JPS62234233A - Magnetic recording medium having aramide resin substrate - Google Patents

Abstract

PURPOSE:To obtain a long-sized magnetic tape of a narrow width having high tape toughness and good electromagnetic conversion characteristic by providing a magnetic layer contg. ferromagnetic metallic powder and binder on a nonmagnetic substrate consisting of an aramide resin and having a prescribed thickness. CONSTITUTION:An 80mm LP type tape is obtd. by providing the magnetic layer contg. the ferromagnetic metallic powder and binder on the nonmagnetic substrate consisting of the aramide resin and having 3-7mum thickness. An orientation method by biaxial stretching is usable to obtain the film-like base having the Young's modulus satisfying the range of >=1,000kg/mm<2> in the longitudinal direction and >=500kg/mm<2> in the transverse direction. A paraphenylene terephthalamide essentially consisting of a para bond among arom. polyamides is suitable as the aramide resin and the resin having a chlorine substituent in a phenyl group is adequate as the excellent base material for the long-sized recording medium of the narrow width.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media, and more particularly to magnetic tape for video.

(Background of the Invention) As magnetic recording becomes more dense, noiseless, and lasts longer, and magnetic recorders 4 become more sophisticated, smaller, and thinner, magnetic recording media (hereinafter referred to as magnetic tapes) are required to Performance is also becoming wider and higher.

Particularly in the field of video, the current VTIS and β systems are transitioning to 8mm video and electronic cameras.
In the future, the trend is toward smaller size, higher density, and crystal precision. For example, when it comes to magnetic tape, not only its electromagnetic conversion characteristics and tape film physical properties, but also the uniformity of the magnetic tape layer surface. There is a need for a magnetic tape that has good film quality and is free from tape deformation and quirks. However, on the other hand, as video tapes become narrower and longer, the tape becomes thinner and its toughness is lost, making edge damage more likely to occur during high-speed feeding, high-speed winding, loading, and unloading in video decks. It has become.

That is, conventional magnetic tape generally has a total thickness of 12μ or more.
The magnetic tape had enough stiffness to withstand the physical stress of bending, crimping, and rubbing when it is stretched over the head while running, but due to the above requirements, a length of 8 mm (narrow width) was required. In order to store it in a limited space as shaku tape (LP quib tape), it is necessary to reduce the total thickness to less than 12JL R. Simply making the film thinner will result in a lack of tape toughness and a drop in output due to poor head contact. , causing deterioration of Sc.

The toughness of a magnetic tape depends mostly on its support, and the toughness is expressed in Young's modulus, so we focused on this point and created biaxially stretched polyethylene terephthalate whose longitudinal Young's modulus was set to 700 and 97 x m''. (1'ET) has been proposed (Japanese Unexamined Patent Publication No. 53-93804), and in reality, a support having a Young's modulus of 800 to 1000 kg/rxx" is used.

However, for an 8 mm video LP tape with a total thickness of 7 to 12 μl including the magnetic layer, back coat layer, protective layer, etc., the allowable thickness of the support is 3 to 7 μl! At this thickness, the Young's modulus is 800 to io00 kg#v''L.

With a magnetic tape using a round support, head contact becomes extremely poor, and deterioration of the rectangularity of the RF envelope shape and deterioration of the RF specific output luminance and chroma S/H are unavoidable.

It should be noted that commonly used resins such as polyethylene terephthalate can be made into a film with a Young's modulus in the above range by modifying or copolymerizing them by introducing appropriate atoms, groups or heptad units, or by stretching and orienting them. Although it is possible to obtain a support, this is not preferable because it increases technical complexity and cost.

(Objective of the Invention) An object of the present invention is to provide a narrow-width long magnetic tape having sufficient tape toughness and good electromagnetic conversion characteristics, specifically, an LP type tape for 8 mm video.

(Structure of the Invention) The object of the present invention is to provide a magnetic recording medium in which a magnetic layer containing ferromagnetic metal powder and a binder is provided on a non-magnetic support, the non-magnetic support being made of an aramid resin and having a thickness of 3
This is achieved by a magnetic recording medium characterized by ~7 μl.

Next, the present invention will be explained in detail.

Since the support used in the present invention is an 8 mm LP type tape that is sufficiently durable for long-term recording, its thickness is selected to be in the range of 3 to 7 μm.

Anything below 3μ is practically unnecessary, and 7μ! If it is more than that, the recording time will be insufficient.

On the other hand, when the thickness of the support is set within the range, the head per head when a magnetic tape using the above-mentioned support is stretched over a head is determined when the Young's modulus of the support is 1000k in the longitudinal direction.
g/shoulder 12 or more preferably l300 to 9/xx" or more"2,
In addition, in the width direction, it is 5GGkg/II” or more, preferably 70
It has become clear that head contact of the magnetic tape is guaranteed when the Young's modulus is 0&g/II" or more, and the present invention selects aramid resin (aromatic polyamide) as the support base material resin that satisfies the above Young's modulus range. It is something.

Orientation by biaxial stretching is usually used as a method for obtaining a film-like support with a high Young's modulus, but the Young's modulus in both directions obtained by biaxial stretching has hyperbolic reciprocity.
When stretching is carried out across the entire surface, there is a relationship in which if one is made large, the other cannot be made very large. 2. It is preferable to apply stretching that brings the Young's modulus within the above-mentioned range.

The extent of the stretching described above is 0.8 to 7.0 times as an area magnification, regardless of whether the film forming method is a wet-dry method or a dry method. It is also preferable to relax. The areal magnification is the product of the stretching ratio in the length direction of the film and the stretching ratio in the width direction. The area magnification is from 0.8, ■, ↓+, l--+,
, 1. I gave it to you, and I asked you to give it to me.
If f-11j is larger than 7.0, the risk of breakage increases.

The aramid (aromatic polyamide) of the present invention is composed of, for example, para-phenylene terephthalamide, para-phenylene isophthalamide, meta-phenylene terephthalamide, meta-phenylene terephthalamide, etc., and further contains halogen (chlorine, bromine, fluorine, etc.) in the phenyl nucleus. Such)
Also included are those having substituents such as a nitro group, an alkyl group, and an alkoxy group. Among these aromatic polyamides, paraphenylene terephthalamide, which is mainly composed of para bonds, is more preferable, and those having a chlorine substituent on the phenyl nucleus have high mechanical strength, 9 elastic modulus, low moisture absorption, and furthermore have good heat resistance. It has excellent mechanical and thermal dimensional stability, making it suitable as an f:1 material for narrow and long recording media.

1) When synthesizing a polymer from acid chloride and diamine, the heavy substances constituting the aromatic polyamide having the structure described above are terephthalic acid chloride, 2-chloroterephthalic acid chloride, and 2,6-dichloride. l-Isophthalic acid chloride, 2-Promterephthalic acid chloride, 2-
Examples include methyl 5-chloroterephthalic acid chloride, para-phenylene diamine, 2-chloro para-phenylene diamine, and meta-phenylene diamine.

On the other hand, in the aromatic diamine, two amino groups are preferably bonded via at least one carbon, and the divalent linking group connecting the monomers is preferably at least one aromatic diamine. The number of carbon atoms is preferably 25 or less, such as para-xylylene diamine, meta-phenylene diamine, benzidine, 4.4
°-Diaminodiphenyl ether, 4.4'-diaminodiphenylmethane.

4.4°-diaminodiphenyl sulfone, 3.3°-dimethyl-4,4'diaminodiphenylmethane, 1°5-
Diaminonaphthalene, 3,3°-dimethoxybenzidine, 1,4-bis(3methyl-5-aminophenyl)benzene, and the like. It goes without saying that these acid components and amine components may be used alone or in combination.

114 The aromatic polyamide according to the present invention can be synthesized by solution polymerization in an organic polar amide solvent such as N-medylpyridone, dimethylacetamide, or dimethylformamide, or by interfacial polymerization using an aqueous medium. Ru.

When acid chloride and diamine are used as propellants, hydrogen chloride is produced as a by-product of the polymer solution, so an inorganic neutralizing agent such as calcium hydroxide or an organic neutralizing agent such as ethylene oxide is added to neutralize this hydrogen chloride. This polymer solution may be used as it is as a film-forming stock solution for forming a film, or it may be used as a film-forming stock solution by once removing the polymer and redissolving it in the above-mentioned solvent. In some cases, an inorganic salt such as calcium chloride or magnesium chloride may be added to the membrane forming stock solution as a solubilizing agent. The polymer concentration in the membrane forming stock solution is preferably about 2 to 40% by weight.

On the other hand, a solution of polyamic acid can be prepared by reacting a tetracarboxylic dianhydride with an aromatic diamine in an organic polar amide solvent such as N-methylpyrrolidone, dimethylacetamide, or dimethylformamide.

The aromatic polyamide (aramid) resin obtained in the above manner is subjected to a stretching process to have a Young's modulus of 1 in the longitudinal direction.
It is possible to form a film with a width of 500 ky/12 shoulders in the width direction.

In addition, the magnetic tape as a whole can be improved by selecting the binder used for the magnetic layer, back coat layer, or protective layer.
Alternatively, the Young's modulus can be increased by supplementarily utilizing the film property strengthening effect of fillers, binder curing agents, etc. dispersed in a binder containing magnetic powder.

As the magnetic layer according to the present invention, a dispersed magnetic layer coated with a magnetic paint consisting of magnetic powder, powder, a dispersant, a lubricant, etc. is used.

Examples of magnetic materials include Fc, Ni, Go, Fe-
Ni alloy, T'c-Gn alloy, Fe-Ni-
P alloy, Fa-NiCo alloy, Fc-Mn-7,n alloy, Fc-Ni-7,n alloy, Fa-Go-Ni-C
r alloy, F C-Co-Ni-■) alloy, Go-Ni
alloy, Go-P alloy, GO-Cr alloy, etc. Fe, Ni, G
Examples include various ferromagnetic materials such as metal magnetic powder containing o as a main component. It is sufficient that elements such as these metal magnetic materials C" or compounds thereof are contained.

In the present invention, conventional techniques can be used to create the magnetic tape of the present invention.

As the binder used in the magnetic tape +1 growth layer such as the magnetic layer and back coat layer according to the present invention, abrasion-resistant polyurethane may be used. It has strong adhesion to other substances, is mechanically strong to withstand repeated stress or bending, and has good abrasion resistance and weather resistance.

In addition to polyurethane, cellulose resin and vinyl chloride! (If polymers are also included, the dispersibility of the filler in the constituent layers will improve and the mechanical strength will increase. However, if only a small polymer is included, the layer will be hard. However, this can be prevented by adding polyurethane (1) as described in -1-.

Cellulose ether, cellulose inorganic acid ester, cellulose rt-sulfur organic acid ester, etc. can be used as the r'rf-capable cellulose resin. The above vinyl chloride.

Preferable examples of the vinyl chloride copolymer include copolymers containing vinyl chloride and vinyl acetate.

Phenoxy resins can also be used.

Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

These binders have mutually complementary strengths and weaknesses, and together they can significantly improve the stability of the physical properties of the tape over time.

In addition to the above-mentioned binders, resins generally used in magnetic tapes, various modified resins with hydrophilic groups, thermoplastic resins with characteristic behavior, thermosetting resins, reactive resins, electron beam irradiation-cured resins, etc. Mixtures with mold resins may also be used.

Among the above binders, a combination of polyurethane resin and cellulose resin, particularly nitrocellulose, is preferred as the resin used for the back coat layer. The mixing weight ratio of both is 9/1 to 278, preferably 872 to 3/7, based on polyurethane as a molecule.

In C1 of the present invention, polyisocyanate can be added to the binder as a curing agent.

Aromatic polyisocyanates that can be used include, for example, tolylene diisocyanate (TDI) and adducts of these polyisocyanates and active hydrogen compounds, and those having an average molecular weight of 100 to 3,000 are suitable.

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (IIMDI) and adducts of these isocyanates and active hydrogen compounds. Among these aliphatic polyisocyanates and adducts of these polyisocyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to a.ooo are preferred. Among the aliphatic polyisocyanates, non-alicyclic polyisocyanates and adducts of these compounds and active hydrogen compounds are preferred.

The amount of the polyisocyanate added to the binder is 0.1 to 0.7 of the sum of both weights, particularly preferably 0.
．． It is 15-0.5.

The coating material used to form the above-mentioned constituent layers may contain additives such as a dispersant, a lubricant, and an antistatic agent, if necessary.

Dispersants used in the constituent layers of the present invention include lecithin, phosphoric acid esters, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid esters, known surfactants, etc. and these salts, and
Salts of polymeric dispersants with negative organic groups (eg -C0011, -PO311) can also be used. These dispersants can be used alone or in combination with two types,
May be used in combination with h. These dispersants binder 10
It is added in an amount of 1 to 20 parts by weight per 1 part of 0 weight 1i.

In addition, as lubricating agents, fatty acids such as silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, palmitate, oleic acid, stearic acid, behenic acid, myristic acid, and butyl stearate are used. , octyl palmitate, octyl myritate, and other fatty acid esters can also be used. These lubricants are added in an amount of 0.02 to 20 parts by weight per 100 parts of binder.

Antistatic agents include carbon black, graphite, conductive powders such as tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds, natural surfactants such as saponin, alkylene oxides, and glycerin. Cationic surfactants such as higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, phosphoniums or sulfoniums; Carboxylic acids, sulfonic acids, phosphoric acids, sulfuric acids Examples include anionic surfactants containing acidic groups such as ester groups and phosphoric acid ester groups; bifacial active agents such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric acid esters of amino alcohols.

In the present invention, carbon black may be added to the magnetic layer and the back coat layer to impart conductivity and light shielding properties.

By dividing and adding carbon black to the two layers, it is possible to avoid the difficulty in dispersing carbon black and provide sufficient light-shielding properties.

Furthermore, an abrasive can be added if necessary. The polishing agent is commonly used materials such as fused alumina,
Silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main ingredients: corundum and magnetite), etc. are used. These abrasives have an average particle diameter of 0.05 to 57zi+, preferably 0.1 to 2 μl. These abrasives are used in an amount of 1 part by weight per 100 parts by weight of the binder.
It is added in a range of 20 parts by weight.

Solvents to be blended in the back coat and magnetic paint or diluting solvents during application of this paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; methyl acetate,
Esters such as ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol senoacetate; Ethers such as nigericol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, Halogenated hydrocarbons such as ethylene chloride, carbon tetrachloride, chloroform, and dichlorobenzene can be used.

Further, the magnetic tape of the present invention may be provided with an auxiliary layer such as an intermediate layer for improving adhesion in addition to the back coat layer or the magnetic layer.

Application methods for forming the above layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, and casting. Coat, spray coat, etc. can be used, but are not limited to these.

(Example) The present invention will be specifically explained using examples.

Magnetic tapes having a common magnetic layer and back coat layer under the same conditions, but with different base materials and thicknesses are prepared and their characteristics are compared.

Magnetic paint formulation: (1 part weight) Fe-based ferromagnetic metal powder 80 polyurethane resin and Tuboran 2304. Made by Japan Polyurethane)
5 Phenoxy tree 1 ton!
1lr (PKH former Union Carbide) lecithin
4α-Aluminum oxide (abrasive) 4cyclohexanone
200 toluene
30 Methyl ethyl ketone 30 The composition according to the above formulation was thoroughly stirred and mixed in a ball mill,
Add 3 parts by weight of polyfunctional sardine (Coronate I, manufactured by Nippon Polyurethane) as a binder curing agent, and
After stirring, filter and dry thickness 3μχ1, -rr
Shi'I 1. -eh *l) l,
X −J＜−411ノ'／ '／ 三几 1
1! r, there was.

Back coat paint formulation: (parts by weight) Carbon black 50 Nitrocell [l-s (Seltsuba, manufactured by Fukkasei) 20 Polyurethane resin with Tuboran 2304, manufactured by Nippon Polyurethane) 20 Polyisocyanate (Cholenate L; manufactured by Nippon Polyurethane) 1G methyl edil Ketone 200 toluene
200" was dispersed in a ball mill for 5 hours, and applied to the back surface of the support having the magnetic layer to a dry thickness of 0.5 .mu.l and dried to form a back coat layer.

The above-mentioned wide magnetic tape film 11 was cut into 8xx pieces to prepare example samples and comparative samples, which were placed in 8-layer G video tape cassettes and their characteristics were measured.

Support: In the practical samples in the examples, aramid resin was used as the base material, and in the comparative samples, polyethylene terephthalate was used as the base material, and all of the supports were stretched to form films.

Each implementation sample 1 to 3 and the corresponding comparative sample (1) to
The support conditions and property evaluation results of (3) are listed in Table-1.

Evaluation items: (a) RP envelope shape expressed as the ratio (%) of the minimum amplitude to the maximum amplitude in one trace of the two video heads.

(b) RF specific output (c) Lumi S/N, (d) Chroma S
/N(i+) and subsequent measurements were carried out in accordance with the conventional measurement method, and the reference values were obtained by applying a magnetic layer and a back coat to a stretched polyethylene terephthalate (+3ET) support with a thickness of 10 μl separately from the above-mentioned sample under the same conditions as above. As the thickness of the basic support provided with the layer decreases, inferior properties are observed, but at the same time the effects of the present invention become more pronounced.

(Effects of the Invention) It has been shown that the characteristics of narrow and long (thin) magnetic tapes can be improved by selecting a magnetic tape with strong toughness, particularly for the support.

Applicant: Konishi Rokusha l'S Industry Co., Ltd.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer containing ferromagnetic metal powder and a binder on a non-magnetic support, characterized in that the non-magnetic support is made of aramid resin and has a thickness of 3 to 7 μm. .