JPH07225198A - Line inspection method of glass substrate - Google Patents

Abstract

PURPOSE:To obtain the line inspection method in which the quality and the yield of a glass substrate for a magnetic recording medium or a liquid-crystal display plate are enhanced. CONSTITUTION:Before a magnetic film or the like is formed on a substrate 1, the outward appearance of the substrate 1 is inspected by an automatic transmission-type outward-appearance inspection apparatus 6. That is to say, a laser beam from a laser light source 12 is shone at the substrate 1 via a collimator 13, a polygon mirror 14 and a Fourier lens 15, and a transmitted beam is receibed by sensors 17, 18 via a Fourier lens 16, a detection signal by the sensors 17, 18 is thresholdprocessed by a comparator or the like, it is then taken into a computer, it is changed into a two-dimensional image, the image is processed, and the existence of a flaw is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line inspection method for inspecting defects in a glass substrate production line for a magnetic recording medium, a glass substrate for a liquid crystal display panel or the like using an automatic appearance inspection apparatus.

[0002]

2. Description of the Related Art The process of producing a disk-type magnetic recording medium substrate can be roughly divided into a process of manufacturing the substrate itself and a process of forming a magnetic film or the like on the substrate.
The substrate used in the past is an aluminum substrate, and this aluminum substrate reflects light.Therefore, as a visual inspection to check whether there are any defects such as scratches or foreign matter on the surface of the substrate, it is necessary to check the appearance of the substrate at the time of receiving and The same appearance inspection method that uses reflected light is used at the time of shipping after the film.

As a visual inspection method, there is a visual inspection in which a halogen lamp light or the like is applied to the surface of the substrate and the reflected / scattered light from a defect on the surface is visually inspected. In this visual inspection, scattered light has directivity depending on the type of defect, so when a person looks at a defect, the person manipulates it so that the defect can be seen easily by changing the irradiation angle to the substrate. is doing.

Further, by shining light on the surface of the substrate and reflecting it.
The scattered light is captured by a CCD camera or the like, and the features of the defect are extracted from the defect image to determine the presence or absence of the defect, or the laser spot light is irradiated onto the substrate surface, and the reflected / scattered light from the substrate is received by the light receiving element. There is an automatic appearance inspection device that determines whether or not there is a defect by converting the electric signals into electric signals. Here, when the laser spot is used, it is necessary to scan the surface of the substrate. Therefore, after the image is recombined into a two-dimensional image on a computer, the same image processing as that of a CCD camera is usually performed to determine the presence or absence of a defect.

[0005]

By the way, a magnetic recording medium is becoming higher in density and thinner, and a glass substrate has been used as a substrate applicable to the magnetic recording medium. However, the glass substrate has a transparency in visible light. Since it is higher than the aluminum substrate, the conventional automatic visual inspection device cannot support it.

That is, since the glass substrate has a low reflectance,
In the defect detection method that depends on the change in the amount of reflected light, the incident angle of the light on the substrate is limited.As a result, the direction dependency for defect detection increases, and oversight often occurs in automatic visual inspection. To do. On the other hand, in the visual inspection, the above-mentioned restrictions can be supplemented by experience, but if an inspection that depends on experience is included in the process, quality will vary.

[0007]

In order to solve the above-mentioned problems, the present invention provides a method of forming a magnetic film or the like on a glass substrate by using a transmission type automatic visual inspection apparatus before adding a value to the glass substrate. A visual inspection was performed.

[0008]

In a thin glass substrate used as a glass substrate for a magnetic recording medium, most of visible light is transmitted and the transmitted light is changed due to a defect on the substrate. Therefore, the defect can be inspected with the transmission type automatic appearance device before the process of adding value such as the film forming process, and further, it can be regenerated by cleaning the substrate and the dust that are definitely defective at the product stage. It can be classified as a substrate.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a block process diagram of a substrate production line in which the line inspection method for a magnetic recording medium substrate to which the present invention is applied is implemented, and FIG. 2 is a conceptual configuration diagram of a transmission type automatic appearance inspection device.

Explaining the production process of a glass substrate for a magnetic recording medium, the substrate 1 as a material is cut into a circular shape through a glass cutting process 2, and at this time, a clamp portion for holding the substrate is also processed and the donut is processed. Become a state.
The processed substrate 1 is chamfered at the cut portion in the chamfering step 3, and is then polished in the polishing step 4 so that the surface becomes a mirror surface. After the cleaning step 5, the abrasive grains and the like after polishing are removed. After being washed off, the appearance inspection of the substrate surface is further performed by the transmission type automatic appearance inspection device 6.

Then, a magnetic film or the like is formed on the substrate which is confirmed by the appearance inspection that the surface of the substrate is normal, and a lubricating oil is applied in the lubricant applying step 8,
After that, foreign substances and the like on the surface of the magnetic film are removed in a burnishing step 9, performance evaluation as a medium is performed in an evaluation step 10, and finally a visual inspection is performed to check and the product 11 is shipped.

Here, the appearance inspection by the automatic appearance inspection device 6 will be described. In this appearance inspection, the chipping or cracking of the inner and outer peripheral edge portions of the substrate that occurs when the substrate is molded or during polishing, and the substrate that occurs during substrate polishing Detects scratches on the surface, stains such as cleaning marks generated during substrate cleaning, stains attached during line movement, and defects such as handling scratches.

As shown in FIG. 2, the automatic visual inspection apparatus 6 collects the laser light from the laser light source 12 on the substrate 1 after the polishing and cleaning process through the collimator 13, the polygon mirror 14 and the Fourier lens 15. The light radiated and transmitted through the substrate 1 is received by the sensor 17 such as a photomultiplier or a photodiode via the Fourier lens 16, and a sensor 18 is provided in the vicinity of the bright field image received by the sensor 17. After the detection signals of 18 are thresholded by a comparator or the like, they are taken into a computer for two-dimensional imaging and image processing to determine the presence or absence of defects.

Further, in order to inspect the inner and outer edge portions of the substrate 1, a fiber light source 21 using a halogen lamp, CCD cameras 22 and 23 for the inner circumference, and CCD cameras 24 and 25 for the outer circumference are provided. The CCD cameras 22 to 25 are arranged, and image processing is performed on the detection signals of the CCD cameras 22 to 25 to inspect for defects in the edge portion.

The operation of the automatic inspection device 6 will be described below.
Laser light from the laser light source 12
The polygon mirror 14 scans through the lens a and the lens 13, and at the same time, the substrate 1 is rotated to scan the entire surface of the substrate 1. At this time, if there is a defect such as a foreign substance or a scratch in the spot of the laser beam applied to the surface of the substrate 1,
Since the light intensity of the laser light transmitted through the substrate 1 changes,
It is possible to determine a defect having a large amount of change as a defect.

Further, the sensor 17 to which the light transmitted through the substrate 1 is directly incident is sensitive to a defect that absorbs light such as foreign matter and dirt, but is arranged at a position deviated from the optical path. The sensor 18 thus diffracts light on the surface of the substrate 1.
When there is a scattering defect, the laser light is incident through the optical path shown by the dotted line in FIG. 2 and reacts sensitively to this.

Therefore, when the signal intensity change of the sensor 17 is larger than the signal intensity change of the sensor 18 by the signal intensity of the sensors 17 and 18, it can be discriminated as a light absorbing defect, and the signal intensity change of the sensor 17 is changed. When the change is smaller than the signal intensity change of the sensor 18, it can be identified as a light diffraction / scattering defect.

Further, by image-processing the received light signals of the CCD cameras 22 to 25, unlike the glass substrate,
It is possible to inspect defects such as cracks and cracks in the inner and outer peripheral portions that greatly affect the strength of the substrate 1 itself.

In this way, by performing an external appearance inspection in the substrate production line before the film forming step, the defective product caused by the glass substrate can be removed from the line without passing to a high value-added post-process such as film forming. Can be removed. Also, by monitoring the yield generation status in the board production process, it is possible to grasp various information online, such as that many defects occur at the inner and outer peripheral edges and many defects occur on the entire substrate. As a result, it becomes possible to quickly search what has occurred in the previous process based on the information, and to promptly take countermeasures in the light of past cases.

In the above embodiment, an example in which the present invention is applied to a production line for a glass substrate for a magnetic recording medium has been described.
It can also be applied to the case of inspecting 100% of scratches and foreign substances existing on a transparent glass substrate for (Color Flat Panel).

[0021]

As described above, according to the present invention,
Since the appearance inspection of the glass substrate is performed by the transmission type automatic appearance inspection device before adding the added value such as the step of forming a magnetic film on the glass substrate, the defective glass substrate should be removed early. As a result, the quality of the product is improved, the yield is improved, and the feedback to the production line regarding the occurrence of defects can be promptly provided.

[Brief description of drawings]

FIG. 1 is a block process diagram of a substrate production line in which a line inspection method for a substrate for a magnetic recording medium to which the present invention is applied is carried out.

FIG. 2 is a conceptual configuration diagram of a transparent automatic visual inspection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Cutting process, 3 ... Chamfering process, 4 ... Polishing process, 5 ... Cleaning process, 6 ... Automatic visual inspection apparatus, 7 ... Film forming process, 8 ... Lubricant applying process, 9 ... Burnish process 10,
... Evaluation process, 11 ... Product, 12 ... Laser light source, 14 ...
Polygon mirrors, 17, 18 ... Sensors.

Claims (3)

[Claims] 1. A line inspection method for inspecting defects on a glass substrate production line, wherein the appearance inspection of the glass substrate is performed by a transmission type automatic appearance inspection device before the step of adding value to the glass substrate. Line inspection method for glass substrates. 2. The glass substrate line inspection method according to claim 1, wherein the glass substrate is a glass substrate for a magnetic recording medium or a liquid crystal, and the step of adding value adds a film on the glass substrate. A glass substrate line inspection method, which is a process. 3. The glass substrate line inspection method according to claim 1, wherein the transmission type automatic visual inspection device includes a sensor device for detecting transmitted light, and the sensor device includes a sensor arranged on an optical path. A line inspection method for a glass substrate, comprising: a sensor arranged at a position deviated from an optical path, and detecting a defect based on a detection signal of these sensors.