Method for manufacturing sealing sheet

Abstract

To manufacture a sealing sheet in which a resin composition layer is sufficiently dried and is prevented from absorbing moisture during storage, etc.SOLUTION: In a method for manufacturing a sealing sheet having a laminate structure sequentially including a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer, the resin composition layer is dried before the second moisture-proof layer is formed, and the second moisture-proof layer is formed while the resin composition layer is kept in a low-moisture atmosphere from when drying of the resin composition is finished to when the second moisture-proof layer is formed.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sealing sheet useful for sealing electronic devices.

Background Art

[0002] In order to protect electronic devices (such as organic EL (Electroluminescence) devices, solar cells, etc.) that are vulnerable to moisture from moisture, electronic devices are sealed using a sealing sheet having a resin composition layer.

[0003] On the other hand, when moisture is contained in the resin composition layer of the sealing sheet, it may be difficult to sufficiently protect the electronic device. For example, in Patent Document 1, a sealing sheet having a first moisture-proof film, a resin composition layer, and a second moisture-proof film has been proposed in order to suppress moisture absorption of the resin composition layer during storage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If it is a sealing sheet having a laminated structure including a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer in this order as described in Patent Document 1, it is possible to prevent the resin composition layer from absorbing moisture during storage, transportation, etc. of the sealing sheet. However, even if the absorption of moisture by the resin composition layer during storage is prevented, when moisture is contained in the resin composition layer during the production of the sealing sheet, the internal moisture may accelerate the deterioration of the electronic device. Further, in the case of the sealing sheet having the laminated structure, even if an attempt is made to remove the moisture of the resin composition layer by a dryer, since the first moisture-proof layer and the second moisture-proof layer prevent the movement of moisture from the resin composition layer, it is difficult to efficiently dry the resin composition layer.

[0006] The present invention has been made paying attention to the above circumstances, and an object thereof is to manufacture a sealing sheet in which the resin composition layer is sufficiently dried and moisture absorption of the resin composition layer during storage etc. can be prevented.

Means for Solving the Problems

[0007] The present invention that can achieve the above object is as follows. [1] A method for manufacturing a sealing sheet having a laminated structure including a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer in this order, wherein the resin composition layer is dried in a state where the second moisture-proof layer is absent, and the second moisture-proof layer is provided while maintaining the resin composition layer in a low humidity atmosphere from the end of drying until the second moisture-proof layer is provided. [2] The method according to [1] above, wherein the water vapor transmission rate of the first moisture-proof layer and the second moisture-proof layer is each independently 0 to 5 (g / m 2 / 24hr). [3] The method according to [1] or [2] above, wherein the moisture concentration (volume fraction) of the low humidity atmosphere is 3,300 ppm or less. [4] The method according to any one of [1] to [3] above, wherein the resin composition layer is dried by heating. [5] The method according to [4] above, wherein the resin composition layer is dried by heating a sheet having a laminated structure including a first moisture-proof layer and a resin composition layer, and the surface of the resin composition layer on the side opposite to the side where the first moisture-proof layer is present is exposed. [6] The method according to [4] or [5] above, wherein the drying temperature is 80 to 220 °C. [7] The method according to any one of [1] to [6] above, wherein the resin composition layer contains semi-calcined hydrotalcite and / or calcined hydrotalcite. [8] The method according to any one of [1] to [7] above, wherein the sealing sheet is a sheet used for sealing an electronic device. [9] The method according to [8] above, wherein the electronic device is an organic EL device or a solar cell. [Advantages of the Invention]

[0008] According to the present invention, it is possible to manufacture a sealing sheet in which the resin composition layer is sufficiently dried and moisture absorption of the resin composition layer during storage or the like can be prevented. [Embodiments for Carrying Out the Invention]

[0009] The sealing sheet manufactured by the present invention has a laminated structure including a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer in this order. Such a laminated structure can prevent moisture absorption of the resin composition layer during storage or the like. The first moisture-proof layer and the second moisture-proof layer may be the same or different. Further, the sealing sheet may include layers different from the first moisture-proof layer, the resin composition layer, and the second moisture-proof layer (for example, a release layer, an adhesive layer) between the layers, or may include different layers as outer layers.

[0010] The water vapor transmission rate (hereinafter sometimes abbreviated as "WVTR") of the first moisture-proof layer and the second moisture-proof layer is preferably, independently of each other, 5 (g / m 2 / 24 hr) or less, more preferably 2 (g / m 2 / 24 hr) or less, and even more preferably 1.5 (g / m2 / 24 hr) or less, more preferably 1 (g / m 2 / 24 hr), even more preferably 0.1 (g / m 2 / 24 hr), particularly preferably 0.05 (g / m 2 / 24 hr) or less. There is no particular limitation on the lower limit of the water vapor transmission rate of the first moisture-proof layer and the second moisture-proof layer. The water vapor transmission rates of the first moisture-proof layer and the second moisture-proof layer are each independently, for example, 0 (g / m 2 / 24 hr) or more.

[0011] From the viewpoint of maintaining the high moisture-proof property of the sealing sheet, it is preferable that the WVTR of the first moisture-proof layer and the second moisture-proof layer is a low value. On the other hand, when an electronic device or the like is sealed with a sealing sheet, one of the moisture-proof layers is removed and discarded before sealing. Therefore, from the viewpoint of cost, a moisture-proof film with a relatively high WVTR and low cost may be used for the moisture-proof layer removed before sealing, and a moisture-proof film with a relatively low WVTR may be used for the moisture-proof layer that is not removed. For example, a moisture-proof film with a WVTR of 0.1 (g / m 2 / 24 hr) or more is used for the moisture-proof layer removed before sealing, and a moisture-proof film with a WVTR of less than 0.1 (g / m 2 / 24 hr) may be used for the moisture-proof layer that is not removed. That is, either one of the first moisture-proof layer and the second moisture-proof layer of the sealing sheet in the present invention has a relatively high WVTR (for example, 0.1 (g / m 2 / 24 hr) or more), and either one of the moisture-proof layers has a relatively low WVTR (for example, less than 0.1 (g / m 2 / 24 hr)).

[0012] The water vapor transmission rates of the first moisture-proof layer and the second moisture-proof layer can be measured as follows. First, a test piece punched out to 60 mmφ from the moisture-proof layer is prepared. According to JIS Z 0208:1976, the permeation area is 2.826×10 -3 m 2Weigh 7.5 g of calcium chloride into a moisture-permeable cup made of aluminum with a diameter of (60 mm φ), and attach the test piece to this moisture-permeable cup. Measure the initial mass of the moisture-permeable cup containing calcium chloride and attached with the test piece using an analytical balance. Then, after leaving the moisture-permeable cup in a thermostatic test chamber at a temperature of 40 °C and a humidity of 90% RH for 24 hours, measure the mass of the moisture-permeable cup containing calcium chloride and attached with the test piece using an analytical balance after moisture permeation. The mass increase (= mass after moisture permeation - initial mass) is taken as the water vapor transmission rate. From the water vapor transmission rate, the permeation area, and the standing time, calculate the water vapor permeability (g / m 2 / 24 hr). The water vapor permeability of the first moisture-proof layer and the second moisture-proof layer may be measured by separating the moisture-proof layer from the sealing film, or the water vapor permeability of the moisture-proof film used for the moisture-proof layer may be measured.

[0013] The structures of the first moisture-proof layer and the second moisture-proof layer may each be a single-layer structure or a laminated structure. Preferably, the structures of the first moisture-proof layer and the second moisture-proof layer are laminated structures having a barrier layer and a substrate. Here, the substrate means the part other than the barrier layer in the laminated structure. The moisture-proof layer may be formed by a moisture-proof film having a barrier layer and a substrate.

[0014] The structure of the base material constituting the moisture-proof layer or moisture-proof film may be a single-layer structure or a laminated structure. Examples of the base material constituting the moisture-proof layer include plastic films such as polyolefins such as polyethylene and polypropylene (PP), polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), cycloolefin polymer (COP), and polyvinyl chloride. Only one type of plastic film may be used, or two or more types may be used in combination. The base material is preferably a polyethylene terephthalate film, a cycloolefin polymer film, a polyethylene naphthalate film, or a polycarbonate film, more preferably a polyethylene terephthalate film or a cycloolefin polymer film. The thickness of the base material (when the base material is a laminated film, the total thickness thereof) is preferably 5 to 150 μm, more preferably 6 to 100 μm, and even more preferably 12 to 75 μm.

[0015] Examples of the barrier layer constituting the moisture-proof layer or moisture-proof film include inorganic films such as metal foils (e.g., aluminum foil), silica vapor deposition films, silicon nitride films, and silicon oxide films. The barrier layer may be composed of multiple layers of multiple inorganic films (e.g., a metal foil and a silica vapor deposition film). Further, the barrier layer may be composed of an organic substance and an inorganic substance, or may be a composite multilayer of an organic layer and an inorganic film. The thickness of the barrier layer is preferably 0.01 to 100 μm, more preferably 0.05 to 50 μm, and even more preferably 0.05 to 30 μm.

[0016] As the moisture-proof layer, a commercially available moisture-proof film may be used. Examples of commercially available products include "Clarista CI" manufactured by Kuraray Co., Ltd., "Tech Barrier HX", "Tech Barrier LX", and "Tech Barrier L" manufactured by Mitsubishi Chemical Corporation, "IB-PET-PXB" manufactured by Dai Nippon Printing Co., Ltd., "GL, GX series" manufactured by Toppan Printing Co., Ltd., "PET Tsuki AL1N30" manufactured by Toyo Aluminum Co., Ltd., "X-Barrier" manufactured by Mitsubishi Chemical Corporation, and the like.

[0017] In a preferred embodiment of the present invention, the sealing sheet includes a first moisture-proof layer, a first release layer, a resin composition layer, and a second moisture-proof layer in this order, and has a laminated structure in which the first release layer and the resin composition layer are in contact with each other. In another preferred embodiment of the present invention, the sealing sheet includes a first moisture-proof layer, a resin composition layer, a second release layer, and a second moisture-proof layer in this order, and has a laminated structure in which the resin composition layer and the second release layer are in contact with each other. In a more preferred embodiment of the present invention, the sealing sheet includes a first moisture-proof layer, a first release layer, a resin composition layer, a second release layer, and a second moisture-proof layer in this order, and has a laminated structure in which the first release layer and the resin composition layer are in contact with each other, and the resin composition layer and the second release layer are in contact with each other.

[0018] Examples of the release agent for forming the release layer include silicone-based release agents, alkyd-based release agents, fluorine-based release agents, olefin-based release agents, and the like. The release layer is preferably formed from a silicone-based release agent or an alkyd-based release agent. The thickness of the release layer is preferably 0.05 to 1 μm, more preferably 0.05 to 0.5 μm, and even more preferably 0.05 to 0.1 μm.

[0019] In the present invention, the resin composition layer is not particularly limited, and a known resin composition can be used to form the resin composition layer. In order to seal an organic EL device or the like well, the resin composition layer preferably contains an olefin-based resin and / or an epoxy resin. The olefin-based resin and the epoxy resin are not particularly limited, and known ones (for example, those described in WO2018 / 181426A1) can be used.

[0020] There is no particular limitation on the amount of the olefin resin. From the viewpoint of good coatability and the like, when using an olefin resin, the amount thereof is preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, further preferably 60% by mass or less, still further preferably 55% by mass or less, particularly preferably 50% by mass or less per unit of the entire resin composition layer (i.e., per unit of the total non-volatile content of the resin composition). On the other hand, from the viewpoint of improving moisture resistance and transparency, the amount of the olefin resin is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, further preferably 7% by mass or more, still further preferably 10% by mass or more, particularly preferably 20% by mass or more, and most preferably 30% by mass or more per unit of the entire resin composition layer (i.e., per unit of the total non-volatile content of the resin composition).

[0021] There is no particular limitation on the amount of the epoxy resin. When using an epoxy resin, the amount thereof is preferably 10 to 80% by mass, more preferably 15 to 75% by mass, and still more preferably 20 to 70% by mass per unit of the entire resin composition layer (i.e., per unit of the total non-volatile content of the resin composition).

[0022] From the viewpoint of moisture barrier properties of the sealing sheet of the present invention, the resin composition layer preferably contains semi-calcined hydrotalcite and / or calcined hydrotalcite, more preferably contains semi-calcined hydrotalcite. Either semi-calcined hydrotalcite or calcined hydrotalcite may be used alone, or two or more thereof may be used in combination.

[0023] A sealing sheet having a resin composition layer containing semi-calcined hydrotalcite and / or calcined hydrotalcite can exhibit high moisture barrier properties. However, since semi-calcined hydrotalcite and calcined hydrotalcite have hygroscopicity, the moisture absorption of the resin composition layer increases. However, according to the present invention, the resin composition layer can be sufficiently dried during production, and the obtained sealing sheet can prevent moisture absorption of the resin composition layer during storage and the like by the first and second moisture-proof layers. Therefore, the present invention is suitable for the production of a sealing sheet having a resin composition layer containing calcined hydrotalcite and / or calcined hydrotalcite.

[0024] Hydrotalcite can be classified into uncalcined hydrotalcite, semi-calcined hydrotalcite, and calcined hydrotalcite.

[0025] Uncalcined hydrotalcite is a metal hydroxide having a layered crystal structure represented by, for example, natural hydrotalcite (Mg6Al2(OH) 16 CO3·4H2O), and for example, a layer [Mg 1-X Al X (OH)2] X+ and an intermediate layer [(CO3) X / 2 ·mH2O] X- consisting of. The uncalcined hydrotalcite in the present invention is a concept including hydrotalcite-like compounds such as synthetic hydrotalcite. Examples of hydrotalcite-like compounds include those represented by the following formula (I) and the following formula (II).

[0026] [M 2+ 1-x M 3+ x (OH)2] x+ ·[(A n- ) x / n ·mH2O] x- (I) (wherein M 2+ represents divalent metal ions such as Mg 2+ , Zn 2+ , etc., and M3+ represents trivalent metal ions such as Al 3+ , Fe 3+ , etc., and A n- represents n-valent anions such as CO3 2- , Cl - , NO3 - , etc., where 0 < x < 1, 0 ≤ m < 1, and n is a positive number.) In formula (I), M 2+ is preferably Mg 2+ , and M 3+ is preferably Al 3+ , and A n- is preferably CO3 2- .

[0027] M 2+ x Al2(OH) 2x+6-nz (A n- ) z ·mH2O (II) (In the formula, M 2+ represents divalent metal ions such as Mg 2+ , Zn 2+ , etc., A n- represents n-valent anions such as CO3 2- , Cl - , NO3 - , etc., x is a positive number of 2 or more, z is a positive number of 2 or less, m is a positive number, and n is a positive number.) In formula (II), M 2+ is preferably Mg 2+ , and A n- is preferably CO3 2- .

[0028] Semi-calcined hydrotalcite refers to a metal hydroxide having a layered crystal structure obtained by calcining uncalcined hydrotalcite, in which the amount of interlayer water is reduced or disappeared. "Interlayer water" refers to "H2O" described in the composition formulas of the above-mentioned uncalcined natural hydrotalcite and hydrotalcite-like compounds when explained using the composition formula.

[0029] On the one hand, calcined hydrotalcite is a metal oxide having an amorphous structure obtained by calcining uncalcined hydrotalcite or semi-calcined hydrotalcite, in which not only the interlayer water but also the hydroxyl groups disappear by condensation dehydration.

[0030] Uncalcined hydrotalcite, semi-calcined hydrotalcite, and calcined hydrotalcite can be distinguished by their saturated water absorption rates. The saturated water absorption rate of semi-calcined hydrotalcite is 1% by mass or more and less than 20% by mass. On the other hand, the saturated water absorption rate of uncalcined hydrotalcite is less than 1% by mass, and the saturated water absorption rate of calcined hydrotalcite is 20% by mass or more.

[0031] The "saturated water absorption rate" in the present invention means the mass increase rate with respect to the initial mass when 1.5 g of uncalcined hydrotalcite, semi-calcined hydrotalcite, or calcined hydrotalcite is weighed on a balance, the initial mass is measured, and then left standing for 200 hours in a small environmental test chamber (SH-222 manufactured by Espec Corporation) set at 60°C and 90% RH (relative humidity) under atmospheric pressure, as represented by the following formula (i): Saturated water absorption rate (% by mass) = 100 × (mass after moisture absorption - initial mass) / initial mass (i) and can be determined by this.

[0032] The saturated water absorption rate of semi-calcined hydrotalcite is preferably 3% by mass or more and less than 20% by mass, more preferably 5% by mass or more and less than 20% by mass.

[0033] Also, uncalcined hydrotalcite, semi-calcined hydrotalcite, and calcined hydrotalcite can be distinguished by the thermogravimetric reduction rate measured by thermogravimetric analysis. The thermogravimetric reduction rate of semi-calcined hydrotalcite at 280°C is less than 15% by mass, and the thermogravimetric reduction rate at 380°C is 12% by mass or more. On the other hand, the thermogravimetric reduction rate of uncalcined hydrotalcite at 280°C is 15% by mass or more, and the thermogravimetric reduction rate of calcined hydrotalcite at 380°C is less than 12% by mass.

[0034] Thermogravimetric analysis can be carried out using a TG / DTA EXSTAR6300 manufactured by Hitachi High-Tech Science Corporation. Weigh 5 mg of hydrotalcite into an aluminum sample pan, and under the atmosphere of a nitrogen flow rate of 200 mL / min, without a lid (in an open state), perform the analysis under the condition of a temperature rising rate of 10 °C / min from 30 °C to 550 °C. The thermogravimetric reduction rate can be obtained by the following formula (ii): Thermogravimetric reduction rate (mass%) = 100×(mass before heating - mass when reaching a predetermined temperature) / mass before heating (ii) and can be determined thereby.

[0035] Moreover, uncalcined hydrotalcite, semi-calcined hydrotalcite, and calcined hydrotalcite can be distinguished by the peaks and relative intensity ratios measured by powder X-ray diffraction. The semi-calcined hydrotalcite shows two split peaks at around 2θ = 8 - 18° by powder X-ray diffraction, or a peak with a shoulder formed by the combination of two peaks. The relative intensity ratio (low-angle side diffraction intensity / high-angle side diffraction intensity) of the diffraction intensity of the peak or shoulder appearing on the low-angle side (= low-angle side diffraction intensity) and the diffraction intensity of the peak or shoulder appearing on the high-angle side (= high-angle side diffraction intensity) is 0.001 - 1,000. On the other hand, the uncalcined hydrotalcite has only one peak around 8 - 18°, or the relative intensity ratio of the diffraction intensity of the peak or shoulder appearing on the low-angle side and the peak or shoulder appearing on the high-angle side is outside the aforementioned range. The calcined hydrotalcite does not have characteristic peaks in the region of 8° - 18°, but has a characteristic peak at 43°. The powder X-ray diffraction measurement was carried out using a powder X-ray diffractometer (Empyrean manufactured by PANalytical), with a counter cathode CuKα (1.5405 Å), voltage: 45 V, current: 40 mA, sampling width: 0.0260°, scanning speed: 0.0657° / s, and measurement diffraction angle range (2θ): 5.0131 - 79.9711°. The peak search can be carried out using the peak search function of the software attached to the diffractometer under the conditions of "minimum significance: 0.50, minimum peak tip: 0.01°, maximum peak tip: 1.00°, peak base width: 2.00°, method: minimum value of second derivative".

[0036] The BET specific surface areas of the semi-calcined hydrotalcite and the calcined hydrotalcite are both preferably from 1 to 250 m 2 / g, more preferably from 5 to 200 m 2 / g. These BET specific surface areas can be calculated using the BET multi-point method by adsorbing nitrogen gas on the sample surface using a specific surface area measuring device (Macsorb HM Model 1210 manufactured by Mountech Co., Ltd.) in accordance with the BET method.

[0037] The particle diameters of the semi-calcined hydrotalcite and the calcined hydrotalcite are both preferably from 1 to 1,000 nm, more preferably from 10 to 800 nm. These particle diameters are the median diameters of the particle size distribution when the particle size distribution is created on a volume basis by laser diffraction scattering particle size distribution measurement (JIS Z 8825).

[0038] For both the semi-calcined hydrotalcite and the calcined hydrotalcite, those surface-treated with a surface treatment agent can be used. There is no particular limitation on the surface treatment agent used for the surface treatment, and known ones (for example, those described in WO2018 / 181426A1) can be used.

[0039] There is no particular limitation on the amount of the semi-calcined hydrotalcite. From the viewpoint of the moisture barrier property of the sealing sheet, when using the semi-calcined hydrotalcite, the amount is preferably from 3 to 80% by mass, more preferably from 5 to 75% by mass, and even more preferably from 10 to 70% by mass per unit of the entire resin composition layer (that is, per unit of the total non-volatile content of the resin composition).

[0040] Examples of the semi-calcined hydrotalcite include "DHT-4C" (manufactured by Kyowa Chemical Industry Co., Ltd., particle diameter: 400 nm), "DHT-4A-2" (manufactured by Kyowa Chemical Industry Co., Ltd., particle diameter: 400 nm), etc. On the other hand, examples of the calcined hydrotalcite include "KW-2200" (manufactured by Kyowa Chemical Industry Co., Ltd., particle diameter: 400 nm), etc., and examples of the uncalcined hydrotalcite include "DHT-4A" (manufactured by Kyowa Chemical Industry Co., Ltd., particle diameter: 400 nm), etc.

[0041] The resin composition layer may contain other components different from the above-described olefin resin, epoxy resin, and semi-calcined hydrotalcite. There is no limitation on the other components, and those known as components of the resin composition for sealing (for example, those described in WO2018 / 181426A1) can be used.

[0042] The thickness of the resin composition layer is preferably 3 to 75 μm, more preferably 3 to 50 μm, and still more preferably 5 to 50 μm.

[0043] The sealing sheet having a laminated structure including the first moisture-proof layer, the resin composition layer, and the second moisture-proof layer in this order can be manufactured, for example, by applying and drying a resin composition varnish to the first moisture-proof layer to form the resin composition layer, and laminating the second moisture-proof layer on the obtained resin composition layer. An adhesive may be used for laminating the second moisture-proof layer.

[0044] The sealing sheet having a laminated structure including the first moisture-proof layer, the first release layer, the resin composition layer, the second release layer, and the second moisture-proof layer in this order, wherein the first release layer is in contact with the resin composition layer and the resin composition layer is in contact with the second release layer, can be manufactured, for example, by applying and drying a resin composition varnish to the first release layer of a laminate having a structure of the first release layer / the first moisture-proof layer to form the resin composition layer, and laminating a laminate having a structure of the second release layer / the second moisture-proof layer on the obtained resin composition layer so that the resin composition layer is in contact with the second release layer. The sealing sheet having a laminated structure including the first moisture-proof layer, the first release layer, the resin composition layer, and the second moisture-proof layer in this order, wherein the first release layer is in contact with the resin composition layer, and the sealing sheet having a laminated structure including the first moisture-proof layer, the resin composition layer, the second release layer, and the second moisture-proof layer in this order, wherein the resin composition layer is in contact with the second release layer, can be manufactured in the same manner.

[0045] As the laminate having a structure with a release layer / moisture-proof layer, a commercially available product (for example, a moisture-proof film with a release layer) may be used. Alternatively, a release agent may be applied to and dried on the moisture-proof layer to produce a laminate having a structure with a release layer / moisture-proof layer.

[0046] The resin composition varnish can be produced by mixing the components of the resin composition and an organic solvent using a kneading roller, a rotary mixer, or the like. The nonvolatile content of the resin composition varnish is preferably 20 to 80% by mass, more preferably 30 to 70% by mass.

[0047] Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; acetate esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitols such as cellosolve and butyl carbitol; aromatic hydrocarbons such as toluene and xylene; dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.; and aromatic mixed solvents such as solvent naphtha. Examples of commercial products of aromatic mixed solvents include "Swasol" (manufactured by Maruzen Oil Co., Ltd.) and "Ipzol" (manufactured by Idemitsu Kosan Co., Ltd.). The organic solvent may be used alone or in combination of two or more.

[0048] The present invention is characterized in that the resin composition layer is dried in a state where the second moisture-proof layer is absent, and the second moisture-proof layer is provided while maintaining the resin composition layer in a low-humidity atmosphere from the end of drying until the second moisture-proof layer is provided. By this feature, moisture absorption of the resin composition layer during production can be prevented, and a sealing sheet including a sufficiently dried resin composition layer can be produced.

[0049] The drying of the resin composition layer may be performed simultaneously with the formation of the resin composition layer by drying the resin composition varnish. That is, the formation and drying of the resin composition layer by drying the resin composition varnish may be performed in one step, and the second moisture-proof layer may be provided while maintaining the resin composition layer in a low-humidity atmosphere from the end of drying until the second moisture-proof layer is provided.

[0050] The drying of the resin composition layer may be performed separately from the formation of the resin composition layer by drying the resin composition varnish. That is, in addition to the step of forming the resin composition layer by drying the resin composition varnish, the step of drying the formed resin composition layer may be performed separately. After the drying is completed and until the second moisture-proof layer is provided, the second moisture-proof layer may be provided while maintaining the resin composition layer in a low-humidity atmosphere. When the step of forming the resin composition layer and the step of drying the resin composition layer are not performed continuously, in order to prevent adhesion of dust or the like to the resin composition layer, a cover film is provided on the resin composition layer, and the cover film is peeled off before the drying step, or if the cover film has sufficient water permeability (corresponding to the moisture permeable layer described below), it may be dried as it is.

[0051] In the mode of drying the resin composition layer without the second moisture-proof layer, (1) a mode of drying the resin composition layer with at least one surface of the resin composition layer exposed, and (2) a mode of drying the resin composition layer with at least one surface of the resin composition layer covered with a moisture permeable layer are included. From the viewpoint of drying efficiency, the mode of (1) above is preferable, but from the viewpoint of suppressing adhesion of dust or the like to the resin composition layer, the mode of (2) above is preferable. The surface of the resin composition layer opposite to the exposed surface or the surface covered with the moisture permeable layer may be exposed or may be covered with another layer (for example, the first moisture-proof layer).

[0052] Examples of the film and sheet used as the moisture permeable layer include a porous polyolefin film, a low-crystalline polyolefin film, and the like. If it has a certain water permeability, the above-mentioned plastic film may be used, or films and sheets commercially available as breathable films, moisture permeable sheets, etc. may be used. The water vapor transmission rate of the moisture permeable layer is preferably 10 (g / m 2 / 24hr), more preferably 30 (g / m 2 / 24hr), still more preferably 50 (g / m 2 / 24hr) or more, particularly preferably 100 (g / m2 above 150 (g / m² / 24 hr), most preferably above 150 (g / m² / 24 hr). 2 / 24 hr) or more. The upper limit is not particularly limited, for example, 20,000 (g / m² / 24 hr). The thickness of the water permeable layer is preferably 1 to 200 μm, more preferably 1 to 75 μm, and even more preferably 1 to 25 μm. 2 / 24 hr). The thickness of the water permeable layer is preferably 1 to 200 μm, more preferably 1 to 75 μm, and even more preferably 1 to 25 μm.

[0053] The drying of the resin composition layer may be carried out, for example, by any of heat drying and vacuum drying, or a combination thereof. Also, the drying of the resin composition layer may be carried out in an air atmosphere or in an inert gas atmosphere.

[0054] In the present invention, it is preferable to dry the resin composition layer by heating, and it is more preferable to dry the resin composition layer by heating a sheet having a laminated structure in which the resin composition layer is exposed on the surface opposite to the side where the first moisture-proof layer exists, the laminated structure including the first moisture-proof layer and the resin composition layer. The drying conditions such as the drying temperature, drying time, and degree of vacuum vary depending on the moisture content contained in the resin composition layer, the desired moisture content, the type of dryer, etc.

[0055] The drying temperature is generally appropriately set in the range of 80 to 220°C. When the resin composition is a thermosetting resin composition, it is preferably 80 to 150°C. When the resin composition is a thermoplastic resin composition or a pressure-sensitive adhesive resin composition, it is preferably 100 to 180°C. The drying time is preferably 1 to 180 minutes, more preferably 3 to 150 minutes, and even more preferably 5 to 120 minutes. Here, the drying temperature means the temperature inside the dryer when drying is carried out by a dryer, and means the temperature of the heating part of the heater when heat drying is carried out by a heater (for example, a hot plate).

[0056] The drying of the resin composition layer may be carried out separately from the formation of the resin composition layer by drying the resin composition varnish, or may be carried out simultaneously with the formation of the resin composition layer by drying the resin composition varnish. The drying temperature and drying time are the same as those in the above range.

[0057] When performing vacuum drying, the degree of vacuum is not particularly limited as long as it is lower than atmospheric pressure, but is preferably 10 to 100,000 Pa, more preferably 10 to 10,000 Pa, and even more preferably 10 to 1,000 Pa.

[0058] The lower the moisture concentration (mass fraction) of the resin composition layer after drying, the better (ideally 0 ppm), preferably 1500 ppm or less, more preferably 1000 ppm or less, even more preferably 500 ppm or less, even more preferably 200 ppm or less, and even more preferably 100 ppm or less.

[0059] The drying of the resin composition layer can be carried out by a known dryer. The dryer may be a batch dryer or a continuous dryer. The dryer may be one that brings a high-temperature object into contact with the object to be dried, or one that irradiates the object to be dried with light. Examples of the former include a hot air circulation furnace and a heating conveyor roll. Examples of the latter include a near-infrared irradiation furnace. Also, a heater (for example, a hot plate) may be installed in a container (for example, a glove box) that can maintain the internal atmosphere as a low-humidity atmosphere, and the resin composition varnish or the resin composition layer may be heated by this heater to perform drying.

[0060] After providing the second moisture-proof layer, substantially, it becomes difficult to dry the resin composition layer, or the drying efficiency significantly decreases. Therefore, in the present invention, the end of drying means the end of the drying operation or the time when the second moisture-proof layer is provided. Also, for example, when drying by a continuous dryer, the end of the drying operation means the time when the object to be dried is taken out of the continuous dryer. Also, for example, when drying by a heater such as a hot plate, the end of the drying operation means the end of heating.

[0061] In the aspect of maintaining the resin composition layer in a low humidity atmosphere from the end of drying until the second moisture-proof layer is provided, as long as the resin composition layer is maintained in a low humidity atmosphere "from the end of drying until the second moisture-proof layer is provided", both the aspect of maintaining the resin composition layer in a low humidity atmosphere even outside this period (for example, during drying) and the aspect of not maintaining the resin composition layer in a low humidity atmosphere outside this period are included.

[0062] In the aspect of providing the second moisture-proof layer while maintaining the resin composition layer in a low humidity atmosphere from the end of drying until the second moisture-proof layer is provided, the following aspects are included: (i) After the resin composition layer is maintained in a low humidity atmosphere, the drying operation is terminated, and the second moisture-proof layer is provided while the resin composition layer is maintained in a low humidity atmosphere, and (ii) Even after the resin composition layer is maintained in a low humidity atmosphere, the drying operation is not terminated, and the second moisture-proof layer is provided while continuing the drying in a low humidity atmosphere. In addition, in the aspect of (ii) above, "the end of drying" and "the time when the second moisture-proof layer is provided" are the same. Therefore, in the aspect of (ii) above, "from the end of drying until the second moisture-proof layer is provided" = "the end of drying" = "the time when the second moisture-proof layer is provided".

[0063] As an aspect of providing the second moisture-proof layer while maintaining the resin composition layer in a low humidity atmosphere, for example, (a) While maintaining the resin composition layer in a low humidity atmosphere, a film containing the second moisture-proof layer or the second moisture-proof layer is laminated on the exposed surface of the resin composition layer. (b) While maintaining the resin composition layer in a low humidity atmosphere, a film containing the second moisture-proof layer or the second moisture-proof layer is laminated on the moisture permeable layer on the resin composition layer. (c) While maintaining the resin composition layer in a low humidity atmosphere, a precursor layer capable of forming the second moisture-proof layer is formed on the exposed surface of the resin composition layer by coating or the like, and a treatment such as heating is applied to form the second moisture-proof layer. (d) While maintaining the resin composition layer in a low humidity atmosphere, a precursor layer capable of forming a second moisture-proof layer is formed on the moisture permeable layer on the resin composition layer by coating or the like, and a treatment such as heating is applied to form the second moisture-proof layer. (e) While maintaining the resin composition layer in a low humidity atmosphere, an inorganic substance forming a barrier layer is vapor-deposited on the exposed surface of the resin composition layer to form a second moisture-proof layer. (f) While maintaining the resin composition layer in a low humidity atmosphere, an inorganic substance forming a barrier layer is vapor-deposited on the moisture permeable layer on the resin composition layer to form a second moisture-proof layer. Examples thereof include these. Among these, the mode (a) is preferable from the viewpoint of simplicity of operation.

[0064] The modes (a) to (d) can be carried out, for example, while maintaining the atmosphere in a dryer in which the resin composition layer has been dried or in the above-described container (for example, a glove box) at a low humidity atmosphere, by laminating the above-described second moisture-proof layer, or by applying and drying a moisture-proof resin composition.

[0065] The modes (e) and (f) can be carried out, for example, in a facility in which a dryer, a connection space having a transport mechanism, and a vapor deposition apparatus are connected in this order, and all spaces are maintained under reduced pressure (preferably, for example, 10 -7 (Torr) or less), after drying the resin composition with a dryer, transferring the resin composition to the vapor deposition apparatus by a transport mechanism, and forming a barrier layer with the vapor deposition apparatus.

[0066] The moisture concentration (volume fraction) of the low humidity atmosphere is preferably lower from the viewpoint of drying (ideally 0 ppm), preferably 3300 ppm or less, more preferably 2,000 ppm or less, still more preferably 1000 ppm or less, still more preferably 500 ppm or less, still more preferably 200 ppm or less, still more preferably 100 ppm or less, still more preferably 50 ppm or less, still more preferably 10 ppm or less, still more preferably 5 ppm or less, still more preferably 1 ppm or less, still more preferably 0.5 ppm or less, still more preferably 0.1 ppm or less.

[0067] In the present invention, by heating a sheet having a laminated structure including a first moisture-proof layer and a resin composition layer, with the surface of the resin composition layer on the side opposite to the side where the first moisture-proof layer is present being exposed, the resin composition layer is dried. From the end of drying until a film including a second moisture-proof layer or the second moisture-proof layer is laminated, while maintaining the resin composition layer in a low-humidity atmosphere, it is particularly preferable to laminate a film including the second moisture-proof layer or the second moisture-proof layer on the exposed surface of the resin composition layer.

[0068] According to the present invention, a sealing sheet can be manufactured in which the resin composition layer is sufficiently dried and moisture absorption of the resin composition layer during storage or the like can be prevented. Therefore, the sealing sheet obtained by the present invention is useful for sealing electronic devices (for example, organic EL devices, solar cells, etc.).

Examples

[0069] Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and it is of course possible to appropriately modify and implement within the range that can conform to the above and below gists, and all of them are included in the technical scope of the present invention.

[0070] Film The films used in the examples and comparative examples are described below. PET film with a release layer: "E7004" manufactured by Toyobo Co., Ltd. (polyethylene terephthalate (PET) film with a release layer, release layer: silicone release layer, thickness of the base material (PET film): 38 μm, water vapor permeability: 34 g / m 2 / 24hr) Moisture-proof film 1: "Tech Barrier HX" manufactured by Mitsubishi Chemical Corporation (PET film with a barrier layer, barrier layer: silica vapor deposition film, thickness of the base material (PET film): 12.5 μm, water vapor permeability: 0.5 g / m 2 / 24hr) Moisture-proof film 2: "Bereal UD" manufactured by Reiko Co., Ltd. (PET film with a barrier layer, barrier layer: silica vapor deposition film, thickness of the base material (PET film): 50 μm, water vapor transmission rate: 0.01 g / m 2 / 24hr)

[0071] Production Example 1: Production of Moisture-Proof Film with Release Layer The PET film surface on the opposite side of the release layer of the PET film with a release layer and the base material (PET film) surface on the opposite side of the barrier layer of the moisture-proof film 1 were bonded together with an adhesive to produce a moisture-proof film with a release layer having a laminated structure of (release layer / PET film) / adhesive layer / moisture-proof film 1 (PET film / barrier layer) (total thickness of the moisture-proof film with a release layer: 55 μm). In the moisture-proof film with a release layer, the moisture-proof film 1 corresponds to the moisture-proof layer.

[0072] Production Example 2: Production of Resin Composition Varnish To 130 parts by mass of a 60% by mass solution of a cyclohexane ring-containing saturated hydrocarbon resin ("Alcon P125" manufactured by Arakawa Chemical Industries, Ltd.) in Swazol, 35 parts by mass of maleic anhydride-modified liquid polyisobutylene ("HV-300M" manufactured by Toho Chemical Industry Co., Ltd.), 60 parts by mass of polybutene ("HV-1900" manufactured by JXTG Energy Corporation), and 100 parts by mass of semi-calcined hydrotalcite ("DHT-4C" manufactured by Kyowa Chemical Industry Co., Ltd.) were dispersed with a three-roll mill to obtain a mixture. To the obtained mixture, 200 parts by mass of a 20% by mass solution of a glycidyl methacrylate-modified polypropylene-polybutene copolymer ("T-YP341" manufactured by Starlight PMC Co., Ltd.) in Swazol, 0.5 parts by mass of a curing accelerator (2,4,6-tris(dimethylaminomethyl)phenol), and 16 parts by mass of toluene were added, and the obtained mixture was uniformly dispersed with a high-speed rotary mixer to obtain an olefin resin composition varnish.

[0073] Production Example 3: Production of Un-Dried Sealing Sheet The resin composition varnish obtained in Production Example 2 was uniformly applied to the release layer surface of the moisture-proof film with a release layer obtained in Production Example 1 using a die coater, and heated at 130°C for 60 minutes to obtain a sealing sheet having a resin composition layer with a thickness of 20 μm (residual solvent amount in the resin composition layer: about 1% by mass). Next, while laminating these so that the resin composition layer of the obtained sealing sheet was in contact with the release layer surface of the moisture-proof film with a release layer obtained in Production Example 1, the sealing sheet was wound into a roll. The roll-shaped sealing sheet was cut into 40 mm × 80 mm to produce an undried sealing sheet. The undried sealing sheet had a laminated structure of a temporary moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0074] Production Example 4: Production of Moisture-Proof Film with Adhesive Layer A moisture-proof film with an adhesive layer having a laminated structure of a polyolefin-based adhesive film (thickness: 10 μm) adhered to the barrier layer surface of the moisture-proof film 2, i.e., moisture-proof film 2 (base material / barrier layer) / adhesive layer, was produced.

[0075] Example 1 A hot plate (150 °C) was prepared in a nitrogen glove box with a moisture concentration (volume fraction) of less than 0.1 ppm (the detection limit of the apparatus is 0.1 ppm). A sheet obtained by removing a moisture-proof film with a release layer (i.e., a film having a laminated structure of a temporary moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer) from the undried sealing sheet obtained in Production Example 3 (i.e., a sheet having a laminated structure of a resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1)) was heated on the hot plate with the resin composition layer facing up for 30 minutes to dry the resin composition layer (the obtained sheet is hereinafter abbreviated as "dried unfinished sheet"). After 10 minutes had elapsed since the heating was stopped, in the glove box as it was, a moisture-proof film with a release layer obtained in Production Example 1 (i.e., a film having a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer) was pressed against the resin composition layer of the dried unfinished sheet with a rubber roller heated to 60 °C at a pressure of 0.3 MPa or more to laminate them, and a sealing sheet was produced. The obtained sealing sheet had a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0076] Example 2 The sheet obtained by removing the moisture-proof film with a release layer (i.e., a film having a laminated structure of a temporary moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer) from the undried sealing sheet obtained in Production Example 3 (i.e., a sheet having a laminated structure of a resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1)) was dried with the resin composition layer facing up in a hot air drying oven at a temperature of 150°C. Next, the moisture-proof film with a release layer obtained in Production Example 1 (i.e., a film having a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer) and the sheet having the dried resin composition layer were conveyed to a roll laminator in a box where the relative humidity was 6% RH (moisture concentration (volume fraction): 1,800 ppm) at 1013 hPa and 25°C and the temperature was adjusted to 30°C. The moisture-proof film with a release layer obtained in Production Example 1 was pressed against the resin composition layer with a rubber roller heated to 60°C at a pressure of 0.3 MPa or more to bond them together, thereby producing a sealing sheet. The obtained sealing sheet had a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0077] Example 3 A 150°C hot plate was prepared in a nitrogen glove box with the moisture concentration (volume fraction) less than 0.1 ppm (the detection limit of the apparatus was 0.1 ppm). After removing the moisture-proof film with a release layer (i.e., a film having a laminated structure of a temporary moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer) from the undried sealing sheet obtained in Production Example 3, a PET film with a release layer (water vapor permeability: 34 g / m 2 / 24 hours, used as a water-permeable layer) was pressed on a hot plate with a rubber roller at a pressure of 0.3 MPa or more to bond it without generating defects such as bubbles, and a laminated structure including a PET film with a release layer, a resin composition layer, and a moisture-proof film with a release layer in this order was manufactured. More specifically, the obtained sheet had a laminated structure of PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1). This sheet was heated for 30 minutes with the PET film with a release layer (i.e., a film having a laminated structure of PET film / release layer) on top to dry the resin composition layer. After 10 minutes had elapsed since the heating stopped, inside the glove box as it was, on the PET film with a release layer of the sheet having a laminated structure including a PET film with a release layer, a dried resin composition layer, and a moisture-proof film with a release layer in this order, the adhesive layer side of the moisture-proof film with an adhesive layer (i.e., a film having a laminated structure of the second moisture-proof layer (moisture-proof film 2) / adhesive layer) manufactured in Production Example 4 was pressed with a rubber roller heated to 60 °C at a pressure of 0.3 MPa or more to bond it, and a sealing sheet having a laminated structure including a moisture-proof film with an adhesive layer, a PET film with a release layer, a resin composition layer, and a moisture-proof film with a release layer in this order was manufactured. More specifically, the obtained sealing sheet had a laminated structure of the second moisture-proof layer (moisture-proof film 2) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0078] Comparative Example 1 The dried unfinished sheet obtained in the same manner as in Example 1 was left in an air atmosphere at 25°C and 40% RH (moisture concentration (volume fraction): 12,500 ppm) for 10 minutes with the resin composition exposed, and then, the moisture-proof film with a release layer obtained in Production Example 1 was pressed against the resin composition layer of the sheet with a rubber roller heated to 60°C at a pressure of 0.3 MPa or more to laminate and produce a sealing sheet. The obtained sealing sheet had a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0079] Comparative Example 2 A sealing sheet was produced in the same manner as in Example 1, except that a PET film with a release layer was used instead of the moisture-proof film with a release layer obtained in Production Example 1. The obtained sealing sheet had a laminated structure of a non-moisture-proof layer (PET film) / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0080] Comparative Example 3 Without removing the part of "temporary moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer" from the undried sealing sheet obtained in Production Example 3, this temporary moisture-proof layer was used as the second moisture-proof layer and dried under the same drying conditions as in Example 1 (heating and drying for 30 minutes with the first moisture-proof layer facing the hot plate in a nitrogen glove box (moisture concentration (volume fraction): less than 0.1 ppm) on a hot plate (150°C)) to produce a sealing sheet. The obtained sealing sheet had a laminated structure of a second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer / resin composition layer / release layer / PET film / adhesive layer / first moisture-proof layer (moisture-proof film 1).

[0081] <Evaluation of the resin composition layer of the sealing sheet> The water concentration (mass fraction) of the resin composition layer immediately after production (hereinafter referred to as "water concentration (mass fraction) immediately after production") and the water concentration (mass fraction) of the resin composition layer after standing in an atmosphere of 25°C and 40% RH for 24 hours (hereinafter referred to as "water concentration (mass fraction) after standing") of the sealing sheets obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were calculated by the following method. The results are shown in Table 1.

[0082] In a nitrogen glove box with a water concentration (volume fraction) of less than 0.1 ppm (detection limit of the device: 0.1 ppm), the resin composition layer was taken out from the sealing sheet. The resin composition layer was folded into an appropriate size to prepare a sample, and its weight was measured. Then, while preventing contact with the moist space, the sample was put into the vaporization cylinder of a Karl Fischer moisture measuring device ("Trace Moisture Measuring Device CA-200" manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and heated to 130°C. From immediately after the start of heating until the amount of water detected per second became less than 0.15 μg / second, the total amount of vaporized water aggregated and the weight of the sample were used to calculate the water concentration (mass fraction) (ppm) of the sample (i.e., the resin composition layer). A water concentration (mass fraction) of 500 ppm or less was evaluated as ○, and a water concentration (mass fraction) exceeding 500 ppm was evaluated as ×.

[0083]

Table 1

[0084] For the sealing sheets obtained in Examples 1 to 3, both the water concentration (mass fraction) immediately after production and the water concentration (mass fraction) after standing were sufficiently low. On the other hand, in Comparative Example 1 where a film containing a second moisture-proof layer was laminated in an atmosphere with a high water concentration, the water concentration (mass fraction) immediately after production was high. Also, in Comparative Example 2 where a non-moisture-proof layer was used instead of the second moisture-proof layer, the water concentration (mass fraction) after standing was high. Further, in Comparative Example 3 where it was dried with a temporary moisture-proof layer attached, the water concentration (mass fraction) immediately after production was high.

[0085] In Comparative Example 1, when forming the second moisture-proof layer, it is considered that the moisture adhering to the moisture-proof film with a release layer migrated to the resin composition layer, so the moisture concentration of the resin composition layer after standing increased.

[0086] Also, the reason why the moisture concentration was high immediately after production in Comparative Example 3 is that during drying, moisture migrated from the resin composition layer to the moisture-proof film with a release layer (that is, a film having a laminated structure of the second moisture-proof layer (moisture-proof film 1) / adhesive layer / PET film / release layer), and the moisture migrated back to the resin composition layer during standing.

Industrial Applicability

[0087] The sealing sheet obtained by the present invention is useful for sealing electronic devices (for example, organic EL devices, sensor devices, solar cells, etc.).

[0088] This application is based on Japanese Patent Application No. 2019-180593 filed in Japan, and the content thereof is incorporated in its entirety in the specification of this application.

Claims

1. A method for manufacturing a sealing sheet having a laminated structure including a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer in this order, comprising drying the resin composition layer in a state where the second moisture-proof layer is absent, and providing the second moisture-proof layer while maintaining the resin composition layer in a low humidity atmosphere from the end of drying until the second moisture-proof layer is provided.

2. The water vapor transmission rate of the first moisture-proof layer and the second moisture-proof layer is, independently, 0 to 5 (g / m ２ / 24 hr), respectively, in the method according to claim 1.

3. The method according to claim 1 or 2, wherein the moisture concentration (volume fraction) of the low humidity atmosphere is 3,300 ppm or less.

4. The method according to any one of claims 1 to 3, wherein the resin composition layer is dried by heating.

5. The method according to claim 4, wherein the resin composition layer is dried by heating a sheet having a laminated structure including a first moisture-proof layer and a resin composition layer, and having a surface of the resin composition layer on the side opposite to the side where the first moisture-proof layer is present exposed.

6. The method according to claim 4 or 5, wherein the drying temperature is 80 to 220°C.

7. The method according to any one of claims 1 to 6, wherein the resin composition layer contains semi-calcined hydrotalcite and / or calcined hydrotalcite.

8. The method according to any one of claims 1 to 7, wherein the sealing sheet is a sheet used for sealing an electronic device.

9. The method according to claim 8, wherein the electronic device is an organic EL device or a solar cell.

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