JPS60261028A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is less tacky and has good preservability, small running friction and excellent film strength, head touch characteristic, etc. by providing a top coat layer contg. a specific phosphoric acid compd. and specific aldehyde on a magnetic layer. CONSTITUTION:Monoester - triester phosphate compds. expressed by formulas I, II (R1 is an alkyl of 10-20C, Y1, Y2 are respectively H, alkyl, preferably alkyl of the same C as the C of R1, or cation of a metal or onium, Y1 and Y2 may form together bivalent cation, R2 is an alkyl of 9-21C) or the salt thereof and the aldehyde expressed by formula II are formed by vapor deposition on a thin continuous film type magnetic layer consisting of Co, Co-Ni, Co-O, etc. to form the top coat layer. A back layer may be formed on the surface of the substrate opposite from the magnetic layer. The magnetic recording medium which has no tack and has improved film strength, lubricity and head touch characteristic, high running durability and still durability and less drop-out is obtd. by the provision of such top coat layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background Technical Field of the Invention The present invention relates to an improvement in a top coat film of a magnetic recording medium, particularly a magnetic recording medium having a continuous thin film type magnetic layer.

Prior art and its problems As magnetic recording media for video, audio, etc., media having a continuous thin film type magnetic layer are being actively developed because of their compactness when wound into tapes.

Due to its characteristics, the magnetic layer of such a continuous thin film type medium is made of Co, Co-Ni, or Co, which is formed by the so-called oblique deposition method, in which deposition is performed at a predetermined angle to the normal to the substrate.
-0, Co--Ni--, etc.-based vapor deposited films are most suitable.

However, such a magnetic layer has high running friction, low film strength, poor head touch, particularly low running durability, and output decreases due to repeated running.

In addition, video media have a short durability in a still image mode called still.

Furthermore, there are many so-called dropouts.

Under these circumstances, various top coat films for obliquely deposited magnetic layers have been proposed.

For example, evaporated or coated films of straight chain saturated fatty acids or their esters (JP-A-53-88704, JP-A-55-1)
33533, etc.).

But 1. All of the conventional top coat films have still produced unsatisfactory results in terms of running durability, still characteristics, dropout, and the like.

Under these circumstances, the present inventors have previously proposed a top coat film consisting of a phosphoric acid mono-, di-, or triester or a salt thereof having an alkyl group having 10 to 22 carbon atoms (patent application). No. 57-234818, No. 58-1
No. 884122, No. 58-187523, No. 5B-1
No. 87985, No. 5B-187988, etc.).

According to this top coat film, the above-mentioned drawbacks are improved.

However, this film has a drawback in that it causes so-called adhesion between the tape and the back surface during running after winding the tape.

Moreover, it is also insufficient in terms of storage stability. Furthermore, the temperature characteristics of the friction coefficient are poor, and running friction is particularly large at low temperatures.

■ Purpose of the Invention The present invention was developed in view of the above-mentioned circumstances, and its main purpose is to provide a material with low adhesion, excellent storage stability, low running friction, excellent film strength, lubricity, and head touchability. It is an object of the present invention to provide a magnetic recording medium having a continuous thin film type magnetic layer having a novel top coat film having high running durability and still durability, less occurrence of dropouts, and less running friction at low temperatures.

Such objects are achieved by the invention described below.

That is, the present invention provides a magnetic recording medium having a continuous thin film type magnetic layer on a substrate and a top coat film on the magnetic layer, wherein the top coat film comprises a compound represented by the following formula (I),
A magnetic recording medium characterized by containing a compound represented by the following formula (II).

Formula (1) % Formula % Formula (II) 2 CHO (In the above formulas CI) and (II), R1 represents an alkyl group having 10 to 22 carbon atoms, and Yl and Y2 are hydrogen and an alkyl group, respectively. Alternatively, it represents a metal or onium cation, but Yl and Y2 may be combined with each other to form a divalent cation, and R2 represents an alkyl group having 9 to 21 carbon atoms. ) A second invention provides a magnetic recording medium having a continuous thin magnetic layer on a substrate and a top coat film on the magnetic layer, wherein the top coat film is a compound represented by the following formula (I). and,
A compound represented by the following formula (n), a compound represented by the following general formula (m), a compound represented by the following formula (IV), and one type of unsaturated chain hydrocarbon having 10 to 22 carbon atoms. This is a magnetic recording medium characterized by including the above.

Formula CI) R100Y.

\ / / \ 0Y2 Formula (II) 2 CHO Formula (m) R3C0OH Formula (IV) 4 0H (Formula CI) (n) (m) and (IV), R1 is alkyl having 10 to 22 carbon atoms Yl and Y2 each represent hydrogen, an alkyl group, or a metal or onium cation, but Yl and Y2 may be combined with each other to form a divalent cation; R2 and R3 are each It represents an alkyl group having 9 to 21 carbon atoms, and R4 represents an alkyl group having 1θ to 22 carbon atoms. (2) Specific Structure of the Invention The specific structure of the present invention will be explained in detail below.

The magnetic recording medium of the present invention has a magnetic layer on a substrate.

The magnetic layer may be of various continuous thin film types, and usually contains cobalt, nickel, or an alloy thereof as a main component.

In this case, in the present invention, CO is an essential component, and C
It is preferable to consist of Go+Ni+O, Co+Ni, Co+O, or Go+Ni+O.

That is, it may be made of Co alone, or it may be made of CO and Ni.

In the case of Co+Ni, the weight ratio of Co/Ni is
It is preferable that it is 1.5 or more.

Furthermore, in addition to CO or Co+Ni, 0 may be included. When O is included, more favorable results can be obtained in terms of electromagnetic conversion characteristics and running durability.

In such a case, the atomic ratio of O/Co (if Ni is not included) or O/(Co+Ni) is preferably 0.5 or less, particularly 0.15 to 0.45.

On the other hand, the magnetic layer contains Co, Co+Ni.

When Cr is contained in addition to Co+0 or Co+Ni+O, even more favorable results are obtained.

This is because electromagnetic conversion characteristics are improved, output and S/N ratio are improved, and film strength is further improved.

In such cases, Cr/Co (if Ni is not included)
Alternatively, the weight ratio of Cr/(Co+Ni) is preferably 0.1 or less, particularly o, ooi to 0.1.

In this case, Cr/Co or Cr/(C.

Even more preferable results are obtained when the weight ratio of +N i) is 0.005 to 0.05.

Note that such a magnetic layer also contains other trace components,
Particularly transition metal elements, such as Fe, Mn,
V, Zr, Nb, Ta, Mo
.

W, Ti, Cu, Zn, etc. may be included.

Preferably, such a magnetic layer is an aggregate of particles having a columnar crystal structure tilted with respect to the normal to the main surface of the substrate.
This improves electromagnetic conversion characteristics.

In such a case, the particles having a columnar crystal structure are preferably inclined within a range of 20 to 60'' with respect to the normal to the main surface of the substrate.

Also, each columnar crystal grain usually has a magnetic layer thickness? '') It has a length that spans the entire length, and its short axis is generally 50 mm.
~500 people.

Then, CO and Ni added as necessary.

Cr etc. constitute this columnar crystal itself, and 0
When 0 is added, 0 usually exists mainly in the form of oxide on the surface of each columnar crystal grain.

Such a magnetic layer is usually formed to a thickness of 0.05 to 0.5-.

In this case, the magnetic layer may be provided directly on the substrate, or may be provided on the substrate via an underlayer.

Further, although the magnetic layer is usually formed as a single layer, it may be formed by laminating a plurality of layers with an intermediate layer interposed therebetween as the case may be.

Such a magnetic layer is usually formed by an oblique deposition method.

As the oblique evaporation method used, a known oblique evaporation method may be used, and the minimum value of the incident angle with respect to the normal to the substrate is preferably 30'' or more.

Incidentally, the vapor deposition conditions, post-treatment method, etc. may be in accordance with known conditions and methods. In this case, effective post-treatment methods include various known treatment methods for introducing O into the magnetic layer. .

A top coat film made of a compound represented by the above formula (I) and a compound represented by the above formula (II) is formed on such a magnetic layer.

In the above CI) formula, R1 is a carbon atom number lθ~22
is a straight chain saturated alkyl group.

When the number of carbon atoms in R1 is less than 10, running friction increases, running durability and still durability decrease, and dropout also increases.

Furthermore, when the number of carbon atoms in R1 exceeds 22, film forming properties deteriorate and fluctuations in running friction become large.

Note that when the number of carbon atoms in R1 is 12 to 22, running friction is further reduced, running durability is further improved, and dropout is further reduced.

Furthermore, Yl and Yl are both H, and may be a phosphoric acid monoalkyl ester.

Alternatively, one or both of Yl and Yl is Na"
, K'', Li+, or onium (particularly ammonium) cations such as NH4'', N''(Ca R9)4, and may also be a heptanoalkyl phosphate salt.

In addition, when Yl and Yl are both cations, they are Mg 4+.

It may be a metal cation such as Zn4+ or an onium cation.

Further, one or both of Yl and Yl may be an alkyl group, and may form a phosphoric acid dialkyl ester, a salt thereof, or a phosphoric acid trialkyl ester.

When Yl is an alkyl group, the number of carbon atoms thereof is not particularly limited, but is preferably the same as R]. Also, when it is a triester, R3, Y,
The total number of carbon atoms in Yl is preferably 50 or less.

Two or more types of these phosphoric esters or salts thereof may be contained.

In addition to the above phosphoric acid ester or its salt, the top coat film further contains an aldehyde represented by the above formula (II).

And the number of carbon atoms of R2 in formula (n) is 9 to 21
It is.

If it is less than 9, adhesion increases, running durability deteriorates, temperature characteristics of the friction coefficient deteriorates, and storage stability deteriorates.

If it exceeds 22, the film formation efficiency will deteriorate and the fluctuations in running friction will increase.

In the case of the present invention, R2 is a straight chain alkyl group, preferably having 11 to 21 carbon atoms.

Furthermore, R2 preferably has one fewer carbon atom than R1.

Two or more kinds of aldehydes represented by R2CHO can be contained, but the content thereof is preferably 30 mol% or less, particularly 5 to 20 mol% or less of the total.

When it exceeds 30 mol%, running properties deteriorate.

Furthermore, in addition to these, a carboxylic acid represented by formula (m) may be contained.

This improves running performance and running durability.

In formula [■], R3 is an alkyl group having 9 to 21 carbon atoms, and is particularly preferably a straight-chain alkyl group.

If the number of carbon atoms in R3 is less than 9, running properties, running durability, etc. will deteriorate.

Furthermore, when the number of carbon atoms in R3 exceeds 21, film formability deteriorates.

In addition, it is preferable that the number of carbon atoms of R3 is 11-21.

Note that R3 usually has one fewer carbon atoms than R1 in formula (I), and is preferably the same as R2.

Two or more types of these carboxylic acids may be contained.

Furthermore, in addition to these, an alcohol represented by formula (1'V) may be contained.

This improves running performance and running durability.

In formula [IV), R4 is an alkyl group having 10 to 22 carbon atoms, and is particularly preferably a straight-chain alkyl group. - When the number of carbon atoms in R4 becomes less than 1O, running properties, running durability, etc. deteriorate.

Furthermore, when the number of carbon atoms in R4 exceeds 22, film formability deteriorates.

In addition, it is preferable that the number of carbon atoms of R4 is 12-22.

Incidentally, R4 is preferably 1, which is usually the same as R1 in the above formula (I).

Two or more kinds of these alcohols may be contained.

The top coat film contains a compound represented by the above formula CI),
In addition to the compound represented by formula (II) above, and if necessary, the compound represented by formula (m) above, and/or the compound represented by formula (■) above, an unsaturated chain hydrocarbon is further contained. It's okay.

The number of carbon atoms is 10 to 22.

When it is less than 10, running performance and running durability deteriorate.

If it exceeds 22, film formability deteriorates.

In such a case, the unsaturated chain hydrocarbon is preferably a straight chain.

Further, the unsaturated hydrocarbon is preferably an olefin, and its double bond is usually located at the terminal.

Two or more types of these unsaturated chain hydrocarbons may be contained.

The total amount of one or more of the compound represented by formula [■], the compound represented by formula (IV), and the unsaturated chain hydrocarbon is preferably 50 mol% or less.

Such a top coat film has a thickness of more than a monomolecular layer and a thickness of 300 Å.
Hereinafter, the thickness is more preferably 5 to 100 people.

This is because when the number of people exceeds 300, the electromagnetic conversion characteristics deteriorate.

Preferably, such a top coat film is formed by vapor phase deposition such as vapor deposition or sputtering.

When using coating rather than vapor deposition, sputtering, etc., it is difficult to form a thin layer with a uniform thickness.

For vapor phase deposition, it may be carried out using two crucibles or two hearths using the corresponding compounds as evaporation sources.
Wear.

However, the aldehyde of formula (II), the carboxylic acid of formula (m), the alcohol of formula (IV), and the unsaturated hydrocarbon are
Since it is also a decomposition product of the phosphoric ester of formula CI),
Vapor phase deposition may be carried out using the phosphoric ester of formula (I) as an evaporation source.

At this time, the substrate temperature, substrate-hearth spacing, evaporation source temperature, etc. can be easily determined experimentally.

Note that the substrate-hearth spacing may be 1 to 20 cm, and the substrate temperature may be 0 to 30°C.

Although there are no particular restrictions on the substrate used, a particularly flexible substrate, particularly one made of resin such as polyester, polyimide, polypropylene, etc., is preferred.

In addition, the thickness may be various, but especially 5.
It is preferable that it is -20-.

A back coat layer is preferably formed on the back surface of the magnetic layer forming surface.

The back coat layer consists of a pigment, a binder, and, if necessary, a lubricant.

In this case, since the top coat film of the present invention has extremely low adhesion, any known material can be used as the material for the back coat layer.

That is, the binder may be of any thermosetting type, radiation curing type, etc., and the lubricant may also be of any type.

(2) Specific effects of the invention The magnetic recording medium of the present invention is useful as a magnetic recording medium for video, audio, and the like.

According to the present invention, running friction is extremely low.

Furthermore, its film strength, lubricity, and head touchability are extremely high.

Furthermore, the running durability and still durability are extremely high, and the occurrence of dropouts is extremely low.

It also has an extremely high shelf life.

Also, there is very little occurrence of adhesion with the back side of the tape.

■Specific embodiments of the invention Hereinafter, specific embodiments of the present invention will be described in detail.

Example Co/Ni c7) Co/N in a weight ratio of 4/1
i alloy, and Co/Ni/Cr(F)
Weight ratio 75/20/5t7) Go/N
Samples AO and BO were prepared by forming magnetic layers of 0 and 2% thickness using an i/Cr alloy on a 10-thick polyethylene terephthalate (PET) film by concentrated oblique vapor deposition, respectively.

The incident angle in oblique evaporation was 45°, and the evaporation atmosphere was as follows: PAr=2X10-2Pa, Po2=1×1O−2Pa.

The obtained magnetic layers both have the corresponding alloy composition,
Both have O/(Co+N1)=Q,2.(atomic ratio), and are inclined by about 40" with respect to the normal to the main surface of the substrate, with a minor axis of 0.
It was an aggregate of columnar crystal grains that grew over the entire thickness direction of 01-.

In addition, when performing Auger spectroscopy analysis while performing ion milling, it was found that CO was low near the surface, O was chemically shifted, and there was a profile where it was large near the surface, with 0 bonding with metal on the surface of columnar particles. It was confirmed that it existed in this state.

Next, on the above magnetic layers of AO and BO, various phosphoric acid esters were used as evaporation sources in an atmosphere of FA = 4 x 10-3 Pa, and the substrate-to-substrate hearth spacing and substrate temperature were changed, and 100 layers were deposited. Sample Al-A1 was prepared by forming the top coat film shown in 1.
3 and B1-B2 were obtained.

In addition, aldehyde samples were obtained by vapor deposition of aldehydes. Note that the top coat film composition and composition ratio were determined by solvent extraction after vapor deposition in a model experiment, and by gas chromatography.

Each of these samples had the following back coat layer on the back surface of the substrate.

Parts by weight Zinc oxide 80 ■#L 200 Hardening agent Coronate L 20 Lubricant Stearic acid-modified silicone 4 Butyl stearate 2 Nitrified cotton 40 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (
A mixture of 250 parts by weight of S-LEC A) 30 polyurethane elastomer 30 (B, Erasene 5703, manufactured by F Gutdrich) mixed solvent (MIBK/) luene, manufactured by Building Block Chemical Co., Ltd., is thoroughly mixed and dissolved.

This paint was applied onto the substrate, the solvent was dried using an infrared lamp or hot air, and after surface smoothing treatment, the roll was kept in an oven maintained at 80°C for 48 hours to promote the crosslinking reaction by incyanate. Ta.

The following measurements were performed for each of these samples.

l) The dynamic friction coefficient of the running friction sample was measured at 40°C and 80% relative humidity initially and after 50 passes.

The measuring pin is made of stainless steel with a surface roughness of 0.01.
A tape having a diameter of less than μ and 2■■φ was used, the angle of the tape to the pin was 180'', and the tension (T1) at the entrance of the tape was 20 g/12.5 layers.

? ) Adhesive After cutting each sample into 1 m length, wrap it around a 5mmφ glass tube with a load of Ikg, fix it, and heat it at 40℃ for 8 hours.
It was stored at 0% for 24 hours.

After that, the sample was peeled off and the adhesion on the front and back sides of the tape was observed.

The evaluation was in four stages: Olo, Δ, and ×.

These results are shown in Table 1.

From the results shown in Table 1, the effect of the present invention is clear.

In other words, it can be seen that the sample of the present invention exhibits extremely little adhesion.

Claims (13)

[Claims] (1) A magnetic recording medium having a continuous thin magnetic layer on a substrate and a top coat film on the magnetic layer, wherein the top coat film is a compound represented by the following formula CI),
A magnetic recording medium comprising a compound represented by the following formula (n). Formula CI) RIOOYl \ / / \ o oy2 Formula (11) %Formula% (Formula CI) and (II), R1 represents an alkyl group having 1θ to 22 carbon atoms, and Yl and Y2 are each, It represents hydrogen, an alkyl group, or a metal or onium cation, but yi and Y2 may be combined with each other to form a divalent cation, and R2 represents an alkyl group having 9 to 21 carbon atoms.) (2) The magnetic recording medium according to claim 1, wherein the alkyl groups represented by R1 and R2 are linear. (3) The magnetic recording medium according to claim 1 or 2, wherein the top coat film is a film formed by vapor phase deposition. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein the top coat film has a thickness of 300 Å or less. (5) The magnetic layer is COI or Co and Ni. The magnetic recording medium according to any one of claims 1 to 4, containing one to three of Cr and 0. (6) The magnetic recording medium according to claim 5, wherein the magnetic layer contains Ni and has a Co/Ni weight ratio of 1.5 or more. (7) The magnetic layer contains Cr, Cr/(Co or Co
The magnetic recording medium according to claim 5 or 6, wherein the weight ratio of +Ni) is not more than o,1. (8) The magnetic layer contains O, O/(Co or Co+N
The magnetic recording medium according to any one of claims 5 to 7, wherein the atomic ratio of i) is 0.5 or less. (9) Claims 1 to 8, wherein the magnetic layer is an aggregate of grains with a columnar crystal structure tilted with respect to the normal to the substrate.
The magnetic recording medium according to any one of paragraphs. (10) The magnetic recording medium according to any one of claims 1 to 9, wherein the magnetic layer has a thickness of 0.05 to 0.5. (11) A magnetic recording medium having a continuous thin magnetic layer on a substrate and a top coat film on the magnetic layer, the top coat film comprising a compound represented by the following formula (I),
One of a compound represented by the following formula (II), a compound represented by the following formula (m), a compound represented by the following formula (IV), and an unsaturated chain hydrocarbon having 10 to 22 carbon atoms.
A magnetic recording medium comprising at least one species. Formula (I) Formula [II) 2 CHO Formula (m) R3C0OH Formula (IV) aOH (Formula CI) (II) In (m) and (rV), R1 represents an alkyl group having 10 to 22 carbon atoms. In the following, Yl and Y2 each represent hydrogen, an alkyl group, or a metal or onium cation, but Yl and Y2 may be combined with each other to form a divalent cation, and R2 and R3 are each a carbon atom. represents an alkyl group having 9 to 21 carbon atoms, and R4 represents an alkyl group having 10 to 22 carbon atoms.) (12) The magnetic recording medium according to claim 11, wherein the alkyl group and unsaturated chain hydrocarbon represented by RI R2R3 and R4 are linear. (13)) The magnetic recording medium according to claim 11 or 12, wherein the tube coat film is a film formed by vapor phase deposition.