JPH03194721A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability by forming a nonmagnetic, conductive metallic thin film between a supporting body and a magnetic layer and between the supporting body and a back coating layer, or between the supporting body and back coating layer. CONSTITUTION:A nonmagnetic, conductive metallic thin film of 0.1-1.5mum thickness is formed on a supporting body composed of polymer material of <=12 mum thickness, on which a magnetic layer is formed. By forming the nonmagnetic, conductive metallic thin film on both sides of the supporting body or on the side of the back coating layer, bending rigidity or twisting rigidity of the tape can be increased since the metallic thin film having high elastic modulus generates force against external force caused when the tape is locally bent. Thereby, the obtd. tape has improved traveling durability.

Description

[Detailed description of the invention] Industrial applications The present invention relates to magnetic recording media.

Conventional technology Generally, paint-on type magnetic recording media involves preparing a coating material in which oxide-based magnetic powder or metal-based magnetic powder is dispersed with a binder, and applying this onto a polyethylene terephthalate (hereinafter referred to as PET) film. , dry.

After calendering, a back coat layer is formed on the surface opposite to the magnetic layer to improve running properties. In recent years, the overall thickness of magnetic recording media has been reduced in order to increase the density and capacity of magnetic recording, and as a result, the thickness of the magnetic layer, support, etc. has been reduced. The reality is that However, when the thickness of a magnetic recording medium is reduced, the rigidity of the medium decreases, and the running durability, which is an important characteristic for the medium, deteriorates. For this reason, the rigidity of a magnetic recording medium has generally been increased by increasing the elastic modulus of the support, magnetic layer, or backcoat layer, or by changing the thickness distribution between the support and the magnetic layer. However, the upper limit of the elastic modulus of the support is 1.000 kg/wa at most in the case of PET, etc.
In addition, when the elastic modulus of the magnetic layer is increased, the electric M1
It becomes extremely difficult to balance practical properties such as conversion properties and still properties, and the adhesion to a support such as PET deteriorates, leading to deterioration in running durability. moreover,
Since increasing the elastic modulus of the bank coat layer increases dropout due to powder falling off from the bank coat layer during running, there is a natural limit to increasing the rigidity of the medium.

Problems to be Solved by the Invention As mentioned above, with the increase in the density and capacity of magnetic recording, media have become thinner and it has become difficult to maintain sufficient durability. It was desired to provide a medium.

Means for Solving the Problems The present inventor has conducted various studies in view of the current situation, and has found that:
Between the support and the magnetic layer, and between the support and the Banokko-1 layer,
Alternatively, it has been found that running durability can be significantly improved by forming a non-magnetic and conductive metal thin film between the support and the bank coat layer. In this invention, the film thickness is preferably 0.1 um to 1.5 um, more preferably 0.1 um or more and 1 um or less.

Function: In the present invention, such improvements have been made possible because metal thin films having a higher elastic modulus than the support are formed on both sides of the support or on the surface of the back coat.

Example In this invention, running durability is improved by forming a non-magnetic and conductive metal thin film between the support and the magnetic layer, between the support and the bank coat layer, or between the support and the back coat layer. performance is significantly improved. The film thickness at this time is preferably 0.1 μm to 1.5 μm, and more preferably 0.111 m or more and 1 μm or less, that is, the nonmagnetic metal yIIl! The film thickness of J is 1.5μm
If the magnetic recording medium exceeds this value, the metal thin film is likely to peel off, and when the magnetic recording medium is sharply bent, the strength of the medium decreases.

If the thickness is less than 0.1 μm, the non-magnetic metal thin film does not have a high elastic modulus, so no improvement in running durability can be expected.Furthermore, when metal thin films are placed on both sides of the support, both film thicknesses The total is preferably 2 μm or less.

By the way, a typical magnetic recording medium is one in which a magnetic layer made of a mixture of magnetic powder, a binder, and various additives is formed on a support such as PET, and is mainly made of insulating material. There is.

In particular, magnetic powder such as Cor-Fe2O3 has high electrical resistance, so magnetic recording media are extremely susceptible to static electricity, such as dust and dirt.
Dust and the like tend to adhere to it, so by providing a non-magnetic and conductive metal thin film, the electrical resistance is reduced and the above problem does not occur. The metal thin film at this time is An, Cu, and Cr.

There are Mg, N+, etc., but from a practical point of view, especially Al.

Alloys containing Cr are preferred.

In the present invention, such an improvement was made possible because a metal thin film having a higher elastic modulus than the support was formed on both sides of the support or on the bank coat side. In other words, magnetic recording media, such as magnetic tape for video tape recorders, are wound around various posts at a certain angle and run. A regulatory post has been established. When the tape attempts to detach from the regulation post and travel, it must basically use the rigidity of the tape itself to prevent the tape from detaching.However, as the overall thickness of the tape becomes thinner, The rigidity of the tape decreases, resulting in the tape bending, the edges of the tape becoming wakame-like, or in the worst case scenario, the tape breaking and important information being lost. By forming a non-magnetic and conductive metal thin film on both sides of the support or on the back coat layer side, a metal mW with a high elastic modulus is arranged when the tape is locally bent. Therefore, a reaction force acts, increasing the bending rigidity and torsional rigidity of the tape, and greatly improving running durability.

Example 1 First, film thicknesses of 6.5, 7, and 7.5.8 μm were prepared in a vapor deposition apparatus.
/l on one side of PET of 2 and 1.5°1.
0.5 μm vapor deposited, total film thickness of Al and PET is 8.5
Make it so that it is μm. At this time, the film thickness was adjusted by changing the feeding speed of the PET.0 Next, magnetic paint was applied to the other side of the PET.The magnetic paint was made into a paint by using a ball mill and dispersing the following composition for 5 hours. .

<Composition of magnetic paint> Vinyl chloride-vinyl acetate copolymer 12 parts by weight Polyurethane 12 parts by weight Magnetic powder (Cor
Fe,,03) 100 parts by weight FJNa material (A120
3) 3 parts by weight hardening agent
3 parts by weight myristic acid
3 parts by weight Methyl ethyl ketone 450 parts by weight Toluene 300 parts by weight Cyclohexanone 150 parts by weight Further drying,
Perform calender treatment, and the film thickness after calender treatment is 2.5
A back paint having the following composition was applied to the surface on which the 0th order /1 was deposited to a thickness of μm and dried.

Composition of backing paint> Carbon 100 parts by weight Polyurethane 15 parts by weight Nitrocellulose 15 parts by weight myristic acid
5 parts by weight abrasive (Afi203)
3 parts by weight hardening agent 10
Parts by weight Methyl ethyl ketone 400 parts Toluene 200 parts cyclohexanone 150 parts by weight The thickness of the bank layer was approximately 0.6 μm so that the thickness of the medium was 11.6 μm. The back paint was also dispersed in a ball mill for 24 hours in the same way as the magnetic paint.

Next, for comparison, the above magnetic paint was applied onto PET with a film thickness of 8.5 μm, dried, and calendered. The thickness of the magnetic layer was adjusted to 2.5 μm after calendering. Furthermore, the thickness of the medium on the side opposite to the magnetic layer is 1
A back coat layer of about 0.6 μm was provided so that the thickness was 1.6 μm. Cut these tapes into 1/2 inch width.
A VTR tape was obtained.

The stiffness and breaking strength in the length direction of the VTR tape thus obtained were measured, and
Dropout was measured.

For dropout, record the color par signal and use a Shibatsu dropout counter at 15 μs per minute.
, -16dB dropout number was measured. Also, V
Durability was confirmed by conducting a 300-pass repeated running test using an H3 system VTR.

The results are shown in Table 1.

(Margin below) As is clear from the table, the magnetic recording medium according to the present invention shows no increase in dropouts and has excellent running durability.

In this example, an example was explained in which a metal thin film was placed only on the back coated side of the support, but the same effect can be obtained when a metal thin film of 0.1 am or more and 1 μm or less is placed on both sides of the support. It will be done.

Effects of the Invention As is clear from the above examples, according to the present invention, a non-magnetic and By providing a conductive metal thin film, a magnetic recording medium with excellent running durability can be provided.

Claims (3)

[Claims] (1) A magnetic layer is arranged on a support made of a polymer formed with a film thickness of 12 μm or less on which a non-magnetic and conductive metal thin film with a film thickness of 0.1 μm to 1.5 μm is formed. magnetic recording media. (2) The magnetic recording medium according to claim (1), wherein the metal thin film is located on the opposite side of the magnetic layer with the support interposed therebetween, and a back coat layer is disposed thereon. (3) A metal thin film is formed on both sides of the support, a magnetic layer is formed on one side, and a back coat layer is formed on the other side. magnetic recording medium.