JP4775898B2 - Laminated sheet - Google Patents

Description

  The present invention is a laminated sheet used for holding and fixing a surface of a lens, an optical material such as a reflection mirror, a semiconductor wafer such as a silicon wafer, a glass substrate, a metal substrate, and a disk, to a polishing head. The present invention relates to a laminated sheet (adhesive sheet) used for holding or protecting a product in a process of precisely processing a semiconductor product such as a (holding sheet, backing sheet) or a semiconductor wafer, or an optical system product, and a method for manufacturing the same.

  A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers have a highly accurate surface in each process of stacking and forming oxide layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI, and other manufacturing processes. It is required to finish flat. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a material to be polished such as a silicon wafer is fixed to a polishing head.

  Conventionally, as a method of fixing a material to be polished such as a silicon wafer or glass to a polishing head, (1) a wax mounting method in which the polishing head and the material to be polished are fixed via a wax, and (2) a method for fixing the material by suction. A vacuum chuck method in which the abrasive is fixed to the polishing head, or (3) a no-wax mounting method in which the material to be polished is fixed with artificial leather or a polymer foam sheet attached to the polishing head.

  Since the wax mounting method uses wax, it takes time to attach and detach the material to be polished, or it is necessary to clean the material after polishing to remove the wax, and the work process is complicated. have.

  The vacuum chuck method has a problem that the material to be polished is deformed at the suction port portion, and the surface accuracy of the material to be polished after polishing is thereby deteriorated.

  The no-wax mounting method has the advantage that the material to be polished is easy to attach and detach and has excellent production efficiency. However, if the surface accuracy of the holding surface of artificial leather or polymer foam sheet is poor, the coated material after polishing will be removed. There was a problem that the surface smoothness of the abrasive was also deteriorated.

  As a method for solving the problems of the no-wax mounting method, it has been proposed to use a backing material in which an adhesive resin layer made of a resin is provided on the surface of a foamed layer (Patent Document 1). In addition, a sheet-like elastic foam characterized in that closed cells having an elongated shape and a diameter increasing toward the surface of the foam layer is provided in the foam layer (Patent Document 2).

  However, the manufacturing method of the backing material of Patent Document 1 requires a separate adhesive resin layer, and the manufacturing process is complicated because the elastic layer is manufactured by wet coagulation. In addition, since a solvent must be used, there is a large environmental load, and there are manufacturing problems such that a large amount of water is required for solvent extraction.

  In Patent Document 2, it is difficult to form bubbles as described above, and since the porosity of the foam layer surface is large, the deformation of the foam layer becomes large. As a result, the surface smoothness of the polished material after polishing is increased. Is considered to be worse, and the stability of the polishing rate is reduced. In addition, air sticking occurs when the material to be polished is attached to the foamed layer, or water absorption of the slurry occurs between the foamed layer and the material to be polished due to low water absorption, reducing the adsorptivity of the material to be polished. There was a problem to do.

JP 2002-355754 A JP-A-6-23664

  An object of this invention is to provide the lamination sheet which is excellent in the adsorptivity of a to-be-polished material, and is excellent in durability.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the laminated sheet shown below, and have completed the present invention.

  The present invention provides a laminated sheet comprising a base sheet and a polyurethane foam layer, wherein the polyurethane foam layer has elliptical cells whose major axis is parallel to the thickness direction of the polyurethane foam layer, The present invention relates to a laminated sheet characterized in that the ratio (L / S) of the average major axis L to the average minor axis S (L / S) of the elliptical bubbles in the cut surface of the foam layer is 1.5-3.

  The present inventors have changed the bubbles in the polyurethane foam layer from conventional bubbles to elliptical bubbles (which are elliptical and spherical but may not be strictly balanced elliptical), and the elliptical By arranging the major axis of the bubbles in parallel (substantially parallel) to the thickness direction of the foam layer, it is possible to increase the elastic modulus compared to the conventional polyurethane foam layer and to suppress deformation of the foam layer. I found out that I can do it. Since the laminated sheet of the present invention has a high surface accuracy of the holding surface for holding the material to be polished, when the material to be polished is held using the laminated sheet, the surface smoothness of the material to be polished after polishing is excellent. It will be. In addition, since the laminated sheet of the present invention is excellent in durability, when the material to be polished is held using the laminated sheet, the stability of the polishing rate during polishing is improved.

  The air bubbles in the polyurethane foam layer may contain spherical air bubbles, but in order to sufficiently achieve the intended effect, the number ratio of the elliptical air bubbles is preferably 30% or more of the total air bubbles.

  The elliptical bubble is preferably an open cell. When the elliptical bubble is an open cell, the air can be discharged to the outside via the open cell even if the air is bitten when the material to be polished is attached to the polyurethane foam layer. Thereby, the material to be polished can be attached to the polyurethane foam layer with high flatness. In addition, even when the slurry enters between the foam layer and the material to be polished, the slurry can be absorbed into the polyurethane foam layer through the open cells, so the water film of the slurry between the foam layer and the material to be polished. Can be prevented. Therefore, it is possible to effectively prevent a decrease in the adsorptivity of the material to be polished.

  The laminated sheet of the present invention includes a base sheet and a polyurethane foam layer.

  Polyurethane resin is preferable as a material for forming a foamed layer of a laminated sheet because fine elliptical bubbles can be easily formed by a mechanical foaming method. The polyurethane resin is composed of an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modified MDI (for example, commercial products) Name Millionate MTL, manufactured by Nippon Polyurethane Industry), 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate and other aromatic diisocyanates, ethylene diisocyanate, 2,2 1,4-trimethylhexamethylene diisocyanate, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, 1,4-cyclohexane San diisocyanate, cyclohexane diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, isophorone diisocyanate, and cycloaliphatic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.).

  Of the above isocyanate components, 4,4'-diphenylmethane diisocyanate or carbodiimide-modified MDI is preferably used.

  Examples of the high molecular weight polyol include those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate And polymer polyol which is a polyether polyol in which polymer particles are dispersed.These may be used alone or in combination of two or more.

  Among the high molecular weight polyols, it is preferable to use a high molecular weight polyol having 2 to 4 functional groups and a hydroxyl value of 20 to 100 mgKOH / g. The hydroxyl value is more preferably 25 to 60 mgKOH / g. When the number of functional groups is 5 or more, the cross-linking degree of the polyurethane foam becomes too high, and the adsorptivity of the material to be polished tends to decrease. When the hydroxyl value is less than 20 mgKOH / g, the amount of polyurethane hard segments tends to decrease and the durability tends to decrease. When the hydroxyl value exceeds 100 mgKOH / g, the degree of crosslinking of the polyurethane foam becomes too high. There exists a tendency for the adsorptivity of a to-be-polished material to fall.

  When the polyurethane foam layer has an open-cell structure, it is preferable to use a polymer polyol, and it is particularly preferable to use a polymer polyol in which polymer particles made of acrylonitrile and / or styrene-acrylonitrile copolymer are dispersed. The polymer polyol is preferably contained in the total high molecular weight polyol to be used in an amount of 20 to 100% by weight, more preferably 30 to 60% by weight. By using a specific amount of the polymer polyol, the cell membrane is easily broken, and an open cell structure is easily formed.

  When the polyurethane foam layer has an open cell structure, these specific high molecular weight polyols are preferably contained in an active hydrogen-containing compound (polyol component and chain extender) in an amount of 60 to 85% by weight, more preferably. Is 70 to 80% by weight. By using a specific amount of the specific high molecular weight polyol, the cell membrane is easily broken, and the intended open cell is easily formed.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 1500 to 6000 from the viewpoint of the elastic properties of the resulting polyurethane. If the number average molecular weight is less than 1500, polyurethane using the same does not have sufficient elastic properties and tends to be a brittle polymer. For this reason, the foamed layer made of polyurethane is too hard, and the retention of the wafer and glass tends to deteriorate. On the other hand, when the number average molecular weight exceeds 6000, a polyurethane resin using the number average molecular weight becomes too soft, and the foamed layer made of this polyurethane tends to have poor durability.

  Along with a high molecular weight polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3- Low molecular weight polyols such as methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, and 1,4-bis (2-hydroxyethoxy) benzene may be used. Moreover, you may use together low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine. Moreover, you may use together the polyol which added alkylene oxides, such as ethylene oxide and a propylene oxide, to the said low molecular weight polyol or low molecular weight polyamine.

  When the polyurethane foam layer has an open cell structure, it is preferable to use a low molecular weight polyol having a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g. The hydroxyl value is more preferably 700 to 1250 mgKOH / g, and the amine value is more preferably 400 to 950 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, the distance between the hard segments of the polyurethane is shortened, and the effect of improving the adsorptivity of the polishing material cannot be sufficiently obtained. There is a tendency. In particular, it is preferable to use diethylene glycol, triethylene glycol, or 1,4-butanediol.

  Moreover, it is preferable to make these low molecular weight polyol and / or low molecular weight polyamine contain 2 to 15 weight% in an active hydrogen containing compound, More preferably, it is 5 to 10 weight%. By using a specific amount of the low molecular weight polyol and / or the low molecular weight polyamine, the cell membrane is easily broken and not only the target open cell is easily formed, but also the mechanical properties of the polyurethane foam layer are improved.

  When the polyurethane resin is produced by the prepolymer method, a chain extender is used for curing the isocyanate-terminated prepolymer. The chain extender is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Diphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xyl And polyamines exemplified by N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the above-mentioned low molecular weight polyols and low molecular weight polyamines. be able to. These may be used alone or in combination of two or more.

  The ratio of the isocyanate component, the polyol, and the chain extender can be variously changed depending on the molecular weight of each, the desired physical properties of the polyurethane foam layer, and the like. In order to obtain a foamed layer having desired characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the polyol and the chain extender is preferably 0.80 to 1.20. More preferably, it is 0.99 to 1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity, hardness, compression ratio, etc. tend not to be obtained.

  The polyurethane resin can be produced by applying a known urethanization technique such as a melting method or a solution method, but it is preferably produced by a melting method in consideration of cost, working environment, and the like.

  The polyurethane resin can be produced by either the prepolymer method or the one-shot method.

  In the production of the polyurethane resin, a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound are mixed and cured. In the prepolymer method, the isocyanate-terminated prepolymer becomes an isocyanate group-containing compound, and the chain extender becomes an active hydrogen group-containing compound. In the one-shot method, the isocyanate component becomes an isocyanate group-containing compound, and the chain extender and the polyol component become active hydrogen group-containing compounds.

  The polyurethane resin foam which is a material for forming the polyurethane foam layer of the present invention can be produced by a mechanical foaming method, a chemical foaming method or the like. In addition, you may use together the method of adding a hollow bead as needed.

  In particular, a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether is preferable. Examples of suitable silicon surfactants include SH-192, SH-193, and L5340 (manufactured by Toray Dow Corning Silicone).

  In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.

  An example of a method for producing a polyurethane foam layer having elliptical cells according to the present invention will be described below. The manufacturing method of this polyurethane foam layer has the following processes.

1) Foaming step and mixing step for producing a cell-dispersed urethane composition Case A. The first component obtained by adding a silicon-based surfactant to an isocyanate-terminated prepolymer obtained by reacting an isocyanate component and a high-molecular-weight polyol is mechanically stirred in the presence of a non-reactive gas so that the non-reactive gas becomes fine bubbles. Disperse into a bubble dispersion. Then, a second component containing an active hydrogen-containing compound such as a high molecular weight polyol or a low molecular weight polyol is added to the cell dispersion and mixed to prepare a cell dispersed urethane composition. A filler such as a catalyst and carbon black may be appropriately added to the second component.
Case B. A silicon-based surfactant is added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen-containing compound, and the component added with the silicon-based surfactant is not reacted. Mechanically stirred in the presence of reactive gas to disperse the non-reactive gas as fine bubbles to obtain a bubble dispersion. Then, the remaining components are added to the cell dispersion and mixed to prepare a cell-dispersed urethane composition.
Case C. A silicon-based surfactant is added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen-containing compound, and the first component and the second component are made non-reactive. Mechanically stirring in the presence of gas to disperse non-reactive gas as fine bubbles to prepare a cell-dispersed urethane composition.

2) Casting process After the above-mentioned cell-dispersed urethane composition is poured into a mold, the mold is clamped.

3) Curing step The inside of the mold is compressed or decompressed while heating and reaction-curing the cell-dispersed urethane composition poured into the mold, and the state is maintained until it does not flow.

  As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. In view of cost, it is most preferable to use air that has been dried to remove moisture.

  As a stirrer for dispersing the non-reactive gas in the form of fine bubbles and the first component containing the silicon-based surfactant, a known stirrer can be used without particular limitation. Specifically, a homogenizer, a dissolver, A two-axis planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a cell dispersion in a foaming process, and the stirring which adds and mixes the active hydrogen containing compound in a subsequent mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

  As described above, in order to produce a polyurethane resin foam containing elliptical cells, it is necessary to perform an operation different from the conventional mechanical foaming method in the casting process and the curing process. Specifically, the following operations are performed.

1) Case 1
In the casting step, after the amount of the cell-dispersed urethane composition is poured into a movable mold whose one side surface or the opposite side surface is about 50% by volume, the upper surface of the mold is covered with a top cover and the mold is clamped. The upper lid of the mold is preferably provided with a vent hole for discharging excess cell-dispersed urethane composition when the mold is compressed. Thereafter, in the curing step, while the cell-dispersed urethane composition is heated and reacted and cured, the side surface of the mold is moved to compress the mold, and the state is maintained until it does not flow. The degree of compression is preferably 50 to 95% of the original width, and more preferably 80 to 90%. Moreover, it is preferable to compress so that the excess cell-dispersed urethane composition is sufficiently discharged from the vent hole. In this case, the major axis of the elliptical bubble is substantially perpendicular to the moving direction of the mold side surface.

2) Case 2
In the casting step, an amount of about 50% by volume of the cell-dispersed urethane composition is poured into the mold, and then the upper surface of the mold is covered and the mold is clamped. Preferably, at least one side surface of the mold is provided with a vent hole for discharging excess cell-dispersed urethane composition when the mold is compressed. Thereafter, in the curing step, while the cell-dispersed urethane composition is heated and reactively cured, the upper lid and / or the lower surface of the mold is moved to compress the mold, and the state is maintained until it no longer flows. The degree of compression is preferably 50 to 98% of the original height, and more preferably 85 to 95%. Moreover, it is preferable to compress so that the excess cell-dispersed urethane composition is sufficiently discharged from the vent hole. In this case, the major axis of the elliptical bubble is substantially perpendicular to the moving direction of the upper lid or lower surface of the mold.

3) Case 3
In the casting step, after pouring an amount of the bubble-dispersed urethane composition into the mold so as to leave a space, an upper lid is placed on the upper surface of the mold and the mold is clamped. The upper lid is provided with a hole for decompressing the inside of the mold. Thereafter, in the curing step, while the cell-dispersed urethane composition is heated and reacted and cured, the inside of the mold is decompressed and kept in a decompressed state until it no longer flows. The degree of decompression is preferably 90 to 30 kPa, and more preferably 90 to 70 kPa. In this case, the major axis of the elliptical bubble is substantially perpendicular to the height direction of the mold.

  In the method for producing a polyurethane resin foam, heating and post-curing the foam block that has reacted until it no longer flows is effective in improving the physical properties of the foam, which is extremely suitable.

  In the polyurethane resin foam, a known catalyst that promotes a polyurethane reaction such as tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  Thereafter, the obtained polyurethane resin foam block is sliced using a bowl-like or band saw-like slicer to produce a polyurethane foam layer. In that case, it slices so that the long axis of an elliptical bubble may become parallel with the thickness direction of a foaming layer.

  The polyurethane foam layer obtained by the above production method has elliptical cells whose major axis is parallel to the thickness direction of the polyurethane foam layer, and the average major axis L of the elliptical cells at the cut surface of the foamed layer. And the ratio of the average minor axis S (L / S) is 1.5 to 3, preferably 1.5 to 2. When L / S is less than 1.5, the foamed layer cannot have a high elastic modulus, and therefore deformation of the foamed layer cannot be effectively suppressed. As a result, the surface accuracy of the holding surface for holding the material to be polished is deteriorated, and when the material to be polished is held using the laminated sheet, the surface smoothness of the material to be polished after polishing is lowered. Moreover, since the durability of the laminated sheet is also reduced, when the material to be polished is held using the laminated sheet, the stability of the polishing rate during polishing is lowered. On the other hand, when L / S exceeds 3, the slurry easily penetrates into the foamed layer, whereby the foamed layer swells and the polishing rate becomes unstable.

  The average major axis of the elliptical bubbles is preferably 50 to 150 μm, and the average minor axis is preferably 10 to 100 μm. When deviating from this range, the stability of the polishing rate tends to deteriorate.

  In addition, the bubbles in the polyurethane foam layer may contain spherical bubbles, but in order to sufficiently achieve the intended effect, the number ratio of elliptical bubbles is preferably 30% or more of the total bubbles, More preferably, it is 40% or more. The number ratio of the elliptical bubbles can be adjusted to a target range by adjusting the degree of compression of the mold or the pressure reduction inside the mold.

  The thickness of the polyurethane foam layer is not particularly limited, but is preferably 0.2 to 1.2 mm, and more preferably 0.6 to 1 mm.

  The specific gravity of the polyurethane foam layer is preferably 0.2 to 0.5, more preferably 0.25 to 0.4. When the specific gravity is less than 0.2, the bubble rate becomes too high and the durability tends to deteriorate. On the other hand, when the specific gravity exceeds 0.5, it is necessary to make the material have a low crosslinking density in order to obtain a certain elastic modulus. In that case, permanent set increases and durability tends to deteriorate.

  The hardness of the polyurethane foam layer is preferably 10 to 50 degrees in terms of Asker C hardness, more preferably 15 to 35 degrees. When the Asker C hardness is less than 10 degrees, the durability tends to decrease or the surface smoothness of the polished material after polishing tends to deteriorate. On the other hand, when it exceeds 50 degrees, the retainability of the material to be polished tends to deteriorate.

  The compression ratio of the polyurethane foam layer is preferably 2 to 10%, more preferably 4 to 8%. When the compression rate is less than 2%, the retention of the material to be polished is deteriorated, and when the compression rate exceeds 10%, the durability and the surface smoothness of the material to be polished after polishing tend to be deteriorated. is there.

  The thickness variation of the polyurethane foam layer is preferably 100 μm or less, more preferably 60 μm or less. When the thickness variation exceeds 100 μm, the laminated sheet has large undulations. As a result, the surface smoothness of the polished material after polishing tends to deteriorate. As a method for suppressing the thickness variation of the foam layer, a method of buffing the surface of the foam layer sliced to a predetermined thickness can be mentioned. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  The material for forming the base sheet is not particularly limited, and examples thereof include fluorine-containing resins such as polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, and polyfluoroethylene, nylon, and cellulose. Can do.

  The thickness of the base sheet is not particularly limited, but is preferably about 0.05 to 0.3 mm from the viewpoints of strength, flexibility and the like.

  The laminated sheet of the present invention can be produced by bonding the base sheet and the polyurethane foam layer.

  Examples of means for bonding the base sheet and the polyurethane foam layer include a method of bonding via an adhesive, a method of pressing the base sheet and the polyurethane foam layer with a double-sided tape, and the like. The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives.

  A double-sided tape for attaching to the polishing head may be provided on the surface of the base sheet of the laminated sheet.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

(Measurement of average major axis and average minor axis of elliptical bubbles, ratio of elliptical bubbles)
A sample for measurement was obtained by cutting the produced polyurethane resin foam sheet in the thickness direction with a microtome cutter. The cut surface of the measurement sample was photographed at 100 times with a scanning electron microscope (S-3500N, manufactured by Hitachi Science Systems, Ltd.). And the major axis and minor axis of all elliptical bubbles in an arbitrary range are measured using image analysis software (manufactured by MITANI Corporation, WIN-ROOF), and the average major axis L, average minor axis S, and L / S was calculated. In addition, the number ratio (%) of elliptical bubbles to all bubbles was calculated.

(Measurement of open cell ratio)
The open cell ratio was measured according to the ASTM-2856-94-C method. However, 10 sheets of polyurethane resin foam sheets punched out in a circular shape were used as measurement samples. As a measuring instrument, an air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.) was used. The open cell ratio was calculated by the following formula.
Open cell ratio (%) = [(V−V1) / V] × 100
V: Apparent volume calculated from sample size (cm ³ )
V1: Sample volume (cm ³ ) measured using an air-comparing hydrometer

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. The produced polyurethane resin foam sheet was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used as a sample, which was allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. . The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Hardness measurement)
This was performed according to JIS K-7312. The produced polyurethane resin foam sheet was cut into a size of 5 cm × 5 cm (thickness: arbitrary) and used as a sample and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. At the time of measurement, the samples were overlapped to have a thickness of 10 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker C-type hardness meter, pressure surface height: 3 mm), the hardness 30 seconds after contacting the pressure surface was measured.

(Compression rate measurement)
A polyurethane resin foam sheet cut into a circle (thickness: arbitrary) having a diameter of 7 mm was used as a sample, and allowed to stand for 40 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. For the measurement, a compression ratio was measured using a thermal analysis measuring instrument TMA (manufactured by SEIKO INSTRUMENTS, SS6000). The calculation formula of the compression rate is shown below.
Compression rate (%) = {(T1-T2) / T1} × 100
T1: Thickness of the sample when a stress of 4.9 kPa (50 g / cm ² ) is applied to the sample from an unloaded state and held for 60 seconds.
T2: The thickness of the sample when a stress of 29.4 kPa (300 g / cm ² ) is applied from the state of T1 and held for 60 seconds.

(Evaluation of adsorptivity)
A glass plate having a smooth surface (50 mmφ × 10 mm thickness) is suspended by a load sensor through a universal joint and is applied at a pressure of 150 g / cm ² on a laminated sheet (□ 80 mm) affixed to a support plate. Adsorbed for 2 seconds. Thereafter, the glass plate was pulled upward at a constant speed (tensile speed: 200 mm / min), and the peel strength (kPa) when the glass plate peeled from the laminated sheet was measured.

(Evaluation of polishing rate stability)
SPP600S (Okamoto Machine Tool Co., Ltd.) was used as a polishing device. The glass plate was bonded to the produced laminated sheet, and the polishing rate stability was evaluated. The polishing conditions are as follows.
Glass plate: 6 inches φ, thickness 1.1 mm (optical glass, BK7)
Slurry: Ceria slurry (CeO ₂ , 5 wt%)
Slurry amount: 250 ml / min
Polishing pad: MH C14B (made by Nitta Haas)
Polishing pressure: 20kPa
Polishing platen rotation speed: 45rpm
Glass plate rotation speed: 40rpm
Polishing time: 10 min / number of polished glass plates: 500 First, an average polishing rate (Å / min) for each polished glass plate is calculated. The calculation method is as follows.
Average polishing rate = [weight change amount of glass plate before and after polishing [g] / (glass plate density [g / cm ³ ] × polishing area of glass plate [cm ² ] × polishing time [min])] × 10 ⁸
The polishing rate stability (%) is the maximum average polishing rate, the minimum average polishing rate, and the total average polishing rate (from the first sheet) from the first glass plate to the number of processed sheets (100 sheets, 300 sheets, or 500 sheets). An average value of each average polishing rate up to the number of processed sheets) is calculated and the value is substituted into the following equation. As the polishing rate stability (%) is lower, the polishing rate is less likely to change even when a large number of glass plates are polished. In the present invention, the polishing rate stability after processing 500 sheets is preferably within 10%.
Polishing rate stability (%) = {(maximum average polishing rate−minimum average polishing rate) / total average polishing rate} × 100

Example 1
High-molecular-weight polyol EX-5030 (Asahi Glass Co., Ltd., OHV: 33, functional group number: 3) 60 parts by weight, polycaprolactone triol (manufactured by Daicel Chemical Industries, Plaxel 305, OHV: 305, functional group number: 3) 40 parts by weight, 5 parts by weight of a silicon-based surfactant (SH-192, manufactured by Toray Dow Corning Silicone) and 0.18 parts by weight of a catalyst (No. 25, manufactured by Kao) are added and mixed to obtain a second. Ingredients (25 ° C.) were prepared. And it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, 40.3 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the second component (NCO / OH = 1) 0.1) Stirred for about 1 minute to prepare a cell dispersed urethane composition.

  The cell-dispersed urethane composition was poured into a mold (width 800 mm, height 1300 mm, height 35 mm) until the liquid level was 31 mm (88 vol%). Thereafter, the upper surface of the mold was covered with an upper cover provided with 3 mm vent holes at intervals of 3 mm, and the mold was clamped. Thereafter, while the composition was heated at 70 ° C. for reaction curing, the side surface of the mold was moved to compress the width of the mold from 800 mm to 700 mm, and this state was maintained until the mixed liquid stopped flowing. In addition, the excess composition was discharged | emitted from the vent hole. Then, post cure was performed at 70 ° C. for 1 hour to obtain a polyurethane resin foam block.

  The polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) so that the major axis of the elliptical cell was parallel to the thickness direction, to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 0.8 mm to adjust the thickness accuracy. The buffed sheet was punched out with a diameter of 17 cm to obtain a polyurethane foam layer. Then, the polyurethane foam layer and the base material sheet (polyethylene terephthalate, thickness: 0.2 mm) were bonded together using a double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape). Thereafter, a template was attached to the buff surface of the polyurethane foam layer, and a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was attached to the surface of the base sheet using a laminator to prepare a laminated sheet.

Example 2
Polymer polyol EX-940 (manufactured by Asahi Glass Co., Ltd., OHV: 28, converted to functional group number: 3) 45 parts by weight, polytetramethylene ether glycol (Mitsubishi Chemical Co., Ltd.) in which polymer particles made of styrene-acrylonitrile copolymer are dispersed in a container PTMG2000, OHV: 56, functional group number: 2 35 parts by weight, Plaxel 305 (10 parts by weight), diethylene glycol (10 parts by weight), SH-192 (5 parts by weight), and catalyst (No. 25) ) 0.25 part by weight was added and mixed to prepare the second component (25 ° C.). And it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, Millionate MTL (39 parts by weight, 25 ° C.) as the first component was added to the second component (NCO / OH = 1.1) and stirred for about 1 minute to prepare a cell dispersed urethane composition. Thereafter, a laminated sheet was produced in the same manner as in Example 1.

Example 3
A cell-dispersed urethane composition was prepared in the same manner as in Example 1. The cell-dispersed urethane composition was poured into a mold (width 800 mm, height 1300 mm, height 35 mm) until the liquid level was 31 mm (88 vol%). Thereafter, the upper surface of the mold was covered with an upper cover provided with 3 mm vent holes at intervals of 3 mm, and the mold was clamped. Thereafter, the mold was placed in a vacuum oven, and the composition was heated at 70 ° C. while being reaction-cured, the pressure was reduced to 80 kPa, and the state was maintained until the mixed liquid stopped flowing. In addition, the excess composition was discharged | emitted from the vent hole. Then, post cure was performed at 70 ° C. for 1 hour to obtain a polyurethane resin foam block. Thereafter, a laminated sheet was produced in the same manner as in Example 1.

Example 4
In a container, put EX-5030 (90 parts by weight), Plaxel 305 (8 parts by weight), diethylene glycol (2 parts by weight), SH-192 (5 parts by weight), and catalyst (No. 25) 0.36 parts by weight, A second component (25 ° C.) was prepared by mixing. And it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, Millionate MTL (21 parts by weight, 25 ° C.) as the first component was added to the second component (NCO / OH = 1.1) and stirred for about 1 minute to prepare a cell-dispersed urethane composition. Thereafter, a laminated sheet was produced in the same manner as in Example 1.

Comparative Example 1
A cell-dispersed urethane composition was prepared in the same manner as in Example 1. The cell-dispersed urethane composition was poured into a mold (width 800 mm, height 1300 mm, height 35 mm). Thereafter, the composition was heated at 70 ° C. for reaction curing. Then, post cure was performed at 70 ° C. for 1 hour to obtain a polyurethane resin foam block. Thereafter, a laminated sheet was produced in the same manner as in Example 1.

Comparative Example 2
A polyurethane resin foam block was obtained in the same manner as in Example 1. The polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) so that the major axis of the elliptical cell was perpendicular to the thickness direction to obtain a polyurethane resin foam sheet. Thereafter, a laminated sheet was produced in the same manner as in Example 1.

  As is clear from Table 1, it can be seen that the laminated sheet of the present invention is excellent in the stability of the polishing rate for a long time because it is excellent in the adsorptivity of the material to be polished and in the durability.

Claims (2)

In a laminated sheet comprising a base sheet and a polyurethane foam layer,
The polyurethane foam layer has elliptical bubbles whose major axis is parallel to the thickness direction of the polyurethane foam layer,
The elliptical bubble is an open cell,
A laminated sheet for holding an abrasive , wherein a ratio (L / S) of an average major axis L and an average minor axis S of elliptical bubbles in a cut surface of the polyurethane foam layer is 1.5 to 3. The laminated sheet according to claim 1, wherein the number ratio of the elliptical bubbles is 30% or more of the total bubbles.