JPH01109519A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, in which the binder constituting the magnetic layer has an epoxy group as a polar group in the molecule. By using a butadiene-based copolymer having - and a vinyl chloride-based copolymer containing a tertiary amine, -
The aim is to improve the dispersibility of the magnetic powder and the surface properties of the magnetic layer, thereby improving the durability, magnetic properties, electromagnetic conversion properties, etc. of the resulting magnetic recording medium.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), are required to have improved magnetic properties, electromagnetic conversion properties, etc. in order to obtain high playback output even when recording at short wavelengths. ing. As a measure to this end, efforts have been made to make the magnetic powder particles finer and to increase the magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, so-called banking density.

Therefore, the proportion of the binder in the magnetic coating film is extremely small. In a magnetic coating film containing such a small amount of binder, there is a risk that the magnetic layer will peel off when used as a magnetic recording medium.In order to prevent such deterioration in the strength of the magnetic coating, it is necessary to need to be improved.

To this end, it has been proposed to improve the mechanical strength of the magnetic coating by crosslinking the binder in the magnetic coating.

As mentioned above, binders that increase the mechanical strength of magnetic coatings by forming a crosslinked structure include those that form a crosslinked structure using a compound that has an electron beam-sensitive bond in the molecule, or those that use a compound that uses a hydroxyl group in the molecule to form a crosslinked structure. It has been proposed to form a crosslinked structure by utilizing the reaction between active hydrogen and isocyanate.

However, for example, a binder made of a compound having an electron beam-sensitive bond as described above requires extremely expensive equipment in order to form a crosslinked structure, and is therefore impractical.

On the other hand, in the case of the above-mentioned binder in which the active hydrogen of the hydroxyl group reacts with an isocyanate compound etc. to form a crosslinked structure, the reaction is aimed at -NCO+ -0H-IkkiO O, whereas in the actual reaction, ,-NC
Incyanate reacts with water as shown in O+ H, O-4, -NH, 10Co□, and the amino group formed by this reaction reacts with other isocyanates as shown, therefore, isocyanate When reacting a compound with a hydroxyl group, the -NGO group, which is effective, is affected by moisture as shown in the above reaction formula, and the amount of NGO groups that contribute to crosslinking decreases, making it impossible to form a sufficient crosslinked structure. It has inferior durability.

As mentioned above, binders that form a crosslinked structure through electron beam sensitive bonding and increase the mechanical strength of the coating film, or utilize the reaction between isocyanate and hydroxyl groups to form a crosslinked structure and increase the mechanical strength of the coating film. Binders and the like used as binders lack practicality due to equipment problems, and the reaction itself is susceptible to moisture and does not form a good crosslinked structure. Therefore, magnetic recording media using these binders do not have sufficient durability. The problem is that it is not possible to obtain

Therefore, as a binder that forms a crosslinked structure without being affected by moisture during the reaction to form a crosslinked structure, for example, a vinyl chloride-vinyl acetate copolymer containing an epoxy group in the side chain and an acrylic resin. A technology that uses a polymer containing a hydroxyl group or a carboxyl group in the side chain (Japanese Patent Publication No. 56-51414) as a binder! Plan M has been proposed.

[Problems to be solved by the invention] However, in this case, the crosslinked structure of the acrylic resin is not sufficient, and although it shows some effect in improving durability compared to conventional binders, its performance is insufficient. However, the durability, magnetic properties, electromagnetic conversion properties, etc. of the resulting magnetic recording medium were not satisfactory.

Therefore, the present invention was devised in order to eliminate the above-mentioned drawbacks in the technical field, and it greatly improves the dispersibility of magnetic powder and the surface properties of the magnetic layer, and has excellent durability and magnetic properties.
The object is to provide a magnetic recording medium with good electromagnetic conversion characteristics.

[Means for solving problems]

The inventors of the present invention have conducted intensive research over a long period of time in order to achieve the above-mentioned objective, and as a result, they have discovered a bond consisting of a butadiene copolymer having an epoxy group in the side chain and a vinyl chloride copolymer having a tertiary amine. The present invention was completed based on the discovery that the agent exhibits excellent durability.

That is, the present invention provides a magnetic recording medium in which a magnetic layer mainly consisting of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the binder comprises a butadiene copolymer having an epoxy group and a butadiene copolymer having an epoxy group. It is characterized by containing a vinyl chloride copolymer having 3 amines.

The butadiene-based copolymer having an epoxy group used as a binder in the present invention is mainly composed of a butadiene-based copolymer, and the epoxy group and the butadiene-based compound are introduced into this to form a crosslinked structure. It is obtained by copolymerizing a monomer having a double bond that can be copolymerized with.

Here, the butadiene compounds constituting the butadiene copolymer include butadiene rubber mainly composed of 1,3-butadiene, butadiene-styrene rubber (SBR) which is a copolymer of 1,3-butadiene and styrene, and 1 .3
-butadiene-acrylonitrile rubber (NBR), which is a copolymer of butadiene and acrylonitrile, and the like. Furthermore, a monomer copolymerizable with the butadiene compound may be included as a third component.

Monomers copolymerizable with the above butadiene compound include vinyl chloride, vinylidene chloride, vinyl acetate, vinyl alcohol, maleic acid, maleic anhydride, acrylic acid,
Examples include methacrylic acid, acrylic ester, methacrylic ester, hydroxyacrylate, hydroxymethacrylate, and vinyl propionate. By selecting one or more of these monomers and copolymerizing them, it is possible to control to some extent the solubility in the solvent, the dispersibility of the ferromagnetic powder, the crosslinkability, etc. of the physical properties of the coating film.

However, in this case, the proportion of butadiene in the copolymer is preferably in the range of 95 to 50% by weight, and if the content of butadiene is less than 50% by weight, the original characteristics of the butadiene copolymer will be lost. For example, the SN ratio deteriorates.

Moreover, it is preferable that the average molecular type is about 5000 to 1oooooo.

In addition, examples of monomers having a double bond copolymerizable with the butadiene compound and having an epoxy group introduced to form a crosslinked structure include unsaturated alcohols such as acryl glycidyl ether and methacryl glycidyl ether. Glycidyl ethers of unsaturated acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl-p-vinylbenzoate methylglycidyl itaconate, glycidyl ethyl maleate, glycidyl vinyl sulfonate, glycidyl (meth)allylsulfonate, butadiyl esters of unsaturated acids, butadiyl monoxide , vinylcyclohexene monooxide, 2-methyl-5,6
-Epoxide olefins such as nipoxyhexene and the like can be mentioned.

The above-mentioned butadiene-based copolymer may have an active hydrogen (e.g., hydroxyl group) in its molecule, and in this case, the ring can be opened by the catalytic effect of the tertiary amine in the vinyl chloride-based copolymer, which will be described later. The butadiene copolymers react with the epoxy groups to form a crosslinked structure between the butadiene copolymers, and in combination with the crosslinked structure composed of the butadiene copolymer and the vinyl chloride copolymer, the mechanical strength of the binder can be increased. can.

The amount of epoxy groups contained in the butadiene copolymer is preferably about 0.02 to 21 IIlol/g. If the amount of this epoxy group is small, durability will deteriorate, and if it is large, it will be difficult to make it into a paint.

On the other hand, the vinyl chloride copolymer contained in the binder in the present invention is a vinyl chloride copolymer with a polar group (tertiary amine) introduced into the side chain, and has the general formula % formula % ( In the formula, X represents a monomer having a vinyl group copolymerizable with vinyl chloride, Y represents a monomer having a vinyl group copolymerizable with vinyl chloride and a tertiary amine, and t and j each represent the degree of polymerization. ).

In addition, in the above general formula, each component of the compound is described as being arranged regularly in sequence for convenience, but in addition to the case shown in General 2 above, each component is arranged regularly in a fixed proportion. It goes without saying that they may be arranged repeatedly or randomly.

Here, the degree of polymerization (i+j+
k) is preferably within the range of 100≦(i+j+)0≦1000; if this value is less than 100, the durability of the resulting coating film will deteriorate; on the contrary, if it exceeds 1000,
The solubility in solvents deteriorates, making it difficult to form into paints.

The proportion of the vinyl chloride component contained in the vinyl chloride copolymer is preferably 50 to 95% by weight. If this value is less than 50% by weight, the durability will deteriorate;
If it exceeds 5% by weight, thermal deterioration is likely to occur.

The amount of tertiary amine copolymerizable with vinyl chloride contained in the vinyl chloride copolymer is 0.01 to 1.0 m
It is preferable that this value is about mol/g.
If it is less than 0.1 mmol/g, the dispersibility will deteriorate;
．． If it exceeds 0 mmol/g, the solubility in the solvent will decrease and at the same time the moisture resistance during coating film formation will deteriorate.

Next, the monomers X and Y will be explained in order.

First, the monomer X mentioned above includes vinyl acetate, vinyl alcohol, maleic acid, and maleic anhydride.

Acrylic acid, acrylic ester, methacrylic acid.

In addition to methacrylic acid ester, acrylonitrile, vinylidene chloride, vinyl propionate, etc., 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate,
Examples include hydroxyl group-containing monomers such as hydroxypropyl acrylate. These are added as appropriate from the viewpoints of solubility in solvents, improvement of crosslinking properties, improvement of coating film strength, etc., and two or more types may be used as a mixture.

Next, there is a monomer Y having a vinyl group and a tertiary amine that can be copolymerized with vinyl chloride, and examples of this include the following substances.

CHz=eCOO(CHg)sN(R)ziii)
R' CH2・CC0NII(CHz)t, N(R)z (wherein, R represents an alkyl group having 1 to 3 carbon atoms, and R
゛represents hydrogen or a methyl group, respectively.

The tertiary amine-containing vinyl chloride copolymer may be used in combination with other binders. As such binders, those conventionally used as binders for magnetic recording media can be used, including vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, and vinyl chloride-vinyl acetate copolymer. Vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-
Acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin , polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenolic resin, Examples include epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, and mixtures thereof. Among these, polyurethane resins, polyester resins, acrylonitrile butadiene copolymers, etc., which are said to impart flexibility, are preferred. Moreover, if a trifunctional isocyanate compound, a reaction product of 1 mole of trimethylolpropane and 3 moles of tolylene diisocyanate, etc. are used in combination as a crosslinking agent, durability etc. can be further improved.

In the present invention, by combining the butadiene-based copolymer having the epoxy group and the vinyl chloride-based copolymer having the tertiary amine, the tertiary amine contained in the vinyl chloride-based copolymer can be converted into a butadiene-based copolymer. Promotes ring-opening reaction of epoxy groups contained in the copolymer. Therefore, a crosslinked structure is developed between the butadiene copolymer and the vinyl chloride copolymer or between the butadiene copolymer, resulting in a coating film with excellent durability.

The ratio of the butadiene copolymer to the vinyl chloride copolymer is preferably from 2/8 to 8/2 (butadiene copolymer/vinyl chloride copolymer).

A tertiary amine compound may be added alone as a crosslinking promoter to the binder used in the magnetic recording medium of the present invention.

By using this tertiary amine compound in combination, the ring-opening reaction of the epoxy group contained in the vinyl copolymer can be further promoted.

Furthermore, the binder used in the magnetic recording medium of the present invention includes:
It is also possible to add polyisocyanate as a curing agent and form a crosslinked structure by utilizing the reaction between this polyisocyanate and the hydroxyl group in the butadiene copolymer or the hydroxyl group in the vinyl copolymer. By using it in combination with a crosslinked structure based on groups, a magnetic coating film with even greater strength can be obtained.

The above-mentioned epoxy group-containing butadiene copolymer and tertiary amine-containing vinyl chloride copolymer may be used in combination with other binders.

As such other binders, those conventionally used as binders for magnetic recording media can be used, such as vinyl chloride-vinyl acetate copolymer.

vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride-vinylacetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid Ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer Polyvinyl butyral, cellulose derivatives, styrene-butadiene copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, and mixtures thereof. It will be done. Among them, polyurethane resin and polyester resin are said to impart flexibility.

Acrylonitrile butadiene copolymer and the like are preferred.

The above epoxy group-containing butadiene copolymer or the third
A hydrophilic polar group may be introduced into the amine-containing vinyl chloride copolymer or other binder used in combination for the purpose of further improving dispersibility. The above-mentioned hydrophilic polar groups include ~S (hM group, -05036 group, -PO (Oa)
2 groups, -C00M group, -11G3J group (where M is a hydrogen atom or an alkali metal atom, and M is a hydrogen atom or an alkali metal atom.

is a hydrogen atom, an alkali metal atom or a hydrocarbon atom, G
represents an alkyl group, and J represents a halogen, respectively.

In the magnetic recording medium of the present invention, the magnetic layer is formed by applying, for example, a magnetic paint prepared by dispersing ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent onto the surface of the non-magnetic support. .

Here, the material for the non-magnetic support may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polypropylene, etc. cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; plastics such as polycarbonate, polyimide, polyamide, and polyamideimide;
Examples include metals such as copper, aluminum, and copper, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. Examples of the forms of this non-magnetic support include film and tape.

It may be a sheet, disk, card, drum, etc.

In addition, the ferromagnetic powder used in the magnetic layer includes:

Any ordinary one can be used. Therefore, usable ferromagnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, hexagonal barium ferrite particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles include -M type Fed.

When expressed as
50) ,? Dannetite (Fed, x = 1.33) and their solid solutions (F e O, 1,33< x <1
．． 50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing iron oxides are roughly divided into two types: doped type and deposited type.

The above-mentioned ferromagnetic chromium dioxide may include Crow or Ru for the purpose of improving the coercive force thereof.

A material containing at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fa-Ni, Fe-Co-Ni.

Co-Ni, Fe-Co-B, Fe-Co-Cr-B,
Mn-B1. Mn-Aj, Fe-Co-V, etc. can be used, and AI can be applied to these to improve various properties.
, Si, Ti, Cr, Mn, Cu.

A metal component such as Zn may also be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
A rust preventive agent or the like may be added. These dispersants, lubricants,
Any conventionally known abrasives, antistatic agents, and rust preventives can be used.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent and coated on a non-magnetic support.The solvent for the magnetic paint may be acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketone solvents, methyl acetate, ethyl acetate, butyl acetate,
Ethyl lactate.

Ester solvents such as acetic acid glycol monoethyl ether, glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.
Aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane and heptane, methylene chloride, ethylene chloride, carbon tetrachloride,
Examples include cutting using organic chlorine compounds such as chloroform, ethylene chlorohydrin, and dichlorobenzene.

[Effect]

By using the epoxy group-containing butadiene copolymer and the tertiary amine-containing vinyl chloride copolymer resin together, the tertiary amine in the vinyl chloride copolymer exhibits a catalytic effect,
The ring-opening reaction of the epoxy group of the butadiene copolymer is promoted, and a crosslinked structure is developed between the active hydrogen of the butadiene copolymer or the active hydrogen of the vinyl chloride copolymer.

Further, the crosslinking reaction due to the action of the tertiary amine described above proceeds almost unaffected by moisture. Therefore, a good crosslinked structure is formed, resulting in a binder with excellent durability.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Table 1 shows the butadiene copolymers used as binders in this example, and Table 2 shows the vinyl chloride copolymers used as binders.

Table 1 (blank below) Table 2 Magnetic recording media were prepared using the butadiene copolymers shown in Table 1 above and the vinyl chloride copolymers shown in Table 2 as binders.

Conducted flaming Co deposition r-Fe! Os too parts by weight (specific surface area 40r+?/g) Butadiene copolymer A-18 parts by weight Vinyl chloride copolymer B-116 parts by weight Carbon black (antistatic agent) 2 parts by weight Cr, O, (abrasive ) 2 parts by weight stearic acid (lubricant) 1 part by weight butyl stearate (I8
Lubricant) 1 part by weight methyl ethyl ketone
100 heavy toluene
60 parts by weight cyclohexanone
60 parts by weight The above composition was mixed in a ball mill for 24 hours, filtered through a 3 μm filter, and then 14 μml
It was applied onto a polyethylene terephthalate film of 'J so that the film thickness after drying was 6 μm. Next, after performing a magnetic field orientation treatment, it was dried and wound up.

After further supercalendering, an additional 75
A sample tape was prepared by heating at ℃ for 24 hours and cutting into a width of 172 inches.

In the composition of the magnetic paint, the butadiene copolymer used was one of the butadiene copolymers shown in Table 1, and the vinyl chloride copolymer was used as the vinyl chloride copolymer shown in Table 2. Sample tapes were prepared in the same manner as in Example 1 except for which copolymer was used and the type was changed as shown in Table 3.

Comparison of magnetic paints: Which of the butadiene copolymers shown in Table 1 was used in the composition of the magnetic paint, and which of the chloride copolymers shown in Table 2 was used as the vinyl chloride copolymer. Sample tapes were prepared in the same manner as in Example 1 except for which vinyl copolymer was used and the type was changed as shown in Table 3.

Table 3 shows the types of butadiene copolymers and vinyl chloride copolymers used in Examples 2 to 4 and Comparative Examples 1 to 3.

(The following is a blank space.) Table 3 Still characteristics and powder fall-off were measured for each of the obtained sample tapes.

Note that the above still characteristics are based on a sample tape of 4.2M1L.
The video signal of z was recorded, and the time until the playback output attenuated to 50% was taken as the time. Also, powder removal takes 60 minutes by shuttle 100.
After running twice, the amount of powder falling onto the head drum, guide, etc. was visually observed and evaluated using a point deduction method (-5 to 0). The results are shown in Table 4.

(The following is a blank space) Table 4 As is clear from the above Table 4, it can be seen that the sample tapes according to the present invention not only had less powder falling off, but also had significantly improved still characteristics.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
By using a butadiene copolymer containing an epoxy group and a vinyl chloride copolymer containing a tertiary amine, the epoxy group of the butadiene copolymer is The ring-opening reaction is promoted, and a crosslinking reaction occurs between the butadiene copolymer and the vinyl chloride copolymer, resulting in a binder with excellent mechanical strength.

Furthermore, since this reaction proceeds almost unaffected by moisture, the binder can be made to have very good durability.

Therefore, by using this binder, a magnetic recording medium with excellent durability can be provided without deteriorating the electromagnetic conversion characteristics.

Patent applicant: Sony Corporation Agent Patent Attorney Mi Koike Episode Sakae Tamura

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, the binder comprising a butadiene copolymer having an epoxy group; A magnetic recording medium comprising a vinyl chloride copolymer having a tertiary amine.