JPS62192917A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a low coefft. of friction and improved durability and running stability by providing a magnetic coated film layer for which a binder contg. nitrocellulose and specific polyurethane resin at a specific weight ratio on an under coating layer. CONSTITUTION:The magnetic coated film layer for which the binder contg. the nitrocellulose and the polyurethane resin having 50-100kg/cm<2> 100% modulus at 60:40-70:30 weight ratio is used is provided on the under coating layer. The attraction of a magnetic head and the magnetic coated film is improved but the dispersibility of the magnetic powder and other optional components to be incorporated into the binder is not satisfactory and the head output is decreased if the 100% modulus of the polyurethane resin to be used exceeds 100kg/cm<2>. the coefft. of friction increases; in addition, the magnetic head and the magnetic recording medium attract to each other to increase starting torque when both making long-term contact with each other in a static state. The durability is degraded if the ratio of the nitrocellulose in the binder increases. The starting torque is considerably increased if the ratio decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media used as magnetic tapes and floppy disks. It's about the medium.

Conventional Techniques Conventionally, many magnetic recording media have been used, in which an undercoat layer containing carbon black is formed on a support such as polyester, and a magnetic coating film is formed on the undercoat layer. . (Tokuko Showa 50-104
(Japanese Patent Publication No. 003, Japanese Patent Publication No. 6B-150121) Problems to be Solved by the Invention In recent years, magnetic recording media are required to have higher magnetic recording densities.
For this reason, magnetic powder has been packed at a high density to make the magnetic layer as thin as possible and to provide high surface smoothness.

However, for example, when the packing density of the magnetic powder is increased, the adhesion of the magnetic layer to the substrate deteriorates, and the strength of the coating film decreases. In order to improve this problem, it has traditionally been done to form an undercoat layer made of polyester resin containing carbon black, etc. However, in conventional magnetic recording media, the magnetic head and large surface area are When the magnetic recording medium and the magnetic head are in sliding contact with each other for a long period of time in a stationary state, there is a problem that the two stick together, significantly increasing the starting torque.

The present invention solves these problems and provides a magnetic recording/pushing medium with a low coefficient of friction and improved durability and running stability +'1.

Means for Solving the Problems In order to solve the above problems, the present invention (d) forms an undercoat layer containing a carbon blank on a polyester support. % Moji, Las 6o~” Okg/cJ of polyurethane resin 71
(The amount ratio is between 60:40 and 70:30.)
The configuration with the magnetic coating layer used was (7).

Function As described above, by forming a polyester coating layer containing carbon black on a polyester support, the conductivity, light-shielding properties and adhesive properties of the magnetic coating film can be improved. If this undercoat layer is not formed, carbon black must be added to the magnetic coating layer in a large amount, and the proportion of polyurethane resin must be relatively large, resulting in a low coefficient of friction. , Improved TI with durability +/1 and running stability at the same time? .

The first objective of the present invention is not achieved.

That is, in the present invention, the proportion of nitrified cotton used as the undercoat layer and the binder and the specific polyurethane resin is J[l;
This was the first time that a combination of silk and silk was realized.

The 100% moji and lath of the present invention weighs 50-100 kg/
R-gong polyurethane (☆ 1 fat, obtained at the mountain area (7
For example, there are product names N-2304, N-2302°R-101, and N-3022 manufactured by Boliureta 711 Gyosha.

The 100% modulus of the polyurethane resin used is 1
When the casting temperature exceeds ookg/c, the adsorption phenomenon between the magnetic head and the magnetic coating film is improved, but the magnetic powder and other arbitrary components mixed in the binder, such as the charge 1 (1 month) 1
The dispersibility of abrasives, abrasives, etc. will be insufficient, and -\rad output will be small.

However, if a polymethane resin with a 100% modulus smaller than 50 kg/rA is used, the coefficient of friction of the magnetic coating film formed using MIO1 increases, and [7] the magnetic head and magnetic recording medium become static. When in contact for a long time in the 11 state, both touch for 1 second and increase the starting l.
.

In the binder used in the present invention, it is preferable to use the nitrified cotton and the specific polyurethane resin in a weight ratio of 60:40 to 70:30.

If the ratio of nitrified cotton falls outside the above range, that is, if the ratio of Boliu 1/Tan resin becomes small, the friction coefficient and adsorption properties will be improved, but the magnetic coating film formed will become hard and break. The elongation rate decreases and the durability deteriorates.

Conversely, when the proportion of nitrified cotton decreases, that is, when the proportion of polyurethane resin increases, the surface of the magnetic coating becomes soft, the coefficient of friction increases to -, adsorption with the magnetic head occurs, and the starting torque increases significantly. This is not a good idea.

In addition, the nitrified cotton used together with the specific polyurethane resin is, for example, manufactured by Mukasei Kogyo Co., Ltd. under the trade name 5L-1 and HIG1.
A! , , BTHv2, etc.

Examples Examples of the present invention will be described below. In the Examples, all parts are by weight.

61, -7 [Example 1] Formation of undercoat layer 0.4 mol of isophthalic acid, 0.4 mol of terenotaric acid.

Sulfonodium isophthalic acid 0.2 mol, ethyl glycol 1.6 mol, neopentyl glycol 0.4
The total mole of zinc acetate was esterified with a catalyst at about 17,200"C, and then antimony dioxide was used as a catalyst, lmm
Polycondensation reaction was carried out by heating E7 at about 250"C under Hg or less, and the melt viscosity was 5000 voise (Koka flow tester, 1
90°C) polyester resin was produced.

100 parts of this granular crushed resin was dissolved in a mixed solution of 200 parts of water heated at 75°C CVrC and 200 parts of Improv alcohol, and conductive carbon black 08-
150-12 (manufactured by Cabot) was added and dispersed in a ball mill for 100 hours to form a paint. Apply this undercoat layer paint to both sides of the polyester film and dry it to a thickness of approximately 1.
A coating film of No. 1 was formed.

Formation of magnetic coating Next, 100 parts of Go-containing magnetic iron oxide powder and nitrified cotton (manufactured by Mukasei Kogyo Co., Ltd., trade name S L -) were added as shown in Table 1 below.
1) 18.2 parts, various polyurethane resins with different 100% modulus and elongation at break (all of these are manufactured by Nippon Polyurethane Kogyo Co., Ltd. and are indicated by trade name).
9.8 parts (weight ratio of nitrified cotton to polyurethane resin 435:
35,1. 2 parts lecithin, 6 parts carbon black, 4 parts alumina powder.

2 parts n-butyl stearate, 6 parts dioleyl adipate
part, tristearyl phosphate) 0.7 part.

140 parts of toluene, 14o parts of thyl ethyl ketone.

After mixing 90 parts of cyclohexanone in a ball mill for 12 hours, 6 parts of a polyisocyanate compound (manufactured by Nippon Polyurethane Kogyo Co., Ltd., trade name: Coronet L) was added, and the magnetic paint prepared by mixing well was applied to the undercoat layer on both sides. After applying the film to a dry coating thickness of 1,311m and smoothing the surface by calendering,
The material was cured by heating for 4 hours to obtain an original fabric.

Next, the obtained original fabric was punched out into a disk shape, the surface was polished, and a floppy disk was made.

When the head exit burr friction coefficient and starting torque, which are one of the electromagnetic conversion characteristics, of each sample obtained were measured, the results shown in Table 1 were obtained.

In Table 1, polyurethane resin N-3118, H-503
2, N-5033, NR-90 and N-2301 are
The 100% modulus is a comparative example other than the present invention.

(Hereinafter referred to as gold and white) 9 beno 10 beno [Example 2] In Example 1, the binders used were nitrified cotton (SL-1) and polyurethane resin (
A prototype fabric was produced under the same conditions except that the total amount of R-101) was 28 parts. The friction coefficient, starting torque, and acceleration durability of each sample obtained were measured, and the results shown in Table 2 were obtained.

(Hereinafter referred to as gold and white) Line spacing 1oG2-192917 (4) Based on the standard of the flat disk shown in each of the above embodiments. U〈mark (, test machine ・1
11, To, record 2f bow on ri 39/S after ζ
, ril; t, the average signal amplitude when
did.

100 Φ modulus, lath, and elongation JQ-rate at break were determined by adding 10 Phr of polyisocyanate (Coronate L) to polyurethane resin [7. After curing, the film was buried at a depth of about 10,077 m. Coefficient of kinetic friction (l:j:, cursor type coefficient of kinetic friction 411
Measurement was carried out using a fixed device (manufactured by Kyowa Azasha).

Itto k, starting torque increase rate d1.26”c-: 60
In FIH, the disk described in 1. was loaded into a double-sided drive, and the disk was driven for 30 minutes, stopped for 10 minutes, and then cycled for a total of 10 cycles (7 cycles).

Acceleration durability was measured at 25°C and 6000RH using a double-sided disc with the head pressure increased to 47.5gr.
-7. It was loaded into the drive and fixed at 1jllll.

As shown in Table 1 and the Examples of the second person, it can be seen that according to the present invention, a disk with good head output, friction coefficient, starting 1-run increase rate, and acceleration durability can be obtained.

According to the present invention, an undercoat layer containing carbon black is formed on a polyester support, and on this undercoat layer, nitrified cotton and 100% modulus of 60 to 100% are coated.
kg/cm2 polyurethane resin weight ratio is 60:40
~70: By using a binder consisting of 30 and providing a magnetic coating layer, a magnetic recording medium with a low coefficient of friction, high durability and running stability can be obtained, which is of great industrial value. It is.

Claims (1)

[Claims] An undercoat layer containing carbon black is formed on a polyester support, and on this undercoat layer, a weight ratio of nitrified cotton and a polyurethane resin having a 100% modulus of 50 to 100 kg/cm^2 is 60:40 to 70:30. 1. A magnetic recording medium comprising a magnetic coating layer using a binder comprising: