JPS61133015A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To strengthen a back coat layer and to improve the durability and traveling stability of the titled medium without deteriorating the electromagnetic transducing characteristic by incorporating a monomeric compd. having a specified polar group in the molecule into the back coat layer along with a curing agent. CONSTITUTION:A monomeric compd. having, in the molecule, >=2 kinds of polar groups selected from -PO(OM)2, -OPO(OM)2, -SO3M, -COOM, -NH2, -OH, and -CONH- (where M is H, Li, Na, K, NH2, or NH4) is used as the monomeric compd. which is used in a back coat layer. The >=2 kinds of polar groups are excellently adsorbed on the surface of a filler, and sufficiently cross-linked with a curing agent. Either a monomeric compd. shown by formulas I, II, III, IV, and V [where R is a 8-22C hydrocarbonic group, and (n) is a 3-12 integer) or a monomeric compd. shown by formula VI is appropriately used as the monomeric compd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium comprising a substrate having a magnetic layer on its surface and a back coat layer provided on the back surface thereof.

[Conventional technology]

In general, magnetic recording media such as magnetic tapes have a magnetic layer on their surface to effectively prevent winding irregularities and base film scraping during high-speed winding, and to improve running stability and durability. A bank coat layer is provided on the back side of the substrate, and in order to improve running stability and durability, a back coat layer with various fillers dispersed in binder resin is provided. . (Unexamined Japanese Patent Publication No. 57-92421) [Problems to be Solved by the Invention] However, the binder resin commonly used in the bank coat layer cannot disperse the filler well enough. Because the cross-linking with the hardening agent is not sufficient, the output fluctuation becomes large (or the filler powder falls off while the tape is running, and when the tape is wound, the fallen filler powder is transferred to the surface of the magnetic layer. However, there are disadvantages such as a decrease in output and a decrease in durability and running stability.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and in the molecule, -PO(OM)2, OP
O(OM)2, SO3M, OSO3M, -CO
A monomer compound having two or more polar groups selected from OM, -N, H2, -OH, -CONH- (where M is HSL i, Na, K, NH2 or NH) By including the filler in the back coat layer in combination with a hardening agent, the dispersibility of the filler in the binder resin is sufficiently improved, and the crosslinking with the hardener is sufficient to make the back coat layer strong. It has sufficiently improved durability and running stability without degrading electromagnetic conversion characteristics.

In this invention, the monomer compound used for the back coat layer has PO(OM) 2, OPO in the molecule.
(OM)2, SO3Ml 0803M, -C00M
, -NH2, -OH, -CONH- (However, M is H1L
i 1N a % K SN H2 or NH. ) fflf having two or more polar groups selected from
In the i-form compound, these two or more types of polar groups are well adsorbed onto the surface of the filler and also cross-linked well with the curing agent. Therefore, when this type of monomer compound is used together with a curing agent and is included in the back coat layer, the adsorption of these two or more types of polar groups to the filler surface and the crosslinkability with the curing agent can be improved. Depending on the difference, if one polar group is adsorbed to the filler surface, the other polar group will crosslink with the curing agent, and conversely, if one polar group is crosslinked with the curing agent, the other polar group will form a filling bond. The dispersibility of the filler in the bank coat layer is sufficiently improved by adsorption to the surface of the filler, and the abrasion resistance of the bank coat layer is also sufficiently improved, resulting in good electromagnetic conversion characteristics and excellent durability and running stability. A magnetic recording medium is obtained.

In such a molecule, -po <0M)2, -OPO
(OM)2, SO3M, OSO3M.

-COOM, NH2, -OH, -CONH (however,
M is H, Li, Na, NH2 or NH4. ), for example, a monomer compound having two or more polar groups selected from the general formula % (%) (where R is a hydrocarbon group having 8 to 22 carbon atoms, and n is 3 to 22).
It is an integer of 12. ), and a monomer compound represented by the structural formula CH3(CH2
)e CH(CH2)y NH25O3Na CH3(CH2)e CH(CH2)y NH2S
Any monomer compound represented by O3H is preferably used.

Monomer compounds having two or more types of polar groups as described above are usually obtained by a method similar to the method for manufacturing surfactants in general, and these two or more types of polar groups introduced in this way are It adsorbs well to the filler surface and also cross-links well with the curing agent.

Therefore, when a monomer compound having two or more of these polar groups is used together with a curing agent in the back coat layer, the adsorption of these two or more polar groups to the surface of the filler and the crosslinking property with the curing agent can be achieved. Due to the difference in Since these two or more types of polar groups are adsorbed on the surface of the filler, the dispersibility of the filler in the back coat layer is sufficiently improved, and the abrasion resistance of the back coat layer is also sufficiently improved, resulting in improved electromagnetic conversion characteristics. A magnetic recording medium with good durability and running stability can be obtained. It is preferable to use this type of monomer compound within the range of 0.1 to 10% by weight based on the filler; if it is too small, the desired effect cannot be obtained, and if it is too large, magnetic Abrasion resistance and heat resistance decrease because the amount of monomer compounds that remain unadsorbed on the powder surface increases.

In this way, in a monomer compound having two or more types of polar groups, the two types of introduced polar groups are -PO(OM)2
, OPO(OM)2, -303M, -OSO3M,
If it is acidic, such as -COOM, it will adsorb well to a filler whose surface is basic, and conversely -NH2, -CO
When it is basic like NH-, it is well adsorbed on the surface of the filler having an acidic surface, improving the dispersibility and filling properties of the filler. In particular, -PO(OM)2, -OPO(OM
) Monomer compounds with polar groups such as 2 are used as the best because they have good interaction with fillers, and monomer compounds with polar groups such as -303M and OSO3M are used for bonding. It is particularly well used because of its good compatibility with the agent resin. Furthermore, those with a polar group -COOM are easy to use because they dissolve well in organic solvents.
Those having polar groups -NH2 and -CONH- adsorb particularly well to fillers with acidic surfaces, and are therefore particularly suitable when using fillers with acidic surfaces.

Curing agents used in combination with such monomeric compounds having two or more types of polar groups in the molecule include - cross-linking agents such as two or more isocyanate groups, epoxy groups, or ethyleneimine rings in the molecule; Isocyanate compounds, epoxy compounds, and ethyleneimine compounds having a functional group are preferably used, and specific examples include Coronate, manufactured by Nippon Polyurethane Industries, Ltd., 3
Functional Image Molecular Weight Isocyanate Compound), Evicron 8
00 (manufactured by Dainippon Ink & Chemicals Co., Ltd., bifunctional bisphenol type epoxy resin), PAZ33 (manufactured by Nippon Shokubai Kagaku Co., Ltd., trifunctional tyrene imine compound), and the like. When these curing agents are used in combination with the above-mentioned monomer compounds having two or more types of polar groups in their molecules, they form a good cross-linking bond with the remaining polar groups of the monomer compounds that are not adsorbed on the filler surface. Therefore, a tough back coat layer is formed and wear resistance is sufficiently improved. Therefore, the dispersibility of the filler in the back coat layer is sufficiently improved, and the abrasion resistance of the back coat layer is also sufficiently improved.
A magnetic recording medium with good electromagnetic conversion characteristics, excellent durability and running stability can be obtained. When these curing agents are used together with the above-mentioned monomer compounds having an acidic polar group such as -5o3H1-COOH as a crosslinking polar group, the curing agents having an ethyleneimine ring are particularly difficult to use. It is preferable to use a curing agent having an ethyleneimine ring in order to react well with the monomer compound and form a crosslinking bond, and the curing agent has a polar group exhibiting basicity such as -NH2 or -CONH- as a polar group for crosslinking. When used in combination with the above-mentioned monomer compounds, it is recommended to use curing agents such as isocyanate compounds and epoxy resins, as curing agents having isocyanate groups and epoxy groups crosslink well with these monomer compounds. is preferred. In addition, when used in combination with the above-mentioned monomer compound having a 10H group as a polar group for crosslinking, both curing agents are preferably used because they crosslink well, and especially in this case, It is preferably used because the back coat layer paint has good stability. Such a hardening agent is used in an amount of 1 to 4 based on the total amount of binder components.
It is preferable to use it within the range of 0% by weight; if it is too small, the desired effect will not be obtained, and if it is too large, the stability of the back coat layer paint will decrease, resulting in increased viscosity, gelation, poor dispersion, etc. .

Such a backcoat layer usually contains 2 in the molecule.
A monomer compound having more than one type of polar group, a binder component,
A back coat layer paint is prepared by mixing and dispersing it with a hardening agent, filler, organic solvent, etc., and this is applied to the back side of a substrate such as a polyester film on which a magnetic layer has been previously formed, and then dried. . If the thickness of such a back coat layer is thinner than 0.1μ, the desired effect cannot be obtained;
．． If it is thicker than 0μ, curling occurs with the back coat layer inside, so it is preferably within the range of 0.1 to 3.0μ, and preferably within the range of 0.5 to 2.0μ. More preferred.

Here, the binder resin used as the binder component is vinyl chloride resin, vinylidene chloride resin, vinyl acecool resin, cellulose resin, which is generally used as a binder resin for magnetic recording media. Polyurethane resins, polyester resins, acrylonitrile-butadiene copolymers, polyethylene resins, polyamide resins, epoxy resins, polyether resins, acrylic resins, and the like are all preferably used.

In addition, as the filler used, if the Mohs hardness exceeds 5, there is a risk of damaging the magnetic layer during winding, so fillers with a Mohs hardness of 5 or less are preferably used. For example, carbon black with a Mohs hardness of 5 or less is used. , cx-Fe20
3 powder, Cr2O3 powder, Al2O3 powder, Al(OH
)3 powder, BaSO4 powder, CaCO3 powder, MgO powder, BaCO3 powder, ZnO powder, Cu2O powder, Cu
O powder, MoS2 powder, WS2 powder, goethite, etc. are preferably used. These fillers have an average particle size of 0.05 to 5 μm and are added to the total solid components of the back coat layer so that fine irregularities can be formed on the surface of the back coat layer and good running stability can be obtained. It is preferable to use it within a range of 20 to 80% by weight based on the total amount.

Examples of organic solvents include methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane, dimethyl formamide, and other organic solvents commonly used to melt binder resins, either alone or in combination of two or more. used.

The magnetic layer formed on the substrate is made of γ-Fe203 powder, F
It was prepared by mixing various conventionally known magnetic powders such as e3O4 powder, Co-containing r-Fe203 powder, CO-containing Fe3O4 powder, Fe powder, CO powder, Fe-Ni powder, and barium ferrite together with a binder resin and an organic solvent. A magnetic paint is applied onto the substrate and dried, or C.

, Ni, Fe, Co-Ni, Co-Cr, Co-P, C
It is formed by depositing a ferromagnetic material such as o-N1-P on a substrate by means such as vacuum deposition, ion blating, sputtering, or plating.

〔Example〕

Next, embodiments of the invention will be described.

Example I Co-containing Fe203 powder 80 parts by weight VAGH
(Manufactured by U, C, C, vinyl chloride 10-vinyl acetate-vinyl alcohol copolymer) Vandenox T5201 (Dainippon 8, manufactured by Ink Chemical Industry Co., Ltd., urethane elastomer) Coronate L (Nippon Polyurethane 2, manufactured by Kogyo Co., Ltd., Trifunctional low molecular weight isocyanate compound) Methyl isobutyl ketone 50〃Toluene
50 This composition was mixed and dispersed in a ball mill for 70 hours to prepare a magnetic paint. This magnetic paint was applied to the surface of a polyester film having a thickness of 11 μm to a dry thickness of approximately 3 μm, dried, and surface treated to form a magnetic layer.

Next, on the back side of the polyester film on which the magnetic layer was formed, a back coat layer paint consisting of the following composition was prepared using a monomer compound represented by the general formula (11, where n is 3). A hack coat layer was formed by coating and drying to a dry thickness of 2 μm, and was cut to a predetermined width to produce a magnetic tape.

Back coat layer paint monomer compound 1 part by weight Bandesox T5201 150 Coronat
10 〃Red Gara
30〃H3-500 (manufactured by Asahi Carbon Co., Ltd. 7
0〃Carbon blank) Methyl isobutyl ketone 500〃Toluene
500 Example 2 In the composition of the back coat layer paint in Example 1, in place of the monomer compound represented by general formula (11), a monomer compound represented by general formula (2) where n is 9 was used. A back coat layer was formed in the same manner as in Example 1, except that the same amount of the compound was used, and a magnetic tape was produced.

Example 3 In the composition of the back coat layer paint in Example 1,
A back coat layer was formed in the same manner as in Example 1, except that the same amount of the monomer compound represented by Structural Formula (11) was used in place of the monomer compound represented by General Formula +11, I made magnetic tape.

Example 4 In the composition of the back coat layer paint in Example 1,
Except that the monomer compound represented by general formula (8), where R is an alkyl group having 22 carbon atoms and n is 12, was used in the same amount instead of the monomer compound represented by general formula (1). A bank coat layer was formed in the same manner as in Example 1 to produce a magnetic tape.

Example 5 In the composition of the back coat layer paint in Example 1,
Nitrocellulose H instead of Bandesox T5201
A back coat layer was formed in the same manner as in Example 1, except that the same amount of 1,/2 (manufactured by Asahi Kasei Corporation, nitrocellulose) was used, and a magnetic tape was produced.

Example 6 In the composition of the back coat layer paint in Example 1,
Takenate L100 instead of Pandenox T5201
A back coat layer was formed in the same manner as in Example 1, except that the same amount of 7 (urethane prepolymer manufactured by Narita Pharmaceutical Industries, Ltd.) was used, and a magnetic tape was produced.

Example 7 In the composition of the back coat layer paint in Example 1,
In place of the monomer compound represented by general formula (1), the same amount of the monomer compound represented by structural formula (11) was used, and in place of Coronate, Epiclon 800 (Dainippon Ink Chemical Co., Ltd. A back coat layer was formed in the same manner as in Example 1, except that the same amount of difunctional bisphenol type epoxy resin (manufactured by Nippon Steel Co., Ltd.) was used, and a magnetic tape was attached.

Comparative Example 1 In the composition of the back coat layer paint in Example 1,
A back coat layer was formed in the same manner as in Example 1, except that the monomer compound represented by general formula (11) was omitted, and a magnetic tape was produced.

Comparative Example 2 In the composition of the back coat layer paint in Example 1,
A back coat layer was formed in the same manner as in Example 1, except that the same amount of Garfasoku (manufactured by Toho Chemical Co., Ltd., phosphoric acid ester) was used in place of the monomer compound represented by general formula (11),
I made magnetic tape.

Regarding the magnetic tapes obtained in each Example and each Comparative Example, in order to examine the dispersibility of the filler, durability, and running stability, output fluctuations and output decreases were measured, and winding irregularities of the magnetic tapes were observed. The output decrease and output fluctuation were measured after the magnetic tape was run 100 times on an oven deck. Regarding the winding disorder of the magnetic tape, cases in which no winding disorder was observed at all are marked as (○), cases in which slight winding disorder was observed (Δ), and cases in which noticeable winding disorder was observed (×).
).

The table below shows the results.

〔Effect of the invention〕

As is clear from the table above, the magnetic tapes obtained in Examples 1 to 7 showed no winding disorder at all, and had a lower output than the magnetic tapes obtained in Comparative Examples 1 and 2. As a result, the magnetic recording medium obtained by this invention has good filler dispersibility in the back coat layer, and has sufficiently improved durability and running stability without deteriorating electromagnetic conversion characteristics. I can see that it is being done.

Claims (1)

[Claims] 1. In the molecule: -PO(OM)_2, -OPO(OM)_2, -SO_
3M) -OSO_3M, -COOM, -NH_2, -O
H, -CONH- (However, M is H, Li, Na, K, NH_2 or NH
It is _4. ) A back coat layer comprising a monomer compound having two or more types of polar groups selected from magnetic recording medium provided in