JP2006071284A - Inside and outside discrimination method of flaw of glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple inside and outside discrimination method of the flaw of a glass substrate for making the inside and outside discrimination of the flaw simultaneously with the detection of the flaw. <P>SOLUTION: In the inside and outside discrimination method of the flaw of the glass substrate for discriminating whether the flaw is present on an either one of the inside and outside of the glass substrate, the glass substrate is irradiated with the inspection light emitted from an inspection light source, which is provided so as to leave an interval from the bed glass substrate, at a constant incident angle, and the surface flaw of the glass substrate is detected by a detection camera, which detects the scattering of inspection light due to the surface flaw when the scattering of the inspection light due to the flaw is detected by the detection camera provided so as to leave an interval from the glass substrate, and the scattered light propagated through the glass substrate to be reflected by the back of the glass substrate is twice detected by the detection camera while the back flaw of the glass substrate is only once detected by the detection camera for detecting the scattering of the inspection light entering inside of the glass substrate due to the back flaw, thereby discriminating the inside and outside of the flaw of the glass substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a glass substrate defect front-and-back identification method for identifying whether a defect exists on either the front or back side of a glass substrate, and is a simple glass substrate defect front-and-back type that simultaneously detects a defect and identifies the front and back of the defect. It relates to an identification method. Furthermore, the present invention relates to a glass substrate defect identification method for detecting internal defects in addition to front and back identification of glass substrate defects.

  For example, Patent Literature 1, Patent Literature 2, Patent Literature 3, and Patent Literature 4 are known as methods for identifying the front and back of the position of a glass substrate defect for an FPD or the like.

  Japanese Patent Application Laid-Open No. 2004-133620 is a method of identifying the front and back of a defect position in an imaged state by reducing the depth of focus of a detection camera for detecting a defect and aligning the in-focus position with the surface of a glass substrate. However, in order to reduce the depth of focus, a long focus lens with a narrow angle of view must be used and used near the wide aperture, resulting in a narrow inspection area.

  Patent Document 2 is a method of irradiating a laser beam in a slit shape, picking up an image of a substrate with a detection camera arranged at a specular reflection position, and identifying the front and back of the position of the defect from the deviation of the detection position of the defect by the detection camera. is there. However, a defect front / back discrimination apparatus using this method is expensive, and optical adjustment such as optical axis adjustment is difficult.

  In Patent Document 3, two sets of detection cameras are arranged at different detection angles with respect to the glass substrate, and the front and back of the position of the defect are identified from the amount of deviation of the detection timing of the defect. However, since two sets of detection cameras and arithmetic processing devices for measuring the amount of deviation are required, the devices become expensive and the arithmetic processing becomes complicated.

Patent Document 4 irradiates the surface of an inspection object with two kinds of light beams obliquely at different angles 2, and receives each scattered light from the inspection object via a condenser lens. Detecting with an element, processing the detected signal with a signal processing circuit, and processing the processed signal with an arithmetic processing circuit to determine whether the foreign matter has adhered to the front surface or the back surface of the inspection object Although it is a device for determination, since two sets of detection cameras and arithmetic processing devices for measuring the amount of deviation are required, the device becomes expensive and the arithmetic processing becomes complicated.
JP 2002-139454 A JP-A-8-82602 JP-A-7-113757 Japanese Patent No. 3480176

  The required quality of a glass substrate for a flat panel display (hereinafter abbreviated as FPD) differs between the front surface side and the back surface side depending on the application. Defects in the glass substrate include surface defects such as scratches, protrusions, dirt, and deposits, and internal defects such as millet and cracks. A transparent conductive film is formed in a plasma display panel (hereinafter abbreviated as PDP), and a glass substrate surface side as a processed surface for forming a transparent conductive film or a light shielding film in a liquid crystal display (hereinafter abbreviated as LCD) Usually, the required quality is stricter than the back side where the processing is not performed.

  Usually, for PDP, a glass substrate having a plate thickness of 3.0 mm or less, for example, a plate thickness of 2.8 mm is generally used, and the allowable diameter of surface defects such as adhesion of foreign substances in the required quality is strictly When the diameter is not more than 50 μm, loosely means that the diameter is not more than 300 μm. For LCDs driven by a thin film transistor (hereinafter abbreviated as TFT), a non-alkali glass substrate having a thickness of 0.5 mm or more, for example, a thickness of 0.7 mm or 1.1 mm is generally used. In general, the allowable diameter of the surface defect is strictly that the diameter is not more than 20 μm, and loosely, the diameter is not more than 100 μm.

  In the past, inspectors have judged the presence or absence of defects by visual inspection with a glass substrate in their hands, and at that time, have identified whether the defects are present on the front or back. However, at present, the size of FPD glass substrates has become larger than the meter angle due to the increase in the size of displays for PDP and LCD, the increase in the size of television displays, and the multi-face layout after forming the black matrix for the small display for personal computers in LCD. It is impossible for inspectors to inspect on hand, and automatic inspection machines have been used.

  In an automatic inspection machine, it is difficult to detect whether a defect is present on the front or back or at the same time as it is detected in the automatic inspection machine. It has been identified again whether it is front or back.

  The present invention is a glass substrate defect front-and-back identification method for identifying whether a glass substrate has a defect on either side, and a simple glass substrate defect front-and-back identification method for performing defect detection simultaneously with defect detection. The purpose is to provide.

  The glass substrate defect front / back identification method of the present invention is a glass substrate defect front / back identification method by detecting light scattering of the defect by a detection camera, and detecting while irradiating the glass substrate with a constant incident angle. When the reflected image of the glass substrate by the inspection light is captured by the camera, the surface defect is detected by the camera to detect the scattering of the inspection light by the surface defect, and then the scattered light from the scattering propagates inside the glass substrate and is reflected back. The detection camera detects the detected two times, and the back surface defect is detected by the detection camera detecting and detecting the scattering caused by the back surface defect of the inspection light incident on the inside of the glass substrate. It is characterized by identifying the front and back of a glass substrate defect.

  That is, the present invention is a glass substrate defect front / back identification method for identifying whether a defect exists on either the front or back of a glass substrate, and is irradiated from an inspection light source provided at a distance from the glass substrate being conveyed. The inspection light is irradiated at a constant incident angle with respect to the glass substrate, and surface defects are detected when the detection camera provided at a distance from the glass substrate detects the scattering of the inspection light due to the defects. The detection camera detects the scattering, and then the detection camera detects the scattered light caused by the scattering that has propagated through the glass substrate and reflected from the back surface. The back surface defect is detected by the inspection light incident on the glass substrate. A glass substrate defect front and back identification method characterized in that the front and back of a glass substrate defect is discriminated by detecting a scattering caused by a back surface defect of the glass substrate and detecting only once. .

  Further, according to the present invention, the detection camera detects the scattering of the inspection light due to the surface defect, and further, the detection camera detects that the scattered light due to the scattering propagates through the glass substrate and is reflected from the back surface, and the surface defect is detected twice. The difference S between the real image position of the surface defect due to scattering of the inspection light detected by the detection camera and the virtual image position of the surface defect due to the scattered light due to the scattering propagating through the inside of the glass substrate and reflecting the back surface is expressed. The above-described glass substrate defect front / back identification method, wherein the irradiation width of the inspection light orthogonal to the transport direction of the substrate to be transported is 2 times or more and 10 times or less with respect to the difference S in Equation (1) It is.

In Equation 1, the angle with respect to the normal of the glass substrate surface of the detection camera is represented by θ, the refractive index of the glass substrate is represented by n, and the thickness of the glass substrate is represented by t.

  Further, in the internal identification method for glass substrate defects according to the present invention, in order to identify the internal defects, the difference S between the real image position and the virtual image position of the surface defect represented by the formula 1 is calculated for TFT-LCD or PDP. When a glass substrate having a thickness of 0.5 mm or more and 3.0 mm or less is used, an allowable diameter as a required quality in which surface defects are allowed in defect inspection, strictly, a diameter not exceeding 20 μm, The inspection light incident angle is adjusted to 0 degrees or more and 10 degrees or less, and the detection camera angle is adjusted to 15 degrees or more and 45 degrees or less with respect to the allowable diameter of surface defects such as 20 μm and 300 μm without the diameter of 300 μm or more. Thus, the difference S between the real image position and the virtual image position of the surface defect is set to be 8 times or more of the allowable diameter, and the internal defect is detected and identified. The defect diameter in the present invention is the maximum diameter of one defect, and is normally used as an inspection specification for an allowable defect diameter as required quality, and is measured with an optical microscope, a laser microscope, or the like.

  Furthermore, the present invention provides the above glass substrate in a defect inspection in which the allowable diameter of surface defects is set between 20 μm and 300 μm for a glass substrate having a plate thickness of 0.5 mm or more and 3.0 mm or less. In the defect front / back identification method, the incident angle of the inspection light with respect to the normal of the glass substrate is adjusted to 0 degree or more and 10 degrees or less, and the angle of the detection camera with respect to the normal of the glass substrate is adjusted to 15 degrees or more and 45 degrees or less, A glass substrate characterized in that an internal defect is identified by making a difference S between a real image position and a virtual image position of a surface defect represented by the above formula 1 equal to or more than eight times the allowable diameter. This is a defect identification method.

  In an automatic inspection machine, it is difficult to detect whether a defect is present on the front or back or at the same time as it is detected in the automatic inspection machine. It has been identified again whether it is front or back. According to the glass substrate defect front / back identification method for identifying whether a defect exists on either the front or back of the glass substrate according to the present invention, a simple glass substrate defect front / back identification method for performing defect front / back discrimination simultaneously with the detection of a defect is provided. Furthermore, by adjusting the incident angle of the inspection light with respect to the glass substrate surface and the camera angle with respect to the glass substrate surface, it is also possible to identify internal defects in the glass substrate, so that inspection was performed in accordance with inspection standards for surfaces with strict requirements. Thereafter, it is not necessary to identify again whether the defect position is front or back, and an internal defect is also detected.

  First, an embodiment of the configuration of a defect inspection apparatus used for the glass substrate defect front / back identification method of the present invention will be described.

  FIG. 1 is a schematic side view of one embodiment of a glass substrate defect inspection apparatus.

  As shown in FIG. 1, the apparatus used for the glass substrate defect front / back identification method of the present invention comprises an inspection light source 1 and a detection camera 2, and the detection camera 2 detects scattering of inspection light due to the defect, and the glass substrate. A surface defect attached to the surface of G, a back surface defect attached to the back surface, and / or an internal defect existing inside the glass substrate G are identified. The arrow in FIG. 1 is the conveyance direction of the glass substrate G. In the present invention, the side where the inspection light source 1 and the detection camera 2 are located is the glass substrate surface, and the opposite side is the back surface.

  The conveyance of the glass substrate G is performed by horizontal conveyance or vertical conveyance in which the substrate is laid horizontally, and defect inspection is performed while performing vertical conveyance or horizontal conveyance. In the front / back identification method for a glass substrate defect according to the present invention, as shown in FIG. 1, the inspection light source 1 is obliquely incident on the inspection light source 1 with respect to the glass substrate G transported in a laid state or standing state. The glass substrate G is spaced from the glass substrate G so as to be constant. In other words, the glass substrate G is placed away from the glass substrate G so as not to come into contact therewith. Subsequently, the detection camera 2 is spaced from the glass substrate G so that the optical axis of the camera lens is inclined with respect to the glass substrate G, in other words, the angle θ of the detection camera 2 is inclined. Install so as not to contact the substrate G.

  The inspection light source 1 preferably illuminates the glass substrate G in a thin strip shape. When the inspection light is irradiated in a direction perpendicular to the transport direction of the glass substrate G to be transported so as to form a thin strip, the defect of the glass substrate G to be transported is efficiently performed in the front and back identification method of the glass substrate defect of the present invention. Inspected, it is possible to detect a defect of the glass substrate G and identify the front and back of the defect. For example, LEDs (light emitting diodes) and optical fibers are linearly arranged so as to be orthogonal to the conveyance direction of the glass substrate G and adjusted to an appropriate irradiation width by a condensing lens, or a plurality of light sources are arranged and slit in a light source box And irradiate the inspection light from the slit so as to form a thin strip on the glass substrate G. Specifically, a high-frequency fluorescent lamp is placed in a vertically long light source box, a slit is provided in the light source box, and the inspection light has a slit width. For example, it is possible to adjust the irradiation width of the inspection light with respect to the traveling direction of the glass substrate G. The inspection camera 2 scans the glass substrate G while keeping the angle constant with respect to the glass substrate G while using the inspection light from the inspection light source 1 as a beam in a direction orthogonal to the conveyance direction of the glass substrate G to be conveyed. Although imaging may be performed, the apparatus becomes complicated.

  The detection camera 2 detects light scattered by each defect. The detection camera 2 is preferably a CCD camera using a charge coupled device (CCD) having excellent resolution, and is convenient for imaging a glass substrate while performing arithmetic processing using signals from the CCD. It is. In the inspection of the defects on the glass substrate G using the glass substrate defect front / back identification method of the present invention, it is preferable to use a plurality of CCD cameras because the inspection is efficient.

  Next, the front / back identification method for glass substrate defects according to the present invention will be described.

  FIG. 2 is an enlarged schematic side view for explaining the detection of the surface defect of the glass substrate in the glass substrate defect front / back identification method of the present invention. A dotted line indicates the irradiation range of the inspection light. As shown in FIG. 2, the surface defect 3 is detected twice by a detection camera 2 (not shown). That is, the scattered light detected by the detection camera 2 is directly detected and detected by the detection camera 2 as the inspection light is scattered by the surface defect 3 as shown in FIG. As shown in FIG. 4, after the scattered light propagates through the glass substrate G, the detection camera 2 captures and detects the scattered light reflected from the back surface inside the glass substrate G. These two scattered lights are in the optical path. Is different.

  FIG. 3 is an enlarged schematic side view for explaining detection of a back surface defect of a glass substrate in the front and back identification method for a glass substrate defect of the present invention. As shown in FIG. 3, the back surface defect 4 is detected only once by the detection camera 2 (not shown) detecting the scattering of the inspection light incident on the inside of the glass substrate G by the back surface defect 4. The scattered light from the back surface defect 4 detected by the detection camera 2 is scattered light that is scattered by the back surface defect 4, propagates through the inside of the glass substrate G, is refracted at the surface of the glass substrate G, and reaches the detection camera 2. Only.

  In the front and back identification method for a glass substrate defect according to the present invention, the detection camera 2 detects scattered light due to a defect in the glass substrate G. Therefore, the angle θ formed by the lens optical axis of the detection camera 2 and the glass substrate G, and When the incident angle 8 formed by the inspection light and the glass substrate G coincides, regular reflection occurs, and the inspection light is affected by the reflected light reflected by the glass substrate G, so that the detection camera 2 is overexposed and it is difficult to detect a defect. Therefore, it is preferable to arrange the inspection light source 1 and the detection camera 2 so as not to cause regular reflection.

  While irradiating the inspection light from the inspection light source 1 with a constant incident angle with respect to the glass substrate G surface, the surface of the glass substrate G is photographed by the detection camera 2 provided above the glass substrate G. , Detecting a back surface defect 4 and / or an internal defect. As shown in FIG. 2, when the detection camera 2 provided at a distance from the glass substrate G detects the scattering of the inspection light due to the defect, as shown in FIG. The detection camera 2 detects the scattering of the inspection light due to the surface defect 3, and then, as shown in FIG. 2 (B), the detection camera 2 detects the scattered light propagated through the glass substrate G and reflected from the back surface. Is detected twice. As shown in FIG. 3, the back surface defect 4 is detected only once by the detection camera 2 detecting scattering due to the back surface defect of the inspection light incident on the inside G of the glass substrate.

  As shown in FIG. 2B, when the surface defect 3 is detected twice, the real image position 5 of the surface defect 3 due to the scattering of the inspection light detected by the detection camera 2 and the scattered light due to the scattering are the glass substrate. The distance represented by the deviation from the virtual image position 6 of the surface defect 3 due to propagation through the inside of G and reflection from the back surface, in other words, the difference S is expressed by the equation (1).

  In Equation 1, the angle of the detection camera 2 with respect to the normal line of the glass substrate G is represented by θ, the refractive index of the glass substrate G is represented by n, and the thickness of the glass substrate G is represented by t. Equation 1 is obtained by multiplying the glass substrate thickness t multiplied by sin θ by using the refractive index n of the glass substrate to correct the real image position 5 of the surface defect 3 and the scattering. Is a formula for obtaining a difference S which is a distance represented by a deviation from the virtual image position 6 of the surface defect 3 due to the scattered light propagated through the glass substrate G and reflected from the back surface. For example, when θ = 30 degrees, the difference S = plate thickness t / 1.4142. If the unit of t is μm, the difference S between the real image position 5 and the virtual image position 6 of the surface defect is calculated in units of μm.

  In the glass substrate defect front / back identification method of the present invention, if the irradiation width 7 of the inspection light shown in FIG. 2 is smaller than the distance between the real image position 5 and the virtual image position 6, that is, the difference S, the surface defect 3 is detected twice. It is difficult to detect, and the light irradiation width 7 is preferably at least twice the difference S. Further, in order to detect the surface defect 3, the light irradiation width 7 is preferably at least 10 times the difference S or less. It is not necessary to increase it further, leading to a decrease in detection sensitivity.

  In the glass substrate defect inspection using the glass substrate defect front / back identification method according to the present invention, the difference S is the time difference between the detection timing of the real image and the virtual image of the surface defect 3 by the detection time of the glass substrate G. It is actually measured as the calculated distance.

  Next, detection of internal defects in the front / back identification method for glass substrate defects of the present invention will be described. By using the glass substrate defect front / back identification method of the present invention, the internal defect is also detected by adjusting the incident angle 8 of the inspection light and the angle θ of the detection camera 2.

  FIG. 4 is an enlarged schematic side view for explaining detection of internal defects of the glass substrate in the glass substrate defect front / back identification method of the present invention.

  In the glass substrate defect front / back identification method of the present invention, by increasing the incident angle 8 of the inspection light with respect to the normal line of the glass substrate G, a difference that is a distance as a deviation between the real image position 5 and the virtual image position 6 of the surface defect 3 S increases and is measured by adjusting the angle θ of the detection camera 2 with respect to the normal of the glass substrate G.

In the front and back identification method of the glass substrate defect of the present invention, the allowable diameter of the surface defect 3 in the glass substrate G having a plate thickness of 0.5 mm to 3.0 mm is set between 20 μm and 300 μm. In the glass substrate defect front / back identification method of the present invention, when performing defect inspection, the inspection light incident angle 8, that is, the inspection light incident angle 8 with respect to the normal of the glass substrate G is set to 0 degree or more and 10 degrees or less. Then, the angle θ of the detection camera 2 with respect to the normal line of the glass substrate G is set to 15 degrees or more and 45 degrees or less by changing sin θ and sin ² θ in the expression 1 and is expressed by the expression 1 above. If the difference S represented by the deviation between the real image position 5 and the virtual image position 6 of the surface defect 3 is set to be 8 times or more of the allowable diameter of the surface defect 3, as shown in FIG. The difference S ′, which is the distance represented by the deviation between the real image position 10 due to the scattering of light and the virtual image position 11 of the internal defect 9 due to the back surface reflection of the inspection light incident inside the glass substrate G, is different from the real image position 5 of the surface defect 3. The difference S, which is the distance represented by the deviation from the virtual image position 6 By making it smaller, the internal defect 9 can be identified. If the angle θ of the detection camera 2 with respect to the glass substrate G is smaller than 15 degrees or larger than 45 degrees, the sensitivity of the detection camera 2 is lowered and it becomes difficult to detect the internal defect 9.

  Further, the thickness of the glass substrate for FPD is usually 0.5 mm or more in the glass substrate for TFT-LCD and never thicker than 3.0 mm, and is 3.0 mm or less in the glass substrate for PDP. It is not thinner than 5 mm, and is 0.5 mm or more and 3.0 mm or less. In the glass substrate defect front and back identification method of the present invention, the reason why the thickness of the glass substrate G is 0.5 mm or more and 3.0 mm or less in order to identify the inside of the glass substrate defect is that of the glass substrate G for LCD. In addition to the plate thickness being usually 0.5 mm or more and 3.0 mm or less, the plate thickness is 0.5 mm or less, which is a distance represented by the deviation between the real image position 5 and the virtual image position 6 of the surface defect 3. This is because a certain difference S is small and the internal defect 9 is difficult to identify. In addition, the glass substrate G thicker than 3.0 mm is not used for FPD and is mainly a glass plate for construction, but the allowable diameter of defects of the glass plate for construction is much larger than the glass substrate for FPD. This is because the required quality does not usually differ between the front and back sides.

  In general, in a glass substrate for PDP, the allowable diameter in the required quality of surface defects such as adhesion of foreign matters is strictly not more than 50 μm and loosely not more than 300 μm. In the TFT-LCD glass substrate, strictly speaking, it should be 20 μm or more, and loosely, it should be 100 μm or more. In order to distinguish and detect the internal defect 9 from the surface defect 3 and the back surface defect 4 when using the glass substrate defect front / back identification method of the present invention, the real image position of the surface defect 3 represented by the formula 1 above is detected. 5 and the virtual image position 6 and the difference S, which is the distance represented by the displacement, is an allowable diameter as a required quality that allows surface defects of an FPD glass substrate such as a TFT-LCD glass substrate or a PDP glass substrate. Is 8 times or more of the allowable diameter of 20 μm, 300 μm, etc. when there is no diameter of 20 μm or more, or loosely without the diameter of 300 μm or more. Otherwise, as shown in FIG. 4, the deviation between the real image position 10 due to the scattering of the inspection light by the internal defect 9 and the virtual image position 11 of the internal defect 9 due to the back surface reflection of the scattered light propagating through the glass substrate, as shown in FIG. And the difference S ′, which is the distance represented by the deviation between the real image position 5 and the virtual image position 6 of the surface defect, are not greatly different, and the internal defect 9 is difficult to identify.

  The internal defect 9 is detected accompanying the use of the glass substrate defect front / back identification method of the present invention.

  As shown in FIG. 1, with respect to a glass substrate G having a thickness of 2.8 mm that is vertically conveyed in an upright state, the inspection light is spaced from the glass substrate G so that the incident angle 8 is 5 degrees. And the inspection light source 1 was installed. Next, the detection camera 2 is spaced from the glass substrate G so that the angle θ of the optical axis of the camera lens with respect to the normal line of the glass substrate G is 30 degrees, that is, the angle θ of the detection camera 2 is 30 degrees. Installed. The glass substrate G was imaged by the detection camera 2 provided above the glass substrate G while irradiating the inspection light from the inspection light source 1 with the incident angle 8 kept constant at 5 degrees with respect to the glass substrate G.

  For the detection camera 2 provided at a distance from the glass substrate G, a plurality of CCD cameras were used in order to efficiently identify the front and back of the defect of the glass substrate G being conveyed. The resolution of the CCD, that is, the size of one pixel was determined by the size of the smallest defect existing in the glass substrate G, and one pixel having a size of 20 μm × 20 μm was used.

  The inspection light source 1 used was an inspection light source 1 that irradiates the glass substrate G in a thin band shape in order to efficiently identify the front and back of the defect of the glass substrate G being conveyed. In order to adjust the irradiation width, the inspection light source 1 has optical fibers arranged in a straight line in a light source box provided with a condensing lens, propagates light from the halogen light source, and illuminates the inspection light by illuminating the glass substrate G in an elongated band shape. did.

  The irradiation width 7 of the inspection light shown in FIG. 2 is represented by a deviation between the real image position 5 due to the scattering of the inspection light by the surface defect 3 and the virtual image position 6 of the surface defect 3 due to the back surface reflection of the scattered light propagated inside the glass substrate G. The condensing lens provided in the light source box was slid to adjust the irradiation width to 10.0 mm so that the difference S, which is the distance to be measured, was 5 times 2.0 mm.

  When the glass substrate G transported at a transport speed of 50.0 mm / sec was imaged using the plurality of CCD cameras using the front and back identification device for the glass substrate defect thus produced, the surface defect 3 The real image position 5 due to the scattering of the inspection light by the defect 3 and the virtual image position 6 of the surface defect 3 due to the back surface reflection of the scattered light propagated inside the glass substrate G are represented by a distance represented by the deviation between the real image position 5 and the virtual image position 6. The back surface defect 4 is detected twice with a certain difference S of 2.0 mm, and the back surface defect 4 is detected only once by the back surface defect 4 of the inspection light incident on the inside of the glass substrate G, so that the front surface defect 3 and the back surface defect 4 can be identified. It was. The difference S, 2.0 mm was calculated as a distance by multiplying the time difference between the detection times of the surface defects 3 twice, 0.04 sec, by the conveyance speed of the glass substrate G, 50.0 mm / sec.

  Further, the internal defect 9 has an inspection light incident angle 8 on the glass substrate G of 5 degrees in the defect inspection of the glass substrate G having a plate thickness of 1.5 mm and the allowable diameter of the surface defect 3 of 100 μm. Further, an angle θ of the detection camera 2 with respect to the normal line of the glass substrate G is set to 30 degrees, and a difference S that is a distance represented by a deviation between the real image position 5 and the virtual image position 6 of the surface defect is 11 times the allowable diameter. That is, when the thickness is 1.1 mm, as shown in FIG. 4, the real image position 10 due to the scattering of the inspection light by the internal defect 9 and the internal defect 9 due to the back reflection of the scattered light propagating through the glass substrate G. The difference S ′, which is a distance represented by a deviation from the virtual image position 11, is 0.5 mm smaller than the difference S, 1.1 mm, which is a distance represented by a deviation between the real image position 5 of the surface defect 3 and the virtual image position 6. Thus, the internal defect 9 was identified.

  INDUSTRIAL APPLICABILITY The present invention is useful as a front and back and internal identification method of glass substrate defects in automatic inspection of thin glass substrates, and glass substrates for flat panel displays such as plasma display panels and liquid crystal displays, which are sometimes required to have strict quality requirements.

It is a schematic side view of one form of the glass substrate defect inspection apparatus. It is an expansion schematic side view for demonstrating the detection of the surface defect of the glass substrate in the front and back identification method of the glass substrate defect of this invention. It is an expansion schematic side view for demonstrating the detection of the back surface defect of the glass substrate in the front and back identification method of the glass substrate defect of this invention. It is an expansion schematic side view for demonstrating the detection of the internal defect of the glass substrate in the front and back identification method of the glass substrate defect of this invention.

Explanation of symbols

G glass substrate 1 inspection light source 2 detection camera 3 surface defect 4 back surface defect 5 (surface defect) real image position 6 (surface defect) virtual image position 7 irradiation width 8 incident angle 9 internal defect 10 (internal defect) real image position 11 ( Virtual image position (internal defect)

Claims (3)

A glass substrate defect front / back identification method for identifying whether a defect exists on either the front or back side of a glass substrate, the inspection light emitted from an inspection light source provided at a distance from the glass substrate being conveyed to the glass substrate Irradiation is performed at a constant incident angle, and the surface camera detects the scattering of the inspection light due to the surface defect when the detection camera provided at a distance from the glass substrate detects the scattering of the inspection light due to the defect. Then, the scattered light caused by the scattering propagates through the inside of the glass substrate and is reflected twice by the detection camera, so that the back surface defect is detected by the back surface defect of the inspection light incident on the inside of the glass substrate. A front and back identification method for a glass substrate defect, wherein the front and back identification of the glass substrate defect is performed by detection by the detection camera and detection only once. When the detection camera detects the scattering of the inspection light due to the surface defect, the detection camera detects that the scattered light due to the scattering propagates through the glass substrate and is reflected from the back surface, and the detection camera detects the surface defect twice. The difference in the equation (1) that represents the difference S between the real image position of the surface defect due to the scattering of the inspection light detected by and the virtual image position of the surface defect due to the scattered light propagated through the glass substrate and reflected from the back surface. 2. The method for identifying the front and back of a glass substrate defect according to claim 1, wherein the irradiation width of the inspection light orthogonal to the transport direction of the substrate to be transported is 2 to 10 times.

In Equation 1, the angle with respect to the normal of the glass substrate surface of the detection camera is represented by θ, the refractive index of the glass substrate is represented by n, and the thickness of the glass substrate is represented by t. 3. The defect inspection according to claim 1 or 2 in a defect inspection in which an allowable diameter of a surface defect is set between 20 μm and 300 μm for a glass substrate having a thickness of 0.5 mm or more and 3.0 mm or less. In the front and back identification method for glass substrate defects, the incident angle of inspection light with respect to the normal of the glass substrate is adjusted to 0 ° to 10 °, and the angle of the detection camera with respect to the normal of the glass substrate is adjusted to 15 ° to 45 °. Then, the internal defect is identified by making the difference S between the real image position and the virtual image position of the surface defect represented by the equation (1) of claim 2 equal to or more than eight times the allowable diameter. And a method for identifying a glass substrate defect.

Images