JPH06109649A - Method for inspecting optical information recording disc - Google Patents

Abstract

PURPOSE:To more accurately detect defects of the thickness unevenness, etc., of a surface of a hard coat film formed on a transparent substrate. CONSTITUTION:The title disc 21, in which a transparent hard coat film is applied on a translucent substrate and at least a reflecting film is formed on the back surface of the substrate, is inspected by the reflected light from the said reflecting film. In this case, an incident angle theta0 of the inspecting light emitted from an optical source 27 on the surface of the hard coat film and incident upon the substrate side is made not less than 15 deg. and smaller than a critical angle thetac of the interface between the hard coat film and the air. By this, when the surface of the hard coat film has thickness unevenness thereof, the quantity of the reflected inspecting light received by a light-receptor 28 becomes smaller, and the film thickness unevenness is easy to detect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method and an inspection apparatus for inspecting scratches on the surface of a substrate of an optical information recording disk and defects such as foreign matter and bubbles present inside.

[0002]

2. Description of the Related Art Optical information recording discs include a read-only optical information recording disc that only reads information recorded on the disc and an optical information recording disc that can record information. The former optical information recording disk is composed of a translucent substrate made of, for example, polycarbonate, a reflective film formed by vapor deposition of aluminum or gold, a protective layer for protecting the reflective film, and the like. The latter optical information recording disk is a translucent substrate formed of polycarbonate, a recording layer coated with an organic dye,
It is composed of a reflective film formed by vapor deposition of aluminum or gold, a protective layer for protecting the reflective film, and the like.

By the way, when recording or reproducing on such an optical information recording disk, the surface of the translucent resin substrate through which the reproducing or recording light beam is transmitted may be scratched,
If dust is mixed in the resin substrate or if minute holes (pinholes) are formed in the reflective film, accurate information reproduction and recording cannot be performed. Therefore, in the process of manufacturing the optical information recording disk, it is necessary to inspect for defects such as scratches, dust, and pinholes.

Conventionally, as a method of inspecting such a defect, for example, light from a halogen lamp is applied to the surface of an optical information recording disk as an inspection object through a slit,
A method is adopted in which the reflected light or the transmitted light is received by a light receiver to perform an inspection. For example, FIG. 4 shows an outline of such an inspection device. Here, the center of the optical information recording disk 1 is clamped by the clamper 2 and is rotated by the motor 3. An inspection optical pickup 9 including a light source 7 and a light receiver 8 is arranged on the transparent substrate side of the optical information recording disk 2 thus rotated, and the inspection optical pickup 9 is controlled by a servo controller 10 by a servo mechanism 6. Is used to move the optical information recording disk 1 in the radial direction. On the other hand, while the light amount is controlled by the controller 13, the inspection light is emitted from the light source 7 such as a halogen lamp through the half mirror 5 and the focusing lens 4 onto the substrate surface of the optical information recording disk. Then, this light passes through the transparent substrate and is reflected by the reflective film behind it. The reflected light is reflected by the half mirror 5 and received by the light receiver 8, and the amount of light is measured by the measuring device 11. This measured value is calculated by the calculator 12 and numerically processed.

Here, if there is some defect on the path until the inspection light emitted from the light source 7 is received by the light receiver 8, the inspection light is absorbed, scattered, or scattered by this defective portion. Since it is reflected, the amount of light received by the light receiver 8 appears differently from other portions. For example, when the inspection optical pickup 9 is inspected while scanning the surface of the substrate of the optical information recording disk as described above, if there is a partial defect, as shown in FIG. Is measured. That is, the time on the horizontal axis in FIG. 4 is the coordinates corresponding to the scanning position on the surface of the transparent substrate, and the voltage value is the quantity of electricity measured by photoelectrically converting the quantity of light received by the light receiver 8. The coordinates are shown.

[0006]

Among the recent optical information recording disks, particularly those using a resin substrate such as polycarbonate, a so-called harder material than the substrate material is used to prevent scratches on the surface. Hard coat is applied. By the way, if the hard coat film is formed with some foreign matter attached to the surface of the transparent substrate,
The thickness of the hard coat film may be uneven in the surrounding area. Such unevenness in the thickness of the hard coat film acts like a lens and refracts a recording or reproducing laser beam in an abnormal direction during recording or reproduction on an optical information recording disk. There is a defect that normal recording and reproduction cannot be performed.

However, in the above-mentioned conventional defect inspection method and apparatus, such unevenness in the thickness of the hard coat film could not be detected. FIG. 5 shows the inspection light reflected from the substrate a side through the hard coat film and into the air.
Further, FIG. 3 is a graph showing an example of the relationship between the incident angle θ and the reflectance R / (T + R) when light is incident on the interface between two substances having different refractive indices from the side of the substance having a high refractive index. . As in the conventional inspection apparatus, the inspection light incident from the surface of the hard coat film b at an angle substantially perpendicular to the surface of the hard coat film b
As shown on the left side of FIG. 5, the reflected light is reflected by the reflection film (not shown in FIG. 5) through the substrate a, and is almost perpendicular to the interface between the hard coat film b and the air, or a very small incident angle θ.
Injects at 1. Therefore, as can be seen from the graph of FIG. 3, the amount of the reflected light R1 is small, and most of the light is transmitted as the transmitted light T1 through the surface of the hard coat film b and is received by the light receiver 8. On the other hand, as shown in the right side of FIG. 5, the hard coat film b
If the surface has unevenness and the surface is convex, the incident angle θ2 of the reflected light on the surface becomes slightly larger than the incident angle θ1 at the flat part, but When the angles θ1 and θ2 are in a small range, specifically, θ1 is 10 ° or less, even if the difference between θ2 and θ1 is about 10 °, R1 and R2
And the transmitted light T1 and T2 received by the light receiver 8 is small.
There is no big difference. Therefore, the above-mentioned defects cannot be detected.

In view of the above-mentioned conventional problems, the present invention provides an optical information recording disk capable of more accurately detecting defects such as film thickness unevenness of a hard coat film formed on a transparent substrate. An object is to provide an inspection method and an inspection device.

[0009]

That is, according to the present invention,
In order to achieve the above object, an optical information recording disk in which a transparent hard coat film is provided on a transparent substrate and at least a reflective film is formed on the back side of the substrate is inspected by light reflected from the reflective film. In the method for inspecting an optical information recording disk, the incident angle when the reflected light from the reflective film is incident on the interface between the hard coat film and the air is a critical angle θc−15 at the interface between the hard coat film and the air. Provided is a method for inspecting an optical information recording disk, characterized in that it is not less than ° and smaller than θc.

[0010]

In the above-described optical information recording disk inspection method, when the inspection light from the light source directed to the surface of the hard coat film is incident, the reflected light from the reflection film is incident on the interface between the hard coat film and air. Since the incident angle is set to the critical angle θc−15 ° or more at the interface between the hard coat film and air, as is apparent from FIG. 3, the inspection is performed at the portion where the slope of the reflectance-incident angle curve starts to become steep. As a result, even if there is a slight difference in the incident angle due to the unevenness of the thickness of the hard coat film, the difference in reflectance becomes large, so that the transmitted light transmitted from the surface of the hard coat film into the air can be reduced. The difference also increases. For this reason, there is a large difference in the amount of light received by the photodetector between where the hard coat film has unevenness and where it does not, and it is easy to detect unevenness in film thickness. Further, since the reflection angle when the reflection light from the reflection film is incident on the interface between the hard coat film and the air is smaller than the critical angle θc, the reflection light is totally reflected and there is no transmission light. Never,
The reflected light of the inspection light can be reliably received by the light receiver in the flat portion where the thickness of the hard coat film is uniform.

[0011]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows an outline of an optical information recording disk inspection apparatus according to an embodiment of the present invention. The optical information recording disk 21 has its center clamped by a clamper 22,
It is rotated by the motor 23. An inspection optical pickup 29 including a light source 27 and a light receiver 28 is arranged on the transparent substrate side of the rotated optical information recording disk 21, and the inspection optical pickup 29 is controlled by a servo controller 30 by a servo mechanism 26. Is used to move the optical information recording disk 21 in the radial direction. The optical pickup 29 is provided with a light source 27 of a laser oscillator for emitting inspection light and a light receiver 28 for receiving reflected light of the inspection light from the optical information recording disk 21 side. The optical axes of the optical receiver and the light receiver 28 are arranged so as to form an angle of θ0 with respect to a perpendicular line standing on the surface of the optical information recording disk 21. In this θ0, the light reflected from the reflection film is hard. From the condition of the incident angle when entering the interface between the coat film and air,
It is set by the following formula. sin ⁻¹ (n2 sin (θc−15 °) −λ / p) ≦ θ
0 θ0 <sin ⁻¹ (n2 sin θc−λ / p) where n2 is the refractive index of the hard coat film, λ is the wavelength of the inspection light, p is the group formed on the disk substrate,
That is, the pitch of the spiral groove. Further, the critical angle θc is represented by θc = sin ^-1 (n1 / n2), as is known,
n1 is the refractive index of air, and n2 is the refractive index of the hard coat film as described above.

In FIG. 1, reference numeral 33 is the light source 27.
31 is a controller for controlling irradiation of inspection light from
Is a measuring device that measures the amount of light received by the light receiver 28, and reference numeral 32 is these measuring device 31 and controller 33.
It is a computing unit that computes the numerical value obtained from and processes the inspection result. In this optical information recording disk inspection device, while rotating the optical information recording disk 21 by the motor 23,
The servo mechanism 6 moves the optical pickup 29 in the radial direction of the optical information recording disk 21. Thereby, while scanning the surface of the substrate of the optical information recording disk 21, the inspection light is made incident on the surface of the substrate, and the light reflected from the reflective film is received by the light receiver 28.

FIG. 2 schematically shows a path of light which is incident on the optical information recording disk from the light source 27. here,
Light incident from the light source 27 on the surface of the hard coat film b at an incident angle θ 0 is refracted at the surface of the hard coat film b and the interface between the hard coat film b and the substrate a, and the interface c between the substrate a and the reflection film c. Is reflected by. This reflected light is reflected by the hard coat film b.
The light is refracted at the interface between the substrate a and the surface of the hard coat film b, penetrates into the air, and is received by the light receiving film device 28. If the surface of the hard coat film b is uneven and the flatness is partially lost, the incident angle θ1 at which the reflected inspection light is incident on the interface with the air from the hard coat film b.
Will be even larger. Therefore, the reflectance of the light reflected to the hard coat film b side at the interface between the hard coat film b and the air becomes large, and the amount of light that is transmitted to the light receiver 28 side and received is reduced accordingly. In this way, the photodetector 2 in the portion where the hard coat film has thickness unevenness and the portion where there is no thickness unevenness
Since the amount of received light at 8 largely changes, it is possible to easily detect the film thickness unevenness existing in the hard coat film. The light received by the light receiver 28 is converted into an electric signal by the light receiver 28, measured by the measuring device 31 by the electric quantity such as the voltage, and the value is calculated by the calculator 32 to determine whether there is a defect. To be inspected.

[0014]

As described above, according to the present invention, the inspection of the optical information recording disk capable of more accurately detecting the defect such as the film thickness unevenness of the hard coat film formed on the transparent substrate. It is possible to provide a method and an inspection device.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical information recording disk inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a path of light incident on an optical information recording disk from a light source in the example.

FIG. 3 is a graph showing an example of a relationship between an incident angle when light is incident on the interface between two substances having different refractive indices from the side having a high refractive index and the reflectance at the interface at that time.

FIG. 4 is a graph showing the principle of a method for inspecting an optical information recording disc.

FIG. 5 is a schematic view of a conventional optical information recording disk inspection apparatus.

FIG. 6 is a diagram schematically showing a path of light incident on an optical information recording disc from a light source in the conventional example.

[Explanation of symbols]

 21 optical information recording disk 22 clamper 23 motor 26 servo mechanism 27 light source 28 light receiver 29 inspection optical pickup 30 servo controller 31 measuring instrument 32 arithmetic unit 33 controller

Claims (1)

[Reference Number] 0040147-01 [Claims] 1. An optical information recording optical disc in which a transparent hard coat film is provided on a translucent substrate, and at least a reflective film is formed on the back side of the substrate by the reflected light from the reflective film. In the method for inspecting a recording disk, when the reflected light from the reflective film is incident on the interface between the hard coat film and the air, the incident angle is not less than the critical angle θc −15 ° at the interface between the hard coat film and the air. And a method for inspecting an optical information recording disk, characterized in that it is smaller than θc.