JP2553533B2 - Magnetic recording media - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium using a metal magnetic powder containing a metal or alloy ferromagnetic powder as a main component, and particularly to a magnetic recording medium having stable running properties. It is about.

2. Description of the Related Art With the recent progress of magnetic recording technology, recording media are required to have higher density. In order to meet this demand, recently, the following two points have been improved in magnetic recording media.

The first point is to replace the magnetic powder mainly composed of iron oxide, which has been conventionally used to attain higher coercive force and higher residual magnetic flux density, with magnetic powder mainly composed of metal or alloy. The magnetic characteristics of the medium are remarkably improved, and the medium can endure high density.

Next, the second point is to improve the surface property of the medium in order to suppress the output loss due to the short recording wavelength as much as possible, thereby reducing the air gap loss between the head and the medium and increasing the output loss due to the high recording density. Can be suppressed. For this reason, what is called a metal tape requires the surface of the medium to be more mirror-finished than before. However, as the surface becomes a mirror surface, various measures are required to secure the medium running property in the deck. For example, an attempt to improve running properties by adding a lubricant and an inorganic substance to a magnetic paint (for example, Japanese Patent Laid-Open No. 61-42).
733, 61-73240, etc.) and mechanical strength (eg Young's modulus)
Attempts to obtain more stable runnability by using an excellent binder (for example, JP-A-61-915,61-9826,6).
1-9827, 61-9829, 61-9830, 61-9831) are raised.

Problems to be Solved by the Invention However, such a conventional configuration has the following problems. First, it can be said that the addition of a lubricant is a very effective method up to a certain amount, but excessive addition causes problems such as a decrease in coating film strength and a protrusion of a lubricant. Next, regarding the use of binders with excellent mechanical strength,
In magnetic recording media, since inorganic substances such as magnetic powder and low molecular weight organic substances such as fatty acids are added to the binder, the mechanical properties of the binder itself may change depending on the type and amount of the additive when produced as a medium. There was a problem that it was difficult to demonstrate.

Means for Solving the Problems In order to solve this problem, the magnetic recording medium of the present invention supports a magnetic layer in which a metal magnetic powder containing a metal or alloy ferromagnetic powder as a main component is dispersed in a binder. A magnetic recording medium provided on the body, wherein the ratio of the imaginary part and the real part of the Young's modulus (so-called tan δ) is -10 in viscoelasticity measurement at a frequency of 200 Hz or less in a state including the support and the magnetic layer. It has a minimum value of 0.03 or less in the temperature range of ℃ to 75 ℃.

Action The present invention is based not only on the composition of the magnetic layer but also on the result of studying the relationship between the medium characteristics in the state of being completed as a medium and the running property. By improving the viscoelastic characteristics of the medium itself and reducing the viscoelastic loss due to contact with each post, cylinder, head, etc. during traveling in the deck, stable traveling performance can be obtained. That is, tan δ is the ratio of the viscous term and the elastic term, and the fact that it is small means that it is not viscous. In the case of a magnetic recording medium, there are many parts such as a support and a magnetic layer which are composed of a polymer substance, and mechanical properties generally change with temperature. In this case, when the temperature becomes high or low, the value of tan δ becomes large, and it becomes sticky, which deteriorates the running property. Therefore, it was found that stable running can be obtained by reducing the stickiness, that is, by reducing the tan δ in the temperature range in which the medium is used (approximately -10 ° C to 75 ° C). At this time, using the parameter tan δ does not mean that stable running can be obtained because the Young's modulus is high (so-called hard), and even if the Young's modulus is low (so-called soft), the minimum value of the ratio of viscous term and elastic term is This is because it is important to make it small. Further, as a result of earnest studies, the present inventors have found that in a magnetic recording medium having a minimum tan δ value of 0.03 or less within a temperature range of −10 ° C. to 75 ° C., within a practical running temperature range of a tape (−5 ° C. From 40
We found that there was no problem in practical use.

Examples Examples of the present invention will be described below.

The viscoelasticity tan δ in the magnetic recording medium is mainly determined by the properties and the amount of the binder itself used in the magnetic layer. Here, the medium characteristics suitable for the constitution of the present invention were realized by changing the characteristics of the binder or changing the amount of the low molecular weight compound to be added without changing the binder.

Example 1 The composition shown in Table 1 was well kneaded and applied, and then 3% was applied as a base on polyethylene terephthalate having a thickness of 10 μm.
It was applied in a thickness of μm and sufficiently cured to prepare an 8 mm metal tape. At this time, the polyurethane resin used as a binder together with the vinyl chloride-vinyl alcohol copolymer had a glass transition temperature Tg of 70 ° C., 20 ° C., and −20 ° C., and were referred to as Samples A, B, and C, respectively. Frequency of these three samples in the temperature range from -10 ℃ to 75 ℃ 11
Table 2 shows the minimum value of tan δ at 0 Hz, and the results of the deck running test in the environment where the temperature is −5 ° C., 25 ° C., 40 ° C. and the relative humidity is 60%. In the deck running test, a sample tape recording a video signal (here, color bar signal) is 8 mm
It was set on the deck, run in the test environment, and the tape running state including RF output and output video screen was observed. From Table 2, it can be seen that tape squeaking and jitter occur at high temperatures when tan δ exceeds 0.03.

Example 2 Samples D, E, and F were manufactured by using the polyurethane used in Sample A in Example 1 and adding myristic acid as a lubricant in an amount different from 3, 4, and 5 parts. Table 3 shows the tan δ at each measured frequency of 110Hz from -10 ℃ to 75 ℃.
The minimum value and the result of the environmental test are described. As can be seen from this, even with the same binder, the properties as a medium change depending on the amount of additives, and when using it, it is carefully determined what the tan δ as a medium becomes, and 0.03
The composition must have the following minimum values.

In the above example, the metal magnetic powder coating is applied on the support, but the present invention further comprises the inorganic particles mainly composed of carbon black and the binder mainly composed of the polymer resin on the back surface of the support. Which has a back coat layer formed of
The same applies to the case where an anchor layer comprising a magnetic or non-magnetic material or a mixture thereof and a binder mainly composed of a polymer resin is provided on a support and a magnetic layer is formed thereon. When the viscoelasticity of the medium as a whole is measured, the minimum value of tan δ is 0.03 or less (the maximum value does not matter).

The value of tan δ in the above examples is a sample vibration type viscoelasticity measuring instrument (REHOVIBRON DDV-II- manufactured by Orientec Co., Ltd.).
EA) and a sample length of 3 mm in length and 4 mm in width.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain the effect that the running property of the metal tape is improved in a wide temperature range of −5 ° C. to 40 ° C. which is the practical running temperature range of the tape.

Claims (3)

(57) [Claims] 1. A magnetic recording medium comprising a support and a magnetic layer having a magnetic metal powder containing a metal or alloy ferromagnetic powder as a main component dispersed in a binder, the support and the magnetic layer comprising: When included, the ratio of the imaginary part and the real part of the Young's modulus (so-called tan δ) was -10 ° C in viscoelasticity measurement at a frequency of 200 Hz or less
A magnetic recording medium having a minimum value of 0.03 or less within a temperature range from 1 to 75 ° C. 2. A back coat layer is provided on the back surface of the support,
In the state of containing the support, the magnetic layer and the back coat layer,
When viscoelasticity is measured at a frequency of 200 Hz or less, tan δ is from -10 ℃ to 75
The magnetic recording medium according to claim 1, which has a minimum value of 0.03 or less within a temperature range of ° C. 3. A support having an anchor layer, which is a lower layer, formed on a support, and the magnetic layer formed on the support.
The magnetic recording medium according to claim 1 or 2, wherein tan δ has a minimum value of 0.03 or less in a temperature range of −10 ° C. to 75 ° C. when measured by viscoelasticity at 0 Hz or less.