JPH0782638B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, a floppy disk, a hard disk used in audio equipment, video equipment, computers and the like.

2. Description of the Related Art Conventionally, various substances have been added and contained in a magnetic layer of a magnetic recording medium, but many substances have been mixed in at the stage of coating preparation. One of them is a fragment of glass beads when using a sand mill, for example, and is shavings on the inner wall of the mill. In particular, the main component of the former glass beads is sodium silicate, so that a large amount of sodium ions (Na ⁺ ) are mixed in the magnetic coating film produced. This Na ⁺ is a cause of "cylinder blocking," which is one of the product characteristics of magnetic tape, and is a cause of chlorine ion (C
l ^-) in company is well known. Therefore, how to remove or invalidate this Na ⁺ is a means for improving the cylinder blocking property. Cylinder blocking refers to the following phenomenon. That is, when bringing the magnetic layer of the magnetic tape into a high temperature and humidity environment while keeping it in contact with the upper cylinder of the VTR, a few hours later, due to dew condensation, a part of the magnetic layer of the tape adheres to the aluminum surface of the upper cylinder and peels off. It is a phenomenon. The essence of this phenomenon, the water-soluble magnetic layer Na ^+, Cl ^- is that the corroding the Al, thus, Na ^+, Cl ^- it is clear that it once to capture. Therefore the may be added to each of the scavenger, Cl ^-
As the scavenger, a commercially available scavenger that is already known may be used. On the other hand, as the Na ⁺ scavenger, there is no commercially available product, and it has been known that the crown ether which the present inventor has already applied for a patent is preferable.

Problems to be Solved by the Invention In this crown ether, there is 15-Crown-5 in which the inner pore radius is close to Na ⁺ , and there is a clear and remarkable effect for improving cylinder blocking.
However, this has a problem in that it is a liquid at room temperature, which is not preferable in terms of the tape bleeding phenomenon.

In view of the above problems, the present invention provides a magnetic recording medium using a Na ⁺ scavenger that is solid (powder) at room temperature and has a large effect even in a small amount.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention is characterized by containing a clip stand in the magnetic layer. As a result of various studies on Na ⁺ scavengers that replace crown ethers, the present inventor found that cryptand, which is a nitrogen-containing cyclic compound, is effective.
In particular, the cryptand of the chemical formula C ₁₂ H ₂₆ N ₂ O ₄ is a colorless microcrystal (mp.110-11202) at room temperature, and as a result of the experiment, Na ⁺ was trapped and the cylinder blocking property of the magnetic tape was determined to be crown ether. We have been able to greatly improve the above.

Action The function of this cryptand, needless to say, is to entrap and trap Na ⁺ in its own intramolecular vacancy, similar to crown ether. As a result, the water-soluble Na ⁺ is changed from hydrophilic to lipophilic and remains in the magnetic layer. As described above, although the cylinder-blocking is a phenomenon that does not occur if there is no condensation in the temperature and humidity, even if dew condensation occurs in the cylinder tape system, Na ^+, Cl ^- is unless not occur embossed phenomenon But also. When Na ⁺ in the magnetic layer is thus made lipophilic by cryptand, therefore,
The cylinder blocking characteristics will be improved.

Implementation example magnetic powder (commercially _{available, Co-r-Fe 2 O} 3) ...... 100 parts polyurethane (Nippon Polyurethane Industry Co., part number R10
1) ...... 10 parts Vinyl chloride (manufactured by UCC, product name VAGH) ...... 10 parts Carbon black (product number BP-2000) ...... 4 parts Abrasive (α-Al ₂ O ₃ , Sumitomo Co., Ltd.) Chemistry, product number AKP-20) ...
… 3 parts Dispersant (GAFAC, product number RE610) …… 4 parts Lubricant (n-butyl stearate) …… 3 parts Organic solvent methyl ethyl ketone …… 100 parts Organic solvent toluene …… 100 parts Organic solvent cyclohexanone …… 50 parts The number of parts of each material indicates the number of parts by weight when the magnetic powder is 100.

The above mixture was formed into a magnetic paint by a usual method, and cryptand having a chemical formula of C ₁₂ H ₂₆ N ₂ O ₄ was added to the paint at a ratio as shown in the following table, and mixed by stirring. The cryptand is a cyclic compound containing nitrogen [Merck Japan Co., Ltd., product name Kryptofix 22].
It is a substance that forms a complex with alkaline earth metal ions and has been widely applied and studied in the fields of analytical chemistry and synthetic organic chemistry, and has the following structural formula.

To this magnetic paint, hardener (20 phr (pat
rs hundred resin)), and apply it to a PET base film with a thickness of 15 μm so that the magnetic layer has a thickness of 5 μm, calender it, cure at 60 ° C. for 20 hours, and make it 1/2 inch wide. It cut and produced the video tape. The cylinder blocking properties of these sample tapes were evaluated.

As an evaluation method, a sample tape is cut into a length of 25 cm, wrapped around the upper cylinder of the VTR deck with the magnetic layer inside, and a weight of 60 g is hung. 40 ℃ -80 in this state
It was brought into a thermo-hygrostat of% RH and left for 7 days. After that, the sample tape was peeled off, and the peeling condition of the tape magnetic layer and the adhesion condition of the magnetic layer to the upper cylinder were compared with a limit sample prepared in advance, and five-step indexing was performed using the numbers 1 to 5. It was The measurement of n = 5 is performed, and the 5-step display corresponds to ◯ ... 5 (no peeling at all), Δ ... 3, × ... 1 (almost all peeling). As shown in the table below, the effect of the addition of cryptand is clearly recognized.
In particular, when the added amount is 0.1 wt% or more relative to the magnetic paint, the index is about 5, and cylinder blocking hardly occurs.

<Cylinder blocking characteristics by adding Kryptofix22> It is clear from the extraction experiment that a large amount of Na ⁺ is present in the magnetic paint, and this cryptand captures Na ⁺ as well as the effect of adding crown ether to improve the cylinder blocking property.

EFFECTS OF THE INVENTION As described above, according to the present invention, by adding a small amount of cryptand to a magnetic recording medium, the cylinder blocking property can be easily improved, and the present invention can be widely used for all magnetic recording media.

Claims (1)

[Claims] 1. A magnetic recording medium containing cryptand in a magnetic layer.