JPS60133530A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve windability, S/N, etc. by providing an intermediate layer contg. polyester polyol having plural (meth)acryloyl groups in one molecule at the intermediate of a nonmagnetic base having specific surface roughness and a nonmagnetic base and curing the layer by radiations. CONSTITUTION:An intermediate layer contg. polyester polyol having >=0.01mu surface roughness is easily obtd. by irradiating radiations, i.e., electron rays, UV rays, etc. to said layer and polymerizing and curing the same. A magnetic layer is formed on the intermediate layer by depositing a thin ferromagnetic metallic film by evaporation or a method for coating a material contg. ferromagnetic powder and binder on said layer. The magnetic recording medium having good runnability and winding style and excellent S/N and C/N is thus obtd.

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 suitable for high-density recording.

[Prior art]

In recent years, in magnetic recording media for high-density recording, which has been developed, it is necessary to improve the surface properties of the magnetic layer in order to reduce the so-called gap loss between the magnetic head and the magnetic tape. required. For this purpose, the manufacturing technology of the magnetic layer is used.

That is, it is necessary to improve the surface properties of the magnetic layer by improving techniques such as dispersion of magnetic particles, coating, and surface molding, and it is also necessary to improve the surface properties of the support. (As the recording density increases, the recording wavelength becomes smaller, and attempts have been made to make the magnetic layer thinner in order to avoid thickness loss. As a result, the surface properties of the support become more magnetic. The influence on the superficiality of the layer is becoming increasingly important.

However, there are limits to improving the surface properties of supports used in magnetic recording media for the following reasons. In other words, in the process of forming and winding a film, if the surface of the film is good, the frictional resistance against the conveyance rollers will be significant, often causing meandering or wrinkles. Furthermore, the frictional resistance between the films increases and the shape of the take-up roll may become distorted.

Various attempts have been made to solve the above-mentioned contradictory problems. For example, Tokkaku 53-10
Publication No. 9605 describes a method in which fine particles of a thermoplastic resin are made to protrude on a support, and after being wound up, the resin is dissolved and removed using a solvent during formation of a magnetic layer. However, this method not only requires a step of dissolving and removing the material, but also does not provide satisfactory characteristics as a magnetic recording medium for high-density recording.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a magnetic recording medium suitable for high-density recording.

Another object of the present invention is to provide a magnetic recording medium with excellent S/N or C/N.

Still another object of the present invention is to provide a magnetic recording medium having an intermediate layer having high adhesion to a nonmagnetic support.

Another object of the present invention is to provide a magnetic recording medium having an intermediate layer with excellent coating suitability.

Still another object of the present invention is to provide a magnetic recording medium with excellent durability.

[Structure of the invention]

The present inventors have achieved the above object (as a result of intensive study,
Surface roughness Rα) is 0.01 μm (cutoff 0.2
A polyester polyol (hereinafter referred to as polyester acrylate) having two or more acryloyl groups or methacryloyl groups in the molecule is contained between the non-magnetic support and the magnetic layer, and is polymerized and cured by radiation irradiation. The present invention was based on the discovery that the above objects can be achieved and significant effects can be obtained by providing an intermediate layer.

That is, the present invention is characterized in that an intermediate layer containing polyester acrylate is provided between a nonmagnetic support having a surface roughness of 0.01μ or more and a magnetic layer, and the intermediate layer is irradiated with radiation. It is a magnetic recording medium.

Further, in particular, in the magnetic recording medium of the present invention, it is preferable that the surface roughness of the intermediate layer is not more than "-o, oi .mu.m.

The present invention will be explained in detail below.

Although it is possible to use a non-magnetic support used in the present invention with different surface roughness for the front and back sides, the preparation of such a support requires advanced technology and also reduces production efficiency. low. Therefore, in the present invention, the main object of application is a support prepared to have the same surface roughness on both the front and back surfaces, but the scope of the present invention is not limited to this.

Supports used in the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene: cellulose triacetate, cellulose diacetate, cellulose acetate notylate, and cellulose acetate propionate. Cellulose derivatives such as:
Vinyl resins such as polyvinyl chloride and polyvinylidene chloride: In addition to plastics such as polycarbonate, polyimide, and polyamideimide, aluminum, copper, tin, zinc, or non-magnetic alloys containing these, and non-ferrous copper, etc. Non-magnetic metal @: paper, baryta or polyethylene,
Paper coated or laminated with α-polyolefins having 2 to 1 carbon atoms, such as polypropylene and ethylene-butene copolymers.

The surface roughness in the present invention refers to JIS-BO
The cutoff value is 0.25 mm.

The surface roughness of the support used in the present invention is o, oiμm
−0.5 μ7n, and < ni o, oz s l1
It is preferable that it is more than m.

A so-called back layer can be provided on the back surface of the support for the purpose of improving running properties and the like. In this case, the surface roughness of the back layer should be o, oi μm or more, preferably 0.01 μm or more.
The effects of the present invention can be similarly exhibited by setting the thickness to 5 μm or more.

The polyester acrylate used in the intermediate layer of the present invention is a polyester polyol (including polyester polyol) composed of a polyhydric alcohol and a polybasic acid, a polyester polyol produced by polymerization of lactone rings or self-condensation of an OH group-containing carboxylic acid, etc. 0H groups are modified with acrylate or methacrylate. Specifically, the polyhydric alcohols include ethylene glycol, propylene glycol butanediol, pentanediol neopentyl licorol/l/, hesandiol, ophronediol, and cyclohexane 1,4
-diol, cyclohexane 1,4-dimetatool, diethylene glycol, triethylene glycol, glycerin, trimethylolpronoξone, pentaerythritol, dipentaerythritol, etc., or mixtures thereof; polybasic acids include fumaric acid, maleic acid, Polyester polyols consisting of succinic acid, adipic acid, sebacic acid, fucuric acid, isophthalic acid, terephthalic acid, cyclohexane-1,4-dicarboxylic acid, etc., 42 such as γ-butyrolactone, hydroxybutyric acid, hydroxyvaleric acid, 4-hydroxybenzoic acid, etc. Examples include compounds obtained by modifying acryloyl or methacryloyl polyester polyols in which the terminal C02H group of a realester is modified into an OH group.

The preferred molecular weight of polyester acrylates is 300
or more, preferably 500 or more.

5.000 or less.

According to the present invention, when a polyester acrylate is provided on a support and irradiated with radiation to polymerize and harden it to form an intermediate layer, an intermediate layer with good adhesion to the support can be obtained, and the surface roughness is zero. Even if a support with a surface roughness of .01 μm or more is used (supports with such surface roughness are preferred for winding operations during film formation), an intermediate layer with good surface properties (for example, one surface roughness of 0.01 μm or less) can be formed. can.

Therefore, the surface properties of the magnetic layer formed thereon can be significantly improved. Furthermore, when the intermediate layer according to the present invention is provided, the coatability of the magnetic layer is also improved, and together with the above-mentioned surface properties, it is possible to obtain a magnetic recording medium that has excellent durability and is particularly suitable for high-density recording. can.

In the intermediate layer of the present invention, thermoplastic resins such as vinyl chloride-vinylidene chloride resin, urethane resin, acrylonitrile butadiene resin, vinyl chloride-vinyl acetate copolymer, cellulose resin, acetal resin, etc. can be used with urethane acrylates.

The radiation used in the present invention is an electron beam and ultraviolet radiation. When using ultraviolet light, it is preferred to add a sensitizer to the above compound. Examples of the sensitizer include, but are not limited to, 254, 313, 35, which produce luminous powder particles from mercury lamps commonly used as ultraviolet irradiation light sources.
It is preferable that the odor at the wavelength of 5TLm has a relatively thick extinction coefficient.

Typical examples include acetophenone, benzophenone, vanzoin ethyl ether, benzylethyl ketal, benzylethyl ketal, vanzoin imptyl ketone, human 80 xydimethyl phenyl ketone, 1-human 8
0xycyclohexylphenylketone, 2-2:) Ethoxyacetophenone.

Aromatic ketones such as Mitchell ketone can be used.

The mixing ratio of the sensitizer is 0.5 to 100 parts by weight of the compound.
~20 parts by weight, preferably 2 to 15 parts by weight, 2I-1π
Fresh L is a 3 to 10-heavy part.

When the intermediate layer is coated on a support, organic solvents such as organic solvents can be used as necessary. When the intermediate layer coating liquid is a liquid, it may be solvent-free. Organic solvents that can be used include ketones such as acetone, methyl ethyl ketone, methyl isomethyl ketone, and cyclohexanone; alcohols such as methanol, efnol, propatool, and butanol; methyl acetate, ethyl acetate, methyl acetate, ethyl lactate, and glycol monoacetate. Ester systems such as ethyl ether; ether,
glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.; glycol ethers such as benzene, toluene, xylene, etc. (aromatic hydrocarbons); methylene chloride, ethylene chloride, carbon tetrachloride-chloroform, ethylene chlorhydrin, Examples include dichlorobenzene.

The thickness of the intermediate layer is preferably 0.1 to 2 μm as measured after polymerization and curing by radiation irradiation, and the surface roughness is preferably 0.01 μm or less. For this purpose, one effective means is to keep the viscosity low by adding a relatively low viscosity compound or an organic solvent to provide a so-called leveling effect during coating.

The polyester acrylate used for the intermediate layer of the present invention has a low viscosity, so it is easy to apply a thin layer as described above, and the surface roughness of the intermediate layer can be smoothed by the leveling effect. It has the characteristics of being able to provide a magnetic recording medium with good properties and durability.

As the electron beam accelerator, a scanning method, a double scanning method, or a curtain beam method can be adopted, but the curtain beam method is preferable because it is relatively inexpensive and can provide a large output. As for the electron beam characteristics, the accelerating voltage is 1
0 to 10,001 (V, preferably 50 to 300 kV, and the absorbed dose is 0.5 to 20 megarads F, preferably 1 to 10 megarads. If the accelerating voltage is 10 kV or less, the amount of energy transmitted is insufficient. 1000k
If it exceeds V, the energy efficiency used for polymerization decreases and is not economical.

If the absorbed dose is less than 0.5 megarads, the curing reaction will be insufficient, and if it exceeds 20 megarads, the energy efficiency used for curing will decrease, the irradiated object will generate heat, and especially the plastic support will deform, so it is preferable. do not have.

The magnetic layer provided on the polymerized hardened layer of the present invention may be mainly composed of ferromagnetic powder and a binder, or may be a magnetic metal thin film.

The method for forming the magnetic metal thin film applied to the present invention may be a method of forming the film in a vacuum chamber or a plating method, and the following methods may be used: A method of forming a film in a vacuum chamber is preferred, since it has advantages such as not requiring any treatment. A method of forming a film in a vacuum chamber is a method in which the substance or its compound to be deposited is deposited as vapor or ionized vapor on a substrate in a dilute gas or vacuum space, such as vacuum evaporation method or sputtering. This corresponds to the method, ion blating method, chemical vapor phase plating method, etc.

Further, in the present invention, the ferromagnetic metal layer to be the magnetic recording layer may be iron, cobalt, nickel or other ferromagnetic metals, or Fe-Go-Ft-Ni, Go-Ni, F.
e-8i, Fe-RA, Go-P, Go-B,
Go-8i, Go-V%Go-Y, Go-La, G
o-Cue, C1)-Pr, Go-3m.

C(+-Pt, Go-tJrL, Fe-Go-Ni
, Go-Ni-P, Go-Ni-B-Go-Ni-
Ay-Go-Ni-Na, C(+ -Ni-Cg, G
o -Ni-Zn, Go-Ni-Gu-Go -Ni
-W, Go-Ni-Re.

A ferromagnetic alloy such as Go-8m-Gw is formed into a thin film by forming a film in a vacuum chamber or by a plating method, and the film thickness is 0.03 μm to 2 μm when used as a magnetic recording medium. range, especially 0.07μm~
0.4 μm is preferred.

Ferromagnetic powder and various additives used in the magnetic layer of the present invention,
For details on organic solvents, dispersion, coating methods, etc., see JP-A Nos. 52-108,804 and 54-21,804.
No. 54-46,011, and can be applied to the present invention as necessary.

〔Example〕

The present invention will be explained in more detail below using Examples.

In the examples, "parts" indicate parts by weight.

Example 1 Aronix M6100 manufactured by Toagosei Co., Ltd. (molecular weight 1
000 polyester diacrylate) was coated, and electron beam irradiation was performed at an acceleration voltage of 165 kV and a beam current of 577 LA with an absorbed dose of 2 Mrad.

The surface roughness of the support is 0.101 μm, and the coating layer thickness is 0.5 μm.

A magnetic coating liquid having the following composition was mixed and dispersed in a ball mill for 10 hours.

After dispersion, the trimethylol tetrapane adduct of the triisocyanate compound (about 760 molecules, N, CO content 13.3
wt%, product name: Bayer A, G. A 75 wt% ethyl acetate solution of “Desmodur L-75J” manufactured by
A magnetic coating solution was prepared by adding a portion of the mixture and dispersing it under high-speed shearing for 1 hour.

The obtained coating liquid was applied to the upper side of the layer so that the thickness after drying was 4 μm.
It was painted so that Then, it was oriented in a DC magnetic field and dried by blowing hot air at 100°C. After drying, it was calendered and slit into 1/2 inch width to obtain video magnetic tape sample J461.

Comparative Example 1 Magnetic tape sample/162 was obtained in the same manner as in Example 1 except that the intermediate layer was not applied.

Example 2 In Example 1, a coating liquid with the following composition was prepared instead of Aronix M6100, and after coating, it was heated with a mercury lamp of soW/α for 1
UV rays were irradiated for seconds.

polyester diacrylate Inzophenone Part 5 The thickness after polymerization and curing was 0.5 μm.

Otherwise, magnetic tape sample/163 was prepared in the same manner as in Example 1.
I got it.

Example 3 A magnetic tape sample/I64 was obtained in the same manner as in Example 1 except that a polyethylene terephthalate support having a surface roughness of 0.015 μm was used.

Comparative Example 2 Mistape Sample/165 was obtained in the same manner as in Comparative Example 1 except that a polyethylene terephthalate support with a surface roughness of 0.015 μm was used.

Example 4 Magnetic tape sample A6.6 was obtained in the same manner as in Example 1 except that a polyethylene terephthalate support having a surface roughness of 0.020 μm was used in Example 1.

Comparative Example 3 Magnetic tape sample 167 was obtained in the same manner as in Comparative Example 1 except that a polyethylene terephthalate support with a surface roughness of 0.020 μm was used.

Example 5 An intermediate layer was provided in the same manner as in Example 1. A C0-Ni (Ni; 2Q wt%) magnetic film was provided on the layer by oblique vapor deposition to a thickness of 100 OA to obtain a magnetic tape sample/168.

Comparative Example 4 In Example 5, the intermediate layer was not coated, and the rest was the same as in Example 1, but the coating was similar to that of Example 1. Example 6 Polyethylene terephthalate with a surface roughness of 0.020 μm and a thickness of 1511 m. Aronix M6 of Example 1 on top of
Example 1 Using polyester diacrylate (a diacrylate compound of polyester diol of ethylene glycol and adipic acid, molecular weight approximately 500) in place of 100
A magnetic sample tape AIO was prepared in the same manner as above.

Comparative Example 5 Aronix M61 of Example 1 was placed on polyethylene terephthalate with a surface roughness of 0.015 μm and a thickness of 15 μm.
00 was replaced with polyester monoacrylate (monoacrylate compound of polyester diol of ethylene glycol and adipic acid, molecular weight approximately 500-), and treated in the same manner as in Example 1, magnetic sample tape/16],
1 'j was created.

Video sensitivity and C/N were measured for the above samples. An outline of the measurement method is shown below.

Video sensitivity: The playback output at 4MH2 was measured using a VE (S method VTR (manufactured by Matsushita Electric Corporation, trade name: NV-8800J).

07N: 3 MHz and 3.5 MHz carrier wave (
The ratio of carrier to noise (corresponding to S/N) when the carrier was recorded and reproduced was measured using Comparative Example 1 as a standard (±0 cLB).

The results are shown in the table.

〔Effect of the invention〕

As is clear from the table, the surface roughness of the support is 0.01
It has been found that an improved magnetic recording medium can be obtained by providing an intermediate layer containing polyester acrylate between the support and the magnetic layer.

(3 others) 4. 7゜8゜Procedural Amendment February 1980 J,, 11-1 1988 Patent Application No. 241051 Name of the invention Relationship to the magnetic recording medium amendment case ゛Patent application Person Name (520) Fuji Photo Film Co., Ltd. Kasumigaseki Building Post Office PO Box No. 49 Eiko Patent Office Telephone (581)-9601 (Representative) Subject of Amendment Contents of Amendment to ``Detailed Description of the Invention'' The text in "Detailed Explanation" has been corrected as follows.

. 1) In the 12th line of the 4th line of the detailed text, ``Atta 1,'' is corrected to ``Attata.''

2) On page 7, lines 1 and 2, "change" is corrected to "denaturation."

6. On page 8, line 6 from the bottom, "durable" is corrected to "durable".

4) On page 9, line 9, ``Oiga'' is amended to ``'S-ite''.

5) Same page 14, line 8, [0°01μmJ is “0.0
10 μm”. 1 6) Direction Page 19, line 1, add [Comparative Example 1 (Sample Store 2) as reference (±0 dI3)] after "Reproduction output". .

7) Same page 20, front A, “Surface roughness of support fi
rrL) J column, [Sample A I Km, A, 2
Jim,) 3 grabs, late column 8, machine 9 Kusunoki J's "υ, 01"
Correct it as "mouth, 010.J.

that's all

Claims (2)

[Claims] (1) An intermediate layer containing a polyester polyol having two or more acryloyl groups or methacryloyl groups in the molecule is provided between the nonmagnetic support having a surface roughness of 0.01 μm or more and the magnetic layer, and the layer is exposed to radiation. A magnetic recording medium characterized by being irradiated. (2) The magnetic recording medium according to claim (1), wherein the intermediate layer has a surface roughness of 0.01 μm or less.