JPS60150227A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled medium having excellent video characteristics and S/N, C/N by regulating the viscosity of a nonmagnetic layer, when radiant ray are irradiated, to a value lower than a specified value in the magnetic recording medium whose nonmagnetic layer is irradiated with rays. CONSTITUTION:Polyesters, polyolefins, nonmagnetic metals such as zinc, a nonmagnetic alloy contg. zinc, and stainless steel in accordance with uses, paper, or the paper coated or laminated with baryta or polyolefins having 2-10C such as polyethylene, polypropylene, and an ethylene-butene copolymer are used as a supporting body. The surface roughness of the supporting body to be used is regulated to >=0.01mum. A compd. having >=1 unsaturated carbon-carbon bond in one molecule is used as the compd. which is used as the intermediate layer and can be polymerized with the irradiation of rays, and acrylic esters, etc. can be exemplified. The viscosity before curing of the layer contg. the compd. which is polymerizable with the irradiation of rays is regulated to <=300cp, or preferably <=100cp. The viscosity is the viscosity before curing, namely before the rays are irradiated.

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 magnetic recording media for high-density recording, which has been developed in recent years, 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. be done. For this purpose, the manufacturing technology of the magnetic layer, i.e. dispersion of magnetic particles, coating,
At the same time, it is necessary to improve the surface properties of the magnetic layer by improving surface molding techniques, etc., and it is also necessary to improve the surface properties of the support. In particular, as the recording density increases, the recording wavelength decreases, so the thickness ^
Attempts have been made to make the magnetic layer thinner to avoid losses. As a result, the influence of the surface properties of the support on the surface properties of the magnetic layer is becoming increasingly large.

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 film forming and winding process, if the surface of the film is good, the frictional resistance against the conveyance roller will be large, 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, JP-A-53-1
Publication No. 09605 describes a method in which fine particles of a thermoplastic resin are made to protrude on a support, and then dissolved and removed with a solvent to form a magnetic layer on the surface thereof. However, this method has not yet been able to provide satisfactory characteristics as a magnetic recording medium for high-density recording.

Further, Japanese Patent Application No. 58-187519 describes that a radiation-polymerizable layer is provided on the magnetic layer side of a rough support to obtain a smooth surface by irradiation with radiation. As a result of further intensive research, the inventors of the present invention discovered a magnetic recording medium that has even higher characteristics than the above-mentioned invention.

[Purpose of the invention]

The first object of the present invention is to provide a magnetic recording medium with excellent video characteristics. Second, there is K, which provides magnetic recording media with excellent S/N and C/N.

[Structure of the invention]

As a result of intensive study by the present inventors to achieve the above object,
We found the following.

A smooth surface can be obtained by coating a layer containing a radiation-polymerizable compound between the support and the magnetic layer, which has a surface roughness of 0, io io μm or more, and curing it by irradiation with radiation. However, it has been found that the smoothness is highly dependent on the viscosity of the layer before curing, ie, before irradiation. In other words, this means that if the coating liquid has a low viscosity of 300 cp (centipoise) or less, the self-leveling effect will be large, and the fine coating streaks and uneven coating that occur when applying the polymerized hardened layer will be greater. It is presumed that this is because a smooth polymerized and cured layer was obtained. However, in the case of a layer of 300 Cp or more, it takes time for coating streaks and uneven coating to disappear.
It has been found that in a practical process, the coating is hardened by irradiation with coating streaks and uneven coating remaining, which does not improve smoothness. As a result, they discovered that by limiting the viscosity to 30007) or less, the electromagnetic characteristics could be improved and an extremely good magnetic recording medium could be produced.

That is, in the present invention, a nonmagnetic layer containing a compound that can be polymerized by radiation irradiation is provided between a nonmagnetic support having a surface roughness of 0, 0 ioμ or more and a magnetic layer, and the layer is irradiated with radiation. The present invention is a magnetic recording medium characterized in that the viscosity of the layer when irradiated with radiation is 3000p or less.

Although it is possible to prepare the surface roughness of the nonmagnetic support used in the present invention to be different 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.

The supports used in the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-7-talate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, cellulose acetate notylate, and cellulose acetate propylene Cellulose derivatives such as pionate;
Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; in addition to plastics such as polycarbonate, polyimide, and polyamideimide, aluminum, copper,
Non-magnetic metals such as tin, zinc or non-magnetic alloys containing these, and rust-free copper; paper 1.6 lighter or polyethylene;
These include papers coated or laminated with α-polyolefins having 2 to 10 carbon atoms, such as polypropylene and ethylene-butene copolymers.

The surface roughness in the present invention refers to the center line average roughness defined in Section 5 of JIS-BO601, and the cutoff value is 0.25 mx.

The surface roughness of the support used in the present invention is 0.010
It is more than μm.

A so-called double layer can be provided on the back side of the support for the purpose of improving running properties and the like.

The compound polymerizable by radiation irradiation used in the intermediate layer of the present invention is a compound having one or more carbon-carbon unsaturated bonds in the molecule, and includes acrylic esters, acrylamides, methacrylic esters, and methacrylamide. ,
Allyl compounds, vinyl ethers, vinyl esters,
Hinyl heterocyclic compounds, N-vinyl compounds, styrenes,
Examples include croton Fa, itaconic acids, olefins, and olefins. Among these, acryloyl group or methacryloyl group is preferable.
Examples include the following compounds containing at least 1. diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate~),
)! J Acrylates such as methylolpropane triacrylate, pentaerythritol tetraacrylate, methacrylates such as diethylene glycol dimethacrylate, triethylene glycol trimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpronocentrimethacrylate, pentaerythritol tetramethacrylate, or other Esters of bifunctional or higher functional polyols and acrylic acid/methacrylic acid, etc.

Moreover, these compounds may be of high molecular weight. Preferably, it is a compound having an ester bond with acrylic acid or methacrylic acid at the end of the main chain or in the side chain of the polymer;
pec CorLgres,? -1119 (1972)
quoted in. For example, the polyester skeleton of the compound shown below may be a polyurethane skeleton, an epoxy resin skeleton, a polyether skeleton, a polycarbonate skeleton, or a mixture thereof. The molecular weight is preferably 1.000 to 20,000, but is not particularly limited.

The above-mentioned compounds that can be polymerized by radiation irradiation can be used alone or in combination in any proportion.

Furthermore, vinyl chloride-vinylidene chloride-based copolymers, cellulose resins, acetal-based resins, vinyl chloride-vinylidene chloride-based resins, urethane resins,
A thermoplastic resin such as acrylonitrile butadiene resin can be used in combination with the compound polymerizable by radiation irradiation, if necessary.

The radiation used in the present invention is an electron beam and ultraviolet radiation. When using ultraviolet light, it is necessary to add a photopolymerization initiator to the above-mentioned compound.

Aromatic ketones are used as photopolymerization initiators.

The aromatic ketone is not particularly limited, but one preferably has a relatively large extinction coefficient at a wavelength of 254.313.365 nm, which produces the bright line spectrum of a mercury lamp commonly used as an ultraviolet irradiation light source.

Representative examples include acetophenone, benzophenone, indiyne ethyl ether, benzyl methyl ketal, benzyl ethyl ketal, benzoin isobutyl ketone, hydroxydimethylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 2-2 diethoxyacetophenone, There are Michl=r's ketones, etc.
A variety of aromatic ketones can be used.

The mixing ratio of the aromatic ketone is 0.5 to 2.0 parts by weight, preferably 2 to 15 parts by weight, and more preferably 3 to 10 parts by weight per 100 parts by weight of compound (α). - The layer containing the compound that can be polymerized by radiation irradiation preferably has a viscosity of 3000p or less before curing, more preferably io 0 cp or less.

The above viscosity is the viscosity before curing, that is, before irradiation with radiation. If the layer has a high viscosity at room temperature, it is possible to reduce the viscosity to the above range by heating.

The thickness of the coating layer is preferably 0.1 to 2 μm as measured after polymerization and curing by radiation irradiation.

The surface roughness of the layer is preferably 0.010 μm or less.

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 1,000 kV, preferably 50 to 300 kV, and the absorbed dose is 0.5 to 20 megarads, preferably 1 to 10 megarads.9 If the accelerating voltage is less than 10 AV, the amount of energy transmitted is insufficient and the amount of energy transmitted is 10,001 V.
If it exceeds 100%, the efficiency of energy used for polymerization decreases and is not economical.

If the absorbed dose is less than 0.5 Mt9, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained; if it exceeds 20 Md, the energy efficiency used for curing will decrease, the irradiated object will generate heat, and especially This is not preferred because the plastic support will be deformed.

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 as a substrate in a dilute gas or vacuum space. , e-Tuttering method, ion blating method, chemical vapor phase plating method, etc. correspond to this method.

Furthermore, 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-(E(1, Fe-Ni).

Co-Ni Fa-E3i Fg-Yih Go-P
Go -BGo-8i Go -V Go -Y Go
-La C1)-CjgGo-Pr Go-8771C
o-Pt Go-Mn Ft-Co-NiCjo-Ni
-P, Go-Ni-B, Go-N number-Ay, Ca
-N number-Nα.

Co-Ni-0a, Go-Ni-Zn, CCo-N
1-C,co-Ni-W.

(A ferromagnetic alloy such as 36-Ni-Rg or Go-8m-Cm is formed into a thin film by forming a film in a vacuum chamber or by plating, and the thickness of the film is determined by the thickness required for use as a magnetic recording medium. In this case, it is in the range of 0.05 μm to 2 μm, and preferably 1 μm to 0.4 μm.

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-52-108,804 and JP-A-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, "1 part" indicates parts by weight.

Example 1 Diethylene glycol diacrylate was coated on a polyethylene terephthalate support having a thickness of 14.5 μm, and irradiated with an electron beam at an accelerating voltage of 100 kV, a current of 5 F+1 A, and a radiation dose of 5 Mγαd.

The surface roughness of the back surface of the support is 0.010 μm,
The coating layer thickness is 0.5 μm.

The viscosity of diethylene glycol diacrylate at 25°C was 23 Cp.

- Cross-dispersion was carried out for 10 hours using a magnetic coating liquid with the following composition in a ball mill.

After dispersion, the trimethylolprocene adduct of the triisocyanate compound (molecular 760, NCO content 13.3
u+t%, trade name:)zinyl A, manufactured by G0 Co., Ltd. 1゛Desmodule L-75J) (7) 22 parts of a 75 wt% ethyl acetate solution was added and dispersed under high speed shearing for 1 hour to prepare a magnetic coating liquid. The obtained coating liquid was applied on the upper side of the layer so that the thickness after drying was 4 μm. 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/161.

Example 2゜In Example 1, a coating liquid with the following composition was prepared in place of diethylene glycol diacrylate, and after coating it was 80W/c.
It was irradiated for 1 second with a wL mercury lamp.

The viscosity of the above coating liquid at 25°C was 36CP.

The thickness after polymerization and curing was 0.5μ.

Otherwise, magnetic tape sample/i62 was prepared in the same manner as in Example 1.
I got it.

Example 3 Magnetic tape sample/163 was obtained in the same manner as in Example 1 except that nonaethylene glycol diacrylate (viscosity at 25°C: 100 ep) was used as diethylene glycol diacrylate in Example 1.

Example 4 In Example 1, diethylene glycol diacrylate was replaced with heptadecaethylene glycol diacrylate (25
Magnetic tape sample No. 4 was obtained in the same manner as in Example 1 except that the viscosity at °C was 270 Cp.

Comparative Example 1 In Example 1, diethylene glycol diacrylate was replaced with eicosaethylene glycol diacrylate (25°C
A magnetic tape sample 5 was obtained in the same manner as in Example 1 except that the viscosity was 320 Cp.

Comparative Example 2 Magnetic tape sample 6 was obtained in the same manner as in Example 1, except that diethylene glycol diacrylate was replaced with tetracosa glycol diacrylate (viscosity at 25° C.: 430 Cp).

Ta.

Comparative Example 3 Magnetic tape sample No. 7 was obtained in the same manner as in Example 1 except that the radiation polymerized cured layer was not applied and the radiation was not irradiated.

Example 5 Magnetic tape sample No. 8 was obtained in the same manner as in Example 1 except that a polyethylene terephthalate support having a back surface roughness of 0.030 μm was used.

Comparative Example 4 Magnetic tape sample No. 9 was obtained in the same manner as in Comparative Example 3 except that a polyethylene terephthalate support with a back surface roughness of 0.030 μm was used.

Example 6 A radiation-cured layer 1 was provided in the same manner as in Example 1. Co-Ni (Ni; 20wt
%) A magnetic film was provided to have a thickness of 100 OA, and magnetic tape sample 10 was obtained.

Comparative Example 5 Magnetic tape sample All was obtained in the same manner as in Example 5, except that the radiation polymerization cured layer was not applied and the radiation was not irradiated.

The surface roughness of the radiation polymerized layer, visual video sensitivity of the magnetic layer, and C/N of the above samples were measured. An outline of the measurement method is shown below.

Video sensitivity: The playback output at 4 MHz was measured using a VH8 type VTR (manufactured by Matsushita Electric Corporation, trade name [Nv-asooJ)].

C/N: Carrier waves (carriers) of 3 MHz and 3.5 MHz were recorded, and the ratio of carrier to noise (corresponding to S/H) when reproduced was measured using Comparative Example 1 as a standard (±odB).

The results are shown in the table below.

〔Effect of the invention〕

As is clear from the table, the surface roughness of the support is 0.01
0 μm or more, and the viscosity of the radiation-polymerized layer between the support and the magnetic layer before radiation irradiation is 3000p or less, whereby a magnetic recording medium with significantly improved video sensitivity and G/N can be obtained. Recognize.

Procedural amendment dated June 1989 Patent application No. 5675 Column 2, Name of invention Magnetic recording medium 3, Person making the amendment Relationship to the case: Name of patent applicant (520) Fuji Photo Film Co., Ltd. Kasumigaseki Building Post Office PO Box No. 49 Eikou Patent Office Telephone (581)-9601 (Representative) 1
) Correct as shown in the attached sheet.

2) The "Detailed Description of the Invention" column is amended as follows.

0 specification, page 4, line 1 and line 1 from the bottom, “0.010J
Correct it to 0.01J.

0 specification, page 6, line 16, “0.010J [0,01
Correct it with J.

O Specification, page 10, line 4, "Compound (all '(r
r the above-mentioned compound".

0 page 10 of the specification, line 4 from the bottom, "0.o 10J"
0.01”.

0 page 14 of the specification, line 4 from the bottom, “molecule” is replaced by “molecular weight”
and correct it.

0 page 18, line 10 of the specification, after "reproduction output", "
Insert "with Comparative Example 6 as standard (±OdB)". .

0 page 18 of the specification, line 6 from the bottom, "Comparative Example 1" is corrected to "Comparative Example 6".

Claims A compound that can be polymerized by radiation irradiation is placed between the non-magnetic support having a surface roughness of 0.01 μm or more and the magnetic layer.
In a magnetic recording medium in which a nonmagnetic layer containing a core layer is irradiated with radiation, the viscosity of the nonmagnetic layer is 600 centipoise (cp) or less at the time of radiation irradiation. A magnetic recording medium characterized by the following.

Claims (1)

[Claims] A magnetic recording medium in which a nonmagnetic layer containing a polymerizable compound is provided between a nonmagnetic support having a surface roughness of 0.010 μm or more and a magnetic layer by radiation irradiation, and the layer is irradiated with radiation, A magnetic recording medium characterized in that the viscosity of the nonmagnetic layer is 300 centipoise (CP) or less when irradiated with radiation.