JPS59129938A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a magnetic layer having good dispersibility of magnetic powder, excellent durability, etc. by incorporating magnetic powder coated with the resulted reaction product of a silane coupling agent contg. an isocyanate group with a copolymer of specific vinyl monomers. CONSTITUTION:An organosilicone polymer soln. obtd. by the reaction of a silane coupling agent contg. an isocyanate group such as the one expressed by the formula for example, with >=1 kind copolymer from the group of copolymers of either 5-70mol% vinyl monomer contg. OH or 5-70mol% vinyl monomer contg. COOH and 30-95mol% hydrophobic vinyl monomer is prepd. A magnetic medium having a magnetic layer dispersed with the magnetic powder coated with the organosilicon polymer by dipping the magnetic powder into such soln. in a binder resin is manufactured. The magnetic layer having uniform dispersion of the magnetic powder, a smooth surface and an excellent electromagnetic conversion characteristic is thus obtd.

Description

[Detailed description of the invention] The present invention relates to improved magnetic recording media.

More specifically, the present invention relates to a magnetic recording medium that has excellent magnetic properties and durability and is manufactured using a magnetic paint that improves the dispersibility of magnetic powder and the adhesion between the magnetic powder and a binder.

Magnetic powder in magnetic recording media such as magnetic tapes and magnetic disks is required to have a high degree of dispersibility.

Magnetic recording media are generally manufactured by kneading magnetic powder, binder, various additives, and solvents, and then uniformly coating a magnetic paint on a plastic film or sheet substrate and drying it. Although it is formed by finishing, it is not possible to create a uniform and smooth magnetic layer with a high packing density unless the magnetic powder in the magnetic paint is sufficiently dispersed to remove any aggregated particles.

Non-uniformity in the magnetic layer due to agglomerated particles of magnetic powder has a serious negative effect on the electromagnetic conversion characteristics and magnetic properties of the magnetic tape.

In other words, it causes a decrease in output, an increase in noise, dropouts, etc.

Also, if the adhesive force between the magnetic powder and the binder is weak,
In addition to the sliding movement between the magnetic recording medium and the recording or reproducing head, magnetic particles from the magnetic coating layer tend to separate (so-called "powder falling off"), and the coating surface becomes rough, causing magnetic The durability of the recording medium is impaired.In reality, conventional magnetic recording media have been put into practical use with insufficient durability.

As described above, the dispersibility of the magnetic powder in the magnetic paint and the adhesion with the binder are very important in improving the performance of the magnetic recording medium.

Improvements in the dispersibility of magnetic powder have been studied from various viewpoints, and it has been proposed to improve the dispersibility by adding a suitable surfactant to the magnetic paint formulation. Such surfactants include those using alkylimidacillin compounds (Japanese Patent Laid-Open No. 54-52504), and those using alkyl polyoxyethylene phosphates neutralized with alkyl amines (Japanese Patent Laid-open No. 53-78810). , those using long-chain alkyl phosphate esters (Japanese Patent Application Laid-Open No. 1987-L47507)
, % Application H53-491529), amines and their derivatives, phosphoric esters, polyoxyethylene phosphoric esters, etc. are often used. In addition, there has been a proposal that dispersibility can be improved by surface-treating magnetic powder and then turning it into a paint, and methods using alkyl polyoxyethylene phosphoric acid esters (JP-A-54-94308, JP-A-54-94308;
49769), and one that measures metal powder with a titanium coupling agent to measure dispersion stability and at the same time prevents deterioration of the magnetic coating film over time [JP-A-56-88471]. Also,
A method for improving the durability of the magnetic coating film by improving the adhesiveness between the magnetic powder and the binder is to use a silane coupling agent having a functional group reactive with the binder (Japanese Patent Application Laid-Open No. 7310/1983). , which is coated with a reaction product of an aminofunctional silane coupling agent, an isocyanate compound, and an epoxy compound (Japanese Patent Application Laid-open No.
6-145535), a method in which magnetic powder is treated with a titanium coupling agent having a double bond in the binder and an unsaturated bond capable of radical polymerization (JP-A-5.5-11112)
9) A compound having at least four radiation-sensitive acrylic double bonds in the molecule is used as an inder.
(Japanese Unexamined Patent Publication No. 57-40744). As described above, although much research has been carried out on improving the dispersibility of magnetic powder in magnetic coatings and the durability of magnetic coatings, a satisfactory stage of improvement has not yet been reached.・.

The present inventors have solved the problem of the above magnetic recording medium,
As a result of extensive research, we have discovered that magnetic recording media with excellent dispersibility of magnetic powder and durability of coating layers are needed, and a combination of a silane coupling agent containing an isocyanate group and a certain copolymer has been developed. The magnetic recording medium containing the magnetic powder coated with the reaction product has good dispersibility of the magnetic powder and excellent durability of the coating layer. I let it happen.

That is, the present invention provides an isocyanate group-containing silane coupling agent and the following (Il and (III) (I) hydroxyl group-containing vinyl monomers 5 to 70
Copolymer α) consisting of 7 mol% and hydrophobic vinyl monomer 30 to 95 mol% α) Copolymer consisting of 5 to 70 mol% carboxyl group-containing vinyl monomer and 50 to 95 mol% hydrophobic vinyl monomer α) The object of the present invention is to provide a magnetic recording medium containing magnetic powder coated with an organosilicon polymer obtained by reaction with one or more copolymers of at least 2 at.

Examples of the incyanate group-containing silane coupling agent according to the present invention include the following compounds f.

Abbreviation (02H50)5SiC3H6NHOONHO6H42
NGo (G-1) (OH, O), 5iO5H6
NHC2H4NHGONHC6H12NGo (C-2
)(OH30)2Si-06H,NHO2H4NHGO
NHC6H12NC:O(Ct-3)H5 0H20820H (Hereinafter, abbreviated as abbreviation) Hydroxyl group-containing vinyl monomers according to the present invention include hydroxyethyl methacrylate, hydroxyethyl acrylate, 7-lyl alcohol, acrylic acid (or methacrylic acid) 1 Examples of carboxyl group-containing vinyl monomers include methacrylic acid, acrylic acid, and esters obtained from 1 mole of diol.
Crotonic acid, itaconic acid, fumaric acid, maleic acid,
Acryloyloxypropionic acid, allyl alcohol 1
Examples include esters obtained from 1 mole of dicarboxylic acid and 1 mole of dicarboxylic acid.

In addition, the hydrophobic and nil monomers related to the present invention include:
Butylene, isobutylene, hexene, diisobutylene,
Olefins such as 1-decene, acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl 7-acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylate Ethyl methacrylates such as ethyl acid, dodecyl methacrylate, and hexadecyl methacrylate; vinyl ethers such as methyl vinyl ether, isobutyl vinyl ether, octyl vinyl ether, and α-chloroethyl vinyl ether; styrene such as styrene, α-methylstyrene, and p-methylstyrene; Rust conductors, other 7crylonitrile, vinyl acetate, vinyl chloride,
Examples include vinylidene chloride.

The copolymer of (I) and (II) used in the present invention is
It can be obtained by ordinary radical polymerization using a polymerization initiator such as penzoyl peroxide and a chain transfer agent such as furkyl mercaptan. The copolymerization ratio of the hydroxyl group- or carboxyl group-containing vinyl monomer and the hydrophobic and nyl monomer in the copolymer is important;
The hydrophobic vinyl monomer must be used at a molar ratio of 5/95 to 70,150. When using a copolymer in which the proportion of vinyl monomers containing hydroxyl groups or carboxyl groups exceeds 70 mol%, it is too hydrophilic and is therefore undesirable (
If this ratio is less than 5 mol %, it is not preferable because there are too few bonds with the incyanate group-containing silane camping agent.

The organosilicon polymer according to the present invention contains an incyanate group-containing silane coupling agent and the above (I) and (I).
It can be obtained by heating one or more copolymers selected from the group consisting of I) in an inert organic solvent and further applying pressure if necessary. In such a reaction, although the reaction does not progress chemistratically due to the bubbling effect of the copolymer, it is possible to The yield of the product can be improved.The organosilicon polymer preferably has a molecular weight of 800 to 100,000, more preferably 2,000 to 20,000.If the molecular weight is less than 800, the magnetic properties in the magnetic recording medium may be reduced. The dispersibility of the powder and the durability of the coating film tend to decrease, and if the molecular weight exceeds 100,000, the dispersibility of the magnetic powder tends to decrease.

The magnetic powder according to the present invention includes needle-shaped fine γ-
Fe20. ．． Metal oxides such as Fe3O4, CrO2, also Co deposited - I/e 203.00 doped r
-γ-Fθ20 processed like Fe20°
3. Examples include iron mekuru powder. Among these, iron metal powder has particularly poor chemical stability, so to improve this, a small amount of nickel, cobalt, titanium, silicon X, 7/I/ minilum, etc. in the form of metal atoms, salts, and oxides is added to the surface. These may also be used although they may be processed. Iron metal powder may also form a thin oxide film7 on its surface in a weakly oxidizing atmosphere to stabilize it.
Metal powder treated in this way can also be used.

The size of these magnetic powders is from 1μ to 0.15μ on the long axis.
It is preferable that the minor axis is 0.15μ to 0.015μ.

If the long axis is larger than 1 μm, dispersion becomes easier, but recording of short wavelengths becomes disadvantageous and noise becomes large, which is not preferable. When the long axis is smaller than 0.15μ, even the magnetic recording medium of the present invention is unlikely to have sufficient dispersibility.

The coated magnetic powder according to the present invention can be obtained by heating the organosilicon polymer and magnetic powder in an inert organic solvent.
It can be obtained by further applying pressure if necessary. Examples of the inert organic solvent used here include methyl ethyl ketone, methyl imbutyl ketone, diethyl ketone, cyclohexanone, benzene, xylene, and toluene. The organosilicon polymer used in the present invention weighs approximately 0.5 to 10 weight percent, preferably 1.0 to 5.0 weight percent, relative to the magnetic powder.

The magnetic recording medium of the present invention can be obtained by adding a binder and a solvent to the coated magnetic powder to form a paint, and applying the paint to a polyester film or the like.

The binder used to make coatings from the coated magnetic powder is a resin binder that is soluble in organic solvents, and it fixes the above magnetic powder onto the substrate with the necessary strength and forms an arsenic layer. It is sufficient to use a material that can fulfill its role with as little g as possible, and even materials that are likely to deteriorate the dispersibility of magnetic powder in conventional coatings can be used in ordinary coating methods. Examples of these resin binders include polyurethane, polyester, and polyvinyl chloride. Vinyl chloride vinyl acetate copolymer, polyacrylonitrile, 2) lyl rubber, epoxy resin 61 alkyd, polyamide, polyacrylic ester, polymethacrylic ester, polyvinyl acetate, polyvinyl butyral, vinylidene chloride, chloride Vinylidene copolymer, cotton wool, ethyl cellulose, etc. may be used alone, but two or more types are usually used as a mixture.

It is also possible to add a plasticizer or a hardening agent to the product to increase its hardness.

The blending amount of the binder is generally 15 to 60 parts by weight per 100 parts of the magnetic powder. Even if the binder has the largest bonding force, if it is less than the 15-fold pupil area, the strength of the magnetic coating will be weak and the adhesive force between the substrate and the magnetic coating will be insufficient.

If the amount is more than 60 parts, the concentration of magnetic powder in the magnetic coating film becomes small, which is disadvantageous because the reproduction output decreases, and the properties of the coating film may also deteriorate.

(The solvent used for making the paint should be used) (It is preferable to use a solvent that has a dissolving power for the inder and has a boiling point between 50°C and 150°C. If the boiling point is too low, the magnetic powder will not be oriented in the magnetic field after coating. (The heel part of the inner shoe is selected from the above viewpoints, but it goes without saying that it should be selected in consideration of toxicity and environmental issues.)

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Example 1 200 ml of toluene was added to a 5 C1 Oml 4 flask equipped with a stirrer and a condenser. 0.5 g of the above G-1, which is an incyanate group-containing silane coupling agent, and a methacrylic acid (hereinafter referred to as MAA)/lauryl methacrylate (hereinafter referred to as LMA) copolymer (copolymerization molar ratio MAA/L M A = 20780, molecular weight 240
0)2.8 and li' were added to make the system homogeneous, and then stirred at 90°C for 3 hours. During this period, we sampled over time and measured the infrared absorption spectrum, and found that it was 2260c.
-NCo-based absorption of yn gradually decreases,
-NHCOO-K group near 1700-1 (it was observed that the absorption increased, and it was confirmed that the above incyanato group-containing silane coupling agent and the M A A / L M A copolymer had reacted. .

Next, the major axis diameter was 0.35 μm.
Add 100 g of Fe203 to the above toluene solution and
A surface-treated magnetic powder was obtained by stirring at 90° C. for 2 hours and washing with excess toluene.

Furthermore, 80 parts by weight of said magnetic powder, 7 mn parts of polyurethane (Nilaporan 2304, manufactured by Nippon Polyurekun Industries Co., Ltd.) as a binder, 16 weight parts of vinyl chloride and acetate resin (vAcH, manufactured by Union Carbide Co., Ltd., USA), and a strip of magnetic tape. 'Carbon black as an inhibitor 3.574
H part, oleic acid 0- as a dispersant for carbon black
A magnetic coating material was obtained by mixing 3 parts of Fitm15, 50 parts of the solvent toluene, and 50 parts of methyl ethyl ketone, and blending the mixture in a ball mill for 48 hours. This magnetic paint was applied to a 12-μm-thick reinforced polyethylene terephthalate film to a dry film thickness of 7 μm, oriented in a magnetic field, dried, and then calendered into mirror-finished waves and cut into a predetermined width. A magnetic tape was obtained. The dispersibility of the magnetic powder in the magnetic tape was evaluated by measuring the squareness ratio, and the wear resistance was evaluated by sliding the tape surface using a simulated head at a speed of 0-8 m/s 60 for 90 minutes. The degree of wear was determined by measurements and microscopic observation. The results are shown in Table 3.

Examples 2 and 6 Surface-treated magnetic powder, magnetic paint, and magnetic tape were obtained using the incyanate group-containing silane coupling agent and copolymer shown in Table 1 in the same manner as in Example 1. The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1. The results are shown in Table-6.

Coating-1 Examples 4 to 12 Surface-treated magnetic powder, magnetic paint, and magnetic tape were obtained in the same manner as in Example 1 using the isocyanate group-containing silane coupling agent and copolymer shown in Table-2. The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1. The results are shown in Table-6.

Table-2 ω i-aMA: Isobutyl methacrylate OMA
: Octyl methacrylate SMA : Stearyl methacrylate HEMA : Hydroxy ether methacrylate A : St itaconic acid : Styrene Comparative Example 1 MAA/LMA was used instead of the copolymer of MAA/LMA = 20/80 and molecular weight 2400 used in Example 1.
A surface-treated magnetic powder, a magnetic paint, and a magnetic tape were obtained in the same manner as in Example 1 except that a copolymer having a molecular weight of 3,500 and a molecular weight of 3,500 was used. The squareness ratio of the magnetic tape was measured and the face abrasion property was evaluated in accordance with Example 1.

The results are shown in Table-3.

Comparative Example 2 IIA/LMA used in Comparative Example 1 = 2798, molecule f
Instead of copolymer of i6100, MAA /LMA=
2/98. Surface-treated magnetic powder, magnetic paint, and magnetic tape were obtained in the same manner as in Example 1 except that a copolymer with a molecular weight of 8100 was used. The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1. The results are shown in Table-3.

Comparative Example 3 Instead of incyanato group-containing silane camping agent c-i and MAA/LMA copolymer used in Example 1, incyanato group-containing silane camping agent 0-6 was used.
0.5g and rA/St/LMA=80/10/10
A surface-treated magnetic powder, a magnetic paint, and a magnetic tape were obtained in the same manner as in Example 1, except that 1.0 g of a copolymer having a molecular weight of 5,900 was used. The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1.

The results are shown in Table-3.

Comparative Example 4 MAA/LMA = 20780 used in Example 1, instead of the copolymer of 12400 molecules
80.720, molecular weight 1000 copolymer 2. OI
A surface-treated magnetic powder, a magnetic paint, and a magnetic tape were obtained in the same manner as in Example 1 except for the use of the following. The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1. The results are shown in Table-6.

Comparative example 5 Toluene/methyl ethyl ketone (s　/　/s　.

Heavy lid ratio) lauryl phosphate in 100ml of mixed solvent)
1. OF was dissolved and the major axis ratio used in Example 1 was 0.658.
m1 axial ratio % Oo*'3iγ-Fe20310 CII
A slurry of magnetic powder was obtained. Thereafter, the binder resin used in Example 1 and carbon black water and oleic acid were added to the slurry in amounts similar to those in Example 1 to obtain a magnetic paint and a magnetic tape.

The squareness ratio and abrasion resistance of the magnetic tape were measured in accordance with Example 1. The results are shown in Table-6.

Table 3 As is clear from Table 5, the magnetic recording medium of the present invention has a large squareness ratio and good wear resistance. This simply shows that the magnetic recording medium is excellent in both the dispersibility of the magnetic powder and the durability.

Applicant's agent Kaoru Furuya Procedural amendment (spontaneous) 1 Indication of the case Patent Application No. 58-5454 2 Name of the invention Magnetic recording medium 3 Person making the amendment Relationship to the case Patent applicant (0911 Kao Soap Co., Ltd. 4 Agent Nakai Building, 1-3 Yokoyama-cho, Nihonbashi, Chuo-ku, Tokyo Column 6 Detailed explanation of the invention in the specification Inclusion of amendments (1) Replacement with seeds or 2s or more of “metal powder” on page 10 of the specification, lines 15-14 magnetic powder, Oo.

"Ultrafine powder of metals or alloys such as Fe-CO, Fe-Ni, etc." (Spontaneous) April 16, 1981 Commissioner of the Japan Patent Office Kazuo Wakasugi 1, patent application for indication of the case 1982 -5454 No. 2, Name of the invention Magnetic recording medium 3, Relationship to the amended person's case Patent applicant (091) Kao Soap Co., Ltd. Founder Nee 4, Agent Nakai Building 3, 1-1 Nihonbashi Yokoyama-cho, Chuo-ku, Tokyo Details Cabinet 6 of the Detailed Description of the Invention of the Book, Contents of Amendment (1) Page 23 of the Specification, Lines 5-6, "Nothing else." Next to the line break, insert the following statement: "Example 13 Example 1 100 parts by weight of the surface-treated magnetic powder obtained above, each of the following components, binder, 50% by weight of anti-magnetic powder, anti-static agent
~ 0.4 ・Abrasive // 0.2 // ・II Bone //
Q, 7 //・Solvent
〃, 1100 l' were mixed and kneaded in a ball mill for 72 hours, and a hardening agent (Japan Polyurethane Kogyo's Coronate L>' was added in an amount of 8% by weight based on the magnetic powder) and stirred until the system became uniform to form a magnetic paint. In addition, to explain each of the above components, the binder is vinyl chloride-vinyl acetate copolymer (VAGH of Union Carbide), 1!: polyurethane resin (Nysten 50),
33) in a 1:2 (weight ratio) mixture, the antistatic agent is carphone blank (Lion Akzo's Ketjen Black E), the abrasive is alumina with an average particle size of 0.7μ, the lubricant is butyl stearate, and the solvent is methyl ethyl ketone/
Cyclohexanone/toluene 1:1:1 (weight ratio)
It is a mixture.

Further, the magnetic paint was applied onto a polyester film using a 30 μm applicator, dried with hot air without magnetic field orientation, and then calendered to smooth the coating and punched out into a disk shape to form a magnetic recording medium.

Glossiness and residual magnetic flux density (Br) for the magnetic recording medium
, durability (output drop after 10 million buses/trunks) and FR-out were measured. The results are shown in Table-4. However, the measurement conditions for PR-out are as follows.

Relative velocity; 4. Qm/sec Recording frequency; 4 MHz Recording head; Sendust reproduction head; Ferrite Comparative Example 6 The magnetic powder used in Example 1 was used as a dispersant (AFACRE610 (polyoxyethylene-added alkylaryl sesquivalent) without any surface treatment. Phosphate) was added in an amount of 3% by weight based on the magnetic powder, and a magnetic paint and a magnetic recording medium were prepared by the method of Example 13, and the four items shown in Example 13 were measured.The results are shown in Table- 4.

Table-4 *FR-out is O for the magnetic recording medium of Comparative Example 6.

Claims (1)

[Scope of Claims] An isocyanate group-containing silane coupling agent;
Copolymer (n) consisting of 30 to 95 mol% of hydrophobic vinyl heptamer and carboxyl group-containing vinyl heptamer 5 to 70 mol%
Magnetic powder coated with an orca silicone polymer obtained by reaction with one or more copolymers from the group consisting of copolymers consisting of mol% and hydrophobic vinyl monomers from 60 to 95 mol%. A magnetic recording medium characterized by containing.