JPH08203061A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To maintain a stable adhesive strength by incorporating one aminoquinone structure among the aminoquinone structures expressed by general formulas I and II as a structural unit in one resin composition in a binder component of a magnetic layer. CONSTITUTION: The magnetic recording medium is composed by applying a magnetic layer containing a ferromagnetic powder. Then, at least one aminoquinone structure among the aminoquinone structures expressed by the general formulas I and II is incorporated as the structural unit in at least one resin composition in a binder (binder resin) component of the magnetic layer. And, in this case, the glass transition point Tg of the magnetic layer is +20 to 50 deg.C (or +50 to 80 deg.C or -180 to 120 deg.C).

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, in which particularly good electromagnetic conversion characteristics can be maintained for a long period of time and high-density recording capable of running and durability of a coating film can be achieved. It is intended to provide a magnetic recording medium.

[0002]

2. Description of the Related Art In a coating type magnetic recording medium, a magnetic coating material containing a binder (binder resin) and magnetic powder is coated on a support to form a magnetic layer. As the binder resin, a mixture of various resins is often used instead of a single resin. Conventional binder resins are poor in rust preventive property against metal magnetic powder such as metal powder, and the rust preventive property is left to the surface treatment of magnetic powder, but it is still insufficient.

[0003]

Recently, an aminoquinone compound having a high rust preventive property is introduced into a binder resin, and a binder resin excellent in rust preventive property of magnetic powder is being developed. However, even if these binder resins are excellent in rust prevention, when they are used in the magnetic layer of a magnetic recording medium, those satisfying dispersibility, coating film adhesion, running property and durability are obtained. The current situation is not. Further, in recent years, a magnetic recording medium capable of high-density recording is required to have improved runnability and durability of a coating film in order to maintain high magnetic characteristics and prevent the output of a recorded signal from being reduced by repeated use. ing.

The present invention solves the above problems and improves the rust preventive property of magnetic powder by introducing an aminoquinone compound, and is excellent in running property and durability. It is intended to provide a medium.

[0005]

In order to solve the above problems, the present invention focuses on the glass transition point Tg of a magnetic layer containing a binder into which an aminoquinone compound is introduced. In a magnetic recording medium obtained by coating a magnetic layer containing body powder, the following general formula (1-
1) and (1-2), at least one aminoquinone structure among the aminoquinone structures is contained in a constitutional unit, and the glass transition point Tg of the magnetic layer is +20 to + 50 ° C.
(Or +50 to + 80 ° C, or +80 to +120
C.) The magnetic recording medium is provided.

[0006]

[Chemical 1]

[0007]

The present invention is a magnetic recording medium comprising a non-magnetic support coated with a magnetic layer containing ferromagnetic powder,
In at least one resin composition in the binder (binder resin) component of the magnetic layer, the above-mentioned general formulas (1-1), (1)
-2), at least one of the aminoquinone structures represented by the formula (2) is contained in the structural unit, and the glass transition point Tg of the magnetic layer is +20 to + 50 ° C (or +).
50 to + 80 ° C., or +80 to + 120 ° C.).

A known material can be used as the ferromagnetic powder used. For example, γ-FeOx (x =
1.33 to 1.5), Co-modified γ-FeOx (x = 1.
33 to 1.5), fine particles of ferromagnetic alloy containing Fe, Ni or Co as a main component (75% or more), hexagonal ferrite such as barium ferrite and strontium ferrite can be used. These ferromagnetic powders include Al, Si, S, Sc, Ti, V, Cr, C in addition to the specified atoms.
u, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te,
Ba, Ta, W, Re, Au, Hg, Pb, Bi, L
a, Ce, Pr, Nd, P, Co, Mn, Zn, Ni,
It may contain atoms such as Sr and B.

The general formula (1) contained in the binder resin
The content of the aminoquinone structure represented by -1) or (1-2) is 0.01 to 40 wt%, preferably 0.1 to 30 wt% based on the total composition of the binder resin (based on the total binder).
%. Further, a known polar group may be introduced as a functional group for further improving dispersibility. General formula (1-
In 1) and (1-2), if N is nitrogen in the form of a tertiary amine, it is particularly effective in terms of anticorrosiveness against magnetic powder.

The support on which the magnetic layer is coated is not specified, but the surface roughness is 20 nm or less, preferably 15 nm.
It is preferably less than nm. This is because the surface roughness of the support affects the surface roughness of the magnetic layer. For the same reason, it is necessary to select an additive that does not affect the surface property of the additive used in the magnetic layer. Regarding the manufacturing method of magnetic recording media,
It is possible to manufacture using a conventionally known manufacturing method,
Regarding dispersion, it is desirable to carry out so-called "stiffening", in which kneading is performed in a state where the viscosity of the coating is high at the initial stage of dispersion. It is also desirable to adopt a method for obtaining a good surface in the calendering step for forming the surface property, for example, a method such as steel calendering.

As the resin used for the binder resin, known resins that can be used for magnetic recording media can be used. For example, polyester resin, polyurethane resin, vinyl chloride copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-styrene copolymer, polyvinyl butyral, cellulose derivative, phenol resin, phenoxy resin, epoxy resin, polyamide resin ,
Silicon resin and the like can be mentioned.

The aminoquinone structures represented by the general formulas (1-1) and (1-2) are introduced into the binder resin by the aminoquinone monomers represented by the following general formulas (3) and (4).
(In the formula, R1 has the same contents as in the general formula (1-1))

[0013]

Embedded image

Specific examples of the aminoquinone monomer include the following.

[0015]

Embedded image

Next, a method of introducing the aminoquinone structure into a polyurethane resin which is one composition of the binder resin will be described. The polyurethane resin can be produced from a polyol, a diisocyanate and optionally a chain extender by a production method known per se. (1) A method in which a part of the dicarboxylic acid component is used as a starting material for polyester polyol or the like.

[0017]

[Chemical 4]

(2) A method in which a part of the diol component is used as a starting material for polyester polyol or the like.

[0019]

Embedded image

(3) A method in which a polyvalent isocyanate is subjected to a condensation reaction and an addition reaction together with a polyol as a part of the diol component.

[0021]

[Chemical 6]

The above method can be considered as an introduction method, but there is no problem even if it is introduced by another method. In the present invention, examples of the polyol component having no aminoquinone structure used in the production of polyurethane resin include polyether diol, polyester diol, polycarbonate diol, polycaprolactone diol, and other known polyurethane production may be used. . As the diisocyanate component, known diisocyanate compounds such as 2,4-, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate and isophorone diisocyanate, or their It may be a polyisocyanate produced by condensation of isocyanates such as a reaction product with a polyalcohol. Known polyhydric alcohols as chain extenders,
Examples thereof include aliphatic polyamine and aromatic polyamine.

Although the method of introducing the aminoquinone structure into the polyurethane resin has been described, the method is not particularly limited to the polyurethane resin. The ratio of the resin having the aminoquinone structure introduced in the present invention in the total binder is preferably 10 to 80 wt%. There is no problem even if a known additive such as a lubricant is contained in the magnetic layer. Examples of the lubricant include liquid lubricants such as fatty acids, fatty acid esters, and silicone. The glass transition point Tg of the magnetic layer can be controlled by adjusting the ratio of the amount of various resins used as a binder, the type and amount of a curing agent such as isocyanate, and the temperature and time for curing the coating film. Also,
There is no problem even if it is performed by a method other than this.

Specific examples will be described below.
Here, a magnetic tape (DAT tape) having a back coat layer was prepared as a magnetic recording medium. First, an example in which the glass transition point Tg of the magnetic layer is +20 to + 50 ° C. will be described.

<Composition of magnetic paints used in Examples and Comparative Examples> 100 parts by weight of ferromagnetic alloy powder (composition: 94% Fe, 2% Ni 2 coercive force: 1600 Oe specific surface area: 55 m2 / g major axis length: 0. 2 μm) Binder: See Table 1 below for the addition amount and ratio of the following binder. Polyurethane A (number average molecular weight Mn 30,000, molecular formula (b) -based aminoquinone structure content of Chemical Formula 3 20
wt%) Polyurethane B (number average molecular weight Mn 30,000, content of molecular formula (d) type aminoquinone structure of the above chemical formula 20)
wt%)-Polyurethane C (number average molecular weight Mn 30,000, not including aminoquinone structure) -Vinyl chloride resin (other than Examples 6 and 7 manufactured by Zeon Corporation)
MR110) -Nitrocellulose (Asahi Kasei BTH1 / 2) Other additives-Isoamyl palmitate 2 parts by weight-α-alumina 3 parts by weight-Methyl ethyl ketone 100 parts by weight-Cyclohexanone 100 parts by weight Examples 1 to 7 in Table 1 are compared. The type and addition amount (parts by weight) of the binder resin used in Examples 1 to 3 are shown. The vinyl chloride resin used in Examples 6 and 7 has the same molecular formula (b) type aminonquinone structure of Chemical Formula 3 as the above vinyl chloride resin.
It is a vinyl chloride resin containing wt%.

[0026]

[Table 1]

After the above mixture was kneaded, mixed and dispersed by a sand mill, 4 parts by weight of Coronate L (manufactured by Nippon Polyurethane) was added and stirred to prepare a magnetic paint.
It was coated on a support to form a magnetic layer. Further, a back coat layer containing carbon black as a main component was provided on the surface of the support opposite to the surface on which the magnetic layer was provided. PET for the support
A (polyethylene terephthalate) film was used. The film-shaped medium thus prepared was cut into a width of 3.81 mm to obtain a magnetic tape (DAT tape) for a sample.

A DAT deck (XD-Z505 manufactured by Victor Company of Japan) was used to measure the electromagnetic conversion characteristics of the magnetic tape for sample. This measurement was performed by partially modifying the head amplifier on the deck. The modification is that the head amplifier is modified so that a signal is directly input to the head from the outside, and that the input / output signal of the head can be directly measured. The following measurements and evaluations were performed on the sample magnetic tape. A) To evaluate the stability over time, a storage test was carried out for 30 days in an environment of 60 ° C. and 90% RH, and evaluation was made by comparison with the initial value of the saturation magnetic flux density Bm (−ΔBm). B) Output drop measurement is 7 MH using the DAT deck.
After recording the z-sine wave signal and measuring the playback output,
This is an examination of deterioration of reproduction output after running 100 times in an environment of% RH. C) The adhesive strength was measured by the force required when the adhesive tape was evenly attached to the magnetic layer of the magnetic tape and peeled off. 6
The measurement was performed before and after the storage test for 30 days in an environment of 0 ° C. and 90% RH. (Equivalent to evaluation of coating film adhesion) The above evaluation results are also shown in Table 1 above.

From the results shown in Table 1, in Comparative Example 3 in which the binder resin (binder) does not contain an aminoquinone structure, the saturation magnetic flux density Bm after storage at high temperature and high humidity (-ΔBm) includes an aminoquinone structure. (Examples 1 to 7, Comparative Example 1,
It is much larger than 2). It is considered that this is because the rust preventive property of the binder resin against the magnetic powder is low. In Comparative Example 1 in which the glass transition point Tg of the magnetic layer is as low as 16 ° C., the coating film adhesion is very weak, and the output drop due to repeated running is extremely large, and there is a great problem in storage durability. On the other hand, in Comparative Example 2 in which the glass transition point Tg of the magnetic layer is as high as + 64 ° C., the coating film adhesion is weak, and the deterioration of the coating film adhesion after storage at high temperature and high humidity is particularly large as compared with each example. Further, the output reduction due to repeated running is larger than that of each example.

On the other hand, in Examples 1 to 7 containing the aminoquinone structure and the glass transition point Tg of the magnetic layer is in the range of 21 to 49 ° C., the saturation magnetic flux density Bm is extremely lowered even after storage at high temperature and high humidity. In addition to being small, a large coating film adhesive force can be maintained (that is, coating film durability is excellent), and further, output reduction after 100 runs is small. From the above, by introducing an aminoquinone compound, it is possible to improve the rust preventive property of the magnetic powder and maintain good electromagnetic conversion characteristics for a long period of time, and also it has excellent durability (especially stable adhesive strength with little change over time is maintained. It is understood that the glass transition point Tg of the magnetic layer should be 20 to 50 ° C. in order to obtain a magnetic recording medium (having good coating film durability).

Next, the glass transition point Tg of the magnetic layer is 50 to
An example in which the temperature is 80 ° C. will be described. Example 1 in Table 2
7 to 7 and Comparative Examples 1 to 3 (Example numbers and Comparative Example numbers are different from those shown in Table 1 and double in Table 1). (Same as those described in 1) and addition amount (parts by weight)
Indicates. The vinyl chloride resin used in Examples 6 and 7 is a vinyl chloride resin obtained by adding 20 wt% of the molecular formula (b) type aminonquinone structure of Chemical Formula 3 to the vinyl chloride resin.

[0032]

[Table 2]

The composition of the magnetic coating material used in the examples and comparative examples and the method for producing the magnetic tape for the sample are the same as those described above. Table 2 also shows the results of measurement and evaluation of the sample magnetic tape. Among the measurements and evaluations of the magnetic tape for samples, the evaluation of stability over time (-ΔBm) and the measurement of output reduction were performed in the same manner as in Table 1. For the measurement of the dynamic friction coefficient (μk) of the magnetic coating film, which is one index of the running property, a storage test was performed for 30 days in an environment of 60 ° C. and 90% RH, before storage (initial value).
And the values after storage were measured. Then, the degree of preservation of running property was evaluated.

From the results shown in Table 2, in Comparative Example 3 in which the binder resin does not contain an aminoquinone structure, the decrease in the saturation magnetic flux density Bm after storage at high temperature and high humidity contains an aminoquinone structure (Examples 1 to 7, Comparative Examples). It is very large compared to Examples 1 and 2. It is considered that this is because the rust preventive property of the binder resin against the magnetic powder is low. Glass transition point Tg of magnetic layer is 49 ° C
In Comparative Example 1, which has a low value, the initial value of the dynamic friction coefficient (μk) is larger than that of Examples 1 to 7, and the dynamic friction coefficient is further increased by storage at high temperature and high humidity. (Drivability deteriorates due to high temperature and high humidity storage) On the other hand, in Comparative Example 2 in which the glass transition point Tg of the magnetic layer is as high as 92 ° C., the output decrease after repeated running is larger than that in Examples. Further, the increase in the dynamic friction coefficient due to the high temperature and high humidity storage is larger than that in Examples 1 to 7. (Drivability deteriorates due to high temperature and high humidity storage)

On the other hand, in Examples 1 to 7 containing the aminoquinone structure and the glass transition point Tg of the magnetic layer is in the range of 53 to 78 ° C., the saturation magnetic flux density Bm is extremely decreased even after storage at high temperature and high humidity. At the same time, there is little increase in the dynamic friction coefficient μk (that is, excellent running performance can always be maintained with little change over time), and output reduction due to repeated running is also small. From the above, by introducing an aminoquinone compound, it is possible to improve the rust prevention of magnetic powder and maintain good electromagnetic conversion characteristics for a long period of time, and at the same time, it is possible to always maintain excellent running properties with little change over time. In order to obtain an excellent magnetic recording medium, the glass transition point Tg of the magnetic layer is 50 to 50.
It is understood that the temperature may be 80 ° C.

Next, the glass transition point Tg of the magnetic layer is 80 to
An example in which the temperature is 120 ° C. will be described. It is used in Examples 1 to 7 and Comparative Examples 1 to 3 in Table 3 (Example numbers and Comparative Example numbers are different from those shown in Tables 1 and 2 and Table 1 and Table 2.). The type of binder resin (the type of this resin is the same as that shown in Table 1) and the addition amount (parts by weight) are shown. The vinyl chloride resin used in Examples 6 and 7 is a vinyl chloride resin in which 20 wt% of the molecular formula (b) type aminonquinone structure of Chemical Formula 3 is contained in the vinyl chloride resin.

[0037]

[Table 3]

The composition of the magnetic coating material used in the examples and comparative examples and the method for producing the magnetic tape for the sample are the same as those described above. Table 3 also shows the results of measurement and evaluation of the sample magnetic tape. In measuring and evaluating magnetic tape for samples,
The evaluation of stability over time (-ΔBm) and the measurement of the reproduction output were carried out in the same manner as in Table 1, and both the initial value and the value after storage (or after running) were shown as the measured values.

From the results shown in Table 3, in Comparative Example 3 in which the binder resin does not contain an aminoquinone structure, an example in which the saturation magnetic flux density Bm after storage at high temperature and high humidity contains an aminoquinone structure (Examples 1 to 7, Comparative Example) It is very large compared to Examples 1 and 2. It is considered that this is because the rust preventive property of the binder resin against the magnetic powder is low. The glass transition point Tg of the magnetic layer is 73 ° C.
In Comparative Example 1, which is low, the reproduction output after 100 times of running has a large decrease compared to the Examples. This is considered to be because the mechanical strength of the magnetic coating film is lower than that in the example. In Comparative Example 2 in which the glass transition point Tg of the magnetic layer is as high as 125 ° C., although the decrease in the reproduction output after running 100 times is small, the reproduction output value itself is lower than that in the example. This is because the magnetic coating film has a high mechanical strength, but due to poor dispersion of the magnetic coating material, a large number of aggregates are generated and the surface roughness of the magnetic coating film becomes large, which causes
It is considered that this is because the spacing loss between the magnetic tape and the magnetic head increases.

On the other hand, in Examples 1 to 7 containing the aminoquinone structure and the glass transition point Tg of the magnetic layer is in the range of 81 to 118 ° C., the saturation magnetic flux density Bm is extremely lowered even after storage at high temperature and high humidity. In addition to having a small amount, the magnetic coating composition has excellent dispersibility, a reduction in reproduction output after running 100 times is small, and a magnetic layer having excellent mechanical strength with little change over time can be obtained. From the above, by introducing an aminoquinone compound can improve the rustproof property of the magnetic powder and maintain good electromagnetic conversion characteristics for a long period of time, and yet, the magnetic layer has excellent dispersibility,
It is understood that the glass transition point Tg of the magnetic layer should be 80 to 120 ° C. in order to obtain a magnetic recording medium with excellent output stability and a magnetic layer having excellent mechanical strength with little change over time.

[0041]

As described above, the magnetic recording medium according to the present invention has the following effects. (A) The magnetic recording medium according to claim 1, wherein the glass transition point Tg of the magnetic layer is set to 20 to 50 ° C., the aminoquinone compound is introduced to improve the rust preventive property of the magnetic powder and to provide good electromagnetic conversion characteristics for a long time. It can be retained and has excellent durability (particularly, stable adhesive strength with little change over time can be maintained and coating film durability is excellent).

(B) The glass transition point Tg of the magnetic layer is 50 to
The magnetic recording medium according to claim 2, which is set to 80 ° C., has an aminoquinone compound introduced thereinto to improve the rust preventive property of the magnetic powder and maintain good electromagnetic conversion characteristics for a long period of time, and also has excellent running property with little change with time. It can be held at all times and has excellent magnetic coating storage durability.

(C) The glass transition point Tg of the magnetic layer is 80 to
The magnetic recording medium according to claim 3, which is set to 120 ° C., has an aminoquinone compound introduced thereinto to improve the rust preventive property of the magnetic powder and maintain good electromagnetic conversion characteristics for a long period of time, and also has excellent magnetic layer dispersibility. Moreover, a magnetic layer having excellent mechanical strength with little change over time is obtained, and output stability is excellent.

Claims (3)

[Claims] 1. A magnetic recording medium comprising a support coated with a magnetic layer containing ferromagnetic powder, wherein at least one resin composition in the binder component of the magnetic layer has the following general formula (1): -1) and (1-2), at least one aminoquinone structure among the aminoquinone structures is contained in the constitutional unit, and the glass transition point Tg of the magnetic layer is +20 to +.
A magnetic recording medium having a temperature of 50 ° C. Embedded image 2. A magnetic recording medium comprising a support coated with a magnetic layer containing ferromagnetic powder, wherein at least one resin composition in the binder component of the magnetic layer has the above general formula (1). -1) and (1-2), at least one aminoquinone structure among the aminoquinone structures is contained in the constitutional unit, and the glass transition point Tg of the magnetic layer is +50 to +.
A magnetic recording medium having a temperature of 80 ° C. 3. A magnetic recording medium comprising a support coated with a magnetic layer containing ferromagnetic powder, wherein at least one resin composition in the binder component of the magnetic layer has the above general formula (1). -1), containing at least one aminoquinone structure among the aminoquinone structures represented by (1-2) as a constituent unit, and having a glass transition point Tg of the magnetic layer of +80 to +
A magnetic recording medium having a temperature of 120 ° C.