JPH04167225A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a satisfactory strength even when the recording medium is made thin by a method wherein the undercoating layer contains specific needlelike particles in a resin binder which is hardened by being irradiated with electromagnetic waves such as radiant rays, ultraviolet rays. CONSTITUTION:An undercoating layer 2 which is laid between the surface of a nonmagnetic support body 1 composed of a polyester or the like and a magnetic layer 3 is formed of a material which contains needlelike particles having a needle-shape ratio of larger than 3.0 in a resin binder which is hardened by being irradiated with electromagnetic waves such as radiant rays, ultraviolet rays or the like. A compound containing one or more carbon-carbon unsaturated bonds, e.g. an acrylate compound, a methacrylate compound or the like, is preferable as the resin which is hardened by being irradiated with electromagnetic waves. Thereby, even when the thickness of a magnetic recording medium is made thin, a satisfactory strength is obtained, and a long-hour recording operation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

(Prior Art) As shown in FIG. 1, the general structure of a magnetic tape is that a magnetic layer 3 is formed on one side of a non-magnetic support 1 made of polyester or the like with an undercoat layer 2 made of urethane or the like interposed therebetween. Further, a carbon back coating layer 4 for dissipating static electricity is formed on the surface of the nonmagnetic support 1 opposite to the magnetic layer 3.

(Problem to be solved by the invention) Recently, there has been an increasing demand for long-term recording on magnetic recording media, and for this reason magnetic recording media are being made thinner. Attempts have been made to address this problem by improving the tensile modulus of the support or changing the material, but these efforts have not been sufficiently effective.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an undercoat layer interposed between the surface of a non-magnetic support and a magnetic layer using a resin that is cured by irradiation with electromagnetic waves such as radiation and ultraviolet rays. It was made of a material containing acicular particles having an acicular ratio of more than 3.0 in a binder.

Here, examples of resins that cure by irradiation with electromagnetic waves include compounds having one or more carbon-carbon unsaturated bonds in the molecule;
Examples include cycrylate esters, acrylamides, vinyl ethers, vinyl esters, methacrylate esters, methacrylamides, allyl compounds, styrenes, and olefins, with acrylate compounds and methacrylate compounds being particularly preferred.

The acicular ratio should be greater than 3.0, but the preferred range is 7.0 to 20. A more preferable range for O is 10.0 to 20.0.

(Function) An undercoat paint made by kneading acicular particles in a binder is applied to the surface of a non-magnetic support made of polyester or the like, and this paint is cured by irradiation with radiation, etc., and then an undercoat layer is formed. Apply magnetic paint to the surface.

(Example) Examples and comparative examples of the present invention will be described below by giving specific formulation examples.

[Example 1] An undercoat paint and a magnetic paint having the following compositions are prepared.

(Undercoat paint) a-FeOOH (acicular ratio = 7.0) 60 parts by weight Urethane acrylate 30 parts by weight Methyl ethyl ketone/toluene = 1:1 450 parts by weight (Magnetic paint) Co-7-Fezos magnetic powder 10
0 parts by weight Carbon black 5 parts by weight Vinyl chloride-vinyl acetate copolymer 10 parts by weight Polyurethane 10 parts by weight Isocyanate curing agent 7 parts by weight Methyl ethyl ketone/toluene = 1:1 360 parts by weight Obtained by dispersing for 4 hours using a sand mill The undercoat paint having the above composition was applied to the surface of a 6.0 μm thick polyester support to a thickness of 0.5 μm, and was cured by irradiation with radiation.

On the other hand, a magnetic paint having the above composition obtained by dispersing for 4 hours using a sand mill was applied onto the undercoat so that the film thickness after drying was 4.0 μm, and then calender treatment (smoothing treatment) was performed. The tape was then cut into a 172-inch width to obtain a magnetic tape.

[Example 2] Acicular ratio constituting the undercoat paint of Example 1 =
7.0 (7) a - F eo OH, acicular ratio = I
A magnetic tape was obtained using the same conditions as in Example 1 except that Q, Q(7) α-FeOOH was used.

[Example 3 Acicular ratio constituting the undercoat paint of Example 1 =
7.0(7) a-FeoOH, acicular ratio = 1
A magnetic tape was obtained under the same conditions as in Example 1 except that 5.0 (7) α-F eo OH was used.

[Example 4] Acicular ratio constituting the undercoat paint of Example 1 =
7.0(7) a −F eo 0 H, acicular ratio =
A magnetic tape was obtained under the same conditions as in Example 1, except that 20.0(7) α-FeOOH was used.

[Comparative Example 1] A magnetic tape was obtained under the same conditions as in Example 1 except that the undercoat paint of Example 1 was not used at all.

[Comparative Example 2] A magnetic tape was obtained under the same conditions as in Example 1 except that α-Fe00H was not added to the undercoat paint of Example 1 and an undercoat layer was formed on a polyester support.

[Comparative Example 3] Acicular ratio constituting the undercoat paint of Example 1 =
a-FeOOH of 7.0 and α-Fe of acicular ratio = 3.0
A magnetic tape was obtained under the same conditions as in Example 1 except that OOH was used.

The experimental results regarding the scratch resistance, stiffness, and head contact properties of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in the table below.

(Effects) As is clear from the above explanation and [Table], according to the present invention, the material of the undercoat layer interposed between the non-magnetic support surface and the magnetic layer of a magnetic recording medium can be By containing acicular particles having an acicular ratio of more than 3.0 in a resin binder that is cured by irradiation with electromagnetic waves such as

Even if the thickness of the magnetic recording medium is reduced, the strength can be satisfied and the magnetic recording medium can be used for long-time recording.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a magnetic tape. 1... Nonmagnetic support, 2... Undercoat layer, 3
...magnetic layer, 4...back coating layer. Patent applicant: Japan Victor Co., Ltd. Agent
Person Patent attorney 2 1) Yu Koyama Patent attorney 1...Nonmagnetic support 2...Undercoat layer 3...Magnetic layer 4...Back coating layer

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer is formed on the surface of a non-magnetic support via an undercoat layer, the undercoat layer has an acicular ratio of 3.0. A magnetic recording medium characterized in that it contains acicular particles larger than 0.