Packaging material and packaging structure made by using same

A packaging material for a transdermal patch containing isopropyl myristate, the packaging material comprising:

• an inner layer film consisting essentially of polyethylene terephthalate-based resin having heat sealing properties;
• and
• a substrate film, wherein:
• the inner layer film is a multi-layer film consisting essentially of at least two resin layers including:
• (a) a heat sealing surface side layer consisting essentially of a first isophthalic acid-modified polyethylene terephthalate resin containing only ethylene terephthalate units and modifying isophthalate units, wherein the first isophthalic acid-modified polyethylene terephthalate resin has a copolymerization ratio of isophthalate units of 10 mol % to 20 mol %, and
• (b) a substrate film side layer adjacent to the heat sealing surface side layer consisting essentially of a second isophthalic acid-modified polyethylene terephthalate resin containing only ethylene terephthalate units and modifying isophthalate units, wherein the second isophthalic-acid modified polyethylene terephthalate resin has a copolymerization ratio of isophthalate units of 0.1 mol % to 5 mol %,
• the heat sealing surface side layer and the substrate film side layer are both unstretched,
• the thickness of the heat sealing surface side layer is from above 2 μm to 5 μm,
• the thickness of the substrate film side layer is 10 μm to 28 μm,
• the packaging material exhibits a heat sealing strength at 110° C. measured according to JIS-Z1707 of at least 15 N/15 mm;
• and,
• the packaging material exhibits a rate of isopropyl myristate absorption of less than 0.1% of a 30 μm LDPE film under the same conditions.