1. Field of the Invention
This invention relates to a magnetic head, and more particularly, to a ring-shaped magnetic head, having a metal magnetic core, for recording and reproducing signals efficiently and for preventing electrostatic noise thereof.
2. Description of the Related Art
Recently, systems handling signals in a wide band, such as high definition VTR (Video Tape Recorder) and digital VTR, have been intensively developed. In this situation, the recording medium is enhanced in density so as to be capable of recording a large quantity of information, and the iron oxide compounds are being replaced by alloy powder, metal evaporated film, and other recording media having a higher coercive force. By contrast, the ferrite magnetic head for recording and reproducing signals on a recording medium has a maximum saturated magnetic flux density of only about 5,000 gauss, and the pole tip is saturated in the recording of the high coercive medium with Hc of 1,000 Oe or more as mentioned above, and sufficient recording is therefore impossible. Accordingly, a ring-shaped magnetic head structured as shown in FIG. 1 using metal magnetic material such as sendust and amorphous magnetic alloy having a high maximum magnetic flux density has been developed. In this structure, a metal magnetic core 200 is held by a nonmagnetic substrates 100.
In a thus composed magnetic head, when the non-magnetic substrates 100 holding the metal magnetic core 200 are insulators, spotty noise may be formed on the reproduced image of the VTR. Such noise is also experienced in a ferrite head. The cause of such noise is considered to be due to discharge generated on the head surface due to electrostatic charge with the tape, and it was believed to be sliding by grounding the magnetic core so as to allow this electric charge to escape. In the Japanese Utility Model Publication No. 52-41377 is disclosed a head structure capable of preventing such noise by adhering the magnetic core to the head base with a conductive adhesive and grounding the magnetic core electrically. However, the adhesion of the conductive adhesive is weak as compared with that of general adhesives, and the reliability of adhesion tends to be inferior, and when the entire magnetic head is not conductive, such as the magnetic head in a structure in which the metal magnetic core is held by a ceramic substrate, if the metal magnetic core is thin, conduction may not be always obtained perfectly depending on the size of the conductive particles of the conductive adhesive. Alternately, in the case of a magnetic head mounted on an insulating ceramic head base such as dynamic tracking head using a piezoelectric element, it is necessary to wind around the conductor in order to ground the magnetic core, which results in a complicated structure.