JPH03228215A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape having excellent heat resistance by providing a magnetic layer on a specified base film and specifying the total thickness. CONSTITUTION:Such a base film showing thermal shrinkage of <=0.4% in the longitudinal direction and <=0.3% in width direction when heated at 80 deg.C for 60 minutes is used. A magnetic layer is provided on this base film to obtain <=10 mum total thickness. As for the base film, a plastic film satisfying the requirements is used, for example, polyethyleneterephthalate film or polyethylenenaphthalate film. Thereby, thermal shrinkage of the base film is suppressed and heat resistance of the magnetic recording medium is improved, which effectively prevents omission in reproduction signals due to thermal deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a magnetic recording medium such as a magnetic tape having a total thickness of 10 μm or less and excellent heat resistance.

[Conventional technology]

In recent years, attempts have been made to make the thickness of magnetic tape as thin as possible in order to extend the recording and playback time as much as possible when it is incorporated into a cartridge case. This weakens the mechanical strength, causing poor contact with the magnetic head during recording and playback, which may impede electromagnetic conversion characteristics, or cause the edge of the magnetic tape to come into contact with the magnetic tape regulating flange of the guide member, etc. It may bend or break. It also tends to cause curls and wrinkles.

For this reason, when manufacturing plastic films such as polyethylene terephthalate film, reinforced plastic films that are strengthened by stretching them in the longitudinal and width directions under high heat are used as base films for magnetic tapes.
Efforts have been made to strengthen the mechanical strength of magnetic tapes with thinner combs.

[Problem to be solved by the invention]

However, magnetic tapes that use a polyethylene terephthalate film that has been stretched and strengthened in the longitudinal and width directions as a base film can be assembled into a cartridge case.
For example, if the magnetic tape is left on the dash board of a car heated by the midsummer sun, the playback signal will be lost.This loss of playback signal is especially noticeable near the core of the magnetic tape, and on the reel side where the magnetic tape is wound a lot. However, the thinner the magnetic tape, the worse it becomes.

[Means for Solving the Problems] In view of the current situation, the inventors conducted intensive research into the cause of reproduction signal loss and found that the conventional polyethylene terephthalate film, which is stretched and strengthened in the longitudinal and width directions, does not work well under high heat. Internal strain occurs during the stretching and strengthening process, and when a cartridge case incorporating a magnetic tape is exposed to high heat, the internal strain generated during the stretching and strengthening process is relaxed and the magnetic tape shrinks due to heat. It turns out that this is because the magnetic tape winding core becomes tightly wound, which in turn leads to playback signal loss.

This invention was made as a result of further studies based on this knowledge, and after heating at 80°C for 60 minutes, the heat shrinkage rate in the longitudinal direction is 0.4% or less, and the heat shrinkage rate in the width direction is 0.4% or less.
By using a base film of 3% or less and providing a magnetic layer on this base film to have a total thickness of 10 μm or less, thermal shrinkage of the base film is suppressed and the heat resistance of the magnetic recording medium is improved. This effectively prevents loss of reproduced signals due to deformation.

The base film used in this invention is 80°
It is preferable that the heat shrinkage rate in the longitudinal direction after heating at 80°C for 60 minutes is 0.4% or less, and the heat shrinkage rate in the width direction is 0.3% or less. If a magnetic layer is formed on a base film with a larger heat shrinkage rate in both the direction and the width direction, the base film will shrink when left at a relatively high temperature, and the heat resistance will not be improved. Thermal deformation occurs, resulting in loss of reproduced signals.

A preferable base film is a polyethylene terephthalate film or a polyethylene naphthalate film, which has a heat shrinkage rate of 0.63% or less in the longitudinal direction and 0.25% or less in the width direction after heating at 80°C for 60 minutes. Tinku film is used, and a specific example is Nippon Magfan Co., Ltd.; 5.5RWO3H1.
Examples include 6RWO3H1 polyethylene naphthalate film manufactured by Teijin.

Furthermore, it is preferable that the base film has a heat shrinkage rate of 0.4% or less in the longitudinal direction and 0.3% or less in the width direction after heating at 80°C for 60 minutes to have a thickness of 5 μm or more. ,
If the thickness of the base film is thinner than 5 μm, the heat resistance of the obtained magnetic recording medium will not be sufficiently improved, and thermal deformation will occur, resulting in loss of reproduced signals.

The magnetic layer formed on the base film is
Co, Ni, Fe, Co-Ni alloy, Co -Cr
Ferromagnetic materials commonly used in magnetic recording media, such as alloys, Co-Fe alloys, and co-Fe-Cr alloys, are vacuum-deposited,
The magnetic paint can be formed by applying it by means such as ion blasting, sputtering, plating, etc., or by mixing and dispersing magnetic powder, binder resin, organic solvent, etc. with other necessary components to prepare a magnetic paint. was formed by coating and drying on the base film, and the total thickness was 10um.
The following magnetic recording medium is formed.

Here, as the magnetic powder, 7-Fe2O, powder, Fe
, O, powder, CO-containing 1-Fe2O, powder, Co-containing F
A wide variety of conventionally known magnetic powders are included, such as e, O, powder, Fe powder, CO powder, and Fe-Ni powder. In addition, binder resins include vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, polyurethane resins,
Conventional binder resins such as cellulose resins and isocyanate compounds are widely used, and as organic solvents,
Organic solvents commonly used in magnetic recording media, such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dimethylformamide, and dioxane, are used alone or in a mixture of two or more.

As mentioned above, after heating at 80°C for 60 minutes, the heat shrinkage rate in the longitudinal direction is 0.4% or less and the heat shrinkage rate in the width direction is 0.3%.
A magnetic layer is formed on the following base film so that the total thickness is 1
When a magnetic recording medium such as a magnetic tape of 0 μm or less is manufactured, even if it is assembled into a cartridge case and left on a car dash board heated by the midsummer sun and exposed to high temperatures, the magnetic tape will undergo thermal deformation due to thermal contraction. The heat resistance is sufficiently improved, and reproduction signal loss is prevented.

〔Example] Next, embodiments of the invention will be described.

Example I Co-containing 7-Fe, 03 powder 80 parts by weight VAGH
(manufactured by U, C, C; vinyl chloride 10-vinyl acetate-vinyl alcohol copolymer) CRYSBO 7209 (manufactured by Dainippon Ink Chemical Co., Ltd.; urethane elastomer) Coronate Nippon Polyurethane 2. trifunctional low molecular weight isocyanate compound) n-butyl stearate 0.5 Carbon black 4 Cyclohexanone
50 l methyl ethyl ketone
50 This composition was mixed and dispersed in a ball mill for 70 hours to prepare a magnetic paint. Next, apply this magnetic paint to 80°
The longitudinal heat shrinkage rate after heating at C for 60 minutes is 0.14%.
Then, on a base film with a thickness of 6.3 μm made of polyethylene naphthalate with a heat shrinkage rate of 0.22% in the width direction, it was applied to a dry thickness of 1.7 μm, dried, and surface treated. Afterwards, it was cut to a specified width to create magnetic tape.

Example 2 In Example 1, the heat shrinkage rate in the longitudinal direction after heating in SO'C for 60 minutes was 0.14%, and the heat shrinkage rate in the width direction was 0.14%.
The thickness is 6. Made of 22% polyethylene naphthalate.
Instead of a 3 μm base film, a base of the same thickness made of polyethylene terephthalate with a heat shrinkage rate of 0.25% in the longitudinal direction and 0.05% in the width direction after heating at 80°C for 60 minutes. A magnetic tape was produced in the same manner as in Example 1 except that the film was used.

Comparative Example 1 In Example 1, the heat shrinkage rate in the longitudinal direction after heating at 80°C for 60 minutes was 0.14%, and the heat shrinkage rate in the width direction was 0.14%.
The thickness is 6. Made of 22% polyethylene naphthalate.
Instead of a 3 μm base film, the film was stretched in the longitudinal and width directions, and after heating at 80°C for 60 minutes, the heat shrinkage in the longitudinal direction was 0.34%, and the heat shrinkage in the width direction was 0.3.
A magnetic tape was made in the same manner as in Example 1, except that a base film of 5% polyethylene naphthalate of the same thickness was used.

Comparative Example 2 In Example 2, the heat shrinkage rate in the longitudinal direction after heating at 80°C for 60 minutes was 0.25%, and the heat shrinkage rate in the width direction was 0.25%.
05% polyethylene terephthalate with a thickness of 6
．． Instead of a 3 μm base film, the film was stretched and strengthened in the longitudinal direction and the width direction, and after heating at 80°C for 60 minutes, the heat shrinkage rate in the longitudinal direction was 0.51%, and the heat shrinkage rate in the width direction was 0.51%.
A magnetic tape was made as in Example 2, except that a base film of the same thickness consisting of 15% polyethylene terephthalate was used.

The magnetic tapes obtained in Example 2 and Comparative Example 2 were assembled into a cartridge case and left for 72 hours at 60°C and 180% RH. I checked the output waveform. FIG. 1 illustrates the output waveform of the magnetic tape obtained in Example 2, and output waveform 1 was normal.

Further, FIG. 2 illustrates the output waveform of the magnetic tape obtained in Comparative Example 2, and a signal dropout portion 3 was observed in the middle of the normal output waveform 2.

In addition, the magnetic tape obtained in each example and comparative example was assembled into a cartridge case at 60°C, 180% RH.
The magnetic tape was left for 72 hours under the following conditions, and the thermal deformation of the magnetic tape after being left was visually observed.
Those with slight thermal deformation were evaluated as (△), and those with irreproducible thermal deformation were evaluated as (x).

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from FIGS. 1 and 2, signal loss is observed in the magnetic tape obtained in Comparative Example 2, but in Example 2, signal loss is observed.
The magnetic tape obtained by
As is clear from Table 1 above, thermal deformation was observed in the magnetic tapes obtained in Comparative Examples 1 and 2, but no thermal deformation was observed in the magnetic tapes obtained in Examples 1 and 2. Therefore, the total thickness obtained by this invention is 10
It can be seen that magnetic recording media with a diameter of μm or less have excellent heat resistance.

[Brief explanation of drawings]

FIG. 1 is an output waveform diagram of the magnetic tape obtained in Example 2,
FIG. 2 is an output waveform diagram of the magnetic tape obtained in Comparative Example 2.

Claims (1)

[Claims] 1. Thermal shrinkage rate in the longitudinal direction after heating at 80℃ for 60 minutes is 0.
．． A magnetic recording medium with a total thickness of 10 μm or less, comprising a magnetic layer on a base film with a heat shrinkage rate of 4% or less and a widthwise heat shrinkage rate of 0.3% or less.