JPH0562153A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium of a magnetic tape, a magnetic disk etc., with an extremely superb dispersion property of magnetic powder within a magnetic layer, an extremely high electrical characteristic, and an improved durability. CONSTITUTION:A magnetic layer containing a magnetic powder and a binder is provided on a non-magnetic support. A comb-shaped acryl resin containing a polar group where an acryl polymer molecule containing a plurality of polar groups is connected in comb-teeth shape through urethane connection or urea connection at a single end and an organic compound with one or more epoxy groups at a single end are used together as the binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape having a magnetic layer containing magnetic powder and a binder on a non-magnetic support,
The present invention relates to a magnetic recording medium such as a magnetic disk.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium of this type comprises a non-magnetic support such as a polyester film, a magnetic powder,
A magnetic coating material containing a binder, an organic solvent, and various additives that are added as necessary is applied and dried to form a magnetic layer, but in order to exhibit high electrical characteristics,
It is required that the dispersibility of the magnetic powder in the magnetic layer is good, and that the mechanical properties of the magnetic layer are excellent in terms of durability.

Conventionally, as a binder for the magnetic layer in such a magnetic recording medium, polyurethane resin, vinyl chloride resin, fibrin resin, butyral resin, acetal resin, polyester resin, etc. have been used. It is widely used, and among them, polyurethane-based resins are widely used as those capable of imparting excellent mechanical properties to the magnetic layer. However, ordinary polyurethane-based resins have excellent mechanical properties, but on the other hand, they have a low ability to disperse the magnetic powder and have a drawback that the electrical properties of the magnetic recording medium become insufficient.

Therefore, in recent years, as a binder,
A polyurethane-based resin in which a resin containing a polar group such as a hydroxyl group is used together with the above polyurethane-based resin, or a polar group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, a tertiary amino group, or a salt thereof is introduced into the main chain. Using resin,
Means for improving the dispersibility of magnetic powder have been adopted (JP-A-55-38693, JP-A-57-92422, and JP-A-57-92422).
9-30235, etc.).

[0005]

However, with the recent technological progress, it has been strongly demanded to further increase the recording density and reliability of the magnetic recording medium. As described above, the polyurethane-based binder is used as the binder. Means such as the combined use of a resin and a resin containing a polar group or the use of a polyurethane-based resin having various polar groups introduced is no longer sufficient to meet the above demand.

In view of the above-mentioned circumstances, the present invention has extremely high dispersibility of the magnetic powder in the magnetic layer and exhibits extremely high electric characteristics, and also has good durability, and has a recent high recording density. It is an object of the present invention to provide a magnetic recording medium that can sufficiently meet the demands for high reliability and high reliability.

[0007]

The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, as a binder component of the magnetic layer, a polar group-containing acrylic resin having a specific polymer morphology. When a resin and an organic compound having an epoxy group at one end are used together, in addition to maximizing the affinity between the binder based on the polar group and the magnetic powder, the steric repulsion effect of the organic compound As a result, magnetic particles are prevented from agglomerating, so that the dispersibility of the magnetic powder is remarkably improved, and it is found that a magnetic recording medium exhibiting extremely high electrical characteristics and sufficient durability can be obtained. Invented the invention.

That is, the present invention provides a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder on a non-magnetic support, wherein the binder contains a plurality of polar group-containing acrylic polymer molecules at one end. A magnetic recording medium containing a polar group-containing comb-shaped acrylic resin bonded in a comb-teeth shape via a urethane bond or a urea bond, and an organic compound having one or more epoxy groups at one end. It is related to.

Further, according to the present invention, in the above magnetic recording medium, the polar group of the polar group-containing comb-shaped acrylic resin is selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group, a tertiary amino group, salts thereof, and betaine. The number average molecular weight of the polar group-containing comb-shaped acrylic resin is in the range of 5,000 to 100,000, and the number average molecular weight of the organic compound having one or more epoxy groups at one end is 150 to Each of the configurations in the range of 20,000 is a preferable mode.

[0010]

As described above, the polar group-containing comb-shaped acrylic resin used as the binder component of the magnetic layer in the present invention has a plurality of polar group-containing acrylic polymer molecules each having a urethane bond or a urea bond at one end. Are combined in the shape of a comb tooth, and each polar group-containing acrylic polymer chain forming the comb-shaped tooth portion is spatially swingable like a string tied only at one end side. Since the degree of freedom in the vicinity of the polar group is much higher than that of polyurethane resin having a polar group in the main chain, the polar group is very easily adsorbed on the surface of the magnetic powder and has a very good affinity for the magnetic powder. Show.

The organic compound, which is a binder component used in combination with the acrylic resin, has one or more epoxy groups at one end, has good compatibility with the acrylic resin, and has an epoxy at one end. Since the group reacts with the active sites on the surface of the magnetic powder and is immobilized, the steric repulsion effect of this organic compound acts to prevent aggregation of the magnetic powders.

Therefore, in the magnetic coating material containing both of these binder components, the magnetic powder is in a very good dispersed state and there is no increase in viscosity after dispersion of the coating material. Has a very uniform magnetic layer in which magnetic powder is highly dispersed, and therefore exhibits extremely high electrical characteristics and good durability based on the excellent mechanical characteristics of the acrylic resin. It will be done.

The above polar group-containing comb-shaped acrylic resin can be synthesized by any method as long as a plurality of polar group-containing acrylic polymer molecules are comb-like bonded at one end via urethane bond or urea bond. It may be one. As a typical example thereof, one obtained by the following synthesis method can be mentioned.

That is, the following (a) to (d); (a) Acrylic polymer having a diol at one end and another polar group at the other site (b) Organic diisocyanate compound (c) Chain Extender (d) Of the components of the polyol compound having hydroxyl groups at both ends, at least the components (a) and (b) are reacted with each other, and if necessary, the components (c) and (d) are added. It is an acrylic resin obtained by reaction.

In the above synthesis method, the component (a) and the component (b) are used.
Due to the reaction with the component, a plurality of acrylic polymer chains of the component (a) are bonded to each other via urethane bonds at both ends with the component (b) sandwiched between them, and the backbone mainly composed of the component (b) is connected by urethane bonds. A comb-shaped polymer composed of a ridge portion and a plurality of tooth portions composed of an acrylic polymer chain of the component (a) is produced. Further, by reacting the component (c) or the component (d) with this, the above-mentioned polymers are bonded to each other at the end of the back ridge via these components, and a comb-shaped polymer having a larger molecular weight is produced.

At this time, if diamines are used as the component (c), the bonding part becomes a urea bond by the reaction with the isocyanate group based on the component (b). Further, the bonding part when diols are used as the component (c) and the bonding part of the component (d) are urethane bonds. The ratio of these components (a) to (d) may be appropriately adjusted according to the required properties of the polar group-containing comb-shaped acrylic resin.

The acrylic polymer as the component (a) may be produced by any method. For example, when radically polymerizing an acrylic monomer,
An acrylic polymer produced by using thioglycerin as a chain transfer agent and using a polar group-containing acrylic monomer as at least a part of the above acrylic monomer can be preferably used.

The number average molecular weight of the acrylic polymer produced by such a method is about 1,000 to 20,000, and particularly preferably 1,000 to 5,000. If it is too small, the properties as an acrylic polymer are hard to be expressed, and if it is too large, the degree of freedom as a comb-shaped tooth portion is reduced, and the dispersibility of the magnetic powder in the magnetic paint described above cannot be sufficiently enhanced. ..

Here, as the acrylic monomer used for producing the acrylic polymer of the component (a), for example,
Methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate,
Butyl methacrylate, hexyl acrylate, hexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, and the like. These are two types. You may use together the above.

The polar group-containing acrylic monomer may be acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, 2-acrylamido-2-methyl-1.
-Propanesulfonic acid, 2-methacryloxyethyl acid phosphate, etc. may be mentioned, and these may be used in combination of two or more kinds.

Further, it is also possible to copolymerize a monomer having a reactive functional group such as glycidyl methacrylate and react another compound with the reactive functional group to introduce a new polar group. .. It is also possible to copolymerize another monomer such as a styrene derivative with an acrylic monomer.

As the polymerization initiator, an azo compound such as α.α'-azobisisobutyronitrile or a common peroxide such as benzoyl peroxide may be used. Alternatively, a polymerization initiator having a hydroxyl group may be used.

Examples of the organic diisocyanate compound as the component (b) include tolylene diisocyanate, 4 ·
4-diphenylmethane diisocyanate, hexamethylene diisocyanate, 4-dicyclohexylmethane diisocyanate and the like are preferably used.

As the chain extender of the component (c), ethylene glycol, 1,3-propanediol, 1,4-butanediol, diols such as neopentyl glycol, ethylenediamine, Diamines such as tolylenediamine, those not having polar groups such as water, and 2.2
Examples thereof include those having a polar group such as dimethylolpropionic acid, sodium bis (hydroxybutyl) -5-sulfoisophthalate, N-methyldiethanolamine and potassium 2,3-dihydroxy-1-propanesulfonate.

The component (d) is a polyol such as polypropylene glycol or polytetramethylene glycol, polyterylene, polybutylene adipate,
Polyester geo such as polybutylene terephthalate
Polylactone di-, such as poly, poly ε-caprolactone
Polycarbonate diol such as poly (1,6-hexanecarbonate diol) is preferably used.

The polar group-containing comb-shaped acrylic resin obtained by reacting each of the above components has an acrylic polymer component content of about 10 to 70% by weight, particularly preferably 20 to 5%.
Those in the range of 0% by weight are desirable. If the content is too small, the properties as an acrylic resin will not be sufficiently exhibited, and if it is too large, it becomes brittle, which is not preferable.

The number average molecular weight of the polar group-containing comb-shaped acrylic resin is preferably about 5,000 to 100,000, and particularly preferably 10,000 to 50,000.
If it is too small, the mechanical properties deteriorate, and if it is too large, the viscosity when dissolved in an organic solvent or the like becomes high and it becomes difficult to make it into a paint.

The polar group of the polar group-containing comb-shaped acrylic resin is preferably a carboxyl group, a sulfonic acid group, a phosphoric acid group, a tertiary amino group, salts thereof, betaine (including sulfobetaine), or the like. These polar groups are introduced, for example, from the polar group-containing acrylic polymer of the component (a) used in the above-mentioned synthesis method, and are usually attached to the acrylic polymer chain constituting the comb tooth portion. At the same time, for example, by using a chain extender having a polar group as the component (c), it may be introduced into the comb-shaped back ridge.

The amount of these polar groups introduced into the resin is
About 0.01 to 1.0 mmol / g, particularly preferably 0.1.
If the amount is too small, the dispersibility of the magnetic powder cannot be sufficiently improved. On the contrary, if the amount is too large, it is dissolved in an organic solvent due to aggregation of polar groups. The viscosity increases, which makes it difficult to make a paint.

On the other hand, examples of the organic compound having one or more epoxy groups at one end used in combination with the above-mentioned polar group-containing comb-shaped acrylic resin include epoxy group-containing aliphatic compounds such as 1.2-epoxyoctadecane, and acryl. Examples thereof include resins, vinyl chloride resins, and copolymers of these resin components with other resin components into which an epoxy group is introduced.

The number average molecular weight of such an organic compound is
100 to 20,000, particularly preferably 150 to 1
The range of 10,000 is preferable. If it is too small, the steric repulsion effect necessary to disperse the magnetic powder becomes insufficient, and if it is too large, the degree of freedom of the epoxy group in the compound decreases and it becomes difficult to adsorb on the surface of the magnetic powder. Cause decline.

The amount of such an organic compound having one or more epoxy groups at one end is about 1 to 50% by weight, particularly preferably 5 to 30% by weight, based on the above polar group-containing comb-shaped acrylic resin. It is good to set the range. If the amount is too small, the dispersibility of the magnetic powder cannot be sufficiently improved. On the contrary, if the amount is too large, the mechanical properties of the magnetic layer are deteriorated and durability is deteriorated.

In order to sufficiently improve the dispersibility of the magnetic powder, the polar group-containing comb-shaped acrylic resin and the above organic compound are added in an amount of 10 to 35 parts by weight based on 100 parts by weight of the magnetic powder. It is recommended to use in a range of about 15 to 30 parts by weight, particularly preferably 15 to 30 parts by weight.

In the present invention, as the binder for the magnetic layer, the above polar group-containing comb-shaped acrylic resin and the organic compound having one or more epoxy groups at one end may be used in combination with other binder resins. Such other binder resins include polyurethane resins, vinyl chloride-vinyl acetate copolymers, fibrin resins, polyvinyl butyral resins, polyester resins, polyacrylic resins, epoxy resins. Any of those conventionally known for magnetic layers of magnetic recording media such as phenolic resins and polyisocyanate compounds as crosslinking agents can be used.

To manufacture the magnetic recording medium of the present invention,
According to a conventional method, a magnetic paint containing the above-mentioned binder, magnetic powder and various additives to be blended as needed is prepared, and the paint is sprayed or roll-coated on a non-magnetic support such as a polyester film. After coating and drying by an appropriate means such as working to form a magnetic layer, if necessary, surface treatment such as calendering may be performed and then cutting into a desired width or shape.

Further, a magnetic layer may be provided on one surface of the above non-magnetic support and a back coat layer may be provided on the opposite surface thereof.
As the binder for the back coat layer, the above-mentioned polar group-containing comb-shaped acrylic resin and an organic compound having one or more epoxy groups at one end can also be used.

As the above magnetic powder, for example, γ-
Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe ₃ O ₄
Iron oxide in an intermediate oxidation state with, γ-Fe ₂ O ₃ containing Co,
Co-containing _{Fe 3 O 4, CrO 2,} Ba oxide-based magnetic powder such as ferrite, Fe, Co, Fe-Co alloy, Fe
-Ni alloy, Fe-Co-Ni alloy, Fe-Ni-Cr
Any magnetic powder conventionally used for magnetic recording media, such as metal magnetic powder such as alloys and nitride magnetic powder such as iron nitride, can be used.

If these magnetic powders consist of acicular particles, the average major axis diameter is about 0.2 to 1.0 μm,
An average axial ratio (average major axis diameter / average minor axis diameter) of about 5 to 10 is preferable, and an average plate diameter of plate particles is preferably about 0.07 to 0.3 μm.

As the solvent used for the magnetic paint, any of various organic solvents generally used for magnetic paints such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane and dimethylformamide can be used.

As additives to be added to the magnetic coating as required, lubricants, abrasives, antistatic agents, dispersants,
Examples include fillers and colorants.

[0041]

According to the present invention, since a polar group-containing acrylic resin having a specific polymer morphology and an organic compound having an epoxy group at one end are used together as a binder for the magnetic layer, the magnetic powder is dispersed. It is possible to provide a magnetic recording medium which has excellent properties, exhibits extremely high electrical characteristics based on this, has good durability, is suitable for high recording density, and has high reliability.

The polar groups of the above polar group-containing acrylic resin are carboxyl group, sulfonic acid group, phosphoric acid group, 3
According to the constitution of at least one selected from the group consisting of a primary amino group, a salt thereof and betaine, the dispersibility of the magnetic powder can be further improved.

Furthermore, the above-mentioned polar group-containing acrylic resin has a number average molecular weight in the range of 5,000 to 100,000, and the number average molecular weight of the organic compound having one or more epoxy groups at one end is 150 to 100. When the composition is in the range of 20,000, the effect of improving the dispersibility of the magnetic powder can be more reliably exhibited, and particularly in the former composition, the magnetic paint used for forming the magnetic layer can be easily made into a paint. There are advantages.

[0044]

EXAMPLES Next, examples of the present invention will be specifically described in comparison with comparative examples. The polar group-containing comb-shaped acrylic resin in the examples was synthesized by the following method. In the following, parts and% mean parts by weight and% by weight, respectively.

<Synthesis of Carboxyl Group-Containing Comb Acrylic Resin> Methylmethacrylate 72 parts α · α′-azobisisobutyronitrile 1 part Thioglycerin 9 parts Tetrahydrofuran 100 parts

The above composition was placed in a flask equipped with a condenser, the atmosphere of which was sufficiently replaced with nitrogen, and the mixture was stirred at 60 ° C. for 8 hours.
After reacting for a period of time, the obtained reaction product was separated in a toluene-water system and dried under reduced pressure at 60 ° C. for 48 hours to obtain a one-end diol acrylic polymer-A. The number average molecular weight of this polymer A was 1,500 as measured by the vapor pressure permeation method.

Methyl methacrylate 66 parts α · α′-azobisisobutyronitrile 1 part Thioglycerin 9 parts Acrylic acid 9 parts Tetrahydrofuran 100 parts

The above composition is reacted in the same manner as the above-mentioned Polymer A, and liquid separation and vacuum drying are carried out to obtain a carboxyl group-containing one-end diol acrylic polymer.
B was obtained. This polymer B has a number average molecular weight of 1,500 and a carboxyl group content of 0.
It was 67 mmol / g.

The following composition containing the one-end diol acrylic polymers A and B thus obtained was reacted at 80 ° C. for 10 hours in a nitrogen gas atmosphere to obtain a carboxyl group-containing comb-shaped acrylic resin. Obtained. One end diol acrylic polymer A 30 parts One end diol acrylic polymer B 30 parts Neopentyl glycol 5 parts Poly 1,6-hexanecarbonate diol 90 parts (Number average molecular weight 1,000 ) 4.4-Diphenylmethane diisocyanate 45 parts Octyl tin 0.05 part Cyclohexanone 400 parts Toluene 100 parts

This carboxyl group-containing comb-shaped acrylic resin had an acrylic polymer component content of 30% and a number average molecular weight of 20,000 in terms of polystyrene by GPC measurement.
0, the content of carboxyl group was 0.10 mmol / g.

<Synthesis of Phosphate Group-Containing Comb Acrylic Resin> Methyl methacrylate 66 parts α · α′-azobisisobutyronitrile 1 part Thioglycerin 9 parts 2-Methacryloxyethyl citrate phosphate 3 .1 part Tetrahydrofuran 100 parts

The above composition is reacted in the same manner as the above-mentioned one-end diol acrylic polymer A, and liquid separation and vacuum drying are carried out to obtain one-end diol containing a phosphate group.
A acrylic polymer C was obtained. This polymer C had a number average molecular weight of 1,500 and a phosphate group content of 0.65 mmol / g as measured by a vapor pressure permeation method.

Next, except that the one-end diol acrylic polymer C was used in the same amount in place of the one-end diol acrylic polymer B, the procedure was the same as in the synthesis of the above-mentioned carboxyl group-containing comb-shaped acrylic resin. Then, a synthetic reaction was performed in a nitrogen gas atmosphere to obtain a phosphoric acid group-containing comb-shaped acrylic resin.

This phosphoric acid group-containing comb-shaped acrylic resin has an acrylic polymer component content of 30%, a number average molecular weight of 20,000 in terms of polystyrene by GPC measurement, and a phosphoric acid group content of 0.10 mmol / It was g.

<Synthesis of Comb-Shaped Acrylic Resin Containing Potassium Sulfonate Group> Methyl methacrylate 66 parts α · α′-azobisisobutyronitrile 1 part Thioglycerine 9 parts 3-Sulfopropyl methacrylate potassium salt 2. 6 parts Tetrahydrofuran 50 parts Methanol 50 parts

The above composition is reacted in the same manner as in the above-mentioned one-end diol acrylic polymer A, and liquid separation and vacuum drying are carried out to obtain one-end diol acrylic polymer containing potassium sulfonate group. -I got D. This polymer D has a number average molecular weight of 1,50 as measured by vapor pressure permeation.
0, the content of potassium sulfonate group was 0.67 mmol / g.

Next, except that this one-end diol acrylic polymer D was used in the same amount in place of the one-end diol acrylic polymer B, the same procedure as in the synthesis of the above carboxyl group-containing comb-shaped acrylic resin was carried out. A synthetic reaction was performed in a nitrogen gas atmosphere to obtain a comb-shaped acrylic resin containing a potassium sulfonate group.

This potassium sulfonate group-containing comb-shaped acrylic resin had an acrylic polymer component content of 30% and a number average molecular weight of 2 in terms of polystyrene by GPC measurement.
1,000, content of potassium sulfonate group 0.10
It was mmol / g.

<Synthesis of Sulfobetaine-Containing Comb Acrylic Resin> Methylmethacrylate 66 parts α · α′-azobisisobutyronitrile 1 part Thioglycerin 9 parts Dimethylaminoethyl methacrylate 4.1 parts Tetrahydrofuran 100 Department

The above composition was placed in a flask equipped with a condenser, purged with nitrogen, and stirred at 60 ° C. for 8 hours.
After reacting for 1 hour, 1 equivalent of propanesartone was added to the amino group of dimethylaminoethyl methacrylate and reacted at 80 ° C. for 5 hours, followed by reprecipitation with toluene and water for purification. It was dried under reduced pressure at 48 ° C for 48 hours to give a sulfobetaine-containing one-terminal di-
The acrylic resin E was obtained. This polymer E had a number average molecular weight of 1,500 and a sulfobetaine content of 0.67 mmol / g as measured by a vapor pressure permeation method.

The following composition containing the one-ended diol acrylic polymer E thus obtained and the above-mentioned one-ended diol acrylic polymer A was added in a nitrogen gas atmosphere at 80
Reaction was carried out at 0 ° C. for 10 hours to obtain a sulfobetaine-containing comb-shaped acrylic resin.

One-end diol acrylic polymer A 30 parts One-end diol acrylic polymer E 30 parts Tolylenediamine 3.6 parts Poly 1,6-hexanecarbonate diol (the same as above) 90 Parts 4.4-diphenylmethane diisocyanate 45 parts octyltin 0.05 parts cyclohexanone 400 parts toluene 100 parts

The sulfobetaine-containing comb-shaped acrylic resin had an acrylic polymer component content of 30% and a number average molecular weight of 2100 in terms of polystyrene by GPC measurement.
0, the content of sulfobetaine was 0.10 mmol / g.

<Synthesis of Tertiary Amino Group-Containing Comb Acrylic Resin> Methyl methacrylate 66 parts α · α′-azobisisobutyronitrile 1 part Thioglycerin 9 parts Dimethylaminoethyl methacrylate 4.1 parts Tetrahydrofuran 100 parts

The above composition is reacted in the same manner as the above-mentioned one-end diol acrylic polymer A, and liquid separation and vacuum drying are carried out to obtain a one-end diol acrylic polymer containing a tertiary amino group. -I got F. This polymer F is
The number average molecular weight was 1,500 and the content of the tertiary amino group was 0.66 mmol / g as measured by the vapor pressure permeation method.

Next, except that the one-end diol acrylic polymer F was used in the same amount in place of the one-end diol acrylic polymer B, the same procedure as in the above synthesis of the carboxyl group-containing comb-shaped acrylic resin was carried out. Then, a synthetic reaction was performed in a nitrogen gas atmosphere to obtain a comb-shaped acrylic resin containing a tertiary amino group.

This tertiary amino group-containing comb-shaped acrylic resin had an acrylic polymer component content of 30% and a number average molecular weight of 2100 in terms of polystyrene by GPC measurement.
The content of 0- and tertiary amino groups was 0.10 mmol / g.

Example 1 α-Fe magnetic powder 300 parts (coercive force 1,500 oersted, saturation magnetization 120 emu / g) Comb-shaped acrylic resin containing carboxyl group 55 parts 1.2-epoxyoctadecane 6 parts Trifunctional low molecular weight isocyanate Compound 10 parts (trade name: Coronet L manufactured by Nippon Polyurethane Company) Carbon black 10 parts α-Al ₂ O ₃ powder 3 parts myristic acid 6 parts n-butyl stearate 8 parts cyclohexanone 395 parts toluene 395 parts

A magnetic coating material was prepared by mixing and dispersing the above composition in a ball mill for 72 hours. This paint has a thickness of 2
On a 0μm polyester film, the thickness after drying is 5
The magnetic layer is formed by coating and drying so that the thickness becomes μm, and after calendering, it is cut into a width of 8 mm and the magnetic tape is applied.
I made a cup.

Example 2 A magnetic tape was produced in the same manner as in Example 1 except that the amount of 1.2-epoxyoctadecane used was changed to 15 parts.

Example 3 A magnetic tape was produced in the same manner as in Example 1 except that the amount of 1,2-epoxyoctadecane used was changed to 3 parts.

Example 4 Example 2 was repeated except that 10 parts of an acrylic resin containing a epoxy resin having a number average molecular weight of 1,500 and an epoxy group content of 0.65 mmol / g was used in place of 1,2-epoxyoctadecane. A magnetic tape was produced in the same manner as in Example 1.

Example 5 A magnetic tape was produced in the same manner as in Example 1 except that the above-mentioned phosphoric acid group-containing comb-shaped acrylic resin was used in the same amount instead of the carboxyl group-containing comb-shaped acrylic resin. did.

Example 6 A magnetic tape was produced in the same manner as in Example 5 except that the amount of 1,2-epoxyoctadecane used was changed to 15 parts.

Example 7 A magnetic tape was produced in the same manner as in Example 5 except that the amount of 1,2-epoxyoctadecane used was changed to 3 parts.

Example 8 Example 2 was repeated except that 10 parts of an acrylic resin containing a single-end epoxy group having a number average molecular weight of 1,500 and an epoxy group content of 0.65 mmol / g was used in place of the 1,2-epoxyoctadecane. A magnetic tape was produced in the same manner as in Example 5.

Example 9 A magnetic tape was produced in the same manner as in Example 1 except that the above-mentioned potassium sulfonate group-containing comb-shaped acrylic resin was used in the same amount in place of the carboxyl group-containing comb-shaped acrylic resin.

Example 10 A magnetic tape was produced in the same manner as in Example 9 except that the amount of 1.2-epoxyoctadecane used was changed to 15 parts.

Example 11 A magnetic tape was produced in the same manner as in Example 9 except that the amount of 1.2-epoxyoctadecane used was changed to 3 parts.

Example 12 Example 1 was repeated except that 10 parts of an acrylic resin containing a single-end epoxy group having a number average molecular weight of 1,500 and an epoxy group content of 0.65 mmol / g was used in place of 1.2-epoxyoctadecane. A magnetic tape was produced in the same manner as in Example 9.

Example 13 A magnetic tape was produced in the same manner as in Example 1 except that the same amount of the above-mentioned sulfobetaine-containing comb-shaped acrylic resin was used instead of the carboxyl group-containing comb-shaped acrylic resin.

Example 14 A magnetic tape was produced in the same manner as in Example 13 except that the amount of 1.2-epoxyoctadecane used was changed to 15 parts.

Example 15 A magnetic tape was produced in the same manner as in Example 13 except that the amount of 1.2-epoxyoctadecane used was changed to 3 parts.

Example 16 Example 16 was repeated except that 10 parts of an acrylic resin containing a one-end epoxy group having a number average molecular weight of 1,500 and an epoxy group content of 0.65 mmol / g was used in place of the 1,2-epoxyoctadecane. A magnetic tape was produced in the same manner as in Example 13.

Example 17 A magnetic tape was produced in the same manner as in Example 1 except that the same amount of the tertiary amino group-containing comb-type acrylic resin was used instead of the carboxyl group-containing comb-type acrylic resin.

Comparative Example 1 Neopentyl Glycol 8.4 parts Dimethylolpropionic acid 1 part Poly 1.6-hexanecarbonate diol (the above) 90 parts 4.4-diphenylmethane diisocyanate -To 45 parts Octyl tin 0.05 part Cyclohexanone 400 parts Toluene 100 parts

The above composition was reacted in a nitrogen atmosphere at 80 ° C. for 10 hours to obtain a carboxyl group-containing polyurethane resin having a number average molecular weight of 22,000 in terms of polystyrene by GPC measurement. Next, a magnetic tape was produced in the same manner as in Example 1 except that this polyurethane resin was used in the same amount instead of the carboxyl group-containing comb-shaped acrylic resin.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that 1.2-epoxyoctadecane was not used.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 5 except that 1.2-epoxyoctadecane was not used.

The chroma S / N ratio, C / N ratio, and RF output of each magnetic tape of the above Examples and Comparative Examples were measured by the following methods. The results are shown in Table 1 below.

<Chroma S / N ratio> Using a VTR of 8 mm system, a chroma signal of 0.75 MHz is set to 0.7 on a magnetic tape.
Recording was performed on the luminance modulation signal at 14 Vp-p, and the noise portion of the reproduced signal was measured by a chroma noise measuring machine to obtain the chroma S / N ratio. The results are shown as relative values with the magnetic tape of Comparative Example 1 as the reference (0 dB).

<C / N ratio> A 7 MHz signal was recorded on a magnetic tape using a VTR of 8 mm system, and noise generated within a range of 7 ± 1 MHz when this signal was reproduced was measured. The ratio of the reproduced signal to the noise was measured using an output level measuring device (trade name ED-V900 manufactured by Sony Corporation). The results are based on the magnetic tape of Comparative Example 1 (0d
The relative value is shown as B).

<RF Output> Using a VTR for RF output measurement, after recording a signal of 7 MHz on a magnetic tape at a constant level, the output when reproducing was measured, and the magnetic tape of Comparative Example 1 was used as a reference. The relative value is (0 dB).

[0094]

[Table 1]

From the results shown in Table 1 above, the magnetic tape of the present invention (Examples 1 to 17) in which a polar group-containing comb-shaped acrylic resin and an organic compound having an epoxy group at one end were used together as a binder for the magnetic layer ) Is a chroma S / N ratio, C / N ratio, RF compared to a conventional magnetic tape (comparative example 1) using a normal polar group-containing polyurethane resin as the binder.
It is apparent that all of the outputs are extremely high and have excellent electromagnetic conversion characteristics.

On the other hand, in the magnetic tape using only the polar group-containing comb-shaped acrylic resin as the binder of the magnetic layer (Comparative Examples 2 and 3), the respective characteristics are higher than those of the conventional magnetic tape. It can be seen that the magnetic tape of the present invention is considerably inferior to the magnetic tape of the present invention, and the electromagnetic conversion characteristics are slightly insufficient.

Claims (4)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a magnetic powder and a binder on a non-magnetic support, wherein a plurality of polar group-containing acrylic polymer molecules are bonded at one end with a urethane bond as the binder. A magnetic recording medium comprising: a polar group-containing comb-shaped acrylic resin bonded in a comb-like shape via a urea bond; and an organic compound having one or more epoxy groups at one end. 2. The polar group of the comb-shaped acrylic resin containing a polar group is at least one selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group, a tertiary amino group, salts thereof, and betaine. Magnetic recording medium. 3. The magnetic recording medium according to claim 1, wherein the number-average molecular weight of the polar group-containing comb-shaped acrylic resin is in the range of 5,000 to 100,000. 4. The magnetic recording medium according to claim 1, wherein the organic compound having one or more epoxy groups at one end has a number average molecular weight in the range of 150 to 20,000.