CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C 119 to Japanese Patent Application No. 2019-086681 filed on Apr. 26, 2019. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording medium and a magnetic recording and reproducing apparatus.

2. Description of the Related Art

A magnetic recording medium (for example, see JP2012-043495A) is a recording medium useful as a data storage medium for storing a large capacity of data (information) for a long period of time.

SUMMARY OF THE INVENTION

A magnetic recording medium used for data storage application may be used in a data center in which a temperature and a humidity are controlled. On the other hand, the data center is required to save power in order to reduce costs. In order to save power, it is desirable that control conditions of the temperature and the humidity in the data center can be more relaxed than a current level or the controlling can be made unnecessary. However, in a case where the control conditions of the temperature and the humidity are relaxed or the controlling is not performed, it is assumed that the magnetic recording medium is exposed to environmental changes caused by weather changes, seasonal changes, and the like, or is stored under various temperature and humidity environments. An example of the environmental changes is a temperature change from a low temperature to a high temperature under a high humidity. An example of the temperature and humidity environments is a high temperature and high humidity environment. Since the magnetic recording medium is always required to exhibit excellent electromagnetic conversion characteristics, it is desirable to provide a magnetic recording medium in which a deterioration of electromagnetic conversion characteristics after such an environmental change and after a storage in such a temperature and humidity environment is suppressed more than in the magnetic recording medium of the related art.

Incidentally, the magnetic recording medium generally has a configuration having a non-magnetic support and a magnetic layer containing ferromagnetic powder. As for the non-magnetic support, for example, a paragraph 0036 of JP2012-043495A discloses various films that can be used as the non-magnetic support.

The present inventor has studied the above-mentioned points and it has been clarified that in a case where a magnetic recording medium including an aromatic polyamide support as a non-magnetic support is stored under a high temperature and high humidity environment after a temperature change from a low temperature to a high temperature occurs under a high humidity, a phenomenon in which electromagnetic conversion characteristics deteriorate occurs.

An object of an aspect of the present invention is to suppress a deterioration of electromagnetic conversion characteristics after a temperature change from a low temperature to a high temperature under a high humidity and further after a storage under a high temperature and high humidity environment in a magnetic recording medium including an aromatic polyamide support.

An aspect of the present invention relates to a magnetic recording medium comprising: a non-magnetic support; and a magnetic layer including ferromagnetic powder, in which a difference (Safter−Sbefore) (hereinafter, also referred to as a “spacing difference (Safter−Sbefore) before and after methyl-ethyl-ketone cleaning” or simply a “difference (Safter−Sbefore)”.) between a spacing Saftermeasured on a surface of the magnetic layer by optical interferometry after methyl-ethyl-ketone cleaning and a spacing Sbeforemeasured on the surface of the magnetic layer by optical interferometry before methyl-ethyl-ketone cleaning is more than 0 nm and 15.0 nm or less, and the non-magnetic support is an aromatic polyamide support having a moisture absorption of 2.2% or less.

In an embodiment, the difference (Safter−Sbefore) may be 3.0 nm or more and 15.0 nm or less.

In an embodiment, the moisture absorption of the aromatic polyamide support may be 2.0% or less.

In an embodiment, the moisture absorption of the aromatic polyamide support may be 1.0% or more and 2.0% or less.

In an embodiment, the magnetic recording medium may further comprise a non-magnetic layer including non-magnetic powder between the non-magnetic support and the magnetic layer.

In an embodiment, the magnetic recording medium may further comprise a back coating layer including non-magnetic powder on a surface side of the non-magnetic support opposite to a surface side provided with the magnetic layer.

In an embodiment, the magnetic recording medium may be a magnetic tape.

Another aspect of the present invention relates to a magnetic recording and reproducing apparatus comprising: the magnetic recording medium described above; and a magnetic head.

According to an aspect of the present invention, it is possible to provide a magnetic recording medium that includes an aromatic polyamide support and has a small deterioration of electromagnetic conversion characteristics even though being stored under a high temperature and high humidity environment after a temperature change from a low temperature to a high temperature under a high humidity, and a magnetic recording and reproducing apparatus including the magnetic recording medium.

