JPS5829126A - 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 a terminal of oligoester consisting of phthalic acid and alkylene glycol by esterification, and magnetic powder, is formed on a substrate and hardened by irradiation to produce a magnetic layer. The perferred 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, and excellent magnetic properties and surface smoothness of the magnetic layer. It's about doing.

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 oligomers such as urethane acrylate oligomers are mixed and dispersed with magnetic powder and other necessary components to prepare magnetic paint, and after coating this magnetic paint on a substrate, radiation A method has been proposed in which a magnetic layer is formed by irradiating the oligomer with radiation and polymerizing the oligomer, but although this method improves the pollution problem, it is still insufficient in improving the dispersibility and filling properties of the magnetic powder. However, fully satisfactory results have not yet been obtained.

The inventors conducted various studies in view of the current situation, and found that the general formula (%) (%) (in the formula, 8 is a hydrocarbon group, and X is 100 or sag
e or -PO(OH)-0-PO.

Y is a hydrocarbon group or →0-ILt)t, and B1 is an alkyl group. ), a magnetic paint containing a titanium coupling agent shown in the formula, an oligomer consisting of phthalic acid and alkylene glycol with acrylic acid or methacrylic acid ester bonded to the terminal end, and magnetic powder, and then irradiated with radiation. However, if the above oligomer is polymerized and cured to form a magnetic layer, there will be no pollution problems, and the dispersibility and filling properties of the magnetic powder will be sufficiently improved, and the magnetic properties and surface smoothness of the magnetic layer will be further improved. I discovered this and came up with this invention.

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 both sides of the powder particle surface, 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 of the substance via oxygen. Therefore, when this kind of coupling agent is contained in the magnetic layer, it will firmly adhere to the surface of the magnetic powder particles, forming a film and sufficiently improving the dispersibility of the magnetic powder. The titanium coupling agent has a particularly excellent effect of lowering the viscosity of the magnetic coating material, so that the filling properties of the magnetic powder are sufficiently improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. Specific examples of such titanium coupling agents include PlenAct TTS, BlenAct 98, and BlenAct 888 manufactured by Kenritzhi Petrochemical Co., Ltd., which are represented by the following structural formulas.

BlenAct T'I'8 (isopropyl triisostearoyl titanate) BlenAct 9S (isopropyl tridecylbenzenesulfonyl titanate) BlenAct 88S [isopropyl tris (dioctyl pyrophosphate) titanate] These titanium coupling agents Either dissolve it in a solvent and add the solution obtained by this dissolution when preparing magnetic paint, or immerse the magnetic powder in this solution to pre-treat the surface of the magnetic powder, and use this magnetic powder. Contained in magnetic paint by methods such as preparing magnetic paint,
used. The amount to be used is 0.0% based on the magnetic powder in the magnetic layer.
If it is less than 1% by weight, the desired effect cannot be obtained, and 10'M
If it exceeds Jii%, there is a risk of bleed-out, so it is preferably within the range of 0.1 to 10% by weight.
It is more preferable to use it within the range of 0.5 to 5% by weight.

In addition, the oligomer used in this invention, which has acrylic acid or methacrylic acid ester bonded to the end of the oligoester consisting of phthalic acid and alkylene glycol, has the general formula % formula % (0((!H,) -000-1R , is a hydrocarbon group, and n is an integer of 1 to 20.) with a molecular weight of 500 to 20,000.
are preferably used. This type of oligoester acrylate' and oligoester methacrylate has a low viscosity and has good filling properties for magnetic powder, and when used in combination with the titanium coupling agent mentioned above, the viscosity becomes even lower and the filling property for magnetic powder is sufficiently improved. Also, when it is applied to a substrate together with magnetic powder and the titanium coupling agent and then irradiated with radiation, the double bond at the end or both ends opens and polymerizes or crosslinks, giving the magnetic powder excellent filling properties. At the same time, a suitably polymerized and hardened magnetic layer is formed, and the magnetic properties and surface smoothness of the magnetic layer are further improved, and the wear resistance is also improved. The amount used is preferably within the range of 20 to 60% by weight based on the total amount of magnetic powder. If it is too small, the desired effect cannot be obtained, and if it is too large, the content of magnetic powder will be too low. Good electromagnetic conversion characteristics cannot be obtained.

The radiation used to polymerize and crosslink the oligomers mentioned above is preferably beta rays such as electron beams, and gamma rays such as ultraviolet rays or X-rays. Sensitizers are used simultaneously to make the effect more efficient. It is preferable to irradiate such radiation using radiation with an accelerating voltage of 150 to 750 KV so that the absorbed dose is 8 to 15 Mr&11. If the absorbed dose is too small, the crosslinking of the oligomers will be insufficient and the desired result will not be achieved. I can't get the desired effect.

Examples of the magnetic powder used in this invention include 1-F
egO@ powder, Fe@04 powder, CO containing r Fe1
In addition to on powder, CO-containing 4iiFe@04 powder, and 0r02 powder, various conventionally known magnetic powders such as Fe powder, Co powder, and metal powder such as Fe-N1Hj powder are widely included. When a film layer is formed and used, the effect of using the 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, Magnetic powder and a titanium coupling agent or magnetic powder whose surface has been treated with a titanium coupling agent are dispersed and mixed in this melt wave in the same manner as described above to prepare a magnetic paint, and this is applied onto a substrate such as a polyester film. This is done by preheating to remove the organic solvent contained in the magnetic paint and then irradiating it with radiation to polymerize and harden it.

In this case, when an organic solvent is used, the viscosity of the magnetic paint becomes 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-hebutane 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 These low boiling point solvents can be easily removed by preheating after coating the paint, making it easy to recover the solvent.

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

Next, embodiments of the invention will be described.

Example 1 Using an oligoester acrylic oligomer represented by the structural formula, CO-containing 1-FegO1 magnetic powder 60 parts by weight Oligoester acrylic oligomer 40
#Isobrobyl tridecylbenzenesulcanyl titanate) ethyl alcohol/methyl ethyl ketone 25
A magnetic paint was prepared by mixing and dispersing a composition consisting of a mixed solvent (mixing ratio 1/1) in a ball mill for 72 hours, and this magnetic paint was coated on a 15μ thick polyester base film to a coating thickness of 4μ. I applied it to make it look like this. Next, after preheating at 90°C for 1 minute to remove the ethyl alcohol/methyl ethyl ketone mixed solvent, the resin was cured by irradiation with an electron beam at a dose of 7 Mracl using Nissin High Voltage EPS-750, and then calendered. After that, it was cut to a specified width to make magnetic tape.

Example 2 In the composition of the magnetic paint in Example 1, the ethyl alcohol/methyl ethyl ketone mixed solvent was omitted, and the amount of oligoester acrylic oligomer used was changed from 40M parts to 4 parts.
A magnetic tape was produced in the same manner as in Example 1 except that the amount was changed to 5 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 Preact 9S was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 The composition of the magnetic paint in Example 1 was changed to tetrastearyl titanate (Ti) instead of Blenact 9S.
A magnetic tape was prepared in the same manner as in Example 1 except that the same amount of (001sHs 4) was used.

The video S/N ratio and color 8N ratio were measured for the magnetic tapes obtained in each Example and each Comparative Example. The video 8N ratio and the color 8N ratio were measured by loading the obtained magnetic tape into a video deck (V'I'-5000 manufactured by Hitachi, Ltd.) and performing recording and playback, and using a color video noise meter 9260 manufactured by Sibaku Corporation. The video 8N ratio and color SN ratio of the magnetic tape obtained in Comparative Example 1 were assumed to be 0, and the difference therebetween was expressed.

As is clear from the above table, the magnetic tapes obtained by this invention (Examples 1 and 2) are different from conventional magnetic tapes.

Compared to the tape (Comparative Examples 1 and 2), both the video 8N ratio and the color 8N ratio are higher, which indicates that the magnetic recording medium obtained by the present invention has excellent dispersibility and filling properties of the magnetic powder, and has excellent magnetic properties. It can be seen that the surface smoothness of the magnetic layer is further improved.

Claims (1)

[Claims] 1. On the substrate, the general formula %) (However, in the formula, 凰 is a hydrocarbon group, and X is -co or 1t-8
0, a) or 1i-PO(OR)-0-PO,. Y is a hydrocarbon group or →0-Rl), and R1 is an alkyl group. ), a coating film containing a titanium coupling agent shown by the formula, an oligomer made of an oligoester consisting of phthalic acid and alkylene glycol with acrylic acid or methacrylic acid ester bonded to the end, and magnetic powder is formed, and this is exposed to radiation. A magnetic recording medium characterized by having a magnetic layer hardened by irradiation.