JP5789557B2 - Method for polishing glass-based substrate - Google Patents

Description

  The present invention relates to a method for polishing a glass-based substrate with high accuracy by chemical mechanical polishing.

  Conventionally, as a method of polishing a glass-based substrate while maintaining high flatness, chemical mechanical polishing (CMP) in which a glass-based substrate is pressed and polished while a slurry containing ceria particles is dropped 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 molded body containing abrasive particles and a slurry containing ceria particles. A method of polishing is disclosed.

JP-A-6-114742 JP 2007-073796 A

  When a glass-based substrate is subjected to CMP polishing using a polishing pad made of a polyurethane molded body and a slurry containing ceria particles as disclosed in Patent Document 1 and Patent Document 2, the polyurethane molded body is too rigid. Because of the poor followability of the glass-based substrate surface, the slurry containing ceria particles and the surface of the glass-based substrate are not compatible, and polishing by the chemical reaction between the surface of the ceria particles and the surface of the glass-based substrate. The effect was not sufficiently obtained. Also, in order to increase the contact between the ceria particles and the glass-based substrate, when the contact pressure between the polishing pad and the glass-based substrate is increased, the flatness is lowered, or force is applied to the abrasive aggregates. As a result, there is a problem that scratches are likely to occur.

  In the present invention, the above-described problem, that is, when the surface of the glass-based substrate is subjected to CMP polishing while dripping the slurry containing ceria particles, the polishing can be maintained at a high polishing rate and flatness, and the generation of scratches is also suppressed. It aims at realizing.

One aspect of the present invention is a polishing method for polishing a surface of a glass-based substrate by pressing the glass-based substrate while supplying the slurry to the polishing pad, the slurry containing ceria particles, An entangled body of fiber bundles composed of ultrafine fibers of an average fiber having an average fineness of 0.01 to 0.9 dtex, and a polymer elastic body impregnated and integrated with the entangled body, and the ultrafine fibers have a saturated water absorption rate at 50 ° C. 0.2 to 2% by mass, the polymer elastic body has a saturated water absorption at 50 ° C. of 0.2 to 5% by mass, an apparent density of 0.6 to 0.9 g / cm ³ , and a D hardness of 36 to 65, and the average interval (Sm) of the unevenness of the polished surface is 29.5 to 100 μm.

The polishing pad used in the above polishing method contains an entangled body of fiber bundles made of ultrafine fibers of long fibers and a polymer elastic body in a mass ratio of 55/45 to 90/10. Such a polishing pad is a highly rigid polishing pad because it includes an entangled body of fiber bundles in which ultrafine fibers are bundled like a single thick fiber. Further, the fiber bundle existing in the surface layer is separated during polishing and exists in the state of ultrafine fibers. As a result, the slurry containing the ceria particles being polished is easily held by the ultrafine fibers. Furthermore, the average spacing (Sm) of the irregularities on the polished surface is adjusted to 29.5 to 100 μm, so that the hardness of the polished surface becomes moderate, high polishing efficiency and stability can be maintained, and scratches are generated. Can be suppressed.

  According to the present invention, it is possible to realize CMP polishing of a glass-based substrate having a high degree of flatness with suppressed generation of scratches.

FIG. 1 is a schematic view for explaining a state in which a glass-based substrate is being polished by the CMP polishing apparatus of the present embodiment. FIG. 2 is a schematic cross-sectional view of a polishing pad of a CMP polishing apparatus used in the polishing method of this embodiment.

  Hereinafter, a method for polishing a glass-based substrate according to an embodiment of the present invention will be described.

  FIG. 1 is a schematic diagram for explaining how a glass-based substrate is polished by a CMP polishing apparatus. In FIG. 1, 10 is a polishing pad, 11 is a glass-based substrate, and 12 is a glass-based substrate 11. A carrier supported while rotating, 13 is a turntable, 14 is a slurry containing ceria, 15 is a slurry supply pipe, and 16 is a conditioner. The polishing pad 10 is affixed to the surface of the turntable 13.

  The turntable 13 is rotated at a high speed by a motor (not shown) provided in the CMP polishing apparatus. In CMP, the slurry 14 is supplied little by little from the slurry supply pipe 15 to the polishing pad 10 attached to the turntable 13 that rotates at high speed. A load is applied to the carrier 12 by a load means (not shown), and the glass-based substrate 11 is pressed against the polishing pad 10 that rotates at a high speed, and the surface thereof is polished. Further, the surface of the polishing pad 10 is periodically sharpened by a conditioner 16 in order to suppress a change with time of polishing. For example, a nylon brush is used as the conditioner. Conditioning may be performed before polishing or during polishing.

  The slurry 14 used for polishing the glass-based substrate 11 contains ceria particles (cerium oxide particles) and an aqueous medium. By using a slurry containing ceria particles, a high polishing rate can be obtained by a chemical reaction of ceria on the surface of the glass-based substrate.

  The average particle diameter of the ceria particles is preferably 0.1 to 10 μm. If the average particle size of the ceria particles is too large, it tends to settle in the slurry, tends to aggregate, and the polishing efficiency tends to decrease, and if it is too small, the polishing efficiency tends to decrease There is.

  Although the density | concentration of the ceria particle in the slurry 14 is not specifically limited, It is preferable that it is 1-40 mass%, Furthermore, it is 1-30 mass%. If the concentration of ceria particles is too low, the polishing rate tends to decrease. If it is too high, the cost increases, but the effect of further improving the polishing property tends to be poor.

  The slurry may contain abrasive grains other than ceria particles and other additives. Examples of abrasive grains other than ceria particles include silica particles (silicon oxide particles), indium particles, zirconia particles (zirconium oxide particles), and the like. Examples of other additives include various basic components, various acidic components, and surfactants.

  Next, the polishing pad 10 used for polishing the glass-based substrate will be described in detail.

  As shown in FIG. 2, the polishing pad 10 contains an entangled body of fiber bundles 1 composed of ultrafine fibers 1 a of long fibers, a polymer elastic body 2, and voids 3.

  The average fineness of the long ultrafine fiber 1a is 0.01 to 0.9 dtex, preferably 0.05 to 0.9 dtex. In the case of such ultrafine fibers having an average fineness, the superfine fiber bundle on the surface layer of the polishing pad 10 is sufficiently divided during polishing, thereby improving the holding power of the slurry 14 and improving the polishing efficiency and polishing uniformity. Will improve. When the average fineness of the ultrafine fibers is less than 0.01 dtex, the fiber bundle is 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. Or the stress applied to the surface when the glass-based substrate 11 is polished becomes too high, and scratches are likely to occur.

  Further, the average length of the ultrafine fibers 1a of long fibers is not particularly limited, but is preferably 100 mm or more, and 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 fiber 1a is too short, it tends to be difficult to increase the fiber density of the entangled body, and the fiber tends to easily come off during polishing. An upper limit is not specifically limited, For example, when it contains the fiber entanglement body derived from the nonwoven fabric manufactured by the spunbond method mentioned later, unless it cut | disconnects physically, several m, several hundred m, several km Alternatively, longer fibers may be included.

  The ultrafine fiber 1a has a water absorption rate (saturated water absorption rate) of 0.2 to 2 mass% when saturated with water absorption at 50 ° C. In such a case, since the polishing pad is suppressed from excessively absorbing the slurry, a decrease in rigidity over time is suppressed, and as a result, a decrease in planarization performance with time is suppressed, A polishing pad is obtained in which the polishing rate and polishing uniformity do not vary easily.

  The glass transition temperature (Tg) of the ultrafine fiber 1a is preferably 50 to 200 ° C, more preferably 50 to 150 ° C. In such a case, since the time-dependent hardness during polishing hardly changes, polishing flatness and polishing stability are improved.

Specific examples of the resin for forming the ultrafine fiber 1a include, for example, polyethylene terephthalate (PET, T _g 77 ° C., saturated water absorption at 50 ° C. (hereinafter the same) 1% by mass), isophthalic acid-modified PET (T _g 67 ˜77 ° C., water absorption 1 mass%), sulfoisophthalic acid modified PET (T _g 67-77 ° C., water absorption 1-3 mass%), polybutylene naphthalate (T _g 85 ° C., water absorption 1 mass%), Aromatic polyester fiber formed from polyethylene naphthalate (T _g 124 ° C., water absorption 1 mass%), etc .; terephthalic acid, nonanediol, and methyloctanediol copolymer polyamide (T _g 125-140 ° C., water absorption 1- And semi-aromatic polyamide fibers formed from 3% by mass). These may be used alone or in combination of two or more. In particular, modified PET such as PET and isophthalic acid-modified PET has a dense and high-density fiber entanglement because it is greatly crimped in a wet heat treatment process for forming ultrafine fibers from a web-entangled sheet made of sea-island fibers, which will be described later. It is also preferable from the viewpoints of being able to form a coalescence, easily increasing the rigidity of the polishing sheet, and less likely to change with time due to moisture during polishing.

  The fiber bundle 1 has a form in which a plurality of ultrafine fibers 1a are bundled. Specifically, for example, it is preferable that 5 to 200, further 10 to 50, and particularly 10 to 30 ultrafine fibers 1a are present as bundled. Thus, when the ultrafine fibers 1a are present in the form of the fiber bundle 1, the apparent density of the entangled body can be increased.

Apparent density of the fiber-entangled body 0.20 g / cm ³ or more, and more preferably from 0.40~0.80g / cm ^3. When the polishing pad 10 contains a dense entangled body having a high apparent density, high rigidity can be maintained during polishing, and therefore the glass substrate can be polished with high flatness.

  Next, the polymer elastic body 2 impregnated and integrated into the entangled body of the fiber bundle 1 will be described. The polymer elastic body 2 has a saturated water absorption rate at 50 ° C. of 0.2 to 5 mass%.

  The polymer elastic body 2 has a water absorption rate (saturated water absorption rate) of 0.2 to 5% by mass, preferably 0.5 to 3% by mass when saturated with water absorption at 50 ° C. Since the water absorption rate of the polymer elastic body is within such a range, the high wettability of the slurry with respect to the polishing pad can be maintained during polishing. When the saturated water absorption at 50 ° C. of the polymer elastic body 2 is less than 0.2% by mass, the wettability of the slurry becomes insufficient and the polishing rate tends to decrease, and the saturated water absorption at 50 ° C. is 5 When it exceeds mass%, there is a tendency that rigidity is gradually lowered by gradually absorbing moisture during polishing. The water absorption rate of the polymer elastic body can be controlled by adjusting the composition of the polymer constituting the polymer elastic body, the crosslinking density, the amount of hydrophilic functional groups, and the like. The water absorption rate of the polymer elastic body is the water absorption rate when the dried polymer elastic body film is immersed in warm water at 50 ° C. and saturated and swelled. Moreover, when it contains two or more types of polymer elastic bodies, it is calculated as the sum of values obtained by multiplying the saturated water absorption of each polymer elastic body by the mass fraction.

  The glass transition temperature (Tg) of the polymer elastic body 2 is preferably −10 ° C. or lower. In such a case, since the deterioration of the binding property to the fiber entanglement can be suppressed, the temporal stability during polishing is improved.

  The polymer elastic body preferably has a storage elastic modulus at 23 ° C. and 50 ° C. of 90 to 900 MPa, and more preferably 200 to 800 MPa. When the storage elastic modulus at 23 ° C. and 50 ° C. is 90 MPa or more, the rigidity of the polishing pad can be sufficiently maintained during polishing to maintain high flatness, and the slurry can swell with slurry during polishing. Therefore, the stability over time tends to be excellent. Further, when the storage elastic modulus at 23 ° C. and 50 ° C. is 900 MPa or less, the polymer elastic body is less likely to fall off during polishing, so that scratches are less likely to occur, and the convergence force of the ultrafine fibers is high. Thus, the stability over time during polishing tends to be excellent.

  The resin for forming the polymer elastic body 2 is not particularly limited, and specific examples thereof include, for example, polyurethane resins, polyamide resins, (meth) acrylate resins, (meth) acrylate esters-styrene. Resin, (meth) acrylic ester-acrylonitrile resin, (meth) acrylic ester-olefin resin, (meth) acrylic ester- (hydrogenated) isoprene resin, (meth) acrylic ester-butadiene Resin, styrene-butadiene resin, styrene-hydrogenated isoprene resin, acrylonitrile-butadiene resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, (meth) acrylic acid ester-vinyl acetate resin, ethylene-acetic acid Vinyl resin, ethylene-olefin resin, silica Over emissions based resins, fluorine based resins, and include an elastic body made of a polyester resin. These may be used alone or in combination of two or more. The polymer elastic body may contain two or more kinds of polymer elastic bodies in order to adjust performance, manufacturability and the like. Theoretically calculated as the sum of the values obtained by multiplying the storage elastic modulus of the molecular elastic body by the mass fraction.

  The polymer elastic body 2 is particularly preferably a hydrogen-bonding polymer elastic body from the viewpoint of high binding properties to the ultrafine fibers 1a. The resin that forms the hydrogen-bonding polymer elastic body is a polymer elastic body that crystallizes or aggregates by hydrogen bonding, such as polyurethane resin, polyamide resin, and polyvinyl alcohol resin. Since the hydrogen-bonding polymer elastic body has high adhesiveness and excellent shape retention of the fiber-entangled body, it is easy to suppress the removal of the fiber.

  Among these, polyurethane-based resins are preferred because they are excellent in adhesion to ultrafine fibers, and also have high polishing pad hardness and excellent temporal stability during polishing. Below, the case where a polyurethane-type resin is used as the polymer elastic body 2 is demonstrated in detail as a representative example.

  Examples of the polyurethane resin include various polyurethane 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 the polymer polyol include, for example, polyether 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 co Polyester polyols such as polymerized polyol, cyclohexanol copolymer polyol, polycaprolactone diol, and copolymers thereof; polyhexamethylene carbonate diol, poly (3-methyl-1,5- Polycarbonate-type polyols such as poly (ethylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, poly (methyl-1.8-octamethylene carbonate) diol, polynonanemethylene carbonate diol, polycyclohexane carbonate diol, and the like. Polymer: Polyester carbonate polyol and the like. If necessary, a trifunctional alcohol such as trimethylolpropane or a polyfunctional alcohol such as tetrafunctional alcohol such as pentaerythritol, or ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol. Etc. 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, it is possible to contain a polycarbonate polyol, in particular, an amorphous polycarbonate polyol having a melting point of 0 ° C. or less in an amount of 60 to 100% by mass of the total amount of the polyol component, so that the storage elastic modulus becomes moderate and polishing is in progress. This is preferable because it is particularly excellent in stability over time. Further, when about 0.1 to 10% by mass of a polyalkylene glycol having 5 or less carbon atoms, particularly 3 or less carbon atoms is used, it is preferable from the viewpoint that wettability with water becomes particularly good.

Specific examples of the organic polyisocyanate include, for example, non-yellowing diisocyanates such as aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate; 2,4-tri Examples thereof include aromatic diisocyanates such as range isocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and xylylene diisocyanate polyurethane. Moreover, you may use together polyfunctional isocyanates, such as trifunctional isocyanate and tetrafunctional isocyanate, 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 adhesion to fibers, Moreover, it is preferable from the point by which a polishing pad with high hardness is obtained.

  Specific examples of the chain extender include, for example, diamines such as hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and derivatives thereof, 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; Aminoethyl alcohol, Aminopropyl alcohol Which amino alcohols and the like. These may be used alone or in combination of two or more. Among these, hydrazine, piperazine, hexamethylenediamine, isophoronediamine and derivatives thereof, and triamines such as ethylenetriamine are used in combination of two or more to provide high adhesion to fibers and high hardness polishing. This is preferable because a pad can be obtained. In addition, during the chain extension reaction, together with the chain extender, monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-aminobutanoic acid and 6-aminohexanoic acid; methanol, ethanol, propanol, butanol, etc. Monools may be used in combination.

  In addition, a polyurethane containing a carboxyl group-containing diol such as 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,2-bis (hydroxymethyl) valeric acid, etc. By introducing an ionic group such as a carboxyl group into the skeleton of the resin, the wettability to water can be further improved.

  Moreover, in order to control the water absorption rate and storage elastic modulus of the polyurethane resin, a crosslinking agent containing two or more functional groups capable of reacting with the functional group of the monomer unit forming the polyurethane, or a polyisocyanate type A cross-linked structure may be formed by adding a self-crosslinking compound such as a compound or a polyfunctional blocked isocyanate compound.

  The combination of the functional group of the monomer unit forming the polyurethane resin and the functional group of the crosslinking agent includes 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 aziridine group, carbonyl group and hydrazine derivative or hydrazide derivative. Among these, a combination of a monomer unit having a carboxyl group and a crosslinking 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 crosslinking agent having a blocked isocyanate group, and carbonyl A combination of a monomer unit having a group and a hydrazine derivative or a hydrazide derivative is particularly preferred because crosslinking is easy and the resulting polishing pad has excellent rigidity and wear resistance. The cross-linked structure is preferably formed in the heat treatment step after applying the polyurethane resin to the fiber entangled body from the viewpoint of maintaining the stability of the aqueous liquid of the polyurethane resin. Among these, a carbodiimide group and / or an oxazoline group are particularly preferable because they are excellent in crosslinking performance and pot life of an aqueous liquid and have no problem in safety. Examples of the crosslinking agent having a carbodiimide group include water-dispersed carbodiimide compounds such as “Carbodilite E-01”, “Carbodilite E-02”, and “Carbodilite V-02” manufactured by Nisshinbo Industries, Ltd. Examples of the crosslinking agent having an oxazoline group include water-dispersed oxazoline compounds such as “Epocross K-2010E”, “Epocross K-2020E”, and “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. As a compounding quantity of a crosslinking agent, it is preferable that the active ingredient of a crosslinking agent is 1-20 mass% with respect to a polyurethane-type resin, It is more preferable that it is 1.5-1 mass%, 2-10 mass % Is more preferable.

  Moreover, the adhesiveness with the ultrafine fiber is increased to increase the rigidity of the fiber bundle, the glass transition temperature is set to −10 ° C. or lower, the saturated water absorption rate at 50 ° C. is set to 0.2 to 5% by mass, Since the storage elastic modulus at 23 ° C. and 50 ° C. can be appropriately adjusted, the content of the polymer polyol component in the polyurethane resin is 40 to 65% by mass, and further 45 to 60% by mass. It is preferable.

  Moreover, water absorption and hydrophilicity are adjusted 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. be able to. Thereby, the wettability with respect to the abrasive slurry of a polishing pad in the case of grinding | polishing can be improved. Such a hydrophilic group can be introduced into a polyurethane resin by copolymerizing a monomer component having a hydrophilic group as a monomer component for producing a polyurethane resin. The copolymerization ratio of the monomer component having such a hydrophilic group is 0.1 to 10% by mass, and further 0.5 to 5% by mass while minimizing swelling and softening due to water absorption. From the point that water absorption and wettability can be improved.

  The polyurethane resin is preferably non-porous. The non-porous state is a state that does not substantially have voids (closed cells) such as a porous or sponge-like (hereinafter, also simply referred to as porous) polyurethane-based resin. means. Specifically, it means that it is not a polyurethane-based resin having a large number of fine bubbles, for example, obtained by coagulating solvent-based polyurethane. Making the polyurethane resin that focuses and restrains the ultrafine fibers or binds the ultrafine fiber bundles non-porous increases the restraint force of the ultrafine fibers and improves the flexural modulus. In addition, since the polishing stability is increased, and slurry scraps and pad scraps at the time of polishing are less likely to accumulate in the gaps, the polishing pad is difficult to wear, and therefore a high polishing rate can be maintained for a long time. Furthermore, since the adhesive strength with respect to the ultrafine fibers is increased, it is possible to suppress the occurrence of scratches due to the loss of the fibers. Furthermore, since higher rigidity is obtained, a polishing pad having excellent planarization performance can be obtained.

  Polyurethane resins are penetrants, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, extenders, curing accelerators, antioxidants, UV 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 10, the polymer elastic body 2 is impregnated into the fiber bundle 1 of the ultrafine fiber 1 a, and a part or most of the ultrafine fiber 1 a constituting the fiber bundle 1 is restrained by the polymer elastic body 2. It is preferable. When the fiber bundle 1 is constrained by the polymer elastic body 2, rigidity is imparted to the fiber bundle 1 and high planarization performance is obtained. Further, it is possible to prevent the fibers from coming off and to prevent the abrasive grains from agglomerating from agglomerating, thereby suppressing the scratches. Further, the fact that the plurality of fiber bundles 1 are also bound by the polymer elastic body 2 existing outside the fiber bundle 1 improves the shape stability of the polishing pad 2 and improves the polishing stability. preferable.

  The converging / restraining state of the ultrafine fibers 1a and the binding state of the fiber bundles 1 can be easily confirmed by an electron micrograph of the cross section of the polishing pad 10.

The surface of the polishing pad 10 is in the vicinity of the surface by performing a pad flattening process by buffing or the like, a seasoning process (conditioning process) before polishing using a pad dressing such as diamond, or a dressing process or a brushing process at the time of polishing. The fine fiber 1a is formed on the surface of the polishing pad 10 by splitting or fibrillating the fiber bundle 1 present in FIG. The fiber density of the ultrafine fibers 1a on the surface of the polishing pad 10 is preferably 600 fibers / mm ² or more, more preferably 1000 fibers / mm ² or more, and particularly preferably 2000 fibers / mm ² or more. When the fiber density is too low, the retainability of the slurry 14 tends to decrease. The upper limit of the fiber density is not particularly limited, but is about 1,000,000 pieces / mm ² from the viewpoint of productivity. Further, the ultrafine fibers 1a on the surface of the polishing pad 10 may be napped or may not be napped. When the ultrafine fiber 1a is napped, the surface of the polishing pad 10 becomes softer, so that the effect of reducing scratches becomes higher. On the other hand, when the degree of napping of the ultrafine fiber 1a is low, it is advantageous for applications in which micro-flatness is important. Thus, it is preferable to appropriately select the surface state according to the application.

  The mass ratio of the entangled body of the fiber bundle 1 of the ultrafine fiber 1a and the polymer elastic body 2 (fiber bundle entangled body / polymer elastic body) in the polishing pad 10 is 55/45 to 90/10, 60/40 to 85/15 is preferable from the viewpoint of easily adjusting the bending elastic modulus of the polishing pad to an appropriate range. Since the ratio of the entangled body is 55% by mass or more, there is a tendency that the temporal stability during polishing is improved or the polishing efficiency is improved. In addition, since the mass ratio of the entangled body is 90% or less, the ultrafine fiber 1a is sufficiently restrained by the polymer elastic body 2 to improve the flatness and reduce the pad wear during polishing, thereby improving the temporal stability. It becomes easy to improve.

Moreover, the average space | interval (Sm) of the unevenness | corrugation of the polishing surface of the polishing pad 10 is 29.5-100 micrometers , Preferably it is 29.5-80 micrometers . When the average interval (Sm) of the irregularities exceeds 100 μm, the polishing rate and the polishing uniformity are improved, but the fibers fall off and scratches are likely to occur. Moreover, when Sm is less than 29.5 , the recess (void) serving as a slurry reservoir is insufficient, and the polishing rate and the polishing stability with time tend to decrease. In addition, the average space | interval (Sm) of an unevenness | corrugation is measured according to the surface roughness measurement based on JISB0601-1994. The average interval of the irregularities on the polished surface means the surface roughness immediately after the pad flattening process by buffing or the like.

  Moreover, the average space | interval (Sm) of the unevenness | corrugation of the polishing surface of the polishing pad 10 is 15-100 micrometers, Preferably it is 15-80 micrometers. When the average interval (Sm) of the irregularities exceeds 100 μm, the polishing rate and the polishing uniformity are improved, but the fibers fall off and scratches are likely to occur. In addition, when Sm is 15 or less, there are insufficient recesses (voids) serving as a slurry reservoir, and the polishing rate and the polishing stability with time tend to decrease. In addition, the average space | interval (Sm) of an unevenness | corrugation is measured according to the surface roughness measurement based on JISB0601-1994. The average interval of the irregularities on the polished surface means the surface roughness immediately after the pad flattening process by buffing or the like.

The apparent density of the polishing pad 10 is 0.6 to 0.9 g / cm ³ , and preferably 0.6 to 0.85 g / cm ³ . When the apparent density exceeds 0.9 / cm ³ , the liquid retention of the slurry is lowered, the polishing rate is lowered, and scratches are likely to occur. Moreover, when the apparent density is less than 0.6 / cm ³ , the rigidity tends to be low, and the flattening characteristics and the polishing stability over time tend to decrease.

  Moreover, it is preferable that the polishing pad 10 has a saturated water absorption at 50 ° C. of 10 to 80 mass%, more preferably 15 to 70 mass%. When the saturated water absorption at 50 ° C. is 10% by mass or more, the slurry is easy to hold and the polishing rate is improved and the polishing uniformity tends to be improved. In addition, when the saturated water absorption at 50 ° C. is 80% by mass or less, the polishing rate is improved, and the characteristics such as hardness are hardly changed during polishing. Tend to be better.

[Production method of polishing pad]
Next, an example of a method for manufacturing the polishing pad 10 will be described in detail.

  The polishing pad 10 includes, for example, a web production process for producing a long fiber web composed of sea-island fibers obtained by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and a plurality of the long fiber webs are stacked. A web entanglement step of forming a web entanglement sheet by entanglement, a wet heat shrinkage treatment step of shrinking the web entanglement sheet so that the area shrinkage rate is 40% or more, and a web A fiber entanglement forming step for forming a fiber entangled body made of ultrafine fibers by dissolving the water-soluble thermoplastic resin in the entangled sheet in hot water, and impregnating the fiber entangled body with an aqueous liquid of a polymer elastic body And a method for producing a polishing pad comprising a polymer elastic body filling step for drying and solidifying.

  In such a manufacturing method, the web entangled sheet containing the short fiber is subjected to the wet heat shrink process, and the web entangled sheet containing the short fiber is subjected to the wet heat shrink. The fiber density of the ultrafine fibers becomes dense. And the fiber entanglement body which consists of an ultrafine fiber bundle is formed by melt-extracting the water-soluble thermoplastic resin of a web entanglement sheet. At this time, voids are formed in the portion where the water-soluble thermoplastic resin is dissolved and extracted. Then, by impregnating and drying and solidifying the polymer liquid with an aqueous liquid of the polymer elastic body, the ultrafine fibers constituting the ultrafine fiber bundle are focused, and the ultrafine fiber bundles are also focused. In this way, a highly rigid polishing pad with high fiber density and converged ultrafine fibers 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.

  A sea-island type 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. Then, the ultrafine fiber is formed by dissolving or removing the water-soluble thermoplastic resin from the sea-island fiber. The thickness of the sea-island fiber is preferably 0.5 to 3 dtex from the industrial viewpoint.

  In this embodiment, the sea-island type fiber will be described in detail as a composite fiber for forming the ultra-fine fiber, but a known ultra-fine fiber generating type fiber such as a multilayer laminated cross-section fiber is used instead of the sea-island type fiber. Also good.

  The water-soluble thermoplastic resin is preferably a thermoplastic resin that can be dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like and that can be melt-spun. Specific examples of such a water-soluble thermoplastic resin include, for example, polyvinyl alcohol resins (PVA resins) such as polyvinyl alcohol and polyvinyl alcohol copolymers; copolymers of polyethylene glycol and / or alkali metal sulfonates. Modified polyesters contained as components; polyethylene oxide and the like. Among these, PVA-based resins are particularly preferably used for the following reasons.

  When sea-island 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. In addition, when sea-island type fibers containing PVA-based resin as a water-soluble thermoplastic resin component are used, when the PVA-based resin is dissolved, the formed ultrafine fibers and polymer elastic body are not substantially decomposed or dissolved. The physical properties of ultrafine fibers and polymer elastic bodies are unlikely to deteriorate. Furthermore, the environmental load is small. Further, even if a trace amount remains, the adverse effect on the polishing performance is small, and conversely, the wettability of the polishing pad tends to be improved. A preferred ratio of the PVA-based resin remaining on the polishing pad is about 0.01 to 0.2% by mass, and further about 0.02 to 0.1% by mass.

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

  As a specific example of the water-insoluble thermoplastic resin, various thermoplastic resins used to form the ultrafine fibers constituting the polishing pad described above can be used.

  The water-insoluble thermoplastic resin may contain various additives. Specific examples of additives include, for example, catalysts, anti-coloring agents, heat-resistant agents, flame retardants, lubricants, antifouling agents, fluorescent whitening agents, matting agents, coloring agents, gloss improvers, antistatic agents, and fragrances. , Deodorants, antibacterial agents, acaricides, inorganic fine particles and the like.

  Next, a method for forming a sea-island fiber by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin and forming a long fiber web from the obtained sea-island fiber will be described in detail.

  The long fiber web is obtained, for example, by compounding by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and then stretching and depositing by a spunbond method. Thus, by forming a web by the spunbond method, a long fiber web made of sea-island fibers with less fiber loss, high fiber density, and good shape stability can be obtained. In addition, a long fiber is a fiber manufactured without passing through a cutting process like manufacturing a short fiber.

  In the production of sea-island type 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 to the water-insoluble thermoplastic resin is within such a range, a high-density fiber entangled body can be obtained, and the formability of ultrafine fibers is 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 molten resin strands are discharged simultaneously from different spinnerets. Then, after the discharged strands are combined with the composite nozzle, the sea-island fibers are formed by discharging from the nozzle holes of the spinning head. In the melt composite spinning, the number of islands in the sea-island fiber is 4 to 4000 islands / fiber, more preferably 10 to 1000 islands / fiber from the point of obtaining a fiber bundle with small single fiber fineness and high fiber density. preferable.

After the sea-island type fiber is cooled by a cooling device, it is drawn by a high-speed air stream at a speed corresponding to a take-up speed of 1000 to 6000 m / min so as to obtain a desired fineness using a suction device such as an air jet nozzle. Thereafter, the stretched composite fibers are deposited on a movable collection surface to form a long fiber web. At this time, the long fiber web deposited may be partially crimped as necessary. The basis weight of the fiber web is preferably in the range of ^{20 to} 500 g / m ² , and a uniform fiber entangled body can be obtained, and is preferable from the viewpoint of industrial properties.

(2) Web entanglement process Next, the web entanglement process which forms a web entanglement sheet | seat by accumulating and intertwining a plurality of obtained long fiber webs is demonstrated.

  The web entangled sheet is formed by performing an entanglement treatment on the long fiber web using a known nonwoven fabric manufacturing method such as needle punching or high-pressure water flow treatment. Below, the entanglement process by a needle punch is demonstrated in detail as a typical example.

  First, a silicone oil agent or a mineral oil agent such as a needle breakage prevention oil agent, an antistatic oil agent, and an entanglement improving oil agent is applied to the long fiber web. In order to reduce unevenness in weight per unit area, two or more fiber webs may be overlapped with a cross wrapper and an oil agent may be applied.

Thereafter, for example, an entanglement process is performed in which the fibers are entangled three-dimensionally by a needle punch. By performing the needle punching process, a web entangled sheet having a high fiber density and hardly causing the fiber to come off can be obtained. The basis weight of the web-entangled sheet is appropriately selected according to the thickness of the target polishing pad, and specifically, for example, the handling property is in the range of 100 to 1500 g / m ² . From the point which is excellent in it.

The conditions for increasing the delamination force of the web entangled sheet are appropriately selected as the needle conditions such as the type and amount of the oil agent, the needle shape in the needle punch, the needle depth, and the number of punches. The number of barbs is preferably as large as possible without causing needle breakage. Specifically, for example, the number of barbs is selected from 1 to 9 barbs. The needle depth is preferably set so that the barb penetrates to the overlapped web surface, and in a range where 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, and specifically, 500 to 5000 punches / cm ² is preferable. In addition, the fiber density can be obtained by performing the entanglement process so that the basis weight after the entanglement process is 1.2 times or more by mass ratio of the basis weight before the entanglement process, and further 1.5 times or more. A high fiber entangled body can be obtained, and it is preferable from the viewpoint that the loss of fibers can be reduced. The upper limit is not particularly limited, but is preferably 4 times or less from the viewpoint of avoiding an increase in manufacturing cost due to a decrease in processing speed.

  The delamination force of the web entangled sheet is 2 kg / 2.5 cm or more, more preferably 4 kg / 2.5 cm or more, the shape retention is good, the fibers are not easily pulled out, and the fiber density is high. This is preferable from the viewpoint of obtaining a fiber entangled body. Note that the delamination force is a measure of the degree of three-dimensional entanglement. When the delamination force is too small, the fiber density of the fiber entangled body is not sufficiently high. Moreover, although the upper limit of the delamination force of an entangled nonwoven fabric is not specifically limited, It is preferable that it is 30 kg / 2.5 cm or less from the point of an entanglement process efficiency.

(3) Wet heat shrinkage treatment step Next, a wet heat shrinkage treatment step for increasing the fiber density and the degree of entanglement of the web entangled sheet by shrinking the web entangled sheet with heat and moisture will be described. In this step, the web-entangled sheet containing long fibers is contracted by wet heat, so that the web-entangled sheet is contracted greatly compared to the case where the web-entangled sheet containing short fibers is contracted by wet heat. As a result, the fiber density of the ultrafine fibers is particularly high. The wet heat shrinkage treatment is preferably performed by steam heating. As the steam heating condition, it is preferable to perform heat treatment for 60 to 600 seconds at an ambient temperature of 60 to 130 ° C. and a relative humidity of 80% or more, and further a relative humidity of 90% or more. In order to adjust the average interval (Sm) of the unevenness of the polishing surface of the polishing pad 10 to 15 to 100 μm, it is preferable that the web entangled sheet is highly contracted under steam heating conditions. In addition, when relative humidity is too low, there exists a tendency for shrinkage | contraction to become inadequate because the water | moisture content which contacted the fiber dries rapidly.

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

The area shrinkage rate (%) is expressed by the following formula (1):
(Area of sheet surface before shrinking process−Area of sheet surface after shrinking process) / Area of sheet surface before shrinking process × 100 (1) The said area means the average area of the area of the surface of a sheet | seat, and the area of a back surface.

  The web entangled sheet thus subjected to the wet heat shrinkage treatment may be further increased in fiber density by heating roll or hot pressing at a temperature equal to or higher than the thermal deformation temperature of the sea-island fiber. Regarding the change in the basis weight of the web-entangled sheet before and after the wet heat shrinkage treatment, the basis weight after the shrinkage treatment is 1.2 times (mass ratio) or more compared to the basis weight before the shrinkage 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 the ultra-fine fiberization treatment of the web entangled sheet, for the purpose of increasing the form stability of the web entangled sheet and reducing the porosity of the resulting polishing pad, If necessary, a fiber bundle may be bound in advance by impregnating the web-entangled sheet subjected to the shrink treatment with an aqueous liquid of a polymer elastic body and drying and solidifying it.

  In this step, the web entangled sheet is filled with the polymer elastic body by impregnating the contracted web entangled sheet with the aqueous liquid of the polymer elastic body and drying and solidifying it. The polymer elastic body can be formed by impregnating the polymer elastic body in the state of an aqueous liquid and drying and coagulating it. Since the aqueous liquid of the polymer elastic body has a high concentration and a low viscosity and is excellent in impregnation permeability, it is easy to be filled with a high amount. Moreover, the adhesiveness with respect to a fiber is also excellent. Therefore, the polymer elastic body filled in this step firmly binds the long sea-island type fibers.

  The aqueous liquid of the polymer elastic body is an aqueous solution in which the component forming the polymer elastic body is dissolved in the aqueous medium, or the aqueous dispersion liquid in which the component forming the polymer elastic body is dispersed in the aqueous medium. The aqueous dispersion includes a suspension dispersion and an emulsion dispersion. In particular, it is more preferable to use an aqueous dispersion from the viewpoint of excellent water resistance. The average particle size of the aqueous dispersion is 0.01 to 0.2 μm, which improves the water resistance and improves the stability over time during polishing, and improves the restraint of the fiber bundle. And it is preferable from the point that the rigidity of a polishing pad becomes moderate.

  For example, the method of making a polyurethane-based resin into an aqueous solution or aqueous dispersion imparts dispersibility to an aqueous medium to the polyurethane resin by including a monomer unit having a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group. Or a method of emulsifying or suspending a polyurethane resin by adding a surfactant. Further, such an aqueous polymer elastic body has excellent wettability to water, and thus has excellent characteristics for holding a large amount of abrasive grains.

  Specific examples of the surfactant used for emulsification or suspension include, for example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene tridecyl ether acetate, sodium dodecylbenzene sulfonate, sodium alkyldiphenyl ether disulfonate, dioctyl sulfosuccinic acid Anionic surfactants such as sodium; nonionic properties such as polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene-polyoxypropylene block copolymer Surfactant etc. are mentioned. Moreover, you may use what is called reactive surfactant which has reactivity. Moreover, heat-sensitive gelation property can also be provided to a polyurethane resin by selecting the cloud point of surfactant suitably. However, when a large amount of surfactant is used, it may have an adverse effect on the polishing performance and its stability over time, so it is preferable to minimize the necessary amount.

  In this step, in order to form the polymer elastic body, it is preferable to use an aqueous liquid of the polymer elastic body instead of using an organic solvent solution of the polymer elastic body generally used conventionally. Thus, by using the aqueous liquid of the polymer elastic body, the resin liquid containing the polymer elastic body can be impregnated at a higher concentration.

  Examples of the method of impregnating the web entangled sheet with the aqueous polymer elastic liquid include a method using a knife coater, a bar coater, or a roll coater, or a dipping method.

  The polymer elastic body can be solidified by drying the web entangled sheet impregnated with the aqueous liquid of the polymer elastic body. As a drying method, the method of heat-processing in a 50-200 degreeC drying apparatus, the method of heat-processing in a dryer after infrared heating, etc. are mentioned.

  When the web entangled sheet is impregnated with an aqueous liquid of a polymer elastic body and then dried, the aqueous liquid migrates to the surface layer of the web entangled sheet, thereby obtaining a uniform filling state. It may not be possible. In such a case, the particle size of the polymer elastic body of the aqueous liquid is adjusted; the kind and amount of ionic groups of the polymer elastic body are adjusted, or the stability is adjusted by pH or the like. Monovalent or divalent alkali metal salts or alkaline earth metal salts, nonionic emulsifiers, associative water-soluble thickeners, associative thermosensitive gelling agents such as water-soluble silicone compounds, water-soluble polyurethane compounds, Alternatively, migration can be suppressed by, for example, reducing the water dispersion stability at about 40 to 100 ° C. by using, for example, an organic substance or an inorganic substance whose pH is changed by heat. In addition, you may make it migrate so that a polymeric elastic body may be unevenly distributed on the surface as needed.

(5) Ultrafine fiber formation process Next, the ultrafine fiber formation process, which is a process of forming ultrafine fibers by dissolving a water-soluble thermoplastic resin in hot water, will be described.

  This step is a step of forming ultrafine fibers by removing the water-soluble thermoplastic resin. At this time, voids are formed in the portion of the web entangled sheet where the water-soluble thermoplastic resin is dissolved and extracted. Then, in this void, a polymer elastic body filling step, which will be described later, is filled with the polymer elastic body, thereby restraining the ultrafine fibers.

  The ultrafine fiber treatment is performed by hydrothermally treating a web entangled sheet or a composite of a web entangled sheet and a polymer elastic body with water, an aqueous alkaline solution, an acidic aqueous solution, etc. 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 a first stage, after being immersed in hot water at 65 to 90 ° C. for 5 to 300 seconds, further as a second stage, hot water at 85 to 100 ° C. It is preferable to perform the treatment for 100 to 600 seconds. Moreover, in order to improve dissolution efficiency, you may perform the nip process by a roll, a high pressure water flow process, an ultrasonic process, a shower process, a stirring process, a stagnation process, etc. as needed.

  In this step, the ultrafine fiber is greatly crimped when the ultrafine fiber is formed by dissolving the water-soluble thermoplastic resin from the sea-island fiber. Since the fiber density becomes dense by this crimping, a high-density fiber entangled body is obtained.

(6) Polymer elastic body filling step Next, the ultrafine fiber is restrained by filling the inside of the ultrafine fiber bundle formed from the ultrafine fiber with the polymer elastic body, and the ultrafine fiber bundle is restrained. The process of binding the bundles will be described.

  In the ultrafine fiber forming step (5), the sea-island fiber is subjected to ultrafine fiber treatment, whereby the water-soluble thermoplastic resin is removed and a void is formed inside the ultrafine fiber bundle. In this step, the voids of the polishing pad are reduced and the flexural modulus is improved by binding the ultrafine fiber bundles by filling such voids with a polymer elastic body. When the ultrafine fibers form a fiber bundle, the ultrafine fibers are more easily focused and constrained because the aqueous polymer liquid is easily impregnated by capillary action.

  The aqueous polymer liquid used in this step may be the same as the aqueous polymer elastic liquid described in the fiber bundle binding step (4).

  A method similar to the method used in the fiber bundle binding step (4) can be applied to the method of filling the polymer elastic body into the ultrafine fiber bundle formed from the ultrafine fibers in this step. In this way, a polishing pad is formed.

[Post-processing of polishing pad]
The obtained polishing pad may be subjected to post-processing treatment such as molding treatment, flattening treatment, raising treatment, surface treatment, and washing treatment, if necessary.

  The forming process and the flattening process are processes in which the obtained polishing pad is hot-press formed to a predetermined thickness by grinding or cut into a predetermined outer shape. The polishing pad is preferably ground to a thickness of about 0.5 to 3 mm.

  The raising process is a process for separating the focused ultrafine fibers by applying mechanical frictional force or polishing force to the surface of the polishing pad with sandpaper, needle cloth, diamond or the like. By such raising treatment, the fiber bundle existing in the surface portion of the polishing pad is fibrillated, and a large number of ultrafine fibers are formed on the surface.

  The surface treatment is a process of forming grooves, holes such as lattices, concentric circles, and spirals on the surface of the polishing pad in order to adjust the retention and discharge of the abrasive slurry.

  In the cleaning process, 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. It is a process to wash with.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited at all by the Example.

[Evaluation method]
First, the evaluation method in a present Example is demonstrated collectively.

(1) Confirmation of average fineness of ultrafine fibers and converging state of ultrafine fibers inside fiber bundle The obtained polishing pad was cut in the thickness direction using a cutter blade to form a cut surface in the thickness direction. The obtained cut surface was stained with osmium oxide. Then, the cut surface was observed with a scanning electron microscope (SEM) at 500 to 1000 times, and an image thereof was taken. And the cross-sectional area of the ultrafine fiber which exists in a cut surface was calculated | required from the obtained image. The average fineness was calculated from the density of the resin forming the fiber, with the average cross-sectional value being the average of 100 randomly selected cross-sectional areas.

(2) Storage elastic modulus of polymer elastic body at 23 ° C. and 50 ° C. A film sample having a length of 4 cm, a width of 0.5 cm, and a thickness of 400 μm ± 100 μm of the polymer elastic body constituting the polishing pad was prepared. Then, after measuring the sample thickness with a micrometer, using a dynamic viscoelasticity measuring device (DVE Rheospectr, manufactured by Rheology Co., Ltd.), the temperature is 23 ° C. under conditions of a frequency of 11 Hz and a temperature rising rate of 3 ° C./min. The dynamic viscoelastic modulus at 50 ° C. was measured, and the storage elastic modulus was calculated. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum which multiplied the mass ratio was made into the value of the elastic modulus of a polymer elastic body.

(3) Glass transition temperature of polymer elastic body A film having a length of 4 cm, a width of 0.5 cm, and a thickness of 400 μm ± 100 μm was prepared from the polymer elastic body constituting the polishing pad. Then, after measuring the sample thickness with a micrometer, using a dynamic viscoelasticity measuring device (DVE Rheospectr, manufactured by Rheology Co., Ltd.), the sample thickness is dynamically adjusted under conditions of a frequency of 11 Hz and a temperature rising rate of 3 ° C./min. Viscoelasticity was measured, and the main dispersion peak temperature of the loss elastic modulus was taken as the glass transition temperature. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum which multiplied the mass ratio was made into the value of the glass transition temperature of a polymer elastic body.

(4) Water Absorption Rate of Polymer Elastic Body A 200 μm thick film obtained by drying the polymer elastic body at 50 ° C. was heat-treated at 130 ° C. for 30 minutes, and then subjected to conditions of 20 ° C. and 65% RH. The sample left for 3 days was used as a dry sample, and the dry sample was immersed in water at 50 ° C. for 2 days. Then, the water-swollen sample was obtained after wiping off excess water droplets and the like on the outermost surface of the film immediately after being taken out of water at 50 ° C. with JK Wiper 150-S (manufactured by Crecia Corporation). The masses of the dried sample and the water-swelled sample were measured, and the water absorption rate was determined according to the following formula. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum multiplied by the mass ratio was used as the water absorption value of the polymer elastic body.

Water absorption (%) = [(mass of water swelled sample−mass of dried sample) / mass of dried sample] × 100

(5) Average particle diameter of aqueous polyurethane Measured by dynamic light scattering method using “ELS-800” manufactured by Otsuka Chemical Co., Ltd., cumulant method (“Colloid Chemistry Volume IV Colloid Chemistry Experiment Method” published by Tokyo Chemical Doujinsha) The average particle size of the water-dispersed polymer elastic body was measured.When two types of polymer elastic bodies were used, the sample was measured separately and the sum of the mass ratio was multiplied. Is the value of the average particle size of the polymer elastic body.

(6) Surface roughness of polishing pad (average interval of irregularities; Sm)
Using a shape measurement laser microscope “VK-X200” manufactured by KEYENCE, the surface roughness of the polishing pad (average interval of unevenness; Sm) was measured. Five measurement points were selected at random, and the aforementioned surface roughness was analyzed from the obtained image.

(7) Polishing performance evaluation of polishing pad After sticking an adhesive tape on the back surface of the circular polishing pad, it was attached to a CMP polishing apparatus ("PP0-60S" manufactured by Nomura Seisakusho Co., Ltd.). Next, a polishing slurry “SHOROX A-31” manufactured by Showa Denko KK was supplied at a rate of 100 ml / min under the conditions of a platen rotation speed of 70 rotations / minute, a head rotation speed of 69 rotations / minute, and a polishing pressure of 40 g / cm ^2. However, synthetic quartz having a diameter of 4 inches was polished for 30 minutes. And the thickness of arbitrary 25 points | pieces in the surface of the synthetic quartz after grinding | polishing was measured, and the grinding | polishing rate (nm / min) was calculated | required by remove | dividing the polished thickness in each point by grinding | polishing time. And the average value of 25 polishing rates was made into polishing rate (R), and the standard deviation ((sigma)) was calculated | required.

And the nonuniformity of the polishing surface was calculated by the following formula. Note that the smaller the non-uniformity value, the more uniformly the polished surface is polished, indicating that higher-precision polishing can be realized.
Nonuniformity (%) = (σ / R) × 100

  Then, the polishing rate and non-uniformity are determined every 30 minutes, and each polishing rate (R) and non-uniformity are determined up to a cumulative 600 minutes, and the maximum value (Rmax), minimum value (Rmin) and average are obtained. From the value (Ravg), the polishing rate stability (%) was determined by the following formula.

  Polishing rate stability (%) = (polishing rate maximum value (Rmax) −polishing rate minimum value (Rmin)) / polishing rate average value (Ravg) × 100

In addition, the shape measurement laser microscope “VK-X200” manufactured by KEYENCE was observed at a magnification of 20 times, and the number of scratches of the synthetic quartz after polishing was determined from the image. The number of scratches was observed at a size of 675 μm × 506 μm at the center, middle, and end portions of the synthetic quartz, and the number of scratches having a length of 10 μm or more was averaged.

[Example 1]
Water-soluble thermoplastic polyvinyl alcohol resin (hereinafter referred to as PVA resin) and isophthalic acid-modified polyethylene terephthalate having a degree of modification of 6 mol% (water absorption 1% by mass when saturated with water at 50 ° C., glass transition) A sea-island fiber was formed by discharging the melt composite spinning base at a temperature of 77 ° C. (hereinafter referred to as modified PET) at a ratio of 20:80 (mass ratio). The melt compound spinning die had 64 islands / fiber and a die temperature of 260 ° C. Then, by adjusting the ejector pressure to a spinning speed of 3700 m / min and collecting long fibers having an average fineness of 2.0 dtex on the net, a spunbond sheet (long fiber web) having a basis weight of 40 g / m ² is collected. )was gotten.

The resulting spunbonded sheets stacked 12 sheets by cross lapping, the total basis weight was produced overlay web 480 g / m ^2. And the needle | hook breaking prevention oil agent was sprayed on the obtained overlapping web. Next, using a needle needle with a needle count of 42 with one barb and a needle needle with a needle count of 42 with six barbs, the overlap web is entangled by needle punching at 2000 punches / cm ² . Thus, a web entangled sheet was obtained. The basis weight of the obtained web entangled sheet was 760 g / m ² . Moreover, the area shrinkage rate by the needle punch process was 38%.

Next, the obtained web-entangled sheet was steam-treated for 90 seconds under the conditions of 70 ° C. and 90% RH. The area shrinkage rate at this time was 47%. And after drying in 120 degreeC oven, the web entanglement sheet | seat with a fabric weight of 1315g / m < ² >, apparent density 0.63g / cm < ³ >, and thickness 2.1mm was obtained by heat-pressing at 120 degreeC. .

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastic body A (solid content concentration 20% by mass) as the first polyurethane elastic body. The polyurethane elastic body A is 99.7: 0.3 (molar ratio) of an amorphous polycarbonate-based polyol and a polyalkylene glycol having 2 to 3 carbon atoms, and the carboxyl group-containing monomer is 1. An amorphous polycarbonate-based non-yellowing polyurethane resin containing 5 wt%. Polyurethane elastic body A has a saturated water absorption at 50 ° C. of 3 mass%, a storage elastic modulus at 23 ° C. of 300 MPa, a storage elastic modulus at 50 ° C. of 150 MPa, a glass transition temperature of −20 ° C., and the average particle size of the aqueous dispersion is 0.03 μm. At this time, the solid content adhesion amount of the aqueous dispersion was 13% by mass with respect to the mass of the web-entangled sheet. The web entangled sheet impregnated with the aqueous dispersion was dried and solidified at 90 ° C. and 50% RH, and further dried at 140 ° C., with a basis weight of 1500 g / m ² and an apparent density of 0.83 g / A sheet of cm ³ and a thickness of 1.8 mm was obtained.

Next, the PVA resin is dissolved and removed by continuously performing a nip treatment for 10 minutes while immersing the web entangled sheet filled with the polyurethane elastic body A in 95 ° C. hot water, and further drying. Thus, a composite of polyurethane elastic body A and fiber entangled body having an average fineness of ultrafine fibers of 0.04 dtex, a basis weight of 1200 g / m ² , an apparent density of 0.63 g / cm ³ and a thickness of 1.9 mm was obtained. .

Then, the composite was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration 20% by mass) as a second polyurethane elastic body. The polyurethane elastic body B was obtained by adding 100 parts by mass of a non-yellowing polyurethane resin obtained from a composition containing an amorphous polycarbonate polyol as a polyol component and 1.7% by mass of a carboxyl group-containing monomer. It is a polyurethane resin having a crosslinked structure formed by adding a mass part and heat-treating it. The polyurethane elastic body B has a saturated water absorption at 50 ° C. of 2% by mass, a storage elastic modulus at 23 ° C. of 480 MPa, a storage elastic modulus at 50 ° C. of 330 MPa, a glass transition temperature of −25 ° C., and the average particle size of the aqueous dispersion. It was 0.05 μm. At this time, the solid content adhesion amount of the aqueous dispersion was 13% by mass relative to the mass of the composite. Next, the web entangled sheet impregnated with the aqueous dispersion was coagulated at 90 ° C. in an atmosphere of 50% RH, and further dried at 140 ° C. Then, it was hot pressed at 150 ° C. to obtain a polishing pad precursor. The obtained polishing pad precursor had a basis weight of 1390 g / m ² , an apparent density of 0.82 g / cm ³ , and a thickness of 1.7 m. The mass ratio between the fiber entangled body and the polyurethane elastic body was 77/23, and the ratio between the polymer elastic body A and the polymer elastic body B was 51:49.

The obtained polishing pad precursor is ground for surface flattening to have a basis weight of 1150 g / m ² , an apparent density of 0.82 g / cm ³ , a thickness of 1.4 mm, and a circle having a diameter of 51 cm. A circular polishing pad was obtained by cutting into a shape and forming grooves with a width of 2.0 mm and a depth of 1.0 mm on the surface in a grid pattern at intervals of 15.0 mm. And polishing evaluation was implemented by the above-mentioned method. When a microscopic image of the obtained cross-section was observed, it was observed that not only the ultrafine fibers constituting the outer periphery of the fiber bundle but also the internal ultrafine fibers were bonded and integrated by the polymer elastic body. In addition, as a slurry in polishing, polishing slurry “SHOROX A-31” manufactured by Showa Denko Co., Ltd. containing 20% by mass of ceria was used. The results are shown in Table 1.

[Example 2]
A polishing pad was prepared by the same method as in Example 1 except that the wet heat shrinkage treatment of the web entangled sheet of Example 1 was processed by the method described below, and polishing evaluation was performed. The results are shown in Table 1. As the wet heat shrinkage treatment conditions for the web-entangled sheet, steam treatment was performed for 90 seconds at a relative humidity of 80%. The area shrinkage rate at this time was 40%. And after drying in 120 degreeC oven, the web entanglement sheet | seat of the fabric weight of 1270g / m < ² >, apparent density 0.60g / cm < ³ >, and thickness 2.1mm was obtained by heat-pressing at 120 degreeC. .

[Comparative Example 1]
As a slurry, instead of using a polishing slurry "SHOROX A-31" made by Showa Denko Co., which contains ceria, it does not contain ceria, except that a slurry containing 15% by mass of silica was used, The polishing performance of the polishing pad was evaluated. The results are shown in Table 1.

[Comparative Example 2]
A polishing pad was prepared by the same method as in Example 1 except that the wet heat shrinkage treatment of the web-entangled sheet was processed by a postoperative method, and polishing evaluation was performed. The results are shown in Table 1. As the wet heat shrinkage treatment conditions of the web-entangled sheet, steam treatment was performed for 90 seconds under the conditions of 60 ° C. and 70% RH. The area shrinkage rate at this time was 30%. And after drying in 120 degreeC oven, the web entanglement sheet | seat of the fabric weight 1190g / m < ² >, apparent density 0.54g / cm < ³ >, thickness 2.2mm was obtained by heat-pressing at 120 degreeC. .

[Comparative Example 3]
The polishing performance of the polishing pad was evaluated in the same manner as in Example 1 except that the polishing pad was changed to a polyurethane-based molded pad. The results are shown in Table 1.

  The results are shown in Table 1.

  The polishing pad according to the present invention is used as a polishing pad for polishing a glass-based substrate that is flattened or mirror-finished, specifically, a glass-based substrate such as a liquid crystal display member, a glass product, or the like. it can. In addition, the polishing can be used for any polishing such as primary polishing, secondary polishing (adjustment polishing), and final polishing.

DESCRIPTION OF SYMBOLS 1 Fiber bundle 1a Microfiber 2 Polymer elastic body 3 Cavity 10 Polishing pad 11 Glass-type base material 12 Carrier 13 Turntable 14 Slurry 15 Slurry supply pipe 16 Conditioner

Claims (4)

A polishing method for polishing a surface of a glass-based substrate by pressing the glass-based substrate while supplying a slurry to a polishing pad,
The slurry contains ceria particles,
The polishing pad is
An entangled body of fiber bundles composed of ultrafine fibers of long fibers having an average fineness of 0.01 to 0.9 dtex and a polymer elastic body impregnated and integrated with the entangled body,
The ultrafine fiber has a saturated water absorption at 50 ° C. of 0.2 to 2% by mass,
The polymer elastic body has a saturated water absorption at 50 ° C. of 0.2 to 5% by mass,
A polishing method characterized by an apparent density of 0.6 to 0.9 g / cm ³ , a D hardness of 36 to 65, and an average interval (Sm) of irregularities on the polished surface of 29.5 to 100 μm.   The mass ratio of the entangled body of the fiber bundle and the polymer elastic body is 55/45 to 90/10, and the storage elastic modulus of the polymer elastic body at 23 ° C and 50 ° C is 90 to 900 MPa. 2. The polishing method according to 1.   The polymer elastic body is a polyurethane resin having a unit derived from polyol, polyamine and polyisocyanate having a glass transition temperature of −10 ° C. or less as a constituent unit, and 60 to 100% of the polyol component is amorphous. The polishing method according to claim 1, wherein the polishing method is a polycarbonate diol.   The polishing method according to claim 1, wherein the ultrafine fiber is a polyester fiber.