Mitsuaki Ono

Magnetic tape duplication by contact printing at short wavelengths

Magnetic tape duplication by the contact printing method was first developed in 1949, but there were still many difficulties in the way of successful duplication at short wavelength signals of a few micrometers. The bifilar tape winding system has been newly developed for successful duplication of signals as short as 2 μm. The optimum strength of the transfer field for maximum output of the duplicated slave tape is exactly the same value even at very short wavelengths. The optimum coercivity of the master tape is about two and half times that of the slave tape. The decrease of the recorded master tape at 2-μm wavelength is within 2 dB for the first duplication with no further decrease after more than hundreds duplications. This system is applied to a video tape duplicator and can transfer automatically a 1-hour program within 2 minutes. The duplicated picture quality is almost undiscernible from the master. This system is also adaptable to the duplication of audio, digital, and any other magnetic tapes or sheet information.

Magnetic head for magnetic recording and reproducing unit

In a magnetic head comprising a head gap and a magnetic core composed of both a high permeability ferrite and a magnetic alloy, said magnetic alloy being disposed in the vicinity of said head gap, the improvement comprising a corrugation provided at a junction portion between said ferrite and said magnetic alloy, a height of said corrugation being not less than a value of the longest wavelength of luminance signals and color signals recorded on a magnetic recording medium, a distance defined between adjacent two crests or bottoms of said corrugation being smaller than a width of a head track.

A study of the thermal transfer process

The thermal transfer process takes place at high temperatures, and the temperature which freezes the magnetization is distributed in some wide range depending upon the signal field strength, but most magnetization is frozen between 115°C and 120°C. The time constant of the changing magnetization and demagnetization field from frozen magnetization are very significant in the thermal transfer process. Because of the demagnetization field, thermoremanent magnetization becomes small and is limited to only the tape surface. The computed magnetization pattern of the slave tape indicates that the transfer characteristics of thermoremanent magnetization are similar to that of the anhysteretic method. In the thermoremanent magnetization process the magnetization recovers about 3 times the high temperature magnitude when it is cooled to room temperature. Consequently, a high output can be obtained by thermoremanent magnetization.