JPS5829130A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having superior magnetic characteristics and superior surface smoothness of the magnetic layer and contg. magnetic powder with high dispersibility and fillability by hardening a coated film contg. a specified coupling agent, a specified oligomer and magnetic powder under radiation so as to produce the magnetic layer. CONSTITUTION:A coated film contg. a titanium coupling agent represented by the general formula, an oligomer obtd. by bonding acrylic acid or methacrylic acid to both the terminals of the condensation product of bisphenol-A with an alkylene glycol polymer by esterification, and magnetic powder, is formed on a substrate and hardened by irradiation to produce a magnetic layer. The preferred amount of the coupling agent to be used is 0.1-10wt% of the amount of the magnetic powder in the magnetic layer, and that of the oligomer to be used is 20-60wt% of the total amount of the powder and the coupling agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and its purpose is to provide a magnetic recording medium with good dispersibility and filling properties of magnetic powder, excellent magnetic properties and surface smoothness of the magnetic layer. It is about providing.

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 Attempts have been made to improve the surface smoothness and abrasion resistance of the magnetic layer, but they are still not fully satisfactory, and furthermore, this method involves the harmful effects of dissolving binder components during the preparation of magnetic coatings. There are pollution problems because large amounts of organic solvents are used.

Therefore, as a method to improve this, in recent years, various oligo i- such as urethane acrylate oligomers are mixed and dispersed with magnetic powder and other necessary components to prepare a magnetic paint, and after coating this magnetic paint on a substrate, A method has been proposed in which a magnetic layer is formed by radiation polymerization of oligomers by irradiation with radiation, but although this method improves the pollution problem, the dispersibility and filling properties of the magnetic powder are still not sufficiently improved. Unfortunately, we have not been able to obtain fully satisfactory results.

The inventors conducted various studies in view of the current situation, and found that the general formula % (%) (in the formula, R is a hydrocarbon group, and X is -CO or -5O
-() or -PO(OI'l) -〇-PO%Y
is a hydrocarbon group or 10-R,)2, and R1 is an alkyl group. ) and bisphenol A.
A magnetic paint containing magnetic powder and an oligomer in which acrylic acid or methacrylic acid is ester-bonded to both ends of a condensate of a condensate and an alkylene glycol polymer is applied, and then radiation is irradiated to polymerize and harden the oligomer to make it magnetic. The present inventors have discovered that by forming a layer, the magnetism is sufficiently improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved, and the present invention has been completed.

When the titanium coupling agent of the general formula used in this invention comes into contact with magnetic powder, it reacts strongly with the hydroxyl groups on the surface of the powder particles, and the bond between the titanium atom and -OR is broken, and the titanium atom is transferred to the magnetic powder. It is strongly bonded to the surface via oxygen. Therefore, when this type of titanium coupling agent is contained in the magnetic layer, it strongly adheres to the particle surface of the magnetic powder, forming a film and sufficiently improving the dispersibility of the magnetic powder. The titanium coupling agent is particularly effective in reducing the viscosity of the magnetic paint, so it sufficiently improves the filling properties of the magnetic powder and further improves the magnetic properties and surface smoothness of the magnetic layer. Specific examples of the ring agent include, for example, PreneAct (TTS), GlenAct 9S, GlenAct 885, manufactured by Kenrich Betro Chemical Co., Ltd., which are represented by the following structural formulas.

These titanium coupling agents are is dissolved in a suitable solvent, and the solution obtained by this dissolution is added when preparing a magnetic paint, or the magnetic powder is immersed in this solution to perform surface topography of the magnetic powder in advance. Contained in magnetic paint by methods such as preparing magnetic paint using
used. The amount used is O, based on the magnetic powder in the magnetic layer.
If the amount is less than 1% by weight, the desired effect can be obtained, but if it exceeds 10% by weight, there is a risk of bleed-out, so 0.
It is preferably within the range of 1 to 10 weight, and 0.5
It is more preferable to use it within the range of -5 weight.

First, the oligomer used in this invention, in which acrylic acid or methacrylic acid is ester-bonded at both ends of the condensate of bisphenol A and alkylene glycol polymer, has the general formula (where RFiH or CH, R2 is a hydrocarbon base, n
teeth! ~20 integer. ) with a molecular weight of 400 N10,000
are preferably used. This type of oligomer, which is a condensate of bisphenol A and an alkylene glycol polymer, has ester bonds with acrylic acid or methacrylic acid at both ends, and has relatively good filling properties for magnetic powder.
When used in combination with the titanium coupling agent described above, the viscosity is lowered by this titanium coupling agent, so that the filling properties of the magnetic powder are sufficiently improved. When exposed to radiation, the double bonds at both ends are opened and cross-linked, forming a magnetic layer that has excellent filling properties for magnetic powder and is moderately polymerized and hardened, improving magnetic properties and smoothing the surface of the magnetic layer. The properties are further improved, and the wear resistance is also improved.

The amount used is 20 to 60% by weight based on the total amount including magnetic powder.
If it is too small, the desired effect cannot be obtained, and if it is too large, the content of magnetic powder is too low and good electromagnetic conversion characteristics cannot be obtained.

As the radiation used to polymerize and crosslink the oligomers, β-rays such as electron beams, and gamma-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 the process more efficient. It is preferable for such radiation irradiation to use radiation with an accelerating voltage of 150 to 750 KV so that the absorbed dose is 8 to 15 Mrad; if the absorbed dose is too small, the crosslinking of the oligomers will be insufficient and problems will occur. The effect of the period cannot be obtained.

Examples of the magnetic powder used in this invention include 1-F
eO powder, Fe3O4 powder, Co-containing -3 Fe20g powder, Co-containing Fe s Oa powder, Cr
In addition to O2 powder, various conventionally known magnetic powders such as metal powders such as Fe powder, Co powder, and Fe-Ni powder are widely included.In particular, metal powders, when used with a thin oxide film layer formed on their surfaces, have the above-mentioned properties. The effect of using a titanium coupling agent in combination becomes greater.

To form the magnetic layer of the present invention on a substrate, magnetic powder and the titanium coupling agent dissolved in a solvent are dispersed and mixed in the oligomer, or the titanium coupling agent is preliminarily mixed with the titanium coupling agent. A magnetic paint is prepared by dispersing and mixing the surface-treated magnetic powder, and after coating this on a substrate such as a polyester film, it is polymerized and cured by irradiation with radiation, or the oligomer is dissolved in an organic solvent, In this solution, magnetic powder and titanium coupling agent or magnetic powder surface-treated with titanium coupling agent are dispersed and mixed in the same manner as described above to prepare a magnetic paint, and this is coated on a substrate such as a polyester film, and the preliminary This is done by heating to remove the organic solvent contained in the magnetic paint and then irradiating it with radiation to polymerize and harden it.

When an organic solvent is used in this case, the viscosity of the magnetic paint appears lower, so that the filling properties of the magnetic powder are further improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. As such an organic solvent, any of the solvents conventionally used in preparing magnetic paints, such as methyl isobutyl ketone, cyclohexanone, toluene, and dimethylformamide, can be suitably used. Because ethanol is good,
Solvents with low boiling points and low toxicity such as n-heptane and n-hexane can also be suitably used. Therefore, if these low boiling point and low toxicity solvents are used, pollution problems will be solved, and magnetic paints. These low boiling point solvents can be easily removed by preheating after coating, making it easy to recover the solvents.

Additionally, various commonly used additives, such as dispersants, abrasives, antistatic agents, etc., may be added to the magnetic coating material as necessary.

Next, embodiments of the invention will be described.

Example 1 Using 2, bis(diphenyl in 4-methacryloxyshed) propane represented by the structural formula, Co containing r-Fe20. Magnetic powder 60 parts by weight 2.2 bis(4-methacrylic acid) 40#
xyphenyl) Propane Prene Act 9S (Kenritzhi Betrochem, 2 parts by weight, manufactured by Cal Co., Ltd., Inpro Piltridecylbenzenesulfonyl titanate) Ether alcohol/methyl ethyl ketone mixed solvent 254 (mixing ratio 1/1). A magnetic paint was prepared by mixing and dispersing in a ball mill for 72 hours, and this magnetic paint was applied onto a polyester base film with a thickness of 15 to a coating thickness of 411 mm. Next, after preheating at 90°C for 1 minute to remove the ethyl alcohol/methyl ether ketone mixed solvent, ? It is cured by irradiating it with an electron beam at an irradiation dose of Mrad,
After calendering, it was placed in a predetermined width to make a magnetic tape.

Example 2'' In the composition of the magnetic paint in Example!, the ethyl alcohol/methyl ethyl ketone mixed solvent was omitted*, and the amount of i-bis(4-methacryloxyjetoxyphenyl) 4-pane was increased from 40 parts by weight to 45 parts by weight. A magnetic tape was produced in the same manner as in Example 1, except that the temperature was changed to 1.5 mm and the preheating was omitted.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that Preneac) 9S was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 In the composition of the magnetic paint in Example 1, PreneAct 9S was replaced with Nato 2 Stearyl Titanium) [Ti
(OC1g H87): A magnetic tape was prepared in the same manner as in Example 1 except that the same amount of 1 was used.

The video S/N ratio and color S/N ratio were measured for the magnetic tapes obtained in each Example and each Comparative Example. The video SN ratio and color SN ratio were measured by loading the obtained magnetic tape into a video deck (VT-6000 manufactured by Hitachi, Ltd.) for recording and playback, and using a color video noise meter 9250 manufactured by Shibaku Corporation. The video SN ratio and color SN ratio of the obtained magnetic tape were set to 0, and the difference therebetween was expressed.

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained by the present invention (Examples 1 and 2) have a higher video SN ratio and color SN ratio than conventional magnetic tapes (Comparative Examples 1 and 2). are both high, which indicates that the magnetic recording medium obtained by Karamu's invention has excellent dispersibility and filling properties of the magnetic powder, and further improved magnetic properties and surface smoothness of the magnetic layer.

Claims (1)

[Claims] L on the substrate, general formula % formula %) (wherein R is a hydrocarbon group, and X is 10O1 or 18O
Heart or -PO(OH)-0-PO1! Y is a hydrocarbon group (+0-R, )2, and R1 is an alkyl group. ) and bisphenol A.
A coating film is formed containing an oligomer in which acrylic acid or methacrylic acid is ester-bonded to both ends of a condensate of a condensate with an alkylene glycol polymer, and magnetic powder, and this is cured by irradiation with radiation to form a good magnetic layer. A magnetic recording medium characterized by providing