JPH0618075B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a magnetic layer having excellent dispersibility of magnetic powder and excellent abrasion resistance.

[Conventional technology]

A magnetic recording medium is usually prepared by applying a magnetic coating consisting of magnetic powder, a binder component, an organic solvent and other necessary components onto a substrate such as polyester film and drying it, and it is excellent in electromagnetic conversion characteristics and resistant to What is excellent in wear resistance is desired.

For this reason, a surfactant having a hydrophilic group at one end and a lipophilic group at the other end in the molecule, for example, a polyalkylene oxide alkyl phosphate ester is contained in the magnetic layer as a dispersant, and It has been attempted to improve the dispersibility of powders and to use hardeners such as trifunctional low molecular weight isocyanate compounds together with these dispersants in order to improve the wear resistance of the magnetic layer. .
(Japanese Patent Publication No. S40-40103) [Problems to be solved by the invention] However, when a surfactant such as polyalkylene oxide alkyl phosphate of this kind is used as a dispersant and it is adhered to the surface of the magnetic powder. However, since the binding force between the magnetic powder and the binder resin is weakened, wear resistance deteriorates, powder drops, head stains, etc. increase, and a part of the surfactant is added to the surface of the magnetic powder. Don't stick
There are problems such as bleeding out on the surface of the magnetic layer, leading to head jamming. Further, when the curing agent is used at the same time, the curing agent and the binder resin may be cross-linked and the abrasion resistance may be improved, but it is not sufficient, and the dispersibility of the magnetic powder and the magnetic layer still remain. No one with sufficiently improved wear resistance has been obtained.

[Means for solving problems]

This invention, as a result of various studies in view of the current situation,
In the molecule, -PO (OM) ₂ , -OPO (OM) ₂ ,-
_{SO 3 M, -OSO 3 M,} -COOM, -NH 2, -O
H, -CONH- (where M is H, Li, Na, K, N
H ₂ or NH ₄ . ) Having two or more polar groups selected from (However, n is an integer of 3 to 12.) A compound having at least one skeleton represented by is used as a dispersant, and when this is used together with a curing agent,
These two or more polar groups have different capacities in the adsorptivity to the magnetic powder surface and the crosslinkability with the curing agent, and when one polar group is adsorbed to the magnetic powder surface, the other polar group is the curing agent. When one polar group is crosslinked with the curing agent, the other polar group is adsorbed on the surface of the magnetic powder. Therefore, by having two or more kinds of these polar groups, the dispersibility of the magnetic powder is improved. It has been made known that it is possible to obtain a magnetic recording medium which is sufficiently improved and also has sufficiently improved abrasion resistance, and which is excellent in electromagnetic conversion characteristics and abrasion resistance.

In the present invention, in the molecule used as the dispersant,
_{-PO (OM) 2, -OPO (} OM) 2, -SO 3 M,
_{-OSO 3 M, -COOM, -NH 2} , -OH, -CO
NH- (provided that M is H, Li, Na, K, NH ₂ or NH ₄ ), and has at least two polar groups, and has the general formula (However, n is an integer of 3 to 12.) Examples of the compound having at least one skeleton represented by the general formula (1) (2) (3) (Four) (Five) (6) (7) (8) (9) (Ten) (However, R is a hydrocarbon group having 8 to 22 carbon atoms, and n is 3 to
It is an integer of 12. ) And a structural formula (11) (12) Any of the compounds represented by is preferably used.

The above-mentioned compound having two or more polar groups is generally obtained by a method similar to the method for producing a surfactant, and the two or more polar groups thus introduced are magnetic. Adsorbs well on the powder surface and cross-links well with the curing agent. Therefore, when the above compound having two or more kinds of polar groups is used together with a curing agent,
When one polar group is adsorbed on the surface of the magnetic powder, the other polar group is crosslinked with the curing agent due to the difference in the adsorptivity of the two or more polar groups on the surface of the magnetic powder and the crosslinkability with the curing agent. On the contrary, when one polar group is cross-linked with the curing agent, the other polar group is adsorbed on the surface of the magnetic powder, so that the dispersibility of the magnetic powder is sufficiently improved by these two or more polar groups. At the same time, the wear resistance is sufficiently improved, and high S
With the / N ratio, a magnetic recording medium having excellent electromagnetic conversion characteristics and excellent durability can be obtained.

As described above, in the above-mentioned compound having two or more kinds of polar groups, the introduced two kinds of polar groups are —PO (OM)
_{2, -OPO (OM) 2,} -SO 3 M, OSO 3 M, -
As a COOM, if those acidic surface well adsorbed to basic magnetic powder, _-NH 2 Conversely, -CON
In the case of a basic substance such as H-, the surface is well adsorbed on the surface of the acidic magnetic powder, and the dispersibility, filling property and orientation of the magnetic powder are improved. In particular, -PO (O
The above-mentioned compounds having a polar group such as M) ₂ and —OPO (OM) ₂ are used as the best compounds because of their good interaction with the magnetic powder, and —SO ₃ M, OSO ₃ M
The above-mentioned compounds having a polar group such as, for example, have good compatibility with other binder resins used in combination, and thus are used as particularly favorable compounds. Further, those having a polar group -COOM are easy to use because they are well dissolved in an organic solvent, and polar group -NH ₂ ,
Since those having —CONH— are particularly well adsorbed on the magnetic powder having an acidic surface, they are particularly preferably used when the magnetic powder having an acidic surface is used. Such a compound of this kind is preferably used in the range of 0.1 to 10% by weight with respect to the magnetic powder. If the amount is too small, the desired effect cannot be obtained. The amount of remaining compounds increases, and the wear resistance and heat resistance of the magnetic layer decrease.

As such a curing agent used in combination with the above-mentioned compound having two or more kinds of polar groups in the molecule, there are two or more isocyanate groups in one molecule, or an epoxy group, or a crosslinkable agent such as an ethyleneimine ring. Isocyanate compounds having functional groups, epoxy compounds, and ethyleneimine compounds are preferably used. Specific examples include Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd., 3
Functional low molecular weight isocyanate compound), Epiclon 8
00 (manufactured by Dainippon Ink and Chemicals, Inc., bifunctional bisphenol type epoxy resin), PAZ33 (manufactured by Nippon Shokubai Kagaku, trifunctional ethyleneimine compound) and the like. When these curing agents are used together with the compound having two or more polar groups in the molecule, they cross-link well with the polar groups remaining without being adsorbed on the surface of the magnetic powder of the compound, so that they have a strong magnetic property. The layer is formed and the abrasion resistance is sufficiently improved. Therefore, the dispersibility of the magnetic powder is sufficiently improved and the abrasion resistance is also sufficiently improved, and a magnetic recording medium having a high S / N ratio, excellent electromagnetic conversion characteristics and excellent durability can be obtained. When using these curing agents, -S
When used in combination with the above compound having a polar group showing acidity such as O ₃ H or —COOH as a polar group for crosslinking, a curing agent having an ethyleneimine ring particularly reacts well with these compounds and crosslinks. Therefore, it is preferable to use a curing agent having an ethyleneimine ring, and --NH ₂ , --CO
When used in combination with the compound having a polar group having basicity such as NH- as a polar group for crosslinking, a curing agent having an isocyanate group or an epoxy group crosslinks well with these compounds, and therefore an isocyanate compound And it is preferable to use a curing agent such as an epoxy resin. Further, when used in combination with the above-mentioned compound having a -OH group as a polar group for crosslinking, any curing agent is preferably used because it crosslinks well with any curing agent. Since it has good properties, it is preferably used. Such a curing agent is 1 based on the total amount of the binder component.
It is preferable to use it within the range of 40% by weight. If it is too small, the desired effect cannot be obtained, and if it is too large, the stability of the magnetic coating composition is lowered due to an increase in viscosity.

The magnetic recording medium of the present invention may be produced according to a conventional method. For example, a polyester film or other substrate may have a magnetic powder, a binder component, and two or more polar groups in the molecule. A compound, a curing agent that crosslinks with this compound, a magnetic coating material containing an organic solvent and other additives is applied by any means such as spraying or roll coating,
Just dry.

Here, the binder resin used as the binder component is a vinyl chloride resin, a vinylidene chloride resin, a vinyl acetal resin, a fibrin resin, a polyurethane resin, which is generally used as a binder resin for magnetic recording media. A resin, a polyester resin, an acrylonitrile-butadiene copolymer, a polyethylene resin, a polyamide resin, an epoxy resin, a polyether resin, an acrylic resin, or the like is preferably used.

The magnetic powder used is, for example, γ-Fe ₂ O.
₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co-containing F
In addition to e ₃ O ₄ powder and CrO ₂ powder, various conventionally known magnetic powders such as metal powders such as Fe powder and Co powder and barium ferrite are widely included.

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

In the magnetic paint, various additives that are usually used, for example, abrasives such as α-Fe ₂ O ₃ powder, Al ₂ O ₃ powder, Cr ₂ O ₃ powder, lubrication of fatty acids and fatty acid esters, etc. Agents, antistatic agents such as carbon black, dispersants such as lecithin, etc. may be optionally added and used.

〔Example〕

 Next, an embodiment of the present invention will be described.

Example 1 Using a compound represented by the general formula (1) in which n is 3, Co-containing γ-Fe ₂ O ₃ powder 80 parts by weight Compound 1 〃 VAGH (manufactured by UCC, vinyl chloride-vinyl acetate-vinyl alcohol) Copolymer) 10〃 Pandex T5201 (Dainippon Ink and Chemicals,
Urethane elastomer) 8〃 Coronate L (Nippon Polyurethane Industry Co., Ltd., trifunctional low molecular weight isocyanate compound) 2〃 Methyl isobutyl ketone 50〃 Toluene 50〃 Each component except Coronate L is put in a ball mill for 70 hours. After mixing and dispersing, Coronate L was added and further mixed and dispersed for 1 hour to prepare a magnetic coating material. This magnetic paint was applied onto a polyester film having a heat of 11 μm so as to have a dry thickness of about 5 μm and dried to form a magnetic layer. Then, this was cut into a predetermined width to make a magnetic tape.

Example 2 In the composition of the magnetic coating material in Example 1, the general formula (1)
A magnetic tape was produced in the same manner as in Example 1 except that the same amount of the compound represented by the general formula (2) and n was 9 was used in place of the compound represented by.

Example 3 In the composition of the magnetic coating material of Example 1, the general formula (1)
A magnetic tape was produced in the same manner as in Example 1 except that the compound represented by the structural formula (11) was used in the same amount in place of the compound represented by.

Example 4 In the composition of the magnetic coating material in Example 1, the general formula (1)
A magnetic tape was prepared in the same manner as in Example 1 except that the compound represented by the general formula (8), R was an alkyl group having 22 carbon atoms, and n was 12 in the same amount, instead of the compound represented by Made.

Example 5 In the composition of the magnetic coating material of Example 1, the general formula (1)
In place of the compound represented by, the compound represented by the structural formula (12) is used in the same amount, and γ-F is used in place of the Co-containing γ-Fe ₂ O ₃ powder.
Use the same amount of e ₂ O ₃ powder, and replace P with Coronate L.
A magnetic tape was produced in the same manner as in Example 1 except that the same amount of AZ33 (manufactured by Nippon Shokubai Kagaku Co., Ltd., trifunctional ethyleneimine compound) was used.

Example 6 A magnetic tape was produced in the same manner as in Example 1 except that the same amount of nitrocellulose H1 / 2 (Nitrocellulose manufactured by Asahi Kasei Co., Ltd.) was used in place of VAGH in the composition of the magnetic paint in Example 1. It was

Example 7 A magnetic tape was prepared in the same manner as in Example 1 except that the same amount of Takenate L1007 (Takeda Yakuhin Kogyo Co., Ltd., urethane prepolymer) was used in place of the Bandex T5201 in the composition of the magnetic coating material of Example 1. I made it.

Example 8 In the composition of the magnetic coating material of Example 1, the general formula (1)
The same amount of the compound represented by the structural formula (11) was used in place of the compound represented by
A magnetic tape was prepared in the same manner as in Example 1 except that the same amount of 0 (bifunctional bisphenol type epoxy resin, manufactured by Dainippon Ink and Chemicals, Inc.) was used.

Comparative Example 1 In the composition of the magnetic coating material in Example 1, the general formula (1)
A magnetic tape was produced in the same manner as in Example 1 except that the compound represented by

Comparative Example 2 In the composition of the magnetic coating material of Example 1, the general formula (1)
A magnetic tape was produced in the same manner as in Example 1 except that the same amount of Gafferk (manufactured by Toho Kagaku Co., Ltd., phosphoric acid ester) was used instead of the compound represented by.

With respect to the magnetic tapes obtained in Examples and Comparative Examples, squareness was measured and abrasion resistance was tested.

In the abrasion resistance test, the magnetic tape was loaded into the tape recorder, and the tape recorder was repeatedly run to remove powder due to abrasion of the magnetic layer.
The number of head passes was measured until head stains and scratches on the surface of the magnetic layer became significant.

The table below shows the results.

[Effects of the Invention] As is clear from the above table, the magnetic tapes obtained in Examples 1 to 8 have higher squareness than the magnetic tapes obtained in Comparative Example 1, and Comparative Examples 1 and 2 Wear resistance is better than that of the magnetic tape obtained in 1. Therefore, the magnetic recording medium obtained according to the present invention has good dispersibility of magnetic powder, excellent electromagnetic conversion characteristics, and excellent wear resistance. I understand.

Claims (1)

[Claims] 1. In the molecule, --PO (OM) ₂ , --OPO (OM) ₂ , --SO ₃ M,
_{-OSO 3 M, -COOM, -NH 2} , -OH, -CO
NH- (however, M is H, Li, Na, K, NH ₂ or NH ₄
Is. ) Having two or more polar groups selected from (However, n is an integer of 3 to 12.) A magnetic recording medium having a magnetic layer comprising a compound having at least one skeleton represented by: and a hardener crosslinkable with the compound together with magnetic powder.