Base material for mounting electronic device

Abstract

A base material for mounting an electronic device is characterized in that a metal foil (A), a hygroscopic layer, and a barrier sheet are laminated in this order, and the thickness of the metal foil (A) is 5-20 μm.

Description

Substrate for mounting electronic devices

[0001] The present invention relates to a substrate for mounting an electronic device, and more particularly to a substrate for mounting an electronic device that is used to block and absorb moisture and keep the electronic device dry.

[0002] Conventionally, moisture-absorbing sheets having a moisture-absorbing resin layer in which a desiccant is dispersed have been widely used for absorbing moisture and preventing moisture. Various layer configurations have been proposed for such moisture-absorbing sheets. Patent Document 1 proposes a moisture-absorbing sheet comprising a desiccant layer, a moisture-permeable sheet provided on one surface of the desiccant, and an adhesive layer provided on the other surface of the desiccant layer, and describes that a cellophane sheet, an acetate sheet, a nylon sheet, or the like can be used as the moisture-permeable sheet.

[0003] Recently developed electronic devices such as organic electroluminescence (organic EL) displays, solar cell panels, liquid crystal touch panels, and electronic paper are sensitive to charge leakage, and therefore require high moisture barrier properties for plastic substrates forming circuit boards or films sealing circuit boards.

[0004] However, the known moisture-absorbing sheets disclosed in Patent Document 1 and elsewhere do not exhibit satisfactory performance as encapsulants for keeping the interior of such electronic devices dry. That is, they absorb large amounts of moisture that penetrate from the outside of the device, causing the desiccant present in the moisture-absorbing sheet to reach saturation in a short period of time. Further improvement is needed because the moisture absorption properties are impaired or the absorbed moisture is released into the device.

[0005] Furthermore, as electronic devices have increasingly complex structures, plastic substrates such as sealing films may be subjected to bending stress during installation, attachment, etc., and there is a demand for flexibility that does not impair moisture barrier properties even when subjected to such stress.

[0006] Furthermore, in Patent Document 2, the present applicant has proposed a moisture barrier laminate (film) that stably exhibits excellent moisture barrier properties for a long period of time, and this has already been patented.

[0007] The technology of Patent Document 2 is a technology in which a thick organic layer with excellent moisture diffusivity is formed with a thickness of 10 μm or more between an inorganic barrier layer and a moisture absorptive layer, which are arranged on the high-humidity atmosphere side, thereby effectively suppressing deactivation of the moisture absorptive layer and providing excellent moisture barrier properties for a long period of time. That is, defects such as cracks are formed locally in the inorganic barrier layer, and moisture flows into the moisture absorptive layer through these defects, causing the moisture absorptive layer to be rapidly consumed. However, with the technology of Patent Document 2, moisture that flows through the defects in the inorganic barrier layer is quickly diffused by the organic layer with a large thickness (10 μm or more), effectively preventing the problem of moisture flowing into the moisture absorptive layer in a locally concentrated manner. As a result, consumption of the moisture absorptive layer is mitigated and excellent moisture barrier properties are provided for a long period of time.

[0008] However, there is a limit to how long the moisture barrier property can be extended according to Patent Document 2, and it is desired to further maintain the moisture barrier property for a long period of time.

[0009] JP 2006-326838 A Japanese Patent No. 6657651 A

[0010] An object of the present invention is to provide a substrate for mounting an electronic device that is capable of preventing moisture penetration and keeping the electronic device dry, and that has excellent flexibility.

[0011] According to the present invention, there is provided a substrate for mounting an electronic device, which comprises a metal foil (A), a moisture absorbing layer, and a barrier sheet laminated in this order, and the thickness of the metal foil (A) is 5 to 20 μm.

[0012] In the substrate for mounting an electronic device of the present invention, (1) the metal foil (A) is made of aluminum, (2) the moisture absorption layer contains a resin composition in which a moisture absorbent (ii) is dispersed in an ionic polymer (i), (3) the barrier sheet contains a resin layer and has an inorganic barrier layer on at least one surface of the resin layer, (4) the resin layer is made of at least one of an olefin resin, a polyester resin, a polyimide resin, a polyamide resin, or a cyclic olefin resin, (5) the inorganic barrier layer is made of a vapor-deposited film of a metal or a metal oxide, (6) the barrier sheet has a metal foil (B) made of aluminum, and the thickness of the metal foil (B) is 5 to 20 μm, (7) a quasi-moisture absorption layer is provided at at least one location between the metal foil (A) and the moisture absorption layer or between the moisture absorption layer and the barrier sheet, (8) The quasi-hygroscopic layer is formed from at least one of an ionic polymer, a polyamide resin, a polyvinyl alcohol-based resin, and an ethylene-vinyl alcohol copolymer resin; (9) An ultraviolet blocking layer is provided on one surface of either the metal foil (A) or the barrier sheet, the surface on which the hygroscopic layer is not laminated; and (10) The overall thickness is preferably 25 to 250 μm.

[0013] In the substrate for mounting an electronic device of the present invention, the metal foil (A) blocks the passage of most moisture, and even trace amounts of moisture that have penetrated pinholes in the metal foil (A) are absorbed by the moisture absorbing layer. Furthermore, a barrier sheet is further provided on the device-facing surface of the moisture absorbing layer, blocking the passage of moisture that has not been absorbed by the moisture absorbing layer. As a result, moisture is prevented from penetrating the device, and the device can be kept dry for a long period of time. In another aspect of the substrate for mounting an electronic device of the present invention, the barrier sheet blocks the passage of most moisture, and even trace amounts of moisture that have penetrated the barrier sheet are absorbed by the moisture absorbing layer. Furthermore, a metal foil (A) is further provided on the device-facing surface of the moisture absorbing layer, blocking the passage of moisture that has not been absorbed by the moisture absorbing layer. As a result, moisture is prevented from penetrating the device, and the device can be kept dry for a long period of time. Furthermore, the substrate for mounting an electronic device of the present invention is flexible and has excellent bending resistance. That is, the substrate for mounting an electronic device of the present invention is easy to handle, and the moisture barrier properties of the substrate are not impaired even when stress such as bending is applied.

[0014] In the present invention, since the substrate for mounting an electronic device comprises a metal foil, it is basically used in a portion of the device where light transmittance is not required (for example, a back sheet of a solar cell, other non-light-receiving surfaces of a solar cell or non-light-emitting surfaces of an organic electroluminescence element, or the side surfaces of these devices).

[0015] 1 is a schematic cross-sectional view showing an example of the layer structure of the substrate for mounting an electronic device of the present invention, FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the substrate for mounting an electronic device of the present invention, FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the substrate for mounting an electronic device of the present invention,

[0016] 1 to 3, the substrate for mounting an electronic device of the present invention, generally designated by 1, comprises a metal foil (A) 3, a moisture absorbing layer 9, and a barrier sheet 11 in this order.

[0017] <Metal foil (A) 3> The metal foil (A) 3 is provided on the outer surface side or one surface on the device side of the moisture absorbing layer 9.

[0018] When the metal foil (A) 3 is provided on the electronic device side of the moisture absorption layer 9, it serves to block most of the moisture (water vapor) that attempts to penetrate into the device. When the metal foil (A) 3 is provided on the electronic device side of the moisture absorption layer 9, it serves to block moisture that has not been absorbed by the moisture absorption layer 9. As a result, it becomes possible to keep the inside of the device dry for a long period of time.

[0019] From the viewpoints of flexibility, ease of thin film formation, and cost reduction, the metal foil (A) 3 is preferably formed from aluminum. The thickness of the metal foil (A) 3 is 5 to 20 μm, more preferably 6 to 20 μm, and particularly preferably 6 to 15 μm. A metal foil (A) 3 with a thickness of less than 5 μm is difficult to manufacture. On the other hand, a metal foil (A) 3 with a thickness of more than 20 μm has insufficient flexibility and is difficult to handle.

[0020] Here, flexibility, also referred to as flex resistance, refers to the property of having flexibility while being durable against bending, etc. The thinner the metal foil (A) 3, the more flexible it is. Furthermore, the thinner the metal foil (A) 3, the less the amount of metal foil (A) 3 used can be, and therefore the overall manufacturing cost of the substrate 1 can be reduced.

[0021] However, it is generally known that the thinner the metal foil (A) 3, the more pinholes there are. Therefore, when the thickness of the metal foil (A) 3 is small, the amount of moisture that permeates increases compared to when the thickness of the metal foil (A) 3 is large, and there is a risk that sufficient moisture barrier properties will not be exhibited. Therefore, in the present invention, when the metal foil (A) 3 is provided on the outer surface side of the moisture absorption layer 9, the moisture absorption layer 9 can absorb the small amount of moisture that has permeated through the pinholes in the metal foil (A) 3, thereby preventing moisture from permeating into the electronic device and maintaining the electronic device in a dry state. In other words, most moisture attempting to penetrate the device from the outside is blocked by the metal foil 3, but the small amount of moisture that has permeated through the pinholes in the metal foil (A) 3 is also absorbed by the moisture absorption layer 9, so that the moisture absorption layer 9 compensates for the reduced moisture barrier properties caused by the thin thickness of the metal foil (A) 3. Furthermore, when the metal foil (A) 3 is provided on the electronic device side of the moisture absorption layer 9, the metal foil (A) 3 plays a role in blocking moisture that has not been absorbed by the moisture absorption layer 9. In this case, the amount of moisture that reaches the metal foil 3 is extremely small, and there is almost no effect of moisture penetration due to an increase in pinholes caused by the thin thickness of the metal foil (A) 3.

[0022] <Protective Resin Layer 5> Alternatively, a structure having only the metal foil (A) 3 may be used, or a protective resin layer 5 may be formed on the metal foil (A) 3 via an adhesive layer 7, which will be described later. The protective resin layer 5 is a resin layer provided to prevent scratches and oxidative degradation of the metal foil (A) 3. Therefore, it is preferable to provide the protective resin layer 5, particularly when the metal foil (A) 3 is provided on the outer surface side of the moisture-absorbing layer 9. The protective resin layer 5 may be formed using various known resins, but is generally formed from polyester resins such as polyethylene terephthalate or polyolefin resins such as polyethylene or polypropylene, preferably polyester resins. Such a protective resin layer 5 may typically have a thickness of about 1 to 200 μm.

[0023] <Adhesive Layer 7> The adhesive layer 7 is a layer that bonds the metal foil (A) 3 and the protective resin layer 5 together.

[0024] The adhesive used to form the adhesive layer 7 is preferably an epoxy adhesive or a urethane adhesive known as a dry laminating adhesive.

[0025] Epoxy adhesives: The above-mentioned epoxy adhesives are adhesives that bond by curing a liquid epoxy resin with an epoxy curing agent. Such epoxy resins are liquid resins that have epoxy groups in their molecules, and typical examples include those obtained by reacting epichlorohydrin with a phenol compound, an amine compound, or a carboxylic acid, and those obtained by oxidizing an unsaturated compound such as butadiene with an organic peroxide, and either type can be used.

[0026] Specific examples of epoxy adhesives include, but are not limited to, bisphenol A or bisphenol F epoxy resins, novolac epoxy resins, cyclic aliphatic epoxy resins, long-chain aliphatic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, etc. In the present invention, glycidyl amine epoxy resins are particularly suitable because they can form an adhesive layer 7 with a high elastic modulus.

[0027] Furthermore, known epoxy curing agents such as amine-based, acid anhydride, and polyamide curing agents can be used. However, from the viewpoint of being able to form a coating film (adhesive layer 7) that has a particularly high elastic modulus and is easily adapted to thermal shrinkage, amine-based curing agents, and in particular aromatic polyamines such as metaphenylenediamine, are preferably used.

[0028] The ratio of the amount of epoxy resin to the amount of curing agent may be set in accordance with the epoxy equivalent of the epoxy resin so that a sufficient cured film is formed.

[0029] Urethane adhesive: A urethane adhesive is a reaction product of polyisocyanate and polyol. This adhesive typically contains a known curing catalyst such as an amine catalyst, a metal catalyst, or a phosphate-modified compound. The amount of curing catalyst is determined depending on the type of curing catalyst so that a dense cured film (adhesive layer 7) can be formed at a temperature and for a time that does not cause thermal deformation of the underlying resin.

[0030] The polyol used to form the polyurethane adhesive is a compound having two or more OH groups per molecule, and representative examples include the following compounds: di-, tri-, tetra-, penta-, and hexa-hydroxy compounds; polyester polyols containing two or more OH groups per molecule; polyether polyols containing two or more OH groups per molecule; polycarbonate polyols containing two or more OH groups per molecule; polycaprolactone polyols containing two or more OH groups per molecule; and polyacrylic polyols containing two or more OH groups per molecule. The most suitable polyols in the present invention are polyester polyols.

[0031] The polyisocyanate to be reacted with the polyol is a compound having two or more NCO groups in one molecule. Specific examples of the polyisocyanate include, but are not limited to, the following compounds: Aliphatic isocyanates such as ethylene diisocyanate, trimethylene diisocyanate, and tetramethylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate, norbornane diisocyanate, bis(isocyanatomethyl)cyclohexane, and 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2,2,1]-heptane; aromatic isocyanates such as xylylene diisocyanate, bis(isocyanatoethyl)benzene, bis(isocyanatomethyl)naphthalene, and bis(isocyanatomethyl)diphenyl ether; sulfur-containing aliphatic isocyanates such as thiodiethyl diisocyanate; aliphatic sulfide isocyanates such as bis[2-(isocyanatomethylthio)ethyl]sulfide; aromatic sulfide isocyanates such as diphenyl sulfide-2,4'-diisocyanate; Aromatic disulfide-based isocyanates such as diphenyl disulfide-4,4'-diisocyanate; Aromatic sulfone-based isocyanates such as diphenyl sulfone-4,4'-diisocyanate; Sulfonic acid ester-based isocyanates such as 4-methyl-3-isocyanate benzenesulfonyl-4'-isocyanate phenol ester; Aromatic sulfonic acid amide-based isocyanates such as 4-methyl-3-isocyanate benzenesulfonyl anilide-3'-methyl-4'-isocyanate; Sulfur-containing heterocyclic isocyanates such as thiophene-2,5-diisocyanate;

[0032] The polyisocyanate is usually used in an amount such that the amount of isocyanate groups (NCO groups) is about 0.8 to 1.2 moles per mole of hydroxyl groups contained in the polyol.

[0033] The above-mentioned epoxy adhesive and urethane adhesive are applied to a predetermined location using a volatile organic solvent such as a hydrocarbon, alcohol, ketone, ester, or ether solvent, and then dried to form the adhesive layer 7. The adhesive layer 7 thus formed is typically cured by being held at a temperature of about 30 to 50°C for 24 hours or more.

[0034] The thickness of the adhesive layer 7 is 0.1 to 10 μm, preferably 2 to 6 μm. If the thickness of the adhesive layer 7 is less than 0.1 μm, the adhesion between the layers may be insufficient. If the thickness of the adhesive layer 7 exceeds 10 μm, the adhesion between the layers can be ensured, but the manufacturing cost increases unnecessarily.

[0035] <Moisture absorption layer 9> The moisture absorption layer 9 can also be called a moisture trapping layer. The moisture absorption layer 9 is a layer that absorbs trace amounts of moisture that have permeated the metal foil (A) 3 or the barrier sheet 11 provided on the outer surface side of the moisture absorption layer 9, and is a layer in which a moisture absorbent is dispersed in a resin. In the present invention, most of the moisture that attempts to penetrate into the device is blocked by the metal foil (A) 3 or the barrier sheet 11, making the moisture absorption layer 9 less likely to swell, and therefore the moisture absorption ability of the moisture absorption layer 9 can be maintained for a long period of time.

[0036] Such a moisture-absorbing layer 9 has a moisture-absorbing agent dispersed in a resin matrix. In particular, when a high barrier property against moisture is required, a layer in which a moisture-absorbing agent is dispersed in an ionic polymer, as described in the aforementioned Patent Document 2, is preferred, from the viewpoint of having excellent moisture-trapping properties and effectively preventing deformation such as swelling caused by moisture absorption.

[0037] The ionic polymer forms the matrix of the moisture-absorbing layer 9 and contains cationic groups (NH ２ There are cationic polymers having anionic groups (such as COONa groups and COOH groups) as ionic groups, and anionic polymers having anionic groups (such as COONa groups and COOH groups) as ionic groups. Generally, polymers with a lower ultimate humidity than ionic polymers are used as adsorbents.

[0038] That is, in the moisture absorbing layer 9 having the above-mentioned ionic polymer as a matrix, the small amount of moisture that has entered through the metal foil (A) 3 or the barrier sheet 11 is absorbed by this matrix (ionic polymer). That is, the matrix itself exhibits high moisture absorption properties, and captures and absorbs moisture.

[0039] However, if moisture is simply absorbed into the matrix, the absorbed moisture will easily be released due to environmental changes such as a rise in temperature. Furthermore, the penetration of moisture widens the spacing between the polymer molecules that form the matrix, resulting in the moisture absorption layer 9 swelling and a large increase in volume. However, if an adsorbent with a lower ultimate humidity than the matrix (ionic polymer) is dispersed, the moisture absorbed in the matrix will be further captured by the moisture absorbent, which has a higher hygroscopicity (i.e., a lower ultimate humidity) than the matrix. This not only effectively suppresses swelling due to the absorbed water molecules, but also traps the water molecules within the moisture absorption layer 9, effectively preventing moisture release from the moisture absorption layer 9.

[0040] In this way, when the moisture absorbing layer 9 is formed by dispersing a moisture absorbent in an ionic polymer, it has a high moisture absorption capacity and the dual function of capturing and trapping moisture, so that it can capture moisture even in an extremely low humidity atmosphere and capture moisture at a speed that is much faster than the speed at which moisture permeates through the metal foil (A) 3 or the barrier sheet 11, thereby achieving significantly high moisture barrier properties.

[0041] Ionic polymer (cationic polymer): Among the ionic polymers used in the present invention to form the matrix as described above, the cationic polymer is a polymer having, in the 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, or a quaternary pyridinium group. Such cationic polymers are capable of forming a hygroscopic matrix because the cationic group has a strong nucleophilic action and captures water through hydrogen bonds. The amount of cationic groups in the cationic polymer is generally such that the water absorption rate of the formed hygroscopic matrix (JIS K-7209-1984) is 20% or more, particularly 30% to 45%, at a humidity of 80% RH and an atmosphere of 30°C.

[0042] The cationic polymer is obtained by polymerizing or copolymerizing at least one cationic monomer, such as an amine monomer (e.g., allylamine, ethyleneimine, vinylbenzyltrimethylamine, [4-(4-vinylphenyl)-methyl]trimethylamine, or vinylbenzyltriethylamine; a nitrogen-containing heterocyclic monomer (e.g., vinylpyridine or vinylimidazole); or a salt thereof, together with other copolymerizable monomers, and optionally partially neutralizing the polymer by acid treatment. Examples of the copolymerizable monomer include, but are not limited to, styrene, vinyltoluene, vinylxylene, α-methylstyrene, vinylnaphthalene, α-halogenated styrenes, acrylonitrile, acrolein, methyl vinyl ketone, and vinylbiphenyl.

[0043] 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 after polymerization, a treatment such as amination or alkylation (quaternary ammonium chloride) may be carried out to obtain a cationic polymer.

[0044] In the present invention, among the above cationic polymers, allylamine is particularly suitable from the viewpoint of film-forming properties and the like.

[0045] The above-mentioned cationic polymer is generally produced by radical polymerization using a polymerization initiator under heating, as described in Patent Document 2. When polymerization is carried out using a monomer into which a cationic functional group can be introduced, a cationic group introduction treatment such as amination or alkylation treatment may be carried out after polymerization.

[0046] In the present invention, it is preferable to introduce a crosslinked structure into the matrix formed using the cationic polymer described above, in order to ensure mechanical strength without reducing moisture absorption capacity and at the same time improve dimensional stability. That is, if a crosslinked structure is introduced into a moisture-absorbing matrix, when the matrix absorbs water, the molecules of the cationic polymer are bound to each other by the crosslinks, suppressing volume changes due to swelling (moisture absorption), and improving mechanical strength and dimensional stability. The crosslinked structure can be introduced by incorporating a crosslinking agent into the coating composition for forming the moisture-absorbing layer 9. As described in Patent Document 2, such a crosslinked structure can be formed using 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, and in particular, a compound represented by the following formula (2): X-SiR １ ｎ (OR ２ ) ３－ｎ (2) 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. That is, a crosslinked structure can be introduced by blending the above-mentioned crosslinking agent in a coating composition for forming a moisture absorbing layer containing the above-mentioned cationic polymer and then forming a film.

[0047] Ionic polymer (anionic polymer): The anionic polymer used to form the hygroscopic matrix is ​​a polymer having an anionic functional group that can become negatively charged in water, such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group, or an acidic base formed by partially neutralizing these groups, in the molecule. Anionic polymers having such functional groups can form a hygroscopic matrix because the functional groups trap water through hydrogen bonds. The amount of anionic functional groups in the anionic polymer varies depending on the type of functional group, but, similar to the cationic polymer described above, it is sufficient that the amount is such that the water absorption rate of the formed hygroscopic matrix (JIS K-7209-1984) is 20% or more, particularly 30% to 45%, at a humidity of 80% RH and an atmosphere of 30°C.

[0048] Examples of anionic polymers having such functional groups include those obtained by polymerizing or copolymerizing at least one anionic monomer, such as carboxylic acid monomers (e.g., methacrylic acid, acrylic acid, maleic anhydride, etc.); sulfonic acid monomers (e.g., α-halogenated vinyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, etc.); phosphonic acid monomers (e.g., vinyl phosphoric acid, etc.); and salts of these monomers, together with other copolymerizable monomers, and optionally partially neutralizing the resulting polymer by alkali treatment. Examples of 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.

[0049] Alternatively, instead of using the above-mentioned anionic monomers, an anionic polymer can be obtained by using esters of the above-mentioned anionic monomers or monomers having a functional group into which an anionic functional group can be introduced, such as styrene, vinyltoluene, vinylxylene, α-methylstyrene, vinylnaphthalene, and α-halogenated styrenes, and then carrying out treatments such as hydrolysis, sulfonation, chlorosulfonation, and phosphonium formation after polymerization.

[0050] In the present invention, preferred anionic polymers are poly(meth)acrylic acid and its partially neutralized products (for example, a part of which is an Na salt).

[0051] The anionic polymers described above are generally produced by radically polymerizing a monomer having an anionic group by heating using a polymerization initiator. When a monomer capable of introducing an anionic functional group is used as the monomer, the anionic group can be introduced after polymerization by a treatment such as hydrolysis, sulfonation, chlorosulfonation, or phosphonium conversion.

[0052] In the present invention, it is particularly preferable to introduce a crosslinked structure into the hygroscopic matrix formed using the anionic polymer described above, which further enhances the moisture-trapping ability of the hygroscopic layer 5 and further improves dimensional stability. That is, unlike cationic polymers, anionic polymers only trap water through hydrogen bonds. Therefore, by introducing a network structure (crosslinked structure) with spaces suitable for moisture absorption into the matrix, its moisture absorption can be significantly improved. Such a crosslinked structure, for example, contains hydrophobic moieties such as alicyclic structures within the network structure, thereby further enhancing the moisture-absorbing effect of the hydrophilic moieties. Furthermore, by introducing a crosslinked structure into the hygroscopic matrix, when the matrix absorbs water, the molecules of the anionic polymer are bound to each other by the crosslinks, suppressing volume changes due to swelling (moisture absorption), and improving dimensional stability. This effect of improving dimensional stability is similar to that of the cationic polymer described above.

[0053] As in the case of cationic polymers, the crosslinked structure is introduced by incorporating a crosslinking agent into the coating composition for forming the moisture absorbing layer 9. As described in Patent Document 2, this crosslinking agent is a compound having two or more crosslinkable functional groups (e.g., epoxy groups) that can react with the ionic groups of the anionic polymer, and is, for example, a diglycidyl ester represented by formula (1): G-O(C═O)-A-(C═O)O-G (1) In the formula, G is a glycidyl group, and A is a divalent hydrocarbon group having an alicyclic ring, such as a cycloalkylene group. That is, a crosslinked structure can be introduced by incorporating the crosslinking agent into the coating composition for forming the moisture absorbing layer, which contains the anionic polymer, and then forming a film.

[0054] Moisture absorbent: The moisture absorbent dispersed in the moisture absorbent layer 9 having the above-mentioned ionic polymer as a matrix (moisture absorbent matrix) has a lower ultimate humidity than the ionic polymer (cationic or anionic polymer) that forms the matrix, and has extremely high moisture absorption performance. By dispersing a moisture absorbent having a moisture absorption ability higher than that of the matrix in this way, moisture absorbed in the matrix formed by the above-mentioned ionic polymer is immediately captured by the moisture absorbent, and the absorbed moisture is effectively trapped in the matrix, so that not only can the moisture absorption ability be effectively exhibited even in an extremely low-humidity atmosphere, but swelling of the moisture absorbent layer 9 due to moisture absorption is also effectively suppressed.

[0055] As the highly hygroscopic moisture absorbent described above, one that achieves a humidity of 6% or less under environmental conditions of 80% RH and 30°C, as shown in the examples described below, is preferably used, provided that the ultimate humidity is lower than that of an ionic polymer. That is, if the ultimate humidity of this moisture absorbent is higher than that of an ionic polymer, the moisture absorbed in the matrix is ​​not sufficiently confined, and moisture release, etc., is likely to occur, making it difficult to expect a significant improvement in moisture barrier properties. Furthermore, even if the ultimate humidity is lower than that of an ionic polymer, if the ultimate humidity measured under the above conditions is higher than the above range, moisture trapping in a low-humidity atmosphere, for example, may be insufficient, and the moisture barrier properties may not be fully exhibited.

[0056] The moisture absorbents described above generally have a water absorption rate of 50% or more (JIS K-7209-1984) in an atmosphere of 80% RH and 30°C, and are available in both inorganic and organic forms. Examples of inorganic moisture absorbents include zeolite, alumina, activated carbon, clay minerals such as montmorillonite, silica gel, calcium oxide, and magnesium sulfate. Examples of organic moisture absorbents include anionic polymers or crosslinked products of their partially neutralized products. Examples of such anionic polymers include those obtained by polymerizing or copolymerizing with other monomers at least one anionic monomer, such as a carboxylic acid monomer (e.g., (meth)acrylic acid or maleic anhydride), a sulfonic acid monomer (e.g., halogenated vinyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid), a phosphonic acid monomer (e.g., vinyl phosphoric acid), or a salt of one of these monomers. Organic moisture absorbents are particularly effective in applications where transparency is required. For example, fine particles of cross-linked sodium poly(meth)acrylate are a typical organic moisture absorbent.

[0057] In the present invention, a moisture absorbent having a small particle size is preferred (for example, an average primary particle size of 100 nm or less, particularly 80 nm or less) from the viewpoint of increasing the specific surface area and exhibiting high moisture absorption, and an organic polymer moisture absorbent having a small particle size is particularly optimal. That is, organic polymer moisture absorbents not only have extremely good dispersibility in the ionic polymer matrix and can be uniformly dispersed, but also can be produced by employing emulsion polymerization or suspension polymerization as a polymerization method to form fine, uniform spherical particles, and by incorporating a certain amount of these, extremely high transparency can be ensured. Furthermore, organic fine moisture absorbents not only have the aforementioned extremely low ultimate humidity and exhibit high moisture absorption, but also can minimize volume change due to swelling through crosslinking, and are therefore optimal for reducing the humidity of the ambient atmosphere to an absolute dry state or near an absolute dry state while suppressing volume change. As such organic moisture absorbent particles, for example, cross-linked polyacrylic acid Na particles (average particle diameter: about 70 nm) are commercially available in the form of a colloidal dispersion (pH=10.4) from Toyobo Co., Ltd. under the trade name Tuftic HU-820E.

[0058] In the present invention, the amount of the moisture absorbent as described above is determined according to the type of ionic polymer from the viewpoint of fully exhibiting its properties, significantly improving moisture barrier properties, effectively suppressing dimensional changes due to swelling, and maintaining moisture barrier properties higher than those exhibited by the metal foil (A) 3 or the inorganic barrier layer 11b for a long period of time. For example, in the moisture absorption layer 9 having the above-mentioned ionic polymer as a matrix in which the moisture absorbent is dispersed, if the matrix is ​​formed of a cationic polymer, the moisture absorbent is present in an amount of 50 parts by weight or more, particularly 100 to 900 parts by weight, and more preferably 200 to 600 parts by weight, per 100 parts by weight of the ionic polymer in the moisture absorption layer 9. If the matrix is ​​formed of an anionic polymer, the moisture absorbent is present in an amount of 50 parts by weight or more, particularly 100 to 1,300 parts by weight, and more preferably 150 to 1,200 parts by weight, per 100 parts by weight of the anionic polymer in the moisture absorption layer 9.

[0059] The thickness of the moisture absorbing layer 9 varies depending on the application of the substrate 1 for mounting an electronic device and the required level of barrier property. －２ g / m ２ ・Day or less, especially 10 －３ g / m ２ To ensure a water vapor transmission rate of 1000 m / s or less, the thickness should be set to 1 to 20 μm, particularly 1 to 15 μm. If the thickness is too thin, the moisture absorption capacity will reach its upper limit in a short period of time, impairing the moisture barrier properties. Furthermore, if the thickness is too thick, the amount of moisture that can be absorbed will increase, but as this increase occurs, the volume change due to swelling will also increase, making delamination more likely to occur.

[0060] <Barrier Sheet 11> The barrier sheet 11 is provided on the surface of the moisture absorption layer 9 opposite to the surface on which the metal foil (A) 3 is provided. When the barrier sheet 11 is provided on the outer surface of the moisture absorption layer 9, it serves to block most of the moisture (water vapor) that attempts to penetrate into the device. On the other hand, when the barrier sheet 11 is provided on the electronic device side of the moisture absorption layer 9, it serves to block moisture that has not been absorbed by the moisture absorption layer 9. In either case, the result is that the inside of the device can be kept dry for a long period of time. The barrier sheet 11 has two forms: one having an inorganic barrier layer 11b on at least one surface of the resin layer 11a, and the other having a metal foil (B) 11c. The moisture barrier property is exhibited by the inorganic barrier layer 11b or the metal foil (B) 11c.

[0061] <Resin layer 11a> First, an embodiment in which the barrier sheet 11 has an inorganic barrier layer 11b on at least one surface of the resin layer 11a will be described. The resin layer 11a serves as a base for the inorganic barrier layer 11b, and is usually made of a thermoplastic or thermosetting resin and molded by injection or coinjection molding, extrusion or coextrusion molding, film or sheet molding, compression molding, cast polymerization, or the like, depending on the form. Generally, from the standpoints of moldability and cost, a thermoplastic resin is preferred.

[0062] Examples of such thermoplastic resins include the following: Olefin-based resins: 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, as well as cyclic olefin copolymers and cyclic olefin polymers; Ethylene-vinyl compound copolymers: ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer, etc.; Styrenic resins: polystyrene, acrylonitrile-styrene copolymer, ABS, α-methylstyrene-styrene copolymer, etc.; Polyvinyl compounds: polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polymethyl acrylate, polymethyl methacrylate, etc.; Polyamides: nylon 6, nylon 6-6, nylon 6-10, nylon 11, nylon 12, etc.; Thermoplastic polyesters: polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), etc.; Others: 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; and further, blends of the above resins and resins appropriately modified by copolymerization (for example, acid-modified olefin resins).

[0063] The resin layer 11a may be formed from a gas barrier resin with excellent oxygen barrier properties, such as an ethylene-vinyl alcohol copolymer, and may have a multilayer structure including a layer formed from such a gas barrier resin. That is, the inorganic barrier layer 11b can be formed on the resin layer 11a containing such a gas barrier resin as a base.

[0064] In the present invention, it is more preferable to use a film of a polyester resin such as polyethylene terephthalate (PET), polybutylene terephthalate, or polyethylene naphthalate, or a polyimide resin, or a cyclic olefin resin such as a cyclic olefin copolymer or a cyclic olefin polymer, as the resin layer 11a, from the viewpoints of availability, cost, formability, or the fact that the resin exhibits some degree of barrier property against oxygen and moisture, and furthermore, is suitable as a base for the inorganic barrier layer 11b described below.

[0065] Although the thickness of the resin layer 11a is not particularly limited, if the thickness is too large, flexibility may be impaired and handling may become difficult. Therefore, the thickness of the resin layer 11a is usually set to 200 μm or less, more preferably 125 μm or less, and within this range, an appropriate moisture permeability can be ensured. Furthermore, it is preferable to set the thickness to a value that allows for effective deposition of the inorganic barrier layer 11b, for example, 20 μm or more.

[0066] <Inorganic Barrier Layer 11b> The inorganic barrier layer 11b is an inorganic vapor-deposited film, for example, a film formed from various metals or metal oxides, by physical vapor deposition, such as sputtering, vacuum deposition, or ion plating, or chemical vapor deposition, such as plasma CVD. In particular, a vapor-deposited film (a vapor-deposited film of a metal or metal oxide) formed by plasma CVD is preferred, since it can be uniformly formed even on an uneven surface and exhibits excellent barrier properties not only against moisture but also against oxygen, etc. Such an inorganic barrier layer 11b is formed on the resin layer 11a.

[0067] The deposition film by plasma CVD is obtained by placing the resin layer 11a that will support the inorganic barrier layer 11b in a plasma processing chamber maintained at a predetermined vacuum level, supplying a gas (reactive gas) of the metal or a compound containing the metal to be used for film formation and an oxidizing gas (usually oxygen or NOx gas) together with an appropriate carrier gas such as argon or helium through a gas supply pipe into the plasma processing chamber shielded by a metal wall and decomposed to a predetermined vacuum level, and generating a glow discharge in this state using a microwave electric field or a high-frequency electric field, generating plasma using the resulting electrical energy, and depositing the decomposition reaction product of the compound on the surface of the plastic substrate to form a film. When forming a film using a microwave electric field, the film is formed by irradiating microwaves into the plasma processing chamber using a waveguide or the like, and when forming a film using a high-frequency electric field, the resin layer 11a in the plasma processing chamber is positioned between a pair of electrodes, and a high-frequency electric field is applied to the electrodes to form the film.

[0068] As the above-mentioned reaction gas, it is generally preferable to use a gas such as an organometallic compound, for example, an organoaluminum compound such as trialkylaluminum, an organotitanium compound, an organozirconium compound, or an organosilicon compound, from the viewpoint of being able to form a film having a flexible region containing a carbon component in the resin layer 11a and a region thereon with a high degree of oxidation and excellent barrier properties. In particular, an organosilicon compound is most preferable from the viewpoint of being able to form an inorganic barrier layer 11b with a high barrier property against oxygen relatively easily and efficiently.

[0069] Examples of such organosilicon compounds include organosilane compounds such as hexamethyldisilane, vinyltrimethylsilane, methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, methyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane, and organosiloxane compounds such as octamethylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, and hexamethyldisiloxane. In addition to these, aminosilanes and silazanes can also be used. The above-mentioned organometallic compounds can be used alone or in combination of two or more.

[0070] When forming a film by plasma CVD using the above-mentioned organometallic compound reactive gas and oxidizing gas, it is preferable to lower the glow discharge output (e.g., microwave or high-frequency output), start film formation at low output, and then perform film formation by plasma reaction at high output.

[0071] That is, the organic group (CH ３ and CH ２ etc.) are usually CO ２ At low output, some of it is converted into CO ２ On the other hand, the higher the output, the more the organic group is decomposed into CO ２ Therefore, by increasing the output, it is possible to reduce the C content in the film and form a film in which the metal contained in the organometallic compound has a high degree of oxidation. However, a film with a high degree of metal oxidation has extremely high barrier properties against gases such as oxygen, but poor flexibility and insufficient adhesion to the resin layer, whereas a film with a low degree of metal oxidation and a high organic component content does not have sufficient barrier properties against gases, but is highly flexible and exhibits high adhesion to the resin layer 11a.

[0072] As can be understood from the above explanation, in the present invention, an organometallic compound is used as a reactive gas, and film formation is performed at a low output in the early stages of film formation by plasma CVD, and then the output is increased to perform film formation. As a result, a highly adhesive region containing a large amount of organic components (carbon) is formed in the portion in contact with the surface of the resin layer 11a, and a region with a high degree of metal oxidation and high gas barrier properties is formed on top of this.

[0073] Therefore, in order to ensure excellent gas barrier properties, the inorganic barrier layer 11b in the present invention preferably includes a high-oxidation region in which the oxidation degree x of the metal (M) is 1.5 to 2.0 (where x = atomic ratio of O / M). Furthermore, below this high-oxidation region (the side in contact with the surface of the resin layer 11a), an organic region is preferably formed in which the carbon (C) concentration is 20 elemental % or more based on the three elements of the metal (M), oxygen (O), and carbon (C). Furthermore, silicon (Si) is most preferred as the metal (M).

[0074] It is preferable that the highly oxidized region in the inorganic barrier layer 11b occupies 60% or more of the total thickness of the inorganic barrier layer 11b, and it is preferable that the organic region is formed on the side in contact with the surface of the resin layer 11a with a thickness of approximately 5 to 40% of the total thickness of the inorganic barrier layer 11b.

[0075] The glow discharge output when forming the inorganic barrier layer 11b having the organic region and the highly oxidized region by plasma CVD varies slightly between microwave and high-frequency waves. For example, in the case of microwaves, the organic region is formed at a low output of about 30 to 100 W, while the highly oxidized region is formed at a high output of 90 W or more. In the case of high-frequency waves, the organic region is formed at a low output of about 20 to 80 W, while the highly oxidized region is formed at a high output of 100 W or more. The film formation time may be set so that the thickness of each region falls within the aforementioned range.

[0076] The total thickness of the inorganic barrier layer 11b varies depending on the application of the electronic device mounting substrate 1 and the required level of barrier properties, but is generally about 10 －２ g / m ２・Day or less, especially 10 －３ g / m ２ It is preferable that the thickness is such that a water vapor transmission rate of 0.5 to 1.5 days or less can be ensured. Although this varies depending on the proportion of the highly oxidized region described above, a thickness of 4 to 500 nm, particularly 30 to 400 nm, is generally sufficient.

[0077] <Metal foil (B) 11c> Next, an embodiment in which the barrier sheet 11 has a metal foil (B) 11c will be described. The same metal foil (B) 11c as the metal foil (A) 3 can be used as the metal foil (B) 11c. That is, from the viewpoints of flexibility, ease of thin film formation, and cost reduction, the material of the metal foil (B) 11c is preferably aluminum. The thickness of the metal foil (B) 11c is 5 to 20 μm, more preferably 6 to 20 μm, and particularly preferably 6 to 15 μm. A metal foil (B) 11c with a thickness of less than 5 μm is difficult to manufacture. On the other hand, a metal foil (B) 11c with a thickness of more than 20 μm has insufficient flexibility and is difficult to handle.

[0078] In addition, when the metal foil (B) 11c is used, the substrate 1 has two metal foils, the metal foil (A) 3 and the metal foil (B) 11c. When the substrate 1 having such a configuration is attached to an electronic device, there is a possibility that malfunctions may occur due to electrical current passing through the substrate 1. Therefore, it is necessary to apply the substrate 1 taking into consideration the type of electronic device, the environment in which the electronic device is used, and the like.

[0079] <Protective Resin Layer 11d> Alternatively, a structure having only the metal foil (B) 11c may be used, or a protective resin layer 11d may be formed on the metal foil (B) 11c via an adhesive layer 11e (described later). The protective resin layer 11d may be the same as the protective resin layer 5. The protective resin layer 11d is a resin layer provided to prevent scratches and oxidative degradation of the metal foil (B) 11c. Therefore, it is preferable to provide the protective resin layer 11d, especially when the metal foil (B) 11c is provided on the outer surface of the moisture-absorbing layer 9. The protective resin layer 11d may be formed using various known resins, but is generally formed from polyester resins such as polyethylene terephthalate, olefin-based resins such as polyethylene and polypropylene, and particularly polyester resins. Such a protective resin layer 11d typically has a thickness of approximately 1 to 200 μm.

[0080] <Adhesive layer 11e> The adhesive layer 11e is a layer that bonds the metal foil (B) 11c and the protective resin layer 11d. The adhesive layer 11e may be the same as the adhesive layer 7.

[0081] <Semi-hygroscopic layer 13> In the present invention, the semi-hygroscopic layer 13 is a layer that exhibits a certain degree of hygroscopicity, although not as much as the hygroscopic layer 9. The semi-hygroscopic layer 13 can be provided in at least one location between the metal foil (A) and the hygroscopic layer or between the hygroscopic layer and the barrier sheet.

[0082] In the present invention, the quasi-moisture absorbing layer 13 is formed only from resin without blending any moisture absorbent. Such a quasi-moisture absorbing layer 13 can be formed at a lower cost than the moisture absorbing layer 9 because it does not contain any moisture absorbent.

[0083] Examples of resins used to form the quasi-moisture absorbent layer 13 include ionic polymers with a lower concentration of cationic or anionic groups than the ionic polymers used to form the moisture absorbent layer 9. In particular, ionic polymers, polyamide resins, polyvinyl alcohol resins, ethylene-vinyl alcohol copolymer resins, etc. are preferred, with polyamide resins being the most preferred. Typical examples of such polyamides include nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12.

[0084] The thickness of the semi-hygroscopic layer 13 is preferably less than 150 μm, particularly in the range of 2 to 100 μm. If this thickness is greater than necessary, the volume change due to swelling together with the hygroscopic layer 9 becomes large, making delamination more likely to occur. On the other hand, if this thickness is too thin, it becomes difficult to extend the life of the hygroscopic layer 9 due to supplementary moisture absorption.

[0085] 1 to 3 , an ultraviolet blocking layer 15 can be provided on one surface of either the metal foil (A) or the barrier sheet of the substrate for mounting an electronic device, that is, on the side on which the moisture absorption layer 9 is not laminated. This ultraviolet blocking layer 15 has the role of reflecting or absorbing ultraviolet rays, thereby preventing ultraviolet rays from penetrating into the substrate and the device.

[0086] The range of ultraviolet wavelengths reflected or absorbed by the ultraviolet blocking layer 15 is 200 nm to 400 nm, preferably 250 nm to 400 nm, and particularly preferably 280 nm to 400 nm. The ultraviolet transmittance of the ultraviolet blocking layer 15 is 0.1% to 20%, preferably 0.1% to 15%, and more preferably 0.1% to 10%. If the ultraviolet transmittance is less than 0.1%, the quality will be excessive and costs will increase. On the other hand, if the ultraviolet transmittance exceeds 20%, deterioration of the substrate or electronic device will progress.

[0087] The UV-blocking layer 15 can be formed from a general thermoplastic resin. However, from the viewpoints of weather resistance and cost, it is preferable to form it from a resin such as a polycarbonate resin, a silicone resin, a polyester resin, a fluorine-based resin, or an acrylic resin. The resin forming the UV-blocking layer 15 can be dispersed with an inorganic pigment such as carbon black, which absorbs UV rays, or titanium oxide, which scatters UV rays, as a UV-blocking agent. To absorb UV rays, an organic UV-absorber such as a benzotriazole-based, benzophenone-based, or triazine-based additive can be dispersed in the resin. When the UV-blocking layer 15 is formed from a resin, it is preferable that the UV-blocking layer 15 and the protective resin layer 5 or 11d are bonded together with an adhesive layer 17, which will be described later. The UV-blocking layer 15 can also be formed by directly applying a coating containing the UV-blocking agent or an organic UV-absorber to the surface of the protective resin layer 5 or 11d. In this case, all or part of the UV rays can be blocked or absorbed, thereby blocking UV rays from penetrating the device. As such a paint, fluorine-based, silicone-based, urethane-based, acrylic-based paint, etc. are preferably used.

[0088] <Adhesive Layer 17> The adhesive layer 17 is a layer that bonds the ultraviolet blocking layer 15 to the protective resin layer 5 or the protective resin layer 11d, and the same adhesive as the adhesive layer 7 can be used.

[0089] <Application of Substrate> The substrate for mounting an electronic device of the present invention can be produced by the method described in the Examples below. Such a substrate 1 has an overall thickness of 25 to 250 μm, preferably 25 to 230 μm, and more preferably 25 to 200 μm. If the overall thickness of the substrate 1 is less than 25 μm, the strength of the entire substrate is insufficient, and there is a risk of tearing, holes, etc. On the other hand, if the overall thickness of the substrate 1 exceeds 250 μm, sufficient flexibility is not obtained, making handling difficult.

[0090] The electronic device is not particularly limited, and the substrate of the present invention can be applied to all electronic devices that are susceptible to charge leakage due to the presence of moisture, such as organic EL elements, solar cell panels, touch panels, etc. The method for installing the substrate 1 is not particularly limited, and the substrate is installed by a method appropriate for the application. For example, when the substrate of the present invention is used as a back sheet for a solar cell, it is fixed integrally with the cell or the like by a frame.

[0091] Furthermore, when used in organic EL devices, etc., the metal foil (A) 3 or barrier sheet 11 can be coated with a known pressure-sensitive adhesive such as an acrylic, silicone, or butadiene-based adhesive, or can be attached to the device surface with a thermocompression-bonded sealing sheet such as an ethylene-vinyl acetate copolymer resin, polyvinyl butyral, or olefin-based adhesive, or a UV-curable adhesive such as an epoxy or acrylic adhesive. In this form, when the moisture absorption ability of the moisture absorption layer 9 is lost, the substrate can be peeled off and replaced. Furthermore, since the substrate 1 of the present invention has the metal foil (A) 3 or the metal foil (B) 11c, it can be used on the side of the above-mentioned device where light transparency is not required, such as the non-light-receiving surface of a solar cell backsheet, the non-light-emitting surface of an organic electroluminescent element, or the side surface of various devices.

[0092] <Preparation of Inorganic Barrier Layer-Coated Polyethylene Terephthalate (PET) Film> A silicon oxide inorganic barrier layer 11b was formed on one side of a 25 μm-thick biaxially stretched PET film serving as the resin layer 11a using a plasma CVD apparatus. The film formation conditions are as follows: A CVD apparatus was used, equipped with a high-frequency output power source with a frequency of 27.12 MHz and a maximum output of 2 kW, a matching box, a metal cylindrical plasma treatment chamber with a diameter of 300 mm and a height of 450 mm, and an oil rotary vacuum pump for evacuating the treatment chamber. The PET film was placed on parallel flat plates in the treatment chamber, and 3 sccm of hexamethyldisiloxane and 45 sccm of oxygen were introduced. A high-frequency oscillator was operated at a 50 W output to generate a film for 2 seconds, forming an adhesive layer. Next, a high-frequency oscillator was operated at a 200 W output to generate a film for 100 seconds, forming silicon oxide, and an inorganic barrier layer-coated PET film was obtained as the barrier sheet 11. The obtained inorganic barrier layer-coated PET film had a water vapor permeability of 1×10 measured under an atmosphere of 40° C. and 90% RH. －２ g / m ２ ・day.

[0093] <Preparation of Coating Solution A for Fabricating Moisture Absorbing Layer 9> Polyallylamine (manufactured by Nittobo Medical Co., Ltd., PAA-15C, aqueous solution, solids content 15 wt%) was used as an ionic polymer, and diluted with water to a solids content of 5 wt% to obtain a polymer solution. Meanwhile, γ-glycidoxypropyltrimethoxysilane was used as a crosslinking agent, and dissolved in water to a solids content of 5 wt% to prepare a crosslinking agent solution. Next, the polymer solution and the crosslinking agent solution were mixed so that γ-glycidoxypropyltrimethoxysilane was 15 parts by weight per 100 parts by weight of polyallylamine. Furthermore, a crosslinked product of polyacrylic acid Na (manufactured by Toyobo Co., Ltd., Tuftic HU-820E, aqueous dispersion, solids content 13%) was added as a moisture absorbent to this mixed solution in an amount of 400 parts by weight relative to the polyallylamine. The solids content was further adjusted with water to 5% and then thoroughly stirred to prepare Coating Solution A for fabricating moisture absorbing layer 9.

[0094] <Preparation of Substrate> The coating liquid A for preparing the moisture absorption layer 9 obtained above was applied to the side of the inorganic barrier layer-coated PET film on which the inorganic barrier layer 11b had been formed using a bar coater. The coated film was heat-treated in a box-type electric oven under conditions of a peak temperature of 120°C and a peak temperature retention time of 6 seconds to form a 3 μm-thick ionic polymer as the moisture absorption layer 9, thereby obtaining a coating film A. Next, in a glove box adjusted to a nitrogen concentration of 99.95% or higher, a 15 μm-thick aluminum foil serving as a metal foil (A) was dry-laminated via a 2.0 μm-thick urethane adhesive to the side of the coating film A on which the moisture absorption layer 9 had been formed. Furthermore, a 25 μm-thick PET film serving as a protective resin layer 5 was dry-laminated via a 2.0 μm-thick urethane adhesive to the side of the aluminum foil opposite to the moisture absorption layer 9, thereby obtaining a substrate A. In addition, the thicknesses of the metal foil (A), protective resin layer 5, resin layer 11a, and protective resin layer 11d were appropriately changed, and a quasi-moisture absorbing layer 13 and an ultraviolet blocking layer 15 were further provided as necessary, thereby producing substrates A to L shown in Table 1.

[0095]

[0096] Experimental Example 1 Calcium Corrosion Method (without bending test) The effect of moisture permeation on the substrate A prepared above was measured using the calcium corrosion method (JIS K7129-7). Under an inert gas atmosphere, a calcium film was formed on the surface of a glass substrate to a thickness of 100 nm, and then a pressure-sensitive adhesive was attached. The inorganic barrier layer-coated PET film of substrate A was then attached to the adhesive so that the PET film surface was in contact with the adhesive, to prepare an evaluation cell. The evaluation cell was stored in a constant temperature and humidity chamber at 40°C and 90% RH for 1000 hours, and the state of the calcium thin film was observed from the glass substrate side using a microscope. The evaluation criteria were as follows. The results are shown in Table 2. Evaluation Criteria ◯: No corrosion of the calcium film was observed. ×: Corrosion of the calcium film was confirmed.

[0097] <Calcium corrosion method (with bending test)> A bending test was performed on substrate A using a tabletop durability tester (manufactured by Yuasa System Co., Ltd.) in an environment of 23°C and 50% RH, with a diameter of 5 mm, in both bending directions, 10,000 times each. Substrate A after the bending test was used to prepare an evaluation cell in the same manner as above. The evaluation cell was stored in a constant temperature and humidity chamber in an environment of 40°C and 90% RH for 1,000 hours, and the state of the calcium thin film was observed from the glass substrate side using a microscope. The evaluation criteria were the same as above. The results are shown in Table 2.

[0098] Experimental Example 2 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate B.

[0099] Experimental Example 3 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate C.

[0100] Experimental Example 4 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the surface of the substrate A to be bonded to the adhesive was changed to the surface of a 25 μm thick PET film serving as the protective resin layer 5 .

[0101] Experimental Example 5 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate D.

[0102] Experimental Example 6 In a glove box adjusted to a nitrogen concentration of 99.95% or higher, a 25 μm nylon film was dry-laminated via a 2.0 μm urethane adhesive to the surface of the coating film A on which the moisture-absorbing layer 9 was formed, serving as the semi-moisture-absorbing layer 13. Furthermore, a 15 μm aluminum foil was dry-laminated via a 2.0 μm urethane adhesive to the surface of the nylon film opposite the moisture-absorbing layer 9, serving as the metal foil (A). Furthermore, a 25 μm PET film was dry-laminated via a 2.0 μm urethane adhesive to the surface of the aluminum foil opposite the semi-moisture-absorbing layer 13, serving as the protective resin layer 5, to obtain a substrate E. Measurements were performed using the calcium corrosion method in the same manner as in Experimental Example 1.

[0103] Experimental Example 7 An acrylic resin UV cut film (55 μm thick) was dry laminated as an ultraviolet blocking layer 15 onto the surface of the protective resin layer 5 of the substrate A via a 2.0 μm thick urethane adhesive to prepare a substrate F. Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1.

[0104] Experimental Example 8 A fluorine-based UV-cut coating layer (10 μm) was formed as the ultraviolet blocking layer 15 on the surface of the protective resin layer 5 of the substrate A to prepare a substrate G. Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1.

[0105] Experimental Example 9 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate H.

[0106] Experimental Example 10 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate I.

[0107] Experimental Example 11 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate J.

[0108] Experimental Example 12 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate K.

[0109] Experimental Example 13 Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that the substrate A was changed to the substrate L.

[0110]

[0111] In the calcium corrosion method (with bending test), no calcium corrosion was observed for any of the substrates A to I, and the substrate appearance after the bending test was also good. In other words, it can be said that all of the substrates A to I are substrates that combine moisture barrier properties and flexibility. On the other hand, for substrate J, no calcium film corrosion was observed, but creases appeared on the surface. It is believed that the creases occurred during the bending test for substrate J because the total thickness of the substrate was large and the flexibility was insufficient. Furthermore, corrosion of the calcium film was observed for substrates K and L. For substrates K and L, the metal foil (A) was thick and insufficient in flexibility, and therefore many pinholes occurred in the metal foil during the bending test, allowing a large amount of moisture to penetrate, causing the hygroscopic resin layer to swell in a short period of time, and the moisture that was not completely absorbed reached the calcium film.

[0112] 1: Substrate for mounting electronic device 3: Metal foil (A) 5: Protective resin layer 7: Adhesive layer 9: Moisture absorption layer 11: Barrier sheet 11a: Resin layer 11b: Inorganic barrier layer 11c: Metal foil (B) 11d: Protective resin layer 11e: Adhesive layer 13: Semi-moisture absorption layer 15: Ultraviolet blocking layer 17: Adhesive layer

Claims

1. A substrate for mounting an electronic device, comprising a metal foil (A), a moisture absorbing layer and a barrier sheet laminated in this order, the metal foil (A) having a thickness of 5 to 20 μm.

2. The electronic device mounting substrate according to claim 1, wherein the metal foil (A) is made of aluminum.

3. The substrate for mounting an electronic device according to claim 1, wherein the moisture absorbing layer comprises a resin composition in which a moisture absorbent (ii) is dispersed in an ionic polymer (i).

4. The electronic device mounting substrate according to claim 1, wherein the barrier sheet includes a resin layer and has an inorganic barrier layer on at least one surface of the resin layer.

5. The electronic device mounting substrate according to claim 4, wherein the resin layer is formed from at least one of an olefin resin, a polyester resin, a polyimide resin, a polyamide resin, and a cyclic olefin resin.

6. The electronic device mounting substrate according to claim 4, wherein the inorganic barrier layer is a vapor-deposited film of a metal or a metal oxide.

7. The electronic device mounting substrate according to claim 1, wherein the barrier sheet has a metal foil (B) made of aluminum, and the thickness of the metal foil (B) is 5 to 20 μm.

8. The substrate for mounting an electronic device according to claim 1, further comprising a semi-hygroscopic layer provided at least at one location between the metal foil (A) and the hygroscopic layer or between the hygroscopic layer and the barrier sheet.

9. The electronic device mounting substrate according to claim 8, wherein the semi-hygroscopic layer is formed from at least one of an ionic polymer, a polyamide resin, a polyvinyl alcohol-based resin, and an ethylene-vinyl alcohol copolymer resin.

10. The substrate for mounting an electronic device according to claim 1, wherein an ultraviolet blocking layer is provided on one surface of either the metal foil (A) or the barrier sheet, the surface on which the moisture absorbing layer is not laminated.

11. The electronic device mounting substrate according to claim 1, which has an overall thickness of 25 to 250 μm.

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