JPH0636262A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable the securing of compatibility in output characteristic between a thick medium and a thin medium on the same system and moreover, the expanding of a recording capacity with a less thickness of a magnetic recording medium. CONSTITUTION:In the vertical strength of a non-magnetic support, a breaking strength is 40-60Kg/mm<2>, a Young modulus 800-1,000Kg/mm<2> and a 5% elongation load 15-30Kg/mm<2> while the ratio between the vertical strength and the horizontal strength is 1.8 or more in the breaking strength. 1.8 or more in the Young modulus and 1.8 or more in the 5% elongation load. This enables the minimization output degrading attributed to a less thickness of a recording medium thereby improving contact condition between a magnetic head and the medium by the less thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape.

[0002]

2. Description of the Related Art For example, in a camera-integrated VTR represented by an 8 mm system and a VHS-C system, a small tape cassette is used in order to reduce the size and weight. Therefore, it is difficult to secure the recording time.
In the mm system, the maximum recording time is 2 hours, and in the VHS-C system, the recording time is 20 minutes in the standard mode.

Therefore, as a means for solving such a problem of the recording / reproducing time and increasing the recording capacity, by using a magnetic tape having a small thickness as a magnetic tape accommodated in the tape cassette, a tape cassette is used. The length of the tape wound in the winding area of
For example, the recording area may be expanded. At this time, there are two different types of media on the same system, that is, a medium before lengthening (thick material) and a medium after lengthening (thin material), but ideally, both have the same characteristics. Is desirable.

In reality, however, it is often reported that when the above-mentioned two types of media are used in the same system, the contact state between the magnetic head and the medium is different and the output characteristics of the two media are different. Has been done.

For example, the two media may have different thicknesses of PET.
It is assumed that a (polyethylene terephthalate) base film is used and the thickness of the base film is 10 to 12 μm for a thick material and 5 to 7 μm for a thin material. Physical properties of the base film at this time are as shown in Table 1 below.

[0006]

When the above-mentioned two types of PET base films were coated with a magnetic coating material and each produced medium was evaluated in the same system, the output of the thin medium was very unstable as compared with that of the thick medium. Was confirmed.
In FIG. 1, output waveforms obtained for various media are shown by an oscilloscope. The thick material corresponds to Comparative Example 1 and the thin material corresponds to Comparative Example 2.

From the results shown in FIG. 1, it is clear that the output becomes very unstable when a thin base film is used. This is because the contact state of the medium with the magnetic head is unstable. Seem.

However, the expansion of the storage capacity of the medium is
It will be indispensable in the future, and it is thought that the media will become thinner. In order to enable this, it is necessary to solve the problem of the difference in the output characteristics between the two types of media described above.

[0010]

The objects of the present invention are as follows.
It is to provide a magnetic recording medium capable of (1) to (4).

(1) It is possible to reduce characteristic deterioration due to thinning of the magnetic recording medium. (2) To improve the contact condition between the magnetic head and the medium due to the thinning of the magnetic recording medium. (3) It is possible to ensure compatibility of characteristics between thick media and thin media on the same system. (4) The recording capacity can be expanded by making the magnetic recording medium thinner.

[0012]

That is, according to the present invention, in a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support, the breaking strength as the longitudinal strength of the non-magnetic support is
40-60Kg / mm ² , Young's modulus 800-1000Kg / mm ² (especially
850 to 1000 kg / mm ² ), 5% elongation load is 15 to 30 kg / mm ² , and the ratio of the longitudinal strength of the non-magnetic support to its lateral strength (longitudinal strength / lateral strength) However, the breaking strength is 1.8 or more (especially 2.0 or more), the Young's modulus is 1.8 or more (especially 2.0 or more), and the 5% elongation load is 1.8 or more (especially 2.0 or more).
The above) relates to the magnetic recording medium.

In the present invention, the breaking elongation in the machine direction of the non-magnetic support is 20 to 40%, and the ratio of the breaking elongation in the machine direction to the breaking elongation in the cross direction of the non-magnetic support. It is desirable that (elongation at break in longitudinal direction / elongation at break in lateral direction) is 0.25 or less.

In the present invention, the thickness of the non-magnetic support is 5
This is effective for a magnetic recording medium that is as thin as -10 μm.

The present inventor recognizes that the difference in the output characteristics described above depends on the thickness of the non-magnetic support used for the medium, and obtains stable output even with a thin material. The present invention has reached the present invention by improving its mechanical strength and finding out that it should be set within a specific numerical range.

That is, the strength in the longitudinal direction (strength in the longitudinal direction) of the non-magnetic support is set to the above-mentioned specific range, and the ratio to the strength in the lateral direction (strength in the width direction) is also set to the above-specified range. Only after setting the desired effect can the desired effect be obtained.

As for the ratio of the strength in the longitudinal direction and the strength in the lateral direction, when the breaking strength, Young's modulus and 5% elongation load are below the lower limits mentioned above, the non-magnetic support is thin, and therefore the longitudinal direction. Becomes too small, resulting in poor contact with the magnetic head. On the other hand, if it exceeds the above-mentioned upper limit value, it is rather not practical.

In order to set the mechanical strength of the non-magnetic support within the above range, for example, after the non-magnetic support is molded, the stretching ratio at the time of stretching in the machine direction and the transverse direction may be controlled. .

As the non-magnetic support usable in the magnetic recording medium of the present invention, polyethylene terephthalate,
Examples thereof include polyesters such as polyethylene naphthalate, polyimide, polyamide imide, and polyaramid.

The magnetic layer provided on the non-magnetic support is preferably a magnetic coating film formed by applying a magnetic paint mainly containing magnetic powder and a binder to the surface of the non-magnetic support. .

When the magnetic layer is a magnetic coating film, magnetic powder,
Any conventionally known binder can be used as the binder, and the binder is not limited in any way.

As the magnetic powder, γ-Fe ₂ O ₃ , ferromagnetic iron oxide type particles such as γ-Fe ₂ O ₃ coated with cobalt, ferromagnetic chromium dioxide type particles, metals such as Fe, Co, Ni and the like are used. Examples thereof include ferromagnetic metal-based particles made of an alloy containing, hexagonal plate-shaped hexagonal ferrite fine particles, and the like.

As the binder, a polymer of vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylic acid ester, methacrylic acid ester, styrene, butadiene, acrylonitrile, or the like, or a copolymer of two or more kinds thereof is combined. , Polyurethane resin, polyester resin, epoxy resin and the like. A hydrophilic group such as a sulfonic acid group, a carboxyl group, or a phosphoric acid group may be introduced into these binders in order to improve the dispersibility of the magnetic powder.

In addition to the above magnetic powder and binder, a dispersant, an abrasive, an antistatic agent, a rust preventive, etc. may be added to the magnetic coating film.

In the magnetic recording medium of the present invention, a topcoat layer made of a rust preventive or a lubricant is provided on the magnetic layer, or the magnetic layer on the non-magnetic support is not formed. A back coat layer may be provided.

FIG. 5 shows a (VTR magnetic tape) as an example of the magnetic recording medium of the present invention. That is,
A magnetic layer 2 containing magnetic powder, a binder, etc. is provided on one surface of the non-magnetic support 1. Further, the other surface may have a back coat layer 3 mainly composed of a non-magnetic powder and a binder.

[0027]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to the following examples.

A magnetic paint having the following composition was prepared. Co deposited γ-Fe ₂ O ₃ 100 parts by weight N-3127 (polyurethane) 13 parts by weight (solid amount) VAGH (vinyl chloride copolymer) 9 parts by weight (solid amount) Al ₂ O ₃ 20 parts by weight carbon black 4 Parts by weight Butyl stearate 1 part by weight Myristic acid 1 part by weight Methyl ethyl ketone 110 parts by weight Sirochexanone 110 parts by weight

That is, the above materials were placed in a ball mill pot, mixed for about 48 hours, filtered and defoamed, added with 7 parts by weight of a polyisocyanate curing agent, stirred for about 30 minutes,
Magnetic paint was created. This was applied to a PET base film having the characteristics shown in Tables 2 and 3 below by a doctor blade method so that the coating thickness would be 1.5 μm, and dried at about 80 ° C. The sample tape was treated, cured in a constant temperature bath at 60 ° C. for about 20 hours, and slitted to a predetermined width to prepare a sample tape for study.

In each example, the mechanical properties of the base film used were controlled by controlling the stretching ratio during molding in the longitudinal or width direction. Also,
The Young's modulus was determined by a tensile test, and the 5% elongation load was determined by a known measurement method such as measuring the load when the film was stretched and stretched by 5%. The thickness of the base film was adjusted by its molding thickness.

[0031]

[0032]

[0033]

Samples were prepared as described above, and examinations were conducted on these samples. Comparative Example 1 is a conventional thick medium, and Comparative Examples 2 and 3 and Example 1 are thin mediums having a base film thickness of 5 to 7 μm (for example, 7 μm). Also,
In Comparative Examples 2 and 3 and Example 1, the longitudinal strength and the longitudinal / horizontal strength balance are arbitrarily changed, and how the output characteristics are changed due to the difference and how compared with the conventional thick medium. It was investigated. Comparative Examples 4 and 5 and Example 2 are media having a base film thickness of 7 to 9 μm (for example, 9 μm).

The output characteristics were evaluated from the output waveform as follows. Output waveform: Using a magnetic recording medium recording / reproducing device with a fixed head, recording / reproducing each sample tape,
The output waveform at that time was observed with an oscilloscope. Each output waveform is shown in FIGS. Output level: As shown in Fig. 1, the state where each sample is completely hit is 100%, and when the output drop due to a hit is X, this is relative to the reference. The percentage of output was calculated. The results are shown in FIGS. 3 and 4, respectively. Note that FIG.
The tendency shown in FIG. 4 is the same for other parameters.

From the results shown in FIGS. 1 and 3, the following is clear. (1) It can be seen that Comparative Example 1 is very stable. On the other hand, Comparative Examples 2 and 3 using a commonly used thin base film are more unstable than Comparative Example 1, because the change in the contact state between the head and the medium due to the difference in the thickness of the base film. It is due to.

(2) In comparison with this, Example 1 is Comparative Examples 2 and 3
It can be seen that a stable output waveform is obtained despite the same thickness as, and the output waveform is equivalent to that of the thick medium of Comparative Example 1. Differences between Comparative Examples 2 and 3 and Example 1 are:
It can be seen that the physical properties of the base film used in Example 1 are effective only in the physical properties of the base film.

(3) Further, Comparative Examples 2 and 3 and Example 1 are vertical /
The horizontal strength balance has the following relationship. On the other hand, the respective output waveforms are good as the output waveforms = good example 1> comparative example 3> comparative example 2 =
There is a bad relationship, and the weaker the longitudinal / lateral strength balance of elongation at break, and the stronger the other longitudinal / lateral strength balance, the better the output waveform.

(4) Further, it has been clarified that when the vertical / horizontal strength balance satisfies the following conditions for each parameter, the thin medium can obtain an output waveform equivalent to that of the thick medium.

Furthermore, from the results shown in FIGS. 2 and 4, the following is clear. (5) When the thickness of the base film is 9 μm, the output waveform is likely to be unstable because it is relatively thicker than the above, but it can be considerably improved by satisfying the conditions of the present invention as in the second embodiment. I understand.

(6) In Example 2, a more stable output waveform was obtained despite the same thickness as in Comparative Examples 4 and 5, and it can be seen that the physical properties of the base film used in Example 2 are effective. .

(7) In addition, Comparative Examples 4 and 5 and Example 2 are vertical /
The horizontal strength balance has the following relationship. On the other hand, the respective output waveforms are output waveforms ... Good = Example 2> Comparative Example 5> Comparative Example 4 =
There is a bad relationship, and the stronger the vertical / horizontal strength balance, the better the output waveform.

(8) Further, it was revealed that the output waveform of the thin medium is improved when the vertical / horizontal strength balance satisfies the following conditions for each parameter.

From the above, by applying the magnetic paint to the base film satisfying the conditions of the present invention, it is possible to reduce the output deterioration due to the thinning of the recording medium, and the contact state between the magnetic head and the medium due to the thinning. Can be improved. As a result, the compatibility of the output characteristics of the thick medium and the thin medium on the same system can be ensured, and the recording capacity can be expanded by making the magnetic recording medium thinner.

[0045]

As described above, the present invention has a breaking strength of 40 to 60 kg / mm ² , a Young's modulus of 800 to 1000 kg / mm ² , and a 5% elongation load of 15 to 15 as longitudinal strength of the non-magnetic support. 30 kg
/ Mm ² , and the ratio of the longitudinal strength of the non-magnetic support to its transverse strength (longitudinal strength / lateral strength) is 1.8 or more for breaking strength, 1.8 or more for Young's modulus and 5% elongation. Since the load is 1.8 or more, the output deterioration due to the thinning of the recording medium can be reduced, and the contact state between the magnetic head and the medium due to the thinning can be improved. This allows
The compatibility of the output characteristics of the thick medium and the thin medium on the same system can be ensured, and the recording capacity can be expanded by making the magnetic recording medium thinner.

[Brief description of drawings]

FIG. 1 is an output waveform diagram obtained for four types of samples.

FIG. 2 is an output waveform chart obtained for three other samples.

FIG. 3 is a graph showing changes in output level according to vertical / horizontal balance of base film strength for each sample of FIG.

FIG. 4 is a graph showing changes in output level according to vertical / horizontal balance of base film strength for each sample of FIG.

FIG. 5 is a schematic cross-sectional view showing one structural example of a magnetic recording medium to which the present invention is applied.

[Explanation of reference numerals] 1 ... Non-magnetic support 2 ... Magnetic layer 3 ... Back coat layer

Claims (3)

[Claims] 1. A magnetic recording medium having a magnetic layer formed on a non-magnetic support, wherein the breaking strength of the non-magnetic support is 40 to 60 kg / mm ² , and Young's modulus is 800 to 1000 kg. / Mm ² , 5% elongation load is 15 to 30 kg / mm ² , and the ratio of the longitudinal strength of the non-magnetic support to its lateral strength (longitudinal strength / lateral strength) is the breaking strength. Is 1.8 or higher, Young's modulus is 1.8 or higher, and 5% elongation load is 1.8 or higher. 2. The breaking elongation in the longitudinal direction of the non-magnetic support is 20 to.
40%, and the ratio of the breaking elongation in the longitudinal direction of the non-magnetic support to the breaking elongation thereof in the lateral direction (longitudinal breaking elongation / lateral breaking elongation) is 0.25 or less. The magnetic recording medium according to item 1. 3. The magnetic recording medium according to claim 1, wherein the non-magnetic support has a thickness of 5 to 10 μm.