Moisture trapping film

Abstract

This moisture trapping film contains a cationic polymer (a) and a highly hygroscopic polymer (b) that attains a lower humidity than that is attained by the cationic polymer. This moisture trapping film is characterized in that the highly hygroscopic polymer (b) is an anionic polymer neutralized product which has a light transmittance of 90% or more at the wavelength of 400 nm as measured at 21°C in the form of an aqueous dispersion having a solid content concentration of 10 mass%.

Description

Moisture-trapping film

[0001] The present invention relates to a moisture-trapping film that exhibits moisture-trapping properties and is suitable for use in drying, blocking moisture, and the like, and further relates to a gas barrier laminate that includes the moisture-trapping film and a coating composition that is used in producing the moisture-trapping film.

[0002] As a means for improving the properties of various plastic substrates, particularly the gas barrier properties, it is known to form an inorganic barrier layer made of silicon oxide or the like on the surface of the plastic substrate by vapor deposition (Patent Document 1).

[0003] Incidentally, in various electronic devices developed and put into practical use in recent years, such as organic electroluminescence (organic EL), solar cells, touch panels, and electronic paper, charge leakage is undesirable, and therefore high moisture barrier properties are required for the plastic substrates forming the circuit boards or the films sealing the circuit boards. The formation of the inorganic barrier layer described above cannot meet such high requirements for moisture barrier properties, and therefore various proposals have been made to improve the moisture barrier properties, i.e., the moisture trapping properties.

[0004] Typical examples of films that exhibit moisture-trapping properties include films made of hygroscopic polymers such as polyamide, and also known are those in which a hygroscopic material such as silica gel or aluminum oxide is dispersed in a polymer binder such as an electron beam or ultraviolet curable resin. For example, Patent Document 2 proposes a gas barrier film having a structure in which a layer of a film that exhibits moisture-trapping properties as described above is laminated on the inorganic barrier layer as a moisture-trapping layer. However, even laminate films using such films that exhibit moisture-trapping properties do not yet ensure the high level of moisture barrier properties required for various electronic devices.

[0005] Meanwhile, the present applicant has proposed a laminate film (gas barrier laminate) as a gas barrier film exhibiting high moisture barrier properties, in which a moisture-trapping layer, in which a specific moisture absorbent is dispersed in an ionic polymer matrix, is formed on an inorganic barrier layer on a plastic substrate (Patent Documents 3 and 4). The moisture-trapping layer in this laminate film has a structure in which a granular moisture absorbent with a lower moisture content than the cationic polymer is dispersed in an ionic polymer matrix. The moisture is trapped by the water absorption exhibited by the ionic polymer, and the moisture released from the cationic polymer is captured by the granular moisture absorbent. As a result, the laminate film exhibits high moisture barrier properties required for various electronic devices over a long period of time. Examples of granular moisture absorbents include inorganic moisture absorbents such as zeolite, and organic moisture absorbents such as crosslinked anionic polymers and crosslinked partially neutralized anionic polymers (e.g., crosslinked sodium poly(meth)acrylate).

[0006] Japanese Patent Application Laid-Open No. 2000-255579 Japanese Patent Application Laid-Open No. 2009-90633 Japanese Patent No. 6287288 Japanese Patent No. 6519974

[0007] However, the moisture-trapping film developed by the applicant has low transparency, making it difficult to apply to applications requiring transparency, and therefore requires improvement in terms of its surface smoothness, which also requires improvement in terms of lamination with other films. Furthermore, when laminated with a barrier film having an inorganic vapor deposition layer, the moisture barrier property deteriorates in a short period of time.

[0008] Therefore, an object of the present invention is to provide a moisture-trapping film that is also excellent in optical properties and surface smoothness. Another object of the present invention is to provide a laminate film that is composed of a moisture-trapping film and a barrier film having an inorganic barrier layer, and that effectively suppresses deterioration of moisture-trapping properties over time. A still further object of the present invention is to provide a coating composition that can be used in producing the moisture-trapping film.

[0009] The present inventors have conducted further research into the moisture-trapping layer formed in the laminate film (gas barrier laminate) proposed in the above-mentioned Patent Documents 3 and 4, and as a result have discovered that the moisture-trapping ability can be maintained for a long period of time by using a neutralized anionic polymer, the aqueous dispersion of which exhibits high light transmittance under certain conditions, instead of a granular moisture-absorbing agent dispersed in a cationic polymer. Based on this discovery, the present invention has been completed.

[0010] That is, according to the present invention, there is provided a moisture-trapping film comprising a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer, wherein the highly hygroscopic polymer (b) is a neutralized anionic polymer that exhibits a light transmittance of 90% or more at a wavelength of 400 nm when measured at 21°C using an aqueous dispersion having a solids concentration of 10% by mass.

[0011] The moisture-trapping film of the present invention preferably employs the following aspects. (1) The highly hygroscopic polymer (b) is a neutralized product of an anionic polymer having an anionic functional group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a phosphate group. (2) The highly hygroscopic polymer (b) is a neutralized product of (meth)acrylic acid. (3) The highly hygroscopic polymer (b) exhibits a pH of 10 or less in a 5% by mass aqueous dispersion at 25°C. (4) The highly hygroscopic polymer (b) is present in an amount of 11 to 1,000 parts by mass per 100 parts by mass of the cationic polymer (a). (5) The film exhibits a haze of 4.7% or less. (6) The film exhibits a surface roughness Sa (ISO 25178-2:2012) of 11 nm or less.

[0012] The present invention also provides a gas barrier laminate having a layer structure in which the above-mentioned moisture-trapping film and a barrier film having an inorganic barrier layer formed on the surface of a plastic substrate are laminated together.

[0013] The present invention further provides a coating composition comprising a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer, dissolved or dispersed in a solvent, wherein the highly hygroscopic polymer (b) is a neutralized anionic polymer that exhibits a light transmittance of 90% or more at a wavelength of 400 nm when measured at 21°C in an aqueous dispersion having a solids concentration of 10% by mass.

[0014] In the coating composition, similarly to the moisture-trapping film described above, it is preferable that: (1) the highly hygroscopic polymer (b) exhibits a pH of 10 or less in a 5% by mass aqueous dispersion at 25°C; (2) the highly hygroscopic polymer (b) is used in an amount of 11 to 1,000 parts by mass per 100 parts by mass of the cationic polymer (a); and further, it is preferable that: (3) the solvent is a mixed solvent of water and alcohol.

[0015] The moisture-trapping film of the present invention contains as its basic components a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer. That is, similar to conventionally known moisture-trapping films (or moisture-trapping layers), the moisture absorption of the cationic polymer blocks moisture permeation, and moisture released from the cationic polymer (a) is captured by the highly hygroscopic highly hygroscopic polymer (b). In this basic structure, the present invention uses a neutralized anionic polymer as the hygroscopic polymer (b). This neutralized polymer must have a light transmittance of 90% or more at 400 nm when measured at 21°C in an aqueous dispersion having a solids concentration of 10% by weight. The use of such a neutralized polymer ensures long-term moisture-trapping ability.

[0016] That is, the neutralized anionic polymer exhibiting the above-mentioned light transmittance contains a large amount of non-crosslinked linear molecules and a small amount of granulated crosslinked molecules. In conventionally known moisture-trapping films, a polymer containing a large amount of crosslinked components is used as the highly hygroscopic polymer. Such moisture-trapping films (see Comparative Example 1 below) have high haze and a large surface roughness Sa of the film. However, the moisture-trapping film of the present invention (see Example 1 below) contains a small amount of granulated crosslinked components in the highly hygroscopic polymer (b) and a large amount of non-crosslinked components dispersed in layers, resulting in excellent optical properties, low haze, and a small surface roughness Sa of the film. Therefore, the moisture-trapping film of the present invention can be effectively used in applications requiring transparency, and can also be suitably used for lamination with other films.

[0017] Furthermore, the gas barrier laminate obtained by laminating the moisture-trapping film of the present invention with an inorganic barrier layer exhibits a water vapor transmission rate (WVTR: g / m) that decreases over time. ２ / day) is suppressed, and therefore the film is extremely useful as a sealing material in various electronic devices that require high moisture barrier properties.

[0018] 1 is a diagram showing a laminate structure of a moisture-trapping film and a barrier film of the present invention.

[0019] <Moisture-trapping film> The moisture-trapping film of the present invention is formed from a blend of a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer, and exhibits the function of trapping moisture through the moisture absorption of both polymers.

[0020] Cationic polymer (a): The cationic polymer (a) used in the present invention is a polymer having in its molecule a cationic group that can become positively charged in water, such as a primary to tertiary amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group, etc. Such cationic polymers exhibit hygroscopicity because the cationic group has a strong nucleophilic action and traps water through hydrogen bonds.

[0021] The amount of cationic groups in the cationic polymer (a) may generally be such that the water absorption of the polymer (JIS K-7209-1984) is 20% or more, particularly 30% to 45%, in an atmosphere of 80% RH and 30°C.

[0022] Examples of the cationic polymer (a) having the above-mentioned cationic group include those prepared by polymerizing or copolymerizing at least one cationic monomer, such as amine monomers (e.g., allylamine, ethyleneimine, vinylbenzyltrimethylamine, [4-(4-vinylphenyl)-methyl]-trimethylamine, and vinylbenzyltriethylamine); nitrogen-containing heterocyclic monomers (e.g., vinylpyridine and vinylimidazole); and salts thereof, together with other copolymerizable monomers, and optionally partially neutralizing the resulting polymer by acid treatment to adjust the amount of cationic group. Examples of other copolymerizable monomers include, but are not limited to, styrene, vinyltoluene, vinylxylene, α-methylstyrene, vinylnaphthalene, α-halogenated styrenes, acrylonitrile, acrolein, methyl vinyl ketone, and vinylbiphenyl. Polyfunctional monomers such as divinylbenzene can also be used.

[0023] Alternatively, instead of using the above cationic monomers, a monomer having a functional group into which a cationic functional group can be introduced, such as styrene, bromobutylstyrene, vinyltoluene, chloromethylstyrene, vinylpyridine, vinylimidazole, α-methylstyrene, or vinylnaphthalene, may be used, and the resulting polymer may be subjected to amination, alkylation (quaternary ammonium chloride), or other treatment after polymerization to obtain the cationic polymer (a).

[0024] In the present invention, among the above cationic polymers (a), polyallylamine is particularly preferred from the viewpoint of film-forming properties, etc. Furthermore, from the viewpoint of suppressing swelling due to moisture absorption, it is preferred that a crosslinked structure be introduced into the cationic polymer (a). The crosslinked structure can be formed by introducing a polyfunctional monomer such as divinylbenzene as a copolymerization component in the polymerization step for forming the cationic polymer (a).

[0025] The crosslinked structure can also be introduced using a crosslinking agent separate from the monomer. As described in, for example, JP-A-2015-96320, a compound having a crosslinkable functional group (e.g., an epoxy group) that can react with a cationic group and a functional group (e.g., an alkoxysilyl group) that can form a siloxane structure in the crosslinked structure through hydrolysis and dehydration condensation can be used as such a crosslinking agent. Specifically, a compound represented by the following formula (1): X-SiR １ ｎ (OR ２ ) ３－ｎ (1) In the formula, X is an organic group having an epoxy group at the terminal, and R １ and R ２ are each a methyl group, an ethyl group, or an isopropyl group, and n is 0, 1, or 2.

[0026] In such silane compounds, the epoxy-containing organic group X in the above formula (1) is typically a γ-glycidoxyalkyl group, and for example, γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropylmethyldimethoxysilane are preferably used as crosslinkers. Furthermore, compounds in which the epoxy group in the above formula (1) is an alicyclic epoxy group such as an epoxycyclohexyl group are also suitable as crosslinkers. For example, when a compound having an alicyclic epoxy group such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane is used as a crosslinker, an alicyclic structure is introduced along with the siloxane structure. The introduction of such an alicyclic structure is advantageous in that it forms a network structure of spaces suitable for moisture absorption.

[0027] Furthermore, in order to introduce an alicyclic structure into the above-mentioned crosslinked structure, a compound having multiple epoxy groups and an alicyclic group, for example, a diglycidyl ester represented by the following formula (2): G-O(C═O)-A-(C═O)O-G (2) wherein G is a glycidyl group, and A is a divalent hydrocarbon group having an alicyclic ring, such as a cycloalkylene group, can be used as a crosslinking agent. A representative example of such a diglycidyl ester is represented by the following formula (2-1).

[0028]

[0029] That is, although the diglycidyl ester of formula (2) does not have an alkoxysilyl group, it is effective in that it introduces an alicyclic structure into the crosslinked structure, thereby forming a network structure of spaces suitable for moisture absorption in the cationic polymer.

[0030] The above-mentioned crosslinking agent is preferably used in an amount of 5 to 60 parts by mass, particularly 15 to 50 parts by mass, per 100 parts by mass of the cationic polymer, and it is desirable that at least 70% by mass, preferably 80% by mass or more of such crosslinking agent be the silane compound of formula (1) described above.

[0031] In principle, the introduction of a crosslinked structure using the above-mentioned crosslinking agent can also be achieved by blending the crosslinking agent in the coating composition for forming the moisture-trapping film described below, but the use of such a crosslinking agent should be avoided because it alters the physical properties of the highly hygroscopic polymer (b) used in combination. In other words, the introduction of a crosslinked structure must be carried out at a stage prior to mixing with the highly hygroscopic polymer (b).

[0032] The cationic polymer (a) may have a molecular weight sufficient to form a film.

[0033] Highly hygroscopic polymer (b): The highly hygroscopic polymer (b) used in the present invention is a polymer that reaches a lower humidity than the cationic polymer (a), i.e., it exhibits higher hygroscopicity than the cationic polymer (a). By using such a highly hygroscopic polymer (b) in combination with the cationic polymer (a), when moisture absorbed in the cationic polymer (a) is released, this moisture is absorbed by the highly hygroscopic polymer (b), preventing moisture from being released to the outside and ensuring moisture trapping properties for a long period of time.

[0034] The humidity attained by this highly hygroscopic polymer (b) can be evaluated by the moisture content measured under a certain bone-dry condition, as shown in the examples described later. For example, the moisture content of the above-mentioned cationic polymer (a) measured under a certain bone-dry condition is about 2%, while the moisture content of the highly hygroscopic polymer (b) measured under the same conditions is 7% or more, which indicates that the moisture attained by the highly hygroscopic polymer (b) is lower than that of the cationic polymer (a). In other words, by using such highly hygroscopic polymer (b), excellent moisture absorption properties can be exhibited even under dry conditions where the cationic polymer (a) cannot exhibit sufficient moisture absorption properties, and high moisture barrier properties can be exhibited.

[0035] A neutralized product of an anionic polymer is used as such a highly hygroscopic polymer (b). An anionic polymer has an anionic functional group that can become negatively charged in water, such as an acidic group such as a carboxylic acid group, a sulfonic acid group, a phosphate group, or a phosphonic acid group. In the present invention, these anionic groups must be neutralized with an alkali. If they are not neutralized, they will react with the cationic groups of the cationic polymer used in combination, resulting in a loss of hygroscopicity. Furthermore, in the case of partial neutralization, even if a certain degree of hygroscopicity can be ensured, alkali atoms such as Na and K will inevitably be present, and these alkali atoms will diffuse into the film, causing a decrease in moisture-trapping ability. For example, when this moisture-trapping film is laminated on a barrier film, the inorganic barrier layer of the barrier film will be deteriorated, resulting in a large amount of moisture flowing into the moisture-trapping film and reducing its moisture-trapping ability. In the present invention, the use of a neutralized product of an anionic polymer as the highly hygroscopic polymer (b) effectively prevents such adverse effects caused by alkali atoms.

[0036] For example, since the highly hygroscopic polymer (b) used in the present invention is a neutralized anionic polymer, the pH of its aqueous dispersion is higher than that of a non-neutralized polymer but lower than that of a partially neutralized polymer, and is 10 or less in an aqueous dispersion of 5% by mass at 25° C. The partially neutralized polymer contains many excess alkali atoms, so its pH is higher than 10, and these alkali atoms are the cause of the deterioration of its moisture-trapping ability over time.

[0037] Furthermore, the neutralized product of the anionic polymer must have a light transmittance of 10% or more, particularly 90% or more, at a wavelength of 400 nm, measured at 21°C in an aqueous dispersion having a solids concentration of 10% by mass. This light transmittance indicates the level of non-crosslinked components (i.e., chain polymer components) contained in the neutralized product, and a light transmittance of the above value indicates that the neutralized product contains a large amount of chain polymer components and a very small amount of crosslinked polymer components. In the present invention, the use of such a chain polymer as the highly hygroscopic polymer (b) can improve the smoothness and optical properties of the film surface.

[0038] That is, the linear polymer component contained in a large amount in the neutralized product of the anionic polymer can be mixed and dispersed with the cationic polymer (a) without granulation, and exists in a phase-like dispersed state in the film, dispersed in the form of a continuous layer. This effectively prevents particle aggregation, preventing the unevenness caused by aggregates from being reflected on the surface, resulting in a highly smooth film surface. For example, the moisture-trapping film of the present invention has a surface roughness Sa (ISO 25178-2:2012) of 11 nm or less, particularly 7 nm or less. Ra, which represents the arithmetic mean height of this line, is a parameter expanded to the surface. That is, the moisture-trapping film of the present invention having the above-mentioned surface roughness Sa exhibits high surface smoothness, thereby providing excellent lamination with other films and exhibiting uniform moisture-trapping properties (moisture barrier properties).

[0039] Furthermore, the neutralized anionic polymer (highly hygroscopic polymer (b)) exhibiting such high light transmittance as described above is prevented from becoming coarse due to particle aggregation, and therefore, the moisture-trapping film of the present invention exhibits high transparency and exhibits a haze of, for example, 4.7% or less, particularly 2.0% or less.

[0040] The gel fraction is known as a parameter indicating the crosslinked state of a polymer component; however, this gel fraction cannot indicate the crosslinked state (non-crosslinked state) of the neutralized anionic polymer (highly hygroscopic polymer (b)) used in the present invention. That is, the gel fraction is determined by measuring the amount dissolved in a certain solvent and calculating the ratio of the amount dissolved in the solvent to the amount not dissolved in the solvent. Here, when attempting to measure the gel fraction of a neutralized anionic polymer, water is used as the solvent because the chain-like anionic polymer component is water-soluble. However, it is not possible to accurately separate the chain-like component dissolved in water from the crosslinked component not dissolved in water. This is because the crosslinked polymer not dissolved in water is also highly hygroscopic and therefore disperses in water, making it impossible to separate using filter paper or the like.

[0041] Therefore, in the present invention, light transmittance functions as a parameter indicating the content of linear polymer. For example, if the entire amount of a neutralized anionic polymer is dissolved in water, it will exhibit the same light transmittance (100%) as water, and as the proportion of crosslinked polymer contained in this neutralized polymer increases, the light transmittance decreases. In other words, light transmittance can be measured for a solution in which a neutralized anionic polymer is dispersed in water without separating the non-crosslinked component from the crosslinked component, so the content proportion of the non-crosslinked component can be accurately determined from the light transmittance.

[0042] Such highly hygroscopic polymer (b) (neutralized product of anionic polymer) can be obtained by polymerizing or copolymerizing at least one anionic monomer, typified by carboxylic acid monomers such as methacrylic acid, acrylic acid, maleic anhydride, etc.; sulfonic acid monomers such as α-halogenated vinyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, etc.; phosphonic acid monomers such as vinyl phosphoric acid, etc.; and salts of these monomers, together with other copolymerizable monomers, as appropriate, and further neutralizing the resultant by alkali treatment.

[0043] Examples of other copolymerizable monomers include, but are not limited to, styrene, vinyl toluene, vinyl xylene, α-methyl styrene, vinyl naphthalene, α-halogenated styrenes, acrylonitrile, acrolein, methyl vinyl ketone, vinyl biphenyl, etc. Alternatively, instead of using the above anionic monomers, esters of the above anionic monomers or monomers having a functional group into which an anionic functional group can be introduced, such as styrene, vinyl toluene, vinyl xylene, α-methyl styrene, vinyl naphthalene, α-halogenated styrenes, etc., can be used, and after polymerization, the resulting polymer can be subjected to treatments such as hydrolysis, sulfonation, chlorosulfonation, and phosphonium formation to obtain an anionic polymer, which can then be neutralized to obtain a neutralized product of the anionic polymer to be used as the highly hygroscopic polymer (b).

[0044] Since the highly hygroscopic polymer (b) used in the present invention contains a large amount of non-crosslinked linear polymer, polyfunctional monomers having two or more functionalities are not generally used to obtain the anionic polymer. Even if they are used, they are used in such a small amount that the light transmittance falls within the aforementioned range. Furthermore, similar to the cationic polymer (a), the highly hygroscopic polymer (b) only needs to have a molecular weight sufficient to form a film.

[0045] In the present invention, the highly hygroscopic polymer (b) preferably used is sodium poly(meth)acrylate in terms of availability and cost. For example, sodium polyacrylate is commercially available from Nippon Shokubai Co., Ltd. under the name AQUALIC DL-522 and is represented by the following formula:

[0046] In the formula, n is a positive integer.

[0047] In the present invention, it is preferable that the cationic polymer (a) and the highly hygroscopic polymer (b) are present in the moisture-trapping film in a certain balance in order to maintain moisture-trapping properties for a longer period of time, and if either one is present in excess of what is necessary, it tends to be difficult to fully demonstrate the moisture-trapping properties. For example, it is suitable that the highly hygroscopic polymer (b) is present in the film in an amount of 11 to 3,122 parts by mass, preferably 40 to 1,500 parts by mass, and more preferably 55 to 400 parts by mass per 100 parts by mass of the cationic polymer (a).

[0048] <Production of Moisture-Trapping Film> The moisture-trapping film of the present invention, which contains the above-mentioned cationic polymer (a) and highly hygroscopic polymer (b), is formed by dissolving or dispersing these polymer components (a) and (b) in a solvent to prepare a coating composition, applying this composition to a predetermined substrate, and drying to remove the solvent.

[0049] The solvent used here is not particularly limited as long as it can be evaporated and removed by heating at a relatively low temperature. For example, alcoholic solvents such as methanol, ethanol, propyl alcohol, butanol, etc.; ketone solvents such as acetone, methyl ethyl ketone, etc.; mixed solvents of these solvents with water; or aromatic hydrocarbon solvents such as benzene, toluene, xylene, etc. can be used. However, from an environmental perspective, it is desirable to use water or a mixed solvent of water and an alcoholic solvent.

[0050] The above-mentioned solvent is used in an amount that will give the coating composition a viscosity suitable for coating, but a nonionic polymer can also be blended in an appropriate amount to adjust the viscosity of the coating composition or to adjust the water absorption rate of the moisture-trapping film to an appropriate range.

[0051] Examples of such nonionic polymers include saturated aliphatic hydrocarbon polymers such as polyvinyl alcohol, ethylene-propylene copolymers, and polybutylene; styrene-based polymers such as styrene-butadiene copolymers; and polyvinyl chloride, or copolymers of these with various comonomers (for example, styrene-based monomers such as vinyltoluene, vinylxylene, chlorostyrene, chloromethylstyrene, α-methylstyrene, α-halogenated styrene, and α,β,β'-trihalogenated styrene; monoolefins such as ethylene and butylene; and conjugated diolefins such as butadiene and isoprene).

[0052] In addition, this coating composition can be blended with a crosslinking agent such as a silane compound or an epoxy compound to introduce a crosslinked structure into the cationic polymer (a) or the highly hygroscopic polymer (b). However, as mentioned above, the introduction of a crosslinked structure into the highly hygroscopic polymer (b) causes changes in the physical properties of the polymer (b), resulting in a deterioration in the optical properties and surface smoothness of the moisture-trapping film. Therefore, the use of such crosslinking agents should be avoided.

[0053] Drying after coating is carried out using a heating device such as a heating oven, for example, by heating to a temperature of about 80 to 160°C. The heating time is generally from a few seconds to a few minutes. This heating removes the solvent, and a moisture-trapping film is obtained.

[0054] <Uses of moisture-trapping film> The moisture-trapping film of the present invention obtained as described above not only exhibits excellent moisture-trapping properties over a long period of time, but also has excellent optical properties and surface smoothness, making it applicable to a variety of uses as a single-layer film or a laminate film laminated on other films.

[0055] For example, in the case of a monolayer film, a moisture-trapping film can be formed on a substrate film having releasability (e.g., a polyethylene terephthalate film or a metal foil), peeled off from the substrate film, and then attached to a film that needs to be kept dry using an adhesive or the like. However, it is also possible to apply the above-mentioned coating composition directly to a film that needs to be dried and heat-dry it to form the moisture-trapping film of the present invention directly on the film.

[0056] When the film is used as a laminate film laminated on another film (e.g., a barrier film), the coating composition described above can be applied directly onto the other film in the same manner as above, and dried to form a moisture-trapping film, which can then be used.

[0057] <Gas Barrier Laminate> In the present invention, the properties of the moisture-trapping film are particularly utilized, and it is most suitable to laminate the film on a barrier film having an inorganic barrier layer and use the film as a gas barrier laminate.

[0058] Referring to FIG. 1 showing the layer structure of such a gas barrier laminate, such a gas barrier laminate 10 has a layer structure in which the moisture-trapping film 1 of the present invention is laminated on a barrier film 3 .

[0059] Barrier Film 3: The barrier film 3 is composed of a plastic substrate 5 and an inorganic barrier layer 7 formed on the surface of the substrate 5.

[0060] In this barrier film 3, the plastic substrate 5 may be formed from a known thermoplastic or thermosetting resin.

[0061] Examples of such resins include, but are not limited to, the following: polyolefins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, and cyclic olefin copolymers; ethylene-vinyl compound copolymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and ethylene-vinyl chloride copolymer; styrene-based resins such as polystyrene, acrylonitrile-styrene copolymer, ABS, and α-methylstyrene-styrene copolymer; polyvinyl compounds such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polymethyl acrylate, and polymethyl methacrylate; polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12; thermoplastic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate (PEN); Other examples include biodegradable resins such as polycarbonate, polyphenylene oxide, polyimide resin, polyamideimide resin, polyetherimide resin, fluororesin, allyl resin, polyurethane resin, cellulose resin, polysulfone resin, polyethersulfone resin, ketone resin, amino resin, and polylactic acid; blends of the above resins, resins modified by appropriate copolymerization, and multilayer structures of the above resins;

[0062] In particular, for applications requiring transparency, polyester resins such as PET and PEN are suitable, and for applications requiring heat resistance as well, polycarbonate and polyimide resins are suitable. Of course, the above-mentioned various resins may be blended with known resin compounding agents, such as antioxidants and lubricants.

[0063] The form of the plastic substrate 5 is not particularly limited as long as it satisfactorily exhibits the barrier properties of the inorganic barrier layer 7 and the moisture-trapping film 1, and may have any suitable form depending on the intended use, but is most commonly in the form of a plate, film, or sheet. Furthermore, the thickness and other properties thereof are set within an appropriate range depending on the intended use's properties (e.g., flexibility, pliability, strength, etc.).

[0064] Such a plastic substrate 5 can be molded by known molding methods such as injection or coinjection molding, extrusion or coextrusion molding, film or sheet molding, compression molding, cast polymerization, etc., depending on the form and type of plastic.

[0065] The inorganic barrier layer 7 formed on the plastic substrate 5 exhibits excellent barrier properties, particularly against gases such as oxygen, and is formed from various metals or metal oxides. The formation method is not particularly limited, and may be, for example, an inorganic vapor deposition film formed by physical vapor deposition, such as sputtering, vacuum deposition, or ion plating, or chemical vapor deposition, such as plasma CVD or ALD (atomic layer deposition), or a coating method such as a sol-gel method. Formation by physical vapor deposition or chemical vapor deposition is desirable, particularly in terms of utilizing the optical properties (transparency) of the moisture-trapping film 1 and maintaining the transparency of the laminate 10. Furthermore, a vapor deposition film formed by plasma CVD is most preferred, as it can be formed uniformly even on uneven surfaces, ensures high adhesion to the underlying layer (plastic substrate 5), and exhibits excellent barrier properties. In this case, the high surface smoothness of the moisture-trapping film 1 is also effectively utilized, and the gas barrier properties of the inorganic barrier layer 7 and the moisture-trapping properties (moisture barrier properties) of the moisture-trapping film 1 can be uniformly exhibited without variation in each part.

[0066] The thickness of the inorganic barrier layer 7 may be set to a level that allows the desired barrier properties to be exhibited depending on the application, and is generally 5 nm or more, and particularly 10 nm or more. In order to maintain transparency and a suitable level of smoothness and to make the most of the surface smoothness of the moisture-trapping film 1, it is preferable that the thickness be 800 nm or less, and particularly 450 nm or less.

[0067] Moisture-trapping film 1: In the present invention, the moisture-trapping film 1 is formed on the inorganic barrier layer 7, as can be seen from Fig. 1. That is, it is possible to provide the moisture-trapping film 1 on the opposite surface of the plastic substrate 5 (the surface on which the inorganic barrier layer 7 is not formed), but in this case the inorganic barrier layer 7 is exposed to the surface and is therefore susceptible to damage. However, by providing the moisture-trapping film 1 on the inorganic barrier layer 7, damage to the inorganic barrier layer 7 can be effectively prevented.

[0068] In the gas barrier laminate 10 provided with such a moisture-trapping film 1, the thickness of the moisture-trapping film 1 is not particularly limited, and can be set to an appropriate thickness depending on the intended use and the required level of moisture barrier. Generally, by setting the thickness to 1 μm or more, particularly 2 to 10 μm, thickness unevenness can be avoided and the water vapor permeability can be increased to 100%. －５ g / m ２ / day or less can be stably exhibited for a long period of time.

[0069] Furthermore, in this gas barrier laminate 10, a decrease in transparency due to particle aggregation in the moisture-trapping film 1 is suppressed, and the haze of the film 1 is low, so that the haze of the gas barrier laminate 10 can be set accordingly to be low, at 6% or less, particularly 4% or less, and thus exhibit high transparency. Therefore, such a gas barrier laminate is suitable for applications requiring high transparency (for example, as an encapsulant for solar cells or organic EL devices).

[0070] Furthermore, this gas barrier laminate 10 exhibits high smoothness, with the surface roughness Sa of the moisture-trapping film 1 being 11 nm or less, particularly 7 nm or less, and therefore has excellent lamination properties with other films, allowing for the formation of multilayer structures suited to various applications by laminating with other films. For such lamination, for example, an epoxy-based or urethane-based dry laminating adhesive can be used to laminate another film onto the surface of the moisture-trapping film 1 of the gas barrier laminate 10. Of course, depending on the application, it is also possible to laminate another film onto the plastic substrate 5 side. Furthermore, by laminating multiple gas barrier laminates 10 together using a dry laminating adhesive, it is possible to achieve even higher levels of gas barrier properties.

[0071] The following examples illustrate the superior performance of the moisture-trapping films of the present invention.

[0072] <Evaluation of Ultimate Humidity (Moisture Content)> A sample polymer solution was dropped into a bottle for a Karl Fischer moisture meter and dried in an oven at 130°C for 30 minutes. After drying, the dried polymer was allowed to absorb moisture in an environment of 40°C and 50% RH, and then dried at 40°C in a nitrogen atmosphere (0% RH) for 8 days. The amount of moisture absorbed was measured by the Karl Fischer method, and the moisture content (amount of moisture per gram) was determined. This moisture content was used as an index of the ultimate humidity. That is, a sample with a higher moisture content had a lower ultimate humidity, and a sample with a lower moisture content had a higher ultimate humidity.

[0073] <Light Transmittance (Degree of Non-Crosslinking)> A polymer solution was prepared so that the solid content of the highly hygroscopic polymer was 10% by mass, and the polymer solution was placed in a disposable cell (made of PMMA, Spectr. UV cuvette PMMA standard), and transmittance was measured at a wavelength of 400 m in an environment of 21° C. using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by Shimadzu Corporation, product name: UV-3600i Plus). This transmittance was defined as the light transmittance (degree of non-crosslinking).

[0074] <Polymer pH Measurement> A sample polymer was diluted to 5% by mass with pure water at 25° C., and the pH was measured using a pH meter (pH METER D-52 manufactured by HORIBA).

[0075] <Measurement of Total Light Transmittance of Gas Barrier Laminate> Total light transmittance was measured in accordance with ASTM D 1003 using a HAZE METER NDH8000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[0076] <Haze Measurement of Gas Barrier Laminate> Haze (cloudiness) was measured according to ASTM D 1003 using a HAZE METER NDH8000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[0077] <Surface Roughness (ISO25178-2:2012) Measurement> Using an environmentally controlled scanning probe microscope (manufactured by Hitachi High-Tech Corporation, product name: AFM5300E) and a probe (manufactured by Hitachi High-Tech Corporation, product name: Si-DF3, tip curvature radius: 10 nm, spring constant: 1.6 N / m), measurements were performed in DFM mode over an area of ​​2 μm × 2 μm on the surface of the sample film, and the average surface roughness (Sa) was determined.

[0078] <Measurement of Total Light Transmittance and Haze of Moisture-Trapping Film> The coating liquid of each example was applied to a 0.7 mm thick glass substrate using a bar coater. After application, the glass substrate was heat-treated in a box-type electric oven at an oven temperature of 100°C for 60 seconds to form a 1.5 μm thick moisture-trapping film. The total light transmittance and haze of the moisture-trapping film were measured using a HAZE METER NDH8000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with ASTM D 1003. Since it is very difficult to measure the total light transmittance and haze of a moisture-trapping film alone, the film was measured after being formed on a glass substrate as described above. Because the glass substrate is transparent, the measurements on the glass substrate can be considered to be the values ​​of the moisture-trapping film alone.

[0079] <Measurement of Trapping Effect (Water Vapor Permeability)> The coating solution of each example was applied to the vapor deposition surface of a vapor-deposited PET film (GL-AE, manufactured by Toppan Printing Co., Ltd.) using a bar coater. The coated film was then heat-treated in a box-type electric oven at an oven temperature of 100°C for 60 seconds to form a 1.5 μm-thick moisture-trapping film, yielding a laminate for measuring the trapping effect. A 50 μm-thick PET film (Cosmoshine A4360, manufactured by Toyobo Co., Ltd.) was dry-laminated to both sides of the gas barrier laminate via a 3 μm-thick urethane adhesive, followed by aging at 40°C for 5 days to produce a laminate for measuring the trapping effect. Vacuum drying was performed at 100°C for 6 hours, and measurements were performed using a PERMATRAN (manufactured by MOCON Co., Ltd.) in a 40°C-90% RH environment. As an index of the trapping effect, the water vapor transmission rate during the measurement time of 3.5 to 4 hours was shown as WVTR (3.5 to 4). When this value was 0.1 g / m ２ / day was judged to be good (◯) in trapping ability, and 0.1 or more was judged to be unsatisfactory (×) in trapping ability. The water vapor transmission rate from 9 to 10 hours after the start of measurement was also shown as WVTR (9-10).

[0080] Example 1 The following polyallylamine was prepared as a cationic polymer. Polyallylamine: PAA-15C (aqueous solution) manufactured by Nittobo Medical Co., Ltd. Solids content: 15% by mass. A solution of the above polyallylamine was prepared to have a solids content of 10% by mass, water of 76.5% by mass, and 2-propanol of 13.5% by mass. Using γ-glycidoxypropyltrimethoxysilane as a crosslinking agent, a crosslinker solution was prepared to have a solids content of 10% by mass, water of 76.5% by mass, and 2-propanol of 13.5% by mass. The water content (an index of the humidity reached) of the cured polyallylamine obtained from this solution was 2.1%.

[0081] On the other hand, an anionic polymer solution was prepared using a sodium polyacrylate polymer (Nippon Shokubai, Aqualic DL-522, aqueous solution, solids content 30% by mass, Mw 170,000, water content (ultimate humidity) 7.3%, light transmittance (degree of non-crosslinking) 90.5%) as a highly hygroscopic polymer, so as to have a solids content of 10% by mass. The pH of this highly hygroscopic polymer, measured by the method described above, was 8.5.

[0082] Next, the cationic polymer solution and the moisture absorbent solution were mixed so that the moisture absorbent was 12 parts by mass per 100 parts by mass of the cationic polymer, and further, a curing agent solution was added to this mixed solution so that the crosslinking agent was 7.4 parts by mass relative to the cationic polymer, and the mixture was thoroughly stirred to prepare a coating liquid for the moisture-trapping layer.

[0083] The coating solution obtained above was applied to the vapor-deposited surface of a vapor-deposited PET film (GL-AE, Toppan Printing, substrate: PET (12 μm)) using a bar coater. The coated film was then heat-treated in a box-type electric oven at an oven temperature of 100°C for 60 seconds to form a 5 μm-thick moisture-trapping film on the vapor-deposited PET film, yielding a gas barrier laminate consisting of the vapor-deposited PET film and the moisture-trapping film. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1. The total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2. The total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured as described above, are shown in Table 3.

[0084] Example 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that the highly hygroscopic polymer was blended in amounts of 55 parts by mass and the crosslinking agent was blended in amounts of 10 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0085] Example 3 A gas barrier laminate was obtained in the same manner as in Example 1, except that the highly hygroscopic polymer was blended in amounts of 319 parts by mass and the crosslinking agent was blended in amounts of 28 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0086] Example 4 A gas barrier laminate was obtained in the same manner as in Example 1, except that the highly hygroscopic polymer was blended in amounts of 3,122 parts by mass and the crosslinking agent was blended in amounts of 212 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0087] Example 5 A gas barrier laminate was obtained in the same manner as in Example 1, except that polyethyleneimine (PEI-70000, manufactured by Nippon Shokubai, solids content 30% by mass, Mw 70000, moisture content (ultimate humidity) 0.5%) was used as the cationic polymer, and the highly hygroscopic polymer and crosslinking agent were blended in amounts of 11 parts by mass and 3.5 parts by mass, respectively, per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0088] Example 6 A gas barrier laminate was obtained in the same manner as in Example 5, except that the highly hygroscopic polymer was blended in amounts of 48 parts by mass and the crosslinking agent was blended in amounts of 4.6 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0089] Example 7 A gas barrier laminate was obtained in the same manner as in Example 5, except that the highly hygroscopic polymer was blended in amounts of 204 parts by mass and the crosslinking agent was blended in amounts of 10 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0090] Example 8 A gas barrier laminate was obtained in the same manner as in Example 5, except that the highly hygroscopic polymer was blended in amounts of 280 parts by mass and the crosslinking agent was blended in amounts of 12 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0091] Example 9 A gas barrier laminate was obtained in the same manner as in Example 5, except that the highly hygroscopic polymer was blended in amounts of 1,497 parts by mass and the crosslinking agent was blended in amounts of 49 parts by mass per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0092] Example 10 A gas barrier laminate was obtained in the same manner as in Example 1, except that a polyacrylate sodium polymer (Nippon Shokubai, AQUALIC YS-100, aqueous solution, solids content 45% by mass, pH 8.4, Mw 5500, water content (ultimate humidity) 7.3%, light transmittance (degree of non-crosslinking) 99.4%) was used as the highly hygroscopic polymer, and the highly hygroscopic polymer was mixed in an amount of 318 parts by mass and 28 parts by mass of crosslinker per 100 parts by mass of cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0093] Example 11 A gas barrier laminate was obtained in the same manner as in Example 1, except that a polyacrylate sodium polymer (Nippon Shokubai, AQUALIC DL-453, aqueous solution, solids content 35% by mass, pH 8.5, Mw 50,000, water content (ultimate humidity) 7.3%, light transmittance (degree of non-crosslinking) 90.5%) was used as the highly hygroscopic polymer, and the highly hygroscopic polymer was mixed in an amount of 319 parts by mass and 28 parts by mass of crosslinker per 100 parts by mass of cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0094] Example 12 A gas barrier laminate was obtained in the same manner as in Example 1, except that polyethyleneimine (manufactured by Fujifilm Wako, polyethyleneimine, solids content 99% by mass, Mw 10,000, moisture content (ultimate humidity) 0.6%) was used as the cationic polymer, and the highly hygroscopic polymer and crosslinking agent were blended in amounts of 280 parts by mass and 12 parts by mass, respectively, per 100 parts by mass of the cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured using the methods described above, are shown in Table 3.

[0095] Comparative Example 1 A gas barrier laminate was obtained in the same manner as in Example 1, except that a crosslinked product of sodium polyacrylate (Tuftic HU-820E, water dispersion, solids content 13% by mass, pH 10.1, water content (ultimate humidity) 15.5%, light transmittance (degree of non-crosslinking) 1.2%, manufactured by Toyobo Co., Ltd.) was used as the highly hygroscopic polymer, and the highly hygroscopic polymer was mixed in an amount of 55 parts by mass and 10 parts by mass of crosslinking agent per 100 parts by mass of cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0096] Comparative Example 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a crosslinked product of sodium polyacrylate (Tuftic HU-820E, water dispersion, solids content 13% by mass, pH 10.1, water content (ultimate humidity) 15.5%, light transmittance (degree of non-crosslinking) 1.2%, manufactured by Toyobo Co., Ltd.) was used as the highly hygroscopic polymer, and the highly hygroscopic polymer was mixed in an amount of 204 parts by mass and 20 parts by mass of crosslinking agent per 100 parts by mass of cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0097] Comparative Example 3 A gas barrier laminate was obtained in the same manner as in Example 1, except that a crosslinked product of sodium polyacrylate (Tuftic HU-820E, water dispersion, solids content 13% by mass, pH 10.1, water content (ultimate humidity) 15.5%, light transmittance (degree of non-crosslinking) 1.2%, manufactured by Toyobo Co., Ltd.) was used as the highly hygroscopic polymer, and the highly hygroscopic polymer was mixed in an amount of 319 parts by mass and 28 parts by mass of crosslinking agent per 100 parts by mass of cationic polymer. The light transmittance (degree of non-crosslinking) of the highly hygroscopic polymer and the composition of the moisture-trapping film are shown in Table 1, the total light transmittance, haze, and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze, and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0098] Comparative Example 4 A gas barrier laminate was obtained in the same manner as in Example 1, except that no highly hygroscopic polymer was used and the crosslinking agent was blended in an amount of 7 parts by mass per 100 parts by mass of the cationic polymer. The composition of the moisture-trapping film is shown in Table 1, the total light transmittance, haze and surface roughness (Sa) of the moisture-trapping film are shown in Table 2, and the total light transmittance, haze and water vapor permeability of the gas barrier laminate, measured by the methods described above, are shown in Table 3.

[0099]

[0100]

[0101]

[0102] 1: Moisture-trapping film 3: Barrier film 5: Plastic substrate 7: Inorganic barrier layer 10: Gas-barrier laminate

Claims

1. A moisture-trapping film comprising a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer, wherein the highly hygroscopic polymer (b) is a neutralized anionic polymer that exhibits a light transmittance of 90% or more at a wavelength of 400 nm when measured at 21°C in an aqueous dispersion having a solids concentration of 10% by mass.

2. The moisture-trapping film according to claim 1, wherein the highly hygroscopic polymer (b) is a neutralized product of an anionic polymer having an anionic functional group selected from the group consisting of a carboxyl group, a sulfonic acid group and a phosphoric acid group.

3. The moisture-trapping film according to claim 2, wherein the highly hygroscopic polymer (b) is a neutralized product of (meth)acrylic acid.

4. The moisture-trapping film according to any one of claims 1 to 3, wherein the highly hygroscopic polymer (b) exhibits a pH of 10 or less in an aqueous dispersion at 25°C with a concentration of 5% by weight.

5. The moisture-trapping film according to any one of claims 1 to 4, wherein the highly hygroscopic polymer (b) is present in an amount of 11 to 1000 parts by weight per 100 parts by weight of the cationic polymer (a).

6. The moisture-trapping film according to any one of claims 1 to 5, which exhibits a haze of 4.7% or less.

7. The moisture-trapping film according to claim 6, which exhibits a surface roughness Sa (ISO25178-2:2012) of 11 nm or less.

8. A gas barrier laminate having a layer structure in which the moisture-trapping film according to any one of claims 1 to 7 and a barrier film having an inorganic barrier layer formed on the surface of a plastic substrate are laminated together.

9. A coating composition comprising a cationic polymer (a) and a highly hygroscopic polymer (b) that reaches a lower humidity than the cationic polymer, dissolved or dispersed in a solvent, the highly hygroscopic polymer (b) being a neutralized anionic polymer that exhibits a light transmittance of 90% or more at a wavelength of 400 nm when measured at 21°C in an aqueous dispersion having a solids concentration of 10% by mass.

10. The coating composition according to claim 9, wherein the highly hygroscopic polymer (b) exhibits a pH of 10 or less in an aqueous dispersion at a concentration of 5% by mass at 25°C.

11. The coating composition according to claim 9 or 10, wherein the highly hygroscopic polymer (b) is used in an amount of 11 to 1,000 parts by mass per 100 parts by mass of the cationic polymer (a).

12. The coating composition according to any one of claims 9 to 11, wherein the solvent is a mixed solvent of water and an alcohol.

Images