JPS61115231A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a magnetic layer and the mechanical strength of a nonmagnetic support by forming the magnetic layer on the nonmagnetic support obtd. by biaxially stretching and cross-linking polyethylene terephthalate. CONSTITUTION:Polyethylene terephthalate contg. a compound sensitive to ionized radiation is biaxially stretched and cross-linked by irradiating ionized radiation to obtain a nonmagnetic support, and a magnetic layer is formed on the support. The compound sensitive to ionized radiation acts as a cross- linking agent in the polyethylene terephthalate resin, and the cross-linking action is accelerated by irradiating ionized radiation. The nonmagnetic support is made of a composition having a three-dimensional network structure, and when the support is used, a magnetic recording medium having superior mechanical strength even at high temp. is obtd. The compound sensitive to ionized radiation may be diallyl phthalate.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is applicable to magnetic tapes, flexible disks, etc. 2 A flash of light appears on the recording medium.

(Prior Art) Magnetic recording media that are commonly used generally have a nonmagnetic support made of polyester (especially polyethylene terephthalate) and a magnetic layer provided on one or both sides of the nonmagnetic support. The characteristics of a magnetic recording medium are not only dominated by the characteristics of the magnetic layer provided on the nonmagnetic support, but are also greatly influenced by the characteristics of the nonmagnetic support.

In the future, as the performance of magnetic recording media improves, for example, thinner non-magnetic supports will be required for long-term recording on magnetic tapes, and as recorders become more versatile, Magnetic recording media are required to withstand use under harsher conditions.

(Problems to be Solved by the Invention) Therefore, it is an object of the present invention to improve the mechanical strength, particularly the dimensional stability, of a magnetic rolling medium.

(Means for Solving the Problems) That is, the present invention involves stretching polyethylene terephthalate containing an ionizing radiation-functional compound and then subjecting it to irradiation with the ionizing radiation Q# gland to perform M correction treatment. It is characterized by providing a magnetic layer on a non-magnetic support.

(Function) The ionizing radiation-functional compound acts as a crosslinking agent within the polyethylene terephthalate resin, and the crosslinking action is promoted by irradiation with ionizing radiation. As a result, the non-magnetic support made of polyethylene/terephthalate resin becomes a composition having a three-dimensional network structure, and a magnetic recording medium having excellent mechanical properties and particularly excellent mechanical strength even at high temperatures can be obtained.

Ionizing radioactive compounds include compounds containing two or more allyl groups such as diallyl phthalate, triallyl in cyanurate, triallyl anurate, triallyl trimellilate, diallyl chlorendate, etc. Compounds containing two or more acryloyl groups such as acrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,3-butyne/glycol diacrylate, ethoxylated bisphenol A diacrylate, tris(acryloyloxyethyl) phosphate, or Polyethylene glycol dimecacrylate, polypropylene glycol dimethacrylate), 1,3-butylene glycol dimethacrylate, neobentyl glycol dimecacrylate, trimethylolpropa/trimethacrylate,
Examples include compounds containing two or more methacryloyl groups, such as tetramethylolmethanetetramethacrylate. The compounding amount of these compounds responsible for the ionizing radiation-functional unsaturated bonds is 1 to 1! per polyethylene terephthalate resin! 0 weight %, especially 2 to 7 weight % is preferred. If the skin does not contain IM amount%, ionizing radiation irradiation cannot be expected to have much effect. Moreover, if it is blended in an amount exceeding 10% by weight, the melt viscosity decreases and the Nepkky ratio becomes large, making it extremely difficult to form a film.

In addition, biaxial stretching is performed by biaxially stretching 1.5 to 45 times at a temperature above the glass transition point and below the melting point, 180
It is preferable to heat set at a temperature of ℃ to 240℃.

TL female radiation that can be used include α rays, β rays, γ rays, xI! , accelerated electron beams, and radiation obtained by reflection and scattering of these beams.

Examples of the ionizing radiation is a nuclear reactor, a radioisotope, an X* generator, an electron beam accelerator α, and the like.

The required dose varies depending on the size, thickness, shape, etc. of the non-magnetic support coated with the magnetic coating liquid, which is the irradiated object.
Usually 10-80 Mrad, preferably 20-50 Mrad
ad is appropriate. If this is done without a drop of 10 Mrλd, the dose is too small and the desired crosslinking effect cannot be expected.
Even if irradiation exceeds 0 Mrad, no further effect can be expected; on the contrary, it is necessary to increase the capacity of the ionizing radiation source and to lengthen the irradiation time, which is uneconomical.

The nonmagnetic support may be in any form such as a film, tape, sheet disk card, or drum. These nonmagnetic supports may have, for example, a backfoot on the back surface for the purpose of preventing static electricity, preventing transfer, preventing wow and fluff, and the like.

The magnetic layer provided on the non-magnetic support may be either a metal thin film or a cloth film. Examples of the magnetic layer made of the gold 81 thin film include the vacuum vaporization method, the sputtering/gluing method, the ion blating method, and the plating method. All of these conventionally known methods can be applied. Typical examples of metal thin films include evaporation thickness of Fav Co, Ni, etc., Ca-C2 evaporation marks, Co-Ni-P evaporation GG, reactive evaporation of iron oxide 0I12, C6-Cr-Rk spafted film,
C6-R%
There are Co-Ni-Mvs-P plating films, etc.

For the magnetic layer formed by a coating film, a magnetic paint in which magnetic powder is dispersed in 8 liquids along with appropriate additives is applied onto a support to form a magnetic layer, and the magnetic layer is subjected to magnetic field alignment treatment while the magnetic layer is still wet. The film is then subjected to VT heat drying or electron beam irradiation, and further calendered and cut as necessary.

In general, magnetic paints mainly consist of magnetic powder, binder, and coating solvent, and may also contain additives such as dispersants, lubricants, abrasives, antistatic agents, and rust preventive agents as necessary. good.

As the magnetic powder, y-Fez031F Tomoe 30 is also γ-
C
D-containing 7-F (Z 05, Co-containing 7-pazQ
3 and FtsO+, C6-coated iron oxide, C1Oz Crz05- (:1-O2, F
a4 Magnetic powder made of oxides such as N or magnetic powders such as nitrides, metals such as Fas Cox I'L, Ft-CO gold alloy, Fa-Ni alloy, Fa-Co-Ni alloy, Co-
N1-P alloy, Co-Ni-Fe, -13 alloy, Fa-
N+-Zr alloy, Ft-Me=-Z% alloy, Fa-Co
There are ferromagnetic fine powders of alloys such as -Ni-P alloys, barium ferrites, hexagonal ferrites such as S)O7 aluminum ferrites, and lead ferrites.

ii? As the binder, conventionally known thermosetting resins, thermosetting resins, reactive resins, electron beam curable resins, and mixtures thereof can be used.

In addition, as a solvent, acetate/, methyl ethyl keto/, methyl isobutyl ketone, ethyl acetate, butyl acetate,
Low-boiling solvents such as hexane, tolueno, xylene and hexamers containing electron beam functional groups can be used. Various kneading machines can be used to warm the magnetic serum. Examples include a ball mill, a drill mill attritor, a burr mill, a high-speed inopeller dispersion mill, a vibration mill, a kneader, a roll mill, a high-speed mixer, a homogenizer, an ultrasonic dispersion machine, and the like.

The method for applying the magnetic paint onto the non-magnetic support is as follows:
Dr. Brate Co. F1 air knife coat, reverse roll coat, gravure coat, first coat, spray coat, subino coat, etc. can be used, and other methods are also possible.

In addition, the Ta field orientation method is approximately 500 to 8
A magnetic field strength of about 000 Gauss can be used.

(Example) The present invention will be described below in more detail by examples and comparatively. In the following examples, "parts" refers to parts by weight.

“Example I” 5% by weight of ionizing radiation and triallyl cyanurate were added and mixed to polyethylene terephthalate resin, formed into a film by extrusion molding, and heated at a temperature above the glass transition point and below the melting point. After biaxial stretching (1.5 times), the film was heat-set at 210°C and was irradiated with an accelerated electron beam of 20 MriLd using a 750 kv electron beam accelerator. Next, while running this film, 3
Co, Ni (C
(N+: 25%) was added to 7N. The heat shrinkage rate of the produced first tape is 1.2% and 0.5% in the longitudinal direction and width direction, respectively, and there is little dropout (10 to 20 pieces/min - 40 μS/16 dB). showed that.

“Comparative Example ■” On the other hand, a vapor-deposited tape made by the same method as in Example I without adding triallyl cyanurate had a longitudinal heat shrinkage rate of 2.2%. The heat shrinkage rate in the width direction is large at 2-5%, and the dropout is noticeable (150-300 pieces/min - 40μs/16
dB).

“Example ■” 5% by weight of triallyl cyanurate with ionizable q1 gland functionality was added and mixed to polyethylene terephthalate resin, formed into a film by extrusion molding, and heated at a temperature above the glass transition point and below the melting point. After biaxial stretching (1.5 times), the film was heat-set at 210°C and irradiated with an accelerated electron beam of 20 Mrad using a 750 kv electron beam accelerator. Next, the composition shown in Table 1 was placed on this film in a ball mill, and after 48 hours of dispersion 6A kneading, the average pore size was 1 um.
A magnetic paint filtered through a filter was applied to a film thickness of 5 μm using a doctor blade, oriented in a 2000 Gauss DC magnetic field, and then dried at 100°C.
In Example 11-2, a magnetic tape was obtained by irradiating with an electron beam of 5 Mrad and then performing a curling process.

“Comparative Example ■” As a comparative example, the above (Example ■) was prepared using polyethylene terephthalate to which triallyl cyanurate was not added.
The temperature of the magnetic tape prepared by the same method as
) and 5% elongation load at 90°C (IEC Standard, Mechanical Properties of Tape 6013 (C,O,)44) are shown in Table 2.

Table 1 Example ■-1 Co-7-FezO 32 parts Carbon black 4 parts Alumina powder 2 parts Lecithin
2nd part stearin m
i-bu stearin! 1lln-butyl 1 part silico/oil 1g PVC acetate vinyl alcohol copolymer 20 parts MEK
150 parts Toluev 15C1 Example n-2 Hexagonal B&-ferrite 100 parts Alumina powder 2 parts Lecithin
2 parts stearic/acid
1 part stearic;/fin-butyl 1 part silico/oil 1 part urethane acrylate 20 parts N-vinyl biaride 7
Part 5 Trimethytol Iishikintori T Acrylate
5 part MEK

150 parts Toluene 150 parts Example ■-3 Fe meckle powder 100 parts Lecithin
Part 2 Milisti 7F11
1 part hexyl laurate
1 part silicone oil 1 part nitrocellulose 20 parts MEK
150 parts toluene
150 copies Table 2 F5 (hg) 20℃ 80℃ Example ■-12,6λ3 II-22,8Z3 ■-32,6Z3 Comparative example IF-I Z6 L, S[I-
22,61,8 ■ -32,61,6 (Effects of the invention) As detailed above, according to the present invention, it is possible to improve the wear resistance of the magnetic layer and the mechanical strength of the nonmagnetic support. .

Claims (2)

[Claims] (1) A magnetic layer is provided on a non-magnetic support made by biaxially stretching polyethylene terephthalate containing an ionizing radiation-functional compound and then crosslinking it by irradiating it with ionizing radiation. magnetic recording media. (2) The magnetic recording medium according to claim 1, wherein the magnetic layer is a metal thin film.