JPH0462036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a protective body for a magnetic recording medium, such as a magnetic shielding case, for preventing magnetic signals recorded on a magnetic recording medium, such as a cash card floppy disk, from attenuating or disappearing due to the influence of external magnetism. The present invention relates to a magnetic shielding laminate and a magnetic shielding composite useful as a constituent material of a magnetically shielded room or a wall panel material of a magnetically shielded room. In recent years, the use of cash cards and credit cards at banks and department stores has become popular, and many people carry them on a daily basis. Furthermore, the automation (OA) of offices is remarkable, and the use and transportation of floppy disks and magnetic tapes in the office has become indispensable for daily office work. As described above, the spread of magnetic recording media is widespread and rapidly progressing. On the other hand, permanent magnets are rapidly becoming popular in daily necessities, office supplies, etc., such as handbag clasps,
Clips, magnetic buttons for blackboards, magnetic boards, and other health products such as stiff shoulder treatment items, health pillows, health suits, and other toys, etc.
Permanent magnets with a strength of several thousand Gauss are widely used in many places around us. By the way, the magnetic signals of magnetic recording media are affected by permanent magnets, causing the recorded signals to attenuate or disappear, causing malfunctions in automatic teller machines or office automation equipment, for example, and becoming a major social problem. ing. Conventionally, magnetic shielding cases made of various constituent materials have been proposed for the purpose of preventing these troubles. For example, in Utility Model Application Publication No. 56-16707, a magnetic shielding case made entirely of a single magnetic material was proposed, and in Utility Model Application Publication No. 56-29827, a crystalline magnetic metal with high saturation magnetic flux density and an amorphous material with high magnetic permeability were proposed. A magnetic card shield case has been proposed that is made of a laminate with quality metals. However, none of these methods are fully satisfactory as they do not have the expected magnetic shielding effect and have various problems, such as the need for special metal materials. Under these circumstances, there is a strong demand for a constituent material that can provide a magnetic recording body protector that is simple, low cost, and has a high magnetic shielding effect without using special metal materials. An object of the present invention is to provide a constituent material for a protector for a magnetic recording medium that has an excellent magnetic shielding effect, that is, an inexpensive constituent material that does not use special metals or the like. Generally, the maximum value of external magnetic force that does not affect the magnetic signal of a magnetic recording medium is about 200 Gauss or less. The present inventors completed the present invention as a result of various studies regarding the constituent materials and structures of various magnetic recording body protectors, for example, magnetic recording body storage cases. In other words, the present inventors have discovered that a plate-shaped body made of ferromagnetic materials facing each other with an appropriate distance between them exhibits a large magnetic shielding ability, and that inside a partition wall using the plate-shaped body as a partition wall, The present invention was completed based on experimental results showing that the influence of external magnetism can be reduced to 200 Gauss or less. The present invention provides a laminated plate in which two or more ferromagnetic materials are spaced apart from each other, the sum of the spaces is 0.5 mm or more, and a non-conductive material is sandwiched within each space. The present invention relates to a magnetic shielding composite which is sandwiched between two non-magnetic sheets, and the four edges of the two non-magnetic sheets are welded to each other. As already mentioned, there have been many proposals to achieve the purpose of magnetic shielding by using specific ferromagnetic materials, such as permalloy, as magnetic shielding plates. However, in the present invention, the magnetic shielding effect is exerted by the presence of the spacing formed between the ferromagnetic materials, so the ferromagnetic materials to be used are specific [type, thickness, form, etc.] For example, there is no need to choose between plate-shaped, corrugated plate-shaped, etc.)
A barrier wall with maximum magnetic shielding effect can be provided using extremely inexpensive materials. Regarding the thickness of the ferromagnetic material used, please note that the thickness of the ferromagnetic material to be used is
It is preferably 0.05 mm or more. Incidentally, the magnetic shielding material is required to have a property that hardly any magnetism remains even when the magnetic shielding material itself is repeatedly removed from contact with a permanent magnet. In other words, it is necessary that the magnetism quickly and almost completely disappear from the magnetic shielding material by the operation of contacting and removing the permanent magnet. Therefore, in the present invention, although the ferromagnetic material is not particularly limited, it is preferable to use a ferromagnetic material having the above-mentioned properties, that is, a so-called magnetically soft ferromagnetic material for a better magnetic shielding effect. It is preferable to demonstrate this. Examples of such magnetically soft ferromagnetic materials include iron, silicon steel, and other alloys. As described above, in the present invention, it is essential to have a spacing between the ferromagnetic materials, but this is due to, for example, the first
This does not mean only the existence of a single interval formed by only two ferromagnetic materials as shown in Figure a;
A multiplex with two or more spacings, such as a case with two spacings formed from three ferromagnetic materials as shown in Figure 1b, or a case with three spacings formed from four ferromagnetic materials. It may be of a structure. In the present invention, as a result of repeated experiments on the magnetic shielding effect of this interval, we found that the total interval is 0.5
They found that it must be at least mm. That is, when forming a multilayer structure using three or more ferromagnetic materials, the total distance formed must be 0.5 mm or more. The two or more ferromagnetic materials used in the present invention do not necessarily have to be of the same type and the same shape, and furthermore, if they have two or more intervals, it is also necessary that each of the intervals be the same. do not. For example, two pieces of iron and one piece of silicon steel as ferromagnetic materials are made to face each other alternately to form two intervals, one of which is 0.3mm, the other one is 0.2mm, and the total interval is 0.5. It is possible to set it to mm. In the present invention, a non-conductive substance is held within the gap formed as described above, thereby maintaining the gap, but the substance to be held may be any non-conductive substance; Although the form does not matter, a relatively light one is preferable. For example, styrofoam,
In addition to urethane foam, sponge bodies, fiber aggregates, nonwoven fabrics, felts, etc., honeycomb structures made of non-conductive substances are preferred because they are lightweight. Note that the non-conductive material is sandwiched between the ferromagnetic materials at the four peripheries, three peripheries, or two peripheries of the spacing. (For example, Figure 1). By using only the peripheral portion in this manner, weight reduction has been achieved without any loss in the magnetic shielding effect. Note that the magnetic shielding laminate in the present invention does not necessarily refer only to a state in which a ferromagnetic material and a non-conductive material are bonded to each other; for example, a state in which a ferromagnetic material and a non-conductive material are bonded together, In other words, when a non-magnetic sheet is used as a core material in a processed plate or the like as an outer peripheral material, the ferromagnetic material and the non-conductive material are not bonded to each other, but simply overlapped. It also includes those forming a set of plates. Next, specific numerical values will be exemplified regarding the effect that the spacing formed between ferromagnetic materials has on magnetic shielding. The values in the table below assume that a 0.3mm thick iron plate is used as the ferromagnetic material, and that one side of the shielding wall made of the iron plate is
This is the value obtained by bringing a 2000 Gauss permanent magnet into contact and measuring the decrease in magnetism on the opposite side using a Gaussmeter 3251 manufactured by Yokogawa Electric Corporation.

[Table] In magnetic shielding by shielding walls, it is clear from actual measurement results how effective the formation of gaps within the shielding walls is. If the magnetic shielding laminate of the present invention is used as a component of a magnetic shielding case for a magnetic recording medium such as a floppy disk, the floppy disk housed in the case will be completely protected from external magnetism. The magnetic shielding laminate according to the first invention is
By sandwiching two non-magnetic sheets together and welding the four peripheries together to form a composite, it is possible to provide a component for a magnetic shielding case or a magnetic shielding wall panel material with a high external cosmetic effect. . FIG. 2 is a schematic partial cross-sectional view of the magnetic shielding composite of the present invention. That is, as specifically shown in FIG. 2, a magnetic shielding laminate 3 is sandwiched between two nonmagnetic sheets 4 that are cut wide so that each of the four sides protrudes from the magnetic shielding laminate 3 by approximately 2 mm or more. Each of the four sides of 4 is welded 5 and the magnetic shielding laminate 3 is attached to two non-magnetic sheets 4.
It is completely covered with . The nonmagnetic sheet referred to in the present invention may be any material that can be welded together, such as polyvinyl chloride, ethylene vinyl acetate copolymer, and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a magnetic shielding laminate of the present invention, and FIG. 2 is a schematic partial cross-sectional view of a magnetic shielding composite. 1...Ferromagnetic material, 2...Non-conductive material, 3...
Magnetic shielding laminate, 4... Non-magnetic sheet, 5...
Welder joint.

Claims (1)

[Claims] 1 A non-conductive substance is sandwiched between two or more ferromagnetic materials at four, three, or two peripheral regions, and the total distance between the ferromagnetic materials is 0.5 mm or more. 1. A magnetic shielding composite comprising a laminate sandwiched between two non-magnetic sheets, and four edges of the two non-magnetic sheets welded to each other.