JP7620798B2 - Glass polishing equipment - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act. Presented at the 2019 Japan Society of Precision Engineering Spring Meeting Academic Lecture held at Tokyo Denki University on March 13, 2019.

The present invention relates to a glass polishing method.

In recent years, there has been remarkable development in the field of optics using short-wavelength light. EUV lithography, a next-generation semiconductor exposure device, 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 SPring-8 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 order to develop excellent optical systems and optical equipment 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.

In polishing the glass materials used in such optical elements, polishing techniques using inorganic materials such as cerium oxide and colloidal silica as free abrasive grains are widely used (see, for example, Patent Document 1). These materials can achieve good surface roughness, but because of their high density, they lack dispersibility in the processing liquid, 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.

In response to this, the present inventors have already developed Organic Abrasive Machining (OAM method), a polishing technique that uses organic particles such as acrylic or urethane as free abrasive grains (see Patent Document 2). The advantages of using organic particles include that the particles have a specific gravity close to that of water, making them highly dispersible; 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 readily available. In the OAM method, corrective polishing with a spatial resolution of 100 μm has been achieved using acrylic particles.

However, such polishing techniques using free abrasive grains require the concentration and state of the free abrasive grains to be kept constant during processing, which makes them difficult to manage and increases costs. In addition, the abrasive grains on the workpiece surface must be cleaned after processing, which can be an environmental burden and a cost increase.

JP 2009-160680 A Patent No. 6446590

In view of the above-mentioned situation, the present invention aims to provide a method and apparatus for polishing glass that allows easy management of the processing fluid, reduces costs, simplifies cleaning of the abrasive grains on the workpiece surface after processing, and reduces environmental impact and costs.

While exploring the mechanism of the above-mentioned OAM method using organic particles as free abrasives, the inventor discovered that acrylic materials can accurately polish glass surfaces in pure water that does not contain abrasives. He discovered that by using acrylic materials as a processing tool, glass can be accurately polished using a processing fluid 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 with the above-mentioned polishing technology using free abrasives (problems such as management of the processing fluid, costs, and environmental impact), and thus completed the present invention.

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.

(2) The method for polishing glass described in (1), in which the tool is an acrylic platen, and the glass workpiece is pressed against and polished flat against the surface of the rotating acrylic platen.

(3) The glass polishing method described in (2), in which the workpiece is brought into pressurized contact with the surface of the acrylic platen while rotating about an axis parallel to the axis of rotation of the acrylic platen.

(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.

(5) A glass polishing device comprising: an acrylic tool; a processing fluid supplying means for supplying a processing fluid between a glass workpiece and the acrylic tool, which is pure water or an aqueous solution with an adjusted pH and does not contain abrasive grains; 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 in pressurized contact state caused by the pressurizing means.

(6) The glass polishing device according to (5), in which 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.

(7) The glass polishing device according to (6), in which 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 the workpiece is pressed against the surface of the acrylic platen while being rotated, thereby polishing the workpiece flat.

(8) The glass polishing device according to (6) or (7), in which the processing liquid supply means supplies the processing liquid to the surface of the rotating acrylic platen.

According to the present invention, glass surfaces can be polished with high precision using abrasive-free processing fluid, which not only solves the problems associated with polishing techniques that use free abrasives (such as fluid management, costs, and environmental impact), but also enables large areas to be polished efficiently and flat.

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. Another photo of glass polishing equipment. FIG. 2 is an explanatory diagram showing the structure of a resin having an ester group. An explanatory diagram of the principle of processing glass with an acrylic tool. FIG. 5 is a schematic diagram of a glass polishing apparatus according to a second embodiment of the present invention. 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. 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. 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. The left side is a surface observation image of the machining marks made by the PBT tool, and the right side is the depth profile. The left side is a surface observation image of the machining marks made by a PTFE tool, and the right side is a depth profile. Surface observation images of processing marks made by different organic material tools. Surface observation images of the machining marks made by an acrylic tool at different machining times. Graph showing the machining depth with an acrylic tool at different machining times. Surface observation images of machining marks made by an acrylic tool under different machining loads. Graph showing the cutting depth with an acrylic tool at different cutting loads. Surface observation images of machining marks made with an acrylic tool at different temperatures. Surface observation images of machining marks made by an acrylic tool using different types of machining fluids. Surface observation images of machining marks made by an acrylic tool using machining fluids with different pH values. 1 is a graph showing machining depths using an acrylic tool with machining fluids having different pH values. Images showing the surface roughness after machining with an acrylic tool in machining fluids with different pH values. 1 is a graph showing surface roughness after machining with an acrylic tool using machining fluids with different pH values. Images showing the surface roughness after machining with an acrylic tool in machining fluids with different pH values. 1 is a graph showing surface roughness after machining with an acrylic tool using machining fluids with different pH values. 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. 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. Image showing surface roughness after machining with an acrylic tool in a sulfamic acid aqueous solution. Image showing surface roughness after machining with an acrylic tool in an acetic acid aqueous machining fluid. 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. 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. Images showing the surface roughness after machining with an acrylic tool in different types of alkaline machining fluids. 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. The left image shows the surface roughness after 60 hours of flattening a glass substrate using an acrylic plate and pure water, and the right image shows the depth profile. 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.

Next, an embodiment of the present invention will be described in detail with reference to the attached drawings.

Figure 1 shows the configuration of a glass polishing device 1A according to the first embodiment of the present invention, where (a) is a schematic diagram of the device, (b) shows the acrylic fixed tool, and (c) shows the synthetic quartz to be processed.

The glass polishing device 1A of this embodiment includes an acrylic tool 2, a processing fluid supplying means 3 for supplying processing fluid between a glass workpiece 9 and the acrylic tool 2, a pressurizing 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 by moving the workpiece 9 and the tool 2 relative to each other while in pressurized contact state by the pressurizing means 4.

The workpiece 9 is 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 replaceably fixed under a jig 21 attached to the tip of a rod 20.

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. Methods other than immersion, such as a means for spraying the machining fluid on the machining surface of the workpiece 9, may also 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 that machining can be performed while maintaining good surface roughness. 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 machining depth is also required, it is preferable to use an aqueous solution with a pH of 3 or more. It is also preferable to use an alkaline calcium hydroxide solution with a pH of about 10 to obtain a better machining depth (machining speed), although this will result in a worsening of the surface roughness.

The relative motion means 5 includes a motor 51 that rotates the vertically extending bar 20 of the tool 2 around the axis of the bar, causing the tool 2 to rotate, and a vibration device (shaker) 52 that causes the workpiece 9 to reciprocate 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 reciprocates linearly together with the container 30 over a certain distance.

The pressure applying means 4 has a plate 41 attached to the upper end of the rod 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 the 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. In the device of this embodiment, linear glass polishing can be performed by combining rotation and reciprocation, and point-shaped glass polishing can also be performed by stopping the vibration device and rotating only.

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 were caused by mechanical force alone, synthetic quartz should be processed using tools made of materials with higher hardness, such as PC.

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 processing is caused only by the dissolution of glass into the processing liquid, any organic material should be able to be used as a processing tool, but the results in Figure 7 show that this is not the case, and materials other than acrylic were unable to process glass in pure water.

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 liquid bind to this CO-, forming a surface terminated with hydroxyl groups (-OH), and it is believed that the acrylic tool bonds with Si in the glass via oxygen atoms, and Si is pulled out from the glass surface and removed by the tool side.

Next, we will explain the second embodiment of the present invention.

Figure 5 shows the schematic configuration of the glass polishing device 1B according to the second embodiment.

The glass polishing device 1B of this embodiment is an apparatus suitable for flattening a large area of glass, and as shown in FIG. 5, it is equipped with an acrylic platen processing tool 2, processing liquid supply means 3 for supplying processing liquid 8 between a glass plate workpiece 9 and the processing 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 by moving the workpiece 9 and the tool 2 relative to each other while in pressurized contact state by the pressure means 4.

In this embodiment, the relative motion means 5 comprises a turntable 53 as a first rotation means incorporating a mechanism for rotating the tool 2 of the acrylic platen, and a rotation device 54 as a second rotation means for rotating the workpiece 9 around an axis parallel to the rotation axis of the acrylic platen (tool 2). 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).

The rotating device 54 is equipped with a holding plate 540 with holding holes that hold multiple workpieces near the surface of the tool 2 in a state where they can be moved up and down, and a pressure cylinder 42 at its lower end as a pressure means 4 that applies pressure from above to the workpieces held in each holding hole and presses them against the surface of the tool 2, and is configured to rotate these together with an internal motor. The rotating device 54 rotates the multiple workpieces around the rotation axis, and the tool 2 simultaneously polishes them flat.

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.

The polishing device of this embodiment can be constructed using a known flat polishing device equipped with the same pressure means 4, relative movement means 5, and processing liquid supply means 3, with only the processing tool being changed from the normally used polishing pad to an acrylic surface plate. The processing liquid 8, workpiece 9, other configurations, and processing principles are basically the same as those of the first embodiment described above, so their explanation will be omitted.

<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.

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

(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 processing 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 processing results showed that clear processing marks were obtained using the acrylic, PC, and ABS tools, but not the others. In addition, the deepest processing marks were obtained with the acrylic tool. The surfaces processed with the PC and ABS tools had many processing streaks, while the surfaces processed with the acrylic tool were relatively smooth.

<Tool material comparison test 2: Linear polishing>
Similarly, using the apparatus of the first embodiment, an experiment was conducted 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.

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

(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 show that clear processing marks were obtained using the acrylic tool, but processing marks could not be formed using other organic material tools.
Only for the acrylic tools on which clear processing marks were obtained, the entire processing marks were measured, and for the other tools on which no processing marks were obtained, only a location approximately 3.7 mm from the left end was measured.

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

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

(result)
The results are shown in Figures 8 and 9. Figure 8 shows the measurement results 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. From the results of this experiment, it can be seen that the processing depth increases as the processing time increases.

<Comparative test of processing load>
The results of an experiment conducted using the device and acrylic tool of the first embodiment to confirm the difference in linear polishing (in this case, no rotation was used, only reciprocating motion by the vibration device) by changing only the processing load will be described.

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

(result)
The results are shown in Figures 10 and 11. Figure 10 shows the results of measurements made using a scanning white light interferometer (Zygo's NewView 700s white light interferometer). 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.

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

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

(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 those under the condition of 23 degrees.

<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 performed. Specifically, the results of an experiment to confirm the difference in linear polishing processing by changing only the machining fluid (pure water/Fluorinert) using the device and acrylic tool of the first embodiment will be described.

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

(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 the 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.

<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 machining liquid using the apparatus and acrylic tool of the first embodiment will be described. The acidic machining liquid used was a sulfamic acid solution with an adjusted pH.

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

(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.

Figures 14 and 15 show that as the pH decreases, the machining depth becomes shallower. This is believed to be due to a decrease in the concentration of hydroxide ions. Figures 16 and 17 also show 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, a comparative experiment was conducted to confirm whether good surface roughness could be achieved even when the machining depth is the same.

<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 machining liquids, performing line polishing for different times to achieve the same machining depth, and confirming the difference in surface roughness.

(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 aqueous solution for up to 5 hours, and in pure water for 1 hour.

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

<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 were described below using the device of the first embodiment, an acrylic tool, and sulfamic acid and acetic acid with pH 2.2 as machining fluids.

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

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 when processing for 3 hours in different types of acid liquids with the same pH are essentially the same. Also, Figure 21 shows the surface roughness before and after processing in an aqueous sulfamic acid solution. Figure 22 shows the surface roughness before and after processing in an aqueous acetic acid solution.

In conclusion, it can be seen that for processing 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.

<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 sodium carbonate solution and calcium hydroxide solution, each having a pH of 10, will be described.

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

(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 70 nm or more. It is possible that the machining speed was increased because calcium hydroxide can corrode synthetic quartz.

Figure 24 shows the results of surface roughness processing. After processing with sodium carbonate aqueous solution, the surface roughness was reduced to RMS 0.275 nm and PV 5.7 nm. After processing with calcium hydroxide processing 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. Also, strong bases have a corrosive effect on acrylic, which may cause the acrylic to adhere to the surface of the workpiece.

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

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

(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 with a processing fluid consisting only of pure water that does not contain abrasive grains.

Reference Signs List 1A, 1B Glass polishing device 2 Processing tool 20 Bar 21 Jig 3 Processing liquid supply means 30 Container 4 Pressurizing means 40 Linear bush 41 Plate 42 Pressurizing cylinder 5 Relative movement means 51 Rotation motor 52 Vibration device 53 Rotation table 54 Rotation device 540 Holding plate 8 Processing liquid 9 Workpiece

Claims (4)

An acrylic tool having an abrasive grain-free surface on which acrylic is positioned ;
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: 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. 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. 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.