JPS63153719A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristics of a medium and to increase the density thereof by providing a min. value of <=0.3 to tan delta which is the ratio between the imaginary part and rear part of Young's modulus in the measurement of viscoelasticity at <=200Hz oscillation frequency in the state of contg. a base and magnetic layer. CONSTITUTION:This magnetic recording medium is formed by providing the magnetic layer dispersed with the metal magnetic powder essentially consisting of ferromagnetic powder of a metal or alloy in a binder onto a base. The tan deltawhich is the ratio between the imaginary part and real part of the Young's modulus in the measurement of the viscoelasticity at <=200Hz oscillation frequency in the state of contg. the base and magnetic layer of such medium has the min. value of <=0.03. The running performance of a metal taps is thereby improved by a wide temp. range.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium using a metal magnetic powder whose main component is a metal or alloy ferromagnetic powder.9 In particular, it relates to a magnetic recording medium with stable running properties. It's about the medium.

BACKGROUND OF THE INVENTION With recent advances in magnetic recording technology, recording media are required to have higher density. In order to meet this demand, magnetic recording media have recently been improved in the following two points.

The first point is to change the magnetic powder mainly composed of iron oxide, which was conventionally used, to a magnetic powder mainly composed of metal 9 alloy in order to quickly achieve higher coercive force and higher residual magnetic flux density. The magnetic properties of the medium are significantly improved and it can withstand higher densities.

The second point is to improve the surface properties of the medium in order to minimize the output loss due to the short recording leakage length, thereby reducing the gap loss between the head and the medium.
Output loss associated with high recording density can be suppressed.

For this reason, what is called metal tape,
It is necessary to finish the media surface more mirror-like than before. However, as the surface becomes mirror-finished, various measures are required to ensure media runnability in the deck. For example, an attempt was made to improve the runnability of magnetic paint by adding lubricants and inorganic substances.

JP-A No. 61-42733, 61-73240, etc.) and attempts to obtain more stable runnability by using binders with excellent mechanical strength (e.g., Young's modulus) (e.g., JP-A No. 61-915. 61-9826.61-98
27”, 61-9829.

61-9830, 61-9831, etc.).

Problems to be Solved by the Invention However, such conventional configurations have the following problems. First, adding a lubricant can be said to be a very effective method up to a certain amount, but adding too much causes problems such as a decrease in coating film strength and the lubricant coming out. Next, regarding the use of a binder with excellent mechanical strength, in magnetic recording media, inorganic substances such as magnetic powder and low molecular weight organic substances such as fatty acids are added to the binder.
Depending on the type and amount of additives, there is a problem in that the mechanical properties of the binder itself may not be exhibited when it is produced as a medium.

Means for solving the problem In order to solve this problem, the magnetic recording medium of the present invention has the following features:
A magnetic recording medium comprising, on a support, a magnetic layer in which metal magnetic powder mainly composed of metal or alloy ferromagnetic powder is dispersed in a binder, wherein the magnetic layer including the support and the magnetic layer is subjected to vibration. The ratio of the imaginary part and the real part of the Young's modulus (so-called tan δ) in viscoelasticity measurement at 200112 or less has a minimum value of 0.03 or less.

Function The present invention is based on the study of the relationship between not only the composition of the magnetic layer but also the characteristics of the medium in its finished state and running properties.
By improving the viscoelastic properties of the medium itself and reducing viscoelastic losses due to contact with posts, cylinders, heads, etc. during running on the deck, stable running properties can be obtained.

In other words, -δ is the ratio of the viscosity term to the elastic term, and a small value indicates a lack of stickiness. In the case of magnetic recording media, many parts, such as the support and the magnetic layer, are made of polymeric substances, and their mechanical properties generally change depending on temperature. In this case, when the temperature becomes high or low, this -δ saliva becomes larger and becomes sticky, resulting in poor runnability. Therefore, the temperature range in which the medium is used (dog breast 1
0°C to 75°C) to reduce stickiness.
In other words, it has been found that stable running can be obtained by reducing -δ. Furthermore, as a result of intensive studies, the present inventors found that in a magnetic recording medium where the minimum value of -δ is 0.03 or less within the temperature range of -10'C to 75°C, the practical running temperature range of the tape is It was found that there is no practical problem within the temperature range (-5°C to 40°C).

Example Examples of the present invention will be described below.

The viscoelasticity -δ in a magnetic recording medium is mainly determined by the properties and amount of the binder itself used in the magnetic layer. Here, media properties suitable for the configuration of the present invention were achieved by changing the properties of the binder, or by changing the amount of the low molecular weight compound added without changing the binder.

Example 1 After thoroughly kneading the composition shown in Table 1 and making it into a paint, the thickness was 10.
It was applied to a thickness of 3 μm on polyethylene terephthalate (μm) and cured sufficiently to produce a metal tape of 8ff1m. The polyurethane resin used at this time had a glass transition temperature Tg of 70°Cl2O°C1-20°C.
Samples A and B, respectively.

It was set as C. One of these three samples was 75° from 10'C.
-δ at frequency 110F in temperature range up to C
Table 2 shows the minimum values of and the results of deck running tests in environments with temperatures of 15°C, 25°C, and 40°C and a relative humidity of 60 degrees, respectively. From Table 1, it can be seen that tape squeal and jitter occur at high temperatures when -δ exceeds 0.03.

Table 1 (blank below) Example 2 Using the polyurethane used in Samplem in Example 1, the amount of myristic acid as a lubricant was changed to 3 parts, 4 parts, and 5 parts.
sample D.

I made E and F. Table 3 shows the number of measurements for each type: 11
The minimum value of tan δ in olZ ranging from -10°C to 75°C and the results of environmental tests are listed. As can be seen from this, even with the same binder, the characteristics as a medium change depending on the amount of additive, and when using C, the characteristics as a medium change.
Carefully figure out what δ will be, and set it to 0. The composition must be such that S is Oo3 or less.

(The following is a blank space) In the above examples of coagulation, a metal magnetic powder coating is applied onto a support, but the present invention further includes forming a back coat layer on the back surface of the support, and/or coating a metal magnetic powder coating on the support. The same applies to the case where an anchor layer is first formed on the anchor layer and a magnetic layer is formed thereon. In this regard, the structure of the magnetic layer and back coat layer will be studied.

Note that the value of -δ above was measured using a normal bipron (vibrating sample magnetometer), and the value of -δ naturally changes depending on the measurement frequency, but in this invention, the normal frequency of the bipron is used. The value of -δ was regulated under the condition of 200Hz or less.

Effects of the Invention As described above, according to the present invention, the running properties of the metal tape are improved over a wide temperature range.

Claims (3)

[Claims] (1) A magnetic recording medium in which a magnetic layer in which metal magnetic powder mainly composed of metal or alloy ferromagnetic powder is dispersed in a binder is provided on a support, which includes the support and the magnetic layer. In the viscoelasticity measurement at a frequency of 200 Hz or less, the ratio of the imaginary part and the real part of Young's modulus (so-called tan δ) is 0.03.
A magnetic recording medium characterized by having the following minimum value. (2) A back coat layer is provided on the back surface of the support, and in a state including the support, magnetic layer, and back coat layer, tan δ has a minimum value of 0.03 or less in viscoelasticity measurement at a frequency of 200 Hz or less. The first claim characterized in that
Magnetic recording medium described in Section 1. (3) Form the magnetic layer on the anchor layer on the support, and confirm that tan δ has a minimum value of 0.03 or less in viscoelasticity measurement at a frequency of 200 Hz or less when the magnetic layer is formed on the support. A magnetic recording medium according to claim 1 or 2 characterized by: