JPH0562155A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a magnetic recording medium capable of improving the durability of a magnetic layer and a back coat layer. [Structure] A magnetic layer formed on a polyethylene terephthalate film contains N, N-dimethyl-n-octadecylamine stearate and a binder having a glass transition point Tg of 45 ° C. or higher. A magnetic layer and a back coat layer are formed on both sides of the polyethylene film, and the back coat layer contains N, N-dimethyl-n-octadecylamine stearate and a binder having a glass transition point Tg of 45 ° C. or higher. Has been.

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 having a magnetic layer formed on a non-magnetic support such as a magnetic tape.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium such as a magnetic tape or a magnetic disk, a ferromagnetic powder, a resin binder, a dispersant, various additives and the like are dispersed in an organic solvent on a non-magnetic support such as a polyester film. A so-called coating type magnetic recording medium in which a magnetic layer is formed by coating a kneaded magnetic coating material is widely used. Such a magnetic recording medium is used while always in sliding contact with the magnetic head or guide member of the recording / reproducing device, the drum, etc., so that good traveling properties can be obtained in order to exhibit stable and excellent electromagnetic conversion characteristics,
Durability is required. Therefore, in the usual case, a curing agent is added to the magnetic paint, and the resin binder is three-dimensionally cross-linked through a thermosetting process to improve the durability.

[0003]

However, in the case of such a conventional example, various problems have occurred depending on the glass transition point Tg of the resin binder and the type of the curing agent. For example,
When a binder having a glass transition point Tg of 45 ° C. or higher is used, a sufficient curing reaction does not occur when a toluylene diisocyanate (TDI) -based curing agent is added, and durability is not improved so much. Further, when a hexamethylene diisocyanate (HDI) -based curing agent is added, the curing reaction is carried out, but there is a problem that tackiness occurs in the curing step. On the other hand, when a binder having a glass transition point Tg of 45 ° C. or less is used, the curing reaction is sufficiently performed by adding any curing agent, but the durability is not improved so much.

By the way, in this kind of magnetic recording medium, it is widely practiced to provide a back coat layer on the side where the magnetic layer is not provided in order to prevent winding disturbance of the tape or the like, to prevent electrification, and to improve running properties. ing. This back coat layer is
It is formed by applying a back coat paint in which a non-magnetic powder such as a conductive carbon material is dispersed in a binder on a non-magnetic support. It is required to have excellent durability.
In this case, as a means for improving the durability of the back coat layer, it is known to carry out a dispersion treatment for a long time when the back coat coating is prepared to promote the interaction with the binder or the like. However, when the dispersion treatment is carried out for a long time, the smoothing of the back coat layer becomes too high and the friction coefficient at the time of contact with the running system increases. On the other hand, it is conceivable to add a curing agent to three-dimensionally crosslink the resin binder as in the case of forming the magnetic layer, but as described above, when the glass transition point Tg of the binder is 45 ° C. or higher, curing It could not be adopted due to problems such as insufficient reaction with the agent.

The present invention has been made in view of the above points of the conventional example, and an object thereof is to provide a magnetic recording medium capable of improving the durability of the magnetic layer and the back coat layer. ..

[0006]

The present invention provides a magnetic recording medium comprising a non-magnetic support and a magnetic layer comprising a ferromagnetic powder and a binder as a main component, and a tertiary amine in the magnetic layer. While containing a carboxylic acid amine salt having
The binder is characterized by having a glass transition point of 45 ° C. or higher. Further, the present invention provides a magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer mainly containing non-magnetic powder and a binder is formed on the other surface. The backcoat layer contains a carboxylic acid amine salt having a tertiary amine, and the binder is a binder having a glass transition point of 45 ° C. or higher. In this case, the method of forming the magnetic layer is not limited to the application of the magnetic paint, and the ferromagnetic metal may be vacuum-deposited.

The addition amount of the carboxylic acid amine salt having a tertiary amine is 1 to 10 parts by weight, preferably 2 to 6 parts by weight. If the amount added is too large, the dispersibility deteriorates, the binder plasticizes, and the magnetic layer becomes soft. The carboxylic acid amine salt in which the amine is tertiary can be synthesized by using a tertiary amine and a carboxylic acid as starting materials. And
Such a compound may be added to a suitable organic solvent together with a magnetic powder, a non-magnetic powder, a binder and the like when preparing a magnetic coating material for forming a magnetic layer or a back coating material for forming a back coating layer. As this organic solvent,
It may be appropriately selected from ethers, esters, ketones, aromatic hydrocarbons, aliphatic hydrocarbons and the like depending on the kind of the binder and the like.

As the magnetic powder used in the present invention, any conventionally known magnetic powder can be used, and it may be an oxide magnetic powder or a metal magnetic powder.

On the other hand, non-magnetic powders include, for example, contact black, channel black, roll black,
All kinds of carbon black such as disk black, CaCO ₃ powder, BaSO ₄ powder, ZnO powder, TiO
Inorganic pigments such as ₂ powder, Al ₂ O ₃ powder and Cr ₂ O ₃ powder can be used.

Further, as the binder, the glass transition point Tg
At 45 ° C. or higher, those commonly used as binders for magnetic recording media, for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, cellulose derivatives such as nitrocellulose resins. Any of epoxy resin, phenoxy resin and the like can be used.

[0011]

In the present invention having such a constitution, the reaction between the binder and the curing agent in the magnetic layer is promoted by the carboxylic acid tertiary amine salt contained in the magnetic layer, and the three-dimensional crosslinking of the binder is achieved. Well done. Further, in the present invention, the carboxylic acid tertiary amine salt contained in the backcoat layer promotes the reaction between the binder and the curing agent in the backcoat layer, thereby sufficiently performing three-dimensional crosslinking of the binder. Be seen.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 This example is an example of a magnetic tape containing N, N-dimethyl-n-octadecylamine stearate as a carboxylic acid amine salt in which the amine is tertiary. The N, N-dimethyl-n-octadecylamine stearate of this example has a structure shown in Table 2 below.

This magnetic tape was manufactured by the following method. First, the basic composition of the magnetic paint is shown below. Oxide magnetic powder (Co-γ-Fe ₂ O ₃ specific surface area 45 m ² / g) 100 parts by weight Vinyl chloride (Tg 73 ° C.) 10 parts by weight Polyurethane resin (Tg 60 ° C.) 10 parts by weight Carbon 5 parts by weight Methyl ethyl ketone 150 parts by weight Part Methyl isobutyl ketone 150 parts by weight

Next, 1 part by weight of N, N-dimethyl-n-octadecylamine stearate was added to this basic composition, and the mixture was dispersed and mixed in a ball mill for 24 hours, filtered, and immediately before polymerization, a curing agent was added. 4 parts by weight was added and stirred for 30 minutes to prepare a magnetic paint.

Thereafter, this magnetic paint is applied to a thickness of 12 μm.
Was applied to the polyethylene terephthalate film of (3) so that the thickness of the coating film after drying was 5 μm. Then, magnetic field orientation was performed, and after drying, it was wound up. After a heat-curing step, calendering was performed, and then the sheet was cut into a 1/2 inch width to prepare a magnetic tape.

Examples 2 to 4 In Example 1, the amount of N, N-dimethyl-n-octadecylamine stearate added was set to 2,3,5 parts by weight, and the other magnetic fields were the same as in Example 1. A tape was made.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 without adding N, N-dimethyl-n-octadecylamine stearate, and was used as Comparative Example 1.

Comparative Examples 2 and 3 2.5 parts by weight of N, N-dimethyl-n-octadecylamine or stearic acid was added instead of N, N-dimethyl-n-octadecylamine stearate, and the other examples were used. A magnetic tape was produced in the same manner as in 1.

With respect to each of the magnetic tapes thus produced, a durability test and a resin uncrosslinking rate were measured. The results are shown in Table 1. In this case, the uncrosslinked ratio was determined from the amount of binder eluted by immersing the tape containing no curing agent and the tape containing the curing agent in methyl ethyl ketone for a predetermined time. That is, it is an amount represented by the following equation.

[0021]

[Equation 1]

On the other hand, the durability was evaluated by visually observing the amount of powder falling on the head drum, guide, etc. after 100 times of running for 60 minutes. Good: good, slightly bad: bad, bad Was evaluated as x.

[0023]

[Table 1]

As can be seen from Table 1, in Examples 1 to 4 to which the present invention was applied, the uncrosslinked ratio was small, the three-dimensional crosslinking of the resin binder was sufficiently performed, and the durability was remarkably improved. ing.

Examples 5 to 8 In Example 1, instead of N, N-dimethyl-n-octadecylamine stearate, four compounds shown in Table 2, that is, a carboxylic acid amine salt in which the amine is tertiary is 5 Each magnetic tape was produced in the same manner as in Example 1 except that the parts by weight were added.

[0026]

[Table 2]

Each magnetic tape thus produced was subjected to a durability test to measure the resin uncrosslinked ratio. The results are shown in Table 3.

[0028]

[Table 3]

It can be understood that even if any of the compounds shown in Table 2 is used, the uncrosslinked ratio is small and the durability is remarkably improved.

Examples 9 to 11 In Example 1, the amount of N, N-dimethyl-n-octadecylamine stearate added was 5 parts by weight, the binder was 20 parts by weight of the polyurethane resin, and the glass transition point of the polyurethane resin was Tg was set to 45 ° C., 60 ° C., 70 ° C., and other magnetic tapes were manufactured by the same method as in Example 1.

Comparative Example 4 In Example 1, the amount of N, N-dimethyl-n-octadecylamine stearate added was 5 parts by weight, the binder was 20 parts by weight, and the glass transition point Tg of the polyurethane resin was set to 20 parts by weight. A magnetic tape was produced by the same method as in Example 1 except that the temperature was 38 ° C.

The tapes of Examples 9 to 11 and Comparative Example 4 thus produced were subjected to a durability test to measure the resin uncrosslinked ratio. The results are shown in Table 4.

[0033]

[Table 4]

As can be seen from Table 4, in the case of Comparative Example 4 in which the binder having the glass transition point Tg of 38 ° C. was used, the uncrosslinked ratio was small, but the durability was poor. On the other hand, Examples 9 to 1 using a binder having a glass transition point Tg of 45 ° C. or higher.
In the case of 1, the uncrosslinked ratio is small and the durability is improved.
From the above results, when the magnetic coating material forming the magnetic layer contains a carboxylic acid amine salt whose amine is tertiary and a binder having a glass transition point Tg of 45 ° C. or higher, three-dimensional crosslinking of the binder is sufficiently achieved. It was found that a magnetic layer having excellent durability was obtained.

Next, an example of a magnetic tape containing N, N-dimethyl-n-octadecylamine stearate as a carboxylic acid amine salt having a tertiary amine in the back coat layer will be described.

Example 12 First, the basic composition of the back coat paint is as follows. Color carbon 100 parts by weight (acidic pH 2.5, particle size 23 mμ) Polyurethane resin (Tg 60 ° C.) 60 parts by weight Methyl ethyl ketone 400 parts by weight

Next, 1 part by weight of N, N-dimethyl-n-octadecylamine stearate used in Example 1 was added to this basic composition, dispersed and mixed in a ball mill for 24 hours, and then filtered. Furthermore, immediately before the polymerization, the curing agent 10
A part by weight was added and stirred for 30 minutes to prepare a back coat paint.

Further, the back coat paint was applied to the back surface of a polyethylene terephthalate film having a thickness of 12 μm and having a magnetic layer previously formed thereon so that the thickness after drying was 2 μm, and the magnetic layer was magnetically oriented. Rolled up. Then, this was calendered and then cut into a width of 1/2 inch to prepare a sample tape.

Examples 13 and 14 Sample tapes were prepared in the same manner as in Example 12 except that the amount of N, N-dimethyl-n-octadecylamine stearate added was 2 or 5 parts by weight. did.

Comparative Example 5 A magnetic tape was produced by the same method as in Example 12 without adding N, N-dimethyl-n-octadecylamine stearate.

Comparative Examples 6 and 7 2.5 parts by weight of N, N-dimethyl-n-octadecylamine or scialic acid was added in place of N, N-dimethyl-n-octadecylamine stearate, and other examples were used. A magnetic tape was produced in the same manner as in 12.

With respect to the magnetic tapes of Examples 12 to 15 and Comparative Example 5 thus produced, a durability test, that is, measurement of powder falling was performed. For the powder falling, after visually observing the amount of powder falling on the head drum, the guide pin, etc. after 100 times of running for 60 minutes, 0 point was found when there was almost no powder falling.
An item with a very large amount of powder falling was evaluated as 5 points. The measurement results are shown in Table 5.

[0043]

[Table 5]

As is clear from Table 5, in Examples 12 to 14 to which the present invention was applied, the amount of powder falling was small and the durability was remarkably improved.

Examples 15 to 18 In Example 12, 5 parts by weight of four kinds of compounds shown in Table 2, that is, a carboxylic acid amine salt in which the amine is tertiary is used instead of N, N-dimethyl-n-octadecylamine stearate. Each part was added, and other magnetic tapes were produced by the same method as in Example 12. The results are shown in Table 6.

[0046]

[Table 6]

As can be seen from Table 6, even if any of the compounds shown in Table 2 is used, powder drop is small and the durability is remarkably improved.

Examples 19 to 21 In Example 12, the amount of N, N-dimethyl-n-octadecylamine stearate added was 2 parts by weight, the binder was 60 parts by weight, and the glass transition point of the polyurethane resin was Tg is 45 ° C, 60 ° C, 70 ° C,
Others were the same as in Example 12, and each magnetic tape was produced.

Comparative Example 8 In Example 12, the addition amount of N, N-dimethyl-n-octadecylamine stearate was 2 parts by weight, the binder was 60 parts by weight, and the glass transition point Tg of the polyurethane resin was 38 ° C., other than Example 1
A magnetic tape was produced by the same method as in 2.

With respect to the tapes of Examples 19 to 21 and Comparative Example 8 thus produced, powder falling was measured. The results are shown in Table 7.

[0051]

[Table 7]

As can be seen from Table 7, in the case of Comparative Example 8 in which a binder having a glass transition point Tg of 38 ° C. was used, the glass transition point Tg was 4 although the powder drop was large and the durability was poor.
In the case of Examples 19-21 using a binder of 5 ° C or higher,
Less dust is removed and durability is improved.

From the above results, if the backcoat coating material for forming the backcoat layer contains a carboxylic acid amine salt having a tertiary amine and a binder having a glass transition point Tg of 45 ° C. or higher, the tertiary bond of the binder is obtained. It was found that the original cross-linking was sufficiently performed and a back coat layer having excellent durability was obtained.

[0054]

As described above, in the present invention, the magnetic layer contains a carboxylic acid amine salt having a tertiary amine and a binder having a glass transition point Tg of 45 ° C. or more, The durability of the magnetic layer can be improved. Moreover, the durability of the backcoat layer can be improved by containing a carboxylic acid amine salt having a tertiary amine and a binder having a glass transition point Tg of 45 ° C. or higher in the backcoat layer. Therefore, according to the present invention, recording and reproducing can be performed at high density and high speed, and high quality recording and reproducing can be performed.

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[Procedure amendment]

[Submission date] December 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

[Table 2]

Claims (2)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer mainly composed of a ferromagnetic powder and a binder, wherein the magnetic layer contains a carboxylic acid amine salt having a tertiary amine. And the binder has a glass transition point of 45 ° C.
A magnetic recording medium comprising the above binder. 2. A magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer mainly containing non-magnetic powder and a binder is formed on the other surface of the non-magnetic support. A magnetic recording medium comprising a carboxylic acid amine salt having a tertiary amine in the coating layer and wherein the binder is a binder having a glass transition point of 45 ° C. or higher.