JPH0792914B2 - Magnetic recording medium and manufacturing method thereof - Google Patents

Description

The present invention relates to a magnetic recording medium and a method for manufacturing the same,
More specifically, the present invention relates to a magnetic recording medium having good dispersibility of magnetic powder and excellent electromagnetic conversion characteristics and durability, and a method for producing the same.

[Conventional technology]

Generally, a magnetic recording medium prepared by applying a magnetic coating material comprising a magnetic powder, a binder component, an organic solvent and other necessary components onto a substrate such as a polyester film and drying the magnetic coating medium has a dispersibility of the magnetic powder in a magnetic layer. Is particularly important in improving the surface smoothness and magnetic characteristics of the magnetic layer, and it is difficult to obtain excellent electromagnetic conversion characteristics such as high output and low noise with those having poor dispersibility. .

Therefore, as a means for improving the dispersibility of the magnetic powder, conventionally, the surface treatment of the magnetic powder with an appropriate surface treatment agent has been performed together with the selection of the binder resin.
For example, a silane coupling agent is known as a particularly effective surface treatment (JP-A-59-129938, JP-A-SHO).
58-155703).

[Problems to be solved by the invention]

However, the above-mentioned conventionally known silane coupling agent generally has a hydrolyzable group such as a methoxy group and an ethoxy group at the end of the molecule, and is reactive with an organic substance such as a vinyl group, an epoxy group, and an amino group at the other end. It has a certain group. Therefore, in the silane coupling agent, a silanol group produced by hydrolysis is chemically bonded to the surface of the magnetic powder, and a group reactive with an organic substance such as the vinyl group, epoxy group, or amino group is outside the powder. Adhesive form that is suitable for the magnetic powder, because such reactive groups cause a chemical reaction with the reactive groups that may be contained in the binder resin, the viscosity of the magnetic paint is abnormally increased, and the magnetic powder There was a case where the dispersiveness of was rather damaged. Further, the silane coupling agent is chemically bonded to the glass surface, but is said to have a weak bonding force to iron oxide powder and metallic iron powder, and the silane coupling agent is not bonded to the magnetic powder surface. After formation of the magnetic layer, the agent may seep out to the surface of the magnetic layer and impair the durability as a magnetic recording medium.

[Means for solving problems]

The present invention has been made as a result of various studies in order to solve the above-mentioned drawbacks of the prior art. [Wherein R is R ₁ (R ₂ O) m (CH ₂ ) n, R ₁ is an alkoxy group having 1 to 6 carbon atoms, an epoxy group or an acetyl group, and R ₂ is 2 to 6 carbon atoms. Alkyl group, m is 1 to
An integer of 30 and n is an integer of 0 to 5 and R'and R "are an alkyl group or an amino group having 1 to 6 carbon atoms.] An organosilazane compound containing an alkylene oxide represented by It is used by immersing the magnetic powder in a treatment liquid containing this type of organosilazane compound for treatment, and by using this treated magnetic powder, the thickening due to the reaction with the binder resin during the preparation of the magnetic coating is eliminated. ,
In addition, the exudation of the surface treatment agent on the surface of the magnetic layer is well suppressed, the dispersibility of the magnetic powder and the durability of the magnetic layer are improved, and the electromagnetic conversion characteristics and durability of the obtained magnetic recording medium are sufficiently improved. It is an improvement. The repeating unit represented by R ₂ O of the organosilazane compound represented by the general formula may be composed of a mixture of at least two kinds of ethylene oxide group, propylene oxide group and butylene oxide group, and is a mixture. Consists of
Each unit may be random or block. Further, in the case of a block, the order of addition is not particularly limited, and the repeating unit represented by R ₂ O is preferably an integer of 1 to 30, and when the repeating unit is larger than 30, it is dissolved in a solvent. The property is remarkably deteriorated and the surface treatment of the magnetic powder becomes impossible. One of R'and R "may be an alkyl group and the other may be an amino group.

The organosilazane compound containing an alkylene oxide used in the present invention has extremely high reactivity with the OH group on the surface of the magnetic powder as compared with a conventional silane coupling agent,
-NH-bonding moiety easily formed by polymerizing some basic units of the organosilazane compound, or -NH
_{2 The} bond is broken and NH ₃ is released, and a chemical bond is formed with the surface of the magnetic powder such as iron oxide powder or metallic iron powder through oxygen atoms, and is fixed on the surface. However, since it does not have a free amino group in the molecule, a vinyl group, or a reactive group that reacts with a binder resin such as an isocyanate group, the binder resin has a reactive group such as a hydroxyl group, a carboxyl group, or an isocyanate group. There is no possibility of causing the phenomenon of thickening of the magnetic coating even when the one containing is included. Also, by adjusting the type of alkylene oxide in the alkylene oxide structure portion and the number of moles added, affinity with the binder resin and the organic solvent can be favorably imparted to the magnetic powder. Therefore, the dispersibility of the magnetic powder and the dispersion stability of the magnetic powder are remarkably improved even when various binder resins are used or when the magnetic powder having a very small particle size is used.

The amount of the organosilazane compound containing such an alkylene oxide is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the magnetic powder, 2 to 10 parts by weight.
It is preferably within the range of parts by weight. If the amount used is too small, a sufficient effect of improving the dispersibility cannot be obtained, and if the amount is too large, the surface smoothness of the magnetic layer is rather impaired or durability deteriorates, which is not preferable.

In the present invention, the means for incorporating the organosilazane compound containing alkylene oxide into the magnetic layer is as follows.
A method may be adopted in which an organosilazane compound of this kind is added to a magnetic paint containing a magnetic powder, a binder resin and an organic solvent, the magnetic paint is applied onto a substrate and dried to form a magnetic layer. However, according to a conventionally known method, the organosilazane compound of this kind is previously attached to the particle surface of the magnetic powder, the magnetic paint is prepared using this magnetic powder, and the magnetic layer is formed in the same manner as described above. Preferably.

The latter method is to prepare a solution of this type of organosilazane compound in an appropriate solvent, add magnetic powder to the solution, mix and disperse with a homomixer, filter, and heat-dry to obtain magnetic properties. A predetermined amount of this type of organosilazane compound is attached to the particle surface of the powder, and in this latter method, a more uniform layer of this type of organosilazane compound can be attached and formed on the surface of the magnetic powder, improving the dispersibility. It is recognized that the effect is particularly great.

As a solvent for dissolving such an organosilazane compound of this kind, alcohols having 3 to 8 carbon atoms, acetone,
Ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, aromatics such as benzene and toluene, ethers such as tetrahydrofuran and dioxane are preferably used, and among them, those having 3 carbon atoms. Alcohols of to 8 give a particularly favorable effect on the dispersibility of the final magnetic powder and are therefore more preferably used. The concentration of the organosilazane compound in these solvents varies considerably depending on the type of the solvent, but generally it is preferably within the range of 0.1 to 2.0% by weight, and about 0.5 to 1% by weight. Is particularly preferable.

As the magnetic powder applied to the present invention, any conventionally known one can be used, for example, γ-Fe ₂ O ₃ powder, Fe ₃
O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, hexagonal ferrite powder such as barium ferrite and strontium ferrite, oxide-based magnetic powder such as CrO ₂ powder, Fe Examples thereof include powder, Co powder, and metal powder such as Fe—Ni powder. Among these, those having a small particle size and those having a large specific surface area by the nitrogen adsorption method (about 40 to 100 m ² / g) have been used in recent years, and the effect of the present invention on these magnetic powders is obtained. It is useful because it is particularly large. Further, the present invention is a plate-like, granular,
It also has a great effect on magnetic powder such as rice cake.

Further, as the binder resin, vinyl chloride-vinyl acetate-based copolymer, polyvinyl butyral resin, fibrin-based resin, polyurethane-based resin, polyester resin, polyisocyanate compound or any other binder resin that has been widely used in the past. It can be used. Also, various electron beam curable resins can be used.

Further, as the organic solvent for magnetic coating adjustment, cyclohexanone, methyl ethyl ketone, ketone-based solvents such as methyl isobutyl ketone, ethyl acetate, ester-based solvents such as butyl acetate, benzene, toluene, aromatic hydrocarbon solvents such as xylene, Solvents suitable for dissolving the binder resin to be used, such as alcohol solvents such as isopropyl alcohol, acid amide solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, ether solvents such as tetrahydrofuran and dioxane, are particularly preferable. There is no limitation, and they may be used alone or in combination of two or more.

Needless to say, in magnetic paints containing such magnetic powder, binder resin, organic solvent and organosilazane compound, there are usually used additives such as lubricants, abrasives, antistatic agents. You may add an agent etc. suitably. Further, it can be used in combination with a silane coupling agent which has been conventionally used and has a functional group such as an amino group, a hydroxyl group, an isocyanate group or an unsaturated bonding group which reacts with a binder resin.

The magnetic recording medium of the present invention is formed by mounting a magnetic coating material composed of such constituents on a non-magnetic substrate such as a polyester film to form a magnetic layer, and also by adopting an orientation treatment or a mirror surface treatment which is usually adopted. And it can be obtained by performing a cutting (punching) process or the like.

[Examples] Next, examples of the present invention will be described.

Example 1 Structural formula Using organosilazane represented by, 100 parts by weight of Co-containing γ-Fe ₂ O ₃ powder (specific surface area by nitrogen adsorption method: 40 m ² / g) Organosilazane 10 〃 Isopropyl alcohol 1000 〃 The mixture was mixed and dispersed for 4 hours with a mixer, left standing for 24 hours, and then filtered. Then, it was dried at 80 ° C. for 15 hours to obtain a magnetic powder surface-treated with organosilazane. To this treated magnetic powder, 1.0 mg of organosilazane per 1 m ² , that is, 4 parts by weight of organosilazane per 100 parts by weight of Co-containing γ-Fe ₂ O ₃ powder was uniformly attached.

Then, using the treated magnetic powder thus obtained, a magnetic coating material having the following composition is applied by a ball mill.
The magnetic paint was prepared by mixing and dispersing for 100 hours.

Surface-treated magnetic powder 100 parts by weight Fiber-based resin (product name HIG1 / 2 manufactured by Asahi Kasei) 9〃 Polyurethane resin (product name T-5250 manufactured by Dainippon Ink and Chemicals) 8〃 Polyisocyanate compound (Japan Polyurethane Co., Ltd.) Product name: Coronate L) 3〃 Myristic acid 3〃 Cyclohexanone 90〃 Toluene 90〃 This magnetic paint was applied to a polyester film of 12μm in thickness so that the dry thickness would be about 4μm and then mirror-finished. A magnetic tape was made by cutting it into a predetermined width.

Example 2 In the same manner as in Example 1, except that the organosilazane used in Example 1 was replaced with the same amount of organosilazane represented by the following structural formula in the surface treatment of the magnetic powder in Example 1. I made a magnetic tape.

Structural formula Example 3 In the surface treatment of the magnetic powder in Example 1, the same procedure as in Example 1 was performed except that the organosilazane represented by the following structural formula was used in the same amount in place of the organosilazane used in Example 1. I made a magnetic tape.

Structural formula Example 4 The surface treatment of the magnetic powder in Example 1 was omitted, and Example 1 was omitted.
A magnetic tape was prepared in the same manner as in Example 1 except that 4 parts by weight of the same organosilazane as that used for the surface treatment of the magnetic powder was newly added to the magnetic coating composition.

Example 5 In the same manner as in Example 1, except that the same amount of organosilazane represented by the following structural formula was used in place of the organosilazane used in Example 1 in the surface treatment of the magnetic powder in Example 1. I made a magnetic tape.

Structural formula Example 6 In the same manner as in Example 1, except that the organosilazane used in Example 1 was replaced with the same amount of organosilazane represented by the following structural formula in the surface treatment of the magnetic powder in Example 1. I made a magnetic tape.

Structural formula Example 7 In the same manner as in Example 1, except that the same amount of organosilazane represented by the following structural formula was used instead of the organosilazane used in Example 1 in the surface treatment of the magnetic powder in Example 1. I made a magnetic tape.

Structural formula Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that the surface treatment of the magnetic powder was omitted.

Comparative Example 2 In the surface treatment of the magnetic powder in Example 1, the same amount of the silane coupling agent represented by the following structural formula was used instead of the organosilazane used in Example 1,
A magnetic tape was prepared in the same manner as in Example 1.

Structural formula Comparative Example 3 In the surface treatment of the magnetic powder in Example 1, the same amount of organosilazane represented by the following structural formula was used instead of the organosilazane used in Example 1, but the organosilazane was dissolved in isopropyl alcohol. Since this was not done, it was not possible to produce a magnetic tape.

Structural formula Regarding the magnetic tapes obtained in the respective examples and comparative examples,
The results of measuring the magnetic properties, surface smoothness, C / N ratio and running stability are shown in the table below.
The magnetic characteristics are square (Br / Bs) and residual magnetic flux density (Br).
And were measured. The surface smoothness was measured at a cutoff of 80 μm using a stylus type surface roughness meter, and the center line average roughness (R
Shown in a). The C / N ratio is measured at a recording wavelength of 4 MHz,
The magnetic tape of Comparative Example 1 is shown as a reference (0 dB). For running stability, wow and flutter was measured.

[Effects of the Invention] As is clear from the above table, the magnetic tapes obtained in the present invention (Examples 1 to 7) have a rectangular shape and a residual magnetic flux as compared with the conventional magnetic tapes (Comparative Examples 1 and 2). The density and C / N ratio are high, the surface smoothness is small, and the running stability is good. Therefore, the magnetic recording medium obtained by the present invention has good magnetic characteristics and surface smoothness, and electromagnetic conversion characteristics. It can be seen that the durability is further improved and the durability is further improved.

Claims (4)

[Claims] 1. A magnetic recording medium having a magnetic layer comprising a magnetic powder treated with an organosilazane compound. 2. An organosilazane compound is a basic unit. [Wherein R is R ₁ (R ₂ O) m (CH ₂ ) n, R ₁ is an alkoxy group having 1 to 6 carbon atoms, an epoxy group or an acetyl group, and R ₂ is 2 to 6 carbon atoms. Alkyl group, m is 1 to
An integer of 30, n is an integer of 0 to 5, R'and R "are an alkyl group or an amino group having 1 to 6 carbon atoms.] An organosilazane compound represented by The magnetic recording medium described. 3. The magnetic powder is immersed in a treatment liquid containing an organosilazane compound for treatment, and then the treated magnetic powder is mixed and dispersed with a binder component, an organic solvent and the like to prepare a magnetic paint. A method for producing a magnetic recording medium, which comprises applying a coating material onto a substrate and drying the coating to form a magnetic layer. 4. An organosilazane compound is a basic unit [Wherein R is R ₁ (R ₂ O) m (CH ₂ ) n, R ₁ is an alkoxy group having 1 to 6 carbon atoms, an epoxy group or an acetyl group, and R ₂ is 2 to 6 carbon atoms. Alkyl group, m is 1 to
An integer of 30, n is an integer of 0 to 5, R'and R "are an alkyl group or an amino group having 1 to 6 carbon atoms.] An organosilazane compound represented by A method for manufacturing the magnetic recording medium described.