JP6399393B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad, and more particularly, to a polishing pad suitable for polishing a surface of an object to be polished with a change in thickness.

  Conventionally, different types of mobile devices such as mobile phones, smartphones, tablet PCs, or various small portable electronic devices such as music players, game devices, or industrial systems are differentiated from other products. In order to achieve this, various shapes are adopted in its appearance and design. In recent years, as a shape of a small portable electronic device, a shape with a change in thickness, such as a shape in which a thickness is reduced toward the outer periphery and a curved surface is formed along the outer periphery, is frequently used. Moreover, by adopting such a shape, in addition to the effect of improving the designability, an information display section or an operation button can be provided on the side surface of the device, thereby improving the degree of freedom of design. be able to.

  And when processing the housing | casing etc. of the small portable electronic device of the shape which gave the change as mentioned above, it is possible to use the technique of cutting and metal mold.

  When machining a shape with a change in thickness by cutting, the workpiece is cut into a predetermined shape using a ball end mill or an R-shaped diamond tool. However, when a ball end mill is used, arc-shaped cutting traces are formed on the processed surface in accordance with the ball diameter of the ball end mill. In addition, when an R-shaped diamond tool is used, it is necessary to form the flat surface and the curved surface by separate cutting processes, so a step is formed at the boundary line between the flat surface and the curved surface, and a uniform surface is processed. I can't. Similarly, when a shape having a change in thickness is formed by a mold, unevenness influenced by the surface quality of the mold is formed on the entire surface that is in contact with the mold.

  Accordingly, as a means for removing cutting traces, steps, and irregularities generated by the above-described cutting and mold forming, polishing having a polishing surface smaller than the surface to be processed as described in Patent Document 1 or 2 after cutting. In many cases, a method is used in which a tool is moved in a three-dimensional manner by a predetermined processing program, and the surface to be processed is polished by scanning the surface to be processed.

JP 2003-62751 A Japanese Patent No. 3030681

  However, the method of scanning the polishing tool as described in Patent Document 1 or 2 has a problem that it is difficult to keep the polishing pressure on the object to be polished constant, and the polishing accuracy is never high. It was. In addition, when the polishing tool is scanned, it is necessary to make the passing amount of the polishing tool constant over the entire surface to be polished, but it is extremely difficult to perform such scanning, and in reality, polishing spots are generated. There was a problem that.

  Therefore, the present invention has been made to solve the above-described problems, and can polish the polishing accuracy when polishing the surface of the object to be polished with a change in thickness. It is an object to provide a polishing pad that can be suppressed.

  In order to solve the above-described problems, the present invention is a polishing pad configured by bonding at least two sheets of an upper layer sheet and a lower layer sheet having a polishing surface, and the thickness of the upper layer sheet is 1.0 mm to 2.0 mm, Shore A hardness of the polishing surface is 20 to 90, and 25% compression hardness when measured using an indenter with a diameter of 10 mm is 0.15 to the entire polishing pad. 0.27 MPa.

  As in the present invention thus configured, the thickness of the upper layer sheet is 1.0 mm to 2.0 mm, the Shore A hardness of the polishing surface is 20 to 90, and the diameter is 10 mm with respect to the entire polishing pad. When the 25% compression hardness when measured using an indenter of 0.15 to 0.27 MPa is used, the polishing surface can maintain sufficient hardness to polish the object to be polished, and The followability of the entire polishing pad to the surface shape of the object to be polished, that is, the followability of the polishing surface to the surface shape of the object to be polished can be maintained. Therefore, according to the polishing pad according to the present invention, fine unevenness on the surface to be polished can be suitably polished, and when polishing the surface to be polished having a change in thickness, polishing is performed. Since the pad is deformed according to the shape of the surface to be polished, polishing accuracy can be improved and polishing spots can be suppressed.

  In the present invention, the upper layer sheet is a foamed polyurethane sheet, and the lower layer sheet is a polyethylene foam sheet. In this case, the bulk density of the foamed polyurethane sheet is 10 times the bulk density of the polyethylene foam sheet. It is preferably ˜20 times.

  Moreover, in this invention, it is preferable that the thickness of the said lower layer sheet is 2-15 mm.

  In the present invention, the ratio of 25% compression hardness when measured using an indenter having a diameter of 10 mm to 25% compression hardness when measured using an indenter having a diameter of 20 mm is 1.70 to 2.70. Preferably there is.

  According to the present invention thus configured, 25% compression hardness when measured using an indenter having a diameter of 10 mm, that is, 25% compression hardness in a narrow region, was measured using an indenter having a diameter of 20 mm. It can be made larger than the 25% compression hardness at the time, that is, 25% compression hardness in a wide area. As a result, the polishing pad exhibits a relatively high hardness when focusing on a narrow area, and exhibits a relatively low hardness when focusing on a wide area, and exhibits a high hardness against minute irregularities. Since it can be equated with a relatively large unevenness, it exhibits a low hardness for the portion where the thickness changes. Therefore, according to the polishing pad of the present invention, fine irregularities can be suitably polished, and polishing processing with higher surface quality can be performed.

  As described above, according to the present invention, it is possible to provide a polishing pad that can improve polishing accuracy and suppress polishing spots when polishing the surface of an object to be polished whose thickness has been changed. can do.

1 is a side sectional view of a polishing pad according to an embodiment of the present invention. It is a sectional side view of the polishing pad by embodiment of this invention, and is a figure for demonstrating a use condition.

  Hereinafter, a polishing pad according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of the polishing pad according to the present embodiment.

  As shown in FIG. 1, the polishing pad 1 is formed by laminating an upper layer sheet 3 formed of a foamed polyurethane sheet and a lower layer sheet 5 formed of a polyethylene foam sheet. The upper layer sheet 3 and the lower layer sheet 5 are bonded to each other via a double-sided tape 7. And the surface of the upper layer sheet 3 where the double-sided tape 7 is not attached, in other words, the surface of the upper layer sheet 3 that does not face the lower layer sheet 5 constitutes the polishing surface 9 of the polishing pad 1. And the double-sided tape 11 for affixing the polishing pad 1 to a polishing surface plate is affixed on the surface of the lower layer sheet 5 that is not opposed to the upper layer sheet 3. In addition, about the core material of the double-sided tape 7 and the double-sided tape 11, if a rigidity is the range which does not lose | disappear the effect of this invention, a material will not be specifically limited. Examples thereof include flexible films such as PET and polypropylene. Further, the double-sided tapes 7 and 11 may be non-support type adhesive tapes that do not have a core material, and an adhesive may be used instead of the double-sided tape.

  And it is preferable that the polishing pad 1 formed by laminating | stacking such an upper layer sheet | seat 3 and the lower layer sheet | seat 5 has the Shore A hardness of the polishing surface 9 of 20-90. If the Shore A hardness of the polished surface is 20 or more, the hardness for sufficiently polishing the object to be polished can be maintained. Conversely, if the Shore A hardness of the polished surface 9 is 90 or less, the object to be polished is covered. This is preferable because scratches on the polished surface can be reduced.

  The thickness of the polishing pad 1 is not particularly limited, but is preferably 3 to 17 mm.

  Further, the polishing pad 1 preferably has a 25% hardness obtained by a test according to Japanese Industrial Standard (JIS K 6767) of 0.15 to 0.27 MPa. Here, the test according to JIS K 6767 is the same as JIS K 6767 in that the compression speed is 25% of the initial thickness, and the load is measured after 20 seconds. The thickness of the test piece is 30 mm × 30 mm, and the thickness of the test piece is measured with a single piece without overlapping even if it is less than 25 mm, and the indenter is a test using a disk-shaped tip having a diameter of 10 mm. If the 25% compression hardness is 0.15 MPa or more, the pressing force applied to the object to be polished can be secured, so that polishing can be performed reliably, and conversely if the 25% compression hardness is 0.27 MPa or less. This is preferable because the pressure does not become too low, a pressing force works evenly from a flat surface to a curved surface, and polishing spots hardly occur.

  The upper layer sheet 3 is obtained by cutting a foamed polyurethane sheet into, for example, a disk shape, and the thickness thereof is preferably 1.0 to 2.0 mm. By setting the thickness of the upper layer sheet 3 to 1.0 mm or more, the product life can be sufficiently ensured. On the contrary, by setting the thickness of the upper layer sheet 3 to 2.0 mm or less, the physical properties of the polishing pad 1 as a whole are increased. It is difficult to be controlled only by the physical properties of the upper layer sheet 3, and it is possible to achieve both grinding force and followability. Moreover, the Shore A hardness which shows the hardness of the polishing surface 9 of the upper layer sheet 3 is preferably 20 to 90, more preferably 20 to 70, and most preferably 20 to 60. By setting the Shore A hardness of the upper layer sheet 3 to 20 or more, the hardness for sufficiently polishing the object to be polished can be maintained, and by setting the Shore A hardness to 90 or less, the object to be polished is polished. Scratches on the surface can be reduced.

  For the upper layer sheet 3, it is preferable to use a polyurethane foam produced by a dry molding method. When producing foamed polyurethane using a dry molding method, it can be produced, for example, using the following production method. That is, polyisocyanate compound, polyol compound, curing agent, foaming agent, catalyst, preparatory step for preparing nonreactive gas for each component, mixing each component and nonreactive gas for each component Mixing step for obtaining a mixture for foam molding, foam molding step for molding a polyurethane resin foam from the mixture for foam molding, and slicing the polyurethane resin foam to a thickness required for the polishing pad 1 It can manufacture through each process of the slicing process.

  The lower layer sheet 5 is obtained by cutting a polyethylene foam sheet into a disk shape having the same diameter as that of the upper layer sheet 3, and the thickness thereof is preferably 2 to 15 mm. By setting the thickness of the lower layer sheet 5 to 2 mm or more, it is possible to sufficiently sink the object to be polished with respect to the polishing pad 1, excellent followability, and excessively adjusting the thickness of the lower layer sheet 5 to 15 mm or less. The polishing layer is less likely to be peeled off due to the deformation. The lower layer sheet 5 preferably has a Shore A hardness of 5 to 20. By setting the Shore A hardness of the lower layer sheet 5 to 5 or more, local deformation of the lower layer sheet 5 can be made difficult to occur, the in-plane uniformity of the object to be polished is excellent, and the Shore A hardness of the lower layer sheet 5 By setting the value to 20 or less, scratches on the workpiece can be reduced.

Moreover, it is preferable that the bulk density of the polyurethane foam sheet which comprises the upper layer sheet 3 is 0.3-0.6 g / cm < ³ >, and the bulk density of the polyethylene foam sheet which comprises the lower layer sheet 5 is 0.03- is preferably 0.06 g / cm ^3, a bulk density of foamed polyurethane sheet constituting the upper layer sheet 3 is particularly preferably a 10 to 20 times the bulk density of the polyethylene foam sheet constituting the lower layer sheet 5. By setting the bulk density of the lower layer sheet 5 to 10 times or more the bulk density of the upper layer sheet 3, both the grinding force of the upper layer sheet 3 and the followability by the lower layer sheet 5 can be achieved. In addition, by setting the bulk density of the lower layer sheet 5 to 20 times or less of the bulk density of the upper layer sheet 3, even when the polishing pad 1 is repeatedly compressed, the lower layer sheet 5 is less likely to be crushed, which is preferable.

  The polishing pad 1 has a 25% compression hardness (hereinafter sometimes referred to as H (10 mmφ)) when measured using an indenter having a diameter of 10 mm, and 25 when measured using an indenter having a diameter of 20 mmφ. It is preferable that the ratio to the% compression hardness (hereinafter sometimes referred to as H (20 mmφ)) is 1.70 to 2.70. Thereby, 25% compression hardness when measured using an indenter having a diameter of 10 mm, that is, 25% compression hardness in a wide area, that is, 25% compression hardness when measured using an indenter having a diameter of 20 mm, that is, It can be larger than the 25% compression hardness in a narrow region. Accordingly, the polishing pad 1 exhibits a relatively high hardness when focusing on a narrow region, and exhibits a relatively low hardness when focusing on a wide region, and exhibits a high hardness against minute irregularities. It exhibits a low hardness for the portion where the thickness is changed so that it can be regarded as a relatively large unevenness. Therefore, according to the polishing pad 1 according to the present embodiment, it is possible to suitably polish fine irregularities and perform polishing processing with higher surface quality.

  FIG. 2 is a side sectional view of the polishing pad 1 according to the embodiment, and is a view for explaining a use state. FIG. 2 is a diagram for explaining an operation when polishing the workpiece W having a shape in which the outer peripheral portion of the surface to be polished is curved when the vertical cross section is viewed with a change in thickness.

  As shown in FIG. 2, the polishing surface 9 of the polishing pad 1 is larger than the surface to be polished of the workpiece W, and the polishing pad 1 is arranged so that the polishing pad 1 protrudes in the outer peripheral direction of the workpiece W. The When a polishing pressure is applied to the workpiece W by the polishing pad 1, the polishing pad 1 is deformed according to the shape of the workpiece W. And since the thickness of an upper layer sheet is 1.0 mm-2.0 mm, and the Shore A hardness of a grinding | polishing surface is 20-90, a grinding | polishing surface bends and it follows a to-be-polished surface of a to-be-polished object moderately. And has the grinding power necessary for polishing. Further, by setting the 25% compression hardness of the polishing pad 1 to 1.70 to 2.70, the polishing pressure applied from the polishing surface 9 to the surface to be polished is made relatively weak and depends on the shape of the surface to be polished. Therefore, the polishing pressure can be applied uniformly. Thereby, the polishing spot at the time of grinding | polishing can be suppressed.

  As described above, according to the embodiment of the present invention, it is possible to improve the polishing accuracy and suppress the polishing spots when polishing the surface of the object to be polished whose thickness is changed.

  Hereinafter, the Example and comparative example of this invention are explained in full detail.

(Polishing pad manufacturing method)
In Examples and Comparative Examples, the upper layer sheet 3 made of foamed polyurethane and the lower layer sheet 5 made of polyethylene foam sheet described in Table 1 and Table 2 below were bonded together via a double-sided tape 7, and then the lower layer sheet 5 A double-sided tape 11 was further attached to the surface opposite to the upper layer sheet 3 to prepare a polishing pad 1. In Example 1 and Comparative Example 1 only, the polyethylene foam sheets of the lower layer sheet 5 are 10 mm and 5 mm thick, and 10 mm and 10 mm thick are pasted through double-sided tapes (not shown), respectively. They were made together.

  Various physical properties of the produced polishing pad 1 were measured as follows.

(Compression rate)
The compressibility and the compressive elastic modulus can be determined using a shopper type thickness measuring instrument (pressure surface: circular shape with a diameter of 1 cm) in accordance with Japanese Industrial Standard (JIS L 1021). Specifically, it is as follows. The thickness t ₀ after applying the initial load for 30 seconds from the unloaded state is measured, and then the thickness t ₁ after applying the final load for 30 seconds from the state of thickness t ₀ is measured. Then, except for all the loads from the thickness t ₁ state, after it allowed to stand 5 minutes (and a no-load state), to measure the thickness t _{0 'after} over 30 seconds initial load again. The compression ratio can be calculated by an expression of compression ratio (%) = 100 × (t ₀ −t ₁ ) / t ₀ . The compression elastic modulus can be calculated by the equation of compression elastic modulus (%) = 100 × (t ₀ ′ −t ₁ ) / (t ₀ −t ₁ ). (Note that the initial load is 300 g / cm ² and the final pressure is 1800 g / cm ^2. )

(Shore A hardness)
For the measurement of Shore A hardness, a sample piece (10 cm × 10 cm) was prepared and measured with an A-type hardness meter (Japanese Industrial Standard, JIS K 7311). The measurement was performed on the upper layer sheet 3 alone, the lower layer sheet 5 alone, and the polishing pad 1 itself of the example and the comparative example, which constitute the polishing pad 1 of the example and the comparative example. For the upper layer sheet 3 alone and the lower layer sheet 5 alone, when the thickness of the sample was less than 4.5 mm, a plurality of samples were stacked so that the total thickness was 4.5 mm or more. With respect to the polishing pad 1, the measurement was performed with one piece without overlapping, with the polishing surface 9 side facing up, and the obtained numerical value was taken as the Shore A hardness of the polishing surface 9.

(Average bubble diameter and number of bubbles)
The average bubble diameter (μm), the number of bubbles per 1 mm ² is enlarged by 175 times in the 1.3 mm square area (excluding the groove) of the pad surface with a microscope (VH-6300, manufactured by KEYENCE). Observe and binarize the obtained image with image processing software (Image Analyzer V20LAB Ver. 1.3, manufactured by Nikon) to confirm the number of bubbles. Also, from the area of each bubble, the equivalent circle diameter and its The average value (average bubble diameter) was calculated. Note that the cutoff value (lower limit) of the bubble diameter was 10 μm, and noise components were excluded.

(25% compression hardness)
The 25% compression hardness was measured according to the Japanese Industrial Standard (JIS K 6767). That is, the polishing pad 1 of the example and the comparative example was allowed to stand for 24 hours or more in an environment having a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and then punched to 30 mm × 30 mm to produce a sample piece. One sample piece was compressed in parallel with an indenter of a predetermined size from the polishing surface 9 side at a speed of 10 mm / min, and the stress when compressed by 25% from the original thickness was read. Other test conditions were in accordance with JIS K 6767.

  The release paper of the double-sided tape 11 opposite to the polishing surface 9 of the polishing pad 1 produced by the method described above is peeled off and attached to the upper polishing surface plate, and the surface to be polished of the object to be polished is placed on the opposing lower polishing surface plate. Fixed on the top. Next, a polishing test was performed under the following polishing conditions, and the polishing rate, polishing spots, and scratches were evaluated.

(Polishing conditions)
-Polishing machine used: Double-side polishing machine manufactured by Fujikoshi Kikai Kogyo Co., Ltd.-Polishing speed (retention plate rotation speed): 40 rpm
Polishing pressure: 1100 g / cm ²
・ Abrasive: 10% aqueous solution of cerium oxide slurry ・ Polished object: glass substrate (65 mm × 65 mm × 10 mm curved at end) × 10 sheets / batch ・ Polishing time: 15 min / batch

(Polishing rate)
The polishing rate is the amount of polishing per minute expressed by thickness, polished 120 objects to be polished, the amount of polishing determined from the weight reduction of the substrate before and after polishing, the polishing area of the object to be polished, and From the specific gravity, an arithmetic average of each polishing rate was obtained.

(Evaluation of polishing spots)
With respect to each surface to be polished of 120 objects to be polished after completion of polishing, the presence or absence of a polishing spot portion having a texture different from other portions was visually confirmed. All of 120 objects to be polished had no polishing spots and at least one gloss was confirmed ◎, all had no polishing spots ○, some of which were confirmed polishing spots The case where it was contained was evaluated as Δ, and the case where polishing spots were confirmed in more than half of the objects to be polished was evaluated as ×. The results are shown in the table.

(Scratch confirmation)
About the generation | occurrence | production condition of a scratch, the presence or absence of the scratch was determined by carrying out a visual mirror observation with respect to the to-be-polished surface of the to-be-polished thing after grinding | polishing. That is, the case where no scratch was confirmed was judged as ◯, and the case where it was confirmed was judged as ×.

  In Examples 1 to 8, since the Shore A hardness of the polishing surface 9 is in the range of 20 to 90 and H (10 mmφ) is in the range of 0.15 to 0.27 MPa, it has a moderate grinding force. Since the curved surface was traced well, the polishing rate was excellent, and polishing spots and scratches were not confirmed. Among them, gloss was confirmed in Examples 2 to 6 and Example 8 in which H (10 mmφ) / H (20 mmφ) was in the range of 1.70 to 2.70. The reason for this is considered that the polishing pad 1 was moderately along the curvature of the curved surface of the object to be polished, and was able to remove even the swell.

  For Comparative Examples 1, 3, and 4 in which the value of 25% compression hardness H (10 mmφ) was higher than those of Examples 1 to 8, the Shore A hardness was in the range of 20 to 90, so the polishing rate was carried out. Although the scratches were not confirmed to be as good as those in Examples 1 to 8, but because stress was required for sinking, there was a difference in the pressing force applied to the flat surface and curved surface, resulting in the occurrence of polishing spots. It was. On the contrary, in Comparative Example 2 in which the value of H (10 mmφ) was low compared to Examples 1 to 8, although the Shore A hardness was in the range of 20 to 90, no scratch was confirmed, The applied pressing force was reduced, and the polishing rate was lower than those in Examples 1-8. Further, since the pressing force was small, polishing could not be performed reliably, and polishing spots were confirmed in more than half of the objects to be polished.

  In Comparative Example 5 in which the Shore A hardness of the polishing surface 9 was low as compared with Examples 1 to 8, the polishing rate was low because the grinding force was small, and the grinding force was not sufficient, so polishing could be performed reliably. Polishing spots were generated. In addition, since the Shore A hardness was a value lower than 90, no scratch was confirmed. Further, in Comparative Example 6 in which the values of Shore A hardness and H (10 mmφ) were higher than those of Examples 1 to 8, the polishing rate was high because the grinding force was large. However, since the followability was low, polishing spots were confirmed in more than half of the objects to be polished, and the Shore A hardness of the polishing surface was too high, and scratches were confirmed on the surface to be polished of the objects to be polished.

1 Polishing pad 3 Upper layer sheet 5 Lower layer sheet

Claims (4)

  A polishing pad configured by laminating at least two sheets of an upper layer sheet and a lower layer sheet having a polishing surface, and the thickness of the upper layer sheet is 1.0 mm to 2.0 mm, and the Shore A hardness of the polishing surface is A polishing pad having a hardness of 20 to 90 and a 25% compression hardness of 0.15 to 0.27 MPa when measured using an indenter having a diameter of 10 mm with respect to the entire polishing pad.   The upper layer sheet is a foamed polyurethane sheet, the lower layer sheet is a polyethylene foam sheet, and the bulk density of the foamed polyurethane sheet is 10 to 20 times the bulk density of the polyethylene foam sheet. The polishing pad as described.   The polishing pad according to claim 1 or 2, wherein the lower layer sheet has a thickness of 2 to 15 mm.   The ratio of 25% compression hardness when measured using an indenter having a diameter of 10 mm to 25% compression hardness when measured using an indenter having a diameter of 20 mm is 1.70 to 2.70. 4. The polishing pad according to any one of 3 above.

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