Intermediate film for laminated glass, and laminated glass

An interlayer film for laminated glass having a one-layer or two or more-layer structure,

• the interlayer film including a first layer containing a resin,
• when the interlayer film is arranged between two sheets of clear float glass having a thickness of 2.5 mm to obtain a laminated glass X with a size of 150 mm in length and 300 mm in width, and the obtained laminated glass X is subjected to measurement of optical strain, an optical strain value being 3.00 or less,
• when the interlayer film is arranged between two sheets of clear float glass having a thickness of 2.1 mm to obtain a laminated glass Y having a size of 950 mm in length and 1500 mm in width, and the obtained laminated glass Y is subjected to measurement of damping ratio, a damping ratio at a resonance frequency of 50 Hz or more and 80 Hz or less being 5.0% or more:
• the measurement of optical strain including:
• preparing an optical strain inspection apparatus including a light source unit for emitting irradiation light, a projection plane for projecting the irradiation light having penetrated a measuring object, an image inputting part that photographs the projection plane to generate a gray image, and an image processing part that detects an optical strain in a longitudinal direction and in a widthwise direction of the measuring object on the basis of a degree of variation in shading of the gray image;
• preparing as the measuring object, two measuring objects, namely, the laminated glass X, and a laminated glass for calibration obtained by arranging a monolayer interlayer film for calibration having a visible light transmittance of 88% between two sheets of clear float glass having a thickness of 2.5 mm;
• measuring an optical strain value of the laminated glass X by using the optical strain inspection apparatus that is adjusted such that the optical strain value in a condition that no measuring object is placed is 1.30, and an optical strain value of the laminated glass for calibration is 1.14;
• measurement conditions including an atmospheric temperature of 23° C. and a surface temperature of the measuring object of 25° C.;
• and
• of the obtained optical strain value in the longitudinal direction of the measuring object, and the obtained optical strain value in the widthwise direction of the measuring object, a smaller optical strain value being determined as an optical strain value of the measuring object,
• the measurement of damping ratio including:
• dividing a first surface of the laminated glass Y into regions such that each region has a length of 5 cm or less and a width of 5 cm or less;
• when a longitudinal length of the laminated glass Y is defined as L1, a widthwise length is defined as L2, and one vertex of the first surface is defined as vertex O, in the first surface of the laminated glass Y, installing an accelerometer at three positions:
• a position of 0.3L1 in the longitudinal direction and 0.3L2 in the widthwise direction from the vertex O, a position of 0.7L1 in the longitudinal direction and 0.5L2 in the widthwise direction from the vertex O, and a position of 0.6L1 in the longitudinal direction and 0.8L2 in the widthwise direction from the vertex O;
• in each of the regions, exciting a middle position in the longitudinal direction and a middle position in the widthwise direction of the region in the first surface with an impact hammer, and calculating a transfer function;
• and
• calculating a damping ratio at a resonance frequency of 50 Hz or more and 80 Hz or less according to the obtained transfer function.