JPS6173233A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesiveness between a magnetic layer and nonmagnetic base and to obtain a magnetic recording medium which obviates mingling of the magnetic layer and primer coating layer with each other in the stage of forming the magnetic layer by incorporating perfluoroalkylamine oxide into the primer coating layer. CONSTITUTION:The perfluoroalkylamine oxide to be used in the primer coating layer is a compd. having a fluoroalkyl group of about 3-15C in the molecule and provides a remarkable effect in improving the adhesiveness of the primer coating layer. Polyisocyanate and a binder having active hydrogen such as a hydroxyl group which can react therewith are used as the binder for the primer coating layer. Carbon black powder is used as a packing material. The paint for the primer coating layer formed by mixing and dispersing various components by a dispersing machine is diluted and is then coated on the nonmagnetic base; thereafter the coating is dried and cured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes and magnetic sheets used in audio and video equipment, computers, and the like.

Conventional Structures and Problems In recent years, each of these magnetic recording media has become suitable for high-density recording, and for this purpose, the recording wavelength has been shortened, the recording track thickness has been narrowed, and the recording medium has become thinner. For this reason, the signal-to-noise ratio, sensitivity, and frequency characteristics are generally disadvantageous, but as a countermeasure, the surface properties of the magnetic layer can be further improved by pulverizing the magnetic powder and using a highly smooth non-magnetic support. Methods such as increasing the filling of magnetic powder into the magnetic layer, and increasing the strength (Young's modulus, wear resistance) of the binder forming the magnetic layer have been adopted.

However, all of these countermeasures generally tend to reduce the adhesion between the magnetic layer and the non-magnetic support, resulting in the magnetic layer becoming more likely to fall off during use, increasing dropouts, etc. This not only causes deterioration of the characteristics of the magnetic recording medium, but also causes damage to the reproducing device by adhering to the magnetic head of the recording/reproducing device.

Various studies have been made in the past as measures to improve the decrease in adhesion between the magnetic layer and the nonmagnetic support. For example, a method in which corona discharge treatment is performed on the surface of a nonmagnetic support before forming a magnetic layer to improve adhesion with the magnetic layer, or a method in which a magnetic layer is formed after forming an undercoat layer on the nonmagnetic support. etc. are known. However, each of these methods has its own problems, and a magnetic recording medium with sufficient adhesion has not yet been obtained. Although improvements can be expected, as the processing conditions (discharge voltage, processing time, etc.) become stricter, phenomena such as thermal adhesion of the non-magnetic support and scattering of low-molecular compounds (volatile components) in the non-magnetic support may occur. Limits are rare because of this.

On the other hand, in the latter method of forming an undercoat layer, when the magnetic layer is applied, the undercoat layer already formed on the support is redissolved by the organic solvent used in the paint for the magnetic layer.
If the magnetic layer and undercoat layer partially mix together due to swelling, the homogeneity and surface properties of the magnetic layer will deteriorate.
This often had an adverse effect on electromagnetic conversion characteristics. Although this tendency can be improved by using a thermosetting resin for the undercoat layer and forming the magnetic layer after the undercoat layer has been sufficiently cured, it is possible to improve the undercoat layer during thermosetting. It has been difficult to put this into practical use because of the King phenomenon problem and a significant drop in productivity.

For the above reasons, there has been a strong desire for an undercoat layer that can efficiently improve the adhesion between the magnetic layer and the nonmagnetic support without adversely affecting the magnetic layer.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium in which a magnetic layer has excellent adhesion to a nonmagnetic support, and as a result, reliability and durability are improved.

Structure of the Invention The present invention provides a magnetic recording medium in which an undercoat layer containing a filler dispersed in a binder is formed on a non-magnetic support,
By containing perfluoroalkylamine oxide in the undercoat layer, the adhesion between the magnetic layer and the non-magnetic support is significantly improved, and the magnetic layer is not mixed with the undercoat layer during formation of the magnetic layer. This was done based on the fact that a recording medium could be obtained.

DESCRIPTION OF EMBODIMENTS Below, the magnetic recording medium of the present invention will be explained in more detail.

The perfluoroalkylamine oxide used in the undercoat layer, which is a feature of the present invention, has 3 to 1 carbon atoms in the molecule.
This compound has about 5 oo alkyl groups and is not only effective in improving the adhesion of the undercoat layer, but also has the effect of accelerating the reaction of thermosetting resins used in combination with conventional polyisocyanate compounds. are doing. From the above,
The binder for the undercoat layer of the present invention is preferably a binder having active hydrogen such as polyiso/anate and a hydroxyl group that can react with the polyiso/anate. Representative examples of these include polyurethane resins, polyester resins, vinyl chloride resins such as vinyl chloride/vinyl acetate/vinyl alcohol copolymer resins, and cellulose resins such as nitrocellulose. They can be used alone or in a mixed system. In addition, the filler used in the undercoat layer of the present invention is mainly used for the purpose of preventing blocking of the undercoat layer coating film, but it is also used to impart conductivity to the coating film, and V) light-shielding properties. Since this is often desired, it is desirable to use carbon blank powder as the filler. The perfluoroalkylamine oxide can be added in an amount of 1 to 10 parts by weight per 100 parts by weight of the mixed system. The preferred addition ratio is 2 to 5 parts by weight.

If necessary, a dispersant such as lecithin or other additives may be used in the undercoat film of the present invention within a range that does not impede the effect of the addition of perfluoroalkylamine oxide.

Formation of undercoat layer aS Conventionally known ball mill,
It is obtained by diluting an undercoating paint in which various components are mixed and dispersed using a dispersing machine such as a sand mill, as required, and then coating it on a non-magnetic support and drying and curing it.

The thickness of the undercoat layer is preferably 0.2 μm to 2.0 μm.

Hereinafter, the present invention will be specifically explained with reference to Examples.

It should be noted that all parts of component ratios stated in the Examples are by weight.

(Example 1) On the surface of a biaxially stretched polyethylene terephthalate film with a thickness of 14.0 μm, a film with a thickness of 0.3 μm having the composition shown below was applied.
A thick undercoat layer was formed.

(Undercoat layer composition) Polyurethane resin: 8 parts Nitrocellulose: Old 20 i Trifunctional low molecular weight incyanate compound: 18 parts Carbon black ( Manufactured by Tokai Carbon Co., Ltd., Geast S)
・Old...20 parts perfluoroalkylamine oxide (manufactured by Asahi Glass Co., Ltd., Surflon S-14
1) 6 parts Immediately after forming the above undercoat layer, apply a magnetic paint having the composition below and dry it to form a magnetic layer (thickness: 6.0 μm), then apply a magnetic tape according to the usual method. A sample was prepared.

(Composition of magnetic paint) Go-containing-Fe205 magnetic iron oxide powder...1
00 part Boliureta/1! Old...13 parts Vinyl chloride, vinyl acetate, 0 vinyl alcohol copolymer resin...6 parts Nitrocellulose resin...6 parts trifunctional low molecular weight Incyanate compound: 5 parts Soybean oil lecithin: 1 part: Butyl stearate: 1 part: Methyl ethyl ketone: 150 parts Toluene: 120 parts Ncrohexano/: 80 parts (Comparative Example 1)
) A magnetic tape sample was prepared in the same manner as in Example 1 except that the perfluoroalkylamine oxide was removed from the undercoat layer components of Example 1, and the same undercoat layer and magnetic layer as in Example 1 were formed.

(Example 2) After corona discharge treatment was applied to the surface of a biaxially stretched polyethylene terephthalate film with a thickness of 11.0 μm so that the contact angle with water was 45 degrees, a film with a thickness of 0.3 μm having the composition shown below was applied. An undercoat layer was formed.

(Undercoat layer composition) Polyester resin...100 parts Trifunctional low molecular weight incyanate compound...2 parts Carbon black (manufactured by Kabonoto BP2000)... ... 5 parts bar 70 loalkylamine oxide (manufactured by Asahi Glass Co., Ltd.,
Surfloor S-141)... 6 parts Immediately after forming the above undercoat layer, apply a magnetic paint having the same composition as in Example 1 and dry it to form a magnetic layer (thickness 0.6 μm). Tape samples (one portion 2 inches wide) were made.

(Comparative Example 2) A raw film obtained by forming the same undercoat layer as in Example 2 except that perfluoroalkylamine oxide was removed from the undercoat layer components in Example 2 was rolled up for 60 min.
'C, left to heat for 18 hours.

Next, a magnetic paint having the same composition as in Example 1 was applied onto the original film, and then a τ magnetic tape sample (each portion having a width of 2 inches) was prepared in exactly the same manner as in Example 2.

The following evaluation tests were conducted on the magnetic tape samples obtained in each of the above Examples and Comparative Examples.

(1) Adhesive strength of magnetic layer Comparison was made by reading the maximum load when the adhesive tape attached to the magnetic surface of each sample was peeled off at a constant speed.

(2) Number of dropouts Measuring the number of dopouts i, VUS method VTR.

A video signal was recorded using NY-8200 (manufactured by Matsushita Electric Industrial Co., Ltd.), and a momentary dropout (15ttB6Q, 16dB) of the reproduced output signal in the recorded portion was measured using a dropout counter. The numbers are average values per minute. The number of dross and knobouts was measured at the initial stage and after running 100 passes.

(3) Surface roughness of magnetic layer The surface roughness of the magnetic layer of each magnetic tape sample was measured using a stylus type surface roughness meter. The 10-point average roughness Rz was calculated based on the "surface roughness" of JIS B6o○1.

The evaluation test results for each magnetic tape sample are shown in the table below.

As is clear from the table above in the margin below, the magnetic tape with the undercoat layer containing perfluoroalkylamine oxide has high adhesive strength between the magnetic layer and the non-magnetic support, and the tape has good durability. , and the surface properties of the magnetic layer are also impaired.
1. do not have. Further, even if the formation of the undercoat layer and the magnetic layer are performed continuously, the characteristics of the undercoat layer can be fully exhibited, which is very convenient from the viewpoint of productivity of the magnetic tape.

Although magnetic tape has been described in the above embodiments, the present invention can be applied not only to magnetic tapes but also to other magnetic recording media such as magnetic disks and magnetic cards.
Needless to say.

Effects of the Invention As detailed above, the magnetic recording medium provided with the undercoat layer of the present invention has excellent durability without degrading the surface properties of the magnetic layer. There is a great practical value.

Claims (3)

[Claims] (1) A magnetic recording medium having an undercoat layer containing a filler dispersed in a binder formed on a non-magnetic support, characterized in that the undercoat layer contains perfluoroalkylamine oxide. magnetic recording media. (2) The magnetic recording medium according to claim 1, wherein the binder for the undercoat layer is at least a hydroxyl group-containing resin and a polyisocyanate compound. (3) The magnetic recording medium according to claim 1, wherein the filler for the undercoat layer is carbon black.