JP7054481B2 - How to manufacture flat glass - Google Patents

Description

The present invention relates to a method for manufacturing a flat glass, which comprises a step of inspecting the presence or absence of internal defects in the flat glass.

With the remarkable development of technologies related to various display devices, technologies related to flat panel displays (FPDs) such as liquid crystal displays and organic EL displays have made great progress. In particular, flat panel displays that realize large-scale, high-definition displays are undergoing advanced technological innovation in order to reduce manufacturing costs and improve image quality. Flat glass used for such displays is also required to have higher dimensional quality and higher precision surface texture than ever before. In the manufacture of flat glass for displays, flat glass is molded using various manufacturing equipment, but in all cases, it is common practice to heat and melt the glass raw material, homogenize the molten glass, and then mold it into a predetermined shape. It has been.

In this manufacturing method, defects such as abnormal surface quality on the flat glass are caused by various causes such as insufficient melting of the glass raw material, unintended contamination of foreign substances during manufacturing, aging of the molding equipment, and temporary malfunction of molding conditions. May occur.

Although various measures have been taken so far to suppress the occurrence of such defects in the flat glass, it is difficult to completely suppress the occurrence of defects. In addition, even if the occurrence of defects can be suppressed to a certain extent, if there is no technology for clearly identifying defective flat glass, defective products that should be originally defective are mixed in the flat glass judged to be non-defective. It will end up. Therefore, the technique of accurately measuring the defect of the flat glass is very important.

For example, Patent Document 1 describes a method for manufacturing a plate glass including an inspection step of measuring the size and depth (distance from the glass surface) of defects existing inside the plate glass (hereinafter referred to as "internal defects") with a laser microscope. Is disclosed.

Japanese Unexamined Patent Publication No. 2015-205811

With the recent increase in the definition of flat panel displays, the circuit pattern formed on the glass substrate tends to be further miniaturized. Therefore, even if the internal defects existing near the surface of the glass substrate are minute, they can cause disconnection or short circuit of the circuit. Therefore, in the measurement of internal defects of a glass substrate, it has been desired to accurately measure the depth, size, and the like of internal defects existing near the surface, and to reduce the increase in measurement time associated therewith. In the case of a glass substrate obtained by the overflow downdraw method, the depth and size of internal defects existing near the mating surface located in the center of the glass substrate in the thickness direction are accurately measured, and the depth and size thereof are accurately measured. It was also desired to reduce the increase in measurement time.

A first object of the present invention is to provide a method for manufacturing a flat glass capable of accurately and efficiently measuring internal defects existing in a specific region such as the vicinity of a surface or the vicinity of a mating surface. A second object of the present invention is to provide a method for manufacturing a plate glass capable of accurately and efficiently measuring internal defects that may affect the surface texture of the surface of the plate glass.

The present invention is for solving the above-mentioned problems, and in a method for manufacturing a plate glass including an inspection step of inspecting an internal defect of the plate glass by imaging the inside of the plate glass a plurality of times with the image pickup device, the image pickup device is used. In the plurality of imaging shots, the focal position of the imaging device is distributed at a predetermined pitch along the thickness direction of the plate glass, and the predetermined pitch is in the first internal region in the thickness direction. , It is characterized in that it is smaller than the second internal region in the thickness direction.

According to such a configuration, for example, the vicinity of the mating surface and / or the guaranteed surface of the flat glass is set as the first internal region, and the first internal region is imaged at a small pitch, thereby causing an internal defect existing in the first internal region. The depth etc. can be measured accurately. Further, by imaging the second internal region at a large pitch, the time required for measuring the internal defects existing in the second internal region can be reduced, and the measurement can be performed efficiently.

It is desirable that the first internal region is near the guaranteed surface of the flat glass, and the second internal region is a region farther from the guaranteed surface than the first internal region.

According to such a configuration, by imaging the internal region near the guaranteed surface at a small pitch, it is possible to accurately measure the depth and the like of the internal defects existing near the guaranteed surface. Further, by imaging the region away from the guaranteed surface at a large pitch, the time required for measuring the internal defects existing in the region away from the guaranteed surface can be reduced, and the measurement can be performed efficiently. Here, the "guaranteed surface" means a surface of both surfaces of the plate glass that is subjected to a film forming process or the like in the manufacturing process of FPD and whose surface properties should be guaranteed, and the non-guaranteed surface is. , Means a surface that does not require as much surface quality as a guaranteed surface.

Further, the image pickup device may be configured to take an image of the inside of the plate glass from the guarantee surface side.

In the method for manufacturing a flat glass having the above configuration, in the inspection step, the predetermined pitch is set as the first pitch in the first internal region near the guaranteed surface, and the second interior is farther from the guaranteed surface than the first internal region. It is desirable that the predetermined pitch is the second pitch in the region, and the first pitch is smaller than the second pitch.

In the method for manufacturing a flat glass having the above configuration, in the inspection step, after the imaging at the second pitch is performed in the first internal region and the second internal region, the imaging at the first pitch is performed in the first internal region. It is desirable to do it in the area. Alternatively, in the inspection step, after the imaging at the first pitch is performed in the first internal region, the imaging at the second pitch may be performed in the second internal region.

In the above-mentioned method for manufacturing a flat glass, it is desirable that the first pitch is 1 μm or more and 10 μm or less. Further, it is desirable that the second pitch is 20 μm or more and 50 μm or less.

According to the present invention, it is possible to accurately and efficiently measure internal defects existing in a specific region in the thickness direction of a plate glass (for example, internal defects that may affect the surface texture of the surface of the plate glass).

It is a side view which shows a part of the plate glass manufacturing apparatus which concerns on 1st Embodiment. It is a side view of an inspection apparatus. It is a flowchart which shows the manufacturing method of a flat glass. It is a flowchart which shows the inspection process. It is a side view which shows one process of the manufacturing method of a flat glass. It is a side view which shows one process of the manufacturing method of a flat glass. It is a side view which shows one step of the manufacturing method of the flat glass which concerns on 2nd Embodiment. It is a side view which shows one process of the manufacturing method of a flat glass.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1 to 6 show an embodiment of a flat glass manufacturing apparatus and manufacturing method according to the present invention.

As shown in FIG. 1, the manufacturing apparatus 1 has a molding unit 2 for continuously molding molten glass GM into a glass ribbon GR by a down draw method, and a slow cooling unit for removing internal strain of the glass ribbon GR below the molding unit 2. 3, a cooling unit 4 provided below the slow cooling unit 3, a first cutting unit 5 provided below the cooling unit 4, and a transport unit 6 for transferring the plate glass GS cut out by the first cutting unit 5. , A packing unit 8 for placing the plate glass GS on the pallet 7, a second cutting unit 9 for cutting the plate glass GS taken out from the pallet 7, and an inspection unit 10 for inspecting the plate glass GS.

The molding unit 2 includes a molded body 11 that executes an overflow down draw method and an edge roller 12 that pulls out the molten glass GM overflowing from the molded body 11 as a glass ribbon GR inside the furnace wall.

The molded body 11 is formed in a long shape, and includes an overflow groove 13 formed at the top, a vertical surface portion 14 and an inclined surface portion 15 forming a pair of side wall portions facing each other. The pair of inclined surface portions 15 intersect with each other by gradually approaching downward to form the lower end portion 16 of the molded body 11. The edge roller 12 sandwiches both ends of the glass ribbon GR in the width direction.

The slow cooling section 3 slowly cools the glass ribbon GR descending from the molding section 2 to remove the internal strain thereof. That is, the temperature is set so as to have a predetermined temperature gradient in the slow cooling unit 3. The temperature of the glass ribbon GR gradually decreases as it descends in the slow cooling portion 3. The slow cooling unit 3 guides the glass ribbon GR vertically downward via a plurality of upper and lower guide rollers 17 arranged inside.

The cooling unit 4 further cools the glass ribbon GR by passing the glass ribbon GR transferred from the slow cooling unit 3. That is, the cooling unit 4 cools the glass ribbon GR to near room temperature. The glass ribbon GR cooled by the cooling unit 4 is sent to the lower first cutting unit 5.

The first cutting portion 5 has a folding device 18 that cuts out a plate glass GS having a predetermined size from the glass ribbon GR that is transferred downward from the cooling portion 4. The glass ribbon GR continuously molded by the molding unit 2 is cut into a rectangular plate glass GS by the folding device 18. The thick-walled portions formed at both ends in the width direction (horizontal direction) of the cut flat glass GS are cut and removed as needed. In addition, various inspections are performed on the flat glass GS as needed. After that, the flat glass GS is sent to the packing unit 8.

When the flat glass GS is used for a flat panel display such as a liquid crystal display, the first surface Ga as a product surface on which a circuit such as a TFT is formed and the second surface located on the opposite side of the first surface Ga. It has Gb. The thickness of the flat glass GS (distance between the first surface Ga and the second surface Gb) is preferably 100 μm or more and 700 μm or less. The first surface Ga corresponds to the guaranteed surface of the present invention, and the second surface Gb corresponds to the non-guaranteed surface of the present invention.

As the material of the flat glass GS, silicate glass and silica glass are used, preferably borosilicate glass, soda lime glass, aluminosilicate glass, and chemically strengthened glass are used, and most preferably non-alkali glass is used. Here, the non-alkali glass is a glass that does not substantially contain an alkaline component (alkali metal oxide), and specifically, a glass having a weight ratio of an alkaline component of 3000 ppm or less. be. The weight ratio of the alkaline component in the present invention is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

The transport unit 6 is configured as a transport device including a plurality of holding portions 19 for moving the flat glass GS. Each holding portion 19 has a clamp mechanism 19a capable of gripping the flat glass GS. The transport unit 6 grips the upper portion of the plate glass GS by the clamp mechanism 19a of the holding unit 19, and the plate glass GS so that the surface (first surface Ga or second surface Gb) of the plate glass GS faces in the moving direction thereof. To carry. Further, the transport unit 6 transports the flat glass GS without holding the lower portion of the flat glass GS. Each holding portion 19 can be moved three-dimensionally by a robot arm or other various moving mechanisms. The transport unit 6 is not limited to the above, and may be configured by a roller conveyor, a belt conveyor, or other various transport devices.

The pallet 7 arranged in the packing portion 8 has a first support surface 20 that supports one surface of the plate glass GS and a second support surface 21 that supports the lower end portion of the plate glass GS. The first support surface 20 and the second support surface 21 intersect so as to form 90 °. The first support surface 20 is inclined at a predetermined angle with respect to the vertical direction. Further, the second support surface 21 is inclined at a predetermined angle with respect to the horizontal direction.

The pallet 7 can be transported by a transport vehicle, a transport trolley, or the like in a state of accommodating a predetermined number of flat glass GS. When the pallet 7 arrives at the transport destination, the flat glass GS is taken out from the pallet 7.

The second cutting portion 9 cuts the flat glass GS taken out from the pallet 7 to a predetermined size. The second cutting portion 9 has a cutting device 22 and a mounting table 23 that supports the flat glass GS. In the present embodiment, as the cutting device 22, various types such as a mechanical scribing type, a laser scribing type, and the like can be used. The mounting table 23 may be configured to be movable in the vertical direction and the horizontal direction so that the position of the flat glass GS can be changed. If necessary, the end face of the plate glass GS after cutting is subjected to grinding and / or polishing with a grindstone. Further, if necessary, the first surface Ga and the second surface Gb of the flat glass GS are subjected to a cleaning treatment.

The inspection unit 10 includes an image pickup device 24, an image processing device 25 (computer) that analyzes image data acquired by the image pickup device 24, and a mounting table 26 that supports the flat glass GS. The image pickup apparatus 24 includes an optical microscope, and can acquire an enlarged image of the inside of the flat glass GS as data. The image pickup apparatus 24 is configured to be movable in the horizontal direction and the vertical direction by the moving mechanism 27. The image pickup apparatus 24 images the inside of the plate glass GS at predetermined pitches PS and PL while changing the focal position FP in the thickness direction of the plate glass GS (direction away from the first surface Ga) by the operation of the moving mechanism 27. .. The distance from the image pickup apparatus 24 to the first surface Ga at the time of imaging is shorter than the distance from the image pickup apparatus 24 to the second surface Gb.

As shown in FIG. 2, the image pickup apparatus 24 is located inside the flat glass GS at a position farther from the first internal region G1 near the first surface Ga and the first surface Ga than the first internal region G1 ( The second internal region G2 (on the second surface Gb side) is imaged at a different pitch. That is, the image pickup apparatus 24 performs imaging at the first pitch PS in the first internal region G1 existing near the first surface Ga, and second in the second internal region G2 located away from the first surface Ga. Imaging is performed with pitch PL. The first pitch PS is smaller than the second pitch PL. In the following, the "first pitch" is also referred to as "small pitch", and the "second pitch" is also referred to as "large pitch".

In the present embodiment, the first internal region G1 is a portion in the range from the first surface Ga to 70 to 100 μm, and the second internal region G2 is a portion excluding the first internal region G1. The range of the first internal region G1 (the distribution range of the focal position FP by the first pitch PS) is not limited to the above, and may be appropriately set according to the thickness of the flat glass GS.

The image processing device 25 incorporates a CPU, RAM, ROM, and HDD, and also implements hardware such as a display 28 and an input interface 29. The image processing device 25 is connected to the image pickup device 24 and the moving mechanism 27. The image processing device 25 includes a calculation unit mainly composed of a CPU, a storage unit composed of RAM, ROM, and an HDD, and a communication unit that transmits / receives signals between the image pickup device 24 and the moving mechanism 27. Be prepared. The image processing device 25 controls the operations of the image pickup device 24 and the moving mechanism 27 by executing an image analysis program stored in the storage unit by the calculation unit, and communicates a large number of image data acquired by the image pickup device 24. While receiving from the unit, various image processes are executed for each image data.

The mounting table 26 supports a flat glass GS cut by the second cutting portion 9. Specifically, the mounting table 26 supports the second surface Gb of the flat glass GS. As a result, the flat glass GS is supported on the mounting table 26 with the first surface Ga facing upward.

Hereinafter, a method of manufacturing the flat glass GS by the manufacturing apparatus 1 having the above configuration will be described. As shown in FIG. 3, this method mainly includes a molding process S1, a slow cooling process S2, a cooling process S3, a first cutting process S4, a transporting process S5, a packing process S6, a second cutting process S7, and an inspection process S8. Prepare for.

In the molding step S1, the molten glass GM supplied to the molded body 11 of the molding portion 2 overflows from the overflow groove 13 and flows down along the vertical surface portion 14 and the inclined surface portion 15. The molten glass GM is fused and integrated at the lower end portion 16 of the molded body 11 to be molded as a glass ribbon GR. Among the surfaces of the plate-shaped molten glass GM that flows down along the inclined surface portion 15 of the molded body 11, the surface that merges and is fused and integrated is the mating surface. The edge roller 12 sandwiches both ends of the glass ribbon GR in the width direction and guides the glass ribbon GR downward.

In the slow cooling step S2, the glass ribbon GR descending from the molding section 2 passes through the slow cooling section 3. At this time, the glass ribbon GR is slowly cooled according to a predetermined temperature gradient while being guided downward by the guide roller 17, and its internal strain is removed.

In the cooling step S3, the glass ribbon GR is further cooled by natural cooling in the cooling unit 4. After that, the glass ribbon GR is cut to a predetermined size by the folding device 18 in the first cutting step S4, whereby a rectangular flat glass GS is obtained. If necessary, in the both-end cutting step, the thick portions formed at both ends in the width direction (horizontal direction) of the plate glass GS are removed. In addition, various inspections are performed on the flat glass GS as needed. In the subsequent transfer step S5, the flat glass GS is conveyed toward the pallet 7 arranged in the packing unit 8.

In the transfer step S5, the upper portion of the flat glass GS is held by the holding unit 19 of the transfer unit 6. The flat glass GS is conveyed from the first cutting portion 5 to the pallet 7 in a suspended state in which the lower portion of the flat glass GS is separated from the floor surface together with the flat glass GS.

In the packing step S6, the flat glass GS conveyed by the conveying unit 6 is sequentially placed on the pallet 7. A protective sheet is sandwiched between the flat glass GS loaded on the pallet 7. When a predetermined number of flat glass GSs are loaded on the pallet 7, a protective cover is covered over the entire laminate composed of the plurality of flat glass GSs. After that, the pallet 7 is transferred to a predetermined transport destination.

In the second cutting step S7, the flat glass GS is taken out from the pallet 7 arriving at the transport destination and placed on the mounting table 26 of the second cutting portion 9. After that, the flat glass GS is cut to a predetermined size by the cutting device 22. Alternatively, the cutting device 22 cuts out a plurality of flat glass GS from one flat glass GS. The plate glass GS after cutting is placed on the mounting table 26 of the inspection unit 10. After that, the inspection step S8 is carried out on this flat glass GS.

As shown in FIG. 4, the inspection step S8 includes a first inspection step S81, a second inspection step S82, and a third inspection step S83.

In the first inspection step S81, a known inspection device (not shown) arranged on the upstream side of the inspection unit 10 inspects the flat glass GS for the presence or absence of an internal defect ID. As the inspection device, for example, an edge light type inspection device is used, but the inspection device is not limited to this. When an internal defect ID is detected in the flat glass GS, information regarding the position (position in the plane direction) and size of the internal defect ID is input to the image processing device 25 and stored in the storage unit. On the other hand, when the internal defect ID is not detected in the flat glass GS, information indicating that the internal defect ID does not exist is input to the image processing device 25 and stored in the storage unit. Among the flat glass GSs in which the internal defect ID is detected, the flat glass GS in which the size of the internal defect ID exceeds the standard (for example, about 10 μm) is supplied to the second inspection step S82 and the third inspection step S83. Other flat glass GS is certified as non-defective.

In the second inspection step S82 and the third inspection step S83, the depth, size, and the like of the internal defect ID detected in the first inspection step S81 are measured. The size of the internal defect ID measured in the first inspection step S81 is an approximate size, and in the second inspection step S82 and the third inspection step S83, the internal defect ID is larger than that in the first inspection step S81. Measure the size of. The details of the second inspection step S82 and the third inspection step S83 will be described below.

In the second inspection step S82, the image pickup device 24 takes an image of the flat glass GS by the operator operating the image processing device 25 or by automatic control (imaging step). In the image pickup step, the image pickup apparatus 24 photographs the plate glass GS from the guaranteed surface side of the plate glass GS, that is, from the first surface Ga side. Specifically, in the imaging step, the imaging device 24 is moved by the operation of the moving mechanism 27 so that the internal defect ID detected in the first inspection step S81 is located in the field of view. In that state, the image pickup apparatus 24 moves downward at a predetermined pitch (large pitch PL) and images the inside of the plate glass GS a plurality of times. That is, as shown in FIG. 5, the image pickup apparatus 24 changes its focal position FP with a large pitch PL, and at each focal position FP, the entire interior of the plate glass GS, that is, the first internal region G1 and the second internal region. G2 is continuously imaged.

Subsequently, in the third inspection step S83, as shown in FIG. 6, in the first internal region G1, imaging by the imaging device 24 at a small pitch PS is executed.

In the second inspection step S82 and the third inspection step S83, the image data inside the flat glass GS acquired by the image pickup apparatus 24 is transmitted to the image processing apparatus 25 and displayed on the display 28. Subsequently, the operator visually observes the internal image of the flat glass GS displayed on the display 28, or the image analysis program of the image processing device 25 measures the internal defect ID. In this embodiment, the size and depth of the internal defect ID are measured. At the same time, the type of the internal defect ID is determined. The size (maximum dimension) of the internal defect ID is measured, for example, by the operator using an image analysis program based on the image displayed on the display 28.

The depth of the internal defect ID means the distance from the first surface Ga to the internal defect ID in the thickness direction of the flat glass GS. The depth of the internal defect ID is measured, for example, as follows. That is, the operator visually selects the most focused image data from the plurality of image data of the internal defect IDs captured at the plurality of focal position FPs on the display 28 or by the image analysis program of the image processing device 25. do. Then, the operator measures the distance from the focal position FP to the first surface Ga of the flat glass GS using an image analysis program. Alternatively, the depth of the internal defect ID is calculated by the calculation unit based on the image analysis program.

The type of the internal defect ID is visually recognized by the operator based on the image data displayed on the display 28. The internal defect ID is, for example, a bubble, that is, a bubble containing some gas or a vacuum bubble containing no gas. In the case of bubbles containing some kind of gas, the types of gas are oxygen, carbon dioxide, carbon monoxide, Knox (NO _X ), nitrogen, chlorine, brom, hydrogen, argon, helium, neon, xenon, steam, socks ( SO _X ), sulfite gas, etc. Further, in the case of a vacuum bubble, the component at the time of bubble generation may be deposited as a solid on the inner wall of the bubble in some state.

The bubbles constituting the above internal defect ID include those having a shape close to a spherical shape with little variation in the radius of curvature of the bubble surface, those having a shape extended in one direction, and those having a shape extended in one direction. There are various forms such as a flat cross section perpendicular to the extension direction. Alternatively, the above-mentioned internal defect ID includes, for example, a solid foreign substance. The solid foreign matter as the internal defect ID does not have transparency to visible light like bubbles, but has a shielding property, and is, for example, fine foreign matter such as refractory or platinum, or residual glass raw material. Those that do not have transparency such as foreign matter fall under this category. The type of internal defect ID as described above is confirmed by the operator.

Next, the operator certifies the quality of the flat glass GS based on the size, depth and type of the internal defect ID. Specifically, when it is determined that the internal defect ID adversely affects the surface properties of the first surface Ga, that is, it is determined that the internal defect ID causes unevenness or the like on the first surface Ga of the plate glass GS, the plate glass GS is rejected. Certified as a good product. On the other hand, if the internal defect ID does not adversely affect the surface properties of the first surface Ga, the flat glass GS is recognized as a non-defective product.

The operator determines whether or not the flat glass GS is defective based on the size, depth and type of the internal defect ID. Based on the size, depth, and type of the detected internal defect ID, the operator can say that the internal defect ID adversely affects the surface properties of the first surface Ga, that is, the internal defect ID is the first of the flat glass GS. If it is determined that it causes unevenness or the like on one surface Ga, the flat glass GS is recognized as a defective product.

Here, the internal defect ID existing in the first internal region G1 has a great influence on the surface texture (unevenness) of the first surface Ga as a guarantee surface even if it is minute. On the other hand, the internal defect ID existing in the second internal region G2 is located at a position away from the first surface Ga as compared with the internal defect ID of the first internal region G1. Therefore, even if the internal defect ID of the second internal region G2 is large, it is unlikely to affect the surface properties of the first surface Ga. Therefore, in certifying the quality of the flat glass GS, the reference value (maximum value in the allowable range) of the size of the internal defect ID changes according to the depth of the internal defect ID, and is larger than the second internal region G2. The first internal region G1 is smaller. Therefore, when the internal defect ID exists in the first internal region G1, it is required to measure the depth more accurately. For example, when both the first internal region G1 and the second internal region G2 are imaged at the same pitch and the pitch is set to 15 to 30 μm, the measurement of the internal defect ID existing in the first internal region G1 becomes inaccurate. .. Reducing the pitch to ensure accuracy increases the time required for the measurement.

According to the plate glass GS manufacturing apparatus and manufacturing method according to the present embodiment, the first surface Ga side (specifically, the first internal region G1), which is the guaranteed surface of the plate glass GS, is imaged with a small pitch PS. The internal defect ID existing in the vicinity of the first surface Ga can be accurately measured. Therefore, it becomes possible to determine the quality of the flat glass GS for a flat panel display, which is required to have high definition, more accurately than before.

Further, by imaging the side opposite to the first surface Ga side (specifically, the second internal region G2) which is the guaranteed surface with a large pitch PL, the internal defect ID existing in the region away from the first surface Ga is obtained. The time required for the measurement can be reduced, and the measurement can be performed efficiently. In the region away from the first surface Ga, the accuracy is slightly lower by imaging with a large pitch PL than in the vicinity of the first surface Ga, but the measurement error also has an effect on the surface texture of the first surface Ga. Since it becomes smaller, the accuracy of the judgment of good or bad can be ensured.

From the viewpoint of more accurately measuring the internal defect ID existing in the vicinity of the first surface Ga, the small pitch PS is preferably 1 μm or more and 10 μm or less. The large pitch PL may be larger than the small pitch PS, but is preferably 20 μm or more and 50 μm or less from the viewpoint of more efficient measurement.

7 and 8 show a second embodiment of the method for manufacturing a flat glass according to the present invention. In the above first embodiment, an example is shown in which the entire inside of the plate glass GS is imaged with a large pitch PL in the second inspection step S82, and then the first internal region G1 is imaged with a small pitch PS in the third inspection step S83. However, in this embodiment, the aspect of this inspection step S8 is different from that of the first embodiment.

That is, in the method for manufacturing a flat glass GS according to the present embodiment, as shown in FIG. 7, in the inspection step S8, after the first internal region G1 of the flat glass GS is imaged with a small pitch PS, the pitch (focus) of the image pickup apparatus 24 is taken. The distribution mode of the position FP) is changed from the small pitch PS to the large pitch PL, and the second internal region G2 is imaged as shown in FIG. In the present embodiment, when the imaging of the first internal region G1 is completed, the movement of the imaging device 24 by the moving mechanism 27 is temporarily stopped, and the pitch is changed (change from small pitch PS to large pitch PL). The correction step of the moving mechanism 27 is carried out. Also in this embodiment, the size and depth of the internal defect ID are measured based on the captured image data, and the type of the internal defect ID is determined. The quality of the flat glass GS is determined based on the size, depth, and type of the obtained internal defect ID.

The present invention is not limited to the configuration of the above embodiment, and is not limited to the above-mentioned action and effect. The present invention can be modified in various ways without departing from the gist of the present invention.

In the above embodiment, the first internal region G1 is set near the first surface Ga, but the first internal region G1 may be near the mating surface. In this case, the second internal region G2 can be the remaining region of the first internal region G1.

When the first internal region G1 is in the vicinity of the first surface Ga, the region is divided into two regions, the first internal region G1 and the second internal region G2, and the image is not limited to these regions at different pitches. The pitch on the Ga side of the first surface may be smaller than the pitch on the Gb side of the second surface. For example, it may be divided into three or more regions, and the regions may be imaged at different pitches. In this case, the pitch is changed so as to become smaller as it approaches the first surface Ga of the flat glass GS. Further, the format is not limited to the format in which the pitch is changed for each region (step-like), and a format in which the pitch is gradually changed may be adopted.

In the above embodiment, after imaging is performed in the second inspection step S82 and the third inspection step S83, the size and depth of the internal defect ID are measured based on the captured image data, but the present invention is not limited thereto. .. In the first embodiment, after the first internal region G1 and the second internal region G2 are imaged with a large pitch PL in the second inspection step S82, the second internal region G2 is an internal defect based on the imaged image data. The size and depth of the ID may be measured, the type of the internal defect ID may be determined, and the quality of the flat glass GS may be determined based on the result. In this embodiment, only the flat glass GS determined to be good has the first internal region G1 imaged with a small pitch PS in the third inspection step S83, and then the first internal region in the second inspection step S82 and the third inspection step S83. The size and depth of the internal defect ID are measured based on the image data captured by G1, the type of the internal defect ID is determined, and the quality of the flat glass GS is determined again based on the result.

Further, in the second embodiment, after the first internal region G1 is imaged with a small pitch PS, the size and depth of the internal defect ID are measured based on the image data captured by the first internal region G1. At the same time, the type of the internal defect ID may be determined, and the quality of the flat glass GS may be determined based on the result. In this embodiment, only the flat glass GS determined to be good has the second internal region G2 imaged with a large pitch PL, and then the size and depth of the internal defect ID based on the image data captured by the second internal region G2. The type of the internal defect ID is determined, and the quality of the flat glass GS is determined again based on the result.

In the above embodiment, the method for manufacturing the flat glass GS including the packing step S6 has been exemplified, but the present invention is not limited thereto. In the method for manufacturing the flat glass GS, an inspection step S8 may be provided between the first cutting step S4 and the transfer step S5. In this case, step S7 may be omitted. Alternatively, steps S1 to S6 may be omitted. In this case, for the flat glass GS, for example, one manufactured in another factory may be used. Alternatively, the packing step S6 may be omitted.

In the above embodiment, the configuration in which the image pickup device 24 is moved by the moving mechanism 27 has been exemplified, but the present invention is not limited to this configuration. The focal position FP of the image pickup apparatus 24 may be changed by equipping the mounting table 26 that supports the flat glass GS with a moving mechanism and moving the mounting table 26 at a predetermined pitch (small pitch PS, large pitch PL). ..

In the above embodiment, the method of manufacturing the flat glass GS (glass ribbon GR) by the overflow downdraw method is shown, but the present invention is not limited to this, and the flat glass GS may be manufactured by a float method or other molding method.

In the above embodiment, an example in which the inspection step S8 (second inspection step S82, third inspection step S83) is executed by one image pickup apparatus 24 is shown, but the present invention is not limited to this configuration. The inspection step S8 may be performed by a plurality of image pickup devices 24.

In the above embodiment, the image pickup device 24 shows an example of photographing the inside of the plate glass GS from the guaranteed surface side (first surface Ga side) of the plate glass GS, but the image pickup device 24 shows the non-guaranteed surface side (second surface Gb). The inside of the flat glass GS may be photographed from the side).

24 Imaging device FP Focus position G1 First internal area G2 Second internal area GS Plate glass ID Internal defect PS First pitch (small pitch)
PL second pitch (large pitch)
S8 inspection process

Claims (8)

In a method for manufacturing a plate glass, which comprises an inspection step of inspecting an internal defect of the plate glass by imaging the inside of the plate glass a plurality of times with an image pickup device.
In the plurality of imagings with the image pickup device, the focal positions of the image pickup device are distributed at a predetermined pitch along the thickness direction of the plate glass.
A method for manufacturing a flat glass, wherein the predetermined pitch is smaller in the first internal region in the thickness direction than in the second internal region in the thickness direction. The first internal region is near the guaranteed surface of the flat glass.
The method for manufacturing a flat glass according to claim 1, wherein the second internal region is a region farther from the guaranteed surface than the first internal region. The method for manufacturing a flat glass according to claim 2, wherein the image pickup apparatus is configured to take an image of the inside of the flat glass from the guaranteed surface side. In the inspection step, the predetermined pitch is set as the first pitch in the first internal region, and the predetermined pitch is set as the second pitch in the second internal region.
The method for manufacturing a flat glass according to claim 2 or 3, wherein the first pitch is smaller than the second pitch. 4. The fourth aspect of the present invention, wherein in the inspection step, imaging at the second pitch is performed in the first internal region and the second internal region, and then imaging at the first pitch is performed in the first internal region. How to manufacture flat glass. The method for manufacturing a flat glass according to claim 4, wherein in the inspection step, imaging at the first pitch is performed in the first internal region, and then imaging at the second pitch is performed in the second internal region. The method for producing a flat glass according to any one of claims 4 to 6, wherein the first pitch is 1 μm or more and 10 μm or less. The method for producing a flat glass according to any one of claims 4 to 7, wherein the second pitch is 20 μm or more and 50 μm or less.

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