JPH0675028B2 - Method and apparatus for evaluating surface hardness of coating film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for evaluating the surface hardness of a coating film, and is used for comparatively evaluating the surface hardness of a coating type magnetic recording medium, for example. .

Conventional Technology With recent advances in magnetic recording technology, recording density has improved,
The recording wavelength has become shorter. In the progress of the higher density, the running property of the medium itself has begun to be noticed as an important factor in addition to the magnetic characteristics of the medium and the head.
However, the runnability of this medium is still unclear.
This is mainly because it is very difficult to grasp the state of the surface of the medium. Especially regarding surface hardness, it cannot be said that even the evaluation method is prepared.

Conventionally, for measuring the surface hardness of a coating film, pressing a diamond needle like the Vickers method or measuring the indentation thereof,
Like a micro-Vickers method, press a diamond needle to change the load, measure the displacement of the deepened part and the history of load change, or measure the Young's modulus of the medium by the pull test method or vibration test method. Was used as a substitute for surface hardness. In the case of magnetic recording media, these methods
Compared with a thin film medium formed by vapor deposition or plating, the coating type medium was not satisfactory due to the elastic properties of the film.

Problems to be Solved by the Invention That is, there are the following problems with respect to the above conventional methods. First, in the case of measuring the indentation like the Vickers method, the film thickness of the magnetic recording medium is very thin, and since the elastic modulus of the coating film part is higher than that of metal etc., the coating film shakes when the load is heavy, When the load was light, the measurement could not be performed because no indentation remained. Next, in the micro-Vickers method, since the measured displacement amount is on the order of the surface roughness of the medium, there is a problem in the reproducibility of the measurement. Further, when trying to measure the Young's modulus of the medium, stable measurement can be performed when the thickness of the medium is several tens of μm, but when the coating thickness of several μm is obtained, such as with an actual tape, After all there was a problem in accuracy and reproducibility. The present invention intends to easily and accurately evaluate the surface hardness of a coating type medium with respect to the problems of the prior art.

Means for Solving the Problems In order to solve the above problems, the method for evaluating the surface hardness of a coating film of the present invention is such that a transparent body having a hardness higher than that of the coating film to be measured is pressed against the coating film. The hardness of the coating film is evaluated by measuring the contact area by the interference fringes of the light that is irradiated from the backside and reflected at the contact portion.

With the above configuration, when the coating film of the coating type magnetic recording medium is evaluated by the method of the present invention, a transparent body (for example, glass, diamond, sapphire) having a hardness higher than that of the coating layer of the coating type magnetic recording medium is used. , Quartz, etc.) is processed into a hemispherical shape or a compound curvature surface or a flat surface, etc., and its reaction body surface is finished into a mirror surface so that the tip can be seen from the back, and controlled between several hundred mg to several g. The surface hardness can be evaluated by measuring the contact area between the medium and the transparent body by pressing against the medium surface with the applied load and examining the interference fringes of light.

It is known that the real contact area of two materials is determined by the ratio of load and softer plastic flow pressure. The apparatus of the present invention presses the transparent material and the magnetic medium against each other by the means as described above, and judges the minute contact area of the transparent material and the magnetic contact area to be almost proportional to the true contact area, thereby making comparative evaluation of the plastic flow pressure of the medium surface as the surface hardness. It is for. This can be achieved by examining the size of the contact area of a standard sample whose plastic flow pressure is known in advance. That is, when the surface hardness is higher than that of the standard sample, the contact area is small, and when it is low, the contact area is large.

Example Hereinafter, a specific example of the present invention will be described. FIG. 1 is a diagram schematically showing the method of the present invention. In FIG.
From above the coating film sample 2 fixed on the support 1,
The transparent body 6 attached to the tip of the arm 5 attached to the stage 4 movable up and down by the micrometer 3 can be brought closer to it. The transparent body 6 used here was ordinary glass, and the tip was finished in a semicircular shape of 2 mmR, and the opposite surface was flatly mirror-finished. Arm 5
A strain gauge 7 is attached to the root of the, and it is possible to detect the load by pressing with the output of the strain gauge by calibrating with a standard weight beforehand. The tip of the transparent body 6 was pressed against the sample 2 with a weight of 1 g, and the observer 11 measured the contact area between the tip of the transparent body 6 and the sample 2 through the objective lens 8, the prism 9 and the eyepiece lens 10. If the light from the light source 13 above the lens barrel 12 is observed like the optical path 14, this contact area can be observed as an area of an O-th order black stripe due to light interference.

The surface hardness of the magnetic coating film having the composition shown in Table 1 was comparatively evaluated using the measuring device having such a configuration.

The magnetic paint kneaded with the composition shown in Table 1 has a thickness of 15μ.
It was applied to a PET film of 3 m in thickness of 3 μm and calendered to give almost the same surface roughness. Here, the polyurethanes in Table 1 were changed as follows to obtain samples A, B and C.
And

Sample A: Tg = -20 ° C polyurethane used Sample B: Tg = 20 ° C polyurethane used Sample C: Tg = 80 ° C polyurethane used Tg indicates the glass transition temperature.

The contact area of this sample was measured by the method described above.

Table 2 shows the measurement results. In the table, the contact area is almost circular, so the diameter is used instead of the contact area.
Table 2 shows the Young's modulus of each sample having the same composition and having a film thickness of about 15 μm measured by the pulling test method for reference.

It can be seen from Table 2 that the contact area decreases with increasing Young's modulus of the film, that is, the hardness increases.
As a result, the hardness of a coating film having a thickness of several μm could be comparatively evaluated.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to compare and evaluate the hardness of the film by examining the contact area. As a result, when the coating thickness is several μm, the hardness of the coating film, which was conventionally difficult to measure, was used as the standard sample. The effect that it can be compared and evaluated is obtained,
It will be very useful for coating film development.

[Brief description of drawings]

The figure is a schematic view showing the method of the present invention. 1 ... Support base, 2 ... Coating sample, 3 ... Micrometer, 4 ... Stage, 5 ... Arm, 6 ... Transparent body,
7 ... Strain gauge, 8 ... Objective lens, 9 ... Prism,
10 …… eyepiece, 11 …… observer, 12 …… lens barrel, 13 ……
Light source, 14 ... optical path.

Claims (2)

[Claims] 1. A transparent body having a hardness higher than that of a coating to be measured is pressed against the coating, and the contact area is measured by interference fringes of light irradiated from the back of the transparent body and reflected at a contact portion, A method for evaluating the surface hardness of a coating film, which comprises evaluating the hardness of the coating film. 2. A pressing member made of a transparent body having a hardness higher than that of the coating film to be measured, an arm for moving the pressing member up and down to press the coating film, a light source arranged behind the pressing member, and a light source. An apparatus for evaluating the surface hardness of a coating film, which comprises a measuring means for observing an interference fringe of light reflected by the contact portion with the coating film that passes through the pressing member to measure the area of the contact portion.