JPS5829146A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a magnetic layer with superior wear resistance, magnetic characteristics and surface smoothness by applying 2 kinds of specified oligomers to a substrate together with magnetic powder and by binding and hardening them by irradiation. CONSTITUTION:An oligomer of epoxy acrylate or epoxy methacrylate obtd. by reacting a compound contg. >=2 epoxy groups with acrylic acid or methacrylic acid and an oligomer obtd. by bonding acrylic acid or methacrylic acid to a terminal of polyalkylene glycol or polyol by esterification are applied to a substrate together with magnetic powder. The oligomers are bonded by irradiation to form a binder for the magnetic powder. For example, epoxy acrylic oligomer represented by formulaIand nonaethylene glycol dimethacrylate represented by formula II are used as said oligomers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium and a manufacturing method thereof, and its object is to provide a magnetic recording medium having a magnetic layer having excellent wear resistance, purity, magnetic properties, and surface smoothness. Our goal is to provide the following.

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
It is required to have excellent magnetic properties and surface smoothness, as well as excellent durability.

Therefore, the magnetic properties and surface smoothness of the magnetic layer can be improved by selecting a binder component that has excellent dispersibility for magnetic powder and excellent wear resistance, such as a vinyl chloride-vinyl acetate copolymer. Attempts have been made to improve durability, but this is not yet fully satisfactory.Furthermore, this method involves the use of large amounts of harmful organic solvents that dissolve binder components during the preparation of magnetic paints, resulting in pollution problems. There is.

Therefore, as a method to improve this, in recent years, a magnetic paint has been prepared by mixing and dispersing oligomers such as siatarylate or epoxy methacrylate together with magnetic powder and an organic solvent, and after coating this magnetic paint on a substrate, radiation In contrast, the oligomer was radiation-polymerized to form a magnetic layer of Y.
! - However, since the viscosity of the oligomer such as epoxy acrylic resin used in this method is relatively high, the dispersibility and filling properties of the magnetic powder are still insufficient (and the improvement of wear resistance is not sufficient). is still not fully satisfactory.

The inventors conducted various studies in view of the current situation, and found that an oligomer of niboxy acrylate (or epoxy methacrylate) obtained by reacting a compound containing two or more epoxy groups with acrylic acid or methacrylic acid, and a polyalkylene glycol. Or an oligo with acrylic acid or methacrylic acid attached to the end of a polyhydric alcohol! −
Use these oligos in conjunction with! A magnetic paint containing - and magnetic powder is applied onto the substrate, or a magnetic paint further containing a solvent is applied onto the substrate and preheated to remove the solvent contained in the magnetic paint. When the applied magnetic paint is irradiated with radiation to bond and harden the oligomers to form a magnetic layer, the dispersibility and filling properties of the magnetic powder are sufficiently improved without causing any pollution problems, and the magnetic properties and the magnetic layer are improved. It was discovered that surface smoothness is further improved, abrasion resistance is also improved, and durability is further improved, and this invention has been completed.

The oligomer of niboxy acrylate or epoxy methacrylate, which is obtained by reacting a compound containing two or more epoxy groups with acrylic acid or methacrylic acid, used in the present invention has, for example, the general formula (wherein R1 is H or CB, , a is an integer from 1 to 20,
m is an integer from 1 to 20. ) Both bisphenol type and novolac type compounds having a molecular weight of 500 to 2000G are preferably used. This type of epoxy acrylic resin or epoxy methacrylic oligomer has a relatively high viscosity, so the dispersibility and filling properties of the magnetic powder are not sufficient. When used together with an oligomer that has an acid bonded to an ester, this combined oligomer! Since the viscosity is adjusted and appropriately lowered by -1, the dispersibility and filling properties of the magnetic powder are sufficiently improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. In addition, when these oligomers used in combination were coated on a substrate together with magnetic powder, etc. and then irradiated with radiation, the double bonds at the ends of each oligomer were opened, and oligomers of the same or different types were crosslinked and moderately cured. The magnetic layer is formed, and the flexibility of the magnetic layer is improved by the oligomer used in combination, the viscosity of which can be adjusted appropriately, so that the abrasion resistance of the magnetic layer is further improved.

The oligomer in which acrylic acid or methacrylic acid is ester-bonded to the terminal of polyalkylene glycol used in this invention has the general formula % (where R1 is H or (, R3, R2 are hydrocarbon groups,
1 is an integer from 1 to 50. ) An oligomer with a molecular weight of 100 to 1500 is preferably used, and an oligomer in which acrylic acid or methacrylic acid is ester-bonded to the terminal of a polyhydric alpool has the general formula %, ROHl group, ROHl or R, OR, and at least one of them is necessarily R4OR, and Rg and UR,
is a hydrocarbon group, R1 is CH, -CH-C0-1 or C
H, -C(CH,)-CO-1p is an integer from 1 to 10 (F). ) Oligomers having a molecular weight of 100 to 2,000 are preferably used. In this type of oligomer, in which acrylic acid or methacrylic acid is attached to the terminal end of polyalkylene glycol, the hardness of the coating film after curing changes depending on the polymerization degree of the prealkylene glycol, and if the polymerization degree of the prealkylene glycol is 7 or more, It will become softer. Therefore, when an oligomer that provides such a relatively soft coating film is used in combination with the relatively hard epoxy acrylate or epoxy methacrylate oligomer, the viscosity is reduced and the dispersibility and filling properties of the magnetic powder are improved, resulting in improved magnetic properties. Furthermore, the surface smoothness of the magnetic layer is improved, the flexibility of the magnetic layer is also improved, and the wear resistance is further improved.

Oligo of the above-mentioned acrylic acrylate or methacrylate! The mixing ratio of the oligomer in which acrylic acid or methacrylic acid is ester-bonded to the end of polyalkylene glycol or polyhydric alcohol is preferably within the range of 1:3 to 3:1 by weight. Epo life cyacrylage is also an i-year-old! Boxymethacrylate oligo! If - is too small, the abrasion resistance of the coating film will be reduced, and if it is too large, the viscosity of the oligomer will be high and the dispersibility and filling properties of the magnetic powder will not be sufficient. Or an oligo that is a mixture of both! - The amount used is 20 to 6% of the total amount with magnetic powder.
It is preferable that the amount is within the range of 0 weight jl 1%; if it is too small, the desired effect cannot be obtained, and if it is too large, the content of magnetic powder decreases and good electromagnetic conversion characteristics cannot be obtained.

As the radiation used to polymerize and crosslink the oligomers, β-rays such as electron beams, T-rays such as ultraviolet rays and X-rays are preferably used. When ultraviolet rays are used, the effects of irradiation A sensitizer is used at the same time to make it more efficient. It is preferable to use radiation with an accelerating voltage of 150 to 750 KV for such radiation irradiation so that the absorbed dose is 3 to 15 Mrad. If the absorbed dose is too small, the crosslinking of the oligomers will be insufficient and the desired result will not be achieved. effect cannot be obtained.

As the magnetic powder used in this invention, for example, r-
Fe, O, powder, Fe, 04 powder, Co containing r -F
e 203 powder, Co-containing WFesoa powder, Cry
.

In addition to powder, F6 powder, Co powder 1. Various conventionally known magnetic powders such as metal powders such as Fe-Ni powders are widely included.

In order to form the magnetic layer of the present invention on a substrate, the above-mentioned epoxy acrylate or epoxy methacrylate oligomer is mixed with an oligomer of polyalkylene glycol or polyhydric alcohol with acrylic acid or methacrylic acid ester bonded to the terminal. A magnetic paint is prepared by dispersing and mixing magnetic powder in the mixed oligomer, and after coating this on a substrate such as a polyester film, the mixture is bonded and cured by irradiation with radiation, or the mixed oligomer is mixed with an organic solvent. Dissolve and mix the magnetic powder in this solution to make a magnetic paint. After applying this onto a substrate such as a polyester film, preheating is performed to remove the organic solvent contained in the magnetic koji material. After that, the bond is cured by irradiation with radiation. In this case, when an organic solvent is used, the viscosity of the magnetic paint becomes lower, so that the dispersibility and filling properties of the magnetic powder are further improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved.

When using an organic solvent, any of the solvents conventionally used in the preparation of A-based paints, such as methyl isobutyl ketone, cyclohexanone, toluene, and dimethylformamide, can be suitably used; Since all oligomers have good solubility in organic solvents, low-boiling point, weakly toxic solvents such as ethanol, n-hebutane, and n-hexane can also be suitably used. The use of weaker solvents also eliminates pollution problems and also facilitates solvent recovery since these low boiling point solvents are easily removed by preheating after application of the magnetic paint.

In addition, various commonly used additives such as dispersants, abrasives, antistatic agents, etc. may be appropriately added to the magnetic coating material as needed.

Next, embodiments of the invention will be described.

Example 1 Using an epoxy acrylic oligomer represented by the structural formula and nonaethylene glycol dimethacrylate represented by the structural formula, Co-containing r-FelO1 magnetic powder 60 parts by weight Epoxy acrylic oligomer 20 #Nonaethylene glycol dimethacrylate 20 l Tafrylate □ Ethyl A magnetic paint was prepared by mixing and dispersing a composition of alcohol/methyl ether 25 1 methyl ketone mixed solvent (mixing ratio 1/1) in a ball mill for 72 hours.
It was applied onto a #1 polyester base film to a coating thickness of 4 μm. Next, after preheating at 90°C for 1 minute to remove the ethyl alcohol/methyl ethyl ketone mixed solvent, EPS-7 manufactured by Nisshin Hebrtage Co., Ltd.
50, was cured by irradiation with radiation at an irradiation dose of 7 Mrmd, and after calendering was cut into a predetermined width to produce a magnetic tape.

Example 2 In the composition of the magnetic paint in Example 1, the ethyl alcohol/methyl ethyl ketone mixed solvent was omitted, the amount of epoxy acrylic oligomer used was changed from 20 parts by weight to 15 parts by weight, and the amount of nonaethylene glycol dimethacrylate was changed. A magnetic tape was produced in the same manner as in Example 1, except that the amount was changed from 20 parts by weight to 35 parts by weight, and the preheating was omitted.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that nonaethylene glycol dimethacrylate was omitted and the amount of epoxy acrylic oligomer was changed from 20 parts by weight to 40 parts by weight in the composition of the magnetic paint in Example 1. I made it.

Comparative Example 2 Co-containing r-Fe203 magnetic powder 78 double lid part VA
GH (U, C, (manufactured by Ni Co., Ltd., USA, 12 vinyl chloride-vinyl acetate-vinyl alcohol copolymer) Nistan 5702 (manufactured by Gutsutori 81, USA, urethane elaszimmer): yW Nate L (Japan's urethane 21 Co., Ltd., trifunctional low molecular weight isocyanate F compound) Schiff Seal xanone 90 #) Luene
90 N This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint. This magnetic paint was applied onto a polyester base film having a thickness of 15 tones so that the dry thickness would be 4 tones, dried, calendered, and then cut to a predetermined width to produce a magnetic tape.

For the magnetic tapes obtained in each example and each comparative example, the angle If (Br/Bm) was measured, and in order to further examine the durability, each magnetic tape was loaded into a tape recorder and run at approximately ＠eI11/sec. The output fluctuation was measured after running the vehicle 600 times at high speed.

The table below shows the results.

As is clear from the above table, the magnetic tapes obtained according to the present invention (Examples 1 and 2) have a larger square shape and smaller output fluctuations than the conventional magnetic tapes (Comparative Examples 1 and 2).
This indicates that the magnetic recording medium obtained by the present invention has good dispersibility and filling properties of the magnetic powder, further improved magnetic properties and surface smoothness of the magnetic layer, and improved durability. Recognize.

Claims (1)

[Scope of Claims] An oligomer of oxyatatylate or epoxymethacrylate obtained by adding acrylic acid-type metaxalic acid to a metal compound containing two or more L xI groups, and polyalkylene glycol or polyalkylene glycol. Atari at the end of the alcohol #
A magnetic recording medium characterized in that a binder for the magnetic powder is obtained by irradiating an oligomer with an ester bond with a magnetic powder and radially bonding the oligomer with the oligomer by irradiating with radiation on a substrate coated with a magnetic powder. 1. Oligomers of epoxy methacrylic acid or methacrylic acid encased in a compound containing 211 or more I-oxy groups on the 1-a body, and 1-polar alkylene derivatives. - For the polyol or polyhydric alcohol or acrylic acid type gate, a magnetic paint that absorbs an oligomer with ester bonded methacrylic acid and magnetic powder is applied, and then radiation is irradiated to form the oligomer! - A method for producing a magnetic recording medium, characterized in that a magnetic layer is formed by bonding and curing the EVO layer, which is formed by reacting acrylic acid or methacrylic acid with a compound containing two or more hydroxyl groups on a substrate. an oligomer of acrylate or epoxy methacrylate;
A magnetic paint containing an oligomer in which acrylic acid or methacrylic acid is ester-bonded to the end of polyalkylene glycol or polyhydric alcohol, magnetic powder, and a solvent is applied, and then preheating is performed before irradiation with radiation. A method for manufacturing a magnetic recording medium according to claim #12, in which a solvent contained in a magnetic paint is removed.