JPS63103416A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the surface smoothness, durability, magnetic characteristics, etc., of a magnetic layer by forming a binder resin of a polyurethane resin having an amino group at the main chain and/or side chain alone or a mixture composed of said resin and other binder resin. CONSTITUTION:The binder resin is formed of the polyurethane resin having the amino group at the main chain and/or side chain alone or the mixture composed of said resin and the other binder resin. Such specific polyurethane resin may be prepd. by any methods and is more preferably formed by using polyol having primary tertiary amino groups of amino group made into quater nary amino group at the time of forming the polyurethane resin by using a chain extender at need from polyol and org. polyisocyanate compd. in accor dance with the conventional method. A high degree of the surface smoothness and the uniform dispersibility of magnetic particles are thereby attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks. The present invention relates to a high-performance magnetic recording medium with excellent performance.

(Prior Art) Conventionally, magnetic recording media used in audio equipment, video recorders, computers, etc. are composed of magnetic particles Y, a binder resin, and a press solvent on a magnetic support such as a polyester film. Obtained by forming a magnetic layer from magnetic paint.

Such a magnetic layer is formed by applying or transferring a magnetic paint in which magnetic particles Y are dispersed in a solvent containing a binder resin to a non-magnetic support. .

Conventionally, binder resins include polyester resins,
Cellulose resins, polyurethane resins, phenolic resins, epoxy resins, polyamide resins, acrylic esters, methacrylic esters, styrene, acrylonitrile, butadiene, vinyl esters, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, etc. Although polymers or copolymers have been used, a magnetic layer with sufficient surface smoothness, dispersibility, durability, and magnetic properties has not been obtained.

In particular, polyurethane resins are highly durable, but
1', the interaction with the particles was weak, making it difficult to obtain sufficient dispersibility and surface smoothness. This is because these magnetic particles have a strong cohesive property in an organic solvent, and therefore it is impossible to obtain a stable magnetic paint or a magnetic recording medium as is.

For this purpose, various dispersants have been proposed and used in order to improve the dispersion stability of magnetic particles.

(The invention or the problem the problem is being solved) However,
Conventional dispersants cannot overcome the strong cohesive force of electrical particles, and once dispersed magnetic particles re-agglomerate within a short period of time, so they must be used immediately after preparing the magnetic paint. There are various drawbacks in terms of the quality of magnetic coatings and magnetic recording media.

Historically, even with this method, conventional dispersants contain small to medium molecules -9 that differ in terms of Tτ from the binder resin used.
Because it is an organic compound, it migrates to the surface of the magnetic layer after it is formed, causing problems that damage the recording head.

Therefore, there is a strong demand for a binder resin that can overcome the strong cohesive force of magnetic particles and provide a stable magnetic paint and eventually a magnetic recording medium without using large amounts of dispersants that cause problems such as those described in F. .

As a result of intensive research in order to solve the drawbacks of the prior art as described above and to meet the demands as described in L., the present inventor has discovered that when using a specific binder resin in the magnetic paint used in the production of magnetic recording media, The present invention was completed based on the finding that the above-mentioned drawbacks of the prior art can be solved without substantially using dispersants that cause various problems.

(Means for Solving the Problems) That is, the present invention provides a magnetic recording medium in which a magnetic layer in which @ particles are dispersed in a binder resin is provided on a non-magnetic support. The present invention is a magnetic recording medium characterized by being made of a polyurethane resin having amino groups in the t-chain and/or side chain, alone or in a mixture with other binder resins.

To explain the present invention in more detail, the binder resin used in the present invention and which primarily characterizes the present invention is a polyurethane resin having an amino group in the t-chain and/or side chain.

Such a specific polyurethane resin may be prepared by any method, but a preferred manufacturing method is to prepare a polyurethane resin from a polyol and an organic polyisocyanate compound according to a conventional method, using a 3N extender as necessary. During production, primary to tertiary amino groups or
It can be produced by using a polyol having graded amino groups. Particularly preferred polyols having such an amino group in the present invention include those represented by the following general formula (1) or (2).

R-r-N-R6 R,, R2 and R4 in the above formula are -((:ll□to or -((:lI□Cl1R70) n-(n is 1 to 3
0 and R7 is a hydrogen atom or a methyl group), and R3, R5 and R6 are C3 to C2° alkyl groups.

As having the structure shown in (1) above, N-methyljetanolamine, N-ethyljetanolamine, N-propyldibrobanolamine.

N-butyldibrobanolamine, N-bentyldibutanolamine, N-cyclohexylgetanolamine, etc., or those to which alkylene oxides such as ethylene oxide and propylene oxide or caprolactones such as ε-caprolactone are added, Further examples include those obtained by adding the above alkylene oxide or caprolactone to methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, etc.

Those having the structure shown in (2) include 3-dimethylaminopropylamine, 3-dimethylaminobutylamine, 3-diethylaminopropylamine, 4-sibrobylaminodetramethyleneamine, 6-sibutylamino Examples include those obtained by adding alkylene oxides such as ethylene oxide and propylene oxide, and caprolactones such as ε-caprolactone to substances having primary and tertiary amino groups such as hexamethylene diamine.

1-The amino group-containing polyol may be used alone or in combination with conventionally known general polyols, and when used in combination, the amino group-containing polyol accounts for 1% of the entire polyol. It is preferable that the polyol accounts for at least 1% by weight.As such other polyols, preferable examples include
For example, polyethylene adipate, polyethylene propylene adipate, polyethylene butylene adipate, polydiethylene acybate, polybutylene adipate, polyethylene succinate, polybutylene succinate, polyethylene sebacate, polybutylene sebacate, with a molecular weight of 300 to 4,000. carbonate, polytetramethylene ether glycol, poly-ε-caprolactone diol, polyhexamethylene adipate, carbonate polyol, polypropylene glycol, and the like.

The organic polyisocyanate used in the present invention is
It is a compound having at least two isocyanate groups in an aliphatic or aliphatic compound, and has been widely used as a synthetic raw material for polyurethane resins.

Any of these known organic polyisocyanates are useful in the present invention. Particularly preferred organic polyisocyanates are as follows: toluene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3 -phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate-diphenyl ether.

Mesitylene diisocyanate, 4.4-methylenebis(phenylisocyanate), shrylene diisocyanate, 1.5-naphthalene diisocyanate, henzidine diisocyanate, 0-nitrobenzidine diisocyanate, 4.4-dibenzyl diisocyanate, 1.4-tetramethylene diisocyanate, 1.6-tetramethylene diisocyanate, 1.10-decamethylene diisocyanate, 1.4
- Cyclohexylene diisocyanate, xylylene diisocyanate, 4.4-methylenebis(cyclohexylisocyanate), 1.5-detrahydronaphthalene diisocyanate, and adducts of these 41 polyisocyanates with other compounds can also be used. .

As a chain extender, ethylene glycol, Propylene glycol, diethylene glycol, 1.4-butanediol, 1.6-hexanediol, ethylenediamine, 1.2-propylene diamine, trimethylenediamine, tetramethylenediamine, hexamethylene diamine, decamethylene diamine, isophoronediamine, m-xylylenediamine, Examples include hydrazine and water.

The magnetic recording medium of the present invention uses 1. as a binder resin for forming a magnetic layer. A special feature is the use of a specific binder resin as described above, and a particularly preferred one has a molecular weight of approximately 30,000 to 500,000. Furthermore, in the present invention, when using the above-mentioned specific binder resin, conventionally known binder resins can be used in combination in any proportion.

Examples of binder resins that can be used in combination include vinyl chloride resins and vinylidene chloride resins.

Vinyl chloride/vinyl acetate/vinyl alcohol copolymer resin, alkyd resin.

Epoxy resin, acrylonitrile-butadiene resin, polyurethane
V-resin, polyurea resin, nitrocellulose resin, polybutyral resin, polyester resin, silicone resin, melamine resin.

urea resin, acrylic resin, Examples include polyamide resins.

These resins can be used alone or as a mixture, and in forming the magnetic layer, they are used in the form of a magnetic paint, which may be a solution or a dispersion in an organic solvent.

The organic solvent may be any inert organic solvent. For example, preferred organic solvents include methyl ethyl ketone, methyl-n-propyl ketone, methyl isobutyl ketone, diethyl ketone, methyl formate, ethyl formate, propyl formate, Methyl acetate, ethyl acetate, butyl acetate, acetone, cyclohexane, tetrahydrofuran,
Dioxane, methanol, ethanol, isopropyl alcohol, butanol, methyl cellosolve, butyl cellosolve, cellosolve acetate, dimethyl formamide, dimethyl sulfoxide, pentane, hexane, cyclohexane, heptane, octane, mineral spirits,
Examples include petroleum ether, gasoline, benzene, toluene, xylene, chloroform, carbon tetrachloride, chlorobenzene, perchlorethylene, trichlorethylene, and the like.

The magnetic particles used in the present invention include, for example, iron, chromium, nickel, cobalt, alloys or oxides of iron, and modified products thereof, specifically, for example, γ
-Fe2O3, ferrite magnetite, CrO2, etc.
Examples include a bertolide compound of cobalt-doped γ-Fe2O3 and Fe, 04.

The magnetic particles shown below are just examples, and various types of magnetic particles other than those exemplified in F can of course be used in the same manner in the present invention, and C can also be used as a mixture.

The magnetic paint used to form the magnetic layer in the present invention has the above-mentioned components as essential components, and the proportions used are the same as in the conventional magnetic paint of magnetic particles.For example, the total magnetic paint is 100 parts by weight. In this case, the magnetic particles account for about 10 to 50% by weight, the medium accounts for about 50 to 90% by weight, and the binder resin generally ranges from about 5 to 20% by weight. .

As long as the magnetic paint used in the present invention contains these components as essential components, it may also contain other subcomponents other than those mentioned above, such as pigments,
It may contain arbitrary additives such as extender pigments, plasticizers, antistatic agents, surfactants, lubricants, crosslinking agents, anti-aging agents, stabilizers, foaming agents, and antifoaming agents.

The method for producing the magnetic paint used in the present invention, which consists of essential components and optional components as described below, may be any conventionally known method, and generally involves ball milling while adding the necessary components simultaneously or sequentially. , mixer processing, roll milling, bead milling, gravel milling, sand milling.

Mixing and dispersing methods such as high speed impeller processing are preferred.

Such a dispersion method itself requires the magnetic 17 to be dispersed.
Conditions vary depending on the type of T, size, purpose, etc., but generally it is sufficient to treat it at a temperature of room temperature to 100°C for about 5 minutes to 20 hours.

In addition, any conventionally known non-magnetic support can be used, such as polyester film, polypropylene film, cellulose triacetate film, cellulose diacetate film, polycarbonate film, etc. with a thickness of 5 to 50 μm. It can be used for.

The magnetic layer can be formed by applying a magnetic coating as shown in the figure on at least one side of the support as shown in the figure L, using any method such that the J′ when dried is preferably about 0.5 to 20 μm. It can be formed by coating and then drying. In addition, 1) Apply magnetic paint as described in t1 to a base sheet such as release paper.
The magnetic layer may be formed by coating and drying the magnetic layer on a non-magnetic support, and then transferring the magnetic layer to a non-magnetic support using a transfer method. The coating method, drying method, rolling method, etc. may be any conventionally known method.

(Function/Effects) The magnetic recording medium of the present invention obtained as described above has excellent surface lubricity, electromagnetic conversion characteristics, and uniform dispersion of the magnetic layer that have never been seen in the prior art. It shows excellent durability.

Such a remarkable effect can be obtained by using a polyurethane resin having an amino group in the main chain and/or side chain as described in 1) as the binder resin used in the present invention to form a magnetic recording medium. Depends on what you did.

That is, even in the conventional technology, L of polyurethane resin
Attempts have been known to improve the affinity for magnetic particles by directly introducing hydrophilic groups such as carboxyl groups or sulfonic acid groups into the chains, thereby achieving high dispersibility of the magnetic particles. Such conventional modified polyurethane resins could not achieve satisfactory uniform dispersibility or excellent surface smoothness of the magnetic layer.

In addition, in the present invention, as a result of using such a specific polyurethane resin as a binder resin, the magnetic particles can be uniformly and stably dispersed even without the use of a dispersant that causes various problems as in the prior art. When a magnetic coating is obtained, and a magnetic layer is formed on a non-magnetic support using this magnetic coating, a previously unknown level of high surface smoothness and uniform dispersion of magnetic particles can be achieved. As a result, various problems caused by the lack of surface smoothness and the presence of dispersants in the prior art have been solved.

Next, the present invention will be explained in more detail with reference to Examples. In addition, unless otherwise specified, parts or percentages in the text refer to weights.
It is a standard.

Example 1 300 parts of polycaprolactone, 1.
30 parts of 3-butanediol, 16 parts of polyoxypropylene dimethylaminopropylaminoether, 4.4'-
130 parts of diphenylmethane diisocyanate and 884 parts of methyl ethyl ketone were mixed and reacted at 80 to 85°C for 8 hours to obtain the amino group-modified polyurethane resin (I) used in the present invention. This polyurethane resin had a molecular weight of about 70,000.

Example 2 Nitrogen introduction tube, thermometer, stirrer, and 1 equipped with a distillation tube 2
Polycarbonate polyol 30 in a little flask
0 parts, 30 parts of 1,4-butanediol, 220 parts of dimethylaminopropylaminopolycaprolact, 90 parts of 2,4- and 2,6-dolylene diisocyanate (80/20 mixture), and 817 parts of methyl ethyl ketone,
The reaction was carried out at 80 to 85°C for 8 hours to obtain the amino group-modified polyurethane resin (II) used in the present invention. This polyurethane resin had a molecular weight of about 70,000.

Example 3 Polycarbonate polyol 2 was placed in a 2 liter flask equipped with a nitrogen inlet tube, thermometer, stirrer and distillation tube.
50 parts, 1,3-butanediol 25 parts, N-methyljetanolamine 7.5 parts, 4,4'-diphenylmethane diisocyanate 118 parts, methyl ethyl ketone 74 parts
4 parts were mixed and reacted at 80 to 85°C for 8 hours to prepare the amino group-modified polyurethane resin (III) used in the present invention.
) was obtained. This polyurethane resin has a min-7' content of approximately 7
It was 0,000.

Example 4 300 parts of polybutylene adipate was added to a 2-liter flask equipped with a nitrogen inlet tube, a thermometer, a stirrer, and a distillation tube.
1.3-butanediol 30 parts, polyoxypropylene dimethylaminopropylamino ether 10 parts, N-methyljetanolamine 2 parts, 4,4'-diphenylmethane diisocyanate 125 parts, methyl ethyl ketone 8 parts
67 parts of the amino store-modified polyurethane resin (1'
/) was obtained. This polyurethane resin had a min-f''lc of about 70,000.

Examples 5 to 8 Components F were dispersed in a ball mill for 45 hours, and 3.2 parts of Tis module OL was added and dispersed for 3 hours to obtain magnetic paints (I) to (TV) used in the present invention. Ta.

Cobalt dope 7 Fe2O, 3too part Example 1~
4. Polyurethane resin (■~■) 35% solution 71 parts methyl ethyl ketone 82 parts toluene
82 part cyclohexanone
82 parts of the above magnetic paints (I) to (rV) to a thickness of 15
The magnetic recording media (I) to (IV) of the present invention were prepared by coating a polyester film with a thickness of 1,800 gauss and applying magnetic field orientation at 1,800 gauss to form a magnetic layer with a thickness of about 5 μm.

Comparative Examples 1 to 3 As the binder resin in Example 1, polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., Daiferami?/
MAυ-2010) 35% solution (V), vinyl chloride-
Vinyl acetate copolymer resin (Made by Miki Kagaku, Nislex A) 35% solution (vl) and nitrocellulose resin (manufactured by Asahi Kasei, Seltsuba BTII%) 35% solution (VI
I), and magnetic recording media (V) to (VII) for comparison were made by the same company as Examples 5 to 8! ! Made by J.

Surface V of each magnetic recording medium obtained in the above Examples 5 to 8 and Comparative Examples 1 to 3 - Lubricity <Surface of HFI layer)
When the magnetic properties were investigated, the results were as shown in Table 1 below.

γ-J 1 Go, - One 艷一 - Nausea back and - U'' Gen° A° Turtle-shaped north Hosei power 1E Example 5 96 96102 86 660 1
．． 500 Example 6 96 97105 86 6
60 1.550 Example 7 90 94 99 8
4 850 1.400 Example 8 98 99104
87 655 1.550 Comparative example 1 3 10
43 75 663 1.300 Comparative example 2
Io 18 44 81 655 1.350
Comparative example 3 27 44 96 81 663 1
．． 350 Patent Applicant Dainichiseika Kagyo Co., Ltd. Attorney Yoshi 1) Katsuhiro, -1°° 2.
゛

Claims (1)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer in which magnetic particles are dispersed in a binder resin on a non-magnetic support, the binder resin is a polyurethane resin having an amino group in the main chain and/or side chain. A magnetic recording medium characterized in that it consists of a single binder resin or a mixture with other binder resins.