JP2006259629A - End-surface polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end-surface polishing method capable of comparatively easily and highly precision of performing polishing in a numerous fiber connector plug, having a plurality of optical fibers. <P>SOLUTION: The end surface polishing method for polishing an end surface of the numerous fiber connector plug, having the plurality of optical fibers 20, held in a state with at least the tip parts being aligned substantially in parallel to a connector plug main frame 30 constituting a multicore optical connector, is equipped with a first polishing process for projecting the tip parts of the optical fibers 20 from the connector plug main frame 30 and a second polishing process for polishing end surfaces of the projected optical fibers, the same polishing sheet 80 and polishing liquid 90 are used in the first and second polishing processes and in the second polishing process, polishing is performed, by setting a load for pressing the multicore optical connector plug to the polishing sheet as smaller than the load in the first polishing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an end surface polishing method for polishing an end surface of a multi-fiber optical connector plug holding a plurality of optical fibers.

  Conventionally, multi-fiber optical connectors such as MT type and MPO type are known, which can perform high-speed transmission of large-capacity data by pressing end faces of a plurality of optical fibers and optically connecting them. Yes.

  The multi-fiber optical connector plug constituting the multi-fiber optical connector is composed of a plurality of optical fibers and a connector plug main body for holding the plurality of optical fibers, and each optical fiber has a tip portion located closer to the end face of the connector plug main body. It is fixed in a fixed protruding state. A plurality of optical fibers can be simultaneously optically connected to each other by causing the multi-fiber optical connectors to face each other and pressing the tip surfaces of the optical fibers.

  In such a multi-fiber optical connector plug, in the manufacturing process, a first polishing step for projecting the end portion of the optical fiber from the connector plug body, and a second polishing step for polishing the end surface of the projected optical fiber to a highly accurate convex surface. The polishing step is performed.

  Specifically, for example, there is a method of polishing using a buff cloth in the first step and using a rubber pad in the second step (see Patent Document 1). Also, in the first step, the connector plug body, which is softer than the optical fiber, is polished by using large particles in order to protrude the optical fiber from the connector plug body, and then in the second step, it protrudes from the connector plug body. In order to make the end face of the optical fiber into a mirror state, a method of polishing with particles smaller than those in the first step has been proposed (see Patent Document 2).

  As described above, in the conventional polishing method, in the first step, in order to preferentially grind the connector plug main body over the optical fiber, it is necessary to enlarge the abrasive particles and increase the grinding force so that the optical fiber protrudes. As a result, the polishing surface of the end face of the optical fiber is rough, and in the next process, the polishing sheet or the abrasive particles must be replaced. Therefore, the polishing liquid in the first process is completely removed. After that, it was necessary to carry out the second step. Further, in such a conventional first process, the core portion of the optical fiber is softer than the cladding portion of the peripheral portion, so that the core portion of the protruding optical fiber is recessed from the cladding portion, and fine abrasive particles are used. In the second step, there is a problem that the peripheral edge portion harder than the core portion is hard to be cut, the core portion is further recessed (0.5 μm or more), and the loss of light when the optical connector is connected is increased.

JP 2003-334749 A US Pat. No. 5,743,785

  In view of such circumstances, an object of the present invention is to provide an end surface polishing method capable of polishing a polishing process of a multi-fiber optical connector plug having a plurality of optical fibers relatively easily and with high accuracy.

  A first aspect of the present invention that solves the above problems is a multi-fiber optical connector plug having a plurality of optical fibers that are held in a connector plug body constituting the multi-fiber optical connector in a state where at least tip portions thereof are aligned substantially in parallel. In the end surface polishing method for polishing the end surface of the optical fiber, the method includes a first polishing step for projecting a tip portion of the optical fiber from the connector plug body, and a second polishing step for polishing the end surface of the projected optical fiber, In the first and second polishing steps, the same polishing sheet and the same polishing liquid are used. In the second polishing step, a load that presses the multi-fiber optical connector plug against the polishing sheet is used as the first polishing step. An end face polishing method is characterized in that polishing is performed by setting the load smaller than the load in the process.

  According to a second aspect of the present invention, in the first aspect, a load for pressing the connector plug body against the polishing sheet is 150 g or more per connector plug body in the first polishing step, In the second polishing step, the end face polishing method is characterized in that the connector plug main body is made smaller than 150 g.

  According to a third aspect of the present invention, in the second aspect, a load for pressing the connector plug body against the polishing sheet is 180 g or more per connector plug body in the first polishing step. An end surface polishing method characterized by the above.

  According to a fourth aspect of the present invention, in the second or third aspect, a load for pressing the connector plug body against the polishing sheet is 80 g or less per connector plug body in the second polishing step. An end surface polishing method is characterized in that:

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, an end surface polishing method is characterized in that the average particle diameter of the abrasive particles contained in the polishing liquid is 1 μm or less.

  A sixth aspect of the present invention is the end face according to any one of the first to fifth aspects, wherein the polishing sheet has a thickness of 0.2 mm to 1.2 mm and a hardness of Shore 55Hs or more. There is a polishing method.

  A seventh aspect of the present invention is the end surface polishing method according to the sixth aspect, wherein the polishing sheet has a thickness of 0.5 mm to 0.8 mm and a hardness of Shore 60 Hs or more.

  According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the polishing sheet is a non-woven fabric or a foamed polyurethane sheet.

  According to the present invention, the first step of projecting the optical fiber from the connector plug body and the second step of finish polishing the end face of the optical fiber can be performed without changing the polishing liquid and the polishing sheet. In addition, since there is no work of exchanging the polishing liquid and there is no mixing of abrasive particles in the previous process, the finish polishing of the optical fiber end face can be performed with high accuracy, and there is no damage to the end face of the optical fiber. As a result, the dent of the core is reduced, and as a result, the optical loss is significantly reduced when the optical connector is connected.

  Hereinafter, the present invention will be described in detail based on embodiments.

(Embodiment 1)
1 is a perspective view of a multi-fiber optical connector according to Embodiment 1 of the present invention, and FIG. 2 is a plan view and a cross-sectional view of an optical fiber used in the multi-fiber optical connector.

  As illustrated, the multi-fiber optical connector 10 includes a plurality of optical fibers 20 and a connector plug body 30 that fixes the plurality of optical fibers.

  As shown in FIG. 2, the optical fiber 20 of the present embodiment has, for example, a core portion 22 having a diameter D1 of about 50 μm or 62.5 μm, for example, at the approximate center of a clad portion 21 having a diameter D2 of about 125 μm. A so-called GI (graded index) fiber.

  The connector plug body 30 has an optical fiber insertion hole 31 to which a plurality of optical fibers 20 are fixed. In the region facing the optical fiber insertion hole 31 on the side surface of the connector plug body 30, the optical fiber insertion hole 31 is provided. An exposed through hole 32 is provided. The optical fiber 20 is bonded and fixed to the connector plug body 30 by introducing the adhesive 40 from the through hole 32.

  Note that a guide pin insertion hole 33 into which a guide pin for positioning is inserted when connecting to another multi-fiber optical connector is formed on the end surface of the connector plug body 30 where the optical fiber insertion hole 31 is opened. Is provided.

  Examples of the material used for the connector plug body 30 include an epoxy resin material containing glass or polyphenylene sulfide (PPS) containing glass.

  Hereinafter, a method for manufacturing such a multi-fiber optical connector 10 will be described.

  First, as shown in FIG. 3, the multi-fiber optical connector 10 puts the adhesive 40 through the through hole 32 with the tip of the optical fiber 20 protruding a predetermined amount from the end face of the connector plug body 30, and It is formed by adhering to the connector plug body 30. At this time, the tip of each optical fiber 20 protruding from the end face of the connector plug body 30 is covered with the adhesive 41.

  And first, as shown in FIG. 4, the adhesive agent 41 which has covered the front-end | tip part of the optical fiber 20 is removed as pre-processing. Specifically, the polishing surface plate 50 is rotated in a state in which the tip portion (adhesive 41) of the optical fiber 20 is in contact with the polishing sheet 60 provided on the polishing surface plate 50 of the polishing apparatus. The adhesive 41 covering the surface is removed by polishing.

  The abrasive sheet 60 used at this time is, for example, one in which abrasive particles such as silicon carbide having a particle size of about 30 μm are attached to a PET film having a thickness of 75 μm.

  The step of removing the adhesive 41 on the surface of the optical fiber 20 by polishing is not particularly limited, and for example, a rubber pad may be provided between the polishing surface plate 50 and the polishing sheet 60. Even if the front end portion (adhesive 41) of the optical fiber 20 is pressed relatively strongly against the polishing sheet 60, the rubber pad is deformed so that an excessive load is not applied to the optical fiber 20, and the optical fiber 20 is not broken. Therefore, the adhesive 41 can be removed well.

  Next, as shown in FIG. 5A, the tip portion (adhesive 41) of the optical fiber 20 is polished and flattened using a polishing sheet 70 for flattening finishing. Specifically, the tip of the optical fiber (adhesive 41) protruding from the connector plug body 30 is completely removed until the end surface of the connector plug body 30 becomes substantially flat. Polishing is performed (see FIG. 5B). Here, the polishing sheet 70 for flattening finish is obtained by adhering silicon carbide having a particle size of about 3 to 15 μm to a PET film having a thickness of 75 μm, for example.

  As described above, the end surface polishing method of the present invention is performed on the connector plug body 30 that has been flattened by removing the adhesive 41 adhering to the end surface.

  First, a first step of causing the tip end portion of the optical fiber 20 to protrude from the end face of the connector plug main body 30 by a predetermined amount is performed. Specifically, as shown in FIG. 6 (a), the end face of the connector plug body 30 is pressed against the surface of a polishing sheet 80 which is relatively soft, for example, a suede-type buff cloth, non-woven fabric or foamed polyurethane. A part of the connector plug body 30 is removed by polishing the end face of the connector plug body 30 while abutting with pressure and supplying a polishing liquid containing abrasive particles having a predetermined hardness and a predetermined particle diameter.

  Here, the polishing sheet 80 has a thickness of 0.2 mm to 1.2 mm, preferably 0.5 mm to 1.0 mm, more preferably 0.5 to 0.8 mm, and a hardness of Shore 55 Hs or more. , Preferably, it is Shore 60Hs or more.

  On the other hand, the abrasive particles contained in the polishing liquid used in the present invention have an average particle diameter of 1 μm or less, preferably 0.8 μm or less. Further, the abrasive particles must be abrasive particles having a hardness higher than that of the connector plug body 30 and the optical fiber 20, that is, an abrasive particle having a hardness higher than that of the clad of the optical fiber 20, and alumina, diamond, zirconia, silicon carbide, oxidized Cerium and the like can be mentioned, and silicon carbide is preferred. The polishing liquid is prepared by dispersing abrasive particles in a solvent such as water, fats and oils, and alcohol, and contains various additives as necessary. In this embodiment, a polishing liquid containing silicon carbide having an average particle size of 0.3 μm is used.

  In the first step of the end surface polishing method of the present invention, the load for pressing the connector plug body 30 against the polishing sheet 80 is 150 g or more, preferably 180 g or more, more preferably about 200 g per connector plug body. In this embodiment, the load is 200 g.

  Thus, even if finer abrasive particles are used than in the conventional case by using a higher load than in the conventional case, as shown in FIG. It will be in the state which protruded only the predetermined amount from the end surface of 30. The polishing in the first step may be performed until the optical fiber 20 protrudes by a predetermined amount, for example, about 1 μm. For example, it takes about 2 minutes in time.

  Next, the 2nd process of the end surface grinding | polishing method of this invention is implemented. That is, the polishing is performed with the polishing sheet 80 and the polishing liquid remaining in the first step, and the load on the connector plug body 30 is made smaller than that in the first step.

  Here, in the second step, the load for pressing the connector plug body 30 against the polishing sheet 80 is smaller than 150 g per connector plug body, preferably 100 g or less, more preferably 80 g or less, suitably About 60 g. In this embodiment, the load was 60 g.

  In the end surface polishing method of the present invention, the end surface of the optical fiber 20 is set without changing the polishing sheet and the polishing liquid used in the first step by setting the load in the second step lower than that in the first step. In addition, since the polishing process is performed using finer abrasive particles than the conventional one from the first process, the dent of the core part with respect to the cladding part is 0.5 μm of the conventional level. Compared to the above, it can be set to 0.2 μm or less, and the loss during optical coupling can be remarkably reduced. In the second step, the end face of the optical fiber 20 is finish-polished, and the time is not particularly limited. For example, it is 30 seconds to 90 seconds, and in this embodiment, the second step was performed for about 60 seconds.

  Here, FIG. 7 is a view schematically showing the state of polishing in the first and second steps of the end surface polishing method of the present invention.

  As shown in FIG. 7A, in the first step, an abrasive sheet 80 that is relatively thin compared to the prior art but has some elasticity is used, and very fine abrasive particles 90 are used as compared with the prior art. The optical fiber 20 is projected from the connector plug body 30 by increasing the length of the connector plug body 30. As a result, there is an advantage that the end face of the optical fiber 20 protrudes in a state of being polished with higher accuracy than in the prior art, and the edge of the optical fiber 20 is not chipped or scratched.

  Further, as shown in FIG. 7B, in the second step, the polishing is performed by setting the load lower than that in the first step while using the polishing sheet 80 and the abrasive particles 90 used in the first step. Therefore, there is an advantage that the end face of the optical fiber 20 can be polished with high accuracy. In the second step, the polishing sheet 80 that is relatively thin but elastic to some extent is used, and polishing is performed using very fine abrasive particles 90 as compared with the prior art, so the time to finish the optical fiber 20 is relatively long. There is an advantage that it can be set with a width, for example, there is an advantage that there is no great difference in the end face of the optical fiber 20 even if polishing is performed around 30 seconds with respect to a suitable finishing time. Further, according to the first and second steps, there is an advantage that the recess of the core portion with respect to the cladding portion can be finished as very small as about 0.2 μm.

  On the other hand, the schematic diagram of an example of the conventional end surface grinding | polishing method is shown in FIG. FIG. 8A is a schematic diagram of the first conventional process, in which the optical fiber 20 is projected using a relatively thick abrasive sheet 108 and relatively large abrasive particles 109. According to this, there is a problem that the edge of the protruding optical fiber 20 is chipped.

  Further, in the second step, as shown in FIG. 8B, relatively small abrasive particles 209 are added and polished using a polishing sheet 208 such as a thin and less elastic PET film. When transferring from the process to the second process, there is a problem that the replacement of the polishing sheet and the replacement of the polishing liquid are difficult, and the abrasive particles of the first process are often mixed. As a result, the finished state is not good, and the recess of the core part with respect to the clad part results in a maximum of about 0.5 μm. Further, in the conventional second process, the polishing sheet 208 is hard, so that there is a problem that the time for final polishing must be controlled very strictly. For example, when finishing polishing can be performed in 5 seconds, 3 seconds is insufficient, and if it is performed for 7 seconds or more, there is a problem that all end faces of the protruding optical fiber 20 are lost.

  As described above, the end surface polishing method of the present invention includes the first step of projecting the optical fiber from the connector plug main body and the second step of finish polishing the optical fiber end surface without changing the polishing liquid and the polishing sheet. Therefore, the workability is remarkably improved, and the polishing liquid is not replaced, so that polishing particles in the previous process are not mixed, and the end polishing of the optical fiber end face can be performed with high accuracy. As a result, the end face of the optical fiber is not damaged and the dent of the core is reduced. As a result, there is an effect that the loss of light when the optical connector is connected is remarkably reduced.

  The polishing apparatus for carrying out the end face polishing method of the present invention is not particularly limited as long as the load can be changed, but an example will be described below.

  FIG. 9 is a partial sectional view showing an example of an end surface polishing apparatus used in the present invention.

  As shown in FIG. 9, the central portion of the first rotation transmission board 302 is fixed to the rotation shaft of the motor 301 for rotation, and the first rotation transmission board 302 has a plurality of concentric circles with the rotation center as a fulcrum. The first connecting pin 303 is fixed. Each first connection pin 303 is rotatably connected to an eccentric portion of each corresponding rotation transmission disc 304, and each rotation transmission disc 304 has a second connection pin 305 fixed to the eccentric portion. Each second connection pin 305 is rotatably connected to the second rotation transmission board 306.

  On the other hand, the central portion of the drive gear 308 is fixed to the rotation shaft of the revolution motor 307, and the driven gear 309 is engaged with the drive gear 308. The driven gear 309 is fixed to the outer periphery of the lower part of the revolution transmission shaft 310, and the bearing cylinder portion 312 of the apparatus main body 311 is fitted to the upper outer periphery of the revolution transmission shaft 310. Then, the rotation transmission shaft 313 is rotatably inserted into the revolution transmission shaft 310 at a position eccentric from the rotation center by a predetermined amount, and the lower end portion of the rotation rotation shaft 313 is located at the center of the second rotation transmission plate 306. It is consolidated.

  Further, the upper end portion of the rotating shaft 313 is coupled to the polishing plate 315 via a coupling member 314, and a polishing sheet 80 is attached to the upper surface portion of the polishing plate 315.

  On the other hand, a jig board 330 is supported on the apparatus main body 311 by a support mechanism 320. The jig board 330 is provided with a jig board body 331 having a recess (not shown) in which the connector plug body 30 is fitted on the side surface, and a connector facing the recess of the jig board body 331. And a holding member 332 for holding the plug body 30 between the plug body 30 and the recess. The holding member 332 is fixed to the jig board main body 331 by holding the connector plug main body 30 in the recess by the fixing screw 333.

  The jig board 330 to which the plurality of connector plug bodies 30 are fixed in this way is restricted in movement in the rotational direction by the pressing parts 322 and 323 of the support part 321 and is urged in the direction of the polishing board 315 to be connected to the connector board 330. The end faces of the plurality of optical fibers 20 protruding from the end face of the plug body 30 by a predetermined amount are pressed against the polishing sheet 80 attached on the polishing board 315. Thereby, the end surface of each optical fiber 20 can be protruded from the connector plug main body 30 in the first step, and the end surface of the optical fiber 20 can be finish-polished in the second step.

  Here, the operation of the above-described end surface polishing apparatus will be described with reference to FIG.

  As shown in FIG. 9, first, regarding the revolving motion, the revolving transmission shaft 310 is rotated via the gears 308 and 309 by driving the revolving motor 307, and the polishing disc 315 revolves by a predetermined amount of eccentricity. . In this case, the revolution transmission shaft 310 includes the rotation shaft 313 for rotation, but a plurality of rotation transmission plates 304 are arranged between the rotation transmission plate 302 and the rotation transmission plate 304. Each of them rotates around the first connecting pin 303 with the same phase as the rotation of 310. Therefore, even if the first rotation transmission board 302 is stopped or rotating, the rotation of the revolution transmission shaft 310 is not restricted.

  On the other hand, with respect to the rotation motion, the first rotation transmission board 302 is rotated by driving the rotation motor 301. However, since the first connection pin 303 is on the concentric circle of the first rotation transmission board 302, the same locus as described above. , The rotation shaft 313 for rotation is eccentric by a predetermined amount, but since it is connected via the rotation transmission board 304, the rotation with the same rotational speed as that of the first rotation transmission board 302 is transmitted to the rotation shaft 313 for rotation. The

  As described above, when the revolution transmission shaft 310 and the rotation shaft 313 rotate, the polishing disk 315 revolves while rotating, so that the end surface of the optical fiber 20 protruding from the end surface of the connector plug body 30 is polished onto the polishing sheet 80. Polishing with the above polishing liquid is possible.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, the basic composition of a multi-fiber optical connector is not limited to what was mentioned above.

  For example, in the above-described embodiment, a multi-fiber optical connector using a GI fiber as an optical fiber has been illustrated and described. However, the present invention is not limited to this, and an SM (single mode) fiber, for example, is used as the optical fiber. The present invention can also be applied to a multi-fiber optical connector.

  In the above-described embodiment, the MT type multi-fiber optical connector is exemplified. However, the present invention can be applied to multi-fiber optical connectors having other structures such as an MTO type.

(Example)
A connector plug body holding 12 single-mode optical fibers is used, and as shown in FIG. 7A, a non-woven fabric having a thickness of 0.8 mm and a hardness of Shore 60 Hs is used as the polishing sheet 80, and an average particle size of 0. The first step was performed using a polishing liquid containing 8 μm silicon carbide as abrasive particles 90. The polishing load was 200 g per connector plug body, and the polishing time was about 2 minutes.

  Next, as shown in FIG. 7B, the polishing sheet 80 and the abrasive particles 90 were left as they were, the polishing load was 60 g per connector plug body, and the polishing time was about 1 minute.

(Comparative example)
As shown in FIG. 8A, a non-woven fabric having a thickness of 1.35 mm and a hardness of Shore 50Hs is used as the polishing sheet 108, and a polishing liquid containing alumina having an average particle diameter of 3 μm as the polishing particles 109 is used for the first polishing. The process was carried out. The polishing load was 150 g per connector plug body, and the polishing time was about 2 minutes.

  Next, as shown in FIG. 8B, a PET film having a thickness of 75 μm and a hardness of Shore 90Hs is used as the polishing sheet 208, and a polishing liquid containing alumina having an average particle diameter of 0.5 μm as the polishing particles 209 is used. The second step was performed. The polishing load was 150 g per connector plug body, and the polishing time was 5 seconds.

(Test example)
A plurality of multi-fiber connector plugs polished in the examples and comparative examples are prepared, and the connection loss (dB), which is an attenuation when the multi-fiber connector plugs polished in the examples are connected to each other, and polished in the comparative example. The connection loss (dB) when the multi-fiber connector plugs connected to each other were measured. The connection loss was measured for one optical fiber of each multi-fiber connector plug. The result is shown in FIG. FIG. 10 is a distribution diagram showing the frequency for each connection loss, where (a) is an example and (b) is a comparative example.

  Comparing FIGS. 10A and 10B, it was found that the connection loss was reduced in the example compared to the comparative example.

1 is a perspective view of a multi-fiber optical connector according to Embodiment 1 of the present invention. It is the top view and sectional drawing of the optical fiber which comprise the multi-core optical connector which concerns on Embodiment 1 of this invention. It is the perspective view and top view explaining the multi-fiber optical connector which concerns on Embodiment 1 of this invention. It is the schematic which shows the manufacturing process of the multi-fiber optical connector which concerns on Embodiment 1 of this invention. It is the schematic which shows the manufacturing process of the multi-fiber optical connector which concerns on Embodiment 1 of this invention. It is the schematic which shows the manufacturing process of the multi-fiber optical connector which concerns on Embodiment 1 of this invention. It is a figure which represents typically the end surface grinding | polishing method which concerns on Embodiment 1 of this invention. It is a figure which represents typically the conventional end surface grinding | polishing method for the comparison. It is a partial cross section figure which shows an example of the end surface grinding | polishing apparatus of this invention. It is a figure which shows the result of the test example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Multi-fiber optical connector 20 Optical fiber 30 Connector plug main body 31 Optical fiber insertion hole 32 Through hole 33 Guide pin insertion hole 40, 41 Adhesive 50 Polishing surface plate 80 Polishing sheet

Claims (8)

In an end surface polishing method for polishing an end surface of a multi-fiber optical connector plug having a plurality of optical fibers held in a state where at least tip portions thereof are aligned substantially parallel to a connector plug body constituting the multi-fiber optical connector,
A first polishing step for projecting the tip of the optical fiber from the connector plug body, and a second polishing step for polishing the end face of the projected optical fiber, wherein the first and second polishing steps In the second polishing step, the load for pressing the multi-fiber optical connector plug against the polishing sheet is set smaller than the load in the first polishing step. A method for polishing an end face, comprising: 2. The load for pressing the connector plug body against the polishing sheet is 150 g or more per connector plug body in the first polishing step, and the connector plug body is used in the second polishing step. A method for polishing an end face, characterized in that it is smaller than 150 g per piece. 3. The end surface polishing method according to claim 2, wherein a load for pressing the connector plug body against the polishing sheet is 180 g or more per connector plug body in the first polishing step. 4. The end face polishing method according to claim 2, wherein a load for pressing the connector plug body against the polishing sheet is 80 g or less per connector plug body in the second polishing step. 5. The end face polishing method according to claim 1, wherein an average particle diameter of the abrasive particles contained in the polishing liquid is 1 [mu] m or less. The end surface polishing method according to claim 1, wherein the polishing sheet has a thickness of 0.2 mm to 1.2 mm and a hardness of Shore 55Hs or more. 7. The end surface polishing method according to claim 6, wherein the polishing sheet has a thickness of 0.5 mm to 0.8 mm and a hardness of Shore 60 Hs or more. The end surface polishing method according to claim 1, wherein the polishing sheet is a nonwoven fabric or a foamed polyurethane sheet.

Images