JPH0618078B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic sheet, and a magnetic disk, and more particularly to surface slipperiness of the medium.

(Prior Art) Generally, a magnetic recording medium is manufactured by applying a magnetic coating material containing at least magnetic powder, a binder and the like on a support and then drying it. In these magnetic tapes for video, computers, audio, etc., high tape performance is required. Stillness durability and stable running property are particularly required for video tapes having a high relative speed of tapes. Therefore, not to mention the abrasion resistance of the tape itself,
It is extremely important to reduce the friction of the tape during running.

Up to now, various lubricants (for example, silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, carbon atoms of 12 to 16) have been used for the purpose of reducing the friction of the magnetic layer. It is known to add a monobasic fatty acid and a fatty acid ester consisting of a monohydric alcohol having 21 to 23 carbon atoms in total with the number of carbon atoms of the fatty acid.
However, even if these lubricants are added, sufficient characteristics have not yet been obtained, and an undesirable phenomenon such as blooming cannot be prevented.

On the other hand, as seen in JP-B-51-39081, in the magnetic layer,
A technique for incorporating a fatty acid ester having an RCO group having 10 to 16 carbon atoms and a fatty acid having a melting point of 44 to 70 ° C has been proposed. It is said that the above phenomenon can be prevented by using these fatty acid esters in combination with fatty acids, but the results are not always satisfactory.

Furthermore, with the development of magnetic recording equipment and the expansion of the range of applications, magnetic recording media (hereinafter collectively referred to as magnetic tapes) have high recording density, high-performance electromagnetic conversion characteristics, and good tape physical properties such as surface slipperiness. Is being requested.

The above-mentioned electromagnetic conversion characteristics or physical properties of the tape are alleviated by reducing the magnetic resistance contained in the magnetic layer or other magnetic tape constituent layers by reducing the frictional resistance of the tape surface at the contact surface or antistatic. Particle size and specific surface area (BET value: unit m ²
/ G) and is required to have a large BET value particularly in terms of electromagnetic conversion characteristics and recording density. But B
A large ET value tends to impair the surface slip property of the tape properties.

(Object of the Invention) It is an object of the present invention to provide a magnetic tape having good surface slipperiness regardless of the composition of constituent layers including the magnetic layer of the magnetic tape.

(Structure and Operation and Effect of the Invention) The above-mentioned object of the present invention is a magnetic recording medium comprising a support and a constituent layer provided for magnetic recording, wherein the constituent layer contains a fatty acid and a fatty acid ester. The extraction amount of the fatty acid and the fatty acid ester from the constituent layer with a nonpolar hydrocarbon solvent is 15 to 75 mg / cm ³ in total per volume of the constituent layer provided on the same side of the support. This is achieved by a magnetic recording medium.

The extraction ratio of the fatty acid and the fatty acid ester (fatty acid / fatty acid ester) is preferably 1/10 to 2/1.

In the present invention, the constituent layer means a magnetic layer, an overcoat layer, a backcoat layer, an adhesive layer, etc., which are directly involved in magnetic recording or directly or indirectly involved in electromagnetic conversion characteristics and tape properties. It is a layer provided on the support in order to smoothly perform recording, recording retention or reproduction by electromagnetic conversion with good performance.

The nonpolar hydrocarbon solvent according to the present invention is, for example, cyclohexane or n-hexane.

In the extraction operation, a certain amount of the constituent layers was peeled off, and the mixture was immersed in boiling water, for example, cyclohexane for 4 hours for immersion. After the residue was removed, cyclohexane was distilled off and the residue was analyzed by gas chromatography to determine the extraction amount. .

Next, the present invention will be described in detail.

As described above, the BET value of various solid powders such as magnetic powder contained in the constituent layers of the magnetic tape is required to be large, and in the case of carbon black or the like, the BET value is required.
The value 200 meters ² / g approximately is common, 30 m ² even at the magnetic powder
/ G or more and about 100 m ² / g are aimed at.

Even in a fine powder having a BET value less than this level, most of the fatty acids added are sorbed on the surface or the inner surface thereof, and the amount extracted with cyclohexane or the like may be only 5 wt% of the added amount. Even in the case of fatty acid ester, the added amount is 50
It may stop at wt%.

The specific surface area indicated by BET value varies greatly depending on the material, but of course the same material can be used for the manufacturing method and the elapsed time after the manufacture, or the size of the secondary particle structure such as continuous beads or tufts (structure level). Fluctuates depending on.

Also, the adsorption or sorption efficiency differs depending on the material or pH, and the adsorption area naturally changes depending on the amount of fine powder contained in the constituent layers.

The added fatty acid and fatty acid ester are immobilized by the above-mentioned factors and deviate from the lubricating action, and at the same time, the diffusivity of fatty acid and the like varies depending on the binder structure and the curing agent used and the degree of curing, which contributes to the lubricating action. The amount of free lubricant is different.

As described above, the effective amount of the surface lubricity of the fatty acid-based lubricant added varies a lot depending on the composition of the constituent layers, and it is difficult to determine the effective amount as an ambiguous paste.

Therefore, it is not possible to establish a technical system relating to surface slipperiness at least by determining the addition amount of the lubricant based on one component of the constituent layer. That is, for example, the amount of the lubricant added determined based on the weight of the magnetic powder has no technical meaning as far as the surface slipperiness is concerned.

The so-called surface slipperiness is distinguished from the effect of the matting agent which improves the slippage by reducing the contact area of the surface.

Based on the above-mentioned circumstances, the present invention determines the effective amount of lubricant that is actually involved in the surface slipperiness and has a meaning as a technical system by the free amount of the lubricant in the constituent layers.

In addition, according to the results of the analysis, the effective lubricant amount deviates from the range specified by the present invention even in the case where the conventional magnetic powder having a BET value not sufficiently large and the sample using the filler are sampled. is doing.

In the present invention, the free fatty acids and fatty acid esters contained in the constituent layers are 15 to 75 mg / cm ³ per unit volume of the constituent layers provided on the same side of the support, but when the amount is less than this range, The surface slipperiness is insufficient, and if it exceeds this range, other problems such as blooming occur, which is not preferable.

The abundance ratio of free fatty acids and fatty acid esters in the constituent layers on the same side of the support (fatty acid / fatty acid ester)
Is preferably 1/10 to 2/1 and is adjusted depending on the type of fatty acid and fatty acid ester and the addition amount.

Fatty acids as the lubricant used in the present invention include, for example, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and the like having 8 to 18 carbon atoms. Fatty acids (R represented by R-COOH is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms); the above-mentioned fatty acid alkali metal (Li, Na, K, etc.) or alkaline earth metal ( M
g, Ca, Ba, etc.) and the like.

As fatty acid esters, fatty acid esters composed of monobasic fatty acids having 12 to 16 carbon atoms and monohydric alcohol having 3 to 12 carbon atoms, monobasic fatty acids having 17 or more carbon atoms and total 21 carbon atoms are included. Examples thereof include fatty acid esters consisting of monohydric alcohols that give ~ 23.

Examples of magnetic materials include γ-Fe ₂ O ₃ and Co-containing γ-F.
e ₂ O ₃ , Co deposition γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , C
o Oxide magnetic substance such as Fe ₃ O ₄ , CrO ₂ or Fe, N
i, Co, Fe-Ni alloy, Fe-Co alloy, Fe-N
i-P alloy, Fe-Ni-Co alloy, Fe-Mn-Zn
Alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-Cr
Alloy, Fe-Co-Ni-P alloy, Co-Ni alloy, C
Examples include various ferromagnets such as metal magnetic powders containing Fe, Ni, and Co as main components such as o-P alloys and Co-Cr alloys.
Additives to these metallic magnetic materials include Si and C
Elements such as u, Zn, Al, P, Mn, and Cr or compounds thereof may be included. Further, hexagonal ferrite such as barium ferrite and iron nitride are also used.

Examples of the binder for forming the constituent layer according to the present invention include polyurethane having abrasion resistance. It has a strong adhesive force to other substances, is mechanically tough against repeated stress or bending, and has good wear resistance and weather resistance.

When a fibrin resin and a vinyl chloride copolymer are contained in addition to polyurethane, the dispersibility of the magnetic powder and the like in the magnetic layer is improved and the mechanical strength thereof is increased. However, the layer becomes too hard only with the fiber-based resin and the vinyl chloride-based copolymer, which can be prevented by the above-described inclusion of polyurethane.

As usable fibrin-based resins, cellulose ether, cellulose inorganic acid ester, cellulose organic acid ester and the like can be used. The vinyl chloride copolymer may be partially hydrolyzed. The vinyl chloride-based copolymer is preferably a copolymer containing vinyl chloride-vinyl acetate. Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate alcohol,
Examples thereof include vinyl chloride-vinyl acetate-maleic anhydride and vinyl chloride-vinyl acetate-vinyl alcohol-maleic anhydride.

Further, regarding the entire binder composition, the ratio of the above-mentioned polyurethane and the other resin (the total amount of the fiber-based resin and the vinyl chloride-based copolymer) is 90/10 to 20 / by weight.
It has been confirmed that 80 is preferable, and 85/15 to 30/70 is more preferable. If the amount of polyurethane is out of this range, poor dispersion tends to occur and the still properties are likely to deteriorate, and if the amount of other resins is large, the surface properties are likely to be poor and the still properties also deteriorate. The physical properties of the coating film become less favorable overall.

As the binder according to the present invention, a mixture of the above-mentioned binder and a thermoplastic resin, a thermosetting resin, a reactive resin, or an electron beam irradiation curable resin may be used. As the thermoplastic resin, the softening temperature is 150 ° C or lower, the average molecular weight is 10,
000 to 200,000, having a degree of polymerization of about 200 to 2,000, for example, acrylic ester-acrylonitrile copolymer,
Acrylic acid ester-vinylidene chloride copolymer, acrylic acid ester-styrene copolymer and the like are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and is condensed after coating and drying,
Those which are insolubilized by a reaction such as addition are used. Among these resins, those that do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin and the like.

As the electron beam irradiation curable resin, an unsaturated prepolymer,
For example, maleic anhydride type, urethane acryl type, polyester acryl type, polyether acryl type, polyurethane acryl type, polyamide acryl type, etc., or as a polyfunctional monomer, ether acryl type, urethane acryl type, phosphate ester acryl type, aryl type , Hydrocarbon type, and the like.

In order to improve the durability of the constituent layers of the magnetic tape according to the present invention, the constituent layers can contain various curing agents,
For example, an isocyanate can be contained.

Aromatic isocyanates which can be used are, for example, tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), guisylylene diisocyanate (XDI), metaxylylene diisocyanate (MXDI) and addition of these isocyanates with active hydrogen compounds. There is a body, etc., and the average molecular weight is 100 to 3,0
A range of 00 is preferred.

On the other hand, as aliphatic isocyanate, hexamethylene diisocyanate (HMDI), lysine isocyanate, trimethylhexamethylene diisocyanate (TM
DI) and adducts of these isocyanates with active hydrogen compounds. Among these aliphatic isocyanates and adducts of these isocyanates with active hydrogen compounds, those having a molecular weight of 100 to 3,000 are preferable. Among the aliphatic isocyanates, non-alicyclic isocyanates and adducts of these compounds and active hydrogen compounds are preferable.

The coating material forming the constituent layers of the magnetic tape of the present invention may optionally contain additives such as a dispersant, a matting agent, a lubricant other than the above-mentioned lubricant, an abrasive and an antistatic agent. .

As the dispersant, for example, lecithin, higher alcohol having 12 or more carbon atoms, and sulfuric acid ester can be used. Moreover, a commercially available general surfactant can also be used. These dispersants may be used alone or in combination of two or more. When using these dispersants in the magnetic layer is added in the range of 1 to 20 parts by weight to 100 parts by weight of the magnetic material, when used in the backcoat layer 2 to 20 parts by weight to 100 parts by weight of the binder Part may be added.

As the matting agent, organic powders or inorganic powders are used individually or as a mixture.

The organic powder used in the present invention is preferably acrylic styrene resin, benzoguanamine resin powder, melamine resin powder, phthalocyanine pigment, but polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin. Powders, polyfluorinated ethylene resin powders, etc. can also be used, and as inorganic powders, silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, α −Fe ₂ O
₃ , talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide.

As the lubricant other than the above-mentioned lubricant, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, etc. are used.

Further, an abrasive can also be used for the magnetic layer, and as the abrasive, generally used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main component is Corundum and magnetite), titanium dioxide, etc. are used. As these abrasives, those having an average particle diameter of 0.05 to 5 μ are used, and those having an average particle diameter of 0.1 to 2 μ are particularly preferable. These abrasives are 1 to 20 for 100 parts by weight of magnetic powder.
It is added in the range of parts by weight.

In addition to carbon black as an antistatic agent,
Conductive powder such as graphite, tin oxide-antimony oxide compound, titanium oxide-tin oxide-antimony oxide compound, carbon black graft polymer; natural surfactant such as saponin; alkylene oxide-based, glycerin-based, glycidol-based, etc. Nonionic surfactant; cationic surfactant such as pyridine and other heterocyclics, phosphonium or sulfonium compounds; anionic surfactant containing acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, phosphoric acid ester group; amino acid And amphoteric activators such as aminosulfonic acid, sulfuric acid or phosphoric acid ester of amino alcohol, and the like.

You may add these surfactants individually or in mixture. These are used as antistatic agents, but may be used for other purposes such as dispersion, improvement of magnetic properties, improvement of lubricity, and coating aid.

As the solvent to be blended in the above paint or a diluent solvent at the time of applying this paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, butanol; methyl acetate, ethyl acetate , Esters such as butyl acetate, ethyl lactate, ethylene glycol monoacetate; ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, xylene; methylene chloride, ethylene chloride, Halogenated hydrocarbons such as carbon tetrachloride, chloroform and dichlorobenzene can be used.

Further, as the support, polyethylene terephthalate,
Polyesters such as polyethylene-2,6-naphthalate; polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; plastics such as polyamide and polycarbonate; metals such as Cu, Al and Zn;
Ceramics such as glass, BN, Si carbide, porcelain and pottery can also be used.

The thickness of these supports is about 3 to 100 μm, preferably 5 to 50 μm in the case of film or sheet, 30 μm to 10 mm in the case of disc or card, and cylindrical in the case of drum. It is used and its type is determined according to the recorder used.

As a coating method for forming the constituent layer by coating the constituent layer coating material on a support, air doctor coat, blade coat, aa knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, Gravure coat, kiss coat, cast coat, spray coat, etc. can be used, and other methods are also possible.

The constituent layers are applied by such a method. The magnetic layer is subjected to a treatment for orienting the magnetic powder in the layer if necessary, and then the constituent layers of the formed magnetic tape are dried. If necessary, the surface is smoothed or cut into a desired shape to manufacture the magnetic tape according to the present invention.

(Example) Next, the present invention will be described with reference to an example.

Example 1 Magnetic paint formulation Magnetic powder 100 parts Carbon black 5 〃 Polyester urethane 15 〃 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 15 〃 Cyclohexanone 130 〃 Toluene 130 〃 Fatty acid (palmitic acid) Table-1 Contents fatty acid ester ( Butyl stearate) Amount shown in Table-1 The characteristics of the magnetic powder and carbon black in which sorption is a problem are as follows.

Magnetic powder A BET value 50 m ² / g, pH10 γ-Fe ₂ O ₃ , magnetic powder B BET value 50 m ² / g, pH 7 γ-Fe ₂ O ₃ , carbon C BET value 100 m ² / g, pH 7, black 〃 D 〃 200 〃 〃
8. The above formulation was kneaded and dispersed in a ball mill, coated and dried, and subjected to supercalender treatment to obtain Samples 1 to 4 of the present invention and Comparative Samples (1) and (2).

The magnetic layers of these samples were removed, and the samples were refluxed and extracted in cyclohexane for 4 hours.

Table 1 shows the amounts of fatty acids and fatty acid esters added and the amounts of fatty acids and fatty acid esters extracted per cm ^{3 of the} magnetic layer.

Next, the characteristic measurement results of these samples are listed in Table 2.

Measurement of characteristics: Measurement of dynamic friction coefficient: After leaving the magnetic tape in an atmosphere of 25 ° C and 55% relative humidity (atmosphere in rainy weather) for 24 hours (humidity adjustment), measure the friction coefficient of each magnetic tape. The dynamic friction coefficient was measured using a rotating drum type surface measuring instrument manufactured by Shinto Chemical Co., Ltd., with a rod having a diameter of 4 mm, a load of 30 g, and a rotation speed of 159 rpm.

The surface of the blooming tape was visually evaluated with a 100 × microscope.

The tape was reproduced with Stick Slip NV-6200 (Matsushita Electric) and the drum portion was visually judged.

Still durability NV-6200 (Matsushita Electric Industrial Co., Ltd.) is used for still playback of tape and its RF
The time was set so that the output drop would be 2 dB.

Table 1 clearly shows that the amount of free lubricant extracted is different even if the binder is the same and the lubricant is the same, and it can be seen that the dynamic friction coefficient and other characteristics differ depending on the amount.

Example 2. A sample was prepared in the same manner as in the sample 1 of the present invention of Example 1 except that the amounts of fatty acid and fatty acid ester added were changed as shown in Table 3, and the characteristics were measured.

The above results are shown in Table-3.

From Table 3, it can be seen that according to the present invention (the extraction amount of fatty acid and fatty acid ester is 15 to 75 (mg / cm ³ ), its purpose and effect (sliding property of tape and still durability) can be excellently achieved. .

(Effects of the Invention) According to the present invention, the effective lubricant amount for surface slipperiness is determined irrespective of the composition of magnetic tape constituent layers and the number of constituent layers, and there is no variation among product lots, and in terms of production technology and quality assurance. It has brought great convenience.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a support and a constituent layer provided for magnetic recording, wherein the constituent layer contains a fatty acid and a fatty acid ester, and the fatty acid and the fatty acid ester are included in the constituent layer. The total amount of the non-polar hydrocarbon solvent extracted is 15 per volume of the constituent layers provided on the same side of the support.
A magnetic recording medium characterized by having a content of up to 75 mg / cm ³ .