JPS60211622A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having a high S/N by using a urethane resin which is a mixture composed of the resin having one COOM (M is H or Na, etc.) in polyester skeleton and the resin having no COOM, has reactive double bonds and has the mol.wt. within a specific range as a binder for magnetic powder. CONSTITUTION:Polyester is so synthesized as to have one COOH in one molecule by adjusting the molar ratio of glycol, triol and dibasic acid such as adipic acid, terephthalic acid or the like. Since the molar ratio is so adjusted that one COOH exists in the same molecule as a whole, the presence of a small quantity of the molecules having no COOH is equally satisfactory. The polyester is then treated with the hydroxide of Li, Na, K to convert the COOH into the salt thereof. The presence of the non-converted COOH is of no problem. Diisocyanate is then brought into reaction with the polyester and further 2-hydroxy (meth) acrylate or the like is brought into reaction therewith, by which the resin having 1,000-100,000mol.wt. and <=56.1X10<3> acid value in terms of COOH X mol.wt. is obtd. Such resin is used for the binder of the magnetic powder, by which the dispersibility of the magnetic powder is improved and the recording medium having excellent electromagnetic transducing characteristics, etc. is obtd.

Description

[Detailed description of the invention] [Technical field and purpose] The purpose of this magnetic recording medium is to provide a magnetic recording medium with good dispersibility of magnetic powder in the magnetic layer and excellent electromagnetic conversion characteristics. The goal is to provide a medium.

[Background technology]

Magnetic recording media are usually made by coating a substrate such as a polyester film with a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components, and then drying the coating. The binder component used in this case is preferably one that has excellent dispersibility of the magnetic powder, can impart excellent electromagnetic characteristics such as high sensitivity and high S/N ratio to the magnetic recording medium, and has excellent durability. It will be done.

For this reason, various research and developments have been conducted on binder resins.
In order to improve the dispersibility of the magnetic powder, a hydroxyl group having good affinity with the magnetic powder is introduced into the molecules of the binder resin, or -COOM (where M is H, Li, Na
Or K. ), etc. (Japanese Unexamined Patent Publication No. 57-92421), attempts have been made to improve the electromagnetic properties using this type of binder resin. ing.

However, at least one -COOM of this type is present in the molecule.
A binder resin consisting of a compound having 11 & 1 or more has the same -
-COOM contains a large amount of compound molecules containing two or more -COOM in its skeleton and thus has a high affinity with magnetic powder.
If a compound molecule containing 2 (11,1 or more) is included in the same skeleton, these two or more 1000M molecules act as a chain that connects multiple magnetic powders, so agglomeration of the magnetic powders tends to occur, and the magnetic powder It is difficult to improve the dispersibility of , and the electromagnetic conversion characteristics cannot be sufficiently improved.

[Summary of the invention]

This invention was developed as a result of various studies based on the current situation.
It is composed of a molecule with a molecular weight of 1000 to 1oooooo and a molecule that has one -COOM (where M is I], Li, Na or K) and a molecule that does not have -COOM in the same ゛1゛1 case. The total amount is calculated as the product of the acid value and the molecular weight when converted to carboxyl groups. I x 10
When a urethane resin containing less than 3 and having a reactive unsaturated bond is used as a binder component of the magnetic layer, this type of binder resin has two or more -CO
Since it does not contain compound molecules having OM, agglomeration of the magnetic powder does not occur, and the dispersibility of the magnetic powder is sufficiently improved, resulting in a magnetic recording medium with a high S/N ratio and excellent electromagnetic conversion characteristics. The molecular weight was 100'O to 100,000, and the structure contained -CO
OM (However, M is H, I-i, Na or K.

) is composed of a molecule with one molecule and a molecule without one, −
The total amount of 000M is the product of the acid value and the molecular weight when converted to carboxyl groups, and is 56.1 x 1 (Urethane resin containing less than 13 and having reactive unsaturated bonds is used as the binder component of the magnetic layer. It is characterized by containing.

-CO used as a binder component in this invention
OM (where M is I(, Li, Na or K).

) and having a reactive unsaturated bond, the urethane resin has a molecular weight of 1000 to 100000 and is composed of molecules having and not having -COOM in the same skeleton, and -000M in total amount, The product of acid value and molecular weight when converted to carboxyl group is 56. I
It contains less than 103
The 1,000M or more acts as a chain to connect multiple magnetic powders, and there is no possibility of agglomeration of the magnetic powders.
The effects of hydrophilic -C00M, which has excellent affinity with magnetic powder, are well exhibited, the dispersibility of magnetic powder is sufficiently improved, and a magnetic recording medium with a high S/N ratio and excellent electromagnetic conversion characteristics is obtained. It will be done. In addition, as a result of improved dispersibility of magnetic powder,
The filling properties of the magnetic powder are also improved, and a magnetic recording medium capable of performing high-output, high-density recording can be obtained.

Such a compound has a molecular weight of 1000 to 100000 and has 1000M in the same skeleton (however, M is II, 1-i, Na
Or K. ), and the total amount of -COOM is 56. IX
The urethane resin containing less than 103 and having a reactive unsaturated bond is at least one of diols such as ethylene glycol, propylene glycol, and butanediol, and triols such as glycerol and trimethylolpropane, and adipic acid, terephthalic acid, etc. By polycondensing at least one dibasic acid or its anhydride by adjusting the molar ratio so as to leave a predetermined amount of carboxyl groups, and then treating with a metal hydroxide, -COOl (-C00L i, -COONa,
A polyester resin is synthesized by converting it into a metal salt such as -COOK, an isocyanate group is added to this polyester resin, it is urethanized, and then a reactive unsaturated bond is introduced into this urethane resin.

Examples of reactive unsaturated bonds introduced into the polyurethane resin include CH2=CH-C00-1CH2=C(
CH3) Coo-1Cll2= CI-CO-N 1
Reactive unsaturated bonds such as 1-1CH2=C(CH3)-C0-N1-1- are preferably introduced. Such a reactive unsaturated bond can be introduced by reacting the -NCO group at the end or side chain of the polyurethane resin with the -OH group of 2-hydroxyethyl methacrylate, or by reacting -NGO! of one of the diisocyanate compounds. i to 2-
After reacting with the 10H group of hydroxyethyl methacrylate, the other -NCO group is converted to -01 in the polyurethane resin.
It is carried out by reacting a polyurethane resin having -COOI groups in its molecule with a compound having an acrylic double bond and an epoxy group, such as glycidyl methacrylate. The number of saturated bonds introduced is preferably adjusted so that the molecular weight per functional reactive unsaturated bond is 500 to 5,000. Specific examples of commercially available polyurethane resins incorporating such acrylic unsaturated bonds include Sanyo Kasei +MUVU-508, LI
Examples include VU-513.

The magnetic recording medium of the present invention may be manufactured in accordance with Toyama. For example, a magnetic powder having a molecular weight of 1,000 to 100,000 is coated on a substrate such as a polyester film.
and 1000M in the same skeleton (however, M is H, Li,
It is Na or K. ) is composed of those with and without 1II, and the total amount of -COOM is 5 as the acid value and intermolecular product when converted to carboxyl group.
6. A magnetic paint containing a binder component made of urethane resin containing less than 103 l x 103 and having reactive unsaturated bonds, an organic solvent, and other additives is applied by any means such as spraying or roll coating, and is dried. Bye. At this time, in order to sufficiently harden the magnetic layer, it is preferable to perform electron beam irradiation. In this case, a scanning method or a curtain beam method can be employed as the electron beam accelerator. As for the electron source characteristics, the accelerating voltage is 150~5
Using a 00KV electron beam, the absorbed dose is 0.1 to 20Mr.
It is preferable to irradiate so that the acceleration voltage is 1.
If the voltage is lower than 50KV, the amount of energy passing through will decrease.
If the voltage is higher than 500 KV, the labor and energy used for curing will decrease, making it uneconomical. Also, the absorption line p is 0.1
If the amount is less than 20 Mrad, curing will not be sufficient.
If the amount is more than ad, the irradiated object will generate heat, which is not preferable.

Here, as the magnetic powder used, for example, 7F
e203 powder) powder, Fe3O4 powder, CO-containing r-Fe
Various conventionally known magnetic powders are widely included, such as metal powders such as 203 powder, Co-containing Fe3O4 powder, cro2 powder, CO powder, and barium ferrite.

Further, as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane, dimethylformamide, etc. are used alone or in combination of two or more.

In addition, various additives commonly used in magnetic paints, such as αF ez 038'5) powder, A12031
5) Additionally, abrasive agents such as Cr2O3 powder, IfI lubricants such as fatty acids and fatty acid esters, antistatic agents such as carbon black, dispersants such as lecithin, etc. may be optionally added.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 uvu-513 (manufactured by Sanyo Chemical Co., Ltd., 18 parts by weight of urethane acrylate, molecular weight 8,000, designed hydroxyl value 40, designed acid value 3, acrylic functionality 3) rx-Fe magnetic powder (particle size 0.3 100) μ, axial ratio 1/1O-) ex-Fe203 powder 6...Carbon Bra 2 31L Myristic acid 3 n-butyl stearate 4 // Cyclohexanone 52 Toluene 52 Put the above composition into a ball mill After mixing and dispersing for 72 hours, a dry thickness of 3
It was coated so as to have a particle diameter of μ, and after being oriented in a magnetic field, the solvent was dried. Next, a surface smoothing treatment is performed and a nitrogen atmosphere (
Electron beam irradiation was performed at an accelerating voltage of 165 KV and an irradiation amount of 8 M rad in an oxygen residual amount of 500 ppm. Thereafter, this was cut into a predetermined size to create a videotape.

Example 2 In the composition of the magnetic paint in Example 1, UVU-5
Instead of 13, the molecular weight is 8000 and the designed hydroxyl value is 40.
A videotape was made in the same manner as in Example 1, except that the same amount of urethane acrylate having a designed acid value of 5 and an acrylic functionality of 3 was used.

Example 3 In the composition of the magnetic paint in Example 1, UVU-5
A videotape was produced in the same manner as in Example 1, except that the same amount of UV1l-508 (urethane acrylate manufactured by Sanyo Chemical Co., Ltd., molecular weight 8000, designed hydroxyl value 40, designed acid value O, acrylic functionality 3) was used instead of 13. I made it.

Comparative Example 1 In the composition of the magnetic paint in Example 1, UVU-5
A videotape was made in the same manner as in Example 1, except that the same amount of UVU-507 (urethane acrylate manufactured by Sanyo Chemical Co., Ltd., molecular weight 8000, designed hydroxyl value 40, designed acid + 1lli9, acrylic functionality 3) was used in place of 13. Ta.

Regarding the binder resin used in each example and comparative example,
The results of measuring the hydroxyl value and acid value are as shown in Table 1 below.

Table 1 Also, the video S/N ratio and squareness ratio were measured for each videotape obtained in each Example and each Comparative Example.

Table 2 below shows the results.

Table 2 [Effects of the Invention] As is clear from Table 1, the video tapes obtained in Examples 1 to 3 had better video S/N ratios and angles than the video tapes obtained in Comparative Example 1. Both type ratios are iMi <
From this, it can be seen that the θ-magnetic recording medium obtained by the present invention has good dispersibility of magnetic powder and excellent electromagnetic conversion characteristics.

Claims (1)

Scope of Claims: (1) 9 has a molecular weight of 1,000 to 100,000, and has 1 COOM (provided that M is [■, Li, Na, or K) in the same skeleton.
-COO
The total amount of M is the product of the acid value and the molecular weight when converted to carboxyl groups, and is 56. A magnetic recording medium having a magnetic layer comprising, as a binder component, a urethane resin containing less than I x 103 and having a reactive unsaturated bond.