JP2015006729A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad which stabilizes a foaming shape, and can enhance flatness of a polished object.SOLUTION: A polishing pad 10 has a foam sheet 2 formed of an urethane resin. The foam sheet 2 has a skin layer 4 having micro flatness formed on the side of a polished face P. The foam sheet 2 has a continuous foam structure formed by a wet film-forming method. An aggregate 5, which is formed due to agglomeration of a structure of a carbon black, is contained in the foam sheet 2. The aggregate 5 is covered with an ABS resin of a dispersant. The aggregate 5 is substantially uniformly contained in the foam sheet 2 at a ratio in a range of 2 wt.% to 10 wt.%. The aggregate 5 does not form a large aggregate, which is formed due to further agglomeration, during wet film formation.

Description

  The present invention relates to a polishing pad, and more particularly, to a polishing pad provided with a urethane resin foam sheet formed by a wet film forming method.

  Conventionally, in materials that are required to have flatness with high accuracy, such as optical materials such as lenses, parallel flat plates, and reflective mirrors, aluminum substrates for hard disks, silicon wafers for semiconductor devices, and glass substrates for liquid crystal displays, Polishing using a polishing pad is performed. In semiconductor devices, miniaturization and multilayer wiring for the purpose of increasing the density of semiconductor circuits have progressed, and techniques for flattening silicon wafers have become important. Even in the liquid crystal display, higher flatness of the glass substrate is required as the size increases.

  In general, a foamed sheet made of urethane resin formed by a wet film forming method is used for a polishing pad for finish polishing. In the wet film-forming method, a resin solution in which a urethane resin is dissolved in a water-miscible organic solvent is applied to a sheet-shaped film-forming substrate, and then immersed in an aqueous coagulation solution to resolidify and regenerate the resin into a sheet. The In the obtained foamed sheet, a large number of foams are formed in the interior due to the solidification regeneration of the urethane resin. That is, it has a surface layer (skin layer) in which micropores are formed on the polishing surface side for polishing the object to be polished, and foam is continuously formed inside the surface layer. In such a foam sheet, when the foam size variation formed inside or uneven foam formation occurs, physical properties such as elasticity of the foam sheet are not stable, and high flatness of the workpiece can be obtained. It becomes difficult. In order to stabilize foam formation, an additive such as carbon black that acts as an aggregate may be added to the resin solution.

  On the other hand, in a polishing pad using a foamed sheet formed by a wet film forming method, in order to reinforce its physical strength and facilitate handling, a foamed sheet is directly placed on a rigid support instead of a film forming substrate. May form. However, the foam sheet has a weak bonding force with the rigid support and peels off. This is considered to be caused by the fact that carbon black or the like is blended in the urethane resin that is inherently adhesive in order to stabilize the foamed shape. That is, in carbon black, it is known that there are active oxygen-containing groups such as carboxyl group, phenol group, carbonyl group, quinone group on the surface, and this active oxygen-containing group interacts with urethane resin, Moreover, since the cohesion force between the urethane groups of the urethane resin is increased, the bonding force of the urethane resin to the rigid support is reduced.

  In order to prevent the foamed sheet from peeling from the rigid support, the foamed sheet produced on the film-forming substrate was forcibly peeled off from the film-forming substrate and reattached to the rigid support with an adhesive. In this case, since the foam sheet is laminated on the rigid support through the adhesive, it is difficult to improve the polishing accuracy of the wafer due to variations in the application thickness of the adhesive used and lack of flatness. Disadvantages arise. On the other hand, a foamed sheet directly bonded to a rigid support having excellent thickness accuracy (for example, polyethylene terephthalate) is prepared by blending a vinyl polymer together with carbon black in a urethane resin solution. A technique is disclosed (see Patent Document 1). With this technology, it is not necessary to peel the foam sheet from the film-forming substrate and re-adhere it to another rigid support, and the active groups on the surface of the carbon black are consumed by the interaction between the carbon black and the vinyl polymer. The urethane group does not interact with the active group on the surface of the carbon black, and the cohesive force of the urethane group is weakened by the vinyl group. For this reason, the number of urethane groups in which the ester groups and van der Waals forces on the polyethylene terephthalate surface of the rigid support are bonded by hydrogen bonding increases, and a strong bonding force is obtained between the foamed sheet and the rigid support. Moreover, in addition to blending carbon black with urethane resin, a technique for hydrophilizing (wetting) the surface of a silicon wafer by blending a vinyl polymer is disclosed (for example, see Patent Document 2). .

Japanese Patent Publication No. 5-20268 JP 2004-335713 A

  However, although the technique of Patent Document 1 can suppress the peeling between the foam sheet and the rigid support, the dispersion state and content of carbon black to be blended in the urethane resin are not limited. For this reason, large agglomerates of carbon black are formed in a large amount in the resin solution at the time of wet film formation and are unevenly distributed in the foamed sheet, thus affecting the polishing performance. In other words, since carbon black has an active group on the surface as described above and easily forms particle aggregates, primary aggregates (aggregates) in which several to several tens of carbon black particles are fused are formed. In addition, secondary aggregates (agglomerates) in which primary aggregates further aggregate may be formed. These aggregates have a size of several tens of micrometers or more when poor dispersion occurs in the resin solution. The secondary aggregate is usually several tens to several hundreds of μm in size, and when such a secondary aggregate is contained in a large amount in the foamed sheet, there is a variation in the size of foaming and uneven foam formation. There is a possibility that it may occur, and it is difficult to carry out stable polishing, and the polishing efficiency is lowered. Further, the secondary aggregate of carbon black is exposed on the polished surface as the foam sheet is worn during polishing. For this reason, defects such as scratches are caused on the surface of the object to be polished, and it is difficult to achieve high-precision flattening. Moreover, although the technique of patent document 2 can achieve surface hydrophilization of a to-be-polished object, like patent document 1, it becomes difficult to improve the flatness of the to-be-polished object by mix | blending carbon black.

  An object of the present invention is to provide a polishing pad that can stabilize the foamed shape and improve the flatness of an object to be polished.

  In order to solve the above problems, the present invention provides a polishing pad provided with a urethane resin foam sheet formed by a wet film forming method, and the foam sheet has a polishing surface for polishing an object to be polished. A skin layer is formed on the side, and an aggregate formed of amorphous carbon particles is contained in a ratio in the range of 2 wt% to 10 wt% with respect to the foamed sheet. In the foamed sheet, the foamed sheet is substantially uniformly dispersed and used for finish polishing.

  In the present invention, the foamed sheet made of urethane resin contains aggregates formed of amorphous carbon particles in a substantially uniformly dispersed state. Therefore, the content of aggregates is set to the foamed sheet. Even when the content is limited to the range of 2% by weight to 10% by weight, the aggregate can act as an aggregate that reinforces the foam structure, so that the foam shape can be stabilized, and the content of the aggregate is 2% by weight. By limiting to the range of -10% by weight, the effect of suppressing scratches during polishing is enhanced, and the surface of the skin layer formed on the polishing surface side is flat. Can be improved.

  In this case, the amorphous carbon may be carbon black. Carbon black may be at least one selected from channel black, furnace black, and acetylene black. In addition, the aggregate is formed by agglomeration of primary aggregates formed by fusing carbon black particles, and the distribution of grind gauges in a wet film mixture containing urethane resin and aggregates It is good also considering the dispersion state of the aggregate by a projection method as 3.0 micrometers or less.

  According to the present invention, the foamed sheet made of urethane resin contains aggregates formed of amorphous carbon particles in a substantially uniformly dispersed state. However, even when the content is limited to the range of 2% to 10% by weight, the aggregate can act as an aggregate that reinforces the foam structure, so that the foam shape can be stabilized, and the content of the aggregate is 2 By limiting to the range of 10% by weight to 10% by weight, the effect of suppressing scratches during polishing is enhanced, and the surface of the skin layer formed on the polishing surface side is flat. The effect that the flatness can be improved can be obtained.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is explanatory drawing which shows typically the structure of the carbon black particle contained in the polishing pad of embodiment. It is process drawing which shows the outline of the manufacturing process of the polishing pad of embodiment.

  Hereinafter, embodiments of a polishing pad to which the present invention is applied will be described with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, the polishing pad 10 of the present embodiment includes a foam sheet 2 formed of urethane resin. The foam sheet 2 has a substantially flat polished surface P.

  On the foamed sheet 2, a fine micropore (not shown) is formed on the polishing surface P side, and a skin layer 4 having micro flatness is formed. Inside the skin layer 4 (inside the urethane resin), a foam 3 having a triangular cross section rounded along the thickness direction of the foam sheet 2 is formed. The foam 3 is formed so that the size on the polishing surface P side is smaller than the surface side opposite to the polishing surface P. In the urethane resin between the foams 3, foams that are larger than the micropores formed in the skin layer 4 and smaller than the foams 3 are omitted. The foam 3 and the foam (not shown) are connected in a mesh pattern with communication holes (not shown) larger than the microporous diameter formed in the skin layer 4. That is, the foam sheet 2 has a continuous foam structure formed by a wet film forming method. The foamed sheet 2 contains an aggregate 5 formed of amorphous carbon carbon black particles. Aggregate 5 is contained in foam sheet 2 at a ratio in the range of 2 wt% to 10 wt%, and is dispersed substantially uniformly within foam sheet 2.

  Here, the carbon black aggregate 5 will be described. As shown in FIG. 2, carbon black has a complicated structure in which a plurality of spherical carbon black particles are fused, and in this example, a structure in which these particles are fused and connected (primary aggregate) is structured. It is called 9. This is because active functional groups such as hydroxyl groups and carboxyl groups are present on the surface of the carbon black particles, and interaction between these functional groups works. The structure 9 usually has several to several tens of carbon black particles fused and has a size of several tens to several hundreds of nanometers. The structure 9 is aggregated to form an aggregate 5 (secondary aggregate).

  The size of the structure 9 is indirectly represented by the oil absorption amount of Japanese Industrial Standard (JISK6217-4, carbon black for rubber-basic characteristics-Chapter 4: Determination of oil absorption amount (including compressed sample)). . In the structure 9, the porosity and the size have a positive correlation. That is, as the number of carbon black particles constituting the structure 9 increases, the voids between the particles increase, so that the amount of oil absorbed in the voids of the structure 9 (oil absorption amount) also increases. An absorption meter is used to measure the oil absorption, and dibutyl phthalate (hereinafter abbreviated as DBP) or paraffin oil is used as the oil. In this example, the size of the structure 9 is represented by the DBP absorption amount measured using DBP.

  The aggregate 5 in which the structures 9 are aggregated is dispersed substantially uniformly in the foamed sheet 2, and this is the aggregate 5 in the mixed liquid of the aggregate dispersion liquid and the urethane resin solution prepared in the preparation step (details will be described later). It is determined by the distributed state. In other words, the dispersion state of the aggregates 5 can be improved by suppressing the aggregation of the structures 9. This dispersion state is expressed in units of length according to a grind gauge distribution projection method of Japanese Industrial Standard (JIS K5600-2-5, Paint General Test Method-Part 2: Properties and Stability of Paint-Section 5: Dispersion). For example, it can be expressed by μm). In the grind gauge distribution projection method, measurement is performed using a gauge in which grooves (for example, 15, 25, 50, or 100 μm) having a uniform depth gradient from one end to the other end of zero depth are formed in the longitudinal direction.

  In the measurement of the dispersed state, a urethane resin solution is filled in the groove of the gauge using a scraper, and a scale indicating the depth of the groove at a position where particles are observed on the liquid surface is read. As a result, the dispersion state of the aggregate 5 present in the urethane resin solution is measured. In this example, the dispersion state of the aggregates 5 is adjusted to 3.0 μm or less by the grind gauge distribution projection method. Since the aggregate 5 is formed by the aggregation of the structure 9, when the size of the structure 9, that is, the DBP absorption amount increases, the dispersion state of the aggregate 5 may exceed 3.0 μm. For this reason, in Structure 9, it is preferable that the DBP absorption amount is 150 ml / 100 g or less.

  As the size of the structure 9 (DBP absorption amount) becomes smaller, the cohesive force becomes stronger and the dispersed state of the aggregate 5 becomes larger. For this reason, the aggregate 5 is coated with a dispersant for dispersing the aggregates. In the aggregate 5 coated with the dispersant, the active groups on the surface are consumed by the dispersant, so that the aggregate 5 is dispersed almost uniformly without further aggregation. That is, when the aggregate 5 is coated with the dispersant, the dispersion state becomes 3.0 μm or less. As the dispersant, one selected from acrylonitrile / butadiene / styrene (hereinafter abbreviated as ABS) resin, polyurethane, styrene / butadiene resin, cellulose acetate, and vinyl compound can be used. In this example, ABS resin is used as the dispersant.

  Further, the polishing pad 10 has one surface of the support 6 that supports the foamed sheet 2 bonded to the surface opposite to the polishing surface P. In this example, a sheet made of polyethylene terephthalate (hereinafter abbreviated as PET) is used as the support 6. On the other surface side of the support 6, the other surface side of the double-sided tape 7 having the release paper 8 on one surface side (lowermost surface side) for mounting the polishing pad 10 on the polishing machine is bonded.

(Manufacture of polishing pad)
As shown in FIG. 3, the polishing pad 10 is manufactured by laminating the foamed sheet 2 produced through each process of the wet film forming method with the support 6 and the double-sided tape 7 in the laminating process. In the wet film forming method, first, an aggregate dispersion obtained by mixing carbon black and an ABS resin as a dispersant in the preparation step, and a water-miscible organic solvent N, N-dimethylformamide (hereinafter, referred to as a urethane resin) can be dissolved. And a urethane resin solution in which a urethane resin is dissolved in DMF). In the coating step, the aggregate dispersion liquid and the urethane resin solution are mixed, and the mixed liquid is applied to the film forming substrate. In the coagulation regeneration process, the urethane resin is coagulated and regenerated into a sheet. In the washing / drying step, the sheet-like polyurethane resin is washed and dried. The foam sheet 2 is produced through these steps. Hereinafter, it demonstrates in order of a process.

  In the preparation step, an aggregate dispersion in which carbon black and an ABS resin as a dispersant are mixed is prepared. The aggregate dispersion liquid is filtered through a filter to remove carbon black aggregates having a size exceeding 3.0 μm. Aggregate 5 has a size of 3.0 μm or less and a content of 2 to 10% by weight. The ABS resin is set to 0.2 to 2.0 times the content of the aggregate 5. On the other hand, urethane resin, DMF and additives are mixed to dissolve the urethane resin. The urethane resin is selected from polyurethane resins such as polyester, polyether and polycarbonate, and is dissolved in DMF so that the urethane resin becomes 30%, for example. As the additive, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes the coagulation regeneration of the urethane resin, and the like can be used. The resulting solution is degassed under reduced pressure to obtain a urethane resin solution.

  In the coating process, a mixed liquid is prepared by mixing the aggregate dispersion liquid prepared in the preparation process and the urethane resin solution. By mixing the aggregate dispersion liquid in which the carbon black aggregate 5 is dispersed and the urethane resin solution, the aggregate 5 is dispersed in a state of being coated with the ABS resin. The dispersion state of the aggregate 5 in the mixed solution is measured by the above-described grind gauge distribution method. At this time, if the dispersion state of the aggregate 5 exceeds 3.0 μm, the mixed solution is not used. A mixed solution in which the dispersion state of the aggregate 5 is 3.0 μm or less is used. In the mixed liquid of this example, the dispersion state of the aggregate 5 was 1.5 μm or less. This mixed solution is applied substantially uniformly to the belt-shaped film forming substrate by a knife coater or the like at room temperature. At this time, the application thickness (application amount) of the urethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. Although the resin-made nonwoven fabric and film, such as PET resin, can be used for the film-forming substrate, in this example, the film-forming substrate is described as a PET sheet.

  In the coagulation regeneration step, the mixed solution applied to the film forming substrate is immersed in a coagulation solution containing water as a main component, which is a poor solvent for the urethane resin. In the coagulating liquid, first, a micropore is formed on the surface side of the applied mixed liquid, and a skin layer 4 having a thickness of about several μm is formed. Thereafter, the urethane resin coagulates and regenerates into a sheet form on the film forming substrate by the progress of substitution between the DMF in the mixed solution and the coagulating solution. When the DMF is desolvated from the mixed solution and the DMF and the coagulating liquid are replaced, the foam 3 and the foam not shown are formed in the urethane resin inside the skin layer 4, and the foam 3 and the foam not shown are formed. Communicates in a mesh pattern. At this time, since the PET sheet of the film forming substrate does not permeate water, desolvation occurs on the surface side (skin layer side) of the mixed solution, and a foam 3 having a larger film forming substrate side than the surface side is formed.

  In the washing / drying step, the urethane resin coagulated and regenerated in the coagulation regeneration step is washed in a cleaning solution such as water to remove DMF remaining in the urethane resin. After washing, the urethane resin is dried with a cylinder dryer to obtain the foam sheet 2. The cylinder dryer includes a cylinder having a heat source therein. The urethane resin is dried by passing along the peripheral surface of the cylinder.

  In the laminating step, the surface opposite to the polishing surface P of the foam sheet 2 and one surface side of the support 6 are bonded together, and the release paper 8 is provided on the other surface side of the support 6 on the one surface side (lowermost surface side). Affix the affixed double-sided tape 7 together. The polishing pad 10 is completed by performing an inspection such as confirming that there is no adhesion of dirt or foreign matter.

(Function)
Next, the operation and the like of the polishing pad 10 of this embodiment will be described.

  In a conventional polishing pad provided with a foam sheet formed by a wet film formation method, carbon black acting as an aggregate is added to a resin solution during wet film formation in order to stabilize foaming. However, since carbon black has an active functional group on the particle surface, it has the property of easily forming an aggregate. For this reason, large aggregates of carbon black are formed in the resin solution during wet film formation, and the large aggregates are unevenly distributed in the obtained foamed sheet. In a polishing pad using such a foamed sheet, variation in foam size and uneven foam formation occur, making it difficult to perform stable polishing and lowering the polishing efficiency. Further, during the polishing process, large aggregates are exposed on the polishing surface as the foamed sheet is worn, so that scratches are generated on the object to be polished and the flatness is impaired. The present embodiment is a polishing pad that can solve these problems.

  In the polishing pad 10 of this embodiment, the aggregate 5 in which the structures 9 are aggregated is contained in the foamed sheet 2 in a state of being coated with the ABS resin as the dispersant. For this reason, since the aggregate 5 is dispersed substantially uniformly in the foam sheet 2 without forming a large aggregate that is further aggregated during wet film formation, the foam formation is stabilized and the size of the foam is equalized. The Thereby, since the foam sheet 2 is formed substantially uniformly, stable polishing can be performed without impairing the polishing efficiency.

  Further, in the polishing pad 10 of the present embodiment, the size of the structure 9 is limited to 150 ml / 100 g or less in terms of DBP absorption, and the dispersion state of the aggregates 5 is limited to 3.0 μm or less. Since the aggregates 5 are coated with the dispersant, the aggregates 5 are dispersed substantially uniformly without forming aggregates when the foamed sheet 2 is produced. Thereby, the number of aggregates per unit volume increases, and the effect | action which stabilizes foam formation of carbon black (aggregate 5) becomes strong. For this reason, even if it limits content of the aggregate 5 to 2 to 10 weight%, the aggregate 5 acts as an aggregate which reinforces a foam structure, and the effect which stabilizes foam formation is acquired. When the content of the aggregate 5 is less than 2% by weight, the action as an aggregate for reinforcing the foam structure of the aggregate 5 is not sufficiently exhibited, and the tensile elongation becomes excessively large. It may be damaged. When the content of the aggregate 5 exceeds 10% by weight, the tensile elongation decreases, so that it is easy to break during the polishing process, resulting in a decrease in life. Further, when the size of the structure 9 exceeds 150 ml / 100 g in DBP absorption, the dispersed state of the aggregate 5 may exceed 3.0 μm, and scratches are likely to occur during polishing.

  Furthermore, in the polishing pad 10 of the present embodiment, since the dispersion state of the aggregates 5 is equalized in the foam sheet 2, even if the content of the aggregates 5 is reduced to 10% by weight or less, foam formation is achieved. Can be stabilized. Thereby, since the tensile elongation of the foamed sheet 2 is improved, breakage during the polishing process is suppressed, and the life of the polishing pad 1 can be extended.

  In this embodiment, the carbon black (structure 9) aggregate is exemplified as the aggregate 5 to be contained in the foamed sheet 2, but the present invention is not limited to this, and an amorphous carbon material is used. I just need it. For example, amorphous carbon coal may be used instead of carbon black. In addition, there are various types of carbon black, such as channel black, furnace black, and acetylene black, depending on the production method thereof, but the present invention is not limited to the production method of carbon black, and any of these may be used. Also good. It is also possible to use a mixture of carbon blacks having different manufacturing methods.

  Further, in the present embodiment, an example in which the dispersion state of the aggregate 5 is measured by a grind gauge distribution projection method is shown, but the present invention is not limited to this. For example, a general particle size measurement method may be used as long as the dispersion state of the aggregate 5 can be confirmed to be 3.0 μm or less. In consideration of confirming the dispersion state of the aggregate 5 during the manufacturing process, it can be easily confirmed by a grind gauge distribution projection method. Furthermore, in the present embodiment, an example in which the dispersion state of the aggregate 5 is set to 3.0 μm or less is shown. However, considering that there is a possibility that the aggregate 5 may be exposed to the polishing surface P during polishing, the aggregate 5 is 1 It is preferable to be 5 μm or less. In this way, since the size of the aggregate 5 is further limited, the effect of suppressing scratches when exposed to the polishing surface P can be enhanced, and the flatness of the object to be polished can be further improved. Since the dispersion state of the aggregate 5 is set to 3.0 μm or less, the aggregate 5 is dispersed substantially evenly in the foamed sheet 2. Therefore, even if the content of the aggregate 5 is reduced, the aggregate 5 strengthens the foam structure. By acting as a material, an effect of stabilizing foam formation can be obtained. Moreover, in this embodiment, although content of the aggregate 5 was made into the range of 2-10 weight%, the range of 2-5 weight% is preferable. If it does in this way, the number of the aggregates 5 which may be exposed to the grinding | polishing surface P at the time of grinding | polishing processing can be reduced, and a scratch can be suppressed.

  Furthermore, in this embodiment, although the example which represents the magnitude | size of the structure 9 by DBP absorption amount was shown, this invention is not restrict | limited to this, The magnitude | size of the structure 9 is 150 ml / 100g or less in DBP absorption quantity. Anything can be used as long as it can be evaluated. The DBP absorption amount of the structure 9 is preferably 130 ml / 100 g or less, particularly preferably 90 ml / 100 g or less, considering the dispersion state of the aggregate 5.

  Furthermore, in the present embodiment, as an example of the method for dispersing the aggregate 5, an example in which the aggregate 5 is coated using an ABS resin that is a dispersant is shown, but the present invention is not limited to this, Any method can be used as long as the structure 9 has a size (DBP absorption amount) of 150 ml / 100 g or less and a dispersion state of the aggregate 5 is 3.0 μm or less. Moreover, although the example which uses an ABS resin as a dispersing agent was shown, this invention is not limited to this. For example, the above-described effects can be obtained even when polyurethane, styrene-butadiene resin, cellulose acetate, or vinyl compound is used in place of the ABS resin. Of course, two or more of these dispersants may be mixed and used. When a vinyl compound is used as the dispersant, it is preferable to use a non-halogen compound that does not contain a halogen molecule. In this way, it is possible to reduce the influence on the environment when the polishing pad is discarded.

  Furthermore, in the present embodiment, the urethane resin is coagulated and regenerated using the film forming base material when the foam sheet 2 is produced, and then the film forming base material is peeled off to form the foam sheet 2 and the PET support 6. However, the present invention is not limited to this. For example, the foam sheet 2 may be directly solidified and regenerated on the support 6 by using the support 6 as a film-forming substrate during wet film formation. Since the aggregate 5 contained in the foamed sheet 2 is coated with the ABS resin, the influence of active groups present on the particle surface of the carbon black (structure 9) forming the aggregate 5 can be suppressed. That is, when the active group on the particle surface interacts with the urethane resin, the adhesive force between the urethane resin and the PET of the support 6 may be reduced and may be peeled off during polishing. On the other hand, in the aggregate 5 which is coated with ABS resin and suppresses the influence of the active group, the interaction with the urethane resin is reduced, so that the adhesive force between the foam sheet 2 and the support 6 can be secured. it can. The material of the support 6 is not limited to PET, and any material can be used as long as it is made of a resin having rigidity.

  Hereinafter, examples of the polishing pad 10 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the urethane resin. A urethane resin solution was prepared by dissolving 30% by weight of this polyurethane resin in DMF. Further, 5% by weight of carbon black and 20% by weight of ABS resin were mixed with DMF to prepare an aggregate dispersion. A commercially available carbon black (manufactured by Tokai Carbon Co., Ltd.) was used as the carbon black. The size of the carbon black structure 9 used (DBP absorption amount) was 130 ml / 100 g. 40 parts of the aggregate dispersion were mixed with 100 parts of the obtained urethane resin solution to obtain a mixed liquid. As a result of measuring the dispersion state of the aggregate 5 of this mixed liquid using a grind gauge distribution projection method, it was 1.5 μm or less. A foamed sheet was produced from the obtained mixed liquid by a wet film forming method to produce a polishing pad. Table 1 below shows the agglomerate content, dispersion state, and structure size.

(Example 2)
As shown in Table 1, in Example 2, a polishing pad was produced in the same manner as in Example 1 except that the aggregate dispersion was prepared by changing the size of the structure 9 and the content of the aggregate 5. . That is, carbon black having a structure 9 size of 90 ml / 100 g was used, and the content of the aggregate 5 in the aggregate dispersion was 2% by weight. In the mixed solution of the aggregate dispersion and the urethane resin solution, the dispersion state of the aggregate 5 was 1.5 μm or less.

(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, a polishing pad was prepared in the same manner as in Example 1 except that the aggregate dispersion was prepared by changing the size of the structure and the content of the aggregate. That is, carbon black having a structure size of 200 ml / 100 g was used, and the aggregate content in the aggregate dispersion was 20% by weight. In the mixed liquid of the aggregate dispersion and the urethane resin solution, the dispersion state of the aggregate 5 was 25 μm or less.

(Comparative Example 2)
As shown in Table 1, in Comparative Example 2, a polishing pad was produced in the same manner as in Example 1 except that the aggregate dispersion was prepared by changing the size of the structure and the content of the aggregate. That is, carbon black having a structure size of 200 ml / 100 g was used, and the content of aggregates in the aggregate dispersion was 5% by weight. In the mixed liquid of the aggregate dispersion and the urethane resin solution, the dispersion state of the aggregate 5 was 25 μm or less.

(Comparative Example 3)
As shown in Table 1, in Comparative Example 3, a polishing pad was produced in the same manner as in Example 1 except that the aggregate dispersion was prepared by changing the size of the structure and the content of the aggregate. That is, carbon black having a structure size of 130 ml / 100 g was used, and the content of aggregates in the aggregate dispersion was 1% by weight. In the mixed solution of the aggregate dispersion and the urethane resin solution, the dispersion state of the aggregate 5 was 1.5 μm or less.

(Evaluation)
For each example and comparative example, the tensile strength and tensile elongation of the foamed sheet after wet film formation were measured. For the measurement, a tensile elongation measuring device (manufactured by A & D Co., Ltd., Tensilon universal testing machine RTC) was used. The measuring method was measured by a method according to Japanese Industrial Standard (JIS K6550). The measurement results of tensile strength and tensile elongation are shown in Table 2 below.

As shown in Table 2, in Comparative Example 1, the foam sheet had a tensile strength of 0.09 kg / mm ² and a tensile elongation of 128%. In the polishing pad 10 of Example 1, the foam sheet 2 had a tensile strength of 0.24 kg / mm ² and a tensile elongation of 282%, and both the tensile strength and the tensile elongation were improved. As a result, the aggregates are almost uniformly dispersed by being coated with the dispersant. Therefore, even if the aggregate content is reduced, the aggregates act as aggregates that reinforce the foam structure and have stable physical properties. It was found that can hold. Further, in the polishing pad 10 of Example 1, even when the aggregate content was 5% by weight, which is 10% by weight or less, breakage of the polishing pad during the polishing process was suppressed, and it could be said that the life could be extended. .

In Comparative Example 2, the tensile strength was 0.14 kg / mm ² and the tensile elongation was 224%. In the polishing pad 10 of Example 1, the tensile strength was 0.24 kg / mm ² and the tensile elongation was 282%. In Comparative Example 2, since the size of the structure forming the aggregate (DBP absorption amount) is 200 ml / 100 g, which is larger than Example 1, the dispersion state of the aggregate is also large. On the other hand, in Example 1, since the DBP absorption amount is 130 ml / 100 g, which is smaller than Comparative Example 2, the aggregates are also in a small dispersion state. Therefore, in Example 1, the number of aggregates 5 per unit volume of the foamed sheet 2 is increased, and the action of stabilizing the foam formation of the aggregates 5 is strengthened, so that the tensile strength and the tensile elongation are improved. Conceivable.

In Comparative Example 3, the tensile strength was 0.21 kg / mm ² and the tensile elongation was 370%. In the polishing pad 10 of Example 2, the tensile strength was 0.26 kg / mm ² and the tensile elongation was 278%. Thereby, in the comparative example 3, the effect | action which strengthens the foam structure of an aggregate is not fully exhibited by reducing the content of the aggregate to 1 weight%, and tensile elongation is compared with Example 2. It is thought that the value was excessively high. When the polishing process is performed with a polishing pad having an excessively high tensile elongation, the polishing performance is impaired. On the other hand, in Example 2, since the aggregate content was 2% by weight, an appropriate tensile elongation could be obtained. Therefore, it is considered that the aggregate content is preferably 2% by weight or more.

(Polishing)
Using the polishing pads of the examples and comparative examples, the hard disk aluminum substrate was polished under the following polishing conditions, and the polishing rate and waviness were measured. Further, the polished aluminum substrate was irradiated with a high-intensity halogen lamp and visually evaluated for the presence or absence of scratches on the surface of the aluminum substrate.
(Polishing conditions)
Polishing machine: 9F-5P polishing machine manufactured by Speed Fam Co., Ltd. Polishing speed (rotation speed): 30 rpm
Processing pressure: 100 g / cm ²
Slurry: Colloidal silica slurry (pH: 11.5)
Slurry supply amount: 100cc / min
Object to be polished: Aluminum substrate for hard disk

(Polishing rate)
The polishing rate is one of the numerical values indicating the polishing efficiency, and represents the polishing amount per minute in terms of thickness. It calculated from the grinding | polishing amount calculated | required from the weight reduction of the aluminum substrate before and behind grinding | polishing processing, the grinding | polishing area of an aluminum substrate, and specific gravity.

(undulation)
Waviness is one of the measurement items for evaluating the surface accuracy (flatness) of objects to be polished such as disk substrates, silicon wafers, etc. per unit area observed with an optical non-contact surface roughness meter. The surface image waviness (Wa) is expressed in angstroms (Å). Evaluation was performed using a filter that transmits a wavelength of 80 μm to 500 μm using a Zygo New View 5022 as a test evaluation machine. When the numerical value of the measurement result is low, the undulation of the object to be polished is small, and the polishing surface is flatter.

  Regarding the polishing performance using the polishing pads of Examples and Comparative Examples, the polishing rate and the swell evaluation results are shown in Table 3 below. In addition, whether or not scratches are generated in the polishing process using the polishing pads of Examples and Comparative Examples is also shown.

  As shown in Table 3, in Examples 1 and 2, the polishing rate exceeded the polishing rate of Comparative Examples 1 and 2. Further, in Examples 1 and 2, an aluminum substrate having excellent flatness with reduced waviness due to polishing could be obtained. This is presumably because foam formation could be stabilized by improving the dispersion state of the aggregates even when the aggregate content was reduced. Further, in Examples 1 and 2, since the aggregate structure was smaller and the content was less than those in Comparative Examples 1 and 2, the occurrence of scratches and the like on the object to be polished was suppressed during polishing. In Comparative Example 3, the polishing rate was significantly reduced as compared with Examples 1 and 2. This is considered to be because, in Comparative Example 3, the content of aggregates is small, the effect of strengthening the foam structure of the aggregates is not sufficiently exhibited, the tensile elongation is excessively high, and the polishing performance is impaired. obtain. In Examples 1 and 2, since the content of the aggregate 5 was 2% by weight, the tensile elongation was an appropriate value and the polishing rate was improved. Such a polishing pad can be suitably used for finish polishing of a hard disk aluminum substrate or the like.

  The present invention provides a polishing pad that can stabilize the foam shape and improve the flatness of the object to be polished, and thus contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability. .

P Polishing surface 2 Foam sheet 5 Aggregate 10 Polishing pad

Claims (4)

  In a polishing pad provided with a urethane resin foam sheet formed by a wet film-forming method, the foam sheet has a skin layer formed on the polishing surface side for polishing an object to be polished. Aggregates formed of crystalline carbon particles are contained in a ratio of 2% by weight to 10% by weight with respect to the foamed sheet, and the aggregates are dispersed substantially uniformly in the foamed sheet. A polishing pad that is used for finish polishing.   The polishing pad according to claim 1, wherein the amorphous carbon is carbon black.   The polishing pad according to claim 2, wherein the carbon black is at least one selected from channel black, furnace black, and acetylene black.   The agglomerates are formed by agglomerating primary agglomerates formed by fusing the carbon black particles. In a mixed liquid for wet film formation containing a urethane resin and the agglomerates, a grind gauge is used. The polishing pad according to claim 2, wherein a dispersion state of the aggregates by a distribution diagram method is 3.0 μm or less.

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