JP4775897B2 - LAMINATED SHEET MANUFACTURING METHOD AND 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. Further, in Patent Document 2, it is difficult to form bubbles as described above, and since the porosity of the foam layer surface is large, deformation of the foam layer increases, and as a result, the surface of the material to be polished after polishing is obtained. It is thought that the smoothness becomes worse.

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

  An object of this invention is to provide the method of manufacturing a lamination sheet with the high surface precision of a holding surface very easily. Moreover, it aims at providing the lamination sheet obtained by this manufacturing method.

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

  That is, the present invention includes a step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a base sheet, and a foamed polyurethane layer by curing the cell-dispersed urethane composition. It is related with the manufacturing method of the lamination sheet including the process and the process of adjusting the thickness of a polyurethane foam layer uniformly.

  Another aspect of the present invention is a step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a base sheet, and a release sheet laminated on the cell-dispersed urethane composition. The present invention relates to a method for producing a laminated sheet, comprising a step, a step of curing a cell-dispersed urethane composition with a uniform thickness by a pressing means to form a polyurethane foam layer, and a step of peeling a release sheet on the polyurethane foam layer. .

  As described above, a gas such as air is dispersed as fine bubbles in a raw material by a mechanical foaming method to prepare a cell-dispersed urethane composition, and the cell diameter is extremely small by curing the cell-dispersed urethane composition, and A polyurethane foam layer having spherical (including substantially spherical) cells can be formed very easily. Further, in the mechanical foaming method of the present invention, since gas such as air is dispersed without being dissolved in the raw material, new bubbles are generated after the step of uniformly adjusting the thickness of the polyurethane foam layer ( There is an advantage that the post-foaming phenomenon) can be suppressed and the thickness accuracy and specific gravity can be easily controlled. Moreover, since it is not necessary to use a solvent, it is not only excellent in cost but also preferable from the environmental viewpoint. And since this polyurethane foam layer has extremely high surface accuracy of the holding surface for holding the material to be polished, when the material to be polished is held using a laminated sheet having the foam layer, the material to be polished after polishing is used. The surface smoothness is extremely excellent. Moreover, since the said polyurethane foam layer has a spherical cell, it is excellent in durability. Therefore, when the material to be polished is polished using the laminated sheet having the foam layer, the stability of the polishing rate is improved.

  The laminated sheet of the present invention is obtained by the production method.

  The polyurethane foam layer preferably has spherical fine bubbles having an average cell diameter of 20 to 300 μm.

  The polyurethane foam layer preferably has an average cell diameter difference in the thickness direction (average cell diameter maximum value−average cell diameter minimum value) of 50 μm or less. When the variation in the cell diameter is large in the thickness direction of the polyurethane foam layer, the durability of the region having a low resin density is inferior to that of the other regions, so that a thickness change (sagging phenomenon) is likely to occur in that portion. As a result, the surface accuracy of the holding surface for holding the material to be polished tends to decrease, and the surface smoothness of the material to be polished after polishing tends to decrease. Further, the stability of the polishing rate tends to deteriorate. If the average bubble diameter difference in the thickness direction is 50 μm or less, the thickness change of the polyurethane foam layer can be effectively suppressed.

  The specific gravity of the polyurethane foam layer is preferably 0.2 to 0.5. The Asker C hardness of the polyurethane foam layer is preferably 10 to 50 degrees. Furthermore, the compression ratio of the polyurethane foam layer is preferably 2 to 10%.

  The method for producing a laminated sheet of the present invention includes a step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a base sheet, and a polyurethane foam by curing the cell-dispersed urethane composition. Forming the layer and uniformly adjusting the thickness of the polyurethane foam layer.

  Another method for producing a laminated sheet of the present invention includes a step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a substrate sheet, and a mold release on the cell-dispersed urethane composition. A step of laminating sheets, a step of curing the cell-dispersed urethane composition with a uniform thickness by a pressing means to form a polyurethane foam layer, and a step of peeling the release sheet on the polyurethane foam layer.

  The cell-dispersed urethane composition may be prepared by a mechanical foaming method (including a mechanical floss method), and the others are not particularly limited. For example, the cell-dispersed urethane composition is prepared by the following method.

  (1) The first component obtained by adding a silicon 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, and the non-reactive gas is removed. Disperse as fine bubbles to obtain a cell 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.

  (2) A component in which a silicon-based surfactant is added to at least one of a first component containing an isocyanate component (or an isocyanate-terminated prepolymer) and a second component containing an active hydrogen-containing compound, and a silicon-based surfactant is added Is mechanically stirred in the presence of a non-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.

  (3) 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 added. A foam-dispersed urethane composition is prepared by mechanically stirring in the presence of a non-reactive gas and dispersing the non-reactive gas as fine bubbles.

  Polyurethane is preferable as a material for forming the foamed layer of the laminated sheet because spherical fine bubbles can be easily formed by a mechanical foaming method.

  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. When the polyurethane foam layer has a closed cell structure, it is preferable to use only polyether polyol.

  On the other hand, 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 a 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. The polymer polyol is preferably contained in the active hydrogen-containing compound in an amount of 60 to 85% by weight, more preferably 70 to 80% 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.

  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.

  The ratio between the high molecular weight polyol and the low molecular weight polyol is determined by the properties required for the polyurethane foam layer produced therefrom.

  When the polyurethane foam layer has an open-cell structure, the low molecular weight polyol and / or the low molecular weight polyamine is preferably contained in the active hydrogen-containing compound in an amount of 2 to 15% by weight, more preferably 5 to 10% by weight. It is. 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 is easy to form open cells, but also the mechanical properties of the polyurethane foam layer are improved.

  In the case of producing polyurethane by a 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.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 800 to 5000 are preferable because of excellent processability and physical characteristics. Further, when the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.

  Examples of the silicon-based surfactant include those containing a copolymer of polyalkylsiloxane and polyether. Examples of suitable silicon surfactants include SH-192 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.

  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 the stirring device for dispersing the non-reactive gas in the form of fine bubbles, a known stirring device can be used without any particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), a mechanical A floss foaming machine etc. are illustrated. 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 order to obtain the target polyurethane foam layer, the rotational speed of the stirring blade is preferably 500 to 2000 rpm, more preferably 800 to 1500 rpm. The stirring time is appropriately adjusted according to the target density.

  In addition, it is also a preferable aspect that stirring for preparing the cell dispersion in the foaming step and stirring for mixing the first component and the second component use different stirring devices. The agitation in the mixing step may not be agitation that forms bubbles, and it is preferable to use an agitation 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 for preparing the bubble dispersion and the mixing step for mixing each component, and the stirring conditions such as adjusting the rotation speed of the stirring blades are adjusted as necessary. It is also suitable to use after adjustment.

  And the cell dispersion | distribution urethane composition prepared by the said method is apply | coated on a base material sheet, this cell dispersion | distribution urethane composition is hardened, and a polyurethane foam layer is formed.

  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.

  As a method for applying the cell-dispersed urethane composition onto the base sheet, for example, a roll coater such as gravure, kiss, or comma, a die coater such as slot or phanten, a squeeze coater, or a curtain coater is adopted. Any method may be used as long as a uniform coating film can be formed on the base sheet.

  Heating and post-curing the polyurethane foam that has reacted until the cell-dispersed urethane composition is applied to the base sheet and no longer flows is effective in improving the physical properties of the polyurethane foam. is there. Post-cure is preferably performed at 40 to 70 ° C. for 10 to 60 minutes, and it is preferable to perform at normal pressure because the bubble shape becomes stable.

  In the production of the polyurethane foam layer, a known catalyst that promotes a polyurethane reaction, such as a tertiary amine, may be used. The kind and addition amount of the catalyst are selected in consideration of the flow time for application on the base sheet after the mixing step of each component.

  The polyurethane foam layer may be produced by a batch method in which each component is weighed and put into a container and mechanically stirred. In addition, each component and a non-reactive gas are continuously supplied to a stirrer and mechanically stirred. Further, a continuous production method in which a cell-dispersed urethane composition is sent out to produce a molded product may be used.

  In the method for producing a laminated sheet of the present invention, it is necessary to uniformly adjust the thickness of the polyurethane foam layer after forming the polyurethane foam layer on the base sheet or simultaneously with forming the polyurethane foam layer. . A method for uniformly adjusting the thickness of the polyurethane foam layer is not particularly limited, and examples thereof include a method of buffing with an abrasive and a method of pressing with a press plate. When buffing is performed, a laminated sheet having no skin layer on the surface of the polyurethane foam layer is obtained, and when pressed, a laminated sheet having a skin layer on the surface of the polyurethane foam layer is obtained. The conditions for pressing are not particularly limited, but it is preferable to adjust the temperature above the glass transition point.

  On the other hand, the cell-dispersed urethane composition prepared by the above method is applied onto a substrate sheet, and a release sheet is laminated on the cell-dispersed urethane composition. Thereafter, the foam-dispersed urethane composition may be cured by making the thickness uniform with a pressing means to form a polyurethane foam layer. This method is a particularly preferable method because the thickness of the laminated sheet can be controlled extremely uniformly.

  The material for forming the release sheet is not particularly limited, and examples thereof include the same resin and paper as those for the base sheet. The release sheet preferably has a small dimensional change due to heat. The surface of the release sheet may be subjected to a release treatment.

  The pressing means for making the thickness of the sandwich sheet composed of the base material sheet, the cell-dispersed urethane composition (cell-dispersed urethane layer), and the release sheet is not particularly limited. For example, the thickness may be constant by a coater roll, a nip roll, or the like. The method of compressing is mentioned. In consideration of the fact that the bubbles in the foamed layer become about 1.2 to 2 times larger after compression, during the compression, (coater or nip clearance)-(base sheet and release sheet thickness) = (after curing) The thickness of the polyurethane foam layer is preferably 50 to 85%. In order to obtain a polyurethane foam layer having a specific gravity of 0.2 to 0.5, the specific gravity of the cell-dispersed urethane composition before passing through the roll is preferably 0.24 to 1.

  Then, after the thickness of the sandwich sheet is made uniform, the reacted polyurethane foam is heated until it does not flow, and post-cured to form a polyurethane foam layer. Post cure conditions are the same as described above.

  Thereafter, the release sheet on the polyurethane foam layer is peeled off to obtain a laminated sheet. In this case, a skin layer is formed on the polyurethane foam layer. Note that the skin layer may be removed by buffing the polyurethane foam layer after the release sheet is peeled off.

  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 air bubbles in the polyurethane foam layer may be closed cells or open cells.

  The average cell diameter of the bubbles in the polyurethane foam layer is preferably 20 to 300 μm, more preferably 50 to 150 μm. When deviating from this range, the surface smoothness of the polished material after polishing tends to deteriorate.

  The polyurethane foam layer preferably has an average cell diameter difference in the thickness direction (average cell diameter maximum value−average cell diameter minimum value) of 50 μm or less, more preferably 30 μm or less. The calculation method of the average bubble diameter difference is described in detail in the examples.

  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.

  The laminated sheet having a skin layer on the polyurethane foam layer of the present invention has a high surface accuracy of the holding surface, and the skin layer itself has adhesiveness so that the material to be polished can be sufficiently retained. May be.

  On the other hand, the laminated sheet having no skin layer on the polyurethane foam layer of the present invention has a high surface accuracy of the holding surface and can sufficiently hold the material to be polished by moistening the holding surface with water or the like. An adhesive layer may be provided.

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

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

[Measurement and evaluation methods]
(Measurement of average bubble diameter)
A sample obtained by cutting the produced polyurethane foam layer in parallel with a razor blade as thin as possible to a thickness of 1 mm or less was used as a sample. The sample was fixed on a glass slide and observed at 100 times using SEM (S-3500N, Hitachi Science Systems, Ltd.). Using the image analysis software (WinRoof, Mitani Shoji Co., Ltd.) for the obtained image, the total bubble diameter in an arbitrary range was measured, and the average bubble diameter was calculated.

(Measurement of average bubble diameter difference)
The cross section of the produced polyurethane foam layer was observed 65 times using SEM. Three straight lines dividing the polyurethane foam layer into four equal parts in the thickness direction were drawn on the obtained image. The average value of the length of the line segment of the straight line intersecting with the bubbles was determined between any 2 mm of the straight line, and this was taken as the average bubble diameter. The average bubble diameter was determined for each of the three straight lines, and the average bubble diameter difference (maximum value−minimum value) in the thickness direction was determined from the maximum and minimum values of the average bubble diameter obtained.

(Measurement of specific gravity)
This was performed according to JIS Z8807-1976. The produced polyurethane foam layer was cut into a 4 cm × 8.5 cm strip (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%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Measurement of hardness)
This was performed according to JIS K-7312. A sample obtained by cutting the produced polyurethane foam layer into a size of 5 cm × 5 cm (thickness: arbitrary) was used as a sample and allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 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.

(Measurement of compression rate)
A polyurethane foam layer cut into a 7 mm diameter circle (thickness: arbitrary) 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 polyurethane foam layer when a stress of 4.9 KPa (50 g / cm ² ) is applied to the polyurethane foam layer from an unloaded state and held for 60 seconds.
T2: The thickness of the polyurethane foam layer 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 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
In the container, 90 parts by weight of EP330N (manufactured by Mitsui Takeda Chemical), 10 parts by weight of diethylene glycol, 5 parts by weight of a silicon-based surfactant (SH-192, manufactured by Toray Dow Corning Silicone), and a catalyst (No. 25, Kao) (Product made) 0.2 part by weight was added and mixed. 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, 38.5 parts by weight of Millionate MTL (manufactured by Nippon Polyurethane Industry) was added and stirred for about 1 minute to prepare a cell dispersed urethane composition.

  The prepared cell-dispersed urethane composition was applied on a base sheet (polyethylene terephthalate, thickness: 0.2 mm) to form a cell-dispersed urethane layer. Then, a release sheet (polyethylene terephthalate, thickness: 0.2 mm) subjected to a release treatment was put on the cell-dispersed urethane layer. The cell-dispersed urethane layer was made 1.0 mm thick with a nip roll, and then cured at 70 ° C. for 40 minutes to form a polyurethane foam layer. Thereafter, the release sheet on the polyurethane foam layer was peeled off. Next, the surface of the polyurethane foam layer was buffed using a buffing machine (manufactured by Amitech) to make the thickness 0.8 mm, and the thickness accuracy was adjusted. 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. FIG. 1 shows a micrograph of a cross section of the polyurethane foam layer. It can be seen that spherical bubbles are formed in the polyurethane foam layer.

Example 2
The cell-dispersed urethane composition prepared in Example 1 was applied on a base sheet (polyethylene terephthalate, thickness: 0.2 mm) to form a cell-dispersed urethane layer. Then, it was cured at 70 ° C. for 40 minutes to form a polyurethane foam layer. Next, the surface of the polyurethane foam layer was buffed using a buffing machine (manufactured by Amitech) to make the thickness 0.8 mm, and the thickness accuracy was adjusted. 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. FIG. 2 shows a micrograph of a cross section of the polyurethane foam layer. It can be seen that spherical bubbles are formed in the polyurethane foam layer.

Example 3
The cell-dispersed urethane composition prepared in Example 1 was applied on a base sheet (polyethylene terephthalate, thickness: 0.2 mm) to form a cell-dispersed urethane layer. Then, a release sheet (polyethylene terephthalate, thickness: 0.2 mm) subjected to a release treatment was put on the cell-dispersed urethane layer. The cell-dispersed urethane layer was made 0.8 mm thick with a nip roll, and then cured at 70 ° C. for 40 minutes to form a polyurethane foam layer. Thereafter, the release sheet on the polyurethane foam layer was peeled off. A skin layer was formed on the polyurethane foam layer. Thereafter, a template was affixed on the skin layer, and a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was adhered to the surface of the base material sheet using a laminator to prepare a laminated sheet. FIG. 3 shows a micrograph of a cross section of the polyurethane foam layer. It can be seen that spherical bubbles are formed in the polyurethane foam layer.

Comparative Example 1
A urethane solution is prepared by dissolving 10 parts by weight of thermoplastic urethane (Rezamin 7285, manufactured by Dainichi Seika) in 90 parts by weight of dimethylformamide, and the urethane solution is placed on a base sheet (polyethylene terephthalate, thickness: 0.2 mm). To form a urethane film. Then, the urethane membrane-base sheet is immersed in a DMF-water mixture (DMF / water = 30/70) for 30 minutes, and further immersed in water for 24 hours to replace dimethylformamide with water to form a polyurethane foam layer. did. Thereafter, a template was affixed to the surface of the polyurethane foam layer, and a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was affixed to the surface of the base material sheet using a laminator to produce a laminated sheet. FIG. 4 shows a micrograph of a cross section of the polyurethane foam layer. It can be seen that elongated cocoon-shaped bubbles are formed in the polyurethane foam layer.

  As is apparent from Table 1, it can be understood that the polishing rate hardly changes even when a large number of wafers are polished by using the laminated sheet prepared by the manufacturing method of the present invention.

Micrograph (SEM photograph) of polyurethane foam layer of laminated sheet in Example 1 Micrograph (SEM photograph) of polyurethane foam layer of laminated sheet in Example 2 Micrograph (SEM photograph) of polyurethane foam layer of laminated sheet in Example 3 Micrograph (SEM photograph) of polyurethane foam layer of laminated sheet in Comparative Example 1

Claims (11)

A step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a base sheet, a polyurethane foam layer by curing the cell-dispersed urethane composition (however, the polyurethane foam layer is heated) A method for producing a laminate sheet for holding a material to be polished , comprising a step of forming a plastic resin-free material) and a step of uniformly adjusting the thickness of a polyurethane foam layer. The step of preparing the cell-dispersed urethane composition by the mechanical foaming method, the step of applying the cell-dispersed urethane composition on the base sheet, the step of laminating the release sheet on the cell-dispersed urethane composition, and the thickness by the pressing means A step of curing the cell-dispersed urethane composition while making it uniform to form a polyurethane foam layer (the polyurethane foam layer does not contain a thermoplastic resin) , and a step of peeling the release sheet on the polyurethane foam layer A method for producing a laminated sheet for holding an abrasive . A laminated sheet for holding a material to be polished manufactured by the method according to claim 1. The laminated sheet for holding a material to be polished according to claim 3, wherein the polyurethane foam layer has spherical fine bubbles having an average cell diameter of 20 to 300 µm. The polyurethane foam layer is a laminated sheet for holding a material to be polished according to claim 4, wherein an average cell diameter difference in the thickness direction (average cell diameter maximum value-average cell diameter minimum value) is 50 µm or less. The laminated sheet for holding a material to be polished according to any one of claims 3 to 5, wherein the specific gravity of the polyurethane foam layer is 0.2 to 0.5. The laminated sheet for holding a material to be polished according to any one of claims 3 to 6, wherein the polyurethane foam layer has an Asker C hardness of 10 to 50 degrees. The laminate sheet for holding a material to be polished according to any one of claims 3 to 7, wherein a compression ratio of the polyurethane foam layer is 2 to 10%. The polyurethane foam layer contains an isocyanate component and an active hydrogen-containing compound as raw material components,
The method for producing a laminated sheet for holding an abrasive according to claim 1 or 2, wherein the isocyanate component is 4,4'-diphenylmethane diisocyanate or carbodiimide-modified MDI. The polyurethane foam layer contains an isocyanate component and an active hydrogen-containing compound as raw material components,
The active hydrogen-containing compound contains a high molecular weight polyol,
The high molecular weight polyol includes a polymer polyol in which polymer particles made of acrylonitrile and / or a styrene-acrylonitrile copolymer are dispersed,
10. The material to be polished according to claim 1, wherein the polymer polyol is contained in the high molecular weight polyol in an amount of 20 to 100% by weight and in an active hydrogen-containing compound in an amount of 60 to 85% by weight. A method for producing a laminated sheet for holding. The said active hydrogen containing compound contains 2-15 weight% of low molecular weight polyols and / or low molecular weight polyamines, The manufacturing method of the laminated sheet for to-be-polished material of Claim 10 characterized by the above-mentioned.

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