JPH0241807B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coated magnetic recording medium. BACKGROUND ART In recent years, as video tape recorders and the like have become smaller and lighter and have higher recording density, recording media are increasingly required to have higher performance and reliability. In terms of videotape performance, improving characteristics such as still life, dropout growth, and tape friction coefficient, which are related to durability, will adversely affect characteristics such as head wear and S/N ratio due to head and tape conformity. When the performance of each characteristic decreases, a contradiction arises between the performance of each characteristic, and it is extremely difficult to improve the performance of all characteristics in a well-balanced manner. An object of the present invention is to reduce the causes of such contradictions between characteristics and to provide a coated magnetic recording medium (hereinafter simply referred to as a magnetic recording medium) in which each characteristic is improved in a well-balanced manner. A magnetic recording medium is constructed by providing a magnetic layer on a non-magnetic support, and the support is generally a polyester base film, and the magnetic layer is coated with a magnetic paint whose main components are magnetic powder and binder resin. It is formed by painting. Regarding such magnetic recording media, the present inventors
As a result of various studies on tape characteristics, tape constituent materials, and their physical properties, it was revealed that the viscoelastic properties of the tape are extremely involved in one of the causes of the contradiction between the above characteristics, and the present invention has been made. Reached. The viscoelastic properties of the magnetic layer can be in a glass state, a transition region state from glass to rubber state, or a rubber state depending on the material of the binder resin constituting the magnetic layer or the temperature conditions of the atmosphere. The performance of various properties of the tape is closely related to the viscoelastic state of the viscous layer of the magnetic layer. Properties such as still life, dropout growth, and coefficient of friction are extremely high performance when in the glass state.
On the other hand, head wear, S/N ratio, etc., are higher in the transition range or in the rubber state. However, in this state, the magnetic layer is easily deformed, resulting in deterioration of skew characteristics, envelope characteristics, etc. The magnetic recording medium of the present invention is characterized in that an elastomer layer is provided between the support and the magnetic layer, and with this structure, even if the magnetic layer is in a glass state, Head wear, S/N
Performance such as ratio is improved in the same way as in the transition range or rubber state, and an increase in the level of all properties is achieved. The present invention will be explained in more detail below. The elastomer layer forming the intermediate layer of the present invention is
Basically, it is made of polymeric material, and its Young's modulus is 1×10 ⁸ to 1× in the temperature range of 0 to 50°C.
It is between 10 ^{and 10} dyne/ ^cm2 . 1×
The effect decreases significantly when the Young's modulus exceeds 10 ¹⁰ dyne/cm ² . Further, when the concentration is less than 1×10 ⁸ dyne/cm ² , flow occurs, causing problems. These polymeric substances include polyurethane, polyester,
Polyolefins, thermoplastic elastomers such as styrene-butadiene copolymers, etc. can be applied. These elastomers are applied as a solution or paint onto a base film and dried to form a uniform film to form an intermediate layer. The thickness of this intermediate layer must be appropriately adjusted depending on the Young's modulus of the elastomer material, the thickness of the base film, the thickness of the magnetic layer, and Young's modulus. A magnetic coating material is applied onto the base film on which the intermediate layer is formed by a conventional method, followed by drying, calendering, etc. to produce the magnetic recording medium of the present invention. Examples of the present invention will be specifically described below. It should be noted that all parts in the component ratios described in the examples are parts by weight. Example 1 On a 10μ thick polyester base film,
Glass transition temperature is at -20℃, 0℃ and 50℃
Methyl ethyl ketone solutions of urethane elastomers with Young's moduli of 3 x 10 ⁹ dyne/cm ² and 5 x 10 ⁸ dyne/cm ² were applied and dried to a thickness of 0.8 μm.
An intermediate layer was formed. Next, a base film with an intermediate layer formed of a magnetic paint mainly composed of 20 parts of a binder resin consisting of a polyurethane resin, a copolymer resin of vinyl chloride, vinyl acetate, and vinyl alcohol, and an isocyanate curing agent, and 100 parts of metal magnetic powder is applied. and finished into a 1/2 inch wide tape using conventional methods. The thickness of the magnetic layer was 2.5μ. Only the binder used to form the magnetic layer was cured into a film under the same heat treatment conditions as for tape production. The glass transition temperature of this film is 85℃
The Young's modulus at 0℃ and 50℃ is respectively
They were 4.2×10 ¹⁰ dyne/cm ² and 3.4×10 ¹⁰ dyne/cm ² . Comparative Example 1 The magnetic paint used in Example 1 was directly applied to the base film used in Example 1.
It was made into a tape under the same conditions. The thickness of the magnetic layer of this tape was 2.6μ. Example 2 On a 7μ thick polyester base film,
When the vitrification temperature is -10℃, the Young's moduli at 0℃ and 50℃ are 2× ¹⁰⁹ dyne/ ^cm2 and 4× ¹⁰⁸ dyne/ ^cm2, respectively.
A toluene-methyl ethyl ketone solution of polyester resin was coated and dried to form an intermediate layer with a thickness of 1 μm. Next, the same magnetic paint used in Example 1 was applied onto this intermediate layer, and the tape was finished in the same manner as in Example 1. The thickness of the magnetic layer was 2.1μ. Comparative Example 2 The magnetic paint used in Example 2 was directly applied to the base film used in Example 2, and a tape was finished under the same conditions as Example 2. The magnetic layer thickness was 2.0μ. The tapes of the above Examples and Comparative Examples were compared in terms of runnability, output level, and head wear. The evaluation is video tape recorder deck (Matsushita Electric Industrial)
The tests were carried out at 23°C, 60% RH and at 5°C, 80% RH. The tapes of Examples 1 and 2 had better compatibility with the head and better running properties than Comparative Examples 1 and 2, respectively. In addition, the output level of the tapes of Examples 1 and 2 was 2 to 2 compared to the tapes of Comparative Examples 1 and 2.
3dB was good. The head wear was as shown in the following table. The value of head wear was determined by passing the tape through the video tape recorder deck 300 times and showing the amount of wear before and after passing the tape.

[Table] In addition, dropout growth, still life,
No difference was observed in properties such as friction coefficient between the example and the comparative example. In addition, measurements of the viscoelastic properties, vitrification temperature, and Young's modulus of the intermediate layer forming material and the binder resin of the magnetic layer in the examples were made by Toyo Baldwin Co., Ltd.
It was performed using a Rheovibron at a frequency of 110Hz. Therefore, Young's modulus is precisely the complex dynamic Young's modulus. As is clear from the above description, in the magnetic recording medium according to the present invention, the contact between the head and the medium is improved due to the elastic influence of the intermediate layer, and as a result, the head output level is improved. Due to the effect of mitigating the grinding of the head by the media,
It has the excellent property of reducing head wear and has great practical value.

Claims (1)

[Claims] 1 A non-magnetic base film support and a base film disposed on the base film support, the Young's modulus of which is 0.
1×10 ⁸ to 1× in the temperature range of ~50℃
1. A coated magnetic recording medium comprising an elastomer layer having an elastomer layer having an elastomer density in the range of 10 ¹⁰ dyne/cm ² and a magnetic layer formed by coating a magnetic paint on the elastomer layer.