JP7111609B2 - Fiber composite polishing pad and method for polishing glass-based substrate using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polishing pad, more specifically, a fiber composite polishing pad preferably used as a polishing layer of a polishing pad for polishing glass-based substrates (optical products, silicon wafers, hard disks, etc.) or various metals.

Conventionally, as a method for polishing a glass-based substrate while maintaining high flatness, chemical mechanical polishing (CMP) is performed by pressing a glass-based substrate while dropping a slurry containing ceria particles onto a rotating polishing pad. )It has been known. As a polishing method used for such CMP, for example, Patent Document 1 and Patent Document 2 below use a polishing pad made of a polyurethane molding containing abrasive particles and a slurry containing ceria particles. Disclosed is a method of polishing with

When polishing a glass-based substrate or the like by CMP using a polishing pad made of a polyurethane molded body as disclosed in Patent Documents 1 and 2 and a slurry containing ceria particles, the polyurethane molded body has too high rigidity. Because the followability to the surface of the base material is poor, the slurry containing ceria particles and the surface of the glass base material are not compatible with each other, and polishing is caused by a chemical reaction between the surface of the ceria particles and the surface of the glass base material. Sufficient effect was not obtained. Further, when the contact pressure between the polishing pad and the glass-based substrate is increased in order to increase the contact between the ceria particles and the glass-based substrate, there is a problem that the flatness is lowered. Therefore, conventionally, a fiber composite sheet obtained by impregnating the internal voids of a nonwoven fabric with an elastic polymer has been preferably used as a polishing pad or the like for polishing that requires high-precision flatness. Patent Document 3 listed below discloses a polishing pad in which a non-woven fabric made of fiber bundles of ultrafine fibers is impregnated with an elastic polymer. Since such a polishing pad has lower rigidity and is more flexible than the polyurethane molded polishing pad that has been widely used, it has excellent conformability to the shape of the surface of the substrate to be polished, and therefore has excellent flattening performance. There was an advantage.

However, a polishing pad containing a non-woven fabric and a high-molecular elastic body has many voids, so ceria abrasive grains and the like tend to accumulate inside the polishing pad, resulting in a reduction in the polishing rate over time.

JP-A-6-114742 JP 2007-073796 A WO2010/016486

The present invention solves the above-described problem, that is, in the case of CMP-polishing the surface of a glass-based substrate or the like while dropping a slurry containing ceria particles, it has a high polishing rate and the polishing rate does not easily change over time. The purpose is to achieve polishing.

One aspect of the present invention is a fiber composite polishing pad composed of a nonwoven fabric of ultrafine fibers and a high molecular weight elastic material attached to the nonwoven fabric, wherein the cross section in the thickness direction is equally divided into three, and both surface layers are removed. In the case of an intermediate layer, Pc (intermediate layer porosity (Pb)/all layer porosity (Pa)) is 0.35 or less, the surface roughness (Sa) of the polished surface is 10 μm or more, and JISD hardness It is a fiber composite polishing pad characterized by being 50 or more.

Further, the fiber composite polishing pad of the present invention was mounted on a CMP polishing apparatus ("NF-300HP" manufactured by Nanofactor Co., Ltd.), and the platen rotation speed was 70 rotations/minute, the head rotation speed was 69 rotations/minute, and the polishing pressure was 130 g. / cm ² , while supplying Showa Denko's polishing slurry "SHOROX A-31" at a rate of 300 ml / min, the initial polishing when polishing a liquid crystal glass with a diameter of 4 inches (polishing time 0.5 It is preferable that the polishing rate ratio (Tb/Ta) of the polishing rate Tb in the later stage of polishing (after 6 hours of polishing) to the polishing rate Ta in the second stage of polishing (Tb/Ta) is 0.85 or more.
In the fiber composite polishing pad, the elastic polymer is non-porous, and has a bundle of ultrafine fibers made up of a plurality of long fibers forming a fiber bundle, and has an apparent density of 0.5 to 1. .2 g/cm ³ , and the mass ratio of the nonwoven fabric and the elastic polymer (nonwoven fabric/elastic polymer) is preferably 90/10 to 55/45.

The present invention also provides a polishing method comprising polishing the surface of a glass-based substrate by pressing the glass-based substrate against the fiber composite polishing pad while supplying slurry thereto.

According to the present invention, in the case of CMP-polishing the surface of an object to be polished (a glass-based substrate including an optical product) while dropping a slurry containing ceria particles, deposition of slurry abrasive grains on the pad is suppressed, and a high The polishing rate and the stability of the polishing rate over time can be maintained.

One embodiment of the fiber composite polishing pad according to the present invention will be described in detail below.

In the fiber composite polishing pad of the present invention, the ultrafine long fibers preferably have an average fineness of 0.01 to 0.9 dtex, more preferably 0.04 to 0.1 dtex. In the case of ultrafine fibers having such an average fineness, the ultrafine fiber bundles on the surface layer of the polishing pad are sufficiently separated during polishing, thereby improving the holding power of the slurry and improving the polishing efficiency and polishing uniformity. do. When the average fineness of the ultrafine fibers is less than 0.01 dtex, the fiber bundles are difficult to separate, and when the average fineness of the ultrafine fibers exceeds 0.9 dtex, the surface of the polishing pad becomes too rough and the polishing rate decreases. Otherwise, the stress applied to the surface during polishing of the glass-based base material becomes too high, and scratches tend to occur.

In addition, the average length of the ultrafine long fibers is not particularly limited, but it is preferably 100 mm or more, more preferably 200 mm or more from the viewpoint of easily increasing the fiber density of the entangled body and suppressing the fiber from coming off. If the length of the ultrafine fibers is too short, it tends to be difficult to increase the fiber density of the entangled body, and the fibers tend to come off easily during polishing. The upper limit is not particularly limited, and for example, in the case of containing a fiber entangled body derived from a nonwoven fabric manufactured by the spunbond method described later, as long as it is not physically cut, it is several meters, several hundred meters, several kilometers. Alternatively, longer fibers may be included.

Specific examples of the resin for forming the ultrafine fibers include polyethylene terephthalate (PET, saturated water absorption at _Tg 77°C and 50°C (hereinafter the same) 1% by mass), isophthalic acid-modified PET ( _Tg 67- 77°C, water absorption 1% by mass), sulfoisophthalic acid-modified PET ( _Tg 67-77°C, water absorption 1-3% by mass), polybutylene naphthalate ( _Tg 85°C, water absorption 1% by mass), polyethylene Aromatic polyester fibers formed from naphthalate (T _g 124° C., water absorption 1% by mass), etc.; terephthalic acid, nonanediol and methyloctanediol copolymer polyamide (T _g 125 to 140° C., water absorption 1 to 3 % by mass), and the like.

These may be used alone or in combination of two or more. In particular, modified PET such as PET and isophthalic acid-modified PET shrink significantly in the wet heat treatment process for forming ultrafine fibers from a web entangled sheet made of sea-island fibers, which will be described later. can be formed, the rigidity of the polishing sheet can be easily increased, and deterioration over time due to moisture during polishing is unlikely to occur.

The fiber bundle has a form in which a plurality of ultrafine fibers are bundled. Specifically, it is preferred that, for example, 5 to 200, more preferably 10 to 50, particularly 10 to 30 ultrafine fibers are present in a bundled manner. The appearance density of the entangled body can be increased by the presence of the ultrafine fibers forming an apparent fiber bundle.

The fiber entangled body preferably has an apparent density of 0.20 g/cm ³ or more, more preferably 0.40 to 0.80 g/cm ³ . When the polishing pad contains dense entanglements with a high apparent density, it is possible to maintain high rigidity during polishing, so that a glass substrate or the like can be polished with high flatness.

Next, the polymer elastic body impregnated and integrated with the entangled body of fiber bundles will be described.

The resin for forming the elastic polymer is not particularly limited, but specific examples thereof include, for example, polyurethane resins, polyamide resins, (meth)acrylic acid ester resins, and (meth)acrylic acid ester-styrene resins. Resin, (meth)acrylic acid ester-acrylonitrile resin, (meth)acrylic acid ester-olefin resin, (meth)acrylic acid ester-(hydrogenated) isoprene resin, (meth)acrylic acid ester-butadiene resin , styrene-butadiene-based resin, styrene-hydrogenated isoprene-based resin, acrylonitrile-butadiene-based resin, acrylonitrile-butadiene-styrene-based resin, vinyl acetate-based resin, (meth)acrylate-vinyl acetate-based resin, ethylene-vinyl acetate Examples include elastic bodies made of resins, ethylene-olefin resins, silicone resins, fluorine resins, polyester resins, and the like. These may be used alone or in combination of two or more.

As the elastic polymer, a hydrogen-bonding elastic polymer is particularly preferred because it has high binding properties to the ultrafine fibers. A resin forming a hydrogen-bonding elastic polymer is, for example, an elastic polymer that crystallizes or aggregates due to hydrogen bonding, such as polyurethane-based resin, polyamide-based resin, and polyvinyl alcohol-based resin. Since the hydrogen-bonding elastic polymer has high adhesiveness and excellent shape retention of the fiber entanglement, it is easy to prevent the fibers from coming off.

Among these, polyurethane-based resins are preferable because they have excellent adhesiveness to ultrafine fibers, increase the hardness of the polishing pad, and are excellent in stability over time during polishing. A case where a polyurethane-based resin is used as the elastic polymer will be described below in detail as a representative example.

Polyurethane-based resins include various polyurethane-based resins obtained by reacting a polymer polyol having an average molecular weight of 200 to 6000, an organic polyisocyanate, and a chain extender in a predetermined molar ratio.

Specific examples of polymer polyols include polyether-based polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly(methyltetramethylene glycol), and copolymers thereof; polybutylene adipate diol, polybutylene sebacate Diol, polyhexamethylene adipate diol, poly(3-methyl-1,5-pentylene adipate) diol, poly(3-methyl-1,5-pentylene sebacate) diol, isophthalic acid copolymer polyol, terephthalic acid copolymer Polyester-based polyols such as polymerized polyols, cyclohexanol copolymerized polyols, and polycaprolactone diols, and their copolymers; polyhexamethylene carbonate diols, poly(3-methyl-1,5-pentylene carbonate) diols, polypentamethylene carbonate diols , polytetramethylene carbonate diol, poly(methyl-1.8-octamethylene carbonate) diol, polynonamethylene carbonate diol, polycyclohexane carbonate diol, and copolymers thereof; and polyester carbonate polyol.

In addition, if necessary, polyfunctional alcohols such as trifunctional alcohols such as trimethylolpropane and tetrafunctional alcohols such as pentaerythritol, or ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol You may use together short chain alcohols, such as. These may be used alone or in combination of two or more.

As the polymer polyol, a polycarbonate-based polyol, particularly an amorphous polycarbonate-based polyol having a melting point of 0° C. or less, is contained in an amount of 60 to 100% by mass based on the total amount of the polyol component. It is preferable from the viewpoint of particularly excellent stability over time. In addition, it is preferable to use about 0.1 to 10% by mass of a polyalkylene glycol having 5 or less carbon atoms, particularly 3 or less carbon atoms, because the wettability with water is particularly good.

Specific examples of organic polyisocyanates include non-yellowing diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, and aliphatic or alicyclic diisocyanates such as 4,4′-dicyclohexylmethane diisocyanate; Aromatic diisocyanates such as diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate polyurethane, and the like are included. Moreover, you may use polyfunctional isocyanate, such as a trifunctional isocyanate and a tetrafunctional isocyanate, together as needed.

These may be used alone or in combination of two or more. Among these, 4,4′-dicyclohexylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate and xylylene diisocyanate have high adhesiveness to fibers. Moreover, it is preferable from the point that a polishing pad with high hardness can be obtained.

Specific examples of chain extenders include diamines such as hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, adipic acid dihydrazide, and isophthalic acid dihydrazide; triamines such as diethylenetriamine; tetramines such as triethylenetetramine; ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4 - diols such as cyclohexanediol; triols such as trimethylolpropane; pentaols such as pentaerythritol; aminoalcohols such as aminoethyl alcohol and aminopropyl alcohol;

These may be used alone or in combination of two or more. Among these, hydrazine, piperazine, hexamethylenediamine, isophoronediamine and its derivatives, and triamines such as ethylenetriamine can be used in combination of two or more to provide high adhesion to fibers and high hardness polishing. It is preferable from the point that a pad can be obtained. In addition, during the chain elongation reaction, along with the chain elongation agent, monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-aminobutanoic acid and 6-aminohexanoic acid; Monools may be used in combination.

In addition, carboxyl group-containing diols such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and 2,2-bis(hydroxymethyl)valeric acid may be used in combination to produce polyurethanes. By introducing an ionic group such as a carboxyl group into the skeleton of the system resin, wettability with water can be further improved.

In addition, in order to control the water absorption rate and storage modulus of the polyurethane-based resin, a cross-linking agent containing two or more functional groups in the molecule that can react with the functional groups of the monomer units that form the polyurethane, or a polyisocyanate-based A crosslinked structure may be formed by adding a self-crosslinking compound such as a compound or a polyfunctional block isocyanate compound.

Combinations of the functional group of the monomer unit forming the polyurethane resin and the functional group of the cross-linking agent include a carboxyl group and an oxazoline group, a carboxyl group and a carbodiimide group, a carboxyl group and an epoxy group, a carboxyl group and a cyclocarbonate group, and a carboxyl group. group and an aziridine group, a carbonyl group and a hydrazine derivative or a hydrazide derivative, and the like. Among these are a combination of a monomer unit having a carboxyl group and a cross-linking agent having an oxazoline group, a carbodiimide group or an epoxy group, a combination of a monomer unit having a hydroxyl group or an amino group and a cross-linking agent having a blocked isocyanate group, and a carbonyl A combination of a monomer unit having a group and a hydrazine derivative or a hydrazide derivative is particularly preferable from the viewpoint of easy cross-linking and excellent rigidity and abrasion resistance of the resulting polishing pad. From the viewpoint of maintaining the stability of the aqueous solution of the polyurethane resin, the crosslinked structure is preferably formed in the heat treatment step after applying the polyurethane resin to the entangled body of fibers. Among these, a carbodiimide group and/or an oxazoline group are particularly preferred because they are excellent in cross-linking performance and aqueous liquid pot life, and pose no problem in terms of safety. Examples of the cross-linking agent having a carbodiimide group include water-dispersible carbodiimide compounds such as “Carbodilite E-01”, “Carbodilite E-02” and “Carbodilite V-02” manufactured by Nisshinbo Co., Ltd. Examples of the cross-linking agent having an oxazoline group include water-dispersible oxazoline compounds such as "Epocross K-2010E", "Epocross K-2020E" and "Epocross WS-500" manufactured by Nippon Shokubai Co., Ltd. The amount of the cross-linking agent is preferably 1 to 20% by mass, more preferably 1.5 to 1% by mass, more preferably 2 to 10% by mass, based on the polyurethane resin. % is more preferred.

Also, from the viewpoint of increasing the adhesion to ultrafine fibers and increasing the rigidity of the fiber bundle, the content of the high-molecular polyol component in the polyurethane resin is 40 to 65% by mass, more preferably 45 to 60% by mass. is preferred.

Further, by introducing at least one hydrophilic group selected from the group consisting of a carboxyl group, a sulfonic acid group and a polyalkylene glycol group having 3 or less carbon atoms into the polyurethane resin, water absorption and hydrophilicity are adjusted. be able to. This makes it possible to improve the wettability of the polishing pad to the abrasive grain slurry during polishing. Such a hydrophilic group can be introduced into the polyurethane-based resin by copolymerizing a monomer component having a hydrophilic group as a monomer component for producing the polyurethane-based resin. The copolymerization ratio of such a monomer component having a hydrophilic group is 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, while minimizing swelling and softening due to water absorption. , is preferable from the point that the water absorption rate and wettability can be increased.

The polyurethane resin is preferably non-porous. The term "non-porous" means a state in which there are substantially no voids (closed cells) that are present in porous or sponge-like polyurethane resins. Specifically, it means that it is not a polyurethane-based resin having a large number of fine cells, such as that obtained by solidifying a solvent-based polyurethane. By bundling/restricting the ultrafine fibers or by making the polyurethane resin that binds the ultrafine fiber bundles together into a non-porous state, the binding force of the ultrafine fibers is increased, and the bending elastic modulus is improved. In addition, the polishing stability is improved, and since slurry debris and pad debris during polishing are less likely to accumulate in the voids, the polishing pad is less likely to wear, and a high polishing rate can be maintained for a long period of time. Furthermore, since the adhesion strength to the ultrafine fibers is increased, the occurrence of scratches due to the coming off of the fibers can be suppressed. Furthermore, since higher rigidity can be obtained, a polishing pad having excellent flattening performance can be obtained.

Polyurethane resins include penetrants, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, bulking agents, curing accelerators, antioxidants, ultraviolet absorbers, antifungal agents, foaming agents, polyvinyl alcohol, It may further contain a water-soluble polymer compound such as carboxymethyl cellulose, a dye, a pigment, inorganic fine particles, and the like.

In the polishing pad, it is preferable that the inside of the fiber bundle of the microfine fibers is impregnated with the macromolecular elastic body, and that part or most of the microfibers constituting the fiber bundle are restrained by the macromolecular elastic body. By constraining the fiber bundles with the elastic polymer, the fiber bundles are imparted with rigidity and high flattening performance can be obtained. In addition, it is possible to prevent the fibers from coming off and to prevent the abrasive grains from aggregating due to the coming off fibers, thereby suppressing scratches. In addition, it is preferable that the plurality of fiber bundles are bound together by a polymer elastic body existing outside the fiber bundles, from the viewpoint of improving the shape stability of the polishing pad and improving the polishing stability.

The bundled/restrained state of the ultrafine fibers and the binding state of the fiber bundles can be easily confirmed by an electron micrograph of the cross section of the fiber composite polishing pad.

The surface of the fiber composite polishing pad is subjected to a pad flattening treatment such as buffing, a seasoning treatment (conditioning treatment) before polishing using a dresser such as diamond, and a dressing treatment and brushing treatment during polishing. Ultrafine fibers are formed on the surface of the polishing pad by splitting or fibrillating the fiber bundles present in the polishing pad. The fiber density of the ultrafine fibers on the surface of the polishing pad is preferably 600/mm ² or more, more preferably 1000/mm ² or more, particularly 2000/mm ² or more. If the fiber density is too low, the slurry retention tends to decrease. Although the upper limit of the fiber density is not particularly limited, it is about 1,000,000 fibers/mm ² from the viewpoint of productivity. Further, the ultrafine fibers on the surface of the fiber composite polishing pad may or may not be raised. When the ultrafine fibers are raised, the surface of the polishing pad becomes softer, so that the effect of reducing scratches becomes higher. On the other hand, when the degree of nap of the ultrafine fibers is low, it is advantageous for applications where microflatness is important. In this way, it is preferable to appropriately select the surface state according to the application.

The ratio of the nonwoven fabric to the elastic polymer (nonwoven fabric/elastic polymer) in the fiber composite polishing pad is 90/10 to 55/45, more preferably 85/15 to 65/35 by mass. preferable. When the ratio of the nonwoven fabric to the elastic polymer is within the above range, the rigidity of the fiber composite polishing pad can be easily increased. Also, the density of the ultrafine fibers exposed on the surface of the fiber composite polishing pad can be sufficiently increased. As a result, polishing stability, polishing rate, and planarization performance can be sufficiently improved.

It is important that the JISD hardness of the fiber composite polishing pad is 50 or more, preferably 50-65. If the D hardness of the fiber composite polishing pad is less than 50, the flattening performance is lowered due to the decrease in rigidity. On the other hand, when the D hardness of the polishing pad exceeds 65, the rigidity becomes too high and scratches are likely to occur.

Moreover, the surface roughness (Sa) of the polishing surface of the fiber composite polishing pad is 10 μm or more. When the surface roughness (Sa) is less than 10 μm, the slurry pool is insufficient, and the polishing rate and polishing stability over time tend to decrease. Seasoning treatment (conditioning treatment) using a diamond dresser is a preferred method for achieving the above range.

The apparent density of the fiber composite polishing pad is preferably 0.5 g/cm ³ or more, more preferably 0.6 to 1.2 g/cm ³ from the viewpoint of maintaining high rigidity and high polishing rate.

[Method for producing polishing pad]
Next, an example of the manufacturing method of the fiber composite polishing pad will be described in detail.

The fiber composite polishing pad is produced by, for example, a web manufacturing process for manufacturing a long fiber web made of sea-island fibers obtained by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and a plurality of long fiber webs. A web entangling step of forming a web entangled sheet by overlapping and entangling them, a wet heat shrinkage treatment step of shrinking the web entangled sheet so that the area shrinkage rate is 40% or more by wet heat shrinking, a step of forming a fiber entangled body composed of ultrafine fibers by dissolving the water-soluble thermoplastic resin in the web entangled sheet in hot water; It can be obtained by a method for manufacturing a polishing pad comprising a step of impregnating and drying and solidifying an elastic polymer.

In such a production method, the web entangled sheet containing the long fibers is subjected to wet heat shrinkage, so that the web entangled sheet is reduced compared to the case where the web entangled sheet containing the short fibers is subjected to wet heat shrinkage. It can be shrunk to a large extent, which makes the fiber density of the ultrafine fibers dense. Then, by dissolving and extracting the water-soluble thermoplastic resin of the web entangled sheet, a fiber entangled body composed of ultrafine fiber bundles is formed. At this time, voids are formed in portions where the water-soluble thermoplastic resin is dissolved and extracted. By impregnating the voids with an aqueous liquid of the elastic polymer and drying and solidifying the ultrafine fibers constituting the ultrafine fiber bundle, the ultrafine fiber bundles are also bundled together. In this way, a highly rigid polishing pad having a high fiber density and bundled microfibers can be obtained.

Each step will be described in detail below.

(1) Web Manufacturing Process In this process, first, a long fiber web made of sea-island fibers obtained by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin is manufactured.

The islands-in-the-sea fiber is obtained by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin having low compatibility with the water-soluble thermoplastic resin, and then combining them. Ultrafine fibers are formed by dissolving or decomposing and removing the water-soluble thermoplastic resin from such islands-in-the-sea fibers. The thickness of the islands-in-the-sea fiber is preferably 0.5 to 3 dtex from the viewpoint of industrial efficiency.

In the present embodiment, sea-island fibers will be described in detail as composite fibers for forming ultrafine fibers. good too.

As the water-soluble thermoplastic resin, a thermoplastic resin that can be dissolved or decomposed and removed with water, an alkaline aqueous solution, an acidic aqueous solution, or the like, and that can be melt-spun is preferably used. Specific examples of such water-soluble thermoplastic resins include, for example, polyvinyl alcohol-based resins (PVA-based resins) such as polyvinyl alcohol and polyvinyl alcohol copolymers; Modified polyester contained as a component; polyethylene oxide and the like. Among these, PVA-based resins are particularly preferably used for the following reasons.

When islands-in-the-sea type fibers containing a PVA-based resin as a water-soluble thermoplastic resin component are used, the ultrafine fibers formed by dissolving the PVA-based resin are greatly crimped. As a result, a fiber entangled body having a high fiber density can be obtained. Further, in the case of using sea-island fibers having a PVA-based resin as a water-soluble thermoplastic resin component, when the PVA-based resin is dissolved, the ultrafine fibers and polymeric elastic bodies formed are not substantially decomposed or dissolved. , physical properties of ultrafine fibers and polymeric elastomers are less likely to deteriorate. Furthermore, the environmental load is also small. Further, even if a trace amount remains, there is little adverse effect on the polishing performance, and conversely, there is a tendency to increase the wettability of the polishing pad. A preferable ratio of the PVA-based resin remaining in the polishing pad is about 0.01 to 0.2% by mass, more preferably about 0.02 to 0.1% by mass.

As the water-insoluble thermoplastic resin, a thermoplastic resin that is not dissolved or decomposed and removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like, and that can be melt-spun is preferably used.

As a specific example of the water-insoluble thermoplastic resin, various thermoplastic resins represented by the above-described polyester fibers used for forming the ultrafine fibers constituting the polishing pad can be used.

The water-insoluble thermoplastic resin may contain various additives. Specific examples of additives include catalysts, anti-coloring agents, heat-resistant agents, flame retardants, lubricants, antifouling agents, fluorescent brightening agents, matting agents, coloring agents, gloss modifiers, antistatic agents, and fragrances. , deodorants, antibacterial agents, anti-mite agents, inorganic fine particles, and the like.

Next, a method of melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin to form islands-in-the-sea fibers and forming a long fiber web from the islands-in-the-sea fibers thus obtained will be described in detail.

The long fiber web is obtained, for example, by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin to form a composite, stretching the composite by a spunbond method, and depositing the composite. By forming a web by the spunbond method in this way, a long fiber web composed of islands-in-the-sea type fibers is obtained, which has a high fiber density and good shape stability, with little fiber dropout. In addition, the long fibers are fibers manufactured without going through a cutting process as in the case of manufacturing short fibers.

In manufacturing islands-in-the-sea fibers, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melt-spun and combined. The mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is preferably in the range of 5/95 to 50/50, more preferably 10/90 to 40/60. When the mass ratio of the water-soluble thermoplastic resin and the water-insoluble thermoplastic resin is within this range, a high-density fiber entangled body can be obtained, and the formability of ultrafine fibers is also excellent.

A method for forming a long fiber web by a spunbond method after combining a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin by melt spinning will be described in detail below.

First, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melt-kneaded by separate extruders, and strands of the molten resin are extruded simultaneously from different spinnerets. Then, after the extruded strands are compounded by a compound nozzle, the strands are ejected from the nozzle holes of the spinning head to form sea-island fibers. In melt composite spinning, the number of islands in the sea-island type fiber should be 4 to 4,000 islands/fiber, or further 10 to 1,000 islands/fiber, from the viewpoint of obtaining a fiber bundle with a small single fiber fineness and a high fiber density. preferable.

The islands-in-the-sea type fiber is cooled by a cooling device, and then stretched by a high-speed air stream at a speed corresponding to a take-up speed of 1000 to 6000 m/min using a suction device such as an air jet nozzle so as to obtain a desired fineness. A filament web is then formed by depositing the drawn bicomponent fibers onto a moving collecting surface. At this time, the deposited filament web may be partially crimped if necessary. It is preferable from the standpoint of industrial efficiency that a uniform fiber entangled body can be obtained when the basis weight of the fiber web is in the range of 20 to 500 g/m ² .

(2) Web entanglement step Next, a web entanglement step of forming a web entangled sheet by stacking and entangling a plurality of the obtained filament webs.

A web entangled sheet is formed by subjecting a long fiber web to entanglement treatment using a known nonwoven fabric manufacturing method such as needle punching or high-pressure water jet treatment. As a representative example, the entangling process by needle punching will be described in detail below.

First, a long fiber web is provided with a silicone-based oil such as an anti-needle-breaking oil, an anti-static oil, or an entanglement-enhancing oil, or a mineral oil-based oil. In order to reduce the unevenness in weight per unit area, two or more fiber webs may be overlapped with a cross-lapper and an oil agent may be applied.

After that, an entangling treatment is performed to three-dimensionally entangle the fibers by, for example, needle punching. By performing the needle punching process, a web entangled sheet having a high fiber density and in which fibers are less likely to come off can be obtained. ^The basis weight of the web entangled sheet is appropriately selected according to the desired thickness of the polishing pad. It is preferable because it is excellent in

Needle conditions such as the type and amount of oil and needle shape, needle depth, and number of needle punches are appropriately selected so as to increase the delamination force of the web entangled sheet. The number of barbs is preferably as large as possible within a range that does not cause needle breakage. Specifically, the number is selected from 1 to 9 barbs, for example. It is preferable that the needle depth be set so that the barbs penetrate to the surface of the superimposed webs and within a range in which the pattern after needle punching does not appear strongly on the web surface. The number of needle punches is adjusted depending on the shape of the needle, the type and amount of oil used, etc. Specifically, it is preferably 500 to 5000 punches/cm ² . In addition, the entanglement treatment is performed so that the basis weight after the entanglement treatment is 1.2 times or more, further 1.5 times or more, in terms of the mass ratio of the basis weight before the entanglement treatment. It is preferable from the viewpoint that a highly entangled body of fibers can be obtained and the loss of fibers can be reduced.

The delamination force of the web entangled sheet is 2 kg/2.5 cm or more, and further, 4 kg/2.5 cm or more. It is preferable from the point that a fiber entangled body can be obtained. Note that the delamination force is a measure of the degree of three-dimensional entanglement. If the delamination force is too small, the fiber density of the fiber entanglement is not sufficiently high. Although the upper limit of the delamination force of the entangled nonwoven fabric is not particularly limited, it is preferably 30 kg/2.5 cm or less from the viewpoint of entangling treatment efficiency.

(3) Wet heat shrink treatment step Next, a wet heat shrink treatment step for increasing the fiber density and degree of entanglement of the web entangled sheet by subjecting the web entangled sheet to wet heat shrinkage. In this step, the web entangled sheet containing long fibers is subjected to wet heat shrinkage, so that the web entangled sheet is shrunk more than the case where the web entangled sheet containing short fibers is subjected to wet heat shrinkage. which results in a particularly high fiber density of the microfibers. The wet heat shrink treatment is preferably performed by steam heating. As steam heating conditions, it is preferable to perform heat treatment at an ambient temperature of 60 to 130° C. and a relative humidity of 80% or higher, preferably 90% or higher, for 60 to 600 seconds. If the relative humidity is too low, moisture in contact with the fibers dries quickly, which tends to result in insufficient shrinkage.

In the wet heat shrink treatment, the web entangled sheet is preferably shrunk so that the area shrinkage ratio is 40% or more, more preferably 43% or more. A high fiber density can be obtained by shrinking at such a high shrinkage rate. Although the upper limit of the area shrinkage rate is not particularly limited, it is preferably about 80% or less from the viewpoint of shrinkage limit and processing efficiency.

The area shrinkage rate (%) is calculated by the following formula.
(Area of sheet surface before shrinkage treatment−Area of sheet surface after shrinkage treatment)/Area of sheet surface before shrinkage treatment×100. The area means the average area of the areas of both surfaces (front surface and back surface) of the sheet.

The web entangled sheet subjected to the wet heat shrinkage treatment in this way may be further increased in fiber density by hot rolls or hot press at a temperature equal to or higher than the thermal deformation temperature of the islands-in-the-sea fibers. As for the change in the basis weight of the web entangled sheet before and after the wet heat shrinking treatment, the basis weight after the shrinking treatment is 1.2 times (mass ratio) or more as compared to the basis weight before the shrinking treatment. It is preferably 5 times or more, 4 times or less, and more preferably 3 times or less.

(4) Fiber bundle binding step Before performing the ultrafine fiberization treatment of the web entangled sheet, for the purpose of improving the morphological stability of the web entangled sheet and reducing the porosity of the resulting polishing pad, The fiber bundles may be bound in advance by impregnating the shrink-treated web entangled sheet with an aqueous liquid of the polymeric elastomer and drying and solidifying the web entangled sheet.

In this step, the shrink-treated web entangled sheet is impregnated with an aqueous liquid of the first polymeric elastomer, dried and solidified to fill the web entangled sheet with the polymeric elastomer. The polymeric elastomer can be formed by impregnating the polymeric elastomer in an aqueous liquid state and drying and solidifying. The aqueous liquid of the first elastic polymer has a high concentration, a low viscosity, and an excellent impregnation permeability, so that it is easy to be highly filled. It also has excellent adhesion to fibers. Therefore, the elastic polymer filled in this step firmly binds the islands-in-the-sea long fibers.

Also, in this step, the water in the aqueous solution of the first elastic polymer impregnated in the web entangled sheet gels at a low temperature. Therefore, it is possible to prevent the migration of the elastic polymer in the web entangled sheet to the surface layer as the evaporation of water progresses. When the emulsion in the nonwoven fabric migrates, the elastic polymer is unevenly distributed in the vicinity of the surface layer of the web entangled sheet, and the elastic polymer in the vicinity of the middle layer decreases, and voids tend to remain in the vicinity of the middle layer. If voids remain in the vicinity of the middle layer, polishing slurry abrasive grains tend to deposit on the middle layer, and the stability of the polishing rate over time decreases. Such migration is suppressed by adding a gelling agent to the aqueous solution of the first elastic polymer to gel the aqueous solution of the first elastic polymer before drying.

As the gelling agent, any water-soluble salt can be used without particular limitation as long as it changes the pH of the aqueous solution of the elastic polymer to the extent that the particles of the aqueous solution of the elastic polymer are gelled by heating. Specific examples thereof include monovalent or divalent inorganic salts such as sodium sulfate, ammonium sulfate, sodium carbonate, calcium chloride, calcium sulfate, calcium nitrate, zinc oxide, zinc chloride, magnesium chloride, potassium chloride, and potassium carbonate. , sodium nitrate, lead nitrate and the like.

Then, the web-entangled sheet is impregnated with the aqueous solution of the first elastic polymer and then heated to gel the aqueous solution of the first elastic polymer in the web-entangled sheet. As the heating conditions for such gelation, for example, conditions such as holding at 40 to 90° C., more preferably 50 to 80° C. for about 0.5 to 5 minutes are preferably used. Heating with steam is preferable because the inner layer can be uniformly heated while suppressing the migration of the aqueous solution of the elastic polymer due to rapid evaporation of water from the surface layer.

After gelling the aqueous solution of the first elastic polymer, the elastic polymer is solidified by heating and drying.

Heat-drying includes a method of heat-drying in a drying apparatus such as a hot air dryer, a method of heat-drying in a dryer after infrared heating, and the like. Conditions for heat drying include, for example, conditions such that the maximum temperature is 130 to 160° C., further 135 to 150° C., and heating is performed for 2 to 10 minutes. Drying by heating evaporates the water in the aqueous solution of the first elastic polymer and uniformly agglomerates the elastic polymer, thereby uniformly providing the elastic polymer in the web entangled sheet even in the thickness direction. Pc (porosity of intermediate layer (Pb)/porosity of all layers (Pa)) can be 0.35 or less. By setting Pc to 0.35 or less, there are few voids in the intermediate portion with respect to the front and back surfaces of the polishing pad. became possible to prevent It is important for Pc to be 0.35 or less, preferably 0.34.

The aqueous liquid of the elastic polymer is an aqueous solution obtained by dissolving the components forming the elastic polymer in an aqueous medium, or an aqueous dispersion obtained by dispersing the components forming the elastic polymer in an aqueous medium. Aqueous dispersions include suspension dispersions and emulsified dispersions. In particular, from the viewpoint of excellent water resistance, it is more preferable to use an aqueous dispersion. When the average particle size of the aqueous dispersion is 0.01 to 0.2 μm, the water resistance is improved, the stability over time during polishing is likely to be improved, and the binding property of the fiber bundle is improved. As a result, the rigidity of the polishing pad is moderate.

For example, in the method of making a polyurethane resin into an aqueous solution or aqueous dispersion, a monomer unit having a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group is added to impart dispersibility in an aqueous medium to the polyurethane resin. Alternatively, a surfactant may be added to the polyurethane resin to emulsify or suspend it. In addition, such a water-based elastic polymer is excellent in wettability with water, and is therefore excellent in holding a large amount of abrasive grains uniformly.

Specific examples of surfactants used for emulsification or suspension include sodium lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene tridecyl ether acetate, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate, and dioctylsulfosuccinic acid. Anionic surfactants such as sodium; nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene-polyoxypropylene block copolymers Examples include surfactants. A so-called reactive surfactant having reactivity may also be used. In addition, by appropriately selecting the cloud point of the surfactant, it is possible to impart heat-sensitive gelling properties to the polyurethane resin. However, when a large amount of surfactant is used, it may adversely affect the polishing performance and its stability over time.

In this step, in order to form the elastic polymer, it is preferable to use an aqueous solution of the elastic polymer instead of using an organic solvent solution of the elastic polymer which is generally used in the past. By using the aqueous liquid of the polymeric elastomer in this way, it is possible to impregnate the resin liquid containing the polymeric elastomer at a higher concentration.

Examples of the method for impregnating the web entangled sheet with the aqueous liquid of the polymeric elastomer include methods using a dip nip, a knife coater, a bar coater, or a roll coater.

By drying the web entangled sheet impregnated with the aqueous liquid of the elastic polymer, the elastic polymer can be coagulated. Examples of the drying method include a method of heat-treating in a drying device at 50 to 200° C., a method of heat-treating in a dryer after infrared heating, and the like.

(5) Ultrafine Fiber Forming Step Next, an ultrafine fiber forming step, which is a step of forming ultrafine fibers by dissolving a water-soluble thermoplastic resin in hot water.

This step is a step of forming ultrafine fibers by removing the water-soluble thermoplastic resin. At this time, voids are formed in the portions of the web entangled sheet where the water-soluble thermoplastic resin has been dissolved and extracted. Then, in the step of filling the elastic polymer into the voids, which will be described later, the ultrafine fibers are bound by filling the elastic polymer.

Ultrafine fiberization is performed by heat-treating the web entangled sheet or the composite of the web entangled sheet and the elastic polymer with water, an alkaline aqueous solution, an acidic aqueous solution, or the like, thereby converting the water-soluble thermoplastic resin. It is a process of dissolving and removing or decomposing and removing.

As a specific example of the hot water heat treatment conditions, for example, as the first step, after immersing in hot water of 65 to 90 ° C. for 5 to 300 seconds, as the second step, immersing in hot water of 85 to 100 ° C. for 100 to 600 seconds. Further, in order to increase the dissolution efficiency, nip treatment with rolls, high-pressure water flow treatment, ultrasonic treatment, shower treatment, stirring treatment, rubbing treatment, or the like may be performed as necessary.

In this step, when forming the ultrafine fibers by dissolving the water-soluble thermoplastic resin from the islands-in-the-sea fibers, the ultrafine fibers are greatly crimped. Since the fiber density is increased by this crimping, a high-density fiber entangled body can be obtained.

(6) A step of hot-pressing the ultrafine fiber-formed body to reduce the void volume of the ultrafine fiber-formed body and to increase the rigidity.

Voids present inside the ultrafine fiber forming body reduce hardness and uniformity of hardness. In this step, voids are reduced by hot-pressing the ultrafine fiber formed body. By reducing the voids in this way, the apparent density of the ultrafine fiber forming body can be increased, the JISD hardness can be increased to 50 or more, and the uniformity and rigidity of hardness and hardness can be increased. As the hot press treatment conditions, the temperature at which the ultrafine fibers and the elastic polymer are not decomposed is preferably such that the metal rolls heated to 150 to 170° C. are pressed at a linear pressure of 30 to 100 kg/cm.

(7) Polymer elastic body filling step Next, by filling the inside of the ultrafine fiber bundle formed from ultrafine fibers with a macromolecular elastic body, the ultrafine fibers are constrained, and the ultrafine fiber bundles are constrained and the ultrafine fibers are A process of binding the bundles together will be described.

In the ultrafine fiber forming step (5), the islands-in-sea fibers are subjected to ultrafine fiberization treatment to remove the water-soluble thermoplastic resin and form voids inside the ultrafine fiber bundle. In this step, by filling such voids with an elastic polymer, Pc (intermediate layer porosity (Pb)/all layer porosity (Pa)) can be made 0.35 or less. By binding the ultrafine fiber bundles together, the porosity of the fiber composite polishing pad can be reduced, the JISD hardness can be increased to 50 or more, and the flexural modulus can be improved. When the ultrafine fibers form a fiber bundle, the ultrafine fibers are more likely to be bundled and bound because the aqueous liquid of the elastic polymer is likely to be impregnated by capillary action.
Furthermore, the above pad was mounted on a CMP polishing apparatus (“NF-300HP” manufactured by Nanofactor Co., Ltd.) under the conditions of platen rotation speed of 70 rotations/minute, head rotation speed of 69 rotations/minute, and polishing pressure of 130 g/cm ² . Polishing speed Ta at the initial stage of polishing (after 0.5 hours of polishing) when polishing liquid crystal glass with a diameter of 4 inches while supplying Showa Denko polishing slurry "SHOROX A-31" at a rate of 300 ml / min. The polishing rate ratio (Tb/Ta) of the polishing rate Tb in the latter stage of polishing (after 6 hours of polishing) to the polishing rate Tb is preferably 0.85 or more, and more preferably 0.90 or more. By making it 0.85 or more, a long-life pad can be obtained, and a stable polishing rate can be obtained from the initial stage of polishing to the final stage of polishing.

The aqueous liquid and gelling agent of the second elastic polymer used in this step are the same as the aqueous liquid and gelling agent of the elastic polymer described in the fiber bundle binding step (4). . Note that they may have different compositions.

As a method for filling the inside of the microfine fiber bundle formed from the microfine fibers with the second elastic polymer in this step, the same method as used in the fiber bundle binding step (4) can be applied. Thus, a fiber composite polishing pad is formed.

[Post-processing of fiber composite polishing pad]
The resulting intermediate polishing pad is treated as described below to obtain a fiber composite polishing pad.

The flattening treatment is a treatment for separating the bundled ultrafine fibers by applying a mechanical frictional force or an abrasive force to the surface with sandpaper or the like in order to make the obtained intermediate polishing pad have a predetermined thickness. . The fiber composite polishing pad is preferably ground to a thickness of about 0.5 to 3 mm. In addition, in order to obtain a surface having an arithmetic mean surface roughness (Sa) of 10 μm or more on the polished surface by the raising treatment described later, coarse to medium grains such as #60 to #240, and further #60 to #120 are used. of sandpaper is preferably used.

The raising treatment is a seasoning treatment (conditioning treatment) before polishing using a dresser such as diamond. It is preferable to use a coarse to medium diamond dresser such as #325 or #60 to #270.

The surface treatment is a process of forming grid-like, concentric, spiral-like grooves or holes on the surface of the polishing pad in order to adjust the retention and discharge properties of the abrasive grain slurry.

In the cleaning treatment, impurities such as particles and metal ions adhering to the obtained polishing pad are washed with cold water or warm water, or an aqueous solution or solvent containing an additive having a cleaning action such as a surfactant is used. It is a processing such as washing with

EXAMPLES Hereinafter, the present invention will be specifically described with reference to Examples. In addition, the present invention is not limited at all by the examples.

[Evaluation method]
First, the evaluation method in the present example will be collectively described.

(1) Confirmation of the average fineness of the ultrafine fibers and the bundled state of the ultrafine fibers inside the fiber bundle The obtained fiber composite polishing pad is cut in the thickness direction using a cutter blade to form a cut surface in the thickness direction. did. Then, the obtained cut surface was dyed with osmium oxide. Then, the cut surface was observed with a scanning electron microscope (SEM) at a magnification of 500 to 1000, and the image was taken. Then, the cross-sectional area of the ultrafine fibers present in the cut surface was obtained from the obtained image. A value obtained by averaging 100 randomly selected cross-sectional areas was defined as the average cross-sectional area, and the average fineness was calculated from the density of the resin forming the fiber. Also, the bundled state of the ultrafine fibers inside the fiber bundle was confirmed from the image.

(2) Apparent Density of Fiber Composite Polishing Pad A value obtained by dividing the mass (g/cm ² ) per unit area of the fiber composite polishing pad by the thickness (cm) was defined as the apparent density (g/cm ³ ). Then, the apparent density was determined by measuring the apparent density of arbitrary 10 points of the fiber composite polishing pad, and calculating the arithmetic mean of the apparent density. The thickness was measured under a load of 240 gf/cm ² according to JISL1096.

(3) JISD Hardness of Surface of Fiber Composite Polishing Pad The D hardness of the surface of the fiber composite polishing pad was measured according to JISK7311. Specifically, the D hardness of the surface of the fiber composite polishing pad is obtained by stacking four fiber composite polishing pads with a thickness of about 1.5 mm, measuring the hardness at three points evenly in the width direction, and taking the average of the hardness of the fiber composite polishing pad. The JISD hardness of the surface of the polishing pad was used.

(4) Surface roughness of fiber composite polishing pad (arithmetic mean roughness: Sa)
The surface roughness (arithmetic mean roughness: Sa) of the fiber composite polishing pad was measured using a surface/layer cross-sectional shape measuring system "VertScan 2.0 (R5500G)" manufactured by Ryoka System Co., Ltd. The measurement points were five randomly selected points, and the above surface roughness was analyzed from the obtained images.

(5) Polishing rate After sticking an adhesive tape to the back surface of the fiber composite polishing pad cut into a circular shape, it was mounted on a CMP polishing apparatus (“NF-300HP” manufactured by Nanofactor Co., Ltd.). Next, under conditions of a platen rotation speed of 70 rotations/minute, a head rotation speed of 69 rotations/minute, and a polishing pressure of 130 g/cm ² , a polishing slurry “SHOROX A-31” manufactured by Showa Denko Co., Ltd. was supplied at a rate of 300 ml/minute. A liquid crystal glass with a diameter of 4 inches was polished for 0.5 hours. Then, the thickness of the polished liquid crystal glass was measured at 25 arbitrary points in the plane of the liquid crystal glass, and the polishing rate (nm/min) was obtained by dividing the polished thickness at each point by the polishing time.

Then, the polishing rate was obtained every 0.5 hours, each polishing rate was obtained up to a cumulative 6 hours, and the polishing rate ratio was obtained by the following formula. A smaller value indicates better stability of the polishing rate over time and a longer pad life.

Polishing rate ratio=0.5 hours after polishing/6 hours after polishing

(6) Cross-sectional porosity of fiber composite polishing pad (measurement of porosity Pa of all layers, porosity Pb of intermediate layer, and calculation of Pc (Pb/Pa))
A porosity is calculated|required as follows. A cross section in the thickness direction of the fiber composite polishing pad is photographed at 100x using a scanning electron microscope (SEM). Then, the obtained photograph was equally divided into three sections in the thickness direction, and both surface layers were removed. Using image analysis software ImageJ, the image was binarized to identify the voids, and the total area of the voids was calculated as the void volume. Then, the values obtained by dividing the obtained void amounts of the intermediate layer and all layers by the cross-sectional area of each region are defined as the void ratio (Pb) of the intermediate layer and the void ratio (Pa) of the entire layer, respectively, and Pc (intermediate layer void ratio (Pb)/porosity (Pa) of all layers).

[Example 1]
Water-soluble thermoplastic polyvinyl alcohol-based resin (hereinafter referred to as PVA-based resin) and isophthalic acid-modified polyethylene terephthalate having a degree of modification of 6 mol% (hereinafter referred to as modified PET) at a ratio of 25:75 (mass ratio). A sea-island type fiber was formed by extruding from a melt composite spinning nozzle at . The spinneret for melt composite spinning had 64 islands/fiber and the spinneret temperature was 260°C. Then, by adjusting the spinning speed to 3700 m/min and collecting long fibers with an average fineness of 2.0 dtex on a net, a spunbond sheet (long fiber web) with a basis weight of 40 g/m ² is obtained. was taken.

Twelve spunbond sheets thus obtained were laminated by cross lapping to prepare a laminated web having a total basis weight of 480 g/m ² . Then, a needle breakage preventing oil was sprayed on the resulting laminated web. Next, the lapped web is needle-punched at 2000 punches/cm ² and entangled using a needle with one barb and a needle count of 42 and a needle with a number of barbs and a needle count of 42 and 6. Thus, a web entangled sheet was obtained. The basis weight of the resulting web entangled sheet was 750 g/m ² . Also, the area shrinkage rate due to needle punching was 38%.

The resulting web entangled sheet was then steamed for 90 seconds at 70° C. and 90% RH. The area shrinkage rate at this time was 47%. Then, it was dried in an oven at 120°C and then hot-pressed at 120°C to obtain a web entangled sheet having a basis weight of 1300 g/m ² , an apparent density of 0.57 g/cm ³ and a thickness of 2.3 mm. .

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastomer A (solid concentration: 20% by mass) as a first polyurethane elastomer. Polyurethane elastomer A was composed of amorphous polycarbonate polyol and polyalkylene glycol having 2 to 3 carbon atoms at a molar ratio of 99.7:0.3, and a carboxyl group-containing monomer at a weight ratio of 1.1. It is an amorphous polycarbonate-based non-yellowing polyurethane resin containing 5 wt %. Further, the aqueous dispersion of polyurethane elastomer A contains 3 parts by mass of ammonium sulfate as a gelling agent.

Next, the web entangled sheet impregnated with the first polyurethane elastic is heated in an atmosphere of 90°C and 50% RH to gel the first polyurethane elastic, and then dried at 150°C. , a basis weight of 1490 g/m ² , an apparent density of 0.75 g/cm ³ and a thickness of 2.0 mm.

Next, the web entangled sheet filled with the polyurethane elastic body A is continuously nipped for 10 minutes while being immersed in hot water at 95° C. to dissolve and remove the PVA resin and dry. The polyurethane elastic body A and the fiber entangled body, which have an average fineness of 0.04 dtex, a basis weight of 1180 g/m ² , an apparent density of 0.59 g/cm ³ and a thickness of 2.0 mm, are formed by hot-pressing at ℃. A complex of

Then, the composite was impregnated with an aqueous dispersion of polyurethane elastomer B (solid concentration: 20% by mass) as a second polyurethane elastomer. Polyurethane elastomer B was obtained from a composition containing amorphous polycarbonate polyol as a polyol component and 1.7% by mass of a carboxyl group-containing monomer. It is a polyurethane resin in which a crosslinked structure is formed by adding parts by mass and heat-treating. Further, the aqueous dispersion of polyurethane elastomer B contains 3 parts by mass of ammonium sulfate as a gelling agent.

Next, similarly to the first polyurethane elastic, the impregnated web entangled sheet is heated in an atmosphere of 90°C and 50% RH to gel the second polyurethane elastic, and further at 150°C. A fiber composite polishing pad precursor was obtained by drying. The resulting polishing pad precursor had a basis weight of 1430 g/m ² , an apparent density of 0.79 g/cm ³ and a thickness of 1.8 mm. The mass ratio between the fiber entangled body and the polyurethane elastic body was 77/23, and the ratio between the polymeric elastic body A and the polymeric elastic body B was 51:49.

The resulting polishing pad precursor was ground using sandpaper for surface flattening to a basis weight of 1200 g/m ² , an apparent density of 0.80 g/cm ³ and a thickness of 1.5 mm. , and a circular polishing pad having a diameter of 30 cm was formed on the surface thereof with grooves having a width of 2.0 mm and a depth of 1.0 mm at intervals of 15.0 mm. Furthermore, a seasoning treatment (conditioning treatment) was performed using a diamond dresser prior to polishing, so that the pad surface had an arithmetic mean surface roughness (Sa) of 19.7 μm. And polishing evaluation was implemented by the above-mentioned method. When the microscopic image of the obtained cross section was observed, it was observed that not only the ultrafine fibers forming the outer periphery of the fiber bundle but also the ultrafine fibers inside were adhered and integrated by the elastic polymer. As the slurry for polishing, a polishing slurry "SHOROX A-31" manufactured by Showa Denko KK containing 7% by mass of ceria was used. Table 1 shows the results.

[Example 2]
A polishing pad was prepared in the same manner as in Example 1, except that the PVA-based resin of Example 1 was removed by dissolution and dried, followed by hot pressing at 150° C. and impregnation with an aqueous dispersion of polyurethane elastomer B by the methods described below. was prepared and polishing evaluation was performed. Table 1 shows the results. By heat-pressing with a weaker heat-press than in Example 1, a composite of the polyurethane elastic body A and the fiber entangled body having a basis weight of 1130 g/m ² , an apparent density of 0.59 g/cm ³ , and a thickness of 1.9 mm got a body Also, the solid content concentration of the aqueous dispersion of the polyurethane elastomer B was changed to 23% by mass. Then, the impregnated web entangled sheet was heated at 90° C. and 50% RH to gel the second polyurethane elastic body, and further dried at 150° C. to obtain a basis weight of 1380 g/m2. ² , a fiber composite polishing pad precursor having an apparent density of 0.77 g/cm ³ and a thickness of 1.8 mm was obtained.
The obtained polishing pad precursor was subjected to the steps after the surface flattening in the same manner as in Example 1 to obtain a circular polishing pad. Furthermore, a seasoning treatment (conditioning treatment) was performed using a diamond dresser before polishing, so that the pad surface had an arithmetic mean surface roughness (Sa) of 11.5 μm. And polishing evaluation was implemented by the above-mentioned method. When the microscopic image of the obtained cross section was observed, it was observed that not only the ultrafine fibers forming the outer periphery of the fiber bundle but also the ultrafine fibers inside were adhered and integrated by the elastic polymer. As the slurry for polishing, a polishing slurry "SHOROX A-31" manufactured by Showa Denko KK containing 7% by mass of ceria was used. Table 1 shows the results.

[Comparative Example 1]
A polishing pad was produced in the same manner as in Example 2 except that the seasoning treatment (conditioning treatment) time before polishing using the diamond dresser of Example 1 was changed, and polishing evaluation was performed. The arithmetic mean surface roughness (Sa) of the pad surface after seasoning treatment (conditioning treatment) before polishing was 8.2 μm. Table 1 shows the results.

[Comparative Example 2]
A polishing pad was prepared in the same manner as in Example 2, except that no gelling agent was added to the aqueous dispersion of polyurethane elastomer B, and polishing evaluation was performed. Table 1 shows the results.

[Comparative Example 3]
A polishing pad was produced in the same manner as in Example 1, except that the wet heat shrinkage rate of the web entangled sheet was changed from 47% to 25%, and polishing evaluation was performed. Table 1 shows the results.

The fiber composite polishing pad according to the present invention is used for CMP polishing for flattening and mirror polishing, specifically for polishing glass-based substrates such as liquid crystal display members, glass products, optical products, etc. It can be used as a pad. Moreover, in polishing, it can be used for any polishing such as primary polishing, secondary polishing (adjustment polishing), and finish polishing.

Claims (4)

A fiber composite polishing pad composed of a nonwoven fabric of ultrafine fibers and a polymeric elastic material attached to the nonwoven fabric, wherein the cross section in the thickness direction is evenly divided into three and both surface layers are removed to form the intermediate layer. , Pc (porosity of the intermediate layer (Pb)/porosity of the entire layer (Pa)) is 0.35 or less, the surface roughness (Sa) of the polished surface is 10 μm or more, and the JISD hardness is 50 or more. and a fiber composite polishing pad. Attached to a CMP polishing apparatus (“NF-300HP” manufactured by Nanofactor Co., Ltd.), under the conditions of platen rotation speed of 70 rotations/minute, head rotation speed of 69 rotations/minute, and polishing pressure of 130 g/cm ² , Showa Denko polishing While supplying the slurry "SHOROX A-31" at a rate of 300 ml / min, when polishing a liquid crystal glass with a diameter of 4 inches, the polishing rate Ta at the early stage of polishing (after 0.5 hours of polishing time) and the late polishing rate (polishing 2. The fiber composite polishing pad according to claim 1, wherein the polishing rate ratio (Tb/Ta) of the polishing rate Tb after 6 hours) is 0.85 or more. The polymeric elastic body is non-porous, and in the fiber composite polishing pad, a bundle of ultrafine fibers made of a plurality of long fibers forming a fiber bundle is bundled, and the apparent density is 0.5 to 1.2 g. /cm ³ , and the mass ratio of the nonwoven fabric and the elastic polymer (nonwoven fabric/elastic polymer) is 90/10 to 55/45. A polishing method comprising polishing the surface of a glass-based substrate by pressing the glass-based substrate while supplying slurry to the fiber composite polishing pad according to any one of claims 1 to 3.