JPS6299916A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain high coercive force by controlling the average crystal grain size of the magnetic layer on an underlying layer contg. Ti and <=1at% O and/or N. CONSTITUTION:The underlying layer contg. Ti and <=1at% O and/or N is provided on a resin substrate having <=150 deg.C thermal deformation temp. and the magnetic layer having a columnar crystal of 10-300nm average grain size is provided on the underlying layer. The coercive force in the direction perpendicular to the film plane decreases if the average crystal grain size of the Ti underlying layer if <10nm and the coercive force decreases similarly and in addition, grain boundary noise increases and such is undesirable for practicability if said size exceeds 300nm. The magnetic recording medium which has the high coercive force in the perpendicular direction and exhibits good magnetic characteristics and physical properties is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to a magnetic recording medium and a method for manufacturing the same. In more detail, Ti and 1at are added to substrate 1.
% or less of O and/or N,
This underlayer has a magnetic thin film having an axis of easy magnetization perpendicular to the film surface. The present invention relates to a so-called perpendicular recording type magnetic recording medium and a manufacturing method thereof.

Prior art and its problems In recent years, the demand for higher density in magnetic recording media has increased and the Hamadao recording method has been proposed. This perpendicular recording method requires a medium having an axis of easy magnetization in the direction perpendicular to the film surface.

Conventionally, it has been reported that such a Co--Cr film can be obtained by sputtering, but this method is difficult to put into practical use due to problems such as deposition rate.

Also, JP-A-56-127934, JP-A-56-165
No. 931, JP-A-57-53828, JP-A-57-2
No. 10452, JP-A-58-9220, JP-A-58-
No. 139338, JP-A-58-148139, etc.,
Proposals have been made to fabricate a Co-Cr-based perpendicularly magnetized film using an ion blating method.

However, in these conventional ion blating methods, it is necessary to introduce a certain amount of gas for ionization.
It is difficult to control the gas introduction, and the pressure during vapor deposition is high, which disturbs the crystal orientation, so it is not possible to obtain a very large coercive force.

Furthermore, it has been reported that a directly magnetized film can be fabricated using a vacuum evaporation method that can be expected to have a high deposition rate (Nat
ional Technical Report Vo.
l.

28 NoJ Dec, 1982 P4-P14)
.

In this report, a heat-resistant polymer material is used as the substrate, and a Co--Cr film is deposited at a substrate temperature of 30 to 350'C. As the plate temperature increases, the coercive force in the direction perpendicular to the film surface increases, and it is said that a coercive force of 10,000 e or more can be obtained at a substrate temperature of 300° C. or more. However, with such conventional techniques, it is difficult to form a Co--Cr center-of-gravity magnetization film with a high coercive force on a film having poor heat resistance such as polyethylene terephthalate.

Incidentally, it is generally known that a thin film of Ti is used as an underlayer of a magnetic recording medium for the purpose of improving adhesive strength (Japanese Patent Publication No. 39-26907, etc.).

And Co-Crt! > A proposal to improve the crystal orientation of a Co-Cr magnetic layer by providing such an underlayer on a heat-resistant substrate such as polyimide as a perpendicular magnetic recording medium (Japanese Unexamined Patent Publication No. 159225/1989, 59-222
Publication No. 36, Publication No. 59-22225, Publication No. 59-33
628, etc.) and proposals to prevent curling of media (Japanese Unexamined Patent Publication Nos. 59-75429 and 59-77621).
No. 59-119541, etc.). However, these proposals do not improve the coercive force in the direction perpendicular to the film surface.

In addition, instead of the aforementioned heat-resistant substrate such as polyimide, polyethylene terephthalate (PET), which has relatively poor heat resistance, can be used.
) is used as a substrate, and a Ti underlayer is similarly provided thereon to prevent curling of the medium (Japanese Patent Laid-Open No. 59-2218
No. 28, No. 59-221829, etc.) have also been carried out. In this case as well, the coercive force in the direction perpendicular to the film surface is not in the same direction as in the above case.

Therefore, polyethylene terephthalate is used as the base layer containing Ti! - (PET) to maintain excellent effects such as crystal orientation, adhesion, and curl prevention of Co-Cr in the magnetic layer, while increasing coercive force in the direction perpendicular to the film surface of the magnetic layer. There is a need for technology to do this.

In view of this situation, the present inventors have proposed that a high coercive force can be obtained by controlling the average crystal grain size of the magnetic layer on the Ti underlayer.

The present invention aims to further improve this proposal and obtain an even higher coercive force.

II. OBJECTS OF THE INVENTION The objects of the present invention are 1. For example, polyethylene terephthalate (
Using a substrate with a heat deformation temperature of 150°C or less, such as PET),
It is an object of the present invention to provide a magnetic recording medium that has higher coercive force in the perpendicular direction and exhibits good magnetic and physical properties, and a method for manufacturing the same.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the first invention provides Tt and O and/or N of 1 at% or less on a resin substrate having a heat distortion temperature of 150° C. or less.
A magnetic recording medium is characterized in that it has an underlayer containing .

In a second aspect of the invention, a base layer containing Ti and 1 at% or less of O and/or N is formed on a resin substrate having a heat deformation temperature of 150° C. or less in a vacuum I! T, l! L.

This method of manufacturing a magnetic recording medium is characterized in that a magnetic layer having columnar crystals with an average grain size of 10 to 300 nm is formed on this underlayer at a substrate temperature of less than 200 DEG C.

■Specific structure of the invention Hereinafter, the specific configuration of the present invention will be explained in detail.

4; The resin substrate used in the invention has a heat distortion temperature of 15
It has physical properties at temperatures below 0°C, particularly from 70 to 120°C.

Suitable substrate materials include polyesters such as polyethylene terephthalate (PET) and polyethylene 2.6 naphthalate.

These materials have extremely good surface smoothness and uniformity when formed into a film, and are inexpensive.

These substrates can have various shapes such as tapes and disks, and their thickness is not particularly limited, but is usually about 5 to 70 mm thick.

On such a substrate, Ti and less than 1 at%, especially 0.1
An underlayer containing ~1 at% of 0 and/or N is deposited.

The total content of 0 and/or N in such a base layer is 1
When it exceeds at%, the coercive force of the medium in the direction perpendicular to the film surface decreases.

Such O and N are usually contained in the form of a compound in which Ti is partially oxidized or nitrided.

In this way, silicon containing O and N contained in the base layer is
It may be measured by elemental analysis methods such as Auger spectroscopy and ESCA.

Such a base layer can be formed using a vapor deposition method or a sputtering method.

It is formed by various vacuum film forming methods such as ion blating method (RF method, arc discharge method). In this case, the film forming conditions may be within a range that is normally used, but in particular, in order to reduce the content of 0°N to 1 at% or less, for example, the substrate may be heated to 160 to 180 It is effective to preheat the substrate to about 80 to 100 degrees Celsius and to maintain the operating pressure at about 0.01 to 0.1 mPa after preheating in vacuum to a temperature of about 80 to 100 degrees Celsius.

The thickness of the base layer formed in this way is 1000 na.
+ or less, particularly preferably from 20 to 600n11.If the film thickness exceeds 11000n, the rigidity of the medium increases, resulting in poor head touch and a tendency to generate noise. Then, the coercive force becomes low f.

Moreover, if it is less than 201111, the effect of improving coercive force is low.

Note that the average crystal grain size of the Ti underlayer is 10 to 300 nm.
, more preferably 20 to 200 nm, especially 20 to 100 nm
It is ns.

A magnetic layer having an axis of easy magnetization in the direction perpendicular to the film surface is provided on L of the underlayer.

Such a magnetic layer usually has a columnar crystal structure, and the average grain size of the crystals is 1O to 300I, more preferably 20
~200r++w, more preferably 20~1100n
It is.

When this value is less than 1On+s, the coercive force in the direction perpendicular to the film surface becomes low, and when it exceeds 300 n■, the coercive force similarly becomes low, and grain boundary noise becomes large, which is not preferred in practice.

The columnar crystals forming such a magnetic layer are oriented substantially perpendicular to the film surface.

The thickness of such a magnetic layer is 120 to 1100 nm, more preferably 150 to 900 nm.

When the thickness of this magnetic layer is less than 120 ns, the strength decreases, and when it exceeds 1l100i, head touch becomes poor and modulation noise becomes large.

In the present invention, the average grain size of the columnar crystals, the film thickness of the magnetic layer, etc. can be usually observed and calculated using electron micrographs [scanning microscope (SEM) and transmission microscope (TEM)] of the surface and fracture surface. I can do it.

The composition of such a magnetic layer is as follows.

Co-Cr, Go-V, Co-N1-P, C.

-P, Mn-B1. Mn-AM-Ge, Nd-Fe, N
d-Co, Co-0, Mn-Sb.

Mn-Cu-B1. Gd-Fe, Gd-Co.

Pt-Co, Tb-Co, Tb-Fe-Co.

Gd-Fe-Co, Tb-Fe-03, Gd-IG,
Gd-Tb-Fe, Gd-Tb-Fe-C
It may be o-Bi, Co-Fe204, etc., but preferably Go-Cr.

The Co-Cr film has magnetic properties and film composition of Cr.
is preferably contained in an amount of 15 to 25 at%.

In addition to CO and Cr, N within a range of 5vt% or less
i, Fe, O, etc. may be contained.

Such a magnetic layer is formed using a vapor deposition method.

In the vacuum evaporation method, the evaporation source is heated in a high vacuum of 10' Torr or less using an electron beam method, resistance heating method, etc. to melt and evaporate it, and the vapor is deposited as a thin film on the surface of the substrate, for example. It's a method. The interlocking energy obtained by the evaporated particles during this evaporation is 0. leV~1e
V degree a te.

The vacuum evaporation method may be performed using various known apparatuses, and conditions such as the distance between the hearth and the substrate and the film deposition rate may be appropriately determined, and are not particularly limited. .

When forming the magnetic layer, the substrate temperature is less than 200°C, more preferably about 150 to 190°C.

In the present invention, since a resin substrate with a heat deformation temperature of 150°C or less is used, the substrate temperature when depositing the magnetic layer is 2.
If the temperature exceeds 00℃, the damage to the board will increase and the manufacturing process will be interrupted.
F Not desirable.

Also, if this temperature is reduced to less than 150°C, for example,
The desired average grain size of the crystal grains constituting the magnetic layer cannot be obtained, and the coercive force of the medium decreases, which is not preferred in practice.

In the present invention, since the time during which the substrate is kept at the above-mentioned temperature is relatively short, even a substrate material having the heat distortion temperature of the present invention can sufficiently withstand the temperature.

Furthermore, the operating pressure during magnetic layer formation is 0,01-
The pressure may be set to about 10 mPa, more preferably about 0.1 to 1 mPa.

Note that it is preferable that various surface treatments of the substrate be performed on at least the magnetic layer forming side of the resin substrate surface described above.

Examples of such ground processing methods include plasma processing methods and vacuum processing methods such as ion bombardment.

The magnetic layer of the magnetic recording body of the present invention may be provided with various known top coat layers, back coat layers may be provided on all four sides of the substrate, or a back coat layer may be provided between the magnetic layer and the substrate. A high magnetic permeability metal thin film such as permalloy or other various known intermediate layers may also be provided.

In this case, the positional relationship between the intermediate layer and the F layer containing Ti is 1. However, usually an intermediate layer is provided below the base layer.

(2) Specific Effects of the Invention According to the present invention, a medium having an extremely high coercive force in the direction perpendicular to the surface of the magnetic layer can be obtained using a substrate with a thermally deformed portion If of 150° C. or less.

Furthermore, the crystal orientation and adhesiveness of the magnetic layer are good, and curling is less likely to occur.

Such magnetic recording media are effective for use in torsion magnetization magnetic tapes, magnetic disks, flexible disks, and the like.

■Specific embodiments of the invention Specific examples of the present invention are shown below.

[Example 1] A 170 mm substrate holder was placed at the 1-25 cm position of the evaporation source, and a 50 mm thick polyethylene terephthalate (PET) film plate was attached to it. Using Ti as an evaporation source, Ti was deposited on the substrate 1-.
A base layer was deposited. Note that during vapor deposition, the working pressure is 0.
．． 05mPa, ) & board holder temperature (substrate temperature)
The temperature was 70"C, the first deposition rate was about 10 nm/see, and the thickness of the deposited Ti film was 20~20cm. After this, the temperature of the substrate holder (temperature of the substrate) was set to 180°C.
and the evaporation source is Co-Cr (Fffua ratio 80/20)
The alloy (25 mmφ pellets) was evaporated using an EB gun with a 270° deflection to form the Ti underlayer.
A Co--Cr magnetic layer was deposited on L.

In addition, prior to vapor deposition, the composition was analyzed using a film thickness controller after melting the alloy, and the Co/Cr ratio was 80/20.
When the temperature was reached, the shutter was opened and vapor deposition was performed.

The conditions for vapor deposition were a working pressure of approximately 0.2 mPa and a vapor deposition rate of 2.
The film thickness is approximately 0 nm#ec, and the Co-crt7) film thickness is 30 nm.
The range was 0 to 500 nm.

In this way, as shown in Table 1, FJ'! ! !
Samples were prepared by varying the layer thickness and composition as well as the Go-Cr magnetic layer thickness and crystal grain size. The composition analysis of the base layer was performed by Auger analysis (Model 800 manufactured by Alpac-Phi).

In addition, in sample No. 008, the temperature of the substrate during formation of the magnetic layer was set to 120''e.

1-For each of these samples as described above, the thickness of the magnetic layer and the average grain size of the columnar crystals were determined.

The measurement method is an electron micrograph of the surface and fracture surface [scanning microscope (SEM) and transmission microscope (TEM)]
Calculated from.

Furthermore, the characteristics shown below were investigated for each sample.

(1) Coercive force in 6 directions perpendicular to the film surface HeJ-(Oe)-- The coercive force of a sample cut into a constant area was measured using a vibrating sample magnetometer (VSM) with a maximum applied magnetic field of 10 KG.

These results are shown in Table 1.

Table 1 Sample Ti underlayer composition Underlayer Magnetic layer On Hc1 0.3 0.6 2
0 20 450 7002 0.2
0.6 ioo 45 380
8803, 0.2 O, 73008050
0102040,10,33008048010805
(Comparison) 0.5 1.5 300 80
500 910B 0.3 0.6 5
00 110 40011207 (comparison) 0.2
0.5 1100 310 42O4508
0,20,7' 300 75 510
4709 (comparison) ---40400390 Table 1
From the results shown in Figure 1, the effects of the present invention are clear.

Claims (4)

[Claims] (1) Ti on a resin substrate with a heat distortion temperature of 150°C or less
and a base layer containing 1 at% or less of O and/or N, and on this base layer, the average particle size is 10 to 300 nm.
1. A magnetic recording medium comprising a magnetic layer having columnar crystals. (2) The magnetic recording medium according to claim 1, wherein the underlayer has a thickness of 1000 nm or less. (3) The magnetic recording medium according to claim 1 or 2, wherein the magnetic layer contains Co and Cr. (4) Ti on a resin substrate with a heat distortion temperature of 150°C or less
A base layer containing 1 at% or less of O and/or N is formed in vacuum, and a magnetic layer having columnar crystals with an average grain size of 10 to 300 nm is formed on the base layer at a substrate temperature of less than 200°C. 1. A method of manufacturing a magnetic recording medium, comprising: forming a magnetic recording medium.