JPH03214423A - Method for inspecting application nonuniformity defect of magnetic recording medium - Google Patents

Abstract

PURPOSE:To quickly perform the inspection of an application nonuniformity defect with high reliability by scanning and irradiating a magnetic recording medium with a laser beam with wavelength of 600-700nm by using a scanner, and detecting transmission light. CONSTITUTION:The magnetic recording medium 1 is a subject to be inspected, and the medium 1 is scanned and irradiated with an optical beam obtained from an HeNe laser 2 from both sides on one side in a direction nearly perpendicular to the travel direction of the medium 1 by using the scanner 3. Also, an optical fiber convergence system 4 is provided at the other plane side of the medium 1, and light transmitting the medium 1 is converged, and is detected with an optical sensor 5. At this time, it is possible to automatically and quickly detect the application nonuniformity defect of the medium 1 without the problem of heat evolution, in a wide area with superior sensitivity and high reliability by setting the wavelength of the laser 2 between 600-700nm, which attains labor saving, high reliability and acceleration in the inspection.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a manufacturing process of a coated magnetic recording medium in which magnetic powder containing 7-Fez01 as a main component is coated on a polymer film together with a binder. This paper relates to a method for inspecting coating unevenness defects on magnetic recording media. (Summary of the Invention) The present invention solves the coating unevenness defect of a magnetic recording medium in the manufacturing process of a coated magnetic recording medium in which magnetic powder containing 7-Fez03 as a main component is coated on a polymer film together with a binder. , the magnetic recording medium has a wavelength of 60 on- to 700 on-
The present invention aims to provide a method that can inspect a wide range of magnetic recording media sensitively, quickly, and reliably by scanning and irradiating n- laser light using a scanner and detecting the transmitted light. It is something.

[Conventional technology]

r-Pez on a polymer film as a magnetic recording medium
Coating-type magnetic recording media, which are manufactured by coating and drying magnetic powder containing 0.03 as a main component to form a magnetic layer, are widely used. In this case, if the magnetic layer is particularly thin in some areas due to coating unevenness, those areas will no longer exhibit satisfactory characteristics as a magnetic recording medium, resulting in a serious defect.

Therefore, in the manufacturing process of coated magnetic recording media,
It is necessary to quickly detect such uneven coating defects and prevent them from being included in products. As an example of a conventional method for this inspection, FIG. 4 schematically shows a visual inspection method. Here, ■ is the magnetic recording medium that is the object to be inspected, and 4
2 is a phosphor for illumination, and 43 is the naked eye of the examiner.

Visual inspection using transmitted light that passes through a traveling magnetic recording medium (in the direction of the arrow in the figure) has good defect detection sensitivity, but it is tiring for the inspector, is prone to oversights, and requires faster inspection. has a problem that is difficult to deal with. FIG. 5 schematically shows a conventional example of automated defect inspection, which is a method for inspecting pinholes and scratch defects occurring in the magnetic layer of a magnetic recording medium. Here, 1 is a magnetic recording medium to be inspected, 52 is a halogen lamp, and 53 is a carbon
It is a CD linear image sensor.

In this method, one side of the traveling magnetic recording medium I (in the direction of the arrow in the figure) is illuminated with a strong light source such as a halogen lamp 52, and a CCD linear image sensor 53 installed on the other side is used to illuminate the magnetic recording medium I. It detects transmitted light and its position. Because this method uses a white light source, it is highly sensitive and effective in detecting defects such as pinholes where the magnetic layer has almost completely fallen off, but it is also effective in detecting coating unevenness where the magnetic layer has become slightly thinner. Anger level is extremely low. In this method, the detection sensitivity for coating unevenness can be improved somewhat by adding an optical filter with a wavelength of 600 nm to 700 nm on the light source side or sensor side, for reasons described in the section on operation below. Since the utilization rate of magnetic recording media is low and a powerful light source is required, the effect of heat generated from the light source on the magnetic recording medium is also a major problem. [Problems to be Solved by the Invention] The present invention is proposed in view of the above-mentioned current situation.
- Resolve coating unevenness defects in magnetic layers of coated magnetic recording media whose main component is Fe2O3, especially when the thickness is thinner than a predetermined thickness, with high sensitivity, speed, and reliability without the problem of heat generation. An object of the present invention is to provide a method for inspecting coating unevenness defects in a magnetic recording medium.

[Means for Solving the Problems] The present invention provides γ-FezO. , a method for inspecting coating unevenness defects in a coated magnetic recording medium formed by coating a magnetic powder containing a binder together with a binder, the method comprising:
In order to inspect a wide area of a magnetic recording medium for coating unevenness, especially coating unevenness that has become thinner than a predetermined coating thickness, with high sensitivity, speed, and reliability, and without problems such as heat generation, magnetic This is a method for inspecting coating unevenness defects in magnetic recording media by scanning and irradiating the recording medium with a laser beam having a wavelength of 600 nm to 700 nm using a scanner and detecting the transmitted light that passes through the magnetic recording medium. Here, the light source of the laser beam is not particularly limited, but a He-Ne laser with a wavelength of 633 nn+ is particularly preferable because it provides a high-quality laser beam and is inexpensive. In addition, as a scanner for scanning laser light, any of the following can be used: a galvano mirror set, a polygon mirror type, a hologram type, an acousto-optic type, etc. Due to the light transmission properties of the magnetic powder, a coated magnetic recording medium coated with a binder hardly transmits light with a wavelength shorter than approximately 600 nm, and tends to transmit light more easily as the wavelength becomes longer. I have. Therefore, the wavelength of light for detecting such coating unevenness on a magnetic recording medium needs to be at least 600 ns or more.

On the other hand, if the wavelength is too long, the amount of transmitted light for a predetermined coating thickness becomes too large, and the detection sensitivity of thin coating unevenness becomes low. As a result of experiments conducted from the above viewpoint, it is preferable to use a light source with a wavelength of 600n- to 700r++++ for detecting coating unevenness, which is the object of the present invention. Further, by scanning a light beam obtained from a laser light source using a scanner, it is possible to quickly and accurately inspect a wide area of a magnetic recording medium, which is an object to be inspected, for coating unevenness defects. Further, in this case, heat generated by the light source hardly becomes a problem.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the method for inspecting coating unevenness defects in a magnetic recording medium according to the present invention. Here, l is a magnetic recording medium, 2 is a He-Ne laser with a wavelength of 633 nm, 3 is a Galhano mirror scanner, 4 is an optical fiber condensing system, and 5 is an optical sensor. The magnetic recording medium 1 to be inspected is a y-Fe.
This is a coating-type magnetic recording medium formed with a magnetic layer containing magnetic powder consisting of 0.03 and a vinyl chloride-vinyl acetate copolymer and a polyurethane resin as a binder. Using a scanner 3, a light beam with a wavelength of 633 nm obtained from the tle-Ne laser 2 is
The magnetic recording medium 1 is irradiated from one side by scanning in a direction substantially perpendicular to the running direction of the magnetic recording medium 1 (arrow direction in the figure). On the other hand, an optical fiber condensing system 4 is provided on the other side of the magnetic recording medium 1.
The light transmitted through the magnetic recording medium is collected by a fiber focusing system 4 and detected by an optical sensor 5 provided at the other end. FIG. 2 shows an example of the detection results of coating unevenness defects on a magnetic recording medium by the method of this embodiment. In FIG. 2, the sharp peak of the transmitted light intensity indicates the presence of a thinned coating unevenness defect.

For comparison, in Figure 3, curve A shows an example of the detection results when a semiconductor laser with a wavelength of 780n is used as the light source, and curve A shows an example of the detection results when a He-Ne laser with a wavelength of 544n is used as the light source. It is shown by curve B.

When a semiconductor laser with a wavelength of 780n is used, as shown by curve A, there is considerable transmitted light intensity even in areas other than defects, which makes it difficult to identify coating unevenness defects.
Become. On the other hand, when a He-Ne laser with a wavelength of 544 nm is used, as shown by curve B, almost no light is transmitted regardless of the presence or absence of uneven coating. Although the optical fiber condensing system 4 was used to condense the transmitted light in this embodiment, the same effect can be achieved even if an optical sensor that can directly receive light in the optical scanning area is provided without using such a condensing system. It is possible to detect

〔Effect of the invention〕

As explained above, y-Fe. 0. In the manufacturing process of a coating-type magnetic recording medium using magnetic powder mainly composed of, by scanning a laser beam with a wavelength of 600 nm to 700 ns+ to detect uneven coating defects on the magnetic recording medium and detecting the transmitted light, Uneven coating defects on magnetic recording media can be detected automatically over a wide area without the problem of heat generation, with high sensitivity, quickly, and with good reliability, resulting in smaller, more reliable, and faster inspections. Yes, the effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the inspection method for coating unevenness defects in magnetic recording media of the present invention, FIG. 2 is an example of detection results for coating unevenness defects obtained in the example, and FIG. 3 is a comparative example. In this example, curve A shows the case where a semiconductor laser with a wavelength of 780 ns is used, and curve B shows the case where a He-Ne laser with a wavelength of 544 nm is used. Fig. 4 is a diagram schematically showing a conventional visual inspection method for coating unevenness defects on magnetic recording media, and Fig. 5 is a diagram schematically showing an example of an automated conventional method for inspecting bottle hole defects. It is. Note that the same numbers are given to common parts in each drawing. 1-・-----1・-・Magnetic recording medium 2-111--------He-Ne (wavelength 633
nm) Laser 3---------・1・-Galvanometer mirror set scanner 4---・・・1 Optical fiber condensing system 5・・1・・-...1...Implementation of one light sensor pinching direction 1] The result of the detection of the lever diagram shown as -{ηl Figure 3 Comparison of r:f) ”

Claims (1)

[Claims] In a method for inspecting coating unevenness defects in a magnetic recording medium obtained by coating a polymer film with magnetic powder mainly composed of γ-Fe_2O_3 together with a binder, a laser beam with a wavelength of 600 nm to 700 nm is applied to the magnetic recording medium. 1. A method for inspecting coating unevenness defects in a magnetic recording medium, characterized in that inspection is performed by scanning and irradiating using a scanner and detecting transmitted light that passes through the magnetic recording medium.