Substrate for mounting electronic devices

Abstract

To provide a base material for mounting an electronic device that prevents water penetration to maintain the electronic device in a dry state, while exhibiting superior flexibility.SOLUTION: 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 a thickness of the metal foil (A) is 5-20 μm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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 an electronic device dry. [Background technology]

[0002] 2. Description of the Related Art Conventionally, moisture-absorbing sheets having a moisture-absorbing resin layer in which a desiccant is dispersed have been widely used for absorbing and preventing moisture. As such moisture-absorbent sheets, sheets having various layer structures have been proposed. Patent Document 1 proposes a moisture-absorbent sheet consisting of a desiccant layer, a moisture-permeable sheet provided on one side of the desiccant, and an adhesive layer provided on the other surface of the desiccant layer, and describes that a cellophane sheet, acetate sheet, nylon sheet, etc. can be used as the moisture-permeable sheet.

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

[0004] However, the known moisture-absorbing sheets disclosed in Patent Document 1 and the like do not exhibit satisfactory performance as a sealant for keeping the inside of such electronic devices dry. That is, by absorbing a large amount of moisture that penetrates from the outside of the device, the desiccant present in the moisture-absorbing sheet reaches a saturated state in a short period of time. Further improvement is required because the moisture absorbency is lost or the absorbed moisture is released into the inside of 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 are therefore required to have flexibility that does not impair their 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 an organic layer with excellent moisture diffusion properties is formed with a thickness of 10 μm or more between the inorganic barrier layer arranged on the high humidity atmosphere side and the moisture absorption layer, thereby effectively suppressing the deactivation of the moisture absorption layer and exhibiting excellent moisture barrier properties for a long period of time. That is, defects such as cracks are locally formed in the inorganic barrier layer, and moisture flows into the moisture absorption layer through these defects, causing the moisture absorption layer to wear out quickly, but in 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 absorption layer in a locally concentrated manner, thereby mitigating the wear of the moisture absorption layer and exhibiting excellent moisture barrier properties for a long period of time.

[0008] However, there is a limit to how long the moisture barrier properties can be extended according to Patent Document 2, and it is desirable to maintain the moisture barrier properties for a long period of time. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2006-326838 A [Patent Document 2] Patent No. 6657651 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a substrate for mounting an electronic device, which is capable of preventing the permeation of moisture to keep the electronic device dry, and which has excellent flexibility. [Means for solving the problem]

[0011] According to the present invention, A metal foil (A), a moisture absorbing layer, and a barrier sheet are laminated in this order, There is provided a substrate for mounting an electronic device, characterized in that the metal foil (A) has a thickness of 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 absorbing layer contains a resin composition in which a moisture absorbent (ii) is dispersed in an ionic polymer (i); (3) The barrier sheet includes a resin layer and has an inorganic barrier layer on at least one surface of the resin layer; (4) 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; (5) The inorganic barrier layer is formed 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 semi-hygroscopic layer is provided at least in one location between the metal foil (A) and the hygroscopic layer, or between the hygroscopic layer and the barrier sheet; (8) 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; (9) An ultraviolet blocking layer is provided on one surface of either the metal foil (A) or the barrier sheet, on the side on which the moisture absorbing layer is not laminated; (10) The total thickness is 25 to 250 μm. is preferred. Effect of the Invention

[0013] In the substrate for mounting an electronic device of the present invention, the metal foil (A) blocks the penetration of most of the moisture, and even a small amount of moisture that penetrates through pinholes in the metal foil (A) is absorbed by the moisture absorbing layer. Furthermore, a barrier sheet is further provided on the device side of the moisture absorbing layer, which blocks the penetration of moisture that cannot be absorbed by the moisture absorbing layer. As a result, it is possible to prevent moisture from entering the device and keep the device dry for a long period of time. In another embodiment of the substrate for mounting an electronic device of the present invention, the barrier sheet blocks most of the moisture from passing through, and the trace amount of moisture that passes through the barrier sheet is absorbed by the moisture absorption layer. Furthermore, a metal foil (A) is further provided on the device-side surface of the moisture absorption layer, which blocks the passage of moisture that cannot be absorbed by the moisture absorption layer. As a result, it is possible to prevent moisture from entering the device and keep the device dry for a long period of time. Furthermore, the substrate for mounting an electronic device of the present invention has flexibility and excellent bending resistance, i.e., the substrate for mounting an electronic device of the present invention is easy to handle, and the moisture barrier property of the substrate is 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 parts of the device that do not require optical transparency (for example, the 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). [Brief description of the drawings]

[0015] [Figure 1]1 is a schematic cross-sectional view showing an example of a layer structure of a substrate for mounting an electronic device according to the present invention. [Diagram 2] FIG. 4 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. [Diagram 3] FIG. 4 is a schematic cross-sectional view showing another example of a layer structure of the substrate for mounting an electronic device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 1 to 3, the substrate for mounting an electronic device of the present invention generally designated by 1 has 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 plays a role in blocking 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 plays a role in blocking 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] The metal foil (A) 3 is preferably made of aluminum from the viewpoints of flexibility, ease of forming a thin film, and cost reduction. 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 having a thickness of less than 5 μm is difficult to manufacture. On the other hand, a metal foil (A) 3 having a thickness of more than 20 μm has insufficient flexibility and is difficult to handle.

[0020] Here, flexibility, also referred to as bending 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. In addition, 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, so 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 cannot 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 penetrated through the pinholes in the metal foil (A) 3, preventing moisture from penetrating into the electronic device and keeping the electronic device dry. In other words, most of the moisture that tries to enter the device from the outside is blocked by the metal foil 3, but the small amount of moisture that has penetrated 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 complements the decrease in moisture barrier property 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 transmission due to an increase in pinholes caused by the thin thickness of the metal foil (A) 3.

[0022] <Protective resin layer 5> Also, the structure may have only the metal foil (A) 3, but a protective resin layer 5 may be formed on the metal foil (A) 3 via an adhesive layer 7 described below. The protective resin layer 5 is a resin layer provided to prevent damage and oxidative deterioration of the metal foil (A) 3. Therefore, it is preferable to have 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 resins known per se, but is generally formed from a polyester resin such as polyethylene terephthalate or a polyolefin resin such as polyethylene or polypropylene, preferably a polyester resin. Such a protective resin layer 5 usually has 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, which are known as dry lamination adhesives.

[0025] Epoxy adhesives; The epoxy adhesive described above is one in which a liquid epoxy resin is cured with an epoxy curing agent to provide adhesion. Such epoxy resins are liquid resins having epoxy groups in the molecule, and representative ones 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 any type of epoxy resin 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, and glycidyl amine epoxy resins. In the present invention, a glycidylamine type epoxy resin is particularly suitable since it can form an adhesive layer 7 having a high elastic modulus.

[0027] Furthermore, as the epoxy curing agent, known agents such as amines, acid anhydrides, polyamides, etc. 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 curing agents, and in particular aromatic polyamines such as metaphenylenediamine, are preferably used.

[0028] The ratio of the amounts of the epoxy resin and the curing agent may be set according to the epoxy equivalent of the epoxy resin so that a sufficient cured film is formed.

[0029] Urethane adhesives; The urethane adhesive is a reaction product of polyisocyanate and polyol. This adhesive usually contains a known curing catalyst such as an amine catalyst, a metal catalyst, or a phosphoric acid-modified compound. The amount of the curing catalyst is set according to 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 in forming the polyurethane adhesive is a compound having two or more OH groups in one molecule, and the following compounds are representative examples. Di-, tri-, tetra-, penta-, hexa-hydroxy compounds; Polyester polyols containing two or more OH groups in one molecule; Polyether polyols containing two or more OH groups in one molecule; Polycarbonate polyols containing two or more OH groups in one molecule; Polycaprolactone polyols containing two or more OH groups in one molecule; Polyacrylic polyols containing two or more OH groups in one molecule; The most preferred polyol in the present invention is a polyester polyol.

[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(isocyanate ethyl)benzene, bis(isocyanate methyl)naphthalene, and bis(isocyanate methyl)diphenyl ether; Sulfur-containing aliphatic isocyanates such as thiodiethyl diisocyanate; Aliphatic sulfide-based isocyanates such as bis[2-(isocyanatomethylthio)ethyl]sulfide; Aromatic sulfide-based 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 diphenylsulfone-4,4'-diisocyanate; Sulfonic acid ester isocyanates such as 4-methyl-3-isocyanate benzenesulfonyl-4'-isocyanate phenol ester; Aromatic sulfonic acid amide 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 above 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 above polyol.

[0033] The above-mentioned epoxy adhesive and urethane adhesive are applied to a predetermined portion 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 usually cured by maintaining it 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 a small amount of moisture that has permeated the metal foil (A) 3 or the barrier sheet 11 provided on the outer surface side thereof, 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 enter the device is blocked by the metal foil (A) 3 or the barrier sheet 11, so that the moisture absorption layer 9 is less likely to swell, and the moisture absorption ability of the moisture absorption layer 9 is maintained for a long period of time.

[0036] Such a moisture absorbing layer 9 has a moisture absorbent dispersed in a resin matrix. In particular, when a high barrier property against moisture is required, a layer having a moisture absorbent dispersed in an ionic polymer, as described in the above-mentioned Patent Document 2, is preferable, from the viewpoints of excellent moisture capture property and effectively preventing deformation such as swelling due to moisture absorption.

[0037] The ionic polymer forms the matrix of the moisture-absorbing layer 9 and contains a cationic group (NH 2There are cationic polymers that have ionic groups (such as COONa groups, COOH groups) as their ionic groups, and anionic polymers that have anionic groups (such as COONa groups, COOH groups) as their ionic groups. Generally, polymers that have 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, a small amount of moisture that has flowed in 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 hygroscopicity, and captures and absorbs moisture.

[0039] However, if the moisture is merely absorbed in the matrix, the absorbed moisture will be easily released due to environmental changes such as a rise in temperature. In addition, the penetration of moisture widens the spacing between the polymer molecules forming the matrix, and as a result, the moisture absorption layer 9 swells and a large increase in volume occurs. However, if an adsorbent with a lower humidity level than the matrix (ionic polymer) is dispersed, the moisture absorbed in the matrix is ​​further captured by the moisture absorbent with a higher hygroscopicity (i.e., a lower humidity level) than the matrix, and not only is swelling due to the absorbed water molecules effectively suppressed, but the water molecules are also trapped in the moisture absorption layer 9, and as a result, the release of moisture from the moisture absorption layer 9 is also effectively prevented.

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

[0041] Ionic polymers (cationic polymers); In the present invention, among the ionic polymers used to form the above-mentioned matrix, 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, a quaternary pyridinium group, etc. Such cationic polymers can form a hygroscopic matrix because the cationic group has a strong nucleophilic action and captures water by hydrogen bonding. The amount of cationic groups in the cationic polymer may generally be such that the water absorption rate (JIS K-7209-1984) of the formed hygroscopic matrix is ​​20% or more, particularly 30% to 45%, at a humidity of 80% RH and an atmosphere at 30°C.

[0042] As the cationic polymer, there is used one obtained by polymerizing or copolymerizing at least one cationic monomer represented by amine monomers such as allylamine, ethyleneimine, vinylbenzyltrimethylamine, [4-(4-vinylphenyl)-methyl]-trimethylamine, vinylbenzyltriethylamine, etc.; nitrogen-containing heterocyclic monomers such as vinylpyridine, vinylimidazole, etc.; and salts thereof, together with other copolymerizable monomers, if necessary, and further partially neutralizing the resulting polymer by acid treatment. 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, and the like.

[0043] Also, instead of using the above cationic monomers, a monomer having a functional group to which a cationic functional group can be introduced, such as styrene, bromobutylstyrene, vinyltoluene, chloromethylstyrene, vinylpyridine, vinylimidazole, α-methylstyrene, vinylnaphthalene, etc., can be used, and after polymerization, a treatment such as amination or alkylation (quaternary ammonium chloride) can 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] As described in Patent Document 2, the above-mentioned cationic polymer is generally produced by radical polymerization by heating using a polymerization initiator. When polymerization is carried out using a monomer into which a cationic functional group can be introduced, a cationic group introduction treatment such as an 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 above-mentioned cationic polymer in order to ensure mechanical strength without reducing the moisture absorption capacity and at the same time improve dimensional stability. In other words, if a crosslinked structure is introduced into a hygroscopic matrix, when the matrix absorbs water, the molecules of the cationic polymer are bound to each other by the crosslinks, suppressing the volume change due to swelling (water absorption) and resulting in improved mechanical strength and dimensional stability. The above-mentioned crosslinked structure can be introduced by incorporating a crosslinking agent in the coating composition for forming the moisture absorbing layer 9 . As described in Patent Document 2, for such a crosslinked structure, a compound having a crosslinkable functional group (e.g., an epoxy group) capable of reacting with a cationic group and a functional group (e.g., an alkoxysilyl group) capable of forming a siloxane structure in the crosslinked structure through hydrolysis and dehydration condensation can be used, 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 its terminal, R 1 and R 2 are respectively a methyl group, an ethyl group, or an isopropyl group, n is 0, 1, or 2; In other words, 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 forming a film.

[0047] Ionic polymers (anionic polymers); 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, 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 similarly to the cationic polymer described above, it is sufficient that the amount is such that the water absorption rate (JIS K-7209-1984) of the formed hygroscopic matrix is ​​20% or more, particularly 30% to 45%, at a humidity of 80% RH and an atmosphere of 30°C.

[0048] As the anionic polymer having the above-mentioned functional group, for example, there can be used one obtained by polymerizing or copolymerizing at least one kind of anionic monomer represented 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, appropriately together with other copolymerizable monomers, and further, if necessary, partially neutralizing the resultant by alkali treatment. 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, and the like.

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

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

[0051] The above-mentioned anionic polymer is generally produced by radical polymerization of 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, an anionic group introduction treatment such as hydrolysis, sulfonation, chlorosulfonation, or phosphonium conversion may be carried out after polymerization.

[0052] In addition, 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 also leads to further improvement in dimensional stability. That is, in the case of anionic polymers, unlike cationic polymers, water is only captured by hydrogen bonds, so the hygroscopicity can be greatly increased by introducing a network structure (crosslinked structure) with spaces suitable for hygroscopicity into the matrix. Such a crosslinked structure has, for example, a hydrophobic portion such as an alicyclic structure in the network structure, which enhances the hygroscopic effect of the hydrophilic portion. 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, and the volume change due to swelling (water absorption) is suppressed, improving the dimensional stability. Such an effect of improving the dimensional stability is the same as that of the cationic polymer described above.

[0053] The above-mentioned crosslinked structure is introduced by blending a crosslinking agent in the coating composition for forming the moisture absorbing layer 9, as in the case of the cationic polymer. As described in Patent Document 2, this crosslinking agent is a compound having two or more crosslinkable functional groups (e.g., epoxy groups) capable of reacting with the ionic groups possessed by the anionic polymer, and is, for example, a compound represented by the formula (1): GO(C=O)-A-(C=O)OG (1) In the formula, G is a glycidyl group; A is a divalent hydrocarbon group having an aliphatic ring, for example, a cycloalkylene group. 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 anionic polymer and 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 attainable humidity than the ionic polymer (cationic or anionic polymer) forming the above-mentioned matrix, and has extremely high moisture absorbing performance. By dispersing a moisture absorbent having a higher moisture absorption capacity than 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 absorbing ability of moisture be effectively exhibited even in an extremely low humidity atmosphere, but the swelling of the moisture absorbent layer 9 due to moisture absorption is also effectively suppressed.

[0055] As the highly hygroscopic moisture absorbent as described above, one that has an ultimate 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 the ionic polymer. That is, if the ultimate humidity of this moisture absorbent is higher than that of the ionic polymer, the moisture absorbed in the matrix is ​​not sufficiently trapped, and moisture is easily released, etc., and a significant improvement in moisture barrier properties cannot be expected. Even if the ultimate humidity is lower than that of the ionic polymer, if the ultimate humidity measured under the above conditions is higher than the above range, for example, moisture trapping in a low humidity atmosphere may be insufficient, and the moisture barrier properties may not be fully exhibited.

[0056] The above-mentioned moisture absorbents generally have a water absorption rate (JIS K-7209-1984) of 50% or more in an atmosphere with a humidity of 80% RH and a temperature of 30° C., and are classified into inorganic and organic types. 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 crosslinked anionic polymers or partially neutralized products thereof. Examples of the anionic polymer include those obtained by polymerizing or copolymerizing at least one of anionic monomers represented by carboxylic acid monomers (e.g., (meth)acrylic acid, maleic anhydride, etc.), sulfonic acid monomers (e.g., halogenated vinyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, etc.), phosphonic acid monomers (e.g., vinyl phosphoric acid), and salts of these monomers with other monomers. In particular, organic moisture absorbents are effective in applications where transparency is required. For example, fine particles of crosslinked sodium poly(meth)acrylate are typical organic moisture absorbents.

[0057] In the present invention, from the viewpoint of increasing the specific surface area and exhibiting high moisture absorption, 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), and an organic polymer moisture absorbent having a small particle size is particularly optimal. That is, the organic polymer moisture absorbent has extremely good dispersibility in the ionic polymer matrix, and can be uniformly dispersed. Furthermore, by adopting emulsion polymerization or suspension polymerization as the polymerization method for producing the organic polymer moisture absorbent, the particle shape can be made fine and uniformly spherical, and by blending a certain amount of this, it is possible to ensure extremely high transparency. Furthermore, organic fine moisture absorbents not only exhibit high moisture absorption properties with an extremely low ultimate humidity, but also minimize volumetric changes due to swelling through crosslinking. Therefore, they are optimal for reducing the humidity of the environmental atmosphere to an absolute dry state or close to an absolute dry state while suppressing volumetric changes. As such organic moisture absorbent particles, for example, crosslinked sodium polyacrylate particles (average particle size: about 70 nm) are commercially available in the form of a colloidal dispersion (pH=10.4) from Toyobo Co., Ltd. under the product name Tuftic HU-820E.

[0058] In the present invention, the amount of the moisture absorbent as described above is set according to the type of ionic polymer from the viewpoint of fully exhibiting its properties, significantly improving the moisture barrier property, effectively suppressing dimensional changes due to swelling, and at the same time, ensuring a moisture barrier property higher than that exhibited by the metal foil (A) 3 or the inorganic barrier layer 11b for a long period of time. For example, when the matrix of the moisture-absorbing layer 9 is made of the above-mentioned ionic polymer and the moisture absorbent is dispersed in the matrix, the moisture absorbent is present in an amount of preferably 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-absorbing layer 9, if the matrix is ​​made of a cationic polymer. When the matrix is ​​made of an anionic polymer, the moisture absorbent is present in an amount of preferably 50 parts by weight or more, particularly 100 to 1300 parts by weight, and more preferably 150 to 1200 parts by weight, per 100 parts by weight of the anionic polymer in the moisture-absorbing layer 9.

[0059] The thickness of the moisture absorbing layer 9 varies depending on the application of the electronic device mounting substrate 1 and the required level of barrier property. -2 g / m 2 · Days or less, especially 10 -3 g / m 2 To ensure a water vapor transmission rate of 1000 sq. m or less per day, the thickness should be set to 1 to 20 μm, particularly 1 to 15 μm. If the thickness is too thin, the amount of moisture absorbed will reach the upper limit in a short period of time, impairing the moisture barrier properties. If the thickness is too thick, the amount of moisture that can be absorbed will increase, but as the amount of moisture increases, the volume change due to swelling will also increase, making it more susceptible to delamination.

[0060] <Barrier sheet 11> The barrier sheet 11 is provided on the surface of the moisture absorbing 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 side of the moisture absorbent 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 absorbent layer 9, it serves to block any moisture that cannot be absorbed by the moisture absorbent 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 modes: 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 is molded according to its form by injection or co-injection molding, extrusion or co-extrusion molding, film or sheet molding, compression molding, cast polymerization, etc. In general, thermoplastic resins are preferable from the viewpoints of moldability and cost.

[0062] Examples of such thermoplastic resins include the following: Olefin resin: Polyolefins such as low density polyethylene, high density polyethylene, polypropylene, poly1-butene, poly4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, etc., as well as cyclic olefin copolymers and cyclic olefin polymers; Ethylene-vinyl copolymer: Ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer, etc; Styrenic resin: 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.; polyamide: Nylon 6, Nylon 6-6, Nylon 6-10, Nylon 11, Nylon 12 etc; Thermoplastic polyester: 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; Furthermore, it may be a blend of the above resins, or one in which these resins have been appropriately modified by copolymerization (for example, an acid-modified olefin resin).

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

[0064] In the present invention, from the viewpoints of availability, cost, formability, or exhibiting some barrier properties against oxygen and moisture, and further, being suitable as a base for the inorganic barrier layer 11b described below, 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.

[0065] Although the thickness of the resin layer 11a is not particularly limited, if the thickness is too large, flexibility may be lost and handling may become difficult. Therefore, the thickness of the resin layer 11a is usually 200 μm or less, more preferably 125 μm or less, and within this range, a suitable moisture permeability can be secured, and further, it is preferable to set the thickness to a value that allows 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 deposition film formed by physical vapor deposition such as sputtering, vacuum deposition, ion plating, etc., or chemical vapor deposition such as plasma CVD, for example, a film formed from various metals or metal oxides, but is preferably a vapor deposition film (a vapor deposition film of a metal or metal oxide) formed by plasma CVD, in that 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 above-mentioned resin layer 11a.

[0067] The deposition film by plasma CVD is obtained by disposing the resin layer 11a that is to 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 forming the film and an oxidizing gas (usually oxygen or NOx gas) together with a carrier gas such as argon or helium through a gas supply pipe into the plasma processing chamber that is shielded by a metal wall and is depressurized 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 electrical energy generated, and depositing the decomposition reaction product of the compound on the surface of the plastic substrate to form a film. When a film is formed using a microwave electric field, the film is formed by irradiating microwaves into the plasma processing chamber using a waveguide or the like. When a high-frequency electric field is used, 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 reactive 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 forming 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 property, and in particular, an organosilicon compound is most preferable from the viewpoint of forming an inorganic barrier layer 11b with high barrier property against oxygen relatively easily and efficiently.

[0069] Examples of such organic silicon compounds include organic silane compounds such as hexamethyldisilane, vinyltrimethylsilane, methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, methyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane, and organic siloxane 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 kinds.

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

[0071] That is, the organic group (CH 3 or CH 2 etc.) are usually CO 2 At low output, some of the gas is vaporized as CO 2 On the other hand, the higher the output, the more the organic groups are 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. A film with a high degree of metal oxidation has extremely high barrier properties against gases such as oxygen, but has 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 stage 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 having a high degree of metal oxidation and high gas barrier property 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 degree region where the oxidation degree of the metal (M) is x (x=atomic ratio of O / M) of 1.5 to 2.0. Also, below this high oxidation degree region (the side in contact with the surface of the resin layer 11a), an organic region with a carbon (C) concentration of 20 element % or more is preferably formed based on the three elements of metal (M), oxygen (O) and carbon (C). Furthermore, silicon (Si) is the most preferable metal (M).

[0074] Furthermore, it is preferable that the highly oxidized region in the inorganic barrier layer 11b is present in an amount of 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 surface and contact side 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 above-mentioned organic region and high oxidation region by plasma CVD is slightly different between the case of using microwaves and the case of using high frequency waves. For example, in the case of using microwaves, the organic region is formed at a low output of about 30 to 100 W, and the high oxidation region is formed at a high output of 90 W or more. In the case of using high frequency waves, the organic region is formed at a low output of about 20 to 80 W, and the high oxidation 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 above-mentioned 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. Generally, the total thickness is about 10 -2 g / m 2 · Days or less, especially 10 -3 g / m 2 It is preferable that the thickness be such that a water vapor transmission rate of 0.1 s or less can be ensured. Although this varies depending on the proportion of the highly oxidized region described above, a thickness of generally 4 to 500 nm, particularly 30 to 400 nm, is sufficient.

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

[0078] 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. Therefore, it is necessary to apply the substrate 1 while taking into consideration the type of electronic device, the environment in which the substrate is used, and the like.

[0079] <Protective resin layer 11d> Alternatively, the 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 the metal foil (B) 11c from being scratched or oxidized and deteriorated. Therefore, it is preferable to have the protective resin layer 11d, particularly when the metal foil (B) 11c is provided on the outer surface side of the moisture absorbing layer 9. The protective resin layer 11d may be formed using various resins known per se, but is generally formed from a polyester resin such as polyethylene terephthalate or an olefin resin such as polyethylene or polypropylene, particularly a polyester resin. Such a protective resin layer 11d may usually have a thickness of about 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. As the adhesive layer 11e, the same adhesive as the adhesive layer 7 can be used.

[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 at least at 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-hygroscopic layer 13 is formed only from resin without blending any hygroscopic agent. Such a quasi-hygroscopic layer 13 can be formed at a lower cost than the hygroscopic layer 9 because no hygroscopic agent is blended.

[0083] Examples of resins used to form the quasi-hygroscopic layer 13 include ionic polymers having a lower concentration of cationic or anionic groups than the ionic polymers used to form the hygroscopic 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. Representative 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 the thickness is unnecessarily thick, the volume change due to swelling together with the hygroscopic layer 9 becomes large, and delamination is likely to occur. On the other hand, if the thickness is too thin, it becomes difficult to extend the life of the hygroscopic layer 9 due to supplementary moisture absorption.

[0085] <UV blocking layer 15> 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, which is the surface on which the moisture absorbing layer 9 is not laminated. This ultraviolet blocking layer 15 has the role of reflecting or absorbing ultraviolet rays, thereby preventing the penetration of ultraviolet rays into the substrate and the device.

[0086] The range of ultraviolet wavelengths that the ultraviolet blocking layer 15 reflects or absorbs 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 the cost will be high. On the other hand, if the ultraviolet transmittance is more than 20%, the deterioration of the substrate or electronic device will progress.

[0087] This ultraviolet blocking layer 15 can be formed from a general thermoplastic resin. From the standpoint of weather resistance and cost, however, it is preferable to form it from a resin such as polycarbonate resin, silicone resin, polyester resin, fluorine-based resin, or acrylic resin. The resin forming the ultraviolet blocking layer 15 may have dispersed therein an inorganic pigment such as carbon black, which absorbs ultraviolet rays, or titanium oxide, which scatters ultraviolet rays, as an ultraviolet screening agent. When absorbing ultraviolet rays, an additive such as a benzotriazole-based, benzophenone-based, or triazine-based organic ultraviolet absorbent may be dispersed in the resin. When the ultraviolet blocking layer 15 is formed from a resin, it is preferable that the ultraviolet blocking layer 15 and the protective resin layer 5 or the protective resin layer 11d are bonded together with an adhesive layer 17, which will be described later. The ultraviolet blocking layer 15 can also be formed by directly applying a paint containing the above-mentioned ultraviolet screening agent or organic ultraviolet absorbing agent to the surface of the protective resin layer 5 or the protective resin layer 11d, in which case it is possible to block or absorb all or a part of the ultraviolet rays, thereby blocking the transmission of the ultraviolet rays to the device. As such a paint, a fluorine-based, silicone-based, urethane-based, acrylic-based paint or the like is 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. The 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 substrate as a whole may lack strength and may be torn or have holes. 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 base material 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, and touch panels. The method for installing the substrate 1 is not particularly limited, and the substrate 1 may be installed by a method suitable for its application. For example, when the substrate of the present invention is used as a back sheet for a solar cell, the substrate 1 is fixed integrally with the cell and the like by a frame.

[0091] When used in an organic EL device or the like, the metal foil (A) 3 or the barrier sheet 11 can be coated with a known pressure-sensitive adhesive such as an acrylic, silicone or butadiene type, or can be attached to the device surface with a thermocompression-bonding sealing sheet such as an ethylene-vinyl acetate copolymer resin, polyvinyl butyral or olefin type, or a UV-curing adhesive such as an epoxy or acrylic type. 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 is used on the side of the above-mentioned device where light transparency is not required, such as the non-light-receiving surface of a back sheet of a solar cell, the non-light-emitting surface of an organic electroluminescence element, and the side surfaces of various devices. EXAMPLES

[0092] <Preparation of polyethylene terephthalate (PET) film coated with inorganic barrier layer> An inorganic barrier layer 11b of silicon oxide was formed on one side of a biaxially stretched PET film having a thickness of 25 μm as the resin layer 11a by using a plasma CVD apparatus. The film forming conditions are as follows. A CVD apparatus was used, which had 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-type cylindrical plasma processing chamber with a diameter of 300 mm and a height of 450 mm, and an oil rotary vacuum pump for evacuating the processing chamber. A PET film was placed on parallel flat plates in the processing chamber, and 3 sccm of hexamethyldisiloxane and 45 sccm of oxygen were introduced. After that, a high-frequency oscillator was used to oscillate a high-frequency wave at an output of 50 W to perform film formation for 2 seconds to form an adhesive layer. Next, a high-frequency oscillator was used to oscillate a high-frequency wave at an output of 200 W to perform film formation for 100 seconds to form 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 transmission rate of 1×10 measured in an atmosphere of 40° C. and 90% RH. -2 g / m 2 ·day.

[0093] <Preparation of Coating Solution A for Producing Moisture Absorption Layer 9> Polyallylamine (manufactured by Nittobo Medical Co., Ltd., PAA-15C, aqueous solution, solid content 15% by weight) was diluted with water to a solid content of 5% by weight to obtain a polymer solution. On the other hand, γ-glycidoxypropyltrimethoxysilane was used as a crosslinking agent, and dissolved in water to a solid content of 5% by weight 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, and further, a crosslinked product of polyacrylic acid Na (manufactured by Toyobo Co., Ltd., Tuftic HU-820E, aqueous dispersion, solid content 13%) was added as a moisture absorbent to this mixed solution so that it was 400 parts by weight per polyallylamine, and further adjusted with water to a solid content of 5% and stirred well to prepare a coating solution A for producing a moisture absorbing layer 9.

[0094] <Preparation of substrate> The coating solution A for producing the moisture absorption layer 9 obtained above was applied to the inorganic barrier layer-coated PET film on the side on which the inorganic barrier layer 11b had been formed, using a bar coater. The film after application 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, forming an ionic polymer with a thickness of 3 μm as the moisture absorption layer 9, and thus a coating film A was obtained. Next, in a glove box adjusted to a nitrogen concentration of 99.95% or more, a 15 μm aluminum foil was dry-laminated as a metal foil (A) via a 2.0 μm urethane adhesive on the surface of the coating film A on which the moisture absorption layer 9 was formed. Furthermore, a 25 μm PET film was dry-laminated as a protective resin layer 5 via a 2.0 μm urethane adhesive on the surface of the aluminum foil opposite to the surface on which the moisture absorption layer 9 was formed, 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 semi-hygroscopic layer 13 and an ultraviolet blocking layer 15 were further provided as necessary to produce substrates A to L shown in Table 1.

[0095] [Table 1]

[0096] <Experimental Example 1> <Calcium corrosion method (without bending test)> The effect of moisture permeation on the substrate A prepared above was measured by the calcium corrosion method (JIS K7129-7). In 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. After that, the inorganic barrier layer-coated PET film of substrate A was attached to the adhesive so that the PET film surface was in contact with the adhesive, and an evaluation cell was prepared. The evaluation cell was stored in a thermo-hygrostat at 40°C and 90% RH for 1000 hours, after which 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 calcium film was confirmed.

[0097] <Calcium corrosion method (with bending test)> A bending test was performed on the substrate A at a diameter of 5 mm in both bending directions 10,000 times each using a tabletop durability tester (manufactured by Yuasa System Co., Ltd.) under an environment of 23°C and 50% RH. An evaluation cell was prepared for the substrate A after the bending test in the same manner as above. The evaluation cell was stored in a thermo-hygrostat at 40°C and 90% RH for 1000 hours, after which 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 attached 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 more, a 25 μm nylon film was dry-laminated as a quasi-hygroscopic layer 13 on the surface of the coating film A on which the hygroscopic layer 9 was formed, via a 2.0 μm urethane adhesive. Furthermore, a 15 μm aluminum foil was dry-laminated as a metal foil (A) on the opposite surface of the nylon film on which the hygroscopic layer 9 was formed, via a 2.0 μm urethane adhesive. Furthermore, a 25 μm PET film was dry-laminated as a protective resin layer 5 on the opposite surface of the aluminum foil on which the quasi-hygroscopic layer 13 was formed, via a 2.0 μm urethane adhesive, to obtain a substrate E. Measurement was performed by 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) was dry-laminated as an ultraviolet blocking layer 15 on 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 performed 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 an 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 Substrate A was changed to 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 Substrate I was used instead of Substrate A.

[0107] <Experimental Example 11> Measurement was carried out by the calcium corrosion method in the same manner as in Experimental Example 1, except that Substrate A was changed to 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 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] [Table 2]

[0111] In the calcium corrosion method (with bending test), no calcium corrosion was observed for any of the substrates A to I, and the appearance of the substrate 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 have both moisture barrier properties and flexibility. On the other hand, for Substrate J, although no corrosion of the calcium film was observed, creases were observed on the surface. It is considered that Substrate J had a large total thickness and insufficient flexibility, which is why creases occurred during the bending test. Corrosion of the calcium film was also observed for substrates K and L. Because the metal foil (A) of substrates K and L was thick and insufficiently flexible, numerous pinholes were generated in the metal foil during the bending test, which allowed a large amount of moisture to penetrate and cause the hygroscopic resin layer to swell in a short period of time, with the moisture that could not be absorbed reaching the calcium film. [Explanation of symbols]

[0112] 1: Substrate for mounting electronic devices 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-hygroscopic layer 15: UV-blocking layer 17: Adhesive layer

Claims

1. A metal foil (A), a moisture absorbing layer, and a barrier sheet are laminated in this order, The thickness of the metal foil (A) is 5 to 20 μm, a semi-hygroscopic layer is provided at least at one location between the metal foil (A) and the hygroscopic layer or between the hygroscopic layer and the barrier sheet; An electronic device mounting substrate having an overall thickness of 25 to 250 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. 5. The electronic device mounting substrate according to claim 4, wherein the resin layer is made of at least one of an olefin resin, a polyester resin, a polyimide resin, a polyamide resin, and a cyclic olefin resin.

6. 5. 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. 2. 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. 2. The electronic device mounting substrate according to claim 1, 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.

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

Images