JPS62134820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent durability, and good magnetic characteristics and electromagnetic conversion characteristic by forming a magnetic layer essentially consisting of ferromagnetic powder and specific binder on a nonmagnetic substrate. CONSTITUTION:The magnetic layer essentially consisting of the ferromagnetic powder and binder is formed on the nonmagnetic substrate. A vinylidene chloride copolymer contg. a tertiary amine in the molecule is incorporated into the binder. A monomer (vinyl chloride, vinyl acetate, etc.,) having a vinyl group which can be copolymerized with the vinylidene chloride may be copolymerized with said copolymer. The degree of polymn. of the copolymer is preferably in a 100-1,000 range. The proportion of the vinylidene chloride component to be incorporated into the copolymer is preferably 30-80mol%. The durability and heat resistance are low when the proportion is not within said range. The proportion of the monomer having the vinyl group copolymerizable with the vinylidene chloride in the copolymer and the tertiary amine is preferably 0.1-2.0mol%. The effect of dispersion into the magnetic powder and the moisture resistance of the coated film are low when the proportion is not within said range.

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 a tertiary amine is added to the binder constituting the magnetic layer in the molecule. By using a vinylidene chloride-based copolymer, we aim to improve the dispersibility of magnetic powder and the surface properties of the magnetic layer, and improve the durability and magnetic properties of the resulting magnetic recording medium.

This is an attempt to improve electromagnetic conversion characteristics.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have been required to have improved magnetic properties and electromagnetic conversion properties in order to obtain high playback output even when recording at short wavelengths. There is.

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.

On the other hand, conventional binders for magnetic recording media include vinyl chloride-based binders such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-propionic acid copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer. Among these, the hydroxyl group force of vinyl alcohol <Vt'z contributes to the dispersibility of the powder, and the active hydrogen of the hydroxyl group reacts with isocyanate compounds to form a crosslinked structure and improve the mechanical properties of the coating film. Vinyl chloride - vinyl acetate - because of its increased strength, etc.
Vinyl alcohol copolymers are widely used.

However, with the above-mentioned increase in backing density and the demand for rings with improved durability, various problems have arisen with these vinyl chloride-based binders.
The current situation is that it is difficult to take adequate measures.

For example, as the specific surface area increases due to finer particles of magnetic powder and the cohesive force increases due to higher magnetic force, satisfactory dispersibility and surface properties cannot be obtained with the above-mentioned binders, and the backing density of the magnetic powder increases. This has also become difficult. Therefore, the durability, magnetic properties, and electromagnetic conversion properties were also insufficient. In particular, performance has been insufficient for ultrafine magnetic powders that are compatible with high recording densities and magnetic powders that have a high amount of magnetization. In this case, for example, a method such as using a surfactant as a dispersant may be considered, but since the surfactant is a low molecular weight, powder falling off and blooming due to changes over time may occur, resulting in poor mechanical strength and durability. There are problems with this.

Furthermore, when using the above-mentioned vinyl chloride binder,
Since the magnetic layer lacks flexibility, it is necessary to add a large amount of plasticizer or to use a large amount of soft resin. As a result, in the former case, problems such as blooming and decreased durability of the magnetic layer may occur; in the latter case, the dispersibility of the ferromagnetic powder may deteriorate, or There is a wide range that causes problems in running performance in hot and humid conditions.

[Problem that the invention seeks to solve]

In this way, the vinyl chloride copolymers that have been used in the past have many problems to be solved in terms of dispersibility in magnetic powders and physical properties of coatings, and it is difficult to achieve the desired durability, magnetic properties, and electromagnetic conversion properties. It was difficult to secure.

Therefore, the present invention was proposed in order to eliminate the above-mentioned drawbacks in the technical field, and provides a binder resin that has excellent dispersibility for magnetic powder and coating film properties, 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]

In order to achieve the above objectives, the present inventors conducted extensive research over a long period of time and found that vinylidene chloride copolymers have good flexibility and that a tertiary amine is introduced into the side chain as a polar group. The present invention has been completed by discovering that a high affinity for magnetic powder can be achieved by In a magnetic recording medium formed of layers,
The binder is characterized in that it contains a vinylidene chloride copolymer having a tertiary amine in the molecule.

The vinylidene chloride copolymer used as a binder for the magnetic layer in the present invention is a copolymer mainly composed of vinylidene chloride with a polar group (tertiary amine) introduced into the side chain. Formula % Formula % () (wherein, X represents a monomer having a vinyl group copolymerizable with vinylidene chloride, and Y represents a monomer having a vinyl group copolymerizable with vinylidene chloride and a tertiary amine. In addition, i and j each represent the degree of polymerization.) This is a compound represented by the following. In addition, in the above general formula,
For convenience, each component of the compound is described as being arranged in a regular order, but in addition to the case shown in the general formula above,
It goes without saying that each component may be arranged in a regular repeating manner at a fixed ratio, or may be arranged randomly.

A copolymer mainly composed of vinylidene chloride has excellent flexibility, good chemical resistance and solvent resistance, and almost no water absorption. In addition, it has excellent adhesion to the base film, which has non-magnetic support. Therefore, it is suitable as a binder for magnetic recording media that require flexibility, such as magnetic tapes and floppy disks.

Here, as a method for introducing the above-mentioned tertiary amine into a copolymer mainly composed of vinylidene chloride, the following method can be considered, for example.

A. A method of copolymerizing a monomer Y having a vinyl group and a tertiary amine copolymerizable with vinylidene chloride with vinylidene chloride.

The above monomer Y has an acrylic group or a meccrylic group in the molecule and a tertiary amine, and specifically, ii) R' CHz=CCONH(CHz) 2N (R) ziv
) R' CHz=CCONH(C1h)J(R)z (wherein R represents an alkyl group having 1 to 4 carbon atoms, and R' represents H or CH, respectively).

B. A method in which a functional group introduced into the end or side chain of a vinylidene chloride copolymer is modified with a compound having a tertiary amine.

This method can be divided into the following two methods depending on the type of functional group introduced into the vinylidene chloride copolymer in advance.

(B-1) After copolymerizing with vinylidene chloride a monomer having a vinyl group copolymerizable with vinylidene chloride and active hydrogen in the molecule, a group capable of reacting with active hydrogen and a tertiary amine are added in the molecule. A method of denaturing with a compound that has

Examples of monomers having a vinyl group copolymerizable with vinylidene chloride and active hydrogen in the molecule include l) R' C112=CCOO(CH2) 20H1i) (wherein R' represents H or CH3 ) and vinyl alcohol.

In addition, examples of compounds having a group capable of reacting with active hydrogen and a tertiary amine in the molecule include i) (wherein R represents an alkyl group having 1 to 4 carbon atoms), etc. can be mentioned.

A monomer having a vinyl group copolymerizable with vinylidene chloride and a group capable of reacting with active hydrogen in the molecule is copolymerized with vinylidene chloride, and then modified with a compound having active hydrogen and a tertiary amine in the molecule. Method.

The monomer having a vinyl group copolymerizable with vinylidene chloride and a group capable of reacting with active hydrogen in the molecule includes:
For example, CB! =CC00CH2CH-CH2R' 0 (wherein R' represents H or CH), and the like.

Further, as a compound having the above-mentioned active hydrogen and a tertiary amine in the molecule, for example, HO(CHz)J(R)z ii) IO(CIl□)iN(R)z i) Cn (CH2) zN (R) 2 ii) CE (CH2) 3N (R) z (However, in the formula, R represents an alkyl group having 1 to 4 carbon atoms 6) In addition, the above-mentioned vinylidene chloride copolymer includes vinylidene chloride A monomer X having a vinyl group copolymerizable with the monomer X may be copolymerized, and such monomers X include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, and maleic anhydride.

Acrylic acid, acrylic ester, methacrylic acid.

Examples include methacrylic acid ester 2-acrylonitrile, vinyl propionate, and the like. By selecting one or more of these monomers and copolymerizing them, you can control to some extent the solubility in solvents, the flexibility of the coating film, the dispersibility of the ferromagnetic powder, the crosslinkability with hardening agents such as isocyanates, etc. can do.

Here, the degree of polymerization (i+
j + k) is 1oo≦(i + j + k) ≦too
.

It is preferable that it is within the range of . If this value is less than 100, the durability of the resulting coating film will deteriorate;
When it exceeds 0, the solubility in solvents deteriorates, making it difficult to form into a paint.

Further, the proportion of the vinylidene chloride component contained in the vinylidene chloride copolymer is preferably 30 to 80 mol%. This vinylidene chloride component is 30 mol%
If it is less than 80 mol %, durability will deteriorate, and if it exceeds 80 mol %, thermal deterioration will be significant, which is not preferable.

A 100% polymer having a vinyl group copolymerizable with vinylidene chloride and a tertiary amine in the above vinylidene chloride copolymer.
The proportion of Y is preferably within the range of 0.1 to 20 mol%. If this proportion is less than 0.1 mol%, the dispersion effect for the ferromagnetic powder will be insufficient, and if it exceeds 20 mol%, the solubility in solvents will deteriorate and the moisture resistance of the resulting coating film will deteriorate.

Furthermore, the vinylidene chloride copolymer is copolymerized with a monomer X having a vinyl group copolymerizable with the vinylidene chloride at a rate of about 20 to 70 mol% in order to improve the physical properties of the coating film. .

The tertiary amine-containing vinylidene chloride copolymer may be used in combination with other binders.

As such a binder, those conventionally used as a binder for magnetic recording media can be used, including vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer,
Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-
Maleic acid co-M polymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer Coalescence, methacrylic acid 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 derivatives,
Examples include styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin, 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 any case, the polar group equivalent (molecular weight per polar group) of the quaternary ammonium salt, which is a polar group in these binders, is preferably within the range of 1,000 to 100,000.

If this polar group equivalent exceeds 100,000, no effect can be expected, and if it is less than 1,000, the effect will not change much, but problems will arise in terms of moisture resistance.

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

The above-mentioned ferromagnetic iron oxide particles are particles whose value of
0), magnetite (F e 304. X = 1
．． 33) and their solid solutions (FeOx, 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.
There are different types.

The above-mentioned ferromagnetic chromium dioxide may include CrO□ 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, Fe-Ni, Fe-Go-Ni, Co-N
i, Fe-Co-B, Fe-Co-Cr-B, Mn-
Bt, Mn-AA, Fe-Co-V, etc. can be used.
In addition, ACSi,
Ti, Cr, Mn, Cu.

- Metal components such as Zn may 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,
Rust inhibitors and the like may also be added.

The above dispersants (pigment wetting agents) include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Fatty acids having 12 to 18 carbon atoms (R+C00H, R is an alkyl or alkenyl group having 11 to 17 carbon atoms) such as lyrinnic acid and stearolic acid, alkali metals (Li, Na, etc.) of the above fatty acids, or Alkaline earth metal (M
(g, Ca, Ba, etc.), compounds containing fluorine of the above fatty acid esters, amides of the above fatty acids,
Polyalkylene oxide alkyl phosphate ester, trialkyl polyolefin oxy quaternary ammonium salt (
The alkyl has 1 to 5 carbon atoms, and the olefin is ethylene, propylene, etc.). In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.

The above lubricants include dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms) ,
Alkoxy has 1 to 4 carbon atoms), silicone oil such as phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl group has 1 to 5 carbon atoms), conductive fine powder such as graphite, molybdenum disulfide, tungsten disulfide, etc. inorganic fine powder, polyethylene, polypropylene, polyethylene, vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, α-olefin polymer,
Unsaturated aliphatic hydrocarbons (compounds in which an n-olefin double bond is bonded to the terminal carbon, approximately 20 carbon atoms), which are liquid at room temperature, monobasic fatty acids with 12 to 20 carbon atoms, and monobasic fatty acids with 3 to 20 carbon atoms.
Fatty acid esters consisting of 12 monohydric alcohols,
Fluorocarbons etc. can be used. These lubricants are added in an amount of 0.62 to 20 parts by weight per 100 parts by weight of the binder.

The abrasives are commonly used materials such as fused alumina, silicon carbide, and chromium oxide (Cr).

03), corundum, artificial corundum, diamond,
Synthetic diamonds, garnet, emery (main ingredients: corundum and magnetite), etc. are used.

These abrasives have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

” - As the antistatic agent, carbon blank is used.

Conductive fine powder such as carbon blank graft polymer,
Natural surfactants such as saponin, alkylene oxide type. Nonionic surfactants such as glycerin and glycidol, and higher alkyl amines.

Quaternary ammonium salts, pyridine and other heterocycles,
Cationic surfactants such as phosphoniums, carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups, amino acids,
Aminosulfonic acids.

Amphoteric surfactants such as sulfuric acid or phosphoric acid esters of amino alcohols, etc. can be used. The conductive fine powder is added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder, and the surfactant is added in an amount of 0.1 to 10 parts by weight. These surfactants may be added alone or in combination.

Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

As the above-mentioned rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular, synchlohexylamine nitride,
Volatile rust inhibitors (amine , amide or imidono-inorganic acid salts or organic acid salts), the rust prevention effect is improved. These rust inhibitors are used in amounts of 0.01 to 20 parts by weight per 100 parts by weight of ferromagnetic powder.
Used in parts by weight range.

In addition, the constituent materials of the magnetic layer are dissolved in an organic solvent to prepare a magnetic paint, which is coated on a non-magnetic support.The solvent for the magnetic paint is acetone, methyl ethyl ketone, or methyl isobutyl ketone.

Ketones such as cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, acetic acid glycol monoethyl ether, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, benzene, toluene, xylene, etc. Aromatic hydrocarbons, aliphatic hydrocarbons such as hexane and heptane, ethylene chloride, carbon tetrachloride, and chloroform.

Examples include chlorinated hydrocarbons such as ethylene chlorohydrin and dichlorobenzene.

Furthermore, examples of the non-magnetic support to which the magnetic material is coated include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, and polyvinyl chloride. , vinyl resins such as polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamideimide, etc. are used. The nonmagnetic support may be in any form such as a film, tape, disk, card, or drum. Alternatively, the nonmagnetic support may be a so-called hard disk by using light alloys such as aluminum alloys and titanium alloys, thermoplastic resins such as polystyrene and ABS resins, ceramics such as alumina glass, single crystal silicon, and the like. in this case,
It is preferable that the surface of the support is made hard by providing an N1-P plating layer in advance or by alumite treatment.

In addition, it is also possible to utilize the vinylidene chloride copolymer containing the above-mentioned tertiary amine as a binder for a back coat layer, an undercoat layer, and the like.

[Effect]

As mentioned above, by using a vinylidene chloride copolymer that has a tertiary amine, which is a polar group, in the molecule as a binder, the affinity for magnetic powder is greatly improved, resulting in ultrafine magnetic powder. Even magnetic powders with a large amount of magnetization can be dispersed well.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Resin synthesis example Butyl acrylate and 2-hydroxyethyl acrylate are selected as the monomer X, and this is copolymerized with vinylidene chloride and a monomer Y having a vinyl group and a tertiary amine that can be copolymerized with vinylidene chloride. Binders having a degree of polymerization of 400 were synthesized by changing the types and proportions as shown in Table 1.

(Left below) Table 1 In addition, in this Table 1, ■ Things? -a is C1h=CCOO(CH2) zN (
CH3) 2,■ Monomer b is CH,・CC0NH(CHz) ZN(
CH3) Is z a thing? -C is CH2=CC0N
II (CH2) KN (CH2CH3) 2, H
3 Monomer d is C1h=CCOO(CHz) J(CI
+) represents z, respectively.

Example 1 Co-adhered r-Fez03 100 parts by weight (specific surface area 35nf/g) Binder A 12 parts by weight Polyurethane resin (N-2304) 8 parts by weight Dimethyl silicone oil (lubricant) 1 part by weight lecithin (dispersant) 1 part by weight Cr40s (abrasive) 2 parts by weight Methyl ethyl ketone 100 parts by weight Methyl isobutyl ketone 50 parts by weight Toluene
50 parts by weight The above composition was mixed in a ball mill for 48 hours, filtered through a 3 μm filter, 2.5 parts by weight of a curing agent (Desmodur L, manufactured by Bayer AG) was added, and further mixed for 30 minutes. The film thickness after drying is 6 μm on a 14 μm thick polyethylene terephthalate film.
It was applied so that Next, after performing a magnetic field orientation treatment, it was dried and wound up. This was supercalendered and then cut to a width of 172 inches to produce a sample tape.

Example 2 A sample tape was prepared in the same manner as in Example 1 except that binder B was used instead of binder A.

Example 3 A sample tape was prepared in the same manner as in Example 1 except that binder C was used instead of binder A.

Example 4 A sample tape was prepared in the same manner as in Example 1 except that a binder was used instead of binder A.

Example 5 A sample tape was prepared in the same manner as in Example 1 except that binder E was used instead of binder A.

Comparative Example A sample tape was prepared in the same manner as in Example 1, except that binder F was used instead of the binder.

Surface gloss, powder removal, and still characteristics were measured for each sample tape obtained.

Note that the above surface gloss is based on the glossy needle (GLO3S METE).
R) was used to measure the reflectance at an incident angle of 75° and a reflection angle of 75°. In addition, powder removal is 60 minutes shuttle 10
After the 0th run, the amount of powder falling onto the head drum, guide, etc. was visually observed and evaluated using the point deduction method (-5 to O). Still characteristics were determined by recording a 4.2 MHz video signal on a sample tape and measuring the time until the playback output attenuated to 50%.

The results are shown in Table 2.

(Left below) Table 2 As is clear from the results in Table 2, by using a vinylidene chloride copolymer containing a tertiary amine as a binder, surface gloss and powder removal are improved, and It can be seen that the still durability is greatly improved. Therefore, the durability, magnetic properties, electromagnetic conversion properties, etc. of the magnetic recording medium are significantly improved.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the binder of the magnetic layer is a vinylidene chloride copolymer that has a tertiary amine as a polar group in the molecule, it has a high affinity for magnetic powder, and even if it is made into ultrafine particles or has a low magnetization amount. Even large magnetic powders have good dispersibility. Therefore, the durability and surface properties of the obtained magnetic recording medium are improved, and the electromagnetic conversion characteristics are also extremely excellent.

Furthermore, due to the flexibility of the vinylidene chloride copolymer, addition of a plasticizer makes it possible to form a highly flexible magnetic layer, and also has excellent adhesion to the support.
Durability can also be improved in these respects.

Claims (1)

[Scope of 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, wherein the magnetic layer is made of vinylidene chloride having a tertiary amine in its molecules. A magnetic recording medium characterized by containing a copolymer as a binder.