JP7632129B2 - 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 composed of a printed part and a plain part formed by printing ink by gravure printing, flexographic printing, on-demand printing such as inkjet printing, etc. 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. The laminating method is generally to apply a uniform amount of adhesive to the entire surface of the printing layer by a gravure coater or roll coater, and then to bond the base film on the bonding side by thermocompression bonding. Therefore, the amount of adhesive applied is the same for the plain part and the printing part, and the amount applied to the plain part where the adhesive does not penetrate is more than the amount required to develop adhesiveness. Therefore, improvement is desired from the viewpoint of economic efficiency and environmental load.

In the above situation, for example, Patent Document 1 discloses a technology that uses a two-component curing solventless adhesive that is highly reactive but has a short pot life by inkjet coating a polyol component and a polyisocyanate component separately onto a printing layer.

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 plain areas where the adhesive does not penetrate in the same way as the printed areas. In general, solvent-free adhesives are designed to have low viscosity to provide application suitability, and therefore have the problem that they are prone to causing poor appearance such as orange peel, particularly in the plain areas.
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 resolving the above-mentioned issues, we have discovered that the following embodiment can resolve the above-mentioned issues, and have 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 consisting of a plain portion and a printed portion, 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 onto the printed layer of a printed matter having at least the substrate 1 and a printed layer consisting of a plain portion and a printed portion such that, when the amount of reactive adhesive applied on the plain portion is CW1 (g/ ^m2 : solid content equivalent) and the amount of reactive adhesive applied on the printed portion is CW2 (g/ ^m2 : solid content equivalent), the relationship 0.5 (g/ ^m2 : solid content equivalent) < CW1 < CW2 is satisfied; and step 2 of laminating the substrate 2 onto the surface to which the reactive adhesive has been applied.

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, and step a2 of applying the reactive adhesive to the printed portion of the printed layer.

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 to the plain and printed areas of the printed layer 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 matter having at least a substrate 1 and a printed layer consisting of a plain portion and a printed portion, the adhesive application method including a step of applying the reactive adhesive so as to satisfy 0.5 (g/ ^m2 : solids equivalent) < CW1 < CW2, where CW1 (g/ ^m2 : solids equivalent) is the amount of reactive adhesive applied onto the plain portion and CW2 (g/ ^m2 : solids equivalent) is the amount of reactive adhesive applied onto the printed portion.

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

<Method of manufacturing laminate>
The present invention is a method for manufacturing a laminate having, in this order, at least a substrate 1, a printed layer consisting of a plain portion and a printed portion, an adhesive layer formed from a reactive adhesive containing a polyol base and a polyisocyanate curing agent, and a substrate 2, and is characterized in that the method includes a step 1 of applying the reactive adhesive onto the printed layer of a printed matter having at least the substrate 1 and a printed layer consisting of a plain portion ^and a printed portion so that, when the amount of reactive adhesive applied on the plain portion is CW1 (g/ ^m2 : converted into solids) and the amount of reactive adhesive applied on the printed portion is CW2 (g/ ^m2 : converted into solids), the relationship 0.5 (g/m2: converted into solids) < CW1 < CW2 is satisfied, and a step 2 of laminating the substrate 2 onto the surface to which the reactive adhesive has been applied.
By satisfying the above-mentioned application amounts for the plain and printed areas, it is possible to obtain a laminate that is economical, reduces the environmental impact, and is free of appearance defects such as orange peel, without applying an excess of adhesive to the plain areas.
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 differs between the printed and uncoated areas. For example, when a gravure coating method is used, the amount of adhesive applied can be adjusted between the printed and uncoated areas by using a gravure cylinder plate according to the design of the printed layer. When an inkjet coating method is used, 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 these, the inkjet coating method is preferred because it is economically superior.

A preferred embodiment of step 1 includes step a1 of applying reactive adhesive to the entire surface of the printed layer, and step a2 of applying reactive adhesive to the printed portion of the printed layer. By applying reactive adhesive uniformly to the entire surface in step a1, and then applying reactive adhesive only to the printed portion, the amount of adhesive applied can be controlled, and the amount of adhesive applied to the printed portion can be made greater than the amount of adhesive applied to the plain portion. Step a1 is preferably performed by a gravure coating method or a spray coating method, and step a2 is preferably performed by an inkjet coating method.

Another preferred embodiment of step 1 includes step b1 of applying the reactive adhesive to the plain and printed areas of the printing layer using an inkjet application method. By using the inkjet application method, the amount of application to the printed and plain areas can be easily controlled on demand, and the amount of application to the printed areas can be made greater than the amount of application to the plain areas.

[Substrate 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 plastic substrates, the substrates are preferably laminated together via an adhesive layer. There are no limitations on the method for 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 matter]
The printed matter in the present invention has at least a substrate 1 and a printed layer consisting of a plain part and a printed part. The printed layer only needs to have a plain part and a printed part, and the method of forming the printed layer is not limited. Examples of the method of forming the printed layer 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 portion in 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 portion 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 at least a substrate 1 and a printed layer of a printed matter having a printed layer consisting of a plain area and a printed area, so as to satisfy "0.5 (g/ ^m2 : solids equivalent) < application amount of reactive adhesive on plain area CW1 (g/ ^m2 : solids equivalent) < application amount of reactive adhesive on printed area CW2 (g/ ^m2 : solids equivalent)".
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.

The amount of reactive adhesive applied preferably satisfies 0.5 (g/ ^m2 : solid content equivalent) < CW1 < CW2 < 5 (g/ ^m2 : solid content equivalent), and more preferably further satisfies 0.5 (g/ ^m2 : solid content equivalent) < CW1 < 3 (g/ ^m2 : solid content equivalent) and 1.5 (g/ ^m2 : solid content equivalent) < CW2 < 5 (g/ ^m2 : solid content equivalent).
The coating amount CW1 is preferably 0.5 to 2.0 g/ ^m2 , the coating amount CW2 is preferably 2.0 to 5.0 g/ ^m2 , and CW2/CW1 is preferably in the range of 1.1 to 6.0. By making the coating amount CW2 of the printed portion larger than the coating amount CW1 of the plain portion, it is possible to suppress the polyisocyanate contained in the reactive adhesive from penetrating into the printed portion. In addition, it is possible to suppress the inhibition of curing caused by the reaction between the moisture remaining in the printed portion and components that can react with polyisocyanate and the polyisocyanate contained in the reactive adhesive. In addition, by making the coating amount CW1 of the plain portion smaller than CW2, it is possible to avoid using an excessive amount of adhesive, improve economy in terms of material costs, and reduce the environmental burden.

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 ratio (molar ratio)) of the polyol base agent and 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 the NCO/OH ratio in the adhesive on the plain area may be the same as or different from the NCO/OH ratio in the adhesive on the printed area.
The NCO/OH ratio in the adhesive on the plain area is preferably in the range of 1.1 to 2.0, and the NCO/OH ratio in the adhesive on the printed area is preferably in the range of 1.5 to 4.0, and it is preferable that the NCO/OH ratio in the adhesive on the printed area is larger than the NCO/OH ratio in the adhesive on the plain area.
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>
In step 1, a substrate 2 is laminated and bonded to the surface coated with the reactive adhesive to obtain a laminate.
The method for bonding the 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.

[Substrate 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
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area 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 in the gravure coating method was patterned with a line number that matched the printed and plain areas of the printing layer, with a 110-line grid pattern for the printed areas and a 180-line grid pattern for the plain areas. The amount of reactive adhesive applied to the printed areas was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied to the plain areas was 1.5 g/ ^m2 (solids equivalent).

Example 2
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area 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 was dried, the base resin A1 was successively ejected from a first inkjet head onto the printed area using an inkjet coating method, and then the curing agent B1 was ejected from a second inkjet head onto the printed area, 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 in the gravure coating method was one that was entirely formed with a 180-line grid. The inkjet head used was KJ4C-00360 (manufactured by Kyocera). The amount of reactive adhesive applied to the printed area was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied to the plain area was 1.5 g/ ^m2 (solids equivalent).

Example 3
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area was 1 μm.
After forming the printed layer, reactive adhesive Ad was applied onto the printed layer by a spray coating method, the solvent was dried in a drying oven, and then main agent A1 was ejected onto the printed portion from a first inkjet head by an inkjet coating method, and curing agent B1 was ejected onto the printed portion from a second inkjet head. The solvent was then dried in a drying oven, and linear low density polyethylene (LLDPE) having a thickness of 100 μm was pressed with a nip roll at 50° C. and aged in an oven at 40° C. for 4 days to cure the adhesive layer, thereby obtaining a laminate having a configuration of PET/printed layer/adhesive layer/LLDPE.
The inkjet head used was KJ4C-00360 (manufactured by Kyocera). The amount of reactive adhesive applied to the printed area was 3.5 g/m ² (solids equivalent), and the amount of reactive adhesive applied to the plain area was 1.5 g/m ² (solids equivalent).

Example 4
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area was 1 μm.
After forming the printed layer, the main agent A1 was successively ejected onto the printed layer from a first inkjet head and the curing agent B1 was ejected from a second inkjet head using an inkjet coating method, with the ejection amounts being varied for the printed and unprinted areas of the printed layer, 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-00360 (manufactured by Kyocera). The amount of reactive adhesive applied to the printed area was 3.5 g/m ² (solids equivalent), and the amount of reactive adhesive applied to the plain area was 1.5 g/m ² (solids equivalent).

Example 5
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area 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 in the gravure coating method was patterned with a line number that matched the printed and plain areas of the printing layer, with a 110-line grid pattern for the printed areas and a 220-line grid pattern for the plain areas. The amount of reactive adhesive applied to the printed areas was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied to the plain areas was 0.7 g/ ^m2 (solids equivalent).

Example 6
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 ink was changed to Aquaecole white ink (manufactured by Toyo Ink Co., Ltd.). The residual moisture of the Aquaecole white ink was 4.8 g/ ^m2 .

(Example 7)
A laminate was obtained in the same manner as in Example 1, except that in Example 2, the printing method was changed to an inkjet printing method and the ink was changed to ink set P1. The residual moisture of ink set P1 was 2.5 g/ ^m2 , and the residual 1,2-propanediol was 3.6 g/ ^m2 .

(Example 8)
A print layer having a print area and a blank area was formed on a 12 μm-thick polyethylene terephthalate (PET) sheet by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.), and the polyethylene terephthalate (PET) sheet with the print layer formed thereon was wound into a roll. The thickness of the print area 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 in the gravure coating method was patterned with a line number that matched the printed and plain areas of the printing layer, with a 110-line grid pattern for the printed areas and a 180-line grid pattern for the plain areas. The amount of reactive adhesive applied to the printed areas was 3.5 g/ ^m2 (solids equivalent), and the amount of reactive adhesive applied to the plain areas was 1.5 g/ ^m2 (solids equivalent).

(Comparative Example 1)
A printed layer having printed and unprinted areas was formed on a 12 μm-thick sheet of polyethylene terephthalate (PET) by gravure printing using LP Bio white ink (manufactured by Toyo Ink Co., Ltd.). The thickness of the printed area was 1 μm.
After forming the printed layer, the main agent A2 was discharged from the first inkjet head and the curing agent B2 was discharged from the second inkjet head onto the entire surface of the printed layer by inkjet coating. Next, a linear low density polyethylene (LLDPE) having a thickness of 100 μm was pressed with a nip roll at 50° C., and the adhesive layer was cured 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-00360 (manufactured by Kyocera). The amount of reactive adhesive applied was 3.5 g/m ² (solids equivalent) for both the printed and uncoated areas.

(Comparative Example 2)
A laminate was obtained in the same manner as in Example 1, except that the coating amount of the reactive adhesive in the uncoated portion was changed to 0.4 g/m ² (solids content equivalent).

<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 of plain area]
The appearance of the laminate in the plain area 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 of plain area and printed area]
The laminate of the plain part and the printed part were each cut into a width of 15 mm and a length of 300 mm to prepare a test piece. Based on JIS K6854, an Instron tensile tester was used to measure the T-peel strength [N/15 mm] between the PET and the LLDPE at a peel rate of 300 mm/min in an environment of 20°C and 65% relative humidity. The measurement was performed five times, and the average value was taken as the adhesive strength. Evaluation was performed based on the obtained adhesive strength and the state of the adhesive after peeling 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]
A coating amount on the plain part that was less than that on the printed part was rated "good", and a coating amount on the plain part that was equal to or greater than that on the printed part was 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

According to the results in Table 1, the laminates produced by the production method of the present invention had good appearance in the plain areas and excellent adhesive strength. Furthermore, the amount of adhesive applied in the plain areas of these laminates was less than that in the printed areas, making them economical and environmentally friendly.
On the other hand, Comparative Example 1 corresponds to Patent Document 1, and the amount of adhesive applied to the plain and printed areas was the same, which resulted in poor economic efficiency and reduced environmental impact. Furthermore, the solvent-free adhesive had low cohesive strength, which resulted in poor appearance and adhesive strength. Comparative Example 2 had a low amount of adhesive applied to the plain areas, which resulted in poor appearance and adhesive strength.

Claims (6)

A method for producing a laminate having at least a substrate 1, a printed layer having a plain portion and a printed portion, 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:
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 consisting of a plain portion and a printed portion, such that, when the amount of reactive adhesive applied on the plain portion is CW1 (g/ ^m2 : solid content equivalent) and the amount of reactive adhesive applied on the printed portion is CW2 (g/ ^m2 : solid content equivalent), the relationship 0.5 (g/ ^m2 : solid content equivalent) < CW1 < CW2 is satisfied;
A step 2 of laminating the substrate 2 onto the surface to which the reactive adhesive is applied;
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 method for manufacturing a laminate according to claim 1 or 2, wherein step 1 includes step a1 of applying the reactive adhesive to the entire surface of the printed layer, and step a2 of applying the reactive adhesive to the printed portion of the printed layer. 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 manufacturing a laminate according to claim 1 or 2, wherein step 1 includes step b1 of applying the reactive adhesive to the plain and printed areas of the printed layer 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 material having at least a substrate 1 and a printed layer composed of a plain portion and a printed portion, comprising:
The adhesive application method includes a step of applying the reactive adhesive so that 0.5 (g/ ^m2 : solids equivalent) < CW1 < CW2 is satisfied, where CW1 (g/ ^m2 : solids equivalent) is the amount of reactive adhesive applied on the plain portion, and CW2 (g/ ^m2 : solids equivalent) is the amount of reactive adhesive applied on the printed portion.