Matsushita Electric Industrial Co., Ltd.

Hirotoshi Niguchi

Mitsuru Ieki

Satoshi Takayama

Osamu Yamamoto

Katsuji Hattori

Kosaku Murata

Erasable optical disk media basically comprise a double layer structure composed of a thermal expansion layer formed of an organic dye and a binder, and a retention layer of metal. In the recording process, the thermal expansion layer is heated to form a dome-like pit in the retention layer. The reproducing process is performed by reading differences in reflectivity from the pit and an area surrounding the pit. In the erasing process, the retention layer including the pit is heated to flatten the same under the tensile stress (residual stress) acting on the thermal expansion layer. The pit size is kept in a stable condition during the recording and reproducing processes, while the erasing can be performed completely without leaving partly erased traces. The erasable optical disk media of the foregoing construction are highly durable and resistant to heat.

Erasable optical disk media and method of recording/erasing the same

A diaphragm for a speaker which is prepared by heating a conjugated sheet obtained by paper-making polyethylene short fibers with other short fibers which have a high modulus of elasticity, such as carbon fiber, to melt and solidify polyethylene short fibers in the conjugated sheet; the process for the production thereof. The diaphragm for a speaker of the invention has a high modulus of elasticity and a high internal loss and a speaker prepared with such a diaphragm has the advantage of having a wider reproducing frequency response and lower distortion. Furthermore, the process for production of the invention possesses another advantage in that diaphragms for speakers can be produced in a continuous process of successively pressing out the speaker diaphragm with a cold mold press.

Speaker diaphragm and method of preparation of the same

A speaker diaphragm molded from a poly-bisphenol phthalate type plastic film having ester linkages prepared from an aromatic dicarboxylic acid such as isophthalic acid or terephthalic acid or a mixture thereof and a bifunctional phenol such as bisphenol A. This speaker diaphragm has an excellent low-pitched sound reproducing performance and is further featured by the flat acoustic pressure-frequency characteristic and improved transduce efficiency.

Speaker diaphragm molded from poly-biphenol phthalate type resin film

An acoustic diaphragm has a substrate of either a hard resin film or cloth of an organic material, and at least one side of the substrate is laid with a polyurethane elastomer layer. In the case of a cloth substrate, the cloth is optionally metallized by evaporation deposition of Al or Ti and/or impregnated with a thermosetting resin. The elastomer is a copolymer given by condensation of bifunctional polymeric alcohol and a glycol with a diisocyanate. This diaphragm features a flat response curve at medium to high frequencies on account of its relatively large value for Young's modulus and adequately great internal loss, and accordingly is particularly useful for tweeters.

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Kashihara, Japan

Hirotoshi Niguchi