JPH02226513A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the traveling property and durability even under the conditions of a high temp. and high humidity by providing the surface of a thin ferromagnetic metallic film with striated projections of prescribed sizes and number and discrete granular projections of prescribed sizes and number. CONSTITUTION:The striated projections 1 and the large and small discrete granular projections 2 are provided. The roots of the discrete granular projections 2 are embedded in a base or are anchored in an under coating layer. The striated projections 1 are formed by the undulations of the under coating layer provided before coating of the magnetic layer on the base surface. The surface having such surface roughness is formed by combining means for giving the conditions to form crepe wrinkles on the under coating layer and means for adding fillers to the paint of the under coating layer or the stock of the base. The discrete granular projections 2 are formed by adding inert fillers in addition to the residues of polymn. catalysts to the plastic of the base stock or the paint of the under coating layer by selecting the material, grain sizes and the amt. of addition. These particles are added prior to biaxial stretching at the latest in the case of adding the same to the base stock. SiO2, alumina, etc., are used as the fillers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with improved durability and runnability.

[Prior art]

Magnetic recording media such as magnetic tapes, magnetic sheets, or magnetic disks are widely used in the audio, video, and computer fields. For example, magnetic tapes of this type are coated with ferromagnetic powder dispersed in a binder, but as the demand for high-density recording has increased recently, it has become necessary to use coated tapes, which reduce the recording density by the amount of binder. Instead, magnetic recording media are now being used that have a large saturation magnetization and are made of a thin ferromagnetic metal film formed on a support by direct vapor deposition, sputtering, ion blasting, etc. without using a binder. It's here.

However, the ferromagnetic layer of such a thin film magnetic recording medium has a large frictional resistance, and when this friction is severe, running may become sluggish. Not only does it have poor running properties, but it is also prone to scratches due to friction with magnetic heads, guide rollers, liners, etc. For this reason,
When used as a videotape, the still durability when viewed as a still image and the repeated durability when recordings are repeatedly played back from this tape are significantly inferior to those of the coated type. It may also cause noise.

In order to solve these problems, a coating film is provided on the ferromagnetic metal thin film, but in this case, in order to reduce the spacing loss that accompanies the loss of output when reproducing records with a magnetic head. Therefore, it is necessary to reduce the thickness of the coating film. Furthermore, various inorganic or organic compounds are attached to or overcoated on the surface of the magnetic layer.

Furthermore, a method of forming irregularities on the surface of the magnetic layer is known for the purpose of improving running properties and durability. For example, (1) Although the expressions vary, Japanese Patent Application Laid-Open No. 116115/1983 includes wrinkle-like protrusions,
JP-A-56-16937 has a mountain-like protrusion and JP-A-58
In No. 68224 and No. 58-100221, crepe wrinkles consisting of curved veins of high and low height, long and short, are formed on the surface under the expression of worm-like protrusions, etc., in order to improve running performance and durability. (2) JP-A-57-127923 discloses that when the support is biaxially stretched, polyester oligomer is precipitated on the surface of the support to form creases, or (3) a binder liquid containing dispersed fine particles is supported. It is applied and fixed onto the body, and a miliary grain surface is formed on the crepe wrinkles, thereby improving runnability and durability.

However, the method mentioned in 1) significantly improves runnability and durability at room temperature and humidity, but it does not reduce the friction noise (sliding noise) at high temperature and humidity.
(tape squeal) problem.

In addition, in areas with high durability and relatively large surface roughness of crepe wrinkles (Rmax 250 to 600 people), the coercive force of the formed metal thin film decreases, resulting in decreased output in the short wavelength range and head sliding noise. There are problems such as an increase in S/H and a decrease in S/H. In addition, in the technology disclosed for the worm-like protrusions, R
It is difficult to form a surface with uniform roughness in the range of 250 to 600 people with good reproducibility.

In addition, the method mentioned in (2) has a major drawback in localizing the polyester oligomer and making it difficult to precipitate the oligomer and make protrusions appear with good reproducibility.

Furthermore, in areas with large surface roughness, the method listed in (3) not only has the same problems as (1), such as a decrease in short-wavelength output and an increase in sliding noise, but also has problems with the peeling off of adhered fine particles. clogging (head clog) is likely to occur.

[Purpose of the invention]

The purpose of the present invention is to provide (1) a magnetic recording medium with good runnability and durability under high temperature and high humidity conditions, (2) a magnetic recording medium with good runnability, durability, and video S/N, which have a reciprocal relationship therewith. (3) To provide a magnetic recording medium that has surface roughness that meets the above objectives and has good productivity.

[Structure of the invention]

The object of the present invention is to provide a magnetic recording medium in which a ferromagnetic metal thin film is provided on a flexible plastic support, with a height of 5G-150A1 average spacing of 3μ on the surface of the ferromagnetic metal thin film.
m or less in height, long and short curved ridges, and (2 to 16
This is achieved by a magnetic recording medium characterized by having discrete grain protrusions with a height of 150 to 600 A.

In an embodiment of the present invention, the above-mentioned vein protrusions are generated by a subbing layer provided on the support, and the discrete grain protrusions are caused by particles dispersed in the support and/or the subbing layer. Preferably, it is formed.

Next, the present invention will be explained in detail.

The surface structure of a ferromagnetic metal thin film (hereinafter referred to as magnetic layer) having striations and discrete grain projections according to the present invention is shown in the electron micrograph (X 20,000) of FIG. In the same figure (a), striations and large and small discrete grain protrusions can be seen. The same figure (b) is a reference photograph in which the amount of filler was increased (outside the present invention) to clearly show the veins, and the veins are also large.

FIG. 2(a) shows a schematic perspective view of the surface, and FIG. 2(b) shows a schematic cross-sectional view. 1 is a striated process, and 2 is a large and small discrete grain process. The roots of the discrete grain protrusions 2 are buried within the support or are rooted in the subbing layer, and the vein protrusions 1 are due to the undulations of the subbing layer provided on the surface of the support before coating the magnetic layer. be. However, in the figures, the protrusions are exaggerated for explanation.

The surface having the surface roughness specified in the present invention is obtained by forming creases on the undercoat layer at the time of forming the support or at the time of forming the undercoat layer before the formation of the undercoat layer on the support surface prior to the installation of the magnetic layer. It can be formed by a combination of means for providing conditions for formation and means for adding a filler to the undercoat layer coating or support material.

In addition to the polymerization catalyst residue, the discrete particle protrusions are formed by adding inert filler particles to the support material, such as plastic or subbing layer paint, by selecting the material, particle size, and amount. can be obtained by adding it at the latest prior to biaxial stretching.

The primary particle size of filler particles is 0.01 to 0.5μ
The shoulder range is preferably 0.03 to 0.3μ. The amount added is 0.0001 to 0.19/9 per plastic or subbing layer paint.

In addition, fillers used in the present invention include s502 (
hydrate, diatomaceous earth, silica sand 9 quartz, etc.), alumina, S
Silicates containing 30vt% or more of iO□ (clay, aluminosilicate, zircon, fly ash, etc.), Zn,
Zr, Ti oxide, Ca, Ba sulfate, Li
, Na, Ca phosphate, Li, Na, benzoate, Ca, Ba, Zn, Mn terephthalate, M
g, Ca, Ba, Zm, Cd, Pb, Sr, Mo, F
e, Go.

Ni titanate, Ba, Pb chromate, carbon (carbon black, graphite, etc.), glass, Mgco
1, fluorite, ZnS, etc.

Particularly preferably used are anhydrous silicic acid, hydrated silicic acid, aluminum oxide, aluminum silicate (including calcined products and hydrated products), lithium phosphate, trilithium phosphorus, calcium phosphate, barium sulfate, titanium oxide, and lithium benzoate. , glass powder, clay (kaolin, bantonite, white clay, etc.),
Examples include talc, diatomaceous earth, and calcium carbonate.

Naturally produced limestone is used as calcium carbonate particles.

There are calcite crystals, argonite crystals, vaterite crystals, etc. obtained by chemical methods from chalk or limestone.

Furthermore, as a method for forming creases of striated protrusions on the surface of the subbing layer, for example, as shown in JP-A No. 58-68223, the formation of minute protrusions is performed on a smooth a-type polyethylene terephthalate film after being stretched in one direction. - Apply an aqueous emulsion liquid containing at least one of silicone with a molecular weight of 30,000 to 300,000, styrene with a molecular weight of 20,000 to 1,000,000, or butadiene rubber and an aqueous polymer with a molecular weight of 10,000 to 2,000,000 as the main components on the surface to be formed. After drying, the film is stretched in the perpendicular direction, or after the film is stretched in the perpendicular direction, it is further stretched in the one direction and then heat treated. Or Japanese Patent Publication No. 57
-127923 and No. 57-37719, in the pre-step or during the stretching film formation of a polyester film support having a smooth surface, a non-crosslinking material such as natural wax or wax is applied to the surface of the polyester film. If a crosslinked polymer containing a large amount of a lubricant or a necessary amount of a surfactant, thickener, etc. is coated, formed into a thin film, and then stretched, creases will occur.

Alternatively, as described in JP-A-53-116115, a polyethylene terephthalate solution, a polypropylene solution, or a 6-nylon solution may be applied onto the polyethylene terephthalate.

In the first method described, the number and height of the veins can be controlled by changing the thickness of the coating film of the crosslinked polymer or by changing the degree of stretching after applying the crosslinked polymer and forming a thin film. can be controlled.

Suitable crosslinked polymers include modified silicone resins modified with alcohol, epoxy, polyester, polyether, amine or melamine, epoxy resins, urethane resins, unsaturated polyester resins, copolymers and mixtures thereof, and the like.

Further, in the present invention, the veins on the ferromagnetic metal thin film may be formed regularly or randomly.

The ferromagnetic metal thin film in the present invention is Fe.

Metals such as Co, Ni or Fe-Co, Fe-Ni
, Co-Ni.

Fe-Co-Ni%Fe-Rh, Fe-Cu, Co
-Cu, Co-Au5Co-Y, C.

-La%Co-Pr, Co-Gd, Co-5s, C
o-Pt, Ni-Cu5Fe-Cr.

Co-Cr, Ni-Cr, Fe-Go-Cr, F
Examples include e-Go-Ni-Cr, and cobalt and cobalt alloys are particularly preferred.

A thin film formed of the above-mentioned ferromagnetic metal or alloy by vacuum evaporation, sputtering, ion blating, etc. is used. The thickness of this metal thin film is 50
Approximately 0 to 2000 people5 preferred. Further, it is preferable that the thickness of this metal thin film is uniform over the entire surface.

Further, better durability can be obtained by performing vapor deposition in an oxygen atmosphere, increasing the strength toward the surface.

Further, as the support for forming the magnetic layer, a plastic base such as polyester, polyethylene terephthalate, polyimide, polyamide, polyamideimide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyetheretherketone, or polyethersulfone is used. It will be done.

In the present invention, in order to obtain even better running properties and durability, it is preferable to provide an overcoat layer on the surface of the magnetic layer side that provides lubricating and protective effects, and a back coat layer that helps running properties on the back side. , conventional techniques are used for the overcoat and backcoat.

(Examples) Next, the present invention will be explained by examples, but the present invention is not limited thereto.

Example 1 After reacting manganese acetate as a transesterification catalyst to dimethyl terephthalate and ethylene glycol, antimony trioxide, lithium acetate dissolved in ethylene glycol, calcium acetate, and ethylene glycol were uniformly dispersed to give an average particle size of 0. 13μ curvature silica (Sin,)
The particles were mixed and then trimethyl phosphate was added to perform a condensation reaction to obtain polyethylene terephthalate. Next, the obtained polyethylene terephthalate was extruded using an extruder to form a film, and after stretching the film in the longitudinal direction, fine silica particles with an average particle size of 180A were dispersed in an MEK solution of saturated polyester resin on the surface on which the magnetic layer was to be formed. Apply the undercoat layer liquid to a wet film thickness of 10 μm,
After drying, it is stretched laterally to form striations and discrete branch processes. At this time, the silica content in the subbing layer liquid was set to 0.
25,0.05.0.025.0. O13 and 0.00
Subbing layer liquid Ua, Ub, Uc varied to 25 g/g.

Undercoat using Ud and Ue, and support 1 a, l
b*1 c, l d and le were obtained. Furthermore, subbing layer liquid U
Wet film thickness 4.7.15.25 and 35μ using c
Undercoating supports 1f, 1g, lh, li and N were obtained.

A Go-Ni (80-20) alloy was vapor-deposited onto the support by oblique incidence at an incident angle of 45° while reacting with oxygen to form a magnetic layer with a thickness of about 1,500 layers, and then perfluoroethylene oxide was deposited. After forming an overcoat layer of a copolymer with propylene oxide, a backcoat layer was formed and the tape was cut into 811@.

Comparative Example (1) A tape having an undercoat layer containing variable amounts of fine silica particles was prepared in the same manner as in Example 1 except for the silica particles added during film formation using the undercoat layer liquid Ua''Ue. ,
Comparative samples 2a, 2b, 2c+2d+2e were obtained.

Comparative Example (2) The same procedure was used as in Example 1 except that the silica particles added during film formation were removed, and the content of fine silica particles was fixed using the subbing layer liquid [Ja], and the wet film thickness was set to 7. 15,2
Comparative samples 3a, 3b, and 3c were prepared by painting tapes at different levels of 5.35 and 50 pm.

3d and 3e were obtained.

Comparative Example (3) A tape was prepared in exactly the same manner as in Example 1, except that Si was added to the undercoat layer liquid when forming a film and subbing in the same manner as in Example 1. I got 4a.

The characteristics of the sample obtained above were measured using the following method.
l1III-ro (5-kll bd l+gl-roro C
0C Roro Roro 0 Roro 220000 units z z z z
z z z Roro ++1-1-x----to N to hehe n
ω ■ From the size above, a base that has both a large particle size filler in the base matrix and a small particle size filler in the undercoat layer has better durability and reliability than a base that has only either one of them. I know it's excellent.

Furthermore, in la with many discrete branch protrusions, the membrane structure becomes brittle and the filler is easily removed, which makes clogging more likely to occur, and in la with few discrete branch protrusions, the effect of the present invention is less effective. I can see that he is not performing to his full potential.

On the other hand, if the size of the striations is less than 50, the filler in the subbing layer cannot be retained and the filler tends to fall off. Furthermore, it can be seen that when the striations become large, the electrical characteristics deteriorate and become a problem.

[Measurement method 1) Surface roughness (protrusion height) Measuring device: Talystep I [Stylus 0. lp
+xX 2.5μm needle pressure 2119 standard length 0.1mm, cut off 0.3
3Hz2) S/N Deck used: 5ONY EVA-300 Brightness S/N was measured with burst off.

3) Calculated by using a runability tester for μ and measuring the load when running the tape against the hard chrome metal bin of ■-.

4) Hc (coercive force) Coercive force was measured at a maximum magnetic field of 50,000 e using USM (manufactured by Kuruma Kogyo Co., Ltd.).

5) DurabitiLy (durability) 60℃, 8
The vehicle was run repeatedly for 100 hours in a 0% environment, and the items of S/N, jitter, skew, tape squeal, and deck stain (clog) were evaluated and judged.

[Brief explanation of the drawing]

Figure 1 is an electron micrograph (×20.
000). FIG. 2 is a perspective view and a sectional view schematically illustrating the surface structure. ...Striate process, 2...Discrete ramus process

Claims (2)

[Claims] (1) In a magnetic recording medium in which a ferromagnetic metal thin film is provided on a flexible plastic support, on the surface of the ferromagnetic metal thin film,
The height is 50-150 Å, the average spacing is 3 μm or less, and the curved veins are long and short, and (2-16) x 10^6 pieces/
A magnetic recording medium characterized in that it has discrete grain protrusions with a height of 150 to 600 Å. (2) The striated projections are caused by a subbing layer provided on the support, and the discrete grain projections are formed by particles dispersed in the support and/or the subbing layer. The magnetic recording medium according to claim 1.