JPS60111319A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent squeals at high humidity and also to reduce remarkably dropout by limiting an area of a projected part of an undercoating layer to a prescribed range to ensure a prescribed value or over of the thickness of the flat part and form a lubricant on a ferromagnetic metal thin film layer. CONSTITUTION:The ferromagnetic metal thin film layer 4 is formed on a plastic film 1 which has projections a, a' comprising a core 2 of solid particles and a resin binder 3 covering the surrounding of the core and the under coating layer having an average area ratio to the flat part of 1:3-1:1,000, the average height of the said projected part of 30-500Angstrom , and the average thickness of the said flat part of >=50Angstrom and the lubricant 5 is placed. Thus, production of abnormal projections caused by generation of surface scratch flaws due to segregation and partial location of solid particles at forming of the undercoating layer is prevented. Moreover, the crystallization of the olygomer crystal to the surface from a base film due to radiating heat is suppressed also so as to reduce remarkably dropout and generation of squeals at high humidity is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and in particular to magnetic recording media most suitable for rotary head type video tape recorders.

The structure of conventional examples and their problems Iron, cobalt, nickel, alloys containing these as main components, or thin films of their oxides are made into polyester films using vacuum film forming methods such as vacuum evaporation, sputtering, and ion blating. Ferromagnetic thin-film magnetic recording media formed on substrates made of polymer films such as polyimide films, non-magnetic metal thin plates, etc. can dramatically improve recording density compared to conventional coating-type magnetic recording media. However, in order to achieve this high density, it is necessary to reduce the gap of the magnetic head and to smooth the surface of the magnetic recording medium to reduce the spacing loss as much as possible. However, if the kneading surface is made too flat, it will cause problems in -, tsudotanote, and orthogonality, so it is necessary to solve this problem by controlling the fine shape of the kneading surface. The surface properties of the ferromagnetic thin film magnetic recording medium are such that the magnetic layer thickness is 0.01~
Since it is very thin at about 0.6 μm, it is highly dependent on the surface shape of the plastic film that is the substrate. Therefore, many proposals have been made regarding the surface properties of films. Examples are JP-A-62-18770, JP-A-62-284264, and JP-A-54-40.
883, JP 63-116115, JP 63-12S6S5 2% JP 54-94574
Publication No. 10455/1983, Japanese Patent Application Laid-Open No. 1987-10455
16937, etc. In all of these examples, the surface shape is roughened relatively finely and uniformly, for example, wrinkle-like protrusions are formed,
"Formation of worm-like or granular protrusions":
The aim is to improve head touch and running performance all at once. The surface condition seen in the above example is head ta-sote at room temperature and humidity.

It is very effective in terms of head running performance.

However, it has the disadvantage that a part of the cylinder of the rotary head tends to generate squealing in high humidity conditions such as 30° C. and 80 to 90% R and H. As a means to solve this problem, an undercoat with steep protrusions made of various resin fine particles, various metal oxide or hydroxide fine particles, carbon black, etc. as a core and resin as a binder is applied to the glass film support. The present inventors have already proposed that the layer is formed by forming a ferromagnetic metal thin film thereon, and that a lubricant is present on the surface of the strip. Although this proposal has sufficiently improved the squeal in high humidity, it has the drawbacks of relatively high dropouts and large variations in their values. The causes of dropouts are: 1. Abnormal protrusions caused by the surface of the plastic film, 2. Abnormal protrusions caused by the undercoat layer, and 3. Abnormal protrusions in the ferromagnetic metal thin film (contamination of foreign matter, molten metal caused by gas generation during ingot melting). 4) Foreign matter adhering to the surface mixed in the lubricant or from outside is considered, and as a result of the present inventors' investigation using a method to separate these separately, the cause of dropout fluctuation is mainly due to the above-mentioned foreign matter. As a result of various studies on countermeasures, we have arrived at the present invention.

Purpose of the Invention The present invention, in addition to the above-mentioned previously proposed improvement in squealing in high humidity environments,
The present invention provides a metal thin film type magnetic recording medium that greatly reduces dropout.

Structure of the Invention The present invention consists of a protruding part made of a core of a solid fine particle and a resin binder surrounding the core, and a flat part made of a resin binder, and the average area of the protruding part and the flat part is A plastic film having an undercoat layer having a ratio of 1=3 to 1:1000, an average height of the protruding portions of 3o to SOO8, and an average thickness of the flat portions of 5oA or more. A magnetic recording medium in which a ferromagnetic metal thin film layer is formed and a lubricant is present on the layer,
The area of the protrusions in the undercoat layer is limited to a certain range,
By ensuring the thickness of the flat part is above a certain value, abnormal protrusions that occur due to uneven distribution and aggregation of solid particles during undercoat layer formation can be suppressed, and surface scratches can be prevented during the process of forming the undercoat layer and layer 0 magnetic layer. As a result, dropout factors mainly caused by the undercoat layer are removed, such as preventing the formation of abnormal protrusions caused by the ferromagnetic layer, and suppressing precipitation on the surface of the oliboar crystals from the substrate film due to radiant heat during ferromagnetic layer formation. Dropouts are greatly reduced, the average height of the protrusions is set to 30 to 600, and the interaction of a lubricant formed on the ferromagnetic metal thin film layer prevents the occurrence of squealing in high humidity environments. It is intended to prevent

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the magnetic recording medium of the present invention. In the figure, 1 is a glass film, 2 is a solid fine particle, 3 is a resin binder for fixing the solid fine particles 2 onto a plastic film 1, 4 is a ferromagnetic metal thin film, and 5 is present on a ferromagnetic metal thin film 5. It is a lubricant. Note that the layer containing the solid fine particles 2 and the resin binder 3 is an undercoat layer. In the undercoat layer, a, a in the figure
The part indicated by ' is the protrusion, h is the protrusion height, and b.

The part indicated by b' is a flat part, and d represents its thickness. In addition to scattering the lubricant 6 on the surface of the undercoat layer as shown in FIG. 1, the lubricant 6 can also partially or entirely cover the surface of the undercoat layer in the form of a layer.

The area ratio between the protruding parts and the flat parts of the undercoat layer is determined by a scanning electron micrograph of the undercoat layer surface (magnification: 3.000 to 30
．． It is determined by the area ratio of the protruding part and the flat part in ○○O), and the average value over a field of view of at least 1° is taken as the average area ratio. This average area ratio is 1:3 to 1
:1000 is appropriate, more preferably 1:3-1
:500 is appropriate. If this area ratio is 1 to 3 or more, dropout will increase rapidly, and if it is less than 1:1000, the squeal prevention effect in high humidity will decrease.

The height of the protruding portion of the undercoat layer was measured using a highly accurate surface roughness measuring device (TALYSTEP-1, TAYLOR-4i).
(manufactured by OBSON), and indicates the distance from the top of the unevenness to the bottom of the valley, and the average value of the heights of at least 10 protrusions is taken as the average height. In addition, the thickness of 9 flat parts is calculated by removing a part of the undercoat layer by a means such as partial dissolution of the undercoat layer with a solvent, and then adjusting the level difference between the flat part of the undercoat layer and the plastic film surface at the boundary to the above surface roughness. It is determined by actual measurement with a measuring device, and the average value of at least 10 or more steps is taken as the average thickness.

The average height of the protruding portions of the undercoat layer is suitably 30 to 300 cm, and more preferably 60 to 300 cm. If it is less than 30 Å, it is difficult to obtain the effect of preventing squealing in high humidity, and if it is used by more than 500 people, the envelope is likely to be disturbed. Further, the average thickness of the flat portion of the undercoat layer is suitably at least 50 Å or more, more preferably 100 Å or more; if it is less than 50 Å, dropout increases and the variation in thickness increases.

Examples of plastic films include polyester film substrates made of polyethylene terephthalate, copolymers and mixtures thereof, polyethylene naphthalate, copolymers and mixtures thereof, polyester imide,
Polyimide film substrates such as polyimide, aromatic polyamide film substrates, etc., which have particularly excellent surface smoothness, and polyester film substrates, for example, contain almost no microprotrusions made of polymerization catalyst residues, etc. A surface with good smoothness, with no microscopic protrusions or less than a few hundred angstroms in size, and a surface with uniform microscopic protrusions, such as the aforementioned wrinkle-like or earthworm-like two-grain shape, with a low surface roughness. Something up to a few hundred or less is appropriate.

The solid particles that form the core of the protruding portions of the undercoat layer are thermoplastic resin particles, crosslinked resin particles, various metal oxide particles, carbon particles, and hydrolysis products of metal alkoxides with an average particle size of 30 to 500. Fine particles consisting of the following can be used. As the thermoplastic resin fine particles, for example, fine particles of polyester, polyamide, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, polyphenylene oxide, phenoxy resin, polyacrylate, polyvinyl chloride, etc. can be used. As the crosslinked resin fine particles, for example, those obtained by emulsion polymerization using polyfunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, and tetranotyolmethanetetraacrylate as main raw materials can be used. As the metal oxide fine particles, for example, sori sol, alumina solurica, fine powder titanium oxide, etc. can be used. As the fine particles made of a metal alkoxide hydrolysis product, for example, fine particles obtained by hydrolysis of aluminum S-butoxide, tetra-1-propoxytitanium, zirconium tetra-t-butoxide, etc. can be used.

As resin binders for undercoating, various resins such as various copolymerized polyesters, various polyamides, polystyrene, polycarbonate, polyarylate, polyacrylate, polyhynyl butyral, polyphenylene oxide, polysulfone, and phenoxy resin are used! ! ．． ? t can be used as a mixture; 1 is epoxy resin, urethane resin,
Crosslinkable resins such as silicone resins, phenolic resins, melamine resins, or modified resins thereof can also be used.

As a method for forming an undercoat layer consisting of solid fine particles and a binder on a plastic film, for example, fine particles having an average particle size of 30 to 500 are coated with 10 to 10. ○
There is a method in which 20 to 20,000 ppm of a resin serving as a resin binder is dissolved in a colloidal solution dispersed at ○○ ppm, and then applied onto a plastic film and dried.

To form a ferromagnetic metal thin film layer on the plastic film on which the undercoat layer has been formed, for example, a ferromagnetic thin film of iron, cobalt, nickel, or an alloy thereof (e.g., cobalt nickel, cobalt chromium, etc.) is vacuum-deposited. , ion brating.

Directly on the undercoat layer by sputtering etc., or
Aluminum, titanium, and
It is formed through a thin base film of chromium or the like. Moreover, it can also be inserted as a separator between these nonmagnetic thin films. In these cases, it is desirable to further improve the adhesion strength with the substrate film by incorporating oxygen into the ferromagnetic thin film and the underlying thin film (partially oxidizing the gold or metal) to improve the still life. In this case, the appropriate oxygen content is 3% or more, more preferably 5% or more in terms of atomic ratio to the metal.

Note that the still life is also related to the thickness of the ferromagnetic metal thin film.
If the thickness is less than 400 Å, the life of the still will decrease rapidly, so it is desirable that the thickness is 400 Å or more.

The lubricant to be present on the surface may be present on the entire surface, or may be present locally on the surface. In addition to coating or vapor-depositing it directly on the surface of the ferromagnetic metal thin film, methods for doing so include coating or vapor-depositing it on the back side of the magnetic recording medium and transferring it to the surface of the ferromagnetic metal thin film when stacking (winding) the magnetic recording medium. method is also possible. It is also possible to use a resin binder or the like to firmly fix the lubricant.

The presence of a lubricant on the ferromagnetic metal thin film significantly exhibits the effect of preventing squealing in high humidity.

As the lubricant, fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins, silicones, fluorine surfactants, inorganic lubricants, etc. can be used. The amount of lubricant present is 0.5-500 per 1 m2 of surface.
mQ is more preferably 5 to 200 mO.

Fatty acids include lauric acid and myristic acid.

palmitic acid, stearic acid, behenic acid, oleic acid,
Those having 12 or more carbon atoms such as linoleic acid and linoleic acid can be used.

Ethyl stearate is a fatty acid ester.

Butyl stearate, amyl stearate, stearic acid monoglyceride, palmitic acid monoglyceride, oleic acid monoglyceride, pentaerythritol tetrastearate, etc. As fatty acid amides that can be used, caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide , stearamide, behenic acid amide.

Oleic acid amide, linoleic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, etc. can be used.

Metallic minerals include zinc and lead such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linuric acid.

Salts with nickel, cobalt, iron, aluminum, magnesium, strontium, copper 2, etc., 1 salts with sulfonic acids such as lauryl, palmityl, myristyl, stearylbehenyl, oleyl, linole, lilune, and the above various metals, etc. can be used.

Cetyl alcohol is an aliphatic alcohol.

Stearyl alcohol etc. can be used.

As the paraffin, saturated hydrocarbons such as n-octadecane, n-nonadecane, n-tridecane, n-tocosane, and n-todoriacontane can be used.

As silicon, polysiloxanes in which hydrogen is partially substituted with alkyl groups or phenyl groups, and polysiloxanes modified with fatty acids, aliphatic alcohols, acid amides, etc. can be used.

Examples of fluorine-based surfactants include perfluoro7-rukylcarboxylic acid and perfluoroargylsulfonic acid themselves, and their combinations of lithium and potassium.

Salts of magnesium, lead, aluminum, iron, cobalt, nickel, etc., barfluoroalkylphosphorus i1:L
Usable examples include perfluoroalkyl betaine, half-fluoroalkyltrimethylammonium salt, perfluoroethylene oxide, and perfluoroalkyl fatty acid ester.

Examples of the inorganic lubricant include graphite powder, molybdenum disulfide powder, tungsten disulfide powder, molybdenum selenide powder, tungsten selenide powder, calcium fluoride powder, and the like.

A rust preventive agent is applied to the front surface, the back surface or the vicinity thereof of the magnetic recording medium of the present invention, the void in the ferromagnetic metal thin film, the interface between the ferromagnetic metal thin film and the plastic film, the inside of the plastic film, etc. by known means.

Various additives such as antistatic agents and antifungal agents may be present as necessary.

As seen in the above example, the magnetic recording medium of the present invention has the following features:
The area of the protrusions in the undercoat layer is limited to a certain range,
By ensuring the thickness of the flat part is above a certain value, abnormal protrusions that occur due to uneven distribution and aggregation of solid particles during the formation of the undercoat layer can be suppressed, and after the formation of the undercoat layer, during the process leading to the formation of the ferromagnetic metal thin film layer. It prevents the formation of abnormal protrusions caused by surface scratches, and also suppresses the precipitation of oligomer crystals on the surface of the plastic film due to radiant heat during the formation of the ferromagnetic metal thin film layer, mainly due to the undercoat layer. As a result of removing dropout factors, dropouts are reduced. Furthermore, the average height of the protruding portions is set to 30 to 500 cm, and the interaction by forming a lubricant on the ferromagnetic metal thin film layer prevents the occurrence of squealing in high humidity.

(Example 1) A polyester film containing almost no particulates due to polymerization catalyst residue, wavy projections ( On the surface of the particles having an average height of 100 people (one cycle of about 0.5 μm), copolymerized saturated polyester resin such as organosilica sol with an average particle size of 260 was mixed in various proportions and diluted with a solvent. By applying and drying various types of solutions, the surface is coated with silica colloid particles as the core of the protrusions, polyester resin is used as the binder, and the area ratio between the protrusions and flat parts and the average thickness of the flat parts are different. Various types of undercoat layers were formed. A CoNi ferromagnetic metal film (Ni = 20w) was deposited on the surface of these films by continuous vacuum oblique evaporation method.
t % and a film thickness of 1000 mm) was formed in the presence of a trace amount of oxygen. The oxygen content of the CoN4 ferromagnetic metal thin film was a factor of 5 in terms of atomic ratio to the metal.

After that, stearic acid amide was added as a lubricant to the surface of the CoNi ferromagnetic metal thin film at a concentration of 50 mo per 1 m2 of the surface.
After making it exist, it was cut into a predetermined width to make a magnetic tape.

Each of these magnetic tapes was hung on a prototype video deck equipped with a dropout counter in an environment of 30 mm and 90% RH to measure the number of dropouts and the presence or absence of squealing. The dropout measurement results are shown in Figure 2. When the average thickness of the flat part of the undercoat layer was 220 Å or more, the average height of the protruding parts was less than 30 Å, which caused squeaking, so the dropout measurement results showed 200 Å. Ta.

(Example 2) There were several granular protrusions (average height 70, average diameter 1 μm) with a gentle slope due to silica particles added inside the plastic film per 10 μm2 of the surface, and these were caused by polymerization catalyst residue. The surface of the polyester film, which minimizes relatively large protrusions caused by fine particles, is coated with zirconium oxide colloid particles with an average particle diameter of 200 obtained by hydrolyzing zirconium isopropoxide as a core, and polyvinyl butyral resin as a binder. After forming an undercoat layer (of various types with different area ratios of the ζ protrusions and flat parts and the average thickness of the flat parts as in Example 1), a ferromagnetic metal thin film was formed according to Example 1. A magnetic tape was prepared after forming 4-fluoroethylene telomer as a lubricant at 30" o/m2 on top of the magnetic tape. The dropout measurement results of these magnetic tapes are shown in FIG.

Note that when the average thickness of the flat portion of the undercoat layer was 180 Å or more, the average height of the protruding portions was less than 30 Å, which caused squeaking, so the measurement results for dronop out showed up to 140 Å.

From Figures 2 and 3, when the area ratio of the protruding parts and flat parts of the undercoat layer is 1 = 1, the number of dropouts is large, and when the ratio is 1:3 or less, the number of dropouts is large. It can be seen that when the average thickness of the flat portion of the undercoat layer is 40 Å or less, dropout increases and its dispersion also increases. Note that in these figures (in which case the above-mentioned area ratio is 1:1), the display of variations is omitted.

Effects of the Invention As described above, the magnetic recording medium of the present invention prevents the occurrence of squealing in high humidity environments and significantly improves dropout, and its practical effects are high.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a magnetic recording medium according to an embodiment of the present invention, and FIGS. 2 and 3 are average thickness and number of dropouts of the flat portion of the undercoat layer of a magnetic recording medium according to other embodiments of the present invention. FIG. 1...Plastic film, 2...
Core of solid fine particles, 3...resin binder, 4...
・Ferromagnetic metal thin film layer, 5...Lubricant. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Average thickness of undercoat 1 flat part A)

Claims (1)

[Claims] It consists of a protruding part made of a core of a solid fine particle and a resin binder surrounding the core, and a flat part made of the resin binder, and the average area ratio of the protruding part and the flat part is 1=3 to 3. 1:1000, and the average height of the protruding portions is 30 to 5 o○, and the average thickness of the flat portions is 50 Å or more. 1. A magnetic recording medium characterized by having a lubricant present thereon.