JPH01143012A - 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. The present invention aims to provide a magnetic recording medium with excellent durability by using a polyurethane resin having a polyurethane resin and a vinyl chloride copolymer having a tertiary amine.

[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 countermeasure, 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, the so-called backing density.

Therefore, the proportion of the binder in the magnetic coating film is extremely small. A magnetic coating containing such a small amount of binder may cause the magnetic layer to peel off when used as a magnetic recording medium, and in order to prevent such deterioration in the strength of the magnetic coating, it is necessary to Need to improve strength.

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 -NGO+ -OH--IO O, whereas in the actual reaction, -NC
Isocyanate reacts with moisture as shown in O+ HzONHz + Cot, and the amino groups formed by this reaction react with other isocyanates as shown in Fig. Therefore, when an isocyanate compound is reacted with a hydroxyl group, the -NGO group that is effective is affected by moisture as shown in the above reaction formula, and the amount of 1-NGO group that contributes to crosslinking decreases, making it difficult to form a sufficient crosslinked structure. This makes it less durable.

[Problem that the invention seeks to solve]

As mentioned above, a binder that forms a crosslinked structure through electron beam sensitive bonding and increases the mechanical strength of the coating film, or a binder that uses 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, the present invention has been proposed to solve the above-mentioned drawbacks in the technical field, and provides a bond that has a good crosslinked structure without being affected by moisture during the reaction to form a crosslinked structure. The object of the present invention is to provide a magnetic recording medium that is highly durable and has good magnetic properties and electromagnetic conversion properties.

[Means for solving problems]

As a result of extensive research over a long period of time, the present inventors have discovered that a binder consisting of a polyurethane resin having an epoxy group in the side chain and a vinyl chloride copolymer having a tertiary amine has been developed. The present invention was completed based on the discovery that it 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 polyurethane resin having an epoxy group and a tertiary amine. It is characterized by containing a vinyl chloride copolymer having the following.

The polyurethane resin having an epoxy group used as a binder in the present invention is a polyurethane resin in which an epoxy group is introduced.

The above polyurethane resin is obtained by a reaction between a polyhydroxy compound and a polyisocyanate, and the polyhydroxy compound is the main component of the resin.

As polyisocyanate, the molecular weight is 500 to 5000.
It is preferable to use a long chain diol having a molecular weight of 50 to 500, a short chain diol having a molecular weight of 50 to 500, and an organic diisocyanate.

The long-chain diols are broadly classified into, for example, polyester diols, polyether diols, polyether ester glycols, and the like. Specific examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or lower alcohol esters thereof, and ethylene glycol. ,1,3-
Propylene glycol, 1,4-butylene glycol,
1゜6-hexane glycol, diethylene glycol,
Examples include polyester diols obtained by reacting neopentyl glycol, ethylene oxide adducts to bisphenol, or mixtures thereof, and lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone. It will be done. Examples of polyether diol include polyethylene glycol,
Examples include polypropylene ether glycol, polytetramethylene ether glycols, and copolymerized polyether glycols thereof. Examples of polyether ester glycols include polyester glycols obtained by reacting the above polyalkylene ether glycol as a polyol component with an aliphatic or aromatic dicarboxylic acid.

If the molecular weight of this long-chain diol is too small, the urethane group concentration of the resulting polyurethane resin will be too high, resulting in poor resin flexibility and poor solubility in solvents, making it difficult to use as a binder for magnetic recording media. Not very desirable for use.

Also, when the molecular weight of the long chain diol is too large,
If the long-chain diol content in the resin becomes too high, the urethane group concentration becomes relatively very small (as a result, the abrasion resistance and heat resistance of the resin decrease).

Examples of the short chain diols include ethylene glycol, propylene glycol, 1,4-butylene glycol, 1.
Ethylene oxide adducts or propion oxide adducts to aliphatic glycols or bisphenols such as 6-hexane glycol and neopentyl glycol;
There are aromatic diols such as ethylene oxide adducts of hydroquinone, and these can be used alone or in combination in different quantitative ratios depending on the properties of the polyurethane resin.

Furthermore, glycerin, ethylene oxide adduct of glycerin, 2-methylpropane-1,2,3-)+7ol, 4-[bis(2-hydroxyethyl))-2-
Hydroxypentane, 3-methylpentane-1,3,5
-triol, 1,2.6-hexane glycol, 1-
It is also possible to use triols such as bis(2hydroxyethyl)amino-2-propatol and a propion oxide adduct of jetanolamine.

Examples of the organic diisocyanates include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, -phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, and 2-phenylene diisocyanate. .6-Tolylene diisocyanate, diphenylmethane diisocyanate, 3,3-dimethoxy-4,4''-biphenylene diisocyanate, 3
．． Aromatic diisocyanates such as 3'-dimethyl-4,4"-biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-naphthalene diisocyanate, 1.3-Diisocyanatomethylcyclohexane, 1
．． 4-diisocyanatomethylcyclohexane, 4,4
Examples include alicyclic diisocyanates such as '-diisocyanate dicyclohexylmethane and isophorone diisocyanate.

In addition, the polyurethane resin referred to in the present invention includes polyurea resin and polyurethane urea resin in addition to the above-mentioned polyurethane resin. The above-mentioned polyurea resin and polyurethane urea resin can be obtained by replacing part or all of the organic diisocyanate constituting the polyurethane resin with a training diamine.

To introduce epoxy groups into the above polyurethane resin,
Glycidol (C3) 160
It may be modified with a compound containing both a hydroxyl group and an epoxy group in the molecule, such as □). As a result, an epoxy group is introduced into the main chain of the polyurethane resin, resulting in a polyurethane resin having the desired epoxy group. Note that the amount of epoxy groups contained in the polyurethane resin is preferably 0.01 to 2 mmol/g. If the amount of this epoxy group is small, the 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 the above general formula, 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+k)≦1000. If this value is less than 100, the durability of the resulting coating film will deteriorate, and 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 tends to occur.

The amount of tertiary amine contained in the vinyl chloride copolymer is preferably about 0.01 to 1.0 mmof/g. If this value is less than 0.01 mmol/g, the dispersibility deteriorates, and conversely, if it exceeds 1.0 LIleAO1/g, the solubility in solvents decreases and at the same time the moisture resistance during coating film formation deteriorates.

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., 2hydroxyethyl methacrylate, 2hydroxyethyl acrylate, 2
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.

(However, in the formula, R represents an alkyl group having 1 to 3 carbon atoms, and Ro represents hydrogen or a methyl group, respectively.).

The tertiary amine-containing vinyl chloride copolymer may be used in combination with other binders. Such binders include those conventionally used as binders for magnetic recording media. Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-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, phenol Examples include resins, 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.

The ratio of the polyurethane resin to the vinyl chloride copolymer is preferably polyurethane resin/vinyl chloride copolymer=179 to 9/1.

The above-mentioned epoxy group-containing polyurethane resin 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.

Examples include 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.

As described above, in the present invention, by combining the polyurethane resin having the epoxy group with the vinyl chloride copolymer having the tertiary amine or other resin, The tertiary amine contained promotes the ring-opening reaction of the epoxy group contained in the polyurethane resin. As a result, the reaction between the epoxy group and the active hydrogen contained in the polyurethane resin, vinyl chloride copolymer, or other resin is promoted, and a crosslinked structure is developed. It is believed that this crosslinked structure contributes to improving the durability of the magnetic recording medium.

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 polyurethane resin can be further promoted.

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

A hydrophilic polar group may be introduced into the epoxy group-containing polyurethane resin, the tertiary amine-containing vinyl chloride copolymer, or other binder used in combination for the purpose of further improving dispersibility.

The above hydrophilic polar groups include SOJ group, -0SO,M
Group, -PO(OM')! group, -C00M group, -1JG,
J group (where M is a hydrogen atom or an alkali metal atom, M
o is a hydrogen atom, an alkali metal atom or a hydrocarbon atom,
G represents an alkyl group, and J represents a halogen.

) etc.

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

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 polyimide-imide;
Examples include paper, metals such as aluminum and copper, light alloys such as aluminum alloy and di-titanium alloy, 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.

Moreover, any ordinary ferromagnetic powder can be used as the ferromagnetic powder used in the magnetic layer. Therefore, ferromagnetic powders that can be used include ferromagnetic iron oxide particles,
Examples include ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles include general 2Fed.

When expressed as
1.50), 7 gnetite (Fezoa, 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. There are two types of cobalt-containing iron oxide: doped type and deposited type.

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

3n, 7'e, Sb, Fe, Ti, V, M
It is possible to use a material containing at least one of the following.

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

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

co-Ni, Fe-Co-B, Fe-Go-Cr-B,
Mn-B 1. Mn-A1. Fe-Co-V, etc. can be used, and Aj! ,
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,
These dispersants, lubricants, etc. may be added with rust preventive agents, etc.
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, and dioxane,
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 organic chlorine compound solvents such as chloroform, ethylene chlorohydrin, and dichlorobenzene.

[Effect]

By using an epoxy group-containing polyurethane resin and a tertiary amine-containing vinyl chloride copolymer resin together, the tertiary amine in the vinyl chloride copolymer exerts a catalytic effect, opening the epoxy groups of the polyurethane resin. The ring reaction is promoted,
A crosslinked structure is developed between the active hydrogen of the polyurethane resin 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 and the binder has 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 polyurethane resins used as binders in this example, and Table 2 shows the vinyl chloride copolymers used as binders.

Table 1 (blank below) Table 2 In Table 2, acrylamide propane dimethylamine was used as the tertiary amine component, and 2-hydroxyethyl methacrylate was used as the hydroxyl group component.

Magnetic recording media were prepared using the polyurethane resins shown in Table 1 above and the vinyl chloride copolymers shown in Table 2 as binders.

Jitsushin IJLL Co-adhered Fezes 100 parts by weight (specific surface area 40nr/g) Polyurethane resin A-112 parts by weight Vinyl chloride copolymer B-112 parts by weight Carbon black (antistatic agent) 2 parts by weight CrzOs<polishing 2 parts by weight dimethyl silicone (lubricant) 1 part by weight butyl stearate (lubricant) 1 part by weight methyl ethyl ketone
10031iffi part 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 mixed with 14 parts by weight.
It was coated onto a polyethylene terephthalate film having a thickness of 6 μm 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.

2-6 In the composition of the magnetic paint, the polyurethane resin is one of the polyurethane resins shown in Table 1, and the vinyl chloride copolymer is one of the vinyl chloride copolymers shown in Table 2. Sample tapes were prepared in the same manner as in Example 1 except that the types were changed as shown in Table 3.

'1 to f'4 In the composition of the magnetic paint, the polyurethane resin is one of the polyurethane resins shown in Table 1, and the vinyl chloride copolymer is one of the vinyl chloride copolymers shown in Table 2. Sample tapes were prepared in the same manner as in Example 1 except for changing the types as shown in Table 3.

Table 3 shows the types of polyurethane resins and vinyl chloride copolymers used in Examples 2 to 6 and Comparative Examples 1 to 4.

Table 3: Still characteristics and powder fall-off were measured for each of the sample tapes obtained.

In addition, the above still characteristics are 4.2MIL on the sample tape.
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.

Table 4 As is clear from the above Table 4, each of 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 polyurethane resin containing an epoxy group and a vinyl chloride copolymer containing a tertiary amine,
The action of the tertiary amine in the vinyl chloride copolymer promotes the ring-opening reaction of the epoxy group in the polyurethane resin.
A crosslinking reaction occurs between the polyurethane resin 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 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 Between Art supplies Sakae Same left knee win Procedures (1 under pressure (voluntary) February 10, 1986

Claims (1)

[Claims] 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 polyurethane resin having an epoxy group and a third A magnetic recording medium comprising a vinyl chloride copolymer having an amine.