JPS6238524A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an S/N ratio and sensitivity by providing a magnetic layer contg. a specific phenoxy resin together with magnetic powder. CONSTITUTION:The phenoxy resin having at least one kind of the hydrophilic group selected from the formula in the molecule is used as a binder component. The phenoxy resin having such kind of the hydrophilic group has good compatibility to a polyurethane resin. The excellent toughness of the polyurethane resin is provided and the wear resistance is improved when said resin is used in combination with the polyurethane resin; further this polyurethane resin has the good affinity to the magnetic powder and the excellent dispersibility of the magnetic powder which contribute to the additional improvement of the magnetic powder. Such polyurethane resin preferably a straight chain polyurethane elastomer having OH groups as both terminals of the molecule and has preferably 10,000-50,000mol.wt. The squareness ratio, S/N ratio and sensitivity are thereby remarkably improved and the magnetic recording medium having the good dispersibility of the magnetic powder, excellent electromagnetic conversion characteristic, wear resistance and heat resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field and Object] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium that has good dispersibility of magnetic powder, excellent electrical properties, and excellent wear resistance.

[Conventional technology]

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 is 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 wear resistance. desired.

For this reason, various research and developments have been conducted on binder resins.
For example, one using phenoxy resin and polyurethane resin has been proposed. (Japanese Patent Publication No. 42-2179) [Problems to be Solved by the Invention] However, with the combination of this type of phenoxy resin and polyurethane resin, although the abrasion resistance is improved, the dispersibility of the magnetic powder is not so great. However, there are disadvantages such as agglomeration of the magnetic powder, resulting in a decrease in the S/N ratio, and poor sensitivity.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and contains -303M, SO3M,
C00M, PO(OM')2 (where M is hydrogen or an alkali metal, and M' is hydrogen or an alkali metal or a hydrocarbon group.

) By using a phenoxy resin having at least one hydrophilic group selected from the following as a binder component, the dispersibility of the magnetic powder is sufficiently improved and the electromagnetic conversion characteristics are sufficiently improved. Furthermore, by using a polyurethane resin and a polyisocyanate compound in combination, the wear resistance is sufficiently improved.

In this invention, the phenoxy resin used as the binder component has -3o3M, -SO3M, - in its molecule.
C00M, -PO(OM')2 (where M is hydrogen or an alkali metal, and M' is hydrogen or an alkali metal or a hydrocarbon group).

), it can be obtained by a method such as introducing at least one hydrophilic group into the hydroxyl group of a phenoxy resin commonly used in the past. Examples of such phenoxy resin include PKHA, PKHC, manufactured by Union Carbide Co., Ltd.
The molecular weight of PKHHlPKHJ etc. is approximately 20,000 to 35
000 phenoxy resin into which at least one of the above hydrophilic groups is introduced is preferably used.

The phenoxy resin into which at least one type of hydrophilic group has been introduced in this manner has good affinity with the magnetic powder, and the introduced hydrophilic group is well adsorbed onto the surface of the magnetic powder.

Therefore, when a phenoxy resin having this type of hydrophilic group is used as a binder component, these hydrophilic groups are well adsorbed to the surface of the magnetic powder, the dispersibility of the magnetic powder is sufficiently improved, and the electromagnetic conversion characteristics are sufficiently improved. will be improved.

In addition, phenoxy resins having this type of hydrophilic group have good compatibility with polyurethane resins, and when used in combination with polyurethane resins, the excellent toughness of the polyurethane resins used in combination is exhibited, improving wear resistance. Since 131 fat has good affinity with magnetic powder and excellent dispersibility of magnetic powder, the dispersibility of magnetic powder is further improved. As such a polyurethane resin, a linear polyurethane elastomer having OH groups at both ends of the molecule is preferably used, and one having a molecular weight of 10,000 to 50,000 is preferably used. Specific examples include Nipporan 2304 manufactured by Nippon Polyurethane Industries, Bandex HI2000 and Vandenx T5 manufactured by Dainippon Ink Chemical Industries, Ltd.
250. Examples include PandexF5201. When such a polyurethane resin and the above-mentioned phenoxy resin having a parent wood group are used together, the blending ratio of both is not particularly limited, but usually, the weight ratio of the above-mentioned phenoxy resin having a hydrophilic group to the polyurethane resin is determined. So, 20:8
They are preferably used together within the range of 0 to 70:30.

In this way, the phenoxy resin having a hydrophilic group is
Although it is well used in combination with polyurethane resin, it can also be used in combination with polyisocyanate compounds with good compatibility.
When a polyisocyanate compound is further used in combination, the isocyanate group contained in this polyisocyanate-1 compound reacts with the hydrophilic group contained in the phenoxy resin and the hydroxyl group contained in the polyurethane resin, resulting in crosslinking. Therefore, the toughness of the magnetic layer is further strengthened, and the wear resistance is further improved. Such polyisocyanate compounds include 2,4-tolylene diisocyanate, 4,4'-biphelene diisocyanate, 1,6
- Hexamethylene diisocyanate, etc. are used alone or in combination; for example, Coronate (manufactured by Nippon Polyurethane Industries, Ltd., a trifunctional image molecular weight isocyanate compound), N189 (manufactured by Dainippon Ink Chemical Industry Co., Ltd., a trifunctional image molecular weight isocyanate compound), molecular weight isocyanate compounds) and the like are preferably used. The amount of such a polyisocyanate compound used is preferably within the range of 1 to 40% by weight based on the total amount of binder components; if it is too small, the abrasion resistance of the magnetic layer will not be sufficiently improved; if it is too large, The stability of magnetic paint decreases due to increased viscosity.

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, on a substrate such as a polyester film, magnetic powder and at least Ifffi in the above-mentioned molecules are prepared.
A phenoxy resin having a hydrophilic group, or a binder component further containing a polyurethane resin and a polyisocyanate compound, is coated with a magnetic paint containing a welding agent and other additives by any means such as spraying or roll coating, Just dry it.

The magnetic powder used is, for example, γ-Fe20
3 powder, Fe3O4 powder, Co-containing -Fe203 powder, Co-containing Fe5o4 powder, CrO□ powder, as well as various conventionally known magnetic powders such as total bending powder such as Fe powder and Co powder, and barium ferrite.

As the organic solvent, methyl isophyl ketone, methyl ethyl ketone, cyclohexanone, l-toluene, ethyl acetate, tetrahydrofuran, dioxane, dimethyl formamide, etc. are used alone or in combination of two or more.

In addition, various additives commonly used in the magnetic paint, such as o-nee Fe2O3 powder, Al2O3 powder, C
Abrasives such as r2O3 powder, 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 I Co-containing r-Fe203 powder 250 parts by weight-3Q3
Na group-containing phenoxy 21〃Resin (-3O3Na group content 2 mol%, molecular weight 20000) Pandenox HI2000 (large 18〃manufactured by Nippon Ink Chemical Industry Co., Ltd., urethane elastomer) Coronate L (manufactured by Nippon Polyurethane 7〃manufactured by Kogyo Co., Ltd., trifunctional) low molecular weight isocyanate compound) granular α-Fe2Q3 powder io = n-butyl stearate 3I liquid paraffin
2 Myristic acid
2 Cyclohexanone 340 Toluene 340 This composition was mixed and dispersed in a ball mill for 70 hours to prepare a magnetic paint.

This magnetic paint was applied onto a 14 μm thick polyester film with good surface smoothness to a dry thickness of 5 μm and dried to form a magnetic layer. Afterwards, this was cut to a predetermined width to make magnetic tape.

Example 2 In the composition of the magnetic paint in Example 1, -3O3N
-PO(OH) instead of phenoxy resin containing a group
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of phenoxy resin containing 2 mole % of 2 groups and having a molecular weight of 25,000 was used.

Example 3 In the composition of the magnetic paint in Example 1, -3O3N
-OS 03 N instead of phenoxy resin containing a group
A magnetic tape was prepared in the same manner as in Example 1, except that the same amount of phenokine resin containing 2 mol % of the a group and having a molecular weight of 30,000 was used.

Example 4 In the composition of the magnetic paint in Example 1, -3O3N
In place of phenoxy resin having a group, 1000H group is replaced with 2
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of phenoxy resin containing mol % and having a molecular weight of 20,000 was used.

Comparative Example 1 In the composition of the magnetic paint in Example 1, -3O3N
Instead of the phenolic resin having a group, a normal phenolic resin without -3O3Na group (U.

C, C? 1. ! ! ! A magnetic tape was prepared in the same manner as in Example 1, except that the same amount of the following materials (1, PKHH) was used.

Claims (1)

[Claims] 1. -SO_3M, -OSO_3M, -COOM, -PO(
OM')_2 (where M is hydrogen or an alkali metal, M' is hydrogen or an alkali metal, or a hydrocarbon group), comprising a phenoxy resin having at least one hydrophilic group selected from the following, together with magnetic powder. A magnetic recording medium 2 having a magnetic layer, the magnetic recording medium according to claim 1, wherein the magnetic layer further contains a polyurethane resin and a polyisocyanate compound.