Intermediate film, laminate, methods for producing these, and laminated glass

Abstract

Disclosed is an intermediate film which satisfies at least one of the requirement (A) and the requirement (B) described below.　Requirement (A): The inclination (21), obtained by (bending stiffness (2) – bending stiffness (1)) / amount of change in thickness, is greater than -10.　Requirement (B): The inclination (31), obtained by (bending stiffness (3) – bending stiffness (1)) / amount of change in thickness, is greater than -10. (Bending stiffnesses (1), (2), and (3) are respective bending stiffnesses [unit: N / mm] at 50°C of laminated glasses (1), (2), and (3) for measurement, which are respectively obtained by bonding two sheets of glass having a thickness of 2.75 mm by the intermediary of one, two, or three intermediate films. The amount of change in thickness is the amount of change [unit: mm] in the thickness of the intermediate films between a pair of glass sheets during the measurement of the bending stiffness (3) or the bending stiffness (2) with respect to the thickness of the intermediate film between a pair of glass sheets during the measurement of the bending stiffness (1).)

Description

Interlayer film, laminate, manufacturing method thereof, and laminated glass

[0001] The present invention relates to an interlayer film used in laminated glass, etc., a laminate having an interlayer film, laminated glass, and methods for producing the interlayer film and laminate.

[0002] Laminated glass is safe because it shatters little even when broken by external impact, and is therefore widely used for window glass in various vehicles such as automobiles, railway vehicles, aircraft, and ships, as well as in buildings. Laminated glass is generally known to be formed by interposing an interlayer film for laminated glass, made of a thermoplastic resin or the like, between a pair of panes of glass to form an integrated glass. When used in buildings, laminated glass is used not only for window glass but also for glass floors, curtain walls, and the like. For these applications, it is sometimes made larger and used as structural glazing.

[0003] Ionomer resins have been used in interlayer films for laminated glass in some cases. Known ionomer resins used in interlayer films for laminated glass include ethylene-unsaturated carboxylic acid copolymers, such as ethylene-(meth)acrylic acid copolymers, in which at least some of the carboxyl groups in the side chains are crosslinked between molecular chains by metal cations (see, for example, Patent Documents 1 to 3).

[0004] International Publication No. 2022 / 065146 Japanese Patent Application Laid-Open No. 2014-58409 International Publication No. 2019 / 054363

[0005] However, when laminated glass is enlarged as described above and used as structural glazing, it is required to have high rigidity. Furthermore, since laminated glass is generally used exposed to outdoor environments, it is required to have good rigidity regardless of changes in outdoor temperature, particularly high rigidity even at high temperatures around 40°C.

[0006] However, although interlayer films for laminated glass using ionomer resins can have a relatively high bending rigidity, studies by the present inventors have revealed that it is difficult to maintain high rigidity even in high-temperature environments.

[0007] Furthermore, laminated glass used in buildings is often required to have impact resistance from the viewpoint of safety, and therefore, a thick interlayer is required. To thicken the interlayer, multiple relatively thin films may be laminated. However, according to studies by the present inventors, laminated glass manufactured in this manner may have a reduced rigidity at high temperatures when multiple films are laminated to increase the thickness. That is, it was found that increasing the thickness of the interlayer disposed between a pair of glass members in laminated glass may reduce the rigidity at high temperatures.

[0008] Therefore, an object of the present invention is to provide an interlayer film that can provide laminates or laminated glass with excellent bending rigidity at high temperatures, and in particular, a first object of the present invention is to provide an interlayer film that can provide laminates or laminated glass with excellent bending rigidity at high temperatures even when the thickness of the interlayer film between a pair of substrates such as glass members is increased by stacking multiple interlayer films, etc. A second object of the present invention is to provide an interlayer film that can provide laminates or laminated glass with excellent rigidity in an environment of 20 to 40°C.

[0009] As a result of extensive investigation, the present inventors have found that the first problem can be solved by setting the bending rigidity at 50°C of a laminated glass to be measured, which is made by sandwiching one interlayer film, the bending rigidity at 50°C of a laminated glass to be measured, which is made by sandwiching two or three interlayer films, and the slope calculated from the thickness change therebetween to a certain level or greater, and have thus completed the present invention in a first aspect described below. That is, the present invention provides the following [1] to

[23] . [1] An interlayer film that satisfies at least one of the following requirements (A) and (B): Requirement (A): The slope (21) calculated by (bending rigidity (2) - bending rigidity (1)) / thickness change is greater than -10. Requirement (B): The slope (31) calculated by (bending rigidity (3) - bending rigidity (1)) / thickness change is greater than -10. (Note that the bending rigidity (1) is the bending rigidity [unit: N / mm] at 50°C of the laminated glass (1) for measurement obtained by bonding two pieces of glass each having a thickness of 2.75 mm with one piece of the interlayer film interposed therebetween. The bending rigidity (2) is the bending rigidity [unit: N / mm] at 50°C of the laminated glass (2) for measurement obtained by bonding two pieces of glass each having a thickness of 2.75 mm with two pieces of the interlayer film interposed therebetween. The bending rigidity (3) is the bending rigidity [unit: N / mm] at 50°C of the laminated glass (3) for measurement obtained by bonding two pieces of glass each having a thickness of 2.75 mm with three pieces of the interlayer film interposed therebetween. The change in thickness is the change in thickness [unit: mm] of the interlayer film between a pair of pieces of glass when measuring the bending rigidity (2) or the bending rigidity (3) relative to the thickness of the interlayer film between the pair of pieces of glass when measuring the bending rigidity (1).) [2] The interlayer film according to the above item [1], wherein the slope (21) is from −9 to 50. [3] The interlayer film according to [1] or [2] above, wherein the bending rigidity of the laminated glass for measurement (1) at 50°C is 700 N / mm or more. [4] The interlayer film according to any one of [1] to [3] above, which contains an ionomer resin. [5] The interlayer film according to [4] above, wherein the ionomer resin contains a structural unit (A) derived from an unsaturated carboxylic acid, a structural unit (B) of a neutralized unsaturated carboxylic acid, and a structural unit (C) derived from ethylene.[6] The interlayer film according to [5] above, wherein the ionomer resin contains a structural unit (A) derived from (meth)acrylic acid, a structural unit (B) of a neutralized (meth)acrylic acid, and a structural unit (C) derived from ethylene. [7] The interlayer film according to [5] or [6] above, wherein the total content of the structural units (A) and (B) in the ionomer resin is 10% by mass or more and 25% by mass or less, based on the total amount of the structural units constituting the ionomer resin. [8] The interlayer film according to any one of [5] to [7] above, wherein the content of the structural unit (B) in the ionomer resin is 4% by mass or more and 17.5% by mass or less, based on the total amount of the structural units constituting the ionomer resin. [9] The interlayer film according to any one of [5] to [8] above, wherein the structural unit (B) contains at least one of magnesium and zinc.

[10] The interlayer film according to any one of [5] to [9] above, wherein the content of structural units derived from alkyl (meth)acrylate in the ionomer resin is 15% by mass or less.

[11] The interlayer film according to any one of [4] to

[10] above, further comprising a silane coupling agent.

[12] The interlayer film according to any one of [1] to

[11] above, wherein the width is 1 m or more.

[13] The interlayer film according to any one of [1] to

[12] above, wherein the interlayer film is an extrusion molded product.

[14] The interlayer film according to any one of [1] to

[13] above, wherein the glass transition temperature is 50°C or more and 75°C or less.

[15] A laminate comprising the interlayer film according to any one of [1] to

[14] above and a pair of substrates, wherein the interlayer film is disposed between the pair of substrates.

[16] The laminate according to

[15] above, wherein the laminate is laminated glass.

[17] The laminate according to

[16] above, wherein the laminate is laminated glass for building structures.

[18] A method for producing the interlayer film according to any one of the above [1] to

[14] , comprising the steps of kneading an ionomer resin with a mixture of an additive and an ethylene-(meth)acrylic acid copolymer to obtain a resin composition, and extruding the resin composition.

[19] A method for producing a laminate, comprising the step of disposing the interlayer film according to any one of the above [1] to

[14] between a pair of substrates.

[20] A method for producing the laminate according to the above

[19] , wherein a plurality of the interlayer films are disposed between the pair of substrates.

[21] An interlayer film in which the slope (21a) calculated by (bending rigidity (2a) - bending rigidity (1)) / thickness change is greater than -10. (Note that the bending rigidity (1) is the bending rigidity [unit: N / mm] at 50°C of a laminated glass (1) for measurement obtained by bonding two pieces of glass each having a thickness of 2.75 mm together via one interlayer film. The bending rigidity (2a) is the bending rigidity [unit: N / mm] at 50°C of a laminated glass (2a) for measurement obtained by bonding two pieces of glass each having a thickness of 2.75 mm together via an interlayer film (2a) whose thickness is different from that of the aforementioned interlayer films. The change in thickness is the change in thickness [unit: mm] of the interlayer film between the pair of glass pieces when the bending rigidity (2a) is measured relative to the thickness of the interlayer film between the pair of glass pieces when the bending rigidity (1) is measured.)

[22] A laminated glass comprising a pair of glass members and one or more interlayer films disposed between the pair of glass members, the pair of glass members being bonded together via the one or more interlayer films, which satisfies at least one of the following requirements (A1) and (B1): Requirement (A1): The slope (21c) obtained by (bending rigidity (2c) - bending rigidity (1c)) / amount of change in thickness is greater than -10. Requirement (B1): The slope (31c) obtained by (bending rigidity (3c) - bending rigidity (1c)) / amount of change in thickness is greater than -10. (Note that the bending rigidity (1c) is the bending rigidity [unit: N / mm] at 50°C of the measurement laminated glass (1c) obtained by bonding the pair of glass members together with one interlayer film interposed therebetween. The bending rigidity (2c) is the bending rigidity [unit: N / mm] at 50°C of the measurement laminated glass (2c) obtained by bonding the pair of glass members together with two interlayer films interposed therebetween. The bending rigidity (3c) is the bending rigidity [unit: N / mm] at 50°C of the measurement laminated glass (3c) obtained by bonding the pair of glass members together with three interlayer films interposed therebetween. The change in thickness is the change in thickness [unit: mm] of the interlayer film between the pair of glass members when measuring the bending rigidity (3c) or the bending rigidity (2c) relative to the thickness of the interlayer film between the pair of glass members when measuring the bending rigidity (1c).

[23] A laminated glass comprising a pair of glass members and an interlayer film disposed between the pair of glass members, the pair of glass members being bonded together via the interlayer film, the laminated glass satisfying the following requirement (E1): (the slope (21ac) calculated by bending rigidity (2ac) - bending rigidity (1ac)) / thickness change is greater than -10. (Note that the bending rigidity (1ac) is the bending rigidity (unit: N / mm) of the laminated glass at 50°C. The bending rigidity (2ac) is the bending rigidity (unit: N / mm) at 50°C of a measurement laminated glass obtained by bonding a pair of glass members together via a single interlayer film having a thickness different from that of the interlayer film. The thickness change is the change in thickness (unit: mm) of the interlayer film between the pair of glass members when the bending rigidity (2ac) is measured relative to the thickness of the interlayer film between the pair of glass members when the bending rigidity (1ac) is measured.)

[0010] As a result of extensive investigation, the present inventors have found that the second problem can be solved by setting the ratio of the bending rigidity at 50°C to the bending rigidity at 25°C of a laminated glass to be measured, which is produced using an interlayer film, to a certain level or higher, and have thus completed the second aspect of the present invention described below. That is, the present invention provides the following

[24] to

[43] .

[24] An interlayer film, in which a laminated glass to be measured, obtained by bonding two sheets of glass having a thickness of 2.75 mm together via an interlayer film, has a ratio of the bending rigidity at 50°C to the bending rigidity at 25°C of 0.5 or higher.

[25] The interlayer film according to

[24] above, in which the bending rigidity at 50°C of the laminated glass to be measured is 700 N / mm or higher.

[26] The interlayer film according to

[24] or

[25] above, which contains an ionomer resin.

[27] The interlayer film according to

[26] above, in which the ionomer resin includes a structural unit (A) derived from an unsaturated carboxylic acid, a structural unit (B) of a neutralized unsaturated carboxylic acid, and a structural unit (C) derived from ethylene.

[28] The interlayer film according to

[26] above, wherein the ionomer resin contains a structural unit (A) derived from (meth)acrylic acid, a structural unit (B) of a neutralized (meth)acrylic acid, and a structural unit (C) derived from ethylene.

[29] The interlayer film according to

[27] or

[28] above, wherein the total content of the structural units (A) and (B) in the ionomer resin is 10% by mass or more and 25% by mass or less, based on the total amount of the structural units constituting the ionomer resin.

[30] The interlayer film according to any one of

[27] to

[29] above, wherein the content of the structural unit (B) in the ionomer resin is 4% by mass or more and 17.5% by mass or less, based on the total amount of the structural units constituting the ionomer resin.

[31] The interlayer film according to any one of

[27] to

[30] above, wherein the structural unit (B) contains at least one of magnesium and zinc.

[32] The interlayer film according to any one of

[27] to

[31] above, wherein the content of structural units derived from alkyl (meth)acrylate in the ionomer resin is 15% by mass or less.

[33] The interlayer film according to any one of

[26] to

[32] above, further comprising a silane coupling agent.

[34] The interlayer film according to any one of

[24] to

[33] above, wherein the width is 1 m or more.

[35] The interlayer film according to any one of

[24] to

[34] above, which is an extrusion molded product.

[36] The interlayer film according to any one of

[24] to

[35] above, having a glass transition temperature of 50°C or higher and 75°C or lower.

[37] A laminate comprising the interlayer film according to any one of

[24] to

[36] above and a pair of substrates, the interlayer film being disposed between the pair of substrates.

[38] The laminate according to

[37] above, which is a laminated glass.

[39] The laminate according to

[38] above, which is a laminated glass for building structures.

[40] A method for producing the interlayer film according to any one of

[24] to

[36] above, comprising: kneading an ionomer resin with a mixture of an additive and an ethylene-(meth)acrylic acid copolymer to obtain a resin composition; and extruding the resin composition.

[41] A method for producing a laminate, comprising disposing the interlayer film according to any one of

[24] to

[36] above between a pair of substrates.

[42] A method for producing a laminate according to

[41] above, in which a plurality of the interlayer films are disposed between the pair of substrates.

[43] Laminated glass having a ratio of bending rigidity at 50°C to bending rigidity at 25°C of 0.5 or more.

[0011] Use of the interlayer film according to the first aspect of the present invention makes it possible to provide laminates and laminated glass with excellent bending rigidity at high temperatures. In particular, even when the thickness of the interlayer film between a pair of substrates such as glass members is increased by stacking multiple interlayer films, the bending rigidity of the laminates and laminated glass at high temperatures can be excellent. Use of the interlayer film according to the second aspect of the present invention makes it possible to obtain laminates and laminated glass with excellent rigidity in an environment of 20 to 40°C.

[0012] FIG. 2 is a schematic diagram showing a method for measuring bending rigidity.

[0013] <<First Embodiment>> A first aspect of the present invention will be described in detail below with reference to the first embodiment. <Bending Rigidity> An interlayer film according to the first embodiment of the present invention satisfies at least one of the following requirements (A) and (B). Requirement (A): The slope (21) obtained by (bending rigidity (2) - bending rigidity (1)) / thickness change is greater than -10. Requirement (B): The slope (31) obtained by (bending rigidity (3) - bending rigidity (1)) / thickness change is greater than -10.

[0014] Here, flexural rigidity (1) is the flexural rigidity (unit: N / mm) at 50°C of a test laminated glass (1) obtained by bonding two 2.75 mm thick glass sheets together via one interlayer film. Flexural rigidity (2) is the flexural rigidity (unit: N / mm) at 50°C of a test laminated glass (2) obtained by bonding two 2.75 mm thick glass sheets together via two interlayer films. Flexural rigidity (3) is the flexural rigidity (unit: N / mm) at 50°C of a test laminated glass (3) obtained by bonding two 2.75 mm thick glass sheets together via three interlayer films. Furthermore, the change in thickness is the change in thickness (unit: mm) of the interlayer film between a pair of glass sheets when measuring flexural rigidity (3) or flexural rigidity (2) relative to the thickness of the interlayer film between a pair of glass sheets when measuring flexural rigidity (1). Therefore, in requirement (A), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring bending rigidity (1) (i.e., in the measurement laminated glass (1)) from the total thickness of two interlayer films when measuring bending rigidity (2) (i.e., in the measurement laminated glass (2)). In addition, in requirement (B), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring bending rigidity (1) from the total thickness of three interlayer films when measuring bending rigidity (3) (i.e., in the measurement laminated glass (3)).

[0015] If the slope (21) or slope (31) of the interlayer film is −10 or less, it becomes difficult to achieve excellent bending rigidity at high temperatures around 40° C. In particular, when multiple interlayer films are laminated and the thickness of the interlayer film between a pair of substrates (for example, between a pair of glass members) becomes large, it becomes difficult to achieve excellent bending rigidity at high temperatures around 40° C. for a laminate such as laminated glass made using the interlayer film.

[0016] In the interlayer film according to the first embodiment, it is preferable that either the slope (21) or the slope (31) is greater than −10, but it is more preferable that both the slope (21) and the slope (31) are greater than −10. When both the slope (21) and the slope (31) are greater than −10, even when the thickness of the interlayer film between a pair of substrates (for example, glass members) in a laminate such as laminated glass is increased, it is possible to more reliably achieve excellent bending rigidity at high temperatures.

[0017] The slope (21) is preferably −9 or greater, more preferably −4 or greater, and even more preferably 0 or greater. As the slope (21) increases, it becomes easier to prevent a decrease in bending rigidity at high temperatures, particularly when the thickness of the interlayer film between a pair of substrates (e.g., glass members) increases. The slope (21) is not particularly limited, but from the viewpoint of easily imparting flexibility, adhesiveness, and the like to the interlayer film, it is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0018] From the same viewpoint as the above-described slope (21), the slope (31) is preferably −9 or greater, more preferably −4 or greater, and even more preferably 0 or greater. The slope (31) is not particularly limited, but from the viewpoint of easily imparting flexibility, adhesiveness, and the like to the interlayer film, it is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0019] The interlayer film according to the first embodiment preferably satisfies at least one of the following requirements (C) and (D): Requirement (C): The slope (21b) obtained by (bending rigidity (2b) - bending rigidity (1b)) / thickness change is 0 or greater. Requirement (D): The slope (31b) obtained by (bending rigidity (3b) - bending rigidity (1b)) / thickness change is 0 or greater.

[0020] Here, the bending rigidity (1b) is the bending rigidity (unit: N / mm) of the measurement laminated glass (1) at 25°C. The bending rigidity (2b) is the bending rigidity (unit: N / mm) of the measurement laminated glass (2) at 25°C. The bending rigidity (3b) is the bending rigidity (unit: N / mm) of the measurement laminated glass (3) at 25°C. The change in thickness is the change in the thickness of the interlayer film between the pair of glass panes when measuring the bending rigidity (3b) or the bending rigidity (2b) relative to the thickness of the interlayer film between the pair of glass panes when measuring the bending rigidity (1b). Therefore, in requirement (C), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring the bending rigidity (1b) from the total thickness of the two interlayer films when measuring the bending rigidity (2b). In addition, in requirement (D), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring bending stiffness (1b) from the total thickness of three interlayer films when measuring bending stiffness (3b).

[0021] The interlayer film according to the first embodiment can have superior bending rigidity at around room temperature by having either the slope (21b) or the slope (31b) greater than or equal to 0. In particular, when a plurality of interlayer films are stacked to increase the thickness of the interlayer film between a pair of substrates (for example, between a pair of glass members), the bending rigidity of a laminate such as laminated glass made using the interlayer film at room temperature can be made superior.

[0022] In the interlayer film according to the first embodiment, it is preferable that either the slope (21b) or the slope (31b) is 0 or greater, and it is more preferable that both the slope (21b) and the slope (31b) are 0 or greater. When both the slope (21b) and the slope (31b) are 0 or greater, even when the thickness of the interlayer film between a pair of substrates (for example, glass members) in a laminate such as laminated glass is large, it is possible to more reliably achieve excellent bending rigidity at room temperature.

[0023] The slope (21b) is preferably 30 or more, more preferably 50 or more, even more preferably 100 or more, and even more preferably 200 or more. An increase in the slope (21b) makes it easier to prevent a decrease in bending rigidity at room temperature, particularly when the thickness of the interlayer film between a pair of substrates (e.g., glass members) is increased. The slope (21b) is not particularly limited, but from the viewpoint of easily imparting flexibility, adhesiveness, etc. to the interlayer film, it is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less. From the same viewpoint as the slope (21b), the slope (31b) is preferably 30 or more, more preferably 50 or more, even more preferably 100 or more, and even more preferably 200 or more. The slope (31b) is not particularly limited, but from the viewpoint of easily imparting flexibility, adhesiveness, etc. to the interlayer film, it is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less.

[0024] The interlayer film according to the first embodiment preferably has a flexural rigidity of 700 N / mm or more at 50°C for the laminated glass (1) to be measured. When the flexural rigidity of the laminated glass (1) to be measured is 700 N / mm or more at 50°C, a laminate or laminated glass having the interlayer film according to the first embodiment tends to have excellent rigidity in a relatively high temperature environment of about 40 to 50°C. The flexural rigidity of the laminated glass (1) to be measured at 50°C is preferably 800 N / mm or more, more preferably 850 N / mm or more, and even more preferably 900 N / mm or more. The higher the flexural rigidity of the laminated glass (1) to be measured at 50°C, the better. However, from the viewpoint of ensuring a certain level of flexibility in the interlayer film, the flexural rigidity is, for example, 3000 N / mm or less, and may be 2000 N / mm or less, 1500 N / mm or less, or 1000 N / mm or less.

[0025] The interlayer film according to the first embodiment preferably has a flexural rigidity of 900 N / mm or more at 25°C for the laminated glass to be measured (1). When the flexural rigidity of the laminated glass to be measured (1) is 900 N / mm or more at 25°C, a laminate or laminated glass having the interlayer film according to the first embodiment tends to have excellent rigidity in a room temperature environment. The flexural rigidity of the laminated glass to be measured (1) at 25°C is preferably 1000 N / mm or more, more preferably 1100 N / mm or more, and even more preferably 1200 N / mm or more. The higher the flexural rigidity of the laminated glass to be measured (1) at 25°C, the better. However, from the viewpoint of imparting a certain degree of flexibility to the interlayer film even in a room temperature environment, the flexural rigidity is, for example, 4000 N / mm or less, and may be 3000 N / mm or less, 2300 N / mm or less, or 2000 N / mm or less.

[0026] The interlayer film according to the first embodiment preferably has a flexural rigidity of 900 N / mm or more at 30°C for the laminated glass to be measured (1). When the flexural rigidity of the laminated glass to be measured (1) is 900 N / mm or more at 30°C, a laminate or laminated glass having the interlayer film according to the first embodiment tends to have excellent rigidity in a room temperature environment. The flexural rigidity of the laminated glass to be measured (1) at 30°C is preferably 1000 N / mm or more, more preferably 1100 N / mm or more, and even more preferably 1200 N / mm or more. The higher the flexural rigidity of the laminated glass to be measured (1) at 30°C, the better. However, from the viewpoint of imparting a certain degree of flexibility to the interlayer film even in a room temperature environment, the flexural rigidity is, for example, 4000 N / mm or less, and may be 3000 N / mm or less, 2300 N / mm or less, or 2000 N / mm or less.

[0027] The interlayer film according to the first embodiment preferably has a flexural rigidity of 800 N / mm or more at 40°C for the laminated glass to be measured (1). When the flexural rigidity of the laminated glass to be measured (1) is 800 N / mm or more at 40°C, a laminate or laminated glass having the interlayer film according to the first embodiment tends to have excellent rigidity in a room temperature environment. The flexural rigidity of the laminated glass to be measured (1) at 40°C is preferably 900 N / mm or more, more preferably 1000 N / mm or more, and even more preferably 1100 N / mm or more. The higher the flexural rigidity of the laminated glass to be measured (1) at 40°C, the better. However, from the viewpoint of imparting a certain degree of flexibility to the interlayer film even in a room temperature environment, the flexural rigidity is, for example, 4000 N / mm or less, 3000 N / mm or less, 2300 N / mm or less, 2000 N / mm or less, or 1500 N / mm or less.

[0028] The bending rigidity can be adjusted by the type of resin, the composition of the monomers constituting the resin, the glass transition temperature (Tg) of the interlayer film, and the thickness of the interlayer film. For example, the use of an ionomer resin facilitates increasing the bending rigidity. Furthermore, using a high-Tg component as the monomer constituting the ionomer resin, while reducing the amount of low-Tg components and increasing the degree of neutralization, increases the bending rigidity at 50°C and also facilitates increasing the slopes (21) and (31). Furthermore, when other resin components are contained in addition to the ionomer resin, reducing the content of the other resin components facilitates maintaining high bending rigidity, particularly bending rigidity at high temperatures, and also facilitates maintaining large values ​​for the slopes (21) and (31). Furthermore, increasing the thickness of the interlayer film tends to increase the absolute value of bending rigidity (particularly bending rigidity at room temperature). The above-mentioned bending rigidities (1) to (3) and (1b) to (3b) at 50°C or 25°C can be measured by pre-pressing two 2.75 mm thick glass sheets together with one to three interlayers therebetween, followed by full-pressing in an autoclave to obtain a laminated glass for measurement, which is then cured for one week, in an environment of 25°C or 50°C. The conditions for producing the laminated glass for measurement may be as described in the laminated glass manufacturing method in the Examples below. The 2.75 mm glass used in measuring the bending rigidities (1) to (3), (1b) to (3b) and the bending rigidities (2a) and (2ab) below is float plate glass, the details of which are as described in the Examples.

[0029] <Glass Transition Temperature> The interlayer film according to the first embodiment preferably has a glass transition temperature (Tg) of 50°C or higher and 75°C or lower. When the interlayer film has a Tg of 50°C or higher, the bending rigidity at 50°C of a laminate, such as laminated glass, including the interlayer film is likely to be high. Furthermore, stacking multiple interlayer films makes it easier to prevent a decrease in the bending rigidity of the laminate (e.g., laminated glass) at high temperatures, even if the thickness of the interlayer film between a pair of substrates (e.g., glass) increases, and the slopes (21) and (31) tend to increase. Furthermore, a Tg of 75°C or lower makes it easier to impart a certain degree of flexibility to the interlayer film. Furthermore, degassing properties during the production of laminated glass are likely to be improved. The glass transition temperature (Tg) of the interlayer film is more preferably 55°C or higher, more preferably 58°C or higher, and even more preferably 60°C or higher. Furthermore, the glass transition temperature (Tg) of the interlayer film is more preferably 73°C or lower, and even more preferably 71°C or lower. The glass transition temperature can be adjusted by the composition of the resin that constitutes the interlayer film. For example, in the ionomer resin described below, the glass transition temperature can be increased by increasing the amount of the structural unit (B) of the neutralized unsaturated carboxylic acid. The glass transition temperature can also be increased by using specific metal ions contained in the structural unit (B). Furthermore, the glass transition temperature can also be increased by reducing the amount of structural units derived from alkyl (meth)acrylate. The glass transition temperature can be detected by measuring the viscoelasticity using a dynamic viscoelasticity measuring device and reading the peak temperature of the loss tangent tanδ obtained from the results of the viscoelasticity measurement. Details of the measurement conditions are as described in the Examples.

[0030] The interlayer film according to the first embodiment may contain a resin. The resin used in the interlayer film is preferably a thermoplastic resin. Using a thermoplastic resin in the interlayer film facilitates bonding a pair of substrates or a pair of glass panes via the interlayer film by thermocompression bonding. Examples of resins used in the interlayer film include polyvinyl acetal resin, ethylene-vinyl acetate copolymer resin, ionomer resin, polyurethane resin, and thermoplastic elastomer, with ionomer resin being preferred among these. The use of an ionomer resin facilitates increasing the bending rigidity at 25°C. Furthermore, as described below, adjusting the monomer composition of the ionomer resin also facilitates increasing the bending rigidity at 50°C. Furthermore, adjusting the monomer composition facilitates preventing a decrease in the bending rigidity of a laminate (e.g., laminated glass) at high temperatures, even when multiple interlayer films are stacked and the thickness of the interlayer film between a pair of substrates (e.g., glass) increases, and the slopes (21) and (31) tend to increase.

[0031] [Ionomer Resin] Examples of ionomer resins include ionomer resins of ethylene-unsaturated carboxylic acid copolymers. Ionomer resins are typically resins obtained by neutralizing ethylene-unsaturated carboxylic acid copolymers with metal ions. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, 2-ethylacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, fumaric anhydride, itaconic anhydride, monomethyl maleate, and monoethyl maleate. In the ionomer resin, the unsaturated carboxylic acid may be used alone or in combination with two or more. Among these, acrylic acid and methacrylic acid are preferred. Therefore, the ionomer resin is preferably an ionomer resin of ethylene-(meth)acrylic acid copolymer. Note that (meth)acrylic acid means at least either methacrylic acid or acrylic acid, and the same applies to similar terms below.

[0032] Examples of metal ions include lithium, potassium, sodium, silver, copper, calcium, magnesium, titanium, zinc, aluminum, barium, beryllium, strontium, tin, lead, iron, cobalt, nickel, cadmium, and mercury. Among these, at least one of magnesium and zinc is preferred, with magnesium being particularly preferred. The metal ions may be used alone or in combination. The use of at least one of magnesium and zinc, particularly magnesium, as the metal ion forms an appropriate crosslinked structure, which facilitates increasing the glass transition temperature of the interlayer film and increasing both the bending rigidity at 25°C and 50°C. Furthermore, even if multiple interlayer films are stacked and the thickness of the interlayer film between a pair of substrates (e.g., glass) increases, the bending rigidity of the laminate (e.g., laminated glass) at high temperatures is more likely to be reduced, and the slopes (21) and (31) tend to increase.

[0033] When the ionomer resin is an ethylene-unsaturated carboxylic acid copolymer, it typically contains a structural unit (A) derived from an unsaturated carboxylic acid, a structural unit (B) derived from a neutralized product of an unsaturated carboxylic acid, and a structural unit (C) derived from ethylene. In particular, when the ionomer resin is an ethylene-(meth)acrylic acid copolymer, it typically contains a structural unit (structural unit (A)) derived from (meth)acrylic acid, a structural unit (structural unit (B)) derived from a neutralized product of (meth)acrylic acid, and a structural unit (C) derived from ethylene. By containing these structural units (A), (B), and (C), the ionomer resin tends to have excellent bending rigidity at 25°C and 50°C. Furthermore, even if multiple interlayer films are stacked and the thickness of the interlayer film between a pair of substrates (e.g., glass) increases, it becomes easier to prevent a decrease in bending rigidity of a laminate (e.g., laminated glass) at high temperatures, and the slopes (21) and (31) also tend to increase. In addition, in the third embodiment described later, the ionomer resin used contains these structural units (A), (B), and (C), which increases the bending rigidity ratio and makes it easier to achieve excellent bending rigidity at 20 to 40°C.

[0034] The monomer constituting the structural unit (A) is not particularly limited as long as it is an unsaturated carboxylic acid, but is preferably at least one of acrylic acid and methacrylic acid. Among these, methacrylic acid is more preferred from the viewpoints of bending rigidity and adhesiveness. The structural unit (A) is a structural unit that is not neutralized with a metal ion. The structural unit (B) is a neutralized product of a structural unit derived from the above-mentioned unsaturated carboxylic acid, but is preferably a neutralized product of a structural unit derived from at least one of acrylic acid and methacrylic acid, and is more preferably a structural unit of a neutralized methacrylic acid. The structural unit (B) is a structural unit in which the hydrogen ion of the carboxy group in the unsaturated carboxylic acid is substituted with a metal ion. That is, the unsaturated carboxylic acid neutralized product in the structural unit (B) is a metal salt of the unsaturated carboxylic acid. The metal ion in the metal salt is as described above, but is preferably at least one of magnesium and zinc, and particularly preferably magnesium. Therefore, the structural unit (B) preferably contains at least one of magnesium and zinc, and particularly preferably contains magnesium.

[0035] In the ionomer resin, the total content of the structural units (A) and (B) is preferably 10% by mass or more and 25% by mass or less, based on the total amount of the structural units constituting the ionomer resin. When the total content of the structural units (A) and (B) is 10% by mass or more, the transparency, heat resistance, mechanical strength, etc. of the interlayer film can be improved. Furthermore, when the total content is 25% by mass or less, the flexibility, processability, adhesiveness, etc. can be improved. The total content of the structural units (A) and (B) is more preferably 12% by mass or more and 23% by mass or less, and even more preferably 15% by mass or more and 20% by mass or less.

[0036] In the ionomer resin, the content of the structural unit (B) is preferably 4% by mass or more and 18% by mass or less, based on the total amount of structural units constituting the ionomer resin. When the content of the structural unit (B) is 4% by mass or more, the degree of crosslinking of the ionomer resin increases, making it easier to increase the bending rigidity, particularly the bending rigidity at 50°C. Furthermore, even if multiple interlayer films are stacked to increase the thickness of the interlayer film between a pair of substrates (e.g., glass), it becomes easier to prevent a decrease in the bending rigidity of a laminate (e.g., laminated glass) at high temperatures. Furthermore, when the content of the structural unit (B) is 4% by mass or more, it becomes easier to improve transparency, heat resistance, etc. Furthermore, when the content of the structural unit (B) is 18% by mass or less, it becomes easier to improve the flexibility, adhesion, mechanical strength, processability, etc. of the interlayer film. The content of the structural unit (B) in the ionomer resin is more preferably 6% by mass or more and 17.5% by mass or less, even more preferably 7% by mass or more and 16% by mass or less, and even more preferably 10% by mass or more and 14% by mass or less.

[0037] The content of the ethylene-derived structural unit (C) is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and still more preferably 82% by mass or more, based on the total amount of structural units constituting the ionomer resin, from the viewpoint of easily increasing the impact resistance of the ionomer resin. Furthermore, from the viewpoints of transparency, mechanical strength, and moldability, the content of the ethylene-derived structural unit (C) is preferably 90% by mass or less, more preferably 89% by mass or less, even more preferably 88% by mass or less, and still more preferably 85% by mass or less.

[0038] In the ionomer resin, the content of the structural unit (A) is not particularly limited, but is preferably 3% by mass or more and 10% by mass or less, more preferably 4% by mass or more and 9% by mass or less, and even more preferably 8% by mass or less, based on the total amount of the structural units constituting the ionomer resin.

[0039] The ionomer resin may be a copolymer of ethylene and a (meth)unsaturated carboxylic acid neutralized with a metal ion, or a copolymer of ethylene, an unsaturated carboxylic acid, and a monomer other than ethylene and the unsaturated carboxylic acid neutralized with a metal ion. Thus, in a preferred embodiment, the ionomer resin may contain, in addition to the structural units (A), (B), and (C), structural units other than the structural units (A), (B), and (C) (hereinafter also referred to as "other structural units").

[0040] Other structural units include structural units (D) derived from alkyl (meth)acrylates. The presence of structural units (D) makes it possible, for example, to adjust the glass transition temperature (Tg) of the ionomer resin. Examples of alkyl (meth)acrylates include alkyl (meth)acrylates having approximately 1 to 10 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl. From the viewpoint of not lowering the glass transition temperature of the interlayer film more than necessary, the content of structural units (D) derived from alkyl (meth)acrylates is preferably 15% by mass or less, more preferably 8% by mass or less, even more preferably 4.5% by mass or less, and even more preferably 2% by mass or less. Furthermore, from the viewpoint of increasing rigidity at high temperatures without decreasing the glass transition temperature and from the viewpoint of preventing a decrease in rigidity at high temperatures even when a plurality of interlayer films are stacked to increase the thickness, the content of the structural unit (D) is better, and the ionomer resin may contain 0 mass % or more. It is preferable that the ionomer resin does not contain the structural unit (D).

[0041] In addition, isobutyl (meth)acrylate is generally preferably used as the alkyl (meth)acrylate in the ionomer resin, but in the present invention, it is preferable that the ionomer resin does not contain any structural units derived from isobutyl (meth)acrylate, or contains only a small amount of such units. Therefore, the content of structural units derived from isobutyl (meth)acrylate is preferably 15% by mass or less, more preferably 8% by mass or less, even more preferably 4.5% by mass or less, and even more preferably 2% by mass or less. The content of structural units derived from isobutyl (meth)acrylate may be 0% by mass or more, and it is preferable that the ionomer resin does not contain any structural units derived from isobutyl (meth)acrylate.

[0042] Furthermore, the ionomer resin may contain, as other structural units, structural units other than the structural units (A), (B), (C), and (D), and may have, for example, structural units derived from vinyl esters such as vinyl acetate and vinyl propionate.

[0043] In the present invention, the degree of neutralization of the ionomer resin is, for example, 30% or more. From the viewpoint of increasing rigidity, it is preferably greater than 40%, more preferably 42% or more, even more preferably 45% or more, and even more preferably 50% or more. Increasing the degree of neutralization of the ionomer resin increases the bending rigidity, particularly the bending rigidity at 50°C. Furthermore, even if the thickness is increased by stacking multiple interlayer films, the rigidity is less likely to decrease at high temperatures. In the present invention, by including at least one of magnesium and zinc (particularly magnesium) in the structural unit (B) and increasing the degree of neutralization, the rigidity at 50°C is more likely to be improved, and even if the thickness is increased by stacking multiple interlayer films, the rigidity is less likely to decrease at high temperatures. Furthermore, the degree of neutralization of the ionomer resin is not particularly limited, but from the viewpoint of improving the flexibility, adhesion, mechanical strength, processability, etc. of the interlayer film, it is preferably 95% or less, more preferably 90% or less, even more preferably 80% or less, and even more preferably 75% or less. The degree of neutralization of the ionomer resin refers to the proportion (%) of carboxyl groups neutralized by metal ions among all carboxyl groups contained in the ionomer resin.

[0044] The degree of neutralization of the ionomer resin can be determined by IR measurement before and after the hydrochloric acid treatment. Specific measurement methods are as described in the Examples below. The content of each structural unit in the ionomer resin can be determined by mass spectrometry and １ H-NMR measurement is carried out, and the degree of neutralization can be calculated from the integrated intensity ratio of the hydrogen peaks derived from each monomer.

[0045] The ionomer resin has a melt mass flow rate (MFR), measured in accordance with JIS K7210:1999 under conditions of 190°C and a load of 2160 g, of, for example, 0.01 g / 10 min or more and 150 g / 10 min or less, preferably 0.01 g / 10 min or more and 50 g / 10 min or less, more preferably 0.1 g / 10 min or more and 30 g / 10 min or less, and even more preferably 0.1 g / 10 min or more and 10 g / 10 min or less, from the viewpoints of processability, mechanical strength, and the like.

[0046] The content of the ionomer resin in the interlayer film is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 88% by mass or more, based on 100% by mass of the entire interlayer film. By setting the ionomer resin content within the above lower limit, the rigidity, interlayer adhesion, and other properties of the resulting laminated glass can be improved. The content of the ionomer resin in the interlayer film may be 100% by mass or less, based on 100% by mass of the entire interlayer film. However, from the viewpoint of including a certain amount or more of additives, it may be, for example, 99.99% by mass or less or 99.9% by mass or less. When the interlayer film contains other resin components described below, the content of the ionomer resin in the interlayer film is preferably a certain amount or less, for example, 98.4% by mass or less, 97.4% by mass or less, or 96.4% by mass or less.

[0047] The method for producing the ionomer resin is not particularly limited, and the ionomer resin can be produced by a known method. For example, the ionomer resin can be produced by radically copolymerizing each monomer component under high temperature and high pressure to obtain an ethylene-unsaturated carboxylic acid copolymer, and then reacting the copolymer with a metal compound.

[0048] [Other Resin Components] The interlayer film according to the first embodiment may contain other resin components in addition to the ionomer resin. The ionomer resin may become too viscous during kneading, resulting in poor formability, such as extrudability. However, the inclusion of other resin components in the interlayer film according to the first embodiment facilitates favorable formability, such as extrudability. The other resin components are preferably resins compatible with the ionomer resin. From the viewpoint of compatibility with the ionomer resin, the other resin components are preferably ethylene-unsaturated carboxylic acid copolymers. The unsaturated carboxylic acids used in the ethylene-unsaturated carboxylic acid copolymers are as described above. Among these, (meth)acrylic acid is preferred, and methacrylic acid is more preferred. Furthermore, from the viewpoints of compatibility and extrudability, the other resin components are preferably copolymers of the same type as the copolymer used in the ionomer resin, and more preferably resins prior to neutralization with metal ions to obtain the ionomer resin. Therefore, when the ionomer resin is an ionomer resin of an ethylene-(meth)acrylic acid copolymer, the other resin component is preferably an ethylene-(meth)acrylic acid copolymer.Furthermore, when the ionomer resin is an ionomer resin of an ethylene-methacrylic acid copolymer, the other resin component is preferably an ethylene-methacrylic acid copolymer.

[0049] The content of the other resin component is preferably 1.5% by mass or more and 25% by mass or less, relative to 100% by mass of the entire interlayer film. By setting the content of the other resin component to 1.5% by mass or more, the viscosity of the ionomer resin is reduced, making it easier to improve extrusion properties. Furthermore, by setting the content to 25% by mass or less, a decrease in bending rigidity can be prevented even when the other resin component is included. The content of the other resin component is more preferably 2.5% by mass or more and 18% by mass or less, and even more preferably 3.5% by mass or more and 11% by mass or less, relative to 100% by mass of the entire interlayer film.

[0050] [Silane Coupling Agent] The interlayer film may contain an additive. The interlayer film preferably contains, for example, a silane coupling agent as an additive. By containing a silane coupling agent, the interlayer film is more likely to improve its adhesion to substrates, glass, and the like. Examples of silane coupling agents include those having a functional group such as a group containing a polymerizable carbon-carbon double bond, such as a vinyl group or a (meth)acryloyl group, an amino group, or an epoxy group, and a hydrolyzable group such as an alkoxy group.

[0051] Examples of silane coupling agents having a polymerizable carbon-carbon double bond include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, and 3-acryloxypropyltriethoxysilane. Examples of silane coupling agents having an amino group include N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride. Examples of silane coupling agents having an epoxy group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. The interlayer film may contain one type of silane coupling agent alone or two or more types.

[0052] Among these, from the viewpoint of improving adhesion to glass and substrates, silane coupling agents having an amino group are preferred, and silane coupling agents having an ethylenediamine structure such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane are particularly preferred. From the viewpoint of improving adhesion to glass and substrates, the content of the silane coupling agent in the interlayer film is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.005% by mass or more and 2% by mass or less, even more preferably 0.01% by mass or more and 1% by mass or less, and even more preferably 0.05% by mass or more and 0.5% by mass or less, based on 100% by mass of the entire interlayer film.

[0053] [Additives] In addition to the silane coupling agent, the interlayer film may contain at least one of an ultraviolet absorber, an antioxidant, and other known additives. Examples of ultraviolet absorbers include conventionally known ultraviolet absorbers such as compounds having a malonic acid ester structure, compounds having an oxalic acid anilide structure, compounds having a benzotriazole structure, compounds having a benzophenone structure, compounds having a triazine structure, compounds having a benzoate structure, and compounds having a hindered amine structure. These ultraviolet absorbers may be used alone or in combination. The ultraviolet absorber absorbs ultraviolet light contained in sunlight and the like, preventing deterioration of the interlayer film due to exposure to sunlight and improving durability. The content of the ultraviolet absorber in the interlayer film is preferably 0.01% by mass to 3% by mass, more preferably 0.05% by mass to 2% by mass, and even more preferably 0.1% by mass to 1.5% by mass, based on 100% by mass of the entire interlayer film.

[0054] Examples of antioxidants include phenolic compounds, phosphoric acid compounds, and sulfur compounds. The antioxidants prevent the interlayer film from oxidative degradation and improve durability. The antioxidants may be used alone or in combination of two or more.

[0055] The interlayer film of the present invention may contain known additives other than those mentioned above. Examples of such additives include plasticizers, light stabilizers, antistatic agents, surfactants, colorants, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, heat ray absorbers, heat ray reflectors, heat dissipation agents, inorganic fillers, organic fillers, impact resistance modifiers, slip agents, crosslinking agents, crosslinking aids, tackifiers, processing aids, mold release agents, hydrolysis inhibitors, antiblocking agents, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, and dispersants.

[0056] (Thickness) The thickness of the interlayer film is not particularly limited, but is preferably 0.2 mm or more and 4 mm or less. By making the thickness of the interlayer film 0.2 mm or more, the bending rigidity, adhesiveness, and penetration resistance when the interlayer film is used to form laminated glass can be improved. Furthermore, by making the thickness 4 mm or less, the interlayer film can be produced in a versatile manner, and further, even when multiple interlayer films are stacked, it becomes easier to prevent a decrease in bending rigidity at high temperatures. It also becomes easier to ensure the transparency of the interlayer film. The thickness of the interlayer film is more preferably 0.4 mm or more, and even more preferably 0.6 mm or more. It is also more preferably 2.5 mm or less, even more preferably 1.6 mm or less, and even more preferably 1.0 mm or less.

[0057] (Width) The interlayer film according to the first embodiment preferably has a width of 1 m or more. A width of 1 m or more makes the interlayer film suitable for use in large-sized laminated glass, laminated glass for architectural structures, and the like. Although a width of 1 m or more may make industrial mass production of the interlayer film difficult, for example, by incorporating a resin other than an ionomer resin (e.g., an ethylene-methacrylic acid copolymer) into the interlayer film using a masterbatch or the like, the viscosity of the resin composition is reduced, improving workability and facilitating mass production. The width of the interlayer film is more preferably 2 m or more. Furthermore, the interlayer film is not particularly limited, but from the viewpoint of improving productivity, it is preferably 5 m or less, and more preferably 4 m or less.

[0058] Furthermore, the interlayer film according to the first embodiment is preferably an extrusion molded product obtained by extrusion molding, as described below. Being an extrusion molded product facilitates industrial mass production of large interlayer films with widths of 1 m or more, as described above. Furthermore, extrusion molded products can have high viscosity, which can lead to reduced productivity. However, by incorporating a resin other than ionomer resin (such as an ethylene-methacrylic acid copolymer) into the interlayer film using a masterbatch or the like, this increase in viscosity can be suppressed, thereby preventing reduced productivity.

[0059] The interlayer film according to the first embodiment preferably comprises a single layer and is constituted by a monolayer film. The layers constituting the monolayer film may be made of a resin composition having the composition described above. That is, the layers constituting the monolayer film may be made of a resin composition containing a resin such as an ionomer resin and, if necessary, containing appropriate additives. The interlayer film according to the first embodiment may also be a multilayer film having two or more layers. The multilayer film may have the overall composition of the interlayer film as described above for the interlayer film, but the resin composition constituting each layer may have the composition described above for the interlayer film. That is, each layer may be made of a resin composition containing a resin such as an ionomer resin and, if necessary, containing appropriate additives, as described above for the interlayer film. In the multilayer film, the compositions of the layers may be different or the same. In the monolayer film or multilayer film, the content of the ionomer resin, the content of other resin components, and the content of each additive in the resin composition constituting each layer may be as described above. However, while the content of each component described above was based on 100% by mass of the interlayer film, in the resin composition constituting each layer, the content of each component is based on 100% by mass of the resin composition instead of 100% by mass of the interlayer film.

[0060] [Method for Manufacturing Interlayer Film] The interlayer film may be prepared by obtaining a resin composition for forming the interlayer film and molding the resin composition. When the interlayer film is composed of a single component, the component (i.e., a resin component such as an ionomer resin) may be appropriately heated and melted and formed into a film by extrusion molding, press molding, roll molding, or the like. When the resin composition is composed of two or more components, the resin components and optional additives that constitute the interlayer film may be mixed to obtain a resin composition, and the resulting resin composition may be appropriately heated and melted and formed into a film by extrusion molding, press molding, roll molding, or the like to obtain the interlayer film. The method for mixing the components to obtain the resin composition is not particularly limited, but a kneading method using an extruder is preferred. When the interlayer film is composed of multiple layers, resin compositions for forming each layer may be prepared, and the resulting resin composition may be appropriately heated and melted and formed into a film by extrusion molding, press molding, roll molding, or the like to form each layer, and the layers may then be laminated to obtain the interlayer film. When the interlayer film is composed of multiple layers, co-extrusion may be used for the extrusion molding. Among the above methods, the interlayer film is preferably formed by extrusion molding, which allows for efficient production of a wide interlayer film.

[0061] In a preferred embodiment, the present invention may produce an interlayer film using a so-called masterbatch. The masterbatch is a mixture (hereinafter sometimes referred to as mixture (A)) of a resin component and an additive. The resin component can be at least one of an ionomer resin and a resin component other than the ionomer resin. The resin component other than the ionomer resin is preferably the other resin component described above, and preferably an ethylene-(meth)acrylic acid copolymer. Using a masterbatch facilitates mixing of the additive with the ionomer resin. Furthermore, adding the other resin component, such as an ethylene-(meth)acrylic acid copolymer, to mixture (A) effectively reduces the viscosity of the resin composition, making it easier to knead the resin composition in an extruder or the like. The additive contained in mixture (A) may be one or more additives selected from the additives described above. Preferably, the additive includes at least one of a silane coupling agent, an ultraviolet absorber, and an antioxidant. Other additives may also be included. The form of mixture (A) is not particularly limited, but it is typically in the form of pellets or other particles.

[0062] Even when a masterbatch is used, the interlayer film is preferably formed by extrusion molding. Therefore, in a preferred embodiment, the method for producing an interlayer film includes step (1) of kneading an ionomer resin and a mixture (A) to obtain a resin composition, and step (2) of extruding the obtained resin composition. In step (1), the mixing ratio of the mixture (A) to the ionomer resin (mixture (A) / ionomer resin) is preferably 2 / 98 or more and 30 / 70 or less, more preferably 3 / 97 or more and 20 / 70 or less, and even more preferably 4 / 96 or more and 12 / 88 or less, by mass ratio. By setting the mixing ratio within the above range, appropriate amounts of additives and other resin components such as an ethylene-(meth)acrylic acid copolymer can be blended into the resin composition.

[0063] The total content of additives in mixture (A) is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less, based on the total amount of mixture (A). By making the total content of additives in mixture (A) equal to or greater than the above-mentioned lower limit, an appropriate amount of additives can be blended into the resin composition without mixing more other resin components, such as ethylene-(meth)acrylic acid copolymers, into the resin composition than necessary. Furthermore, by making the content of additives in mixture (A) equal to or less than the above-mentioned upper limit, the additives can be properly dispersed in mixture (A).

[0064] The interlayer film according to the first embodiment is preferably disposed between a pair of substrates and is more preferably used in a laminate or laminated glass, as described below. The interlayer film may also be used to bond the pair of substrates. The interlayer film is particularly preferably an interlayer film for laminated glass, which is used in laminated glass.

[0065] <Laminate> The laminate according to the present invention includes the interlayer film described above and a pair of substrates, with the interlayer film disposed between the pair of substrates. In the laminate, the pair of substrates may be bonded via the interlayer film. Furthermore, the interlayer film disposed between the pair of substrates in the laminate may be a single film, but preferably multiple interlayer films are disposed between the pair of substrates. By disposing multiple interlayer films between the pair of substrates, even when a larger interlayer film thickness is required between a pair of glass members, such as in laminated glass for architectural structures, an interlayer film of a general thickness can be used. The multiple interlayer films may be integrated between the substrates, and the pair of substrates may be bonded via the integrated multiple interlayer films. The total thickness of the interlayer films between the substrates in the laminate is not particularly limited, but is, for example, 0.2 mm to 6 mm, preferably 0.4 mm to 4.5 mm, and more preferably 0.6 mm to 3.6 mm. Another layer may be disposed between the interlayer film and the substrate, but it is preferable that no additional layer is provided and the interlayer film is disposed so as to directly contact the substrate. Furthermore, when a plurality of interlayer films are used, a separate layer may be provided between the plurality of interlayer films, but it is preferable that no separate layer is provided and the interlayer films are in direct contact with each other.

[0066] Examples of the substrate used in the laminate according to the first embodiment include a resin film and a glass member, and among these, a glass member is preferred. By using glass members as a pair of substrates of the laminate, the laminate becomes laminated glass.

[0067] Examples of resin films used for the substrate include polyester resin films such as (meth)acrylic resin films, polycarbonate films, polyethylene terephthalate (PET) films, and polyethylene naphthalate (PEN) films; polyolefin resin films such as polyethylene films and polypropylene films; cyclic polyolefin (COP) films, triacetyl cellulose (TAC) films, polyethersulfone (PES) resin films, and polyimide resin films. The resin film may consist of a single layer, or may be a laminate of two or more layers. A functional layer such as a hard coat layer may be appropriately provided on the surface of the resin film, or electrodes, sensors, etc. may be attached. The thickness of the resin film used for the substrate is not particularly limited, but is preferably 30 μm or more, more preferably 50 μm or more, and is, for example, 1 mm or less, but is preferably 500 μm or less, and more preferably 450 μm or less.

[0068] Furthermore, a glass plate may be used as the glass member. The glass plate may be either inorganic glass or organic glass, with inorganic glass being preferred. Examples of inorganic glass include, but are not limited to, clear glass, clear float glass, float glass plate, tempered glass, colored glass, polished glass plate, patterned glass, wired glass plate, lined glass plate, ultraviolet-absorbing glass plate, infrared-reflecting glass plate, infrared-absorbing glass plate, and green glass. Examples of organic glass include what is generally called resin glass, and include, but are not limited to, organic glass made of polycarbonate, polymethyl methacrylate, polyester, etc. The two glass members may be made of the same material or different materials. For example, one may be inorganic glass and the other organic glass, but it is preferred that both glass members be inorganic glass or organic glass. The thickness of each of the glass members is not particularly limited, but is preferably 0.5 mm to 5 mm, more preferably 0.7 mm to 3 mm.

[0069] <Laminated Glass> As described above, the laminated glass according to the first embodiment includes a pair of glass members and an interlayer film disposed between the pair of glass members. The glass members and the interlayer film may be the same as those described above. As described above, the glass members may include one interlayer film disposed between the pair of glass members, but preferably include multiple interlayer films.

[0070] The laminated glass according to the first embodiment may satisfy at least one of the following requirements (A1) and (B1): Requirement (A1): The slope (21c) calculated by (bending rigidity (2c) - bending rigidity (1c)) / thickness change is greater than -10. Requirement (B1): The slope (31c) calculated by (bending rigidity (3c) - bending rigidity (1c)) / thickness change is greater than -10.

[0071] Here, the bending rigidity (1c) is the bending rigidity (unit: N / mm) at 50°C of the measurement laminated glass (1c) obtained by bonding a pair of glass members via one interlayer film. The bending rigidity (2c) is the bending rigidity (unit: N / mm) at 50°C of the measurement laminated glass (2c) obtained by bonding a pair of glass members via two interlayer films. The bending rigidity (3c) is the bending rigidity (unit: N / mm) at 50°C of the measurement laminated glass (3c) obtained by bonding a pair of glass members via three interlayer films. The thickness change is the change (unit: mm) in the thickness of the interlayer film between the pair of glass members when measuring the bending rigidity (3c) or the bending rigidity (2c) relative to the thickness of the interlayer film between the pair of glass members when measuring the bending rigidity (1c). Therefore, in requirement (A1), the thickness change is the value obtained by subtracting the thickness of one interlayer film when measuring the bending rigidity (1c) from the total thickness of the two interlayer films when measuring the bending rigidity (2c). In addition, in requirement (B1), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring bending stiffness (1c) from the total thickness of three interlayer films when measuring bending stiffness (3c).

[0072] In the laminated glass according to the first embodiment, if both the slope (21c) and the slope (31c) are −10 or less, it may not be possible to achieve excellent bending rigidity at high temperatures around 40° C. In particular, when a plurality of interlayer films are laminated and the thickness of the interlayer film between a pair of substrates (for example, between a pair of glass members) is large, it becomes difficult to achieve excellent bending rigidity of the laminated glass at high temperatures.

[0073] In the laminated glass according to the first embodiment, it is preferable that either the slope (21c) or the slope (31c) is greater than −10, but it is preferable that both the slope (21c) and the slope (31c) are greater than −10. When both the slope (21c) and the slope (31c) are greater than −10, it is possible to more reliably achieve excellent bending rigidity at high temperatures even when the thickness of the interlayer film between the pair of glass members in the laminated glass is increased.

[0074] From the same viewpoint as for the slope (21), the slope (21c) is preferably −9 or more, more preferably −4 or more, and even more preferably 0 or more. The slope (21c) is not particularly limited, but is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less. From the same viewpoint as for the slope (31), the slope (31c) is preferably −9 or more, more preferably −4 or more, and even more preferably 0 or more. The slope (31c) is not particularly limited, but is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0075] When the laminated glass according to the first embodiment is bonded via one interlayer film, the laminated glass can be used as the measurement laminated glass (1c) as is, and a measurement laminated glass (2c) bonded via two interlayer films and a measurement laminated glass (3c) bonded via three interlayer films can be separately prepared. The bending rigidities (1c), (2c), and (3c) of the measurement laminated glasses (1c), (2c), and (3c) can be measured, respectively. When the laminated glass according to the first embodiment is bonded via two interlayer films, the laminated glass can be used as the measurement laminated glass (2c) as is, and a measurement laminated glass (1c) bonded via one interlayer film and a measurement laminated glass (3c) bonded via three interlayer films can be separately prepared. The bending rigidities (1c), (2c), and (3c) of the measurement laminated glasses (1c), (2c), and (3c) can be measured, respectively. The same applies when the laminated glass according to the first embodiment is bonded via three interlayer films. When the laminated glass according to the first embodiment is bonded via four or more interlayer films, it is preferable to separately prepare a measurement laminated glass (1c) obtained by bonding via one interlayer film, a measurement laminated glass (2c) obtained by bonding via two interlayer films, and a measurement laminated glass (3c) obtained by bonding via three interlayer films. The glass members used in the measurement laminated glasses (1c), (2c), and (3c) are the same as the glass members used in the laminated glass.

[0076] In the first embodiment, in a laminated glass satisfying at least one of requirement (A1) and requirement (B1), when two glass members are bonded via multiple interlayer films, the multiple interlayer films may each have the same composition and the same structure (for example, all single-layer films with the same composition, or all multi-layer films with a layer structure in which each layer has the same composition and the same thickness ratio). The multiple interlayer films may have the same or different thicknesses, but it is preferable that they have the same thickness.

[0077] The laminated glass that satisfies at least one of requirement (A1) and requirement (B1) preferably further satisfies at least one of the following requirement (C1) or requirement (D1): Requirement (C1): The slope (21bc) obtained by (bending rigidity (2bc) - bending rigidity (1bc)) / thickness change is 0 or greater. Requirement (D1): The slope (31bc) obtained by (bending rigidity (3bc) - bending rigidity (1bc)) / thickness change is 0 or greater.

[0078] Here, the bending rigidity (1bc) is the bending rigidity (unit: N / mm) of the measurement laminated glass (1c) at 25°C. The bending rigidity (2bc) is the bending rigidity (unit: N / mm) of the measurement laminated glass (2c) at 25°C. The bending rigidity (3bc) is the bending rigidity (unit: N / mm) of the measurement laminated glass (3c) at 25°C. The thickness change is the change (unit: mm) in the thickness of the interlayer film between a pair of glass members when measuring the bending rigidity (3bc) or the bending rigidity (2bc) relative to the thickness of the interlayer film between a pair of glass members when measuring the bending rigidity (1bc). Therefore, in requirement (C1), the thickness change is the value obtained by subtracting the thickness of one interlayer film when measuring the bending rigidity (1bc) from the total thickness of the two interlayer films when measuring the bending rigidity (2bc). In addition, in requirement (D1), the change in thickness is the value obtained by subtracting the thickness of one interlayer film when measuring bending stiffness (1bc) from the total thickness of three interlayer films when measuring bending stiffness (3bc).

[0079] In the laminated glass according to the first embodiment, it is more preferable that both the slope (21bc) and the slope (31bc) are 0 or greater. From the same viewpoint as the slope (21b), the slope (21bc) is preferably 30 or greater, more preferably 50 or greater, even more preferably 100 or greater, and even more preferably 200 or greater. Although not particularly limited, it is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less. From the same viewpoint as the slope (31b), the slope (31bc) is preferably 30 or greater, more preferably 50 or greater, even more preferably 100 or greater, and even more preferably 200 or greater. Although not particularly limited, it is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less.

[0080] The laminated glass according to the first embodiment preferably has a flexural rigidity at 50°C of 700 N / mm or more. When the flexural rigidity at 50°C of the laminated glass is 700 N / mm or more, the laminated glass is likely to have excellent rigidity in a relatively high temperature environment of about 40 to 50°C. The flexural rigidity at 50°C is preferably 800 N / mm or more, more preferably 850 N / mm or more, and even more preferably 900 N / mm or more. The higher the flexural rigidity of the laminated glass at 50°C, the better, but from the viewpoint of ensuring a certain level of flexibility in the interlayer film, the flexural rigidity is, for example, 3000 N / mm or less, and may be 2000 N / mm or less, 1500 N / mm or less, or 1000 N / mm or less.

[0081] The flexural rigidity of the laminated glass at 25°C is preferably 900 N / mm or more. When the flexural rigidity of the laminated glass at 25°C is 900 N / mm or more, the laminated glass tends to have excellent rigidity in a room temperature environment. The flexural rigidity at 25°C is preferably 1000 N / mm or more, more preferably 1100 N / mm or more, and even more preferably 1200 N / mm or more. The higher the flexural rigidity of the laminated glass at 25°C, the better, but from the viewpoint of imparting a certain degree of flexibility to the interlayer film even in a room temperature environment, the flexural rigidity is, for example, 4000 N / mm or less, or may be 3000 N / mm or less, 2300 N / mm or less, or may be 2000 N / mm or less.

[0082] (Method for manufacturing laminate and laminated glass) The laminate according to the first embodiment can be manufactured, for example, by preparing a pair of substrates and one or more interlayer films, disposing one interlayer film or multiple overlapping interlayer films between the pair of substrates, and bonding them together under pressure. The method of bonding is not particularly limited, but it is preferable to bond them under pressure while heating. Alternatively, after pre-bonding at a relatively low pressure and temperature, the pressure, temperature, or both may be increased to higher levels than those for pre-bonding, for main bonding. When multiple interlayer films are disposed between the pair of substrates, it is preferable to integrate the multiple interlayer films during bonding under pressure.

[0083] Furthermore, when the laminate is a laminated glass, for example, one or more interlayer films are sandwiched between two glass members and passed through a pressure roll, or placed in a rubber bag and subjected to vacuum suction to remove any air remaining between the two glass members and the interlayer films. This is then pre-bonded at approximately 70 to 110°C to obtain a laminated intermediate. The laminated intermediate is then placed in an autoclave or pressed at approximately 120 to 150°C and a pressure of 1 to 1.5 MPa for full bonding. In this manner, laminated glass can be obtained. When multiple interlayer films are disposed between a pair of glass members, the multiple interlayer films can be integrated by either pre-bonding or full bonding.

[0084] The interlayer film, laminate, and laminated glass according to the first embodiment can be used in a variety of fields, including electronic devices such as displays, vehicles such as automobiles, railway cars, aircraft, and ships, and various architectural structures such as buildings, condominiums, detached houses, halls, and gymnasiums. Among these, their use in vehicles and architectural structures is preferred, and their use in architectural structures is particularly preferred. The use of laminated glass in vehicles and architectural structures is preferred. Furthermore, in vehicle applications, the glass may be used as window glass, and in automobiles, for example, it may be used as any of the windshield, rear glass, and side glass. In architectural structures, the glass may be used as window glass, glass floors, curtain walls, and the like. When used in architectural structures, the laminated glass may be enlarged and used as structural glazing, for example. However, in the present invention, the flexural rigidity ratio is relatively high, making it suitable for use in architectural structures.

[0085] <<Second Embodiment>> Next, differences between the first embodiment and the second embodiment as an embodiment of the first aspect of the present invention will be described. In the first embodiment of the present invention, the interlayer film satisfies at least one of requirements (A) or (B), and preferably satisfies at least one of requirements (C) or (D). Furthermore, in the first embodiment of the present invention, the laminated glass preferably satisfies at least one of requirements (A1) or (B1), and preferably satisfies at least one of requirements (C1) or (D1). In contrast, the interlayer film according to the second embodiment of the present invention satisfies the following requirement (E) instead of the above requirements (A) to (D), and preferably satisfies the following requirement (F). Furthermore, the laminated glass according to the second embodiment of the present invention satisfies the following requirement (E1) instead of the above requirements (A1) to (D1), and preferably satisfies the following requirement (F1). The second embodiment will be described in detail below. However, other components, such as the interlayer film, the laminate, and the configuration of the laminated glass, which will not be described below, can be the same as those in the first embodiment, and the manufacturing methods thereof can also be the same as those in the first embodiment.

[0086] [Interlayer Film According to Second Embodiment] The interlayer film according to a second embodiment of the present invention is an interlayer film that satisfies the following requirement (E): Requirement (E): The slope (21a) calculated by (bending rigidity (2a) - bending rigidity (1)) / thickness change is greater than -10.

[0087] Here, the bending rigidity (1) is the bending rigidity (unit: N / mm) at 50°C of the test laminated glass (1) obtained by bonding two 2.75 mm thick glass sheets together via one interlayer film. The bending rigidity (2a) is the bending rigidity (unit: N / mm) at 50°C of the test laminated glass (2a) obtained by bonding two 2.75 mm thick glass sheets together via one interlayer film (2a) with a thickness different from that of the interlayer films.

[0088] Note that "a single interlayer film (2a) with a different thickness from the interlayer film" refers to a film obtained by slicing the interlayer film to a thickness smaller than the original interlayer film (i.e., the target interlayer film). Another example is a single interlayer film obtained by pressing multiple sheets (e.g., two or three sheets) of the target interlayer film together. Furthermore, it may be a film that has a different thickness from the target interlayer film but the same composition and structure (e.g., both are single-layered and have the same composition, or both are multi-layered and have the same layer structure with the same composition and thickness ratio). In this embodiment, if the structure of the interlayer film, such as the composition of the interlayer film, is the same as described above, the bending rigidity of the laminated glass at 50°C and the thickness of the interlayer film are generally proportional to each other. Therefore, even if the thickness of the interlayer film (2a) is adjusted as described above, the slope (21a) obtained will be generally the same.

[0089] However, in order to calculate the slope (21a) with less error, the difference between the thickness of the "single interlayer film (2a) having a different thickness from the interlayer film" and that of the target interlayer film is preferably 100 μm or more, more preferably 200 μm or more. Furthermore, the difference between the thickness of the interlayer film (2a) and that of the target interlayer film is preferably 2000 μm or less, more preferably 1600 μm or less.

[0090] Furthermore, the change in thickness in requirement (E) is the change in thickness (unit: mm) of the interlayer film between the pair of glass panes when measuring bending rigidity (2a) relative to the thickness of the interlayer film between the pair of glass panes when measuring bending rigidity (1). That is, the change in thickness in requirement (E) is the value obtained by subtracting the thickness of the interlayer film when measuring bending rigidity (1) from the thickness of the interlayer film when measuring bending rigidity (2a).

[0091] If the slope (21a) of the interlayer film is −10 or less, it may not be possible to achieve excellent bending rigidity at high temperatures around 40° C. In particular, when the thickness of the interlayer film between a pair of substrates (for example, between a pair of glass members) is large, it becomes difficult to achieve excellent bending rigidity at high temperatures around 40° C. for a laminated glass or other laminate produced using the interlayer film according to this embodiment.

[0092] The slope (21a) is preferably −9 or greater, more preferably −4 or greater, and even more preferably 0 or greater. As the slope (21a) increases, it becomes easier to prevent a decrease in bending rigidity at high temperatures, particularly when the thickness of the interlayer film between a pair of substrates (e.g., glass members) increases. The slope (21a) is not particularly limited, but from the viewpoint of easily imparting flexibility, adhesiveness, and the like to the interlayer film, it is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0093] In addition to the above requirement (E), the interlayer film according to the second embodiment preferably satisfies the following requirement (F): Requirement (F): The slope (21ab) calculated by (bending rigidity (2ab) - bending rigidity (1b)) / thickness change is 0 or greater.

[0094] Here, the bending rigidity (1b) is the bending rigidity (unit: N / mm) of the measurement laminated glass (1) at 25°C. The bending rigidity (2ab) is the bending rigidity (unit: N / mm) of the measurement laminated glass (2a) at 25°C. The change in thickness is the change in the thickness of the interlayer film between the pair of glass panes when the bending rigidity (2ab) is measured relative to the thickness of the interlayer film between the pair of glass panes when the bending rigidity (1b) is measured [unit: mm]. Therefore, in requirement (F), the change in thickness is the value obtained by subtracting the thickness of the interlayer film when the bending rigidity (1b) is measured from the thickness of the interlayer film (2a) when the bending rigidity (2ab) is measured.

[0095] The interlayer film according to this embodiment can have excellent bending rigidity at around room temperature by having a slope (21ab) of 0 or more. The slope (21ab) is preferably 30 or more, more preferably 50 or more, and even more preferably 100 or more. The slope (21ab) is not particularly limited, but is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less.

[0096] [Laminated Glass According to Second Embodiment] The laminated glass according to the second embodiment is a laminated glass bonded via an interlayer film disposed between a pair of glass members, and may be a laminated glass that satisfies the following requirement (E1): Requirement (E1): The slope (21ac) calculated by (bending rigidity (2ac) - bending rigidity (1ac)) / thickness change is greater than -10.

[0097] Here, the bending rigidity (1ac) is the bending rigidity (unit: N / mm) of the laminated glass according to this embodiment at 50°C. The bending rigidity (2ac) is the bending rigidity (unit: N / mm) of a measurement laminated glass (2ac) obtained by bonding a pair of glass members via a single interlayer film (2ac) having a thickness different from that of the interlayer film. The thickness change is the change in the thickness of the interlayer film between the pair of glass members at the time of measuring the bending rigidity (2ac) relative to the thickness of the interlayer film between the pair of glass members at the time of measuring the bending rigidity (1ac) [unit: mm]. Therefore, in requirement (E1), the thickness change is the value obtained by subtracting the thickness of the interlayer film at the time of measuring the bending rigidity (1ac) from the thickness of the interlayer film at the time of measuring the bending rigidity (2ac). Note that "one interlayer film (2ac) having a thickness different from that of the above interlayer film" has the same meaning as "one interlayer film (2a) having a thickness different from that of the above interlayer film" explained in the second embodiment, and the difference between the thickness of the interlayer film (2ac) and the thickness of the target interlayer film is also as explained for "one interlayer film (2a) having a thickness different from that of the above interlayer film." Furthermore, the glass members used in the measurement laminated glass (2ac) are the same as the glass members used in the laminated glass.

[0098] From the same viewpoint as the slope (21a), the slope (21ac) is preferably larger than −10, but is preferably −9 or larger, more preferably −4 or larger, and even more preferably 0 or larger, and is preferably 50 or smaller, more preferably 30 or smaller, and even more preferably 20 or smaller.

[0099] The laminated glass according to the second embodiment preferably satisfies the following requirement (F1) in addition to the requirement (E1): Requirement (F1): The slope (21abc) calculated by (bending rigidity (2abc) - bending rigidity (1bc)) / thickness change is 0 or greater.

[0100] Here, the bending rigidity (1bc) is the bending rigidity (unit: N / mm) of the laminated glass according to this embodiment at 25°C. The bending rigidity (2abc) is the bending rigidity (unit: N / mm) of the above-described laminated glass for measurement (2ac) at 25°C. The change in thickness is the change in the thickness of the interlayer film between the pair of glass members when the bending rigidity (2abc) is measured relative to the thickness of the interlayer film between the pair of glass members when the bending rigidity (1bc) is measured [unit: mm]. Therefore, in requirement (F1), the change in thickness is the value obtained by subtracting the thickness of the interlayer film when the bending rigidity (1bc) is measured from the thickness of the interlayer film when the bending rigidity (2abc) is measured.

[0101] The laminated glass of the present invention can have excellent bending rigidity at around room temperature by having a slope (21abc) of 0 or more. The slope (21abc) is preferably 30 or more, more preferably 50 or more, and even more preferably 100 or more. The slope (21abc) is not particularly limited, but is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less.

[0102] <<Third Embodiment>> Next, a third embodiment, which is an embodiment of the second aspect of the present invention, will be described in detail. <Flexural Rigidity> The interlayer film according to the third embodiment of the present invention has a ratio of 0.5 or more of its flexural rigidity at 50°C to the flexural rigidity at 25°C of a test laminated glass obtained by bonding two 2.75 mm thick glass sheets together via the interlayer film. In the third embodiment of the present invention, if the flexural rigidity ratio is less than 0.5, it becomes difficult to achieve excellent rigidity in any environment from 20 to 40°C. This makes it unsuitable for use in large-sized laminated glass, structural glazing, and the like. From the viewpoint of easily achieving high rigidity in an environment from 20 to 40°C, the flexural rigidity ratio is preferably 0.52 or more, more preferably 0.55 or more, even more preferably 0.56 or more, and even more preferably 0.60 or more. Furthermore, since the flexural rigidity of the test laminated glass generally decreases at higher temperatures, the flexural rigidity ratio is, for example, 1 or less. From the viewpoint of improving degassing properties during the production of laminated glass, the ratio is, for example, 0.9 or less, may be 0.8 or less, or may be 0.7 or less.

[0103] In this embodiment, the specific values ​​of the flexural rigidity at 50°C and 25°C of the interlayer film are the same as those described above for the flexural rigidity at 50°C and 25°C of the laminated glass (1) for measurement using the interlayer film of the first embodiment, and therefore further description is omitted. As described in the first embodiment, the flexural rigidity can be adjusted by the type of resin, the composition of the monomers constituting the resin, the glass transition temperature (Tg) of the interlayer film, and the thickness of the interlayer film. Furthermore, for example, the use of an ionomer resin can easily increase the flexural rigidity, and using a high-Tg component as the monomer constituting the ionomer resin while reducing the low-Tg component or increasing the degree of neutralization can also easily increase the flexural rigidity ratio. Furthermore, when other resin components are contained in addition to the ionomer resin, reducing the content of the other resin components can easily maintain a high flexural rigidity. Furthermore, increasing the thickness of the interlayer film tends to increase the absolute value of the flexural rigidity (particularly the flexural rigidity at room temperature), but tends to decrease the flexural rigidity ratio. The bending rigidity at 25°C or 50°C in the third embodiment can be measured by the same method as that used to measure the bending rigidity at 50°C and the bending rigidity at 25°C of the laminated glass for measurement (1) described in the first embodiment.

[0104] <Glass Transition Temperature> As in the first embodiment, the interlayer film of the third embodiment preferably has a glass transition temperature (Tg) of 50°C or higher and 75°C or lower. When the interlayer film has a Tg of 50°C or higher, the bending rigidity at 50°C is high, making it easier to increase the bending rigidity ratio. Furthermore, when the Tg is 75°C or lower, it is easier to impart a certain level of flexibility to the interlayer film. It also makes it easier to improve degassing properties during the production of laminated glass. From the viewpoint of making it easier to increase the bending rigidity ratio, the glass transition temperature (Tg) of the interlayer film is more preferably 55°C or higher, even more preferably 58°C or higher, and even more preferably 60°C or higher. Furthermore, from the viewpoints of flexibility, adhesion, etc., the glass transition temperature (Tg) of the interlayer film is more preferably 73°C or lower, and even more preferably 71°C or lower. The methods for adjusting and measuring the glass transition temperature are as described in the first embodiment.

[0105] The interlayer film of the third embodiment may contain a resin. The resin used in the interlayer film is preferably a thermoplastic resin. Using a thermoplastic resin for the interlayer film facilitates bonding a pair of substrates or a pair of glass sheets via the interlayer film by thermocompression bonding. Examples of resins used in the interlayer film include polyvinyl acetal resin, ethylene-vinyl acetate copolymer resin, ionomer resin, polyurethane resin, and thermoplastic elastomer, with ionomer resin being preferred among these. The use of an ionomer resin facilitates increasing the bending rigidity at 25°C. Furthermore, adjusting the monomer composition of the ionomer resin, as described below, also facilitates increasing the bending rigidity ratio, thereby facilitating excellent bending rigidity at 20 to 40°C. The ionomer resin, including its content, manufacturing method, and other details, has been described in the first embodiment above, and will be described in detail below.

[0106] The interlayer film of the third embodiment may contain other resin components in addition to the ionomer resin, and may also contain a silane coupling agent or an additive other than a silane coupling agent. Details of these are as described in the first embodiment. Furthermore, other configurations of the interlayer film and the method for manufacturing the interlayer film are the same as those of the first embodiment, and therefore a description thereof will be omitted.

[0107] <Laminate> A laminate according to a third embodiment of the present invention has the above-described interlayer film and a pair of substrates, with the interlayer film disposed between the pair of substrates. In the laminate, the pair of substrates may be bonded via the interlayer film. In addition, in the laminate, the interlayer film disposed between the pair of substrates may be a single film, or multiple interlayer films may be disposed between the pair of substrates. Details of the laminate according to the third embodiment are the same as those of the third embodiment, and therefore description thereof will be omitted.

[0108] <Laminated Glass> The laminated glass according to the third embodiment of the present invention comprises a pair of glass members and an interlayer film disposed between the pair of glass members. The glass members and the interlayer film may be the same as those described above. In the glass members, the interlayer film disposed between the pair of glass members may be one sheet as described above, or multiple sheets.

[0109] In one aspect of the third embodiment, the laminated glass has a ratio of its bending rigidity at 50°C to its bending rigidity at 25°C of 0.5 or more. In the present invention, if the bending rigidity ratio of the laminated glass is less than 0.5, it becomes difficult to maintain excellent rigidity in environments of 20 to 40°C. This makes it unsuitable for use in large-sized laminated glass, structural glazing, and the like. From the viewpoint of easily increasing the rigidity in environments of 20 to 40°C, the bending rigidity ratio of the laminated glass is more preferably 0.52 or more, even more preferably 0.56 or more, and even more preferably 0.60 or more. Furthermore, since bending rigidity generally decreases as the temperature increases, the bending rigidity ratio is, for example, 1 or less, but may also be, for example, 0.9 or less, 0.8 or less, or 0.7 or less.

[0110] Specific values ​​of the bending rigidity at 50°C and the bending rigidity at 25°C of the laminated glass in the third embodiment are as described above in the first embodiment. The methods for producing the laminate and laminated glass in the third embodiment are as described above in the first embodiment. The interlayer film, laminate, and laminated glass according to the third embodiment of the present invention can be used in a variety of fields, and the details thereof are as described above in the first embodiment.

[0111] The present invention has been described above with reference to the first to third embodiments, but the configurations described in the first to third embodiments may be combined as appropriate as long as the effects of the present invention are achieved.

[0112] The present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way.

[0113] First, examples and comparative examples according to the first and second embodiments of the present invention will be described. Measurements and evaluations of various physical properties were carried out as follows.

[0114] [Thickness of Interlayer Film] The thickness of the interlayer film was measured as an average of 10 points using a microscope "DSX500" manufactured by Olympus Corporation.

[0115] [Content and Degree of Neutralization of Each Structural Unit] The mass % of each structural unit of an ethylene / (meth)acrylic acid copolymer and its ionomer resin was determined by the following hydrochloric acid treatment: １ H-NMR and IR measurements were carried out to determine the content. [Hydrochloric acid treatment] 500 μL of ethanol and 1 mL of hydrochloric acid were added to 100 mg of a sample that had been freeze-pulverized using a JFC-2000 (manufactured by Japan Analytical Industry Co., Ltd.), and the mixture was stirred at 60°C for 48 hours. The mixture was then washed three times with ultrapure water to remove the hydrochloric acid, and dried by heating.

[0116] [Degree of Neutralization] The degree of neutralization was determined by subjecting the sample before and after the hydrochloric acid treatment to IR measurement. －１ Based on the methylene peak height of 1700 cm －１ The carboxylic acid peak height was calculated using the following formula: In the following formula, the denominator is the peak height of 1700 cm for the sample after the hydrochloric acid treatment. －１ Peak height / 1460 cm －１ The peak height of the molecule is 1700 cm for the sample before hydrochloric acid treatment. －１ Peak height: 1460cm －１ represents the peak height of

[0117] [ １ H-NMR Measurement] The sample after the hydrochloric acid treatment was dissolved in a solvent (tetrachloroethane:dimethyl sulfoxide = 5:2) to a concentration of about 1 to 3 mass % to prepare a measurement solution. １H-NMR measurement (apparatus: AVANCE 400 (PRODIGY), spectrometer: AVANCE III HD) was carried out. The measurement conditions were an accumulation of 8 times and a temperature of 120°C. In the analysis, the integrated value of H derived from the methyl group of methacrylic acid was used as the reference, and this value was set to 3.00. At that time, the total mass% of the structural units (A) and (B) and the mass% content of the ethylene-derived structural unit (C) were calculated from the integrated intensity ratio of the H peak derived from methylene appearing at 1.15-1.62 ppm. Furthermore, the respective contents of the structural units (A) and (B) were calculated from the above-mentioned degree of neutralization.

[0118] [Glass Transition Temperature (Tg)] The interlayer films obtained in the Examples and Comparative Examples were cut into pieces 10 mm long and 5 mm wide, and the viscoelasticity was measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, trade name "ARES-G2") under the following measurement conditions. The sample was placed at 100°C, and viscoelasticity measurements were performed while the temperature was lowered. The peak temperature of the loss tangent tanδ obtained from the results was read. Of the peak temperatures in the temperature range of 0 to 100°C, the peak temperature at which tanδ reached its maximum value was taken as the glass transition temperature. Table 2 also lists tanδ at the glass transition temperature. (Measurement Conditions) Deformation mode: shear mode, measurement temperature: temperature decrease from 100°C to 0°C, temperature decrease rate: 3°C / min, measurement frequency: 1 Hz, strain: 1%, 8 mm parallel plate

[0119] [Bending Rigidity] The bending rigidity of the laminated glass was evaluated using the test method schematically shown in Figure 1. The measuring device used was an Instron Model 5965 universal testing machine equipped with a three-point bending test fixture. The measurement conditions were a support distance D1 of 13.2 cm, a sample length D2 of 20 cm, and a width of 8 cm. The laminated glass 20 was deformed in the direction F at a displacement rate of 1 mm / min. The stress measured when either a 0.6 mm displacement or a 500 N force was applied was measured, and the bending rigidity was calculated. Data from an indentation depth of 0.2 mm or more was used to calculate the bending rigidity. The bending rigidity was measured in an environment of 25°C, 30°C, 40°C, and 50°C. Three samples were prepared at each level, and the bending rigidity was measured for each. The arithmetic average value of the three values ​​was used. To adjust the temperature, a refrigerator-type high-low temperature thermostatic chamber "H30001A" manufactured by Mita Sangyo Co., Ltd. was used. After production, the laminated glass obtained in each of the Examples and Comparative Examples was left to stand for one week in an environment of 23°C and 50% RH to cure, and then the bending rigidity was measured.

[0120] (Slope) Based on the thickness of the obtained laminated glass and the values ​​of bending rigidity at 25° C. and 50° C., the slopes (21), (31), (21b), and (31b) were determined according to the method described in the specification. In each example and comparative example, if either the slope (21) or the slope (31) was greater than −10, the thickness dependency of bending rigidity (25 to 50° C.) was rated as "OK," and if both were −10 or less, it was rated as "NG."

[0121] (Bending Rigidity Reduction Rate) The bending rigidity reduction rate was calculated from the bending rigidity of the laminated glass at 25°C and 50°C, and each example and comparative example was evaluated. The bending rigidity reduction rate was calculated using the following formula: Bending rigidity reduction rate (%) = [(Bending rigidity at 25°C - Bending rigidity at 50°C) / Bending rigidity at 25°C] x 100

[0122] Details of the ionomer resins and masterbatches used in the examples and comparative examples are as follows: Details of the ionomer resins and masterbatches used in the examples and comparative examples of the third embodiment described later are also as follows. *Ionomers 1 and 2 are ionomer resins made by neutralizing ethylene-methacrylic acid copolymers with magnesium ions. *Ionomer 3 is an ionomer resin made by neutralizing ethylene-methacrylic acid copolymers with zinc ions and magnesium ions. The mass ratio of zinc ions to magnesium ions is 3:7. *Ionomers 4 and 5 are ionomer resins made by neutralizing ethylene-methacrylic acid copolymers with sodium ions. *Resin (MB) is the ethylene-(meth)acrylic acid copolymer used in the master batch (mixture (A)).

[0123] [Preparation of Masterbatch (Mixture (A))] 100 parts by mass of an ethylene / (meth)acrylic acid copolymer was blended with 2 parts by mass of an ultraviolet absorber and 0.1 parts by mass of a silane coupling agent as additives, and the blend was kneaded and pelletized by a strand cutting method to prepare a pelletized masterbatch (Mixture (A)). The ultraviolet absorbers and silane coupling agents used in the masterbatch are as follows: Ultraviolet absorber: trade name "Tinuvin 234", manufactured by BASF; Silane coupling agent: "KBM-602", manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane

[0124] Example 1A (Preparation of Interlayer Film) 95 parts by mass of Ionomer 1 and 5 parts by mass of the masterbatch were charged into an extruder, kneaded at 170° C., and extruded to obtain an interlayer film having a thickness of 0.76 mm and a width of 1 m.

[0125] (Preparation of Laminated Glass) Two sheets of glass (20 cm long x 8 cm wide x 2.75 mm thick, float glass plate (manufactured by Sanshiba Glass Co., Ltd.)) and an interlayer film according to Example 1A measuring 20 cm long x 8 cm wide were prepared. One interlayer film was sandwiched between the two float glass plates to obtain a laminated intermediate. This laminated intermediate was placed in a rubber bag and degassed for 20 minutes at a vacuum of 0.08 MPa. After that, it was transferred to an oven while still degassed and held at 90°C for 30 minutes to vacuum press the laminated intermediate, thereby temporarily bonding the laminated intermediate. The temporarily bonded laminated intermediate was then bonded in an autoclave at 140°C and a pressure of 1.3 MPa for 20 minutes to obtain a laminated glass (1) in which two sheets of glass were bonded with an interlayer film (thickness 0.76 mm). Laminated glass (2) was obtained by sandwiching two float glass sheets with two interlayer films and bonding the two sheets of glass with an integrated interlayer film (thickness 1.52 mm) under the same manufacturing conditions. Furthermore, laminated glass (3) was obtained by sandwiching three interlayer films with two float glass sheets and bonding the two sheets of glass with an integrated interlayer film (thickness 2.28 mm) under the same manufacturing conditions. The bending rigidity of each of the resulting laminated glasses (1), (2), and (3) was measured, and the slopes (21), (31), (21b), and (31b) were calculated from the measured bending rigidity and the thickness of the interlayer film in each laminated glass. Furthermore, the bending rigidity reduction rate (%) was calculated for each laminated glass. The results are shown in Table 2.

[0126] [Example 2A] (Preparation of interlayer film) Ionomer 2 was charged into an extruder, kneaded at 170°C, and extruded to obtain an interlayer film having a thickness of 0.76 mm and a width of 1 m. Laminated glass was prepared using the obtained interlayer film in the same manner as in Example 1A, and the bending rigidity, inclinations (21), (31), (21b), and (31b), and bending rigidity reduction rate (%) were determined.

[0127] Example 3A The same procedure as in Example 2A was repeated except that Ionomer 3 was used instead of Ionomer 2.

[0128] Comparative Example 1A A laminated glass was produced in the same manner as in Example 1A, except that a polyvinyl butyral resin sheet (manufactured by Eastman Co., product name DG-41) was used, and the bending rigidity, inclinations (21), (31), (21b), and (31b), and bending rigidity reduction rate (%) were determined.

[0129] Comparative Examples 2A and 3A The same procedures as in Example 2A were carried out except that Ionomer 4 and Ionomer 5 were used instead of Ionomer 2, respectively.

[0130] * The slope (21) calculated in each example and comparative example is also the slope (21a), slope (21c), and slope (21ac). * The slope (31) calculated in each example and comparative example is also the slope (21a), slope (31c), and slope (21ac). * The slope (21b) calculated in each example and comparative example is also the slope (21bc), slope (21ab), and slope (21abc). * The slope (31b) calculated in each example and comparative example is also the slope (31bc), slope (21ab), and slope (21abc).

[0131] In each of the above examples, for laminated glass obtained from one interlayer film, or two or three interlayer films, the slopes (21) and (31) calculated from the bending rigidity at 50°C and the thickness of the interlayer film were greater than −10, thereby reducing the rate of decrease in bending rigidity at 50°C relative to the bending rigidity at 25°C and improving bending rigidity at high temperatures. This tendency was also observed in laminated glass in which multiple interlayer films were stacked between a pair of glass members, resulting in a larger interlayer film thickness between the glass members. In contrast, in each of the comparative examples, the slopes (21) and (31) were −10 or less, resulting in a high rate of decrease in bending rigidity at 50°C relative to the bending rigidity at 25°C and failing to improve bending rigidity at high temperatures. This tendency was the same whether one interlayer film was placed between a pair of glass members or multiple interlayer films were stacked.

[0132] Next, examples and comparative examples relating to the third embodiment of the present invention will be described. Measurements of various physical properties were carried out in the same manner as described above. Measurements of bending rigidity were carried out in an environment of 25°C and an environment of 50°C using the same method as described above. The ratio of the bending rigidity at 50°C to the obtained bending rigidity at 25°C was calculated, and a value of 0.5 or more was designated "OK," and a value of less than 0.5 was designated "NG."

[0133] [Evaluation] The bending rigidity was measured in an environment of 40°C in the same manner as in the above-mentioned method for measuring bending rigidity.

[0134] The details of the ionomer resins and resins used in the master batches used in the examples and comparative examples of the third embodiment, as well as the method for producing the master batch (mixture (A)) are as described above.

[0135] Example 1B (Preparation of Interlayer Film) Ionomer 2 was charged into an extruder, kneaded at 170°C, and extruded to obtain an interlayer film having a thickness of 0.76 mm and a width of 1 m.

[0136] (Preparation of Laminated Glass) Two sheets of glass (20 cm long × 8 cm wide × 2.75 mm thick, float plate glass (manufactured by Sanshiba Glass Co., Ltd.)) and a 20 cm long × 8 cm wide interlayer film according to Example 1B were prepared, and a laminated glass was prepared in the same manner as in the laminated glass (1) of Example 1A.

[0137] [Example 2B] 95 parts by mass of ionomer 1 and 5 parts by mass of masterbatch were charged into an extruder, kneaded at 170°C, and extruded from the extruder to obtain an interlayer film with a thickness of 0.76 mm and a width of 1 m. Thereafter, a laminated glass was produced in the same manner as in Example 1B.

[0138] Example 3B The same procedure as in Example 1B was carried out, except that Ionomer 3 was used instead of Ionomer 2.

[0139] Examples 4B to 6B Examples 4B to 6B were carried out in the same manner as Examples 1B to 3B, respectively, except that the thickness of the interlayer film was changed as shown in Table 3.

[0140] Examples 7B to 9B Examples 7B to 9B were carried out in the same manner as Examples 1B to 3B, respectively, except that the thickness of the interlayer film was changed as shown in Tables 3 and 4.

[0141] [Example 10B] An operation was carried out in the same manner as in Example 2B, except that the blending amounts of the raw materials were changed to 90 parts by mass of ionomer 1 and 10 parts by mass of masterbatch, and the thickness of the interlayer film was changed as shown in Table 4.

[0142] [Example 11B] The same procedure as in Example 2B was carried out, except that the thickness of the interlayer film was changed as shown in Table 4.

[0143] Comparative Example 1B A laminated glass was produced in the same manner as in Example 1B, except that a polyvinyl butyral resin sheet (manufactured by Eastman Co., product name DG-41) was used.

[0144] Comparative Example 2B Ionomer 4 was charged into an extruder, kneaded at 170° C., and extruded to obtain an interlayer film having a thickness of 0.76 mm. Thereafter, a laminated glass was produced in the same manner as in Example 1B.

[0145] Comparative Examples 3B and 4B Comparative Examples 3B and 4B were carried out in the same manner as Comparative Examples 1B and 2B, respectively, except that two interlayer films were laminated between two sheets of glass.

[0146] Comparative Examples 5B and 6B Comparative Examples 5B and 6B were carried out in the same manner as Comparative Examples 1B and 2B, respectively, except that three interlayer films were laminated between two sheets of glass.

[0147]

[0148]

[0149]

[0150] In the above examples, the ratio of the bending rigidity at 50°C to the bending rigidity at 25°C was 0.5 or more, which enabled excellent rigidity not only near room temperature but also in an environment around 40°C. In contrast, in comparative examples 1B to 6B, the ratio of the bending rigidity at 50°C to the bending rigidity at 25°C was less than 0.5, so even though excellent rigidity was achieved near room temperature, it was difficult to maintain high rigidity in an environment around 40°C. Furthermore, in examples 2B, 5B, 8B, 10B, and 11B, which used a masterbatch, an ethylene-(meth)acrylic acid copolymer was blended as a resin other than the ionomer resin, which made kneading during extrusion easier and enabled the production amount of interlayer film per unit time to be greater than in other examples which did not use a masterbatch.

Claims

1. An interlayer film that satisfies at least one of the following requirements (A) and (B): Requirement (A): The slope (21) obtained by (flexural rigidity (2) - flexural rigidity (1)) / amount of change in thickness is greater than -10. Requirement (B): The slope (31) obtained by (flexural rigidity (3) - flexural rigidity (1)) / amount of change in thickness is greater than -10. (Note that the bending rigidity (1) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (1) obtained by bonding two pieces of glass having a thickness of 2.75 mm with one piece of the interlayer film interposed therebetween. The bending rigidity (2) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (2) obtained by bonding two pieces of glass having a thickness of 2.75 mm with two pieces of the interlayer film interposed therebetween. The bending rigidity (3) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (3) obtained by bonding two pieces of glass having a thickness of 2.75 mm with three pieces of the interlayer film interposed therebetween. The change in thickness is the change in thickness [unit: mm] of the interlayer film between a pair of glasses when measuring the bending rigidity (2) or the bending rigidity (3) relative to the thickness of the interlayer film between the pair of glasses when measuring the bending rigidity (1).) 2. The interlayer film according to claim 1, wherein the slope (21) is greater than or equal to -9 and less than or equal to 50.

3. An interlayer film having a ratio of 0.5 or more of the bending rigidity at 50°C to the bending rigidity at 25°C of a laminated glass for measurement obtained by bonding two pieces of glass with a thickness of 2.75 mm via the interlayer film.

4. The interlayer film according to any one of claims 1 to 3, wherein the bending rigidity of the test laminated glass (1) or the test laminated glass at 50°C is 700 N / mm or more.

5. The interlayer film according to any one of claims 1 to 3, which contains an ionomer resin.

6. The interlayer film according to claim 5, wherein the ionomer resin comprises a structural unit (A) derived from an unsaturated carboxylic acid, a structural unit (B) of a neutralized unsaturated carboxylic acid, and a structural unit (C) derived from ethylene.

7. The interlayer film according to claim 5, wherein the ionomer resin comprises a structural unit (A) derived from (meth)acrylic acid, a structural unit (B) of a neutralized (meth)acrylic acid, and a structural unit (C) derived from ethylene.

8. The intermediate film according to claim 6, wherein the total content of the structural units (A) and (B) in the ionomer resin is 10 mass% or more and 25 mass% or less based on the total amount of the structural units constituting the ionomer resin.

9. The interlayer film according to claim 5, wherein the content of the structural unit (B) in the ionomer resin is from 4 mass % to 17.5 mass % based on the total amount of the structural units constituting the ionomer resin.

10. The interlayer film according to claim 5, wherein the structural unit (B) contains at least one of magnesium and zinc.

11. The interlayer film according to claim 7, wherein the content of structural units derived from alkyl (meth)acrylate in the ionomer resin is 15 mass% or less.

12. The interlayer film according to claim 5, further comprising a silane coupling agent.

13. The interlayer film according to claim 1 or 2, having a width of 1 m or more.

14. The interlayer film according to claim 1 or 2, which is an extrusion molding.

15. The interlayer film according to claim 1 or 2, having a glass transition temperature of 50°C or higher and 75°C or lower.

16. A laminate comprising the interlayer film according to claim 1 or 2 and a pair of substrates, the interlayer film being disposed between the pair of substrates.

17. The laminate of claim 16 which is a laminated glass.

18. The laminate according to claim 17, which is a laminated glass for architectural structures.

19. A method for producing an interlayer film according to claim 1 or 2, comprising the steps of: kneading an ionomer resin with a mixture of an additive and an ethylene-(meth)acrylic acid copolymer to obtain a resin composition; and extruding the resin composition.

20. A method for producing a laminate, comprising the step of placing the interlayer film according to claim 1 or 2 between a pair of substrates.

21. The method for producing a laminate according to claim 20, wherein a plurality of said intermediate films are disposed between said pair of substrates.

22. An interlayer film in which the slope (21a) calculated by (bending rigidity (2a) - bending rigidity (1)) / thickness change is greater than -10. (Note that bending rigidity (1) is the bending rigidity [unit: N / mm] at 50°C of a measurement laminated glass (1) obtained by bonding two pieces of glass having a thickness of 2.75 mm together via one interlayer film. Bending rigidity (2a) is the bending rigidity [unit: N / mm] at 50°C of a measurement laminated glass (2a) obtained by bonding two pieces of glass having a thickness of 2.75 mm together via an interlayer film (2a) having a different thickness from the interlayer film. The thickness change is the change [unit: mm] in the thickness of the interlayer film between a pair of glasses when bending rigidity (2a) is measured relative to the thickness of the interlayer film between the pair of glasses when bending rigidity (1) is measured.) 23. A laminated glass comprising a pair of glass members and one or more interlayer films disposed between the pair of glass members, the pair of glass members being bonded via the one or more interlayer films, which satisfies at least one of the following requirements (A1) and (B1): Requirement (A1): The slope (21c) calculated by (flexural rigidity (2c) - flexural rigidity (1c)) / thickness change is greater than -10. Requirement (B1): The slope (31c) calculated by (flexural rigidity (3c) - flexural rigidity (1c)) / thickness change is greater than -10. (Note that the bending rigidity (1c) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (1c) obtained by bonding the pair of glass members via one sheet of the interlayer film. The bending rigidity (2c) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (2c) obtained by bonding the pair of glass members via two sheets of the interlayer film. The bending rigidity (3c) is the bending rigidity [unit: N / mm] at 50° C. of the measurement laminated glass (3c) obtained by bonding the pair of glass members via three sheets of the interlayer film. The change in thickness is the change in thickness [unit: mm] of the interlayer film between the pair of glass members when measuring the bending rigidity (3c) or the bending rigidity (2c) relative to the thickness of the interlayer film between the pair of glass members when measuring the bending rigidity (1c).) 24. Laminated glass having a ratio of bending rigidity at 50°C to bending rigidity at 25°C of 0.5 or more.

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