JPS59172116A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has the good surface smoothness of a magnetic layer, and has an excellent electromagnetic conversion characteristic, high modulus of elasticity and excellent mechanical strength by using a copolymerized polyester resin contg. a metallic salt of sulfonic acid and nitrogen element contg. compd. in one molecule and a polyisocyanate compd. in combination as a binder component. CONSTITUTION:A copolymerized polyester resin contg. a metallic salt of sulfonic acid and nitrogen element contg. compd. in one molecule and a polyisocyanate compd. are incorporated as a binder component in a magnetic layer. The copolymerized polyester resin contg. a metallic salt of sulfonic acid and nitrogen element contg. compd. in one molecule has an anionic sulfonic acid metallic chloride and cationic nitrogen element contg. compd. in one molecule and has therefore a good mutual effect with magnetic powder, has excellent dispersibility and packability of the magnetic powder and contributes to an improvement in the surface smoothness of the magnetic layer and an electromagnetic conversion characteristic. The polyisocyanate compd. cross-links and bonds the copolymerized polyester resin by reacting with the hydroxyl group and amino group contained therein and contributes to the improvement in the modulus of a elasticity and mechanical strength of the magnetic layer.

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium, and its object is to provide a magnetic recording medium with a magnetic layer having good surface smoothness, excellent electromagnetic conversion characteristics, high elastic modulus, and excellent mechanical strength. The goal is to provide a medium.

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating. The binder component used in this case has excellent dispersibility and filling properties of the magnetic powder, improves the smoothness of the surface of the magnetic layer, and can impart excellent electromagnetic conversion characteristics such as high sensitivity to the magnetic recording medium. It is necessary to choose a material that has excellent durability, high elasticity, and excellent mechanical strength, especially for magnetic tapes, etc., which are becoming more dense and thinner in recent years.
It is desirable to use a binder component that can sufficiently improve the surface smoothness of the magnetic layer, as well as provide high elasticity and good mechanical strength.

For this reason, various research and developments have been conducted on binder resins.
Copolyester resins containing sulfonic acid metal bases have been proposed as having excellent dispersibility and filling properties of magnetic powder.

However, although this type of copolyester resin containing a sulfonic acid metal base has excellent dispersibility and filling properties of magnetic powder, it has the disadvantage that the elastic modulus of the magnetic layer cannot be sufficiently improved.

The inventors conducted various studies in view of the current situation, and found that a copolymerized polyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule, and a polyisocyanate compound were used as binder components for the magnetic layer. When used in combination, the copolyester resin containing this kind of sulfonic acid metal salt compound and nitrogen element-containing compound in one molecule has a higher dispersion of magnetic powder than the conventional copolyester resin containing the sulfonate metal base. In addition, when a polyisocyanate compound is used in combination with this, the polyisocyanate compound crosslinks with the copolymerized polyester resin, improving the dispersibility and filling property of the magnetic powder, and forming a magnetic layer. The surface smoothness of the magnetic layer is improved, and the elastic modulus of the magnetic layer is also improved, and when a low molecular weight polyol is used in combination, the polyisocyanate compound is cross-linked with this low molecular weight polyol, which further increases the elastic modulus of the magnetic layer. It has been discovered that a magnetic recording medium with improved elasticity and even better mechanical strength can be obtained, and this invention has been completed.

The copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule used in this invention contains 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-
Sulfonic acid metal salt compounds such as sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, and hexamethylene diamine, trimethylene diamine, 6-amino-n-caproic acid, 2-amino-1so-caproic acid, ω-amino Caprylic acid, 4-amino-n-1 acid, 2-
It is obtained by copolymerizing compounds such as hydroxyethyl-p-toluidine, p-aminobenzoylhydrazide, 0-aminobenzyl alcohol, ethanolamine, and 1.10-diaminodecane, and these can be used alone or in combination of two or more. and copolymerized.

To produce this resin, for example, acid components such as adipic acid, isophthalic acid, and terephthalic acid; glycol components such as ethylene glycol and neopentyl glycol;
Add a predetermined amount of a sulfonic acid metal salt compound such as 5-sodium sulfoisophthalic acid, a nitrogen element-containing compound such as hexamethylene diamine, etc. together with other necessary components, and perform an esterification reaction and a polycondensation reaction under reduced pressure. The esterification reaction and the polycondensation reaction may be carried out separately by charging them all at once or in any order.

This type of copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule differs from the conventional copolymerized polyester resin containing a sulfonic acid metal base, because it contains an anionic sulfonic acid metal salt compound. Since it contains a cationic nitrogen element-containing compound in one molecule, it has good interaction with the magnetic powder, has excellent dispersibility and filling properties of the magnetic powder, and has good surface smoothness of the magnetic layer. Improve conversion characteristics.

In addition, the polyisocyanate compound used in this invention is an isocyanate having at least two isocyanate groups in the molecule and an adduct thereof, and a polyisocyanate compound having a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule. When used in combination with a polymerized polyester resin, the isocyanate groups of this type of polyisocyanate compound react with the hydroxyl groups and amino groups contained in the copolyester resin containing a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule. These cross-links improve the elastic modulus of the magnetic layer.
A highly elastic magnetic layer is formed, further improving mechanical strength. Specific examples of such polyisocyanate compounds include, for example, 1-methylbenzo-2.4.6-)
Diisocyanate, triphenylmethane-4,4',4
"-triisocyanate, trimethylolpropane tolylene diisocyanate, etc., and specific examples of commercially available products include Coronate L manufactured by Nippon Polyurethane Industries, Desmodur Shi-75 manufactured by Bayer, and Desmodur Shi-75 manufactured by Narita Pharmaceutical Industries, Ltd. Examples include Takene 1-D102.

The blending ratio of the copolymerized polyester resin containing the sulfonic acid metal salt compound and the nitrogen element-containing compound in one molecule and the polyisocyanate compound is 95:5 in weight ratio of the copolymerized polyester resin to the polyisocyanate compound. It is preferable that the ratio be within the range of 65 to 35. If the amount of the copolymerized polyester resin is too small, the dispersibility and filling properties of the magnetic powder and the surface smoothness of the magnetic layer will not be sufficiently improved, and the polyisocyanate If the amount of the compound is too small, the elastic modulus of the magnetic layer will not be sufficiently improved.

Furthermore, the low molecular weight polyols used in combination in this invention include acrylic polyols, polyester polyols, polyether polyols, etc., all of which have an average molecular weight within the range of 200 to 1500 and a hydroxyl value of 2.
It is preferably within the range of 00 to 800. If the average molecular weight exceeds 1,500 or the hydroxyl value is less than 200, the elastic modulus of the magnetic layer decreases. Since the viscosity increases and the amount of organic solvent must be increased, the surface smoothness of the magnetic layer is impaired. Also, if the average molecular weight is lower than 200 or the hydroxyl value is higher than 800, the solubility in organic solvents will be poor, and the compatibility with the copolyester will be poor. It is more preferable that it is below.

Here, the hydroxyl value refers to the number of potassium hydroxides required to neutralize acetic acid bound to an acetylated product obtained from 1 g of a sample. Specific examples of such low molecular weight polyols include Olestar Q-161 (acrylic polyol) manufactured by Mitsui Toatsu Chemical Co., Ltd., and 7 manufactured by Asahi Denka Co., Ltd.
Dekanini-Ace YT-400, Desmohen 800, Desmohen 2200 manufactured by Nippon Polyurethane Co., Ltd. (all polyester polyols), Sunnisox TP- manufactured by Sanyo Chemical Co., Ltd.
400, Sannisokusu GP-600, Sannisokusu GP
-3000, Sunnix FA-908 (all polyether polyols), and the like.

When this type of low molecular weight polyol is used in combination, polyurethane is produced by reaction and curing with the polyisocyanate compound, thereby further improving the elastic modulus of the magnetic layer. The amount used is preferably within the range of 7 to 30% by weight based on the total amount of binder components. If the amount of low molecular weight polyol used is too small, the elastic modulus of the magnetic layer will not be improved sufficiently, and if it is too large, the magnetic layer will be Powder dispersibility and filling properties are reduced.

Examples of the magnetic powder used in this invention include 7-F
e2O3 powder, Fe3O4 powder, Co-containing 7-Fe2O
3 powder, CO-containing F8304 powder, CrO2 powder
Various conventionally known magnetic powders such as metal powders such as e-powder and Co powder are widely included.

Further, as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane, dimethyl formamide, etc. are used alone or in combination.

The magnetic recording medium of the present invention may be manufactured according to a conventional method, for example, by forming a copolymer containing a magnetic powder, a sulfonic acid metal salt compound, and a nitrogen element-containing compound in one molecule on a substrate such as a polyester film. Magnetic paint containing a binder component consisting of a polyester resin and a polyisocyanate compound, or a binder component further containing a low molecular weight polyol, an organic solvent, and other additives is applied by any means such as spraying or roll coating. and dry it.

Next, embodiments of the invention will be described.

Example 1 0.4 mol of terephthalic acid and 0.4 mol of isophthalic acid were placed in a reaction vessel equipped with a thermometer, stirrer, compressor, and partial reflux condenser.
4 mol, adipic acid 0.19 mol, ethylene glycol 0.49 mol, neopentyl glycol 0.49 mol,
0.01 mol of 5-sodium sulfoisophthalic acid and 0.02 mol of hexamethylene diamine were charged, and further 0.01 mol of zinc acetate, 0.005 mol of sodium acetate and 0.01 mol of antimony dioxide were added to give a solution of 140 to 22
React at 0°C, and then at 210-250°C, 1mm/1g
A polycondensation reaction was carried out under the following reduced pressure to produce a copolymerized polyester resin having a sodium sulfonate group and an amino group. Using the copolymerized polyester resin obtained as described above, 500 parts by weight of α-Fe magnetic powder and a copolymerized polyester resin Desmohen 800 (manufactured by Nippon Polyurethane Co., Ltd.) having a sodium sulfonate group and 60 amino groups were prepared. Polyester polyol, average molecular weight 800, hydroxyl value 300) Desmodur L-75 (polyisocyanate compound manufactured by Bay 25 Engineering) Methyl isobutyl ketone 350 Cyclohexanone 350 Toluene
350 Of the above compositions, desmodules are
Each component except for 75 was placed in a ball mill, mixed and dispersed for 488 hours, and then desmodurized -75 was added. After further mixing and dispersion for 1 hour, the mixture was taken out and a magnetic paint was prepared. This magnetic paint was applied to a polyester film with a thickness of 15 μm to a dry thickness of 5 μm, oriented in a 3000 oersted DC magnetic field, heated and dried, surface treated, and then cut to a specified width. I made a tape.

Example 2 In the composition of the magnetic paint in Example 1, Sunnix GP-600 was used instead of 800.15 parts by weight of Desmohen.
(Polyether polyol manufactured by Sanyo Chemical Co., Ltd., average molecular weight 6
A videotape was made in the same manner as in Example 1, except that 16 parts by weight of 00, hydroxyl value 260) were used and the amount of desmodule-75 was changed from 25 parts by weight to 24 parts by weight.

Comparative Example 1 In the composition of the magnetic paint in Example 1, Niraporan 3023 (
21 parts by weight of polyester polyol manufactured by Nippon Polyurethane Co., Ltd. (average molecular weight approximately 2,600, hydroxyl value 170) were used, and the amount of Desmodur L-75 was changed from 25 parts by weight to 1 part by weight.
A videotape was produced in the same manner as in Example 1, except that the amount was changed to 9 parts by weight.

Comparative Example 2 In the composition of the magnetic paint in Example 1, Crisbon 4070 (
A videotape was produced in the same manner as in Example 1, except that 30 parts by weight of urethane prepolymer (manufactured by Dainippon Ink Co., Ltd.) was used and the amount of Desmodur L-75 was changed from 25 parts by weight to 10 parts by weight.

Comparative Example 3 In the composition of the magnetic paint in Comparative Example 1, the same amount of ET1095 (sodium sulfonate-containing copolyester resin manufactured by Toyobo Co., Ltd.) was used instead of the copolyester resin having sodium sulfonate groups and amino groups. A videotape was made in the same manner as in Comparative Example 1.

The surface smoothness, elastic modulus, and sensitivity (output of 5 MHz) of the magnetic layer of each videotape obtained in each Example and Comparative Example were investigated using the following methods, and the results were as shown in the table below. . The ratio of polyol to polyisocyanate compound used in each of the Examples and Comparative Examples was adjusted so that the ratio of hydroxyl group to isocyanate group was 1.0 (equivalent).

Surface smoothness> Using a stylus-type roughness needle, the average surface roughness of the magnetic layer was measured at a stylus speed of 0.06 Cm/sec and a cutoff of 0.08 m.
.

1, 1, 1, 1, 1, 1, 1, 1, 1, 15 <Elastic modulus of example> The elastic modulus of the entire tape was measured under the conditions of a sample length of 1Q cm and a tensile speed of 201 m/min, while the elastic modulus of the entire tape was The elastic modulus is measured, and the elastic modulus of only the magnetic layer is determined from the constant values on both sides according to the formula below.

or+ dM: Thickness of magnetic layer Cl11) dB: Thickness of polyester base film cm) E
T: Elastic modulus of the entire tape EB: Elastic modulus of the polyester base film From the elastic modulus of the magnetic layer of each sample calculated from the above formula, Example 1
A relative value was determined according to the following formula using the reference value as a reference, and it was determined whether the elastic modulus of the magnetic layer was large based on this relative value.

Sensitivity) The output (dB) at 5 MHz of each sample was determined when the one in Example 1 was used as a reference (OdB>).

7 As is clear from the table above, the videotapes obtained in Examples 1 and 2 had better surface smoothness, higher elastic modulus, and higher sensitivity than those obtained in Comparative Examples 1 to 3. This shows that the magnetic recording medium obtained by the present invention has excellent surface smoothness, high elasticity, and good sensitivity characteristics.

Claims (1)

[Claims] 1. Magnetic recording having a magnetic layer containing a copolyester resin having a sulfonic acid metal salt compound and a nitrogen element-containing compound in one molecule and a polyisocyanate compound as binder components. Medium 2: A magnetic recording medium according to claim 1, further comprising a low molecular weight polyol as a binder component in the magnetic layer.