| 摘要 |
PROBLEM TO BE SOLVED: To develop a vacuum heat insulating material having a higher heat insulating property and to improve its thermal durability for improving the heat retaining performance of an electric water heater. SOLUTION: Since a film having good thermal size stability as a deposition base material is used on a gas barrier layer in a laminated film constituting a vacuum heat insulating material 20, a deposition layer is not broken at the temperature of about 100 deg.C, the gas barrier property is good, the vacuum state can be sufficiently held, and the heat insulating property is not deteriorated for a long period. Since the deposition layer is used as the gas barrier layer on the end face kept in contact with a container 2 on the vacuum heat insulating material 20, the heat flowing into a low-temperature section along the gas barrier layer itself form the container 2 side can be suppressed, and the heat insulating performance of the whole vacuum heat insulating material 20 can be improved. An electric water heater having no thermal deterioration for a long period and having improved heat retaining performance can be realized.
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