JPS6271025A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve wear resistance and durability by incorporating pulverous powder of a specific high-temp. calcined black oxide and org. powder as non- magnetic powder. CONSTITUTION:The non-magnetic powder of a magnetic recording medium having the magnetic layer on one side face of a substrate and having a back coat layer contg. the binder and non-magnetic powder contains the pulverous powder of the high-temp. calcined black oxide into which at least >=2 kinds among Fe, Mn, Cu and Cr are incorporated and the org. powder. The average grain size of the black oxide fillers and org. or inorg. fillers is preferably 0.01-0.8mum and the weight ratio of the fillers in the back coat layer by the total solid content is preferably 0.2-0.9. A polyurethane resin and cellusoic resin and particularly a combination with nitrocellulose are preferable as the resin to be used for the back coat layer in the binder. The mixing weight ratio of both is made 9/1-2/8 with the polyurethane as a numerator. The durability and wear resistance are thereby improved and chroma S/N is improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to magnetic recording media, particularly magnetic tape.

(Background of the Invention) Magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks are widely used in the audio, video, and converter fields. Among these, for example, regarding magnetic tape in the video field, when recording or playing back images, the magnetic tape stored in a cassette is loaded into a video deck, and the tape is inserted into a guide pole or a guide pole. It travels on a circuit while its front and back sides are rubbed by a magnetic head, and is scanned by a magnetic head. The surface of the magnetic layer is finished to be smooth so that the sliding condition of the magnetic tape against the magnetic head does not change when the magnetic tape runs on a circuit.

However, other sides of the magnetic layer of the magnetic tape have a similar effect on the above fluctuations, and when the running properties and durability of the magnetic tape are not good, excessive tension may be applied to the running magnetic tape. Not only will the magnetic layer be damaged and powder fall off, but the winding shape will be disturbed and the edges of the tape will become irregular, resulting in poor image or electromagnetic conversion characteristics such as skew, jitter, and chroma 8/N.

Therefore, a back coat layer is provided on the back side of the magnetic tape support to improve running properties and durability against guide poles, guide rolls, guide pins, etc. This layer contains inorganic powder as a filler. This is a method in which the surface of the back coat layer is roughened to reduce the contact area with guide balls, etc., and to reduce the frictional resistance.
No. 1135, No. 57-53825, No. 58-2415
No. 50-3927 all show examples using inorganic powders, and many of these also show those with limited particle sizes. However, even those using these inorganic powders not only do not provide sufficient lubricity, but also cause the back coat layer to come into contact with guide bottles, etc., such as the alumina particles described in Japanese Patent Publication No. 50-3927. When the guide bin, etc. is made of an organic resin material, it may be scraped, damaging the function of the guide bin to smoothly guide the magnetic tape. One of these causes is that the inorganic resin material This is because the powder generally has a wide variety of particle shapes and is not constant, and also has a wide distribution of particle sizes, which causes the surface of the back coat layer to become rougher than necessary.

In addition, in general, inorganic powders do not mix well with binder resins, and there are many problems with dispersibility, which causes particles to separate from the resin and cause particles to fall off. This may cause dropouts in the playback of the layer's images.

In place of the above-mentioned inorganic fillers, attempts have been made to use organic fillers that can control particle size and particle hardness/softness. For example, JP-A-59-112428 proposes using Teflon powder, and it is also known to use benzoguanamine resin.

However, Teflon powder has a long history of being poorly compatible with the binder used in recording media and is not sufficiently dispersed, and benzoguanamine resin powder tends to agglomerate, making it unsatisfactory as a filler for high-density magnetic recording media.

Conventional organic fillers, which replace the inorganic fillers mentioned above, may be practical for low-density recording media such as magnetic cards, but they have poor charging properties, attract dust, cause dropouts, and cause large friction between the eyebrows, causing looseness in the winding width. In high-density media such as video tapes, it tends to cause poor dispersion, agglomeration, and powder drop, and has not yet reached a state of practical use.

Particularly in recent years, the miniaturization and high density of video equipment has made the path of the magnetic tape more complex, and the tape has more opportunities to come into contact with guide balls, guide rolls, and even magnetic heads, resulting in more frequent scratches. There is a need for improved running performance and improved wear resistance and durability to prevent powder falling off.

(Objectives of the Invention) The objects of the present invention are (1) good film properties, (2) no interlayer adhesion, (3) good filler uniform dispersibility, (
4) The durability of repeated running is excellent and ':)S (5) It has a bank coat layer with good paint stability, which causes problems with film properties, unstable running at high temperatures and high humidity, and damage to tapes or video deck guides. The object of the present invention is to provide a magnetic recording medium (hereinafter referred to as a magnetic tape) free from electromagnetic conversion failures.

(Structure of the Invention) The object of the present invention is to provide a magnetic recording medium having a magnetic layer on one side of a support and a back coat layer containing a binder and non-magnetic powder on the other side, as the non-magnetic powder. F
This can be achieved by a magnetic recording medium characterized by containing a fine powder of a high-temperature fired black oxide containing at least 2$1 of e, Mn, Cu, and Cr and an organic powder.

Next, the present invention will be specifically explained.

The high temperature fired black oxide containing at least two of Fe, Mn, Cu and Cr according to the present invention is heated at a temperature of 600 to 1000°C.
It is fired at a high temperature and pulverized, and has excellent heat resistance, as well as acid resistance, alkali resistance, solvent resistance, and weather resistance.

Furthermore, since the dispersibility is good and the binding with the binder is strong, the surface roughness can be easily controlled, there is no powder falling, and it contributes to toughening of the physical properties of the film. In addition, it can be used in place of or in combination with carbon black, which is generally difficult to disperse due to its black color, to ensure light-shielding properties at a specified transmittance of 0.03% or 0.05% or less.

Specific examples of the black oxide include Daibiroki Color (manufactured by Oguchi Seika).

As the organic powder used in the present invention, acrylic styrene resin, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment are preferable, but polyolefin resin powder, polyester resin powder, polyamide resin powder, and polyimide resin are preferred. Powder, polyfluoroethylene resin powder, etc. can also be used.

The average particle size of the black oxide filler and the organic or inorganic filler is preferably 0.01 to 0.8 μm, more preferably 0.05 to 0.5 μm.

The weight ratio of the filler to the total solid content in the back coat layer is preferably 0.2 to 0.9, more preferably 0.3 to 0.
7 is preferable.

In addition, inorganic powders that can be used in combination include silicon oxide, titanium oxide, aluminum oxide, magnesium carbonate, calcium carbonate, barium carbonate, barium sulfate, calcium sulfate, zinc sulfate, zinc oxide, tin oxide, aluminum oxide, chromium oxide, and silicon carbide. , calcium carbide, a-Fe20
1, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

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

Examples of the inder used in the back coat layer of the present invention include abrasion-resistant polyurethane.

It has strong adhesion to other substances, is mechanically strong and durable, can withstand repeated stress or bending, and has good abrasion resistance and weather resistance.

Furthermore, if a cellulose resin and a vinyl chloride copolymer are also contained in addition to polyurethane, the dispersibility of the magnetic powder in the magnetic layer will be improved and its mechanical strength will be increased. However, if only the cellulose resin and vinyl chloride copolymer are used, the layer becomes too hard, but this can be prevented by containing the above-mentioned polyurethane.

Usable fiber and cord resins include cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. The vinyl chloride copolymer described above may be partially hydrolyzed. 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 advantages are complementary to and harmonious with the above-mentioned polyurethane, and can significantly improve the stability over time of the physical properties of the tape.

Furthermore, in addition to the binders described above, mixtures of thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used.

Among the binders, a combination of polyurethane resin and cellulose resin, particularly nitrocellulose, is preferred as the resin used for the bank coat layer. The mixing weight ratio of both is 9/1 to 2A, preferably V2 to 3/7, with polyurethane as the molecule.

In the present invention, the binder may contain polyisocyanate as a curing agent.

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

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HMDI) 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 3,000 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 paint used to form the back coat layer may contain additives such as a dispersant, a lubricant, and an antistatic agent, if necessary.

Dispersants used in the back coat layer according to the present invention include lecithin, phosphoric acid esters, amine compounds, alkyl sulfates, fatty acid amides, high R alcohols, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid esters, and known surfactants. etc. and these salts,
It is also possible to use salts of polymeric dispersants having negative organic groups (eg -00OH, -PO, H). These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder.

In addition, lubricants include fatty acids such as silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, palmitic acid, oleic acid, stearic acid, behenic acid, myristic acid, and butyl stearate. , 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 based on 100 parts by weight of the binder.

Antistatic agents that may be used include carbon black, conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds; natural surfactants such as saponin;
Nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines,
Cationic surfactants such as quaternary ammonium salts, pyridine, other heterocycles, phosphonium or sulfonium; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups. Examples include amphoteric activators such as amino acids, aminosulfonic acids, and sulfuric or phosphoric acid esters of aminoalcohols.

The back coat paint configured as above has a dry thickness of 0.
．． The coating is applied to a thickness of 3 to 2.0 μm, preferably 0.5 to 1.5 μm.

The magnetic layer according to the present invention may be a coated magnetic layer using magnetic powder, a binder, a dispersion, a lubricant, etc., or a thin M layer formed by a vapor deposition method, a sputtering method, a paper deposition method, etc. It may also be a type magnetic layer.

Examples of magnetic materials include r-Fe203, Co-containing r
-Fe, 0. , Co-coated γ-Fe203, Fe3O4
, Co-containing Fe3O4, CO-coated Fe3O4, CrO2
oxide magnetic materials such as Fe, N 11Co,
Fe-Ni alloy, Fe-Co alloy, Fe-Ni-
P alloy, Fe-Ni-Co alloy, Fe-Mn-Zn alloy, F'e-Ni-Zn alloy, Fe-Co-N i -C
r alloy, Fe-Co-Ni P alloy, Co-Ni alloy,
Co-P alloy, Co-Cr alloy, etc. Fe, Ni, c
.

Examples include various ferromagnetic materials such as metal magnetic powder whose main component is . S is an additive added to these metal magnetic materials.
It may contain elements such as i, Cu, Zn, Ag, P, Mn, and Cr, or compounds thereof. Hexagonal ferrite such as barium ferrite and iron nitride are also used.

Furthermore, as for the binder, curing agent, dispersant, lubricant, antistatic agent, and matting agent used in the magnetic layer, those explained for the back coat layer can be used.

Furthermore, fillers such as an abrasive and a capping agent other than those mentioned above may be added if necessary.

Abrasives that may be used include 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 size of 0.05~
A thick field of 5 μm is used, and particularly preferably O,
1 to 2 μm''C. These abrasives have a binding agent of 100
It is added in an amount of 1 to 20 parts by weight.

As the matting agent, organic powder or inorganic powder may be used individually or in combination.

As the organic powder, the resin powders listed above for the bank coat layer can be used, and as the inorganic powder, silicon oxide, titanium oxide, aluminum oxide, barium carbonate, calcium carbonate, barium sulfate, zinc oxide, tin oxide, Examples include aluminum oxide, chromium oxide, silicon carbide, calcium carbide, a-Fe203, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

Solvents to be blended in the bank 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, gropanol, and butanol; Esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, ethylene glycol-lucenoacetate; glycol dimethyl ether, glycol monoethyl ether, dioxane,
Ethers such as tetrahydro-7rane; aromatic hydrocarbons such as benzene, toluene, xylene; and halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, dichlorobenzene, etc. can be used.

In addition, as a support, polyethylene terephthalate,
Examples include polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate, but metals such as Cu, Al, and Zn,
Glass, BN.

Ceramics such as Si carbide, porcelain, and earthenware can also be used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card, the diameter is about 30 μm to 10 μm, and in the case of a drum, the diameter is cylindrical, and the shape is determined depending on the recorder used.

An intermediate layer for improving adhesion may be provided between the support and the back coat layer or magnetic layer.

The coating method for forming the above layer on the support is as follows:
Air doctor coat, blade coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, etc. can be used, but are not limited to these.

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

Example 1 A magnetic layer was coated on a polyphthalate support in advance as follows.

130g of iron-based metal magnetic powder, 4fi phenoxy resin
To a solution of r dissolved in 250 gr of cyclohexanone was added together with 6 gr of alumina, and the mixture was dispersed in a sand mill for 4 hours.

Subsequently, a solution prepared by dissolving 10 gr of polyurethane, 0.05 gr of butyl stearate, and 0.1 gr of myristic acid in a mixed solution of 10 gr of cyclohexanone and tetrahydro 7 run Loopr was mixed with the above dispersion liquid, and dispersed in a sand mill for 1 hour. I did it. Coronate L 39r was added as a curing agent to this dispersion and mixed with stirring to obtain a magnetic paint. This paint was applied onto a polyethylene terephthalate base film under an orienting magnetic field, dried, and then calendered.

Next, the composition of the backcoat paint formulation shown in Table 1 was kneaded in a ball mill for 5 hours to give a backcoat paint. The paint was applied with a reverse roll to the back surface of the support coated with the magnetic layer, dried to form a back coat layer with a dry film thickness of 1.0 μm, and slit into 1/2 width to form Examples and Comparisons. Example magnetic tape The tape condition, physical properties, and electromagnetic conversion characteristics of the sample obtained as described above were checked for the first time (0-pass, virgin tape) and after 200 repeated runs (200-pass). The result◎
BC using dipyroxide color has superior durability and wear resistance compared to BC made only of carbon or titanium oxide (I wonder if BC can be scraped off?).

◎Dipyroxide color has very good dispersion, so it is uniformly dispersed and has good chroma S/N.

◎Measurement method for Examples and Comparative Examples in which the light transmittance is dipyroxide color (a) Pack the tape into a VHS cassette and store it at 20°C for 6
091; In RH, NY-6,200 (Matsu, made by Shimodenki)
Using a deck, I ran it repeatedly for 200 passes. At the same time, the RF output drop was also measured.

(b) Tape damage was visually evaluated after running 200 passes.

(c) BC dynamic friction coefficient at 23°C and 60% RH,
Using a runability tester (TBT-300D) manufactured by Yokohama System Co., Ltd., the input rotor was set to 20I, and the diameter was 3.8.
Wrap 1800 samples of sample tape around the stainless steel bottle shown in ■.
It was run at a speed of 3.3 cm/sec, the outlet tension was measured, and it was calculated from the following equation.

(d) BC surface roughness Ra (μm)...The sample surface was measured using a three-dimensional roughness measuring instrument 5W-3PK (Koita Institute) with a cutoff of 0.25 and a needle force of 30 mg. 5ttm
It was determined by measuring the length.

(e) Measurement of chroma...HR-7100
(manufactured by Victor Japan) with a maximum recording current of 4.5 M.
It was determined by recording the Hz- and measuring the noise voltage during reproduction.

(Adhesion test: Wrap a 1/2 inch wide tape with a pressure of 1'kg, leave it at 60℃ and 80%RH for a long time, leave it at room temperature for another 24 hours, unwind it, Those with resistance when pulled apart were evaluated as M, and those with no resistance were evaluated as Yes.

f) The light transmittance was determined by measuring the rotational cylinder rotation ('ra) and outlet tension (T2) of a VH8 system and a videotape recorder HR-6500 (Japan Victor ■).

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer on one side of a support and a back coat layer containing a binder and non-magnetic powder on the other side, the non-magnetic powder includes at least one of Fe, Mn, Cu and Cr. A magnetic recording medium characterized by containing a fine powder of high-temperature fired black oxide and an organic powder containing two or more of the above.