JPH02227821A - magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media such as audio tapes, video tapes, and magnetic disks, and is a magnetic recording medium with improved performance such as running stability and running durability. Regarding.

2. Description of the Related Art Magnetic recording media are generally manufactured by applying a magnetic paint containing magnetic powder and a binder resin as main components onto a non-magnetic support such as polyethylene terephthalate and drying the coating. In recent years, there has been a particularly strong demand for high-density recording, and magnetic tapes for audio, video, etc. have come to be required to have high tape performance. To achieve this, it is necessary to solve the problems of reducing the coefficient of friction on the surface of the magnetic layer, improving durability and improving running stability. In the tape running system of a video tape recorder (VTR), a magnetic tape comes into contact with various objects of different shapes and materials, including the magnetic surface and back surface, as well as various magnetic heads and tape guides. If the coefficient of friction between the tape and the contact part becomes unstable at even one of these contact parts, the screen will shake or jitter, and normal playback will no longer be possible. Furthermore, in order to achieve high output and high Cβ, the surface of the magnetic layer is finished with a mirror finish, and as a general tendency, the coefficient of friction tends to be large and unstable. Particularly in video tapes for VTRs used for broadcasting where the relative speed between the tape and the magnetic head is high, it is particularly important to have excellent still durability and running stability.

Conventionally, in order to reduce the friction of the magnetic layer, higher fatty acids (e.g., lataric acid, myristic acid, valmitic acid, stearic acid, oleic acid) and higher fatty acid esters (e.g., stearic acid) have been added to the magnetic layer of magnetic recording media. acid-
It is known to add lubricants such as n-butyl, n-butyl oleate). Furthermore, JP-A-61-42
As described in Japanese Patent No. 733, it has been proposed to regulate the mixing ratio of fatty acids and fatty acid esters and the range of their addition amounts.

Problems to be Solved by the Invention However, in the magnetic recording medium having the above structure, it is extremely difficult to judge how much of the added lubricant actually exists on the magnetic layer surface, or how much the so-called "protrusion amount" is. The problem was that

In other words, even if the magnetic layer contains lubricant in the amount regulated by the above method, the amount of lubricant that bleeds out to the surface of the magnetic layer is insufficient, making it impossible to obtain the desired durability and running stability. On the other hand, due to a large amount of bleed-out, the spacing between the magnetic head and the magnetic layer increases, resulting in a decrease in output, and problems such as the phenomenon that the magnetic head and the magnetic layer stick together occur. It had

In view of the above-mentioned problems, the present invention provides a magnetic recording medium that has excellent running stability and running durability, as well as high output and high C.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic recording medium in which a magnetic layer containing magnetic powder and a binder resin is formed on a non-magnetic support, which Critical surface tension γc is 23.0 to 28. .

dyne/c! If it is R, the maximum adhesion work WA-wax expressed by the following formula is ω, o ~ To, O@ r q/c
i), a lubricant is added to the magnetic layer.

WA-max=-10γc+(-1)-(γc)2(γ
c is the critical surface tension, b Id Z isman P l
The present invention replaces the amount of lubricant actually present on the surface of the magnetic layer, the so-called "protrusion amount", with the critical surface tension cuff 0 and the maximum adhesion work WA, ax value on the surface of the magnetic layer. By considering this, we aim to truly determine the type, mixing ratio, and amount of lubricant that are most suitable for improving running stability and running durability.

Therefore, the inventors of the present invention conducted extensive studies on the correlation between the critical surface tension γc of the surface of the magnetic layer, the maximum adhesion work 'A-ma', and the dynamic friction coefficient μ of the magnetic layer, and found that the critical surface tension γc was 23. 0 to 28.0 dyne/am, large rut adhesive work WA6wax is 60.0 to 70.0 x
It has been found that by adding a lubricant to the magnetic coating material so that the ratio is q/cd, a magnetic recording medium with excellent running stability and running durability can be obtained. If it deviates from the above range, problems such as the occurrence of tape running problems such as stick-slip, the occurrence of tape running scratches, and the significant change in the dynamic friction coefficient μ of the magnetic layer due to standing are undesirable.

Example Examples of the present invention will be described in detail below.

In the Examples and Comparative Examples, each part of the material indicates the number of parts by weight when the magnetic powder is taken as 100 parts.

[Example 1] 100 parts of ferromagnetic metal magnetic powder (average major axis diameter 0.18 μm, average axial ratio 1:10) 12 parts of vinyl chloride-acrylic copolymer resin (trade name: Meiko Nuretsu E manufactured by Block Chemical Industry Co., Ltd.) ) Polyurethane resin 12 parts (trade name RM-e manufactured by Nippon Polyurethane Industries Co., Ltd.) Abrasive material (a, AJ320s) 8 parts Carbon black 3 parts Lubricant
4 parts solvent MEK
200 parts Toluene 180 parts Cyclohexanone 40 parts The above composition was mixed and dispersed in a ball mill for 48 hours to obtain a magnetic coating material. Next, 6 parts of a curing agent (trade name: Corone L, manufactured by Nippon Polyurethane Kogyo Co., Ltd.) is added and stirred with a disper. After filtering the paint through a filter with an average pore size of 1 μm, it was applied onto polyethylene terephthalate with a thickness of 10 μm, and subjected to orientation, drying, and calendering. After the curing reaction was completed, a back coat layer was provided on the polyethylene tele-7 tallate on the opposite side to the magnetic layer, and slits were made into 8 parts and 1 width to prepare a 5 gm VTR metal tape.

The critical surface tension TC value and maximum adhesion work WA-max value of the magnetic layer surface of the obtained tape are determined to be 2.
5.9 dyn@/cN1.64.3 e r g/d
It was i.

[Example 2] The same method as in Example 1 was used except that 3 parts of lubricant was used instead of the lubricant in Example 1! 78111
I made metal tape for VTR.

The critical surface tension TC value and maximum adhesion work WA-wax value of the surface of the magnetic layer of the obtained tape were determined to be 26.8 dyne/lym, f5B, and 6 esxq/, respectively.
(It was -.

[Example 3] 100 parts of ferromagnetic metal magnetic powder (average major axis diameter 0.20/jmg average axial ratio 1:12) polyvinyl acetal am s part (trade name Suretsuk K manufactured by Block Chemical Industry Co., Ltd.) polyurethane resin
14 parts (trade name UR-8300 manufactured by Toyobo Co., Ltd.) Abrasive [Cr2O3] 6 parts Carbon black 2 parts Lubricant 3 parts Solvent M E K 170 parts Toluene 1550 parts Cyclohexanone 100 parts The above composition was milled in a ball mill for 36 parts. After time cross-dispersion, a magnetic paint was prepared by cross-dispersing for 4 hours in a sand mill. Next, 6 parts of a curing agent (trade name: Coronate L, manufactured by Nippon Polyurethane Kogyo Co., Ltd.) is added, and the mixture is stirred with a disper. After the paint was filtered through a filter with an average pore size of 1 pxn, it was applied onto polyethylene terephthalate having a thickness of 1 Qpm, and subjected to orientation, drying, and calendering. After the curing reaction was completed, a back coat layer was provided on the polyethylene terephthalate on the opposite side to the magnetic layer, and slits were made to have an aff width to produce a 6 m VTR metal tape.

The critical surface tension cuff 0 value and maximum adhesion work "A-max" value of the magnetic layer surface of the obtained tape are determined to be 2.
4.6 dyne/m, 63.1 erg/d. Ta.

[Comparative Example 1] An 8-fin VTR metal tape was prepared in the same manner as in Example 1 except that 2 parts of the lubricant was used instead of the lubricant in Example 1.

The critical surface tension TC value and the maximum adhesion work W value of the magnetic layer surface of the obtained tape are found to be -maX 32.5 dyne/cm and 72.2 e, respectively.
It was 7j in rg/.

[Comparative Example 2] A metal tape for a paw VTR was prepared in the same manner as in Example 1 except that 10 parts of a lubricant was used instead of the lubricant in Example 1.

The critical surface tension ya value of the magnetic layer surface of the obtained tape and the maximum adhesion work WA, work a! When calculating the value, each
B, 6 dyne/a++, 67.7 erg resistance.

[Comparative Example 3] A metal tape for 8HVTR was produced in the same manner as in Example 3 except that 4 parts of lubricant was used instead of the lubricant in Example 3.

The critical surface tension rC value and maximum adhesion work WA-max value of the magnetic layer surface of the obtained tape are determined to be 2.
It was 7.4 dyne/m and γ4.6 erg/ci.

[Comparative Example 4] A metal tape for a υ5n VTR was prepared in the same manner as in Example 3, except that 3 parts of the lubricant was used instead of the lubricant in Example 3.

The critical surface tension TC value and maximum adhesion work WA-max value of the magnetic layer surface of the obtained tape were determined to be 31, 8 dyne/m, and 3.9 erg〆H, respectively.

Critical surface tension γc and maximum work of adhesion WA-m described above
The method for measuring ax is shown below.

Critical surface tension γc: Drop a wetting index standard solution with known surface tension onto the surface of the magnetic layer,
The contact angle θ of the droplet is measured. Next, the cosine (aosθ) of the contact angle θ is plotted against the surface tension of the wetting index standard solution. (ZismanPlot) The value of the surface tension corresponding to the intersection of the obtained straight line and cos θ = 1 was determined, and that value was taken as the critical surface tension of the surface of the magnetic layer.The surface tension of the wetting index standard solution used was 38 ，
They are 45, 50, and 54 dyne/cm.

Maximum adhesive work "A-maw ' Critical surface tension γc and ZfsmanP determined by the above method
From the slope b of the straight line of lot, the maximum adhesion work was determined using the following formula (%).

Each 8ff VTR obtained in the above examples and comparative examples
The following measurements were performed on the metal tape for

(1) Coefficient of friction The surface of the tape magnetic layer is brought into contact with a stainless steel cylinder with a diameter of 4 nm over half the circumference, and the entrance tension is set to 20 mm on the drum side.
p, the exit tension Xy was measured when the tape running speed was set to 3.0 cn1/''R, and the friction coefficient was determined from the following equation.

It was also confirmed whether stick-slip occurred during the measurement.

(2) Change in friction coefficient due to weather storage 40”C180
%R, H, 0 environment K 1o After several days, calculate the friction coefficient using the same method as in (1) above, and calculate the difference from the friction coefficient in (1) above as the amount of change in the friction coefficient due to weather storage. And so.

(3) C/N (s calm/4.5 III)
We measured the ratio of the signal for 5th grade and the noise for 4.6th grade. The amVTR for C/N measurement is MVS-5000 (K
(Manufactured by ODAK) For use *. The reproducing head uses an amorphous alloy, and Comparative Example 1 No. a wx V T
Relative values are shown using the C/N of the R metal tape as a reference (odB).

(→ Using a videotape recorder modified for Nutil Life Nutil measurement, a still image recorded in advance under -10'C130p load condition was played back, and the time required for the image signal to drop in odB was shown. .

(6) Skew value A parameter that expresses the size of timing deviation during image playback. After repeated playback 100 times at 40°C and 80% R, H, the deviation from the reference signal is measured. The smaller the value, the smaller the deviation and the less distorted the image.

The results are shown below.

Although aliphatic compounds were used as the lubricants in the above examples, the present invention can also be applied to conventionally commonly used lubricants such as hydrocarbon-based lubricants, fluorine-based lubricants, and silicone-based lubricants. Applicable.

Effects of the Invention As described above, the present invention has the advantage that the critical surface tension yc of the surface of the magnetic layer
is 23.0-28. Odyne/m, and the slope b of the line of critical surface tension γc and ZismanPlot
The maximum adhesion work WA-max (= −
T ”rc + (-')・(re)2) is 80.0~
70. By incorporating a lubricant into the magnetic layer such that Oe can.

Claims (1)

[Scope of Claims] A magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder resin formed on a non-magnetic support, wherein the critical surface tension γc of the surface of the magnetic layer is 23.0 to 28.0 dyn.
e/cm, and the maximum adhesion work W is expressed by the following formula:
_A_・__m_a_x is 60.0-70.0erg/c
A magnetic recording medium characterized in that a lubricant is added to the magnetic layer so that m^2. W_A_・__m_a_x=-1/b+γc+(-b/4
)・(rc)^2 (γc is the critical surface tension, b is the slope of the straight line of Zisman Plot)