JPS61110334A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium with which the dispersibility of magnetic powder is excellent and the electric resistance on the surface of the magnetic layer is substantially small and which has a high squareness ratio by providing a magnetic layer contg. a glycidyl type epoxy compd. as a binder component for the magnetic powder. CONSTITUTION:The magnetic soln, prepd. by dispersing magnetic oxide such as Co-contg. gamma-Fe2O3 powder or magnetic metallic powder of Co, Fe-Ni alloy, etc. into a binder soln. of the glycidyl type epoxy compd., more preferably the epoxy compd. contg. glycidyl ester having polyol in ht eskeleton structure or polycarboxylic acid in the skeleton structure combined with the other binder, more preferably resin binder such as vinyl chloride/vinyl acetate copolymer or polyurethane is coated on a substrate and is dried. After the coated substrate is subjected to a calender treatment, the substrate is cut to a prescribed width, by which a magnetic tape is obtd. The magnetic tape or the like having the excellent dispersibility of the magnetic powder and binding power with the bincer, good binding property between the magnetic layer and the substrate, small electric resistance on the surface of the magnetic layer, good running stability and high squareness ratio is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium in which magnetic powder has excellent dispersibility and the electrical resistance of the surface of the magnetic layer is sufficiently small.

[Conventional technology]

A magnetic recording medium is usually made by applying a magnetic material consisting of magnetic powder, a binder component, a growth agent, and other necessary components onto a substrate such as a polyester film, and drying it. The binder component used in this case is desired to be one that has excellent dispersibility of the magnetic powder, can impart excellent magnetic properties or electromagnetic conversion properties to the magnetic recording medium, and has excellent durability. Various research and developments have been carried out on agent resins, and vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane 41 resins, and the like have been widely used as having excellent properties.

[Problem that the invention seeks to solve]

However, although these binder resins have relatively excellent properties, they still do not have sufficient affinity with magnetic powder.
Furthermore, since the reactivity of the +n resins used together is not so high, the dispersibility of the magnetic powder is not quite satisfactory, and the electrical resistance of the surface of the magnetic layer is not sufficiently reduced.

[Means for solving problems]

This invention was made as a result of various studies on binder resins in view of the current state of affairs. By containing a glycidyl-type epoxy compound with excellent properties, the dispersibility of the magnetic powder is improved and the electrical resistance of the surface of the magnetic layer is sufficiently reduced.

In this invention, the glycidyl-type epoxy compound used as a binder component has an epoxy group at the end of the molecule, and this epoxy group is ring-opened by heating during drying after forming the magnetic layer and is present on the surface of the magnetic powder. chemically bonds directly with the OH group. Therefore, this glycidyl type epoxy compound exhibits a very strong bonding force to the magnetic powder and is firmly bonded to the particle surface of the magnetic powder. In addition, this type of glycidyl-type epoxy compound that is firmly bonded to the particle surface of this magnetic powder has very good compatibility with the binder resin used in combination, and therefore, the dispersibility of the magnetic powder in the binder resin is sufficiently improved. Ru. In addition, this type of glycidyl-type epoxy compound has a special property in that the electron density is localized within the molecule, which reduces the electrical resistance of the magnetic layer surface and improves running stability.

Such glycidyl-type epoxy compounds include glycidyl-type epoxy compounds with a molecular weight of 1000 or less, which have a polyol as a skeleton structure and whose main component is polyglycidyl ether containing at least one glycidyl ether in the molecule, and polycarboxylic acids. as a skeleton structure, and whose main component is a polyglycidyl ester containing at least one glycidyl ester in the molecule, and whose molecular weight is 10.
Glycidyl type epoxy compounds having a molecular weight of 00 or less are preferably used. For example, glycidyl type epoxy compounds represented by the following structural formula are preferably used alone or in combination of two or more types.

1.6-hexanethiol diglycidyl ether H2B
r Dibromoobentyl glycol diglycidyl ether 0-phthalic acid diglycidyl ester sorbitol polyglycidyl ether polypropylene glycol diglycidyl ether CH.

Tsuneobentyl glycol diglycidyl ether H20H ■ Litrimethylolpropane polyglycidyl ether Allyl glycidyl ether p-tertiary butylphenyl glycidyl ether (However,
R is an alkyl group having 12 or 13 carbon atoms. ) Alkyl alcohol glycidyl ether dibromophenyl glycidyl ether Specific examples of commercially available glycidyl-type epoxy compounds include Tenaco-7L/manufactured by Nagase Kasei Co., Ltd.
EX-212, De J-Cole EX-221, De+Cole EX-721, De+Cole EX-622, Bunacole EX-931, Bunacole EX-211, Bunacole EX-321, Denaco Jl/EX-11L Dena:l −
Le EX-121, Bunacol gX-141, Dena:y-
Examples include LEX-146, Buna:l-/L/EX-192, and Dena D-Jl/EX-147.

Such glycidyl type epoxy compounds are preferably used in combination with binder resins conventionally generally used for magnetic recording media.
Binder resins conventionally used for magnetic recording media, such as vinyl chloride-vinyl acetate copolymers, cellulose resins, poly and nyl acecool resins, polyurethane resins, polyester resins, and isonorate compounds, are Although they are also preferably used, particularly good results are obtained when used in combination with vinyl chloride-vinyl acetate-vinyl alcohol copolymers and polyurethane resins. When used together with these binder resins, the blending ratio of the glycidyl-type epoxy compound is preferably within the range of 5 to 50% by weight based on the total amount with these binder resins, and if it is too small, it may not be possible to achieve the desired results. If the amount is too high, the heat resistance will be poor.

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, a binder component consisting of a magnetic powder, a glycidyl-type epoxy compound, and a binder resin to be used together, on a substrate such as a polyester film, A magnetic paint containing an organic solvent and other additives may be applied by any means such as spraying or roll coating, and dried.

As the magnetic powder used here, for example, T-F
ezOz powder, Fe, 04 powder, intermediate compound powder between r-Fe203 powder and Fe3O4 powder, CO-containing r-Fe2
03 powder, Co-containing Fed04 powder, CrO2 powder
11. A wide variety of conventionally known magnetic powders are included, such as metal powders such as Fe powder, CO powder, and Fe-Ni powder, and barium ferrite.

In addition, examples of solvents include ketone solvents such as cyclohexanone, methyl isobutyl ketone, and methyl ethyl ketone; ester solvents such as ethyl acetate and butyl acetate;
Solvents suitable for melting the binder resin used are particularly limited, such as aromatic hydrocarbon solvents such as benzene, xylene, and toluene, sulfoxide solvents such as dimethyl sulfoxide, and ether solvents such as tetrahydrofuran and dioxane. They can be used alone or in a mixture of two or more.

In addition, various commonly used additives such as dispersants, 1fIf agents, abrasives, antistatic agents, etc. may be appropriately added to the magnetic paint.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 CO-containing r-Fe203 powder 800! Volume part VAGH
(Manufactured by U, C, C, USA, salt 80# vinyl-vinyl acetate-vinyl alcohol copolymer) Bump 7x T-5201 (Oguchi 60, manufactured by Ink Chemical Industry Co., Ltd., urethane elastomer) Bunacol EX-622 (Nagase 60# Kasei Co., Ltd., Sorbitol Tetraglin Norether) Lentin 16# Lauric Acid
12 l Methyl isobutyl ketone 550# toluene 5
50# these compositions in a ball mill with a capacity of 72
After mixing and dispersing for a period of time, 15 parts by weight of Coronate L (manufactured by Nippon Polyurethane Industries, Ltd., a trifunctional low molecular weight isocyanate compound) was added thereto, and the mixture was further mixed and dispersed for 30 minutes to prepare a magnetic paint. This magnetic paint was spread on a polyester film with a thickness of 12μ so that the dry thickness was 6μ.
It was dried to form a magnetic layer, calendered, and then cut to a predetermined width to produce a magnetic tape.

Implementation F! 42-12 In the composition of the magnetic paint in Example 1, VAGH,
Bump 7x T-5201 and Bunacol EX-62
Magnetic tapes were prepared in the same manner as in Example 1, except that the composition ratio of Example 2 was varied as shown in Table 1 below. The composition ratio of each binder resin is expressed in weight % based on the total amount of needles of these three binder resins.

Table 1 Example 13 In the composition of the magnetic paint in Example 1, Denako J
A magnetic tape was prepared in the same manner as in Example 1, except that the same amount of Bunacol Mi X-211 (manufactured by Nagase Kasei Co., Ltd., neopentyl glycol diglycidyl ether) was used in place of EX-622.

Comparative Example 1 In the composition of the magnetic paint in Example 1, Bunacol BX-622 was omitted, the amount of VAGH (1) was changed from 80 parts by weight to 100 parts by weight, and Bump 7x T-5201 was added.
A magnetic tape was produced in the same manner as in Example 1, except that the amount used was changed from 60 parts by weight to 100 parts by weight.

Regarding the magnetic tapes obtained in each example and comparative example,
Squareness ratio and surface electrical resistance were measured.

Table 2 below shows the results.

Table 2 (Effects of the Invention) As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1-13) are all different from conventional magnetic tapes (Examples 1-13).
Compared to Comparative Example 1), the squareness ratio is high and the surface electrical resistance is small. Therefore, the magnetic recording medium obtained by this invention has excellent dispersibility of magnetic powder and has a sufficient surface electrical resistance of the magnetic layer. It can be seen that this has been reduced to .

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer containing a glycidyl-type epoxy compound as a binder component