Polyvinyl acetal resin film

Abstract

To provide a polyvinyl acetal resin film which exhibits high initial adhesion to a member to be bonded even at relatively low bonding temperatures, keeps exhibiting high adhesion even under high-temperature and high-humidity environments, has low yellowness and transmits only a small amount of water vapor.SOLUTION: There is provided a polyvinyl acetal resin film, wherein a resin composition constituting the polyvinyl acetal resin film comprises a polyvinyl acetal resin and a silane coupling agent, the content of a plasticizer in the resin composition is 0 to 15 pts.mass based on 100 pts.mass of the polyvinyl acetal resin and the average thickness is 30 to 500 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyvinyl acetal resin film. [Background technology]

[0002] When a space (void) exists between components in an optical device, interfacial reflection occurs, resulting in a deterioration of optical properties. Therefore, interfacial reflection is reduced by filling the space with a material having a refractive index close to that of the components and bonding them together. Known examples of such filler and bonding materials include OCA (Optical Clear Adhesive), a film-like adhesive sheet, and OCR (Optical Clear Resin), a liquid adhesive. Because optical devices are required to maintain their optical performance over a long period of time, such filler and bonding materials are also required to have moisture-sealing properties.

[0003] For example, Patent Document 1 discloses a filling bonding material to be filled between a pair of bonded members in an optical device, which is characterized by containing plasticized polyvinyl acetal and a silane coupling agent having an epoxy group, a (meth)acrylic group, or an amino group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-197314 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the study by the present inventors, it was found that the performance (especially sealing performance) of the filling and joining material in Patent Document 1 is insufficient due to the relatively large amount of plasticizer blended in the filling and joining material. Furthermore, although there is a demand for a lower joining temperature from the viewpoints of adverse effects on the joined members, environmental protection, and manufacturing costs, Patent Document 1 does not disclose the joining temperature with the joined members. An object of the present invention is to provide a polyvinyl acetal resin film that exhibits high initial adhesiveness to members to be joined even at a relatively low joining temperature, maintains high adhesiveness even when placed in a high-temperature, high-humidity environment, has low yellowness, and transmits only a small amount of water vapor. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by a polyvinyl acetal resin film comprising a polyvinyl acetal resin and a silane coupling agent, having a plasticizer content of a specific value or less, and having a specific average thickness, and have thereby arrived at the present invention. That is, the present invention includes the following preferred embodiments. [1] A polyvinyl acetal resin film, the resin composition constituting the polyvinyl acetal resin film comprises a polyvinyl acetal resin and a silane coupling agent; the content of the plasticizer in the resin composition is 0 to 15 parts by mass relative to 100 parts by mass of the polyvinyl acetal resin; A polyvinyl acetal resin film having an average thickness of 30 to 500 μm. [2] The polyvinyl acetal resin film according to [1], wherein the polyvinyl acetal resin has a hydroxyl group content of 10 to 80 mol %. [3] The polyvinyl acetal resin film according to [1] or [2], wherein the polyvinyl acetal resin is a polyvinyl butyral resin. [4] The polyvinyl acetal resin film according to any one of [1] to [3], wherein the silane coupling agent has at least one functional group selected from the group consisting of an epoxy group, a (meth)acrylic group, and an isocyanate group. [5] The polyvinyl acetal resin film according to any one of [1] to [4], wherein the content of the silane coupling agent in the resin composition is 0.001 to 8.0 parts by mass per 100 parts by mass of the polyvinyl acetal resin. [6] The polyvinyl acetal resin film according to any one of [1] to [5], wherein at least one surface has a ten-point average roughness Rz of 2 to 7 μm as measured in accordance with JIS B0601-1994. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a polyvinyl acetal resin film that exhibits high initial adhesiveness to members to be joined even at a relatively low joining temperature, maintains high adhesiveness even when placed in a high-temperature and high-humidity environment, has low yellowness, and transmits only a small amount of water vapor. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail, but it is not intended that the present invention be limited to the following embodiments.

[0009] [Polyvinyl acetal resin film] The polyvinyl acetal resin film of the present invention is characterized in that it contains a polyvinyl acetal resin and a silane coupling agent, the content of the plasticizer in the polyvinyl acetal resin film is 0 to 15 parts by mass per 100 parts by mass of the polyvinyl acetal resin, and the average thickness of the polyvinyl acetal resin film is 30 to 500 μm. Also, the polyvinyl acetal resin film of the present invention is characterized in that it is made of a thermoplastic resin composition. The present inventors have found that by using a polyvinyl acetal resin in a film, the polyvinyl acetal resin repels or absorbs moisture, thereby preventing moisture from penetrating from the outside of a component to which the polyvinyl acetal resin film is bonded (e.g., the atmosphere outside an optical device) to the inside (e.g., the interior of an optical device). They have also found that this moisture penetration prevention is particularly effective when the polyvinyl acetal resin film has a specific average thickness and contains a specific amount of plasticizer or less. Therefore, the polyvinyl acetal resin film can maintain high adhesiveness even in a high-temperature, high-humidity environment. The present inventors have also found that when the average thickness of the polyvinyl acetal resin film is a specific value or less, the polyvinyl acetal resin film has a desired low yellowness. The inventors further discovered that, unexpectedly, the use of a silane coupling agent in a polyvinyl acetal resin film can exhibit improved initial adhesion to the bonded components, such as components contained in optical devices (e.g., resin layers, glass, barrier layers such as aluminum oxide, metal or indium tin oxide (ITO) electrode materials, or optical functional layers (e.g., light-emitting layers, light-absorbing layers, light-reflecting layers, wavelength conversion layers), etc.), even at relatively low bonding temperatures of 90 to 150°C, and that this high adhesion can be maintained even in high-temperature, high-humidity environments. The reason for this is unclear, and while not intended to be limiting, the following mechanism of action (reason) is presumed. When a polyvinyl acetal resin film does not contain a silane coupling agent, hydrogen bonds are formed at the interface when the polyvinyl acetal resin film is laminated to the bonded components. When a polyvinyl acetal resin film contains a silane coupling agent, covalent bonds are formed in addition to the hydrogen bonds, resulting in high initial adhesion. Furthermore, when moisture penetrates the interface in a high-temperature, high-humidity environment, the adhesion between the polyvinyl acetal resin film and the bonded member is maintained mainly by covalent bonds, and therefore the formation of covalent bonds has a significant effect on the adhesion. However, it is thought that sufficiently high adhesion (due to the covalent bonds) can be maintained even if the bonding temperature is lowered as long as it is above the temperature at which covalent bonds are formed.From the viewpoints of the adverse effects that high bonding temperatures can have on the members to be bonded, environmental protection, and manufacturing costs, it is a significant advantage to be able to obtain high initial adhesion even at low bonding temperatures and adhesion that can be maintained even in high-temperature, high-humidity environments. On the other hand, when a polyvinyl acetal resin film and a member to be bonded are bonded at a temperature of, for example, 80° C., it is difficult to obtain the desired initial adhesiveness. Due to the above-mentioned characteristics, the polyvinyl acetal resin film of the present invention can exhibit improved initial adhesion to the members to be joined and high adhesion under high temperature and high humidity conditions by thermocompression bonding to the members to be joined, without the need for an adhesive or pressure-sensitive adhesive at the interface with the members to be joined.Furthermore, when multiple members to be joined are joined with the polyvinyl acetal resin film of the present invention, if spaces exist between the members to be joined, the spaces can be filled.

[0010] <Polyvinyl acetal resin> The polyvinyl acetal resin contained in the polyvinyl acetal resin film may be a resin obtained by acetalizing a polyvinyl alcohol resin through a reaction with an aldehyde. The polyvinyl acetal resin film may contain one polyvinyl acetal resin, or two or more polyvinyl acetal resins that differ in one or more of the viscosity-average degree of polymerization, the degree of acetalization, the amount of acetyl groups, the amount of hydroxyl groups, the ethylene content, the type of aldehyde used for acetalization, and the chain length.

[0011] The polyvinyl alcohol resin used as a raw material for preparing the polyvinyl acetal resin is not particularly limited. Polyvinyl alcohol resins are typically obtained by polymerizing a vinyl ester monomer and saponifying the resulting polyvinyl ester. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate, which can be used alone or in combination of two or more. From the standpoint of availability, vinyl acetate is preferred.

[0012] Other monomers may be copolymerized with the vinyl ester monomer as long as the physical properties of the polyvinyl acetal resin film are not significantly impaired. Examples of such monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; (meth)acrylic acid or its salts; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate; (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, diacetone acrylamide, (meth)acrylamidopropanesulfonic acid, and the like. Examples of suitable monomers include (meth)acrylamide derivatives such as (meth)acrylamidopropyldimethylamine or its salts or quaternary salts; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; (meth)acrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts, esters, and anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; and carboxylic acid isopropenyl esters such as isopropenyl acetate. The content of these monomers, expressed as the number of the monomer units relative to the number of vinyl ester monomer units, is typically less than 20 mol%, preferably less than 10 mol%. In this specification, "(meth)acrylic acid" is a general term for methacrylic acid and acrylic acid, and refers to either or both of methacrylic acid and acrylic acid.

[0013] As a method for polymerizing a vinyl ester monomer or a method for copolymerizing a vinyl ester monomer with the other monomer, a conventionally known method such as solution polymerization, bulk polymerization, suspension polymerization, or emulsion polymerization can be applied. A polymerization initiator is usually used, and an azo-based initiator, peroxide-based initiator, or redox-based initiator is appropriately selected depending on the polymerization method. The polymerization may also be carried out in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, or other chain transfer agent.

[0014] The saponification reaction of the polyvinyl ester obtained by polymerization can be carried out by conventional alcoholysis or hydrolysis using an alkali catalyst or an acid catalyst. Among these, the saponification reaction using methanol as a solvent and caustic soda (NaOH) as a catalyst is simple. The degree of saponification is usually 90 mol% or more, preferably 95 mol% or more, more preferably 98 mol% or more, and may be 100 mol%. The degree of saponification can be measured according to JIS K 6726 "Testing Methods for Polyvinyl Alcohol."

[0015] A polyvinyl acetal resin can be obtained by reacting a polyvinyl alcohol resin with an aldehyde to form an acetal.

[0016] Examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, and benzaldehyde. Aldehydes having 1 to 12 carbon atoms are preferred, saturated aliphatic aldehydes having 1 to 6 carbon atoms are more preferred, and saturated aliphatic aldehydes having 1 to 4 carbon atoms are even more preferred. Butyraldehyde is particularly preferred from the viewpoint of the mechanical properties of the polyvinyl acetal resin film. Therefore, the polyvinyl acetal resin is preferably a polyvinyl butyral resin. Aldehydes may be used alone or in combination of two or more. Furthermore, compounds having multiple aldehyde groups in the molecule or aldehydes having functional groups other than aldehyde groups may be used in combination in an amount of up to 20% by mass of the total mass of all aldehydes.

[0017] The acetalization method is not particularly limited. The solvent used in the acetalization reaction is not particularly limited, and for example, water, ethanol, isopropanol, or a mixture thereof can be used. The catalyst used in the acetalization reaction is also not particularly limited, and any of organic acids such as acetic acid and paratoluenesulfonic acid, and inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, and carbonic acid can be used. From the viewpoint of ease of washing the polyvinyl acetal resin after the reaction, the use of an inorganic acid is preferred.

[0018] The hydroxyl group content (amount of vinyl alcohol units) of the polyvinyl acetal resin is preferably 10 to 80 mol %, more preferably 12 to 70 mol %, even more preferably 14 to 60 mol %, and particularly preferably 16 to 50 mol %, based on a repeating unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol resin, which is the raw material for producing the polyvinyl acetal resin (e.g., a vinyl alcohol unit, a vinyl acetate unit, an ethylene unit, etc.). When the hydroxyl group content is within this range, the polyvinyl acetal resin film tends to have a good balance between moisture absorption and barrier properties while maintaining electrical insulation. The hydroxyl group content of the polyvinyl acetal resin can be adjusted within this range by adjusting the amount of aldehyde used during acetalization of the polyvinyl alcohol resin. When the polyvinyl acetal resin film contains two or more different polyvinyl acetal resins, it is preferable that the hydroxyl group content of at least one, preferably more than one, and more preferably all, of the polyvinyl acetal resins is within the above range.

[0019] The acetyl group content (amount of vinyl acetate units) of the polyvinyl acetal resin is preferably 0.1 to 30.0 mol %, more preferably 0.2 to 20.0 mol %, even more preferably 0.3 to 10.0 mol %, particularly preferably 0.4 to 8.0 mol %, even more particularly preferably 0.5 to 6.0 mol %, and even more particularly preferably 0.4 to 6.0 mol %, based on a repeating unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol resin used as the raw material for producing the polyvinyl acetal resin. An acetyl group content within this range tends to inhibit corrosion of bonded components (e.g., components in optical devices) due to acetic acid generated from the polyvinyl acetal resin film and / or shorten the time required for saponification, thereby increasing mass productivity. The acetyl group content can be adjusted within this range by appropriately adjusting the degree of saponification of the polyvinyl alcohol resin. When the polyvinyl acetal resin film contains two or more different polyvinyl acetal resins, it is preferable that the acetyl group amount of at least one, preferably more than one, and more preferably all of the polyvinyl acetal resins is within the above range.

[0020] The degree of acetalization of the polyvinyl acetal resin is preferably 20 to 90 mol%, more preferably 30 to 88 mol%, even more preferably 40 to 86 mol%, and particularly preferably 50 to 84 mol%. The degree of acetalization is the amount of the above-mentioned units forming the acetal, based on one repeating unit, where one repeating unit is a unit consisting of two carbon atoms in the main chain of the polyvinyl alcohol resin, which is the raw material for producing the polyvinyl acetal resin. When the degree of acetalization is within the above range, the polyvinyl acetal resin film tends to have a good balance between moisture absorption and barrier properties while maintaining electrical insulation. The degree of acetalization of the polyvinyl acetal resin can be adjusted within the above range by appropriately adjusting the amount of aldehyde used when acetalizing the polyvinyl alcohol resin. When the polyvinyl acetal resin film contains two or more different polyvinyl acetal resins, it is preferable that the degree of acetalization of at least one, preferably more than one, and more preferably all, of the polyvinyl acetal resins is within the above range.

[0021] The amount of units constituting the polyvinyl acetal resin (for example, vinyl alcohol units, vinyl acetate units, units forming acetal, etc.) can be measured according to JIS K6728 "Testing Method for Polyvinyl Butyral" or by nuclear magnetic resonance (NMR) spectroscopy.

[0022] The weight-average molecular weight of the polyvinyl acetal resin is preferably 10,000 to 60,000, more preferably 15,000 to 55,000, and particularly preferably 20,000 to 50,000. When the weight-average molecular weight of the polyvinyl acetal resin is within this range, the strength of the polyvinyl acetal resin film tends to be high and the moldability tends to be excellent. The weight-average molecular weight of the polyvinyl acetal resin can be adjusted within this range by adjusting the viscosity-average polymerization degree of the polyvinyl alcohol resin, which is the raw material for the polyvinyl acetal resin, or by combining polyvinyl alcohol resins with different viscosity-average polymerization degrees to prepare the polyvinyl acetal resin.

[0023] The weight average molecular weight can be determined by gel permeation chromatography (GPC) using polystyrene of known molecular weight as a standard.

[0024] The content of the polyvinyl acetal resin in the polyvinyl acetal resin film is preferably 83 to 99.99 mass %, more preferably 88 to 99 mass %, and even more preferably 93 to 99 mass %, based on the total mass of the polyvinyl acetal resin film.

[0025] <Silane coupling agent> The polyvinyl acetal resin film of the present invention contains a silane coupling agent in addition to the polyvinyl acetal resin. As described above, by including a silane coupling agent (preferably a silane coupling agent having a functional group), the polyvinyl acetal resin film exhibits high initial adhesion to components included in optical devices even at relatively low bonding temperatures of 90 to 150°C, and maintains high adhesion even in high-temperature, high-humidity environments. The inventors have further discovered that when the silane coupling agent has at least one functional group selected from the group consisting of an epoxy group, a (meth)acrylic group, and an isocyanate group, high initial adhesion to components included in optical devices can be exhibited even at lower bonding temperatures (e.g., 90 to 140°C or 90 to less than 130°C), and high adhesion can be maintained even in high-temperature, high-humidity environments. The functional groups of the silane coupling agent are preferably epoxy groups and / or isocyanate groups, more preferably epoxy groups, from the viewpoint of achieving high adhesion even at lower bonding temperatures and maintaining high adhesion even in high-temperature, high-humidity environments; and are preferably epoxy groups and / or (meth)acrylic groups, more preferably epoxy groups, from the viewpoint of the yellowness of the polyvinyl acetal resin film. In one embodiment of the present invention, from the viewpoints of uniformity of a polyvinyl acetal resin film containing a polyvinyl acetal resin and a silane coupling agent, and adhesion of the polyvinyl acetal resin film to a member to be joined, it is preferable that the silane coupling agent does not have an amino group. In another embodiment of the present invention, from the viewpoint of the adhesiveness between the polyvinyl acetal resin film and the member to be joined, the silane coupling agent only needs to be present on at least the surface of the polyvinyl acetal resin film that comes into contact with the member to be joined, and does not need to be uniformly dispersed within the polyvinyl acetal resin film.

[0026] The silane coupling agent may further have a hydrolyzable group in addition to the above functional group. The hydrolyzable group is not particularly limited, and examples thereof include a chloro group, a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. The silane coupling agent may have one type of these hydrolyzable groups or a combination of two or more types. The number of hydrolyzable groups per molecule of the silane coupling agent is not particularly limited, but is preferably 2 or 3 from the viewpoint of adhesiveness to members included in optical devices.

[0027] Examples of silane coupling agents having an epoxy group include, but are not limited to, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltrimethoxysilane.

[0028] Examples of silane coupling agents having a (meth)acrylic group include, but are not limited to, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropyltrimethoxysilane.

[0029] Examples of silane coupling agents having an isocyanate group include, but are not limited to, 3-isocyanatepropyltriethoxysilane, an organosilane commercially available from Shin-Etsu Chemical Co., Ltd. under the trade name X-12-1159L.

[0030] The content of the silane coupling agent in the polyvinyl acetal resin film is preferably 0.001 to 8.0 parts by mass relative to 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film. When the silane coupling agent is mixed throughout the polyvinyl acetal resin film, the content of the silane coupling agent in the polyvinyl acetal resin film is preferably 0.001 to 8.0 parts by mass, more preferably 0.05 to 6.0 parts by mass, even more preferably 0.10 to 4.0 parts by mass, even more preferably 0.15 to 2.0 parts by mass, even more preferably 0.20 to 1.75 parts by mass, and even more preferably 0.25 to 1.5 parts by mass relative to 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film. When a silane coupling agent is present only on the surface of a polyvinyl acetal resin film that will come into contact with a non-bonded member (for example, when a silane coupling agent is applied to the surface of a polyvinyl acetal resin film that does not contain a silane coupling agent and that will come into contact with a non-bonded member), the content of the silane coupling agent in the polyvinyl acetal resin film is preferably 0.001 to 8.0 parts by mass, more preferably 0.005 to 5.0 parts by mass, even more preferably 0.010 to 3.0 parts by mass, even more preferably 0.015 to 2.0 parts by mass, and even more preferably 0.020 to 1.0 parts by mass, per 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film. When the content of the silane coupling agent is within this range, improved adhesion (initial adhesion and high adhesion maintained even under high-temperature and high-humidity environments) to components contained in optical devices can be achieved. When the content of the silane coupling agent is equal to or greater than the upper limit, the polyvinyl acetal resin film becomes hard, which can reduce the possibility of deterioration in moldability and damage to the members to be joined. In another embodiment of the present invention, when the silane coupling agent is present only near the surface of the polyvinyl acetal resin film that comes into contact with the member to be joined, the amount of silane coupling agent can be calculated on the assumption that the silane coupling agent present on the surface is uniformly dispersed in the polyvinyl acetal resin film.

[0031] <Plasticizer> The content of the plasticizer in the polyvinyl acetal resin film of the present invention is 0 to 15 parts by mass, preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, even more preferably 0 to less than 5 parts by mass, and even more preferably 0 to 3 parts by mass, per 100 parts by mass of the polyvinyl acetal resin. When the plasticizer content is within this range, high adhesion can be maintained even in a high-temperature, high-humidity environment, and the polyvinyl acetal resin film tends to have improved sealing performance (desired water vapor permeability). Furthermore, when the plasticizer content is within this range, a flexible laminate produced by laminating a barrier layer on at least one side of the polyvinyl acetal resin film can have a lower water vapor permeability.

[0032] When the polyvinyl acetal resin film contains a plasticizer, the plasticizer is preferably one or more compounds selected from the following group: Esters of polyhydric aliphatic or aromatic acids, such as dialkyl adipates (e.g., dihexyl adipate, di-2-ethylbutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, hexylcyclohexyl adipate, diheptyl adipate, dinonyl adipate, diisononyl adipate, heptylnonyl adipate); esters of adipic acid with alcohols or alcohols containing ether compounds (e.g., di(butoxyethyl) adipate, di(butoxyethoxyethyl) adipate); dialkyl sebacates (e.g., dibutyl sebacate); esters of sebacic acid with alicyclic or alcohols containing ether compounds; esters of phthalic acid (e.g., butyl benzyl phthalate, bis-2-butoxyethyl phthalate); and esters of alicyclic polyhydric carboxylic acids with aliphatic alcohols (e.g., 1,2-cyclohexanedicarboxylic acid diisononyl ester). Esters or ethers of polyhydric aliphatic or aromatic alcohols or oligoether glycols having one or more aliphatic or aromatic substituents. Examples include esters of glycerin, diglycol, triglycol, tetraglycol, etc. with linear or branched aliphatic or alicyclic carboxylic acids. Specific examples include diethylene glycol bis-(2-ethylhexanoate), triethylene glycol bis-(2-ethylhexanoate) (hereinafter sometimes referred to as "3G8"), triethylene glycol bis-(2-ethylbutanoate), tetraethylene glycol bis-(2-ethylhexanoate), tetraethylene glycol bis-n-heptanoate, triethylene glycol bis-n-heptanoate, triethylene glycol bis-n-hexanoate, tetraethylene glycol dimethyl ether, and dipropylene glycol dibenzoate. Phosphate esters of aliphatic or aromatic alcohols, e.g., tris(2-ethylhexyl) Examples of suitable phosphates include diphenyl-2-ethylhexyl phosphate, triethyl phosphate, diphenyl-2-ethylhexyl phosphate, and tricresyl phosphate. Esters of citric, succinic and / or fumaric acid.

[0033] <Optional ingredients> The polyvinyl acetal resin film may further contain additives such as antioxidants, ultraviolet absorbers, light stabilizers, antiblocking agents, heat-shielding materials (e.g., inorganic heat-shielding fine particles or organic heat-shielding materials having infrared absorbing properties), adhesion modifiers, tackifying resins, emulsifiers, softeners, surfactants, colorants, etc. When the polyvinyl acetal resin film further contains these optional additives, the content thereof may be appropriately selected depending on the type of additive.

[0034] Examples of antioxidants include primary antioxidants such as hindered phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, and hydroxylamine-based antioxidants, as well as secondary antioxidants such as sulfur-based oxidants and phosphorus-based oxidants. These antioxidants can be used alone or in combination of two or more. When the polyvinyl acetal resin film contains an antioxidant, its content is not particularly limited, but is typically 0.01 to 1.5 parts by mass, preferably 0.02 to 1.0 part by mass, and more preferably 0.03 to 0.5 parts by mass per 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film.

[0035] As the hindered phenol-based antioxidant, a phenol-based antioxidant having a hindered phenol structure or a one-side hindered phenol structure in the molecule is preferred from the viewpoint of light resistance. Such hindered phenol-based antioxidants are known. Examples of commercially available hindered phenol antioxidants include the SONGNOX (registered trademark) series manufactured by SONGWON, the SUMILIZER (registered trademark) series manufactured by Sumitomo Chemical Co., Ltd., the IRGANOX (registered trademark) series manufactured by BASF Japan Ltd., the MARK AO series manufactured by ADEKA Corporation, and the NOCRAC series manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0036] Examples of UV absorbers include benzotriazole-based UV absorbers, hydroxyphenyltriazine-based UV absorbers, salicylic acid ester-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, cyanoacrylate-based UV absorbers, and nickel-based UV absorbers. These UV absorbers can be used alone or in combination of two or more. When the polyvinyl acetal resin film contains a UV absorber, its content is not particularly limited, but is typically 0.01 to 3.0 parts by mass, preferably 0.02 to 2.5 parts by mass, and more preferably 0.03 to 2.0 parts by mass, per 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film.

[0037] From the viewpoint of UV absorption and photostability, and of being able to bring about excellent optical properties and transparency, UV absorbers selected from the group consisting of benzotriazole-based UV absorbers, hydroxyphenyltriazine-based UV absorbers, and benzophenone-based UV absorbers are preferred, and benzotriazole-based UV absorbers are more preferred. In particular, benzotriazole-based UV absorbers in which a phenyl group having a group with 6 or more carbon atoms and a hydroxyl group as a substituent is bonded to the nitrogen atom constituting the benzotriazole ring are preferred. Such benzotriazole-based UV absorbers are known. Examples of commercially available benzotriazole-based ultraviolet absorbers include the TINUVIN (registered trademark) series manufactured by BASF Japan Ltd., the Sumisorb (registered trademark) series manufactured by Sumitomo Chemical Co., Ltd., and the ADK STAB series manufactured by ADEKA Corporation. Examples include:

[0038] Examples of the adhesion modifier include alkali metal salts, alkaline earth metal salts, and magnesium salts. The adhesion modifier can be used alone or in combination of two or more. When the polyvinyl acetal resin film contains an adhesion modifier, its content is not particularly limited, but is usually 0.01 to 0.25 parts by mass, preferably 0.02 to 0.20 parts by mass, and more preferably 0.03 to 0.15 parts by mass per 100 parts by mass of the polyvinyl acetal resin contained in the polyvinyl acetal resin film.

[0039] As the adhesion modifier, for example, an alkali metal salt of an organic acid having 2 to 16 carbon atoms, an alkaline earth metal salt of an organic acid having 2 to 16 carbon atoms, and / or a magnesium salt of an organic acid having 2 to 16 carbon atoms can be used. More specific examples include potassium acetate, potassium propionate, potassium 2-ethylbutanoate, potassium 2-ethylhexanoate, magnesium acetate, magnesium propionate, magnesium 2-ethylbutyrate, and magnesium 2-ethylhexanoate.

[0040] The average thickness of the polyvinyl acetal resin film is 30 μm or more. If the average thickness of the polyvinyl acetal resin film is less than 30 μm, the polyvinyl acetal resin film can absorb only a small amount of water, making it difficult for the polyvinyl acetal resin film to have the desired water vapor permeability (permeate only a small amount of water vapor), maintain sufficient adhesiveness under high temperature and high humidity conditions, and sufficiently prevent moisture from penetrating from the outside to the inside of a member to which the polyvinyl acetal resin film is bonded. The average thickness is preferably 40 μm or more, more preferably 50 μm or more, even more preferably 60 μm or more, and particularly preferably 70 μm or more. In addition, the average thickness of the polyvinyl acetal resin film is 500 μm or less, preferably 450 μm or less, more preferably 400 μm or less, even more preferably 350 μm or less, and particularly preferably 300 μm or less, from the viewpoints of yellowness, transparency, lightness, and flexibility (flexibility) of the polyvinyl acetal resin film. The average thickness of the polyvinyl acetal resin film is 30 to 500 μm, preferably 40 to 450 μm, more preferably 50 to 400 μm, still more preferably 60 to 350 μm, and particularly preferably 70 to 300 μm. The thickness can be measured with a thickness meter. The average thickness of the polyvinyl acetal resin film and the flexible laminate described below can be determined by measuring the thickness at any three points with a thickness meter and calculating the average value.

[0041] The ten-point mean roughness Rz of at least one surface, preferably both surfaces, of the polyvinyl acetal resin film, measured in accordance with JIS B0601-1994, is preferably 2 to 7 μm, more preferably 2.5 to 6.5 μm, even more preferably 3.0 to 6.0 μm, even more preferably 3.5 to 5.5 μm, and even more preferably 3.5 to 5.0 μm. When the ten-point mean roughness Rz is within this range, air at the interface between the polyvinyl acetal resin film and the bonded member can be easily removed, achieving high adhesion to members included in optical devices even at relatively low bonding temperatures, and maintaining high adhesion even in high-temperature, high-humidity environments. The ten-point mean roughness Rz can be adjusted within this range by selecting an embossing roll as the surface that comes into contact with the polyvinyl acetal resin film when producing the polyvinyl acetal resin film. For example, when producing a polyvinyl acetal resin film by pressing it with a compression molding machine, an embossed Teflon® sheet or the like can be used as the material for the pressing surface. The ten-point average roughness Rz is measured using a surface roughness meter or a laser microscope in accordance with JIS B0601-1994.

[0042] At least one surface of the polyvinyl acetal resin film may be embossed in a manner different from that which provides the above ten-point average roughness Rz, thereby achieving better degassing properties at the interface between the embossed polyvinyl acetal resin film and the member to be joined.

[0043] The polyvinyl acetal resin film of the present invention may have a light-shielding portion or a light-scattering portion in at least a part thereof. The polyvinyl acetal resin film of the present invention may also be provided with a protective sheet covering the periphery.

[0044] [Manufacturing method of polyvinyl acetal resin film] The method for producing a polyvinyl acetal resin film is not particularly limited. For example, a polyvinyl acetal resin, a silane coupling agent, and optionally a plasticizer, additives, and a solvent are mixed to prepare a resin composition, and the resin composition is formed into a film by a known film-forming method such as extrusion, calendaring, pressing, casting, or inflation. A polyvinyl acetal resin film can also be produced by press-molding pellets of the resin composition. The produced polyvinyl acetal resin film may be stretch-molded.

[0045] When preparing the resin composition, it is preferable to heat it to, for example, 160 to 190° C., preferably 170 to 185° C. The present inventors have discovered that this heating not only uniformly mixes the resin composition, but also unexpectedly chemically bonds functional groups of the silane coupling agent with some of the hydroxyl groups of the polyvinyl acetal resin, resulting in a dehydration reaction between the silanol groups of the silane coupling agent and the hydroxyl groups of the members to be joined, even at a relatively low joining temperature, thereby achieving higher initial adhesion and maintaining higher adhesion even in a high-temperature, high-humidity environment. Therefore, in a preferred embodiment, the polyvinyl acetal resin film can be produced by a method comprising mixing a polyvinyl acetal resin, a silane coupling agent, and optionally a plasticizer, optionally an additive, and optionally a solvent described below under heating at 160 to 190°C to obtain a resin composition.

[0046] Among known film-forming methods, it is preferable to employ a pressing method. The temperature of the resin composition during pressing is preferably 160 to 190°C, more preferably 170 to 185°C. The pressing pressure is usually 3 to 12 MPa, preferably 5 to 10 MPa, and the pressing time is usually 1 to 5 minutes, preferably 2 to 4 minutes.

[0047] Furthermore, a polyvinyl acetal resin film can also be formed on a member to be joined (for example, a barrier layer or glass) by coating or painting using various types of coating or painting equipment. When forming a polyvinyl acetal resin film by coating or painting, the polyvinyl acetal resin, the silane coupling agent, and optionally components such as a plasticizer and additives may be dissolved or dispersed in a solvent and then coated and dried, or a solid resin composition comprising the above components may be coated as is and melted. The solvent is preferably one that can uniformly dissolve or disperse the polyvinyl acetal resin, silane coupling agent, and optional plasticizer and additives, and can be removed from the coating film by drying after application or coating. Examples of such solvents include water, methanol, ethanol, isopropanol, ethyl acetate, and mixtures of two or more thereof.

[0048] When the polyvinyl acetal resin film is embossed to form a concave-convex shape, the processing temperature is preferably 60 to 150° C., more preferably 80 to 140° C. The processing pressure is preferably 0.1 to 15 MPa, more preferably 0.3 to 8 MPa. The film transport speed during embossing is preferably 5 m / min or more, more preferably 10 to 30 m / min.

[0049] [Flexible laminate] The present invention also relates to a flexible laminate comprising the above-mentioned polyvinyl acetal resin film and a barrier layer, wherein the barrier layer is directly laminated on one or both sides of the polyvinyl acetal resin film. In this specification, flexibility means the property of being able to flex flexibly when an external force is applied.

[0050] By including the polyvinyl acetal resin film and a barrier layer, particularly by including the polyvinyl acetal resin film described above as a preferred embodiment and a barrier layer described below as a preferred embodiment, the water vapor permeability of the flexible laminate can be adjusted. The water vapor permeability after leaving the flexible laminate at a temperature of 85°C and a humidity of 85% RH for 100 hours can be evaluated by the method described in the Examples below. This evaluation method utilizes the principle that cobalt chloride paper changes color from dark blue to red when it absorbs water from a dry state. Specifically, the change in color of the cobalt chloride paper before and after leaving it is expressed as a color difference D based on Euclidean distance using the following formula: TIFF2025144964000001.tif6150 [In the above formula, R0, G0, and B0 are the color values ​​of the red (R0), green (G0), and blue (B0) components of the cobalt chloride paper, which were extracted from the JPEG image of a sample prepared by thermally laminating a glass plate, cobalt chloride paper, polyvinyl acetal resin film, and barrier layer in that order, photographed from the glass plate side with a digital camera using the image analysis software ImageJ (Wayne Rasband). R 100 , G 100 and B 100 The sample was left at a temperature of 85°C and a humidity of 85%RH for 100 hours, and then photographed from the glass plate side with a digital camera. The red (R) of the cobalt chloride paper was extracted from the JPEG image in the same way. 100 ) Green (G 100 ) · Blue (B 100 ) component color values] The smaller the color difference D, the lower the water vapor permeation rate of the flexible laminate (lower water vapor permeability). The color difference D is preferably 70 or less, more preferably 65 or less, more preferably 60 or less, more preferably 55 or less, more preferably 50 or less, and even more preferably 45 or less. When the color difference D is equal to or less than the upper limit, the water vapor permeation rate of the flexible laminate is low and the sealing properties of the flexible laminate are high. The smaller the color difference D, the better, so the lower limit of the color difference D is not particularly limited, but is usually 10 or more or 20 or more.

[0051] <Barrier layer> The barrier layer is a layer capable of suppressing the penetration of moisture, and is not particularly limited as long as it is a layer capable of suppressing the penetration of moisture. The barrier layer is, for example, a film formed by laminating a single-layer or multi-layer thermoplastic resin film and a single-layer or multi-layer inorganic material layer with or without an adhesive layer therebetween. When the barrier layer includes a multilayer thermoplastic resin film, the two or more thermoplastic resin films may be the same or different. When the barrier layer includes a multilayer inorganic material layer, the two or more inorganic material layers may be the same or different. When the barrier layer includes a multilayer adhesive layer, the two or more adhesive layers may be the same or different. Furthermore, when barrier layers are laminated on both sides of the polyvinyl acetal resin film, the two barrier layers may be the same or different.

[0052] Examples of various thermoplastic resins include polyolefin resins such as polyethylene resins and polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), poly(meth)acrylic resins, polycarbonate resins, polyvinyl alcohol resins, saponified ethylene-vinyl ester copolymers, polyamide resins such as various nylons, polyurethane resins, acetal resins, cellulose resins, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polyethylene furanoate, polyether ether ketone, polyaryl ether ketone, polyacrylate, polyetherimide, polyarylsulfone, polyethersulfone, polyamideimide, polyimide, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, and polyvinylidene fluoride.

[0053] The thickness of the thermoplastic resin film is preferably 0.3 to 1000 μm, more preferably 1 to 800 μm, even more preferably 5 to 600 μm, still more preferably 10 to 500 μm, and particularly preferably 20 to 400 μm. When the thickness of the thermoplastic resin film is within the above range, the flexible laminate can have the desired barrier properties. The thickness of the thermoplastic resin film is determined, for example, by measuring the thickness at any three or more points on the thermoplastic resin film and averaging the measured values. The thickness of the thermoplastic resin film can be measured by cross-sectional observation using a laser microscope, SEM (scanning electron microscope), TEM (transmission electron microscope), or the like, or by a method using a film thickness meter, or the like. When the barrier layer comprises two or more thermoplastic resin films, the above ranges represent the thickness of each individual thermoplastic resin film.

[0054] Examples of inorganic materials include tin, phosphorus, aluminum, stainless steel, titanium, copper, silicon oxides such as silica, aluminum oxides such as alumina, titanium oxides such as titania, indium oxide, tin oxide, indium tin oxide (ITO), tantalum oxide, zirconium oxide, niobium oxide, aluminum nitride, silicon nitride, boron nitride, aluminum oxynitride, silicon oxynitride, boron oxynitride, zirconium oxyboride, titanium oxyboride, silicon oxycarbide, silicon oxycarbonitride, aluminum oxycarbide, and combinations of two or more thereof.

[0055] The content of the inorganic material in the inorganic material layer is preferably 50 to 100 mass %, more preferably 60 to 100 mass %, and even more preferably 70 to 100 mass %, 80 to 100 mass %, 85 to 99 mass %, or 90 to 98 mass %, relative to the mass of the inorganic material layer. When the content of the inorganic material in the inorganic material layer is within the above range, desired barrier properties can be exhibited.

[0056] The inorganic material layer may be formed by any method capable of forming a thin film. For example, it can be formed by known methods such as physical vapor deposition (PVD) methods such as etching, printing, vacuum heating evaporation, electron beam deposition, sputtering, and ion plating, chemical vapor deposition (CVD), and coating. PVD and CVD methods may also be combined with plasma assistance. Alternatively, thin film metals or the like may also be used. When the inorganic material layer is made up of multiple layers, multiple methods may be used. Each method can be carried out by a method commonly used in the relevant technical field.

[0057] The thickness of the inorganic material layer is preferably 5 nm to 4 μm, more preferably 10 nm to 3 μm, even more preferably 50 nm to 2 μm, even more preferably 0.1 to 1 μm, and particularly preferably 0.2 to 0.8 μm. When the thickness of the inorganic material layer is within this range, the flexible laminate can have the desired barrier properties. The thickness of the inorganic material layer is determined, for example, by measuring the thickness at any three or more points on the inorganic material layer and averaging these values. The thickness of the inorganic material layer can be measured by cross-sectional observation using a laser microscope, SEM (scanning electron microscope), TEM (transmission electron microscope), or the like, or by a method using a film thickness meter, or the like. In addition, when the barrier layer can include two or more inorganic material layers, the above ranges represent the thickness of each inorganic material layer.

[0058] In a preferred embodiment of the present invention, the barrier layer preferably includes at least one inorganic material layer. By including at least one inorganic material layer in the barrier layer, the flexible laminate can have higher barrier properties even if the thickness of the barrier layer is reduced. In this embodiment, the barrier layer may include only at least one inorganic material layer, but preferably includes at least one inorganic material layer and at least one thermoplastic resin film, from the viewpoint of achieving both barrier properties and flexibility.

[0059] In another preferred embodiment of the present invention, the barrier layer preferably includes two or more inorganic material layers. When the barrier layer includes two or more inorganic material layers, the barrier properties of the flexible laminate can be further improved. In this embodiment, the barrier layer may include only two or more inorganic material layers, but preferably includes at least two or more inorganic material layers and at least one thermoplastic resin film, from the viewpoint of achieving both barrier properties and flexibility.

[0060] When the barrier layer includes two or more inorganic material layers (hereinafter sometimes referred to as "I") and at least one thermoplastic resin film (hereinafter sometimes referred to as "O"), for example, when it includes two inorganic material layers and one thermoplastic resin film, the layer structure is not particularly limited, but possible examples are O / I / I, I / O / I, and I / I / O, from the polyvinyl acetal resin film side. When it includes two inorganic material layers and two thermoplastic resin films, possible examples are O / I / O / I, O / I / I / O / , O / O / I / I, I / O / O / I, I / O / I / O, and I / I / O / O. When the barrier layer includes two or more inorganic material layers and at least one thermoplastic resin film, it is preferable that the inorganic material layers or the thermoplastic resin films are not continuous with each other from the viewpoint of flexibility. Furthermore, the more inorganic material layers contained in the barrier layer, the higher the barrier properties can be, but from the viewpoint of flexibility and transparency, it is preferable that the number of inorganic material layers contained in the barrier layer be 5 or less.

[0061] In addition to the thermoplastic resin film and inorganic material layer, the barrier layer may contain layers such as an adhesive layer and a primer layer, as long as the effects of the present invention are not impaired. Furthermore, the surface of the thermoplastic resin film and / or the inorganic material layer may be subjected to a known surface treatment such as plasma treatment or corona treatment.

[0062] Examples of adhesives constituting the adhesive layer include dry-hardening adhesives and chemically reactive adhesives. Examples of chemically reactive adhesives include active energy ray-curable adhesives. Adhesives known in the art can be used as such adhesives. Specific examples of adhesives include polycarbonate-based adhesives, polyether-based adhesives, acrylic-based adhesives, polyurethane-based adhesives, and polyester-based adhesives.

[0063] The thickness of the adhesive layer is not particularly limited as it is determined depending on the type or adhesive strength, but is usually 0.001 to 40 μm, and preferably 0.01 to 10 μm from the viewpoint of processability or durability.

[0064] The primer layer may be made of, but is not limited to, polyol, polyisocyanate, etc. The thickness of the primer layer is, for example, 0.001 to 5 μm, preferably 0.005 to 2 μm, from the viewpoint of flexibility of the flexible laminate.

[0065] The average thickness of the barrier layer is preferably 0.3 to 500 μm, more preferably 1 to 400 μm, even more preferably 10 to 300 μm, and particularly preferably 20 to 240 μm. When the thickness of the barrier layer is within the above range, the desired barrier properties can be exhibited, and the adhesion to the polyvinyl acetal resin film can be improved. Furthermore, the flexible laminate can achieve both flexibility and mechanical strength. The thickness of the barrier layer is determined, for example, by measuring the thickness at any three or more points on the barrier layer and averaging the measured values. The thickness of the barrier layer can be measured using a thickness meter or the like.

[0066] The water vapor transmission rate of the barrier layer at 40°C and 90% RH is preferably 1×10 -2 g / m 2 ·day or less, preferably 8×10 -3 g / m 2 ·day or less, more preferably 5 × 10 -3 g / m 2 days or less, particularly preferably 3 × 10 -3 g / m 2·day or less. When the water vapor transmission rate is equal to or less than the upper limit, the water vapor barrier property of the flexible laminate is enhanced. The lower the water vapor transmission rate, the less water vapor passes through the flexible laminate, which is preferable. Therefore, the lower limit of the water vapor transmission rate is not particularly limited, but is usually 1×10 -5 g / m 2 ·day or more, or 5 × 10 -5 g / m 2 The preferred water vapor transmission rate is 1×10 -5 ~1×10 -2 g / m 2 ·day, more preferably 5×10 -5 ~8×10 -3 g / m 2 day, more preferably 5 × 10 -5 ~5×10 -3 g / m 2 day, particularly preferably 5 × 10 -5 ~3×10 -3 g / m 2 ·day.

[0067] The method for producing the barrier layer is not particularly limited. For example, when the barrier layer includes a thermoplastic resin film and an inorganic material layer, the inorganic material layer can be formed on the thermoplastic resin film by the above-mentioned method. The barrier layer may have convex portions and / or concave portions, and in this case, the barrier layer can be produced by processing and molding using a mold having convex portions and / or concave portions.

[0068] Commercially available barrier layers can also be used, and examples thereof include the oxygen / water vapor high barrier film "CLARISTA (registered trademark)" (manufactured by Kuraray Co., Ltd.), the transparent silica vapor-deposited high gas barrier film "TECHBARIER (registered trademark)" (manufactured by Mitsubishi Chemical Corporation), the DNP transparent vapor-deposited film "IB-Film (registered trademark)" (manufactured by Dai Nippon Printing Co., Ltd.), and the transparent barrier film "GL FILM" (manufactured by TOPPAN Corporation).

[0069] <any layer> The flexible laminate may optionally include another layer as the outermost layer or between one surface of the polyvinyl acetal resin film and the barrier layer. When the flexible laminate includes the another layer between one surface of the polyvinyl acetal resin film and the barrier layer, another barrier layer is laminated on the other surface of the polyvinyl acetal resin film. Examples of other layers that may be optionally included include a light diffusing layer, an ultraviolet / infrared absorbing layer, an ultraviolet / infrared reflective layer, an anti-reflection layer, a wavelength converting layer, a water repellent layer, an impact absorbing layer, a hard coat layer, or a combination of two or more thereof.

[0070] [Method for manufacturing flexible laminate] Known manufacturing methods can be used to manufacture flexible laminates. For example, flexible laminates can be manufactured by a method including the steps of stacking a polyvinyl acetal resin film (hereinafter sometimes abbreviated as "PVA resin film"), a barrier layer, and optional layers, if any, and vacuum-suctioning and heat-pressing the stacked layers. Examples of stacking orders include: PVA resin film / barrier layer, barrier layer / PVA resin film / barrier layer, any layer / PVA resin film / barrier layer, any layer / PVA resin film / barrier layer / any layer, any layer / barrier layer / PVA resin film / barrier layer, any layer / barrier layer / PVA resin film / barrier layer / any layer, barrier layer / any layer / PVA resin film / barrier layer / any layer, barrier layer / any layer / PVA resin film / barrier layer, any layer / barrier layer / any layer / PVA resin film / barrier layer, any layer / barrier layer / any layer / PVA resin film / barrier layer, any layer / barrier layer / any layer / PVA resin film / barrier layer / any layer.

[0071] When manufacturing an optical device including a flexible laminate, such as a solar cell module, the device can be manufactured by a method including the steps of stacking the manufactured flexible laminate with components such as a backsheet, solar cell cell, and surface protective sheet, and vacuum-suctioning and thermocompression bonding them together, but it is also possible to manufacture a solar cell module in one piece without manufacturing a flexible laminate. That is, the solar cell module can also be manufactured by a method including the steps of stacking the backsheet, solar cell cell, polyvinyl acetal resin film, barrier layer, optional layers if included, surface protective sheet, and / or glass, etc., in the desired order, and vacuum-suctioning and thermocompression bonding the stacked components together. The polyvinyl acetal resin film and other bonded members constituting the optical device (e.g., a barrier layer, any layers if included, a backsheet, a solar cell, a surface protection sheet, glass, etc.) can be subjected to a known surface treatment such as a primer treatment or a corona treatment before being stacked, in order to improve adhesion to adjacent members.

[0072] In the step of vacuum suction and heat and pressure bonding, for example, a vacuum laminator is used. Usually, lamination is performed at a predetermined bonding temperature under reduced pressure of 1 to 30,000 Pa. As described above, in the present invention, high initial adhesion of the polyvinyl acetal resin film to the members to be bonded can be exhibited even at a relatively low bonding temperature, and high adhesion can be maintained even in a high-temperature, high-humidity environment. The relatively low temperature is preferably 90 to 150°C, more preferably 90 to 140°C, even more preferably 90 to 130°C, still more preferably 90 to less than 130°C, particularly preferably 90 to 120°C, even more particularly preferably 90 to 110°C, and even more particularly preferably 90 to 100°C (e.g., 90 to less than 100°C).

[0073] When a vacuum bag or vacuum ring is used, lamination is preferably carried out under a reduced pressure of about 20,000 Pa at the above temperature.

[0074] When nip rolls are used, for example, a method may be used in which the first temporary pressure bonding is performed at a temperature equal to or lower than the flow initiation temperature of polyvinyl acetal, and then temporary pressure bonding is performed under conditions close to the flow initiation temperature. Specifically, the mixture may be heated to 30 to 100°C (for example, 30 to less than 100°C) using an infrared heater or the like, degassed with rolls, further heated to the same temperature, and then pressure bonded with rolls.

[0075] The autoclave step, which is additionally performed after temporary pressure bonding, is performed, for example, under a pressure of about 1 to 1.5 MPa at the above temperature for about 2 hours, although this varies depending on the thickness or configuration of the flexible laminate or optical device. However, in the present invention, high initial adhesiveness can be achieved even without performing the autoclave step, and high adhesiveness can be maintained even in a high-temperature, high-humidity environment. [Example]

[0076] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to these examples. The methods for measuring the physical properties of polyvinyl acetal resin films are described below. The physical properties and measurements (or physical property values ​​and measured values) described in this specification, including the examples, are based on values ​​determined by the following methods.

[0077] <Amount of hydroxyl groups in polyvinyl acetal resin> The amount of hydroxyl groups in the polyvinyl acetal resin was measured in accordance with JIS K6728-1977.

[0078] <Average thickness> The average thickness of the polyvinyl acetal resin film was determined by measuring the thickness at any three points with a thickness meter and calculating the average value.

[0079] <Ten-point average roughness Rz> The ten-point average roughness Rz of the surface of the polyvinyl acetal resin film was measured in accordance with JIS B0601-1994 under the following measurement conditions using a stylus surface profiler ("Dektak150" manufactured by ULVAC, Inc.) Note that the ten-point average roughness Rz values ​​were the same on both sides of all of the polyvinyl acetal resin films produced in the Examples and Comparative Examples. Stylus pressure: 5mg Measurement distance: 5mm Measurement time: 50 seconds

[0080] <Yellowness> The yellowness of the polyvinyl acetal resin film was measured in accordance with JIS Z8722:2009 using an ultraviolet-visible-near infrared spectrophotometer ("U4150" manufactured by Hitachi High-Technologies Corporation).

[0081] <Water vapor permeability of the barrier layer> The water vapor permeability of the barrier layer was measured using a gas and water vapor permeability measuring device (manufactured by TI Corporation) in accordance with ISO / TS 20175:2018. The water vapor permeability of the CLARISTA CW#75 used in the Examples and Comparative Examples at a temperature of 40°C and a humidity of 90% RH was 7.8 × 10 -5 g / m 2 The water vapor transmission rate at 85°C and 85% RH is 7.7×10 -3 g / m 2 ·day.

[0082] <Method for evaluating water vapor permeability of flexible laminate> The water vapor permeability of flexible laminates was evaluated based on the principle that cobalt chloride paper changes color from dark blue to red when it absorbs water. Cobalt chloride paper (manufactured by Advantec, 200 μm thick) was dried at 40°C for 12 hours, and the dark blue paper was cut into 7 mm x 7 mm pieces. Glass plates, cobalt chloride paper, polyvinyl acetal resin film, and barrier layers were layered in this order and thermally laminated at 140°C and 30 kPa for 30 minutes. The resulting samples were photographed from the glass plate side with a digital camera, and the red (R0), green (G0), and blue (B0) components of the cobalt chloride paper were extracted from the JPEG images using the image analysis software ImageJ (Wayne Rasband). After that, the sample was left at a temperature of 85°C and a humidity of 85%RH for 100 hours, and then the red (R) 100 ) Green (G 100 ) · Blue (B 100 ) components were extracted in the same manner. The discoloration behavior of cobalt chloride paper is expressed as the color difference D in Euclidean distance using the following formula: The calculation was based on TIFF2025144964000002.tif6150. The larger the color difference D, the greater the discoloration of the cobalt chloride paper, indicating that a larger amount of moisture had permeated the flexible laminate. A color difference D of 70 or less was rated as good, and a color difference D of over 70 was rated as poor.

[0083] <Adhesive strength> The flexible laminates prepared in the Examples and Comparative Examples were left to stand at 25°C and 50% RH for 24 hours, and then cut into 10 mm wide samples for adhesive strength measurement. Using an autograph (Shimadzu Corporation), adhesive strength was measured at the interface between the film included in the flexible laminate and one of the barrier films when T-peeling at 250 mm / min. Three samples for adhesive strength measurement were measured, and the average value was taken as the initial adhesive strength of the flexible laminate. The edges of the flexible laminates prepared in the examples and comparative examples were sealed with copper tape (CU-8T, manufactured by ID Create Co., Ltd.). The sealed flexible laminates were left to stand in a thermo-hygrostat (manufactured by Hitachi Appliances, Inc.) at 85°C and 85% RH for 1000 hours, and then cut to a width of 10 mm to prepare samples for measuring adhesive strength. The adhesive strength of the flexible laminates after storage at 85°C and 85% RH for 1000 hours was determined in the same manner as for the initial adhesive strength.

[0084] Examples 1 to 10 Polyvinyl butyral (PVB) resin (1) (Mowital B45H manufactured by Kuraray Co., Ltd.; hydroxyl group content 26.2 to 30.2 mol%, acetyl group content 0.7 to 3.0 mol%, weight average molecular weight 36,000 to 46,000) or PVB resin (2) (Mowital B30H manufactured by Kuraray Co., Ltd.; hydroxyl group content 26.2 to 30.2 mol%, acetyl group content 0.7 to 3.0 mol%, weight average molecular weight 28,000 to 38,000 and Mowital B75H manufactured by Kuraray Co., Ltd.; hydroxyl group content 26.2 to 30.2 mol%, acetyl group content 0 to 3.0 mol%, weight average molecular weight 96,000 to 106,000) were mixed in an 85:15 ratio with a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.) and optionally a plasticizer in the ratios shown in Table 1. The resulting mixture was melt-kneaded at 180° C. and 60 rpm for 5 minutes using a Laboplastomill (manufactured by Toyo Seiki Seisakusho, Ltd.) to prepare a resin composition. The obtained resin composition was compressed at 180°C and 100 kgf / cm using a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd.). 2 (approximately 9.81 MPa) for 5 minutes to produce a polyvinyl acetal resin film. The obtained polyvinyl acetal resin film was sandwiched between two barrier films (Kuraray Co., Ltd.: Kuralysta CW#75: thickness 75 μm), and a flexible laminate was produced using a vacuum laminator (Nisshinbo Mechatronics Inc.) at a temperature of 140°C, for 12 minutes of vacuuming, at a pressing pressure of 30 kPa, and for 18 minutes. The physical properties and measurements of the produced polyvinyl acetal resin film and flexible laminate are shown in Table 1.

[0085] Example 11 A resin composition was prepared, and a polyvinyl acetal resin film and a flexible laminate were produced in the same manner as in Example 7, except that the bonding temperature was changed to 100° C. The physical properties and measured values ​​of the produced polyvinyl acetal resin film and flexible laminate are shown in Table 1.

[0086] Example 12 A resin composition was prepared, and a polyvinyl acetal resin film and a flexible laminate were produced in the same manner as in Example 9, except that the bonding temperature was changed to 100° C. The physical properties and measured values ​​of the produced polyvinyl acetal resin film and flexible laminate are shown in Table 1.

[0087] Example 13 A resin composition was prepared, and a polyvinyl acetal resin film and a flexible laminate were produced in the same manner as in Example 1, except that the silane coupling agent was changed to KBM-402 and the number of parts of the silane coupling agent per 100 parts by mass of the resin was changed to 0.5 parts by mass. The physical properties and measured values ​​of the produced polyvinyl acetal resin film and flexible laminate are shown in Table 1.

[0088] Examples 14 to 16 Polyvinyl butyral (PVB) resin (1) (Mowital B45H manufactured by Kuraray Co., Ltd.; hydroxyl group content 26.2 to 30.2 mol%, acetyl group content 0.7 to 3.0 mol%, weight average molecular weight 36,000 to 46,000) was compressed at 180 °C and 100 kgf / cm using a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd.). 2 (approximately 9.81 MPa) for 5 minutes to prepare a PVB film. Next, 2 g of a solution prepared by diluting a silane coupling agent with various solvents as shown in Table 2 was dropped onto a PVB film (A4 size) using a dropper. The solution was then applied using a wire bar to a film thickness of approximately 5 μm. The film was placed in a dryer, dried at 100°C for 10 minutes, and then removed to obtain a PVB film coated with the silane coupling agent. The amount of silane coupling agent contained in the PVB film was quantified using an inductively coupled plasma optical emission spectrometer (Thermo Fisher Scientific, iCAP PRO XP). 0.1 g of PVB film was weighed out and placed in a PTFE-TFM container together with 8 mL of nitric acid, which was then sealed. The container was then placed in a rotor. The rotor was attached to a microwave decomposition device (Anton Paar Multiwave 5000). Microwave heating was then performed at 220°C. After cooling, the rotor was removed from the device. The decomposition solution was adjusted to volume with ultrapure water in a 100 mL PFA volumetric flask. The solution was filtered through a 0.45 μm pore size filter (Advantec), and the amount of Si elemental content in the solution was quantified. The amount of silane coupling agent contained in the PVB film was then calculated by converting it into the molecular weight of the silane coupling agent. The resulting amount of silane coupling agent was 0.02 parts by mass per 100 parts by mass of PVB resin. A flexible laminate was produced by sandwiching a PVB film coated with a silane coupling agent between two barrier films (Kuraray Co., Ltd.: Kurarista CW#75: 75 μm thick) and processing it using a vacuum laminator (Nisshinbo Mechatronics Inc.) at a temperature of 140°C, vacuuming for 12 minutes, pressing at a pressure of 30 kPa, and pressing for 18 minutes. The physical properties and measurements of the produced PVB resin film and flexible laminate are shown in Table 2.

[0089] Comparative Example 1 Except for not using a silane coupling agent, a resin composition was prepared, and a film and a flexible laminate were produced in the same manner as in Example 1. The physical property values ​​and measured values ​​of the produced film and flexible laminate are shown in Table 3.

[0090] Comparative Example 2 Resin compositions were prepared, and films and flexible laminates were produced in the same manner as in Example 1, except that the amount of plasticizer was changed as shown in Table 3. The physical property values ​​and measured values ​​of the produced films and flexible laminates are shown in Table 3.

[0091] Comparative Examples 3 and 4 Resin compositions were prepared in the same manner as in Example 1, and films and flexible laminates were produced in the same manner as in Example 1, except that the film thickness was changed as shown in Table 3. The physical property values ​​and measured values ​​of the produced films and flexible laminates are shown in Table 3.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3] [Industrial Applicability]

[0095] The polyvinyl acetal resin film of the present invention exhibits high initial adhesion to bonded members (e.g., resin layers (particularly thermoplastic resin layers), glass, barrier layers such as aluminum oxide, electrode materials such as metals or indium tin oxide (ITO), or optical functional layers (e.g., light-emitting layers, light-absorbing layers, light-reflecting layers, wavelength-converting layers), etc.) even at relatively low bonding temperatures, and maintains this high adhesion even under high-temperature, high-humidity environments. Furthermore, flexible laminates comprising the polyvinyl acetal resin film of the present invention and a barrier layer have excellent water vapor barrier properties. Thus, the polyvinyl acetal resin film of the present invention has the properties required for sealing optical devices, making it suitable for use as a filler and bonding material for optical devices. Examples of optical devices include information terminals (personal computers, mobile phones, tablets, PDAs, smart watches, electronic organizers, etc.), display devices using image display panels (televisions, game consoles, in-vehicle panels, electronic paper, etc.), light-emitting devices (lighting, etc.), light-receiving devices (solar cells, etc.), etc. Examples of the above-mentioned resin layer, thermoplastic resin layer, glass, barrier layer, electrode material, or optical functional layer include those that are commonly used in the exemplified optical devices.

Claims

1. A polyvinyl acetal resin film, the resin composition constituting the polyvinyl acetal resin film comprises a polyvinyl acetal resin and a silane coupling agent; the content of the plasticizer in the resin composition is 0 to 15 parts by mass relative to 100 parts by mass of the polyvinyl acetal resin; A polyvinyl acetal resin film having an average thickness of 30 to 500 μm.

2. 2. The polyvinyl acetal resin film according to claim 1, wherein the polyvinyl acetal resin has a hydroxyl group content of 10 to 80 mol %.

3. The polyvinyl acetal resin film according to claim 1 , wherein the polyvinyl acetal resin is a polyvinyl butyral resin.

4. The polyvinyl acetal resin film according to claim 1 , wherein the silane coupling agent has at least one functional group selected from the group consisting of an epoxy group, a (meth)acrylic group, and an isocyanate group.

5. The polyvinyl acetal resin film according to claim 1, wherein the content of the silane coupling agent in the resin composition is 0.001 to 8.0 parts by mass per 100 parts by mass of the polyvinyl acetal resin.

6. 2. The polyvinyl acetal resin film according to claim 1, wherein at least one surface has a ten-point average roughness Rz of 2 to 7 μm as measured in accordance with JIS B0601-1994.

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