JPH0682457B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium having improved durability, particularly durability under high temperature and high humidity.

[Conventional technology]

Conventionally, for magnetic recording media such as audio tapes, video tapes, computer tapes, magnetic disks, etc., ferromagnetic fine powders such as ferromagnetic iron oxide and ferromagnetic alloy powders are contained in a binder on a non-magnetic support. Those provided with dispersed magnetic layers are mainly used.

Recently, with the development of technology in this field, there has been a demand for higher density and higher performance of magnetic recording media. Particularly, as a material for improving abrasion resistance, for example, polyurethane-based binder, What is blended with the resin of.

However, with this type of binder, blooming due to low molecular weight components causes magnetic heads and clogging,
It causes powder drop and causes dropout.

In order to solve these problems, polycarbonate polyester polyurethane (JP-A-58-60430) and polycarbonate polyurethane (JP-A-59-1953, JP-A-59-3053).
No. 13324) has been proposed as a binder. In addition, it has been proposed to use a fatty acid-modified silicone as a lubricant in order to improve wear resistance (Japanese Patent Publication No. 56-26890).

[Problems to be solved by the invention]

However, when polyester polyurethane is used, there is a problem that the film strength is lowered, and when polycarbonate polyurethane is used, the film strength and durability are improved, but the durability under high temperature and high humidity is slightly inferior. There was a problem.

Further, it has been proposed to use a polycarbonate polyurethane resin and an isocyanate curing agent as an attempt to further improve the film strength and durability (Japanese Patent Laid-Open No. 9830/1986).
Issue).

However, even in such an attempt, the durability under high temperature and high humidity conditions was still insufficient.

On the other hand, it is also known to use a fatty acid-modified silicone in combination with a usual polycarbonate polyurethane in order to lower the dynamic friction coefficient and improve the durability and blooming, but the durability under high temperature and high humidity was not sufficient.

Although the durability was improved to some extent by using the abrasives in combination, the durability under high temperature and high humidity was not sufficiently improved.

Accordingly, it is an object of the present invention to provide a magnetic recording medium having improved durability under high temperature and high humidity.

[Means for solving problems]

That is, the present invention provides a magnetic recording medium in which a magnetic layer having ferromagnetic fine powder dispersed in a binder is provided on a non-magnetic support, wherein the magnetic layer contains 1) a polycarbonate polyurethane resin as a binder, and 2) a fatty acid. A magnetic material containing a modified silicone and at least one of fatty acid ester, fatty acid amide, and α-olefin oxide as a lubricant as a lubricant, and 3) abrasive particles having a Mohs hardness of 6 or more. It is a recording medium.

The present invention has found that the combination of these three makes it possible to significantly improve the durability under high temperature and high humidity, which has never been predicted in the past.

Hereinafter, the present invention will be described in detail.

As the polycarbonate urethane used in the present invention, the polycarbonate polyester polyurethane as described above (JP-A-58-60430) and the polycarbonate polyurethane (JP-A-59-198530, 60-13324).
Used in the range of 10 to 90% by weight of the total binder.

The polycarbonate polyester polyurethane used in the present invention is a polyurethane comprising a polyol, a polyisocyanate, and, if necessary, a chain extender, and the polyol is a polycarbonate polyol, or
It is a polyester polyol composed of 1,10-decanedicarboxylic acid and a polycarbonate polyol. Polycarbonate polyol used here is polyhydric alcohol and phosgene, chloroformic acid ester, dialkyl carbonate,
It can be obtained by condensation with diallyl carbonate or the like.

Further, as the polyhydric alcohol, 1,10-decanediol, 1,6-hexanediol, 1,4-butanediol,
1,3-butanediol, neopentyl glycol, 1,5-
Examples include pentanediol.

As the polyisocyanate to be opposed to the above-mentioned polyol, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate, 0-tolylene diisocyanate and these There are addition compounds of isocyanates and active hydrogen compounds.

Further, the chain extender used as required above includes the above-mentioned polyhydric alcohols, aliphatic polyamines, aliphatic polyamines, aromatic polyamines and the like.

Further, the polycarbonate polyurethane used in the present invention is a polyurethane obtained by a urethanization reaction of a polycarbonate polyol and a polyvalent isocyanate,
The polycarbonate polyol and polyvalent isocyanate used here are the same as those mentioned above for the polycarbonate polyester polyurethane.

At the time of urethanization, other polyhydric alcohols and known chain extenders may be used in combination.

Polycarbonate polyurethane used in the present invention, in the presence of a solvent such as a catalyst and an amide-based, sulfoxide-based, cyclic ether, ketone-based, glycol ether-based, etc., as needed, the above-mentioned polyol and polyvalent isocyanate in a nitrogen atmosphere. It can be produced by reacting at 60 ° C to 100 ° C for several hours.

In the present invention, a thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof which has been conventionally used together with the above polycarbonate polyurethane resin can be used within the above-mentioned use range. These binders are described, for example, in JP-B-56-26890.

As the lubricant used in the magnetic layer in the present invention, a fatty acid-modified silicone and at least one kind of fatty acid ester, fatty acid amide and α-olefin oxide are used.

The total amount of binder is 15 to 50% by weight, preferably 20 to 40% by weight, based on the ferromagnetic fine powder.

Among binders, polycarbonate polyurethane resin is 10 ~
90% by weight.

Examples of the fatty acid-modified silicone include the following general formulas [I] and [I
The silicone represented by I] can be used.

In the above general formula [I], R ₁ and R ₂ are saturated or unsaturated hydrocarbon groups having 7 to 21 carbon atoms, and l is an integer of 0 to 50. In the above general formula [II], R ₃ , R ₄ and R _{5 each} have 7 to 21 carbon atoms.
The saturated and unsaturated hydrocarbon groups m and n are an integer of 0 to 80. Specific examples of the silicone represented by the general formula [I] include capric acid-modified silicone (R ₁ and R are —C ₇ H ₁₅ and 1 is 2).
), Myristic acid-modified silicone (R ₁ and R ₂ are -C ₁₃
H ₂₇ , where l is 2), behenic acid-modified silicone (R ₁ ,
R ₂ is —C ₂₁ H ₄₃ and 1 is 2, and oleic acid-modified silicone (R ₁ and R ₂ are —C ₁₇ H ₃₃ and 1 is 2) and the like. Specific examples of the silicone represented by the general formula [II] include oleic acid-modified silicones (R ₃ , R ₄ are -CH ₃ , and R ₅ is -CH ₃ .
C ₁₇ H ₃₃ with m of 80 and n of 8) and myristic acid-modified silicone (R ₃ , R ₄ and R ₅ of —C ₁₃ H ₂₇ with m of 73 and n of 25).

Examples of the fatty acid ester to be used in combination with the above fatty acid-modified silicone include ethyl stearate, butyl palmitate, hexyl laurate, butyl laurate, butyl myristate, and the like, and further, ptooxyethyl stearate, butoxybutyl stearate, ethoxyethyl stearate. , Ethoxybutyl stearate, butoxyethyl palmitate, and other alkoxy esters can be used. Examples of the fatty acid amide include stearyl amide, oleyl amide, erucyl amide, myristyl amide and the like.

As the α-olefin oxide, a compound represented by the following general formula [III] can be used.

In the above general formula [III], R ₆ represents an alkyl group having 10 to 30 carbon atoms.

The amount of these lubricants added is preferably 0.05 to 10% by weight of the ferromagnetic powder, the fatty acid-modified silicone is 0.1 to 5% by weight, and the other lubricant is 0.5 to 10% by weight of the ferromagnetic powder. .

The abrasive having a Mohs hardness of 6 or more used in the magnetic layer of the present invention has a function of remarkably improving durability, and α-alumina (α
-Al ₂ O ₃ ), fused alumina, chromium oxide (Cr ₂ O ₃ ), corundum, silicon nitride, boron nitride, silicon oxide, molybdenum carbide, boron carbide, tungsten carbide, etc., and the particle size is 5
It is preferably μm or less. Further, the addition amount thereof is preferably 0.1 to 20% by weight of the ferromagnetic powder.

If the amount of the abrasive is 0.1% by weight or less, the effect of the present invention is low, and if it is 20% by weight or more, the electromagnetic conversion characteristics are deteriorated.

As the ferromagnetic fine powder used in the present invention, γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , γ-FeOx (1.3
3 <x ≦ 1.50), Co-containing γ-FeOx (1.33 <x ≦ 1.5
0), CrO ₂ , Co-Ni-P alloy, C-Ni-Fe alloy, Fe-Ni
-Zn alloy, Ni-Co alloy, Co-Ni-Fe-Be alloy, plate-shaped hexagonal barium ferrite, and the like. The average particle size of these ferromagnetic fine powders is about 0.005 to 2 μm, and the axial length / axial width ratio is about 1/1 to 50/1. The specific surface area of these ferromagnetic fine powders is about 1 to 70 m ² / g.

In the present invention, various additives such as a dispersant and an antistatic agent can be added to the magnetic layer. These additives are described in, for example, Japanese Patent Publication No. 56-26890.

In the present invention, the above-mentioned ferromagnetic fine powder, lubricant, abrasive, and binder are kneaded together with other additives, if necessary, using an organic solvent, coated on a non-magnetic support and dried. To form a magnetic layer.

As the solvent for preparing the magnetic coating solution, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, a ketone-based solvent such as tetrahydrofuran, an alcohol-based solvent such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, and methylhexanol. Solvent, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate,
Ester-based solvents such as isopropyl acetate, ethyl lactate, glycol acetate, monoethyl ether, ether ethers, glycol dimethyl ether, glycol monomethyl ether, glycol ether solvents such as dioxane, fragrances such as benzene, toluene, xylene, cresol, chlorobenzene, and styrene. Group hydrocarbon solvents, chlorinated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene, and various solvents such as N, N-dimethylformamide and hexane .

Examples of materials that form the non-magnetic support include polyester resins, polyolefin resins, cellulose derivatives,
Examples thereof include polycarbonate-based resin, polyimide-based resin, and polyamide-imide-based resin. Also, depending on the application, non-magnetic metals such as aluminum, copper, tin and zinc, or non-magnetic metals containing these, plastics deposited with a metal such as aluminum, paper and paper coated with or laminated with polyolefins, etc. Paper can also be used. The form of the non-magnetic support is not particularly limited, but a sheet-like one is usually used. However, the non-magnetic support may have a film shape, a tape shape, a disk shape, a card shape, or a drum shape.

When a sheet-shaped non-magnetic support is used, the non-magnetic support is generally 2.5 to 100 μm, preferably 3 to 70 μm.
It has a thickness within the range of.

The non-magnetic support may be provided with a back coat layer on the surface on the side not provided with the magnetic layer.

The magnetic layer coated on the non-magnetic support is usually dried after a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment. Further, if necessary, surface treatment such as calender treatment is performed, and then cut into a predetermined size.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Part of the following composition was put in a ball mill and kneaded thoroughly, and then the rest was put in a ball mill and kneaded well, and desmoule L
7 parts of -75 (trade name of polyisocyanate compound manufactured by Bayer) was added and uniformly mixed and dispersed to prepare a magnetic coating material.

・ Co-containing γ-Fe ₂ O ₃ 100 parts (specific surface area 30m ² / g) ・ Vinyl chloride-vinyl acetate compound 12 parts (VMCH Union Carbide Co.) ・ Polyurethane Listed in table ・ Phenoxy resin (PKHH, Union Carbite Co.) ) 6 parts ・ Carbon black 10 parts (average particle size 120 mμ) ・ Abrasive material Listed in the appendix (Average particle size 0.45 µ) ・ Fatty acid modified silicone Listed in the appendix ・ Fatty acid ester or fatty acid amide or olefin oxide Listed in the appendix ・ Solvent MEK / Toluene / THF 200 parts (mixing ratio 3/4/3) -Isocyanate compound 10 parts A sample was prepared by coating, orienting, drying and calendering this magnetic coating on the surface of a 15 µm polyethylene terephthalate substrate whose viscosity was adjusted.

The polycarbonate polyurethane used in Example 1 was obtained in the same manner as in the synthesis example of the polycarbonate polyurethane in Example 1 of JP-A-60-13324, and the polycarbonate polyester urethane used in Example 2 was It was obtained by the same method as the synthesis example in Example 1 of JP-A-58-60430.

Performance tests were conducted on the above samples as follows, and the obtained results are shown in the following table.

[Adhesive strength]

Using a micro tableting machine manufactured by Hitachi, Ltd. as shown in the schematic diagram in FIG. 1, the magnetic surface of two sample tapes 1 and 1 having an area of 1.27 cm × 2.5 cm = 3.18 cm ^2. Insert the glass plate between the spacers 2 and 2 so that they fit together, and apply pressure of 60 kg / cm to crimp. After holding at 50 ° C. for 5 hours, both tapes are stretched in the direction parallel to the surface with a tensile tester to measure the adhesive strength. The unit is Kg / 3.18 cm ² .

[Method for measuring glossiness of magnetic layer surface]

According to JISZ 8741, the refractive index is 1.567 at an incident angle of 45 °.
The specular gloss of the glass surface was measured as 100%.

[Squareness ratio]

Use a vibrating sample type magnetometer (manufactured by Toei Industry Co., Ltd.), Br
I asked for / Bm.

[Measurement of dynamic friction coefficient]

50 g of the obtained video tape and stainless ball
Contact the tape with (T ₁ ) tension and tape
The tension (T ₂ ) required to run at a speed of m / sec was measured. The friction coefficient μ of the video tape is calculated from this measured value.

μ = 1 / π · lnT ₂ / T ₁ [Still characteristics] Video signal of image signal 50IRE is recorded, reproduced in still mode, and the reproduced RF output level is recorded by a recorder. It measured the time until it fell to 100.

In addition, in the above test, still durability, adhesive strength,
Regarding the friction coefficient, in order to confirm the effect of the present invention, thermo treatment (60 ° C, 80% (equivalent humidity), 7 days)
Tests were carried out on the prepared samples and those that had not been thermo-treated. Those having a high adhesive strength are not good because they are easily hydrolyzed to form a low molecular weight substance. The thermo treatment was carried out as an accelerated test of aging.

[Effects of the Invention] As is clear from the above results, when polycarbonate urethane, a specific lubricant and an abrasive having a Mohs hardness of 6 or more are used in the magnetic layer according to the present invention, the durability under high temperature and high humidity is high. It can be seen that the property (still durability) is improved.

In addition, in the present invention, it can be seen that the squareness ratio and the glossiness are almost the same as those of the comparative example, the adhesive strength and the friction coefficient are also low, and they hardly change even under high temperature and high humidity.

[Brief description of drawings]

FIG. 1 shows an apparatus for measuring adhesive strength according to an embodiment of the present invention.
It is the schematic which shows an example. 1 …… Sample 2 …… Spacer 3 …… Torque

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Kawamata 2-12-1, Ogimachi, Odawara, Kanagawa Fuji Photo Film Co., Ltd. (56) Reference JP-A-61-260421 (JP, A) 61-178728 (JP, A)

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer having a ferromagnetic fine powder dispersed in a binder on a non-magnetic support, the magnetic layer containing 1) a polycarbonate polyurethane resin as a binder, and 2) a fatty acid. A magnetic material containing a modified silicone and at least one of fatty acid ester, fatty acid amide, and α-olefin oxide as a lubricant as a lubricant, and 3) abrasive particles having a Mohs hardness of 6 or more. recoding media.