JPS62214519A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility, orientational property and packability of magnetic power and to improve electromagnetic conversion charactersitic and durability by incorporating 2 kinds of coupling agents into a magnetic layer on a nonmagnetic substrate. CONSTITUTION:The titanate coupling agent and silane coupling agent are incorporated into the magnetic layer. The balance between the lipophilicity and hydrophilcity of the magnetic power is made adequate by such combination incorporation, by which the performance of a recording medium is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

[Conventional technology]

As this type of magnetic recording medium, one in which a magnetic layer is formed by coating a magnetic paint containing magnetic powder and a binder resin on a non-magnetic support such as a polyester film is known. Since the electromagnetic conversion characteristics of this medium depend on the quality of the dispersibility, filling ability, orientation, etc. of the magnetic powder in the magnetic layer, it is desired that the medium has excellent these characteristics. Furthermore, in order to maintain good electromagnetic conversion characteristics over a long period of time, it is also desired that the magnetic layer has excellent durability.

Conventionally, in order to meet these required characteristics, attempts have been made to select the binder resin constituting the magnetic layer, include a dispersant or coupling agent in the magnetic layer, or include various abrasives. has been done (document unknown).

[Problems to be Solved by the Invention] However, although the use of dispersants and coupling agents has been shown to improve dispersibility, filling properties, and orientation to a certain extent, it is still not satisfactory. Furthermore, even if the above characteristics are relatively satisfied, the durability of the magnetic layer cannot be satisfied, and it is not possible to highly satisfy both the dispersibility, filling property, and orientation of the magnetic powder, and the durability of the magnetic layer. Ta. On the other hand, the addition of an abrasive shows desirable results in the durability of the magnetic layer, but if a large amount is added to the magnetic layer in the hope of further improving this, the dispersibility, orientation, and filling of the magnetic powder will increase. There will be negative effects on sexuality.

Incidentally, in recent years, as the performance of recording media has improved, there has been a tendency to use magnetic powder as fine particles as possible as a recording element. Such fine particle powder has particularly poor dispersibility,
Furthermore, problems tend to occur in terms of the durability of the magnetic layer, and improvement of these is a serious issue for practical use.

Therefore, the present invention improves the dispersibility of the magnetic powder even when using the fine particle magnetic powder as described above.

It is an object of the present invention to provide a magnetic recording medium that has excellent orientation and filling properties, and also excellent durability of a magnetic layer, and highly satisfies both electromagnetic conversion characteristics and durability.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the inventors found that when a combination of two types of coupling agents is contained in the magnetic layer, the magnetic This invention was completed based on the knowledge that very good results were obtained in the dispersibility, orientation, and filling properties of the powder, and that the durability of the magnetic layer was also significantly improved.

That is, the present invention provides a magnetic recording medium in which a magnetic layer containing magnetic powder and a binder resin is provided on a non-magnetic support, in which both a titanate coupling agent and a silane coupling agent are contained in the magnetic layer. The present invention relates to a magnetic recording medium characterized by comprising:

[Structure and operation of the invention] In this invention, it is important to include both a titanate coupling agent and a silane coupling agent in the magnetic layer. Such effects cannot be obtained. That is, the effect of improving the dispersibility, orientation, and filling properties of the magnetic powder is not so great when using only a silane coupling agent, and the durability of the magnetic layer is not sufficient. Additionally, titanate coupling agents alone have poor dispersibility and filling properties for magnetic powders.

Although good results can be obtained in terms of orientation, etc., the effect of improving the durability of the magnetic layer is very low.

On the other hand, when both of the above coupling agents are used in combination as in this invention, not only can good dispersibility, orientation, and filling properties comparable to those of the titanate coupling agent be obtained, but also the titanate coupling agent A unique effect is exhibited in that the durability is further improved than when a silane coupling agent, which contributes to improving the durability of the magnetic layer, is used alone. Although the reason for this is not necessarily clear at present, it is presumed as follows.

In other words, the titanate coupling agent adsorbed on the surface of the magnetic powder has a good affinity with organic solvents due to its lipophilicity, increases the dispersibility of the powder in the magnetic paint, and also improves the filling property when it is formed into a coating. .

Although it gives good results for orientation, it has poor affinity with the binder resin, so using this coupling agent alone reduces the amount of resin adsorbed on the surface of the magnetic powder, and as a result, the amount of adsorption of the resin in the magnetic layer of the magnetic powder decreases. The bonding strength is weakened, resulting in decreased durability such as powder falling off.

On the other hand, the silane coupling agent that is adsorbed to the surface of the magnetic powder has a strong binding force with the binder resin, so it is effective to some extent in preventing the magnetic powder from falling off, but its high hydrophilicity Due to the dispersibility of magnetic powders such as titanate coupling agents, when this coupling agent is used alone.

It does not contribute much to improving orientation and filling properties.

However, when both of the above coupling agents are used together, the balance between lipophilicity and hydrophilicity on the surface of the magnetic powder becomes appropriate, and the binding force with the binder resin due to the silane coupling agent can be expected, so it is difficult to disperse the magnetic powder. In addition to the properties, orientation, and filling properties, a sufficient amount of resin adsorption onto the surface of the powdered rice is also ensured, resulting in magnetic recording that satisfies the electromagnetic conversion characteristics and at the same time highly improves the durability of the magnetic layer. medium can be obtained.

The titanate coupling agents used in this invention include a wide variety of conventionally known titanate coupling agents, including monoalkoxy type, chelate No. 100 tights (having oxyacetic acid residue), and chelate No. 1-200 type (ethylene glycol (having a phosphorus compound residue), coordinated type (a type in which a phosphorous ester is added to various tetraalkyl titanates to improve hydrolysis resistance and at the same time impart the function of a phosphorus compound), etc. can be used.

Examples of commercially available titanate coupling agents include Ajinomoto Co., Inc.'s product names KR-TTS and KR.
-9SSKR-38S, KR-41B.

KR-468, KR-55, KR-1385SKR-2
38S etc.

In addition, as silane coupling agents, alkoxysilane compounds having reactive groups such as amine groups, carboxyl groups, hydroxyl groups, epoxy groups, and groups such as polyalkylene oxide groups in the molecule have been conventionally used in various fields. Anything can be used. A specific example of a commercially available product is the product name KBC1003, K manufactured by Shin-Etsu Chemical Co., Ltd.
BM403, KBM603, KBM903, etc., product names Y9342, Y9338, A1 manufactured by Nihon Nijika Co., Ltd.
100°Y9187, A187, A151, etc.

In this invention, the ratio of the above-mentioned 9II% Y coupling agents is important in terms of achieving both electromagnetic conversion characteristics and durability, and should be appropriately determined depending on the individual types of both coupling agents. . Generally, the weight ratio of titanate coupling agent and silane coupling agent is 1:9 to 9.
:1, particularly preferably 3:1 to 7:3.

If too much titanate coupling agent is used, durability cannot be sufficiently improved, and if too much silane coupling agent is used, electromagnetic conversion characteristics will deteriorate.
Neither is preferable.

The content of both of the above vs'9g coupling agents in the magnetic layer is 0.5 to 20 parts by weight of the titanate coupling agent and 0.1 to 20 parts by weight of the silane coupling agent per 100 parts by weight of the magnetic powder. It is desirable that the amount is in the range of 20 parts by weight, and the total amount of both coupling agents is in the range of 0.5 to 20 parts by weight. If the amount of these coupling agents used is too large relative to the magnetic powder, there is a risk of impairing the surface smoothness of the magnetic layer or causing interlayer adhesion, and it may also be disadvantageous in terms of dispersibility and filling properties of the magnetic powder. This is not preferable because it may lead to negative results and it becomes substantially difficult to obtain the effect of improving electromagnetic conversion characteristics and durability.

In the present invention, any means may be used to incorporate both coupling agents in the above proportions into the magnetic layer. For example, a magnetic powder is pre-treated in an organic solvent in which both of the above-mentioned coupling agents are dissolved or dispersed to form a dry film of both of the above-mentioned coupling agents on the surface of the powder, and this treated powder is used to create a magnetic paint. There is a method in which a magnetic layer is formed by preparing a coating material and applying this coating onto a non-magnetic support such as a polyester film.

Alternatively, a method may be adopted in which both of the coupling agents described above are added and mixed into a magnetic paint, and the magnetic layer is formed using this paint in the same manner as described above.

In these methods, the order of addition of both coupling agents is not particularly limited. That is, in the method of forming a dry film of both coupling agents on the surface of the magnetic powder in advance,
Both coupling agents may be mixed and treated together, or only one of them may be used first and then the other coupling agent may be used for the same treatment.

The magnetic recording medium of the present invention is formed by forming a magnetic layer containing both a titanate coupling agent and a silane coupling agent on a nonmagnetic support as described above. As the magnetic powder and binder resin, the same ones as conventional ones can be used arbitrarily.

Examples of magnetic powder include γ-Fe20. Powder, Fe5
0, powder, oxide magnetic powder such as iron oxide powder in intermediate oxidation state, cobalt-containing iron oxide powder, CrO2 powder, barium ferrite powder, magnetic powder made of metals or alloys such as Fe, Co, Ni, etc. Can be mentioned. Although the particle size of these magnetic powders is not particularly limited, the present invention is particularly effective when applied to fine particle powders having a specific surface area of 40 rrr''/f;1 or more by nitrogen adsorption method.

Examples of the binder resin include vinyl chloride-vinyl acetate copolymer, vinylidene chloride-vinyl acetate copolymer,
Examples include polyurethane resins, polyester resins, epoxy resins, polyether resins, and incyanate compounds. The magnetic layer may further contain various additives such as known lubricants, antistatic agents, and abrasives.

[Effect of the invention 1 As described above, in this invention, by including both the titanate coupling agent and the silane coupling agent in the magnetic layer, even when using fine particles as the magnetic powder, , it is possible to provide a magnetic recording medium that is excellent in both electromagnetic conversion characteristics and durability.

[Example 1] Examples of the present invention will be described below to explain more specifically.

Example 1 Acicular cobalt-containing iron oxide magnetic powder I kg having a specific surface area of 43rrfiy-1 determined by nitrogen adsorption, a coercive force of 650 oersted, and a saturation magnetization of 75 emu/y, isopropyl alcohol 101, and a silane coupling agent ( Product name Y-9342) 300P manufactured by Nippon Unica Co., Ltd.
and titanate coupling agent (trade name K R38S, manufactured by Ajinomoto Co., Inc.) 200P are thoroughly stirred and mixed, dehydrated, and dried to form cobalt-containing particles with both of the above coupling agents coated on the particle surface. Iron oxide magnetic powder was obtained.

Using this treated powder, a magnetic paint was prepared with the following composition. This paint is applied onto a polyester film with a thickness of 13 mm to a thickness of 4 μm after drying to form a magnetic layer, and then subjected to surface treatment, cutting, etc., to produce a magnetic tape according to the present invention. did.

<Blend composition of magnetic paint> Treated magnetic powder 5oop Nitrocellulose 100y Polyurethane resin 80p Polyisocyanate compound 20y Myristic acid 24y n-Butyl stearate 8y (L-F
e203 powder 16yAj'203 powder
16y cyclohexanone 1,2
00y tor en
1,200y Example 2 In the blending composition of the magnetic paint of Example 1, untreated cobalt-containing iron oxide magnetic powder 800y was used in place of the treated magnetic powder 801; A magnetic tape was produced in exactly the same manner as in Example 1, except that the silane coupling agent 8y and titanate coupling agent 16p used in Example 1 were added.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that the amount of silane coupling agent used was changed to 500y and the use of titanate coupling agent was omitted.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1, except that the titanate coupling agent was changed to 500y and the silane coupling agent was omitted.

Comparative Example 3 The untreated cobalt-containing iron oxide magnetic powder was used instead of the treated magnetic powder 800y in the composition of the magnetic paint of Example 1, except that the surface treatment with the titanate coupling agent and the silane coupling agent was completely omitted. A magnetic tape was produced in exactly the same manner as in Example 1, except that 800y was used.

For each of the magnetic tapes according to Examples 1 and 2 and Comparative Examples 1 to 3, the magnetic properties include coercive force, squareness ratio (Br/B
s) and saturated residual magnetic flux density (Br), C/N ratio at 4 MHz as electromagnetic conversion characteristics, and steel characteristics as durability. The results are as shown in the table below. The still characteristics were determined by measuring the time required for the playback signal output (RF small output to become less than % of the initial output) when the tape playback was paused.

As is clear from the above results, the magnetic tape according to the present invention has good magnetic properties, excellent electromagnetic conversion properties, and excellent durability.

Patent applicant: Hitachi Maxell, Ltd. Representative: Patent Attorney Motokunio Negi゛--]shi-j

Claims (3)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder resin on a non-magnetic support, a titanate coupling agent and a silane coupling agent are both contained in the magnetic layer. A magnetic recording medium characterized by: (2) The magnetic recording medium according to claim (1), wherein the weight ratio of the titanate coupling agent to the silane coupling agent is in the range of 9:1 to 1:9. (3) With respect to 100 parts by weight of the magnetic powder, the titanate coupling agent is 0.5 to 20 parts by weight, the silane coupling agent is 0.1 to 20 parts by weight, and the total amount of both coupling agents is 0.5 to 20 parts by weight. The magnetic recording medium according to claim 1 or claim 2, wherein the amount is in the range of 5 to 20 parts by weight.