TWI865623B - Method for manufacturing sealing sheet - Google Patents

Abstract

The present invention provides a method for manufacturing a sealing sheet having a laminated structure sequentially comprising a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer, and comprising drying the resin composition layer without the second moisture-proof layer, and then maintaining the resin composition layer in a low humidity environment from the end of drying to the setting of the second moisture-proof layer while setting the second moisture-proof layer.

Description

Method for manufacturing sealing sheet

The present invention relates to a method for producing a sealing sheet useful for sealing electronic devices.

In order to protect moisture-sensitive electronic devices (such as organic EL (Electroluminescence) devices, solar cells, etc.) from moisture, a sealing sheet having a resin composition layer is used to seal the electronic device.

On the other hand, if the resin composition layer of the sealing sheet contains moisture, it may become difficult to fully protect the electronic device. For example, Patent Document 1 proposes a sealing sheet having a first moisture-proof film, a resin composition layer, and a second moisture-proof film in order to suppress moisture absorption of the resin composition layer during storage. [Prior Technical Document] [Patent Document]

[Patent Document 1] WO2018/181426A1

[The problem that the invention is trying to solve]

If the sealing sheet has 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, the resin composition layer can be prevented from absorbing moisture during storage, transportation, etc. of the sealing sheet. However, even if the resin composition layer is prevented from absorbing moisture during storage, there is a case where moisture is contained in the resin composition layer during the manufacture of the sealing sheet, and the internal moisture accelerates the degradation of the electronic device. In the case of the sealing sheet having the above-mentioned laminated structure, even if the moisture in the resin composition layer is removed by a dryer, it is difficult to effectively dry the resin composition layer because the first moisture-proof layer and the second moisture-proof layer hinder the movement of moisture from the resin composition layer.

The present invention is made with an eye on the above-mentioned situation, and its purpose is to produce a sealing sheet in which the resin composition layer is sufficiently dried and moisture absorption of the resin composition layer can be prevented during storage. [Means for solving the problem]

The present invention that can achieve the above-mentioned object is as follows. [1] A method for producing a sealing sheet having a laminated structure that sequentially contains a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer, and comprising drying the resin composition layer without the second moisture-proof layer, and between the completion of drying and the installation of the second moisture-proof layer, the resin composition layer is maintained in a low humidity environment while the second moisture-proof layer is installed. [2] The method as described in [1] above, wherein the water vapor permeability of the first moisture-proof layer and the second moisture-proof layer is independently 0 to 5 (g/ ^m2 /24hr). [3] The method of [1] or [2] above, wherein the water concentration (volume fraction) of the low humidity environment is 3,300 ppm or less. [4] The method of any one of [1] to [3] above, wherein the resin composition layer is dried by heating. [5] The method of [4] above, wherein the resin composition layer is dried by heating a sheet having a laminate structure comprising a first moisture barrier layer and a resin composition layer, wherein the surface of the resin composition layer opposite to the side where the first moisture barrier layer is present is exposed. [6] The method of [4] or [5] above, wherein the drying temperature is 80 to 220°C. [7] The method of any one of [1] to [6] above, wherein the resin composition layer contains semi-sintered hydrotalcite and/or sintered hydrotalcite. [8] The method of any one of [1] to [7] above, wherein the sealing sheet is a sealing sheet used for electronic devices. [9] The method of [8] above, wherein the electronic device is an organic EL device or a solar cell. [Effects of the Invention]

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 can be prevented.

The sealing sheet produced by the present invention has a laminated structure containing a first moisture-proof layer, a resin composition layer, and a second moisture-proof layer in order. This laminated structure can prevent the resin composition layer from absorbing moisture during storage. The first moisture-proof layer and the second moisture-proof layer may be the same or different layers. In addition, the sealing sheet may contain a layer 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 contain a different layer as an outer layer.

The water vapor transmission rate (hereinafter referred to as "WVTR") of the first and second moisture-proof layers is independently preferably 5 (g/m ² /24hr) or less, more preferably 2 (g/m ² /24hr) or less, more preferably 1.5 (g/m ² /24hr) or less, more preferably 1 (g/m ² /24hr), more preferably 0.1 (g/m ² /24hr), and particularly preferably 0.05 (g/m ² /24hr) or less. The lower limit of the water vapor transmission rate of the first and second moisture-proof layers is not particularly limited, and the water vapor transmission rate of the first and second moisture-proof layers is independently, for example, 0 (g/m ² /24hr) or more.

From the viewpoint of maintaining high moisture barrier properties of the sealing sheet, the WVTR of the first and second moisture barrier layers is preferably low. On the other hand, when electronic devices are sealed with a sealing sheet, one of the moisture barrier layers is removed and discarded before sealing. Therefore, from the viewpoint of cost, the moisture barrier layer removed before sealing can use a relatively high WVTR and inexpensive moisture barrier film, and the moisture barrier layer not removed can use a relatively low WVTR moisture barrier film. For example, the moisture barrier layer removed before sealing can use a moisture barrier film with a WVTR of 0.1 (g/m ² /24hr) or more, and the moisture barrier layer not removed can use a moisture barrier film with a WVTR of less than 0.1 (g/m ² /24hr). That is, the first and second moisture-proof layers of the sealing sheet of the present invention may have a relatively high WVTR (e.g., 0.1 (g/m ² /24hr) or a relatively low WVTR (e.g., less than 0.1 (g/m ² /24hr)) in either moisture-proof layer.

The water vapor permeability of the first and second moisture-proof layers can be measured as follows. First, a test piece punched out to 60 mm φ is prepared from the moisture-proof layer. According to JIS Z 0208:1976, 7.5 g of calcium chloride is weighed into an aluminum permeable cup with a permeable area of 2.826×10 ^-3 m ² (60 mm φ), and the test piece is mounted in the permeable cup. The initial mass of the permeable cup filled with calcium chloride and mounted with the test piece is measured with a precision balance. Next, the above-mentioned moisture permeable cup is placed in a constant temperature test room at a temperature of 40°C and a humidity of 90%RH for 24 hours, and the mass of the moisture permeable cup filled with calcium chloride and mounted with the test piece after moisture permeation is measured with a precision balance. The mass increase (= mass after moisture permeation - initial mass) is defined as the water vapor permeation amount, and the water vapor permeability (g/ ^m2 /24hr) is calculated from the water vapor permeation amount, the permeation area and the standing time. The water vapor permeability of the first moisture barrier layer and the second moisture barrier layer can be measured by separating the moisture barrier layer from the sealing film, or by measuring the water vapor permeability of the moisture barrier film used for the moisture barrier layer.

The structure of the first moisture-proof layer and the second moisture-proof layer may be either a single layer structure or a laminated structure. The structure of the first moisture-proof layer and the second moisture-proof layer is preferably a laminated structure having a shielding layer and a substrate. Here, the substrate refers to the portion other than the shielding layer in the aforementioned laminated structure. The moisture-proof layer may be formed by a moisture-proof film having a shielding layer and a substrate.

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

The shielding layer constituting the moisture-proof layer or moisture-proof film may be, for example, a metal foil (e.g., aluminum foil), a silicon dioxide evaporated film, a silicon nitride film, a silicon oxide film, or other inorganic film. The shielding layer may be composed of a plurality of inorganic film layers (e.g., a metal foil and a silicon dioxide evaporated film). In addition, the shielding 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 shielding layer is preferably 0.01 to 100 μm, preferably 0.05 to 50 μm, and more preferably 0.05 to 30 μm.

The moisture-proof layer may be a commercially available moisture-proof film. Examples of commercially available products include "KURARISTER CI" manufactured by Kuraray, "Techbarrier HX", "Techbarrier LX" and "Techbarrier L" manufactured by Mitsubishi Resin, "IB-PET-PXB" manufactured by Dai Nippon Printing, "GL, GX Series" manufactured by Toppan Printing, "PET Tsuki AL1N30" manufactured by Toyo Alumi, and "X-BARRIER" manufactured by Mitsubishi Resin.

In a suitable aspect of the present invention, the sealing sheet has a laminated structure that includes a first moisture-proof layer, a first release layer, a resin composition layer, and a second moisture-proof layer in order, and the first release layer is in contact with the resin composition layer. In another suitable aspect of the present invention, the sealing sheet has a laminated structure that includes a first moisture-proof layer, a resin composition layer, a second release layer, and a second moisture-proof layer in order, and the resin composition layer is in contact with the second release layer. In a preferred embodiment of the present invention, the sealing sheet has a laminated structure including a first moisture-proof layer, a first release layer, a resin composition layer, a second release layer, and a second moisture-proof layer in 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.

The release agent forming the release layer may be, for example, a silicone release agent, an alkyd release agent, a fluorine release agent, an olefin release agent, etc. The release layer is preferably formed of a silicone release agent or an alkyd release agent. The thickness of the release layer is preferably 0.05 to 1 μm, more preferably 0.05 to 0.5 μm, and more preferably 0.05 to 0.1 μm.

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 the organic EL device well, the resin composition layer preferably contains an olefin resin and/or an epoxy resin. The olefin resin and the epoxy resin are not particularly limited, and known ones (such as those described in WO2018/181426A1) can be used.

The amount of the olefinic resin is not particularly limited. From the viewpoint of good coating properties, when the olefinic resin is used, the amount is preferably 80% by mass or less relative to the total amount of the resin composition layer (that is, relative to the total amount of non-volatile components of the resin composition), preferably 75% by mass or less, more preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less. On the other hand, from the viewpoint of improving moisture resistance and transparency, the amount of the olefinic resin relative to the entire resin composition layer (i.e., relative to the entire non-volatile components of the resin composition) is preferably 1 mass % or more, more preferably 3 mass % or more, still more preferably 5 mass % or more, more preferably 7 mass % or more, even more preferably 10 mass % or more, particularly preferably 20 mass % or more, and most preferably 30 mass % or more.

The amount of epoxy resin is not particularly limited. When epoxy resin is used, its amount is preferably 10 to 80 mass % relative to the total amount of the resin composition layer (i.e., relative to the total amount of non-volatile components of the resin composition), preferably 15 to 75 mass %, and more preferably 20 to 70 mass %.

From the viewpoint of the moisture barrier property of the sealing sheet of the present invention, the resin composition layer preferably contains semi-sintered hydrotalcite and/or sintered hydrotalcite, and more preferably contains semi-sintered hydrotalcite. Semi-sintered hydrotalcite and sintered hydrotalcite may be used alone or in combination of two or more.

A sealing sheet having a resin composition layer containing semi-sintered hydrotalcite and/or sintered hydrotalcite can exhibit high moisture barrier properties, but semi-sintered hydrotalcite and sintered hydrotalcite are hygroscopic, so the moisture absorption of the resin composition layer increases. However, according to the present invention, the resin composition layer can be fully dried during production, and the obtained sealing sheet can prevent the resin composition layer from absorbing moisture during storage, etc. 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 sintered hydrotalcite and/or sintered hydrotalcite.

Hydrotalcite can be classified into unsintered hydrotalcite, semi-sintered hydrotalcite and sintered hydrotalcite.

Unsintered hydrotalcite is a metal hydroxide having a layered crystal structure, such as represented by natural hydrotalcite (Mg ₆ Al ₂ (OH) ₁₆ CO ₃ ･4H ₂ O), and is composed of layers [Mg _1-x Al _x (OH) ₂ ] ^x+ as a basic skeleton and intermediate layers [(CO ₃ ) _x/2 ･mH ₂ O] ^x- . The unsintered hydrotalcite in the present invention includes the concept of hydrotalcite-like compounds such as synthetic hydrotalcite. Examples of hydrotalcite-like compounds include compounds represented by the following formula (I) and the following formula (II).

[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ ･[(A ^n- ) _x/n ･mH ₂ O] ^x- (I) (wherein, M ²⁺ represents a divalent metal ion such as Mg ²⁺ and Zn ²⁺ , M ³⁺ represents a trivalent metal ion such as Al ³⁺ and Fe ³⁺ , ^An- represents an n-valent anion such as CO ₃ ^2- , Cl ^- , NO ₃ ^- , 0＜x＜1, 0≦m＜1, and n is a positive number) In formula (1), M ²⁺ is preferably Mg ²⁺ , M ³⁺ is preferably Al ³⁺ , and ^An- is preferably CO ₃ ^2- .

M ²⁺ _x Al ₂ (OH) _2x+6-nz (A ^n- ) _z ･mH ₂ O (II) (wherein, M ²⁺ represents a divalent metal ion such as Mg ²⁺ and Zn ²⁺ , ^An- represents an n-valent anion such as CO ₃ ^2- , Cl ^- , NO ₃ ^- , x is a positive number greater than or equal to 2, z is a positive number less than or equal to 2, m is a positive number, and n is a positive number) In formula (II), M ²⁺ is preferably Mg ²⁺ , and ^An- is preferably CO ₃ ^2- .

Semi-sintered hydrotalcite can be obtained by sintering unsintered hydrotalcite, and refers to a metal hydroxide having a lamellar crystal structure in which the amount of interlayer water is reduced or absent. When "interlayer water" is explained using a composition formula, it refers to "H ₂ O" described in the composition formula of the unsintered natural hydrotalcite and hydrotalcite-like compounds mentioned above.

On the other hand, sintered hydrotalcite is a metal oxide obtained by sintering unsintered hydrotalcite or semi-sintered hydrotalcite, in which not only interlayer water but also hydroxyl groups disappear due to condensation dehydration, and has an amorphous structure.

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

The "saturated water absorption rate" in the present invention refers to the mass increase rate relative to the initial mass of 1.5 g of unsintered hydrotalcite, semi-sintered hydrotalcite or sintered hydrotalcite measured on a scale, and then placed in a small environmental tester (SH-222 manufactured by ESPEC) set at 60°C and 90%RH (relative humidity) for 200 hours under atmospheric pressure. It can be obtained by the following formula (i): Saturated water absorption rate (mass %) =100×(mass after moisture absorption - initial mass)/initial mass      (i)

The saturated water absorption of the semi-sintered 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.

In addition, unsintered hydrotalcite, semi-sintered hydrotalcite and sintered hydrotalcite can be distinguished by the thermogravimetric loss rate measured by thermogravimetric analysis. The thermogravimetric loss rate of semi-sintered hydrotalcite at 280°C is less than 15% by mass, and its thermogravimetric loss rate at 380°C is 12% by mass or more. On the other hand, the thermogravimetric loss rate of unsintered hydrotalcite at 280°C is 15% by mass or more, and the thermogravimetric loss rate of sintered hydrotalcite at 380°C is less than 12% by mass.

Thermogravimetric analysis can be performed by using TG/DTA EXSTAR6300 manufactured by Hitachi High-Tech Science Co., Ltd., weighing 5 mg of hydrotalcite into an aluminum sample pan, uncovering it, and heating it from 30°C to 550°C at a heating rate of 10°C/min in an open atmosphere with a nitrogen flow rate of 200 mL/min. The thermogravimetric loss rate can be calculated using the following formula (ii): Thermogravimetric loss rate (mass %) =100×(mass before heating - mass at a given temperature)/mass before heating        (ii)

In addition, unsintered hydrotalcite, semi-sintered hydrotalcite and sintered hydrotalcite can be distinguished by the peaks and relative intensity ratios measured by powder X-ray diffraction. Semi-sintered hydrotalcite shows two separate peaks around 2θ of 8 to 18°, or a peak with a shoulder due to the synthesis of two peaks, and 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 to 1,000. On the other hand, unsintered hydrotalcite has only one peak near 8-18°, or the relative intensity ratio of the diffraction intensity of the peak or shoulder appearing on the low-angle side to the peak or shoulder appearing on the high-angle side is out of the aforementioned range. Sintered hydrotalcite has no characteristic peak in the region of 8°-18°, but has a characteristic peak at 43°. Powder X-ray diffraction measurement was performed by a powder X-ray diffraction device (Empyrean manufactured by PANalytical) with cathode CuKα (1.5405Å), voltage: 45V, current: 40mA, sampling width: 0.0260°, scanning speed; 0.0657°/s, and measurement diffraction angle range (2θ): 5.0131-79.9711°. Peak search can be performed using the peak search function of the software included with the diffraction device under the following conditions: "Minimum significant difference: 0.50, minimum peak tip: 0.01°, maximum peak tip: 1.00°, peak base width: 2.00°, method: minimum value of the second derivative".

The BET specific surface area of semi-sintered hydrotalcite and sintered hydrotalcite is preferably 1-250 ^m2 /g, more preferably 5-200 ^m2 /g. These BET specific surface areas can be calculated by the BET method using a specific surface area measuring device (Macsorb HM Model 1210, manufactured by Mountech) by adsorbing nitrogen on the sample surface and using the BET multi-point method.

The particle size of the semi-sintered hydrotalcite and the sintered hydrotalcite is preferably 1 to 1,000 nm, more preferably 10 to 800 nm. This particle size is the median particle size of the particle size distribution when the particle size distribution is prepared on a volume basis by laser diffraction scattering particle size distribution measurement (JIS Z 8825).

Both the semi-sintered hydrotalcite and the semi-sintered hydrotalcite may be surface treated with a surface treatment agent. The surface treatment agent used for the surface treatment is not particularly limited, and a well-known one (such as that described in WO2018/181426A1) may be used.

The amount of semi-calcined hydrotalcite is not particularly limited. From the viewpoint of the moisture barrier property of the sealing sheet, when semi-calcined hydrotalcite is used, its amount is preferably 3 to 80 mass %, more preferably 5 to 75 mass %, and even more preferably 10 to 70 mass % relative to the total amount of the resin composition layer (i.e., relative to the total amount of non-volatile components of the resin composition).

Examples of semi-sintered hydrotalcites include "DHT-4C" (manufactured by Kyowa Chemical Industry Co., Ltd., particle size: 400 nm), "DHT-4A-2" (manufactured by Kyowa Chemical Industry Co., Ltd., particle size: 400 nm), etc. On the other hand, examples of sintered hydrotalcites include "KW-2200" (manufactured by Kyowa Chemical Industry Co., Ltd., particle size: 400 nm), etc., and examples of unsintered hydrotalcites include "DHT-4A" (manufactured by Kyowa Chemical Industry Co., Ltd., particle size: 400 nm), etc.

The resin composition layer may also contain other components other than the above-mentioned olefinic resin, epoxy resin and semi-sintered hydrotalcite. The other components are not limited, and known components of the resin composition for sealing can be used (for example, those described in WO2018/181426A1).

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

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 produced by, for example, applying a resin composition varnish on the first moisture-proof layer, drying it to form a resin composition layer, and bonding the second moisture-proof layer to the obtained resin composition layer. An adhesive may be used to bond the second moisture-proof layer.

A sealing sheet having a laminated structure comprising a first moisture-proof layer, a first mold release layer, a resin composition layer, a second mold release layer, and a second moisture-proof layer in this order, wherein the first mold release layer is in contact with the resin composition layer, and the resin composition layer is in contact with the second mold release layer, can be obtained by, for example, forming a first mold release layer/a second mold release layer. The first release layer of the laminate having a structure of a first moisture-proof layer is coated with a resin composition varnish and dried to form a resin composition layer, and a laminate having a structure of a second release layer/a second moisture-proof layer is laminated to the obtained resin composition layer in such a manner that the resin composition layer and the second release layer are in contact with each other. A sealing sheet having a laminated structure comprising, in sequence, a first moisture-proof layer, a first release layer, a resin composition layer, and a second moisture-proof layer, in which the first release layer is in contact with the resin composition layer, and a sealing sheet having a laminated structure comprising, in sequence, a first moisture-proof layer, a resin composition layer, a second release layer, and a second moisture-proof layer, in which the resin composition layer is in contact with the second release layer can also be manufactured in the same manner.

The laminate having the structure of release layer/moisture-proof layer can use a commercially available product (e.g., a moisture-proof film with a release layer). Alternatively, the laminate having the structure of release layer/moisture-proof layer can be manufactured by applying a release agent on the moisture-proof layer and drying it.

The resin composition varnish can be produced by mixing the components of the resin composition with an organic solvent using a kneading roll or a rotary mixer. The non-volatile component of the resin composition varnish is preferably 20 to 80% by mass, more preferably 30 to 70% by mass.

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

The present invention is characterized in that the resin composition layer is dried without the second moisture-proof layer, and the second moisture-proof layer is set while the resin composition layer is kept in a low humidity environment from the completion of drying to the setting of the second moisture-proof layer. With this feature, the resin composition layer can be prevented from absorbing moisture during manufacturing, and a sealing sheet containing a sufficiently dried resin composition layer can be manufactured.

The drying of the resin composition layer can be performed simultaneously with the formation of the resin composition layer by drying the resin composition varnish. That is, the resin composition layer can be formed and dried by drying the resin composition varnish in one step, and the second moisture-proof layer can be set while the resin composition layer is kept in a low humidity environment from the end of drying to the setting of the second moisture-proof layer.

The drying of the resin composition layer can 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 can be performed separately, and from the end of drying to the setting of the second moisture-proof layer, the resin composition layer is maintained in a low humidity environment while the second moisture-proof layer is set. Furthermore, when the steps of forming the resin composition layer and drying the resin composition layer are not performed continuously, a protective film is first provided on the resin composition layer to prevent dirt from adhering to the resin composition layer, and the protective film is peeled off before the drying step, or when the protective film has sufficient moisture permeability (the case of a moisture permeable layer described later), drying can be performed directly.

The method of drying the resin composition layer without the second moisture-proof layer includes: (1) drying the resin composition layer with at least one side of the resin composition layer exposed; and (2) drying the resin composition layer with at least one side of the resin composition layer covered with a moisture-permeable layer. From the perspective of drying efficiency, the above-mentioned method (1) is preferred, and from the perspective of inhibiting the adhesion of dirt, etc. to the resin composition layer, the above-mentioned method (2) is preferred. The side of the resin composition layer that is exposed or the side opposite to the side covered by the moisture permeable layer may also be exposed, and may also be covered by another layer (such as the first moisture-proof layer).

Examples of films and sheets used as the moisture permeable layer include porous polyolefin films and low-crystalline polyolefin films. As long as they have a certain moisture permeability, the above-mentioned plastic films can be used, or commercially available films and sheets such as breathable films and moisture permeable sheets can be used. The water vapor permeability of the moisture permeable layer is preferably 10 (g/m ² /24hr), preferably 30 (g/m ² /24hr), more preferably 50 (g/m ² /24hr) or more, particularly preferably 100 (g/m ² /24hr) or more, and most preferably 150 (g/m ² /24hr) or more. The upper limit is not particularly limited, and is, for example, 20,000 (g/m ² /24hr). The thickness of the moisture permeable layer is preferably 1 to 200 μm, more preferably 1 to 75 μm, and more preferably 1 to 25 μm.

The drying of the resin composition layer can be carried out by, for example, heat drying, vacuum drying, or a combination thereof. In addition, the drying of the resin composition layer can be carried out in an atmospheric environment or in an inert gas environment.

In the present invention, it is preferred to dry the resin composition layer by heating, and it is more preferred to dry the resin composition layer 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. Drying conditions such as drying temperature, drying time, vacuum degree, etc. vary depending on the moisture content contained in the resin composition layer, the desired moisture content, the type of dryer, etc.

The drying temperature can be appropriately set generally 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, preferably 3 to 150 minutes, and more preferably 5 to 120 minutes. The drying temperature here refers to the temperature inside the dryer when drying is performed by a dryer, and refers to the temperature of the heating part of the heater when heating and drying is performed by a heater (such as a hot plate).

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, or may be performed 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 ranges.

The degree of vacuum in the case of vacuum drying is not particularly limited as long as it is a pressure 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.

The water concentration (mass fraction) of the dried resin composition layer is as low as possible (ideally 0 ppm), preferably 1500 ppm or less, more preferably 1000 ppm or less, more preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

The resin composition layer can be dried by a known dryer. The dryer can be a batch dryer or a continuous dryer. The dryer can be of a type that allows the object to be dried to come into contact with a high-temperature object, or can be of a type that irradiates the object to be dried with light. Examples of the former include hot air circulation furnaces, heated conveyor rollers, etc. Examples of the latter include near-infrared irradiation furnaces, etc. In addition, drying can be performed by installing a heater (e.g., a hot plate) in a container (e.g., a glove box) that can maintain the internal gas environment at a low humidity environment, and heating the resin composition varnish or the resin composition layer with the heater.

After the second moisture-proof layer is provided, it is substantially difficult to dry the resin composition layer or the drying efficiency is significantly reduced. 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. In addition, for example, when drying is performed by a continuous dryer, the end of the drying operation means when the drying object is out of the continuous dryer. In addition, when drying is performed by a heating machine such as a hot plate, the end of the drying operation means when heating is completed.

The state in which the resin composition layer is kept in a low humidity environment from the completion of drying to the installation of the second moisture-proof layer includes both the state in which the resin composition layer is kept in a low humidity environment outside this period (for example, during drying) and the state in which the resin composition layer is not kept in a low humidity environment outside this period, as long as the resin composition layer is kept in a low humidity environment “from the completion of drying to the installation of the second moisture-proof layer”.

From the end of drying to the installation of the second moisture-proof layer, the resin composition layer is kept in a low humidity environment and the second moisture-proof layer is installed at the same time, including the following embodiments: (i) the resin composition layer is kept in a low humidity environment and then the drying operation is terminated, and the resin composition layer is kept in a low humidity environment and the second moisture-proof layer is installed at the same time; and (ii) the resin composition layer is kept in a low humidity environment and the drying operation is not terminated, and the resin composition layer is dried continuously in a low humidity environment and the second moisture-proof layer is installed at the same time. In the above-mentioned aspect (ii), "when drying is completed" is the same as "when the second moisture-proof layer is provided". Therefore, in the above-mentioned aspect (ii), "from when drying is completed to when the second moisture-proof layer is provided" = "when drying is completed" = "when the second moisture-proof layer is provided".

The following are examples of the method of maintaining the resin composition layer in a low humidity environment and providing a second moisture-proof layer: (a) maintaining the resin composition layer in a low humidity environment and laminating a film containing a second moisture-proof layer or a second moisture-proof layer to the exposed surface of the resin composition layer; (b) maintaining the resin composition layer in a low humidity environment and providing a second moisture-proof layer; (c) while the resin composition layer is kept in a low humidity environment, a pre-driving material layer capable of forming a second moisture-proof layer is formed on the exposed surface of the resin composition layer by coating, etc., and heating, etc. is applied. (d) The resin composition layer is kept in a low humidity environment, and a water-permeable layer on the resin composition layer is formed by coating, etc. to form a precursor layer for forming the second moisture-proof layer, and then the second moisture-proof layer is formed by heating, etc. (e) The resin composition layer is kept in a low humidity environment, and a water-permeable layer on the resin composition layer is formed by coating, etc. to form a precursor layer for forming the second moisture-proof layer, and then the second moisture-proof layer is formed by heating, etc. In a low humidity environment, an inorganic substance forming a shielding layer is simultaneously evaporated on the exposed surface of the resin composition layer to form a second moisture-proof layer. (f) The resin composition layer is kept in a low humidity environment, and an inorganic substance forming a shielding layer is simultaneously evaporated through the water on the resin composition layer to form a second moisture-proof layer. Among these aspects, aspect (a) is preferred in terms of ease of operation.

The above-mentioned aspects (a) to (d) can be implemented by, for example, maintaining the gas environment in the dryer used for drying the resin composition layer or the above-mentioned container (such as a hand-covered work box) at a low humidity environment, and at the same time laminating the above-mentioned second moisture-proof layer, or applying a moisture-proof resin composition and drying it.

The above-mentioned aspects (e) and (f) can be carried out, for example, by using a dryer to dry the resin composition in an equipment in which a dryer, a connecting space with a conveying mechanism and an evaporation device are connected in sequence, and the entire space is maintained under a reduced pressure (preferably, for example, below ^10-7 (Torr)), and then transferring the resin composition to the evaporation device by the conveying mechanism to form a shielding layer by the evaporation device.

From the perspective of dryness, the water concentration (volume fraction) in a low humidity environment is as low as possible (ideally 0 ppm), preferably below 3300 ppm, more preferably below 2,000 ppm, more preferably below 1000 ppm, more preferably below 500 ppm, more preferably below 200 ppm, more preferably below 100 ppm, more preferably below 50 ppm, more preferably below 10 ppm, more preferably below 50 ppm, more preferably below 10 ppm, more preferably below 5 ppm, more preferably below 1 ppm, more preferably below 0.5 ppm, and more preferably below 0.1 ppm.

In the present invention, 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, wherein the surface of the resin composition layer on the side opposite to the side where the first moisture-proof layer exists is exposed. From the completion of drying until the film including the second moisture-proof layer or the second moisture-proof layer is attached, the resin composition layer is kept in a low humidity environment, and it is particularly preferred that the film including the second moisture-proof layer or the second moisture-proof layer is attached to the exposed surface of the resin composition layer.

According to the present invention, a hygroscopic sealing sheet can be manufactured, the resin component layer is fully dried, and the resin component layer can be prevented from hydrating during storage. Therefore, the sealing sheet obtained by the present invention is useful for sealing electronic devices (such as organic EL devices, solar cells, etc.). [Example]

The present invention is described in more detail with the following embodiments, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the above and below purposes. Any of these is included in the technical scope of the present invention.

Films The films used in the examples and comparative examples are described below. PET film with release layer: "E7004" manufactured by Toyobo Co., Ltd. (polyethylene terephthalate (PET) film with release layer, release layer: silicone release layer, thickness of substrate (PET film): 38μm, water vapor permeability: 34g/ ^m2 /24hr) Moisture-proof film 1: "Techbarrier HX" manufactured by Mitsubishi Resin Corporation (PET film with shielding layer, shielding layer: silica vapor-deposited film, thickness of substrate (PET film): 12.5μm, water vapor permeability: 0.5g/ ^m2 /24hr) Moisture-proof film 2: "Verreal" manufactured by Reiko Co., Ltd. UD" (PET film with shielding layer, shielding layer: silicon dioxide evaporated film, thickness of base material (PET film): 50μm, water vapor permeability: 0.01g/ ^m2 /24hr)

Manufacturing Example 1: Manufacturing of a moisture-proof film with a release layer The PET film surface of the PET film with a release layer opposite to the release layer and the substrate (PET film) surface of the moisture-proof film 1 opposite to the shielding layer were bonded with an adhesive to manufacture a moisture-proof film with a release layer having a laminated structure of a PET film with a release layer (release layer/PET film)/adhesive layer/moisture-proof film 1 (PET film/shielding layer) (the 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.

Production Example 2: Production of resin composition varnish In 130 parts by mass of a 60% by mass Swasol solution of a saturated hydrocarbon resin containing a cyclohexane ring ("Arkon P125" manufactured by Arakawa Chemicals), 35 parts by mass of maleic anhydride-modified liquid polyisobutylene ("HV-300M" manufactured by Toho Chemical Industries, 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 Industries, Ltd.) were dispersed using a three-roll mill to obtain a mixture. 200 parts by mass of a 20% by mass Swasol solution of a polypropylene-polybutene copolymer modified with glycidyl methacrylate ("T-YP341" manufactured by Starlight PMC), 0.5 parts by mass of a curing accelerator (2,4,6-tris(dimethylaminomethyl)phenol) and 16 parts by mass of toluene were mixed into the obtained mixture, and the obtained mixture was uniformly dispersed with a high-speed rotary stirrer to obtain an olefin resin composition varnish.

Production Example 3: Production of an undried sealing sheet The resin composition varnish obtained in Production Example 2 was uniformly applied to the release layer 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 in the resin composition layer: about 1 mass %). Next, the resin composition layer of the obtained sealing sheet was brought into contact with the release layer of the moisture-proof film with a release layer obtained in Production Example 1, and the two were bonded together, and the sealing sheet was wound into a roll shape. The roll-shaped sealing sheet is cut into 40 mm x 80 mm to produce an undried sealing sheet. The undried sealing sheet has a laminated structure of 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).

Production Example 4: Production of a moisture-proof film with an adhesive layer A polyolefin adhesive film (thickness 10 μm) was attached to the shielding layer of a moisture-proof film 2 to produce a moisture-proof film with an adhesive layer having a laminated structure of a moisture-proof film 2 (base material/shielding layer)/adhesive layer.

Example 1 A hot plate (150°C) was prepared in a nitrogen-gated work box with a water concentration (volume fraction) set to less than 0.1ppm (the detection limit of the device is 0.1ppm). The undried sealing sheet obtained in Production Example 3 from which the moisture-proof film with a release layer was removed (i.e., a film having a laminated structure of temporary moisture-proof layer (moisture-proof film 1)/adhesive layer/PET film/release layer) was heated on a hot plate with the resin composition layer facing upward for 30 minutes to dry the resin composition layer (hereinafter, the obtained sheet is referred to as "dried unfinished sheet"). After 10 minutes of stopping the heating, the moisture-proof film with a release layer obtained in Manufacturing Example 1 (i.e., a film having a laminated structure of the second moisture-proof layer (moisture-proof film 1)/adhesive layer/PET film/release layer) is directly adhered to the resin composition layer of the unfinished sheet after drying in a hand-operated work box by pressing with a rubber roller heated to 60°C at a pressure of more than 0.3 MPa to produce a sealing sheet. The obtained sealing sheet has a laminated structure of 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).

Example 2 The undried sealing sheet obtained in Production Example 3 from which the moisture-proof film with a release layer was removed (i.e., a sheet having a laminated structure of a temporary moisture-proof layer (moisture-proof film 1)/adhesive layer/PET film/release layer) was dried in a hot air drying oven at a temperature of 150°C with the resin composition layer facing upward. Next, the moisture-proof film with a release layer obtained in Production Example 1 (i.e., a film having a laminated structure of the second moisture-proof layer (moisture-proof film 1)/adhesive layer/PET film/release layer) and the sheet having the dried resin composition layer were transported to a roller press located in a box at 1013 hPa and 25°C with a relative humidity of 6% RH (water concentration (volume fraction) = 1,800 ppm) and a temperature adjusted to 30°C. The moisture-proof film with a release layer obtained in Production Example 1 was bonded to the resin composition layer by a rubber roller heated to 60°C and pressed at a pressure of more than 0.3 MPa to produce a sealing sheet. The obtained sealing sheet has a laminated structure of 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).

Example 3 A hot plate at 150° C. was prepared in a nitrogen-gated work box in which the water concentration (volume fraction) was set to less than 0.1 ppm (the detection limit of the device was 0.1 ppm). After removing the moisture-proof film with release layer (i.e., a film having a laminated structure 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, a PET film with release layer (water vapor permeability: 34 g/ ^m2 /24hr, used as a moisture permeable layer) was laminated to the resin composition surface by pressing with a rubber roller at a pressure of 0.3 MPa or more on a hot plate so as not to generate defects such as bubbles, thereby producing a laminated structure including the PET film with release layer, the resin composition layer, and the moisture-proof film with release layer in this order. More specifically, the obtained sheet has 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). The PET film with the release layer attached (i.e., the film having the laminated structure of PET film/release layer) of the sheet is heated upward for 30 minutes to dry the resin composition layer. After 10 minutes of stopping the heating, directly in the hand-operated working box, the adhesive layer side of the moisture-proof film with an adhesive layer produced in Manufacturing Example 4 (i.e., the film having a laminated structure of the second moisture-proof layer (moisture-proof film 2)/adhesive layer) is laminated to the surface of the moisture-proof film with a temperature of 100 ° C. by pressing with a pressure of more than 0.3 MPa using a rubber roller heated to 60 ° C. A PET film with a release layer is prepared by sequentially preparing a sheet having a laminated structure of a PET film with a release layer, a dried resin composition layer, and a moisture-proof film with a release layer, thereby manufacturing a sealing sheet having a laminated structure of sequentially preparing 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. More specifically, the obtained sealing sheet has a laminated structure of 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).

Comparative Example 1 The unfinished sheet obtained in the same manner as in Example 1 was left in an atmosphere of 25°C and 40%RH (water concentration (volume fraction): 12,500ppm) for 10 minutes with the resin composition exposed. Next, the moisture-proof film with a release layer obtained in Example 1 was attached to the resin composition layer of the sheet by pressing with a rubber roller heated to 60°C at a pressure of 0.3MPa or more, thereby producing a sealing sheet. The obtained sealing sheet has a laminated structure of 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).

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 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).

Comparative Example 3 The "temporary moisture-proof layer (moisture-proof film 1)/adhesive layer/PET film/release layer" portion was not removed from the undried sealing sheet obtained in Production Example 3, and the temporary moisture-proof layer was used as the second moisture-proof layer, and dried under the same drying conditions as in Example 1 (heat drying for 30 minutes on a hot plate (150°C) in a nitrogen-gated work box (water concentration (volume fraction) : less than 0.1 ppm), with the first moisture-proof layer on the hot plate side). The obtained sealing sheet has a laminated structure of 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).

<Evaluation of the resin composition layer of the sealing sheet> The moisture concentration (mass fraction) of the resin composition layer of the sealing sheets obtained in Examples 1 and 2 and Comparative Examples 1 to 3 when they were just manufactured (hereinafter referred to as "moisture concentration (mass fraction) when they were just manufactured") and the moisture concentration (mass fraction) of the resin composition layer after standing for 24 hours in a gas environment of 25°C and 40%RH (hereinafter referred to as "moisture concentration (mass fraction) after standing") were calculated by the following method. The results are shown in Table 1.

In a nitrogen gas chamber with a water concentration (volume fraction) set to less than 0.1ppm (the detection limit of the device is 0.1ppm), the resin composition layer is taken out by a sealing sheet. The resin composition layer is folded into an appropriate size to make a sample, and its weight is measured. Next, while preventing contact with the space containing water, the sample is placed in the vaporization cylinder of the Karl Fischer moisture measuring device ("Trace Moisture Measuring Device CA-200" manufactured by Mitsubishi Chemical Analytech) and heated to 130°C. The water concentration (mass fraction) (ppm) of the sample (i.e., the resin composition layer) is calculated from the total vaporized water content from the start of heating until the water content detected per second becomes less than 0.15 μg/second and the weight of the sample. A water concentration (mass fraction) below 500 ppm is rated as ○, and a water concentration (mass fraction) exceeding 500 ppm is rated as ×.

The sealing sheets obtained in Examples 1 to 3 have sufficiently low water concentrations (mass fractions) both immediately after manufacture and after standing. On the other hand, in Comparative Example 1, in which a film containing a second moisture-proof layer is bonded in a gas environment having a high moisture concentration, the water concentration (mass fraction) immediately after manufacture is high. In addition, in Comparative Example 2, in which a non-moisture-proof layer is used instead of the second moisture-proof layer, the water concentration (mass fraction) after standing is high. In addition, in Comparative Example 3, which is dried with a temporary moisture-proof layer attached, the water concentration (mass fraction) immediately after manufacture is high.

In addition, in Comparative Example 1, it is considered that, when the second moisture-proof layer was formed, the moisture of the moisture-proof film attached to the release layer was transferred to the resin composition layer, and thus the moisture concentration of the resin composition layer after standing increased.

In addition, it is believed that the reason why the moisture concentration of Comparative Example 3 is high when it is just manufactured is that during drying, moisture is transferred from the resin composition layer to the moisture-proof film with a release layer (i.e., 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 is transferred to the resin composition layer again during the static process. [Industrial Applicability]

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

The present invention is based on Japanese Patent Application No. 2019-180593 filed in Japan, the entire contents of which are incorporated herein by reference.

Claims (7)

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 sequence, and comprising heating the laminated structure including the first moisture-proof layer and the resin composition layer, wherein the surface of the resin composition layer on the side opposite to the side where the first moisture-proof layer exists is exposed, to dry the resin composition layer, and from the completion of drying to the installation of the second moisture-proof layer, the resin composition layer is maintained in a low humidity environment while the second moisture-proof layer is installed. The method for producing a sealing sheet according to claim 1, wherein the water vapor permeability of the first moisture-proof layer and the second moisture-proof layer are independently 0-5 (g/m ² /24hr). A method for manufacturing a sealing sheet as claimed in claim 1 or 2, wherein the water concentration (volume fraction) of the low humidity environment is less than 3,300 ppm. The method for manufacturing a sealing sheet as claimed in claim 1 or 2, wherein the drying temperature is 80~220℃. A method for manufacturing a sealing sheet as claimed in claim 1 or 2, wherein the resin composition layer contains semi-sintered hydrotalcite and/or sintered hydrotalcite. A method for manufacturing a sealing sheet as claimed in claim 1 or 2, wherein the sealing sheet is a sealing sheet used for electronic devices. A method for manufacturing a sealing sheet as claimed in claim 6, wherein the electronic device is an organic EL device or a solar cell.