Windshield
摘要
說明書
There is no particular limitation on the hardness of the core layer 131 as long as the core layer 131 is softer than the outer layer 132. Although there is no particular limitation on the materials constituting the layers 131 and 132, it is possible to select materials based on the Young's modulus, for example. Specifically, at a frequency of 100 Hz and a temperature of 20° C., the Young's modulus is preferably 1 to 20 MPa, more preferably 1 to 18 MPa, and particularly preferably 1 to 14 MPa. When the Young's modulus is set to be in such a range, it is possible to prevent a decrease in sound transmission loss (STL) in a low frequency range of about 3500 Hz or lower. On the other hand, as will be described later, it is preferable that the outer layers 132 have a large Young's modulus for the purpose of improving the sound insulation performance in a high frequency range, and the Young's modulus can be set to 560 MPa or more, 600 MPa or more, 650 MPa or more, 700 MPa or more, 750 MPa or more, 880 MPa or more, or 1300 MPa or more at a frequency of 100 Hz and a temperature of 20° C. There is no particular limitation on the upper limit of the Young's modulus of each of the outer layers 132, and the Young's modulus can be set from the viewpoint of workability, for example. It is empirically known that when the Young's modulus is set to 1750 MPa or more, for example, the workability decreases, and in particular, cutting is difficult.
