JPS5829129A - 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 polyalkylene glycol or polyol 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 an object thereof is to provide a magnetic recording medium that has good dispersibility and filling properties of magnetic powder, and has excellent magnetic properties and surface smoothness of a 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, it is possible to improve the magnetic properties by improving the dispersibility of the magnetic powder by selecting a binder component with excellent dispersibility of the magnetic powder, or by treating the magnetic powder with a dispersant such as an alkyl titanate. magnetic layer t)
Attempts have been made to improve surface smoothness and abrasion resistance, but they are not yet fully satisfactory.Furthermore, this method requires the use of harmful organic solvents that dissolve binder components during the preparation of magnetic paints. There is a pollution problem because it is used in large quantities.

Therefore, as a method to improve this, in recent years, various oligomers T such as urethane acrylate oligomers are mixed and dispersed together with magnetic powder and other necessary components to prepare a 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 state of KfIi2.
As a result, the general formula % formula %) (However, in the formula, X is a hydrocarbon group, and X is -CO or -5o
, -(>ar) is -PO(OH)-〇-PO, Y is a hydrocarbon group or ÷〇-, R1)2, and R1 is an alkyl group. ) A magnetic paint containing a titanium coupling agent represented by the above formula, an oligomer in which acrylic acid or methacrylic acid is ester-bonded to the end of polyalkylene glycol or polyhydric alcohol, and magnetic powder is applied, and then radiation is applied to It has been discovered that when a magnetic layer is formed by polymerizing and curing oligomers, 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 without causing any pollution problems. , this invention was made.

When the titanium coupling agent having the above general formula used in the invention of 2008-2013 comes into contact with magnetic powder, it reacts strongly with the hydroxyl group on the surface of the powder particles, and the bond between the titanium atom and -OR is broken, and the titanium atom becomes a magnetic powder. It is strongly bonded to the surface of the substance via oxygen. Therefore, when this type of titanium coupling agent is contained in the magnetic layer, it adheres firmly to the particle surface of the magnetic powder, forming a film and sufficiently improving the dispersibility of the magnetic powder. Since the coupling agent is particularly effective in reducing the viscosity of the magnetic coating material, 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 PreneAct TTS, PreneAct 9S, and GlenAct 885 manufactured by Kenritzhi Petrochemical, which are represented by the following structural formulas.

These titanium coupling agents are Dissolved in a suitable 1atk solvent,
9S* obtained by dissolving 0111E and 9S* is added when preparing the magnetic paint, or the surface of the magnetic powder is treated in advance by immersing the magnetic powder in 0111E, and this magnetic powder is used to prepare a magnetic paint. How is it contained and used in magnetic paint? The desired effect can be obtained if the amount used is 0.1% less by weight than the magnetic powder in the magnetic layer.
If it exceeds 10% by weight, there is a risk of bleed-out.It is preferably within the range of 0.1-10% by weight, and more preferably within the range of 0.6-5% by weight.

In addition, the oligomer used in this invention, in which acrylic acid or methacrylic acid is ester-bonded to the terminal end of polyalkylene glycol, has the general formula CH, =C-C0+O-0-CH, or (however,
R1 is H and CHs, R is a hydrocarbon group, and n is 1 to
It is an integer of 50. ) An oligomer having a molecular weight of 100 to 160 G is preferably used as an oligomer, and an oligomer having an ester bond of acrylic acid or methacrylic acid at the end of a polyhydric alcohol has the general formula (however, M, , M,
, Ms, M4 is H, OH, alkyl group, R, OH'! The circle is R40R, and at least one of them must be R4.
OR, where R3 and R4 are hydrocarbon groups, and k is CH! =CH-Co-'t or CH! =C(CH,)-
CO-1l! is an integer from 1 to 10. ), those having a molecular weight of 600 to 2000 are preferably used. This type of oligomer, in which acrylic acid or methacrylic acid is ester-bonded to the end of polyalkylene glycol or polyhydric alcohol, has excellent filling properties for magnetic powder, and its viscosity decreases when used in combination with the titanium coupling agent mentioned above. The 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 the substrate is coated with magnetic powder and the titanium coupling agent mentioned above and then irradiated with radiation, the double bond at the terminal or both terminals opens and polymerizes or crosslinks, resulting in moderately polymerized and hardened magnetic properties. The formation of a layer also improves wear resistance. In particular, with this type of oligomer, the hardness of the film after curing can be varied by adjusting the degree of polymerization n of the polyalkylene glycol, so the viscosity of the oligomer can be lowered to further improve the filling properties of the magnetic powder. The abrasion resistance of the magnetic layer can be further improved by making the softness of the magnetic layer more appropriate.

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 will not be obtained, and if it is too large, the content of magnetic powder will be too low and good electromagnetic conversion characteristics will not be obtained.

The radiation used to polymerize and crosslink the oligomers mentioned above is preferably β-rays such as electron beams, and γ-rays such as ultraviolet rays or X@. When ultraviolet rays are used, the effects of irradiation To make it more efficient, the sensitizer is added at the same time! used. Such radiation irradiation uses radiation with an accelerating voltage of 150 to 760 KV,
It is preferable to irradiate so that the absorbed dose is 8 to 15 Mrad; if the absorbed dose is too small, the crosslinking of the oligomer will be insufficient and the desired effect will not be obtained.

Examples of the magnetic powder used in this invention include r
Fe2O, powder, FeB O4 powder, CO/containing T
-Fe, O, powder, Co-containing Fe3O4 powder, CrO2
In addition to powders, various conventionally known magnetic powders such as metal powders such as Fe powder, Co powder, and Fe-Ni powder are widely included, and when metal powders are used with a thin oxide film layer formed on the surface, the above-mentioned 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 whose surface has been treated with titanium coupling agent are dispersed and mixed in the same manner as described above to prepare a magnetic paint, and this is applied onto a substrate such as a polyester film. After preheating to remove the organic solvent contained in the magnetic paint,
Polymerization and curing by irradiation with radiation is carried out by K. 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 of their good solubility, low-boiling point, low-toxicity solvents such as ethanol, n-heptane, and n-hexane can also be suitably used. Therefore, using these low-boiling point, low-toxicity solvents will reduce pollution. This problem is solved, and since these low-boiling point solvents are easily removed by preheating after applying the magnetic paint, recovery of the solvents is also facilitated.

In addition, various additives commonly used in magnetic coating materials, such as dispersants, abrasives, antistatic agents, etc., may be appropriately added and used as required.

Next, examples of the present invention will be described. Example 1 Nonaethylene glycol dimethacrylate F represented by the structural formula
Co-containing 7-Fez (% magnetic powder 60 parts by weight nonaethylene glycol dimethacrylate 40 N
Prenact 9S (manufactured by Kenritzhi Betrochem 21℃ Lu Co., Ltd., isopropyltridecylbenzenesulfonyl titanate) A composition consisting of ethyl alcohol/methyl ethyl ketone 25# mixed solvent (mixing ratio 1/1) was mixed and dispersed in a ball mill for 72 hours. A magnetic paint was prepared and applied so that the thickness of the magnetic paint was 4 μm. Next, after preheating at 90°C for 1 minute to remove the ether alcohol/methyl ethyl ketone mixed solvent, EPS-750 manufactured by Nissin High Voltage Co., Ltd.
The material was cured by irradiating it with an electron beam at a dose of 7 Mrad, and after calendering, it was cut into a predetermined width to produce a magnetic tape.

Example 2 In the composition of the magnetic paint in Example I, the ethyl alcohol/methy)bx thyl keto/mixed solvent was omitted, the amount of nonaethylene glycol dimethacrylate used was changed from 40 parts by weight to 45 parts by weight, and preheating was omitted. A magnetic tape was produced in the same manner as in Example 1 except for the following.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic coating material in Example I, Plenac) 9S was omitted.

Comparative Example 2 In the composition of the magnetic paint in Example IK, Tetrastearyl Titanate [TI
A magnetic tape was made in the same manner as in Example 1 except that the same amount of (OC, H,,)4) was used.0 Regarding the magnetic tape obtained in each Example and each Comparative Example, the video SN ratio and color SN ratio The ratio was measured. The video S/N ratio and color S/N ratio were obtained using nine magnetic tapes on a video deck (VT-6000 manufactured by A-Tate Seisakusho Co., Ltd.). ,,l[La1ell
! The raw material was measured with a color video noise meter 9250 manufactured by 7 Pasoku Co., Ltd., and the video SN ratio and color SN ratio of the magnetic tape obtained in Comparative Example 1 were expressed as O, and the difference therebetween was expressed.

The table below shows the results. As is clear from the table above, the magnetic tapes obtained by this invention (Examples 1 and 2) are similar to conventional magnetic tapes (Comparative Examples! and 2), and Both the signal-to-noise ratio and the color signal-to-noise ratio are high, which indicates that the magnetic recording medium obtained by the present invention has excellent dispersibility and filling properties of the magnetic powder, and has further improved magnetic properties and surface smoothness of the magnetic layer. I understand.

Claims (1)

[Claims] Tortoise, on the substrate, the general formula % formula %) (wherein R is a hydrocarbon group, X is -CO1 or -so
, -o or -PO(OH)-0-POIY is a hydrocarbon group or +0-R), and R8 is an alkyl group. A blood film containing a titanium coupling agent shown in A magnetic recording medium characterized by having a magnetic layer hardened by irradiation.