Printed item and method for producing recycled board

Abstract

Provided are: a method for producing a recycled board, the method making it possible to suppress coloration of an alkali solution after a coating film is removed from a plastic substrate by a treatment with the alkali solution; and a printed item having a removable coating film, the printed item being suitable for use in the method for producing the recycled board.　The printed item comprises a laminate of a substrate and a coating film which is removable from the substrate by a treatment with an alkali solution, wherein the coating film comprises: a first layer which contains a colorant and at least one resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins; and a second layer which is in contact with the first layer. The second layer contains at least one resin B selected from the group consisting of vinyl chloride / vinyl acetate copolymer resins, poly(vinyl butyral) resins, cellulose acetate propionate resins, and cellulose acetate butyrate resins.

Description

Printed matter and method for manufacturing recycled substrate

[0001] The present invention relates to a printed matter having a coating that can be detached from a substrate, and a method for producing a recycled substrate from the printed matter.

[0002] In recent years, the marine plastic problem has become apparent due to the breakdown of plastic discarded or dumped in the ocean into tiny particles (microplastics) in seawater. These microplastics enter the bodies of marine organisms, where they accumulate, raising concerns that they may impact the health of seabirds and humans through the food chain. Recycling is one way to address this issue. Improving the recycling rate of resources such as flexible packaging and plastic bottles will prevent plastic from entering the ocean. However, current recycling methods pose a challenge: the printed layer on the plastic substrate does not detach during the recycling process and becomes mixed into the plastic, causing a deterioration in color and physical properties, thereby reducing the value of the recycled plastic. Solving this issue by enabling the removal of the coating from the plastic substrate during the recycling process would increase the value of recycled plastic, leading to the entry of new recyclers and the establishment of municipal sorting and collection systems. This would improve recycling rates and potentially alleviate the marine plastic problem. Therefore, there is a need to develop a method for removing the coating from the plastic substrate during the recycling process. Furthermore, film-forming materials widely used on plastic substrates are being replaced with toluene-free and methyl ethyl ketone (MEK)-free materials in consideration of their impact on worker health and the environment. Therefore, materials that solve the above-mentioned problems must be developed taking this into consideration.

[0003] Prior art discloses a method for removing a coating printed on a heat-shrinkable PET film containing a styrene-acrylic acid resin, a phenolic resin, or a styrene-maleic acid resin as a vehicle using alkaline water (Patent Document 1). Similarly, a method for forming a coating layer containing a styrene-maleic acid resin, a rosin-maleic acid resin, or an acrylic acid copolymer resin between the coating layers on the heat-shrinkable PET film and removing the coating layer using alkaline water (Patent Documents 2 and 3). However, these techniques only guarantee properties for specific heat-shrinkable PET substrates and have limitations, such as the need to provide an additional coating layer separate from the coating layer, making them unsuitable for recycling general-purpose plastic substrates, including polyolefins. Meanwhile, organic solvent-based printing inks for alkaline water removal using a urethane resin with an acid value as a binder resin have also been disclosed (Patent Documents 4, 5, and 6). However, when a urethane resin with an acid value is used as the main binder resin, it is expected that adhesion to the substrate will be insufficient. Furthermore, adding an acid value to the urethane resin increases the viscosity of the resin, necessitating the use of solvents with significant health and environmental impacts to adjust the viscosity. Alternatively, the coexistence of an amine value and an acid value is avoided to reduce viscosity, resulting in reduced suitability for laminating applications. These issues pose challenges for the general use of a material with a removable coating. Meanwhile, few technologies developed to promote the removal of the printing coating described above have considered the release of the removed coating into the cleaning solution. In particular, the colored pigments contained in the ink are released and discolored into the cleaning solution during cleaning, which leads to wastewater treatment problems and increases the environmental impact. No effective solution has been clearly demonstrated.

[0004] Japanese Patent No. 3822738 Japanese Patent No. 4653913 Japanese Patent No. 4451071 Japanese Patent No. 6638802 Japanese Patent No. 6631964 Japanese Patent Publication No. 2020-169280

[0005] The problem to be solved by the present invention is to provide a method for producing a recycled substrate that can suppress coloration of the alkaline solution after detachment when a coating is detached from a plastic substrate by treatment with an alkaline solution, and to provide a printed matter having a detachable coating that can be suitably used in the method for producing a recycled substrate.

[0006] As a result of extensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by forming a coating that is detached from a substrate by treatment with an alkaline solution, by laminating at least two layers, a first layer having a colorant and a second layer in contact with the first layer, and by incorporating a specific coloration inhibitor into the second layer, thereby completing the present invention.

[0007] That is, the present invention encompasses the following aspects. [1] A printed matter comprising a laminate of a substrate and a coating that can be detached from the substrate by treatment with an alkaline solution, wherein the coating has a first layer containing a colorant and at least one resin A selected from the group consisting of acrylic resin, urethane resin, polyamide resin, rosin resin, and polyester resin, and a second layer in contact with the first layer, wherein the second layer contains at least one resin B selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, polyvinyl butyral resin, cellulose acetate propionate resin, and cellulose acetate butyrate resin. [2] The printed matter according to [1], wherein the first layer further contains a nitrocellulose resin. [3] The printed matter according to [1], wherein the first layer further contains a vinyl chloride-vinyl acetate copolymer resin. [4] The printed matter described in [1], wherein the first layer contains any one of: (i) a urethane resin and a nitrocellulose resin; (ii) an acrylic resin and a nitrocellulose resin; (iii) a polyamide resin and a nitrocellulose resin; and (iv) an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, and a cellulose acetate butyrate resin. [5] The printed matter described in [1], wherein the second layer contains Resin B at a ratio of 30% by mass or more to the total amount of resins contained in the second layer. [6] The printed matter described in [1], wherein a third layer that promotes detachment is further disposed between the substrate and the coating. [7] A method for producing a recycled substrate, wherein the printed matter described in [1] is treated with an alkaline solution to detach the coating from the substrate, thereby obtaining a recycled substrate. [8] The alkaline solution has a pH of 9 or higher and contains a nonionic surfactant.

[0008] The present invention provides a method for producing a recycled substrate that can suppress coloration of the alkaline solution after detachment when a coating is detached from a plastic substrate by treatment with an alkaline solution, and a printed material having a removable coating that can be suitably used in the method for producing a recycled substrate.

[0009] The present invention will be described in detail below. Note that the following explanation of the constituent elements is an example for explaining the present invention, and the present invention is not limited to these contents.

[0010] (Printed Material) The printed material of the present invention comprises a laminate of a substrate and a coating that can be detached from the substrate by treatment with an alkaline solution. The coating has a two-layer structure including a first layer and a second layer in contact with the first layer. The first layer contains a colorant and at least one resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins. The second layer contains at least one resin B selected from the group consisting of vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, cellulose acetate propionate resins, and cellulose acetate butyrate resins.

[0011] <Coating> The coating according to the present invention has a first layer and a second layer in contact with the first layer. When the coating is removed by treatment with an alkaline solution, the first layer contains a colorant, so the alkaline solution after removal is colored. However, in this embodiment of the present invention, Resin B contained in the second layer exhibits a coloration suppression effect, so coloration of the alkaline solution after removal is significantly suppressed, and a clear alkaline solution can be obtained. Although the mechanism of action by which a significant coloration suppression effect is obtained in the alkaline solution after removal has not been fully elucidated, one example of a presumed mechanism of action will be described.

[0012] Since the alkaline solution used to remove the film is classified as a strong alkaline, the resin contained in the film is decomposed by the alkaline solution (particularly when the film contains nitrocellulose resin (so-called nitrocellulose), the nitrocellulose resin is decomposed in a short time), causing the colorant to diffuse into the alkaline solution and coloring the alkaline solution with the color derived from the colorant. Meanwhile, the film according to the present invention contains at least one resin B selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, polyvinyl butyral resin, cellulose acetate propionate resin, and cellulose acetate butyrate resin. It is believed that this resin B adheres to resins such as nitrocellulose resin and colorant, effectively protecting the resin and colorant from alkali, thereby suppressing coloration of the alkaline solution.

[0013] The coating according to the present invention exhibits a remarkable effect of inhibiting discoloration of the alkaline solution after removal from the substrate by treatment with an alkaline solution. This makes it possible to prevent water pollution and environmental impact caused by colored wastewater. Furthermore, since raw materials and manufacturing equipment for decolorizing colored wastewater are not required, manufacturing costs can be reduced when recycling substrates. Furthermore, since a decolorizing process is not required and the recycling efficiency of substrates is excellent, the coating is highly useful industrially.

[0014] <<First Layer>> The first layer is formed using a composition for forming the first layer (herein, such a composition is also referred to as composition (I)). The composition (I) for forming the first layer contains a colorant. The composition (I) also contains at least one type of resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins. The composition (I) may further contain a nitrocellulose resin (nitrocellulose). The composition (I) may also contain a vinyl chloride-vinyl acetate copolymer resin (also referred to as a vinyl chloride-vinyl acetate resin). The composition (I) may contain other resins in addition to the above-mentioned resin A, nitrocellulose resin, and vinyl chloride-vinyl acetate copolymer resin. The composition (I) may also contain an organic solvent, and may also contain other components such as an auxiliary agent and an acidic additive. The components of the composition (I) are described below.

[0015] <<<Colorant>>> Examples of the colorant component include color dyes and / or color pigments, and among these, color pigments (hereinafter also simply referred to as pigments) are preferred.

[0016] Pigment Examples of the pigment used in the present invention include inorganic pigments and organic pigments used in general inks, paints, recording agents, etc. From the viewpoint of effectively suppressing coloration of the alkaline solution after desorption, organic pigments are preferred.

[0017] Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthanthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, and carbon black pigments. Other examples include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, cromophtal yellow, cromophtal red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigo bordeaux, thioindigo magenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, and daylight fluorescent pigments. Both non-acid-treated and acid-treated pigments can be used. Specific examples of preferred organic pigments are listed below.

[0018] Examples of black pigments include C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, C.I. Pigment Black 9, and C.I. Pigment Black 20.

[0019] Examples of indigo pigments include C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:5, C.I. Pigment Blue 15:6, C.I. Pigment Blue 16, C.I. Pigment Blue 17:1, C.I. Pigment Blue 22, C.I. Pigment Blue 24:1, C.I. Pigment Blue 25, C.I. Pigment Blue 26, C.I. Pigment Blue 60, C.I. Pigment Blue 61, C.I. Pigment Blue 62, C.I. Pigment Blue 63, C.I. Examples of pigments that can be used include C.I. Pigment Blue 64, C.I. Pigment Blue 75, C.I. Pigment Blue 79, and C.I. Pigment Blue 80.

[0020] Examples of green pigments include C.I. Pigment Green 1, C.I. Pigment Green 4, C.I. Pigment Green 7, C.I. Pigment Green 8, C.I. Pigment Green 10, and C.I. Pigment Green 36.

[0021] Examples of red pigments include C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 4, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 8, C.I. Pigment Red 9, C.I. Pigment Red 10, C.I. Pigment Red 11, C.I. Pigment Red 12, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 17, C.I. Pigment Red 18, C.I. Pigment Red 19, C.I. Pigment Red 20, C.I. Pigment Red 21, C.I. C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 38, C.I. Pigment Red 41, C.I. Pigment Red 43, C.I. Pigment Red 46, C.I. Pigment Red 48, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 48:4, C.I. Pigment Red 48:5, C.I. Pigment Red 48:6, C.I. Pigment Red 49, C.I. Pigment Red 49:1, C.I. Pigment Red 49:2, C.I. Pigment Red 49:3, C.I. Pigment Red 52, C.I. Pigment Red 52:1, C.I. Pigment Red 52:2, C.I. Pigment Red 53, C.I. Pigment Red 53:1, C.I. Pigment Red 53:2, C.I. Pigment Red 53:3, C.I. Pigment Red 54, C.I. Pigment Red 57, C.I. Pigment Red 57:1, C.I. Pigment Red 58, C.I. Pigment Red 58:1, C.I. Pigment Red 58:2, C.I. Pigment Red 58:3, C.I. Pigment Red 58:4, C.I. Pigment Red 60:1, C.I. Pigment Red 63, C.I. Pigment Red 63:1, C.I. Pigment Red 63:2, C.I. Pigment Red 63:3, C.I. Pigment Red 64:1, C.I. Pigment Red 68, C.I. Pigment Red 68, C.I. Pigment Red 81:1, C.I. Pigment Red 83,C.I. Pigment Red 88, C.I. Pigment Red 89, C.I. Pigment Red 95, C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 119, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 136, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 147, C.I. Pigment Red 149, C.I. Pigment Red 150, C.I. Pigment Red 164, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 169, C.I. Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 172, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 180, C.I. Pigment Red 181, C.I. Pigment Red 182, C.I. Pigment Red 183, C.I. Pigment Red 184, C.I. Pigment Red 185, C.I. Pigment Red 187, C.I. Pigment Red 188, C.I. Pigment Red 190, C.I. Pigment Red 192, C.I. Pigment Red 193, C.I. Pigment Red 194, C.I. Pigment Red 200, C.I. Pigment Red 202, C.I. Pigment Red 206, C.I. Pigment Red 207, C.I. Pigment Red 208, C.I. Pigment Red 209, C.I. Pigment Red 210, C.I. Pigment Red 211, C.I. Pigment Red 213, C.I. Pigment Red 214, C.I. Pigment Red 216, C.I. Pigment Red 215, C.I. Pigment Red 216, C.I. Pigment Red 220, C.I. Pigment Red 221, C.I. Pigment Red 223, C.I. Pigment Red 224, C.I. Pigment Red 226, C.I. Pigment Red 237, C.I. Pigment Red 238, C.I. Pigment Red 239, C.I. Pigment Red 240, C.I. Pigment Red 242, C.I. Pigment Red 245,C.I. Pigment Red 247, C.I. Pigment Red 248, C.I. Pigment Red 251, C.I. Pigment Red 253, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Red 256, C.I. Pigment Red 257, C.I. Pigment Red 258, C.I. Pigment Red 260, C.I. Pigment Red 262, C.I. Pigment Red 263, C.I. Pigment Red 264, C.I. Pigment Red 266, C.I. Pigment Red 268, C.I. Pigment Red 269, C.I. Pigment Red 270, C.I. Examples of suitable pigments include C.I. Pigment Red 271, C.I. Pigment Red 272, and C.I. Pigment Red 279.

[0022] Examples of purple pigments include C.I. Pigment Violet 1, C.I. Pigment Violet 2, C.I. Pigment Violet 3, C.I. Pigment Violet 3:1, C.I. Pigment Violet 3:3, C.I. Pigment Violet 5:1, C.I. Pigment Violet 13, C.I. Pigment Violet 19 (γ type, β type), C.I. Pigment Violet 23, C.I. Pigment Violet 25, C.I. Pigment Violet 27, C.I. Pigment Violet 29, C.I. Pigment Violet 31, C.I. Pigment Violet 32, C.I. Pigment Violet 36, C.I. Pigment Violet 37, C.I. Examples of suitable pigments include C.I. Pigment Violet 38, C.I. Pigment Violet 42, and C.I. Pigment Violet 50.

[0023] Examples of yellow pigments include C.I. Pigment Yellow 1, C.I. Pigment Yellow 3, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 42, C.I. Pigment Yellow 55, C.I. Pigment Yellow 62, C.I. Pigment Yellow 65, C.I. Pigment Yellow 74, C.I. Pigment Yellow 83, C.I. Pigment Yellow 86, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, Pigment Yellow 125, C.I. Pigment Yellow 128, C.I. Pigment Yellow 129, C.I. Pigment Yellow 137, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 148, C.I. Pigment Yellow 150, C.I. Pigment Yellow 151, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 155, C.I. Pigment Yellow 166, C.I. Pigment Yellow 168, C.I. Examples of pigments that can be used include C.I. Pigment Yellow 174, C.I. Pigment Yellow 180, C.I. Pigment Yellow 185, and C.I. Pigment Yellow 213.

[0024] Examples of orange pigments include C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 16, C.I. Pigment Orange 34, C.I. Pigment Orange 36, C.I. Pigment Orange 37, C.I. Pigment Orange 38, C.I. Pigment Orange 43, C.I. Pigment Orange 51, C.I. Pigment Orange 55, C.I. Pigment Orange 59, C.I. Pigment Orange 61, C.I. Pigment Orange 64, C.I. Pigment Orange 71, and C.I. Pigment Orange 74.

[0025] Examples of brown pigments include C.I. Pigment Brown 23, C.I. Pigment Brown 25, and C.I. Pigment Brown 26. Among these, preferred pigments include C.I. Pigment Black 7 as a black pigment, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, and C.I. Pigment Blue 15:6 as indigo pigments, C.I. Pigment Green 7 as a green pigment, and C.I. Pigment Red 57:1, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, and C.I. Pigment Red 146, C.I. Pigment Red 242, C.I. Pigment Red 185, C.I. Pigment Red 122, C.I. Pigment Red 178, C.I. Pigment Red 149, C.I. Pigment Red 144, C.I. Pigment Red 166, as purple pigments C.I. Pigment Violet 23, C.I. Pigment Violet 37, as yellow pigments C.I. Pigment Yellow 83, C.I. Pigment Yellow 14, C.I. Pigment Yellow 180, C.I. Pigment Yellow 139, as orange pigments C.I. Pigment Orange 38, C.I. Pigment Orange 13, C.I. Pigment Orange 34, C.I. Pigment Orange 64, and the like, and it is preferable to use at least one or two or more selected from this group.

[0026] Examples of inorganic pigments include carbon black, titanium oxide, red iron oxide, aluminum, mica, zinc oxide, barium sulfate, calcium carbonate, and silica. Also usable are glittering pigments (Metashine; Nippon Sheet Glass Co., Ltd.) in which a metal or metal oxide is coated on a base material of glass flakes or aggregate flakes. From the standpoints of cost and coloring power, it is preferable to use carbon black for black ink, titanium oxide for white ink, aluminum for gold and silver ink, and mica for pearl ink.

[0027] The total content of the pigments is not particularly limited, but for example, in the composition forming the first layer, from the viewpoint of ensuring the coloring power of the composition, the content of the pigments is preferably 1 to 60 parts by mass, and more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the total amount of the composition. The total content of the white pigments may be 15 to 60 parts by mass, or may be 20 to 40 parts by mass, relative to 100 parts by mass of the total amount of the composition. The total content of the colored organic pigments may be 1 to 30 parts by mass, or may be 5 to 25 parts by mass, relative to 100 parts by mass of the total amount of the pigment composition. Any combination of these upper and lower limits may be used.

[0028] <<<Resins>>> Composition (I) contains at least one resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins. Composition (I) may contain a resin other than Resin A. For example, it may contain nitrocellulose resin (nitrocellulose). Composition (I) may also contain Resin B, which is contained in the second layer. In particular, Resin B may contain a vinyl chloride-vinyl acetate copolymer resin (also referred to as a vinyl chloride-vinyl acetate resin). Resin B will be described in detail in the section <<Second Layer>> below. Furthermore, Composition (I) may contain, in addition to the resins described above, other resins such as cellulose-based resins, ketone resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubbers, chlorinated rubbers, butyral resins, and petroleum resins (excluding Resin B, described below). These may be used in appropriate combinations.

[0029] - Urethane Resin - The number average molecular weight of the urethane resin is preferably within the range of 15,000 to 100,000. If the number average molecular weight of the urethane resin is less than 15,000, the composition forming the first layer tends to have reduced blocking resistance, chemical resistance, etc., whereas if it exceeds 100,000, the viscosity of the composition increases, making it difficult to obtain a desired print density.

[0030] The urethane resin contained in the composition forming the first layer preferably uses polyester polyol and / or polyether polyol as its reaction raw material.

[0031] The number-average molecular weight of the polyester polyol is preferably 3,000 to 7,000. If the number-average molecular weight of the polyester polyol is less than 3,000, the urethane resin coating tends to be hard, and adhesion to polyester films is likely to be reduced. If the number-average molecular weight is greater than 7,000, the urethane resin coating tends to be brittle, and the blocking resistance of the coating is likely to be reduced. On the other hand, the amount of polyester polyol is preferably 1 to 50 parts by mass per 100 parts by mass of the urethane resin. If the amount of polyester polyol is less than 1 part by mass, the solubility of the polyurethane resin in ketone, ester, and alcohol-based solvents decreases, and adhesion, particularly to high-performance barrier films, tends to decrease. Furthermore, the resolubility of the coating in these solvents decreases, and the reproducibility of printed materials tends to decrease. Furthermore, if the amount exceeds 50 parts by mass, the coating tends to become excessively soft, and blocking resistance tends to be poor.

[0032] The number average molecular weight of the polyester polyol is a value measured by gel permeation chromatography (GPC) under the following conditions: Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were used, connected in series. "TSKgel G5000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G4000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G3000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G2000" (7.8 mm I.D. x 30 cm) x 1 tube Detector: RI (differential refractometer) Column temperature: 40°C Eluent: tetrahydrofuran (THF) Flow rate: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass) Standard sample: A calibration curve was prepared using the following standard polystyrene. (Standard polystyrene) "TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[0033] As the polyester polyol, for example, one obtained by a known esterification reaction between a compound having two or more hydroxyl groups and a polybasic acid can be used.

[0034] The compound having two or more hydroxyl groups is used as a chain extender, and examples thereof include glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, and neopentyl glycol. Examples of compounds that can be used include glycols having a branched structure such as 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,6-hexanediol, 3,5-heptanediol, and 2-methyl-1,8-octanediol; aliphatic polyols such as trimethylolpropane, trimethylolethane, pentaerythritol, sucrose, methylene glycol, glycerin, and sorbitol; and aromatic polyols such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone, each of which has a number average molecular weight in the range of 50 to 400. These chain extenders may be used alone or in combination of two or more.

[0035] Examples of the polybasic acid that can be used include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, and anhydrides of these acids. These polybasic acids may be used alone or in combination of two or more.

[0036] The polyether polyol preferably has a number average molecular weight of 100 to 4000. Examples of polyether polyols include polyether polyols of polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, and the like. Specifically, known, general-purpose polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may be used, with polyethylene glycol being preferred. By incorporating polyester polyol and / or polyether polyol within the above range, adhesion, particularly to the substrate film, is significantly improved, resulting in excellent blocking resistance.

[0037] If the number average molecular weight of the polyether polyol is less than 100, the urethane resin film tends to be hard, and the adhesion to the polyester film is likely to be reduced. If the number average molecular weight is more than 4000, the urethane resin film tends to be brittle, and the blocking resistance of the film is likely to be reduced. The number average molecular weight of the polyether polyol can be determined by measuring it by gel permeation chromatography (GPC) under the same conditions as the polyester polyol.

[0038] Examples of the diisocyanate compound used in the urethane resin in the composition for forming the first layer include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates that are generally used in the production of urethane resins. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dimeryl diisocyanate, isocyanate, isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate; 5-isocyanato-1-(isocyanomethyl)-1,3,3-trimethylcyclohexane), dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, 4,4-diphenylmethane diisocyanate, tolylene diisocyanate, bis-chloromethyl-diphenylmethane-diisocyanate, 2,6-diisocyanato-benzyl chloride, and dimer diisocyanate in which the carboxyl groups of dimer acid are converted to isocyanate groups. These diisocyanate compounds can be used alone or in combination of two or more.

[0039] Examples of chain extenders used in the urethane resin in the composition for forming the first layer include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, etc., as well as amines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. These chain extenders can be used alone or in combination of two or more.

[0040] Furthermore, the amine value of the urethane resin used in the composition for forming the first layer is preferably 10.0 mgKOH / g or less. If the amine value exceeds 10.0 mgKOH / g, blocking resistance tends to deteriorate, and the stability of the second-component composition after addition of a curing agent decreases. From the viewpoint of maintaining good blocking resistance and second-component stability while maintaining plate fogging resistance, adhesion, and extrusion lamination strength, the amine value is more preferably in the range of 1.0 to 5.0 mgKOH / g, and even more preferably in the range of 1.0 to 3.5 mgKOH / g.

[0041] - Acrylic Resin - Acrylic resins can be obtained by copolymerizing various (meth)acrylate monomers and, if necessary, other polymerizable unsaturated group-containing compounds.

[0042] The monomer constituting the acrylic resin is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-pentafluoropropyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate, and glycerol. (Meth)acrylic monomers such as ricidyl (meth)acrylate, allyl glycidyl ether, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, (meth)acrylamide, N-monoalkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, 2-aziridinylethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, acrolein, diacetone (meth)acrylamide, and acetoacetoxyethyl (meth)acrylate can be used. Note that the term "(meth)acrylate" refers to either or both of acrylate and methacrylate, and "(meth)acrylic" refers to either or both of acrylic and methacrylic.

[0043] In addition to the (meth)acrylic monomers, the polymerizable unsaturated group-containing compound may also be vinyl monomers such as vinyl acetate, vinyl propionate, vinyl versatate, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, (meth)acrylonitrile, styrene, α-methylstyrene, divinylstyrene, isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, and N-vinylpyrrolidone. These may be used alone or in combination of two or more.

[0044] The number average molecular weight of the acrylic resin is not particularly limited, but is preferably 3,000 to 50,000, and more preferably 10,000 to 30,000.

[0045] -Polyamide Resin- Polyamide resins can be obtained by reacting a polycarboxylic acid compound with a polyamine or a polyisocyanate compound. Examples of the polycarboxylic acid compound include succinic acid, maleic acid, fumaric acid, itaconic acid, azelaic acid, mesaconic acid, citraconic acid, sebacic acid, glutaconic acid, adipic acid, malonic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, nadic acid, methylnadic acid, octyl succinic acid, and anhydrides of these acids, polymerized fatty acids such as linoleic acid dimers and trimers, dodecanedioic acid, C21 dibasic acids, and dimer acids (polymerized fatty acids obtained by polymerizing unsaturated fatty acids such as oleic acid and linoleic acid).

[0046] Furthermore, aliphatic polycarboxylic acids having 7 to 20 carbon atoms, such as 1,2,4-butanetricarboxylic acid and 1,2,5-hexanetricarboxylic acid, alicyclic polycarboxylic acids having 9 to 20 carbon atoms, such as 1,2,4-cyclohexanetricarboxylic acid, aromatic polycarboxylic acids having 9 to 20 carbon atoms, such as 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid and pyromellitic acid, as well as trivalent or higher polycarboxylic acids, such as anhydrides and lower alkyl (methyl, butyl, etc.) esters of these.

[0047] Examples of polyamines used to obtain polyamide resins include diamines such as ethylenediamine, propylenediamine, diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminodecane, and diaminododecane; and trivalent or higher amines such as diethylenetriamine and triethylenetetramine.

[0048] The number average molecular weight of the polyamide resin is not particularly limited, but is preferably 5,000 to 20,000, and more preferably 500 to 10,000.

[0049] - Rosin Resin - The rosin resin may contain 20% by mass or more of a rosin-derived structure, and preferably has a softening point (ring and ball method) of 30°C to 180°C, more preferably 50 to 170°C. Suitable examples of the rosin resin include polymerized rosin resin, rosin-modified maleic acid resin, and rosin-modified fumaric acid resin. The acid value of the rosin resin is preferably 50 to 350 (mgKOH / g). Suitable examples of the rosin resin include Aradigm R-95 and Marquid No. 32, both manufactured by Arakawa Chemical Industries, Ltd.

[0050] The weight-average molecular weight of the rosin-modified maleic acid resin or the rosin-modified fumaric acid resin is preferably at least 500, more preferably at least 700, and even more preferably at least 1000. By setting the weight-average molecular weight within the above range, it is possible to achieve a good balance between adhesion to the substrate and releasability in an alkaline solution.

[0051] The weight average molecular weight of the rosin-modified maleic acid resin or rosin-modified fumaric acid resin is preferably not more than 50,000, more preferably not more than 30,000, more preferably not more than 10,000, more preferably not more than 5,000, and even more preferably not more than 2,000. By setting the weight average molecular weight within the above range, the viscosity of the ink can be reduced, and a balance can be achieved between adhesion to the substrate and releasability in an alkaline solution.

[0052] The weight average molecular weight of the rosin-modified maleic acid resin or rosin-modified fumaric acid resin is preferably 500 to 50,000, more preferably 700 to 520,000, more preferably 1,000 to 10,000, and even more preferably 1,000 to 5,000. By setting it within the above range, printability can be improved.

[0053] -Polyester Resin- Various known polyester resins can be used as the polyester resin. Polyester resins can be obtained by reacting glycol with a dibasic acid or its derivative as an essential component. Of course, polyester resins can also be obtained by using an ester-forming derivative such as a dibasic acid anhydride or a dibasic acid lower alkyl ester instead of the dibasic acid, not only through a polycondensation reaction but also through an addition reaction or an ester exchange reaction. Examples of such polyester resins include aliphatic polyester polyols obtained by reacting an aliphatic glycol such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, decanediol, or cyclohexanedimethanol with an aliphatic dibasic acid such as succinic acid, adipic acid, sebacic acid, fumaric acid, suberic acid, azelaic acid, 1,10-decamethylenedicarboxylic acid, or cyclohexanedicarboxylic acid as the essential raw material components, and aromatic polyester polyols obtained by reacting an aliphatic glycol such as ethylene glycol, propylene glycol, or butanediol with an aromatic dibasic acid such as terephthalic acid, isophthalic acid, or naphthalenedicarboxylic acid as the essential raw material components. Examples of such polyester resins include the "Polylite" series manufactured by DIC Corporation and the "Kuraray Polyol" series manufactured by Kuraray Co., Ltd.

[0054] - Nitrocellulose Resin (Nitrocellulose) - The inclusion of a nitrocellulose resin makes it easier to form a coating that can be easily removed from the substrate by treatment with an alkaline solution. The nitrocellulose resin contained in the composition for forming the first layer according to the present invention can be a typical cellulose nitrate ester obtained by treating cellulose with a mixed acid of nitric acid and sulfuric acid. Furthermore, in order to adjust the viscosity of the composition, two or more types of nitrocellulose resins with different viscosity standards according to JIS K-6703 (industrial nitrocellulose) (e.g., an H20 equivalent product and an L1 / 4 equivalent product) can be mixed and used.

[0055] The content of the nitrocellulose resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of the total amount of the composition (I) for forming the first layer, from the viewpoint of contributing to the promotion of film detachment, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, from the viewpoint of the film-forming properties of the ink film and the ink viscosity.

[0056] Vinyl chloride-vinyl acetate copolymer resin (vinyl chloride-vinyl acetate resin)—Resin B, such as a vinyl chloride-vinyl acetate copolymer resin, may also be contained. Resin B will be described in detail in the section "Second Layer" below. However, if Resin B is to be contained in the first layer, compatibility with other resins contained in the first layer may become an issue depending on the content of Resin B. Therefore, in the present invention, Resin B, which exhibits the effect of suppressing coloration of the alkaline treatment solution, is contained in a layer (the so-called second layer) separate from the first layer, thereby ensuring freedom in selecting the type and content of the constituent components of the first layer. However, this does not preclude the use of Resin B in the first layer, as long as compatibility with other resins contained in the first layer is not an issue. Resin B may also be contained in the first layer, as long as it does not impede freedom in selecting the type and content of the constituent components of the first layer.

[0057] The content of Resin B is preferably 0.1 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.3 parts by mass or more, relative to 100 parts by mass of the total amount of Composition (I) forming the first layer, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less.

[0058] <<<Preferred Combinations of Resins Contained in Composition (I) for Forming the First Layer>>> The composition (I) for forming the first layer preferably contains at least two or more resins as shown in the following (i) to (iii): (i) Contains at least a urethane resin and a nitrocellulose resin; (ii) Contains at least an acrylic resin and a nitrocellulose resin; (iii) Contains at least a polyamide resin and a nitrocellulose resin. In the present invention, resin B, which exhibits the effect of suppressing coloration of the alkaline treatment solution, is contained in a layer (so-called second layer) separate from the first layer. However, as described above, resin B may be contained in the first layer as long as compatibility with other resins contained in the first layer is not an issue. Therefore, it is also preferable that the composition (I) for forming the first layer contains at least two or more resins as shown in the following (iv): (iv) Contains at least an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, and a cellulose acetate butyrate resin.

[0059] <<<<Resin Content in Composition (I) for Forming First Layer>>> The resin content in composition (I) is not particularly limited, but is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, relative to 100 parts by mass of the total amount of the composition. The total content is preferably 60 parts by mass or less, more preferably 55 parts by mass or less. When two or more types of resins are contained in composition (I), the preferred range of the content is the total amount of the resins contained therein.

[0060] <<<Organic Solvent>>> Composition (I) may contain an organic solvent. The organic solvent is not particularly limited, and examples thereof include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, and Solvesso #150; aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, and decane; and various ester organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, propanol, butanol, isopropyl alcohol, and normal propyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and glycol ethers such as ethylene glycol (mono, di)methyl ether, ethylene glycol (mono, di)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di)methyl ether, diethylene glycol (mono, di)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di)methyl ether, propylene glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono, di)methyl ether. Among these, various ester-based organic solvents and various alcohol-based organic solvents are preferred, with isopropyl alcohol and ethyl acetate being more preferred. These can be used alone or in combination of two or more.

[0061] The content of the organic solvent is not particularly limited, but is preferably 20% by mass or more, and more preferably 30% by mass or more, relative to 100 parts by mass of the total amount of the composition (I), and is preferably 70% by mass or less, more preferably 65% ​​by mass or less, more preferably 60% by mass or less, and more preferably 55% by mass or less.

[0062] <<<<Other Components>>> The composition (I) may further contain other components such as auxiliaries and acidic additives, as necessary.

[0063] Examples of the auxiliary that can be used appropriately include waxes such as paraffin wax, polyethylene wax, and carnauba wax for imparting friction resistance, slipperiness, etc.; fatty acid amide compounds such as oleic acid amide, stearic acid amide, and erucic acid amide; silicone and non-silicone antifoaming agents for suppressing foaming during printing; and dispersants. Nonionic dispersants are preferred as dispersants.

[0064] The acid value of the dispersant is preferably 30 mgKOH / g or less, more preferably 25 mgKOH / g or less, and even more preferably 20 mgKOH / g or less, and may be, for example, 1 mgKOH / g or more, or even 3 mgKOH / g or more.

[0065] The content of the dispersant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, more preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the colorant (e.g., pigment), and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, more preferably 75 parts by mass or less, more preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0066] As the acidic additive, for example, an organic acid or a resin having an acidic group can be used. The acid value of the acidic additive is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, and more preferably 50 mgKOH / g or more. The acid value is preferably 900 mgKOH / g or less, more preferably 850 mgKOH / g or less, more preferably 800 mgKOH / g or less, more preferably 750 mgKOH / g or less, more preferably 700 mgKOH / g or less, more preferably 650 mgKOH / g or less, more preferably 600 mgKOH / g or less, and more preferably 550 mgKOH / g or less. By setting the acid value in the above range, both alkaline solution releasability and adhesion to the substrate can be achieved.

[0067] Furthermore, when emphasis is placed on releasability in an alkaline solution, the OH content is preferably 50 mgKOH / g or more, more preferably 100 mgKOH / g or more, more preferably 200 mgKOH / g or more, more preferably 300 mgKOH / g or more, more preferably 400 mgKOH / g or more, more preferably 500 mgKOH / g or more, and particularly preferably 550 mgKOH / g or more. When emphasis is placed on adhesion to a substrate, the OH content is preferably 550 mgKOH / g or less, more preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, more preferably 300 mgKOH / g or less, and more preferably 200 mgKOH / g or less.

[0068] When importance is placed on both the alkaline solution releasability and the adhesion to the substrate, the acid value is preferably in the range of 1 to 900 mgKOH / g, more preferably 3 to 850 mgKOH / g, more preferably 5 to 800 mgKOH / g, more preferably 10 to 750 mgKOH / g, more preferably 20 to 700 mgKOH / g, more preferably 30 to 650 mgKOH / g, more preferably 40 to 600 mgKOH / g, and more preferably 50 to 550 mgKOH / g.

[0069] When emphasis is placed on releasability in an alkaline solution, 50 to 900 mg KOH / g is preferred, 65 to 900 mg KOH / g is preferred, 80 to 900 mg KOH / g is preferred, 100 to 900 mg KOH / g is more preferred, 200 to 900 mg KOH / g is more preferred, 300 to 900 mg KOH / g is more preferred, 400 to 900 mg KOH / g is more preferred, 500 to 900 mg KOH / g is more preferred, and 550 to 900 mg KOH / g is more preferred. When emphasis is placed on adhesion to the substrate, 1 to 550 mg KOH / g is preferred, 1 to 500 mg KOH / g is more preferred, 1 to 400 mg KOH / g is more preferred, 1 to 300 mg KOH / g is more preferred, and 1 to 200 mg KOH / g is more preferred.

[0070] When both alkaline solution releasability and adhesion to the substrate are satisfied, the molecular weight of the acidic additive is preferably 50 or more, preferably 60 or more, preferably 80 or more, preferably 100 or more, preferably 150 or more, preferably 200 or more, preferably 250 or more, and preferably 300 or more. It is also preferably 2000 or less, preferably 1800 or less, preferably 1500 or less, preferably 1200 or less, and preferably 1000 or less. The molecular weight range is preferably 50 to 2000, preferably 50 to 1800, preferably 50 to 1500, preferably 60 to 1500, preferably 80 to 1500, preferably 100 to 1500, preferably 150 to 1500, preferably 200 to 1500, preferably 250 to 1500, preferably 300 to 1500, preferably 300 to 1200, and preferably 300 to 1000.

[0071] The organic acid refers to a low molecular weight organic compound having an acidic group. Preferred examples of the low molecular weight compound having an acidic group include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives, and these can be used singly or in combination.

[0072] Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, decanoic acid, undecanoic acid, and dodecanoic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, and ketone. Examples of the dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dimer acid, fumaric acid, maleic acid, azelaic acid, etc.; examples of the tricarboxylic acids include aconitic acid and trimer acid, etc.; examples of the oxocarboxylic acids include pyruvic acid and oxaloacetic acid, etc.; examples of the carboxylic acid derivatives include amino acids and nitrocarboxylic acids, and these can be used singly or in combination. In addition, citric acid, butyric acid, caproic acid, enanthic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, eleostearic acid, arachidic acid, sebacic acid, etc. are compliant with the so-called Swiss Ordinance, and it is preferable to use substances that comply with various regulations.

[0073] The acid value of the organic acid is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, more preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, more preferably 70 mgKOH / g or more, more preferably 80 mgKOH / g or more, more preferably 90 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more. The acid value is preferably 900 mgKOH / g or less, more preferably 850 mgKOH / g or less, more preferably 800 mgKOH / g or less, more preferably 750 mgKOH / g or less, more preferably 700 mgKOH / g or less, more preferably 650 mgKOH / g or less, more preferably 600 mgKOH / g or less, and more preferably 550 mgKOH / g or less. By setting the acid value within the above range, it is possible to achieve both alkaline solution releasability and adhesion to the substrate.

[0074] Further, when emphasis is placed on releasability in an alkaline solution, 100 mg KOH / g or more is preferred, 150 mg KOH / g or more is more preferred, 200 mg KOH / g or more is more preferred, 250 mg KOH / g or more is more preferred, 300 mg KOH / g or more is more preferred, 350 mg KOH / g or more is more preferred, 400 mg KOH / g or more is more preferred, 450 mg KOH / g or more is more preferred, 500 mg KOH / g or more is more preferred, and 550 mg KOH / g or more is more preferred. When emphasis is placed on adhesion to the substrate, 550 mg KOH / g or less is preferred, 500 mg KOH / g or less is more preferred, 400 mg KOH / g or less is more preferred, 300 mg KOH / g or less is more preferred, and 200 mg KOH / g or less is more preferred.

[0075] When importance is placed on both the alkaline solution releasability and the adhesion to the substrate, the acid value is preferably in the range of 1 to 900 mgKOH / g, more preferably 3 to 850 mgKOH / g, more preferably 10 to 800 mgKOH / g, more preferably 20 to 750 mgKOH / g, more preferably 30 to 700 mgKOH / g, more preferably 50 to 650 mgKOH / g, more preferably 80 to 600 mgKOH / g, and more preferably 100 to 550 mgKOH / g. Further, when emphasis is placed on releasability in an alkaline solution, 100 to 900 mg KOH / g is preferred, 150 to 900 mg KOH / g is more preferred, 200 to 900 mg KOH / g is more preferred, 250 to 900 mg KOH / g is more preferred, 300 to 900 mg KOH / g is more preferred, 350 to 900 mg KOH / g is more preferred, 400 to 900 mg KOH / g is more preferred, 450 to 900 mg KOH / g is more preferred, 500 to 900 mg KOH / g is more preferred, 550 to 900 mg KOH / g is more preferred. Further, when emphasis is placed on adhesion to the substrate, 1 to 550 mg KOH / g is preferred, 1 to 500 mg KOH / g is more preferred, 1 to 400 mg KOH / g is more preferred, 1 to 300 mg KOH / g is more preferred, 1 to 200 mg KOH / g is more preferred.

[0076] The organic acid preferably has 3 or more carbon atoms, preferably 4 or more, preferably 5 or more, preferably 6 or more, preferably 7 or more, and preferably 8 or more. By setting the number of carbon atoms of the organic acid within the above range, adhesion to the substrate can be improved. Furthermore, the number of carbon atoms of the organic acid is preferably 20 or less, preferably 18 or less, and preferably 16 or less. By setting the number of carbon atoms of the organic acid within the above range, dispersibility in an aqueous medium can be improved. The range of the number of carbon atoms of the organic acid is preferably 3 to 20, preferably 3 to 18, preferably 4 to 18, preferably 5 to 18, preferably 6 to 18, preferably 6 to 16, preferably 7 to 16, and preferably 8 to 16.

[0077] When emphasis is placed on releasability from the substrate and water resistance of the coating, the solubility of the organic acid in 100 g of water at 25°C is preferably less than 2 g, more preferably less than 1.8 g, even more preferably less than 1.5 g, and particularly preferably less than 1.2 g.

[0078] Examples of the resin having an acid group include resins having an acid value such as cellulose-based resins, ketone resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubbers, chlorinated rubbers, butyral resins, and petroleum resins; radical copolymer resins such as styrene-(meth)acrylic resins, styrene-maleic anhydride resins, and terpene-maleic anhydride resins, which are copolymerized with polymerizable monomers having an acid group, such as polymerizable monomers having a carboxyl group (e.g., itaconic acid, maleic acid, fumaric acid, cinnamic acid, or anhydrides thereof), polymerizable monomers having a sulfonic acid group (e.g., sulfonated styrene), and polymerizable monomers having a sulfonamide group (e.g., vinylbenzenesulfonamide); and acid-modified polyolefin resins (excluding the coloring inhibitors and resins). These resins can be used singly or in combination. As the resin having an acid group, styrene-maleic anhydride resins are more preferred.

[0079] The acid value of the resin having an acidic group is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, and particularly preferably 50 mgKOH / g or more. The acid value is preferably 300 mgKOH / g or less, more preferably 280 mgKOH / g or less, more preferably 260 mgKOH / g or less, more preferably 240 mgKOH / g or less, more preferably 220 mgKOH / g or less, and more preferably 200 mgKOH / g or less. By setting it within the above range, alkaline solution releasability and adhesion to the substrate can be both achieved.

[0080] Furthermore, when emphasis is placed on releasability in an alkaline solution, the OH content is preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, more preferably 70 mgKOH / g or more, more preferably 80 mgKOH / g or more, more preferably 90 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more. When emphasis is placed on adhesion to a substrate, the OH content is preferably 200 mgKOH / g or less, more preferably 180 mgKOH / g or less, more preferably 160 mgKOH / g or less, more preferably 140 mgKOH / g or less, more preferably 120 mgKOH / g or less, and more preferably 100 mgKOH / g or less. When importance is placed on both the alkaline solution releasability and the adhesion to the substrate, the acid value is preferably in the range of 1 to 300 mgKOH / g, preferably 3 to 300 mgKOH / g, preferably 5 to 280 mgKOH / g, more preferably 10 to 260 mgKOH / g, more preferably 20 to 240 mgKOH / g, more preferably 30 to 220 mgKOH / g, more preferably 40 to 200 mgKOH / g, and more preferably 50 to 200 mgKOH / g.

[0081] When emphasis is placed on releasability in an alkaline solution, the OH content is preferably 50 to 300 mgKOH / g, more preferably 60 to 300 mgKOH / g, more preferably 70 to 300 mgKOH / g, more preferably 80 to 300 mgKOH / g, more preferably 90 to 300 mgKOH / g, and more preferably 100 to 300 mgKOH / g. When emphasis is placed on adhesion to the substrate, the OH content is preferably 1 to 200 mgKOH / g, more preferably 1 to 180 mgKOH / g, more preferably 1 to 160 mgKOH / g, more preferably 1 to 140 mgKOH / g, more preferably 1 to 120 mgKOH / g, and more preferably 1 to 100 mgKOH / g.

[0082] When the resin having an acidic group is a styrene-maleic (anhydride) resin, the weight average molecular weight of the resin having an acidic group is preferably at least 500, more preferably at least 700, and even more preferably at least 1000. By setting the weight average molecular weight of the resin having an acidic group within the above range, it is possible to achieve a balance between adhesion to a substrate and releasability in an alkaline solution.

[0083] Furthermore, when the resin having an acidic group is a styrene-maleic (anhydride) resin, the weight average molecular weight of the resin having an acidic group is preferably not more than 100,000, more preferably not more than 70,000, more preferably not more than 50,000, and even more preferably not more than 30,000. By setting the weight average molecular weight of the resin having an acidic group within the above range, the viscosity of composition (I) can be reduced, and further, a balance can be achieved between adhesion to a substrate and releasability in an alkaline solution.

[0084] When the resin having an acidic group is a styrene-maleic (anhydride) resin, the weight-average molecular weight range of the resin having an acidic group is preferably 500 to 100,000, more preferably 700 to 30,000, more preferably 1,000 to 50,000, and even more preferably 1,000 to 30,000. By setting the weight-average molecular weight of the resin having an acidic group within the above range, printability can be improved.

[0085] From the viewpoints of resolubility of composition (I), suppression of blocking of printed matter, improvement of print density, and adhesion to the substrate, the content of the acidic additive as solids is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and more preferably 50 parts by mass or less, relative to 100 parts by mass of the total amount of composition (I). The content of the acidic additive as solids is preferably in the range of 0.1 to 60 parts by mass, more preferably 0.5 to 55 parts by mass, more preferably 1 to 50 parts by mass, more preferably 1.5 to 45 parts by mass, and more preferably 2 to 40 parts by mass.

[0086] When the acidic additive is an organic acid, the content of the organic acid as a solid content, relative to 100 parts by mass of the total amount of composition (I), is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, preferably 20 parts by mass or less, more preferably 18 parts by mass or less, more preferably 16 parts by mass or less, more preferably 14 parts by mass or less, more preferably 12 parts by mass or less, more preferably 10 parts by mass or less. The content range of the organic acid as a solid content is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 18 parts by mass, more preferably 0.3 to 16 parts by mass, more preferably 0.5 to 14 parts by mass, more preferably 1 to 12 parts by mass, more preferably 1.5 to 10 parts by mass, more preferably 2 to 10 parts by mass.

[0087] When the acidic additive is a resin having an acidic group, the content of the resin having an acidic group as a solid content, relative to 100 parts by mass of the total amount of composition (I), is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and more preferably 50 parts by mass or less. The content of the acidic additive as a solid content is preferably in the range of 0.1 to 60 parts by mass, more preferably 0.5 to 55 parts by mass, more preferably 1 to 50 parts by mass, more preferably 1.5 to 45 parts by mass, and more preferably 2 to 40 parts by mass.

[0088] In addition to the above, water, wetting agents, adhesion aids, leveling agents, antistatic agents, viscosity modifiers, metal chelates, trapping agents, antiblocking agents, isocyanate-based curing agents, and silane coupling agents may also be used as needed.

[0089] The viscosity of composition (I), as measured at 25°C using a Zahn Cup #4 manufactured by Rigo Co., Ltd., is preferably 6 seconds or more, more preferably 10 seconds or more, and even more preferably 13 seconds or more, and is preferably 25 seconds or less, more preferably 20 seconds or less, and even more preferably 18 seconds or less.

[0090] The surface tension of the composition (I) is preferably 25 mN / m or more, more preferably 33 mN / m or more. Also, it is preferably 50 mN / m or less, more preferably 43 mN / m or less. By appropriately increasing the surface tension of the composition (I), it is possible to maintain the wettability of the composition (I) to the substrate while suppressing dot bridging (staining on the printing surface caused by adjacent dots in a halftone dot area being connected to each other), and by appropriately decreasing the surface tension of the composition (I), it is possible to increase the wettability of the composition (I) to the substrate and suppress repelling.

[0091] <<Second Layer>> The second layer is formed using a composition for forming the second layer (herein, such a composition is also referred to as composition (II)). Composition (II) for forming the second layer contains at least one resin B selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, polyvinyl butyral resin, cellulose acetate propionate resin, and cellulose acetate butyrate resin. In the second layer, the content ratio of resin B relative to the total amount of resins contained in the second layer, i.e., the content ratio of resin B relative to the total amount of resins contained in composition (II), is preferably 30 mass% or more. Composition (II) can also contain resins other than the above-mentioned resin B. For example, composition (II) may contain resin A described in the above section <<First Layer>> or other resins. Furthermore, composition (II) may contain various additives as other components. The components of composition (II) are described below.

[0092] <<<<Resin B>>> Resin B adheres to the resin (particularly, the nitrocellulose resin when the coating contains a nitrocellulose resin) or colorant (e.g., a pigment) contained in the coating (particularly the first layer), thereby protecting the resin or colorant from alkali, and thereby suppressing coloration in an alkaline solution.

[0093] By incorporating resin B, which exhibits a coloring suppression effect, not in the first layer which contains a colorant and has a peeling function, but in a second layer which is a separate layer adjacent to the first layer, there is no need to be concerned about the compatibility of resin B with the resin and colorant contained in the first layer, and the freedom to select the type and content of the constituent components of the first layer can be increased.

[0094] Resin B exhibiting a coloration suppression effect is at least one resin selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, polyvinyl butyral resin, cellulose acetate propionate resin, and cellulose acetate butyrate resin. These resins may be used alone or in combination of two or more.

[0095] Among these, vinyl chloride-vinyl acetate copolymer resins and polyvinyl butyral resins are preferred from the viewpoint of excellent coloration suppression effect, and polyvinyl butyral resins are more preferred from the viewpoint of excellent viscosity stability.

[0096] - Vinyl chloride-vinyl acetate copolymer resin - Vinyl chloride-vinyl acetate copolymer resin (hereinafter sometimes referred to as vinyl chloride-vinyl acetate resin) is a polymer mainly composed of structural units derived from vinyl chloride monomer and structural units derived from vinyl acetate monomer. The vinyl chloride-vinyl acetate resin may contain one or more structural units other than vinyl chloride and vinyl acetate, provided that the effects of the present invention are not impaired.

[0097] The molecular weight of the vinyl chloride-vinyl acetate resin is not particularly limited, but the weight average molecular weight is preferably 5,000 to 100,000, and more preferably 20,000 to 80,000.

[0098] Because a composition having an excellent coloration suppression effect tends to be obtained, the amount of the structure derived from vinyl acetate monomer is preferably 1 to 30 parts by mass, and the amount of the structure derived from vinyl chloride monomer is preferably 70 to 95 parts by mass, per 100 parts by mass of the total amount of the vinyl chloride-vinyl acetate resin.

[0099] The glass transition temperature of the vinyl chloride-vinyl acetate resin is not particularly limited, but is preferably 50°C to 90°C.

[0100] -Polyvinyl butyral resin- Polyvinyl butyral resin is a resin obtained by reacting polyvinyl alcohol with butylaldehyde to convert the hydroxyl groups of polyvinyl alcohol resin into butyral groups, and has a structure containing butyral groups, acetyl groups, and hydroxyl groups.

[0101] The molecular weight of the polyvinyl butyral resin is not particularly limited, but is preferably a weight-average molecular weight of 5,000 to 100,000, and more preferably 10,000 to 60,000. Although not particularly limited, a polyvinyl butyral resin having a higher weight-average molecular weight within the above range tends to provide a composition (I) with a more excellent coloration suppression effect.

[0102] The glass transition temperature of the polyvinyl butyral resin is not particularly limited, but is preferably 50°C to 90°C.

[0103] -Cellulose acetate propionate resin- Cellulose acetate propionate resin (hereinafter sometimes referred to as CAP) is a resin obtained by triesterifying cellulose with acetic acid and propionic acid, followed by hydrolysis.

[0104] A composition having an acetyl group content of 0.3 to 2.5 parts by mass, a propionyl group content of 42 to 46 parts by mass, and a hydroxyl group content of 1.8 to 5 parts by mass per 100 parts by mass of the total amount of CAP tends to be obtained, and therefore a composition having an excellent coloration suppression effect can be suitably used.

[0105] -Cellulose acetate butyrate resin- Cellulose acetate butyrate resin (hereinafter sometimes referred to as CAB) is a resin obtained by triesterifying cellulose with acetic acid and butyric acid, followed by hydrolysis.

[0106] A composition containing 2 to 30 parts by mass of acetyl groups, 17 to 53 parts by mass of butyryl groups, and 1 to 5 parts by mass of hydroxyl groups per 100 parts by mass of the total amount of CAB tends to have an excellent coloration suppression effect.

[0107] <<<Content of Resin B in Composition (II) for Forming Second Layer>>> The content of Resin B is, for example, 2 parts by mass or more, and more preferably 4 parts by mass or more, relative to 100 parts by mass of the total amount of Composition (II) for forming the second layer. The content is preferably 30 parts by mass or less, and more preferably 20 parts by mass or less. When the content of Resin B is equal to or greater than the above lower limit, a composition having an excellent coloration suppression effect tends to be obtained. When the content of Resin B is equal to or less than the above upper limit, a composition having excellent stability tends to be obtained. When two or more types of Resin B are contained, the preferred range of the content is the total amount of the resins contained.

[0108] <<Method for Producing the Composition>> The method for producing the composition (I) and composition (II) according to the present invention (compositions (I) and (II) are collectively referred to simply as the composition) is not particularly limited, and a conventionally known method can be used. The components of the composition may all be blended together at once, or may be blended separately, such that a premix is ​​prepared by blending some of the components first and then blending the premix with the other components. The mixing method is not particularly limited, and examples include a method of stirring and mixing using a mixer or the like, a method using a three-roll mill, and a method using a disperser such as a bead mill.

[0109] The composition of the present invention can be used in any of the known and commonly used applications, such as printing ink, paint, and water-based ink for ink-jet recording.

[0110] <<Printing Ink>> The composition according to the present invention can be used as a printing ink for forming a printed layer. In particular, composition (I) is preferably used as a printing ink. The printing ink is not particularly limited as long as it contains the composition according to the present invention, and can be obtained with a known composition.

[0111] The printing ink may contain, as necessary, various additives that are contained in ordinary printing inks, such as organic or inorganic fillers, antistatic agents, antifoaming agents, viscosity modifiers, polymerization inhibitors, light resistance stabilizers, weather resistance stabilizers, heat resistance stabilizers, ultraviolet absorbers, antioxidants, leveling agents, pigment dispersants, and waxes.

[0112] <<Printing on Substrates>> A printing ink using the composition according to the present invention has excellent adhesion to various substrates and can be used for printing on paper, synthetic paper, cloth, thermoplastic resin films, plastic products, steel plates, etc., and is useful as an ink for gravure printing using a gravure printing plate made by electronic engraving or the like, or for flexographic printing using a flexographic printing plate made by a resin plate or the like.

[0113] The thickness of the printing ink formed by gravure printing or flexographic printing is preferably, for example, 10 μm or less, and more preferably 5 μm or less.

[0114] <Substrate> The substrate is preferably a plastic substrate, and examples thereof include films and laminates made of polyamide resins such as nylon 6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; biodegradable resins such as polyhydroxycarboxylic acids such as polylactic acid; aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate); thermoplastic resins such as polyolefin resins such as polypropylene and polyethylene, polyimide resins, polyarylate resins, and mixtures thereof. Among these, films and laminates made of polyethylene terephthalate, polyester, polyamide, polyethylene, and polypropylene are preferred, and polyethylene terephthalate, polypropylene, or polyethylene are more preferred when the releasability of the composition according to the present invention is important. These substrate films may be unstretched or stretched films, and their manufacturing method is not limited. The thickness of the substrate film is also not particularly limited, but is generally within the range of 1 to 500 μm.

[0115] The printing surface of the substrate is preferably surface-modified by corona discharge treatment or chemical treatment, and may be vapor-deposited with silica, alumina, or the like.

[0116] <Laminate> By printing the composition according to the present invention or a printing ink using the composition onto the surface of a substrate directly or via another layer, a coating having a first layer and a second layer is laminated on the substrate, and a printed matter consisting of a laminate including the substrate and the coating can be obtained. Here, the other layer is not particularly limited and may be a single layer or multiple layers. For example, a third layer that promotes detachment may be disposed between the substrate and the coating.

[0117] <<Specific Layer Structure of Laminate>> The form of the printed matter and laminate of the present invention is not particularly limited, and examples include the following: - Substrate / ink layer (first layer) / OP varnish layer (second layer) - Substrate / primer layer (second layer) / ink layer (first layer) - Substrate / ink layer 1 (second layer) / ink layer 2 (first layer) - Substrate / ink layer 1 (first layer) / ink layer 2 (second layer)

[0118] As shown in the above embodiment, when an ink layer consisting of a first layer containing a colorant is formed on a substrate, a second layer can be formed as a varnish layer containing no colorant. In this case, the layer that serves as the underprint of the ink layer (i.e., the layer between the substrate and the first ink layer) can be referred to as a primer layer, and the layer that serves as the overprint of the ink layer (i.e., the layer disposed on the opposite side of the first ink layer from the substrate) can be referred to as an overprint varnish layer (OP varnish layer). In the present invention, a layer containing a colorant (e.g., a colored pigment) is referred to as an ink layer, while a layer that does not contain the colorant is referred to as a primer layer or OP varnish layer (both collectively referred to as varnish layers). Furthermore, the second layer may contain a colorant or may not contain a colorant. For example, when the ink layer is composed of multiple printed layers (e.g., composed of white and color layers), one layer may be an ink layer consisting of the first layer and the other layer may be an ink layer consisting of the second layer, as shown in the above embodiment.

[0119] Furthermore, an ink layer consisting of a first layer and a second layer may be provided with a primer layer or an OP varnish layer that is separate from the first layer and the second layer, and examples of such layers include the following: - Substrate / primer layer / ink layer 1 (second layer) / ink layer 2 (first layer) - Substrate / ink layer 1 (second layer) / ink layer 2 (first layer) / OP varnish layer

[0120] A third layer (primer layer) that promotes detachment may be disposed between the substrate and the coating, for example, in the following form: substrate / primer layer / ink layer (first layer) / OP varnish layer (second layer)

[0121] Furthermore, an OP varnish layer may be further disposed on the primer layer (second layer) and the ink layer (first layer), and examples thereof include the following: substrate / primer layer (second layer) / ink layer (first layer) / OP varnish layer

[0122] <<<<Composition for forming a varnish layer>> Varnish layers such as a primer layer or an OP varnish layer can be formed using a composition for forming a varnish layer. As the composition for forming a varnish layer, a generally known composition can be used. As described in the section <<Specific layer structure of the laminate>> above, when the second layer is a primer layer or an OP varnish layer, the composition for forming the varnish layer that forms the primer layer or the OP varnish layer contains the above-mentioned resin B.

[0123] The varnish layer-forming composition may be any of the components of commercially available compositions for forming primer layers or OP varnish layers, without any particular restrictions, in addition to resin B. Typical components of varnish layer-forming compositions include a binder resin, a solvent such as an organic solvent or an aqueous solvent, and additives.

[0124] In addition, when a primer layer or OP varnish layer is formed regardless of the second layer, the varnish layer forming composition used to form the primer layer or OP varnish layer is a composition that does not contain resin B and is generally known as a varnish layer forming composition.

[0125] Examples of binder resins include cellulose-based resins, urethane resins, polyamide resins, ketone resins, polyester resins, (meth)acrylic resins, rosin-modified maleic acid resins and rosin-modified fumaric acid resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubber, chlorinated rubber, butyral resins, and petroleum resins (excluding resin B). Also, polymerizable monomers having a carboxyl group such as itaconic acid, maleic acid, fumaric acid, cinnamic acid, or acid anhydrides thereof, polymerizable monomers having a sulfonic acid group such as sulfonated styrene, and polymerizable monomers having a sulfonamide group such as vinylbenzenesulfonamide, copolymerized with polymerizable monomers, such as (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-(anhydride)maleic acid resins, and terpene-(anhydride)maleic acid resins. Examples of binder resins include radical copolymers such as acid-modified polyolefin resins, and these may be used singly or in combination.

[0126] The solvent may be an organic solvent or water, and for example, the same organic solvents as those explained in the above section <<Organic Solvent>> can be used.

[0127] Examples of additives include extender pigments, pigment dispersants, leveling agents, antifoaming agents, waxes, plasticizers, antiblocking agents, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, etc. When the varnish layer contains the above-mentioned resin B, the amount added can be determined appropriately within a range that does not impair the properties of the varnish layer, but it is preferable that the amount be in the range of 0.1 to 10% by mass, for example, relative to the total mass of the varnish layer composition.

[0128] In addition, a varnish layer containing a resin having an acidic group or a low molecular weight compound can also be preferably used. The resin having an acidic group or the low molecular weight compound can be used without any particular limitation as long as it can be easily mixed with the resin B, which is the main component of the varnish layer, and the organic solvent.

[0129] Examples of resins having an acid group include cellulose-based resins, urethane resins, polyamide resins, ketone resins, polyester resins, (meth)acrylic resins, rosin-modified maleic acid resins, rosin-modified fumaric acid resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubber, chlorinated rubber, butyral resins, and petroleum resins to which an acid value has been imparted; resins that are radical copolymers such as (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-(anhydride)maleic acid resins, and terpene-(anhydride)maleic acid resins, which are copolymers of polymerizable monomers having an acid group, such as polymerizable monomers having a carboxyl group such as itaconic acid, maleic acid, fumaric acid, cinnamic acid, or acid anhydrides thereof, polymerizable monomers having a sulfonic acid group such as sulfonated styrene, and polymerizable monomers having a sulfonamide group such as vinylbenzenesulfonamide; and acid-modified polyolefin resins (excluding the binder resins). These may be used singly or in combination.

[0130] Examples of low molecular weight compounds having an acidic group include organic acids such as saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives, and these can be used singly or in combination. Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, decanoic acid, undecanoic acid, and dodecanoic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, and ketone. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dimer acid, fumaric acid, maleic acid, azelaic acid, etc.; examples of tricarboxylic acids include aconitic acid and trimer acid; examples of oxocarboxylic acids include pyruvic acid and oxaloacetic acid; examples of carboxylic acid derivatives include amino acids and nitrocarboxylic acids, and these can be used singly or in combination. Furthermore, citric acid, butyric acid, caproic acid, enanthic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, eleostearic acid, arachidic acid, sebacic acid, etc. are compliant with the so-called Swiss Ordinance, and it is preferable to use substances that comply with various regulations.

[0131] <<Production of Laminate>> The laminate according to the present invention can be produced, for example, by the following method. For example, in the case of a laminate having a plastic substrate, ink layer 1 (first layer), and ink layer 2 (second layer) in this order, a printing ink of composition (I) for forming the first layer is printed on the plastic substrate by a printing method such as gravure printing or flexographic printing to form ink layer 1 (first layer), which is a printed layer. Next, a printing ink of composition (II) for forming the second layer is printed on ink layer 1 by a printing method such as gravure printing or flexographic printing to form ink layer 2 (second layer), which is a printed layer. This allows a laminate (substrate / ink layer 1 (first layer) / ink layer 2 (second layer)) to be obtained.

[0132] (Method for Manufacturing Recycled Substrates) The present invention can produce recycled substrates by treating the printed matter of the present invention with an alkaline solution to detach the coating from the substrate. "Detachment" refers to the coating peeling off due to swelling, dissolution, erosion, or the like caused by the alkaline solution treatment. In one embodiment of the present invention, a layer disposed directly on the substrate must have a detachment function. For example, if an ink layer (first layer) is disposed on the substrate, the first layer alone may have the detachment function; or if a primer layer (second layer) is disposed on the substrate, the second layer alone may have the detachment function. Because the first and second layers are adjacent to each other, detachment of the layer disposed on the substrate also detaches the other layer. Furthermore, since the second layer contains resin B, discoloration of the alkaline solution after detachment is suppressed. Of course, this does not exclude cases where both the first and second layers have the detachment function. In a preferred embodiment, for example, the first layer may have the detachment function, and the second layer may not have the detachment function.

[0133] <Method for removing a coating from a substrate> The removal step involves immersing the printed material in an alkaline solution while heating and stirring at 20 to 90°C or while ultrasonically vibrating. Heating and stirring and ultrasonic vibration may be performed simultaneously. The heating temperature is preferably 30°C or higher, preferably 40°C or higher, preferably 50°C or higher, or preferably 60°C or higher, and it is more preferable to perform heating and stirring and ultrasonic vibration simultaneously.

[0134] The alkaline solution used in the desorption step is not limited, but preferably has a pH of 9 or higher, and is preferably an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium hydrogen carbonate solution, an aqueous potassium hydrogen carbonate solution, an aqueous sodium dihydrogen carbonate solution, an aqueous potassium dihydrogen carbonate solution, etc. The aqueous sodium hydroxide solution, the aqueous potassium hydroxide solution, the aqueous sodium hydrogen carbonate solution, the aqueous potassium hydrogen carbonate solution, the aqueous sodium dihydrogen carbonate solution, the aqueous potassium dihydrogen carbonate solution, etc. are preferably aqueous solutions having a concentration of 0.5% by mass to 10% by mass, and more preferably an aqueous solution having a concentration of 1% by mass to 5% by mass.

[0135] The alkaline solution may also contain a water-soluble organic solvent, such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dibutyl ether, diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol dibutyl ether, and triethylene glycol monomethyl ether (methyl carbitol). Examples include glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methylene dimethyl ether (methylal), propylene glycol monobutyl ether, tetrahydrofuran, acetone, diacetone alcohol, acetonylacetone, acetylacetone, ethylene glycol monomethyl ether acetate (methyl cellosolve acetate), diethylene glycol monomethyl ether acetate (methyl carbitol acetate), diethylene glycol monoethyl ether acetate (carbitol acetate), ethyl hydroxyisobutyrate, and ethyl lactate, and these can be used alone or in combination of two or more.

[0136] The content of the water-soluble organic solvent in the alkaline solution is preferably 0.1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass. The alkaline solution may also contain a water-insoluble organic solvent. Specific examples of the water-insoluble organic solvent include alcohol-based solvents such as n-butanol, 2-butanol, isobutanol, and octanol; aliphatic hydrocarbon-based solvents such as hexane, heptane, and normal paraffin; aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, and alkylbenzene; halogenated hydrocarbon-based solvents such as methylene chloride, 1-chlorobutane, 2-chlorobutane, 3-chlorobutane, and carbon tetrachloride; ester-based solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone-based solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; and ether-based solvents such as ethyl ether and butyl ether. These may be used alone or in combination of two or more.

[0137] The alkaline solution may also contain a surfactant. Examples of the surfactant include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants, nonionic surfactants, and amphoteric surfactants are preferred, and nonionic surfactants are more preferred.

[0138] Examples of anionic surfactants include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfate ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate ester salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and the like. Specific examples of these include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, and dibutylphenylphenol disulfonate.

[0139] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylolamides, alkylalkanolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers. Of these, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers are preferred.

[0140] Other surfactants that can be used include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin.

[0141] These surfactants can be used alone or in combination of two or more. When a surfactant is added, the amount added is preferably in the range of 0.001 to 2% by mass, more preferably 0.001 to 1.5% by mass, and even more preferably 0.01 to 1% by mass, based on the total amount of the alkaline solution.

[0142] When these surfactants are used, the alkaline solution after detachment tends to be more easily colored than when the alkaline solution is used alone. However, by configuring the printed matter of the present invention in such a way that a second layer containing resin B is laminated adjacent to a first layer containing a colorant as a coating that can be detached from the substrate, coloration of the treatment solution can be effectively suppressed.

[0143] The target printed matter or laminate is immersed in, for example, a treatment tank in an alkaline solution heated to 20 to 90° C. or ultrasonically vibrated. The heating method is not particularly limited, and known heating methods using heat rays, infrared rays, microwaves, etc. can be used. Ultrasonic vibration can be achieved, for example, by attaching an ultrasonic vibrator to the treatment tank and applying ultrasonic vibration to the warm water or alkaline solution.

[0144] It is also preferable that the alkaline solution is stirred during immersion. Examples of stirring methods include mechanically stirring the dispersion of the printed matter or laminate contained in the treatment tank with a stirring blade, water jet stirring with a water jet pump, and bubbling with an inert gas such as nitrogen gas, and these may be used in combination to achieve efficient peeling.

[0145] The time for immersing the printed matter or laminate in the alkaline solution varies depending on the composition of the printed matter, but is generally in the range of 2 minutes to 48 hours. Note that in the present invention, it is not necessary for 100% of the coating on the printed matter to be completely detached from the substrate, but it is preferable that 60% by mass or more of the 100% by mass of the coating be detached, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0146] In the desorption step, the film may be immersed in the alkaline solution once or several times. That is, the film may be immersed once and then the separated film substrate may be recovered, or the film may be immersed several times and then the film substrate may be recovered. When the film is immersed multiple times in the desorption step, the concentration of the alkaline solution may be changed. During the desorption step, known steps such as washing with water and drying may be added as appropriate.

[0147] The printed matter of the present invention has a coating formed on a substrate, in which a first layer containing a colorant and a second layer containing resin B are laminated adjacent to each other. Therefore, the presence of resin B can effectively suppress coloration of the alkaline treatment solution when the coating is removed in the removal step.

[0148] The contents and effects of the present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these. Note that "parts" and "%" shown below are all based on mass.

[0149] (Layer-forming composition) The layer-forming compositions used in the examples and comparative examples are as follows. [Ink composition] [[Ink A]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 30% solution Nitrocellulose DLX5-8 manufactured by Nobel, non-volatile content 30%, ethyl acetate:IPA solution Urethane resin 30% solution Urea urethane resin manufactured by DIC Corporation, number average molecular weight 14,000, non-volatile content 30%, ethyl acetate:IPA solution <Organic solvents> Isopropyl alcohol Normal propyl alcohol Ethyl acetate Normal propyl acetate Methylcyclohexane The blending ratios of the above raw materials are as shown in Table 1-1 below.

[0150] [[Ink B]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> 50% acrylic resin solution ACRYDIC WCL-1419 manufactured by DIC Corporation, number average molecular weight 16,000, non-volatile content 50%, dissolved in ethyl acetate:IPA 25% vinyl chloride-vinyl acetate copolymer resin solution Solvine A manufactured by Nissin Chemical Industry Co., Ltd., non-volatile content 25%, dissolved in methyl ethyl ketone 20% cellulose acetate butyrate solution Cellulose acetate butyrate resin (CAB-381-0.1 manufactured by Eastman Chemical Co.), non-volatile content 20%, dissolved in ethyl acetate <Organic solvents> Isopropyl alcohol Methyl ethyl ketone Ethyl acetate Toluene Normal propyl acetate The blending ratios of the above raw materials are as shown in Table 1-2 below.

[0151] [[Ink C]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 40% solution Nitrocellulose DLX5-8 manufactured by Nobel Corporation, non-volatile content 40%, ethyl acetate: IPA solution Acrylic resin 50% solution Acrydic WCL-1419 manufactured by DIC Corporation, number average molecular weight 16,000, non-volatile content 50%, ethyl acetate: IPA solution <Organic solvent> Isopropyl alcohol Normal propyl acetate Propylene glycol monomethyl ether The blending ratios of the above raw materials are as shown in Table 1-3 below.

[0152] [[Ink D]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 30% solution Nitrocellulose DLX5-8 manufactured by Nobel, 30% non-volatile content, ethyl acetate:IPA solution Polyamide resin 40% solution 100 parts of dimer acid (Haridimer 270S; manufactured by Harima Chemicals Co., Ltd.), 1 part of tall oil fatty acid (Harthall FA-1; manufactured by Harima Chemicals Co., Ltd.), 5 parts of sebacic acid, 10 parts of ethylenediamine, 5 parts of hexamethylenediamine, and 0.24 parts of triphenylphosphine were placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the system was emptied into a nitrogen atmosphere. The temperature was then slowly raised to 200°C under uniform stirring under a nitrogen stream. Subsequently, dehydration condensation was carried out at 200°C for 5 hours while stirring, and isopropyl alcohol / industrial ethanol / methylcyclohexane (mass ratio of 20 / 20 / 60) was added to obtain a tall fatty acid-derived dimer acid-modified polyamide resin solution with a solids content of 40%, a softening point of 123°C, an amine value of 2, an acid value of 8, and a number average molecular weight of 10,000. <Organic solvents> - Isopropyl alcohol - Normal propyl alcohol - Methylcyclohexane - Ethylene glycol monopropyl ether The blending ratios of the above raw materials are as shown in Table 1-4 below.

[0153] [Varnish Composition] The raw materials used in varnish composition 1 (also referred to as varnish 1) to varnish composition 15 (also referred to as varnish 15) are as follows. <Resins> CAB1 cellulose acetate butyrate resin (CAB-381-0.1 manufactured by Eastman Chemical Co.) CAB2 cellulose acetate butyrate resin (CAB-151-202 manufactured by Eastman Chemical Co.) 30% non-volatile content, ethyl acetate:IPA solution Vinyl chloride-vinyl acetate copolymer resin (Solbine A manufactured by Nissin Chemical Co.) Vinyl chloride-vinyl acetate copolymer resin (Solbine A manufactured by Nissin Chemical Co., Ltd.) 25% non-volatile content, methyl ethyl ketone solution PVB1 polyvinyl butyral resin (Mowital B14S manufactured by Kuraray Co., Ltd.), 15% non-volatile content, ethanol solution PVB2 polyvinyl butyral resin (Mowital B14S manufactured by Kuraray Co., Ltd.) B30H), 10% non-volatile content, dissolved in ethanol. PVB3 Polyvinyl butyral resin (Mowital B60H manufactured by Kuraray), 10% non-volatile content, dissolved in ethanol. NC1 Nitrocellulose DLX5-8 manufactured by Nobel, 30% non-volatile content, dissolved in ethyl acetate:IPA. NC2 Nitrocellulose DLX5-8 manufactured by Nobel, 40% non-volatile content, dissolved in ethyl acetate:IPA. Rosin Malquid #1 manufactured by Arakawa Chemical Industries, Ltd. (acid value: 30 mg KOH / g, maleated rosin resin). Polyester Polylite OD-X-240 (polyester polyol manufactured by DIC Corporation, molecular weight 2,000). Urethane 1 Urea urethane resin manufactured by DIC Corporation, number average molecular weight 14,000. Urethane 2 Urea urethane resin manufactured by DIC Corporation, number average molecular weight 14,000, non-volatile content 40%, ethyl acetate: IPA solution) Urethane 3 Urea urethane resin manufactured by DIC Corporation, number average molecular weight 14,000, non-volatile content 30%, ethyl acetate: IPA solution) Acrylic Acrydic WCL-1419 manufactured by DIC Corporation, number average molecular weight 16,000, non-volatile content 50%, ethyl acetate: IPA solution

[0154] The blending ratios of the raw materials in Varnish Compositions 1 to 15 are as shown in Tables 2-1 to 2-3 below.

[0155] (Example 1) <Production of Printed Material> The prepared ink composition (also simply referred to as "ink") was used with bar coater #4 to print a solid pattern measuring 240 mm long x 80 mm wide on a substrate, which was then dried with a dryer to form an ink layer. Subsequently, the prepared varnish composition (also simply referred to as "varnish") was printed on the dried ink layer using bar coater #4, and after printing, was dried with a dryer to form an OP varnish layer, obtaining a printed material with the following configuration consisting of a laminate in which an ink layer (first layer) and an OP varnish layer (second layer) are laminated on the substrate. <<Configuration of Printed Material>> Configuration: substrate - ink layer (first layer) - OP varnish layer (second layer) Substrate: PE film

[0156] <Evaluation Item 1: Ink Stripping Test> [Alkaline Solution] A stripping test was conducted under the following conditions, and the ease of stripping under each condition was compared: 1% by mass of sodium hydroxide, 0.3% by mass of surfactant, 85°C. A nonionic surfactant was used as the surfactant.

[0157] [Peel test conditions] The peel test was performed under each condition with a treatment time of 15 minutes. Peeling within 5 minutes of treatment indicates fairly high performance. Test pieces of printed matter cut to a size of 20 mm x 20 mm were immersed in the solution and stirred with a stirrer. After stirring, the state of peeling was confirmed, and then the printed matter was rubbed with a finger to check whether the coating film peeled off. The peelability of the ink coating film under the above conditions was evaluated according to the following evaluation criteria.

[0158] [Evaluation criteria] 5: Ink film detachment confirmed within 5 minutes of stirring. Complete detachment when rubbed 4: Ink film detachment confirmed after 15 minutes of stirring. Complete detachment when rubbed 3: No ink film detachment confirmed after 15 minutes of stirring. Complete detachment when rubbed 2: No ink film detachment confirmed after 15 minutes of stirring. Partial detachment when rubbed 1: No ink film detachment confirmed after 15 minutes of stirring. No detachment confirmed even when rubbed

[0159] The results of the peelability test are shown in Table 3-1 below. From the viewpoint of practical application, a rating of 2 or higher is required.

[0160] <Evaluation Item 2: Coloring Inhibition Test> A coloring inhibition test was carried out using the produced printed matter under the following conditions.

[0161] <<Alkaline Solution>> - 1 mass % sodium hydroxide, 0.3% surfactant, 85°C Here, a nonionic surfactant was used as the surfactant.

[0162] <<Coloration Inhibition Test Conditions>> The coloration inhibition test was performed by treating the printed matter with the alkaline solution for 15 minutes. 50 test pieces were cut into 20 mm x 20 mm pieces, and the pieces were immersed in 500 mL of alkaline solution and stirred with a stirrer. The transparency of the alkaline solution after stirring was measured using a transparency meter according to the method of JIS (Japanese Industrial Standards) K0102.

[0163] Specifically, a transparency meter was filled with an alkaline solution in a glass cylinder with a bottom opening and graduated every 10 mm, equipped with a double cross marking on the bottom. The bottom was viewed from above, and the sample was rapidly poured out of the bottom opening until the double cross marking on the bottom was clearly visible. The water level was read at that point. This process was repeated twice, and the average value was calculated and expressed as transparency in degrees (10 mm = 1 degree). Evaluation was based on the following criteria:

[0164] The blank samples used in Examples 1 to 13 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 1, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank sample used in Example 14 was 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 4, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank samples used in Examples 15 to 27 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 5, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank samples used in Examples 28 to 40 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 8, immersed in 500 mL of alkaline solution, and stirred with a stirrer. As blank samples for Examples 41 to 53, 50 test pieces of 20 mm x 20 mm size cut from the printed matter obtained using the ink composition of Comparative Example 11 were used, which were immersed in 500 mL of alkaline solution and stirred with a stirrer.

[0165] [Evaluation criteria] 5: Transparency 10 times or more that of the blank sample. 4: Transparency 5 times or more that of the blank sample. 3: Transparency 3 times or more that of the blank sample. 2: Transparency 1.5 times or more that of the blank sample. 1: Transparency equivalent to that of the blank sample.

[0166] The results of the coloring inhibition test are shown in Table 3-1 below. From the viewpoint of practical application, a rating of 3 or higher is required.

[0167] (Examples 2 to 53, Comparative Examples 1 to 13) Printed matter was obtained in the same manner as in Example 1, except that the layer structure in Example 1 was changed as shown in Tables 3-1 to 3-9 below. The obtained printed matter was evaluated in the same manner as in Example 1. The results are shown in Tables 3-1 to 3-9. Note that for Example 14 and Comparative Example 4, a varnish composition prepared in the same manner as in Example 1 was printed on a substrate using bar coater #4, and after printing, it was dried with a dryer to form a primer layer. Subsequently, on the dried primer layer, a prepared ink composition was printed using bar coater #4, and after printing, it was dried with a dryer to form an ink layer, thereby obtaining printed matter with the following structure consisting of a laminate in which a primer layer (second layer) and an ink layer (first layer) are laminated in this order on a substrate. <<Structure of Printed Matter>> Structure: Substrate - Primer layer (second layer) - Ink layer (first layer) Substrate: PE film

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[0184] The printed matter of the examples has a coating that can be easily removed from the substrate by treatment with an alkaline solution, and it is clear that the coating has an excellent effect of inhibiting discoloration caused by the alkaline solution treatment liquid.

Claims

1. A printed matter comprising a laminate of a substrate and a coating that can be removed from the substrate by treatment with an alkaline solution, the coating has a first layer containing a colorant and at least one resin A selected from the group consisting of an acrylic resin, a urethane resin, a polyamide resin, a rosin resin, and a polyester resin, and a second layer in contact with the first layer; the second layer contains at least one resin B selected from the group consisting of vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, cellulose acetate propionate resins, and cellulose acetate butyrate resins; A printed matter, wherein the second layer has a content ratio of the resin B relative to the total amount of resins contained in the second layer of 30 mass % or more.

2. The printed matter according to claim 1 , wherein the first layer further comprises a nitrocellulose resin.

3. The printed matter according to claim 1 , wherein the first layer further contains a vinyl chloride-vinyl acetate copolymer resin.

4. The first layer is (i) Contains at least a urethane resin and a nitrocellulose resin; (ii) Contains at least an acrylic resin and a nitrocellulose resin; (iii) containing at least a polyamide resin and a nitrocellulose resin; and (iv) The printed matter according to claim 1, which contains at least an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, and a cellulose acetate butyrate resin.

5. The printed matter according to claim 1 , further comprising a third layer disposed between the substrate and the coating for promoting desorption.

6. A method for producing a recycled substrate, comprising treating the printed matter according to claim 1 with an alkaline solution to remove the coating from the substrate, thereby obtaining a recycled substrate.

7. The method for producing a recycled substrate according to claim 6 , wherein the alkaline solution has a pH of 9 or more and contains a nonionic surfactant.