Glass sheet production method

Abstract

This glass sheet production method includes: a rough polishing step S2 for processing an end face Ga of a glass sheet G by using a grinding wheel 3; and a finish polishing step S3 for processing the end face Ga of the glass sheet G by using a grinding wheel 4 after said rough polishing step S2. In said rough polishing step S2, the end face Ga of the glass sheet G is processed by using a mixed-abrasive-grain grinding wheel in which abrasive grains having different grit numbers are mixed.

Description

Method for manufacturing a glass plate

[0001] The present invention relates to a method for manufacturing a glass plate.

[0002] As is well known, displays such as liquid crystal displays and organic EL displays are being advanced in high definition. Along with this, a fine electric circuit is formed in the glass plate used as a substrate for the display in the manufacturing process of the display.

[0003] It is common practice to perform end face processing such as grinding and polishing on the end face of the glass plate, but minute cracks exist on the surface of the end face (the processed surface by the grindstone) after processing.

[0004] The minute cracks present on the end face after processing grow due to various processes in the manufacturing process of the display, and can cause the generation of glass powder (particles) from the end face. Then, the glass powder generated from the end face becomes a factor that inhibits the formation of the electric circuit (for example, disconnection of the electric circuit, etc.), and is likely to cause manufacturing defects in the display.

[0005] Patent Document 1 discloses a method for manufacturing a glass substrate capable of suppressing glass powder that may be generated from the end face in the manufacturing process of the display. This manufacturing method includes an inspection step of inspecting the properties of the end face of the glass plate after performing end face processing such as a grinding step and a polishing step on the end face of the glass plate, and a determination step of determining the properties of the end face of the glass plate based on the result of the inspection step (see paragraph 0029 of the same document).

[0006] The inspection step includes a cutting step, a treatment step, an imaging step, and a calculation step (see paragraphs 0039 to 0050 of the same document).

[0007] In the cutting step, a glass sample is cut out from a part of the end face of the glass plate. Next, in the treatment step, the glass sample is chemically treated to grow minute cracks contained in the glass sample. As a result, a recess is formed in the glass sample where the minute cracks are coarsened.

[0008] In the imaging step, the end face of the glass sample is imaged using a microscope to obtain a magnified image. In the calculation step, the image is binarized to distinguish between recessed and non-recessed areas. Furthermore, the proportion of the end face occupied by recessed areas, i.e., the crack rate, is calculated.

[0009] In the judgment process, it is determined whether the crack rate is within a predetermined threshold range. That is, if the crack rate is below the threshold, the glass plate is deemed acceptable, and if the crack rate exceeds the threshold, the glass plate is deemed unacceptable.

[0010] Furthermore, in this manufacturing method, after the grinding process with the grinding wheel, a rough polishing process and a finish polishing process are performed (see paragraph 0057 of the same document). In the finish polishing process, the crack rate can be suppressed by adjusting the amount of force applied when the grinding wheel is pressed against the edge of the glass plate (see paragraph 0061 of the same document).

[0011] International Publication No. 2019 / 198558

[0012] In conventional glass plate manufacturing methods, a problem arose where the lifespan of the grinding wheel was shortened if the force applied to the edge of the glass plate during the rough polishing and finish polishing processes was too great. On the other hand, using grinding wheels containing small abrasive particles to improve the lifespan of the grinding wheel sometimes resulted in a higher crack rate. A high crack rate increased the amount of glass powder that could be generated from the edge during the display manufacturing process, while a low crack rate tended to decrease the amount of glass powder.

[0013] This invention has been made in view of the above circumstances, and its technical objective is to reduce the crack rate without impairing the lifespan of the grinding wheel.

[0014] (1) The method for manufacturing a glass plate according to the present invention is for solving the above problems and includes a rough polishing step of processing the end face of the glass plate with a grinding wheel, and a finish polishing step of processing the end face of the glass plate with a grinding wheel after the rough polishing step, wherein in the rough polishing step, the end face of the glass plate is processed with a mixed abrasive grinding wheel which is a mixture of abrasive grains of different grits.

[0015] As a result of diligent research, the inventors have found that by increasing the surface roughness of the edge surface of the glass plate polished in the rough polishing process compared to conventional methods, the amount of microcracks on the edge surface of the glass plate after the finish polishing process can be reduced. In other words, if the surface roughness of the edge surface of the glass plate is reduced in the rough polishing process, the grinding wheel will slip against the edge surface of the glass plate in the subsequent finish polishing process, making it impossible to effectively polish the edge surface.

[0016] As described in the present invention, by using a mixed abrasive grinding wheel in the rough polishing process, the edge surface of the glass plate can be made to a surface roughness suitable for the finish polishing process, that is, a surface roughness that does not cause the grinding wheel to slip. This makes it possible to reduce the amount of microcracks on the edge surface of the glass plate after the finish polishing process and to lower the crack rate.

[0017] Furthermore, the mixed abrasive grinding wheel used in the rough polishing process contains both large and small abrasive grains. This allows for a higher surface roughness on the edge of the glass plate polished in the rough polishing process compared to conventional methods, without increasing the amount of abrasive material removed during the rough polishing process. In addition, the smaller abrasive grains suppress the shedding of the larger abrasive grains, thereby extending the lifespan of the mixed abrasive grinding wheel as much as possible.

[0018] (2) In the method for manufacturing a glass plate described in (1) above, the mixed abrasive grinding wheel includes first abrasive grains and second abrasive grains of a different grit from the first abrasive grains, and the first abrasive grains and the second abrasive grains may be made of the same material.

[0019] With this configuration, by making the first and second abrasive grains from the same material, the effect of increasing the surface roughness of the edge surface of the glass plate polished in the rough polishing process compared to conventional methods is enhanced without increasing the amount of polishing in the rough polishing process. Furthermore, the lifespan of the mixed abrasive grinding wheel can be extended as much as possible, and the mixed abrasive grinding wheel can be manufactured efficiently.

[0020] (3) In the glass plate manufacturing method described in (2) above, the grit size of the first abrasive grain may be #300 to #800, and the grit size of the second abrasive grain may be #500 to #2000.

[0021] With this configuration, the edge surface of the glass plate after the rough polishing process can be made to a surface roughness suitable for the finish polishing process. Furthermore, the second abrasive grains have a smaller particle size than the first abrasive grains. By mixing these second abrasive grains with the first abrasive grains, it is possible to prevent the first abrasive grains from sinking into the bond of the mixed abrasive grinding wheel. In other words, the second abrasive grains have the function of supporting the first abrasive grains together with the bond so that the first abrasive grains do not sink into the bond.

[0022] (4) In the glass plate manufacturing method described in (2) or (3) above, the difference in grain size between the first abrasive grain and the second abrasive grain may be #100 to #1500. By providing such a difference in grain size, the end face of the glass plate after the rough polishing process can be made to have a surface roughness suitable for the finish polishing process.

[0023] (5) In the glass plate manufacturing method described in (2) to (4) above, the first abrasive grain and the second abrasive grain may be superabrasive grains. This makes it possible to suitably polish the end face of the glass plate without impairing the lifespan of the mixed abrasive grinding wheel.

[0024] (6) In the method for manufacturing a glass plate described in any of (1) to (5) above, the mixed abrasive grinding wheel may be a resin bond grinding wheel or a rubber bond grinding wheel.

[0025] If the surface roughness of the edge of a glass plate becomes excessively large, multiple processing steps may be required in the finishing polishing process to remove microcracks. In contrast, by using a resin-bonded grinding wheel or a rubber-bonded grinding wheel as a mixed abrasive, the edge of the glass plate can be made to a state of appropriate surface roughness, and microcracks can be removed in a single processing step. This improves the manufacturing efficiency of glass plates.

[0026] (7) In the method for manufacturing a glass plate described in any of (1) to (6) above, the end face of the glass plate may be processed in the finishing polishing step using a resin bond grinding wheel containing abrasive grains with a grit size of #1000 to #2000.

[0027] With this configuration, the crack rate at the edge of the glass plate can be more effectively reduced by performing a finishing polishing process.

[0028] (8) In the method for manufacturing a glass plate described in any of (1) to (7) above, a grinding step may be included as a step prior to the rough polishing step, in which the end face of the glass plate is processed with a metal bond grinding wheel. This makes it possible to efficiently process the end face of the glass plate into a desired shape.

[0029] According to the present invention, the crack rate can be reduced without impairing the lifespan of the grinding wheel.

[0030] This is a flowchart showing the method for manufacturing a glass plate. This is a plan view showing the method and apparatus for manufacturing a glass plate. This is a graph showing the surface roughness of the examples and comparative examples. This is a graph showing the amount of polishing for the examples and comparative examples. This is a graph showing the crack rate for the examples and comparative examples.

[0031] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Figures 1 and 2 show one embodiment of the method for manufacturing a glass plate according to the present invention.

[0032] As shown in Figure 1, this method comprises a grinding step S1, a first polishing step S2, and a second polishing step S3. Figure 2 shows a glass plate manufacturing apparatus used to carry out this method. The manufacturing apparatus 1 comprises a grinding wheel 2 for performing the grinding step S1, a first polishing wheel 3 for performing the first polishing step S2, and a second polishing wheel 4 for performing the second polishing step S3.

[0033] This method may include a cutting step as a step prior to the grinding step S1, in which the glass plate is cut to a desired size. The cutting step may include, for example, a scribing step in which scribe lines are formed on the glass plate, and a breaking step in which the glass plate is broken along the scribe lines. Such a glass plate has scribe marks on its end face, and cracks are formed in the scribe marks.

[0034] Each grinding wheel 2 to 4 is configured to be movable relative to a rectangular glass plate G supported on a surface plate. Here, "moving relative to" includes both cases where each grinding wheel 2 to 4 moves relative to the glass plate G and cases where the glass plate G moves relative to each grinding wheel 2 to 4. As shown in Figure 2, each grinding wheel 2 to 4 includes a pair of grinding wheels so as to simultaneously grind a pair of end faces Ga and Gb on the glass plate G.

[0035] As shown in Figure 2, the grinding wheel 2 is located at the very front in the direction of travel T. The first grinding wheel 3 is located behind the grinding wheel 2 in the direction of travel T. The second grinding wheel 4 is located behind the first grinding wheel 3 in the direction of travel T.

[0036] The grinding wheel 2, the first grinding wheel 3, and the second grinding wheel 4 maintain this positional relationship and contact the end faces Ga and Gb of the glass plate G, moving along the direction of travel T to process each end face Ga and Gb. Each grinding wheel 2 to 4 processes the end face Ga on a pair of long sides of the glass plate G, and then processes the end face Gb on a pair of short sides of the glass plate G.

[0037] The glass plate G is formed by known molding methods such as the float method, overflow downdraw method, and slot downdraw method. The thickness of the glass plate G is, for example, 0.1 mm or more, preferably 0.2 mm or more, and more preferably 0.3 mm or more. The upper limit of the thickness of the glass plate G is, for example, 1.4 mm or less, preferably 0.7 mm, and more preferably 0.5 mm or less.

[0038] The glass plate G is preferably a glass substrate used in displays, touch panels, solar cells, organic EL lighting, etc. Examples of displays using glass substrates include liquid crystal displays and organic EL displays.

[0039] In grinding step S1, as a preliminary step to the first polishing step S2, the end faces Ga and Gb of the glass plate G are processed into a desired shape (for example, a C-chamfered shape or an R-chamfered shape) using a grinding wheel 2. If the end faces Ga and Gb have scribe marks, these marks are removed in grinding step S1. Grinding step S1 is mainly performed in brittle mode.

[0040] It is preferable that the grinding wheel 2 is a metal bond grinding wheel in which a metal bond (metal binder) is adopted as a binder for abrasive grains. The metal adopted as the binder is preferably one selected from iron, copper, cobalt, nickel, tungsten, etc., or a mixture of two or more selected ones, and particularly preferably one containing iron. The abrasive grains bonded to the grinding wheel 2 are preferably super abrasive grains, and particularly preferably diamond abrasive grains.

[0041] The grit size (mesh number) of the grinding wheel 2 is preferably #300 to #600. Here, the "grit size" is based on JIS R6001, and the same applies to the grit sizes of the other grinding wheels 3 and 4 described later.

[0042] The first polishing step S2 is a rough polishing step of processing the end faces Ga and Gb of the glass plate G with the first polishing wheel 3 after the grinding step S1. The first polishing step S2 is mainly performed in a brittle mode.

[0043] It is preferable that the first polishing wheel 3 is a resin bond grinding wheel or a rubber bond grinding wheel in which a resin bond (resin binder) or a rubber bond (rubber binder) is adopted as a binder for abrasive grains. As the resin bond, it is preferable to adopt a thermosetting resin. As specific examples, phenolic resin, epoxy resin, polyimide resin, polyurethane resin, etc. can be adopted as the resin bond.

[0044] The first polishing wheel 3 is composed of a mixed abrasive grain grinding wheel in which abrasive grains of different mesh numbers are mixed. The mixed abrasive grain grinding wheel includes first abrasive grains and second abrasive grains having a different mesh number from the first abrasive grains. The first abrasive grains and the second abrasive grains are preferably super abrasive grains, and particularly preferably diamond abrasive grains. Also, the first abrasive grains and the second abrasive grains are preferably composed of the same kind of material. That is, when diamond abrasive grains are used as the first abrasive grains, it is preferable to use diamond abrasive grains also for the second abrasive grains.

[0045] The grain size (mesh number) of the first abrasive grains is preferably #300 to #800, and more preferably #325 to #600. The grain size of the second abrasive grains is preferably #500 to #2000, and more preferably #600 to #1500. The grain size difference between the first abrasive grains and the second abrasive grains is preferably #100 to #1500. That is, for example, when the grain size of the first abrasive grains is #400, the grain size of the second abrasive grains is preferably #500 to #1900.

[0046] The second polishing step S3 is a finishing polishing step of processing the end faces Ga and Gb of the glass plate G with the second polishing stone 4 after the first polishing step S2 (rough polishing step). The second polishing step S3 is mainly performed in the ductile mode.

[0047] As the second polishing stone 4, it is preferable to use a resin-bonded grinding stone or a rubber-bonded grinding stone. The abrasive grains in the second polishing stone 4 are preferably superabrasive grains, and particularly preferably diamond abrasive grains. The grain size (mesh number) of the abrasive grains in the second polishing stone 4 is preferably #1000 to #2000, and more preferably #1500 to #2000.

[0048] According to the method for manufacturing the glass plate G according to the present embodiment described above, in the first polishing step S2, by using the first polishing stone 3 made of a mixed abrasive grain grinding stone, the end faces Ga and Gb of the glass plate G can be made to have a surface roughness Ra suitable for the subsequent second polishing step S3.

[0049] That is, the first abrasive grains of the mixed abrasive grain grinding stone can polish the end faces Ga and Gb of the glass plate G to an appropriate surface roughness Ra in the first polishing step S2 with a grain size of #300 to #800.

[0050] On the other hand, the second abrasive grains, which have a smaller particle size than the first abrasive grains, contribute almost nothing to the polishing of the edge faces Ga and Gb of the glass plate G compared to the first abrasive grains. The second abrasive grains, by being present in the bond together with the first abrasive grains, support the first abrasive grains so that they do not sink into the bond during the first polishing step S2. As a result, the first abrasive grains can properly contact the edge faces Ga and Gb of the glass plate G, and the edge faces Ga and Gb can be polished to the desired surface roughness Ra without increasing the amount of polishing in the first polishing step S2.

[0051] Furthermore, the presence of second abrasive grains in the bond suppresses the shedding of first abrasive grains during the first polishing process S2. This allows for the longest possible lifespan of the first polishing wheel 3.

[0052] As described above, by using the first grinding wheel to bring the edge faces Ga and Gb of the glass plate G to an appropriate surface roughness Ra, slippage of the second grinding wheel 4 in the second grinding step S3 can be prevented. This extends the lifespan of the second grinding wheel 4 and reduces the crack rate at the edge faces Ga and Gb of the glass plate G. As a result, the amount of glass powder that may be generated from the edge faces Ga and Gb in the display manufacturing process can be reduced.

[0053] This method may include, as a post-process of the second polishing step S3, a cleaning step for cleaning the glass plate G, an inspection step for inspecting the glass plate G after the cleaning step, and a packaging step for packaging the glass plate G after the inspection step.

[0054] Furthermore, the present invention is not limited to the configuration of the above embodiments, nor is it limited to the effects described above. The present invention can be modified in various ways without departing from the spirit of the invention.

[0055] In the above embodiment, an example was shown in which the first and second abrasive grains of the mixed abrasive grinding wheel were made of the same material (diamond abrasive grains), but the present invention is not limited to this configuration. The first and second abrasive grains may be made of different materials.

[0056] In the above embodiment, a rectangular glass plate was used as an example, but the present invention is not limited to this and can be applied to glass plates of various other shapes.

[0057] In the above embodiment, the end faces Ga and Gb of the glass plate G were processed by grinding step S1, first polishing step S2, and second polishing step S3. However, if necessary, one or more steps may be added between grinding step S1 and first polishing step S2 to grind and / or polish the end faces Ga and Gb of the glass plate G with a grinding wheel. The number of times (number of steps) the end faces Ga and Gb of the glass plate G are processed with a grinding wheel is preferably 3 to 6 times, including grinding step S1, first polishing step S2, and second polishing step S3.

[0058] The following describes examples of the present invention, but the present invention is not limited to these examples.

[0059] The inventors conducted tests to confirm the effects of the present invention. In these tests, the first polishing wheel according to the example and the first polishing wheels according to comparative examples 1 to 3 were manufactured, and rough polishing was performed on the edge surface of a glass plate using each wheel. In this case, the surface roughness (arithmetic mean roughness) Ra of the edge surface of the glass plate after polishing and the amount of polishing were measured.

[0060] Next, a second grinding wheel (a resin-bonded grinding wheel using abrasive grains of #1500) was used to perform finish polishing on the edge surface of the glass plate. After that, the crack rate on the edge surface of the glass plate was measured.

[0061] The first grinding wheel (mixed abrasive grinding wheel) in the example is composed of a rubber-bonded grinding wheel containing diamond abrasive grains. The diamond abrasive grains in the example include first abrasive grains and second abrasive grains. The grit size of the first abrasive grains is #400. The grit size of the second abrasive grains is #600. The amount of abrasive grains (volume fraction) in the grinding wheel in the example is 31.25%.

[0062] The first grinding wheel in Comparative Examples 1 to 3 is composed of a rubber-bonded grinding wheel containing diamond abrasive grains. The grit size of the diamond abrasive grains in Comparative Example 1 is #400. The amount of abrasive grains (volume fraction) in the grinding wheel in Comparative Example 1 is 31.25%. The grit size of the diamond abrasive grains in Comparative Example 2 is #325. The amount of abrasive grains (volume fraction) in the grinding wheel in Comparative Example 2 is 31.25%. The grit size of the diamond abrasive grains in Comparative Example 3 is #400. The amount of abrasive grains (volume fraction) in the grinding wheel in Comparative Example 3 is 22.50%.

[0063] Figure 3 shows the results of measuring the surface roughness (arithmetic mean roughness) of the end face of a glass plate after polishing it with the abrasive wheels according to the Examples and Comparative Examples. As shown in Figure 3, the surface roughness of the end face of the glass plate processed with the abrasive wheel according to the Examples is greater than the surface roughness of the end face of the glass plate processed with the abrasive wheels according to Comparative Examples 1 to 3.

[0064] Figure 4 shows the amount of polishing achieved by the polishing wheels in the example and the comparative examples 1 to 3 on a glass plate. As shown in Figure 4, the amount of polishing achieved by the polishing wheel in the example is smaller than the amount of polishing achieved by the polishing wheels in comparative examples 1 to 3.

[0065] Figure 5 shows the crack rate of the glass plate after the finishing polishing process. As shown in Figure 5, the crack rate is smaller in the example where the surface roughness was large in Figure 3, and in Comparative Example 2. The crack rate was calculated using the method (inspection process) used in the conventional glass plate manufacturing method described above (see Patent Document 1).

[0066] As described above, by performing rough polishing on the edge surface of the glass plate using the first polishing wheel according to the embodiment, the surface roughness Ra of the edge surface of the glass plate can be increased compared to the case where processing is performed using the first polishing wheel of the comparative example. By increasing the surface roughness Ra of the edge surface of the glass plate in this way, the crack rate after the finish polishing process can be reduced as much as possible. Furthermore, since the amount of polishing performed by the first polishing wheel according to the embodiment is smaller than the amount of polishing performed by the first polishing wheel according to the comparative example, the occurrence of defects such as chipping and cracking caused by the first polishing wheel can be suppressed.

[0067] 2. Grinding wheel 3. First polishing wheel (mixed abrasive wheel) 4. Second polishing wheel G. Glass plate Ga. Edge of glass plate Gb. Edge of glass plate S1. Grinding process S2. First polishing process (rough polishing process) S3. Second polishing process (finishing polishing process)

Claims

1. A method for manufacturing a glass plate, comprising a rough polishing step of processing the end face of the glass plate with a grinding wheel, and a finish polishing step of processing the end face of the glass plate with a grinding wheel after the rough polishing step, wherein in the rough polishing step, the end face of the glass plate is processed using a mixed abrasive grinding wheel in which abrasive grains of different grits are mixed.

2. The method for manufacturing a glass plate according to claim 1, wherein the mixed abrasive grinding wheel comprises first abrasive grains and second abrasive grains of a different grit size from the first abrasive grains, and the first abrasive grains and the second abrasive grains are made of the same material.

3. The method for manufacturing a glass plate according to claim 2, wherein the grit size of the first abrasive grain is #300 to #800, and the grit size of the second abrasive grain is #500 to #2000.

4. The method for manufacturing a glass plate according to claim 2 or 3, wherein the difference in grain size between the first abrasive grain and the second abrasive grain is #100 to #1500.

5. The method for manufacturing a glass plate according to claim 2 or 3, wherein the first abrasive grain and the second abrasive grain are superabrasive grains.

6. The method for manufacturing a glass plate according to any one of claims 1 to 3, wherein the mixed abrasive grinding wheel is a resin-bonded grinding wheel or a rubber-bonded grinding wheel.

7. The method for manufacturing a glass plate according to any one of claims 1 to 3, wherein in the finishing polishing step, the end face of the glass plate is processed with a resin-bonded grinding wheel containing abrasive grains having a grit size of #1000 to #2000.

8. A method for manufacturing a glass plate according to any one of claims 1 to 3, comprising a grinding step of processing the end face of the glass plate with a metal bond grinding wheel as a step prior to the rough polishing step.

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