JPS6216236A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve surface smoothness, magnetic characteristics and electromagnetic conversion characteristic as well as running stability and to prevent drop-out by incor porating non-magnetic solid additive powder subjected to a surface treatment by a specific compd. together with magnetic powder and binder resin into a magnetic layer. CONSTITUTION:The surface of the non-magnetic solid additive powder of the magnetic layer which is provided on a substrate and is formed by incorporating the magnetic powder, non-magnetic solid additive powder and binder resin into said layer is treated with the silane coupling agent having the group expressed by the formula (R1 is an alkyl, R' is an alkylene, m is >=1, n is 0-5). Such silane coupling agent having an alkylene oxide group in the molecule is used as the surface treating agent for the additive powder, by which the dispersibility is improved without thickening a magnetic coating compd. in the stage of preparing such compd. and without generating the flocculated lumps of the solid additive powder. The magnetic layer having the excellent surface smoothness is thereby formed. The magnetic recording medium such as mag netic tape which has the excellent magnetic characteristics and electromagnetic conver sion characteristics, decreases the drop-out and has good running stability is thus obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a magnetic tape comprising a support and a magnetic layer containing magnetic powder, non-magnetic solid additive powder, and binder resin;
It relates to magnetic recording media such as magnetic disks.

[Prior Art] In this type of magnetic recording medium, α-F e203 powder, Al2O3
The durability and running stability of the magnetic layer are improved by incorporating non-magnetic solid additive powder such as powder, Ti02 powder, BaSO4 powder, etc. However, the above-mentioned solid additive powders generally have inferior affinity with binder resins compared to magnetic powders, and due to poor dispersion in the magnetic layer, they form agglomerates, impairing surface smoothness, and impairing magnetic properties and electromagnetic conversion. In addition to the drawbacks of frequent deterioration of properties and frequent dropouts, there is also the drawback that the original purpose of using this solid additive powder, particularly running stability, cannot be sufficiently improved.

By the way, as a means to improve the dispersibility of magnetic powder in the magnetic layer, it is often carried out to treat the surface of magnetic powder with a surface treatment agent, and a silane coupling agent is a particularly effective surface treatment agent. known (Japanese Unexamined Patent Publication No. 59-129938, No. 58-155703)
Publication No.). If such a surface treatment agent is applied to the nonmagnetic solid additive powder, that is, if the additive powder is surface treated with the treatment agent, the dispersibility of the solid additive powder in the magnetic layer is improved. It is expected that

[Problems to be Solved by the Invention] However, all of the above-mentioned conventionally known silane coupling agents have 7 amino groups and epoxy groups in the molecule.

Most of them have reactive groups such as incyanate groups, and such reactive groups are polar groups, such as carboxyl groups, which are usually supported on binder resins.

Because a chemical reaction occurs with hydroxyl groups, etc., the viscosity of the magnetic coating material increases abnormally, which may actually impair the dispersibility of the solid additive powder.

Therefore, the present invention uses a specific silane coupling agent that is completely different from the above-mentioned conventionally known surface treatment agents, and applies this to the non-magnetic solid additive powder to be added to the magnetic layer. The purpose of this invention is to obtain a magnetic recording medium such as a magnetic tape that has improved dispersibility of the agent powder in the magnetic layer, has excellent magnetic characteristics and electromagnetic conversion characteristics, has less dropout, and has good running stability. .

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the inventors discovered that a specific silane coupling agent having an alkylene oxide group in the molecule was used as a non-magnetic solid in the magnetic layer. When used as a surface treatment agent for additive powder, a magnetic layer containing an organic compound containing a specific group derived from the silane coupling agent can be formed on the surface of the additive powder together with the additive powder. (The affinity and dispersibility of the additive powder for the binder resin are greatly improved, and this improves the magnetic properties and electromagnetic properties.) The present invention was completed based on the knowledge that it is possible to obtain a magnetic recording medium that is superior in quality, has less dropout, and has good running stability.

That is, the present invention provides a magnetic recording medium in which a magnetic layer containing magnetic powder, non-magnetic solid additive powder, and binder resin is provided on a support, in which the surface of the non-magnetic solid additive powder in the magnetic layer is The part contains a group represented by the following formula; The present invention relates to a magnetic recording medium characterized by containing an organic compound.

[Structure and operation of the invention] In the present invention, a silane coupling agent is used to include an organic compound containing a group represented by the formula itl in the surface portion of the powder together with a non-magnetic solid additive powder in a magnetic layer. is the following formula; (wherein, R1, R2, R
3 is an alkyl group, R' is an alkylene group, l is an integer of 1 to 3, m is an integer of 1 or more, and n is an integer of 0 to 5).

This silane coupling agent does not have any reactive groups in its molecule that react with the binder resin, such as amine 7 groups, epoxy groups, incyanate groups, etc.
Even when a binder resin containing a reactive group such as a hydroxyl group, a carboxyl group, or an incyanate group is used, there is no risk of thickening of the magnetic paint.

Moreover, the above-mentioned silane coupling agent has the property of easily reacting and adsorbing on the surface of the non-magnetic solid additive powder by the hydroxyl group generated by hydrolysis of the alkoxy group (OR2 group) contained in the molecule. Due to this adsorption, an organic compound containing a small amount of the group represented by the formula (1) is deposited on the surface of the additive powder.The alkylene oxide structural portion represented by R'O in this deposit is formed on the surface of the additive powder. By adjusting the type of alkylene oxide and the number of moles added, good affinity for the binder resin and organic solvent can be imparted to the solid additive powder.For this reason, a variety of binder resins can be used. Even in this case, the dispersibility and dispersion stability of the non-magnetic solid additive powder are significantly improved.

Among the above-mentioned silane coupling agents that exhibit such effects, dialkoxy type agents in which r in the formula (2) is 2 or trialkoxy type agents in which l is 3 are preferred.

In addition, R' in the above formula [1), (21) is an alkylene group usually having 2 to 4 carbon atoms, and the repeating unit represented by R'0 is an ethylene oxide group, a propylene oxide group, and a butylene oxide group. It may be composed of a mixture of at least two of the above.When composed of a mixture, each unit may be random or a block, and if it is a block, the order of addition is not particularly limited. Further, m indicates the number of the above-mentioned repeating units, and is usually 1 to 30, preferably 5 to 15.

In addition, R1, R2, and R3 in the formula (11, +21) are alkyl groups usually having 1 to 3 carbon atoms, and the number of carbon atoms in each alkyl group may be the same or different.n
represents the number of repeating methylene groups (-cr-t2-), and can be arbitrarily selected from an integer of 0 to 5.

When n=o, a structure is adopted in which the alkylene oxide group (R'0) is directly bonded to the Si atom.

Such a silane coupling agent is also available as a commercial product, and the manufacturing method thereof is not particularly limited. For example, an alkylene oxide can be added to an alkoxysilane compound and then converted into an alkyl ether, or an alkylene group directly bonded to a Si atom can be introduced by an appropriate method before the addition reaction of the alkylene oxide. Obtainable.

In this invention, a non-magnetic solid additive powder is surface-treated using the above-mentioned silane coupling agent.

Through this treatment, the organic compound containing the group represented by the formula (+) derived from the silane coupling agent is uniformly deposited on the surface of the additive powder. 0.1 per 100 parts by weight
The amount is preferably 20 to 20 parts by weight, preferably 2 to 10 parts by weight. If the amount of this adhesion is too small, a sufficient effect of improving dispersibility cannot be obtained, and if it is too large, the surface smoothness of the magnetic layer will be impaired or the durability will be reduced, both of which are undesirable. As the non-magnetic solid additive powder, a non-magnetic inorganic powder having a particle size of about 0.05 to 4 PL and a Mohs hardness of 5 or more is used. For example, a-Fe203 powder, Al2O3 powder, TiO2 powder, Cr2O3 powder, mullite (3A77203/2SiO2) powder, aluminum titanate (A1203/Ti02) powder, BaSO4 powder, zircon (ZrO2HS 1o2) powder, forsterite (
2MgO-5iO2) powder, enstatite (MgO-5
i 02 bird, spodgy y--men (Li20-AfzO
3・4SiO, ) powder, eucryptite (L i20
- AJ203-2 S 102) powder, cordierite (2Mg0.2A1203.5Sioz) K saphirin (4Mgo.5A12o3.2sio2) powder, hetalite (Li20.AI!2o3.8sio2) powder, beryl (3BeO1'ke203H6SiOz) powder, Cell shift KBaO-AI! 203.2SiO□) powder and the like. This non-magnetic solid additive powder is usually used in an amount of 1 to 20 parts by weight per 100 parts by weight of the magnetic powder.

The surface treatment method is generally to prepare a solution by dissolving the silane coupling agent in an appropriate solvent, add non-magnetic solid additive powder to this solution, mix and disperse with a homomixer, etc., and then heat and dry. is preferably adopted. This method has the advantage that a uniform organic compound layer derived from the silane coupling agent can be deposited on the surface of the nonmagnetic solid additive powder.

Examples of solvents for dissolving the above silane coupling agent include water, alcohols having 1 to 5 carbon atoms, acetone, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, benzene, toluene, etc. Examples include aromatics and ethers such as tetrahydrofuran and dioxane. Among these, alcohols having 1 to 5 carbon atoms give particularly good results to the dispersibility of the final target non-magnetic solid additive powder. The concentration of the silane coupling agent in these solvents varies considerably depending on the type of solvent, but is generally between 0.1 and
2.0% by weight, particularly preferably 0.5-1% by weight.

The magnetic recording medium of the present invention is surface-treated with a specific silane coupling agent as described above, and the surface portion is expressed by the formula (1).
A magnetic paint is prepared by mixing and dispersing a non-magnetic solid additive powder to which an organic compound containing the group represented by is attached in an organic solvent together with a magnetic powder and a binder resin. It can be obtained by coating on a support to form a magnetic layer, or by performing commonly employed orientation treatment, mirror polishing treatment, cutting (punching) treatment, etc.

As the magnetic powder used here, any conventionally known magnetic powder can be used, such as T-Fe203 powder, Fe3
O4 powder, CO-containing T-Fe203 powder, Cd-containing Fe3
In addition to oxide magnetic powders such as O4 powder, hexagonal ferrite powders such as barium ferrite and strontium ferrite, metal powders such as Fe powders, Co powders, and Fe-Ni powders may be used.

, ch; (D'Mija powder 7 (1 needle "powder 0° 1", 6-shaped, granular, rice-crushed, etc.) shape.

In addition, in this invention, as described above, the surface of the non-magnetic solid additive powder to be added to the magnetic layer is treated with a specific silane coupling agent so that the specific organic compound is attached to the surface of the non-magnetic solid additive powder. However, if necessary, the magnetic powder may be further surface-treated with the same silane coupling agent as described above to produce the same effect as described above. According to this, even better results can be obtained by reducing magnetic properties, electromagnetic conversion properties, running stability, and dropouts. When surface-treating magnetic powder in this way, it is operationally convenient to mix the magnetic powder and non-magnetic solid additive powder and surface-treat both at the same time.

Next, as a binder resin for dispersing and binding the magnetic powder and non-magnetic solid additive powder, vinyl chloride-
Any of the binder resins commonly used in the past can be used, such as vinyl acetate copolymers, polyvinyl butyral resins, cellulose resins, polyurethane resins, polyester resins, and polyisocyanate compounds. Furthermore, various electron beam curable resins can also be used.

Further, as organic solvents for preparing magnetic paint, ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, Solvents suitable for dissolving the binder resin used are particularly suitable, such as alcohol solvents such as isopropyl alcohol, acid amide solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, and ether solvents such as tetrahydrofuran and dioxane. They may be used alone or in a mixture of two or more without any restriction.

Needless to say, it is possible to treat the surface with such magnetic powder, binder resin, organic solvent, and the silane coupling agent, and then attach a specific organic compound derived from the silane coupling agent to the surface. Additives commonly used in magnetic paints containing non-magnetic solid additive powder include
For example, a lubricant, an antistatic agent in the form of ultrafine particles such as carbon black, etc. may be added as appropriate. Furthermore, a silane coupling agent containing a functional group such as an amine 7 group, a hydroxyl group, an incyanate group, an unsaturated bonding group, etc. that reacts with a conventionally used binder resin is included within a range that does not impair the characteristics of the present invention. You can also do that.

〔Effect of the invention〕

As detailed above, in the present invention, the specific silane coupling agent is used as a surface treatment agent for the non-magnetic solid additive powder to be added into the magnetic layer, and is applied to the surface of the non-magnetic solid additive powder together with the additive powder. By incorporating a specific organic compound derived from the above-mentioned adhering silane coupling agent into the magnetic layer, the problem of thickening can be avoided even when various binder resins are used in the preparation of magnetic paints. The dispersibility of the solid additive powder can be greatly improved, and a magnetic layer with good surface smoothness in which the solid additive powder is uniformly dispersed without forming agglomerates can be formed, which improves the magnetic properties. Moreover, it is possible to provide a magnetic recording medium such as a magnetic tape that has excellent electromagnetic conversion characteristics, less dropout, and good running stability.

〔Example〕

Next, examples of the present invention will be described in more detail. In addition, in the following, parts shall mean parts by weight. Moreover, the silane coupling agents A to D used in the following examples and comparative examples are as follows.

<Silane coupling agent A> CH30 (-EO←PO云CH2→7Si÷0CH3)
3EO: Ethylene oxide PO: Propylene oxide <Silane coupling agent B> CH30÷poya←CH2yaS i +0CH3)3P
O: Propylene oxide (silane coupling agent C) CH30÷EO+F-+-CH2 large-5i÷0CH3)
.

EO: Ethylene oxide silane coupling agent D〉 H2N (-CI (, EL-5i + oc2H5) 3 Example I CL-Fe203 powder (average particle size 0.87")
Part 5 AI! 203 powder (average particle size 0.3μ)
3-part silane coupling agent A
19 isopropyl alcohol
10 (1) A dispersion consisting of the above components was mixed with a homomixer for 4
The mixture was mixed and dispersed for a period of time, allowed to stand still for 24 hours, and then filtered. Then,
The mixture was dried at 80'C for 15 hours to obtain a surface-treated mixed solid additive. The processing additives include α-Fe203 powder and A
I! 0.5 per 100 parts of each powder for both 203 powders
~2 parts of an organic compound derived from silane coupling agent A was uniformly adhered.

Using this processing additive, a magnetic paint was prepared by mixing and dispersing in a ball mill for about 100 hours with the following composition.

Surface treatment mixed solid additive 8 parts Co containing T
-Fe203 magnetic powder 100 parts Nitrified cotton 9 parts Polyurethane resin 8 parts Trifunctional low molecular weight incyanate compound 3 parts Myristic acid
3 parts cyclohexanone 90 parts
Le en
90 copies Next, the above magnetic paint was applied to a 12/'' thick polyester film to a dry thickness of about 3 μm, dried, mirror-treated, and then cut to a predetermined width.
A magnetic tape was made.

Example 2 Co-containing T-Fe203 magnetic powder 100 parts a
-Fe203 powder (average particle size 0.8,")
Part 5 AI! 203 powder (average particle size 0.3 units)
3-part silane coupling agent A
10 parts isopropyl alcohol 1
,000 parts A surface-treated mixed powder consisting of a surface-treated magnetic powder and a surface-treated mixed solid additive was obtained from the dispersion containing the above-mentioned components in the same manner as in Example 1. This treated powder includes co-containing T-Fe203 magnetic powder, α
0.5 to 4.5 parts of the organic compound derived from the silane coupling agent A per 100 parts of each powder was uniformly adhered to both the -Fe203 powder and the Al2O3 powder.

108 parts of this surface-treated mixed powder was mixed with 8 parts of the surface-treated mixed solid additive in the magnetic paint of Example 1 and Co-containing T.
A magnetic tape was produced in the same manner as in Example 1, except that 100 parts of -Fe203 magnetic powder was used.

Comparative Example 1 Surface treatment with a silane coupling agent was not performed, and surface treatment mixed solid additive 8 was added to the magnetic coating composition of Example 1.
A magnetic tape was produced in the same manner as in Example 1, except that 5 parts of untreated α-Fe203 powder and 3 parts of untreated Al2O3 powder were used instead of 3 parts of untreated α-Fe203 powder.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1, except that the same amount of silane coupling agent A was used instead of silane coupling agent A. In this case, when preparing the magnetic paint, the viscosity clearly increased compared to those of Examples 1 and 2.

Example 3 Ti02 powder (average particle size 0.5/ffi)
8 parts silane coupling agent B
1 part isopropyl alcohol
10 (1) A dispersion consisting of the above components was mixed with a homomixer for 4
The mixture was mixed and dispersed for a period of time, allowed to stand still for 24 hours, and then filtered. Then,
It was dried at 80° C. for 15 hours to obtain a surface-treated solid additive.

This processing additive contains 0.5 parts per 100 parts of TiO2 powder.
~2 parts of the organic compound derived from silane coupling agent B was uniformly adhered.

A magnetic tape was produced in the same manner as in Example 1, except that 8 parts of this surface-treated solid additive was used in place of 8 parts of the surface-treated mixed solid additive in the magnetic paint of Example 1.

Example 4 A magnetic tape was produced in the same manner as in Example 3, except that the same amount of silane coupling agent C was used instead of silane coupling agent B.

Comparative Example 3 (Surface treatment with silane coupling agent B was not performed, and surface treatment solid additive 8 was added to the composition of the magnetic paint of Example 3.
A magnetic tape was produced in the same manner as in Example 3, except that 8 parts of untreated TiO powder was used instead of 8 parts of TiO2 powder.

The magnetic properties, surface smoothness, C/N ratio, dropout, and running stability of each of the magnetic tapes of Examples 1 to 4 and Comparative Examples 1 to 3 were investigated. The results are shown in Table 1 and below. It was as shown in Table 2.

The magnetic properties are based on the square shape (Br/Bs) and the residual magnetic flux density (
Br) was measured. The surface smoothness was measured using a stylus surface roughness meter at a cutoff of 80P, and was expressed as center line average roughness (Ra). The C/N ratio was measured at a recording wavelength of 4 MHz, and in Example 1.2 and Comparative Examples 1 and 2, Comparative Example 1
For Examples 3 and 4 and Comparative Example 3, Comparative Example 3 was expressed as OdB (reference) and its relative value. In addition, the number of dropouts of 5 microseconds or more per minute was investigated, and the running stability was investigated by wow and flutter.

As is clear from the results shown in Table 1 and Table 2, the magnetic tape of the present invention has excellent magnetic properties and surface smoothness, good electromagnetic conversion characteristics expressed by the C/N ratio, and less dropouts. Moreover, it can be seen that the running stability is also excellent.

Claims (1)

[Claims] (1) In a magnetic recording medium in which a magnetic layer containing magnetic powder, non-magnetic solid additive powder, and binder resin is provided on a support, on the surface of the non-magnetic solid additive powder in the magnetic layer, The following formula; R_1O-(R'O■CH_2)-_nSi■...(
1) (wherein R_1 is an alkyl group, R' is an alkylene group, m is an integer of 1 or more, and n is an integer of 0 to 5). magnetic recording media.