JP3125912B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium, and more particularly to a magnetic recording medium capable of high-density recording excellent in storage corrosion resistance and durability.

[0002]

2. Description of the Related Art In the field of magnetic recording, there is a strict demand for higher recording density in transition from analog recording to digital recording. Further, an increase in output is required due to an increase in track density. Further, in order to improve the volume recording density and prolong the recording time, the medium is made thinner (for example, the thickness of the magnetic tape is made thinner). Here, since the tape stiffness (stiffness) is proportional to the cube of the thickness, thinning the tape means a remarkable decrease in the tape stiffness. In order to maintain and improve the rigidity of the tape, it is necessary to improve the strength (Young's modulus and the like) of the magnetic layer, the base film, and the non-magnetic layer (including the back coat) which are the components of the tape. However, the strength of the base film is regulated by the material and the manufacturing method, and it is difficult to obtain a sufficient strength. Therefore, it is desired to improve the strength of the magnetic layer and the non-magnetic layer.

As another problem, there is a problem of rust prevention against magnetic powder. In a coating type magnetic recording medium, a binder (binder resin) in which various resins are mixed is used as a binder for the magnetic layer. However, a conventional binder is a metal magnetic powder suitable for high density and high output. Was poor in rust prevention against the oxidizing property of the magnetic powder. There is also a method of applying a surface treatment to the magnetic powder to improve rust prevention, but this method still does not have sufficient rust prevention.

[0004]

Recently, it has been proposed to introduce a certain kind of aminoquinone compound having high rust-preventive property into a binder in order to improve the above-mentioned problem of rust-preventive property. However, the binder into which the aminoquinone compound having the proposed structure is introduced has a sufficient affinity with the magnetic powder (not sufficient dispersibility of the magnetic powder) even though it has excellent rust prevention properties, At present, the rust preventive properties of the agent itself cannot be sufficiently exhibited as a magnetic recording medium. (Sufficient storage corrosion resistance has not yet been obtained.)

Further, the magnetic layer using the above-mentioned aminoquinone compound-containing binder has a problem that the mechanical strength (magnetic film strength, etc.) is greatly reduced and the stiffness, which is the rigidity of the magnetic tape, is greatly reduced. There is. (That is, the durability is reduced.) The reduction in the strength of the magnetic coating film, for example, lowers the running durability under still conditions in which the same portion is repeatedly run. In addition, a decrease in the strength of the magnetic coating film causes a decrease in storage durability such as heat resistance storage stability, a mark of a tape clamp during high-temperature and high-humidity storage, and a deterioration in surface properties due to transfer of the back surface of the base film. D / O (dropout) occurs frequently. As described above, a magnetic recording medium using a binder in which an aminoquinone compound having a proposed structure has been introduced has not been obtained that has both excellent storage corrosion resistance and durability.

According to the present invention, the dispersibility of the magnetic powder is good,
It can fully demonstrate the high rust prevention properties of aminoquinone compounds, and has excellent mechanical strength of the magnetic layer (magnetic coating).
It is an object of the present invention to provide a magnetic recording medium capable of achieving both excellent storage corrosion resistance and durability.

[0007]

Accordingly, in order to solve the above-mentioned problems, the present invention provides a magnetic recording medium comprising a support and a magnetic layer coated thereon, wherein at least one resin in the binder component of the magnetic layer is provided. In the composition, the following general formula (1-1),
A magnetic recording medium characterized in that at least one aminoquinone structure of the aminoquinone structures represented by (1-2) is included in a structural unit, and the Young's modulus of the magnetic layer is 16 to 25 GN / m ^2. To provide.

[0008]

Embedded image

[0009]

EXAMPLES The present inventors have conducted intensive studies on the aminoquinone structure in order to solve the above problems. as a result,
The binder (binder resin) containing at least one of the aminoquinone structures represented by the general formulas (1-1) and (1-2) has good magnetic powder dispersibility, and It has been found that high rust prevention properties as a compound can be sufficiently exerted, and that when a magnetic layer (magnetic coating film) is formed, mechanical strength is excellent. Furthermore, the present inventor considers the Young's modulus of the magnetic layer (magnetic coating film) to be 16 to 25 GN /
^{With m2} , a sufficient value is obtained as the stiffness, which is the rigidity of the magnetic recording medium, and the running durability is particularly improved.

Further, the present inventor has proposed that a magnetic recording medium having a so-called multi-layer coating film in which a non-magnetic layer is coated on a support and a magnetic layer is coated on the non-magnetic layer is also used as a binder for the magnetic layer. An aminoquinone structure represented by the above general formulas (1-1) and (1-2) is contained, and the Young's modulus of a multilayer coating film composed of a nonmagnetic layer and a magnetic layer is set to 16 to 25 GN / m ^2. As a result, it was confirmed that the same effect as the above effect was obtained.

Binder (binder resin) used in the present invention
A known binder used for a magnetic recording medium can be used. For example, polyester resin, polyurethane resin, vinyl chloride copolymer, acrylate-
Acrylonitrile copolymer, acrylate-styrene copolymer, polyvinyl butyral, cellulose derivative, phenolic resin, phenoxy resin, epoxy resin,
Examples include polyamide resin and silicone resin. For these resins,

[0012]

Embedded image

The polar group may be introduced in an appropriate amount. The content of the aminoquinone structure represented by the general formulas (1-1) and (1-2) contained in the binder resin (binder) is 0 relative to the total composition of the binder resin (based on the total binder). 0.1 to 40 wt%, desirably 0.1 to 30 wt%
%. Further, a known polar group may be introduced as a functional group for further improving dispersibility. The general formula (1)
In -1) and (1-2), if N is nitrogen in a tertiary amine form, it is particularly effective in terms of rust prevention against magnetic powder. The Young's modulus of the magnetic coating film can be changed by changing the type of chain extender of polyurethane, which is one type of binder, the amount of hardener added, the surface treatment of magnetic powder, the dispersant, the ratio of magnetic powder / binder, the other binder /
It can be adjusted by using a known technique such as a polyurethane ratio.

Hereinafter, specific examples (here, a magnetic tape having a back coat layer) will be described. <Example 1> 100 parts by weight of ferromagnetic alloy powder (composition: 70% of Fe, 30% of Co) Coercive force: 160 kA / m Specific surface area: 64 m ² / g, major axis length: 0.08 μm Binder Aminoquinone-containing 6.5 parts by weight of polyurethane resin (the content of the aminoquinone structure [R1: methyl group] of the above general formula (1-1) is 2 wt% and the resin contains -SO3H group at 0.08 mmol / g) Vinyl chloride resin 6.5 parts by weight (MR110 manufactured by Zeon Corporation)-α-alumina 3 parts by weight-palmitic acid 2 parts by weight-butyl myristate 1 part by weight-methyl ethyl ketone 100 parts by weight-cyclohexanone 100 parts by weight

After the above mixture was kneaded and mixed and dispersed by a sand mill, 4 parts by weight of a curing agent (Coronate L, manufactured by Nippon Polyurethane Co.) was added and stirred. The ferromagnetic alloy powder contains Al, Ti, V, C
r, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb,
Te, Ba, Ta, W, Re, Au, Hg, Pb, B
i, La, Ce, Pr, Nd, P, Co, Mn, Zn,
It may contain atoms such as Ni, Sr, and B. A magnetic paint was prepared in the above composition, and a 5.5 μm polyethylene naphthalate (PEN) film was used as a non-magnetic support, and the PEN film was coated with the magnetic paint. A back coat layer containing carbon black as a main component was provided on the side opposite to the magnetic layer, and the film medium was cut into a width of 6.32 mm to obtain a magnetic tape for a sample.

<Example 2> A magnetic tape is obtained in the same manner as in Example 1, except that the addition amounts of the polyurethane resin and the vinyl chloride resin as binders are each 10 parts by weight. Example 3 A magnetic tape is obtained in the same manner as in Example 1, except that the amounts of the polyurethane resin and the vinyl chloride resin as binders are each 8.3 parts by weight. Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that the amount of the curing agent was changed to 7.5 parts by weight. Example 5 A magnetic tape was obtained in the same manner as in Example 1, except that the amounts of the polyurethane resin and the vinyl chloride resin as binders were changed to 6.6 parts by weight and 10 parts by weight.

Example 6 A magnetic tape is obtained in the same manner as in Example 1, except that the aminoquinone structure contained in the polyurethane resin is changed to the aminoquinone structure [R 2: xylyl group] of the above general formula (1-2). <Example 7> In Example 1, an aminoquinone-containing polyurethane resin and a vinyl chloride resin (MR-110) were used instead of an aminoquinone-free polyurethane resin (UR8300 manufactured by Toyobo) and aminoquinone-containing vinyl chloride (the above-described general formula (1-1)). )), The content of the aminoquinone structure [R1: phenyl group] is 1.
5 wt%) to obtain a magnetic tape in the same manner. <Example 8> A magnetic tape is obtained in the same manner as in Example 1, except that the aminoquinone content of the aminoquinone-containing polyurethane resin is 27 wt%. Example 9 A magnetic tape was obtained in the same manner as in Example 1, except that the aminoquinone structure contained in the polyurethane resin was changed to the aminoquinone structure [R1: hydrogen] of the above general formula (1-1).

Comparative Example 1 A magnetic tape was obtained in the same manner as in Example 1, except that the addition amounts of the polyurethane resin and the vinyl chloride resin as binders were each 16.6 parts by weight. <Comparative Example 2> In Example 1, the vinyl chloride resin as the binder was replaced with an epoxy resin, and the added amounts of the polyurethane resin and the epoxy resin were 6.6 parts by weight and 10 parts by weight. A magnetic tape is obtained in the same manner except that the amount is 10 parts by weight. <Comparative Example 3> A magnetic tape is obtained in the same manner as in Example 1 except that the aminoquinone-containing polyurethane resin is changed to a aminoquinone-free polyurethane resin (UR8300 manufactured by Toyobo).

The magnetic layer Young's modulus of each magnetic tape is determined by measuring the Young's modulus of the entire magnetic tape and the Young's modulus of the nonmagnetic support (base film) using an Orientec universal tensile tester. It was calculated from the measured values.
For each of the following evaluations of the magnetic tapes, a V-VHS deck, a running system of HR-W1 manufactured by Victor Company of Japan, Ltd., and a video deck modified around the head were used. The magnetic head is a MIG head having a head gap of 0.25 μm.

The evaluation of the electromagnetic conversion characteristics was performed at a recording wavelength of 0.49.
A rectangular wave of μm was input and recorded on a magnetic tape, and the reproduction output was measured. Evaluation of aging stability (evaluation of storage corrosion resistance)
A storage test was performed for 30 days in an environment of 60 ° C. and 90%, and the reproduction output and the saturation magnetic flux density were measured before and after the storage test, and evaluated by comparing the initial value with the value after the storage. The still characteristics (evaluation of running durability) were such that the initial output was 0 dB and the output was -6.
The time to reach dB was measured up to 60 minutes. For 60 minutes, the output was not reduced to -6 dB or more, and there was no problem in the still reproduction. ○: The time until it became -6 dB was from 30 minutes to 60 minutes, and Δ: 10 minutes to 30 minutes. △
××, 10 minutes or less were evaluated as ×. The surface roughness SRa was measured using a non-contact surface roughness meter made by ZYGO. Table 1 shows the measurement results and the evaluation results.

[0021]

[Table 1]

As shown in Table 1, Comparative Example 3, in which the aminoquinone structure was not contained in the binder, had a large decrease in reproduction output and saturation magnetic flux density after storage at high temperature and high humidity, and had a problem in storage corrosion resistance. Contains an aminoquinone structure, but has a Young's modulus of 14 GN /
Comparative Example 1, which is as small as ^{m 2} , has a small reduction in reproduction output and saturation magnetic flux density after storage at high temperature and high humidity, but has a problem in still characteristics. Comparative Example 2, which contains an aminoquinone structure, but has a magnetic layer Young's modulus of 28 GN / m ^{2, which} is slightly larger than that of each of the Examples, although there is no decrease in reproduction output and saturation magnetic flux density after storage at high temperature and high humidity. There's a problem.

On the other hand, the general formulas (1-1) and (1)
In each of the examples containing at least one aminoquinone structure among the aminoquinone structures represented by -2) in the binder, the initial values of the reproduction output and the saturation magnetic flux density were sufficient, and furthermore, after storage at high temperature and high humidity. Since the reproduction output and saturation magnetic flux density of the magnetic layer are small, the dispersibility of the magnetic powder in the magnetic layer is good and the magnetic layer is excellent in rust prevention. (Because the dispersibility of the magnetic powder in the binder is improved, the high rust-preventive property of the binder itself containing the aminoquinone structure is sufficiently exerted on the magnetic powder, resulting in a magnetic layer having high rust-preventive properties. In each of the examples, the Young's modulus of the magnetic layer (magnetic coating film) was set to be in the range of 16 to 25 GN / m ² , whereby the magnetic layer (magnetic coating film) was excellent in the still property and the stiffness indicating the tape rigidity. Sufficient value is obtained and running durability is excellent. Further, each embodiment is a medium having a smooth surface.

[0024]

According to the magnetic recording media of the first and second aspects, the dispersibility of the magnetic powder in the magnetic layer is good, the rust resistance of the magnetic layer is high, and the magnetic layer (magnetic coating film) It has excellent mechanical strength and can achieve both excellent storage corrosion resistance and running durability.

Continuation of front page (56) References JP-A-5-242451 (JP, A) JP-A-3-73415 (JP, A) JP-A-4-1915 (JP, A) JP-A-5-298654 (JP) JP-A-8-167135 (JP, A) JP-A-8-185621 (JP, A) JP-A-8-194938 (JP, A) JP-A-8-203061 (JP, A) JP-A-8-213224 (JP, A) JP-A-8-231923 (JP, A) JP-A-8-221739 (JP, A) JP-A-6-162485 (JP, A) JP-A-8-87735 (JP, A A) JP-A-8-279140 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/702 C09D 5/23 C09D 179/02 C09D 179/04

Claims (2)

(57) [Claims] 1. A magnetic recording medium comprising a support and a magnetic layer coated thereon, wherein at least one resin composition in the binder component of the magnetic layer contains the following general formula (1-1), (1-2) )
A magnetic recording medium comprising at least one aminoquinone structure among the aminoquinone structures represented by the following formula in a structural unit, and wherein the magnetic layer has a Young's modulus of 16 to 25 GN / m ² . Embedded image 2. A magnetic recording medium comprising a non-magnetic layer coated on a support and a magnetic layer coated on the non-magnetic layer, wherein at least one resin composition in the binder component of the magnetic layer is used. A multilayer coating film comprising at least one aminoquinone structure of the aminoquinone structures represented by the following general formulas (1-1) and (1-2) as a structural unit, and comprising the nonmagnetic layer and the magnetic layer: Wherein the Young's modulus of the magnetic recording medium is 16 to 25 GN / ^m2 . Embedded image