| 摘要 |
<p>Composite disc intended for the lightproof sealing of, for example the sides of a roll consisting of a web of photographic material which is rolled up around a hollow core. The disc is composed of two parts: a rear, large disc made of a sheet of a stiff, opaque material of the desired diameter, and a front, small disc having a smaller diameter which is fastened concentrically on the first disc. The small disc is made of a different material from the first, large disc. The first, large disc is made of a plastic and the second, smaller disc is made of paper or cardboard. The disc may consist of three discs placed in front of one another, the first, or inner disc is made of an opaque synthetic material which is composed of 5 % high-density polyethylene, 5 % soot, 0 to 5 % polybutylene, and made up to 100 % with low-density polyethylene.</p> |
