JPH02254625A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic tape which does not generate sliding noises by specifying the surface roughness of the dry surface of the upper unoverlapped layer of the lowermost magnetic layer nearest a base and the dry thickness of the uppermost magnetic layer overlapped thereon, respectively. CONSTITUTION:The average surface roughness of the dry surface of the upper unoverlapped layer Ra of the lowermost magnetic layer nearest the base is specified to 0.005 to 0.015mum and the max. surface roughness Rmax to 0.08 to 0.200mum and the dry thickness of the uppermost magnetic layer overlapped thereon is specified to 0.1 to 1.0mum. The surface roughness of the lowermost magnetic layer in the constituting layers of the laminated can be confined within the specified range by selecting the particle shape of not only magnetic materials but inorg. powder and carbon black, etc., as well, and controlling the amount of a binder, a coating thickness and speed, and calender conditions. The tape which has less noise components and the good electrical characteristics is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and particularly to the surface properties of the medium having laminated magnetic layers.

[Prior art]

Magnetic recording media in information processing equipment are extremely useful as recording and reproducing elements, and there is a large demand for them, but at the same time, as recording media, they must have advanced and precise electromagnetic conversion characteristics, rich storage capacity, and high density. It is required that the composition be suitable for ensuring runnability, durability, and durability, that it be inexpensive, and that there be no troubles in production technology from a production standpoint. technological efforts have been undermined.

Generally, in order to obtain good electromagnetic conversion characteristics, it is necessary to fill the magnetic layer with high density of magnetic powder, preferably to have a thin layer, and furthermore, it is necessary to smooth the surface of the constituent layers on the magnetic layer side. The particle size of magnetic powder and fillers is selected and calendering is performed.

However, if the surface is too smooth, it will increase the coefficient of friction and cause poor running performance, while if the surface is too rough, spacing loss, powder falling off, and head wear will be severe.

Therefore, the smoothness or roughness of the surface of the magnetic layer is an issue that should be carefully considered, but the surface of the non-magnetic support used in conventional magnetic recording media (hereinafter collectively referred to as magnetic tape) is
In general, the surface of magnetic tape has surface roughness that causes unevenness to the extent that it causes problems in terms of electromagnetic properties. Therefore, even if a certain amount of subbing layer is provided, the surface roughness cannot be absorbed, and this is a highly reliable cause of various noises.

Taking videotape as an example, its electromagnetic conversion characteristics, especially chroma S/N and lumi S/N, are greatly affected by surface properties, but if a support with a surface that is too smooth is used, it may cause poor running,
This causes sliding noise and problems such as cinching.

In addition, in a laminated magnetic layer configuration that is convenient for recording high and internal frequencies, increasing the thickness of the upper surface layer as a means of mitigating the influence of the support surface roughness will impair the low frequency characteristics assigned to the lower magnetic layer. Furthermore, if the smoothing means in the lower layer is relied on, excessive smoothing often results in an increase in sliding noise.

Furthermore, when looking at the electromagnetic conversion characteristics in terms of noise based on the magnetic tape configuration conditions, there are dropouts due to magnetic layer defects or dust, discharge noise or sliding noise due to discharge near the head, and other noise whose causes are still unknown. Sliding noise, which is often a problem, is surface noise related to the surface condition of the magnetic tape, and is thought to be modulation noise caused by fluctuations in signal amplitude due to space variations between the head and the magnetic tape surface.

In other words, unevenness on the magnetic tape surface caused by the surface roughness of the support, agglomeration of magnetic particles, in-plane density distribution, uneven coating, etc., together with the surface friction coefficient, affect recording and reproducing efficiency due to uneven contact with the head. Non-uniform fluctuations in the tape's movement, vibrations in the tape's expansion and contraction in the following direction due to poor running, and fluttering can result in sliding noise.

In the case of a laminated structure, the surface properties of a magnetic tape with respect to surface noise are affected by the overlapping layers, from the support, to the lower layer, and then to the upper layer. Even if an attempt is made to adjust the roughness by focusing only on it, it is not possible to provide good surface properties.

[Purpose of the invention]

An object of the present invention is to provide a magnetic tape having a laminated magnetic layer structure provided on a normal non-magnetic support, which has good low frequency recording and reproduction performance and is free from sliding noise. .

[Structure and effects of the invention]

The object of the present invention is to provide a magnetic recording medium having at least two magnetic layers in the laminated constituent layers provided on a non-magnetic support, the surface of the dry surface of the upper layer of the lowermost magnetic layer closest to the support. The average roughness Ra is 0.005 to 0.015 μm,
Maximum surface roughness RIlax of 0.080 to 0.200 μm
and the dry thickness of the uppermost magnetic layer to be stacked is 0.1 to 1.
．． This is achieved by a magnetic recording medium characterized by Oum.

In the embodiment of the present invention, the surface roughness of the non-magnetic support used is an average roughness RaO of 020 μm or less, and a maximum roughness R
maxo is preferably 500 μm or less. In addition, in order to maintain running properties on the back surface when no back coat layer is provided, RaO,
015μ- or more, RraaxO13uvs or more is preferable.

In the present invention, the surface roughness of the lowermost magnetic layer in the laminated constituent layers is determined by selecting the particle shape of inorganic powder including magnetic material, carbon black, etc., controlling the amount of binder, coating thickness and coating speed, and calendering conditions. Accordingly, it can be kept within the specified range of the present invention. If necessary, a surface property adjusting layer may be provided between the bottom layer and the support or on the bottom magnetic layer.

The surface roughness Ra and Rmax were measured using a stylus method.

In the present invention, equipment and material techniques conventionally used for manufacturing magnetic tapes are used.

Examples of the magnetic material used in the present invention include γ-Fe
, O,, Co-containing γ-Fe, 03. Co deposited - Fe2
J, Fe, O,.

Goo Fe50. , Co-coated Fe5Oa, Cry,
oxide magnetic materials such as Fe, Ni, Fe-Ni alloy, Fe-Co alloy, Fe-N1~P alloy, Fe-Ni-
Co alloy, Fe-Un-Zn alloy, Fe-Ni-Zn alloy, Fe-C.

-Ni-Cr alloy, Fe-Co-N1~P alloy, Co-
Examples include various ferromagnetic materials such as P alloy, Go-Cr alloy, and metal magnetic powder containing Fe, Ni, and Co as main components. Additives to these metal magnetic materials include Si, Cu, and Z.
n, Al1. Elements such as P, Mn, and Cr or compounds thereof may be included. Hexagonal ferrite such as barium ferrite, iron nitride, etc. are also used.

As the binder used in the present invention, conventionally used binders can be used, but from the viewpoint of dispersion of magnetic particles and other fillers, it is modified by introducing a functional group or a functional group that forms an inner salt. Resins, particularly modified vinyl chloride resins, modified polyurethane resins, or modified polyester resins are preferred.

Examples of functional groups in the resins include -3o
, M, -〇SO,M, -COOM, and OM' P-0 0M" (wherein, M is a hydrogen atom, lithium, or sodium, and Ml and M2 are a hydrogen atom, a lithium , potassium, sodium, and an alkyl group.Moreover, Ml and M2 may be different from each other or may be the same.).

These functional groups can be combined with resins such as vinyl chloride resins, polyester resins, and polyurethane resins, such as CQ-002082503M, CQ-co, c
u, os 曵'', Cl2-CH, C00M,
0MICff-CH, -P=0 0M" (M, M', and M2 have the same meanings as above.) It can be obtained by condensation.

Among the resins obtained in this manner, preferred are vinyl chloride resins and resins obtained by introducing negative functional groups into polyurethane resins.

Furthermore, as vinyl chloride resin, for example, vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-vinyl maleate-vinyl alcohol copolymer, vinyl chloride-hinyl propionate-vinyl maleate-vinyl alcohol copolymer Examples include polymers.

In the present invention, in addition to the above-mentioned binder, conventionally used unmodified vinyl chloride resin, polyurethane resin, or polyester resin may be used in combination, if necessary.
Furthermore, cellulose resins, phenoxy resins, thermoplastic resins with specific usage methods, thermosetting resins, reactive resins, electron beam curable resins, etc. may be used in combination.

The resins described above can be used as a constituent binder of the constituent layers of the present invention, such as a magnetic layer, a back coat layer, a protective layer, or an adhesive layer, by selecting the optimum type and amount, with their advantages and disadvantages being complementary.

In order to improve the durability of the magnetic layer of the magnetic tape of the present invention, the magnetic paint can contain various curing agents, such as incyanate.

Examples of the aromatic incyanate include tolylene diisocyanate (TD+) and adducts of these incyanates with active hydrogen compounds, and those having an average molecular weight of 100 to 3000Q are suitable.

Examples of aliphatic isocyanates include hexamethylene diisocyanate (HMDI) and adducts of these incyanates and active hydrogen compounds. Among these aliphatic isocyanates and adducts of these incyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to 3,000 are preferred. Among the aliphatic isocyanates, non-alicyclic incyanates and adducts of these compounds with active hydrogen compounds are preferred.

A dispersant is used in the magnetic paint used to form the magnetic layer, and additives such as a lubricant, an abrasive, a matting agent, an antistatic agent, etc. may be included as necessary. In addition to the phosphoric acid ester according to the present invention, dispersants used in the present invention include amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxides,
Examples include sulfosuccinic acid, sulfosuccinic acid esters, known surfactants, and salts thereof, and salts of polymer dispersants having negative organic groups (for example, -〇〇〇〇) can also be used. These dispersants may be used alone or in combination of two or more. In addition, as lubricants, silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, carbon atoms 12 to 1
Fatty acid esters (so-called waxes) consisting of 6 monobasic fatty acids and monohydric alcohols having 21 to 23 carbon atoms in total can also be used. These lubricants are added in an amount of 0.2 to 20 wt per 100 parts by weight (expressed as wt) of the binder.

As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used. These abrasives have an average particle size of 0.05 to 5 μm,
Particularly preferably, it is 0.1 to 2 μm. These abrasives are added in an amount of 1 to 2 Qwt based on the binder loOwt.

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

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, and inorganic powders include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate,
barium sulfate, zinc oxide, tin oxide, aluminum oxide,
Chromium oxide, silicon carbide, calcium carbide, a-Fe20
s, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

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, glycerin. Nonionic surfactants such as glycidol-based and glycidol-based surfactants: higher alkylamines, quaternary ammonium salts, pyridine, other heterocycles, phosphonium salts, etc.
; is a cationic surfactant such as sulfonium; anionic surfactant containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, and phosphoric acid ester group; sulfuric acid or phosphoric acid of amino acids, aminosulfonic acids, and amino alcohols Examples include amphoteric activators such as esters.

Solvents to be added to the above 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, butanol, etc. Esters such as methyl, ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol senoacetate; Ethers such as glycol dimethyl ether and glycol monoethyl etherrane; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, ethylene Halogenated hydrocarbons such as chloride, carbon tetrachloride, chloroform, and dichlorobenzene 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, plastics such as polyamide and polycarbonate, metals such as Cu, kQ, and Zn, and glass. , boron nitride BN, and ceramics such as Si carbide can also be used.

The thickness of these supports is approximately 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 shape, the thickness is about 30 μm-10mm, and in the case of a drum shape, it is used in a cylindrical shape, and the shape is determined depending on the recorder used.

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

Possible coating methods for forming the laminated magnetic layer on the support include simultaneous extrusion coating and sequential extrusion coating in the case of wet on wet, reverse roll+extrusion, gravure roll+extrusion, and the like.

Furthermore, it is also possible to combine any one of air knife coat, blade coat, air knife coat, squeeze coat impregnated coat, transfer roll coat, kiss coat, cast coat, and spray coat.

Furthermore, in the case of wet on dry, the above coating methods may be combined in any manner.

〔Example〕

The present invention will be specifically explained using examples.

Examples 1 to 4 and Comparative Examples (1) to (6).

Magnetic tape samples were prepared according to the following magnetic coating formulations A (for the lower layer) and B (for the upper layer) and their characteristics were measured.

Magnetic paint formulation A (for lower layer) (豐t) Co-
γ-Fe, 0. 100 Sulfo-modified vinyl chloride/vinyl acetate/vinyl alcohol copolymer 13 Polyurethane resin 4a-A12tOs
2 carbon black
13 myristic acid
l Stearic acid l Butyl stearate 2 cyclohexanone 200 Methyl ethyl ketone
200 toluene
160 magnetic paint formulation B (for upper layer) (wt
) CO-1~Fe, 0. 100
Sulfo-modified vinyl chloride/vinyl acetate/vinyl alcohol copolymer 15 Polyurethane resin 5a /'-
QzOs 3 Carbon Black 10 Myristic Acid
2 stearic acid
2 cyclohexanone 100
Methyl ethyl ketone 100 toluene
160 14 paints from the above
．． On a 5 μm polyethylene terephthalate support, paint A was coated to a dry thickness of 2.5 μm, paint B was coated at the coating speed listed in Table 2 as shown in Table 1, and videotape samples of Examples and Comparative Examples were obtained.

The performance of the obtained sample was evaluated and the results are shown in Table 1. Table 2: Characteristic measurement method 2. RF specific output
The F specific output was measured (unit: dB).

HiFi Audio Output The old Fi audio output at 1.7MHz was measured in the same way as the RF ratio output (unit: dB).

Chroma output Chroma output at 500 KMHz was measured in the same manner as the RF specific output (unit: dB).

Chroma S/N color video noise meter r 5hibasoku9
25 D/I''.

Sliding noise (i) Perform playback without running the tape, and measure system noise with a spectrum analyzer. (■) Replay the sample tape 10 times for 1 minute each, and measure the sliding noise with a spectrum analyzer. (ui)8MHz
Nearby nozzle level is based on system noise (OdB)
Read the noise value of the lO path as .

Scinching A 200 pass tape was run under conditions of 80° C. and 40% RH to examine the occurrence of scinching.

O... Not generated can be provided. Furthermore, it is highly durable and has extremely low occurrence of cinching.

On the other hand, in the comparative examples (1) and (2), which are single layers,
It is superior only in either low frequency or high frequency; it is not possible to achieve both, and it is also inferior to multilayer tape in terms of noise components. In Comparative Example (3), although the roughness of the lower layer is within the specified range, the upper layer is too thick, resulting in particularly poor low frequency output, and the thick upper layer causes cinching.

Comparative Example - (4) and (5) are too rough or too smooth, and (4) causes worsening of sliding noise in chroma S/N1 (5). In Comparative Example-(6), the upper layer film thickness was too thin, resulting in a decrease in RF output, an increase in noise components, and further the occurrence of shinching.

Claims (1)

[Claims] In a magnetic recording medium having at least two magnetic layers in the laminated constituent layers provided on a non-magnetic support, the surface average roughness Ra of the dry surface of the upper unlayered layer of the lowest magnetic layer closest to the support
0.005 to 0.015μm, maximum surface roughness Rmax
0.080 to 0.200 μm, and the dry thickness of the uppermost magnetic layer to be stacked is 0.1 to 1.0 μm.