JPH0562162A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable a specified compound, vinyl chloride resin, and isocyanate compound to be contained within a magnetic layer of a magnetic recording medium, a dissipation property of the magnetic powder to be improved, and electromagnetic conversion characteristics and durability to be improved. CONSTITUTION:A title item is provided with a magnetic layer containing a compound which is expressed by a general expression, R1 (R2)-N-(CH2)m-SO3M (however, R1 and R2 are H or CnH2n+1, n is an integer ranging from 1 to 8, M is any one type which is selected from H, Li, Na, K, Rb, Cs, and Fr, and m is an integer ranging from 2 to 22.). Furthermore, vinyl chloride resin and isocyanate compound are contained as a binder constituent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
More specifically, the present invention relates to a magnetic recording medium having good dispersibility of magnetic powder, excellent electromagnetic conversion characteristics, and excellent durability.

[0002]

2. Description of the Related Art A magnetic recording medium is usually produced by applying a magnetic coating material comprising a magnetic powder, a binder component, an organic solvent and other necessary components on a substrate such as a polyester film and drying it to improve the recording density. At the same time, improvement in durability is required. Therefore, it has been attempted to improve the dispersibility of the magnetic powder and the durability of the magnetic layer by using a dispersant for the magnetic powder. For example, it is possible to include sulfophthalic acid or a metal salt thereof in the magnetic layer. Being tried.
(Japanese Patent Laid-Open No. 1-271914)

[0003]

However, since this kind of sulfophthalic acid or its metal salt does not interact sufficiently with the binder resin, the dispersibility of the magnetic powder and the durability of the magnetic layer are still insufficient. Can not be improved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made as a result of various studies in view of the present situation, and has the general formula R ₁ (R ₂ ) -N- (CH ₂ ) m -SO ₃ M (however, , R ₁ and R ₂ are H or C _n H _{2n + 1} and n is 1
~ Integer 8, M is H, Li, Na, K, Rb, Cs, F
Any one selected from r and m is an integer of 2 to 22. By containing the compound represented by the formula (4) in the magnetic layer, the dispersibility of the magnetic powder is improved, and by using a vinyl chloride resin and an isocyanate compound together, the mechanical strength of the magnetic layer is sufficiently improved. It has been improved and the durability has been sufficiently improved.

The compound represented by the above general formula used in the present invention has a --SO ₃ M group and a --NR ₁ (R
₂ ) Group having both functional groups, one functional group —SO ₃ M group is strongly adsorbed on the particle surface of the magnetic powder. When the other —NR ₁ (R ₂ ) group is used in combination with an isocyanate compound, when at least one of R ₁ and R ₂ is H,
Reacting to form a urea bond, when the vinyl chloride resin is used together, the isocyanate group remaining in the isocyanate compound reacts with the hydroxyl group in the vinyl chloride resin,
A strong crosslinked structure is formed between the magnetic powder, the isocyanate compound, and the vinyl chloride resin through the compound of this type. Further, when both R ₁ and R ₂ in the —NR ₁ (R ₂ ) group are alkyl groups, a urea bond is not formed,
It has a catalytic effect of promoting the reaction between the isocyanate group and the hydroxyl group, and forms a strong crosslinked structure in the binder resin.

Therefore, this type of --SO ₃ M group and --NR
_{When a} compound having both functional groups of ₁ (R ₂ ) group is contained in the magnetic layer, the affinity between the magnetic powder and the binder resin is improved, the dispersibility of the magnetic powder is sufficiently improved, and electromagnetic conversion is performed. The characteristics are sufficiently improved. When used together with an isocyanate compound or a vinyl chloride resin, the magnetic powder is incorporated into the cross-linking structure between these compounds and the binder resin to further improve the dispersibility of the magnetic powder, and at the same time, the magnetic layer. The mechanical strength is sufficiently improved, the powder drop is sufficiently reduced, and the durability is sufficiently improved.

The compound represented by the above general formula having such functional groups of both --SO ₃ M group and --NR ₁ (R ₂ ) group is
R ₁ and R ₂ are H or C _n H _{2n + 1} , n is an integer of 1 to 8, M is any one selected from H, Li, Na, K, Rb, Cs and Fr, and CH ₂ is A polymer having a degree of polymerization n of 2 to 22 is preferably used, and from the viewpoint of firmly fixing the magnetic powder to the crosslinked structure of the binder resin, it is more preferable that at least one of R ₁ and R ₂ is H. used. As a specific example, for example, the chemical formula H ₂ N
Examples include taurine represented by — (CH ₂ ) ₂ —SO ₃ H.

In order to incorporate the compound represented by the above general formula having such functional groups of --SO ₃ M group and --NR ₁ (R ₂ ) group into the magnetic layer, a compound of this kind is used. , A magnetic powder, a binder resin, an organic solvent and other necessary components are mixed and dispersed to prepare a magnetic coating material, and the magnetic coating material is applied onto a substrate such as a polyester film and dried, or a compound of this kind is added. A method in which magnetic powder is mixed and dispersed in a suitable solvent such as water or alcohols, the surface of the magnetic powder is treated with a compound of this type, and then magnetic coating is prepared using this magnetic powder. Done in. When a magnetic paint is prepared by mixing and dispersing this type of compound with magnetic powder, etc., the amount used is 1.0 to 10.0 with respect to the magnetic powder.
Is preferably in the range of weight%, to the surface treatment of the magnetic powder with this type of compound is in the range of 0.1mg / m ² ~10mg / m ² in the deposition amount of the magnetic powder particle surfaces It is preferable to put it inside.

The binder resin used in the present invention is a vinyl chloride resin and a polyisocyanate resin.
Compound is preferably used, and when these binder resins are used in combination, -NR of the compound represented by the above general formula is obtained.
_When at least one of R ₁ and R _{2 in} the ₁ (R ₂ ) group is H, it reacts with an isocyanate compound to form a urea bond, and further the hydroxyl group in the vinyl chloride resin and the isocyanate compound The residual isocyanate groups react with each other to form a strong crosslinked structure between the magnetic powder, the isocyanate compound and the vinyl chloride resin through this type of compound. Thus, the magnetic powder is incorporated into the cross-linking structure between these compounds and the binder resin to further improve the dispersibility of the magnetic powder, and at the same time, the mechanical strength of the magnetic layer is sufficiently improved, resulting in a tough magnetic layer. Is formed and the powder drop is sufficiently reduced.

As the vinyl chloride resin used here, one containing 5 or more hydroxyl groups in one molecule is preferably used. For example, Sekisui Chemical Co .;
S-REC E, manufactured by Zeon Corporation; MR110, UC in the United States
C company; VAGH, VAGF and the like are preferably used.

As the isocyanate compound, any conventionally known one is preferably used. For example, Nippon Polyurethane Industry Co., Ltd .; Coroneate L, Coroneate HL, Coroneate HX, Coronene. -N and the like are preferably used.

Incidentally, together with the vinyl chloride resin and the isocyanate compound, conventionally known binder resins such as polyvinyl butyral resin, fibrin resin,
You may use together polyurethane type resin, polyester type resin, etc.

The magnetic powder used in the magnetic layer is, for example, γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder,
Co-containing γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, CrO ₂ powder, Fe powder, Co powder, Fe-N
Various conventionally known magnetic powders such as metal powders such as i-Cr alloy powders and barium ferrite powders are widely included.

As the organic solvent, methylisobutylketone, methylethylketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane, dimethylformamide and the like generally used in magnetic recording media may be used alone or in combination.

In the magnetic paint, a lubricant, an abrasive,
Additives generally used in magnetic recording media such as antistatic agents and dispersants may be added.

[0016]

EXAMPLES Next, examples of the present invention will be described. Example 1 α-Fe magnetic powder (Al content 4.0% by weight, coercive force 1600 80.0 parts by weight Oersted, BET specific surface area 50 m ² / g) VAGF (UCC; vinyl chloride resin) 10.0 〃 N2301 (Nippon Polyurethane Industry Co., Ltd.) (Urethane resin) 6.0 〃 H ₂ N- (CH ₂ ) _2- SO ₃ H 1.6 〃 alumina 12.0 〃 carbon black 8.0 〃 oleyl oleate 8.0 〃 methyl ethyl ketone 84 〃 cyclohexanone 84 〃 toluene 84 〃 After mixing and dispersing in a ball mill for 72 hours,
Furthermore, 4.0 parts by weight of Colone L (manufactured by Nippon Polyurethane Industry Co., Ltd .; polyisocyanate) in terms of solid content was added, and 1
After mixing for 5 minutes, a magnetic paint was prepared through a filter having a pore size of 0.6 μm. This magnetic paint was applied to both sides of a polyester film having a thickness of 62 μm so that the thickness after drying would be 2.5 μm, and dried to form a magnetic layer, followed by surface smoothing treatment. Next, this was cured at 60 ° C. for 48 hours and then punched out into a 3.5-inch disk to prepare a magnetic disk.

Example 2 Co-deposited γ-Fe ₂ O ₃ powder (BET specific surface area 50 m ²
/ G) 250 parts by weight into 1000 parts by weight of pure water, stirred and dispersed by a homomixer, and then added with H ₂ N- (C
10 parts by weight of H ₂ ) ₂ —SO ₃ H was added, and the mixture was stirred for 1 hour and then stored at 25 ° C. for 48 hours. Next, Co deposition γ-
Fe ₂ O ₃ powder was separated by filtration, washed with 1000 parts by weight of pure water, and then vacuum dried to obtain H ₂ N- (CH ₂ ) ₂
A Co-deposited γ-Fe ₂ O ₃ powder surface-treated with —SO ₃ H was obtained.

Using the surface-treated Co-coated γ-Fe ₂ O ₃ powder thus obtained, 80.0 parts by weight of surface-treated Co-coated γ-Fe ₂ O ₃ powder MR110 (manufactured by Zeon Corporation; vinyl chloride) Resin) 10.0〃 N2301 (Nippon Polyurethane Industry Co., Ltd .; urethane resin) 6.0〃 alumina 4.0〃 carbon black 3.2〃 myristic acid 1.0〃 n-butyl stearate 1.0〃 cyclohexanone 110〃 toluene 110〃 After mixing and dispersing in the same for 48 hours, 4.0 parts by weight of Coronet L (manufactured by Nippon Polyurethane Industry Co., Ltd .; polyisocyanate) in terms of solid content was added, and
After mixing for a minute, a magnetic paint was prepared through a filter having a pore diameter of 4 μm. This magnetic paint was applied onto a polyester film having a thickness of 14 μm while performing a magnetic field orientation treatment so that the thickness after drying was 4 μm, and dried to form a magnetic layer, and a surface smoothing treatment was performed. Then, it was cut into 1/2 inch to prepare a video tape, which was then incorporated into a VHS cassette (120 minutes) to obtain a video cassette.

Example 3 In the composition of the magnetic paint in Example 2, MR110 was used.
A video tape was produced in the same manner as in Example 2 except that the same amount of nitrocellulose (1 second type) was used instead of the above, to obtain a video cassette.

Comparative Example 1 In the composition of the magnetic coating material of Example 1, H ₂ N-
A magnetic disk was produced in the same manner as in Example 1 except that the same amount of 5-sulfoisophthalic acid was used instead of (CH ₂ ) ₂ —SO ₃ H.

Comparative Example 2 In the composition of the magnetic coating material of Example 1, H ₂ N-
(CH ₂₎ except omitting the ₂ -SO ₃ H is a magnetic disk was produced in the same manner as in Example 1.

Comparative Example 3 In the composition of the magnetic coating material of Example 2, H ₂ N-
(CH _{2) 2} -SO ₃ H in the surface-treated Co-coated γ-
Instead of the Fe ₂ O ₃ powder, except that the surface-treated Co-coated γ-Fe ₂ O ₃ powder was used the same amount in the 5-sulfoisophthalic acid, video tape in the same manner as in Example 2 - to prepare a flop Got a video cassette.

Comparative Example 4 In the composition of the magnetic coating material of Example 2, H ₂ N-
(CH _{2) 2} -SO ₃ H in the surface-treated Co-coated γ-
Instead of Fe ₂ O ₃ powder, untreated Co-deposited γ-Fe ₂
A video tape was produced in the same manner as in Example 2 except that the same amount of O ₃ powder was used to obtain a video cassette.

With respect to the magnetic disks and the video tapes obtained in the respective examples and comparative examples, reproduction output and powder drop were examined.

In the case of the magnetic disks obtained in Example 1 and Comparative Examples 1 and 2, the reproduction output was measured at the initial value of 2f reproduction output and after 72 hours running at 40 ° C. and 60% RH. In addition, the powder drop is visually observed on the magnetic head and the slider after running for 72 hours at 40 ° C. and 60% RH.
The one with almost no powder falling was evaluated as 5 points, and the one with much powder falling as 0 point.

The reproduction output in the case of the video cassettes obtained in Examples 2 and 3 and Comparative Examples 3 and 4 is the initial value of the reproduction output and the value after repeated running 250 times under the conditions of 40 ° C. and 60% RH. Was measured. In addition, powder drop is 40 ℃,
Visual observation of powder falling on the magnetic head, head drum, guide pin, etc. of the video recorder after repeatedly running 250 times under the condition of 60% RH.
The point and the one with a large amount of powder falling were set as 0 point, and evaluation was performed in 5 stages during this period. Table 1 below shows the results.

[0027]

[0028]

As is apparent from Table 1 above, Example 1
The magnetic discs obtained in Example 1 and the video tapes obtained in Examples 2 and 3 were compared with the magnetic discs obtained in Comparative Examples 1 and 2 and the video tapes obtained in Comparative Examples 3 and 4. In the magnetic recording medium obtained by the present invention, the dispersibility of the magnetic powder is good, the electromagnetic conversion characteristics are excellent, and the durability is sufficiently high. You can see that it has been improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruhisa Miyata 1-88, Tora, Ibaraki-shi, Osaka Within Hitachi Maxell Co., Ltd. Maxel Co., Ltd.

Claims (2)

[Claims] 1. A compound represented by the general formula R ₁ (R ₂ ) —N— (CH ₂ ) m —SO ₃ M (wherein R ₁ and R ₂ are H or C _n H _{2n + 1} and n is 1).
~ Integer 8, M is H, Li, Na, K, Rb, Cs, F
Any one selected from r and m is an integer of 2 to 22. ) A magnetic recording medium having a magnetic layer containing a compound represented by 2. The magnetic recording medium according to claim 1, further comprising a vinyl chloride resin and an isocyanate compound as a binder component.