JPH0766545B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polymer molded product substrate which is a base of a longitudinal magnetic recording medium.

[Prior art]

As a magnetic recording medium using a polymer molded product substrate,
(Γ-Fe ₂ O ₃ .Co coating γ-Fe ₂ O ₃ , metal, CrO ₂ etc. are the mainstream coating methods, such as Floppy, audio tape, video tape, data file, document file, voice, It is used in various fields as a memory for image processing.In addition, for such wet coating, audio tapes, 8mm video tapes, etc. on which Co or Co-Ni is formed by dry vacuum deposition are commercially available. The technical trends that are common to both digital recording and analog recording as described above are being reduced in size or increased in capacity for computer files, and
For audio and video tapes, image quality or
The quality of voice is being improved. In other words, as a high S / N, it is expected that the coercive force of the medium will be increased and the thickness of the medium will be uniform, and that the density of the medium will be thinned as a magnetic recording medium in the future. .

On the other hand, as a substrate for such a magnetic recording medium, the cost is low. A polyethylene terephthalate (hereinafter abbreviated as PET) film is mainly used because of its mechanical strength. Recently, it has a good surface property. Polyamide-based (hereinafter referred to as aramid) films have begun to be considered because they have better mechanical properties than PET. In any case, such a polymer molded product substrate contains unreacted monomers (monomers) and polymers having a low degree of polymerization (hereinafter referred to as “oligomers”) in the composition, so that the glass transition temperature (eg, At temperatures above about 70 ° C in PET), oligomers precipitate on the surface of the substrate and the surface properties of the substrate deteriorate significantly. Specifically, the height of this oligomer is
Depending on the high and low pressure environment, temperature and holding time, the size can be from 0.2 to several microns.

As described above, when a polymer molded product substrate is used as the substrate of the magnetic recording medium, the temperature environment is equal to or higher than the glass transition during the magnetic film formation process (specifically, in wet coating, magnetic In hot-air drying after coating the body and dry vacuum deposition, heat radiation from the thin film forming source during deposition) and oligomers are deposited on the surface of the polymer molded product substrate. In the generation and vacuum deposition, the surface property of the substrate becomes the surface property after the thin film is formed as it is, so that the head touch between the medium and the head is deteriorated,
Recording / reproducing efficiency is reduced. Furthermore, the protrusions on the medium surface are
There is a problem in that the collision with the head causes scratches and film peeling, which deteriorates the durability of the medium and the head.

Conventionally, in order to eliminate surface protrusions due to oligomer precipitation after forming a film, the protrusions were scraped by lapping or buffing to improve smoothness, but not only the continuity of the film is impaired, but abrasion powder further It had the drawback of scratching the surface. Further, as described above, as the magnetic recording medium is made compact and the capacity is increased, the thickness of the medium is made thinner.
It's getting bigger.

〔Purpose〕

In view of the above points, the present invention eliminates oligomers contained in a polymer molded product substrate that is a base material of a magnetic recording medium before forming the magnetic recording medium, resulting in magnetic recording excellent in smoothness, electromagnetic conversion characteristics, and durability. The purpose is to produce a medium.

〔Overview〕

The present invention is a method for producing a longitudinal magnetic recording medium, which comprises a step of previously subjecting a magnetic recording medium substrate comprising a polymer molded article substrate to a heat treatment, wherein the step of subjecting the heat treatment to a glass transition temperature of the substrate or higher, An oligomer contained in the substrate, characterized in that the substrate is melted, or sublimated, or decomposed at a temperature not higher than the temperature, and the deposit deposited on the surface of the substrate in the step of performing the heat treatment is removed with an organic solvent. Can be removed, and an excellent magnetic recording medium can be manufactured.

〔Example〕

 The present invention will be described in detail with reference to the drawings.

Example 1 FIG. 1 shows oligomer deposition when PET was heat-treated and PET after oligomer removal treatment according to the present invention.
It is a cross section of the surface. Fig. 1 (a) shows the surface of a commercial PET, which has an average surface roughness of 0.005 μm and a maximum surface roughness of 0.06 μm.
It is a cross section of ET1. In addition to the polymer, PET1 contains 3 to 4% of a low molecular weight oligomer. Figure 1 (b) shows PE after heat treatment of PET1 at 180 ℃ for 2h.
A cross section of T2 and oligomer 3. Under the above heat treatment conditions, the size of the oligomer reaches an average height of 1 micron and width of 3 microns. Naturally, the height and width of the oligomer greatly change depending on the heat treatment temperature and treatment time below the PET melting point (about 220 ° C). FIG. 1 (c) is a sectional view of the PET4 surface portion after the oligomer treatment according to the present invention. As a method for removing the oligomer, there are washing with a solvent, specifically, acetone / trichlene, xylene, or the like, or passing through during vapor dissolution. Figure 1 (a) (b)
The reason why so-called PET is divided into 1,2,4 in (c) is because the content of oligomers in PET, which is a polymer, is different. FIG. 1 (d) shows an oligomer treated according to the present invention.
FIG. 3 is a cross-sectional view of the surface of PET5 after heat-treating PET4 at 150 ° C. for 2 hours, showing the effect of the present invention, showing that oligomers have stopped precipitating during heat treatment.

Example 2 PET is used as a substrate for the γ-Fe ₂ O ₃ coating medium,
It is called the so-called Flotpies disk. The structure of the conventional floppy disk is as shown in FIG. PET6
The γ-Fe ₂ O ₃ magnetic recording layer 8 is applied on top, and the steps of orientation, drying, and surface polishing are entered. Especially, since hot air drying is used for drying, the oligomer 7 is deposited on the PET 6 surface by the heat. is doing. After on PET9 second view (b) was subjected to oligomerization process according to the present invention, conventional coated gamma-Fe ₂ O ₃ magnetic recording layer 8, an alignment process, drying was carried out stroke of surface polishing Furotsupi It is a disk structure. According to the present invention, it can be seen that no oligomer is deposited on the PET surface. In the conventional floppy, the magnetic layer thickness is non-uniform due to oligomer deposition and causes media noise, and the S / N ratio is about 30 dB, whereas the floppy using the oligomer-treated PET of the present invention is used. Has an S / N ratio of 5 because the magnetic layer thickness is uniform.
It was over dB.

Example 3 Co-Ni was vapor-deposited on PET using a continuous winding vapor deposition apparatus. A so-called vapor deposition tape was produced. According to the conventional method, Co-Ni is vapor-deposited while the oligomer is deposited on the PET surface by the radiant heat from the vapor deposition source and scattered in a vacuum.
Naturally, the degree of vacuum during deposition deteriorates, and good quality Co-Ni is not formed. A cross-sectional view of the vapor deposition tape is shown in FIG. The feature of vacuum vapor deposition is that, unlike coating, a film is formed along the surface of the substrate. 10 is PET. 11 is a Co-Ni layer, and 12 is an oligomer. Next, PET treated with the present invention,
As shown in FIG. 3 (b), there is no oligomer. 13 is PET treated with oligomer, and 14 is Co-Ni. FIGS. 4 (a) and 4 (b) compare envelopes of the conventional vapor deposition tape and the vapor deposition tape of the present invention, respectively. The conventional vapor deposition tape has a small reproduction output, and a high frequency noise due to a head hit is generated due to the influence of the medium protrusion by the oligomer, whereas the vapor deposition tape according to the present invention has a large reproduction output and a small noise. Further, in terms of the durability of the medium, the effect of the present invention is great, and the conventional vapor deposition medium is apt to be scratched, and it is necessary to remove the protrusions by the oligomer by buffing or the like. The vapor deposition medium does not require a buffing process. It has effects such as high durability.

〔effect〕

As described above, the magnetic recording medium according to the present invention has various effects as compared with the conventional method. The effects are summarized below.

◎ Improvement of reproduction output ◎ Reduction of noise ◎ Improvement of envelope ◎ Reduction of medium defects ◎ Improvement of magnetic characteristics ◎ Improvement of durability Furthermore, when vacuum is used such as vapor deposition tape, PET is set in the vacuum chamber. Since the oligomer is treated before, the degree of vacuum is improved, and the time required to reach a predetermined vacuum layer is shortened, so that the cost can be reduced. It also has the effect of drastically reducing the contamination in the vacuum chamber.

In this example, PET was used as the polymer molded article substrate, but aramid. The present invention is also effective for engineering films such as polyether sulfone, vinyl chloride, polystyrene, polycarbonate, polypropylene, triacetate, polyether ether ketone, and polysulfone, and acrylic resins which are the bases of optical and magneto-optical recording media. In addition, although an example in which an organic solvent is used as an oligomer treatment method is given in this example, the oligomer may be placed in a vacuum chamber or replaced by a gas in a temperature range of the oligomer melting point temperature or higher and the polymer melting point or lower. There is also a method of removing only.

[Brief description of drawings]

1 (a) to 1 (d) are cross-sectional views of the surface of the polymer molded product substrate, and FIGS. 2 (a) and 2 (b) are cross-sectional views of the coating medium surface, and FIG.
FIGS. 4A and 4B are cross-sectional views of the surface of the vapor deposition tape, and FIGS. 4A and 4B are envelopes obtained by recording and reproducing the vapor deposition tape. 1: PET 2: PET heat-treated for 2 hours at 180 ° C 3: Oligomer 4: PET treated with oligomer 5: PET heat-treated for 2 hours at 150 ° C PET 6: PET 7: Oligomer 8: γ-Fe ₂ O ₃ magnetic recording layer 9: Treated with oligomer PET 10: PET 11: Co-Ni layer 12: Oligomer 13: Oligomer treated PET 14: Co-Ni layer

Front page continuation (72) Inventor Sadaichiro Mori 3-3-5 Yamato, Suwa City, Nagano Stock Company Suwa Seikosha Co., Ltd. (72) Inventor Eiji Shimura 3-3-5 Yamato, Suwa City, Nagano Prefecture Stock Company Suwa Seikosha (56) Reference JP-A-57-53829 (JP, A) JP-A-53-109605 (JP, A)

Claims (1)

[Claims] 1. A method for producing a longitudinal magnetic recording medium, comprising a step of previously subjecting a base body of a magnetic recording medium comprising a polymer molded product substrate to a heat treatment, wherein the step of subjecting the heat treatment to a glass transition temperature of the substrate or higher. In addition, the magnetic recording medium characterized in that the substrate is melted, or sublimated, or decomposed within a temperature range not higher than the temperature, and the precipitate deposited on the surface of the substrate in the step of performing the heat treatment is removed with an organic solvent. Manufacturing method.