JPH02260221A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a high gloss value and the excellent surface smoothness of a coated film by incorporating a copolymer contg. a monomer unit having the residual group of an org. alicyclic compd. and vinyl chloride as constituting units into a binder. CONSTITUTION:The copolymer having the vinyl chloride and the monomer unit having the residual group of the org. alicyclic compd. in the constituting units is used as the binder of a magnetic coating compd. The monomer unit having the residual group of the org. alicyclic compd. is adequately the unit expressed by formula I. In the formula, Z denotes the residual group of the org. alicyclic compd. The residual group of the org. alicyclic compd. is formed of 2 or more org. alicyclic carbon rings having 3c or more in common. In the formula, L denotes a mere coupler or bivalent combination group. The bivalent combination group is exemplified by an alkylene group, -NHCOO- group, etc. The high gloss value and smooth magnetic film are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to magnetic recording media, and particularly to improvements in binders used in magnetic layers of magnetic recording media.

<Prior Art> Conventionally, vinyl chloride-vinyl acetate-vinyl alcohol copolymers and vinyl chloride-vinyl acetate-vinyl alcohol-maleic acid copolymers have been widely used as binder resins for magnetic tapes.

As such copolymers, the former is US 000
The company's product name is “VAGH” and the latter is “UCARM.”
AG 528'' is commercially available as a typical example.

Furthermore, we have developed a vinyl chloride-acrylic acid ester-maleic acid copolymer in which a (meth)acrylic acid ester derivative having a hydroxyl group is introduced without using vinyl acetate-vinyl alcohol as a copolymer component.
UCARMAG 527" etc. are known.

These copolymers are easily soluble in solvents, have good compatibility with other resins, and have good affinity with magnetic powders due to the hydroxyl groups present in their molecules. It has advantages such as good properties.

However, in recent years, magnetic powder particles have become increasingly finer in order to achieve higher density recording, and the above-mentioned resins have insufficient dispersibility.

As a result, the gloss of the magnetic paint and coating is low.

Further, at the stage of preparing and applying the magnetic paint, the viscosity and stickiness are high, resulting in a large surface roughness of the paint film.

<Problems to be Solved by the Invention> The main object of the present invention is to provide a magnetic recording medium with excellent dispersibility, high gloss of paint and coating film, and excellent surface smoothness of the coating film.

Means for Solving the Problems> Such objects are achieved by the following inventions (1) to (6).

(1) In a magnetic recording medium in which a magnetic paint containing a binder and magnetic powder is coated on a substrate, the binder comprises a monomer unit having a bridged alicyclic compound residue and vinyl chloride. A magnetic recording medium characterized by containing a copolymer containing as a unit.

(2) The above (1), wherein the copolymer contains 0.5 to 30% by weight of the monomer unit having the bridged alicyclic compound residue.
The magnetic recording medium described in .

(3) The magnetic recording medium according to (1) or (2) above, wherein the copolymer further contains a hydroxyl group-containing monomer.

(4) The magnetic recording medium according to any one of (1) to 3) above, wherein the copolymer further contains a polar group-containing monomer.

(5) The magnetic recording medium according to any one of (1) to 4) above, wherein the copolymer contains 50 to 90% by weight of the vinyl chloride.

(6) Specific configuration of the magnetic recording medium according to any one of (1) to 5) above, wherein the magnetic powder has a BET value of 35 m"/g or more> The specific configuration of the present invention will be described below. Explain in detail.

In the present invention, a copolymer having a monomer unit containing vinyl chloride and a bridged alicyclic compound residue in its constituent units is used as the binder.

As the monomer unit having a bridged alicyclic compound residue, those shown in the following formula are suitable.

Formula % Formula % In the above formula, Z represents a bridged alicyclic compound residue.
The bridged alicyclic compound residue may be any residue of a ring formed from two or more alicyclic carbocycles having three or more carbon atoms in common, but especially It is preferable that it is a residue of a ring formed from an alicyclic carbocyclic ring having about 5 to 8 carbon atoms and 2 having 3 to 4 carbon atoms in common.

Specific examples include bicyclo[2,2,1] to butylbicyclo[2,2,2]octyl, 2-bicyclo[2,2,2]octenyl, etc., to bicyclo[3,1,1] Butane, Bicyclo[2,2,1]hebutane, Bicyclo[2,2,1]heptene, Bicyclo[2,2,2]octane, Bicyclo[3,2,1]octane, Bicyclo[2,2,2 ] Octene, bicyclo[3,3,11nonane, bicyclo[3,2,2]nonane, adamantane, and other compounds belonging to terpenes.

Furthermore, substituents such as alkyl groups, aromatic residues, such as phenyl groups, unsaturated hydrocarbon residues, nitro groups, halogens, and aldehyde groups may be bonded to these bridged alicyclic compound residues. .

Further, a polar group may be bonded to the bridged alicyclic ring directly or via the above-mentioned substituents, such as an alkyl group or an aromatic hydrocarbon residue.

As polar groups, hydroxyl group, carboxylic acid group, phosphoric acid group, phosphorous acid group, hypophosphorous acid group, sulfuric acid group, sulfonic acid group, or their salts, amino group, ammonia group, nitrile group (cyano group) etc.

Details of these will be explained in the section on polar group-containing monomers below.

In addition, the above substituents, especially alkyl groups, aromatic hydrocarbon residues, unsaturated hydrocarbon residues, etc., include carbonyl groups, oxycarbonyl groups, sulfonyl groups, sulfonylcarbonyl groups,
It may be bonded to a bridged alicyclic ring via an imino group, an iminocarbonyl group, an iminosulfonyl group, or the like.

Next, in the above formula, L represents a simple bond or a divalent linking group.

As the divalent linking group, alkylene group, arylene group,
-0- group, -CO- group, SO-group, -NH- group, or a group in which a plurality of these divalent groups are bonded, such as -C
Examples include OO- group, -0CO- group, -NHCO- group, -NHCOO- group, and the like.

Further, R represents a hydrogen atom or an alkyl group (lower alkyl group).

Next, specific examples of the monomer unit having a bridged alicyclic compound residue in the present invention will be given.

monomer No.

To synthesize these monomers, Diels-Alder
It can be easily synthesized by synthesizing a bridged alicyclic compound derivative by a known method such as reaction, or by further introducing a double bond by a known method.

One or more types of monomers contained in such bridged alicyclic compound residues are contained in the copolymer, and the total amount is 0.5 as a structural unit.
It is contained in an amount of about 30% by weight.

If the content of the monomer having a bridged alicyclic compound residue is less than 0.5% by weight, the dispersibility will deteriorate and the effectiveness of the present invention will be lost, and if it exceeds 30% by weight, the solubility and durability will deteriorate. This causes inconvenience in terms of gender, etc.

In this case, the content of the monomer having a bridged alicyclic compound residue is preferably 0.5 to 20% by weight.

A copolymer containing a monomer having a bridged alicyclic compound residue as a constituent unit contains vinyl chloride as an essential constituent unit.

The vinyl chloride unit content is preferably 50 to 90% by weight.

When the vinyl chloride unit content exceeds 90%, solubility deteriorates.

Further, if 50% by weight of the droplets are left undropped, the dispersibility deteriorates.

Furthermore, the copolymer may contain a hydroxyl group-containing monomer.

By containing the hydroxyl group-containing monomer as a structural unit, crosslinkability is obtained and durability is improved.

The hydroxyl group-containing monomer is not particularly limited and includes the following.

(1) Completely or partially saponified vinyl alcohol C1 vinyl alcohol vinyl acetate (2) Hydroxyalkyl (meth)acrylate C22-hydroxyethyl acrylate Il 2-hydroxyethyl methacrylate 2-hydroxypropyl acrylate 2-hydroxypropyl Methacrylate 3-hydroxypropyl acrylate 3-hydroxypropyl methacrylate 2-hydroxybutyl acrylate 2-hydroxybutyl methacrylate 3-hydroxybutyl acrylate 3-hydroxybutyl methacrylate 4-hydroxybutyl acrylate 4-hydroxybutyl methacrylate 5-hydroxypentyl acrylate 5-hydroxypentyl Methacrylate 6-Hydroxyhexyl acrylate 6-Hydroxyhexyl methacrylate Neopentyl glycol acrylate Neopentyl glycol methacrylate Other allyl carbinol Allyl alcohol C22 Crotyl alcohol C23 Citronellol C24 Phytol C25 Cinnamyl alcohol Among these, hydroxyalkyl (meth)acrylate system is preferred.

Such a hydroxyl group-containing monomer is preferably contained as a structural unit in the copolymer in an amount of 40% by weight or less, particularly 1 to 20% by weight.

If the content of the hydroxyl group-containing monomer exceeds 40% by weight, problems will occur in terms of solubility, durability, etc.

Note that the copolymer may contain vinyl acetate as a structural unit.

Addition of vinyl acetate tends to improve solubility, but if the content of vinyl acetate units exceeds 20% by weight, durability deteriorates, so when adding vinyl acetate, the content should be 20% by weight or less. It is preferable that

The copolymer may contain a polar group-containing monomer. This further improves dispersibility.

The polar group-containing monomer used in the present invention is a vinyl monomer containing a polar group.

Polar groups include carboxylic acid groups, phosphoric acid groups, phosphorous acid groups, hypophosphorous acid groups, sulfuric acid groups, sulfonic acid groups or their salts, amino groups, ammonia groups, epoxy groups, etc., as described above. preferable.

In this case, carboxylic acid group C0OH, phosphoric acid group PO4H2
As salts of sulfate group 5O4H and sulfonic acid group 5O3H,
In addition to salts of alkali metals such as K and Na, and alkaline earth metals such as Ca and Mg, ammonium salts and the like may also be used.

Note that the phosphoric acid group, phosphorous acid group, and hypophosphorous acid group may be monophosphoric acid ester groups having an alkyl group, an aryl group, or the like.

The amino group may be an unsubstituted amino group or a monosubstituted amino group substituted with an alkyl group, an aryl group, or the like.

Furthermore, as ammonium groups, in addition to unsubstituted ones,
It may also be a mono-, di-, or tri-substituted amino group substituted with an alkyl group, an aryl group, or the like.

Further, an acid anion such as a halogen may be bonded to the ammonium group.

The polar group-containing monomer used in the present invention has one or more of the above polar groups. The polar group may be directly bonded to the vinyl group, or may be bonded to a substituent that is bonded to the vinyl group.

The substituents bonded to the vinyl group to which the polar group is bonded include R,0CO- R+' O- R, NHCO- R, NHCOO- R, C00- R, NH- R+51-R, NC00CO- In this case, R1 is an alkyl group, especially one having 1 to 1 carbon atoms;
0, aryl groups (phenyl group, naphthyl group, etc.), unsaturated hydrocarbon residues, glycidyl-substituted alkyl groups, etc.

Moreover, Ll is an alkylene group.

Note that these may be further substituted with other substituents.

Usually, only one of these polar groups is bonded directly or indirectly to the vinyl group, but two or more may be bonded to the vinyl group.

Furthermore, other alkyl groups, particularly those having 1 to 10 carbon atoms, aryl groups, etc., and preferably lower alkyl groups may be bonded to the vinyl group.

Specific examples of these polar group-containing monomers are listed below.

(1) Carboxylic acid group-containing monomer DI Acrylic acid D2 Methacrylic acid D3 Crotonic acid D4 Isocrotonic acid D5 Vinyl acetic acid D6 Angelic acid DI tiglic acid D8 Allyl acetic acid D9 β, β-dimethylacrylic acid 010 Pyroterepic acid Dll undecylenic acid 012 Maleic acid 013 Itaconic acid etc.

(2) Phosphate group-containing monomer 014 G)+2 =CHC00(R)n-OPO(O
H)2 where R: Substituted or unsubstituted methylene n such as CH2, C(CH3) 2: about 1 to 10015 G)+2 =CHCOO[C(C)+3)
2]InCH2)m-OPO(OH)2 where m: about 1 to 10, n: about 1 to 10, etc.

(3) Sulfate group-containing monomer Here, A: H or a cation such as Na, etc.

(4) Sulfonic acid group-containing monomer 0171-Sulfonic acid-2-hydroxypropyl acrylate C182-Sulfonic acid ethyl acrylate 019 Vinylsulfonic acid 020 Vinyl sulfonate 0.21 Styrene sulfonic acid 022 Styrene sulfonate C23 CH2=CH ( R)n SO3A where R:CH
2.C(2=CH[C(C:Hs)2In
(CH2)+11303 A where m: about l to 10 n: about l to 1-0 A: cation such as H or Na D25 CH2=CH-C-NH-(CHz) 2-
So 3 A where A: H or a cation such as Na, etc.

(5) Amino group-containing monomer 026 acrylamide C27CH2= CHCOO(CH2) 2-NH20
28 dimethylaminoethyl methacrylate D29 C
Hz:CHCDNH(CH2)2--3O3A
Here, A: H or a cation such as Na, etc.

(6) Ammonium group-containing monomer 030 CH2=C)I-COO(C)1213 N-
(R'), s''X-where R': Alkyl X such as Cs.C2H11: (Anion D31 such as 1.1 diallyldimethyl-ammonium bromide, etc.).

(7) Epoxy group-containing monomer D32 glycidyl methacrylate D33 glycidyl acrylate where R, R': H, CH3, etc. n: about 1 to 10 These polar group-containing monomers are contained in the copolymer as a structural unit, totaling 20 It is preferably contained in an amount of 0.02 to 20% by weight or less, particularly 0.02 to 20% by weight.

When the content exceeds 20% by weight, solubility and durability decrease.

The number average molecular weight of such copolymers is usually 1000
It should be about 0 to 30,000.

If the number average molecular weight is less than ioooo, the physical properties will deteriorate, and if it exceeds 30,000, the dispersibility will deteriorate.

To synthesize such a copolymer, each monomer may be copolymerized according to a conventional method.

Alternatively, an acid group, an ammonium group, etc., and in some cases a bridged alicyclic compound can also be separately introduced according to a conventional method after the copolymer synthesis.

Such copolymers are used as the main binder for magnetic recording media.

In the present invention, the binder contains a thermoplastic elastomer and/or resin of 70% relative to the total resin content in the binder.
It contains not more than 50% by weight, especially 50 to 70% by weight.

As the thermoplastic elastomer, the following are suitable.

i) Polyurethane elastomer As a thermoplastic elastomer, polyurethane elastomer has an excellent balance of abrasion resistance of the magnetic coating film required for magnetic recording media, adhesion with PET film, and wettability with magnetic material particles. Urethane compounds are particularly suitable for the purpose of the present invention.

Examples of such urethane compounds include 2,4-toluene diisocyanate, 2,6
-Toluene diisocyanate, 1.3-xylene diisocyanate, 1°4-xylene diisocyanate, 1.
5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,
3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylbiphenylene diisocyanate, 4°4'-biphenylene diisocyanate, hexamethylene diisocyanate, influoron diisocyanate, dicyclohexylmethane diisocyanate, desmodur, various polyvalent incyanates such as desmodur N, and reticulated saturated polyester (ethylene glycol,
Diethylene glycol, glycerin, trimethylolpropane, 14-butanediol, 1,6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, 1,4-cyclohexane dimetatool,
Polyhydric alcohols such as phthalic acid, isophthalic acid,
(by condensation polymerization with saturated polybasic acids such as terephthalic acid, maleic acid, succinic acid, adipic acid, and sebacic acid)
Polyurethane elastomers made of condensation products of various polyesters such as network saturated polyethers (polyethylene glycol, polypropylene glycol, polytetraethylene glycol), caprolactam, hydroxy-containing acrylic esters, and hydroxy-containing methacrylic esters are effective.

it) Acrylonitrile-butadiene copolymer elastomer An acrylonitrile-butadiene copolymer with a terminal hydroxyl group commercially available as PolyBD Liquinodesin manufactured by Sinclair Petrochemical Co., Ltd. or an elastomer such as Hiker 1432j manufactured by Nippon Zeon Co., Ltd. 1ii) Polybutadiene elastomer Sinclair A prepolymer having a low molecular weight terminal hydroxyl group, such as PolyBD Liquino Resin R-15 manufactured by Petrochemical Co., Ltd., is particularly suitable in terms of compatibility with thermoplastic plastics and affinity with magnetic powder.

In addition, polybutadiene cyclized product Nippon Synthetic Rubber Co., Ltd. CBR-
M901 also exhibits excellent performance when combined with thermoplastics.

Other suitable thermoplastic elastomers include:
Examples include chlorinated rubber, acrylic rubber, isobrene rubber and its cyclized product (ClR701 manufactured by Japan Synthetic Rubber Co., Ltd.), epoxy-modified rubber, internally plasticized saturated linear polyester (Toyobo Vylon #300), and the like.

In addition, as a thermoplastic resin that can be used instead of or added to such an elastomer component, linear saturated polyester resin, desmophene #800, #110 manufactured by Bayer & Co., Ltd.
Low molecular weight polyester resin, epoxy resin phenoxy resin, chlorosulfonated polyethylene resin, which is versatile in two-component type with incyanate such as 0, #2200.
Vinyl isobutyl ether, polyamide resin, polyvinyl butyral resin, polyvinylpyrrolidone resin, etc. can be used.

The binder can also be crosslinked, especially by a compound crosslinker that can react with the hydroxyl groups of the copolymer.

Examples of such crosslinking agents include polyfunctional isocyanate compounds having isocyanate groups or incyanate-containing compounds mentioned above, as well as butylated melamine resins and the like.

To cure such a binder, it is generally necessary to heat it in a heating oven at 50-80° C. for 6-100 hours.

The magnetic powder used in the magnetic paint of the magnetic recording medium of the present invention may be metal magnetic particles, cobalt-coated iron oxide particles, γ-Fe203 particles, barium ferrite particles, or the like.

However, the binder of the present invention is particularly effective when used in combination with fine particle magnetic powder, and binders with such high effects have a BET value of 35 m'/g or more, particularly 40 m'/g or more,
It is usually about 75 m''/g or less.

The mixing ratio of the magnetic powder and these binders is about 10/1 to 1/10 by weight. In addition, various abrasives, lubricants, antistatic agents, dispersants, etc. may be used in the magnetic paint depending on the purpose.

Note that the thickness of the recording layer containing magnetic particles and a binder is usually about 1 to 7 layers.

As the substrate, any one of polyester film, various resins such as polyamide and polyimide, aluminum metal, glass, etc. may be used depending on the purpose.

Further, a back coat layer, a back magnetic layer, etc. may be provided on the opposite surface of such a substrate to the surface on which the recording layer is provided.

<Example> Next, the present invention will be described in further detail by presenting examples of the present invention.

Example 1 Part by weight Magnetic powder 100 Copolymer
10 Polyurethane resin (
Nippon Polyurethane Co., Ltd. Niraporan 2304) 10 Lubricant
1 abrasive
1 methyl ethyl ketone
70 methyl isobutyl ketone
70 Toluene 70 This mixture was dispersed in a ball mill for about 20 hours. After that, Coronate L (polyisocyanate manufactured by Nippon Polyurethane Co., Ltd.) was added as a crosslinking agent, and the mixture was applied to the polyester base of 8 houses. After surface treatment, heat hardening treatment is performed,
We obtained magnetic tape with a coating thickness of 5 units.

In this case, the copolymers used are shown in Table 1 below.

Also, The magnetic powder used was It is from Table 2 below. Ru.

Surface magnetic powder I ■ Composition Metal powder Co-7-Fe2rs
BE ding (m”/gn 55
45Hc (Oe
)' 1500 750a ,,(e
mu/g) 130 75 The glossiness of the coating film immediately after application and the coating film after surface treatment was measured using a crossmeter (Murakami type).

In addition, the surface roughness Ra of the coating film was measured.

These results are shown in Table 3.

From the above, the effects of the present invention are clear.

Effects> According to the present invention, a magnetic recording medium can be obtained in which the affinity between the finely divided magnetic powder and the binder is high, and the magnetic recording medium is excellent in reliability, durability, and electromagnetic conversion characteristics.

In this case, the gloss of the paint and coating is extremely high.

In addition, the viscosity and stickiness of the coating material are low, the surface roughness of the coating film is small, and a smooth magnetic film can be obtained.

These effects are thought to be due to the introduction of bulky functional groups having steric hindrance in the molecular structure into the constituent units of the copolymer.

In addition, there is little change over time in a high temperature and high humidity environment, and there is no deterioration of electromagnetic conversion characteristics.

Claims (6)

[Claims] (1) In a magnetic recording medium in which a magnetic paint containing a binder and magnetic powder is coated on a substrate, the binder comprises a monomer unit having a bridged alicyclic compound residue;
A magnetic recording medium comprising a copolymer containing vinyl chloride as a constituent unit. (2) The magnetic recording medium according to claim 1, wherein the copolymer contains 0.5 to 30% by weight of monomer units having the bridged alicyclic compound residue. (3) The magnetic recording medium according to claim 1 or 2, wherein the copolymer further contains a hydroxyl group-containing monomer. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein the copolymer further contains a polar group-containing monomer. (5) The magnetic recording medium according to any one of claims 1 to 4, wherein the copolymer contains 50 to 90% by weight of the vinyl chloride. (6) The magnetic recording medium according to any one of claims 1 to 5, wherein the magnetic powder has a BET value of 35 m^2/g or more.