JP5885183B2 - Polishing pad - Google Patents

Description

  The present invention is used for polishing processing, and is a foam in which a plurality of foams and a plurality of micropores having an average diameter smaller than the average diameter of the plurality of foams are continuously formed by a wet film forming method. The present invention relates to a polishing pad provided with a foam sheet having a structure.

  Conventionally, in materials that are required to have flatness with high precision (objects to be polished) such as optical materials such as lenses, parallel flat plates, reflecting mirrors, aluminum substrates for hard disks, silicon wafers for semiconductor devices, mother glasses for liquid crystal displays, Polishing using a polishing pad is performed. For example, when both surfaces of an object to be polished are simultaneously polished, a polishing pad is mounted on each facing platen of the double-side polishing machine. In addition, when polishing one surface of an object to be polished, a polishing pad is mounted on one of the facing plates of the single-side polishing machine, and the object to be polished is held on the other. In such a precision polishing process of an object to be polished, a finishing process (secondary polishing) is widely performed after a polishing process (primary polishing) once in order to improve flatness. At the time of polishing, a polishing liquid (slurry) containing abrasive grains is supplied between the object to be polished and the polishing pad. Many slurries have acidic and alkaline properties, and polishing is performed by utilizing the chemical action due to the liquidity of the slurry in addition to the mechanical action by the abrasive grains.

  In general, a foamed sheet made of polyurethane resin formed by a wet film forming method is used as a polishing pad. In the wet film-forming method, a resin solution in which a polyurethane resin is dissolved in a water-miscible organic solvent is applied to a sheet-shaped film-forming substrate, and then immersed in an aqueous coagulating liquid, so that the resin is solidified and regenerated into a sheet. The The obtained foamed sheet has a dense skin layer on the surface that comes into contact with the object to be polished, a plurality of vertically elongated foams in the thickness direction inside the skin layer, and a large number of micropores smaller in size than the foam And have a foamed structure formed in a continuous manner. A polishing pad provided with a foam sheet having such a foam structure has a skin layer and is suitable for finish polishing.

  On the other hand, an opening may be formed on the surface (polishing surface) by subjecting the foamed sheet to a skin layer side to a grinding process such as a buffing process. When a foamed sheet having an opening formed on the polishing surface is used for a polishing pad, the vicinity of the opened foam has flexibility, and can flexibly contact an object to be polished during polishing processing. . For this reason, this polishing pad is widely used mainly for primary polishing. In addition, in a polishing pad with an opening formed in the polishing surface, foaming expands and contracts due to the pressing force applied during polishing processing, so that the object to be polished can be made at a stable polishing rate by flowing in and out while the slurry is held in the foam. Polished. Since foreign matters such as sludge (polishing waste) generated during polishing are stored in the foam, generation of scratches and the like on the processed surface of the object to be polished is suppressed.

  However, in a polishing pad with an opening formed on the polishing surface, a slurry having acidic or alkaline properties enters the foam or fine pores during polishing, so the resin portion of the foamed sheet is caused by the chemical action of the slurry. Therefore, the foamed sheet is eroded from the inside of the fine holes and the foamed sheet is rapidly deteriorated. As the deterioration of the foamed sheet progresses, the foamed sheet and the object to be polished slide in the polishing process, and the shearing stress repeatedly applied to the foamed sheet tends to tear the resin part in which the fine holes of the foamed sheet are formed, The so-called “cohesive failure” is easily generated, in which the foam structure is destroyed and cannot be restored. When cohesive failure occurs, the polishing performance is impaired and stable polishing cannot be performed. In order to suppress the deterioration of the foamed sheet due to the liquidity of the slurry, a polyurethane resin for abrasives having alkali resistance has been disclosed (see Patent Document 1).

JP-A-6-220151

  However, although the technology of Patent Document 1 has alkali resistance, the basic molecular structure of the polyurethane resin is almost the same as that of the conventional one, and therefore a great improvement in the alkali resistance of the polyurethane resin is expected. I can't. If the foamed structure can be maintained even for acidic and alkaline slurries by suppressing the deterioration of the foamed sheet due to the liquidity of the slurry, stable polishing can be expected.

  An object of the present invention is to provide a polishing pad capable of performing a stable polishing process for a long period of time in view of the above cases.

In order to solve the above problems, the present invention is used for polishing processing, and a plurality of foams by a wet film forming method, and a plurality of micropores having an average diameter smaller than the average diameter of the plurality of foams between the plurality of foams. In the polishing pad provided with a foam sheet having a foam structure in which the foam sheet is continuously formed, the foam sheet is formed of a polyurethane-based first resin, and the first pores are formed in the plurality of micropores. The second resin for suppressing the increase in hardness of the polished surface that can come into contact with the object to be polished has a volume of the second resin existing with respect to the volume of the micropores. It is contained so that the ratio is 30% or more, and the foaming is a vertically long triangular shape rounded along the thickness direction of the foamed sheet, and the second resin is a rubber material. Features.

In the present invention, the second resin having higher acid resistance or alkali resistance than the polyurethane-based first resin in the micropores of the foamed sheet has a volume ratio of the second resin to the micropore volume of 30%. By containing as described above, the surface of the micropores is protected by the second resin, so that deterioration of the foamed sheet due to the chemical action of the acidic or alkaline slurry supplied during polishing is suppressed. At the same time, the foam structure is reinforced by the second resin, so that the abrasive particles and polishing debris contained in the slurry are less likely to accumulate in the micropores, and the increase in hardness of the polished surface is suppressed , and is contained in the micropores. In addition, the second resin is a rubber material, and the foaming expansion and contraction at the time of polishing processing is ensured by securing a foaming void having a round triangular cross section that is rounded along the thickness direction. shear Even under force, it is possible to perform polishing with long-term stability and to improve the planarity of the polished object.

  In this case, the second resin is formed so that a film is formed on the surface of a large number of micropores, and the volume ratio in the micropores is 70% or more with respect to the volume of the micropores. It is preferable. The second resin can be formed by impregnating a resin sheet with a foam sheet having a foam structure. The diameter of the dispersed phase of the resin emulsion is preferably 1 μm or less. Silicone rubber, fluoro rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, styrene-butadiene rubber And at least one selected from butadiene rubber. The foam sheet preferably has a tensile strength retention of 80% or more before and after being immersed in an aqueous sodium hydroxide solution having a liquid temperature of 40 ° C. and a pH of 14 for 8 hours. The foam sheet preferably has a tensile strength retention of 80% or more before and after being immersed in an aqueous hydrochloric acid solution having a liquid temperature of 40 ° C. and a pH of 1 for 24 hours.

According to the present invention, the second resin having higher acid resistance or alkali resistance than the polyurethane-based first resin in the micropores of the foam sheet has a ratio of the volume of the second resin to the volume of the micropores. By containing 30% or more, the surface of the micropores is protected by the second resin, so that the deterioration of the foam sheet due to the chemical action of the acidic or alkaline slurry supplied during polishing is suppressed. In addition, the foam structure is reinforced by the second resin, the abrasive particles and polishing debris contained in the slurry are less likely to accumulate in the micropores, and the increase in hardness of the polished surface is suppressed , and the micropores The contained second resin is a rubber material, and because the foamed voids in a vertically long triangular shape rounded along the thickness direction are secured, the foam expands and contracts during the polishing process. On the sheet Even when a shear stress, it is possible to perform polishing with long-term stability and to improve the flatness of the object to be polished, the effect can be obtained as.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. 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.

(Constitution)
As shown in FIG. 1, the polishing pad 10 of the present embodiment includes a foam sheet 2 formed of a polyurethane-based first resin by a wet film forming method. The first polyurethane resin is a resin having a urethane bond in the main chain. In this example, a polyurethane resin is used. The foam sheet 2 has a polishing surface P.

  The foam sheet 2 is buffed on the skin layer side formed during wet film formation so that the thickness is uniform. The foamed sheet 2 is formed in a state where a plurality of foams 3 having a triangular shape with a round cross section rounded along the thickness direction (vertical direction in FIG. 1) are substantially uniformly dispersed. The foam 3 is formed such that the pore diameter on the polishing surface P side is smaller than the surface side opposite to the polishing surface P. That is, the diameter of the foam 3 is reduced on the polishing surface P side. The plurality of foams 3 include a vertically long foam 3 over the entire thickness of the foam sheet 2 and a foam 3 having a length less than the thickness of the foam sheet 2. In the foam sheet 2, the foam layer 3 is opened and the opening 4 is formed on the polished surface P by removing the skin layer by buffing. In the polyurethane resin between the foams 3, a large number of fine holes 6 having an average pore diameter smaller than that of the foams 3 are formed. The equivalent circle diameter of the micropores 6 measured by binarizing the cross-sectional image of the foamed sheet 2 observed with an electron micrograph is set to 15 μm or less. The foam 3 and the fine holes 6 are communicated in a mesh shape with the communication holes. That is, the foam sheet 2 has a continuous foam structure. In the continuous foam structure of the foam sheet 2, the resistant resin 5 as the second resin is present on the surface of at least some of the fine holes 6 so as to form a continuous film. ing. That is, the phase of the resistant resin 5 is formed.

  Here, the resistant resin 5 will be described. The phase of the resistant resin 5 is continuously formed in a state where the surface of the micropore 6 is almost coated through the communication hole (a state of a film). The fine holes 6 are formed as a fine hole 6 in which the phase of the resistant resin 5 is formed in the majority of one fine hole 6 and a fine hole 6 in which the phase of the resistant resin 5 is hardly formed. That is, the amount of the resistant resin 5 present in each micropore 6 varies depending on the thickness of the coating of the resistant resin 5. The filling rate of the resistant resin 5 into the large number of micropores 6 before the formation of the phase of the resistant resin 5 is set to 30% or more. The filling rate of the resistant resin 5 is expressed as a percentage of the volume of the resistant resin 5 to the volume of the voids of the numerous micropores 6 before the phase of the resistant resin 5 is formed.

A method for calculating the filling rate of the resistant resin 5 will be described. First, before the formation of the phase of the resistant resin 5, a cross-sectional photograph of the foam sheet is taken with a scanning electron microscope (SEM), and from the binarized image, the pore diameter of the fine holes 6 is set as the equivalent circle diameter. measuring the five points of the sheet 1 mm ^2, the table value of the mean When a, the volume of the gap portion of the micropores 6 before the formation of the reinforcing resin 5 (volume of the micropores 6) is? pa ^3/6 Is done. Similarly, after forming the phase of the resistant resin 5, the pore diameter of a large number of pores (portions where the phase of the resistant resin 5 is not formed) of the micropores 6 is measured as an equivalent circle diameter. Then, the volume of the gap portion of the micropores 6 after formation of the reinforcing resin 5 is represented by πB ^3/6. Assuming that the volume of the resistant resin 5 is the difference in volume of the voids of the micropores 6 before and after the phase of the resistant resin 5 is formed, that is, π (A ³ −B ³ ) / 6, the resistant resin 5 The filling rate of 5 is calculated by the formula of (A ³ −B ³ ) / A ³ × 100.

  The resistant resin 5 is formed of a resin having higher acid resistance or alkali resistance than the polyurethane resin forming the foamed sheet 2. For acid resistance, the tensile strength after dipping the foamed sheet 2 in which the phase of the resistant resin 5 is formed in a hydrochloric acid aqueous solution having a liquid temperature of 40 ° C. and pH 1 for 24 hours is A1, and the tensile strength before dipping in the aqueous hydrochloric acid solution is A1. When the strength is B1, the tensile strength retention represented by A1 / B1 × 100 is 80% or more. On the other hand, as alkali resistance, when the liquid temperature is 40 ° C. and the tensile strength after immersion in an aqueous sodium hydroxide solution at pH 14 for 8 hours is A2, and the tensile strength before immersion in the aqueous sodium hydroxide solution is B2, The tensile strength retention represented by A2 / B2 × 100 is 80% or more. Examples of such a resin include rubber materials. Specifically, silicone rubber, fluorine rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile butadiene rubber, hydrogenated acrylonitrile- At least one selected from butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, styrene-butadiene rubber, and butadiene rubber is used. In this example, chloroprene rubber having higher acid resistance and alkali resistance properties than polyurethane resin is used as the resistant resin 5. When the resistant resin 5 excellent in acid resistance or alkali resistance is present in the fine holes 6, the resistant resin 5 functions to protect the foamed sheet 2.

  The resistant resin 5 is formed by impregnating the foam sheet 2 with a chloroprene rubber emulsion (resin emulsion). The diameter of the dispersed phase of the resin emulsion is set to 1 μm or less. In the foam sheet 2, an opening 4 in which the foam 3 is opened is formed on the polishing surface P side, and the foam sheet 2 has a foam structure in which the foam 3 and the fine holes 6 are communicated with each other through the communication holes. By impregnating the resin emulsion, the resin emulsion can be permeated into the fine holes 6 through the foam 3 and the communication holes.

  Further, the polishing pad 10 has one surface side of the double-sided tape 7 for attaching the polishing pad 10 to the polishing machine bonded to the surface opposite to the polishing surface P. The double-sided tape 7 has a base material such as polyethylene terephthalate (hereinafter abbreviated as PET), and an adhesive is applied to both surfaces thereof. A release paper 8 is provided on the other surface side (lowermost surface side) of the double-sided tape 7.

(Manufacturing)
As shown in FIG. 2, the polishing pad 10 includes a preparation step for preparing a resin solution in which a polyurethane resin is dissolved, a coating step for continuously applying the resin solution to a film-forming substrate, and a polyurethane resin in an aqueous coagulation liquid. A coagulation regeneration process for coagulating and regenerating into a sheet shape, a cleaning / drying process for cleaning and drying the polyurethane resin that has been coagulated and regenerated, a grinding process for performing a grinding process so as to make the thickness uniform, and impregnating the foamed sheet 2 with a resin emulsion and drying It is manufactured through an impregnation / drying step, a laminating step of bonding the foam sheet 2 and the double-sided tape 7 together. Hereinafter, it demonstrates in order of a process.

  In the preparation step, N, N-dimethylformamide (hereinafter abbreviated as DMF), which is a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive are mixed to dissolve the polyurethane resin. For the polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin, or the like is selected and used. For example, the polyurethane resin is dissolved in DMF so as to be 30% by mass. Examples of additives include pigments such as carbon black, hydrophilic activators that promote foam formation, and hydrophobic activators that stabilize the coagulation regeneration of polyurethane resins in order to control the size and quantity (number) of foam 3. Can be used. The resulting solution is degassed under reduced pressure to obtain a polyurethane resin solution.

  In the application step, the polyurethane resin solution prepared in the preparation step is applied substantially uniformly to the belt-shaped film forming substrate at a normal temperature by an application device such as a knife coater. At this time, the application thickness (application amount) of the polyurethane resin solution is adjusted by adjusting the gap between the knife coater and the film forming substrate. A flexible film, a nonwoven fabric, a woven fabric, etc. can be used for the film-forming substrate. When using a nonwoven fabric or a woven fabric, in order to suppress the penetration of the polyurethane resin solution into the film-forming substrate during application of the polyurethane resin solution, it is preliminarily immersed in water or a DMF aqueous solution (mixed solution of DMF and water). Preprocessing (sealing) is performed. In the case where a flexible film made of PET or the like is used as the film forming substrate, pretreatment is not necessary because it does not have liquid permeability. Hereinafter, in this example, the film forming substrate is described as a PET film.

  In the coagulation regeneration process, the polyurethane resin solution applied to the film forming substrate in the application process is guided to a coagulation liquid (water-based coagulation liquid) whose main component is water which is a poor solvent for the polyurethane resin. In the coagulation liquid, first, a skin layer having a thickness of about several μm is formed on the surface side of the applied polyurethane resin solution. Thereafter, the polyurethane resin coagulates and regenerates in a sheet form on one side of the film forming substrate by the progress of substitution between the DMF in the polyurethane resin solution and the coagulating liquid. When DMF is removed from the polyurethane resin solution and DMF and the coagulating liquid are replaced, foam 3 and a large number of micropores 6 are formed inside the polyurethane layer (in the polyurethane resin). A communication hole for communicating 6 in a mesh shape is formed. At this time, since the PET film of the film forming substrate does not allow water to permeate, desolvation occurs on the surface side (skin layer side) of the polyurethane resin solution, and a foam 3 having a larger film forming substrate side than the surface side is formed. .

  In the cleaning / drying process, the sheet-like polyurethane resin solidified and regenerated in the coagulation regeneration process (hereinafter referred to as a film-forming resin) is peeled off from the film-forming substrate, washed in a cleaning solution such as water and washed into the film-forming resin. Residual DMF is removed. After cleaning, the film forming resin is dried with a cylinder dryer. The cylinder dryer includes a cylinder having a heat source therein. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The film-forming resin after drying is wound up in a roll shape.

  In the grinding process, a grinding process such as buffing is performed on the skin layer formed on the surface of the film-forming resin. That is, the substantially flat surface of the pressure welding jig is pressed against the surface opposite to the skin layer of the film forming resin, and the buff treatment is performed on the skin layer side. Thereby, a part of the foam 3 is opened at the polishing surface P to form the opening 4, and the thickness of the film forming resin is made uniform.

In the impregnation / drying step, a resin emulsion in which chloroprene rubber having acid resistance and alkali resistance is dispersed in a dispersion medium such as water is impregnated or coated on the film-forming resin after buffing. In the film-forming resin impregnated with the resin emulsion, the resin emulsion enters the fine holes 6 through the foam 3 and the communication holes. That is, the film-forming resin is wetted with the resin emulsion. After impregnation, excess resin emulsion is squeezed out by a mangle roller under a low load. The amount of the resin emulsion remaining in the fine holes 6 depends on the size of the fine holes 6 and the distance from the foam 3 of the fine holes 6 but can be adjusted by adjusting the load of the mangle roller. . At this time, since the size of the micropores 6 is smaller than the size of the foam 3, when the film-forming resin is impregnated with the resin emulsion, the surface tension of the resin emulsion works. 6 will enter a lot. Thereafter, the film forming resin is dried with a cylinder dryer. At this time, water or the like of the dispersion medium evaporates first in the resin emulsion, and the chloroprene rubber in the dispersed phase is solidified later. The filling rate is adjusted by repeating the same operation 2 to 5 times, and the foamed sheet 2 is formed in a state where the surface of the micropores 6 is almost coated with the resistant resin 5.

  In the laminating process, one surface of the double-sided tape 7 is bonded to the surface opposite to the polishing surface P of the obtained foamed sheet 2. The other side of the double-sided tape 7 is covered with a release paper 8. 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 this embodiment, the phase of the resistant resin 5 is formed in many micropores 6. In the resistant resin 5, chloroprene rubber having higher acid resistance and alkali resistance than polyurethane resin is used. Since the chloroprene rubber forming the resistant resin 5 is superior in acid resistance and alkali resistance to the polyurethane resin forming the foamed sheet 2, the surface of the micropores 6 is protected by the resistant resin 5, and the slurry supplied during the polishing process is microporous. Even if it enters the inside 6, the resistant resin 5 suppresses the deterioration of the foam sheet 2 due to the chemical action of the slurry. Further, the resistant resin 5 also has a function of reinforcing the foam sheet 2 by being present in the fine holes 6. For this reason, even if a shear stress is applied during the polishing process, the foamed structure is maintained, so that a stable polishing process can be performed for a long period of time. Furthermore, since the foam sheet 2 is protected by the resistant resin 5 on the surface of the micropores 6 to prevent deterioration due to the chemical action of the slurry, the influence of the liquid property of the slurry on the foam structure is reduced. Can do. As a result, it is possible to use a slurry having a liquid property with a suitable pH according to the object to be polished, and improve the polishing efficiency. For example, an aqueous ammonia solution or an organic acid aqueous solution can be used for the slurry in addition to the aqueous sodium hydroxide solution and aqueous hydrochloric acid solution.

  Moreover, in this embodiment, the phase of the resistant resin 5 is formed in many micropores 6 formed in the foamed sheet 2. For this reason, when the fine holes 6 are blocked with the resistant resin 5, it becomes difficult for the abrasive particles and sludge contained in the slurry during the polishing process to be accumulated in the fine holes 6. As a result, since the increase in the partial hardness of the polishing surface P is suppressed, scratches on the object to be polished are reduced, and unevenness in the hardness of the polishing surface P is reduced, so that the flatness of the object to be polished is improved. Can be made.

  Furthermore, in this embodiment, the filling rate of the resistant resin 5 with respect to the numerous fine holes 6 before the formation of the resistant resin 5 is set to 30% or more. When the filling rate of the resistant resin 5 is less than 30%, the ratio of the slurry coming into contact with the surface of the micropores 6 is increased, and the protective function of the resistant resin 5 is insufficient, thereby suppressing the deterioration of the foamed sheet 2 due to the slurry. The effect to do is not obtained. Further, since the amount of the resistant resin 5 becomes insufficient, the micropores 6 are not sufficiently blocked by the resistant resin 5 so that accumulation of sludge and the like in the micropores 6 can be suppressed. On the contrary, the removal of sludge and the like is deteriorated and the scratches are likely to occur due to the small gap.

  Furthermore, in this embodiment, the resistant resin 5 is formed by impregnation with a resin emulsion. The diameter of the dispersed phase of the resin emulsion is set to 1 μm or less. For this reason, when the resin emulsion penetrates to the fine holes 6 through the foam 3 or the communication holes, the resistant resin 5 can be continuously formed in the fine holes 6. In the present embodiment, the plurality of foams 3 are opened by the grinding process. For this reason, in the impregnation / drying step, the resin emulsion can be easily infiltrated into the fine holes 6 through the foam 3 and the communication holes.

  In the present embodiment, an example in which the phase of the resistant resin 5 is formed in the micropores 6 has been shown. However, the present invention is not limited to this, and the phase of the foam 3 is also at least partially. It may be formed. This can be realized by adjusting the size of the opening of the foam 3 on the polishing surface P side, that is, by adjusting the buff amount in the grinding process or by adjusting the load of the mangle roller in the impregnation / drying process. it can. If it does in this way, the tolerance resin 5 can improve the function which reinforces a foaming structure more. Moreover, in this embodiment, although the example in which the filling rate of the resistant resin 5 with respect to the large number of micropores 6 before the formation of the phase of the resistant resin 5 is set to 30% or more is shown, the foamed structure is further reinforced. Is taken into consideration, it is more preferable that the filling rate of the resistant resin 5 is 70% or more.

  Moreover, in this embodiment, although the chloroprene rubber whose both acid resistance and alkali resistance property are higher than a polyurethane resin was illustrated as resistant resin 5, ie, resin used for a resin emulsion, this invention is not limited to this. Any material can be used as long as it is a material having higher acid resistance or alkali resistance than the polyurethane resin forming the foam sheet 2, in other words, a material having at least one of acid resistance and alkali resistance. Examples of such materials include fluorine rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, Mention may be made of at least one selected from styrene-butadiene rubber and butadiene rubber. When a material having only higher acid resistance than the polyurethane resin is used as the resistant resin 5, an acidic one can be used for the slurry. On the other hand, when a material having only high alkali resistance as compared with the polyurethane resin is used, an alkaline material can be used for the slurry.

  Furthermore, in this embodiment, although the example which uses water etc. as a dispersion medium of a resin emulsion was shown, this invention is not limited to this, If the polyurethane-type resin used for the foam sheet 2 is not melt | dissolved, Liquids other than water may be used. For example, a liquid containing alcohol or the like as a dispersion medium may be used. Moreover, in this embodiment, although the example which uses a resin emulsion for formation of the resistant resin 5 was shown, this invention is not limited to this. For example, a resin solution other than the resin emulsion may be used. In this case, it is preferable that the solvent used for the resin solution can dissolve the resin used for the resistant resin 5 and does not dissolve the polyurethane resin used for the foam sheet 2. Moreover, in this embodiment, although the example which makes the diameter of the dispersed phase of a resin emulsion 1 micrometer or less was shown, this invention is not restrict | limited to this, resin emulsion (dispersed phase) is fully in the micropore 6 In addition, considering the permeation without uneven distribution, the diameter of the dispersed phase is preferably 1 μm or less.

  Furthermore, in this embodiment, although the example which uses a polyurethane resin for the foam sheet 2 was shown, this invention is not limited to this, As long as it is a polyurethane system, you may use another resin. For example, a polyurethane graft copolymer or a polyurethane block copolymer may be used.

  Furthermore, in the present embodiment, when the foamed sheet 2 is produced, the polyurethane resin is coagulated and regenerated, and then the film-forming substrate is peeled off, and the double-sided tape 7 is bonded. It is not limited. For example, after the polyurethane resin is solidified and regenerated, the double-sided tape 7 may be bonded without peeling off the film forming substrate. In addition, the polyurethane resin is solidified and regenerated on the film-forming substrate on which a resin having good adhesiveness has been applied in advance so that the film-forming resin and the film-forming substrate are not easily separated. Good. Further, when a non-woven fabric is used as the film forming substrate, it is difficult to peel off the film forming resin, and thus the film forming substrate may be dried as it is without being peeled off. Furthermore, as the double-sided tape 7, an adhesive may be applied to both sides of the base material, or it may be composed of only an adhesive without having a base material.

  Furthermore, in this embodiment, although the example which performs the buff process to the surface by the side of the grinding | polishing surface P of the foam sheet 2 at the grinding process process was shown, this invention is not limited to this. For example, a method capable of removing the skin layer with a slicing machine or the like may be used. Further, depending on the polishing application, the surface opposite to the polishing surface P may be subjected to grinding without leaving the skin layer, without applying the grinding treatment to the polishing surface P side of the foam sheet 2. In this case, the polishing pad 10 is suitable for finishing or the like because the skin layer plays a role of reducing the fine waviness of the object to be polished.

  Hereinafter, the Example of the foam sheet 2 manufactured according to this embodiment is described. In addition, it describes together about the foamed sheet of the comparative example manufactured for the comparison.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for producing the foam sheet 2. A polyurethane resin solution is prepared by adding 45 parts of DMF as a solvent and 40 parts of a DMF dispersion containing 30% by weight of carbon black as a pigment to 100 parts of a 30% by weight solution in which this polyurethane resin is dissolved. Was prepared. The obtained polyurethane resin solution was applied to a film-forming substrate and then coagulated and regenerated in a coagulating liquid. The base material for film formation was peeled from the polyurethane resin after coagulation regeneration, and after washing and drying, the skin layer side was ground so that the thickness was uniform. The operation of impregnating and drying the polyurethane resin after grinding with a resin emulsion in which chloroprene rubber (manufactured by Denki Kagaku Kogyo Co., Ltd., LM-50) is dispersed in water and the like is repeated three times, and the phase of the resistant resin 5 is formed. The foam sheet 2 of Example 1 was obtained. At this time, the filling rate of the resistant resin 5 was 30%.

(Example 2)
In Example 2, the foam sheet 2 of Example 2 was produced in the same manner as in Example 1 except that the number of repetitions in the impregnation / drying process was increased and the filling rate of the resistant resin 5 was set to 70%.

(Comparative Example 1)
In Comparative Example 1, a foamed sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the phase of the resistant resin 5 was not formed in the polyurethane resin after the grinding treatment. That is, the foam sheet of Comparative Example 1 is a conventional foam sheet.

(Comparative Example 2)
In Comparative Example 2, a foamed sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that the number of repetitions in the impregnation / drying process was reduced and the filling rate of the resistant resin 5 was 15%.

(Evaluation 1)
The tensile strength was measured about the foam sheet of each Example and the comparative example, respectively. In the measurement, a tensile universal testing machine (manufactured by A & D, RTC-1210A) was used. The measuring method was measured by a method according to Japanese Industrial Standard (JIS K6550). Thereafter, the foamed sheets of Examples and Comparative Examples were immersed in an aqueous sodium hydroxide solution having a liquid temperature of 40 ° C. and a pH of 14 for 8 hours. After the immersion, the tensile strength of each foamed sheet was measured again. The tensile strength retention before and after being immersed in the sodium hydroxide aqueous solution was calculated. The measurement results of the tensile strength and the tensile strength retention are shown in Table 1 below.

  As shown in Table 1, the tensile strength retention rate was 65% in Comparative Example 1 where the resistant resin 5 was not formed, and 68% in Comparative Example 2 where the filling rate of the resistant resin 5 was 15%. On the other hand, Example 1 in which the filling rate of the resistant resin 5 was 30% showed 85%, and Example 2 in which the filling rate of the resistant resin 5 was 70% showed 92%. That is, Comparative Example 1 showed the lowest value and Comparative Example 2 showed a higher value than Comparative Example 1, but showed a lower value than Examples 1 and 2. This is because the resistant resin 5 is not formed in Comparative Example 1 and the surface of the micropores 6 is not sufficiently covered with the resistant resin 5 in Comparative Example 2, so that both are in contact with the sodium hydroxide aqueous solution on the surface of the micropores 6. This is because the ratio is larger than those of Examples 1 and 2, and the deterioration of the foamed sheet, that is, the progress of hydrolysis cannot be suppressed. On the other hand, in Example 1, 2, the value higher than Comparative Example 1, 2 was shown, and all were 80% or more. This is considered to be because in Examples 1 and 2, the surface of the fine holes 6 was protected by the resistant resin 5, thereby suppressing the deterioration of the foam sheet 2. Thereby, Examples 1 and 2 are excellent in alkali resistance, and even if a shearing stress is applied to the foamed sheet at the time of polishing processing, it can be expected to perform polishing processing stable for a long period of time.

(Evaluation 2)
The tensile strength was measured about the foam sheet of each Example and the comparative example, respectively. In the measurement, a tensile universal testing machine (manufactured by A & D, RTC-1210A) was used. The measuring method was measured by a method according to Japanese Industrial Standard (JIS K6550). Thereafter, the foam sheets of Examples and Comparative Examples were immersed in an aqueous hydrochloric acid solution having a liquid temperature of 40 ° C. and pH 1 for 24 hours. After the immersion, the tensile strength of each foamed sheet was measured again. The tensile strength retention before and after immersion in the aqueous hydrochloric acid solution was calculated. The measurement results of the tensile strength and the tensile strength retention are shown in Table 1 below.

  As shown in Table 2, the tensile strength retention rate was 70% in Comparative Example 1 where the resistant resin 5 was not formed, and 73% in Comparative Example 2 where the filling rate of the resistant resin 5 was 15%. On the other hand, Example 1 in which the filling rate of the resistant resin 5 was 30% showed 85%, and Example 2 in which the filling rate of the resistant resin 5 was 70% showed 88%. That is, Comparative Example 1 showed the lowest value and Comparative Example 2 showed a higher value than Comparative Example 1, but showed a lower value than Examples 1 and 2. This is because the resistant resin 5 is not formed in the comparative example 1 and the surface of the micropores 6 is not sufficiently covered with the resistant resin 5 in the comparative example 2, so that the ratio of contact with the hydrochloric acid aqueous solution on the surface of the micropores 6 is high. It is considered to be larger than Examples 1 and 2 because the deterioration of the foamed sheet, that is, the progress of hydrolysis cannot be suppressed. On the other hand, in Example 1, 2, the value higher than Comparative Example 1, 2 was shown, and all were 70% or more. This is considered to be because in Examples 1 and 2, the surface of the fine holes 6 was protected by the resistant resin 5, thereby suppressing the deterioration of the foam sheet 2. Thereby, Examples 1 and 2 are excellent in acid resistance, and even if a shearing stress is applied to the foamed sheet at the time of polishing processing, it can be expected to perform stable polishing processing for a long period of time.

  Since the present invention provides a polishing pad that can perform stable polishing for a long period of time, it contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability.

2 Foam sheet 3 Foam 5 Resistant resin (second resin)
6 Fine hole 10 Polishing pad

Claims (7)

Used for polishing, has a foam structure in which a plurality of foams are formed by a wet film forming method, and a plurality of micropores having an average diameter smaller than the average diameter of the plurality of foams are continuously formed between the plurality of foams. In the polishing pad provided with the foamed sheet, the foamed sheet is formed of a polyurethane-based first resin, and has a higher acid resistance or alkali resistance than the first resin in the numerous micropores. is contained as the ratio of the volume of the second resin for suppressing the increase in the hardness of the polishing surface that can contact with the polishing compound is present in the second resin to the volume of the micropores is 30% or more The polishing pad is characterized in that the foam has a vertically long triangular shape rounded along the thickness direction of the foam sheet, and the second resin is a rubber material .   The second resin was formed so that a film was formed on the surface of the large number of micropores, and the volume ratio in the micropores was 70% or more with respect to the volume of the micropores. The polishing pad according to claim 1.   The polishing pad according to claim 2, wherein the second resin is formed by impregnating the foamed sheet with a resin emulsion.   The polishing pad according to claim 3, wherein the resin emulsion has a dispersed phase diameter of 1 μm or less.   The resin emulsion is silicone rubber, fluorine rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, styrene. The polishing pad according to claim 4, wherein the polishing pad is formed of at least one selected from butadiene rubber and butadiene rubber.   2. The polishing pad according to claim 1, wherein the foamed sheet has a tensile strength retention of 80% or more before and after being immersed in an aqueous sodium hydroxide solution having a liquid temperature of 40 ° C. and a pH of 14 for 8 hours.   2. The polishing pad according to claim 1, wherein the foamed sheet has a tensile strength retention of 80% or more before and after being immersed in an aqueous hydrochloric acid solution having a liquid temperature of 40 ° C. and a pH of 1 for 24 hours.

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