JPH0522968B2 - - Google Patents

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, magnetic recording media for high-density recording have been developed, and in order to reduce the so-called gap loss between the magnetic head and the magnetic tape, the surface properties of the magnetic layer have been improved. required to do so. For this purpose, it is necessary to improve the surface properties of the magnetic layer by improving the manufacturing technology of the magnetic layer, that is, the dispersion of magnetic particles, coating, surface forming technology, etc. At the same time, it is necessary to improve the surface properties of the support. It is also necessary to improve. In particular, as the recording density increases and the recording wavelength decreases, attempts have been made to make the magnetic layer thinner in order to avoid thickness loss. As a result, the influence of the surface properties of the support on the surface properties of the magnetic layer is becoming more and more significant. [Problems to be Solved by the Invention] However, there are limits to improving the surface properties of supports used in magnetic recording media for the following reasons. That is, in the process of forming and winding a film, if the film has good surface properties, the frictional resistance against the conveying 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-53-109605 describes a method in which fine particles of 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. In addition, in Japanese Patent Publication No. 46-14555, a solution of polymers such as polyamide and polyester was coated on a support.
A method is described in which the material is dried to form fine wrinkles and a magnetic layer is formed on the surface thereof. Special Public Service 1977-
6117 uses copolyester etc. as a polymer to be coated on the support, and
For this purpose, we use thermoplastic polyester etc.
Forms minute wrinkles on the surface in the same way as 46-14555,
A method for forming a magnetic layer on the surface is described. However, none of the above four methods has reached the point where it is possible to stably impart satisfactory characteristics as a magnetic recording medium for high-density recording. An object of the present invention is to control the surface roughness of a nonmagnetic support for high-density magnetic recording by stably forming a layer having a required surface roughness on the surface of the support. The surface roughness referred to above refers to the range that can be measured with a normal stylus-type roughness meter to the roughness of minute structures that cannot be measured with a stylus. [Means for Solving the Problems] That is, the present invention provides: 1) A nonmagnetic layer containing a compound that can be polymerized by radiation irradiation and fine particles is provided between the nonmagnetic support and the magnetic layer; The layer is irradiated and has a surface roughness of 0.001 to 0.01 μm. In addition, the surface roughness in the present invention is defined as JIS-
It refers to the center line average roughness defined in Section 5 of B0601, and the cutoff value is 0.25 mm. The present invention will be explained in detail below. 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. Examples include allyl compounds, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrenes, crotonic acids, itaconic acids, olefins, and olefins. Among these, preferred are the following compounds containing two or more acryloyl groups or methacryloyl groups. Acrylates such as diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate,
Methacrylates such as diethylene glycol dimethacrylate, triethylene glycol trimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, or esters of acrylic acid and methacrylic acid with other bifunctional or higher functional polyols, 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 side chain of the polymer, and these are described in A. Vranckem "Fatipec Congress" 11 19 (1972).
quoted in. For example, the following compounds The polyester skeleton of the exemplified compound may be a polyurethane skeleton, an epoxy resin skeleton, a polyether skeleton, a polycarbonate skeleton, or a mixture of these skeletons. The molecular weight is
It 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. In addition, vinyl chloride-vinylidene chloride copolymers, cellulose resins, acetal resins, vinyl chloride-vinylidene chloride resins,
Thermoplastic resins such as urethane resins and acrylonitrile butadiene resins 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 wavelengths of 254, 313, and 365 nm, which produce the bright line spectrum of a mercury lamp commonly used as an ultraviolet irradiation light source. Representative examples include acetophenone, benzophenone, benzoin ethyl ether, benzyl methyl ketal, benzyl ethyl ketal, benzoin isobutyl ketone, hydroxydimethyl phenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-2 diethoxyacetophenone,
Various aromatic ketones can be used, including Michler's ketone. The mixing ratio of the aromatic ketone is 0.5 to 20 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 (a). The fine particles mixed in the intermediate layer of the present invention are spherical or flake-like particles with a diameter of 100 to 5000 Å. The exposed part of the fine particles on the surface of the intermediate layer has a height of 50 to 2000 Å, and the number of exposed particles is 10 ⁶ to 10 ⁹
It is set in the range of pieces/ ^mm2 . The diameter of the above fine particles,
and the exposed particle density are adjusted to a narrower range depending on the application of the magnetic recording medium. There are various materials for fine particles, but they can be broadly divided into:
It can be divided into organic fine particles and inorganic fine particles. As the organic fine particles, those commercially available as organic mat materials such as benzoguanamine formaldehyde and polytetrafluoroethylene can be used.
Inorganic particles are called inorganic powders or abrasives, and the ingredients include α-alumina, γ-alumina, silicon carbide, titanium oxide, magnesium oxide, iron phosphide, titanium carbide, and titanium nitride. , α- and β-silicon oxides, aluminum, calcium oxalate, iron, α-ferrous oxide, zinc, zinc dioxide, nickel oxide, copper nickel, chromia, magnesium hydroxide, zirconia, ittria, ceria, zircon. , antimony oxide, etc. The surface roughness of the above non-magnetic layer is 0.001 to 0.01 μm
and preferably 0.002 to 0.007 μm. When coating a mixture of a compound polymerizable by radiation irradiation, organic or inorganic fine particles, or an aromatic ketone on a support, various organic solvents can be used as necessary. By adjusting the amount of this solvent added, the amount of surface exposure of the fine particles can be adjusted, and therefore the surface roughness can be adjusted. Organic solvents that can be used include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, acetic acid glycol monoethyl ether, etc. ester system; ether,
Glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, and dioxane; Tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform,
Examples include ethylene chlorohydrin and dichlorobenzene. As the electron beam accelerator, a Vandegraaf scanning method, a double scanning method, or a curtain beam method can be employed, 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 10
~1000kV, preferably 50-300kV, and the absorbed dose is 0.5-20 megarads, preferably 1-300kV.
It is 10 megarads. When the accelerating voltage is less than 10 kV, the amount of energy transmitted is insufficient, and when it exceeds 1000 kV, the energy efficiency used for polymerization decreases, making it uneconomical. If the absorbed dose is less than 0.5 megarads, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained.If the absorbed dose is more than 20 megarads, the energy efficiency used for curing will decrease and the irradiated object will generate heat, especially the plastic support. is undesirable because it deforms. 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 butyrate, cellulose acetate propionate, etc. Cellulose derivatives; vinyl resins such as polyvinyl chloride and polyvinylidene chloride;
In addition to plastics such as polycarbonate, polyimide, and polyamideimide, depending on the purpose, aluminum, copper, tin, zinc, non-magnetic alloys containing these, and non-magnetic metals such as non-rusting copper; paper, Paraita, or polyethylene, polypropylene, and ethylene. -Paper coated or laminated with α-polyolefins having 2 to 10 carbon atoms such as butene copolymers. The surface roughness of the nonmagnetic support used in the present invention is preferably equal to or higher than the surface roughness of the intermediate layer. 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 effects of the present invention can be similarly exhibited by setting the surface roughness of the back layer to 0.010 μm or more, preferably 0.015 μm or more. 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 of 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 base material in a dilute gas or vacuum space, such as vacuum evaporation method or sputtering. This corresponds to the method, ion plating method, chemical vapor 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-Co, Fe-Ni, Co.
-Ni, Fe-Si, Fe-Rh, Co-P, Co-B, Co
-Si, Co-V, Co-Y, Co-La, Co-Ce, Co
−Pr, Co−Sm, Co−Pt, Co−Mn, Fe−Co−
Ni, Co-Ni-P, Co-Ni-B, Co-Ni-Ag,
Co−Ni−Na, Co−Ni−Ce, Co−Ni−Zn, Co
−Ni−Cu, Co−Ni−W, Co−Ni−Re, Co−
A ferromagnetic alloy such as Sm-Cu is formed into a thin film by a method of forming a film in a vacuum chamber or a plating method, and the film thickness is in the range of 0.05 μm to 2 μm when used as a magnetic recording medium. and especially 0.1μ
m to 0.4 μm is preferable. [Example] The present invention will be explained in more detail below with reference to Examples. Example 1 On a 14.5μ thick polyethylene terephthalate support, a 0.5μ thick coating liquid of the following composition was kneaded and dispersed in a ball mill for 10 hours, and irradiated with an electron beam with an absorbed dose of 5 Mrad at an accelerating voltage of 160 kV and a beam current of 5 mA. I did this. The surface roughness of the nonmagnetic layer formed as described above was 0.004 [μ]. Γ Coating liquid: A solution having the following composition was kneaded in a ball mill for 5 hours. Diethylene glycol diacrylate 250 parts Tetrafluoroethylene resin powder (particle size approximately 2000Å)
10 parts toluene 100 parts acetone 100 parts Cobalt nickel (Ni;
A ferromagnetic thin film (film thickness 2000 Å) was formed by vapor deposition (so-called oblique vapor deposition) using a continuous vapor deposition machine, and the film was slit into 1/2 inch width to obtain video magnetic tape sample No. 1. Comparative Example 1 Magnetic tape sample No. 2 was obtained in the same manner as in Example 1 except that only diethylene glycol diacrylate was used as the coating liquid. Comparative Example 2 In Example 1, calcium carbide (particle size
Sample No. 3 was obtained in the same manner as in Example 1 except that 10 parts of 8000 Å) were added. Comparative Example 3 Sample No. 4 was obtained by using the base film used in Example 1 as it was without providing a polymerized layer, except for providing a vapor deposited layer in the same manner as in Example 1. For the above samples, video sensitivity, C/N,
and running durability. (VTR used:
(Manufactured by Matsushita Electric, trade name: "NV-8800") Video sensitivity: Playback output at 4 MHz was measured (±0 dB) based on Comparative Example 1. C/N: 3MHz and 3.5MHz carrier waves (carriers) are recorded and the ratio of carrier to noise when played back is based on Comparative Example 1 (±
0dB) was measured. Running durability: After running 100 times, the decrease in output was measured. The results are shown in the table. [Effects of the invention] As is clear from the table, a radiation-irradiated polymer film is provided on the surface of a non-magnetic support, fine particles are contained in the film, and the surface roughness of the polymer film is adjusted within the range of 0.001 to 0.01 μm. However, it can be seen that the magnetic recording medium in which the ferromagnetic layer is provided on the polymer film has a significant improvement in video S/N and durability. 【table】

Claims (1)

[Claims] 1. A nonmagnetic layer containing a radiation-polymerizable compound and fine particles is provided between the nonmagnetic support and the magnetic layer, the layer is irradiated with radiation, and the surface roughness of the layer is 0.001 to 0.001. A magnetic recording medium characterized by being in the range of 0.01 μm.