AU2020324701A1

AU2020324701A1 - Curing agent, two-component adhesive, adhesive composition, cured product, laminate and method for producing same, packing material, and package

Info

Publication number: AU2020324701A1
Application number: AU2020324701A
Authority: AU
Inventors: Masafumi Horiuchi
Original assignee: Toppan Printing Co Ltd
Current assignee: Toppan Inc
Priority date: 2019-08-06
Filing date: 2020-08-03
Publication date: 2021-03-11
Also published as: JP6940014B2; KR20220040430A; TW202206571A; JPWO2021024981A1; JP2021191869A; WO2021024981A1; CN114174461B; CN114174461A

Abstract

Provided are a laminate and a method for producing the same, the laminate being capable of maintaining the adhesive strength between respective layers high enough under high-temperature hydrothermal treatment conditions. A laminate 300 is provided with a first base material 10, an adhesive layer 30, and a second base material 20 in this order, wherein an electrostatic ink composition 50 is printed on an adhesive surface of at least one among the first base material 10 and the second base material 20, and the adhesive layer 30 includes one or both of a polyurethane and epoxy compound, and a crosslinked product thereof.

Description

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DESCRIPTION Title of Invention CURING AGENT, TWO-COMPONENT ADHESIVE, ADHESIVE COMPOSITION, CURED PRODUCT, LAMINATE AND METHOD OF PRODUCING THE SAME, PACKAGING MATERIAL, AND PACKAGE Technical Field

[0001] The present disclosure relates to a curing agent, a two-component adhesive, an adhesive composition, a cured product, a laminate and a method of producing the same, a packaging material, and a package. Background Art

[0002] Packaging bags for sealing and storing a packaged object such as food are known. Packaging utilizing a thin film or sheet is used for packaging bags. Various pieces of information such as products, brands, and manufacturers are printed on such packaging bags. A digital printer using an electrostatic ink composition is known as a printing device therefor.

[0003] For example, Patent Literature 1 proposes that a primer resin be applied to a first flexible substrate such as a PET film to obtain a coated surface, electrostatic printing be performed on the coated surface using a digital printer (Indigo 20000 digital printer for labels and packaging commercially available from HP), and a crosslinking composition be applied. A technique in which a predetermined step is performed in this manner, and then a first flexible substrate coated with a predetermined component and a second flexible substrate are laminated

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to obtain a packaging material has been proposed. Citation List Patent Literature

[0004] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2018-530478 Summary of Invention Technical Problem

[0005] Packaging materials are used for various applications. For example, packaging materials for food packaging retorts may be heated, for example, under high temperature and hot water treatment conditions. In order to maintain the quality of the packaged object under such heating conditions, it is required to maintain a high level of sealability. However, in a laminate including material printed with an electrostatic ink composition by a digital printer, there is a concern that the adhesive strength between layers constituting the laminate will decrease and the sealability of the packaged object will be impaired.

[0006] Therefore, the present disclosure provides a laminate that can maintain a sufficiently high adhesive strength between layers even under high temperature and hot water treatment conditions and a method of producing the same. In addition, the present disclosure provides a curing agent, an adhesive composition, a two-component adhesive and a cured product, which are useful for obtaining such a laminate. In addition, when such a laminate is provided, a packaging material having excellent sealability is provided. In addition, the present disclosure provides a package packaged with a packaging material having excellent sealability.

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Solution to Problem

[0007] The present disclosure provides an adhesive composition adhering a printed surface on which an electrostatic ink composition is printed, which is an adhesive composition including a main agent containing a polyol, a curing agent containing a polyisocyanate, and an epoxy compound. In the adhesive composition, when these components are contained, the printed surface on which an electrostatic ink composition is printed can adhere with high adhesive strength. In addition, the adhesive composition is considered to have an action of cohering the electrostatic ink composition and improving the strength of an electrostatic ink layer. The electrostatic ink composition generally has low heat resistance and water resistance. However, due to the above action, the adhesive composition can maintain high adhesive strength under high temperature and hot water treatment conditions.

[0008] In the adhesive composition, the molar ratio of epoxy groups contained in the epoxy compound with respect to isocyanate groups contained in the polyisocyanate may be 0.5 to 10. Therefore, it is possible to maintain a sufficiently high adhesive strength under high temperature and hot water treatment conditions.

[0009] In the adhesive composition, the molar ratio of isocyanate groups contained in the polyisocyanate with respect to hydroxy groups contained in the polyol may be 0.5 to 10. Therefore, it is possible to form a cured product having high adhesive strength and excellent flexibility.

[0010] The adhesive composition may contain 3 to 25 parts by mass of the epoxy compound with respect to 100 parts by mass of the polyol.

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Thereby, high adhesive strength is maintained and a shear suppression strength is also excellent. Therefore, when adhesive surfaces are adhered to each other with the adhesive composition, it is possible to prevent the adhesive surfaces shifting from each other and the adhesive being squeezed out after adhesion.

[0011] The adhesive composition may contain 10 to 50 parts by mass of the polyisocyanate with respect to 100 parts by mass of the polyol. Therefore, the seal strength and the adhesive strength under high temperature and hot water treatment conditions can be sufficiently increased.

[0012] The adhesive composition may adhere a printed surface on which an electrostatic ink composition is printed and a substrate. An electrostatic ink composition generally has a low heat resistance and water resistance. However, when the printed surface is adhered using the adhesive composition, it is possible to maintain excellent adhesiveness even under conditions in which it is in contact with heated water. Therefore, it is possible to prevent the adhesive strength between the adhesive surfaces from decreasing.

[0013] The polyol may be an aliphatic polyester polyol. The epoxy compound may have epoxy groups at both ends. Thereby, the adhesive composition has high adhesive strength not only at room temperature but also under high temperature and hot water treatment conditions.

[0014] The epoxy compound may include a bifunctional alicyclic epoxy compound. When such an epoxy compound is bifunctional, the number of crosslinking points between the electrostatic ink composition

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and the primer resin can increase, the curing reaction of the adhesive can be promoted, and curing can be facilitated. In addition, when the epoxy compound is alicyclic, it is possible to restrict a reaction with the polyisocyanate due to steric hindrance. Therefore, the curing function can be stably exhibited.

[0015] The polyisocyanate may include xylylene diisocyanate derivatives. The content of xylylene diisocyanate derivatives with respect to an entire of the polyisocyanate may be 10 mass% or more. This makes it possible to increase the reactivity with the polyol and improve the curability.

[0016] A glass transition temperature determined by dynamic viscoelasticity measurement after the adhesive composition is cured may be 20°C or lower. Since such an adhesive composition has excellent flexibility after curing, it is possible to relieve stress generated during laminating. Therefore, it is possible to further increase the adhesive strength.

[0017] The present disclosure provides a curing agent for an adhesive that adheres a printed surface on which an electrostatic ink composition is printed, and includes a polyisocyanate and an epoxy compound, wherein the molar ratio of epoxy groups contained in the epoxy compound with respect to isocyanate groups contained in the polyisocyanate is 0.5 to 10. Since the curing agent has excellent stability in a liquid, an improved curing function of the polyisocyanate can be maintained. Therefore, even under high temperature and hot water treatment conditions, a printed surface on which an electrostatic ink composition is printed can be adhered with sufficiently high

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strength.

[0018] The epoxy compound in the curing agent may include a bifunctional alicyclic epoxy compound. When such an epoxy compound is alicyclic, it is possible to restrict a reaction with the polyisocyanate due to steric hindrance. Therefore, the quality of the curing agent can be stably maintained. Thus, when the epoxy compound is bifunctional, the number of crosslinking points between the electrostatic ink composition and the primer resin can increase, the curing reaction of the adhesive can be promoted, and curing can be facilitated.

[0019] The polyisocyanate in the curing agent may include xylylene diisocyanate derivatives. The content of xylylene diisocyanate derivatives with respect to an entire of the polyisocyanate may be 10 mass% or more. Thereby, the reactivity with the main agent can increase and the curability can be improved.

[0020] The present disclosure provides a two-component adhesive that adheres a printed surface on which an electrostatic ink composition is printed, and includes a first liquid containing a main agent and a second liquid containing any of the above curing agents. Such a two-component adhesive can restrict a reaction of polyisocyanate and maintain a sufficient function as an adhesive. Therefore, the rise in adhesive strength when the first liquid and the second liquid are mixed is also favorable. Then, when the first liquid and the second liquid are mixed to prepare an adhesive composition, and the above adhesive composition is applied to the electrostatic ink composition and cured, the adhesive composition is considered to have an action of cohering the

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electrostatic ink composition and improving the strength of the ink itself. Therefore, even under high temperature and hot water treatment conditions, the printed surface on which an electrostatic ink composition is printed can be adhered with sufficiently high strength.

[0021] The main agent in the two-component adhesive may contain a polyol. The polyol smoothly reacts with a polyisocyanate and is cured. Thus, since the curing agent contains an epoxy compound, the electrostatic ink composition is cured, and under high temperature and hot water treatment conditions, the printed surface on which an electrostatic ink composition is printed can adhere with a sufficiently high adhesive strength.

[0022] The molar ratio of isocyanate groups contained in the polyisocyanate contained in the curing agent with respect to hydroxy groups contained in the polyol contained in the main agent may be 0.5 to 10. Therefore, it is possible to form a cured product having high adhesive strength and excellent flexibility.

[0023] The polyol contained in the main agent may be an aliphatic polyester polyol. The epoxy compound contained in the curing agent may have epoxy groups at both ends. Therefore, an adhesive having high adhesive strength not only at room temperature but also under high temperature and hot water treatment conditions can be obtained.

[0024] The present disclosure provides a cured product obtained by curing any of the above adhesive compositions. Such a cured product adheres the printed surface on which an electrostatic ink composition is printed with a sufficiently high adhesive strength even under high temperature and hot water treatment conditions.

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[0025] A glass transition temperature of the cured product determined by dynamic viscoelasticity measurement may be 20°C or lower. Since such a cured product has excellent flexibility, it is possible to relieve stress generated due to adhesion. Therefore, it is possible to further increase the adhesive strength.

[0026] The present disclosure provides a laminate including a first substrate, an adhesive layer, and a second substrate in this order, wherein an electrostatic ink layer composed of an electrostatic ink composition is provided between at least one of the first substrate and the second substrate, and the adhesive layer, and wherein the adhesive layer contains one or both of a polyurethane and an epoxy compound, and a crosslinked product thereof.

[0027] The electrostatic ink composition and the electrostatic ink layer composed of the electrostatic ink composition generally have low heat resistance and water resistance. However, the laminate has an adhesive layer containing a polyurethane and an epoxy compound. Such an adhesive layer has excellent adhesiveness to the electrostatic ink layer and is considered to have an action of cohering the electrostatic ink composition and improving the strength of the electrostatic ink layer. Therefore, even under high temperature and hot water treatment conditions, it is possible to maintain a sufficiently high adhesive strength between the layers of the laminate. In addition, such a laminate can be produced with high productivity because it is not necessary to separately provide a coating layer of an epoxy compound.

[0028] The present disclosure provides a laminate including a first substrate, an adhesive layer, and a second substrate in this order,

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wherein an electrostatic ink layer composed of an electrostatic ink composition is provided between at least one of the first substrate and the second substrate, and the adhesive layer, and wherein the adhesive layer contains a polymer of a polyol, a polyisocyanate, and an epoxy compound.

[0029] The laminate has an adhesive layer containing the polymer of the polyol, the polyisocyanate, and the epoxy compound. Such an adhesive layer has excellent adhesiveness to the electrostatic ink layer and is considered to have an action of cohering the electrostatic ink composition and improving the strength of the electrostatic ink layer. Therefore, even under high temperature and hot water treatment conditions, it is possible to maintain a sufficiently high adhesive strength between the layers of the laminate. In addition, such a laminate can be produced with high productivity because it is not necessary to separately provide a coating layer of an epoxy compound.

[0030] The laminate may have a primer layer between the first substrate and the electrostatic ink layer. When the primer layer is provided, printing by a digital printer can be facilitated.

[0031] The present disclosure provides a packaging material including any of the above laminates. Since the packaging material includes the above laminate, it is possible to sufficiently maintain excellent sealability of the packaged object even when it is used for applications exposed to high temperature and hot water treatment conditions. Therefore, the packaging material can be used for various applications.

[0032] The present disclosure provides a package including the packaging material and a packaged object packaged with the packaging

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material. Since the package is packaged with the packaging material, it is possible to maintain sufficient quality of the packaged object.

[0033] The present disclosure provides a method of producing a laminate, including a step of printing an electrostatic ink composition on the side of one surface of a first substrate to obtain a printed surface and a step of adhering the printed surface and one surface on the side of a second substrate using any of the above adhesive compositions. In this production method, the printed surface obtained by printing the electrostatic ink composition is adhered to one surface on the side of the second substrate using the adhesive composition. Therefore, the printed surface can be adhered with high adhesive strength. In addition, the adhesive composition is considered to have an action of cohering the electrostatic ink composition and improving the strength of the ink itself. Therefore, a laminate having high adhesive strength under high temperature and hot water treatment conditions can be obtained. In addition, such a laminate can be produced with high productivity because it is not necessary to separately provide a coating layer of an epoxy compound.

[0034] The present disclosure provides a method of producing a laminate including a step of printing an electrostatic ink composition on the side of one surface of a first substrate to obtain a printed surface, a step of mixing the first liquid and the second liquid in any of the above two-component adhesives to prepare an adhesive composition, and a step of adhering the printed surface and one surface on the side of a second substrate using the adhesive composition. In this production method, the printed surface obtained by printing the electrostatic ink

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composition is adhered to one surface on the side of the second substrate using the adhesive composition prepared by mixing the first liquid and the second liquid. Therefore, the printed surface can be adhered with high adhesive strength. In addition, the adhesive composition is considered to have an action of cohering the electrostatic ink composition and improving the strength of the ink itself. Therefore, a laminate having high adhesive strength under high temperature and hot water treatment conditions can be obtained. In addition, such a laminate can be produced with high productivity because it is not necessary to separately provide a coating layer of an epoxy compound. In addition, since the two-component adhesive containing the first liquid and the second liquid is used, the workability during adhering can be improved. In addition, it is possible to prevent the occurrence of poor mixing when the adhesive composition is prepared and it is possible to sufficiently reduce variation in the adhesive strength. Advantageous Effects of Invention

[0035] According to the present disclosure, it is possible to provide a laminate that can maintain a sufficiently high adhesive strength between layers even under high temperature and hot water treatment conditions and a method of producing the same. In addition, the present disclosure provides a curing agent useful for obtaining such a laminate, an adhesive composition, a two-component adhesive and a cured product. In addition, when such a laminate is provided, it is possible to provide a packaging material having excellent sealability. In addition, it is possible to provide a package packaged with a packaging material

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having excellent sealability. Brief Description of Drawings

[0036] FIG. 1 is a schematic cross-sectional view showing an example of a laminate. FIG. 2 is a plan view showing an example of a packaging bag and a package. FIG. 3 is a plan view showing another example of a packaging bag. FIG. 4 is a graph showing change in the NCO reaction rate of an adhesive composition over time. FIG. 5 is a graph showing change in the adhesive strength of the adhesive composition over time. FIG. 6 is a graph showing change in the pot life of the adhesive composition over time. FIG. 7 is a graph showing results of dynamic viscoelasticity measurement of a cured product obtained by curing an adhesive composition of Example 7. FIG. 8 is a graph showing results of dynamic viscoelasticity measurement of a cured product obtained by curing an adhesive composition of Comparative Example 1. Description of Embodiments

[0037] Embodiments of the present disclosure will be described below with reference to the drawings in some cases. However, the following embodiments are only examples for describing the present disclosure, and the present disclosure is not limited to the following content. In the description, components which are the same or components having

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the same function are denoted with the same reference numerals and redundant descriptions will be omitted in some cases. In addition, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. In addition, dimensional ratios in the drawings are not limited to the illustrated ratios.

[0038] An adhesive composition according to one embodiment contains a polyol, a polyisocyanate, and an epoxy compound. For example, the polyol has a number average molecular weight of 400 or more and has two or more hydroxy groups in one molecule. The polyisocyanate has two or more isocyanate groups in one molecule. The polyol and the polyisocyanate each react as a main agent and a curing agent to produce a polyurethane (polyurethane adhesive). The number average molecular weight of the polyol may be, for example, 10,000 or less.

[0039] The polyol may contain at least one selected from the group consisting of a polyester polyol and a polyether polyol. Among these, the polyol may contain the polyester polyol or may contain an aliphatic polyester polyol in order to sufficiently increase the adhesive strength.

[0040] For example, the polyester polyol can be obtained by a condensation reaction or a transesterification reaction between a multivalent alcohol, and a polybasic acid, an alkyl ester thereof, an acid anhydride thereof, or an acid halide thereof. Examples of multivalent alcohols include a low-molecular-weight diol, a low-molecular-weight triol, and a low-molecular-weight polyol having 4 or more hydroxy groups.

[0041] Examples of low-molecular-weight diols include ethylene glycol,

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propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, 3,3-dimethylolheptane, and 2-ethyl-2-butyl-1,3-propanediol.

[0042] Examples of low-molecular-weight triols include glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-(hydroxymethyl)pentane, and 2,2-bis(hydroxymethyl)-3-butanol.

[0043] Examples of low-molecular-weight polyols having 4 or more hydroxy groups include tetramethylolmethane, pentaerythritol, dipentaerythritol, D-sorbitol, xylitol, D-mannitol, and D-mannite.

[0044] Examples of alkyl esters of polybasic acids include methyl esters and ethyl esters of polybasic acids. Examples of acid anhydrides include acid anhydrides derived from polybasic acids. Examples thereof include oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, 2-alkyl anhydride (12 to 18 carbon atoms) succinic acid, tetrahydrophthalic acid anhydride, and trimellitic acid anhydride.

[0045] Examples of acid halides include acid halides derived from the above polybasic acids. Examples thereof include oxalic acid dichloride, adipic acid dichloride, and sebacic acid dichloride.

[0046] The polyether polyol may be a polyalkylene oxide. For example, it may be obtained by an addition reaction of an alkylene

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oxide such as ethylene oxide and/or propylene oxide using a low-molecular-weight polyol as an initiator. Specific examples include polyethylene glycol, polypropylene glycol, and polyethylene polypropylene glycol (random or block copolymer). In addition, examples thereof include polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran.

[0047] Examples of polyisocyanates include polyisocyanate monomers, polyisocyanate derivatives, and isocyanate group-terminated prepolymers. The adhesive composition may contain a plurality of types of polyisocyanates that are different from each other. The molar ratio (NCO/OH) of isocyanate groups contained in the polyisocyanate with respect to hydroxy groups of the polyol may be 0.5 to 10. Such an adhesive composition can form a cured product having high adhesive strength and excellent flexibility.

[0048] Examples of polyisocyanate monomers include aliphatic polyisocyanates, aromatic polyisocyanates, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0049] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methylcaproate.

[0050] Examples of aromatic aliphatic polyisocyanates include

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xylylene diisocyanate derivatives. Examples of xylylene diisocyanate derivatives include xylylene diisocyanate (1,3-xylylene diisocyanate or 1,4-xylylene diisocyanate) (XDI), tetramethylxylylene diisocyanate (1,3-tetramethylxylylene diisocyanate, or 1,4-tetramethylxylylene diisocyanate) (TMXDI), o,o'-diisocyanate-1,4-diethylbenzene, and polyol modified products of xylylene diisocyanate obtained by a reaction between xylylene diisocyanate and trimethylolpropane.

[0051] The content of xylylene diisocyanate derivatives with respect to the entire polyisocyanates may be 10 mass% or more, 20 mass% or more, 30 mass% or more or 40 mass% or more in order to improve the reactivity with a main agent (for example, polyol). When the content is 30 mass% or more, it is possible to further increase the reactivity.

[0052] Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, and 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate(isophorodiiso cyanate) (IPDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate), and norbornane diisocyanate (NBDI).

[0053] Examples of polyisocyanate derivatives include multimers of the above polyisocyanate monomers, allophanate modified products, polyol modified products, polyol modified products produced by a reaction between monomers and alcohols, biuret modified products, urea modified products, oxadiazine trione modified products, carbodiimide modified products, uretdione modified products, and uretonimine

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modified products.

[0054] The isocyanate group-terminated prepolymer is a urethane prepolymer having at least two isocyanate groups at molecular ends. It can be obtained by a urethanization reaction between at least one selected from the group consisting of polyisocyanate monomers, polyisocyanate derivatives and isocyanate group-terminated prepolymers and polyols. In this case, the molar ratio (NCO/OH) of isocyanate groups contained in the polyisocyanate with respect to hydroxy groups of the polyol may be 0.5 or more, 0.6 or more, 0.8 or more, 1 or more or 1.5 or more. The molar ratio (NCO/OH) may be 10 or less, 5 or less, 4 or less, or 3 or less. Examples of a numerical range of the molar ratio (NCO/OH) include 0.5 to 10, 0.5 to 5, 0.8 to 4, and 0.6 to 3.

[0055] The epoxy compound may be a compound having one or two or more epoxy groups in one molecule and may have an epoxy group at least at both ends. Examples of epoxy compounds include glycidyl ether type epoxy compounds, glydicylamine type epoxy compounds, glycidyl ester type epoxy compounds, and alicyclic epoxy compounds (cyclic aliphatic epoxy compounds).

[0056] The molecular weight of the epoxy compound may be 500 or less, 450 or less, or 400 or less. Such an epoxy compound can be made to penetrate sufficiently into an electrostatic ink composition constituting an electrostatic ink layer. The lower limit of the molecular weight of the epoxy compound may be, for example, 98.

[0057] Examples of alicyclic epoxy compounds include epoxy cyclohexyl methyl-epoxy cyclohexane carboxylate, and

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bis(epoxycyclohexyl)adipate.

[0058] Examples of monofunctional alicyclic epoxy compound having one epoxy group in one molecule include 3,4 epoxy cyclohexyl methyl methacrylate and 1,2-epoxy-4-vinylcyclohexane. Examples of a bifunctional epoxy compound having two epoxy groups in one molecule include 3',4'-epoxycyclohexylmethyl-3,4 epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, and 4-vinylcyclohexene dioxide. In addition, examples of epoxy compounds having one or more epoxy groups in one molecule include a 1,2-epoxy-4-(2-oxylanyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol represented by the following General Formula (I).

[0059] [Chem. 1]

R---0 0-)--H (I)

[0060] In General Formula (I), n may be an integer of 1 to 4.

[0061] The epoxy compound preferably contains a bifunctional alicyclic epoxy compound. When the epoxy compound is bifunctional, the number of crosslinking points between the electrostatic ink composition and the primer resin can increase, the curing reaction of the adhesive can be promoted, and curing can be facilitated. In addition, when the epoxy compound is alicyclic, it is possible to restrict a

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reaction with the polyisocyanate due to steric hindrance. Therefore, the curing function can be stably exhibited.

[0062] In the adhesive composition, the content of the epoxy compound with respect to 100 parts by mass of the polyol may be 3 to 25 parts by mass, 6 to 25 parts by mass, or 8 to 20 parts by mass in order to achieve both high adhesive strength and excellent shear suppression strength. If the content of the epoxy compound is too large, excellent shear suppression strength tends to be impaired. That is, when the adhesive layer is formed, adhesive surfaces may be displaced from each other, or the adhesive composition may be squeezed out. When the amount of the epoxy compound added is too small, the adhesive strength tends to decrease particularly under high temperature and hot water treatment conditions.

[0063] In the adhesive composition, the content of the polyisocyanate with respect to 100 parts by mass of the polyol may be 10 to 50 parts by mass, 15 to 35 parts by mass, or 20 to 30 parts by mass in order to sufficiently increase the seal strength and the adhesive strength under high temperature and hot water treatment conditions.

[0064] The molar ratio of epoxy groups contained in the epoxy compound with respect to isocyanate groups contained in the polyisocyanate may be 0.5 to 10, 1.5 to 9, or 2.0 to 6.5. Therefore, a sufficiently high adhesive strength can be maintained under high temperature and hot water treatment conditions.

[0065] The adhesive composition may contain optional components such as an additive in addition to the above components. Examples of additives include antioxidants, UV absorbers, light stabilizers, fillers,

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silane coupling agents, epoxy resins, catalysts, coatability improving agents, leveling agents, nucleating agents, lubricants, mold release agents, anti-foaming agents, plasticizers, surfactants, pigments, dyes, organic fine particles, inorganic fine particles, antifungal agents, and flame retardants. In addition, organic acid-based, tin-based, lead-based, and amine-based urethane catalysts may be contained. The adhesive composition may contain a solvent such as an organic solvent.

[0066] The adhesive composition can be used as an adhesive for adhering a printed surface on which an electrostatic ink composition is printed to a substrate. The adhesive composition forms urethane bonds by a reaction between the polyol and the polyisocyanate and exhibits a function as an adhesive. Since formation of urethane bonds smoothly proceeds even in the co-presence of the epoxy compound, the printed surface and the substrate can be adhered with a sufficiently high adhesive strength.

[0067] The adhesive composition may have a function of forming urethane bonds and crosslinking the electrostatic ink composition. Therefore, it is possible to improve adhesive strength between the printed surface and the substrate. Even if the ink coverage on the printed surface increases, the content of the epoxy compound contained in the adhesive composition increases accordingly, the epoxy compound can be made to penetrate sufficiently into the electrostatic ink layer composed of the electrostatic ink composition. The penetrated epoxy compound has an action of increasing the strength of the electrostatic ink composition (electrostatic ink layer) by crosslinking the electrostatic ink composition. Therefore, even if the ink coverage on the printed

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surface is high, high adhesive strength can be maintained after the heat treatment under retort conditions of 110 to 135°C.

[0068] The adhesive composition can maintain high adhesive strength even after the heat treatment and also has an excellent pot life. Therefore, workability such as coating and laminating when the printed surface and the substrate are adhered is also excellent. The adhesive composition includes the polyol and the polyisocyanate that form urethane, and the epoxy compound, and these form a cured product, and thereby an adhesive layer is formed. This can reduce the number of layers constituting the laminate compared to when an adhesive layer containing only a polyurethane and an epoxy coating layer are separately provided. Therefore, for example, when a laminate is produced in a roll to roll manner, problems such as roll meandering after aging, and the occurrence of wrinkles due to blocking or the like do not occur. In addition, the aging process after coating can be eliminated and production efficiency can be achieved.

[0069] In a laminate in which the electrostatic ink layer on the printed surface and the adhesive composition are in direct contact with each other, components such as the epoxy compound and/or the polyisocyanate contained in the adhesive composition sufficiently penetrate into the electrostatic ink layer. Therefore, the electrostatic ink composition constituting the electrostatic ink layer can be crosslinked to improve the adhesive strength of the laminate. In addition, even if the printed surface includes a plain part (transparent part) without an electrostatic ink layer composed of the electrostatic ink composition, since the epoxy compound is contained in the adhesive

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layer, stickiness can be eliminated. On the other hand, if an epoxy coating layer is provided separately from the adhesive layer, when the printed surface includes a plain part, the amount of the epoxy compound becomes excessive in the vicinity of the plain part, and stickiness tends to occur. In this manner, the adhesive composition of the present embodiment can eliminate stickiness while adhering the printed surface including a plain part on which no electrostatic ink layer is formed with high adhesive strength.

[0070] A two-component adhesive according to one embodiment adheres the printed surface on which an electrostatic ink composition is printed to the substrate. The two-component adhesive includes a first liquid containing a main agent and a second liquid containing a curing agent. The two-component adhesive may be composed of only the first liquid and the second liquid. The first liquid and the second liquid are present separately and are not mixed. For example, the first liquid may be contained in a first container, and the second liquid may be contained in a second container. For example, the two-component adhesive may include a first container containing the first liquid containing a main agent and the second container containing the second liquid containing a curing agent.

[0071] The main agent contained in the first liquid may contain the above polyol. The curing agent contained in the second liquid may contain the polyisocyanate and the epoxy compound. The above adhesive composition can be obtained by mixing the first liquid and the second liquid. Therefore, the above description of the adhesive composition also applies to the two-component adhesive. The

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two-component adhesive has the same action and effect as the adhesive composition.

[0072] For the two-component adhesive, for example, the first liquid and the second liquid are blended and mixed to prepare an adhesive composition, and then the printed surface and the substrate may be adhered to each other. In this manner, the two-component adhesive is easier to mix than a three-component adhesive and thus workability is excellent. In addition, since it has excellent stability, it is suitable for production on an industrial scale. In addition, since the adhesive composition can be obtained only by blending two liquids, it is possible to sufficiently reduce variation in the adhesive strength due to poor mixing or the like. In addition, since the curing agent has excellent stability, high reaction activity of the polyisocyanate can be maintained. Therefore, even under high temperature and hot water treatment conditions, the printed surface on which an electrostatic ink composition is printed can be adhered with sufficiently high strength.

[0073] The curing agent according to one embodiment is used as an adhesive for adhering the printed surface on which an electrostatic ink composition is printed to the substrate. The curing agent contains the polyisocyanate and the epoxy compound contained in the adhesive composition. Therefore, the above description of the adhesive composition also applies to the curing agent.

[0074] The polyisocyanate and the epoxy compound contained in the curing agent are restricted from reacting with each other. Therefore, even if the curing agent in a liquid state is stored for a long time, it is possible to maintain a high level of the curing function of the

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polyisocyanate. Therefore, it can be suitably used as a material for the two-component adhesive. The adhesive composition prepared using such a curing agent can adhere the printed surface on which an electrostatic ink composition is printed and the substrate even under high temperature and hot water treatment conditions with sufficiently high strength.

[0075] The cured product according to one embodiment is obtained by curing the above adhesive composition. The cured product may form an adhesive layer that adheres the printed surface on which an electrostatic ink composition is printed to the substrate. The cured product may contain one or both of a polyurethane and an epoxy compound, and a crosslinked product thereof. The polyurethane may be a reaction product of the above polyol and polyisocyanate.

[0076] The glass transition temperature of the cured product determined by the dynamic viscoelasticity measurement may be 20°C or lower or 15°C or lower. If the cured product has such a low glass transition temperature, flexibility at room temperature is improved. Therefore, for example, the stress generated when the printed surface and the substrate are adhered to each other can be sufficiently relieved. Therefore, it is possible to further increase the adhesive strength. In order to improve the heat resistance, the glass transition temperature may be 5°C or higher or 10°C or higher. Here, the cured product whose glass transition temperature is measured is obtained by heating the adhesive composition under conditions of 60°C.

[0077] The laminate according to one embodiment includes a first substrate, an adhesive layer, and a second substrate in this order. The

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first substrate and the second substrate are adhered by an adhesive layer. One or both of the first substrate and the second substrate may or may not be in direct contact with the adhesive layer. An optional layer (or optional layers) may be provided between one or both of the first substrate and the second substrate and the adhesive layer. The electrostatic ink composition is printed on the adhesive surface with the adhesive layer on the side of the first substrate and/or the side of the second substrate.

[0078] The electrostatic ink composition is an ink composition used for liquid electrophotographic printing, that is, electrostatic printing, and is printed on a substrate such as paper and a plastic. The electrostatic ink composition may contain a coloring agent or pigment such as a dye, and a resin. In addition, in addition to these, a carrier fluid or a carrier liquid may be contained. In addition, a charge director, a charge adjuvant, a surfactant, a viscosity adjusting agent, an emulsifier and other additives may be contained.

[0079] Examples of coloring agents include cyan pigments, magenta pigments, yellow pigments, and black pigments. Examples of resins include thermoplastic resins such as ethylene acrylic acid copolymers, propylene acrylic acid copolymers, ethylene methacrylic acid copolymers, propylene methacrylic acid copolymers, and ethylene vinyl acetate copolymers.

[0080] Examples of carrier liquids include hydrocarbon, silicone oil, and vegetable oil. Examples of hydrocarbons include aliphatic hydrocarbon, branched chain aliphatic hydrocarbon, and aromatic hydrocarbon. The electrostatic ink composition may be substantially

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free of carrier liquids when printed on a printing substrate, for example, the first substrate. For example, the carrier liquid may be removed in an electrophoresis process during printing or evaporation. Therefore, substantially only the solid content is transferred to a printing substrate.

[0081] The charge director has an action of maintaining sufficient electrostatic charges on particles contained in the electrostatic ink composition. Examples of charge directors include ionic compounds such as metal salts of fatty acids, metal salts of sulfoscusinate, metal salts of oxyphosphate, metal salts of alkylbenzene sulfonic acid, and metal salts of aromatic carboxylic acid or aromatic sulfonic acid, and dual-ionic and non-ionic compounds such as polyoxyethyleneated alkylamine, lecithin, polyvinylpyrrolidone, and organic acid esters of multivalent alcohols.

[0082] The charge adjuvant has an action of increasing or stabilizing charges of particles contained in the electrostatic ink composition. Examples of charge adjuvants include barium petronate, calcium petronate, naphthenic acid Co salt, naphthenic acid Ca salt, naphthenic acid Cu salt, naphthenic acid Mn salt, naphthenic acid Ni salt, naphthenic acid Zn salt, naphthenic acid Fe salt, stearic acid Ba salt, stearic acid Co salt, stearic acid Pb salt, stearic acid Zn salt, stearic acid Al salt, stearic acid Cu salt, stearic acid Fe salt, and metal carboxylate.

[0083] The adhesive layer is formed by heating and curing the above adhesive composition. The adhesive composition may be a so-called two-component curable adhesive including a polyol as a main agent and a polyisocyanate as a curing agent. Therefore, the adhesive layer may contain a polyurethane resin produced by a reaction between the polyol

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and the polyisocyanate, and the epoxy compound. In addition, the adhesive layer may contain a polymer (crosslinked product) obtained by reacting the polyol and the polyisocyanate with the epoxy compound. Such an adhesive layer has high adhesive strength even under high temperature and hot water treatment conditions. In addition, the adhesive layer can maintain high adhesive strength even when in contact with hot water.

[0084] For example, the adhesive layer can be formed by applying the adhesive composition on the electrostatic ink composition, attaching the coated surface of the adhesive composition to the surface of the other substrate, and hardening it by curing it at room temperature or with heating. The coating amount of the adhesive composition may be, for example, 1 to 10 g/m2 , 2 to 6 g/m 2 , or 3 to 5 g/m 2 .

[0085] FIG. 1 is a cross-sectional view schematically showing an example of a laminate. FIG. 1 shows a cross section of the laminate in the thickness direction. A laminate 300 includes a first substrate 10, a primer layer 40, an adhesive layer 30 (adhesive composition or a cured product thereof), and a second substrate 20 in this order. The primer layer 40 is provided on one surface of the first substrate 10 on the side of the second substrate 20.

[0086] At least one of the first substrate 10 and the second substrate 20 may be a flexible substrate. For example, the flexible substrate may include one or both of a metal foil such as an aluminum foil and a film-like thermoplastic polymer. Examples of flexible substrates include films of biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), oriented polyamide (OPA), unstretched

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polypropylene (CPP), linear and low-density polyethylene (LLDPE), and low density polyethylene (LDPE). In addition, a vapor deposition film or a transparent vapor deposition film in which aluminum, aluminum oxide, or the like is vapor-deposited on a PET film may be used. The materials of the first substrate 10 and the second substrate 20 may be the same as or different from each other. The thickness of the first substrate 10 and the second substrate 20 may be 7 to 150 pm, 15 to 90 pm, or 20 to 80 pm.

[0087] The primer layer 40 may contain a resin. Examples of resins include polyvinyl alcohol resins, cellulose resins, polyesters, polyamines, polyethyleneimine resins, polyamide resins, polyurethane, polyacrylic polymer hydroxyl-containing resins, carboxylic group-containing resin, and amine-based polymers. When the primer layer 40 is provided, printing with the electrostatic ink composition can be smoothly performed. The coating amount of the resin constituting the primer layer 40 may be, for example, 0.01 to 1.5 g/m2 or 0.05 to 1.0 2 g/m .

[0088] An electrostatic ink composition 50 is printed on the primer layer 40 by electrostatic printing using a digital printer to form an electrostatic ink layer. In FIG. 1, the plurality of electrostatic ink compositions 50 may have the same composition or may have different colors due to different compositions. The electrostatic ink composition 50 may be crosslinked by components contained in the adhesive composition and/or the primer layer 40. Therefore, it is possible to further increase the adhesive strength between the first substrate 10 and the second substrate 20.

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[0089] The laminate 300 does not have an epoxy coating layer. In this manner, since there is no need to provide the epoxy coating layer, the number of steps can be reduced, and the productivity can be improved accordingly.

[0090] In this example, between adjacent electrostatic ink compositions 50 in a direction perpendicular to a direction in which the first substrate 10 and the second substrate 20 face each other, the adhesive layer 30 and the primer layer 40 are in direct contact with each other. Therefore, when viewed in a direction in which the first substrate 10 and the second substrate face each other, a transparent part (plain part) can be provided in the laminate 300. Therefore, when the laminate 300 is used as a packaging film, a packaged object can be visually recognized via the laminate 300. Even if such a transparent part is provided, stickiness in the adhesive layer 30 can be sufficiently minimized according to a laminating method.

[0091] In another example, adjacent electrostatic ink compositions 50 may be in contact with each other in a direction perpendicular to a direction in which the first substrate 10 and the second substrate 20 face each other. That is, at least one adhesive surface adhered to the adhesive layer 30 may have the electrostatic ink composition 50, or the adhesive surface may be composed of the electrostatic ink composition 50. Since the adhesive layer 30 firmly adheres to the electrostatic ink composition 50, the first substrate 10 and the second substrate 20 can be sufficiently firmly adhered to each other.

[0092] In still another example, the primer layer 40 may not be provided, or the primer layer 40 may be provided on each of facing

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surfaces of the first substrate 10 and the second substrate. In addition, between the first substrate 10 and the second substrate 20, in order to improve the gas barrier property and the water vapor barrier property of the laminate 300, between the first substrate 10 and the primer layer 40, and/or between the second substrate 20 and the adhesive layer 30, at least one of a metal layer such as an aluminum foil and a resin layer such as a nylon film may be provided.

[0093] For example, the laminate 300 is useful as a food packaging material. Since the laminate 300 has excellent adhesive strength under high temperature and hot water treatment conditions and excellent adhesive strength under an environment in which it is in contact with hot water, it can be suitably used as a packaging material for retort food, a packaging material for a microwave oven, and a packaging material for boiling. The thickness of the laminate 300 may be, for example, 15 to 200 [m or 18 to 120 pm.

[0094] A method of producing a laminate 300 according to one embodiment includes a step of forming the primer layer 40 on one surface of the first substrate 10, a step of printing the electrostatic ink composition 50 on the primer layer 40 to obtain a printed surface, and a step of adhering the printed surface to one surface of the second substrate 20 using an adhesive composition.

[0095] The primer layer 40 may be formed by performing gravure printing on one surface of the first substrate 10. The primer layer 40 can be formed by crosslinking a resin raw material with a crosslinking agent. Crosslinking may be performed by emitting ionizing radiation such as ultraviolet light, heating, and electron beams, and non-ionizing

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radiation such as microwave radiation. The electrostatic ink composition 50 can be printed by electrostatic printing using a digital printer.

[0096] Adhesion of the printed surface and one surface of the second substrate 20 with the adhesive composition can be performed by laminating. Laminating can be performed using any device. The epoxy compound and/or the polyisocyanate contained in the adhesive composition may penetrate into the electrostatic ink composition 50 and the primer layer 40 constituting the electrostatic ink layer, and undergo a crosslinking reaction with components contained in the electrostatic ink composition 50 and the primer layer 40. Therefore, the laminate 300 in which interfaces of the layers are sufficiently bonded can be obtained.

[0097] Before the step of performing adhesion using the adhesive composition, a step of mixing the first liquid and the second liquid constituting the above two-component adhesive to prepare an adhesive composition may be provided. When such a two-component adhesive is used, the preparation of the adhesive composition and the adhering operation can be smoothly performed. In addition, since variation in the mixed state of the adhesive composition can be reduced, it is possible to improve the reliability of the laminate 300.

[0098] FIG. 2 is a plan view showing one embodiment of a packaging bag formed using the above laminate. A packaging bag 100 is formed by attaching a pair of packaging materials 60 and 62. The above laminate 300 can be used as the packaging materials 60 and 62. That is, the packaging bag 100 has a sealing part 101 formed by attaching peripheral edges of a pair of film-like substantially rectangular

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packaging materials 60 and 62 and a housing part 102 formed between the pair of packaging materials 60 and 62 by the sealing part 101. That is, the side end part, the lower end part and the upper end part of the packaging bag 100 are sealed by the sealing part 101. The packaging bag 100 includes the housing part 102 in which a packaged object (for example, food) is housed in a non-sealing part (sheet part) surrounded by the sealing part 101. Here, the sealing part 101 at the lower end part may be sealed after the packaged object is filled into the housing part 102.

[0099] The packaging materials 60 and 62 may have a sealant layer on the surface of the laminate 300, and the first substrate 10 or the second substrate of the laminate 300. In this case, the pair of packaging materials 60 and 62 are superimposed so that the sealant layers face each other. The pair of film-like packaging materials 60 and 62 may be adhered at the sealing part 101 with an adhesive. Either the first substrate 10 or the second substrate 20 of the laminate 300 constituting the packaging materials 60 and 62 may be inside.

[0100] It is not essential that the pair of packaging materials 60 and 62 constituting the packaging bag 100 have the same layer structure, and for example, the pair of packaging materials 60 and 62 may be composed of laminates having different layer structures.

[0101] The packaging bag 100 may have an opening unit 120. The opening unit includes a pair of easy-opening processed parts 124 formed of V-shaped notches formed in the sealing part 101 at the side end part and a half-cut line 121 which is an opening trajectory between the pair of easy-opening processed parts 124. The half-cut line 121 can be

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formed using a laser. The easy-opening processed part 124 is not limited to the V-shaped notch, but may be a U-shaped or I-shaped notch, and may have a group of scars.

[0102] A procedure of producing the packaging bag 100 using the packaging materials 60 and 62 will be described below. The laminate 300 is cut into a predetermined shape to obtain the pair of packaging materials 60 and 62. The sealant layers provided on one surface of the packaging materials 60 and 62 are made face to each other and the sealant layers are adhered to each other. Therefore, the sealing part 101 is formed at the upper end part and the side end part and a non-sealing part surrounded by the sealing part 101 in a U shape is formed. In this manner, a packaging bag 110 in which only the upper end part (or only the lower end part) is not sealed as shown in FIG. 3 can be obtained. In some embodiments, in the packaging bag, a part of the peripheral edge may not be sealed as shown in FIG. 3.

[0103] Next, a packaged object is filled from the upper end part (or the lower end part) in the unsealed state. Then, the packaging materials 60 and 62 are adhered to each other at the upper end part (or the lower end part) to form the sealing part 101 at the upper end part (or the lower end part). In this manner, a package 200 including the packaging bag 100 and a packaged object housed therein can be produced.

[0104] Since the packaging bag 100 and the package 200 include, as the packaging materials 60 and 62, a laminate that maintains a sufficiently high adhesive strength between the layers even under high temperature and hot water treatment conditions, they can be particularly suitably used for food that is heated with hot water or in a microwave oven.

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Regarding the package 200, a retort package that is heated by boiling or heated in a microwave oven may be exemplified.

[0105] While some embodiments have been described above, the present disclosure is not limited to the above embodiments. For example, the packaging material may be a packaging film attached to the surface of a PET bottle. In addition, the shape of the packaging bag is not limited to the four-sided bag, and may be, for example, a two-sided bag, a three-sided bag, a butted-seam bag or a standing pouch. The laminate may have one or more optional layers in addition to the first substrate, the primer layer, the electrostatic ink layer, the adhesive layer and the second substrate.

[Examples]

[0106] While details of the present disclosure will be described in more detail with reference to examples, the present disclosure is not limited to the following examples.

[0107] (Example 1)

[Production of adhesive composition and laminate] A polyethylene terephthalate film (PET film, thickness: 12 pm) was prepared as a first substrate. An aqueous primer resin (resin containing polyethyleneimine, product name: DP050 commercially available from Michelman) was applied to one surface of the PET film to form a primer layer. The aqueous polyethyleneimine was applied in a coating amount of 0.10 to 0.18 g/m2 .

[0108] Predetermined printing was performed on the surface of the primer layer using a digital printer (Indigo20000 digital printer for labels and packaging commercially available from HP). The ink

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coverage by one printing was set to 100%. An electrostatic ink composition (HP Indigo Electroink) containing a thermoplastic resin containing a copolymer of ethylene acrylic acid and ethylene methacrylic acid was used as the electrostatic ink composition. Regarding the color of the electrostatic ink composition, as shown in Table 1, white (W), yellow (Y), magenta (M), and cyan (C) were used. A plurality of samples with different colors and ink coverages of the electrostatic ink composition were produced. The ink coverage of each color and a total thereof are shown in Table 1. As shown in Table 1, the total of the ink coverage was 200 to 500%.

[0109] An aliphatic polyester polyol (A) (product name: Takelac A626 commercially available from Mitsui Chemicals Inc) and a polyisocyanate (B) (product name: Takenate A50 commercially available from Mitsui Chemicals Inc) as a main agent, 3',4'-epoxycyclohexylmethyl-3,4 epoxycyclohexanecarboxylate as an epoxy compound (C), and ethyl acetate as a solvent were mixed to prepare an adhesive composition having a solid content concentration of 36.5 mass%. The structure of the epoxy compound was as shown in the following Formula (1). The blending ratio based on the mass of the components is as shown in Table 1. The amount of the polyisocyanate added (parts by mass) with respect to 100 parts by mass of the aliphatic polyester polyol is shown in the column of

[(B)/(A)]x100 in Table 1. The amount of the epoxy compound added (parts by mass) with respect to 100 parts by mass of the aliphatic polyester polyol is shown in the column of [(C)/(A)]x100 in Table 1. The molar ratio of epoxy groups contained in the epoxy compound (C)

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with respect to the isocyanate group contained in the polyisocyanate (B) is shown in the column of "epoxy group/isocyanate group" in Table 1.

[0110] The adhesive composition prepared as described above was applied to the printed surface on which an electrostatic ink composition was printed using a dry laminating device to form an adhesive layer. The coating amount of the adhesive composition was 4.0 g/m2

.

[0111] [Chem. 2] 0

0 0 (1)

[0112] Regarding a second substrate, a base film including an aluminum foil (commercially available from Toyo Aluminium K. K., thickness: 7 pm), a nylon film and an unstretched polypropylene film in this order was prepared. Using the dry laminating device, the adhesive layer and the aluminum foil were brought into contact with each other, and the base film was attached to the adhesive layer to obtain a laminate. The curing time (aging) was 2 days at 40°C. In this manner, a laminated film (laminate) was produced.

[0113] [Measurement of adhesive strength (room temperature)] The adhesive strength of the produced laminate was measured according to JIS K 6854-1: 1999. Specifically, the produced laminate was cut to a width of 15 mm to prepare a measurement sample. After the layers at the end parts of the measurement sample were peeled off, the peeling strength between the layers of the laminate was measured using a tensile testing machine under conditions of an angle of 900, a

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tensile speed of 300 mm/min, and room temperature. The peeling strength was used as the adhesive strength at room temperature (20°C). The measurement results are shown in Table 1.

[0114] (Examples 2 to 6) Laminates were produced in the same manner as in Example 1 except that the formation of the adhesive composition was changed as shown in Table 1 and Table 2, and the adhesive strength was measured. The measurement results are shown in Table 1 and Table 2.

[0115] (Example 7) A first liquid composed of an aliphatic polyester polyol (A) (product name: Takelac A626 commercially available from Mitsui Chemicals Inc) and a second liquid composed of a polyisocyanate (B) (product name: Takenate A50 commercially available from Mitsui Chemicals Inc) and an epoxy compound (C) were separately contained in a container to prepare a two-component adhesive. The first liquid and the second liquid were mixed to prepare an adhesive composition having the formulation shown in Table 2. A laminate was produced in the same manner as in Example 1 except that this adhesive composition was used, and the adhesive strength was measured. The measurement results are shown in Table 2.

[0116] (Comparative Example 1) A laminate was produced in the same manner as in Example 1 except that no epoxy compound (C) was added when the adhesive composition was prepared, and the adhesive strength was measured. The measurement results are shown in Table 2.

[0117] (Comparative Example 2)

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A laminate was produced in the same manner as in Example 1 except that the epoxy compound of Formula (1) was applied to the printed surface on which an electrostatic ink composition was printed to provide an epoxy coating layer, and the adhesive composition of Comparative Example 1 was applied to the epoxy coating layer, and the adhesive strength was measured. The coating amount of the epoxy coating layer was set to an amount corresponding to 0.53 parts by mass in the formulation shown in Table 2. The measurement results are shown in Table 2.

[0118] [Table 1] Example Example Example Example Example 1 2 3 4 5 Blended components Blending proportion (parts by mass) Aliphatic polyester polyol (A) 8 8 8 8 8 Polyisocyanate (B) 1 1 1 1 1 Epoxy compound (C) 0.28 0.58 0.78 1.2 1.6

[(B)/(A)]x 100 12.5 12.5 12.5 12.5 12.5

[(C)/(A)]x 100 3.5 7.3 9.8 15.0 20.0 Epoxy groups/ isocyanate groups 0.8 1.8 2.4 3.6 4.8 Ink coverage Total Adhesive strength (N/15 mm) Y100%+W200%| 300% 1.2 1.6 1.8 2.7 3.0 M100%+W200%| 300% 0.8 1.0 1.2 1.8 2.9 C100%+W200%| 300% 1.3 1.5 1.6 2.8 2.6 K100%+W200%| 300% 0.8 1.2 1.3 2.5 2.5 W200%| 200% 1.7 1.8 2.6 2.5 2.7 C100%+M100%+Y100%+W200% 500% 0.6 1.4 1.2 1.8 2.9 C100%+M100O%+W200% | 400% 0.7 1.0 1.0 1.6 2.8 Y100%+C100%+W200% | 400% 1.2 1.2 1.4 2.3 3.5 M100 % +YlOO%+W200% | 400% 1.2 1.4 1.6 2.5 3.2

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[0119] [Table 2] Example Example Comparative Comparative 6 7 Example 1 Example 2 Blended components Blending proportion (parts by mass) Aliphatic polyester polyol (A) 8 8 8 8 Polyisocyanate (B) 1 1.5 1 1 Epoxy compound (C) 2.0 1.5 0 0

[(B)/(A)]x100 12.5 18.8 12.5 12.5

[(C)/(A)]x100 25.0 18.8 0.0 0.0 Epoxy groups/ isocyanate groups 6.1 3.0 0 0 Ink coverage Total Adhesive strength (N/15 mm) Y100%+W200%| 300% 2.5 3.1 1.1 3.2 M100%+W200%| 300% 1.8 2.7 0.5 3.6 C100%+W200%| 300% 2.5 2.4 0.8 3.8 K100%+W200%| 300% 2.5 2.5 0.8 3.4 W200%| 200% 2.5 2.9 1.2 3.3 C100%+M100%+Y100%+W200%| 500% 3.0 2.9 0.6 2.5 C100 % +M100% + W200% | 400% 2.9 3.0 0.4 2.6 Y100 % +C100% + W200% | 400% 3.6 3.2 0.8 2.7 M100 % +Y100% + W200% | 400% 3.2 3.4 0.7 2.6

[0120] As shown in Table 1 and Table 2, it was confirmed that, when the epoxy compound was added, the adhesive strength was higher than that of Comparative Example 1. Here, in Comparative Example 2, relatively high adhesive strength was obtained, but it was necessary to increase the number of steps in order to form an epoxy coating layer in addition to the adhesive layer. Curing (aging) of the epoxy coating layer took 2 days, and the productivity decreased.

[0121] In the laminate of Comparative Example 1, the layers were peeled off near the interface between the electrostatic ink layer and the primer layer. In the laminate of Comparative Example 2, the electrostatic ink layer was cohesively broken. On the other hand, in the laminates of Examples 1 to 7, the layers were peeled off at the interface between the electrostatic ink layer and the adhesive layer, and no cohesive breaking of the electrostatic ink layer was observed. This suggests that the cohesive force of the electrostatic ink layer was

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improved. Here, the molar ratio of isocyanate groups contained in the polyisocyanate (B) with respect to hydroxy groups of the aliphatic polyester polyol (A) in Examples 1to 7 was in a range of 0.5 to 10.

[0122] Next, the hot adhesive strength, seal strength, and hot water adhesive strength of the laminates of Example 5 and Comparative Example 2 were measured. For measurement, those having a total of the ink coverage of 500% and those having a total of the ink coverage of 200% were used. Details of the measurement procedure were as follows.

[0123] [Measurement of adhesive strength after retort (120°C)] A three-sided bag was produced using a laminate, and water was sealed in the three-sided bag. Then, a retort heat treatment (120°Cxfor 30 minutes) was performed using a retort processing device (commercially available from Hisaka Works, Ltd.). After the retort heat treatment, a laminate sample cut to a width of 15 mm was collected, and the interlayer strength between the ink layer and the layer in contact with the ink layer was measured. The measured peeling strength is shown in the column of "120°C" in Table 3. Here, Table 3 also shows the adhesive strength at room temperature before the heat treatment.

[0124] [Measurement of adhesive strength after retort (130C)] A three-sided bag was produced using a laminate, and water was sealed in the three-sided bag. Then, a retort heat treatment (13 0 °Cxfor 30 minutes) was performed using a retort processing device (commercially available from Hisaka Works, Ltd.). After the retort heat treatment, a laminate sample cut to a width of 15 mm was collected, and the interlayer strength between the electrostatic ink layer and the

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layer in contact with the electrostatic ink layer was measured. The measured peeling strength is shown in the column of "130°C" in Table 3.

[0125] [Measurement of seal strength (before heat treatment)] A pair of laminates of Example 5 were heat-sealed under conditions of 180°C and 0.2 MPa for 1 second so that unstretched polypropylene films overlapped each other. Therefore, the unstretched polypropylene films were heat-welded to produce a measurement sample with a width of 15 mm. The seal strength of the produced measurement sample was measured according to JIS K 7127: 1999. For measurement, the peeling strength between the heat seals was measured under conditions of a peeling angle of 90, a tensile speed of 300 mm/min, and room temperature (20°C) using a tensile testing machine. The peeling strength was used as the seal strength "before the heat treatment." The measurement results are shown in Table 3. The same measurement sample was produced using the laminate of Comparative Example 2, and the same measurement was performed. The measurement results are shown in Table 3.

[0126] [Measurement of seal strength (after boiling)] The measurement sample produced in the above "Measurement of seal strength (before the heat treatment)" was heated in water at 100°C for 30 minutes. Then, the seal strength was measured in the same procedure as in the above "Measurement of seal strength (without heat treatment)." The measurement results are shown in the column of "After boiling" in Table 3.

[0127] [Measurement of seal strength after retort (120°C)]

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The measurement sample produced in the above "Measurement of seal strength (before the heat treatment)" was subjected to a retort heat treatment (120°Cxfor 30 minutes). The peeling strength was measured in the same manner as in "Measurement of seal strength (without heat treatment)" using a tensile testing machine. The measurement results are shown in in the column of "120°C" in Table 3.

[0128] [Measurement of seal strength after retort (130°C)] The measurement sample produced in the above "Measurement of seal strength (before the heat treatment)" was subjected to a retort heat treatment (130°Cxfor 30 minutes). The peeling strength was measured in the same manner as in "Measurement of seal strength (without heat treatment)" using a tensile testing machine. The measurement results are shown in the column of "130°C" in Table 3.

[0129] [Measurement of hot water adhesive strength] After the layers at the end parts of the laminate cut to a width of 15 mm were peeled off, the peeling strength was measured using a tensile testing machine when immersed in hot water at 90°C. That is, the peeling angle was free, and the tensile speed was 300 mm/min. The peeling strength is shown as the hot water adhesive strength in Table 3.

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[0130] [Table 3] Example 5 Comparative Example 2 Ink coverage 200% 500% 200% 500% Adhesive Before heat 3.1 2.9 3.5 2.5 strength treatment (N/15 mm) 12 0 °Cxfor 3.0 3.0 3.6 2.2 30 minutes 13 0 °Cxfor 3.3 3.3 3.4 2.1 30 minutes Seal Before heat 53.0 53.0 51.0 52.0 strength treatment After boiling 44.0 51.0 22.0 35.0 12 0 °Cxfor 55.0 54.0 52.0 53.0 30 minutes 13 0 °Cxfor 52.0 54.0 53.0 54.0 30 minutes Hot water 90 0 C 1.0 1.1 <0.1 <0.1 adhesive strength (N/15 mm)

[0131] As shown in Table 3, it was confirmed that, regardless of

whether the heat treatment was performed, Example 5 had better seal

strength than Comparative Example 2. When the ink coverage was

500%, particularly, Example 5 had higher adhesive strength than

Comparative Example 2. In addition, the seal strength of Example 5

was sufficiently high even after boiling, but the seal strength of

Comparative Example 2 was significantly reduced after boiling.

[0132] (Example 8)

[Production of adhesive composition and laminate]

A polyethylene terephthalate film (PET film, thickness: 12 pm) was prepared as a first substrate. An aqueous primer resin (resin

containing polyethyleneimine, product name: DP050 commercially

available from Michelman) was applied to one surface of the PET film

to form a primer layer. The aqueous polyethyleneimine was applied in

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a coating amount of 0.10 to 0.18 g/m2

.

[0133] Predetermined printing was performed on the surface of the primer layer using a printer (product name: Indigo 2000, commercially available from HP Indigo). An electrostatic ink composition (HP Indigo Electroink) containing a thermoplastic resin containing a copolymer of ethylene acrylic acid and ethylene methacrylic acid was used as the electrostatic ink composition. Regarding the color of the electrostatic ink composition, white (W), yellow (Y), magenta (M), and cyan (C) were used. Regarding the ink coverage, those having W200% and those having C100%+M100%+Y100%+W200% were prepared. In Table 4, the former was designated as "ink coverage (1)" and the latter was designated as "ink coverage (2)." In this manner, two types of samples with different ink coverages of the electrostatic ink composition were produced.

[0134] An adhesive composition was prepared in the same manner as in Example 5. The adhesive composition prepared as described above was applied to the printed surface on which an electrostatic ink composition was printed using a handler laminating machine to form an adhesive layer. The coating amount of the adhesive composition was 4.0 g/m 2 .

[0135] A base film including a nylon film and an unstretched polypropylene film in this order was prepared as a second substrate. The adhesive layer and the nylon film were brought into contact with each other, and the base film was attached to the adhesive layer to obtain a laminate. The curing time (aging) was 40°Cx2 days.

[0136] The adhesive strength (room temperature), hot adhesive strength

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(120°C), seal strength (before the heat treatment) and seal strength (after boiling) of the laminate obtained in this manner were measured in the same procedure as described above. The measurement results are shown in Table 4.

[0137] (Examples 9 to 12) Laminates were produced in the same manner as in Example 8 except that, when the adhesive composition was prepared, the amount of the polyisocyanate (B) added was changed as shown in Table 3. The produced laminate was evaluated in the same manner as in Example 7. The evaluation results are shown in Table 4.

[0138] (Comparative Example 3) A laminate was produced in the same manner as in Comparative Example 1 except that lamination on the printed surface on which an electrostatic ink composition was printed was performed using a handler laminating machine without using a dry laminating device. The color and ink coverage of the electrostatic ink composition are as shown in Table 4. The produced laminate was evaluated in the same manner as in Example 8. The evaluation results are shown in Table 4.

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[0139] [Table 4] Example Example Example Example Example Comparative 8 9 10 11 12 Example 3 Blended components Blending proportion (parts by mass) Aliphatic polyester 8 8 8 8 8 8 polyol (A) Polyisocyanate (B) 1.0 1.2 1.5 2.0 3.0 1.0 Epoxy compound (C) 1.6 1.6 1.6 1.6 1.6 0.0

[(B)/(A)]x100 12.5 15.0 18.8 25.0 37.5 12.5

[(C)/(A)]x 100 20.0 20.0 20.0 20.0 20.0 0.0 Epoxy groups/ 4.8 4.0 3.2 2.4 1.6 0.0 isocyanate groups Adhesive Ink 0.4 0.3 0.4 0.5 0.5 0.3 strength coverage (before (1) heat Ink 0.2 0.5 0.5 0.8 0.6 0.1 treatment) coverage

[N/15 (2) mm] Hot Ink 0.2 0.1 0.2 0.9 0.2 0.0 adhesive coverage strength (1) (120°C) Ink 0.2 0.1 0.3 0.5 0.3 0.0

[N/15 coverage mm] (2) Seal Ink 41.0 42.0 45.0 47.0 46.0 30.0 strength coverage (before (1) heat Ink 43.0 42.0 46.0 49.0 48.0 31.0 treatment) coverage

[N/15 (2) mm] Seal Ink 38.0 40.0 42.0 44.0 45.0 26.0 strength coverage (after (1) boiling) Ink 40.0 39.0 45.0 47.0 42.0 24.0

[N/15 coverage mm] (2)

[0140] As shown in Table 4, it was confirmed that, in the examples, the high adhesive strength and seal strength were obtained even under high temperature and hot water treatment conditions. In addition, it was confirmed that, when the mixing ratio of the polyisocyanate (B) to the aliphatic polyester polyol (A) was adjusted, the hot adhesive strength (120C) and the seal strength (before the heat treatment and after boiling) could be sufficiently increased. On the other hand, it was

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confirmed that, in Comparative Example 3 in which no epoxy compound (C) was used, when exposed to high temperature and hot water treatment conditions, the adhesive strength and the seal strength were significantly reduced. Here, the molar ratio of isocyanate groups contained in the polyisocyanate (B) with respect to hydroxy groups contained in the aliphatic polyester polyol (A) in Examples 8 to 12 was in a range of 0.5 to 10.

[0141] (Examples 13 to 17) An aliphatic polyester polyol (Al) (Takelac A525 commercially available from Mitsui Chemicals Inc), a polyisocyanate (B1) (Takenate A52 commercially available from Mitsui Chemicals Inc), and 3',4'-epoxycyclohexylmethyl-3,4 epoxycyclohexanecarboxylate as an epoxy compound (C) were mixed to prepare an adhesive composition. The mixing ratio is as shown in Table 5. Laminates were produced and evaluated in the same manner as in Example 8 to Example 12 except that such an adhesive composition was used. The evaluation results are as shown in Table 5.

[0142] (Comparative Example 4) An aliphatic polyester polyol (Al) (Takelac A525 commercially available from Mitsui Chemicals Inc) as a polyol and a polyisocyanate (B1) (Takenate A52 commercially available from Mitsui Chemicals Inc) were mixed to prepare an adhesive composition. The mixing ratio is as shown in Table 5. A laminate was produced and evaluated in the same manner as in Comparative Example 3 except that such an adhesive composition was used. The evaluation results are as shown in Table 5.

[0143] [Table 5]

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Example Example Example Example Example Comparative 13 14 15 16 17 Example 4 Blended components Blending proportion (parts by mass) Aliphatic polyester 9.0 9.0 9.0 9.0 9.0 9.0 polyol (Al) Polyisocyanate (B1) 1.0 1.0 1.8 2.0 3.0 1.0 Epoxy compound (C) 1.7 1.7 1.7 1.7 1.7 0.0

[(B1)/(A1)]x100 11.1 11.1 20.0 22.2 33.3 11.1

[(C)/(A1)]x100 18.9 18.9 18.9 18.9 18.9 0.0 Epoxy groups/ 8.4 8.4 4.7 4.2 2.8 0.0 isocyanate groups Adhesive Ink 0.3 0.3 0.3 0.4 0.6 0.2 strength coverage (before (1) heat Ink 0.2 0.3 0.5 0.4 0.5 0.1 treatment) coverage

[N/15 (2) mm] Hot Ink 0.2 0.1 0.3 0.2 0.3 0.0 adhesive coverage strength (1) (120°C) Ink 0.3 0.2 0.2 0.3 0.4 0.0

[N/15 coverage mm] (2) Seal Ink 40.0 43.0 42.0 43.0 46.0 30.0 strength coverage (before (1) heat Ink 39.0 40.0 39.0 40.0 47.0 32.0 treatment) coverage

[N/15 (2) mm] Seal Ink 35.0 41.0 41.0 38.0 42.0 26.0 strength coverage (after (1) boiling) Ink 36.0 40.0 40.0 39.0 44.0 24.0

[N/15 coverage mm] (2)

[0144] As shown in Table 5, it was confirmed that, even if the combination of the aliphatic polyester polyol and the polyisocyanate was changed, the high adhesive strength and seal strength in each example were obtained. In addition, it was confirmed that, when the mixing ratio of the polyisocyanate (B1) to the aliphatic polyester polyol (Al) was adjusted, the hot adhesive strength (120°C) and the seal strength (without heat treatment and after boiling) could be sufficiently increased. On the other hand, it was confirmed that, in Comparative

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Example 4 in which no epoxy compound (C) was used, when exposed to high temperature and hot water treatment conditions, the adhesive strength and the seal strength were significantly reduced. Here, in Examples 13 to 17, the molar ratio of isocyanate groups contained in the polyisocyanate (B1) with respect to hydroxy groups contained in the aliphatic polyester polyol (A1) was in a range of 0.5 to 10.

[0145] [Evaluation of stability] (Example 18) The stability when the aliphatic polyester polyol (A), the polyisocyanate (B), and the epoxy compound (C) used in Example 7 were mixed was evaluated according to the following procedure. First, the following two types of mixtures were prepared. Mixture a: polyisocyanate (42.9 mass%)+epoxy compound (57.1 mass%)

Mixture b: aliphatic polyester polyol (76.1 mass%)+epoxy compound (23.9 mass%)

[0146] The polyisocyanate and the epoxy compound were mixed, and then stored at 50°C. The sample stored for 1 month was designated as a mixture a(1), and the sample stored for 2 months was designated as a mixture a(2). The aliphatic polyester polyol and the epoxy compound were mixed and then stored at 50°C. The sample stored for 1 month was designated as a mixture b(1), and the sample stored for 2 months was designated as a mixture b(2).

[0147] The aliphatic polyester polyol (A) was added to the mixture a(1) and the mixture a(2), and immediately left in a dry atmosphere (silica gel) at 40°C. Then, the change in the residual amount of NCO over

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time (0 to 100 hours) was examined by FT-IR (transmission method). The results are shown in FIG 4. The horizontal axis in FIG 4 represents the time elapsed after the aliphatic polyester polyol (A) was added, and the vertical axis represents an NCO reduction rate based on (0) immediately after mixing as an NCO reaction rate.

[0148] The polyisocyanate (B) was added to the mixture b(1) and the mixture b(2) after storage, and immediately left in a dry atmosphere (silica gel) at 40°C. Then, the change in the residual amount of NCO was examined over time (0 to 100 hours) by FT-IR (transmission method). The results are shown in FIG 4. The horizontal axis in FIG 4 represents the time elapsed after the polyisocyanate (B) was added. FIG 4 also shows, as a control, the results obtained by simultaneously mixing three components (A), (B) and (C) and measuring the residual amount of NCO after immediately after mixing. In all of the mixtures, the mixing ratio of three components was 64.6 mass% for (A), 15.2 mass% for (B), and 20.2 mass% for (C).

[0149] Based on the results shown in FIG 4, it was confirmed that the adhesive composition using the mixture a had slower progress of the reaction during storage than the adhesive composition using the mixture b, and was able to maintain sufficient reaction activity. The reaction activity of the mixture a(1) and the mixture a(2) was the same as that of the adhesive composition immediately after three components (A), (B) and (C) were simultaneously mixed. Accordingly, it was confirmed that the mixture a was able to maintain favorable reaction activity even when stored for a long time.

[0150] (Example 19)

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In the same manner as in Example 18, a mixture a(1), a mixture a(2), a mixture b(1) and a mixture b(2) were prepared. An adhesive composition obtained by adding the aliphatic polyester polyol (A) to the mixture a(1) and the mixture a(2) was applied to an unstretched polypropylene film (CPP film) at 5 g/m 2 , another CPP film was superimposed, and the CPP films were adhered to each other. Then, the sample was left in a dry atmosphere (silica gel) at 40°C, and the change in the adhesive strength over time (0 to 50 hours) was examined. The adhesive strength was measured in the same procedure as in "Measurement of adhesive strength (room temperature)" in Example 1. The measurement results are shown in FIG. 5. The horizontal axis in FIG. 5 represents the time elapsed after the aliphatic polyester polyol (A) was added.

[0151] The change in the adhesive strength of the adhesive composition obtained by adding the polyisocyanate (B) to the mixture b(1) and the mixture b(2) over time was also measured in the same manner as in the mixture a(1) and the mixture a(2). The measurement results are shown in FIG. 5. The horizontal axis in FIG. 5 represents the time elapsed after the polyisocyanate (B) was added. FIG. 5 also shows, as a control, the results of the adhesive strength measured by simultaneously mixing three components (A), (B) and (C) and adhering CPP films immediately after mixing. In all of the mixtures, the blending ratio of A), (B) and (C) was the same.

[0152] Based on the results shown in FIG. 5, it was confirmed that the adhesive composition obtained using the mixture a was able to maintain higher adhesive strength than the adhesive composition obtained using

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the mixture b. The rise in adhesive strength of the adhesive composition using the mixture a(1) and the mixture a(2) was the same as that of the adhesive composition immediately after three components (A), (B) and (C) were simultaneously mixed. Therefore, it was confirmed that the mixture a was able to maintain favorable adhesiveness even when stored for a long time.

[0153] (Example 20) In the same manner as in Example 18, a mixture a(1), a mixture a(2), a mixture b(1) and a mixture b(2) were prepared. The pot life test of the adhesive composition obtained by adding the aliphatic polyester polyol (A) to the mixture a(1) and the mixture a(2) according to the following procedure. Immediately after the aliphatic polyester polyol (A) was added, dilution with a solvent (ethyl acetate) was performed so that the concentration of the adhesive composition was 30 mass%. Using a type B rotational viscometer (rotational speed: 60 rpm, rotor: No. 1), the change in the viscosity of this diluted solution (170 g) over time was examined. Measurement was performed under an atmospheric pressure of 24°C. The measurement was continued at certain time intervals while supplementing ethyl acetate. The measurement results are shown in FIG. 6. The horizontal axis in FIG. 6 represents the time elapsed after measurement of the viscosity started.

[0154] The change in the adhesive strength of the adhesive composition obtained by adding the polyisocyanate (B) to the mixture b(1) and the mixture b(2) over time was also measured in the same manner as in the mixture a(1) and the mixture a(2). The measurement results are shown in FIG. 6. FIG. 6 also shows, as a control, the measurement results of

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the adhesive composition prepared by simultaneously mixing three components (A), (B) and (C). In all of the mixtures, the blending ratio of (A), (B) and (C) was the same.

[0155] Based on the results shown in FIG. 6, the pot life of the adhesive composition obtained using the mixture a and the mixture b was the same as the adhesive composition obtained by simultaneously mixing three components (A), (B) and (C). Therefore, it was confirmed that the mixture a and the mixture b were able to maintain favorable coatability even when stored for a long time.

[0156] [Evaluation of dynamic viscoelasticity] (Example 21) A solvent was blended into the adhesive compositions of Example 7 and Comparative Example 1, the non-volatile content was adjusted to 40 mass%, and thereby a blended solution was obtained. The blended solution was formed into a film with a thickness of 200 pm on mold release paper with a doctor blade. After the solvent was removed by drying for 24 hours at room temperature and under a nitrogen atmosphere, curing was performed at 60°C for 6 to prepare a cured film (film thickness: 40 to 50 pm). This film was cut to a width of 5 mm to prepare a strip-shaped sample. The dynamic viscoelasticity of the strip-shaped sample was measured using a commercially available dynamic viscoelasticity measurement device (device name: DVA-200 commercially available from IT Measurement Control Co., Ltd.). The measurement was performed by raising the temperature at a rate of -50°C to 5°C/min under the following conditions. Length between marked lines: 2 cm

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Width: 0.485 cm Deformation mode: tension Static ratio: 1.4 Setting distortion: 0.16% (>1.00x108 Pa) Measurement frequency: 10 Hz

[0157] FIG. 7 is a graph showing the results of dynamic viscoelasticity measurement of the cured product obtained by curing the adhesive composition of Example 7. FIG. 8 is a graph showing the results of dynamic viscoelasticity measurement of the cured product obtained by curing the adhesive composition of Comparative Example 1. The glass transition temperature of the cured product of Comparative Example 1 was 29.3°C. On the other hand, the glass transition temperature of the cured product of Example 7 was 14.4°C. This indicates that, when the epoxy compound was contained, the flexibility of the cured product at room temperature was improved. It is considered that the adhesive composition of the present disclosure can improve the adhesive strength not only by penetrating into the electrostatic ink layer but also by softening and relieving stress generated caused by laminating. Industrial Applicability

[0158] According to the present disclosure, it is possible to provide a laminate that can maintain a sufficiently high adhesive strength between layers even under high temperature and hot water treatment conditions and a method of producing the same. In addition, the present disclosure provides a curing agent, an adhesive composition, a two-component adhesive and a cured product, which are useful for

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obtaining such a laminate. In addition, when such a laminate is provided, it is possible to provide a packaging material having excellent sealability. In addition, it is possible to provide a package packaged with a packaging material having excellent sealability. Reference Signs List

[0159] 10: First substrate, 20: Second substrate, 30: Adhesive layer, 40 Primer layer, 50: Electrostatic ink composition, 60, 62 Packaging material, 100, 110 Packaging bag, 101: Sealing part, 102: Housing part, 120: Opening unit, 121: Half-cut line, 124: Easy-opening processed part, 200: Package, 300: Laminate.

Claims

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[Claim 1] An adhesive composition adhering a printed surface on which an electrostatic ink composition is printed, comprising: a polyol; a polyisocyanate; and an epoxy compound.
[Claim 2] The adhesive composition according to claim 1, wherein the molar ratio of epoxy groups contained in the epoxy compound with respect to isocyanate groups contained in the polyisocyanate is 0.5 to 10.
[Claim 3] The adhesive composition according to claim 1 or 2, wherein the molar ratio of isocyanate groups contained in the polyisocyanate with respect to hydroxy groups contained in the polyol is 0.5 to 10.
[Claim 4] The adhesive composition according to any one of claims 1 to 3, which contains 3 to 25 parts by mass of the epoxy compound with respect to 100 parts by mass of the polyol.
[Claim 5] The adhesive composition according to any one of claims 1 to 4, which contains 10 to 50 parts by mass of the polyisocyanate with respect to 100 parts by mass of the polyol.
[Claim 6] The adhesive composition according to any one of claims 1 to 5, wherein the polyol is an aliphatic polyester polyol, and

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wherein the epoxy compound has epoxy groups at both ends.
[Claim 7] The adhesive composition according to any one of claims 1 to 6, wherein the epoxy compound includes a bifunctional alicyclic epoxy compound.
[Claim 8] The adhesive composition according to any one of claims 1 to 7, wherein the polyisocyanate includes xylylene diisocyanate derivatives, and wherein the content of the xylylene diisocyanate derivatives with respect to an entire of the polyisocyanate is 10 mass% or more.
[Claim 9] The adhesive composition according to any one of claims 1 to 8, wherein a glass transition temperature determined by dynamic viscoelasticity measurement after curing is 20°C or lower.
[Claim 10] A curing agent for an adhesive that adheres a printed surface on which an electrostatic ink composition is printed, comprising a polyisocyanate and an epoxy compound, wherein the molar ratio of epoxy groups contained in the epoxy compound with respect to isocyanate groups contained in the polyisocyanate is 0.5 to 10.
[Claim 11] The curing agent according to claim 10, wherein the epoxy compound includes a bifunctional alicyclic epoxy compound.

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[Claim 12] The curing agent according to claim 10 or 11, wherein the polyisocyanate includes xylylene diisocyanate derivatives, and wherein the content of the xylylene diisocyanate derivatives with respect to an entire of the polyisocyanate is 10 mass% or more.
[Claim 13] A two-component adhesive that adheres a printed surface on which an electrostatic ink composition is printed, comprising: a first liquid containing a main agent; and a second liquid containing the curing agent according to any one of claims 10 to 12.
[Claim 14] The two-component adhesive according to claim 13, wherein the main agent contains a polyol.
[Claim 15] The two-component adhesive according to claim 14, wherein the molar ratio of isocyanate groups contained in the polyisocyanate contained in the curing agent with respect to hydroxy groups contained in the polyol contained in the main agent is 0.5 to 10.
[Claim 16] The two-component adhesive according to claim 14 or 15, wherein the polyol contained in the main agent is an aliphatic polyester polyol, and wherein the epoxy compound contained in the curing agent has epoxy groups at both ends.

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[Claim 17] A cured product obtained by curing the adhesive composition according to any one of claims 1 to 9.
[Claim 18] The cured product according to claim 17, wherein a glass transition temperature determined by dynamic viscoelasticity measurement is 20°C or lower.
[Claim 19] A laminate comprising: a first substrate; an adhesive layer; and a second substrate in this order, wherein an electrostatic ink layer composed of an electrostatic ink composition is provided between at least one of the first substrate and the second substrate, and the adhesive layer, and wherein the adhesive layer contains one or both of a polyurethane and an epoxy compound, and a crosslinked product thereof.
[Claim 20] A laminate comprising: a first substrate; an adhesive layer; and a second substrate in this order, wherein an electrostatic ink layer composed of an electrostatic ink composition is provided between at least one of the first substrate and the second substrate, and the adhesive layer, and

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wherein the adhesive layer contains a polymer of a polyol, a polyisocyanate, and an epoxy compound.
[Claim 21] The laminate according to claim 19 or 20, wherein a primer layer is provided between the first substrate and the electrostatic ink layer.
[Claim 22] A packaging material having the laminate according to any one of claims 19 to 21.
[Claim 23] A package comprising the packaging material according to claim 22 and a packaged object packaged with the packaging material.
[Claim 24] A method of producing a laminate, comprising: a step of printing an electrostatic ink composition on the side of one surface of a first substrate to obtain a printed surface; and a step of adhering the printed surface and one surface on the side of a second substrate using the adhesive composition according to any one of claims 1 to 9.
[Claim 25] A method of producing a laminate, comprising: a step of printing an electrostatic ink composition on the side of one surface of a first substrate to obtain a printed surface; a step of mixing the first liquid and the second liquid in the two-component adhesive according to any one of claims 13 to 16 to prepare an adhesive composition; and

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a step of adhering the printed surface and one surface on the side of a second substrate using the adhesive composition.