JPS58159240A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To attain an excellent S/N ratio, by providing the 1st magnetic layer such as Co-coated gamma-Fe2O3 on a lower layer which is in contact with a nonmagnetic medium and providing the 2nd magnetic layer made of iron nitride or alloy nitride magnetic material on the 1st layer. CONSTITUTION:A cobalt-doped gamma-Fe2O3 having 500-600-oersted coercive force and 2,000-3,000-gauss residual magnetic flux density is dispersively coated as the magnetic layer 2 of the 1st lower layer on the nonmagnetic film base carrier 1 in 2-4mum thickness of, and the iron nitride or the nitride alloy magnetic material 3 having as much coercive force as possible in the range that the reproducing equalizer of 70musec is used at a chromium bias, i.e., <=800 oersted possible for erasing, is coated in 1.5-3.0mu thickness on the 1st magnetic layer 2. The magnetic flux of the material 3 is 3,000-4,000gauss and a high maximum output level is shown at a high saturation output level with a sufficient residual magnetic flux density without giving effects on the low-frequency sensitivity due to the lower layer.

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium, and more particularly, to a recording medium trap in which two layers of magnetic material are coated on a non-magnetic carrier. In recent magnetic recording media for audio cassettes,
There is a demand for products with better high frequency characteristics. Therefore, magnetic powders with large residual magnetization and coercive force have been developed. The magnetic goobe formed by these has excellent reproduction output in the ^ range, and in order to compensate for this drawback of low reproduction output in the low frequency range, magnetic powder with small coercive force is used in the lower layer to reproduce the low frequency range. In order to reduce the output, a two-layer coated recording medium has been proposed that uses magnetic powder with a large coercive force in the upper layer to share the reproduction output of the two regions, thereby providing a high reproduction output over the entire audible range and a wide dynamic range. However, compared to Orbunotape etc., MOL c @ large output level) and 5QL (saturated output level) are inferior,
The Taina Mitsu cleanser had a narrow drawback. The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to provide a two-layer magnetic recording medium that has excellent characteristics in terms of S/N ratio and can be used with a Talorm bias of 70 Psec in a reproduction equalizer. High MOL by 1lIi8
0L, Y: if i '19 L/7 is wide, m
The present invention provides a magnetic recording medium that exhibits linear a-number characteristics and is acoustically good. According to the present invention, a double magnetic layer of different magnetic materials is provided on a non-magnetic carrier,
This is achieved by providing an a-air recording medium having a two-layer magnetic layer made of iron nitride or alloy nitride as an upper layer on the wJ1f) ai layer. Hereinafter, one embodiment of the present invention will be described together with drawings. FIG. 1 shows a magnetic recording medium of the present invention, in which C. (cobalt) doped j is formed on a non-magnetic film base carrier (1) and has a magnetic flux density of 2000 to 3000 Gauss in the lower layer of path 1. -) '6*Qm is dispersed and coated in a thickness of 2 to 4 AA II, and a reproduction equalizer 704 is applied on the first magnetic layer (2).
Iron nitride or alloy nitride magnetic material (3) with as large a coercive force as possible within the range that can be used with a sec chrome bias, that is, less than the erasable Oersted bias, is used at 1.5 to 3. The nitrided magnetic material applied to the magnetic flux density is 3000~4(X)0
It exhibits a high MoL of 80L due to sufficient residual magnetic flux density without inhibiting the low-frequency sensitivity due to the Gaussian layer. An embodiment of the two-layer coated magnetic recording medium according to the present invention will be described in detail below. Example (1) First, the lower first magnetic layer (2) is made of magnetic powder (cobalt tope-1?esoa)
100 fil (weight) 11 copies of 10 l
Urethane Brevo II Mar]
01 Dispersant (lecithin) 21 Vinyl stabilizer 2I Methyl ether keto 7 150
#Toluene 1
After kneading the 00# composition in a ball mill for 72 hours, 3.5 parts of a bulking agent was added to form the lower magnetic material.
1. Coating thickness 3.
Apply and distribute on 5P, and after drying, perform surface treatment, then 4
It was heated at 0° C. for 48 hours and laid out. Next, the composition of soil layer (3) is iron nitride (Fe1N)
100 parts (weight) vinyl chloride-vinyl acetate copolymer
121 Ureta 7 Brevo 1tmer
12 1 Dispersant (lecithin)
2' Vinyl chloride stabilizer
2' methyl ethyl keto 7 150 #toluene
10
0 ' These were kneaded in a ball mill for 72 hours, coated on the above lower layer (21) to a coating thickness of 2.0μ, and dried.
VK surface treatment was performed to form a 12-layer coated magnetic recording medium shown in FIG. Example (2) Lower layer (21°C ff1WI powder (y+Todo Poor Fears)
100 parts ([1) Cyclized vinyl-vinyl 4-acid copolymer lOl
Ureta/Bo II Mar 10
1 dispersant (shi7chi/)
2' Vinyl chloride stabilizer
2' methyl ethyl keto/150' toluene 10
A non-magnetic carrier (
11, and then the composition of the upper layer (3) is magnetic powder (Fe4-s CI# N) 100s vinyl chloride-vinyl acetate copolymer 1z l urethane + 7mer 12 1
dispersant

[Lecithin] 21 Vinyl chloride stabilizer zI
T methyl ethyl ketone 15
0 #Toluene
Example (2 under the same conditions as 11) as 100 l
A layer-coated magnetic recording medium was formed. Embodiment tl) A characteristic diagram comparing the same wave number characteristics and bias noise due to K and K MetJIJ86)L with the characteristics of a two-layer magnetic recording medium used in a conventional reproduction equalizer-70 sec chromium bias is shown in m2WJK. In Fig. 2, A indicates each characteristic of the dual-layer magnetic recording medium of the present invention, and B indicates the % characteristics of the dual-layer magnetic recording medium of the Iit button (I# which greatly reduces the tl bias noise mg noise). It has a slight difference.

[Brief explanation of drawings]

Figure 1 shows an oblique I! cross-section of a portion of Honkamei's two-layer magnetic recording medium. Figures 1 and 12 are a summary of the comparison of the characteristics of the present invention and a simple two-layer magnetic recording medium. In the figure, 1 is a non-magnetic carrier, (2 is a magnetic layer of the first layer S, (3)
is an iron nitride or alloy nitride magnetic layer, (4) is a female L1 layer,
(5)kX! 3 e Lu1l m, (6) is the armpit number characteristic line, (71 is the bias noise curve. A1) 9 FfI-, $, bush → ri1z-e Procedural amendment (voluntary) 1986 4 Monthly eaves Lawn Raego Laeguo Shiki T incident display Showa 57 % eaves wish No. 43Z80 2nd invention) - The scope of the patent claims is amended as follows: (1) In a magnetic recording medium comprising two layers of different magnetic materials coated on a non-magnetic carrier, A first magnetic layer such as cobalt-covered y-FgsOs is provided in the lower layer in contact with the carrier, and a second magnetic layer made of iron nitride or alloy nitride is provided as an upper layer on the magnetic layer of iji!1. (21) The first magnetic layer coated on the lower layer of the non-magnetic carrier is made of cobalt having a coercive force in the range of 500 to 650 Els de Sod and a residual magnetic flux density of 2000 to 3000 Gauss. Dope γ
-Fe*Os or Kohar) IFJlr-FeIOi
The coating thickness is 2 to 4 A-, and the upper magnetic layer coated on the lower first magnetic layer has a coercivity of 650 to 800.
The residual magnetic flux density is 3000-4.
2. The magnetic recording medium according to claim 1, characterized in that the magnetic recording medium is made of iron nitride or alloy nitride a-based powder of 0.000 Gauss and has a coating thickness of 1.5 to 3.0 l4 m. (3) The upper magnetic layer is made of iron nitride or its alloy nitride J-, and has a particle size of 0.2 to 1. The magnetic recording medium according to claim 8g1, characterized in that the magnetic recording medium is selected from the range of θμ.

Claims (3)

[Claims] (1) Two magnetic layers of different types of magnetic materials are coated on a non-magnetic carrier, and a second mother layer made of iron nitride or alloy nitride magnetic material is provided as an upper layer on the first magnetic layer. A magnetic recording medium comprising: (2) The first magnetic layer coated on the lower layer of the non-magnetic carrier is a cobalt-doped layer having a coercive force in the range of 500 to 650 Oersteds and a residual magnetic flux density of 2000 to 3000 Gauss.
Fe zOs or cobalt coated tube ff - Fe Qs with a coating thickness of 2 to 4. The upper magnetic layer coated on the lower second magnetic layer has a coercive force of 650 to 800.
It is in the Oersted range and the residual magnetic flux density is 3000 to 4
00 Gauss iron nitride or alloy nitride magnetic powder with a coating thickness of 1
．． The magnetic recording medium according to claim 1, characterized in that the magnetic recording medium is comprised of 5 to 3.0/14 gI&. (3) The magnetic layer is made of a layer of iron nitride or its alloy nitride, and the particle size is selected from the range of 0.2 to 1.0 m. The magnetic recording medium according to item 1.