Encapsulating material for photoelectric conversion elements and laminate using the same

Abstract

To provide a encapsulating material for photoelectric conversion elements using a material with excellent transparency and sealing properties. [Solution] An embodiment of the present invention provides a encapsulant for a photoelectric conversion element, comprising a resin layer made of a material containing a carboxylic acid group-containing polymer compound. The polymer compound comprises a polymer polyol (A), a polymer polyol (B), and a tetracarboxylic dianhydride as copolymer components. Polyol (A) has the largest number average molecular weight among the copolymer components of the polymer compound, the number average molecular weight of polyol (B) is 1,000 or more and 10,000 or less, the number average molecular weight of polyol (A) is 6,000 or more greater than the number average molecular weight of polyol (B), and the number average molecular weight of the polymer compound is 1.7 times or less the number average molecular weight of polyol (A). The transmittance of light with a wavelength of 400 nm to 700 nm in the resin layer is 80% or more, and the haze of the resin layer is 0.5% or less.

Description

Technical Field

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[0001] The present invention relates to a sealing material for a photoelectric conversion element and a laminate using the same.

Background Art

[0002] With the recent increase in demand for renewable energy, solar cells with good photoelectric conversion efficiency and excellent transparency are required. Examples of such solar cells include organic thin-film solar cells and perovskite solar cells. Furthermore, when considering commercial use, it is required to be a film type that can be applied to a large area for attachment to the walls and windows of buildings. Such solar cells are being developed for mass production in a roll-to-roll process.

[0003] The photoelectric conversion layers constituting perovskite solar cells and organic thin-film solar cells have a problem that their characteristics are likely to deteriorate due to moisture, oxygen, etc. Therefore, in order to obtain practical perovskite solar cells and organic thin-film solar cells, it is necessary to block the atmosphere from the photoelectric conversion layer to achieve a longer lifespan. For such blocking, for example, a sealing material is used.

[0004] Patent Document 1 discloses a curable resin composition that can be used as a sealing material, which contains a high molecular weight polyisobutylene resin and a polyfunctional (meth)acrylate monomer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 shows an example in which a sealing material is placed in the path from the light incident on the solar cell to the photoelectric conversion layer (Figure 3A of Patent Document 1). In such a configuration, it is desirable that the sealing material transmit as much light of the wavelength used for photoelectric conversion as possible.

[0007] Conventional sealing materials, such as those disclosed in Patent Document 1, require solvent dilution during application. Outgassing occurs due to the solvent itself or the heating during the drying process to remove the solvent after application, resulting in the formation of bubbles. This can lead to delamination between layers and deterioration of sealing performance.

[0008] The present invention aims to provide a encapsulating material for photoelectric conversion elements using a material with excellent transparency and sealing properties, and a laminate in which a photoelectric conversion element is encapsulated with said encapsulating material. [Means for solving the problem]

[0009] In other words, the present invention may include the following embodiments. [1] A sheet-like encapsulant for a photoelectric element, comprising a resin layer made of a material containing a polymer compound with a carboxylic acid group, The carboxylic acid group-containing polymer compound comprises, as copolymer components, a polymer polyol (A), a polymer polyol (B) different from polymer polyol (A), and a tetracarboxylic dianhydride. Among the copolymer components of the carboxylic acid group-containing polymer compound, the polymer polyol (A) is the component with the largest number-average molecular weight. The number-average molecular weight (Mn2) of the polymer polyol (B) is 1,000 or more and 10,000 or less, and the number-average molecular weight (Mn1) of the polymer polyol (A) is 6,000 or more greater than the number-average molecular weight (Mn2) of the polymer polyol (B). The number average molecular weight (Mn3) of the carboxylic acid group-containing polymer compound is 1.7 times or less than the number average molecular weight (Mn1) of the polymer polyol (A). The transmittance of light with a wavelength of 400 nm to 700 nm in the aforementioned resin layer is 80% or more. The haze of the resin layer is 0.5% or less. Encapsulating material for photoelectric conversion elements. [2] The encapsulant for a photoelectric element according to [1], wherein the polymer polyol (A) is a polyester polyol or a polycarbonate polyol, and the polymer polyol (B) is a polyester polyol or a polycarbonate polyol. [3] The encapsulant for photoelectric conversion elements according to [1] or [2], wherein the acid value of the carboxylic acid group-containing polymer compound is 5 mg KOH / g or more and 100 mg KOH / g or less. [4] A laminate comprising a photoelectric conversion element sealed with a resin layer of a photoelectric conversion element encapsulant described in any of [1] to [3]. [Effects of the Invention]

[0010] The resin layer of the encapsulant of the present invention exhibits excellent transparency. Specifically, the transmittance of light with wavelengths between 400 nm and 700 nm in the resin layer and the haze of the resin layer are both within a specific range, which can lead to improved photoelectric conversion efficiency in photoelectric conversion elements using the encapsulant. More specifically, when a photoelectric conversion element is encapsulated with the encapsulant, light of the wavelength used for photoelectric conversion can easily pass through the resin layer and reach the photoelectric conversion layer, thereby reducing the decrease in power generation efficiency caused by the encapsulant. Furthermore, because it is in sheet form, it is suitable for roll-to-roll photoelectric conversion element manufacturing processes.

[0011] The resin layer of the sealing material of the present invention also exhibits excellent sealing properties. For example, the resin layer is bonded to the substrate by heating and pressurizing during sealing, but because the amount of outgassing generated from the resin layer at that time is small, air bubbles are less likely to form, and as a result, delamination between layers is less likely to occur. For example, in a calcium corrosion test in which a metallic calcium layer is sealed with the resin layer of the sealing material, moisture and oxygen can be blocked to prevent the corrosion of metallic calcium from progressing. [Brief explanation of the drawing]

[0012] [Figure 1]A diagram showing an example of a laminate in which photoelectric conversion elements are encapsulated using an adhesive sheet. [Figure 2A] A schematic plan view showing the composition of the calcium substrate used in the calcium corrosion test. [Figure 2B] A schematic cross-sectional view showing the structure when a metallic calcium layer on a calcium substrate is sealed with an adhesive layer. [Modes for carrying out the invention]

[0013] The present invention will be described in more detail below based on the embodiments described below. However, the present invention is not limited by the embodiments described below, and it is certainly possible to implement it with appropriate modifications within the scope that is consistent with the spirit of the preceding and following descriptions, and all such modifications are included within the technical scope of the present invention. In some cases, hatching and component reference numerals may be omitted in the drawings for convenience, in which case refer to the specification or other drawings. Also, the dimensions of various components in the drawings may differ from the actual dimensions, as priority is given to helping to understand the features of the present invention.

[0014] For ease of reference, examples are shown in the drawings and the notations "above" and "below" are used in this specification, but these embodiments are not necessarily limited thereto. For example, objects and methods that can be realized by the ideas disclosed herein even when the orientation is changed, such as by reversing upside down, are within the scope of disclosure of these embodiments. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of." In this specification, "A and / or B" means "either A or B" or "both A and B," and specifically means "A," "B," or "A and B."

[0015] In this specification, regarding the relationship between two components A and B, descriptions such as component B is provided on component A, component B is provided on the upper surface of component A, and component B is in contact with component A may be made. Such descriptions are intended to allow not only the case where components A and B are in direct contact but also the case where other components are interposed as long as the effects are not inhibited.

[0016] Regarding the numerical ranges described step by step in this specification, the upper limit value or the lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of a numerical range at another step. Regarding the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples or a value uniquely derived from the examples. In this specification, a numerical range connected by "~" means a numerical range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[0017] [Polymer compound containing carboxylic acid group] The carboxylic acid group-containing polymer compound according to the present invention contains, as copolymerization components, a polymeric polyol (A), a polymeric polyol (B), and a tetracarboxylic dianhydride. Among the copolymerization components, the number average molecular weight (Mn1) of the polymeric polyol (A) is the largest. The number average molecular weight (Mn2) of the polymeric polyol (B) is 1,000 or more and 10,000 or less. The number average molecular weight (Mn1) of the polymeric polyol (A) is 6,000 or more larger than the number average molecular weight (Mn2) of the polymeric polyol (B), that is, 7,000 or more. The number average molecular weight (Mn3) of the carboxylic acid group-containing polymer compound is 1.7 times or less of the number average molecular weight (Mn1) of the polymeric polyol (A).

[0018] By using a two-component or more polymer polyol containing a polymer polyol (A) with a number-average molecular weight of 7,000 or more and a polymer polyol (B) with a number-average molecular weight of 1,000 or more as the copolymerization component, and further chain-extending with a tetracarboxylic dianhydride, it is possible to improve the heat resistance of an adhesive sheet produced by curing an adhesive composition containing a carboxylic acid group-containing polymer compound described below. That is, by introducing a long-chain polymer polyol (A) block and a short-chain polymer polyol (B) block, it is possible to introduce a sufficient amount of carboxylic acid for imparting heat resistance to the cured adhesive sheet. When the polymer polyol (A) alone is chain-extended with a tetracarboxylic dianhydride, the molecular weight becomes too large, and it may not be possible to obtain the crosslinking necessary for obtaining heat resistance. Also, when a chain extender is used at that time, due to the molar balance relationship, it becomes easier for reaction products of the chain extenders to form, and thus a gel-like substance is likely to occur in the cured coating film of the adhesive composition. Good heat resistance is preferable because it does not deteriorate the sealing property during normal use.

[0019] The glass transition temperature of the carboxylic acid group-containing polymer compound is not particularly limited, and it is preferably 0 °C or higher, more preferably 5 °C or higher, and even more preferably 10 °C or higher. If the glass transition temperature is too low, the tack of the adhesive composition described below becomes strong, and it is likely to trap air bubbles and cause defective bonding during lamination. The glass transition temperature is preferably 80 °C or lower, more preferably 70 °C or lower, and even more preferably 60 °C or lower. If the glass transition temperature is too high, the coating film becomes brittle, and there is a concern that embrittlement may become a problem.

[0020] Among the copolymer components of the carboxylic acid group-containing polymer compound, polymer polyol (A) has the highest number-average molecular weight (Mn1). In addition to polymer polyol (A), polymer polyol (B), and tetracarboxylic dianhydride, other polyol components and chain extenders described later can be used as copolymer components, but polymer polyol (A) has the highest number-average molecular weight (Mn1) among all copolymer components, including these. Because polymer polyol (A) has the highest number-average molecular weight (Mn1), the longest-chain polymer polyol is copolymerized with the carboxylic acid group-containing polymer compound, and an optimal crosslinked structure can be obtained.

[0021] The number-average molecular weight (Mn3) of the carboxylic acid group-containing polymer compound is 1.7 times or less than the number-average molecular weight (Mn1) of the polymer polyol (A) (i.e., Mn3 / Mn1 ≤ 1.7), preferably 1.6 times or less, more preferably 1.4 times or less, and even more preferably 1.2 times or less. If it exceeds 1.7 times, it is thought that the difference between the number-average molecular weight (Mn1) of polymer polyol (A) and the number-average molecular weight (Mn2) of polymer polyol (B) is small, or that the amount of tetracarboxylic dianhydride is excessive. As a result, the carboxylic acid group content of the carboxylic acid group-containing polymer compound may be insufficient, reducing the heat resistance of the adhesive sheet, or the elastic modulus of the cured coating film may become too high, making it easy for the adhesion to decrease. Good heat resistance and adhesion are desirable for blocking moisture and oxygen, so as to make it difficult for the corrosion of metallic calcium to progress in the calcium corrosion test described later. Good adhesion is also desirable so as to make it difficult for delamination between layers to occur even if outgassing occurs during heat sealing, as described later. The number-average molecular weight (Mn3) is preferably 0.8 times or more the number-average molecular weight (Mn1) (Mn3 / Mn1≧0.8), more preferably 0.9 times or more the number-average molecular weight (Mn1), and even more preferably 1.0 times or more the number-average molecular weight (Mn1). If the number-average molecular weight (Mn3) is too small compared to the number-average molecular weight (Mn1), there is a possibility that the reaction between only the polymer polyol (B) and the chain extender (tetracarboxylic dianhydride) will occur frequently, and the polymer polyol (A) blocks may not react sufficiently with the carboxylic acid dianhydride, potentially leading to hardness and brittleness. However, as long as the carboxylic acid group-containing polymer compound is within the above number-average molecular weight (Mn3 / Mn1) range, it is acceptable for it to contain resins consisting only of polymer polyol (A) and carboxylic acid dianhydride, or resins consisting only of polymer polyol (B) and carboxylic acid dianhydride.

[0022] The acid value of the carboxylic acid group-containing polymer compound is preferably 5 mg KOH / g or higher, more preferably 10 mg KOH / g or higher, and even more preferably 15 mg KOH / g or higher. It is also preferably 100 mg KOH / g or lower, more preferably 60 mg KOH / g or lower, even more preferably 40 mg KOH / g or lower, and particularly preferably 20 mg KOH / g or lower. If the acid value is too low, crosslinking may be insufficient, and the adhesive sheet may not have sufficient heat resistance. If the acid value is too high, the crosslinking density may become too high, causing the cured coating film to harden and reducing adhesion. Furthermore, the storage stability of the varnish in which the carboxylic acid group-containing polymer compound is dissolved in a solvent may decrease, and the crosslinking reaction may proceed easily at room temperature, resulting in an inability to obtain a stable sheet life.

[0023] The carboxylic acid group-containing polymer compound is not limited to being composed only of three components: polymer polyol (A), polymer polyol (B), and tetracarboxylic dianhydride. Other high molecular weight components can be used as the fourth copolymer component. Examples of the fourth copolymer component include polymer polyols that are different from both polymer polyol (A) and polymer polyol (B). When using a fourth copolymer component, it is preferable that the number-average molecular weight of the fourth copolymer component is less than or equal to Mn1 of polymer polyol (A) and greater than or equal to Mn2 of polymer polyol (B).

[0024] In carboxylic acid group-containing polymer compounds, the copolymerization ratio of polymer polyol (A) and polymer polyol (B) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, of polymer polyol (B) per 100 parts by mass of polymer polyol (A). Furthermore, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Too much may result in a hard and brittle adhesive sheet, while too little may result in fewer terminals that can react with tetracarboxylic anhydride, leading to insufficient heat resistance of the adhesive sheet.

[0025] In carboxylic acid group-containing polymer compounds, the copolymerization ratio of polymer polyol (A) and tetracarboxylic dianhydride is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, of tetracarboxylic dianhydride per 100 parts by mass of polymer polyol (A). Furthermore, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less. Too little may result in insufficient crosslinking and insufficient heat resistance of the adhesive sheet, while too much may cause the coating film to harden and insufficient adhesion may not be obtained. Good heat resistance and adhesion are desirable for blocking moisture and oxygen, so as to hinder the progression of metallic calcium corrosion in the calcium corrosion test described later. Good adhesion is also desirable to prevent delamination between layers even if outgassing occurs during heat sealing, as described later.

[0026] In the polymer compound containing carboxylic acid groups, the copolymerization amount of polymer polyol (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Increasing the copolymerization amount of polymer polyol (A) can be expected to improve stress relaxation properties. Furthermore, it is preferably 90% by weight or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. If it is too high, the copolymerization amount of polymer polyol (B) and tetracarboxylic dianhydride will decrease, which may reduce the heat resistance and adhesion of the adhesive sheet.

[0027] In carboxylic acid group-containing polymer compounds, the content of polymer polyol (A) in the total copolymer component is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. By increasing this content, an improvement in stress relaxation can be expected. In carboxylic acid group-containing polymer compounds, the content of polymer polyol (A) in the total copolymer component is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. If it is too high, the content of polymer polyol (B) and tetracarboxylic dianhydride in the total copolymer component will decrease, which may reduce the heat resistance and adhesion of the adhesive sheet.

[0028] <High molecular weight polyol (A)> The number-average molecular weight (Mn1) of the polymer polyol (A) is 7,000 or more, preferably 8,000 or more, more preferably 10,000 or more, even more preferably 12,000 or more, and particularly preferably 14,000 or more. If Mn1 is less than 7,000, the crosslinking density will be high, and the coating film obtained from the adhesive composition described later will become hard, which tends to reduce the adhesion strength. Also, Mn1 is 50,000 or less, preferably 40,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and particularly preferably 16,000 or less. If it is too high, crosslinking will be insufficient, and the heat resistance of the adhesive sheet may decrease.

[0029] The acid value (mgKOH / g) of the polymer polyol (A) is not particularly limited, but is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. A low value is not a problem, but if it is too high, it may become impossible to extend the acid addition chain with tetracarboxylic dianhydride. In that case, the reaction between polymer polyols (B) proceeds, increasing the crosslinking density and hardening the coating film obtained from the adhesive composition, which tends to reduce adhesion.

[0030] The hydroxyl value (mgKOH / g) of the polymer polyol (A) is not particularly limited, but is preferably 24 mgKOH / g or less, more preferably 21 mgKOH / g or less, even more preferably 16 mgKOH / g or less, and particularly preferably 14 mgKOH / g or less. If it is too high, the reaction may be insufficient, and the heat resistance of the adhesive sheet may not be achieved. The hydroxyl value (mgKOH / g) of the polymer polyol (A) is preferably 2 mgKOH / g or more, more preferably 3 mgKOH / g or more, and even more preferably 3.5 mgKOH / g or more. If it is too low, the crosslinking density will be low, and the heat resistance of the adhesive sheet may not be achieved.

[0031] The glass transition temperature of the polymer polyol (A) is not particularly limited, but is preferably 0°C or higher, and more preferably 5°C or higher. If the glass transition temperature is too low, the tackiness of the adhesive composition becomes strong, and air bubbles are likely to be trapped during bonding, resulting in defects. The glass transition temperature of the polymer polyol (A) is preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, even more preferably 30°C or lower, and particularly preferably 15°C or lower. If the glass transition temperature is too high, the coating film becomes brittle, and there is a concern that embrittlement may become a problem.

[0032] <High molecular weight polyol (B)> Polymer polyol (B) is a polyol different from polymer polyol (A). Different from polymer polyol (A) means that at least one of its composition or physical properties is different. The number average molecular weight (Mn2) of polymer polyol (B) is 1,000 or more, preferably 1,200 or more, more preferably 1,500 or more, even more preferably 2,000 or more, and particularly preferably 2,500 or more. If it is less than 1,000, polymer polyols (B) tend to bond with each other, resulting in a polymer compound containing carboxylic acid groups that tends to have a low molecular weight and high acid value, making it easier for gel-like substances to form in the coating film obtained from the adhesive composition. The number average molecular weight (Mn2) is 10,000 or less, preferably 8,000 or less, more preferably 6,000 or less, even more preferably 4,000 or less, and particularly preferably 3,500 or less. If it is too high, the amount of carboxylic acid groups that can be added decreases, which can lead to insufficient crosslinking density in the resulting coating film and insufficient heat resistance of the adhesive sheet.

[0033] The acid value (mgKOH / g) of the polymer polyol (B) is not particularly limited, but is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. If it is too high, it may become impossible to extend the acid addition chain with tetracarboxylic dianhydride.

[0034] The hydroxyl value (mgKOH / g) of the polymer polyol (B) is not particularly limited, but is preferably 120 mgKOH / g or less, more preferably 100 mgKOH / g or less, and even more preferably 80 mgKOH / g or less. If the hydroxyl value is too high, the polymer polyols (B) tend to bond with each other, resulting in a polymer compound containing carboxylic acid groups that has a low molecular weight and a high acid value, making it easier for gel-like substances to form in the coating film obtained from the adhesive composition. The hydroxyl value (mgKOH / g) of the polymer polyol (B) is preferably 11 mgKOH / g or more, more preferably 14 mgKOH / g or more, and even more preferably 18 mgKOH / g or more. If the hydroxyl value is too low, it may not be possible to extend the acid-added chain by the tetracarboxylic dianhydride.

[0035] The glass transition temperature of polymer polyol (B) is not particularly limited, but in the case of polyester polyol, it is preferably -20°C or higher, more preferably -10°C or higher, even more preferably 0°C or higher, especially preferably 10°C or higher, particularly preferably 20°C or higher, and most preferably 30°C or higher. In the case of polycarbonate polyol, it is preferably -100°C or higher, more preferably -90°C or higher, even more preferably -80°C or higher, and particularly preferably -70°C or higher. If the glass transition temperature is too low, the tack of the adhesive composition tends to become too strong, and air bubbles tend to get trapped during bonding, leading to defects.

[0036] The glass transition temperature of the polymer polyol (B) is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower in the case of polyester polyols. In the case of polycarbonate polyols, it is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. If the glass transition temperature is too high, the coating film becomes brittle, and there is a concern that embrittlement may become a problem.

[0037] The number-average molecular weight (Mn1) of polymer polyol (A) is greater than the number-average molecular weight (Mn2) of polymer polyol (B). The difference between the number-average molecular weight (Mn1) and number-average molecular weight (Mn2) is not particularly limited, but is preferably 6,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more. By creating such a difference in number-average molecular weight, it is possible to improve the compatibility of the carboxylic acid group-containing polymer compound, the heat resistance of the adhesive sheet, and eliminate hardness and brittleness. Specifically, polymer polyol (A) can be made higher molecular weight by introducing long-chain blocks, and the amount of carboxylic acid groups can be adjusted by short-chain blocks in polymer polyol (B), making it possible to impart heat resistance to the adhesive sheet. This makes it possible to improve the heat resistance of the adhesive sheet. The difference between the number-average molecular weight (Mn1) and the number-average molecular weight (Mn2) is not particularly limited, but is preferably 50,000 or less, more preferably 40,000 or less, even more preferably 30,000 or less, and particularly preferably 15,000 or less.

[0038] The polymer polyol (A) is preferably a polyester polyol or a polycarbonate polyol. The polymer polyol (B) is also preferably a polyester polyol or a polycarbonate polyol. It is more preferable that the polymer polyol (A) is a polyester polyol or a polycarbonate polyol, and furthermore, that the polymer polyol (B) is a polyester polyol or a polycarbonate polyol. As the polymer polyol (A), one of polyester polyols and polycarbonate polyols may be used alone, or two or more may be used in combination. As the polymer polyol (B), one of polyester polyols and polycarbonate polyols may be used alone, or two or more may be used in combination. When the same type of polyol is used alone as the polymer polyol (A) and polymer polyol (B) (for example, when both are polyester polyols, or when both are polycarbonate polyols, etc.), phase separation is relatively unlikely to occur, which is advantageous in that the reaction proceeds efficiently. On the other hand, when using other combinations of polyols as polymer polyol (A) and polymer polyol (B), it becomes possible to impart properties that cannot be obtained when using the same type of polyol individually as polymer polyol (A) and polymer polyol (B). For example, by using a polyester polyol as polymer polyol (A) and a polycarbonate polyol as polymer polyol (B), improved hydrolysis resistance can be expected. Preferably, both polymer polyol (A) and polymer polyol (B) are polyester polyols. In this case, for example, the cured coating film of the carboxylic acid group-containing polymer compound has good adhesion.

[0039] (Polyester polyol) It is preferable that the polyester polyol consists of a polycarboxylic acid component and a polyol component. The polycarboxylic acid component constituting the polyester polyol preferably contains 60 mol% or more of aromatic dicarboxylic acid when the total polycarboxylic acid is considered to be 100 mol%. More preferably, it is 70 mol% or more, even more preferably 80 mol% or more, and 100 mol% is also acceptable. If the amount is too low, the cohesive force of the coating film may be weak, and the adhesive strength to various substrates may decrease.

[0040] Aromatic dicarboxylic acids are not particularly limited and include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and diphenic acid. Examples of aromatic dicarboxylic acids include aromatic dicarboxylic acids having a sulfonic acid group, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5(4-sulfophenoxy)isophthalic acid, as well as aromatic dicarboxylic acids having a sulfonic acid base, such as their metal salts and ammonium salts. One of these may be used alone, or two or more may be used in combination. Among these, terephthalic acid, isophthalic acid, and mixtures thereof are particularly preferred in that they increase the cohesive strength of the coating film.

[0041] Other polycarboxylic acid components include alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and their acid anhydrides, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid. In addition, oxycarboxylic acid compounds having hydroxyl and carboxyl groups in their molecular structure, such as 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenityl alcohol, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, and 4,4-bis(p-hydroxyphenyl)valeric acid, can also be used.

[0042] When the total polyol content of a polyester polyol is considered to be 100 mol%, it is preferable that the glycol component be 90 mol% or more, more preferably 95 mol% or more, and it is also acceptable for it to be 100 mol%.

[0043] The glycol component is preferably an aliphatic glycol, an alicyclic glycol, an aromatic glycol, or an ether bond-containing glycol. Examples of aliphatic glycols include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol (DMH), neopentyl glycol ester of hydroxypivalate, dimethylolheptane, 2,2,4-trimethyl-1,3-pentanediol, and the like. Examples of alicyclic glycols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecanedimethylol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, and the like. Examples of ether-bond-containing glycols include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct. Examples of aromatic glycols include para-xylene glycol, meta-xylene glycol, orthoxylene glycol, 1,4-phenylene glycol, ethylene oxide adduct of 1,4-phenylene glycol, bisphenol A, ethylene oxide adduct of bisphenol A, and propylene oxide adduct, which are glycols obtained by adding 1 to several moles of ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols. One of these may be used alone, or two or more may be used in combination. Aliphatic glycols are preferred, with ethylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, or 1,6-hexanediol being more preferred.

[0044] Polyester polyols may be copolymerized with a trifunctional or higher component to introduce a branched skeleton as needed, specifically with the polycarboxylic acid component and / or the polyol component. When copolymerizing, the concentration of the component is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, preferably 5 mol% or less, and most preferably 3 mol% or less, when the total polycarboxylic acid component and the total polyol component are each 100 mol%. By keeping the concentration within the above range, especially when reacting with a curing agent to produce a cured coating film, a branched skeleton can be introduced, increasing the concentration of end groups (reaction sites) in the resin, resulting in a strong coating film with high crosslink density. Furthermore, exceeding 5 mol% may lead to a decrease in mechanical properties such as the elongation at the breaking point of the coating film, and there is a possibility of gelation during polymerization.

[0045] Examples of polycarboxylic acid components with three or more functions include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic acid dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). On the other hand, examples of polyols with three or more functions include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

[0046] An acid value may be introduced into the polyester polyol. The acid value of the polyester polyol is preferably 10 mg KOH / g or less, and more preferably 8 mg KOH / g or less. A low value does not pose any particular problem, but if it is too high, it may become impossible to extend the acid addition chain with tetracarboxylic dianhydride.

[0047] One method for introducing acid value is to introduce a carboxylic acid into the polyester polyol by acid addition after polymerization. When monocarboxylic acids, dicarboxylic acids, or polycarboxylic acid compounds with three or more functions are used for acid addition, a decrease in molecular weight may occur due to transesterification; therefore, it is preferable to use a compound having at least one carboxylic acid anhydride group. Examples of carboxylic acid anhydrides include succinic anhydride, maleic anhydride, orthophthalic acid, 2,5-norbornenedicarboxylic acid anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic acid dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA), 4,4'-(hexafloysopropylidene)diphthalic acid dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA).

[0048] (Polycarbonate polyol) The polycarbonate polyol is a polyol having a carbonate bond, and is preferably a polycarbonate diol. Commercially available polycarbonate diols can be used. Examples of commercially available polycarbonate diols include: Asahi Kasei Chemicals' trade names Duranol® T-4692 (number average molecular weight 2000), T-5652 (number average molecular weight 2000), T-5651 (number average molecular weight 1000), T-6002 (number average molecular weight 2000), CD-220 (number average molecular weight 2000), CD-220PL (number average molecular weight 2000), and CD-220HL (number average molecular weight 2000). Examples include Kuraray's product names Kuraray Polyol C-2050 (number average molecular weight 2000), C-2090 (number average molecular weight 2000), and C-3090 (number average molecular weight 3000), and Ube Industries' product names ETERNACOLL® UH-100 (number average molecular weight 1000), UH-200 (number average molecular weight 2000), PH-100 (number average molecular weight 1000), and PH-200 (number average molecular weight 2000). Using polyester polyols with low glass transition temperatures as the polymer polyol (B) is disadvantageous in terms of hydrolysis, but by using polycarbonate polyols, it is possible to eliminate ester bonds that are poorly hydrolyzable, and thus improve hydrolysis. As for polycarbonate polyols, liquid types are preferred from the viewpoint of workability, and the Duranol® series is particularly suitable.

[0049] <Tetracarboxylic acid dianhydride> Examples of tetracarboxylic dianhydrides include aromatic tetracarboxylic dianhydrides, aliphatic tetracarboxylic dianhydrides, and alicyclic tetracarboxylic dianhydrides, with aromatic tetracarboxylic dianhydrides being preferred. Specifically, examples include pyromellitic anhydride (PMDA), oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). One of these may be used alone, or two or more may be used in combination. Among these, pyromellitic anhydride is preferred.

[0050] <Chain extender> In addition to polymer polyol (A), polymer polyol (B), and tetracarboxylic dianhydride, chain extenders may be optionally used as copolymer components in the carboxylic acid group-containing polymer compound, as long as the effects of the present invention are not impaired. By using a chain extender, the acid value can be efficiently imparted to the carboxylic acid group-containing polymer compound. When a chain extender is used, the copolymerization amount of the chain extender is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of polymer polyol (A). Furthermore, it is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less. If the copolymerization amount is too high, phenomena such as difficulty in increasing the molecular weight and clouding of the varnish due to reactions between chain extenders may occur.

[0051] As chain extenders, low molecular weight diols with a molecular weight of 1000 g / mol or less are preferred, such as 2,2-dimethyl-1,3-propanediol and dimethylolbutanoic acid. One of these may be used alone, or two or more may be used in combination. Among these, 2,2-dimethyl-1,3-propanediol is preferred from the viewpoint of solubility and compatibility.

[0052] For polymer compounds containing carboxylic acid groups, quaternary ammonium salts or tertiary amines may be used as reaction catalysts, to the extent that they do not impair the effects of the present invention. For example, imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, or 1-cyanoethyl-2-ethyl-4-methylimidazole; triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, N,N-diisopropylethylamine, N,N-dimethylaminopyridine, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, or 6-dibutylamino-1 Examples include tertiary amines such as ,8-diazabicyclo(5,4,0)-undecene-7 and compounds obtained by amine salting these tertiary amines with phenol, octic acid, or quaternary tetraphenyl borate salts; and quaternary ammonium salts such as tetramethylammonium bromide, tetraethylammonium bromide, tetra-n-butylammonium bromide, tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0053] [Adhesive composition] By applying and drying an adhesive composition containing the above-mentioned carboxylic acid group-containing polymer compound, preferably further containing an organic solvent and epoxy resin (D), a resin layer (hereinafter also referred to as an adhesive layer) of a sheet-like encapsulant for a photoelectric conversion element (hereinafter also referred to as an adhesive sheet), as described later, can be obtained. In this way, a resin layer composed of a material containing a carboxylic acid group-containing polymer compound is obtained.

[0054] The content of the carboxylic acid group-containing polymer compound in the adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. The content of the carboxylic acid group-containing polymer compound in the adhesive composition is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. If the content is too low, the adhesiveness and heat resistance may decrease, and if the content is too high, the storage stability of the adhesive composition may decrease.

[0055] The content of the carboxylic acid group-containing polymer compound in the resin layer is preferably 20% by mass, more preferably 30% by mass or more, and even more preferably 40% by mass or more. This content may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more. The content of the carboxylic acid group-containing polymer compound in the resin layer may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. If the content is too low, the adhesion may decrease. Good adhesion is preferable for blocking moisture and oxygen so as to make it difficult for the corrosion of metallic calcium to progress in the calcium corrosion test described later, and is also preferable to make it difficult for delamination between layers to occur even if outgassing occurs during heat sealing described later. Furthermore, having the content of the carboxylic acid group-containing polymer compound in the resin layer within this range is preferable from the viewpoint of reducing the solvent content in the resin layer and reducing the amount of outgassing generated from the resin layer during heat sealing described later.

[0056] <Organic solvents> The organic solvent is not particularly limited as long as it dissolves the polymer compound containing the carboxylic acid group, and is more preferably one that also dissolves epoxy resin (D). Suitable organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; cellsolves such as methyl cellsolve and ethyl cellsolve; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate; and halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform. One or more of these can be used in combination. Among these, a mixed solvent of aromatic hydrocarbons and ketone solvents is preferred, and a mixed solvent of toluene and methyl ethyl ketone is more preferred.

[0057] The content of organic solvent in the adhesive composition is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 100 parts by mass or more, per 100 parts by mass of the carboxylic acid group-containing polymer compound. It is also preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and even more preferably 300 parts by mass or less. Too little may reduce the storage stability of the adhesive composition, while too much may be industrially disadvantageous.

[0058] <Epoxy resin (D)> The epoxy resin (D) is not particularly limited as long as it undergoes a curing reaction with the carboxyl groups of a carboxylic acid group-containing polymer compound to form crosslinks, but it is preferably a polyfunctional epoxy resin having multiple epoxy groups in a single molecule. By using a polyfunctional epoxy resin, the cured coating film obtained from the adhesive composition can easily form three-dimensional crosslinks, improving the heat resistance of the adhesive sheet. Examples of polyfunctional epoxy resins include cresol novolac type epoxy resins, epoxy resins having a dicyclopentadiene skeleton, and phenol novolac type epoxy resins. With cresol novolac type epoxy resins and phenol novolac type epoxy resins, the crosslinking density of the cured coating film can be reduced, resulting in a resin that is not hard or brittle and has good adhesion. A commercially available example of a cresol novolac type epoxy resin is YDCN-700 manufactured by DIC Corporation. On the other hand, with epoxy resins having a dicyclopentadiene skeleton, the hygroscopicity of the cured coating film is extremely low because the dicyclopentadiene skeleton is rigid, which reduces the crosslinking density of the cured coating film and results in a resin that is not hard or brittle and has good adhesion. Low hygroscopicity and good adhesion are desirable for blocking moisture and oxygen, as they reduce the amount of moisture carried in from the adhesive sheet and hinder the progression of metallic calcium corrosion in the calcium corrosion test described later. Good adhesion is also desirable because it reduces the likelihood of delamination between layers even if outgassing occurs during heat sealing, as described later. Examples of commercially available epoxy resins having a dicyclopentadiene skeleton include the HP7200 series manufactured by DIC Corporation. One of these may be used alone, or two or more may be used in combination.

[0059] Furthermore, in addition to the polyfunctional epoxy resins mentioned above, epoxy resins containing nitrogen atoms can also be used. When epoxy resins containing nitrogen atoms are used in combination, the coating film of the adhesive composition can be brought to a semi-cured state (hereinafter sometimes referred to as the B stage) by heating at a relatively low temperature, and the fluidity of the B stage film is suppressed, which tends to improve workability in the bonding operation. It is also preferable because it is expected to have the effect of suppressing foaming of the B stage film. Examples of epoxy resins containing nitrogen atoms include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, tetraglycidylbisaminomethylcyclohexanone, and glycidylamine-based resins such as N,N,N',N'-tetraglycidyl-m-xylenediamine. The amount of these nitrogen-containing epoxy resins blended is preferably 20% by mass or less of the total epoxy resin (D). If the blending amount is greater than 20% by mass, the rigidity tends to increase excessively, the adhesiveness tends to decrease, and the crosslinking reaction tends to proceed more easily during storage of the bonded sheet, which tends to reduce the sheet life. A more preferable upper limit for the blending amount is 10% by mass, and even more preferably 5% by mass.

[0060] Other epoxy resins can also be used as epoxy resin (D). Examples include glycidyl ether types such as bisphenol A diglycidyl ether, bisphenol S diglycidyl ether, and brominated bisphenol A diglycidyl ether; glycidyl ester types such as hexahydrophthalate glycidyl ester and dimer acid glycidyl ester; and alicyclic or aliphatic epoxyides such as triglycidyl isocyanurate, 3,4-epoxycyclohexylmethylcarboxylate, epoxidized polybutadiene, and epoxidized soybean oil. One type may be used alone, or two or more types may be used in combination.

[0061] The epoxy resin (D) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of the carboxylic acid group-containing polymer compound. It is also preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. If the amount is too small, curing may be insufficient, and the adhesiveness and heat resistance may decrease. If the amount is too large, there will be a lot of uncrosslinked epoxy resin, and the heat resistance of the adhesive sheet may decrease.

[0062] A curing catalyst can be used in the curing reaction of epoxy resin (D). Examples include imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, or 1-cyanoethyl-2-ethyl-4-methylimidazole; tertiary amines such as triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, or 6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7, and compounds obtained by amine salting these tertiary amines with phenol, octyl acid, or quaternized tetraphenylborate salts; cationic catalysts such as triallylsulfonium hexafluoroantimonate or diallyiodonium hexafluoroantimonate; and triphenylphosphine. Of these, tertiary amines such as 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, or 6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7, and compounds obtained by amine salting these tertiary amines with phenol, octic acid, or quaternized tetraphenyl borate salts are preferred in terms of thermosetting properties, heat resistance, adhesion to metals, and storage stability after compounding. The amount of curing catalyst added is preferably 0.01 to 1.0 parts by mass per 100 parts by mass of the carboxylic acid group-containing polymer compound. Within this range, the catalytic effect on the reaction between the carboxylic acid group-containing polymer compound and the epoxy resin (D) is further increased, and strong adhesive performance can be obtained.

[0063] <Moisture-absorbing filler> The adhesive composition may or may not contain a hygroscopic filler. By adding a hygroscopic filler, moisture that has penetrated through the adhesive composition can be captured, thereby suppressing moisture penetration into the device for a longer period of time.

[0064] A "hygroscopic filler" is a material that has the ability to absorb moisture, and is not particularly limited as long as it can achieve the objectives of the present invention. Specifically, it is one selected from zeolite, calcium oxide, magnesium oxide, strontium oxide, aluminum oxide, and barium oxide, or a mixture or solid solution of two or more metal oxides selected from these. Examples of mixtures or solid solutions of two or more metal oxides include calcined dolomite (a mixture containing calcium oxide and magnesium oxide) and calcined hydrotalcite (a solid solution of calcium oxide and aluminum oxide). Such hygroscopic fillers are well known as moisture absorbers in various technical fields, and commercially available products can be used. Specifically, examples include calcined dolomite (such as "KT" from Yoshizawa Lime Co., Ltd.), calcium oxide (such as "Moistop #10" from Sankyo Flour Milling Co., Ltd.), magnesium oxide (such as "Kyowa Mag MF-150" and "Kyowa Mag MF-30" from Kyowa Chemical Industry Co., Ltd., and "Pure Mag FNMG" from Tateho Chemical Industry Co., Ltd.), and lightly calcined magnesium oxide (such as "#500", "#1000", and "#5000" from Tateho Chemical Industry Co., Ltd.).

[0065] The average particle size of the hygroscopic filler is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. Using such a small size not only imparts a high degree of moisture resistance to the adhesive sheet but also enhances the adhesive strength. However, if the average particle size of the hygroscopic filler is too small, the particles tend to aggregate, making sheet processing difficult. Therefore, the average particle size of the hygroscopic filler is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

[0066] If the average particle size of a commercially available hygroscopic filler is 10 μm or less, it can be used as is. However, if the average particle size of a commercially available product exceeds 10 μm, it is preferable to crush, classify, or otherwise process it to prepare it as granular material with an average particle size of 10 μm or less before use.

[0067] The term "average particle size" here refers to the median diameter of the particle size distribution of the object being measured (granular material) when the distribution is prepared based on volume. The volume-based particle size distribution can be measured by the laser diffraction-scattering method based on Mie scattering theory, and specifically, the LA-500 manufactured by Horiba, Ltd. can be used as a laser diffraction particle size distribution measuring device. It is preferable to use a sample prepared by dispersing a hygroscopic filler in water using ultrasound.

[0068] The hygroscopic filler can be one that has been surface-treated with a surface treatment agent. By using such a surface-treated hygroscopic filler, the storage stability of the resin composition constituting the adhesive layer can be further enhanced, and it is possible to prevent the hygroscopic filler from reacting with the moisture in the resin before curing.

[0069] Specifically, surface treatment agents that can be used for surface treatment include higher fatty acids, alkylsilanes, silane coupling agents, etc., with higher fatty acids or alkylsilanes being preferred.

[0070] As for the higher fatty acids, specifically, higher fatty acids with 18 or more carbon atoms, such as stearic acid, montanic acid, myristic acid, and palmitic acid, are preferred, with stearic acid being more preferred. These may be used individually or in combination of two or more.

[0071] Examples of alkylsilanes include methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octadecyltrimethoxysilane, dimethyldimethoxysilane, octyltriethoxysilane, and n-octadecyldimethyl(3-(trimethoxysilyl)propyl)ammonium chloride. These may be used individually or in combination of two or more.

[0072] Silane coupling agents include, specifically, epoxy-based silane coupling agents such as 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyl(dimethoxy)methylsilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane and 11-mercaptoundecyltrimethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, N-phenyl-3-aminopropyltrimethoxysilane, N-methylaminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and N-(2-aminoethyl)-3- Examples of such coupling agents include amino-based silane coupling agents such as minopropyldimethoxymethylsilane; ureido-based silane coupling agents such as 3-ureidopropyltriethoxysilane; vinyl-based silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldiethoxysilane; styryl-based silane coupling agents such as p-styryltrimethoxysilane; acrylate-based silane coupling agents such as 3-acrylooxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; isocyanate-based silane coupling agents such as 3-isocyanatetopropyltrimethoxysilane; sulfide-based silane coupling agents such as bis(triethoxysilylpropyl)disulfide and bis(triethoxysilylpropyl)tetrasulfide; and phenyltrimethoxysilane, methacryloxypropyltrimethoxysilane, imidazolesilane, triazinesilane, etc. These may be used individually or in combination of two or more.

[0073] The surface treatment can be specifically carried out by adding and spraying a surface treatment agent while stirring and dispersing the untreated hygroscopic filler at room temperature in a mixer, and stirring for 5 to 60 minutes. Known mixers can be used, including blenders such as V-blenders, ribbon blenders, and bubble cone blenders; mixers such as Henschel mixers and concrete mixers; ball mills; and cutter mills. Alternatively, the surface treatment can be performed by mixing the aforementioned higher fatty acids, alkylsilanes, or silane coupling agents when crushing the hygroscopic material with a ball mill or similar device. The amount of surface treatment agent used varies depending on the type of hygroscopic filler or the type of surface treatment agent, but 1 to 10% by weight relative to the hygroscopic filler is preferred.

[0074] If the content of hygroscopic filler in the adhesive composition becomes too high, the viscosity of the adhesive composition increases, the strength of the cured product decreases and it becomes brittle, and the transparency of the resin is impaired. From this viewpoint, the content of hygroscopic filler is preferably 40% by weight or less, more preferably 35% by weight or less, even more preferably 30% by weight or less, even more preferably 25% by weight or less, and especially preferably 20% by weight or less, based on 100% by weight of the nonvolatile content in the adhesive composition. On the other hand, from the viewpoint of fully obtaining the effects of including hygroscopic filler, the content of hygroscopic filler is preferably 1% by weight or more, more preferably 5% by weight or more, and even more preferably 10% by weight or more, based on 100% by weight of the nonvolatile content in the composition.

[0075] <Other additives> The adhesive composition may further contain various curable resins and / or additives, as long as they do not impair the effects of the present invention. Examples of curable resins include phenolic resins, amino resins, isocyanate compounds, and silicone resins.

[0076] Examples of phenolic resins include formaldehyde condensates of alkylated phenols and cresols. Specifically, examples include formaldehyde condensates of alkylated (e.g., methyl, ethyl, propyl, isopropyl, butyl)phenols, p-tert-amylphenol, 4,4'-sec-butylidenephenol, p-tert-butylphenol, o-cresol, m-cresol, p-cresol, p-cyclohexylphenol, 4,4'-isopropylidenephenol, p-nonylphenol, p-octylphenol, 3-pentadecylphenol, phenol, phenyl-o-cresol, p-phenylphenol, and xylenol. One of these may be used alone, or two or more may be used in combination.

[0077] Examples of amino resins include formaldehyde adducts such as urea, melamine, and benzoguanamine, as well as alkyl ether compounds of these with alcohols having 1 to 6 carbon atoms. Specifically, examples include methoxylated methylolurea, methoxylated methylol N,N-ethyleneurea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, and butoxylated methylol benzoguanamine. Methoxylated methylol melamine, butoxylated methylol melamine, and methylollated benzoguanamine are preferred, and each may be used alone or in combination of two or more.

[0078] Examples of isocyanate compounds include aromatic or aliphatic diisocyanates and polyisocyanates with a valency of 3 or higher, and can be either low-molecular-weight or high-molecular-weight compounds. Examples include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, or trimers of these isocyanate compounds. Furthermore, examples include terminal isocyanate group-containing compounds obtained by reacting an excess amount of these isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, or triethanolamine, or high-molecular-weight active hydrogen compounds such as various polyester polyols, polyether polyols, and polyamides.

[0079] The isocyanate compound may be a blocked isocyanate. Examples of isocyanate blocking agents include phenols such as phenol, thiophenol, methylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime; alcohols such as methanol, ethanol, propanol, and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol; and lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propyllactam. Other examples include aromatic amines, imides, active methylene compounds such as acetylacetone, acetoacetate ester, and ethyl malonate ester, mercaptans, imines, ureas, diaryl compounds, and sodium bisulfite. Blocked isocyanates are obtained by adding the above-mentioned isocyanate compound and an isocyanate blocking agent using a conventionally known method.

[0080] The adhesive composition may optionally contain a silane coupling agent. The inclusion of a silane coupling agent is highly preferable because it improves the adhesion to metals and heat resistance. While not particularly limited, silane coupling agents can include those with unsaturated groups, glycidyl groups, or amino groups. Examples of silane coupling agents with unsaturated groups include vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane. Examples of silane coupling agents with glycidyl groups include γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane. Examples of silane coupling agents with amino groups include N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane. Of these, silane coupling agents having a glycidyl group, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are preferred from the viewpoint of heat resistance. The amount of silane coupling agent is preferably 0.5 to 20 parts by mass per 100 parts by mass of the carboxylic acid group-containing polymer compound. If the amount of silane coupling agent is less than 0.5 parts by mass, the heat resistance of the resulting adhesive sheet may be poor, and if it exceeds 20 parts by mass, poor heat resistance and poor adhesion may occur.

[0081] The adhesive composition may contain, as needed, flame retardants such as bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds, leveling agents, pigments, dyes, and other additives.

[0082] [Adhesive Sheet] An adhesive sheet (a sheet-shaped encapsulant for photoelectric conversion elements) includes a resin layer (hereinafter also referred to as the adhesive layer) which is a coating of the adhesive composition obtained by curing the adhesive composition. The adhesive sheet is obtained, for example, by applying the adhesive composition to a substrate or release substrate, drying it, and curing it. The adhesive sheet has the function of adhering the substrate to the material to be bonded by the adhesive layer. After bonding, the substrate of the adhesive sheet functions as a protective layer for the material to be bonded. If a release substrate is used, the release substrate can be released and the adhesive layer can be transferred to another material to be bonded. Specific configurations of the adhesive sheet include substrate / adhesive layer, release substrate / adhesive layer, release substrate / adhesive layer / substrate, release substrate / adhesive layer / release substrate, etc. In some cases, the adhesive sheet may consist of only the adhesive layer after the release substrate has been peeled off. The adhesive sheet may also contain trace amounts or small amounts of organic solvents.

[0083] Adhesive sheets can be obtained by applying an adhesive composition to various substrates according to conventional methods, removing at least a portion of the solvent, and drying. Furthermore, if a release substrate is attached to the adhesive layer after removing at least a portion of the solvent and drying, it becomes possible to wind the sheet without transfer to the substrate, resulting in excellent operability. Additionally, the adhesive layer is protected, providing excellent storage properties and ease of use. Moreover, after applying and drying the adhesive to the release substrate, if necessary, another release substrate can be attached to transfer the adhesive layer itself to other substrates.

[0084] When manufacturing adhesive sheets, it is preferable to apply the adhesive composition to a substrate and then heat the coated substrate, for example, in an oven, to volatilize the solvent. In this case, the environment may be atmospheric or under an inert gas such as nitrogen (inert oven). The heating temperature is, for example, 80°C to 200°C, preferably 100°C to 170°C, more preferably 110°C to 160°C, and even more preferably 120°C to 150°C. The heating time is not particularly limited as long as the solvent is removed, but for example, if the wet thickness at the time of coating is 200 μm, it is 3 minutes or more. Since the purpose is to remove the solvent, for example, at a low temperature such as 40°C, it is 10 hours or more under nitrogen, more preferably 24 hours or more. Heating in such an oven reduces the solvent content in the adhesive composition, which can reduce the amount of outgassing generated from the resin layer during heat sealing, as described later. These temperature conditions can be combined; for example, after coating, the surface may first be heated at 120°C to evaporate most of the solvent, and then heated in an inert oven at 40°C for 90 hours to remove the solvent and adjust the crosslinking reaction.

[0085] The substrate, or the substrate to which the transfer is made, is not particularly limited and can include film-like resins, metal plates, metal foils, papers, glass, etc. Examples of film-like resins include polyester resins, polyamide resins, polyimide resins, polyamide-imide resins, and olefin resins. When used for encapsulating photoelectric conversion elements, high barrier properties are required for the film-like resin, so it is preferable to provide a high-barrier layer on one or both sides of the substrate. As a method for manufacturing the barrier layer, for example, a method of forming a transparent inorganic film such as silicone oxide, aluminum oxide, aluminum-based compound, or silicon-based compound on a polymer film can be used. Examples of methods for forming a transparent inorganic film on a polymer film include the sol-gel method, PVD method, electron beam evaporation method, plasma CVD method, and reactive sputtering method. Examples of materials for metal plates and metal foils include various metals such as SUS, copper, aluminum, iron, and zinc, as well as their alloys and plated products. Examples of papers include fine paper, kraft paper, roll paper, and glassine paper. Examples of composite materials include glass epoxy. Based on the adhesive strength and durability between the substrate and the adhesive composition, polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, SUS steel sheet, copper foil, aluminum foil, and glass epoxy are preferred.

[0086] The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, on which coating layers of a sealant such as clay, polyethylene, or polypropylene are applied, and then a silicone-based, fluorine-based, or alkyd-based release agent is applied on each of these coating layers. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, applied alone, and films such as polyethylene terephthalate on which the above-mentioned release agent is applied. Due to reasons such as the release force between the release substrate and the adhesive layer, and the adverse effect of silicone on electrical properties, it is preferable to use fine paper that has been treated with polypropylene sealant on both sides and then an alkyd-based release agent is applied on top of it, or to use polyethylene terephthalate on which an alkyd-based release agent is applied.

[0087] When the adhesive sheet includes a base material and / or a release material, it is particularly preferable to use a film-like resin as the base material and / or release material from the viewpoint of further improving adaptability to roll-to-roll processes.

[0088] The method for coating the adhesive composition onto a substrate or release substrate is not particularly limited and includes methods such as a comma coater and a reverse roll coater. Alternatively, the adhesive layer can be applied directly to a barrier layer film or by a transfer method, as needed. The thickness of the adhesive layer after drying can be changed as needed, but is preferably in the range of 5 to 200 μm. The thickness of the adhesive layer is more preferably in the range of 10 to 100 μm, even more preferably in the range of 15 to 80 μm, and particularly preferably in the range of 20 to 60 μm. If the thickness of the adhesive layer is less than 5 μm, the adhesive strength may be insufficient. If it exceeds 200 μm, drying is insufficient and a large amount of residual solvent is generated, which can cause problems such as the adhesive layer adhering to the back surface when stored in roll form for a long period of time. The drying conditions are not particularly limited, but the residual solvent rate after drying is preferably 4% by mass or less, and more preferably 1% by mass or less. If it is greater than 4% by mass, the residual solvent may foam during photoelectric conversion element encapsulation, which can cause blistering.

[0089] The resulting adhesive sheet may be used for lamination without using a release film, or it may be used after being laminated with a release film and stored. The adhesive sheet is preferably transported and stored at low temperatures. Specifically, 15°C or lower, more preferably 10°C or lower, and even more preferably 5°C or lower. Since refrigerated adhesive sheets will condense when handled at room temperature, it is preferable to take measures such as returning them to room temperature in a low-humidity atmosphere such as nitrogen, or packaging them in a nitrogen-purged container.

[0090] Any method can be used to bond the adhesive sheet to the photoelectric conversion element device; for example, it can be bonded using a press or a roll. Alternatively, the two can be bonded while heating is applied, such as by using a heated press or heated roll device.

[0091] The transmittance of light with a wavelength of 400 nm to 700 nm in the adhesive layer (resin layer) of the adhesive sheet is 80% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 98% or more. When the transmittance is 95% or more, it does not hinder the transmission of light used for photoelectric conversion to the photoelectric conversion layer, and furthermore, when the photoelectric conversion device is attached to a window or the like, the adhesive layer is less likely to cause design problems. The above light transmittance is 100% or less, may be 99.8% or less, or 99.6% or less.

[0092] The haze of the adhesive layer (resin layer) of the adhesive sheet is 10% or less, preferably 5% or less, more preferably 1% or less, even more preferably 0.5% or less, even more preferably 0.2% or less, and particularly preferably 0.1% or less. Having the haze of the adhesive layer within this range allows light captured by the photoelectric conversion element to be efficiently utilized without scattering. The above haze may be 0% or more, and may also be 0.005% or more.

[0093] The moisture absorption rate (ratio of mass increase to original mass) of the adhesive layer of the adhesive sheet is preferably 2% or less, and more preferably 1% or less. The moisture absorption rate of the adhesive sheet was determined by measuring a sample using TGA after the sheet had been left standing for 24 hours at 23°C and 50% RH. The weight loss between 80°C and 100°C was taken as the amount of water absorbed, and the ratio to the total weight was calculated as the moisture absorption rate. The TGA was performed under conditions of 30°C to 170°C and 5°C / min. A low moisture absorption rate is preferable for blocking moisture and oxygen, as it reduces the amount of moisture carried in from the adhesive sheet and makes it difficult for the corrosion of metallic calcium to progress in the calcium corrosion test described later, thus reducing damage to the element due to moisture. For example, when performing a calcium corrosion test as described in the examples using the above adhesive sheet, the length of the silvery-white portion of one side of the calcium is 90% or more of the initial length.

[0094] The amount of outgassing generated from the adhesive layer of the adhesive sheet during heat sealing of the adhesive sheet is preferably 200 ppm or less, and more preferably 100 ppm or less. For example, if the amount of outgassing generated when sealing at a heating temperature of about 100°C to 130°C is small, it is less likely for bubbles to form and delamination between layers of the photoelectric conversion element can be suppressed. For example, when checking the bubble area using the above adhesive sheet as described in the example, the area of ​​the bubble portion is less than 70% of the total area (area of ​​the bubble portion + area of ​​the non-bubble portion), preferably less than 50%, and more preferably less than 20%.

[0095] [Laminated structure] Figure 1 shows an example of a laminate 1 in which photoelectric elements are encapsulated using an adhesive sheet (a sheet-shaped encapsulant for photoelectric elements). A photoelectric element is an element that converts light energy into electrical energy. Specifically, examples include crystalline silicon solar cells, amorphous silicon solar cells, CI(G)S solar cells, perovskite solar cells, organic thin-film solar cells, dye-sensitized solar cells, and GaAs solar cells. Among these, organic thin-film solar cells, which are lightweight and flexible and can be produced in a roll-to-roll process, and solar cells having a perovskite compound in the power generation layer (hereinafter referred to as "perovskite solar cells") are preferred. In the following description, terms such as "up," "down," "upward," and "downward" may be used for convenience, but these terms are merely for convenience and are unrelated to, for example, the direction of gravity.

[0096] The laminate 1 has a structure in which, for example, a first substrate 11, a first high-barrier layer 12 made of an inorganic film or the like, a photoelectric conversion element 13, a second high-barrier layer 14, and a second substrate 15 are provided in this order from the bottom. The photoelectric conversion element 13 has a structure in which, for example, a first electrode, a photoelectric conversion layer, and a second electrode are provided in this order from the bottom. A buffer layer, such as an electron transport layer or a hole transport layer, may be provided between the first electrode and the photoelectric conversion layer and / or between the second electrode and the photoelectric conversion layer. Figure 1 shows an example in which the first electrode (labeled 131 in Figure 1) is provided on the first high-barrier layer 12.

[0097] The laminate 1 further includes a resin layer (adhesive layer) 16, and has a structure in which a photoelectric conversion element 13 is sealed by the resin layer 16 between a first high-barrier layer 12 and a second high-barrier layer 14. More specifically, the resin layer 16 seals the photoelectric conversion element 13 so that there is no surface on which the photoelectric conversion element 13 is exposed. In the example of Figure 1, the photoelectric conversion element 13 and the second high-barrier layer 14 are spaced apart, and the laminate 1 has a structure in which a part of the resin layer 16 is provided between the photoelectric conversion element 13 and the second high-barrier layer 14.

[0098] When the photoelectric conversion element 13 performs photoelectric conversion using light L2 incident from the second substrate 15 and second barrier layer 14 side of the laminate 1, the light L2 reaches the photoelectric conversion layer via the resin layer 16. If the resin layer 16 has poor transparency, even light of the wavelength used for photoelectric conversion will be blocked by the resin layer 16, reducing the power generation efficiency of the photoelectric conversion element 13. On the other hand, if the resin layer 16 has excellent transparency, light of the wavelength used for photoelectric conversion can easily pass through the resin layer 16 and reach the photoelectric conversion element 13, reducing the decrease in power generation efficiency due to the resin layer 16. The photoelectric conversion element 13 may also perform photoelectric conversion using light L1 incident from the first substrate 11 and first high barrier layer 12 side of the laminate 1.

[0099] If the resin layer 16 has excellent sealing properties, for example, the amount of outgassing generated from the resin layer 16 during sealing is small, making it less likely for bubbles to form, and thus less likely for delamination between layers to occur. As a result, the loss of electrical energy related to the photoelectric conversion element 13 can be reduced. In addition, damage to the element due to outgassing is suppressed. Furthermore, if the resin layer 16 has excellent sealing properties, for example, the photoelectric conversion element 13 sealed in the resin layer 16 is less likely to be exposed to moisture and / or oxygen in the air. This is particularly beneficial when the photoelectric conversion element 13 is, for example, an organic thin-film solar cell or a perovskite solar cell that is susceptible to damage from moisture and oxygen, and a decrease in photoelectric conversion efficiency is suppressed. [Examples]

[0100] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. In the following, unless otherwise specified, "parts" means "parts by mass".

[0101] (Method for evaluating physical properties) The methods for evaluating the physical properties of polymeric polyols and polymeric compounds containing carboxylic acid groups, which will be discussed later, are explained below.

[0102] (1) Composition of the compound The sample (a polymer compound containing a carboxylic acid group or a polymer polyol) was dissolved in deuterated chloroform, and the molar ratio of each component constituting the sample was determined by 1H-NMR analysis.

[0103] (2) Number average molecular weight (Mn) The sample (carboxylic acid group-containing polymer compound or polymer polyol) was dissolved or diluted in tetrahydrofuran to a sample concentration of approximately 0.5% by mass, and filtered through a 0.5 μm pore size polytetrafluoroethylene membrane filter to be used as the measurement sample. The number-average molecular weight was measured by gel permeation chromatography using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was 1 mL / min and the column temperature was 30°C. Showa Denko KF-802, 804L, and 806L columns were used in series. Monodisperse polystyrene was used as the molecular weight standard. However, if the sample did not dissolve in tetrahydrofuran, N,N-dimethylformamide was used instead. Low molecular weight compounds (oligomers, etc.) with a number-average molecular weight of less than 500 were not counted and were excluded.

[0104] (3) Glass transition temperature Using a differential scanning calorimetry analyzer "DSC220" manufactured by Seiko Electronics Industries, Ltd., 5 mg of the sample (carboxylic acid group-containing polymer compound or polymer polyol) was placed in an aluminum pan, sealed by pressing down on the lid, and held at 250°C for 5 minutes. After rapid cooling with liquid nitrogen, measurements were taken from -150°C to 250°C at a heating rate of 20°C / min. The inflection point of the obtained curve was defined as the glass transition temperature. If there were two or more inflection points, it was considered that block copolymerization had occurred, and each transition point was read and treated as having multiple glass transition temperatures.

[0105] (4) Acid value 0.2 g of the sample (carboxylic acid group-containing polymer compound or polymer polyol) was dissolved in 20 ml of chloroform, and titrated with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator. From the titration volume, the number of mg of KOH consumed in neutralization was converted to the amount per gram of resin to calculate the acid value (mgKOH / g).

[0106] [Examples of polymerization of polymeric polyols] <High molecular weight polyol (A1)> In a reaction vessel equipped with a stirrer, thermometer, and condenser for the outflow, 189 parts terephthalic acid, 435 parts isophthalic acid, 7 parts trimellitic anhydride, 110 parts 2-methyl-1,3-propanediol, 483 parts 1,6-hexanediol, and 0.2 parts tetrabutyl titanate (the catalyst) were charged. The temperature was gradually increased to 250°C, and the esterification reaction was carried out while removing the distilled water from the system. After the esterification reaction was completed, initial polymerization was carried out while gradually reducing the pressure to 10 mmHg, and the temperature was increased to 250°C. Further polymerization was carried out at a pressure of 1 mmHg or less until the predetermined stirring torque was achieved. After that, the pressure was returned to atmospheric pressure with nitrogen, 28 parts trimellitic anhydride were added, and the reaction was carried out at 220°C for 30 minutes to obtain polymer polyol (A1), which is a polyester polyol. The composition and property values ​​of the polymer polyol (A1) obtained in this way were determined and are shown in Table 1. Each measurement and evaluation item was performed according to the method described above.

[0107] <High-molecular-weight polyol (B1)> In a reaction vessel equipped with a stirrer, thermometer, and condenser for the outflow, 390 parts terephthalic acid, 390 parts isophthalic acid, 367 parts ethylene glycol, 362 parts 2,2-dimethyl-1,3-propanediol, and 0.2 parts tetrabutyl titanate (the catalyst) were charged. The temperature was gradually increased to 250°C, and the esterification reaction was carried out while removing the distilled water from the system. After the completion of the esterification reaction, initial polymerization was carried out under reduced pressure, gradually decreasing the pressure to 10 mmHg, while simultaneously increasing the temperature to 250°C. Further polymerization was carried out at a pressure of 1 mmHg or less until a predetermined stirring torque was achieved, thereby obtaining polymeric polyol (B1), a polyester polyol. The composition and characteristic values ​​of the polymeric polyol (B1) obtained in this way were determined and are shown in Table 1. Each measurement and evaluation item was performed according to the method described above.

[0108] <High molecular weight polyol (A2)> Polymeric polyol (A2), a polyester polyol, was obtained using a method similar to that used for the polymerization of polymeric polyol (B1) to obtain the composition shown in Table 1. The characteristic values ​​of the obtained polymeric polyol (A2) were determined and are shown in Table 1.

[0109] [Table 1]

[0110] <High-molecular-weight polyols (B2) and (B3)> The following polymeric polyols (B2) and (B3) were used, respectively. High-molecular-weight polyol (B2): Polycarbonate diol T5652 manufactured by Asahi Kasei Corporation (number average molecular weight 2000) High molecular weight polyol (B3): Polyester polyol P2010 manufactured by Kuraray Co., Ltd. (number average molecular weight 2000)

[0111] [Examples of synthesis of carboxylic acid group-containing polymer compounds] <Carboxylic acid group-containing polymer compound (C1)> In a reaction vessel equipped with a stirrer, thermometer, and reflux tubing, 160 parts of polymeric polyol (A1), 40 parts of polymeric polyol (B1), 5.2 parts of pyromellitic anhydride, and 200 parts of toluene were charged and dissolved in toluene while the temperature was gradually raised to 80°C. After dissolution was complete, 0.1 parts of triethylamine were added as a reaction catalyst, and the temperature was gradually raised to 105°C and the reaction was carried out for 24 hours. After confirming the completion of the reaction by IR, the solution was diluted with 108 parts of toluene to obtain a solution of carboxylic acid group-containing polymer compound (C1) with a solid content of 40% by mass. The composition and characteristic values ​​of the carboxylic acid group-containing polymer compound (C1) obtained in this way were determined and are shown in Table 2. The ratios of polymeric polyol (A), polymeric polyol (B), and tetracarboxylic dianhydride listed in Table 2 are shown in mass%. Each measurement and evaluation item was performed according to the method described above.

[0112] <Carboxylic acid group-containing polymer compound (C2)> Carboxylic acid-containing polymer compound (C2) was synthesized using the same method as for the synthesis of carboxylic acid-containing polymer compound (C1) to the composition shown in Table 2. The characteristic values ​​of the synthesized carboxylic acid-containing polymer compound (C2) were determined and are shown in Table 2. Each measurement and evaluation item was performed according to the method described above.

[0113] <Carboxylic acid group-containing polymer compound (C3)> Carboxylic acid-containing polymer compound (C3) was synthesized using the same method as for the synthesis of carboxylic acid-containing polymer compound (C1) to the composition shown in Table 2. The characteristic values ​​of the synthesized carboxylic acid-containing polymer compound (C3) were determined and are shown in Table 2. Each measurement and evaluation item was performed according to the method described above.

[0114] [Table 2]

[0115] [Examples of adhesive composition manufacturing] <Adhesive composition α> To 100 parts of the solid content of a carboxylic acid group-containing polymer compound (C1), 9 parts of YDCN-700-10 (novolac-type epoxy resin) manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. and 0.1 parts of TETRAD®-X (N,N,N',N'-tetraglycidyl-m-xylenediamine) manufactured by Mitsubishi Gas Chemical Co., Ltd. were added as epoxy resins. The solid content concentration was then adjusted to 35% by mass using methyl ethyl ketone to obtain adhesive composition α.

[0116] <Adhesive composition β> To 100 parts of the solid content of a carboxylic acid group-containing polymer compound (C2), 29 parts of YDCN-700-10 (novolac-type epoxy resin) manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. and 0.4 parts of TETRAD®-X (N,N,N',N'-tetraglycidyl-m-xylenediamine) manufactured by Mitsubishi Gas Chemical Co., Ltd. were added as epoxy resins. The solid content concentration was then adjusted to 35% by mass using methyl ethyl ketone to obtain adhesive composition β.

[0117] <Adhesive composition γ> To 100 parts of the solid content of a carboxylic acid group-containing polymer compound (C3), 12 parts of YDCN-700-10 (novolac-type epoxy resin) manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. and 0.2 parts of TETRAD®-X (N,N,N',N'-tetraglycidyl-m-xylenediamine) manufactured by Mitsubishi Gas Chemical Co., Ltd. were added as epoxy resins. The solid content concentration was then adjusted to 35% by mass using methyl ethyl ketone to obtain adhesive composition γ.

[0118] [Examples of adhesive sheet manufacturing] Adhesive sheets for each example and comparative example were manufactured as described below. Nippon Electric Glass's OA-11 (0.5 mm thick) was used as the glass substrate for each example and comparative example. Tests and measurements described later were performed on each manufactured adhesive sheet, and the results are shown in Table 3.

[0119] <Example 1> Adhesive composition α was applied to a glass substrate using an applicator to a dry thickness of 25 μm. The coated substrate was then placed in an oven and heated at 80°C for 5 minutes, followed by heating at 150°C for 5 minutes to evaporate the solvent. The resulting laminate was placed in an inert oven and heated at 150°C under nitrogen for 5 hours. The transmittance and haze of the adhesive layer were measured using the resulting laminate (adhesive sheet, or sheet-like encapsulant for photoelectric conversion elements) of the glass substrate and the adhesive composition coating (adhesive layer or resin layer). Next, in order to evaluate the sealing properties, samples for calcium corrosion testing and samples for confirming the bubble area were prepared as described below. In Example 1, the laminate of the glass substrate and adhesive layer obtained was placed on top of a calcium substrate (Q-Lights, frame 8.4 mm, calcium substrate outer dimensions 30 mm × 30 mm, Ca film area 13.2 mm × 13.2 mm, calcium thickness 200 nm) (Figure 2A) in a glove box, with metallic calcium deposited in a square shape in the center of the glass substrate. The laminate was temporarily bonded by lamination at 100°C. Subsequently, a sealed calcium substrate for calcium corrosion testing was obtained by heating at 170°C and pressurizing at 2 MPa for 10 minutes using a press machine, thereby sealing the metallic calcium layer with the adhesive layer (Figure 2B). In addition, a sample for checking the bubble area was prepared using a glass substrate instead of the calcium substrate.

[0120] <Example 2> The procedure was carried out in the same manner as in Example 1, except that the temperature used for heating and pressurizing with a press machine was set to 150°C.

[0121] <Example 3> The procedure was carried out in the same manner as in Example 1, except that the dry thickness when applying the adhesive composition α was set to 50 μm and the temperature when heating and pressurizing using a press was set to 150°C.

[0122] <Comparative Example 1> A two-component epoxy adhesive (Konishi Bond E) was used as the adhesive composition. Equal amounts of the two adhesives were pre-mixed on a glass substrate, and the adhesive was coated to achieve a cured adhesive layer thickness of 50 μm. Afterward, the substrate was left to stand for 24 hours to obtain the adhesive-coated glass substrate. The transmittance and haze of the adhesive layer were measured using this sample. For the calcium corrosion test, the adhesive was directly coated onto a calcium substrate in a glove box, and the glass substrate was attached and left to stand for 24 hours to prepare the sample. Due to the room temperature effect, the bubble area was not measured.

[0123] <Comparative Example 2> The procedure was carried out in the same manner as in Comparative Example 1, except that a wet-curing adhesive (Aron Alpha, Color Change, manufactured by Toagosei Co., Ltd.) was used as the adhesive composition.

[0124] <Comparative Example 3> A hot melt sheet was obtained from the hot melt resin as an adhesive layer by sandwiching a hot melt resin (Yokohama Display Museum, MB-1110) between XENOMAX (registered trademark, manufactured by Xenomax Japan), heating it at 150°C and pressurizing it at 2 MPa for 10 minutes, and then rapidly cooling it with ice. The adhesive layer thickness was set to 100 μm by inserting a spacer during pressing. The transmittance and haze of the adhesive layer were measured on a single hot melt sheet obtained. For the preparation of the sealed calcium substrate, the calcium substrate, hot melt sheet, and glass substrate were laminated in this order, temporarily bonded by lamination at 100°C in a glove box, and then pressed. The pressing procedure was the same as in Example 1, except that the temperature was set to 150°C. In addition, a sample for checking the bubble area was prepared using a glass substrate instead of a calcium substrate.

[0125] <Comparative Example 4> Except for using adhesive composition β instead of adhesive composition α as the adhesive composition, the procedure for producing a laminate of a glass substrate and an adhesive composition coating film was carried out in the same manner as in Example 1. However, adhesive composition β gelled, and film formation was not possible.

[0126] <Comparative Example 5> Except for using adhesive composition γ instead of adhesive composition α as the adhesive composition, the procedure for producing a laminate of a glass substrate and an adhesive composition coating film was carried out in the same manner as in Example 1. However, adhesive composition γ gelled, and film formation was not possible.

[0127] <Calcium corrosion test> The metallic calcium layer exhibits a silvery-white appearance with a metallic luster, but as corrosion progresses, the corroded portion becomes transparent calcium hydroxide. Therefore, the length of each piece of the metallic calcium layer decreases after testing. In this test, after sealing, the samples were placed in a 60°C, 90% RH environment for 200 hours. A score of ○ was given if the length of the silvery-white portion of one side of the calcium layer was 90% or more of the initial length, a △ if it was 80% or more but less than 90%, and a × if it was 0% or more but less than 80%. The average length of the four sides of the calcium layer was used. The results were 95% in Example 1, 91% in Examples 2 and 3, 82% in Comparative Example 1, 15% in Comparative Example 2, and 0% in Comparative Example 3.

[0128] <Checking the area of ​​air bubbles> For laminates of glass substrate / adhesive layer / glass substrate prepared for bubble area verification, the bubble area was measured. The bubble area corresponds to the amount of outgassing generated from the adhesive layer during heat sealing. Photographs were taken of the obtained samples using a surface light source, and the resulting images were divided into bubble and non-bubble portions using ImageJ. A × was used if the bubble area accounted for 70% or more of the total area (bubble area + non-bubble area), a △ if it was between 20% and less than 70%, and a ○ if it was less than 20%.

[0129] <Measuring the thickness of the adhesive layer> Measurements were taken using a digital macrometer (manufactured by Mitutoyo). Measurements were taken with each glass substrate, and the thickness of the adhesive layer (resin layer) was determined by subtracting the thickness of the glass substrate.

[0130] <Haze Measurement> The haze of glass substrates with an adhesive layer was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. Three similar measurements were performed, and the arithmetic mean was adopted. A glass substrate without the adhesive layer was used as a blank, and its value was subtracted to obtain the haze value of the adhesive layer (resin layer).

[0131] <Measurement of light transmittance between wavelengths of 400nm and 700nm> The transmittance of light with wavelengths between 400 nm and 700 nm was measured using ultraviolet-visible spectroscopy under the following measurement conditions. Light transmittance was measured using an integrating sphere with a Shimadzu Corporation SolidSpec-3700 UV-Vis-NIR spectrophotometer (software: UVProvever.2.71). <Measurement conditions> Measurement wavelength: 400nm or more and 700nm or less Scan speed: Medium Slit width: 12nm Sampling pitch: 0.5nm Standard whiteboard: Standard reflective Spectralon The average transmittance of light with wavelengths between 400 nm and 700 nm was used as the transmittance of the sample. For samples prepared by coating a glass substrate, the transmittance of the adhesive layer (resin layer) was calculated by subtracting the value of a blank glass substrate without the adhesive layer coating.

[0132] [Table 3]

[0133] <Example: Encapsulation of organic thin-film solar cells> A patterned transparent electrode substrate (Geomatec, 40mm x 50mm) was cleaned with acetone and dried with clean dry air. Avantama ZnO nanoparticle dispersion was dropped onto the substrate, and coating was performed with a 25μm coating gap using a No. 0 bar, followed by heating at 120°C for 10 minutes. This condition resulted in a thickness of approximately 50nm on glass. After wiping off the coating with acetone, leaving a 25mm x 30mm area, the photoelectric conversion layer solution was dropped onto the substrate, and coating was performed with a 50μm coating gap, followed by heating at 140°C for 15 minutes. This condition resulted in a thickness of approximately 250nm on glass. The photoelectric conversion layer solution consisted of equal parts poly(3-hexylthiophene-2,5-diyl) and NanomSpectra (E100H) dissolved in chlorobenzene. After wiping off the coating with chlorobenzene, leaving a 25mm x 30mm area, HTL solar (Heraus) was dropped onto the surface, coating with a 50μm coating gap, and heated at 80°C for 30 minutes. This condition resulted in a thickness of approximately 400nm on the glass. Subsequently, the coating was wiped off with pure water, leaving a 25mm x 30mm area. Patterned silver was vacuum-deposited onto this laminate to a thickness of 90nm. A 35mm x 35mm glass substrate with an adhesive layer, prepared in the same manner as in Example 1, was placed on top with the adhesive layer facing the element side. Then, a metal spacer was placed around the circumference of the substrate with a 5mm margin, and this area was heated and pressurized to obtain an organic thin-film solar cell with the substrate sealed around its periphery. For performance evaluation before sealing, measurements were performed under nitrogen gas purging to suppress the effects of degradation due to moisture, etc., and the photoelectric conversion efficiency was compared with that after sealing. The difference in photoelectric conversion efficiency before and after sealing was less than 5%. Thus, the decrease in photoelectric conversion efficiency was suppressed. [Explanation of symbols]

[0134] 1. Laminate 11 First base material 12. First High Barrier Layer 13 Photoelectric conversion element 131 1st electrode 14. Second High Barrier Layer 15 Second base material 16 resin layer L1,L2 light 21 Metallic calcium layer 22,23 Glass substrate

Claims

1. A sheet-like encapsulant for a photoelectric conversion element, comprising a resin layer made of a material containing a polymer compound with a carboxylic acid group, The carboxylic acid group-containing polymer compound comprises, as copolymer components, a polymer polyol (A), a polymer polyol (B) different from polymer polyol (A), and a tetracarboxylic dianhydride. Among the copolymer components of the carboxylic acid group-containing polymer compound, the polymer polyol (A) is the component with the largest number-average molecular weight. The number average molecular weight (Mn2) of the polymer polyol (B) is 1,000 or more and 10,000 or less, and the number average molecular weight (Mn1) of the polymer polyol (A) is 6,000 or more greater than the number average molecular weight (Mn2) of the polymer polyol (B). The number average molecular weight (Mn3) of the carboxylic acid group-containing polymer compound is 1.7 times or less than the number average molecular weight (Mn1) of the polymer polyol (A). The transmittance of light with a wavelength of 400 nm to 700 nm in the resin layer is 80% or more. The haze of the resin layer is 0.5% or less. Encapsulating material for photoelectric conversion elements.

2. The encapsulant for a photoelectric conversion element according to claim 1, wherein the polymer polyol (A) is a polyester polyol or a polycarbonate polyol, and the polymer polyol (B) is a polyester polyol or a polycarbonate polyol.

3. The encapsulant for a photoelectric conversion element according to claim 1 or 2, wherein the acid value of the carboxylic acid group-containing polymer compound is 5 mg KOH / g or more and 100 mg KOH / g or less.

4. A laminate comprising a photoelectric conversion element sealed with a resin layer of the photoelectric conversion element sealing material described in claim 1 or 2.

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