TW201440956A - Hard sheet and method for manufacturing hard sheet - Google Patents

Abstract

A hard sheet comprising a non-woven fabric of ultrafine fibers and a hard sheet of a polymer elastic body imparted in the nonwoven fabric; the JIS-D hardness is 45 or more, and the cross section in the thickness direction is equalized from the surface side of either side. In the case where each layer in the division is sequentially set as the first surface layer, the middle layer, and the second surface layer, the JIS-D hardness of the first surface layer and the middle layer is measured at a total of three points at arbitrary points, and the total thickness is 6 points. D hardness and the following formula: R (%) = (D hardness maximum - D hardness minimum value / D hardness average value × 100 calculated R% is 0 to 20%; and the pH of the water changes The total content is 400 μg/cm 3 or less.

Description

Hard sheet and method for manufacturing hard sheet

The present invention relates to a hard sheet which is suitable for use as a polishing pad, in particular, as a polishing pad for polishing a semiconductor wafer, a semiconductor device, a germanium wafer, a hard disk, a glass substrate, an optical article, or various metals. The abrasive layer is used.

The integrated circuit formed on the semiconductor wafer is highly integrated and multilayered. For such semiconductor wafers, high flatness is being sought.

As a polishing method for polishing a semiconductor wafer, it is known as chemical mechanical polishing (CMP). The CMP is a method in which a polishing slurry containing abrasive grains (hereinafter, also simply referred to as a slurry) is dropped, and the surface of the substrate to be polished is polished by a polishing pad.

In the following documents 1 to 4, a polishing pad is disclosed which is composed of a polymer foam having a separate foam structure which can be used for CMP. The polymer foaming system is cast and foamed to form a two-liquid hardening type polyurethane. The polishing pad manufactured from the polymer foam is higher in rigidity than the polishing pad in the form of a non-woven fabric to be described later. Therefore, it is preferably used for the polishing of a semiconductor wafer requiring high flatness.

The polishing pad composed of a polymer foam is highly rigid. because Thus, the load is selectively applied to the convex portion of the substrate to be polished. As a result, a higher polishing rate can be obtained. However, in the case where the agglomerated abrasive particles are present on the abrasive surface, the load will be selectively applied to the agglomerated abrasive particles. Therefore, scratches are likely to occur on the polished surface. In particular, in the case of polishing a substrate having a copper wiring or a low dielectric constant material having a weak adhesiveness at the interface, scratches or interfacial peeling are likely to occur (for example, see Non-Patent Document 1). Further, in the casting foam molding, since the polymer elastic body is easily foamed unevenly, the flatness of the substrate to be polished or the polishing rate during polishing tends to be uneven. Also, the abrasive particles or abrasive chips will slowly block the individual pores of the polymer foam, and the polishing rate will gradually decrease.

The following Patent Documents 5 to 14 disclose a non-woven type polishing pad which is obtained by impregnating a wet-solidified porous polyurethane with a nonwoven fabric. Since the non-woven type polishing pad has superior flexibility, the polishing pad will be easily deformed. Therefore, it is difficult to selectively apply a load to the abrasive grains agglomerated on the polishing surface, and scratching is less likely to occur. However, since the non-woven type polishing pad is soft and the polishing rate is low. Further, the non-woven type polishing pad is deformed in accordance with the surface shape of the substrate to be polished, and the flattening performance of the property of flattening the substrate to be polished is lowered.

Further, the following Patent Documents 15 to 18 disclose a polishing pad having a high flattening property containing an ultrafine fiber nonwoven fabric. For example, Patent Document 15 discloses a polishing pad composed of a sheet material in which a polymer elastomer having a polyurethane as a main component is impregnated with a polyester fiber bundle having an average fineness of 0.0001 to 0.01 dtex. Made of non-woven fabric. The same document also discloses that such a polishing pad achieves a higher precision grinding process.

In the polishing pad using a general ultrafine fiber nonwoven fabric, a non-woven fabric obtained by knitting perforated microfibers of short fibers is widely used. Such a non-woven fabric has low rigidity due to low apparent density and high void ratio. Therefore, since the deformation is caused by the surface shape of the polishing surface, the planarization performance is low.

Patent Document 19 discloses a polishing pad comprising a fiber wound body and a polymer elastic body formed of a fiber bundle of extremely fine single fibers, and a part of the polymer elastic body is present inside the fiber bundle, and the ultrafine single fibers are bundled and deducted. The volume ratio of the portion of the void is in the range of 55 to 95%.

Patent Document 20 discloses a polishing pad which is provided in a polishing pad having a polishing layer and a base layer, and a layer having a water absorption ratio of 1% or less between the polishing layer and the base layer, and a D hardness of the polishing layer and a D of the middle layer. The difference in hardness is 20 or less.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-178374

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-248034

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2001-89548

[Patent Document 4] Japanese Patent Laid-Open No. Hei 11-322878

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2002-9026

[Patent Document 6] Japanese Patent Laid-Open No. Hei 11-99479

[Patent Document 7] Japanese Patent Laid-Open Publication No. 2005-212055

[Patent Document 8] Japanese Patent Laid-Open No. 3-234475

[Patent Document 9] Japanese Patent Laid-Open No. Hei 10-128674

[Patent Document 10] Japanese Patent Laid-Open Publication No. 2004-311731

[Patent Document 11] Japanese Patent Laid-Open No. Hei 10-225864

[Patent Document 12] Japanese Patent Publication No. 2005-518286

[Patent Document 13] Japanese Patent Laid-Open Publication No. 2003-201676

[Patent Document 14] Japanese Patent Laid-Open Publication No. 2005-334997

[Patent Document 15] Japanese Patent Laid-Open Publication No. 2007-54910

[Patent Document 16] Japanese Patent Laid-Open Publication No. 2003-170347

[Patent Document 17] Japanese Patent Laid-Open Publication No. 2004-130395

[Patent Document 18] Japanese Laid-Open Patent Publication No. 2002-172555

[Patent Document 19] Japanese Patent Laid-Open Publication No. 2008-207323

[Patent Document 20] Japanese Patent Laid-Open Publication No. 2011-200984

[Non-patent literature]

[Non-Patent Document 1] "Science of CMP", Science Forum Co., Ltd., August 20, 1997, p. 113-119

An abrasive pad is provided which has a high polishing rate and the polishing rate is difficult to change over time.

One aspect of the present invention is a hard sheet characterized by comprising a non-woven fabric of ultrafine fibers having a fineness of 0.0001 to 0.5 dtex and a hard sheet of a polymeric elastomer imparted in the nonwoven fabric; JIS-D hardness of 45 or more in the thickness direction In the case of the first surface layer, the middle layer and the second surface layer are sequentially arranged in the same manner as the first surface layer, the middle layer, and the second surface layer from the surface side of either side. The JIS-D hardness of the surface layer and the middle layer is R% calculated from the following formula: R (%) = (D hardness maximum value - D hardness minimum value) / D hardness average value × 100 using a total D hardness of 6 points. It is 0 to 20%; and the total ion content which changes the pH of water is 400 μg/cm ³ or less.

Moreover, another aspect of the present invention provides a polishing pad comprising the hard sheet as a polishing layer.

Further, another aspect of the present invention provides a method for producing a hard sheet, comprising: (1) an ultrafine fiberizing treatment capable of forming an ultrafine fiber having a fineness of 0.5 dtex or less and an apparent density of 0.35 g/cm ^{3 ;} The above non-woven fabric, a step of preparing a fiber-wound sheet of a long fiber of a very fine fiber-generating fiber; (2) impregnating a first gel of a gel containing an ion having a change in pH of water and a first emulsion containing a polymer elastomer After the filament-wound sheet is formed, the first emulsion is gelled, and further heated and dried to solidify the polymer elastomer; (3) the ultrafine fiber-forming fiber is formed by ultrafine fiberization to form a nonwoven fabric and a polymer elastic layer. (4) the second emulsion containing the gelling agent and the polymeric elastomer is impregnated into the first composite, and further heated and dried to solidify the polymeric elastomer. When the thickness direction is equal to three, the layers in the thickness direction are equal to three, and the first surface layer, the middle layer, and the second surface layer are sequentially formed, and the second composite having a difference in void ratio between the first surface layer and the middle layer of 5% or less is formed. It (5) a step of obtaining a hard sheet by washing the second composite so that the total content of ions is 400 μg/cm ³ or less; and (6) in order to make the surface hardness of the hard sheet JIS-D hardness 45 As described above, the step of thermally pressurizing at least one selected from the group consisting of the first composite, the second composite, and the hard sheet.

A hard sheet is obtained which is used to obtain a polishing pad having a high polishing rate and which is difficult to change in the polishing rate over time.

1‧‧‧nonwoven

1a‧‧‧Microfiber

1b‧‧‧Fiber bundle

2‧‧‧Polymer elastomer

3‧‧‧1st surface

4‧‧‧ Middle

5‧‧‧ second surface

10‧‧‧Hard flakes

Fig. 1 is a schematic cross-sectional view showing an embodiment of a hard sheet.

[Formation of the Invention]

Hereinafter, an embodiment of the hard sheet according to the present invention will be described in detail. Fig. 1 is a schematic cross-sectional view showing a hard sheet 10 of the present embodiment. In Fig. 1, an enlarged schematic view of a part of the area surrounded by a circle is also shown.

As shown in Fig. 1, the hard sheet 10 is a non-woven fabric 1 including a wound body of the ultrafine fibers 1a, and a hard sheet of the polymer elastic body 2 provided in the nonwoven fabric 1. The hard sheet 10 has a JIS-D hardness of 45 or more, and in the thickness direction, each layer when the surface is equally divided into three is sequentially set as the first surface layer 3, the middle layer 4, and the second surface layer 5. The JIS-D hardness of the first surface layer 3 and the middle layer 4 was measured at a total of three points and three points, and the total hardness of six points was used from the following formula: R (%) = (the D hardness was the highest among the six points) The value of the D hardness of the value -6 points is the minimum value of the D hardness of 6 points / the average R hardness of 100 is 0 to 20%. In addition, it is preferable to measure the JIS-D hardness of the second surface layer 5 and the intermediate layer 4 by a total of three points at an arbitrary point and three points, and the R% calculated from the above formula by using the total D hardness of six points is also 0 to 20%. Further, the total ion content of the pH of the water is changed to 400 μg/cm ³ or less.

In the hard sheet 10, the ultrafine fibers 1a forming the nonwoven fabric 1 form a fiber bundle 1b in which a plurality of ultrafine fibers 1a are bundled. Further, the plurality of fiber bundles 1b are adhered to each other by the polymer elastic body 2. More than half of the plurality of fiber bundles 1b are preferably adhered by the polymer elastic body 2. Further, the ultrafine fibers 1a forming the fiber bundle 1b are also adhered to each other by the polymer elastic body 2. More than half of the ultrafine fibers 1a are preferably adhered to the polymer elastic body 2. The dense hard sheet 10 having a small void and a high hardness is contained in the composite system of the non-woven fabric of the non-woven fabric 1 and the polymeric elastomer 2 and the polymeric elastomer. Such a hard sheet 10 has a reinforcing effect by the fiber bundle 1b and a high filling ratio (that is, a low void ratio) due to the hard sheet, and has high rigidity.

The hard sheet 10 contains an ultrafine fiber nonwoven fabric 1 in which a fiber bundle has been formed. The fiber bundles present in the non-woven fabric of the surface will be fibrillated or fibrillated upon grinding. As a result, extremely fine fibers having a high fiber density will be exposed on the polished surface. The exposed ultrafine fibers are in contact with the substrate to be polished over a wide area, and a large amount of slurry can be maintained. Further, the exposed ultrafine fibers are used to soften the surface of the polishing pad and suppress the selective application of the load to the aggregate of the abrasive grains. As a result, the occurrence of scratches will be suppressed.

In addition, the hard sheet 10 has a JIS-D hardness of 45 or more, and the JIS-D hardness of the first surface layer 3 and the middle layer 2 is measured at 6 points in total at three points, so that the total hardness of 6 points is used from the following formula: R (%) = (D hardness maximum - D hardness minimum value) / D hardness average value × 100 calculated R% becomes 0 to 20% of the way, and in the thickness direction to make it a homogeneous way to adjust. In addition, the JIS-D hardness of the second surface layer 5 and the intermediate layer 2 is measured at a total of three points and three points, and it is preferable that the R% calculated by the total D hardness of six points is also 0 to 20%. The thickness direction is adjusted to make it homogeneous. In this manner, it is possible to adjust the hardness so that homogenization is possible.

Further, the hard sheet 10 is adjusted so that the total ion content of the water changes to 400 μg/cm ³ or less. In order to uniformly impart a polymeric elastomer to the thickness direction as described above, a gelling agent can be generally used. The ions contained in the hard flakes will change the pH of the slurry during grinding. In the case where the pH of the slurry changes, the polishing rate is lowered or the abrasive grains are easily aggregated. In such a case, by reducing the ionic compound or the like contained in the hard sheet by water, it is possible to suppress a decrease in the polishing rate due to the pH change of the slurry. Further, the ion which changes the pH of the water is all ions which change the pH when it is dissolved in water.

The hard sheet of the present embodiment will be described later in detail, and is produced by impregnating a polymer elastic body into a dense nonwoven fabric of an ultrafine fiber at a high content in a thickness direction. Further, in the production of such a hard sheet, in order to impregnate the polymer elastomer with a high content, the emulsion of the polymer elastomer containing the gelling agent is preferably used. In the manufacturing process of the hard sheet, it can be produced by washing with water so that the total ion content of the water contained in the gelling agent is changed to 400 μg/cm ³ or less.

Hereinafter, the requirements of the hard sheet of the embodiment are described. Further details.

The nonwoven fabric of the present embodiment is formed of ultrafine fibers, and the ultrafine fibers are preferably formed into a fiber bundle.

The ultrafine fiber has a fineness of 0.0001 to 0.5 dtex, preferably a fineness of 0.001 to 0.01 dtex. When the fineness of the ultrafine fibers is less than 0.0001 dtex, it is difficult to sufficiently separate the ultrafine fibers in the vicinity of the surface during polishing, and as a result, the amount of slurry held will be lowered. When the fineness of the ultrafine fibers exceeds 0.5 dtex, the polishing rate is lowered by making the surface too thick, and the abrasive grains are easily aggregated on the surface of the ultrafine fibers.

The ultrafine fibers are filaments, and specifically, the average fiber length is 100 mm or more, and more preferably 200 mm or more. Although the upper limit of the average fiber length is not particularly limited, as long as the winding step described later is not cut, for example, it may contain fibers of several m, several hundred m, several km or longer. The long fibers of the ultrafine fibers increase the rigidity of the hard sheets by increasing the fiber density. Further, the long fibers are hard to fall off during polishing. Further, it is difficult to increase the fiber density of the short fibers of the ultrafine fibers, and a hard sheet having high rigidity cannot be obtained. Moreover, the short fibers are liable to fall off during polishing.

It is preferable that the ultrafine fibers forming the non-woven fabric bundle a plurality of ultrafine fibers to form a fiber bundle. In particular, from the viewpoint of obtaining a hard sheet having high rigidity, the average cross-sectional area of the fiber bundle having a cross section in the thickness direction is preferably 80 μm ² or more, more preferably 100 μm ² or more, and particularly preferably 120 μm ² or more.

Moreover, it is preferable that the fiber bundle having a cross-sectional area of 40 μm ² or more in the fiber bundle system having a cross-sectional area in the thickness direction is 25% or more with respect to the total number of bundles of the cross-sectional fiber bundles in the predetermined thickness direction. In particular, in the case of a polishing pad for a wafer, a semiconductor wafer, or a semiconductor device which requires high flatness, the fiber bundle having a cross-sectional area of 40 μm ² or more is preferably 40% or more, and more preferably 50. More than %, especially better than 100%. When the ratio of the fiber bundle of 40 μm ² or more is too low, the polishing rate may be lowered or the flattening performance may be lowered.

Further, in the hard sheet of the present embodiment, the bundle density of the fiber bundle per unit area in the thickness direction cross section is preferably 600 Å/mm ² or more, and more preferably 1000 Å/mm ² or more and 4,000 Å/mm ² or less. Further, it is more preferably 3,000 bundles/mm ² or less. In the case of such a bundle density, at the time of polishing, a fiber bundle on the surface is fibrillated or fibrillated to form a plurality of ultrafine fibers, and the amount of slurry held is improved. Further, by fibrillating or fibrillating the fiber bundle, the surface of the polished surface is softened to suppress the occurrence of scratches. When the bundle density is too low, the fiber density of the ultrafine fibers formed on the surface is lowered, and the polishing rate is lowered or the flattening performance is lowered. Further, when the density of the fiber bundle is too high, the surface tends to be excessively dense, which tends to lower the holding amount of the slurry or the polishing rate. Further, in the hard sheet of the present embodiment, from the viewpoint of high polishing stability, the density of the fiber bundle in the thickness direction and the surface direction is small, which is preferable.

The ultrafine fiber is formed of a thermoplastic resin having a glass transition temperature (Tg) of preferably 50 ° C or more, more preferably 60 ° C or more. In the case where the Tg of the thermoplastic resin is too low, the rigidity will be insufficient at the time of polishing to lower the flattening performance, and also the rigidity will pass over time. The tendency to reduce the polishing stability or the polishing uniformity is lowered. Although the upper limit of the Tg is not particularly limited, the industrial production is preferably 300 ° C, and more preferably 150 ° C. Further, in the polishing process, after the treatment in the warm water having a Tg of 50 ° C due to the water absorption state, the Tg measured in the state of maintaining the wetness is preferably 50 ° C or more. Moreover, the water absorption rate of the thermoplastic resin is preferably 4% by mass or less, and more preferably 2% by mass or less. When the water absorption rate exceeds 4% by mass, the rigidity is lowered as the water in the slurry is slowly absorbed during the grinding. In such a case, the flattening performance is lowered as time passes, or the polishing rate or the polishing uniformity is easily changed. The water absorption rate is preferably from 0 to 2% by mass.

Specific examples of the thermoplastic resin include polyethylene terephthalate (PET, Tg 77 ° C, water absorption: 1% by mass), and isophthalic acid modified polyethylene terephthalate (Tg). 67 to 77 ° C, water absorption of 1% by mass), sulfoisophthalic acid modified polyethylene terephthalate (Tg 67 to 77 ° C, water absorption of 1 to 4% by mass), poly(naphthalene dicarboxylate) Aromatic polyester resin such as ester (Tg 85 ° C, water absorption: 1% by mass), polyethylene naphthalate (Tg 124 ° C, water absorption: 1% by mass); terephthalic acid and decanediol and The octyl diol is a semi-aromatic polyamide resin such as a nylon (Tg 125 to 140 ° C, water absorption of 1 to 4% by mass). These may be used individually or in combination of 2 or more types. From the viewpoint of sufficiently maintaining rigidity, water resistance, and abrasion resistance, polyethylene terephthalate (PET), isophthalic acid modified polyethylene terephthalate, and polynaphthalene are preferred. Butylene dicarboxylate, polyethylene naphthalate. In particular, modified PETs such as PET and isophthalic acid-modified PET are from the island type complex described later. In the wet heat treatment step of forming the ultrafine fibers by winding the sheets together with the fibers, the fibers are wound up to form a dense and high-density fiber-wound body, which is easy to increase the rigidity of the hard sheets, and it is difficult to cause moisture during polishing. It is preferable because the viewpoint of changing with time and the like is caused.

Further, it is also possible to contain ultrafine fibers composed of other thermoplastic resins as necessary within the range which does not impair the effects of the present invention. As such a thermoplastic resin, polylactic acid, polybutylene terephthalate, polybutylene terephthalate, polyethylene succinate, polybutylene succinate, polysuccinic acid, or polysuccinic acid may be used in combination. Aromatic polyester or aliphatic polyester and its copolymers such as polybutylene adipate, polyhydroxybutyl ester-polyhydroxypentyl ester copolymer; nylon 6, nylon 66, nylon 10, nylon 11, Aliphatic nylon and its copolymers such as nylon 12; polyolefins such as polyethylene and polypropylene; modified polyvinyl alcohol containing 25 to 70 mol% of ethylene units; and polyurethane elastomers An elastomer such as a nylon-based elastomer or a polyester-based elastomer.

The hard flakes contain a polymeric elastomer imparted in an ultrafine fiber nonwoven fabric.

Specific examples of the polymer elastomer include, for example, a polyurethane, a polyamide-based elastomer, a (meth)acrylate-based elastomer, and a (meth)acrylate-ethylene elastomer. Methyl) acrylate-acrylonitrile-based elastomer, (meth) acrylate-olefin-based elastomer, (meth) acrylate-(hydrogenated) isoprene-based elastomer, (meth) acrylate - Butadiene-based elastomer, styrene-butadiene-based elastomer, styrene-hydrogenated isoprene-based elastomer, acrylonitrile-butadiene-based elastomer, acrylonitrile-butadiene-styrene system Elastomer, vinyl acetate elastomer, (meth) acrylate-vinyl acetate elastomer, ethylene vinyl acetate bomb A physic body, an ethylene-olefin-based elastomer, a siloxane-based elastomer, a fluorine-based elastomer, and a polyester-based elastomer.

The polymeric elastomer is preferably non-porous. In addition, the term "non-porous" means a void (independent bubble) which is substantially not contained in a porous or sponge-like polymeric elastomer. For example, it means that it is not a polymer elastomer having many independent bubbles as obtained by solidifying a solvent-based polyurethane.

When the polymeric elastomer is in a non-porous state, high polishing stability can be obtained and it is difficult to wear, and it is difficult for the slurry or the mat to remain in the void. Therefore, a high polishing rate can be maintained for a long time. Moreover, since the adhesion to the ultrafine fibers is high, it is difficult to cause the fibers to fall off. Also, since it has high rigidity, it has superior planarization performance.

The water absorption of the polymeric elastomer is preferably from 0.5 to 8% by mass, and more preferably from 1 to 6% by mass. When the water absorption of the polymeric elastomer is too low, the wettability to the slurry will be lowered. As a result, there is a tendency that the polishing rate, the polishing uniformity, the polishing stability are lowered, or the abrasive grains are easily aggregated. When the water absorption of the polymeric elastomer is too high, the rigidity of the hard sheet will decrease with time and the flattening performance will be lowered during polishing. Moreover, the polishing rate or the polishing uniformity is easily changed. In addition, the water absorption rate of the polymer elastomer refers to the water absorption rate when the polymer elastomer film after the drying treatment is immersed in water at room temperature to be saturated and swollen. Further, in the case where two or more kinds of polymer elastomers are contained, the sum of the mass fraction and the water absorption value of the polymer elastomer can be theoretically calculated.

The water absorption of the polymeric elastomer can be adjusted by introducing a hydrophilic functional group or adjusting the degree of crosslinking. Examples of the hydrophilic functional group include a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having a carbon number of 3 or less. The hydrophilic group can be introduced by copolymerizing a monomer having a hydrophilic group. The copolymerization ratio as the monomer unit having a hydrophilic group is preferably from 0.1 to 20% by mass, and more preferably from 0.5 to 10% by mass.

The storage elastic modulus [E' (150 ° C, dry)] of the polymer elastic system at 150 ° C is preferably from 0.1 to 100 MPa, further preferably from 1 to 80 MPa. The storage elastic modulus of the polymeric elastomer can be adjusted by adjusting the degree of crosslinking. In the case where two or more types of polymer elastomers are contained, the sum of the mass fractions multiplied by the values of the respective polymer elastomers [E' (150 ° C, dry)] can be theoretically calculated.

The polymeric elastomers may be used singly or in combination of two or more. Among these, from the viewpoint of excellent adhesion to the ultrafine fibers, a polyurethane is preferred.

It is preferable that the ultrafine fibers forming the fiber bundle are bundled by the polymer elastomer, and it is more preferable to use the polymer elastomer to bundle more than half of the ultrafine fibers.

Further, it is preferable that the plurality of fiber bundles are adhered to each other by the polymer elastic body existing outside the fiber bundle, and it is more preferable that the polymer elastic body adheres to more than half of the bundle of the fiber bundles to form a block. The shape stability of the hard sheet is improved by adhering the fiber bundles to each other, and the polishing stability is improved. A hard sheet having high hardness homogeneity can be obtained by collecting ultrafine fibers or adhering fiber bundles with a polymer elastomer.

In the case where the ultrafine fibers forming the fiber bundle are not bundled, It is difficult to obtain high flattening performance due to the softness of the ultrafine fibers. Further, during the polishing, the ultrafine fibers are easily detached, and the abrasive grains are condensed on the detached fibers to cause scratches to easily occur. The fact that the ultrafine fibers are bundled by the polymeric elastomer means that the ultrafine fibers existing inside the fiber bundle are bound by the polymeric elastomer existing inside the fiber bundle.

The ratio of the non-woven fabric to the polymeric elastomer in the hard sheet (non-woven fabric/polymer elastomer) is preferably 90/10 to 55/45, more preferably 85/15 to 65/35. When the ratio of the non-woven fabric to the polymeric elastomer is within the above range, the rigidity of the hard sheet is easily increased. Moreover, the density of the ultrafine fibers exposed on the surface of the hard sheet can be sufficiently increased. As a result, the polishing stability, the polishing rate, and the flattening performance can be sufficiently improved.

The apparent density of the hard flakes is preferably from 0.5 to 1.2 g/cm ³ , and more preferably from 0.6 to 1.2 g/cm ³ from the viewpoint of maintaining high rigidity.

The hard sheet of the present embodiment has a JIS-D hardness of 45 or more, and the cross section in the thickness direction is sequentially set to the first surface layer, the middle layer, and the second surface layer from the surface side of either side. In the case of the JIS-D hardness of the first surface layer and the middle layer at a total of three points and three points, respectively, the total hardness of six points is used from the following formula: R (%) = (D hardness maximum value) -D hardness minimum value / / D hardness average value of 6 points × 100 The calculated R% is 0 to 20%. In addition, the JIS-D hardness of the second surface layer and the middle layer was measured at a total of three points and three points at a predetermined point, and the R% calculated from the above formula was 0 to 20% by the total D hardness of six points.

The hard sheet has a JIS-D hardness of 45 or more, preferably 45 Up to 75, further preferably 50 to 70. By adjusting the hardness of the first surface layer to a JIS-D hardness of 45 or more, high planarization performance can be obtained. In the case where the JIS-D hardness is too high, scratches are likely to occur. Further, the hard sheet of the present embodiment is for exposing the ultrafine fibers having a high fiber density to the surface, and although it is hard, the surface is soft. Therefore, it is difficult to cause scratches.

The JIS-D hardness of the first surface layer and the middle layer of the hard sheet was measured at a total of 6 points at an arbitrary point and at 3 points, and the R% calculated from the above formula was 0 to 20% by the total D hardness of 6 points. It is preferably from 0 to 15%. When the R% of the first surface layer and the intermediate layer is in such a range, when used as a polishing pad, the change in the polishing rate in the first surface layer and the intermediate layer is made small, and stable polishing performance can be obtained. When R% exceeds 20%, the change in the polishing rate becomes large during the polishing, and the stable polishing performance cannot be obtained. Further, the arbitrary point of measuring the JIS-D hardness means that whether or not the measurement system is carried out at any point in the layer is not arbitrary, and the measurement is performed at any point, and R% is 0 to 20%. In such a case, since the hardness does not become uneven in the width direction in the thickness direction, and the polishing rate is uniform in the planar direction, stable polishing performance can be obtained. Similarly, the JIS-D hardness of the second surface layer and the middle layer of the hard sheet is measured by a total of three points at an arbitrary point and three points, and the R% calculated from the above formula by using the total D hardness of six points is preferably 0 to 20%, further preferably 0 to 15%.

In the hard sheet of the present embodiment, the total ion content of the pH of the water is changed to 400 μg/cm ³ or less. In the hard sheet of the present embodiment, for example, after the emulsion of the polymer elastomer is impregnated into the nonwoven fabric, the polymer elastomer is heated and dried to be solidified, and the polymer elastomer is applied to the nonwoven fabric. . In such a step, the moisture in the emulsion impregnated in the nonwoven fabric is dried from the surface. Therefore, as the evaporation of water proceeds, the migration of the emulsion in the nonwoven fabric to the surface layer will be caused. In the case of migration, the polymer elastic body is uneven in the vicinity of the surface layer of the non-woven fabric, and the polymer elastic body in the vicinity of the intermediate layer is reduced, and the voids are likely to remain in the vicinity of the intermediate layer. Such migration is inhibited by blending the gelling agent in the latex and gelling the emulsion prior to drying. The present inventors have found that ions which change the pH of water contained in the obtained gelling agent will remain in the hard sheet at a predetermined amount or more, and the polishing rate will be lowered during polishing.

The total ion content of the water contained in the hard sheet which changes the pH of water is 400 μg/cm ³ or less, preferably 350 μg/cm ³ or less, and more preferably 100 μg/cm ³ or less. Further, the total content of ions is preferably 0μg / cm ^3, based on the efficiency of industrial washing, preferably 1 to 100μg / cm ^3, further preferably 10 to 50μg / cm ³ or so. In the case where the total amount of ions which change the pH of the water contained in the hard sheet exceeds 400 μg/cm ³ , the slurry causes a change in pH to lower the polishing rate, and further causes the abrasive grains to easily aggregate.

In addition, the ion which changes the pH of the water, and all the ions which change the pH when it is dissolved in water, specifically, for example, sulfate ion and nitric acid contained in a general gelation agent are mentioned. Ions, carbonate ions, ammonium ions, sodium ions, calcium ions, potassium ions, and the like.

[Method of Manufacturing Polishing Pad]

Next, a detailed description will be given of an example of a method for producing a hard sheet. . For example, a hard sheet can be manufactured by the following steps.

(1) Step of preparing a fiber-wound sheet of long fibers of an ultrafine fiber-generating fiber

In this step, a fiber-wound sheet of long fibers of the ultrafine fiber-generating fiber is prepared. The filament-wound sheet of the long fiber of the ultrafine fiber-generating fiber can be produced, for example, in the following manner.

First, a long-fiber cotton web composed of a sea-island type composite fiber in which a water-soluble thermoplastic resin is used as a sea component and a water-insoluble thermoplastic resin is used as an island component is produced. The island-in-the-sea composite fiber is an ultrafine fiber-generating fiber which is produced by the ultrafine fibers composed of the resin of the island component by dissolving the sea component. In the present embodiment, the sea-island type conjugate fiber is used as an example of the ultrafine fiber-generating fiber, and a conventional ultrafine fiber-generating fiber such as a multilayer laminated fiber may be used instead of the sea-island type composite fiber. .

The water-soluble thermoplastic resin is a thermoplastic resin which can be dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution or the like, and a melt-spun resin is used. Specific examples of the water-soluble thermoplastic resin include a PVA-based resin such as polyvinyl alcohol (PVA) or a PVA copolymer, and a polyvinyl alcohol and/or an alkali metal sulfonate as a copolymerization component. Polyester; polyethylene oxide and the like. Among these, a PVA-based resin is preferably used.

When the PVA-based resin is dissolved by the sea-island type composite fiber containing the PVA-based resin as a sea component, the ultrafine fibers which are island components are greatly curled. As a result, a nonwoven fabric having a high fiber density can be obtained. Further, the PVA resin is made of a sea-island type composite fiber containing a PVA resin. When it is dissolved, since the ultrafine fibers or the polymeric elastomer which are island components are not decomposed or dissolved, it is difficult to cause deterioration in physical properties of the ultrafine fibers or the polymeric elastomer.

From the viewpoint of increasing the physical properties of the sea-island type composite fiber, it is preferable to use 4 to 15 mol% of the ethylene unit as the PVA-based resin, and it is more preferable to use 6 to 13 mol% of the ethylene-modified PVA.

The viscosity average degree of polymerization of the PVA-based resin is preferably from 200 to 500, further preferably from 230 to 470, particularly preferably from 250 to 450. Moreover, the melting point of the PVA-based resin is preferably from 160 to 250 ° C, more preferably from 175 to 224 ° C, particularly preferably from 180 to 220 ° C, from the viewpoints of excellent mechanical properties and thermal stability and excellent melt spinning property. The scope.

The water-insoluble thermoplastic resin forming the island component is a thermoplastic resin which is not dissolved or removed by dissolution, such as water, an alkaline aqueous solution, or an acidic aqueous solution, and a melt-spun resin can be used. As a specific example of the water-insoluble thermoplastic resin, various resins which form the ultrafine fibers described above can be used, and a thermoplastic resin having a Tg of 50 ° C or higher and a water absorption ratio of 4% by mass or less is preferably used.

Further, the water-insoluble thermoplastic resin may, for example, contain a catalyst, an anti-coloring agent, a heat-resistant agent, a flame retardant, a lubricant, an antifouling agent, a fluorescent whitening agent, a matting agent, a coloring agent, and a gloss improver. Additives such as antistatic agents, fragrances, deodorants, antibacterial agents, anti-caries agents, inorganic particles, and the like.

The sea-island type composite fiber is produced by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin having low compatibility with a water-soluble thermoplastic resin, and then using a composite spinning method in which the composite is combined. Further, it is preferable that the sea-island type composite fiber is subjected to cotton webization while maintaining a long fiber state.

For example, the long-fiber cotton web of the sea-island type composite fiber is obtained by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin by a spunbonding method, and further stretching and then accumulating it. . Further, the long fibers are continuous fibers produced by the cutting step as in the case of producing short fibers. An example of a method for producing a long-fiber cotton web of an island-in-the-sea composite fiber will be described in detail below.

First, the water-soluble thermoplastic resin and the water-insoluble thermoplastic resin are separately melt-kneaded by respective extruders, and the tow of the molten resin is simultaneously discharged from the respective spinning nozzles. Then, the discharged tow is combined by a composite nozzle, and then ejected from the nozzle hole of the spinneret to form a sea-island type composite fiber.

The mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin in the sea-island type composite fiber is not particularly limited, and is preferably from 5/95 to 50/50, further preferably from 10/90 to 40/60. When the mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is in such a range, it is preferable from the viewpoint that a high-density nonwoven fabric and an ultrafine fiber formability are excellent. Further, in the molten composite spinning, the number of islands in the sea-island type composite fiber is preferably from 4 to 4,000 islands/fiber, and further preferably from 10 to 1,000 islands/fiber. Further, although the fineness of the sea-island type composite fiber is not particularly limited, it is preferably about 0.5 to 3 dtex from the viewpoint of industrial properties.

The island-in-the-sea composite fiber system is cooled by a cooling device and then used as an intended fineness by using an inhalation device such as a jet nozzle. It is stretched by a high-speed air stream at a speed equivalent to a drawing speed of 1000 to 6000 m/min. Thereafter, a long fiber web is formed by depositing the drawn composite fiber on a movable collecting surface. At this time, if necessary, the long fiber web which is deposited may be partially pressed.

Next, a plurality of sheets of cotton web are overlapped to be entangled. The winding treatment of the cotton web can be carried out by knit perforation or high-pressure water flow treatment or the like. As a representative example, the winding process by the knitting perforation is described in detail.

First, an oil agent for preventing needle bending, an antistatic oil agent, a sulfonated oil agent such as an oil agent for entanglement, or a mineral oil-based oil agent is applied to the cotton web. Then, the web is wound by knitting the perforations. The basis weight of the wound web is preferably in the range of 100 to 1500 g/m ² from the viewpoint of excellent workability.

Next, the fiber density is increased by shrinking the entangled long fiber web. In comparison with the case where the staple fiber web is shrunk, it is more likely to shrink by shrinking the long fiber web. The shrinkage treatment is preferably a wet heat shrinkage treatment such as steam heating. The steam heating conditions include, for example, conditions in which the ambient temperature is in the range of 60 to 130 ° C, and the relative humidity is 75% or more, or even the relative humidity is 90% or more, and the heat treatment is performed for 60 to 600 seconds.

The wet heat shrinkage treatment preferably has an area shrinkage ratio of 35% or more, and more preferably 40% or more, to shrink the wound long fiber web. In this manner, the fiber density is extremely high by shrinking at a high shrinkage rate. From the viewpoint of the shrinkage limit or the treatment efficiency, the upper limit of the area shrinkage ratio is preferably about 80% or less. Also, area shrinkage (%) is calculated by the following formula.

(The area of the cotton web wound before the shrinkage treatment - the area of the cotton web wound after the shrinkage treatment) / The area of the cotton web wound before the shrinkage treatment × 100

In this manner, the cotton web wound by the wet heat shrinkage treatment can be further increased in fiber density by heating the roll or heating and pressing. The basis weight of the woven cotton web before and after the moist heat shrinkage treatment is preferably 1.2 times (mass ratio) or more, further preferably 1.5 times, compared with the basis weight before shrinkage treatment. The above; preferably 4 times or less, further preferably 3 times or less. In this manner, a long-fiber cotton web of an island-in-sea type composite fiber (hereinafter referred to as a filament-wound sheet) can be obtained.

Such a filament-wound sheet is converted into an nonwoven fabric of 0.35 to 0.90 g/m ³ by extremely fine fiberization of the following sea-island type composite fiber.

In comparison with a cotton web wound with short fibers, the cotton web wrapped with long fibers is largely wet heat-shrinked due to extremely fine fiberization. Therefore, the fiber density of the ultrafine fibers is made denser. Then, a non-woven fabric of a fiber bundle containing extremely fine fibers is formed by selectively removing the water-soluble thermoplastic resin of the sea-island type composite fiber. At this time, a void is formed in a portion where the water-soluble thermoplastic resin is dissolved and extracted. The polymer elasticity is imparted by the high content in the voids, and the ultrafine fibers constituting the fiber bundle are bundled, and the fiber bundles are adhered to each other. In this manner, a hard sheet having a high fiber density, a low void ratio, and a high rigidity can be obtained.

(2) by causing ions containing changes in the pH of water After the gelling agent and the first emulsion containing the polymer substrate are impregnated into the filament-wound sheet, the first emulsion is gelated, and further heated and dried to solidify the polymer elastomer.

In this step, the polymeric elastomer is uniformly filled in the filament wound sheet in the thickness direction. Since the emulsion of the polymeric elastomer is high in concentration, low in viscosity, and excellent in impregnation permeability, it is easy to be highly filled in the filament-wound sheet. Moreover, by including a gelling agent in the emulsion of the polymeric elastomer, it is possible to suppress migration of the emulsion in a thickness direction unevenness during drying.

In the case of using a polymer elastomer solution generally used in the prior art, in the case of using a polymer elastomer emulsion, a non-porous polymer elastomer can be formed.

From the viewpoint of high adhesion to fibers, the polymer elastomer is preferably a hydrogen bond polymer elastomer. The hydrogen bond-type polymer elastomer is, for example, a polymer such as a polyurethane, a polyamide-based elastomer, or a polyvinyl alcohol-based elastomer, which is crystallized or agglomerated by a hydrogen bond. The elastomer that is formed.

Hereinafter, a case where the polyurethane is used as a polymer elastomer will be described in detail as a representative example.

Examples of the polyurethane include various polyurethanes obtained by reacting a polymer polyol having an average molecular weight of 200 to 6000, a chain of an organic polyisocyanate, and a chain extender at a predetermined molar ratio.

Specific examples of the polymer polyol include, for example, polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and poly(methyltetramethylene glycol). Copolymer; polybutylene adipate Glycol, polybutylene terephthalate diol, polyhexamethylene adipate diol, poly(3-methyl-1,5-pentene adipate) diol, poly(3- Polyester polyols such as methyl-1,5-pentene sebacate), polycaprolactone diol, and copolymers thereof; polyhexamethylene carbonate diol, poly(3-methyl) Polycarbonate polyols and copolymers thereof, such as keto-1,5-extended pentyl carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, etc.; polyester carbonate Polyols, etc. Further, if necessary, a polyfunctional alcohol such as a trifunctional alcohol such as trimethylolpropane or a tetrafunctional alcohol such as pentaerythritol may be used in combination; or ethylene glycol, propylene glycol, 1,4-butanediol, or hexa-hexane. Short-chain alcohols such as diols. These may be used alone or in combination of two or more. In particular, from the viewpoint of a hard sheet excellent in durability such as hydrolysis resistance and oxidation resistance, an amorphous polycarbonate polyol, an alicyclic polycarbonate polyol, or a linear polycarbonate is preferably used. A mixture of a polyol and the polycarbonate polyol and a polyether polyol or a polyester polyol. Moreover, from the viewpoint of making the wettability to water particularly excellent, it is preferred to contain a polyurethane having a carbon number of 5 or less and particularly preferably a polyalkylene glycol having a carbon number of 3 or less.

Specific examples of the organic polyisocyanate include aliphatic or alicyclic rings such as hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate. Non-yellowing isocyanate such as diisocyanate; aromatics such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate polyurethane Group diisocyanate and the like. Further, if necessary, a polyfunctional isocyanate such as a trifunctional isocyanate or a tetrafunctional isocyanate may be used in combination. These may be used alone or in combination of two or more. High and hard from the available adhesion to the fiber From the viewpoint of a highly hard sheet, among these, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-di are preferable. Phenylmethane diisocyanate, xylene diisocyanate.

Specific examples of the chain extender include hydrazine, ethylenediamine, propylene diamine, hexamethylenediamine, ninethylenediamine, xylenediamine, isophoronediamine, and piperazine. And derivatives thereof, diamines such as diammonium adipate, dioxonium isophthalate; triamines such as diethyltriamine; tetraamines such as triethylammonium; Glycols such as diol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol a triol such as trimethylolpropane; a pentaol such as pentaerythritol; an amine alcohol such as an amine ethyl alcohol or an aminopropyl alcohol; and the like. These may be used alone or in combination of two or more. From the viewpoint of ending the hardening reaction in a short period of time, among these, it is preferred from hydrazine and piperidine. Two or more kinds are used in combination with hexamethylenediamine, isophorone diamine and a derivative thereof, and a triamine such as diethyltriamine. Further, in the chain elongation reaction, together with the chain extender, a monoamine such as ethylamine, propylamine or butylamine may be used in combination; a monoamine having a carboxyl group such as 4-aminobutyric acid or 6-aminohexanoic acid a compound; a monol of methanol, ethanol, propanol or butanol.

Further, a carboxyl group-containing diol such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid or 2,2-bis(hydroxymethyl)pentanoic acid is used in combination. Alternatively, an ionic group such as a carboxyl group can be introduced into the skeleton of the polyurethane to further improve the wettability to water.

Further, in order to control the water absorption rate or the storage elastic modulus of the polyurethane, it is preferred to form two or more molecules by adding molecules. A crosslinking agent having a functional group reactive with a functional group of a monomer unit of a polyurethane, or a self-crosslinking compound such as a polyisocyanate compound or a polyfunctional block isocyanate compound forms a crosslinked structure.

As a combination of a functional group of a monomer unit and a functional group of a crosslinking agent, 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 cyclic carbonate group, a carboxyl group and a nitrogen cyclopropyl group, a carbonyl group, an anthracene derivative, an anthracene derivative, or the like. From the viewpoint of excellent rigidity or abrasion resistance of the hard sheet, among these, a monomer unit having a carboxyl group is particularly preferable a combination of an oxazoline group, a crosslinking agent having a carbodiimide or an epoxy group; a combination of a monomer unit having a hydroxyl group or an amine group and a crosslinking agent having a blocked isocyanate group; and a monomer unit having a carbonyl group In combination with an anthracene derivative or an anthracene derivative, crosslinking is formed to be easy. Further, from the viewpoint of maintaining the stability of the polymer elastomer emulsion, the crosslinked structure is preferably formed in a heat treatment step after imparting the polyurethane to the fiber-wound sheet. Among these, the cross-linking property or the applicability of the emulsion is excellent, and the carbodiimide group and/or the safety surface are also problem-free. The oxazoline group is particularly desirable. Examples of the crosslinking agent having a carbodiimide include "carbodiimide E-01", "carbodiimide E-02", and "carbodiimide" manufactured by Nisshinbo Co., Ltd. A water-dispersed carbodiimide compound such as amine V-02". Again, with Examples of the oxazoline-based crosslinking agent include water dispersion such as "EPOCROS K-2010E", "EPOCROS K-2020E", and "EPOCROS WS-500" manufactured by Nippon Shokubai Co., Ltd. An oxazoline compound. The active ingredient of the crosslinking agent is preferably from 1 to 20% by mass, more preferably from 1.5 to 1% by mass, still more preferably from 2 to 10% by mass, based on the blending amount of the crosslinking agent. .

In addition, from the viewpoint of improving the adhesion to the ultrafine fibers and increasing the rigidity of the fiber bundle, the content of the polymer polyol component in the polyurethane is preferably 65 mass% or less, and more preferably 60 mass%. the following. Moreover, from the viewpoint of suppressing the occurrence of scratches, it is preferably 40% by mass or more, and more preferably 45% by mass or more by imparting moderate elasticity.

The method of preparing the polyurethane emulsion is not particularly limited, and a conventional method can be used. Specifically, for example, a method in which a monomer having a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group is used as a copolymerization component to impart self-emulsifiability to water to a polyurethane is exemplified. Or a method in which a surfactant is added to a polyurethane to emulsify it. Since a polymer elastic system containing a monomer unit having a hydrophilic group as a copolymerization component has superior wettability to water, a large amount of slurry can be maintained.

Specific examples of the surfactant which can be used for the emulsification include sodium lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene tridecyl ether acetate, sodium tridecylbenzenesulfonate, and alkyl group II. Anionic surfactants such as sodium phenyl ether disulfonate, sodium dioctyl sulfosuccinate; polyoxyethylene nonylphenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene lauryl ether, poly A nonionic surfactant such as ethylene oxide stearyl ether or a polyoxyethylene-polyoxypropylene block copolymer. Further, a reactive so-called reactive surfactant can also be used. Further, the sensible gelling agent can also be imparted to the emulsion by appropriately selecting the cloud point of the surfactant.

Highly filling the polymer elastomer in a uniform manner in the thickness direction The solid matter concentration as the emulsion is preferably from 15 to 40% by mass, and more preferably from 25 to 35% by mass, from the viewpoint of being filled in the filament-wound sheet. Further, the particle diameter as the emulsion is preferably from 0.01 to 1 μm, more preferably from 0.03 to 0.5 μm.

The first emulsion contains a gelling agent for ions which changes the pH of water. The gelling agent is used to gel the emulsion particles by changing the pH of the emulsion. The moisture in the emulsion impregnated in the nonwoven fabric is dried from the surface. Therefore, as the evaporation of water proceeds, it is easy to cause migration of the emulsion in the nonwoven fabric to the surface layer. When the emulsion in the nonwoven fabric has migrated, the polymer elastic body will be uneven in the vicinity of the surface layer of the non-woven fabric, and the polymer elastic body in the vicinity of the middle layer will be reduced, and voids are likely to remain in the vicinity of the intermediate layer. When the void remains in the vicinity of the middle layer, the hardness in the middle layer is lowered, and the hardness is made uneven. Such migration is inhibited by blending the gelling agent in the emulsion and gelling the emulsion prior to drying.

The gelation agent is not particularly limited as long as it is a water-soluble salt that changes the pH of the emulsion to the extent that the emulsion particles are gelled by heating. As a specific example thereof, it is a monovalent or divalent inorganic salt. For example, sodium sulfate, ammonium sulfate, sodium carbonate, calcium chloride, calcium sulfate, calcium nitrate, zinc oxide, zinc chloride, magnesium chloride, potassium chloride, potassium carbonate, sodium nitrate, lead nitrate, etc. are mentioned.

The content ratio of the gelling agent in the first emulsion is preferably 0.5 to 5 parts by mass, and more preferably 0.6 to 4, based on 100 parts by mass of the polymer elastomer, from the viewpoint of imparting the gelation property. Parts by mass.

The first emulsion may further contain a penetrating agent, an antifoaming agent, and a moisturizing agent. Slip agent, water repellent, oil repellent, tackifier, extender, hardening accelerator, antioxidant, ultraviolet absorber, fluorescent agent, antifungal agent, foaming agent polyvinyl alcohol or carboxymethyl cellulose Water-soluble polymer compounds, dyes, pigments, inorganic fine particles, and the like.

The method of impregnating the first emulsion with the filament-wound sheet is not particularly limited, and for example, a method such as dipping, extrusion, knife coating, bar coating, or roll coating can be used.

Further, after the first emulsion is impregnated into the filament-wound sheet, the first emulsion is gelated in the filament-wound sheet by heating. As the heating conditions for such gelation, for example, it is preferably carried out at 40 to 90 ° C, more preferably at 50 to 80 ° C, for about 0.5 to 5 minutes. Further, it is preferable to use steam heating from the viewpoint of suppressing migration of the emulsion due to rapid evaporation of water from the surface layer and heating the inner layer homogeneously.

Then, after the first emulsion is gelated, the polymer elastomer is solidified by heating and drying.

Examples of the heat drying include a method of heating and drying in a drying device such as a hot air dryer, or a method of heating and drying in a dryer after heating by infrared rays. The conditions for the heat drying include, for example, a condition in which the maximum temperature is 130 to 160 ° C or even 135 to 150 ° C for 2 to 10 minutes. By heating and drying, the polymer elastomer is uniformly agglomerated by evaporating the water in the first emulsion, and the polymer elastic body can be uniformly imparted in the thickness direction of the fiber-wound sheet.

(3) Processing of ultrafine fibers by ultrafine fiberization Step of forming a first composite body containing an ultrafine fiber nonwoven fabric and a polymeric elastomer

The sea-island type composite fiber contained in the fiber-wound sheet to which the polymer elastic body is impregnated is impregnated by the ultrafine fiberization to form the first composite body of the nonwoven fabric containing the ultrafine fibers and the polymer elastic body.

This step is a step of forming an ultrafine fiber from the sea-island type composite fiber containing the water-soluble thermoplastic resin of the island component and the seawater-insoluble thermoplastic resin by removing the fine fiberization treatment of the water-soluble thermoplastic resin.

The ultrafine fiberizing treatment is a treatment of dissolving or decomposing and removing the water-soluble thermoplastic resin forming the sea component by heat-treating the fiber-wound sheet containing the sea-island type composite fiber with hot water such as water, an alkaline aqueous solution or an acidic aqueous solution.

As a specific example of the hot water heat treatment, for example, the following method is preferably employed: the first stage is to impregnate the fiber-wound sheet in hot water of 65 to 90 ° C for 5 to 300 seconds, and further, the second stage is at 85. It is treated in hot water to 100 ° C for 100 to 600 seconds. Moreover, in order to improve the dissolution efficiency, if necessary, a pinch process by a reel, a high-pressure water stream process, an ultrasonic process, a shower process, a stirring process, a kneading process, etc. can also be performed.

The fiber-wound sheet is treated by hot water heating, and the water-soluble thermoplastic resin is dissolved from the sea-island type composite fiber to form an ultrafine fiber. Also, when extremely fine fibers are formed, the ultrafine fibers are greatly curled. The fiber density of the ultrafine fibers becomes dense due to the crimping. Further, a void is formed in a portion where the water-soluble thermoplastic resin is present by removing the water-soluble thermoplastic resin from the sea-island type composite fiber. In the subsequent steps, high A molecular elastomer will fill in the void. Further, by heating the filament-wound sheet by hot water, the gelling agent contained in the filament-wound sheet is also dissolved in hot water to be removed. The first composite is formed in this manner.

(4) After the second emulsion containing the gelling agent and the polymeric elastomer is impregnated into the first composite, the second emulsion is gelated, and further, the polymer elastomer is solidified by heating and drying to form a second emulsion. 2 complex steps

As described above, in the first composite formed by removing the water-soluble thermoplastic resin from the sea-island type composite fiber, voids are formed in the portion where the water-soluble thermoplastic resin is present. In the present embodiment, a hard sheet having high hardness is uniformly obtained, and the voids in the first composite are filled with the polymer elastomer to bind the ultrafine fibers.

By filling the polymer elastomer in the void formed by removing the water-soluble thermoplastic resin, the ultrafine fibers can be bundled to lower the void ratio of the hard sheet. In the case where the ultrafine fibers have formed a fiber bundle, the emulsion is easily impregnated according to the capillary phenomenon.

The same emulsion as the first emulsion was used as the second emulsion. Further, the second emulsion and the first emulsion may have the same composition or different compositions.

In this step, the first layer, the middle layer, and the second surface layer are sequentially set to be the first surface layer, the middle layer, and the second surface layer, which are equally divided into three in the thickness direction from the surface side of either side. The difference between the porosity of the surface layer and the intermediate layer is preferably 5% or less, and more preferably 3% or less, to impart a gelation to the second emulsion. By this way In the whole, a hard sheet having a uniform hardness and high hardness can be obtained.

Further, the difference in the void ratio between the first surface layer and the middle layer is calculated by the following formula.

Difference (%) of void ratio between the first surface layer and the middle layer = absolute value (void ratio (%) of the middle layer - void ratio (%) of the first surface layer)

The void ratio of each layer was determined as follows. The cross section of the thickness direction of the second composite was taken at 30 times by a scanning electron microscope. Then, using the software Popimaging (manufactured by Digital being kids. Co., Ltd.) of the image obtained by image analysis, the image is binarized by the dynamic threshold value to specify the gap portion. Then, the inscribed circle is drawn in each of the void portions, and the total of the inscribed circular areas is the full-layer void amount. Then, from the side surface of one side in the thickness direction of the second composite body, the portion in which the thickness direction is divided into 1/3 is used as the first surface layer, and the thickness direction is divided into 1/3 from the other side surface. The portion is referred to as a second surface layer, and the remaining layer is referred to as a middle layer, and the total area of the inscribed circles of each layer is determined to be the amount of voids of each layer. Then, the void ratio of each layer was determined in accordance with the void ratio of each layer = the amount of voids in each layer / the amount of voids in the entire layer × 100 (%).

As a method of impregnating the first emulsion with the first composite, a method of gelling, and a method of heating and drying, a method of impregnating the first emulsion, a method of gelating, and heating may be employed. The same method of drying. The second composite is formed in this manner.

(5) a step of washing the second composite in such a manner that the total ion content of the ion is changed to 400 μg/cm ³ or less

In the hard sheet of the present embodiment, when the polymer elastic body is applied to the nonwoven fabric, the emulsion containing the gelling agent is used to suppress migration to the surface layer of the emulsion. The present inventors have found that in the case where many of the ions contained in the gelling agent remain in the obtained hard sheet, the polishing rate is lowered during polishing. Then, it was also found that the amount of ion remaining was 400 μg/cm ³ or less by washing with water, and the decrease in the polishing rate was suppressed.

The step of washing with water is such that the total ion content of the pH of the water contained in the hard sheet is 400 μg/cm ³ or less, preferably 350 μg/cm ³ or less, and more preferably 100 μg/cm ³ or less. The steps. As the water washing method, for example, from the viewpoint of high water washing efficiency, a water washing treatment is preferred. As a specific condition, for example, the second composite is immersed in hot water of 80 ° C or higher. In detail, for example, the following conditions: after the first stage is immersed in hot water of 65 to 90 ° C for 5 to 300 seconds, the second stage is further treated in hot water of 85 to 100 ° C for 100 to 600 seconds. bell. Further, in order to improve the washing efficiency, it is also possible to carry out a pinch process by a reel, a high-pressure water stream process, an ultrasonic process, a shower process, a stirring process, a kneading process, etc., if necessary.

(6) Step of thermally pressing at least one of the first composite, the second composite, and the hard sheet in order to set the surface hardness of the hard sheet to JIS-D hardness of 45 or more

The voids present inside the hard sheet reduce the hardness or hardness homogeneity. In this step, the voids are reduced by thermally pressing the first composite, the second composite, and/or the hard sheet. In this manner, the apparent density of the hard flakes is increased by reducing the voids, and the homogeneity and rigidity of the hardness or hardness are increased. The conditions of the hot press treatment are preferably as follows: as the ultrafine fibers and the polymer. Elastomer does not decompose The temperature is, for example, pressurized with a metal roll heated to 160 to 180 ° C at a linear pressure of 30 to 100 kg/cm.

Through the above steps, the hard sheet of this embodiment can be obtained. The hard sheet of the present embodiment is preferably used as a polishing layer of a polishing pad. Specifically, the polishing layer can be formed by performing the required processing on the hard sheet as necessary. For example, a creping treatment, a heat press treatment, an embossing process, or the like, which is carried out by sanding paper, card clothing, diamond, or the like, or a reverse sealing is performed. Further, grooves or holes such as a lattice shape, a concentric shape, or a spiral shape may be formed on the surface of the hard sheet.

Further, if necessary, a hard sheet may be used as an abrasive layer to laminate an elastomer layer such as a knitwear, a textile, a nonwoven fabric, an elastic resin film, or an elastic sponge. As the elastic film or the elastic sponge, in addition to the non-woven fabric (for example, "Suba 400" (manufactured by Nitta Haas Co., Ltd.)) which is impregnated with the polyurethane which is currently used, natural rubber, nitrile rubber, Rubber such as polybutadiene rubber or silicone rubber; thermoplastic elastomer such as polyester thermoplastic elastomer, polyamine thermoplastic elastomer, or fluorine thermoplastic elastomer; foamed plastic; polyurethane, etc. . In this manner, by laminating the elastomer layer, the flatness of the roll surface (flatness of the wafer portion) can be improved. Further, the polishing pad is directly bonded to the polishing layer and the elastomer layer by melting or the like, and further includes two layers by means of an adhesive or a double-sided adhesive tape, or the like, or another layer between the two layers. Layer.

The polishing pad using the hard sheet of the present embodiment can be used in a conventional CMP apparatus, and is used under pressure to bring the slurry into the middle at a constant speed and to bring the surface to be polished into contact with the polishing pad for a certain period of time. Learn mechanical grinding (CMP). For example, the slurry contains a liquid medium such as water or oil; an abrasive such as cerium oxide, aluminum oxide, cerium oxide, zirconium oxide or cerium carbide; and a component such as an alkali, an acid or a surfactant. Further, when performing CMP, a lubricating oil, a coolant, or the like is used together with the slurry as necessary.

The article to be polished is not particularly limited, and examples thereof include crystal, enamel, glass, an optical substrate, an electronic circuit board, a multilayer wiring board, and a hard disk. As a target for polishing, it is particularly preferable to be a wafer or a semiconductor wafer. Specific examples of the semiconductor wafer include an insulating film such as yttrium oxide, oxyfluoride, or an organic polymer on the surface; and a wiring metal film such as copper, aluminum, or tungsten; A barrier metal film such as titanium, tantalum nitride or titanium nitride.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples. Further, the present invention is by way of example and not by way of limitation.

First, the evaluation method used in the present embodiment will be described below.

[Apparent Density of Hard Sheets]

The value of the mass per unit area (g/cm ² ) divided by the thickness (cm) of the hard sheet was set as the apparent density (g/cm ³ ). Then, for any ten of the hard flakes, the apparent density was measured and the arithmetic mean value was set as the apparent density. Further, the thickness was measured in accordance with JIS L 1096 at a load of 240 gf/cm ² .

[Measurement of JIS-D hardness of the surface of the hard sheet, the first surface layer and the middle layer, and calculation of R%]

The surface of the hard sheet and the first surface layer were measured in accordance with JIS K 7311. The D hardness of the middle layer. Specifically, the D hardness of the surface of the hard sheet was superposed on eight hard sheets having a thickness of about 1.25 mm, and the hardness in the width direction was measured at three points, and the average was set to the D hardness of the surface of the hard sheet.

Further, the D hardness of the first surface layer was obtained by grinding a hard sheet having a thickness of about 1.25 mm from the second surface layer side to obtain a first surface layer sheet having a thickness of 0.40 mm. Then, the obtained first surface sheet of 25 sheets was superposed, and the hardness in the width direction of three points was measured, and the average was set to the JIS-D hardness of the first surface layer. Further, the D hardness of the middle layer was obtained by uniformly grinding the hard sheet from the first surface layer side and the second surface layer side to obtain a layered sheet having a thickness of 0.40 mm. Then, 25 sheets of the obtained intermediate sheet were stacked, and the hardness in the width direction was measured at three points, and the average was set to the hardness of the middle layer. Then, using the value of the JIS-D hardness of the total of 6 points D hardness of the first surface layer and the 3 point D hardness of the middle layer from the following formula: R (%) = (D hardness maximum - D hardness minimum Value) / D hardness average × 100 to find R%.

[Total total ion content that changes the pH of water]

A piece of the hard sheet cut into a long square shape and 10 mL of water were placed in a test tube for cutting the screw. Then, using a heating block, the screw-end test tube was heated at 90 ° C for 2 hours to extract the water-soluble substance in the hard sheet by hot water. Then, ion chromatography (ICS-1600) was used to detect the ionic component in the extract. Here, the total amount of the sulfate ion and the ammonium ion of the ion which changes the pH of the water is measured, and is converted into the amount of the ion contained in the hard sheet per unit area.

[grinding rate]

The hard sheet was cut into a circular shape having a diameter of 51 cm, and a groove having a width of 1.0 mm and a depth of 0.5 mm was formed on the surface at intervals of 15.0 mm in a lattice shape to form a polishing pad. Then, the adhesive tape was attached to the back surface of the polishing pad, and then attached to a CMP polishing apparatus ("PP0-60S" manufactured by Nomura Manufacturing Co., Ltd.). Next, the slurry was supplied at a rate of 100 mL/min under the conditions of a platen rotation number of 70 rotations/min, a head rotation number of 69 rotations/min, and a polishing pressure of 40 g/m ² (SHOROXA, manufactured by Showa Denko). 31) A synthetic quartz having a diameter of 4 Å was polished for 3 hours. Then, by measuring the thickness of any 25 points in the plane of the polished quartz after polishing, the polishing rate (nm/min) was determined by dividing the average thickness polished at each point by the polishing time.

Further, the polishing rates of the first surface layer of the hard sheet having a thickness of about 1.25 mm and the hard sheet having a thickness of 0.70 mm exposed in the middle layer were measured.

[Example 1]

A water-soluble PVA was used as a sea component, and a phthalic acid-modified PET having a degree of modification of 6 mol% was used as an island component. The water-soluble PVA and the isophthalic acid-modified PET were sprayed at 260 ° C from a nozzle for melt-spinning (number of islands: 25 islands/fiber) at a temperature of 25/75 (mass ratio). Then, the ejector pressure was adjusted so that the spinning speed became 3,700 m/min, and the long fibers having a fineness of 3 dtex were collected on the net to obtain a cotton web having a basis weight of 35 g/m ² .

An overlapped cotton web having a total basis weight of 480 g/m ² was produced by overlapping 16 sheets of cotton web by cross lamination. Then, spray the overlapping cotton web to prevent the needle from bending. Then, the entangled cotton was obtained by using a knitting needle having a number of barbs of 1 and a knitting yarn of No. 42 and a knitting needle having a number of barbs of 6 and a knitting yarn of No. 42 to be knitted by a perforation of 3,150 perforations/cm ² . network. The wrapped cotton web had a basis weight of 770 g/m ² and an interlayer peeling force of 9.6 kg/2.5 cm. In addition, the area shrinkage by knit perforation treatment was 25.8%.

Next, the wound web was steam-treated at 70 ° C and 23.5% RH for 70 seconds. The area shrinkage at this time was 44%. Then, after drying in an oven at 90 to 110 ° C, a fiber-wound sheet having a basis weight of 1312 g/m ² , an apparent density of 0.544 g/cm ³ and a thickness of 2.41 mm was further obtained by hot pressing at 115 ° C. .

Next, the polyurethane emulsion as the first emulsion was impregnated into the filament wound sheet. Further, the polyurethane has a polycarbonate polyol of 99.8:0.2 (mole ratio) and a polyalkylene glycol having 2 to 3 carbon atoms as a polyol component, and contains 1.5% by mass of a carboxyl group. Monomeric non-yellowing polyurethane. Further, the polyurethane is a non-porous polyurethane formed by a heat treatment to form a crosslinked structure. The first emulsion contains 4.6 parts by mass of a carbodiimide-based crosslinking agent and 1.8 parts by mass of ammonium sulfate as a gelling agent with respect to 100 parts by mass of the polyurethane, and the solid of the polyurethane is made. Become a 20% way to adjust.

The first emulsion was gelled by heating the fiber-wound sheet impregnated with the first emulsion in an environment of 90 ° C and 30% RH, and further dried at 150 ° C. Then, it was further adjusted to have a basis weight of 1,403 g/m ² , an apparent density of 0.716 g/cm ³ , and a thickness of 1.96 mm by heat pressurization at 140 ° C.

Then, by using a pinch process and a high-pressure water stream treatment, the fiber-entangled sheet of the polyurethane is immersed in hot water at 95 ° C for 10 minutes to dissolve and remove the water-soluble PVA, and converted into a fine fiber having a fineness of 0.09 dtex. Further drying. In this manner, the first composite having a basis weight of 1009 g/m ² , an apparent density of 0.538 g/cm ³ and a thickness of 1.87 mm was obtained.

Next, an emulsion (solid content: 30% by mass) of the polyurethane as the second emulsion was impregnated into the first composite. Also, the polyurethane is the same as the previously impregnated polyurethane. The second emulsion contains 4.6 parts by mass of a carbodiimide-based crosslinking agent and 1.0 part by mass of ammonium sulfate, and the solid content of the polyurethane is 30%, based on 100 parts by mass of the polyurethane. Adjust things.

The second emulsion was gelled by heating the first composite impregnated with the second emulsion in an environment of 90 ° C and 60% RH, and further dried at 150 ° C. In this manner, a second composite having a basis weight of 1245 g/m ² , an apparent density of 0.748 g/cm ³ and a thickness of 1.66 mm was obtained. The difference in void ratio between the first surface layer and the middle layer of the second composite was 1.8%.

Then, the second composite was immersed in hot water of 95 ° C for 10 minutes by a squeeze treatment and a high-pressure water treatment, followed by water washing. Then, it was dried at 180 °C. Then, an intermediate of a hard sheet having a basis weight of 1212 g/m ² , an apparent density of 0.795 g/cm ³ and a thickness of 1.53 mm was obtained by hot press treatment under conditions of 100 kg/cm and 160 ° C.

A hard sheet having a basis weight of 994 g/m ² , an apparent density of 0.788 g/cm ³ and a thickness of 1.26 mm was processed by using #100 paper, each of which was 0.15 mm, and the double-sided surface layer of the intermediate of the hard sheet was ground. The JIS-D hardness of the hard sheet was 52, and the R% of the JIS-D hardness was 11.3%. Further, the amount of the sulfate ion and the ammonium ion of the ion having a pH change contained in the hard sheet was 26.9 μg/cm ³ .

The evaluation results are shown in Table 1.

[Embodiment 2]

The hard sheet was produced and evaluated in the same manner as in Example 1 except that the first composite before the second emulsion was applied by hot press treatment under the conditions of 100 kg/cm and 160 °C. Further, the obtained hard flakes had a basis weight of 996 g/m ² , an apparent density of 0.808 g/cm ³ and a thickness of 1.23 mm. The results are shown in Table 1.

[Example 3]

In the same manner as in Example 1, except that the degree of water washing of the second composite was lowered, the hard sheet was produced and evaluated. Further, the amount of sulfate ions and ammonium ions of the ions having a total pH change contained in the hard sheet was 300 μg/cm ³ . The results are shown in Table 1.

[Comparative Example 1]

In the first embodiment, the hardened sheet was produced and evaluated in the same manner as in Example 1 except that the second composite was immersed in hot water of 95 ° C for 10 minutes and then washed with water. The results are shown in Table 1.

[Comparative Example 2]

In the first embodiment, the first composite was further subjected to hot press treatment under the conditions of 100 kg/cm and 160 °C. Then, in the same manner as in Example 1, except that the second emulsion containing the gelling agent was impregnated, the hard sheet was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1. Further, the obtained hard flakes had a basis weight of 969 g/m ² , an apparent density of 0.817 g/cm ³ and a thickness of 1.19 mm. The results are shown in Table 1.

[Comparative Example 3]

In the same manner as in Example 1, except that the degree of washing of the second composite was lowered, the hard sheet was produced and evaluated. The amount of sulfate ions and ammonium ions of the ions having a total pH change contained in the hard sheet was 404 μg/cm ³ . The results are shown in Table 1.

[Comparative Example 4]

In the same manner as in Example 1, except that the degree of water washing of the second composite was lowered, the hard sheet was produced and evaluated. The amount of sulfate ions and ammonium ions of the ions having a total pH change contained in the hard sheet was 504 μg/cm ³ . The results are shown in Table 1.

From the results of Table 1, the examples 1 to 3 obtained by using the present invention having a JIS-D hardness of 45 or more, an R% of 0 to 20%, and a total ion content of 400 μg/cm ³ or less were used. In the polishing pad of the hard sheet, the polishing rate of the first surface layer of any of the examples, that is, the initial polishing rate was 120 nm/min, and the average polishing rate was maintained at 90% or more after 5 hours. On the other hand, the polishing rate of the first surface layer of the polishing pad of the hard sheet of Comparative Example 1 in which the gelling agent was blended in the second emulsion and not sufficiently washed with water was remarkably as low as 93 nm/min. Further, instead of mixing the gelling agent in the second emulsion, the polymer elastic body was uniformly filled, and the hard sheet of Comparative Example 2 was subjected to heat and pressure to homogenize the hard sheet. The polishing pad of Comparative Example 2 had a small total ion content, but the R% was 30.2% and was inhomogeneous. As a result, only an average of 89% of the initial polishing rate was maintained up to an average of 5 hours later. Further, the total content of ions of 404μg / cm ³ Comparative Example 3, and 504μg / cm ³ Comparative Example 4 In any one of the rear until the average of 5 hours are maintained only 84% of the initial polishing rate of about.

1‧‧‧nonwoven

1a‧‧‧Microfiber

1b‧‧‧Fiber bundle

2‧‧‧Polymer elastomer

3‧‧‧1st surface

4‧‧‧ Middle

5‧‧‧ second surface

10‧‧‧Hard flakes

Claims (16)

A hard sheet characterized by a non-woven fabric of ultrafine fibers having a fineness of 0.0001 to 0.5 dtex and a hard sheet of a polymeric elastomer imparted in the nonwoven fabric; a JIS-D hardness of 45 or more, a cross section in the thickness direction, from either side The first surface layer, the middle layer, and the second surface layer are sequentially arranged as the first surface layer, the middle layer, and the second surface layer, and the first surface layer and the middle layer are measured at a total of three points at an arbitrary point. The JIS-D hardness is 0 to 20 from the following formula: R (%) = (D hardness maximum - D hardness minimum value) / D hardness average value × 100 calculated from the D hardness of 6 points. %; and the total ion content of the pH of the water is changed to 400 μg/cm ³ or less. A hard sheet according to claim 1, wherein the total content of the ions is from 1 to 100 μg/cm ³ . A hard sheet according to claim 1, wherein the ultrafine fibers are long fibers and a fiber bundle has been formed. The hard sheet of claim 3, wherein the nonwoven fabric has an apparent density of from 0.35 to 0.90 g/cm ³ . The hard sheet of claim 3, wherein at least a portion of the ultrafine fibers forming the fiber bundle have been bundled by the polymeric elastomer in a cross section in the thickness direction. A hard sheet according to claim 5, wherein the fiber is in a section in the thickness direction At least a portion of the bundle is bonded to each other by the polymeric elastomer. The hard sheet according to claim 3, wherein the number of the microfibers forming the fiber bundle in the cross section in the thickness direction is bundled by the polymer elastomer. The hard sheet according to claim 7, wherein in the cross section in the thickness direction, more than half of the bundles of the fiber bundles are adhered to each other by the polymeric elastomer. The hard sheet of claim 1, wherein the polymeric elastomer is a non-porous polymeric elastomer. The hard sheet of claim 1, wherein the mass ratio of the nonwoven fabric to the polymeric elastomer (non-woven fabric/polymer elastomer) is from 90/10 to 55/45. A hard sheet according to claim 10, wherein the apparent density is from 0.50 to 1.2 g/cm ³ . The hard sheet according to claim 1, wherein the JIS-D hardness of the second surface layer is 45 or more, and the JIS-D hardness of the second surface layer and the middle layer is measured by a total of 6 points at arbitrary points and 6 points, respectively. A total of 6 points of D hardness is obtained from the following formula: R (%) = (D hardness maximum - D hardness minimum value) / D hardness average value × 100 calculated R% is 0 to 20%. A polishing pad characterized by comprising the hard sheet according to any one of claims 1 to 12 as an abrasive layer. A method for producing a hard sheet, characterized in that: (1) a non-woven fabric having an apparent density of 0.35 g/cm ³ or more of an ultrafine fiber having a fineness of 0.5 dtex or less can be formed by ultrafine fiberizing treatment, and an ultrafine fiber generating type is prepared. a step of winding a fiber of a long fiber of a fiber with a sheet; (2) impregnating the fiber-wound sheet with a gelling agent containing ions having a change in pH of water and a first emulsion containing a polymer elastomer; The first emulsion is gelled, and further heated and dried to solidify the polymeric elastomer; (3) the microfiber-forming fiber is treated by ultrafine fiberization to form the nonwoven fabric and the polymeric elastomer. (1) a second emulsion containing the gelling agent and the polymeric elastomer is impregnated into the first composite, and further dried by heating to solidify the polymeric elastomer. When each layer is equally divided into three in the thickness direction from the surface side of either side, the first surface layer, the middle layer, and the second surface layer are sequentially formed, and the difference in void ratio between the first surface layer and the intermediate layer is 5% or less. 2nd compound (5) a step of obtaining the hard sheet by washing the second composite so that the total content of the ions is 400 μg/cm ³ or less; and (6) in order to make the surface hardness of the hard sheet The JIS-D hardness is 45 or more, and the step of thermally pressurizing is selected from at least one of the first composite, the second composite, and the hard sheet. A method of producing a hard sheet according to claim 14, wherein the total content of the ions is from 1 to 100 μg/cm ³ . The method for producing a hard sheet according to claim 14, wherein the ultrafine fiber-forming fiber type contains a water-soluble thermoplastic polyvinyl alcohol-based resin as a sea component, and an island of a water-insoluble thermoplastic resin as an island component. The conjugate fiber of the type; the ultrafine fiberization treatment of the step (3) is a step of selectively removing the water-soluble thermoplastic polyvinyl alcohol-based resin by dissolving it in warm water.