Further, the pressure-sensitive adhesive may be a solvent-type pressure-sensitive adhesive, a water-type pressure-sensitive adhesive, or a strong pressure-sensitive adhesive or a re-peelable pressure-sensitive adhesive.

Moreover, you may provide the peeling liner 20 in the surface on the opposite side to the base material 10 side of the adhesive layer 12. FIG.
Examples of the base material of the release liner 20 include paper, synthetic paper, and synthetic resin film. Examples of the paper include paper base materials such as high-quality paper, glassine paper, and coated paper, paper base materials such as laminated paper obtained by laminating a thermoplastic resin such as polyethylene and polypropylene on these paper base materials, and high-quality paper, Examples of the paper base material include glass paper, coated paper, and the like that are treated with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, and the like. Synthetic resin films include, for example, polyolefin resins such as polyethylene resins and polypropylene resins, films made of polyester resins such as polybutylene terephthalate resins and polyethylene terephthalate resins, and films obtained by subjecting these synthetic resin films to easy adhesion treatment. It is preferable that these are coated with a release agent.

  Examples of the release agent include fluorine resins, silicone resins, olefin resins, and long-chain alkyl group-containing carbamates.

  As shown in FIG. 3, the printing sheet 1 </ b> C (1) of the present invention may further include a printing coat layer 13 laminated on the other surface side of the substrate 10.

Also in this case, the printing coat layer 13 includes polyester, a resin having an ultraviolet polymerizable functional group, and a crosslinking agent, as in the printing coat layer 11, and has a surface free energy of 45 mJ / m ² or more. It is preferably 73 mJ / m ² or less.

  As a result, the printing sheet 1 can be printed on both sides, and is particularly suitable for thermal transfer printing, letter press printing, and flexographic printing.

[Printing ink]
As the printing ink used for printing on the printing coat layer 11 of the printing sheet 1 of the present invention, various inks such as thermal transfer ink and ultraviolet curable ink are used.

  As the ultraviolet curable ink, various ultraviolet curable inks are used, and polyacrylate ultraviolet curable inks are preferable.

  By having the acrylic resin in the ink, the familiarity with the acrylic structure contained in the resin having the ultraviolet polymerizable functional group of the above-described printing coat layer 11 is improved, and adhesion with the ink can be improved.

  The thermal transfer ink is an ink in which a thermally transferable dye or pigment is supported by an arbitrary binder resin, and various thermal transfer inks are used. Examples of the thermal transfer ink include, but are not particularly limited to, inks that melt by the heat of the thermal head.

The printing sheet 1 of the present invention has good suitability for letter press printing and flexographic printing using an ultraviolet curable ink since the coating layer 11 for printing contains a resin having an ultraviolet polymerizable functional group. Since the surface free energy of the coating layer 11 for printing is 45 mJ / m ² or more and 73 mJ / m ² or less, it has good suitability for thermal transfer printing.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

  For example, the printing sheet of the present invention has good suitability for printing methods using ultraviolet curable inks other than letter press printing and flexographic printing.

  The printing sheet of the present invention can also be applied to printing methods using inks other than thermal transfer ink and ultraviolet curable ink.

  Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to these examples. In the following description, the treatment that does not particularly indicate the temperature condition is performed at room temperature (23 ° C.) and a relative humidity of 50%. Moreover, what does not show temperature conditions in particular also about various measurement conditions is a numerical value in room temperature (23 degreeC) and 50% of relative humidity.

In the present specification, the surface free energy of the coating layer for printing is determined by measuring the contact angle of the surface using the following measurement solvent whose contact angle is known and the following contact angle meter, and from the obtained contact angle, Kitasaki -The surface free energy γtotal was calculated by the field method (see Kitazaki, N. et al., Journal of Japan Adhesion Association, Vol. 8, No. 3, 1972, pp. 131-141).
Contact angle meter: Kyowa Interface Science Co., Ltd. fully automatic contact angle meter DM-701
Measuring solvent: water, diiodomethane, 1-bromonaphthalene

Example 1
(1) Preparation of coating solution for forming coating layer for printing Urethane modified polyester having a basic structure of aromatic polyester (manufactured by Toyobo Co., Ltd., trade name “Byron UR8700”, number average molecular weight 32000, hydroxyl value 2-4 mgKOH / g, acid value of less than 1 mg KOH / g, glass transition temperature -22 ° C., isocyanate compound (trade name “Coronate HL”, manufactured by Tosoh Corporation) as a crosslinking agent, and dipentaerythritol as a resin having an ultraviolet polymerizable functional group. Pentaacrylate is mixed in a predetermined mass ratio so that the content in the coating layer for printing after drying is a ratio shown in Table 1, and toluene, methyl ethyl ketone, and cyclohexanone as a solvent are mixed in a mass ratio of 10: A mixed printing solvent mixed at a ratio of 10: 1 is mixed and stirred to produce a coating for printing. A layer-forming coating solution was obtained.

(2) Production of printing sheet On one surface of polyethylene terephthalate (thickness 50 μm), the coating layer-forming coating liquid obtained in (1) above has a thickness after drying of 100 nm. It was applied by bar coating in an amount and dried for 1 minute with a hot air dryer at 90 ° C. to prepare a printing sheet.

In the printing sheet of Example 1 thus obtained, the surface free energy of the printing coating layer was 47.7 mJ / m ² .

  In addition, content of each component in Table 1 is described in the mass part with respect to 100 mass parts of urethane-modified polyester.

(Example 2)
In the preparation of the coating liquid for forming a coating layer for printing, dibutyltin dilaurate is further added as a tin-based cross-linking accelerator, and the content ratio in the printing coating layer after drying is a predetermined mass ratio so as to be the ratio shown in Table 1. A coating sheet for forming a coating layer for printing was prepared in the same manner as in Example 1 except that the printing sheet was prepared.

Furthermore, the surface of the coating layer for printing was subjected to corona treatment at a treatment strength of 300 Wmin / m ² .

In the thus obtained printing sheet of Example 2, the surface free energy of the printing coating layer was 47.0 mJ / m ² .

(Example 3)
In the preparation of the coating solution for forming a coating layer for printing, titanium ethyl acetoacetate is further added as a titanium-based crosslinking accelerator. A coating liquid for forming a coating layer for printing was prepared in the same manner as in Example 1 except that the mixing was performed at a mass ratio to prepare a printing sheet.

In printing sheet of Example 3 obtained in this manner, the surface free energy of the coated printing layer was 48.3mJ / m ^2.

(Comparative Example 1)
In the preparation of the coating liquid for forming a coating layer for printing, dibutyltin dilaurate is further added as a tin-based cross-linking accelerator, and the content ratio in the printing coating layer after drying is a predetermined mass ratio so as to be the ratio shown in Table 1. A coating sheet for forming a coating layer for printing was prepared in the same manner as in Example 1 except that the printing sheet was prepared.

In the printing sheet of Comparative Example 1 thus obtained, the surface free energy of the printing coat layer was 41.4 mJ / m ² .

(Comparative Example 2)
In the preparation of the coating solution for forming a coating layer for printing, the content ratio in the coating layer for printing after drying the urethane-modified polyester resin and the resin having an ultraviolet polymerizable functional group is the ratio shown in Table 1. A coating liquid for forming a coating layer for printing was prepared in the same manner as in Example 1 except that the printing sheet was prepared in the same manner as in Example 1, except that the printing sheet was mixed.

In the printing sheet of Comparative Example 2 thus obtained, the surface free energy of the printing coating layer was 46.5 mJ / m ² .

(Comparative Example 3)
In the preparation of the coating liquid for forming a coating layer for printing, the content of the urethane-modified polyester resin, the crosslinking agent, and the tin-based crosslinking accelerator in the printing coating layer after drying is the ratio shown in Table 1. Thus, except having mixed by the predetermined mass ratio, the coating liquid for coating layer formation for printing was prepared similarly to Example 1, and the printing sheet was produced.

In the printing sheet of Comparative Example 3 thus obtained, the surface free energy of the printing coating layer was 42.6 mJ / m ² .

(Comparative Example 4)
In the preparation of the coating liquid for forming a coating layer for printing, the urethane-modified polyester resin and the crosslinking agent are mixed at a predetermined mass ratio so that the content ratio in the coating layer for printing after drying becomes the ratio shown in Table 1. Except for mixing, a coating liquid for forming a coating layer for printing was prepared in the same manner as in Example 1 to prepare a printing sheet.

In the printing sheet of Comparative Example 4 thus obtained, the surface free energy of the printing coating layer was 46.5 mJ / m ² .

[Evaluation of printing sheet]
With respect to the printing sheets of Examples and Comparative Examples produced as described above, suitability for flexographic printing and thermal transfer printing was evaluated.

<Evaluation of suitability for flexographic printing>
For each of the printing sheets obtained in each of Examples and Comparative Examples, a printing ultraviolet curable ink (manufactured by T & K TOKA Co., Ltd., trade name “BESTCURE UV161 Black S”) is used on the surface of the printing coat layer. The flexographic printing machine (Matsuo Sangyo Co., Ltd., Easy Proof, Steel Anilox Roller, 180 lines, cell capacity: 16.6 cm ³ / m ² ) is used for flexographic printing, and UV irradiation (UV-LED lamp) is used for printing images. That is, a printed layer was obtained.

  A cross cut with a 1 mm width is applied to the surface of the printed layer, and an adhesive tape (product name “Cello Tape (registered trademark)” manufactured by Nichiban Co., Ltd.) is pasted on the surface of the printed layer that has been cross cut into a grid. The tape tape peel test was conducted in accordance with the cross-cut tape method of JISK5600-5-6 (cross cut method), and the printing adhesion of the coating layer was evaluated according to the following criteria.

◯: The number of squares in which the printed layer remains after the cellophane peeling test is 90 or more per 100 squares.
X: The number of squares in which the printed layer remains after the cellophane peeling test is less than 90 per 100 squares.

<Evaluation of thermal transfer printing aptitude>
For each of the printing sheets obtained in each Example and each Comparative Example, a resin-based ink ribbon (manufactured by Sony Chemical Co., trade name “TR4070”) is applied to the surface of the coating layer for printing. A barcode pattern was printed at a speed of 3 inches / sec (7.6 cm / sec) under the model name “Zebra140XiIII”). The thermal transferability of the ink ribbon was evaluated according to the following criteria.

○: The barcode could be read.
×: Bar code reading was difficult.

  Table 1 shows the evaluation results of printability of the printing sheets of each example and each comparative example, together with the types and ratios of the constituent components of the coating layer for printing and the surface free energy.

  As is apparent from Table 1, in the printing sheets of Examples 1 to 3 and Comparative Example 1 containing a resin having a UV-polymerizable functional group and a crosslinking agent in addition to polyester in the printing coat layer, good flexo Printability is obtained. On the other hand, in the printing sheets of Comparative Examples 2 and 3 containing only one of the resin having an ultraviolet polymerizable functional group and the cross-linking agent, good flexographic printing suitability has not been obtained.

In the printing sheets of Examples 1 to 3 and Comparative Examples 2 and 4 in which the surface free energy of the coating layer for printing is 45 mJ / m ² or more, good thermal transfer printing suitability is obtained. On the other hand, in the printing sheets of Comparative Examples 1 and 3 in which the surface free energy of the printing coating layer is less than 45 mJ / m ² , good thermal transfer printing suitability is not obtained.

  However, none of the printing sheets of Comparative Examples 1 to 4 has good suitability for both thermal transfer printing and flexographic printing.

On the other hand, in Examples 1 to 3, in which the coating layer for printing contains both a resin having a UV-polymerizable functional group and a crosslinking agent, and the surface free energy is 45 mJ / m ² or more, thermal transfer printing, flexographic printing It has been confirmed that it has good suitability for both printing.

  From Example 2 and Comparative Example 1, it can be seen that the surface free energy can be adjusted by applying a corona treatment to the coating layer for printing.

  Further, it is presumed that the printing sheets of the examples have good suitability for letter press printing using an ultraviolet curable ink as in flexographic printing.

  By using the printing sheet according to the present invention, it becomes suitable for thermal transfer printing and letter press printing and flexographic printing using ultraviolet curable ink, and can be widely used as various printing sheets.

DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C Printing sheet 10 Base material 11 Printing coat layer 12 Adhesive layer 13 Printing coat layer 20 Release liner

Claims (5)

A substrate;
Laminated on one surface side of the substrate, comprising a polyester, a resin having an ultraviolet polymerizable functional group, and a coating layer for printing containing a crosslinking agent,
The printing sheet has a surface free energy of 45 mJ / m ² or more and 73 mJ / m ² or less.   The printing sheet according to claim 1, wherein the polyester is urethane-modified polyester.   3. The printing sheet according to claim 1, wherein the polyester content in the printing coat layer is 50 wt% or more and 95 wt% or less.   The printing sheet according to any one of claims 1 to 3, wherein the resin having an ultraviolet polymerizable functional group has an acrylate group.   The printing sheet according to claim 4, wherein the content of the resin having the ultraviolet polymerizable functional group in the printing coat layer is 2 wt% or more and 20 wt% or less.

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