JPH0770017B2 - Magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an erasing head for a V / T / R audio signal, in which a case body constituting the erasing head and a tape sliding contact surface are integrally formed. The present invention relates to a magnetic head obtained by adding carbon fiber, which is an antistatic agent, to a molding material obtained from the above.

<Prior Art> Conventionally, as shown in FIG. 1, in a magnetic head, a fitting portion 2a is formed in a case body 2 in which a head portion 1 including a coil, a front core, and a back core is incorporated so as to be inserted from the back side. , A front made of a molding material containing a ceramic or an inorganic filler on the tape sliding contact surface 2b side of the case body 2 so that the tip of the front core 1a of the head portion 1 is accurately positioned on the tape sliding contact surface 2b of the case body 2. The block 3 is integrally embedded, and after incorporating the head portion 1 and applying an internal mold, the tape sliding contact surface 2b is polished into a predetermined arc shape, and the magnetic head as shown in FIG. Was manufactured.

However, since an antistatic agent or the like is not added to the molding material of the front block 3 as an antistatic measure, it has a considerably high insulating property, and due to friction between the magnetic tape and the tape sliding contact surface, static electricity is generated. Occurs,
It deteriorated the tape running and caused noise. In particular, the molding material of the front block has a larger charge amount as the insulating property is higher, and also has a larger sheet resistance value, and when the charge amount exceeds a certain value, it is discharged and noise is increased. was there. The term "area resistance" is used here because it is only the tape sliding surface of the erasing head that matters, and we want to eliminate content inserts related to volume. From this point of view, no proper term is found, the term "area resistance" is used, and the surface on which the video tape slides is within 1 cm ^{2 as} is well known, so it is the original value of area resistance. Although Ω / cm ² was used as a unit normalized to an area of 1 cm ² instead of Ω, Ω / □ was used as a unit because the general expression is appropriate.

<Means for Solving Problems> The present invention has been made to solve the above-described conventional drawbacks, and configures an erasing head as a measure for preventing static electricity on the tape sliding surface of the magnetic head. Carbon fiber, which is an antistatic agent, is added to a molding material formed by integrally molding the case body and the tape sliding surface of the head portion, and the area resistance value of the molding material is 10 ¹⁰ Ω / □ ≤ area resistance value ≤
It provides a magnetic head of 10 ¹³ Ω / □.

<Embodiment of the Invention> An embodiment of the present invention will be described in detail below with reference to FIG. In the figure, 10 is a case body integrally formed with the tape sliding contact surface, 11 is a front core of the head portion, 12 is a gap, 13 is mold resin, and 14 is a terminal.

The basic constituent materials of the case body 10 integrally formed with the tape sliding surface are plastics (eg nylon, polyphenylene sulfide, polybutylene terephthalate etc.), inorganic fillers (eg alumina, calcium carbonate, quartz glass etc.) An appropriate amount of carbon fiber antistatic agent is added to prevent static electricity due to friction during tape running.

Here, the basic constituent material is a weight ratio of plastics, inorganic filler, carbon fiber, 35:65 as an example:
4, and the area resistance value was 10 ¹⁰ Ω / □ ≦ area resistance value ≦ 10 ¹³ Ω / □.

In addition, carbon fiber has a bending strength and tensile strength equivalent to or higher than that of conventional glass fiber, and since it has the property of being electrically conductive, it is an additive used in place of glass fiber. It is a thing.

In addition to the basic constituent materials for integrally molding the case body of the magnetic head according to the present invention and the tape sliding contact surface of the head portion,
It is a kind of carbon black, and it is also possible to add ketjen black which is much more conductive than ordinary carbon black, so that abrasion resistance can be sufficiently ensured.

Further, the area resistance value of the basic constituent material according to the present invention is 10 ¹⁰ Ω / □ ≦ area resistance value ≦ 10 ¹³ Ω based on various experimental results.
/ □ is preferable.

The reason is as follows.

Since a plastic material containing an inorganic filler originally has a high resistance, a material that lowers the resistance is added. Therefore, we tried various materials to reduce the resistance, but there is no conflict between the materials that hardly wear during long-term sliding contact running, particles do not fall off from the sliding contact surface, and the dispersibility in the resin is good. Therefore, it is necessary to find out the above-mentioned electrically good characteristics, running stability and optimum resistance range. More specifically, carbon is used as a low-resistance dispersion material that has wear resistance in sliding contact between a magnetic head and a recording medium and dispersibility in a resin, and does not fall off the sliding contact surface or have unevenness when used after molding. We have found that the fiber is optimal.

According to the results of the experiment, the amount of carbon fibers added with almost no particles falling off and good surface roughness due to electrostatic charge removal was 3% by weight, and the sheet resistance value was 7 × 10 ¹² Ω / □. When the carbon fiber content was 2% by weight or less, the sheet resistance value was 5 × 10 ¹³ Ω / □ or more, and the recording medium was attracted to the magnetic head or generated noise due to charging. Further, if the amount of carbon fiber is increased in order to lower the resistance value, the compatibility with the molding resin becomes poor and particles fall off, which damages the recording medium and the sliding contact surface of the head, causing output reduction and noise.

From the above requirements, the optimum range of the amount of carbon fiber added to the resin is 3 to 6% by weight (preferably 3% by weight).
~ 4 weight percent) and the sheet resistance value is 10 ¹⁰ Ω /
□ ≦ Area resistance value ≦ 10 ¹³ Ω / □.

<Effects> As described in detail above, in the magnetic head according to the present invention, a molding material for integrally molding the case main body that constitutes the erasing head and the tape sliding contact surface of the head part is made of plastics or inorganic filler. Besides, an antistatic agent of carbon fiber is added, and the area resistance value of the molding material is 10 ¹⁰ Ω / □ ≦
Area resistance value ≤ 10 ¹³ Ω / □, the amount of charge on the tape sliding contact surface is small, and the tape running is extremely smooth, so noise can be prevented and the performance as an erasing head is improved. There is an effect that it can be improved.

[Brief description of drawings]

1 and 2 are exploded structural views of a magnetic head showing a conventional embodiment, and a perspective view after completion of assembly, and FIG. 3 is a perspective view of a magnetic head according to the present invention. 10 …… Case body, 11 …… Head part, 12 …… Gap,
13 …… Mold resin

Claims (1)

[Claims] 1. In an erasing head having a molded product as a sliding surface, a molding material obtained by integrally molding a case body constituting the erasing head and a tape sliding contact surface is used as an antistatic agent for preventing static electricity. The area resistance value of the above molding material is 10 ¹⁰ Ω / □ ≦ area resistance value ≦ 10 ¹³ Ω / when carbon fiber is added.
A magnetic head characterized by □.