JP7700550B2 - Method for manufacturing laminate and method for applying adhesive - Google Patents

Description

The present invention relates to a method for manufacturing a laminate suitable for use as a packaging material for food, medicines, cosmetics, detergents, miscellaneous goods, etc.

Composite laminates formed by multi-layer lamination of various plastic films are widely used as packaging materials for food, clothing, cosmetics, miscellaneous goods, etc. Such laminates are generally produced by forming a print layer on a plastic film to produce a printed film, and then laminating the resulting printed film with another plastic film using an adhesive.
The printing layer is formed by printing ink by gravure printing, flexographic printing, on-demand printing such as inkjet printing, etc., and the thickness often varies depending on the design of the printed matter. In addition, the laminating adhesive is mainly a two-liquid reactive adhesive consisting of a polyol component and a polyisocyanate component, and forms a urethane adhesive layer. As a laminating method, it is common to apply an adhesive in a uniform amount to the entire surface of the printing layer by a known method, and then laminate the substrate film on the laminating side by thermocompression bonding.
In the above situation, for example, Patent Document 1 discloses a technology in which a polyol component and a polyisocyanate component are separately applied onto a printing layer by an inkjet method to use a two-component curing solventless adhesive that has high reactivity but a short pot life.

JP 2019-098285 A

However, the method described in Patent Document 1 applies the adhesive regardless of the design of the printed layer, and the adhesive is applied to the thin printed layer where the adhesive penetration is small in the same way as to the thick printed layer. Therefore, the amount of adhesive applied is uniform over the entire surface of the substrate, and the amount is the same in the thin printed layer and the thick printed layer. However, since the adhesive is easily absorbed in the thick printed layer, the entire surface of the printed layer, including the thin printed layer where the adhesive penetration is small, is coated with a laminating adhesive in an amount exceeding the amount necessary to exert adhesive force. Therefore, from the viewpoint of economy and environmental load, improvement is desired. In general, solventless adhesives are designed to have a low viscosity to provide coating suitability, and therefore there is a problem that the thin printed layer (including the plain area) is prone to appearance defects such as orange peel.
Therefore, an object of the present invention is to provide a method for producing a laminate which is excellent in terms of economy and reduction of the environmental load and which is free from defects in appearance such as orange peel.

As a result of extensive research into solving the above problems, we discovered that the above problems could be solved by the embodiment shown below, and thus completed the present invention.

An embodiment of the present invention relates to a method for producing a laminate having at least a substrate 1, a printed layer having a thickness distribution, an adhesive layer formed from a reactive adhesive containing a polyol base and a polyisocyanate curing agent, and a substrate 2 in this order, the method including step 1 of applying the reactive adhesive to the printed layer of a printed matter having at least the substrate 1 and the printed layer having a thickness distribution and/or to the substrate 2 such that the amount of reactive adhesive applied is greater at locations where the printed layer is thick than at locations where the printed layer is thin, and step 2 of bonding the printed layer of the printed matter and the substrate 2 together via the adhesive layer formed from the reactive adhesive.

Another embodiment of the present invention relates to a method for producing the laminate, in which the reactive adhesive is applied by a coating method including at least one method selected from the group consisting of an inkjet coating method and a spray coating method.

Another embodiment of the present invention relates to a method for producing the laminate, in which step 1 includes step a1 of applying the reactive adhesive to the entire surface of the printed layer of the printed material comprising the substrate 1 and the printed layer having a thickness distribution and/or the substrate 2, and step a2 of applying the reactive adhesive to the printed layer of the printed material comprising the substrate 1 and the printed layer having a thickness distribution and/or the substrate 2 at a location where the printed layer is thick.

Another embodiment of the present invention relates to a method for producing the laminate, in which step a1 is performed by a gravure coating method or a spray coating method, and step a2 is performed by an inkjet coating method.

Another embodiment of the present invention relates to a method for producing the laminate, in which step 1 includes step b1 of applying the reactive adhesive onto the printed layer of a printed material having the substrate 1 and a printed layer having a thickness distribution, and/or onto the substrate 2, using an inkjet application method.

Another embodiment of the present invention relates to an adhesive application method for applying a reactive adhesive containing a polyol base and a polyisocyanate curing agent onto a printed layer of a printed material having at least a substrate 1 and a printed layer having a thickness distribution, the adhesive application method including a step of applying the reactive adhesive so that the amount of the reactive adhesive applied is greater in areas where the printed layer is thick than in areas where the printed layer is thin.

The present invention provides a method for producing a laminate that is economical, reduces the environmental impact, and is free of appearance defects such as orange peel.

<Method of manufacturing laminate>
The present invention is a method for manufacturing a laminate having at least a substrate 1, a printed layer having a thickness distribution, an adhesive layer formed from a reactive adhesive containing a polyol base agent and a polyisocyanate curing agent, and a substrate 2, in this order, and is characterized by comprising step 1 of applying the reactive adhesive onto the printed layer of a printed matter having at least the substrate 1 and the printed layer having a thickness distribution and/or onto the substrate 2 such that the amount of reactive adhesive applied is greater at areas where the printed layer is thick than at areas where the printed layer is thin, and step 2 of bonding the printed layer of the printed matter and the substrate 2 together via the adhesive layer formed from the reactive adhesive.
By adjusting the amount of adhesive applied depending on the thickness of the printed layer, it is possible to obtain a laminate that is economical, reduces the environmental load, and is free of appearance defects such as orange peel, without applying excessive adhesive to areas where the printed layer is thin.
The present invention will be described in detail below.

<Step 1>
In step 1, the method of applying the reactive adhesive is not particularly limited and can be appropriately selected from known application methods. Examples of such application methods include gravure application, flexo application, roll coater application, inkjet application, and spray application. The application method may be used alone or in combination of two or more methods.
In the present invention, the amount of reactive adhesive applied varies depending on the thickness of the printed layer, and the amount of reactive adhesive applied is greater in areas where the printed layer is thick than in areas where the printed layer is thin. For example, when using a gravure coating method, the amount of adhesive applied can be adjusted in correlation with the thickness of the printed layer by using a gravure cylinder plate according to the design of the printed layer. In addition, when using an inkjet coating method, the amount of adhesive applied can be adjusted on demand according to the design of the printed layer. In addition, the method of changing the amount of adhesive applied is not limited to the above, and may be appropriately selected from known methods such as a method of applying multiple times while changing the application range. Among them, the inkjet coating method is preferable because it is economically superior.

In step 1, the reactive adhesive is applied onto the substrate 1 and/or substrate 2. That is, the reactive adhesive may be applied onto the substrate 1, may be applied onto the substrate 2, or may be applied onto both the substrate 1 and the substrate 2. An example of applying the adhesive onto both substrates is a method in which the adhesive is applied using an inkjet coating method only to portions of the substrate 1 where the printing layer is thick, while the adhesive is applied to the entire surface of the substrate 2 using a gravure coating method.
When the reactive adhesive is applied to both substrate 1 and substrate 2, the amount of adhesive applied represents the sum of the amounts applied to both substrates.

A preferred embodiment of step 1 includes step a1 of applying a reactive adhesive to the entire surface of the printed layer of a printed material comprising a substrate 1 and a printed layer having a thickness distribution, and/or to the entire surface of substrate 2, and step a2 of applying a reactive adhesive to the printed layer of a printed material comprising a substrate 1 and a printed layer having a thickness distribution, and/or to the portions of the printed layer on substrate 2 where the printed layer is thick. By applying the reactive adhesive uniformly to the entire surface in step a1, and then applying the reactive adhesive only to the portions of the printed layer where the printed layer is thick, the amount of application can be controlled, and the amount of application in the portions of the printed layer where the printed layer is thick can be made greater than the amount of application in the portions of the printed layer where the printed layer is thin. Step a1 is preferably performed by a gravure application method or a spray application method, and step a2 is preferably performed by an inkjet application method.

Another preferred embodiment of step 1 includes step b1 of applying a reactive adhesive onto the printed layer of a printed material having a substrate 1 and a printed layer having a thickness distribution, and/or onto the substrate 2, using an inkjet coating method. By using the inkjet coating method, the coating amount can be easily controlled on demand according to the thickness of the printed layer, and the coating amount in areas where the printed layer is thick can be made greater than the coating amount in areas where the printed layer is thin.

[Base material 1]
The substrate 1 used in the present invention is not particularly limited, and may be a film- or sheet-shaped plastic substrate that is generally used for packaging materials. These may also be laminated.
Examples of the plastic substrate include films of thermoplastic resins and thermosetting resins, and preferably films of thermoplastic resins. Examples of the thermoplastic resins include polyolefin resins, polyester resins, polyamide resins, polystyrene resins, vinyl chloride resins, vinyl acetate resins, AS resins, ABS resins, acrylic resins, acetal resins, polycarbonate resins, cellulose resins, and cellulose-based plastics.

More specifically, polyolefin resin films such as polyethylene (PE) and biaxially oriented polypropylene (OPP), polyester resin films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polylactic acid (PLA), polystyrene resin films, polyamide resin films such as nylon 6 and poly-p-xylylene adipamide (MXD6 nylon), polycarbonate resin films, polyacrylonitrile resin films, polyimide resin films, cellophane films, laminates thereof (for example, nylon 6/MXD6/nylon 6, nylon 6/ethylene-vinyl alcohol copolymer/nylon 6) and mixtures thereof, and the like are used. Among these, those having mechanical strength and dimensional stability are preferred.
The plastic substrate may contain additives such as antistatic agents and ultraviolet protection agents as necessary, and may be provided with a vapor-deposited layer of silica, alumina, or the like.

When the substrate 1 is a laminate of multiple substrates, the substrates are preferably laminated together via an adhesive layer, and may have a metal foil layer such as aluminum foil. There are no limitations on the method of forming the adhesive layer, and it can be formed by a known method using a known adhesive.

The thickness of the substrate 1 is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and further preferably 10 μm or more and 50 μm or less. The surface of the substrate 1 may be subjected to a corona treatment or a low-temperature plasma treatment.
The substrate 1 may also have a coating layer such as an anchor coating or a primer coating in order to improve adhesion to a printing layer, which will be described later.

[Printed materials]
The printed matter in the present invention includes at least a substrate 1 and a printed layer having a thickness distribution. The printed layer only needs to have a thickness distribution, and may have a plain portion. The method for forming the printed layer is not limited, and examples thereof include gravure printing, flexographic printing, screen printing, offset printing, offset gravure, liquid electrophotography (LEP), and inkjet (IJ).
The printing ink used to form the printed layer is not particularly limited, and solvent-based ink, water-based ink, UV-curable ink, two-component curable ink, toner ink, etc. can be used.
The thickness of the printed layer is not particularly limited, but is generally adjusted to a range of 0.5 to 3 μm. The thickness of the printed layer can be appropriately changed depending on the design.

[Adhesive layer]
The adhesive layer in the present invention is formed from a reactive adhesive containing a polyol base and a polyisocyanate curing agent, and can be formed by applying the reactive adhesive to the printed layer of a printed matter having at least a substrate 1 and a printed layer having a thickness distribution, and/or to the substrate 2, so that the amount of reactive adhesive applied is greater in areas where the printed layer is thick than in areas where the printed layer is thin. In other words, there is a positive correlation between the thickness of the printed layer and the amount of reactive adhesive applied.
When a reactive adhesive consisting of a polyol base and a polyisocyanate curing agent is applied onto a printed layer, the polyisocyanate curing agent penetrates into the printed layer. The thicker the printed layer, the greater the amount of penetration. If a large amount of polyisocyanate curing agent penetrates, the polyisocyanate curing agent in the adhesive layer will be insufficient, resulting in insufficient curing. By making the thickness of the printed layer and the amount of reactive adhesive applied positively correlated, it is possible to suppress insufficient curing in areas where the printed layer is thick, and there is no need to use excessive adhesive in areas where the printed layer is thin, which improves economic efficiency in terms of material costs and reduces environmental load.
The reactive adhesive may be applied continuously after the printing layer is formed without winding the printed matter into a roll, or may be applied after the printed matter has been wound into a roll.

If the amount of reactive adhesive applied at the thinnest part of the printed layer is CW1 (g/ ^m2 : solids equivalent), and the amount of reactive adhesive applied at the thickest part of the printed layer is CW2 (g/ ^m2 : solids equivalent), the amount of reactive adhesive applied preferably satisfies 0.5<CW1<CW2<5 (g/ ^m2 : solids equivalent), and more preferably further satisfies 1.0<CW1<4 (g/ ^m2 : solids equivalent) and 1.2<CW2<5 (g/ ^m2 : solids equivalent).
The coating amount CW1 is preferably 1.0 to 2.5 g/ ^m2 , the coating amount CW2 is preferably 1.5 to 3.5 g/ ^m2 , and CW2/CW1 is preferably in the range of 1.1 to 6.0.

The adhesive layer in the present invention may be formed from a reactive adhesive containing a polyol base agent and a polyisocyanate curing agent, and a mixture of the polyol base agent and the polyisocyanate curing agent may be applied, or the polyol base agent and the polyisocyanate curing agent may be applied separately.
The method for applying the mixture of the polyol base agent and the polyisocyanate curing agent is preferably, for example, a gravure application method, a flexo application method, or a roll coater application method.
The polyol base agent and the polyisocyanate curing agent can be applied separately by, for example, a gravure coating method, an inkjet coating method, a spray coating method, or the like.

The polyol component contained in the polyol base is not particularly limited, but examples thereof include polyester polyol, polyester urethane polyol, polyether polyol, polyether urethane polyol, polycarbonate polyol, polycarbonate urethane polyol, polycaprolactone polyol, polycaprolactone polyurethane polyol, polyolefin polyol, and acrylic polyol.
Also usable are low molecular weight glycols such as ethylene glycol and propylene glycol, and vegetable oils containing hydroxyl groups such as castor oil, etc. Among these, polyester polyols, polyester urethane polyols, and polyether urethane polyols are preferred from the viewpoint of adhesive strength of the laminate.

The polyisocyanate component contained in the polyisocyanate curing agent is not particularly limited, but examples thereof include aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methylcaproate; 1,4-cyclohexane diisocyanate, 1,3-cyclo Alicyclic diisocyanates such as cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, and 1,3-bis(isocyanatomethyl)cyclohexane; m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, aromatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene or mixtures thereof; triphenyl Polyisocyanate monomers such as organic triisocyanates such as methane-4,4',4"-triisocyanate, 1,3,5-triisocyanate benzene, and 2,4,6-triisocyanate toluene, and organic tetraisocyanates such as 4,4'-diphenyldimethylmethane-2,2'-5,5'-tetraisocyanate; dimers, trimers, biurets, and allophanates derived from the above polyisocyanate monomers, and polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide and the above polyisocyanate monomers.

The polyisocyanate component may be an adduct in which various glycol components shown below are added to the polyisocyanate monomer. Examples of glycol components used to form the adduct include adducts of low molecular weight polyols with a molecular weight of less than 200, such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolpropane, cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, and sorbitol, and polyester polyols, polyether ester polyols, polyester amide polyols, polycaprolactone polyols, polyvalerolactone polyols, acrylic polyols, polycarbonate polyols, polyhydroxy alkanes, castor oil, and polyurethane polyols.

The compounding ratio (NCO/OH (molar ratio)) of the polyol base agent to the polyisocyanate curing agent is not particularly limited, but is generally preferably in the range of 1.1 to 10.
The NCO/OH ratio in the adhesive may be changed depending on the location of the printed layer, and may be changed according to the thickness of the printed layer.
The NCO/OH ratio in the adhesive in the region where the printed layer is relatively thin is preferably in the range of 1.5 to 3.0, and the NCO/OH ratio in the adhesive in the region where the printed layer is relatively thick is preferably in the range of 2.0 to 4.0, and it is preferable that the NCO/OH ratio in the adhesive in the region where the printed layer is relatively thick is greater than the NCO/OH ratio in the adhesive in the region where the printed layer is relatively thin.
When an inkjet coating method is used, for example, the NCO/OH ratio can be adjusted by adjusting the ejection amount of each of the heads ejecting the base agent and the heads ejecting the curing agent, or the ejection amount can be adjusted by increasing or decreasing the number of heads.

The reactive adhesive may be a solventless adhesive, a solvent-based adhesive containing an organic solvent or water, or a water-based adhesive. A solvent-based adhesive containing an organic solvent or water or a water-based adhesive is preferable. The reactive adhesive may further contain additives such as an antioxidant, an ultraviolet absorber, an antifungal agent, a plasticizer, and a lubricant, as necessary.
When an organic solvent or water is contained, after the reactive adhesive is applied, the organic solvent or water can be dried, if necessary, using drying equipment such as a drying oven to form an adhesive layer.

<Step 2>
The substrate 1 and the substrate 2 are laminated and bonded together via a reactive adhesive layer to obtain a laminate.
The method for bonding the substrate 1 and the sealant substrate 2 is not particularly limited and can be appropriately selected from known methods. A preferred example of such a method is a method using a hot nip roll.

[Base material 2]
The substrate 2 used in the present invention may be, for example, a sealant substrate in addition to the substrates exemplified as the substrate 1 described above, and may be a laminate obtained by stacking these.
Examples of the sealant substrate include polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), acid-modified polyethylene, non-oriented polypropylene (CPP), acid-modified polypropylene, copolymerized polypropylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester copolymer, ethylene-(meth)acrylic acid copolymer, and ionomer. The substrate 2 is preferably a sealant substrate, and contains polyolefin.
The substrate 2 may contain additives such as antistatic agents and ultraviolet protection agents as necessary, and may be provided with a vapor-deposited layer of aluminum, silica, alumina, or the like.

The thickness of the substrate 2 is not particularly limited, and is preferably 10 μm to 150 μm, more preferably 20 μm to 70 μm, in consideration of processability into packaging containers or heat sealability. The substrate 2 may be provided with projections and recesses having a height difference of about several μm to impart slipperiness and tearability of the packaging material. The surface of the substrate 2 may be corona-treated or low-temperature plasma-treated.
Furthermore, a sealant layer may be provided on the outermost layer of the substrate 2, and the sealant layer may be either a heat sealant layer or a cold sealant layer.

In this way, by using this invention, the amount of adhesive applied can be optimized according to the design of the printing layer, improving economic efficiency in terms of material costs and reducing the environmental burden by eliminating excessive material use, making it useful in the packaging material field.

The present invention will be specifically described below with reference to examples and comparative examples. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

Preparation and Manufacturing of Reactive Adhesives
(Reactive adhesive Ad1)
17 parts of solvent-based polyester polyol TM-569 (manufactured by Toyo Morton, solid content 62%), 0.8 parts of aliphatic isocyanate CAT-RT37 (manufactured by Toyo Morton, solid content 95%), and ethyl acetate were mixed to obtain a reactive adhesive Ad1 with a solid content of 30%.

(Main component A1)
Solvent-based polyester polyol TM-569 (manufactured by Toyo-Morton, solid content 62%) was diluted with ethyl acetate to obtain main component A1 with a solid content of 20%.

(Main component A2)
98 parts of Sannix PP-200 (manufactured by Sanyo Chemical Industries, Ltd.) and 2 parts of Sannix GP-250 (manufactured by Sanyo Chemical Industries, Ltd.) were mixed together to obtain a base agent A2.

(Curing agent B1)
Aliphatic isocyanate CAT-RT37 (manufactured by Toyo-Morton, solid content 95%) was diluted with ethyl acetate to obtain a curing agent B1 with a solid content of 5%.

(Curing agent B2)
Polymeric MDI Millionate MR-100 (manufactured by Tosoh Corporation) was used as hardener B2.

<Preparing printing ink>
(Water-based ink set P1)
[Preparation of Pigment Dispersions 1C, 1M, 1Y, and 1K]
20 parts of C.I. Pigment Blue 15:3, 20 parts of a varnish (solid content 25%) of a colorant dispersion resin (a water-soluble resin containing styrene, acrylic acid, and stearyl methacrylate as constituent units in a mass ratio of 25:40:35, with a weight average molecular weight of 25,000 and an acid value of 185 mgKOH/g), and 60 parts of water were added to a mixing vessel, and then thoroughly mixed with a stirrer. Next, dispersion was performed using a 0.6 L volume Dyno Mill (a bead mill manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads having a diameter of 0.5 mm, to obtain a cyan pigment dispersion (referred to as pigment dispersion 1C).
In addition, magenta, yellow, and black pigment dispersions (referred to as Pigment Dispersion 1M, Pigment Dispersion 1Y, and Pigment Dispersion 1K, respectively) were obtained in the same manner as Pigment Dispersion 1C, except that the pigments were changed to C.I. Pigment Red 122, C.I. Pigment Yellow 14, and carbon black, respectively.

[Preparation of Binder Resin 1]
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 72.4 parts of 2-butanone and substituted with nitrogen gas. After heating the reaction vessel to 80°C, a mixture of 4.5 parts of methacrylic acid, 5.0 parts of 2-hydroxyethyl methacrylate, 90.5 parts of methyl methacrylate, and 12 parts of V-601 (polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 80°C for 3 hours, and then 0.6 parts of V-601 was added, and the reaction was continued for another 2 hours at 80°C to obtain a solution of binder resin 1, which is a hydrosol. The weight average molecular weight of the binder resin 1 measured using a GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with a TSKgel column (manufactured by Tosoh Corporation) and an RI detector and THF as a developing solvent was about 7,000.
After cooling the solution of binder resin 1 to 50°C, 4.7 parts of dimethylaminoethanol was added to neutralize, and then 140 parts of water was added. Thereafter, the inside of the reaction vessel was heated to 78°C or higher, and 2-butanone was distilled off by azeotropy with water, and then the solid content was adjusted with water to 30%, to obtain a varnish of binder resin 1. The acid value and hydroxyl value of binder resin 1 calculated from the constituent units of the resin were 29.3 mgKOH/g and 21.6 mgKOH/g, respectively. The glass transition temperature (Tg) measured using a DSC (PerkinElmer, DSC6000) was 103°C.

[Preparation of Water-Based Ink Set P1]
20 parts of pigment dispersion liquid 1C, 21 parts of binder resin 1 varnish (solid content 30%), 25 parts of 1,2-propanediol, 1 part of Surfynol 465 (acetylene-based surfactant manufactured by Shin-Etsu Chemical Co., Ltd.), 0.1 part of Proxel GXL (preservative manufactured by LONZA Corporation), and 32.9 parts of water were sequentially charged into a mixing vessel. Next, the inside of the mixing vessel was heated to 50°C, and the mixture was mixed with a stirrer for 1 hour. Then, filtration was carried out using a depth-type filter with a pore size of 1 μm to remove coarse particles, thereby obtaining a cyan water-based ink (referred to as ink 1C).
In addition, magenta, yellow and black water-based inks (referred to as Ink 1M, Ink 1Y and Ink 1K, respectively) were obtained in the same manner as Ink 1C, except that the pigment dispersion was changed to Pigment Dispersion 1M, Pigment Dispersion 1Y and Pigment Dispersion 1K, respectively.
The four color inks, Ink 1C, Ink 1M, Ink 1Y, and Ink 1K, thus prepared were designated as water-based ink set P1.

<Production of Laminate>
Example 1
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, the reactive adhesive Ad1 was successively applied onto the printed layer by gravure coating, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The gravure cylinder used for applying the adhesive had a pattern with different line numbers formed in the area where the blue and white of the printed layer overlapped and in the area where only white was printed, with a 110-line lattice pattern formed in the area where the blue and white overlapped and a 150-line lattice pattern formed in the area where only white was printed. The amount of reactive adhesive applied in the area where the blue and white overlapped was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied in the area where only white was printed was 2.5 g/ ^m2 (solids equivalent).

Example 2
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, the reactive adhesive Ad1 was successively applied onto the printed layer by gravure coating, and the solvent was dried in a drying oven.
After the solvent had dried, the main agent A1 was successively ejected from a first inkjet head onto the overlapping areas of the blue and white printed layers using an inkjet coating method, and then the curing agent B1 was ejected from a second inkjet head onto the overlapping areas of the blue and white printed layers, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The gravure cylinder used for applying the adhesive was a 150-line lattice type with a pattern formed over the entire surface. The inkjet head used was a KJ4C-0360 (manufactured by Kyocera). The amount of reactive adhesive applied in the area where the blue and white of the printed layer overlapped was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied in the area where only the white of the printed layer was printed was 2.5 g/ ^m2 (solids equivalent).

Example 3
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, reactive adhesive Ad was successively applied onto the printed layer by a spray coating method, and the solvent was dried in a drying oven. After that, main agent A1 was ejected from a first inkjet head by an inkjet coating method onto the areas where the blue and white of the printed layer overlap, and curing agent B1 was ejected from a second inkjet head onto the areas where the blue and white of the printed layer overlap, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The inkjet head used was KJ4C-0360 (manufactured by Kyocera). The amount of reactive adhesive applied in the area where the blue and white of the printed layer overlap was 3.5 g/m ² (solid content equivalent), and the amount of reactive adhesive applied in the area where only the white of the printed layer was printed was 2.5 g/m ² (solid content equivalent).

Example 4
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, the main agent A1 was successively ejected onto the printed layer from the first inkjet head and the curing agent B1 was ejected from the second inkjet head using an inkjet coating method, with the amount of ejection being varied at the areas where only the white of the printed layer was printed and at the areas where the blue and white of the printed layer overlapped, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The inkjet head used was KJ4C-0360 (manufactured by Kyocera). The amount of reactive adhesive applied in the area where the blue and white of the printed layer overlap was 3.5 g/m ² (solid content equivalent), and the amount of reactive adhesive applied in the area where only the white of the printed layer was printed was 2.5 g/m ² (solid content equivalent).

(Examples 5 and 6)
A laminate was obtained in the same manner as in Example 4, except that the amount of coating applied to the areas where the indigo and white of the printed layer overlap and the amount of coating applied to the areas where only the white of the printed layer is printed were changed as shown in Table 1.

(Example 7)
A laminate was obtained in the same manner as in Example 2, except that the printing method was changed to a flexographic printing method and the inks were changed to Aquaecol white ink and indigo ink (manufactured by Toyo Ink Co., Ltd.). The residual moisture in the area where only the white of the Aquaecol printed layer was printed was 4.8 g/ ^m2 , and the residual moisture in the area where the indigo and white printed layers overlapped was 7.3 g/ ^m2 .

(Example 8)
In Example 2, the printing method was changed to an inkjet printing method, and the ink was changed to ink set P1. A laminate was obtained in the same manner as in Example 2, except that magenta was printed over the entire surface of the substrate at a printing rate of 150%, and yellow, cyan, and black were printed on a portion of the substrate at a printing rate of 300% by multiplying each of them at a printing rate of 50%, thereby producing a printed matter with a thickness distribution. The thickness of the area where only magenta was printed was 0.8 μm, and the thickness of the area where magenta, yellow, cyan, and black were printed in layers was 1.7 μm.

(Example 9)
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
Thereafter, the polyethylene terephthalate (PET) on which the printed layer was formed and wound into a roll was unwound again, and the reactive adhesive Ad1 was applied onto the printed layer by a gravure coating method, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The gravure cylinder used for applying the adhesive had a pattern with different line numbers formed in the area where the blue and white of the printed layer overlapped and in the area where only white was printed, with a 110-line lattice pattern formed in the area where the blue and white overlapped and a 150-line lattice pattern formed in the area where only white was printed. The amount of reactive adhesive applied in the area where the blue and white overlapped was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied in the area where only white was printed was 2.5 g/ ^m2 (solids equivalent).

(Example 10)
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
Thereafter, the polyethylene terephthalate (PET) on which the printed layer had been wound into a roll was unwound again, and an inkjet coating method was used to apply the base agent A1 from the first inkjet head and then the curing agent B1 from the second inkjet head only to the areas where the indigo and white overlapped, and the solvent was dried in a drying oven.
Next, the reactive adhesive Ad1 was applied onto a 100 μm-thick linear low-density polyethylene (LLDPE) sheet by gravure coating, and the solvent was dried in a drying oven.
Next, the reactive adhesive surface consisting of the base agent A1 and the curing agent B1 formed on polyethylene terephthalate (PET) and the Ad1 surface formed on linear low density polyethylene (LLDPE) were pressed together using a nip roll at 50°C, and the adhesive layer was cured by aging for 4 days in an oven at 40°C, thereby obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The gravure cylinder used for applying the adhesive was a 150-line lattice type with a pattern formed over the entire surface. The inkjet head used was KJ4C-0360 (manufactured by Kyocera). The amount of reactive adhesive applied (i.e., the total of reactive adhesive Ad1, base agent A1, and hardener B1) was 3.5 g/ ^m2 (solid content equivalent) where indigo and white overlapped, and 2.5 g/ ^m2 (solid content equivalent) where only white was printed.

Example 11
A laminate was obtained in the same manner as in Example 1, except that the 12 μm-thick polyethylene terephthalate (PET) in Example 1 was changed to a 12 μm-thick MDO PE Film (manufactured by Windmiller).

(Comparative Example 1)
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, the reactive adhesive Ad1 was successively applied onto the printed layer by gravure coating, and the solvent was dried in a drying oven.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days, obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The gravure cylinder used for applying the adhesive had a pattern with different line numbers formed in the area where the blue and white of the printed layer overlapped and in the area where only white was printed, with a 180-line lattice pattern formed in the area where the blue and white overlapped and a 110-line lattice pattern formed in the area where only white was printed. The amount of reactive adhesive applied in the area where the blue and white overlapped was 1.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied in the area where only white was printed was 3.5 g/ ^m2 (solids equivalent).

(Comparative Example 2)
Using a two-color gravure printer, LP Bio indigo ink (manufactured by Toyo Ink Co., Ltd.) and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) were applied in that order onto a 12 μm thick sheet of polyethylene terephthalate (PET). The indigo ink was applied to a portion of the PET, and the white ink was applied to the entire surface, forming a printed layer with a thickness distribution. The thickness of the area where the indigo and white overlapped was 1.5 μm, and the thickness of the area where only white was printed was 1 μm.
After forming the printed layer, the base material A2 was successively ejected from a first inkjet head onto the entire surface of the printed layer by an inkjet coating method, and further the curing agent B2 was ejected from a second inkjet head onto the entire surface of the printed layer.
Next, a 100 μm thick linear low density polyethylene (LLDPE) was pressed using nip rolls at 50° C., and the adhesive layer was hardened by aging in an oven at 40° C. for 4 days to obtain a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The inkjet head used was KJ4C-0360 (manufactured by Kyocera). The amount of reactive adhesive applied was 3.5 g/m ² (solids equivalent) for both the area where the blue and white printed layers overlapped and the area where only the white printed layer was printed.

<Evaluation of Laminate>
The laminate obtained was evaluated for laminate appearance, laminate strength, and cost efficiency. The results are shown in Table 1.

[Laminate appearance]
The appearance of the obtained laminate was visually inspected and evaluated according to the following criteria.
A: No smudges, defects, or unevenness, and the appearance is good (good)
B: Poor appearance such as blurring, defects, unevenness, etc. is observed (not acceptable)

[Lamination strength]
The laminate obtained was cut into test pieces with a width of 15 mm and a length of 300 mm at the overlapping area of indigo and white and at the area where only white was printed. Based on JIS K6854, the T-type peel strength [N/15 mm] between the PET or HDPE and the LLDPE was measured by pulling at a peel rate of 300 mm/min under an environment of 20°C and 65% relative humidity using an Instron tensile tester. The measurement was performed five times, and the average value was taken as the adhesive strength. The obtained adhesive strength and the state of the adhesive after peeling were evaluated according to the following criteria.
S: Adhesive strength is 3.0 N/15 mm or more (very good)
A: Adhesive strength is 1.0 N/15 mm or more and less than 3.0 N/15 mm, and the adhesive layer has no tack (good)
B: The adhesive strength is 1.0 N/15 mm or more, but less than 3.0 N/15 mm and the adhesive layer has tack, or the adhesive strength is less than 1.0 N/15 mm (not acceptable)

[Economic efficiency and reduced environmental impact]
Those in which the amount of adhesive applied was less than the conventional amount applied, which corresponds to Comparative Example 2, were rated "good", and those which were equal to or greater were rated "poor".

The abbreviations in Table 1 are as follows.
12 μm PET: Futamura Chemical Co., Ltd. biaxially oriented polyester film "FE2001", thickness 12 μm
100 μm LLDPE: Mitsui Chemicals Tocello linear low-density polyethylene film "TUX-FC-D", thickness 100 μm
HDPE: Biaxially oriented high density polyethylene film "MDO PE Film" manufactured by Windmiller, thickness 12 μm

According to the results in Table 1, the laminate produced by the manufacturing method of the present invention had excellent laminate appearance and adhesive strength even when the amount of adhesive applied was reduced, and it was possible to achieve both economic efficiency and reduced environmental impact.
On the other hand, the laminate appearance was deteriorated in Comparative Example 1. This is presumably because the amount of adhesive applied in the area where the indigo and white overlap was less than the amount of adhesive applied in the area where only the white was printed, resulting in a thicker printed layer, and more adhesive penetrated into the printed layer in the area where the indigo and white overlap than in the area where only the white was printed, resulting in an uneven thickness of the adhesive layer on the printed layer.
Comparative Example 2 corresponds to Patent Document 1, and the amount of adhesive applied to the area where the indigo and white overlap is the same as that to the area where only white is printed, so it was inferior in terms of economy and reduction of environmental load. Furthermore, the solvent-free adhesive had low cohesive strength, so the appearance and adhesive strength were reduced.

Claims (6)

A method for producing a laminate having at least a substrate 1, a printed layer having a thickness distribution, an adhesive layer formed from a reactive adhesive containing a polyol base agent and a polyisocyanate curing agent, and a substrate 2 in this order, comprising:
the printed layer having the thickness distribution is formed from one or more printing inks selected from the group consisting of a solvent-based ink, a water-based ink, a UV-curable ink, a two-component curable ink, and a toner ink;
A step 1 of applying the reactive adhesive onto a printed layer of a printed matter having at least a substrate 1 and a printed layer having a thickness distribution and/or onto the substrate 2 such that the amount of the reactive adhesive applied is greater in areas where the printed layer is thick than in areas where the printed layer is thin;
A step 2 of bonding the printed layer of the printed matter and the substrate 2 via an adhesive layer formed from the reactive adhesive;
The method for producing a laminate comprising the steps of: The method for producing a laminate according to claim 1, wherein the reactive adhesive is applied by a coating method including at least one selected from the group consisting of an inkjet coating method and a spray coating method. The step 1 includes a step a1 of applying the reactive adhesive onto a printed layer of a printed matter having the substrate 1 and a printed layer having a thickness distribution and/or onto the entire surface of the substrate 2;
A method for producing a laminate as described in claim 1 or 2, comprising a step a2 of applying the reactive adhesive onto a printed layer of a printed matter having the substrate 1 and a printed layer having a thickness distribution, and/or onto areas of the substrate 2 where the printed layer is thick. The method for producing a laminate according to claim 3, wherein step a1 is performed by a gravure coating method or a spray coating method, and step a2 is performed by an inkjet coating method. The method for producing a laminate according to claim 1 or 2, wherein step 1 includes step b1 of applying the reactive adhesive onto the printed layer of a printed matter having the substrate 1 and a printed layer having a thickness distribution, and/or onto the substrate 2, using an inkjet application method. An adhesive application method for applying a reactive adhesive containing a polyol base agent and a polyisocyanate curing agent onto a printed layer of a printed matter having at least a substrate 1 and a printed layer having a thickness distribution, comprising:
the printed layer having the thickness distribution is formed from one or more printing inks selected from the group consisting of a solvent-based ink, a water-based ink, a UV-curable ink, a two-component curable ink, and a toner ink;
An adhesive application method comprising a step of applying the reactive adhesive so that an amount of the reactive adhesive applied is greater in areas where the printed layer is thick than in areas where the printed layer is thin.