JPH0431753A - Foreign-matter inspecting apparatus - Google Patents

Abstract

PURPOSE:To suppress the effect of the scattered light caused by the surface roughness of a material under inspection to a minimum and to detect the scattered light from a foreign matter readily by specifying the emitting direction of detecting light on the surface of the material under inspection and the detecting direction of the scattered light. CONSTITUTION:A light emitting means 3 is arranged so that the light is emitted in the direction in parallel with the rolling direction of a base material 1. A slant angle theta of detecting light from the light emitting means 3 with respect to the base material 1 is usually selected at 5 - 25 degrees so as to increase the scattered light from a foreign matter. A detecting means 8 for detecting the scattered light from a detecting position is provided so that the optical axis is inclined to the side where the means 3 is arranged with respect to the base material 1. The slant angle alpha is set at 60 degrees or less. The scattered light (noise) caused by the irregularities on a material under inspection itself is suppressed to a minimum by specifying the angle of the optical axis, and the scattered light caused by the foreign matter can be positively detected.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to metal substrates used for manufacturing shadow masks, lead frames, electrodes for fluorescent display tubes, etc., or to forming a resist coating layer on the metal substrate. The present invention relates to a foreign matter inspection device for inspecting the presence or absence of foreign matter, defects, etc. (hereinafter simply referred to simply as foreign matter) on the surface of a base material, etc.

[Conventional technology]

The photofabrication process used to manufacture shadow masks, lead frames, electrodes for fluorescent display tubes, etc. includes pretreatment and degreasing processes for metal substrates, resist coating processes, plate making processes, etching, peeling and cleaning processes, etc. Each of these steps is automated (inlined). However, although automation of monitoring of each process and visual inspection has not been carried out, there is a great need for these. In particular, there is a strong desire to automate visual inspection after resist coating. This is because when a defect occurs in the resist coating, it has a large effect on the yield rate.

[Problem to be solved by the invention]

However, at present, no device has been developed that can be practically used as an automatic foreign matter inspection device for substrates after resist coating. This is because it is difficult to detect foreign matter due to the characteristics of the surface of the material used for photofabrication.

In general, there is a known method for detecting foreign matter attached to a flat surface, in which the surface to be inspected is irradiated with a light beam such as a laser beam, and the light scattered by the foreign matter is detected (for example, JP-A No.
(See Publication No. 67845). Therefore, it is conceivable to apply this technique to the detection of foreign substances on the surface of a substrate after resist coating. However, many of the materials used in photofabrication are rolled metal materials (metal substrates) and have a fairly large surface roughness (compared to glass substrates or silicon substrates). When irradiated with , the irregularities on one surface also cause diffuse reflection, and the scattered light becomes noise and hides the scattered light from the foreign object, making it impossible to detect the foreign object.

Further, when the metal substrate is coated with a resist, the resist surface becomes flat. However, the resists used in photofabrication.

Usually, dichromate is added to a water-soluble colloid such as casein or PVA, and these resists are almost transparent, and are transparent even to the light irradiated to detect foreign substances, so they can be used to detect the surface of metal materials. The roughness of the surface causes diffuse reflection, making it difficult to detect foreign objects.

The present invention has been made in view of the above problems. 1) It is possible to prevent foreign matter on the surface of a material to be inspected, such as a metal substrate with a rough surface or a substrate formed by providing a transparent resist coating layer on the metal substrate. The object of the present invention is to provide a foreign substance inspection device that can detect foreign substances.

[Means to solve the problem]

The present inventors have made extensive studies to achieve the above objective.

By specifying the direction of irradiation of the detection light on the surface of the material to be inspected and the direction of detection of the scattered light, it is possible to minimize the influence of scattered light due to surface roughness of the material to be inspected, and easily detect light scattered by foreign objects. The present invention was completed based on the discovery that the following was true.

In other words, in the present invention, the detection light is directed to the detection position of the material to be inspected,
It includes an irradiation means that irradiates from a direction oblique to the surface of the material to be inspected, and a detection means that detects scattered light from the detection position, and the optical axis of the detection means is arranged so that the optical axis of the detection means irradiates the surface of the material to be inspected. The gist of the present invention is a foreign matter inspection device characterized by being inclined toward the side on which the means is disposed.

Here, the detection light irradiated by the irradiation means is as follows:
It is preferable to use incoherent light emitted from a halogen lamp or the like.

In addition, if the material to be inspected is a rolled metal substrate used for a mask or a base material with a resist coating layer thereon, the detection light is directed toward the material to be inspected in a direction parallel to the rolling direction. and 5 to 25 for the inspected material.
It is preferable to irradiate from an oblique direction.

〔Example〕

The present invention will be described in further detail below with reference to embodiments shown in nine drawings.

FIG. 1 is a schematic side view showing an embodiment in which the present invention is applied to foreign matter detection in a shadow mask base material after resist coating, and FIG. 2 is a schematic plan view of the main parts thereof. In Figures 1 and 2, 1 is the base material that is the material to be inspected, and 2 is the roll I.
It is sent in the form of A and is unwound from the winder IA. As shown in FIG. 3, this base material 1 has a resist coating layer 1b formed on the surface of a metal substrate 1a made by rolling a metal material, and the surface of the metal substrate 1a has minute irregularities caused by rolling. is formed.

In FIGS. 1 and 2, reference numeral 2 denotes a conveyance roller that conveys the base material 1 in its longitudinal direction, that is, in the direction of arrow A.

Note that the longitudinal direction of the base material 1 (direction of arrow A) naturally coincides with the rolling direction of the metal substrate 1a that constitutes the base material 1.

Reference numeral 3 denotes an irradiation means for irradiating the detection position of the base material 1 with the detection light 4. In this embodiment, this detection position is connected to the straight line XX perpendicular to the rolling direction (direction of arrow A) of the base material 1. It is above. The irradiation means 3 includes a light source 5 made of a halogen lamp that irradiates incoherent light, a lens 6 that focuses the light from the light source 5 into a thin strip on a straight line Among them, a yellow filter 7 is provided for canting the portion where the resist coating layer is exposed to light. Furthermore, this irradiation means 3 detects the detection position of the base material 1 (on the straight line XX).

The rays are arranged so as to irradiate the base material 1 from an inclined direction, and from a direction parallel to the rolling direction of the base material 1 when the base material 1 is viewed from above. . Inclination angle θ of detection light 4 from irradiation means 3 with respect to base material 1
(See FIG. 1) is preferably set to be as small as possible in order to increase the amount of light scattered by foreign objects.1 Usually, it is selected to be between 5 and 25 degrees.

8 is a detection means for detecting the scattered light 9 from the detected value IF (on the straight line XX), and includes an imaging lens IOA, a linear image sensor IOB, and the like. This detection means 8 is
As can be clearly seen from FIG. 1, the optical axis is provided so as to be inclined toward the side on which the detection means 3 is disposed with respect to the base material 1. The angle of inclination α is also preferably smaller, and is preferably 60 degrees or less.

Next, the operation of the foreign matter inspection apparatus having the above configuration will be explained.

The base material 1 is traveling in the direction of arrow A, and at this time, the irradiation means 3 irradiates the detection position (on the straight line XX) on the upper surface of the base material 1,
The detection means 8 monitors the scattered light from the detection position. If there is a foreign object, the detection means 8 detects the scattered light caused by the foreign object.
detects foreign objects. In this way, foreign matter on the entire surface of the base material 1 can be automatically detected.

Here, as described above, the surface of the metal substrate 1a (see FIG. 3) of the base material 1 has small irregularities due to the transfer of the roughness of the rolling roll during the rolling process.

These irregularities are covered by the resist coating layer 1b, but since the resist coating layer itself is transparent, when irradiated with the detection light 4, scattered light is generated due to the irregularities on the surface of the metal substrate, which is different from the scattered light due to foreign objects. Difficult to differentiate. However, in this embodiment, the above-mentioned irradiation means 3
and by employing an array of detection means 8.

It is possible to reliably detect light scattered by foreign objects. The reason for this will be explained below.

As shown in FIG. 4, a base material 11 (same as the base material 1 in the embodiment shown in FIG. 1) free of foreign matter is prepared, and a small detection position B on the base material is set with respect to the base material ll. It was irradiated with detection light 13 from a light source (halogen lamp) 12, and scattered light 14 at the detection value WB was detected by detection means 15 arranged on a line perpendicular to position B. The position of the light source 12 at this time is
while keeping the incident angle θ to 30 degrees.

The angle θ of the detection light with respect to the substrate rolling direction A when viewed from the top was changed to various angles. This test was performed on a large number of base materials 11, and the scattered light intensity (reflection intensity) on the surface of the base material 11 was detected by the detection means 15.
The relationship between the angle θ and the angle θ is shown in the graph of FIG. In addition, the relationship between the standard deviation of the scattered light intensity and the angle θ at that time is shown in the graph of Figure 6.As is clear from these graphs, the angle θ
When is set to O or 180 degrees, that is, when the irradiation direction of the detection light when viewed from the top is parallel to the rolling direction of the base material 11, the 1 reflection intensity is small and the variation is small, and vice versa. Furthermore, when the direction of irradiation of the detection light is perpendicular to the rolling direction, the single reflection intensity is large and the variation is also large.

Based on the above, if the detection light is irradiated onto the base material to be inspected in a direction parallel to its rolling direction, it is possible to reduce the intensity of scattered light due to the surface roughness of the base metal substrate itself. can. This scattered light becomes noise when detecting foreign objects, so it is desirable to keep it as small as possible.
In the embodiments shown in FIGS. 1 and 2 described above.

The irradiation means 3 is arranged so as to irradiate the detection light 4 in a direction parallel to the rolling direction A of the base material 1.

Next, in FIG. 7, the position of the light s12 is adjusted so that the irradiation direction of the detection light 13 when viewed from the top coincides with the rolling direction A of the base material 11, and the angle of the detection light 13 with respect to the base material 11 is adjusted. The angle θ was varied and the intensity (N) of scattered light in each case was detected. A similar test was conducted with a foreign object placed at detection position B of the base material 11, and the intensity (S) of scattered light from detection position B was detected.

The ratio (S/N) is calculated from these detected values, and the angle θ
The graph shown in FIG. 8 is the graph shown in FIG. As is clear from this graph, the S/N can be increased by reducing the inclination angle θ, especially by setting it to 25 degrees or less. In other words, foreign matter can be detected reliably. From this point of view, in the above embodiment, the inclination angle θ of the detection light 4 by the irradiation means 3 is set within the range of 5 to 25 degrees.

Next, as shown in FIG.
When the detection light 13 from the base material 11 is viewed from above, it is parallel to the rolling direction A of the base material 11, and the inclination angle θ with respect to the base material 11 is 2.
The angle α formed with respect to the base material 11 is changed while keeping the position of the detection means 15 parallel to the rolling direction A when the tip axis thereof is viewed from above. The intensity (N) of scattered light from the base material 11 was detected by changing the following. A similar test was conducted with a foreign object placed at detection position B of the base material 11, and the intensity (S) of scattered light from position B was detected. The ratio (S/N) was calculated from these detected values and plotted against the angle θ in the graph shown in FIG. In this graph, angle α=0 is a position where the detection means 15 is on the same side as the light source 12 with respect to position B and its optical axis is parallel to the base material 11. As is clear from this graph, if the angle α is made as small as possible.

Therefore, the light source 1 is
If it is arranged on the same side as No. 1 and its optical axis is inclined at a small angle with respect to the base material, the S/N can be increased. From this point of view, in the above embodiment, the detection means 8 is arranged on the same side as the irradiation means 3, and is tilted at a small inclination angle α with respect to the base material 1.

Next, as shown in FIG. 9, the inclination angle θ of the detection light 13 is set to 2.
The angle α of the detection means 15 was maintained at 0 degrees and measurements were performed to determine the S/N. This test was conducted using a halogen lamp and a He-Ne laser as the light source 12, respectively. The results are shown in FIG. 11. As is clear from this graph, the S/N is improved when incoherent light from a halogen lamp is used as the light source rather than laser light. This is thought to be because noise is generated due to speckles when laser light is used due to minute irregularities on the surface of the metal substrate constituting the base material. From this point of view, in the above embodiment, a halogen lamp that emits incoherent light is used as the light source 5 of the irradiation means 3, thereby increasing the S/N ratio and enabling good foreign object detection.

For the above reasons, the embodiments shown in FIGS. 1 and 2 are used.

It is possible to reliably detect light scattered by foreign objects.

In addition, in the above embodiment, the metal substrate 1a constituting the base material 1
has unevenness due to rolling, and since the unevenness has directionality, the irradiation direction of the detection light is set parallel to the rolling direction (that is, the angle e is 0 degrees or 180 degrees). However, depending on the base material, this direction may be different, so the direction of irradiation of the detection light may be appropriately selected depending on the base material.

Further, in the above embodiment, foreign matter detection is performed on a base material provided with a resist coating layer, but the present invention is not limited to this case, but can also be applied to foreign matter detection on the surface of a metal substrate before resist coating. Needless to say,
Furthermore, in the above embodiment, a case was shown in which foreign object inspection was performed continuously on a long base material set in a rolled state.
The present invention is not limited to this case, but can also be applied to a flat base material cut into an appropriate size.

(Effects of the Invention) As described above, the present invention includes an irradiation means that irradiates detection light onto a detection position of a material to be inspected from a direction oblique to the material to be inspected, and detects scattered light from the detection position. Since the optical axis of the detection means is inclined toward the side where the irradiation means is arranged with respect to the surface of the material to be inspected, scattered light (noise) due to the unevenness of the material to be inspected itself is ) and can detect light scattered by foreign objects.

Also, if incoherent light is used as the detection light,
Noise caused by unevenness on the surface of the inspected material can be further suppressed.

- Detection of layer foreign matter becomes reliable.

Furthermore, if the material to be inspected is a single rolled metal substrate or a base material with a transparent resist coating layer formed on the surface of the metal substrate, the detection light is applied to the material to be inspected in the rolling direction. 5 in the parallel direction and against the inspected material
By irradiating from a direction inclined at ~25 degrees, noise caused by unevenness on the surface of the material to be inspected can be further suppressed, and the detection of -layer foreign matter can be ensured.

Thus, according to one aspect of the present invention, it is possible to automatically detect foreign substances on the surface of a long object to be inspected.
In the photo application process, it becomes possible to automatically inspect the appearance of the base material after resist coating, which is extremely useful industrially.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view showing an embodiment in which the present invention is applied to foreign matter detection on the surface of a shadow mask base material after resist coating, Fig. 2 is a schematic plan view thereof, and Fig. 3 is a cross section of the base material. FIG. 4 is a perspective view schematically showing the state in which a test is carried out to examine the influence of the angle e of the detection light on the rolling direction of the base metal substrate, and FIG. 5 is the angle. A graph showing the relationship between θ and the scattered light intensity, FIG. 6 is a graph showing the relationship between the angle θ and the variation (standard deviation) of the scattered light intensity, and FIG. 7 is a graph showing the relationship between the angle θ and the scattering light intensity variation (standard deviation). FIG. 8 is a graph showing the relationship between the angle θ and S/N, and FIG. 9 is a graph showing the angle α of the optical axis of the detection means with respect to the base material. A perspective view schematically showing the state in which a test is conducted to investigate the influence, Fig. 10 is a graph showing the relationship between the angle α and S/N, and Fig. 11 shows the angle α when using different light sources.
It is a graph which shows the relationship between and S/N. 1...Base material, la--metal substrate, 1b-resist coating layer, 2-transport roller, 3--irradiation means, 4
-detection light, 5-light source, 6-lens, 7-filter,
8-detection means, 9-scattered light, 10A-lens, 10
B-linear image sensor, 11-base material, 12--light source, 13--detection light, 14--scattered light, 15-detection means. Agent Patent Attorney Kyo Matsu 3rd figure 4 fig. 7 Fig. 19 fig. 5? 2 fig. 3 -Short Buno- Hajime Kyouyuki Kaoruchi〆〆×

Claims (3)

[Claims] (1) comprising an irradiation means for irradiating detection light onto a detection position of a material to be inspected from a direction oblique to the surface of the material to be inspected; and a detection means for detecting scattered light from the detection position; A foreign matter inspection device characterized in that the optical axis of the means is inclined toward the side where the irradiation means is arranged with respect to the surface of the material to be inspected. (2) The foreign matter inspection device according to claim 1, wherein the irradiation means irradiates incoherent light as the detection light. (3) The material to be inspected is a rolled metal substrate or a base material having a resist coating layer thereon, and the irradiation means applies detection light to the material to be inspected from a direction parallel to the rolling direction of the material. 3. The foreign matter inspection device according to claim 1, wherein the foreign matter inspection device emits light from a direction inclined at an angle of 5 to 25 degrees relative to the object.