JP2013207106A - Production method, transfer method and damage detection method of glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect contact of a device for transferring a glass plate while floating, and the glass plate over the entire surface thereof.SOLUTION: In a process for transferring a glass plate by using a device for floating the glass plate by blowing gas to the lower surface thereof, contact of the glass plate and the device is determined by detecting an elastic wave generated by contact. The method of detecting damage of a glass plate includes a step for setting a threshold in one or more types of information selected from the frequency, amplitude, waveform, generation time and generation interval of an elastic wave generated upon occurrence of damage on the glass plate, and a step for determining damage by comparing the information, extracted by detecting an elastic wave, with a threshold.

Description

  The present invention relates to a glass plate manufacturing method, a conveying method, and a damage detection method.

  Glass substrates used in FPDs (Flat Panel Displays) such as displays for liquid crystal display devices are required to have no scratches on the surface because semiconductor elements such as TFT (Thin Film Transistor) elements are formed by a semiconductor process. Yes. In addition, minute scratches and cracks on the end surface and front and back surfaces of the glass substrate reduce the mechanical strength of the glass substrate and cause problems such as cracking in the FPD manufacturing process.

  In the manufacturing process of a glass substrate, a thin and strip-shaped glass sheet is cut into a raw glass plate of a predetermined length, and then a cut line (scribe line) is put into a predetermined size by a diamond cutter or laser light. The glass substrate of a product size is obtained. In addition, a glass sheet, a base plate glass, or a glass substrate may be cut | disconnected by the thermal stress by a laser beam. Product size glass substrates are subjected to processing such as grinding and polishing of the end faces. Thereafter, the glass substrate is packed and shipped through a cleaning process and an inspection process. Hereinafter, the base plate glass and the product-size glass substrate are collectively referred to as a glass plate.

  For example, in the inspection process described above, an apparatus is used for transporting a glass plate by blowing gas on the back surface of the glass plate and supporting the glass plate substantially horizontally. When the glass plate is lifted and transported by such a transport device, a part of the glass plate and a part of the transport device may come into contact due to the deflection of the glass plate or an abnormality in the flatness of the device. When the glass plate and the conveying device come into contact with each other, damage such as minute scratches and cracks may occur on the glass plate, which may reduce the mechanical strength of the glass plate.

As a technique for preventing such contact between the conveying device and the workpiece, Japanese Patent Application Laid-Open No. 2011-84352 discloses a workpiece levitation device that can detect and correct a partial warpage or deflection of the workpiece. Is disclosed.
A method using an AE sensor is known as a method for detecting the breakage of the glass substrate. Japanese Patent Application Laid-Open No. 2003-247986 discloses a breakage detection method for detecting a sound wave signal due to a crack of a glass substrate by distinguishing it from noise similar to it with high accuracy.

JP 2011-84352 A JP 2003-247986 A

  In the technique described in Patent Document 1, the flying distance of the workpiece is measured by a sensor. However, the distance between the glass plate and the conveying device is very small, for example, several tens of μm, and since the glass plate is enlarged and thinned, it is difficult to monitor contact on the entire surface of the glass plate.

  Moreover, the technique described in the said patent document 2 enables the detection of the crack of the glass substrate which generate | occur | produces at a chemical | medical solution processing process, a washing | cleaning processing process, etc. However, there is no description about effectively detecting contact between a glass substrate and a device that floats and conveys the glass substrate.

  Therefore, the present invention provides a glass plate manufacturing method, a transport method, and a damage detection method capable of effectively detecting contact between a glass plate and a device that floats and transports the glass plate over the entire surface of the glass plate. I will provide a.

The manufacturing method of the glass plate which is 1 aspect of this invention has the process of conveying the said glass plate using the apparatus which sprays gas on the lower surface of a glass plate, and floats the said glass plate, and conveys the said glass plate In the process, the contact is determined by detecting an elastic wave generated by contact between the glass plate and the device.
In addition, the method for transporting a glass plate according to another aspect of the present invention, when transporting the glass plate using a device that blows gas onto the lower surface of the glass plate to float the glass plate, The contact is determined by detecting an elastic wave generated by contact with the apparatus.
According to another aspect of the present invention, there is provided a glass plate damage detection method comprising: one or more selected from a frequency, an amplitude, a waveform, a generation time, and a generation interval of an elastic wave generated when the glass plate is damaged. Setting a threshold value for information; detecting the elastic wave to extract the information; and comparing the threshold value to determine the damage.

  ADVANTAGE OF THE INVENTION According to this invention, the contact of the apparatus which floats and conveys a glass plate and a glass plate can be detected effectively over the whole surface of a glass plate.

It is a figure which shows an example of the manufacturing process of the glass substrate of this embodiment. It is a perspective view which shows an example of a levitation conveyance apparatus. It is a figure which shows an example of the flow of a signal of a levitation conveyance apparatus. It is a figure which shows an example of a structure of a linear guide. It is a figure which shows the modification of a structure of a linear guide. It is a figure which shows another modification of the structure of a linear guide. It is a figure which shows another modification of the structure of a linear guide.

Hereinafter, the manufacturing method of the glass plate of this invention is demonstrated in detail based on this embodiment.
The glass plate manufactured by this embodiment is a glass substrate used for the display for liquid crystal display devices, for example, is 0.5-0.7 mm in thickness, and is a thin plate of the size of 2200 mm x 2500 mm (length x width). is there.

  In addition, the glass plate manufactured by this embodiment is not limited to the above, Cover glass used for the display screen of electronic devices, such as a mobile telephone, a plasma display panel, organic electroluminescence (EL), etc. It may be a plate glass used for a flat panel display (FPD).

Although the glass plate manufactured by this embodiment is not specifically limited, For example, it can be applied to the glass plate of the following composition ratios. For example, any component of Li, Na, and K is not contained, or even if at least one component of Li, Na, and K is contained, It is preferable that the total amount of the components to be contained has a glass composition that is 0.5% by mass or less. The glass composition is preferably exemplified as follows.
(A) SiO ₂ : 50 to 70% by mass,
(B) B ₂ O ₃ : 5 to 18% by mass,
(C) Al ₂ O ₃ : 10 to 25% by mass,
(D) MgO: 0 to 10% by mass,
(E) CaO: 0 to 20% by mass,
(F) SrO: 0 to 20% by mass,
(G) BaO: 0 to 10% by mass,
(H) RO: 5 to 20% by mass (wherein R is at least one selected from Mg, Ca, Sr and Ba, and RO is the total of components contained in MgO, CaO, SrO and BaO),
(I) R ′ ₂ O: more than 0.05% by mass and 0.5% by mass or less (where R ′ is at least one selected from Li, Na and K, and R ′ ₂ O is Li ₂ O, Na ₂ O and the sum of the components contained in K ₂ O),
(J) 0.05 to 1.5% by mass in total of tin oxide and at least one metal oxide selected from iron oxide and cerium oxide.
The compositions (i) and (j) are not essential, but preferably include the compositions (i) and (j). The glass is substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO and contains SnO ₂ .
Moreover, the glass used for the glass plate of this embodiment may be an alkali-free glass in which the content of R ′ ₂ O in (i) is substantially 0% by mass. That is, the glass used for the glass plate of the present embodiment is a glass containing a trace amount of alkali or a non-alkali glass containing the composition (i).

FIG. 1 is a flowchart showing the flow of the glass plate manufacturing method of the present embodiment.
As shown in FIG. 1, the melted glass is formed into a strip-shaped glass sheet having a predetermined thickness by, for example, a down draw method or a float method (step S1).

  Next, the formed strip-shaped glass sheet is scribed and cut to obtain a glass plate of a predetermined size. The base glass is further scribed and cut to obtain a glass substrate having a product size (step S2). The obtained glass substrate is subjected to end face processing including end face grinding, polishing, and corner cutting (step S3).

  In the scribe, a cut line (scribe line) that is a fine streak-like scratch is formed in glass using a diamond cutter or the like. The glass plate including the base glass and the glass substrate is cut along a scribe line by a machine or a manual. Alternatively, the glass plate can be cut by scribing with laser light and thermal shock.

  Thereafter, the glass substrate is cleaned (step S4). The cleaned glass plate is optically inspected for scratches, dust, dirt, or scratches including optical defects (step S5). The glass plates that are suitable for quality by inspection are alternately stacked with paper that protects the glass plates, loaded on a pallet, and packed (step S6). The packed glass plate is shipped to a supplier (step S7).

  For example, the glass plate is carried into and out of the optical automatic inspection machine used for inspection (step S5), and the glass plate being inspected is transported by blowing a gas onto the back surface of the glass plate and supporting it in a horizontal state. A floating transport device is used.

  FIG. 2 is a perspective view showing an example of the levitation transport apparatus. FIG. 3 is a diagram illustrating a signal flow in the levitating apparatus. As shown in FIG. 2, the levitation conveyance apparatus 100 includes a first levitation conveyance unit 10, a second levitation conveyance unit 20, and a linear guide 30. As shown in FIG. 3, the levitation transport apparatus 100 includes an AE sensor 40, an amplifier 50, a band pass filter 60, and a processing unit 70. Although this embodiment demonstrates the example provided with two continuous levitation conveyance parts 10 and 20, there may be one levitation conveyance part or three or more.

  The first levitation transport unit 10 includes a plurality of gas ejection units 11 extending along the transport direction of the glass sheet G. The first levitation transport unit 10 stably floats the glass plate G by ejecting and sucking gas from a plurality of orifices formed in the plurality of gas ejection units 11. The gas ejection part 11 of the first levitation transport part 10 is made of, for example, a solid metal material.

  The second levitation transport unit 20 includes a plurality of gas ejection units 21 extending across the transport direction of the glass sheet G. The second levitation transport unit 20 stably and precisely floats the glass plate G by ejecting and sucking gas from countless minute holes on the surface of the plurality of gas ejection units 21. The gas ejection part 21 of the second levitation transport part 20 is made of, for example, carbon of a porous material.

  The linear guide 30 includes a holding unit 31 that holds the end face of the glass plate G, and a conveyance unit 32 that moves the holding unit 31 along the first levitation conveyance unit 10 and the second levitation conveyance unit 20. Yes. The linear guide 30 is provided so as to output a position information signal for the transport unit 32 of the holding unit 31 to the processing unit 70.

As shown in FIG. 4, the holding unit 31 holds a predetermined position on one side of the glass plate G. The holding unit 31 includes, for example, a suction mechanism for holding the glass plate G. Further, the holding unit 31 is provided with an AE sensor 40.
The conveyance unit 32 includes a linear drive mechanism that moves the holding unit 31 along the conveyance direction of the glass sheet G indicated by an arrow in FIG.

  The AE sensor 40 detects an elastic wave (Acoustic Emission) generated by the contact between the glass plate G and the first levitation conveyance unit 10 or the second levitation conveyance unit 20, and generates an electrical signal corresponding to the elastic wave. Output to the amplifier 50. The AE sensor 40 provided in the holding unit 31 detects an elastic wave that has propagated through the glass plate G.

  The AE sensor 40 may be provided in each of the gas ejection units 11 of the first levitation transport unit 10 or each of the gas ejection units 21 of the second levitation transport unit 20. In this case, the AE sensor 40 detects elastic waves that have propagated through the gas ejection portions 11 and 21. When one AE sensor 40 is provided for each of the gas ejection portions 11 and 21, it is preferable to provide the AE sensor 40 at one end of the gas ejection portions 11 and 21. Two or more AE sensors 40 may be provided in each gas ejection part 11, 21. In this case, it is more preferable to provide at least both ends of each gas ejection part 11, 21. From the viewpoint of preventing the attenuation of the elastic wave, the AE sensor 40 is preferably provided in the gas ejection portion 11 of the solid material rather than the gas ejection portion 21 of the porous material.

The amplifier 50 is provided to amplify the signal input from the AE sensor 40 and output the amplified signal to the band pass filter 60.
The band pass filter 60 is configured to pass a signal in a frequency band corresponding to an elastic wave generated by contact between the glass plate G and the gas ejection part 11 or 21.

  When the signal corresponding to the elastic wave that has passed through the bandpass filter 60 is input, the processing unit 70 determines that the glass plate G and the first levitation conveyance unit 10 or the second levitation conveyance unit 20 are in contact with each other. . At this time, the processing unit 70 may record the contact with the levitation transport unit 10 or 20 in the individual identification information of the glass plate G that has been determined to be in contact. As the processing unit 70, for example, a personal computer (PC) can be used.

  The processing unit 70 processes a signal corresponding to the elastic wave input from the bandpass filter 60 to determine the contact state between the glass plate G and the first levitation conveyance unit 10 or the second levitation conveyance unit 20. You may make it discriminate | determine. Further, the processing unit 70 may process the signal input from the linear guide 30 and specify the position of the glass sheet G in the transport direction.

  The processing unit 70 may store in advance the relationship between the type of damage that occurs in the glass plate G due to the contact between the glass plate G and the floating conveyance units 10 and 20 and the elastic waves that are generated at that time. Good. That is, it is preferable to specify in advance what kind of elastic wave is generated when what kind of damage occurs.

For example, the frequency, amplitude, waveform, and generation of the elastic wave when the glass plate G is damaged by exceeding the standard due to the contact between the glass plate G and the first levitation conveyance unit 10 or the second levitation conveyance unit 20. Information such as time and occurrence interval is collected, and a threshold is set for each information.
Similarly, the frequency, amplitude, and waveform of the elastic wave when a crack exceeding the reference occurs in the glass plate G due to the contact between the glass plate G and the first levitation conveyance unit 10 or the second levitation conveyance unit 20. Information such as occurrence time and occurrence interval is collected, and a threshold is set for each information.

Moreover, the wave number, amplitude, waveform, generation time, generation interval, etc. of the elastic wave when the glass plate G is not damaged beyond the reference by the contact between the glass plate G and the first or second levitating and conveying device. Are collected, and a threshold is set for each piece of information.
The threshold set as described above is stored in the processing unit 70 in advance in association with the type of damage that occurs in the glass plate G.

  It should be noted that the threshold value is determined in accordance with purposes such as detection of contact between the glass plate G and the levitation conveyance unit 10, 20, detection of damage generated in the glass plate G due to contact, or identification of the type of damage generated in the glass plate G. Can be selected. That is, the threshold value may be set to two or more pieces of information such as the frequency, amplitude, waveform, generation time, and generation interval of the elastic wave, or may be set to any one piece of information.

5 to 7 are plan views showing modifications of the linear guide 30. FIG.
As shown in FIG. 5, the linear guide 30 may be provided on both sides of the glass plate G, for example, and the glass plate G may be held by a plurality of holding portions 31.

As shown in FIG. 6, the linear guide 30 may have a holding portion 31 a that holds a plurality of edges of the glass plate G. In this case, the holding unit 31a may be provided with a plurality of AE sensors 40 corresponding to the respective sides of the glass plate G. When the L-shaped holding part 31a as shown in FIG. 6 is used, for example, in order to receive the glass plate G from the previous process or to send the glass sheet G to the subsequent process, the holding part 31a is moved in the vertical direction to It is preferable that a retracting mechanism for retracting from the plate G is provided.
Moreover, as shown in FIG. 7, the linear guide 30 may be provided on both sides of the glass plate G, and the front, rear, left and right of the glass plate G may be held by the holding portions 31a. In this case, the AE sensors 40 may be provided on the front, rear, left and right of the glass plate G.

Next, in the present embodiment, a flow for detecting contact between the glass plate G and the levitation conveyance units 10 and 20 will be described.
For example, the glass plate G that has been cleaned (step S4) shown in FIG. 1 is carried into an automatic inspection machine that performs inspection (step S5) by the levitation conveyance device 100 shown in FIG.
As shown in FIG. 2, the levitation transport apparatus 100 ejects gas from the orifice of the gas ejection section 11 of the first levitation transport section 10 to the lower surface of the glass plate G. Thereby, the levitation conveyance apparatus 100 floats the glass plate G upward about several tens of micrometers from the gas ejection part 11 and supports it in a horizontal state. The gas ejection part 11 may stabilize the behavior during conveyance of the glass sheet G by simultaneously sucking the gas from the plurality of orifices and sucking the gas through the other plurality of orifices.

  The levitation conveyance apparatus 100 holds a predetermined position of the glass plate G by the holding unit 31 of the linear guide 30. The linear guide 30 moves the holding unit 31 holding the glass plate G by the conveyance unit 32 to convey the glass plate G in the conveyance direction, and transmits information on the position of the holding unit 31 relative to the conveyance unit 32 to the processing unit 70. Output. The glass plate G is conveyed by the movement of the holding unit 31 of the linear guide 30 and is transferred from the first levitation conveyance unit 10 to the second levitation conveyance unit 20.

  The levitation transport apparatus 100 ejects gas from the innumerable pores of the gas ejection section 21 of the second levitation transport section 20 to the lower surface of the glass plate G. Thereby, the levitation conveyance apparatus 100 floats the glass plate G upward about several tens of micrometers from the gas ejection part 21 and supports it in a horizontal state. The levitation transport apparatus 100 may stabilize the behavior during transport of the glass sheet G by performing gas suction by the plurality of gas ejection sections 21 simultaneously with ejection of the gas by the plurality of gas ejection sections 21. In the present embodiment, the second levitation transport unit 20 can perform more precise transport than the first levitation transport unit 10. For example, the glass plate G is inspected by an automatic inspector while being conveyed by the second levitation conveyance unit. It is also possible to carry out precise conveyance by the first levitation conveyance unit 10.

The levitation conveyance apparatus 100 detects an elastic wave generated by the contact between the first levitation conveyance unit 10 or the second levitation conveyance unit 20 and the glass plate G by the AE sensor 40.
Specifically, the elastic wave generated by the contact between the glass plate G and the levitation conveyance units 10 and 20 propagates through the glass plate G and reaches the AE sensor 40 provided in the holding unit 31 of the linear guide 30. . Further, when the AE sensor 40 is provided in the levitation transport unit 10, 20, the elastic wave generated by the contact between the glass plate G and the levitation transport unit 10, 20 is generated by the gas ejection unit 11 or the gas ejection unit 21. And reach the AE sensor 40.

  The AE sensor 40 converts the elastic wave propagated as described above into an electric signal and outputs it to the amplifier 50. The amplifier 50 amplifies the input electric signal and outputs it to the band-pass filter 60. The band-pass filter 60 passes an electric signal in a frequency band corresponding to an elastic wave among the electric signals input from the amplifier 50. When the electric signal corresponding to the elastic wave is input, the processing unit 70 determines that the glass plate G and the levitation conveyance device 100 are in contact with each other.

  The above-described elastic wave is generated by the contact between the glass plate G and the levitation conveyance units 10 and 20 regardless of the size of the glass plate G and the place where the glass plate G comes into contact. Therefore, according to the present embodiment, contact between the levitation conveyance units 10 and 20 and the glass plate G can be effectively detected over the entire surface of the glass plate G.

  In addition, if the processing unit 70 records that it has contacted the levitation conveyance units 10 and 20 in the individual identification information of the glass plate G that has been determined to be in contact, the levitation conveyance unit 10 is based on the information in a later step. , 20 can be identified. That is, according to this embodiment, the glass plate G can be selected based on the determination result of the processing unit 70, and the problematic glass plate G can be selectively excluded from the production line.

  Moreover, the conveyance speed of the glass plate G is slow so that it can be disregarded compared with the propagation speed of an elastic wave. Therefore, when the electrical signal corresponding to the elastic wave is input to the processing unit 70, the position when the glass plate G is in contact with the gas ejection unit 11 is determined by the positional information of the holding unit 31 input from the linear guide 30. Almost specified. Thereby, the position of the glass plate G which the contact with the glass plate G and the levitation conveyance parts 10 and 20 generate | occur | produces can be specified.

  One AE sensor 40 is provided not only on the holding part 31 of the linear guide 30 but also on each gas ejection part 11 of each first levitation conveyance part 10 or each gas ejection part 21 of the second levitation conveyance part 20. If it is, the processing unit 70 can specify a region in contact with the floating conveyance units 10 and 20 of the glass plate G.

  For example, when the glass plate G comes into contact with one of the gas ejection portions 11 of the first levitation transport unit 10, an elastic wave is generated and propagates through each of the glass plate G and the gas ejection portion 11. The elastic wave reaches the AE sensor 40 provided in the holding unit 31 and the AE sensor 40 provided in the gas ejection unit 11, and an electric signal corresponding to the elastic wave is input to the processing unit 70.

At this time, by specifying the sensor 40 that has output the signal in the processing unit 70, the gas ejection unit 11 with which the glass plate G is in contact is specified.
Further, when an electrical signal corresponding to the elastic wave is input to the processing unit 70, the position when the glass plate G contacts the gas ejection unit 11 is determined based on the positional information of the holding unit 31 input from the linear guide 30. Almost specified.

  Thereby, in the glass plate G, the strip | belt-shaped area | region facing the said gas ejection part 11 including the area | region which contacted the gas ejection part 11 is pinpointed. Moreover, in the gas ejection part 11, the strip | belt-shaped area | region which includes the area | region which contacted the glass plate G and opposes the specified area | region of the said glass plate is specified.

  Further, in the processing unit 70, a difference between the time when the contact is detected by the AE sensor 40 provided in the holding unit 31 and the time when the contact is detected by the AE sensor 40 provided in the gas ejection unit 11 is obtained. The difference in distance from each AE sensor 40 to the point where the glass plate G and the gas ejection part 11 are in contact with each other is obtained from the time difference and the propagation speed of the elastic wave.

  By calculating a region satisfying the difference in the distance in the band-shaped region of the glass plate G by the processing unit 70, a region in contact with the gas ejection unit 11 on the glass plate G and a region on the gas ejection unit 11 are calculated. The area | region which contacted the glass plate G is calculated | required. At this time, if the AE sensor 40 is provided at one end on the gas ejection part 11, the area in contact with the gas ejection part 11 on the glass plate G and the glass plate G on the gas ejection part 11 are in contact with each other. The determined area can be obtained more reliably.

  When two or more AE sensors 40 are provided in the gas ejection part 11, preferably at least at both ends of the gas ejection part 11, the difference in time at which the elastic waves reach the AE sensors 40 by the processing part 70 is calculated. By taking, the area | region which contacted the glass plate G on the gas ejection part 11 can be pinpointed more correctly and easily. Moreover, the area | region which contacted the gas ejection part 11 on the glass plate G can be specified more easily by combining the positional information on the conveyance part 31 of the linear guide 30, and the positional information on the glass plate G with respect to the conveyance part 31. it can.

  In the second levitation transport unit 20, similarly to the first levitation transport unit 10, a region in contact with the gas ejection unit 21 on the glass plate G and a region in contact with the glass plate G on the gas ejection unit 21. And can be specified.

In addition, as shown in FIG. 5, when the AE sensors 40 are respectively provided in the conveyance units 31 that hold both sides of the glass plate G, elastic waves have reached the AE sensors 40 by the processing unit 70. By taking the time difference, it is possible to more accurately specify the region in contact with the floating conveyance units 10 and 20 of the glass plate G.
Similarly, when a plurality of AE sensors 40 corresponding to the respective edges of the glass plate G are provided in the transport unit 31a that holds the plurality of edges of the glass plate G as shown in FIGS. The difference between the time when the elastic wave arrives at these AE sensors 40 can be taken to specify the region of the glass plate G that has come into contact with the floating conveyance units 10 and 20 more accurately.

  Thus, by specifying the area | region which contacted the gas ejection parts 11 and 21 in the glass plate G, while eliminating wasteful waste and improving a yield, the detection accuracy of damage can be improved. Moreover, by specifying the area | region which contacted the glass plate G in the gas ejection parts 11 and 21, adjustment of an apparatus can be performed and a contact can be prevented.

  When the type of damage that occurs in the glass plate G and threshold values of information such as the frequency, amplitude, waveform, generation time, and generation interval of the elastic wave corresponding to each damage are stored in the processing unit 70 Based on the elastic wave signal detected by the AE sensor 40 provided in the holding portion 31 of the linear guide 30, the state of damage to the glass plate G can be determined.

  That is, the elastic wave generated by the contact between the glass plate G and the levitation conveyance units 10 and 20 propagates through the glass plate G and is detected by the AE sensor 40 provided in the holding unit 31 of the linear guide 30. The AE sensor 40 outputs an electrical signal corresponding to the detected elastic wave. The output electric signal is input to the processing unit 70 through the amplifier 50 and the band pass filter 60, and is processed by the processing unit 70 to extract information such as the frequency, amplitude, waveform, generation time, and generation interval of the elastic wave. Is done.

The extracted information is compared with a threshold value for determining the state of each stored damage in the processing unit 70. As a result of the comparison, the processing unit 70 determines the state of damage to which the extracted information corresponds based on whether or not the threshold value corresponding to each damage is exceeded. As a result, the processing unit 70 determines the state of damage to the glass plate, such as damage such as scratches or cracks exceeding the reference, or occurrence of damage exceeding the reference.
The processing unit 70 records the determined damage state in the solid identification information of the glass plate G. Thereby, the glass plate G in which damage exceeding a reference | standard generate | occur | produced in the post process can be specified, the glass plate G can be selected, and the problematic glass plate G can be selectively excluded from a production line.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to said embodiment. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the glass plate for FPD has been described as the glass plate, but the present invention is not limited to the glass plate for FPD.

DESCRIPTION OF SYMBOLS 10 1st levitation conveyance part 11 gas ejection part 20 2nd levitation conveyance part 21 gas ejection part 30 linear guide 31, 31a holding | maintenance part 32 conveyance part 40 AE sensor 50 amplifier 60 band pass filter 70 processing part 100 levitation conveyance apparatus G Glass plate

Claims (7)

Having a step of transporting the glass plate using a device that blows gas to the lower surface of the glass plate to float the glass plate;
In the step of conveying the glass plate, the contact is determined by detecting an elastic wave generated by contact between the glass plate and the device. Before the step of conveying the glass plate, setting a threshold value to at least one information selected from the frequency, amplitude, waveform, generation time and generation interval of the elastic wave;
A step of determining damage of the glass plate by extracting the information of the elastic wave detected in the step of conveying the glass plate and comparing it with the threshold value.
The manufacturing method of the glass plate of Claim 1. The step of setting the threshold includes the step of extracting the information, the step of associating the information with the type of damage to the glass plate, and the step of setting the threshold for each type of damage,
The step of detecting the damage includes a step of identifying the type of damage by comparing the extracted information with the threshold value.
The manufacturing method of the glass plate of Claim 2. After the step of conveying the glass plate, based on the result of the determination, the step of selecting the glass plate,
The manufacturing method of the glass plate as described in any one of Claim 1 to 3. In the step of conveying the glass plate, the elastic wave is detected at a plurality of different positions, and the position where the contact of the glass plate occurs is specified.
The manufacturing method of the glass plate as described in any one of Claim 1 to 4. When conveying the glass plate by using a device that blows gas to the lower surface of the glass plate to float the glass plate, the contact is determined by detecting elastic waves generated by the contact between the glass plate and the device. A method for transporting a glass plate. A step of setting a threshold according to the type of damage to one or more pieces of information selected from the frequency, amplitude, waveform, generation time, and generation interval of an elastic wave generated when the glass plate is damaged;
Detecting the elastic wave, extracting the information, and determining the damage by comparing with the threshold value.