Glass polishing equipment

Abstract

To provide a method and a device for glass polishing, the method and the device providing easy control of working fluid, suppressed cost, easy washing of abrasive grains remained on a work piece after processing, reduced environmental loads and low cost.SOLUTION: A glass polishing device according to the invention includes an acrylic tool 2, a working fluid supply means 3 for supplying working fluid 8 that is deionized water or solution having an adjusted pH value and no abrasive grains between a glass work piece 9 and the acrylic tool 2, pressurizing means 4 for producing a pressing force for bringing the work piece 9 and the tool 2 into contact with each other, and a relative operation means 5 for moving the work piece 9 and the tool 2 relatively to each other to execute polishing under the pressure-contacted state by the pressurizing means 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a glass polishing method. [Background technology]

[0002] In recent years, there has been remarkable development in the field of optics using short-wavelength light. EUV lithography, a next-generation semiconductor exposure tool, aims to further miniaturize integrated circuits by using EUV (Extreme Ultraviolet) light with a wavelength of 13.5 nm. In addition, large-scale synchrotron radiation facilities such as SPring8 use hard X-rays with wavelengths of 0.1 nm or less to analyze the structure, composition, and chemical state of materials with atomic and molecular level resolution. In the X-ray and EUV range, high-precision optical elements (mirrors, lenses) that do not impair the performance of the light source are essential to develop excellent optical systems and optical equipment.

[0003] In the polishing of glass materials used in such optical elements, a polishing technique using inorganic materials such as cerium oxide and colloidal silica as free abrasive grains is widely used (see, for example, Patent Document 1). Although these materials can achieve good surface roughness, they lack dispersibility in the processing liquid due to their high density, and continuous stirring is required during processing. In addition, there is also the problem that abrasive grains remain on the surface of the workpiece after processing, making them difficult to clean.

[0004] In response to this, the present inventors have already developed Organic Abrasive Machining (OAM), a polishing technique that uses organic particles such as acrylic and urethane as free abrasive grains (see Patent Document 2). The advantages of using organic particles include that the particles have a very high dispersibility due to their similar specific gravity to water, they are softer than the workpiece and less likely to be scratched during processing, they dissolve in organic solvents, making them easy to remove after processing, and they are inexpensive and easy to obtain. In the OAM method, corrective polishing with a spatial resolution of 100 μm has been achieved using acrylic particles.

[0005] However, such polishing techniques using free abrasive grains have the problem that the concentration and state of the free abrasive grains must be kept constant during processing, which makes management difficult and increases costs.In addition, the abrasive grains on the surface of the workpiece must be cleaned after processing, which causes environmental loads and increases costs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-160680 A [Patent Document 2] Patent No. 6446590 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above-mentioned situation, the present invention aims to provide a glass polishing method and glass polishing apparatus that allows for easy management of the processing fluid, reduces costs, and simplifies cleaning of the abrasive grains on the workpiece surface after processing, thereby reducing the burden on the environment and costs. [Means for solving the problem]

[0008] While exploring the mechanism of the above-mentioned OAM method using organic particles as free abrasives, the inventors discovered that acrylic materials can accurately polish glass surfaces in pure water that is free of abrasives. They also discovered that by using acrylic materials as a processing tool, glass can be polished with high precision using a processing liquid consisting only of pure water that does not contain abrasives, and that large areas in particular can be polished flat efficiently, thereby solving the problems associated with the above-mentioned polishing technology using free abrasives (such as issues regarding management of the processing liquid, costs, and environmental impact), and thus completed the present invention.

[0009] That is, the present invention includes the following inventions. (1) A method for polishing glass, comprising the steps of: supplying a processing liquid, which is pure water or an aqueous solution with an adjusted pH and does not contain abrasive grains, between a glass workpiece and an acrylic tool; and moving the workpiece and acrylic tool relative to each other while bringing them into pressurized contact with each other to perform the polishing process.

[0010] (2) The method for polishing glass according to (1), wherein the tool is an acrylic surface plate, and the glass workpiece is pressed into contact with the surface of the rotating acrylic surface plate to polish it flat.

[0011] (3) The glass polishing method according to (2), further comprising the steps of: rotating the workpiece about an axis parallel to the axis of rotation of the acrylic platen while pressing the workpiece against the surface of the acrylic platen.

[0012] (4) The method for polishing glass according to (2) or (3), in which the processing liquid is supplied to the surface of the rotating acrylic platen.

[0013] (5) A glass polishing apparatus comprising: an acrylic tool; a processing liquid supplying means for supplying a processing liquid, which is pure water or an aqueous solution with an adjusted pH and does not contain abrasive grains, between a glass workpiece and the acrylic tool; a pressurizing means for bringing the workpiece and the tool into pressurized contact with each other; and a relative movement means for performing polishing by moving the workpiece and the tool relative to each other while they are in pressurized contact state caused by the pressurizing means.

[0014] (6) A glass polishing apparatus as described in (5), wherein the tool is an acrylic platen, the relative movement means includes a rotation means for rotating the acrylic platen, and the glass workpiece is pressed into contact with the surface of the rotating acrylic platen to polish it flat.

[0015] (7) A glass polishing apparatus as described in (6), wherein the relative movement means includes a second rotation means for rotating the workpiece around an axis parallel to the rotation axis of the acrylic platen, and while rotating the workpiece, the workpiece is brought into pressure contact with the surface of the acrylic platen to be polished flat.

[0016] (8) The glass polishing apparatus according to (6) or (7), wherein the machining liquid supplying means supplies the machining liquid to the surface of the rotating acrylic platen. Effect of the Invention

[0017] According to the present invention as described above, glass surfaces can be polished with high precision using a processing fluid that does not contain abrasive grains, which not only solves the problems associated with polishing techniques that use free abrasive grains (such as management of the processing fluid, costs, and environmental impact), but also enables large areas to be polished flat efficiently. [Brief description of the drawings]

[0018] [Figure 1] 1A is a schematic diagram of a glass polishing apparatus according to a first embodiment of the present invention, FIG. 1B is a photograph of a processing tool, and FIG. 1C is a photograph of a workpiece. [Diagram 2] Another photo of glass polishing equipment. [Diagram 3] FIG. 2 is an explanatory diagram showing the structure of a resin having an ester group. [Figure 4] An explanatory diagram of the principle of processing glass with an acrylic tool. [Diagram 5] FIG. 5 is a schematic view of a glass polishing apparatus according to a second embodiment of the present invention. [Figure 6a] The left side shows a surface observation image of the machining marks made by the acrylic tool, and the right side shows the depth profile. [Figure 6b] The left side shows a surface observation image of the machining marks made by a PC tool, and the right side shows the depth profile. [Figure 6c] The left side shows a surface observation image of the machining marks made by an ABS tool, and the right side shows the depth profile. [Figure 6d] The left side shows a surface observation image of the machining marks made by the PBT tool, and the right side shows the depth profile. [Figure 6e] The left side shows a surface observation image of the machining marks made by the PTFE tool, and the right side shows the depth profile. [Figure 7] Surface observation images of processing marks made by different organic material tools. [Figure 8]Surface observation images of the machining marks made by an acrylic tool at different machining times. [Figure 9] Graph showing the machining depth with an acrylic tool at different machining times. [Figure 10] Surface observation images of machining marks made by an acrylic tool under different machining loads. [Figure 11] Graph showing the cutting depth with an acrylic tool at different cutting loads. [Figure 12] Surface observation images of machining marks made with an acrylic tool at different temperatures. [Figure 13] Surface observation images of machining marks made by an acrylic tool using different types of machining fluids. [Figure 14] Surface observation images of machining marks made by an acrylic tool using machining fluids with different pH levels. [Figure 15] A graph showing the machining depth of an acrylic tool in machining fluids with different pH levels. [Figure 16] Images showing the surface roughness after machining with an acrylic tool in machining fluids with different pH levels. [Figure 17] A graph showing the surface roughness after machining with an acrylic tool using machining fluids with different pH levels. [Figure 18] Images showing the surface roughness after machining with an acrylic tool in machining fluids with different pH levels. [Figure 19] A graph showing the surface roughness after machining with an acrylic tool using machining fluids with different pH levels. [Figure 20a] The left side shows a surface observation image of the machining marks made by an acrylic tool in an acidic machining fluid, and the right side shows the depth profile. [Figure 20b] The left side shows the surface observation images of the machining marks made by an acrylic tool in different types of acidic machining fluids, and the right side shows the depth profile. [Figure 21] Image showing surface roughness after machining with an acrylic tool in a sulfamic acid aqueous solution. [Figure 22] Image showing surface roughness after machining with an acrylic tool in an acetic acid aqueous machining fluid. [Figure 23a]The left side shows a surface observation image of the machining marks made by an acrylic tool using a machining fluid of sodium carbonate aqueous solution, and the right side shows the depth profile. [Figure 23b] The left side shows a surface observation image of the machining marks made by an acrylic tool using a calcium hydroxide aqueous solution as the machining fluid, and the right side shows the depth profile. [Figure 24] Images showing the surface roughness after machining with an acrylic tool in different types of alkaline machining fluids. [Figure 25a] The image on the left shows the surface roughness before flattening a glass substrate using an acrylic plate and pure water, and the image on the right shows the depth profile. [Figure 25b] The image on the left shows the surface roughness after 60 hours of flattening a glass substrate using an acrylic plate and pure water, and the image on the right shows the depth profile. [Figure 25c] The image on the left shows the surface roughness after 120 hours of flattening a glass substrate using an acrylic plate and pure water, and the image on the right shows the depth profile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0020] FIG. 1 shows the configuration of a glass polishing apparatus 1A according to a first embodiment of the present invention, in which (a) is a schematic diagram of the apparatus, (b) shows an acrylic fixed tool, and (c) shows synthetic quartz to be processed.

[0021] The glass polishing processing apparatus 1A of this embodiment comprises an acrylic tool 2, a processing fluid supply means 3 for supplying processing fluid between a glass workpiece 9 and the acrylic tool 2, a pressure means 4 for bringing the workpiece 9 and the tool 2 into pressurized contact with each other, and a relative movement means 5 for performing polishing processing by moving the workpiece 9 and the tool 2 relative to each other while in the pressurized contact state caused by the pressure means 4.

[0022] The workpiece 9 is made of glass such as synthetic quartz. The acrylic tool 2 is a hemispherical tool. The shape is not particularly limited to a hemispherical shape. The acrylic tool 2 is fixed replaceably under a jig 21 attached to the tip of a rod 20.

[0023] The machining fluid supply means 3 is provided with a container 30 for holding the machining fluid on the vibration device 52, and the workpiece 9 is attached to the bottom of the container 30, so that the workpiece 9 is completely immersed in the machining fluid. The machining fluid is pure water or an aqueous solution with an adjusted pH, and does not contain abrasive grains. The tool 2 and the workpiece 9 are immersed in the machining fluid in the container 30, and machining is performed in the machining fluid. A method other than immersion, for example, a means for spraying the machining fluid on the surface to be machined of the workpiece 9 may be used. As the "pH-adjusted aqueous solution," an acidic aqueous solution with a pH of 6 or less or an alkaline sodium carbonate aqueous solution with a pH of about 10 is preferable in terms of maintaining good surface roughness while machining. In order to obtain a better surface roughness, it is preferable to use an acidic aqueous solution with a pH of 4 or less, more preferably 3.5 to 1. However, in the case of an acidic aqueous solution, the lower the pH, the shallower the machining depth becomes, so if the machining depth is also required, it is preferable to use an aqueous solution with a pH of 3 or more. Although the surface roughness deteriorates, it is also preferable to use an alkaline calcium hydroxide aqueous solution having a pH of about 10 in order to obtain a superior machining depth (machining speed).

[0024] The relative motion means 5 includes a motor 51 that rotates the bar 20 extending vertically of the tool 2 around the axis of the bar to rotate the tool 2, and a vibration device (shaker) 52 that reciprocates the workpiece 9 together with the container 30 in a horizontal direction perpendicular to the axis of the bar 20. The tool rotates in the machining fluid in the container 30, and the workpiece 9 linearly reciprocates together with the container 30 within a certain distance.

[0025] The pressure means 4 has a plate 41 attached to the upper end of the bar 20 and a weight placed on it. The weight controls the load applied between the tool 2 and the workpiece 9. The motor 51 is attached to a guide column via a linear bushing 40 so that it can move up and down freely. This means that the total weight of the weight, plate 41, and rotating motor 51 is applied as a load between the tool 2 and the workpiece 9. With the device of this embodiment, a combination of rotation and reciprocation can be used to perform linear glass polishing, and it is also possible to stop the vibration device and perform point-like glass polishing using rotation alone.

[0026] Next, we will explain the processing principle of the present invention. As will be clear from various experiments described later, polishing of glass did not proceed with tools made of materials other than acrylic. If processing is caused only by mechanical force, synthetic quartz should be processed with tools such as PC, which has a higher hardness.

[0027] This shows that the polishing of glass using the acrylic tool of the present invention has a chemical processing effect in addition to mechanical force. Also, if the polishing is caused only by the elution of glass into the processing liquid, any organic material should be usable as a processing tool, but the result in Figure 7 shows that this is not the case, and materials other than acrylic could not polish glass in pure water.

[0028] In consideration, acrylic contains ester groups, which are located on the side chain. In contrast, PBT and PC, which could not process glass, contain ester groups, but these ester groups are located on the main chain (see Figure 3). Ester groups located on the side chain are more easily hydrolyzed and more likely to generate CO- than those located on the main chain. Therefore, as shown in Figure 4, hydroxides in the processing fluid bind to this CO-, forming a surface terminated with hydroxyl groups (-OH), and it is thought that this causes the acrylic tool to bind to Si in the glass via oxygen atoms, and Si is pulled out and removed from the glass surface by the tool side.

[0029] Next, a second embodiment of the present invention will be described.

[0030] FIG. 5 shows a schematic configuration of a glass polishing apparatus 1B according to the second embodiment.

[0031] The glass polishing apparatus 1B of this embodiment is an apparatus suitable for flattening a large area of ​​glass, and as shown in Figure 5, is equipped with an acrylic platen processing tool 2, processing liquid supply means 3 for supplying processing liquid 8 between the glass plate workpiece 9 and the processing tool 2, pressure means 4 for bringing the workpiece 9 and the tool 2 into pressurized contact with each other, and relative movement means 5 for performing polishing by moving the workpiece 9 and the tool 2 relative to each other while they are in pressurized contact state by the pressure means 4.

[0032] In this embodiment, the relative motion means 5 includes a turntable 53 as a first rotation means incorporating a mechanism for rotating the acrylic platen tool 2, and a rotation device 54 as a second rotation means for rotating the workpiece 9 about an axis parallel to the rotation axis of the acrylic platen (tool 2), and while rotating the workpiece 9, it is pressed into contact with the surface of the separately rotating acrylic platen (tool 2) to polish it flat. Since the two rotations have different axial positions and rotational diameters, relative motion occurs between the workpiece machining surface and the tool (acrylic platen).

[0033] The rotating device 54 is provided with a holding plate 540 having holding holes for holding multiple workpieces near the surface of the tool 2 in a vertically movable state, and a pressure cylinder 42 as pressure means 4 for applying pressure from above to the workpieces held in each holding hole and pressing them against the surface of the tool 2, at its lower end, and is configured to rotate these integrally with an internal motor. The rotating device 54 rotates the multiple workpieces around the rotation axis, and the tool 2 simultaneously polishes them flat.

[0034] The machining fluid supplying means 3 is composed of a pump and a nozzle that sprays machining fluid 8 onto the surface of the rotating tool 2 (acrylic platen). In addition to spraying machining fluid onto the tool 2 in this way, it is also possible to configure the tool 2 and the workpiece 9 to be immersed in the machining fluid.

[0035] The polishing apparatus of this embodiment can be configured by using a known flat polishing apparatus equipped with the same pressure means 4, relative movement means 5, and machining liquid supply means 3, and only the machining tool is changed to an acrylic surface plate instead of a polishing pad that is normally used. The machining liquid 8, work 9, other configurations, and machining principles are basically the same as those of the first embodiment described above, so their explanation will be omitted. EXAMPLES

[0036] <Tool material comparison test 1 by spot polishing> The results of an experiment conducted using the device of the first embodiment to confirm the difference in point polishing (processing with the vibration device stopped) by changing only the material of the tool will be described.

[0037] (Processing conditions) The processing conditions are shown in Table 1. The tip of the tool was hemispherical with a diameter of 10 mm.

[0038] [Table 1]

[0039] (result) The results are shown in Figures 6(a) to 6(e). The left side of each figure shows the measurement results of the point-like machining marks made by each tool using a scanning white light interferometer (Zygo's NewView 700s white light interferometer), and the right side shows the depth profile. The machining results showed that clear machining marks were obtained using the acrylic, PC, and ABS tools, but not the others. In addition, the deepest machining marks were obtained with the acrylic tool. The surfaces machined with the PC and ABS tools had many machining streaks, while the surface machined with the acrylic tool was relatively smooth.

[0040] <Tool material comparison test 2: Linear polishing> Similarly, using the device of the first embodiment, an experiment was carried out to confirm the difference in linear polishing (combination of rotation and reciprocating vibration) by changing only the material of the tool. The results will be described.

[0041] (Processing conditions) The processing conditions are shown in Table 2. The tip of the tool was also hemispherical with a diameter of 10 mm.

[0042] [Table 2]

[0043] (result) The results are shown in Figures 7(a) to 7(e). The left side of each figure shows the measurement results of the linear processing marks made by each tool using a scanning white light interferometer. The processing results showed that clear processing marks were obtained using the acrylic tool, but that processing marks could not be formed using other organic material tools. Note that only for the acrylic tools on which clear machining marks were obtained, the entire machining mark was measured, whereas for the other tools on which no machining marks were obtained, only a location approximately 3.7 mm from the left end was measured.

[0044] <Comparative test of processing time> The results of an experiment conducted using the device and acrylic tool of the first embodiment to confirm the difference in linear polishing processing by changing only the processing time will be described.

[0045] (Processing conditions) The processing conditions are shown in Table 3. The tip of the tool was hemispherical with a diameter of 10 mm.

[0046] [Table 3]

[0047] (result) The results are shown in Figures 8 and 9. Figure 8 shows the results of measurements taken using a scanning white light interferometer (Zygo's NewView 700s white light interferometer). Figure 9 is a graph showing the relationship between processing time and processing depth. The results of this experiment show that the processing depth increases as the processing time increases.

[0048] <Comparative test of processing load> We will now explain the results of an experiment conducted using the device and acrylic tool of the first embodiment to confirm the differences in linear polishing (in this case, no rotation was used, only reciprocating motion by the vibration device) by changing only the processing load.

[0049] (Processing conditions) The processing conditions are shown in Table 4. The tip of the tool was hemispherical with a diameter of 10 mm.

[0050] [Table 4]

[0051] (result) The results are shown in Figures 10 and 11. Figure 10 shows the results of measurements taken using a scanning white light interferometer (NewView 700s white light interferometer manufactured by Zygo). Figure 11 is a graph showing the relationship between the processing load and the processing depth. The results of this experiment show that there is no significant change in the processing depth even when the processing load is increased. Although physical frictional force is proportional to the load, the results of this experiment show that an increase in frictional force has almost no effect on the processing depth, indicating that the present invention is a chemical processing method.

[0052] <Comparative test of machining fluid temperature> The results of an experiment conducted using the device and acrylic tool of the first embodiment to confirm the difference in linear polishing processing by changing only the temperature of the processing liquid (pure water) will be described.

[0053] (Processing conditions) The processing conditions are shown in Table 5. The tip of the tool was hemispherical with a diameter of 10 mm.

[0054] [Table 5]

[0055] (result) The results are shown in Figure 12. Figure 12 shows the measurement results using a scanning white light interferometer (Zygo's NewView 700s white light interferometer). The results of this experiment show that under the machining conditions of 40 degrees, the machining marks are larger and deeper than when the angle is 23 degrees.

[0056] <Comparative test with and without water in machining fluid> Pure water contains free ions consisting of hydrogen ions and hydroxide ions. In order to investigate the influence of pure water itself, Fluorinert, which does not contain free ions, has heat transfer ability, is inactive, and is thermally and chemically stable, was selected as the machining fluid for comparison and a comparative experiment was conducted. Specifically, the results of an experiment conducted using the device and acrylic tool of the first embodiment to confirm the difference in linear polishing processing by changing only the machining fluid (pure water / Fluorinert) will be described.

[0057] (Processing conditions) The processing conditions are shown in Table 6. The tip of the tool was hemispherical with a diameter of 10 mm.

[0058] [Table 6]

[0059] (result) The results are shown in Figure 13. Figure 13 shows the results of measurements made using a scanning white light interferometer (Zygo's NewView 700s white light interferometer). The results of this experiment show that synthetic quartz can be machined in pure water, and no machining marks were left in Fluorinert. From these results, it is inferred that the free ions in the water are affecting the machining process.

[0060] <pH comparison test 1 when machining fluid is set to acidic> The results of an experiment conducted to confirm the difference in linear polishing by changing only the pH of the acidic processing fluid using the device and acrylic tool of the first embodiment will be described. The acidic processing fluid used was a sulfamic acid solution with an adjusted pH.

[0061] (Processing conditions) The processing conditions are shown in Table 7. The tip of the tool was a hemisphere with a diameter of 10 mm.

[0062] [Table 7]

[0063] (result) The results are shown in Figures 14, 15, 16, and 17. Figure 14 shows the results of measurements using a scanning white light interferometer (Zygo's NewView 700s white light interferometer), and Figure 15 is a graph showing the relationship between pH and machining depth. Figure 16 shows the surface roughness of a workpiece after machining synthetic quartz in an acid machining fluid with an acrylic tool, and Figure 17 shows the relationship between the pH of the acid machining fluid and the surface roughness of the machined surface.

[0064] It can be seen from Figures 14 and 15 that as the pH decreases, the machining depth becomes shallower. This is thought to be due to a decrease in the concentration of hydroxide ions. Furthermore, from Figures 16 and 17, it can be seen that as the pH decreases, the surface roughness gradually improves. This result suggests that the surface roughness may be good because the machining depth is shallow when the pH is low. Therefore, next we conducted a comparative experiment to confirm whether good surface roughness could be achieved even when the machining depth is the same.

[0065] <pH comparison test 2 when machining fluid is set to acidic> An experiment was conducted using the apparatus of the first embodiment, an acrylic tool, and a sulfamic acid solution of pH 2.7 and pure water of pH 5.6 as the machining liquid, performing line polishing for different times to achieve the same machining depth, and confirming the difference in surface roughness.

[0066] (Processing conditions) The machining conditions are shown in Table 8. The tip of the tool was a hemisphere with a diameter of 10 mm. Machining was performed in the sulfamic acid solution for up to 5 hours, and in pure water for 1 hour.

[0067] [Table 8]

[0068] (result) The results of the surface roughness after processing are shown in Figures 18 and 19. The surface roughness of processing with a sulfamic acid aqueous solution at pH 2.7 was better than that of processing with pure water at pH 5.6 for the same processing depth of 6 nm. This confirmed that the lower the pH, the better the surface roughness for the same processing depth.

[0069] <pH comparison test 3 when machining fluid is set to acidic> Next, a comparative test was conducted to confirm whether the same machining depth and surface roughness could be obtained in different types of acidic machining fluids with the same pH. The results of the experiment to confirm the difference in linear polishing processing using the device of the first embodiment, an acrylic tool, and sulfamic acid and acetic acid with pH 2.2 as the machining fluid will be described.

[0070] (Processing conditions) The processing conditions are shown in Table 9. The tip of the tool was hemispherical with a diameter of 10 mm.

[0071] [Table 9]

[0072] The results of processing are shown in Figures 20, 21, and 22. As can be seen from Figure 20, the width and depth of the processing marks obtained after processing for 3 hours in different types of acid liquids with the same pH are substantially the same. Also, Figure 21 shows the surface roughness before and after processing in a sulfamic acid solution. Figure 22 shows the surface roughness before and after processing in an acetic acid solution.

[0073] In conclusion, it can be seen that for the processing of synthetic quartz with acrylic, it is possible to obtain good surface roughness in acidic liquids with lower pH and regardless of the type of acid.

[0074] <Comparative test of pH when machining fluid is set to alkaline> The results of an experiment conducted to confirm the difference in linear polishing using the apparatus and acrylic tool of the first embodiment and an alkaline machining liquid of a sodium carbonate solution and a calcium hydroxide solution both having a pH of 10 will be described.

[0075] (Processing conditions) The processing conditions are shown in Table 10. The tip of the tool was hemispherical with a diameter of 10 mm.

[0076] [Table 10]

[0077] (result) The results are shown in Figures 23 and 24. The left side of Figures 23(a) and 23(b) shows the measurement results of the linear machining marks made by each tool using a scanning white light interferometer (Zygo's NewView 700s white light interferometer), and the right side shows the depth profile. The result of machining in a sodium carbonate aqueous solution was that the machining marks were not deep, at about 8 nm. It can be seen that the result of machining in a calcium hydroxide aqueous solution was that the machining marks reached a depth of more than 70 nm. It is possible that the machining speed was faster because calcium hydroxide can corrode synthetic quartz.

[0078] Figure 24 shows the machining results of surface roughness. After machining with sodium carbonate aqueous solution, the surface roughness is RMS 0.275 nm, and the PV is reduced to 5.7 nm. After machining with calcium hydroxide machining solution, the surface roughness is very poor. The reason is that calcium hydroxide has a corrosive effect on glass, which may cause deep corrosion pits. And the strong base has a corrosive effect on acrylic, which may cause the acrylic to adhere to the surface of the workpiece.

[0079] <Flatness test> Next, the results of planarization of a glass substrate using the apparatus of the second embodiment equipped with an acrylic surface plate and only pure water will be described.

[0080] (Processing conditions) The processing conditions are shown in Table 11. The "(top)" side of the rotation speed is the rotation speed of the rotation device on the substrate side, and the "(bottom)" side is the rotation speed on the acrylic table side. A scanning white light interferometer (Zygo, NewView 700S) was used to measure the substrate surface.

[0081] [Table 11]

[0082] (result) The results are shown in Figures 25(a) to 25(c). Figure 25(a) shows the state before processing, Figure 25(b) shows the result after 60 hours of processing, and Figure 25(c) shows the result after 120 hours of processing, with the left side of each figure showing the surface roughness and the right side showing the depth profile. These processing results show that large-area planarization of glass substrates is possible using an acrylic surface plate and a processing fluid consisting only of pure water that does not contain abrasive grains. [Explanation of symbols]

[0083] 1A, 1B Glass polishing equipment 2 Processing tools 20 Bar material 21 Jig 3 Processing fluid supply means 30 containers 4. Pressurizing means 40 Linear bushing 41 plates 42 Pressure Cylinder 5 Relative movement means 51 Rotary Motor 52 Vibration device 53 Rotating table 54 Rotating device 540 Retaining Plate 8 Processing fluid 9 Work

Claims

1. An acrylic tool having an abrasive surface on which acrylic is located and which does not contain abrasive grains; A machining fluid supplying means for supplying a machining fluid, which is pure water or an aqueous solution with an adjusted pH and does not contain abrasive grains, between the glass workpiece and the acrylic tool; A pressurizing means for pressing the workpiece and the tool into contact with each other; a relative movement means for performing polishing by moving the workpiece and the tool relative to each other while the workpiece and the tool are in a pressurized contact state by the pressurizing means; A glass polishing apparatus comprising:

2. the tool is an acrylic platen; The relative movement means includes a rotation means for rotating the acrylic base plate, 2. The glass polishing apparatus according to claim 1, wherein the glass workpiece is polished flat by being brought into pressure contact with the surface of a rotating acrylic platen.

3. The relative movement means includes a second rotation means for rotating the workpiece around an axis parallel to the rotation axis of the acrylic surface plate, 3. The glass polishing apparatus according to claim 2, wherein the workpiece is polished flat by being pressed against the surface of the acrylic platen while being rotated.

4. 4. The glass polishing apparatus according to claim 2, wherein said machining liquid supplying means supplies said machining liquid to the surface of said rotating acrylic platen.

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