JP6987584B2 - Laminated body for use in manufacturing of holding pad and its manufacturing method - Google Patents

Description

The present invention relates to a laminate for use in the manufacture of a holding pad and a method for manufacturing the laminate. In particular, a soft resin sheet in which bubbles are formed by the wet film forming method and has a skin layer on the holding surface side for holding the object to be polished (the object to be held), and the adhesiveness arranged on the holding surface. The present invention relates to a laminate provided with a film and a method for producing the same.

Conventionally, materials (objects to be polished) such as semiconductor wafers, glass substrates, and magnetic disks are required to have high-precision flatness, and therefore, polishing using a polishing pad is performed. Usually, a double-sided polishing machine that simultaneously polishes both sides of the object to be polished and a single-sided polishing machine that polishes the object to be polished one side at a time are used for polishing these objects to be polished.
In the polishing process using a single-sided polishing machine, the purpose is to absorb the variation in parallelism between the holding surface plate and the polishing pad and the eccentric load generated during the polishing process, and to hold the object to be polished on the holding surface plate substantially flat. , The holding pad is attached to the holding surface plate. Usually, a foamed sheet made of polyurethane resin formed by a wet film forming method is used for the holding pad. In the wet film forming method, a resin solution obtained by dissolving a polyurethane resin in a water-miscible organic solvent is applied to a sheet-shaped film-forming substrate and then immersed in an aqueous coagulating liquid to solidify and regenerate the resin into a sheet. To. The obtained foam sheet has a skin layer on the surface side in contact with the object to be polished, is vertically elongated in the thickness direction inside the skin layer, and spreads on the opposite surface side (hereinafter referred to as the back surface) side of the skin layer. It has a structure in which a plurality of diameter bubbles (tear-shaped bubbles) and a large number of micropores having an average diameter smaller than the average diameter of the bubbles are continuously formed. By having such a structure, cushioning property is exhibited during the polishing process, and the object to be polished can be held substantially flat. The surface of the skin layer is flat and has excellent contact with the object to be polished, and the object to be polished can be reliably held by fixing the skin layer by water-filled adsorption. That is, the surface of the skin layer serves as a holding surface for holding the object to be polished.

In recent years, digital devices having an image display function (for example, mobile phones, smartphones, tablet terminals, mobile computers, etc.) and devices (electronic devices) such as solar cells, liquid crystal panels, and organic EL panels have become thinner and lighter. The glass substrates and cover glasses used for these devices are becoming thinner. The glass plate is polished to reduce waviness and improve surface quality, but the strength decreases as the glass plate becomes thinner, so when the object to be polished is detached due to insufficient adsorption with the holding pad during polishing. , The problem that the object to be polished is easily damaged has come up. If the objects to be polished are damaged in the polishing machine, it takes time to collect and clean them, and the productivity is significantly reduced.
Further, due to the thinning of the object to be polished, the unevenness of the surface of the holding pad, which has not been a problem in the past, has come to affect the flatness of the object to be polished. The causes of unevenness on the surface of the holding pad include the insufficiently dissolved resin content generated during the preparation of the resin solution and the inclusion of insufficiently dispersed carbon black agglomerates in the resin solution in the sheet, and the mixture in the aqueous coagulation liquid. Adhesion of suspended matter to the resin surface, adhesion of suspended matter to the surface of the resin solution in the atmosphere before immersion in the aqueous coagulant, water-based coagulant with a surfactant eluted from the resin solution into the aqueous coagulant, etc. It can be mentioned that the contact with the liquid is hindered, that is, the unevenness of solidification regeneration caused by the so-called repelling phenomenon. These form spot-like protrusions and recesses protruding on the surface of the skin layer. Normally, the holding pad having these irregularities is eliminated as a defective product in the inspection process at the time of manufacturing, but micron-order irregularities that are not visually excluded have come to affect the flatness of the object to be polished.

Conventionally, as a method of improving the adsorptivity of a holding pad, a technique of sandwiching both sides of a polyurethane sheet between smoothing members and heating and pressurizing the polyurethane sheet (Patent Document 1), or a wet film-forming polyurethane sheet is pressed and adhered to a film-like substrate. A method is known in which a rolled-up body wound into a roll is held at a heating temperature of 30 to 50 ° C. and a heat treatment time of 12 to 48 hours (Patent Document 2).

Japanese Patent No. 5436959 Japanese Patent No. 4961191

However, in the method of Patent Document 1, since air bubbles (pores) on the surface of the skin layer are crushed and smoothed by heating and pressurizing, the apparent smoothness is high, but the adsorption force becomes too strong due to the smoothness. There is a problem that it becomes difficult to peel off the object to be polished after the polishing is completed. Therefore, especially when holding a thin object to be polished, there is a problem that the holding pad is damaged when the holding pad is peeled off. In addition, for smoothing, the thick part of the holding pad is crushed by pressurization at high temperature to equalize the thickness, but the density of the part becomes high and it becomes hard, and the hard part due to pressurization during polishing. Since it is harder to sink than other parts, the contact with the object to be polished in the portion becomes stronger, so that there is a problem that the local polishing load of the object to be polished becomes uneven and polishing spots occur. Further, since a smooth and dense layer exists, there is no escape place for air bitten between the surface of the skin layer and the object to be polished when the object to be polished is attached, and air is allowed to flow between the surface of the skin layer and the object to be polished. It is easy to be stored in. If the polishing process is performed while the air is stored, the pressure applied to the object to be polished increases at the air storage area, so that the processed surface of the area is greatly polished (the air storage area is transferred to the object to be polished) and polished. The object to be polished after processing impairs flatness. In particular, when the object to be polished is large, it is difficult to attach it so as not to bite air, and there is a problem that the flatness is more likely to deteriorate.
In the method of Patent Document 2, since the polyurethane sheet is made into a scroll and then heat-treated, the holding pad is easily curled, the work of attaching to the polishing surface plate becomes difficult, and the workability deteriorates. Also, the adsorptivity is not sufficient.

The present invention has been made in view of the above problems, and has excellent adsorptivity and flatness during polishing of the object to be polished (performance to polish the object to be polished more flatly), and has appropriate peelability (subject). It is an object of the present invention to provide a laminate for use in manufacturing a holding pad having (removability from a holding pad for an polished object), and a method for manufacturing the laminate.

As a result of diligent studies on the above problems, the present inventors have obtained adhesiveness and polishing by using a holding pad formed by peeling the adhesive film from a laminate formed by laminating an adhesive film on a polyurethane sheet. The present invention has been completed by finding that a holding pad having excellent flatness during polishing of an object and having appropriate peelability can be obtained.
That is, the present invention provides the following.

[1] A step of preparing a polyurethane sheet having a plurality of tear-shaped bubbles and having a holding surface for holding an object to be polished;
A step of preparing an adhesive film having an adhesive layer on one side of the film; and a step of laminating the adhesive film and the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet to obtain a laminate.
A method of manufacturing a laminate for use in the manufacture of holding pads, including.
[2] The production method according to [1], wherein the adhesive film and the polyurethane sheet are bonded together without heating.
[3] The production method according to [1] or [2], wherein the peel strength between the adhesive film and the polyurethane sheet is in the range of 0.020 to 0.150 kg / 10 mm.
[4] A method for manufacturing a holding pad, which comprises a step of peeling an adhesive film from the laminate obtained by the method according to any one of [1] to [3] to obtain a holding pad.
[5] For use in manufacturing a holding pad including a polyurethane sheet having a plurality of tear-shaped bubbles and a holding surface for holding an object to be polished, and an adhesive film having an adhesive layer on one side of the film. It ’s a laminated body,
The adhesive film is bonded onto a polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, and the films constituting the adhesive film are a polyolefin film and polyvinyl chloride. The laminate selected from a film and a polyester film.
[6] The laminate according to [5] for peeling off the adhesive film and using it as a holding pad.
[7] The laminate according to [5] or [6], wherein the polyurethane sheet has a skin layer on the holding surface side thereof.
[8] The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is selected from an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a fluororesin-based pressure-sensitive adhesive, a natural rubber-based pressure-sensitive adhesive, and a synthetic rubber-based pressure-sensitive adhesive, [5] to [7]. ] The laminate according to any one of.
[9] The laminate according to any one of [5] to [8], wherein the peel strength between the adhesive film and the polyurethane sheet is in the range of 0.020 to 0.150 kg / 10 mm.
[10] A holding pad obtained by peeling an adhesive film from the laminate according to any one of [5] to [9].
[11] A step of preparing the laminate obtained by the method according to any one of [1] to [3] or the laminate according to any one of [5] to [9];
A step of peeling the adhesive film from the laminate to obtain a holding pad; and a step of polishing the object to be polished with the polishing pad while holding the object to be polished using the holding pad.
A method for polishing an object to be polished, including.

Compared with the conventional holding pad, the holding pad of the present invention has excellent adsorptivity, flatness of the object to be polished during polishing, and has appropriate peelability. It is also possible to prevent air from getting caught.

It is an enlarged photograph (1000 times) of the polyurethane sheet holding surface before adhering the adhesive film to a polyurethane sheet in Example 1. FIG. It is an enlarged photograph (1000 times) of the polyurethane sheet holding surface after peeling off the adhesive film attached to the polyurethane sheet in Example 1. It is an enlarged photograph (10000 times) of the polyurethane sheet holding surface before adhering the adhesive film to a polyurethane sheet in Example 1. FIG. It is an enlarged photograph (10000 times) of the polyurethane sheet holding surface after peeling off the adhesive film attached to the polyurethane sheet in Example 1.

Hereinafter, embodiments for carrying out the present invention will be described.

<< Manufacturing method of holding pad laminate >>
A first aspect of the present invention is a step of preparing a polyurethane sheet having a plurality of teardrop-shaped bubbles and having a holding surface for holding an object to be polished; preparing an adhesive film having an adhesive layer on one side of the film. A laminated body for use in manufacturing a holding pad, which comprises a step of laminating the adhesive film and the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet to obtain a laminated body. It is a manufacturing method of.
Hereinafter, each step will be described in detail.

<(1) Process of preparing polyurethane sheet>
In the process of preparing the polyurethane sheet, a polyurethane sheet containing a polyurethane resin is prepared. The polyurethane sheet preferably has a plurality of teardrop-shaped bubbles (formed by the wet film formation method). Further, the polyurethane sheet preferably has a skin layer on the holding surface for holding the object to be polished. As the polyurethane sheet, a commercially available one may be used, or a polyurethane sheet manufactured by oneself may be used. The polyurethane sheet can be manufactured, for example, through the following steps (i) to (iv).

(I) Preparation of Polyurethane Resin-Containing Solution A polyurethane resin-containing solution is prepared by dissolving the polyurethane resin, which is the raw material of the polyurethane sheet, in a water-miscible organic solvent capable of dissolving the polyurethane resin. Further, after dissolving in an organic solvent, the obtained solution may be defoamed under reduced pressure.

(A) Polyurethane resin The type of polyurethane resin is not particularly limited, and may be selected from various polyurethane resins according to the purpose of use. For example, polyester-based, polyether-based, polycarbonate-based, or copolymer-based or mixed-based resins thereof can be used.
Examples of the polyester-based resin include a polymer of a polyester polyol containing ethylene glycol, butylene glycol or the like and adipic acid, and a diisocyanate such as diphenylmethane-4,4'-diisocyanate.
Examples of the polyether resin include a polymer of a polyether polyol such as polytetramethylene ether glycol or polypropylene glycol and an isocyanate such as diphenylmethane-4,4'-diisocyanate.
Examples of the polycarbonate-based resin include a polymer of a polycarbonate polyol and an isocyanate such as diphenylmethane-4,4'-diisocyanate.
These resins are available on the market, such as the product name "Chrisbon" manufactured by DIC Corporation, the product name "Samplen" manufactured by Sanyo Chemical Industries, Ltd., and the product name "Resamine" manufactured by Dainichi Seika Kogyo Co., Ltd. An available resin may be used, or a resin having desired properties may be produced by itself.
The polyurethane resin is preferably contained in an amount of 50 to 98% by mass, more preferably 60 to 95% by mass, and more preferably 70 to 90% by mass with respect to the total solid content contained in the polyurethane resin-containing solution. Even more preferable.

(Modulus)
Modulus is an index showing the hardness of the resin, and is the value obtained by dividing the load applied when the non-foamed resin sheet is stretched 100% (when stretched to twice the original length) by the unit area. (Hereinafter, it may be referred to as 100% modulus.). The higher this value, the harder the resin.
The polyurethane resin preferably has a resin modulus of 1 to 20 MPa, more preferably 2 to 10 MPa, and even more preferably 3 to 8 MPa. When the modulus is within the above range, the flatness of the object to be polished after polishing can be improved, and the risk of damage and scratches due to stress concentration can be reduced when the object to be polished is polished using the polishing pad.

(B) Organic Solvent The organic solvent can be used without particular limitation as long as it can dissolve a polyurethane resin and is miscible with water. Examples include N, N-dimethylformamide (DMF), methylethylketone (MEK), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetone, Examples thereof include 1,3-dimethyl-2-imidazolidinone (DMI). Among these, DMF or DMAc is preferably used.
The solid content concentration in the polyurethane resin-containing solution is preferably 10 to 40% by mass, more preferably 15 to 35% by mass. If the concentration is within the above range, the polyurethane resin-containing solution has an appropriate fluidity and can be uniformly applied to the film-forming substrate in the subsequent coating step.

Further, the polyurethane resin-containing solution may contain components other than the above components as long as the effects of the present invention are not impaired. Other components include pore-forming agents, pigments, hydrophilic additives, hydrophobic additives and the like.
Examples of the pore-forming agent include polyols and cellulose derivatives. Examples of the polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polycaprolactone diol, and polycarbonate diol. Examples of the cellulose derivative include ester-based cellulose derivatives such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose ballerate, and cellulose acetate butyrate, ether-based cellulose derivatives such as ethyl cellulose and hydroxypropyl cellulose, acetylethyl cellulose, and acetoxypropyl. Examples thereof include ether ester-based cellulose derivatives such as cellulose. When the pore-forming agent is contained, the pore-forming agent is preferably contained in an amount of 0.001 to 5% by mass, more preferably 0.01 to 2% by mass, based on the total solid content contained in the polyurethane resin solution. It is preferable that it is contained in an amount of 0.01 to 1.0% by mass, and even more preferably. By including the pore forming agent, the opening portion can be easily formed and adjusted on the holding surface.

Examples of the pigment include carbon black. When the pigment is contained, the pigment is preferably contained in an amount of 0 to 20% by mass, more preferably 0.1 to 20% by mass, and 0.5 to 20% by mass, based on the total solid content contained in the polyurethane resin solution. It is even more preferably contained in an amount of 10% by mass, further preferably contained in an amount of 1 to 8% by mass, and even more preferably contained in an amount of 2 to 7% by mass. It is desirable that the pigment is contained within the above range because the bubble shape is stabilized.
Examples of the hydrophilic additive include anionic surfactants such as sodium lauryl sulfate, carboxylate, sulfonate, sulfate ester salt, and phosphoric acid ester salt, hydrophilic ester type, ether type, ester ether type, and amide. Examples thereof include nonionic surfactants such as those used in the system. Further, as the hydrophobic additive, for example, a nonionic surfactant having an alkyl chain having 3 or more carbon atoms added, more specifically, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxy. Examples thereof include propylene alkyl ether, perfluoroalkyl ethylene oxide adduct, glycerin fatty acid ester, and propylene glycol fatty acid ester. When a surfactant is contained, the surfactant is preferably contained in an amount of 0.01 to 10% by mass, more preferably 0.1 to 10% by mass, based on the total solid content contained in the polyurethane resin solution. It is more preferably contained in an amount of 0.2 to 8% by mass, and even more preferably contained in an amount of 0.3 to 8% by mass. When the surfactant is contained within the above range, foaming can be promoted and the solidification and regeneration of the polyurethane resin can be stabilized.

(Ii) Coating The polyurethane resin-containing solution obtained above is continuously coated on the film-forming substrate by a knife coater, a reverse coater, or the like so as to be substantially uniform. At this time, the coating thickness (coating amount) of the urethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater or the like and the film-forming substrate. As the film-forming substrate, any substrate usually used in the present technical field can be used without particular limitation. Examples thereof include a flexible polymer film such as a polyester film and a polyolefin film, a non-woven fabric impregnated and fixed with an elastic resin, and the polyester film is preferably used.

(Iii) Coagulation The substrate coated with the polyurethane resin-containing solution is immersed in a coagulating liquid containing water, which is a poor solvent for the polyurethane resin, as a main component.
As the coagulating liquid, water, a mixed solution of water and a polar organic solvent such as DMF, or the like is used. Examples of the polar organic solvent include water-miscible organic solvents used to dissolve the polyurethane resin, such as DMF, DMAc, THF, DMSO, NMP and acetone. The concentration of the polar organic solvent in the mixed solvent is preferably 0 to 20% by mass. Among these, as the coagulating liquid, water or a mixed liquid of water and DMF is preferable, and a mixed liquid of water and DMF (the ratio of DMF in the mixed liquid is preferably 1 to 20% by mass, preferably 5 to 15% by mass). Is more preferable) is more preferable.
The temperature and soaking time of the coagulating liquid are not particularly limited, and for example, the coagulant may be soaked at 10 to 60 ° C. (preferably 15 to 50 ° C.) for 5 to 120 minutes.
In the coagulation liquid, first, a dense skin layer is formed on the surface side of the urethane resin solution. After that, as the replacement of the solvent and the coagulating liquid in the urethane resin solution progresses through the skin layer, the urethane resin is solidified and regenerated into a sheet on the film-forming substrate (that is, when the holding surface is the upper surface). A resin sheet in which a plurality of tear-shaped bubbles are formed (below the skin layer) is formed.

(Iv) Washing and Drying The sheet-shaped polyurethane resin obtained by coagulating in a coagulation bath is washed and dried after being peeled from the film-forming substrate or without peeling.
The cleaning treatment removes the organic solvent remaining in the polyurethane resin. Examples of the cleaning liquid used for cleaning include water.
After cleaning, the polyurethane resin is dried. The drying treatment may be carried out by a conventional method, for example, it may be dried in a dryer at 80 to 150 ° C. for about 5 to 60 minutes. A polyurethane sheet can be obtained through the above steps.

If necessary, the polyurethane sheet may be ground on a surface opposite to the surface of the adhesive film in contact with the adhesive layer (holding surface for holding the object to be polished). The method of grinding is not particularly limited, and grinding can be performed by a known method. Specific examples include grinding with sandpaper. Further, a buffing machine, a slicing machine or the like can be used for the grinding process. As a result, a polyurethane sheet having a uniform thickness of the film-forming resin can be obtained.

<(2) Step of preparing an adhesive film having an adhesive layer on one side of the film>
The production method of the present invention includes a step of preparing an adhesive film having an adhesive layer on one side of the film. The film constituting the adhesive film is a film selected from a polyolefin film (polyethylene film, polypropylene film, etc.), a polyvinyl chloride film, and a polyester film. Among these, a polyolefin film is even more preferable, a polyolefin film having an olefin having 2 to 8 carbon atoms as a monomer unit is even more preferable, a polyethylene film, a polypropylene film, and a polybutylene film are even more preferable, and a polyethylene film is used. It is particularly preferable to have.

(Adhesive layer)
The adhesive film has an adhesive layer on one side of the film. By having the adhesive layer, the adhesive film can be adhered to the polyurethane sheet without applying heat, and the adhesive film is brought into contact with the holding surface of the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the polyurethane sheet. It can be laminated (bonded) on top. Further, due to the presence of the adhesive layer, the number of openings per unit area of the holding surface of the polyurethane sheet after the adhesive film is peeled off is determined by the number of openings per unit area of the holding surface of the polyurethane sheet before the adhesive film is attached. It can be increased more than the number.
The pressure-sensitive adhesive component constituting the pressure-sensitive adhesive layer is preferably selected from an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a fluororesin-based pressure-sensitive adhesive, a natural rubber-based pressure-sensitive adhesive, and a synthetic rubber-based pressure-sensitive adhesive. It is more preferable to select from an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a urethane-based pressure-sensitive adhesive, and even more preferably an acrylic-based pressure-sensitive adhesive. Examples of the acrylic pressure-sensitive adhesive include an acrylic acid ester copolymer containing ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like as a main monomer.
The adhesive strength of the adhesive layer is preferably 0.05 to 1.0 N / 25 mm, and more preferably 0.1 to 0.5 N / 25 mm. The adhesive strength is a measured value when a tape having an adhesive component on one side is attached to a stainless steel plate and peeled off in the 180 ° direction after a certain period of time, and can be measured based on JIS Z 0237.

<(3) Laminating process>
The manufacturing method of the present invention includes a step of laminating the adhesive film and the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet to obtain a laminate.
By adhering the adhesive film onto the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, a laminate for use in manufacturing a holding pad can be obtained.
As a method of adhering the adhesive film to the holding surface of the polyurethane sheet, laminating processing can be mentioned. At this time, it is preferable to bond the adhesive film and the polyurethane sheet without heating, and it is more preferable to bond the adhesive film and the polyurethane sheet at room temperature (about 15 ° C to 25 ° C). By laminating without heating, it is possible to prevent the shrinkage or disappearance of minute holes on the surface of the skin layer due to heating. This facilitates peeling of the object to be polished. In addition, it can be taken into the inside of the polyurethane sheet through the micropores when air is caught, and deterioration of the flatness of the object to be polished after polishing due to air biting can be suppressed.
In the production method of the present invention, the peel strength between the adhesive film and the polyurethane sheet to which the adhesive layer of the adhesive film is attached so as to be in contact with the holding surface of the polyurethane sheet is 0.020 to 0.150 kg / 10 mm. It is preferably 0.023 to 0.100 kg / 10 mm, even more preferably 0.025 to 0.080 kg / 10 mm, and even more preferably 0.028 to 0.075 kg / 10 mm. Even more preferably, it is even more preferably 0.030 to 0.070 kg / 10 mm. By adhering the adhesive film and the polyurethane sheet so that the peel strength is within the above range, the surface smoothness of the holding surface of the holding pad is improved when the adhesive film is peeled off to obtain the holding pad. This makes it difficult for the slurry to penetrate between the holding pad and the object to be polished during polishing, and it is possible to suppress a decrease in adsorptivity over time due to the penetration. In addition, it is possible to suppress air biting that occurs when the object to be polished is brought into close contact with the object. Further, the numerical aperture and the opening diameter can be adjusted, and the peeling force can be controlled within an appropriate range.

<(4) Other optional processes>
In the method for manufacturing a holding pad of the present invention, after the laminating step, another layer (lower layer, support layer) may be attached to the surface of the polyurethane sheet opposite to the surface holding the object to be polished. The characteristics of the other layers are not particularly limited, but it is preferable that a layer harder (higher in A hardness) than the polyurethane sheet is bonded. Workability is improved by providing a layer harder than the polyurethane sheet.

When another layer is provided, the plurality of layers may be bonded and fixed to each other by using double-sided tape or an adhesive while applying pressure as necessary, and it is preferable to bond and fix the layers without heating. The double-sided tape and adhesive used at this time are not particularly limited, and can be arbitrarily selected and used from the double-sided tapes and adhesives known in the art.

<< Manufacturing method of holding pad >>
A second aspect of the present invention is a step of peeling an adhesive film (that is, a film and an adhesive layer) from the laminate obtained by the production method of the first aspect or the laminate of the third aspect below to obtain a holding pad. It is a manufacturing method of a holding pad including.
It is preferable that the adhesive film is peeled off from the laminate when it is used as a holding pad, that is, immediately before it is used as a holding pad for holding an object to be polished.
The holding pad of the present invention is obtained by peeling the adhesive film from the polyurethane sheet body. Therefore, the holding pad of the present invention does not include an adhesive film.
In the method for manufacturing a holding pad of the present invention, holding of the polyurethane sheet (holding pad) after peeling the adhesive film from the laminate with respect to the number of openings of the polyurethane sheet holding surface before bonding the adhesive film on the polyurethane sheet. The ratio of the number of openings on the surface is preferably larger than 1, more preferably 1.5 or more, further preferably 2 or more, still more preferably 3 or more, and 3 to 20. It is even more preferably 3 to 15, and even more preferably 4 to 12.
Further, in the method for manufacturing a holding pad of the present invention, after the adhesive film is peeled off from the laminate with respect to the average opening diameter of the openings existing in the polyurethane sheet holding surface before the adhesive film is bonded onto the polyurethane sheet. The ratio of the average opening diameter of the openings present on the polyurethane sheet holding surface (hereinafter, may be simply referred to as the average opening diameter ratio) is preferably larger than 1, more preferably 1.1 or more, and 1 .2 to 2.0 is even more preferred, and 1.2 to 1.5 is even more preferred.

<< Laminated body for use in manufacturing holding pads >>
A third aspect of the present invention includes a holding pad comprising a polyurethane sheet having a plurality of teardrop-shaped bubbles and a holding surface for holding an object to be polished, and an adhesive film having an adhesive layer on one side of the film. It is a laminated body for use in the production of
The adhesive film is bonded onto a polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, and the films constituting the adhesive film are a polyolefin film and polyvinyl chloride. The laminate selected from a film and a polyester film.
The laminate of the present invention can be preferably used for removing (peeling) the adhesive film and using it as a holding pad. It is preferable that the adhesive film of the laminate of the present invention is peeled off (removed) immediately before it is used as a holding pad for holding an object to be polished.

<Polyurethane sheet>
Polyurethane sheets have multiple teardrop-shaped bubbles. The teardrop-shaped bubbles are bubbles formed inside the polyurethane sheet by the wet film formation method (air bubbles having an anisotropic structure and having a structure having a large diameter from the upper part to the lower part (the side in contact with the base material) of the resin sheet). It is intended and is used to distinguish it from the substantially spherical bubbles formed by the dry molding method. Therefore, the polyurethane sheet having a plurality of tear-shaped bubbles of the present invention can be rephrased as a polyurethane sheet formed by a wet film forming method. In the wet film forming method, the resin to be formed is dissolved in an organic solvent, the resin solution is applied to a sheet-shaped substrate, and then the organic solvent is dissolved but the resin is not dissolved. It means a method of substituting an organic solvent, coagulating it, and drying it to form a foamed layer. Usually, when a polyurethane sheet is manufactured by a wet film forming method, substantially tear-shaped macro bubbles (tear-shaped bubbles) are generated inside the polyurethane sheet.
In the present specification and claims, the polyurethane sheet is mainly composed of a polyurethane resin (50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 85% by mass or more). It means a sheet containing the above, and is clearly distinguished from a sheet containing another resin (silicon resin, etc.) as a main component.

The type of polyurethane resin used as a raw material for the polyurethane sheet is not particularly limited, and may be selected from various polyurethane resins according to the purpose of use. For example, the polyester-based, polyether-based, or polycarbonate-based resin exemplified in the first aspect can be used.

(Skin layer)
The polyurethane sheet preferably has a skin layer on the holding surface side that holds the object to be polished. That is, it is preferable that the surface of the skin layer serves as a holding surface. The skin layer is a dense skin with fewer bubbles than the inside of the polyurethane sheet, which is formed in the region from the surface of the polyurethane sheet (surface on the holding surface side) to 3 μm in the depth direction (thickness direction) by the wet film formation method. It is a layer. The skin layer has fewer bubbles (or smaller bubble size) than the inside of the polyurethane sheet, and therefore has a higher density than the inside of the sheet. Therefore, the skin layer can be rephrased as a dense layer formed in a thickness region of 3 μm or less in the depth direction (thickness direction) from the surface of the polyurethane sheet (surface on the holding surface side) formed by the wet film forming method. .. By having the skin layer, the object to be polished can be brought into close contact with the holding surface and sufficiently adsorbed.
As described above, the skin layer is a high-density and dense layer existing in the polyurethane sheet, and is obtained from the same raw material as the polyurethane sheet. The skin layer is not a different layer than the polyurethane sheet laminated on the polyurethane sheet. The skin layer is a layer containing a polyurethane resin as a main component (50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 85% by mass or more), and other resins. It is not a layer containing (such as a silicone resin (for example, polyorganosiloxane)) as a main component.

(Thickness)
The thickness of the polyurethane sheet is not particularly limited, but is preferably 0.3 to 3 mm, more preferably 0.5 to 2.5 mm, and even more preferably 0.5 to 2 mm. When the thickness of the polyurethane sheet is within the above range, cushioning properties can be exhibited and the surface quality of the object to be polished can be improved.

<Adhesive film>
As the adhesive film, the adhesive film described in the first aspect can be used.

(Peeling strength)
Within the scope of the present specification and patent claims, the peel strength is obtained by cutting out a laminate containing the adhesive film and the polyurethane sheet, which are bonded so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, to a size of 20 mm × 150 mm. A test piece was prepared, and the polyurethane sheet and the adhesive film portion at one end in the longitudinal direction of the test piece were attached to the gripping part of the tensile tester so that the gap was 10 mm, and the tensile speed was 200 mm per minute. This is the maximum load when the pasted portion (that is, 20 mm × 50 mm) having a length of 50 mm is peeled off (T-shaped peeled) in the long side direction.
The peel strength can be measured using a Tensilon tensile tester (A & D Co., Ltd., Tensilon universal tester, RTF-1210) by a method according to the Japanese Industrial Standards (JIS K6772). ..
In the laminate of the present invention, the peel strength between the adhesive film and the polyurethane sheet, which are bonded so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, is 0.020 to 0.150 kg / 10 mm. Is more preferable, 0.023 to 0.100 kg / 10 mm is more preferable, 0.025 to 0.080 kg / 10 mm is even more preferable, and 0.028 to 0.075 kg / 10 mm is further preferable. It is more preferably 0.030 to 0.070 kg / 10 mm, and even more preferably. When the peel strength is within the above range, the surface smoothness of the holding surface can be improved. This makes it difficult for the slurry to penetrate between the holding pad and the object to be polished during polishing, and it is possible to suppress a decrease in adsorptivity over time due to the penetration. Further, since the number of openings of the polyurethane sheet holding surface after peeling can be increased as compared with that before peeling, and / or the opening diameter of the polyurethane sheet holding surface after peeling can be made larger than that before peeling, the surface to be polished can be increased. It becomes easier to suppress air biting that occurs when the product is in close contact with an object. That is, by changing the peel strength, the number of holes opened and the opening diameter of the holding surface of the polyurethane sheet can be adjusted, and the holding force (peeling property) and the like can be controlled within the optimum range.
On the other hand, if the peel strength is less than 0.020 kg / 10 mm, the effect of sticking the adhesive film is poor, the effect of improving smoothness is reduced, and the slurry penetrates between the holding pad and the object to be polished during polishing. It becomes easy to get in. As a result, the adsorption force tends to decrease over time. If the peel strength is larger than 0.150 kg / 10 mm, the number of openings and the opening diameter of the skin layer increase too much at the time of peeling, and the roughness of the holding surface of the polyurethane sheet becomes rather large, and the slurry becomes a holding pad during polishing. The slurry easily penetrates between the objects to be polished. As a result, the adsorption force tends to decrease over time.

(Ratio of number of openings)
In the present specification and claims, the number of openings means the number of openings existing on the surface (holding surface) of the polyurethane sheet. The number of openings can be measured by binarizing an image of the surface of the skin layer taken by a scanning electron microscope (SEM) with image processing software.
In the laminate of the present invention, the ratio of the number of openings in the polyurethane sheet holding surface after peeling the adhesive film from the laminate to the number of openings in the polyurethane sheet holding surface before the adhesive film is bonded onto the polyurethane sheet (hereinafter referred to as “the number of openings”). , It may be simply referred to as the number of openings ratio.) It is preferable that the adhesive film is bonded on the polyurethane sheet so that the ratio is more than 1. The opening number ratio is preferably 1.5 or more, more preferably 2 or more, further preferably 3 or more, still more preferably 3 to 20, and 3 to 15. Is even more preferable, and 4 to 12 is even more preferable.

(Number of openings)
^{In the laminated body of the present invention, the number of openings existing per 10000 μm 2} of the holding surface of the polyurethane sheet before laminating (laminating) the adhesive film is preferably less than 100, and is preferably 80 or less. Is more preferable.
^{In the laminated body of the present invention, the number of openings existing per 10000 μm 2} of the holding surface of the polyurethane sheet after the adhesive film is peeled off from the laminated body is preferably 5 to 800, preferably 5 to 700. It is more preferably there, and even more preferably 5 to 600 pieces. Further, the number of the openings is preferably 50 to 800, preferably 100 to 600, preferably 150 to 500, and preferably 200 to 400.

(Average aperture diameter ratio)
In the present specification and claims, the average opening diameter means a circle-equivalent diameter calculated based on the area of minute gaps existing on the surface of the skin layer. The average aperture diameter can be measured by binarizing an image of the surface of the skin layer taken by a scanning electron microscope (SEM) with image processing software.
The laminate of the present invention is formed on the polyurethane sheet holding surface after the adhesive film is peeled off from the laminate with respect to the average opening diameter of the openings existing in the polyurethane sheet holding surface before the adhesive film is bonded onto the polyurethane sheet. It is preferable that the adhesive film is bonded onto the polyurethane sheet so that the ratio of the average opening diameters of the existing openings (hereinafter, may be simply referred to as the average opening diameter ratio) is larger than 1. The average aperture diameter ratio is more preferably 1.1 or more, further preferably 1.2 to 2.0, and even more preferably 1.2 to 1.5.

(Average aperture diameter)
The average opening diameter of the openings existing in the holding surface of the polyurethane sheet before laminating (laminating) the adhesive films is preferably 0.25 to 0.70 μm, preferably 0.30 to 0.60 μm. Is more preferable.
The average opening diameter of the openings present on the holding surface of the polyurethane sheet after peeling the adhesive film and the adhesive layer from the laminate is preferably 0.30 to 1.00 μm, preferably 0.35 to 0.90 μm. It is more preferably 0.40 to 0.90 μm, and even more preferably 0.40 to 0.90 μm. Further, the average opening diameter of the opening is preferably 0.50 to 0.80 μm, and preferably 0.60 to 0.70 μm.

The laminate of the present invention has the number of openings and / or the average opening diameter of openings present on the polyurethane sheet holding surface after the adhesive film is peeled off from the laminate, as compared with the polyurethane sheet before the adhesive film is bonded. Can be increased (see FIGS. 1 to 4). This makes it possible to prevent air biting in which air is taken into the contact surface when the object to be polished is brought into close contact with the holding pad. When air biting occurs, the object to be polished in contact with the air biting portion rises in a convex shape and is over-polished. However, the holding pad of the present invention allows air to be taken into the polyurethane sheet more easily than before. It is possible and the problem of partial overpolishing is less likely to occur. Therefore, it is possible to improve the flatness of the object to be polished during the polishing process. The reason why the average opening diameter of the holding surface of the polyurethane sheet after peeling the adhesive film from the laminate is large is not clear, but when the adhesive film is peeled off, the opening end of the holding surface having a thin skin layer is used. Is presumed to be because it is pulled and stretched.

<< Holding pad >>
A fourth aspect of the present invention is a holding pad obtained by peeling (obtaining) the adhesive film from the laminate.
The holding pad of the present invention is obtained by peeling the adhesive film from the laminate. Therefore, the retention pad of the present invention does not include an adhesive film (ie, film and adhesive layer).
The holding pad of the present invention can be suitably used as a holding pad when polishing a silicon wafer or a glass substrate. Among these, the holding pad of the present invention can be suitably used as a holding pad for a glass substrate (particularly a glass substrate for a liquid crystal display or a cover glass substrate).
In the holding pad of the present invention, ^{the number of openings existing per 10000 μm 2} of the holding surface is preferably 5 to 800, more preferably 5 to 700, and more preferably 5 to 600. Even more preferable. Further, the number of the openings is preferably 50 to 800, preferably 100 to 600, preferably 150 to 500, and preferably 200 to 400.
In the holding pad of the present invention, the average opening diameter of the openings existing on the holding surface is preferably 0.30 to 1.00 μm, more preferably 0.35 to 0.90 μm, and 0.40. Even more preferably, it is ~ 0.90 μm. Further, the average opening diameter of the opening is preferably 0.50 to 0.80 μm, and preferably 0.60 to 0.70 μm.

<< Polishing method >>
A fourth aspect of the present invention is a step of removing (peeling) the adhesive film from the laminate obtained by the production method of the first aspect or the laminate of the third aspect to obtain a holding pad; and the holding. A method for polishing an object to be polished includes a step of polishing the object to be polished with a polishing pad while holding the object to be polished using a pad.
Examples of the object to be polished include a silicon wafer and a glass substrate. Among these, a glass substrate (particularly a glass substrate for a liquid crystal display or a cover glass substrate) is preferable as the object to be polished.
Examples of the method for polishing the object to be polished include a method of polishing the surface of the glass substrate using a polishing liquid containing an abrasive selected from cerium oxide, colloidal silica and the like.

(Action effect)
Since the holding surface of the conventional holding pad is not protected, scratches and foreign matter are likely to adhere during storage. Further, in the film forming process of the polyurethane sheet, foreign matter may become apparent on the surface of the skin layer serving as the holding surface, and convex defects due to the foreign matter or concave defects from which the foreign matter has been removed may be formed on the surface of the holding pad. If foreign matter or scratches are present on the surface of the holding pad, the suction force will decrease, causing a difference in the suction force within the holding pad surface, and the slurry will enter the part where the suction force is insufficient during the polishing process, and the object to be polished Floats and becomes easy to detach. Further, if foreign matter adheres to the surface of the holding pad, the portion to be polished in contact with the foreign matter portion of the holding pad is raised and over-polished. As a result, uneven polishing occurs, and the flatness of the object to be polished after polishing is lowered (see Comparative Example 1).
On the other hand, since the holding surface of the holding pad of the present invention is protected by an adhesive film until use, it is not easily scratched and foreign matter can be prevented from adhering. Therefore, the adsorptivity is high, and the flatness of the object to be polished is less likely to decrease when the object to be polished is polished. Further, the minute recesses on the holding surface are pulled out to the surface by attaching an adhesive film, and after the adhesive layer is peeled off, the holding surface becomes a flat holding surface from which the recesses are removed. On the other hand, the micron-order convex portion of the holding surface, which seems to be an agglomerate contained in the holding pad, is pushed by the adhesive film by sticking the film. Further, the foreign matter adhering after the polyurethane sheet is formed can be removed together when the adhesive film is peeled off. As a result, the flatness of the object to be polished when polished is improved, and the adsorptivity is stabilized.

Further, as a conventional holding pad having improved adsorptivity, there is a holding pad manufactured by sandwiching both sides of a polyurethane resin with a smoothing member, heating and pressurizing the surface, and then peeling off the smoothing member (Patent Document 1). Since this holding pad traces the shape of the flat member by pressurization and heating, bubbles existing near the opening and the holding surface existing on the surface of the skin layer of the holding pad are crushed. As a result, the peelability is significantly reduced, and it takes a very long time to peel off the object to be polished after the polishing process of the object to be polished. Furthermore, when used as a holding pad for holding the object to be polished, the flatness of the object to be polished after polishing is inferior (see Comparative Example 2 of the present specification).
On the other hand, the holding pad of the present invention has an appropriate opening on the holding surface, and appropriate peelability can be obtained. Further, when used as a holding pad for holding the object to be polished, it is excellent in flatness during polishing of the object to be polished.

Further, as a conventional pad for reducing the surface roughness of the holding surface and improving the suction force, there is a holding pad in which smoothing members are brought into close contact with each other to form a scroll and then heated (Patent Document 2). , The step at the beginning of winding is transferred, streak-like defects are formed, and the defects are transferred to the object to be polished. In addition, winding habits are formed, the ends tend to face upward, and the sticking workability is poor. As a result, when used as a holding pad for holding the object to be polished, the flatness of the object to be polished after polishing is inferior. In addition, it is difficult to maintain the suction force because the suction force is low and the slurry is infiltrated (see Comparative Example 3 of the present specification).
On the other hand, since the holding pad of the present invention does not have a curved shape, when used as a holding pad for holding the object to be polished, the flatness after polishing of the object to be polished is excellent. In addition, the suction force is high, and the slurry does not penetrate between the object to be polished and the holding pad, so that the suction force can be maintained.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
Unless otherwise specified, in each of the examples, comparative examples and Table 1, "parts" shall mean "parts by mass".

[Example 1]
In Example 1, a polyester MDI (diphenylmethane diisocyanate) polyurethane resin having a 100% modulus of 6 MPa was used as the polyurethane resin. For 100 parts of this polyurethane resin 30% DMF solution, 45 parts of DMF for adjusting viscosity, 15 parts of DMF dispersion containing 10% of carbon black, 0.1 part of cellulose acetate butyrate, surfactant (large). A polyurethane resin solution was prepared by mixing two parts of Nippon Ink Co., Ltd., trade name: Chrisbon SD-11), a PET film was prepared as a base material for film formation, and the above resin solution was applied thereto. .. At this time, the clearance of the coating device was set to 1.2 mm. Next, the obtained coating film is immersed in a coagulation bath consisting of a 10 mass% DMF aqueous solution which is a coagulation liquid together with a film-forming substrate, the resin is coagulated and regenerated, and then taken out from the coagulation bath to form a film-forming group. After the material was peeled off from the polyurethane sheet, it was immersed in a cleaning solution (solvent-free bath) consisting of water at room temperature to remove DMF as a solvent to obtain a resin sheet. Then, the resin sheet was wound while being dried to obtain a polyurethane sheet having a thickness of 1 mm. The surface side of the obtained polyurethane sheet opposite to the holding surface was buffed by about 100 μm to make the thickness uniform, and then double-sided tape was attached to the buffed surface.
Next, a polyethylene film having an acrylic acid ester adhesive having an adhesive strength of 0.45 N / 25 mm is prepared on one side, and the surface (adhesive layer) to which the adhesive of the polyethylene film is attached comes into contact with the holding surface of the polyurethane sheet. In this way, the polyethylene film was bonded to the holding surface side of the polyurethane sheet by a laminating machine to produce a laminated body for use as a holding pad. Immediately before each evaluation test, the adhesive film was peeled off from the laminate of Example 1 to form a holding pad.
In the laminate of Example 1, the peel strength between the polyethylene film having the acrylic adhesive on one side and the polyurethane sheet was 0.060 kg / 10 mm.
The peel strength was measured by a method according to the Japanese Industrial Standards (JIS K6772) using a Tensilon tensile tester (A & D Co., Ltd., Tensilon universal tester, RTF-1210). That is, a polyurethane sheet and an adhesive film are bonded together (so that the adhesive layer is in contact with the holding surface) to prepare a test piece cut out to a size of 20 mm × 150 mm, and the polyurethane sheet and the adhesive film at one end in the longitudinal direction of the test piece are formed. Each was attached to the tensile tester so that the gripping interval was 10 mm at the grip of the tensile tester. It was pulled at a tensile speed of 200 mm per minute, and the pasted portion (that is, 20 mm × 50 mm) having a length of 50 mm was peeled off (T-shaped peeling) in the long side direction to obtain the maximum load. The number of measurements was set to 2 and the average value was evaluated.

[Example 2]
A holding pad laminate was produced in the same manner as in Example 1 except that a polyethylene film having an acrylic acid ester adhesive having an adhesive strength of 0.25 N / 25 mm was used on one side. In the laminate of Example 2, the peel strength between the polyethylene film having the acrylic adhesive on one side and the polyurethane sheet was 0.040 kg / 10 mm.

[Example 3]
A holding pad of Example 3 was obtained in the same manner as in Example 1 except that the amount of the pore forming agent added was 0.01 part.

[Comparative Example 1]
The holding pad of Comparative Example 1 was obtained in the same manner as in Example 1 except that the adhesive film was not bonded.

[Comparative Example 2]
A polyurethane sheet having a thickness of 1.2 mm was formed based on the contents described in Patent Document 1. Specifically, as the polyurethane resin, a polyester MDI polyurethane resin having a 100% modulus of 6 MPa was used. For 100 parts of this polyurethane resin 30% DMF solution, 45 parts of DMF for viscosity adjustment, 20 parts of DMF dispersion liquid containing 30% carbon black, surfactant (manufactured by Dainippon Ink Co., Ltd., trade name: Two parts of Chrisbon SD-11) were mixed to prepare a polyurethane resin solution, which was applied onto a PET film as a substrate for film formation. The clearance is set to 1.3 mm, the obtained coating film is immersed in a coagulation bath consisting of a 10 mass% DMF aqueous solution which is a coagulating liquid together with a film-forming substrate, and the resin is coagulated and regenerated, and then the coagulation bath is performed. After removing the substrate for film formation from the polyurethane sheet, the polyurethane sheet having a thickness of 1.2 mm is obtained by immersing it in a cleaning solution (solvent-free bath) consisting of water at room temperature to remove the DMF as a solvent. A film was formed. Then, both surfaces of the obtained polyurethane sheet were sandwiched between two smooth PET films and passed between two heat rolls heated to 150 ° C. with a gap of 1.0 mm at 1.0 m / min. After the heat roll, the PET film was removed from both surfaces of the polyurethane sheet, and a double-sided tape was attached to one side of the polyurethane sheet in the same manner as in Example 1 to obtain a holding pad of Comparative Example 2.

[Comparative Example 3]
A polyurethane sheet was formed in the same manner as in Example 1. After that, the surface of the obtained polyurethane sheet on the skin layer side and the surface of the PET base material having a surface roughness Ra of 0.39 μm were brought into close contact with each other at a pressing pressure of 0.5 MPa, and a take-up draft (PET base material was pressed). The ratio of the surface speed of the roller for winding the polyurethane sheet to which the PET base material is adhered to the surface speed of the pair of pressure rollers for adhering to the polyurethane sheet) is 1.06 to obtain a wound body. rice field. The obtained roll was heated at 40 ° C. for 24 hours. After the heat treatment, the PET base material was removed from the polyurethane sheet, the side opposite to the holding surface was buffed in the same manner as in Example 1, and double-sided tape was attached to obtain a holding pad of Comparative Example 3.

After manufacturing the laminates of Examples 1 to 3 and the holding pads of Comparative Examples 1 to 3, the following evaluation tests 1 to 3 were performed using each of the laminates and the holding pads. The laminates of Examples 1 to 3 were used as holding pads by peeling off the adhesive film immediately before each evaluation test.
^{In Examples 1 to 3, the number of openings (per 10000 μm 2 of the} holding surface) and the average opening diameter of the opening of the holding surface of the polyurethane sheet before attaching the adhesive film having the adhesive layer on one side, and the adhesive film are peeled off. Table 1 shows the number of openings and the average opening diameter of the openings on the holding surface of the polyurethane sheet (holding pad). Table 1 also shows the number of openings and the average opening diameter of the openings of the holding pads of Comparative Examples 1 to 3. The number of openings and the average aperture diameter were observed at 9 locations by magnifying a range of about 5 mm square 1000 times with a scanning electron microscope (JSM-5500LV, manufactured by JEOL Ltd.). This image is binarized by image processing software (Image Analyzer V20LAB Ver.1.3, manufactured by Nikon) to check the number of openings, and the area equivalent to the circle and its average value are used as the average opening diameter from the area of each opening. Calculated.

(Evaluation test 1: Flatness test of the object to be polished)
Using the holding pads of each Example and Comparative Example, the glass substrate was polished under the polishing conditions shown below, and the flatness of the object to be polished (glass substrate) after the polishing process was evaluated. In this evaluation, the flatness a was measured from the filter wave center swell by a method according to the Japanese Industrial Standards (JIS B0601: 1982). In the measurement of the flatness a, a surface roughness shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 480A) was used, and the measurement conditions shown below were set. From the measurement curve obtained due to the unevenness of the surface of the glass substrate after polishing, the width W between the adjacent convex portion (mountain part) and the convex part, and the height between the convex part and the concave part (valley part). After calculating the value S, a scatter diagram was created with the width W as the horizontal axis and the height S as the vertical axis. From the obtained scatter plot, an approximate straight line of the linear equation S = aW was obtained, and the slope a was defined as the final flatness a after polishing. In general, the higher the flatness, the larger the width W and the smaller the height S, so that the slope a becomes smaller. That is, the smaller the inclination a, the better the flatness. The flatness of the object to be polished after polishing was evaluated based on the following criteria. The polishing conditions are as follows.
-Object to be polished: Glass substrate (370 mm x 235 mm x 0.4 mm)
・ Polishing pad: Hard urethane foam ・ Polishing machine used: Oscar polishing machine (Speedfam, SP-1200)
・ Polishing speed (rotation speed): 30 rpm
-Processing pressure: 100 gf / cm2
・ Slurry: Cerium slurry ・ Polishing time: 20 minutes
[Evaluation criteria]
A: Flatness a of the object to be polished after polishing is 0.003 or less B: Flatness a of the object to be polished after polishing exceeds 0.003 to 0.08 or less C: Flatness of the object to be polished after polishing a exceeds 0.008

(Result of evaluation test 1)
When the holding pads of Examples 1 to 3 were used, the waviness was reduced and the flatness of the object to be polished was improved as compared with the conventional Comparative Example 1 in which the adhesive film was not attached. In Comparative Example 2 and Comparative Example 3, although the periodic swell was improved as compared with Comparative Example 1, the improvement in flatness was small as compared with the Example.

(Evaluation test 2: Adhesive force test)
The holding pads of Examples 1 to 3 and Comparative Examples 1 to 3 were cut into squares of about 100 mm × 100 mm. Further, a glass substrate having a diameter of φ60 mm and a thickness of about 1 mm was prepared as an object to be adsorbed. The cut-out holding pad was mounted on the fixed surface plate. Next, an appropriate amount of water was sprayed on the holding surface of the resin sheet provided on the holding pad, the water was drained appropriately, and then the glass substrate was firmly pressed against the holding pad to be adsorbed. Next, a tensioning jig was firmly pressed and attached to the surface of the glass substrate opposite to the holding pad side via a double-sided tape of the same size as the glass substrate. Then, the tensioning jig was pulled to the side opposite to the glass substrate, and the maximum value of the tensile load when the glass substrate was pulled away from the holding pad was read. A TENSILON (manufactured by ORIENTEC) was used as a tensile tester. The above operation is repeated 40 times without replacing the holding pad attached to the object holder (however, from the second time onward, the holding pad holds the glass substrate with the tensioning jig attached to the glass substrate. ) All the data were arithmetically averaged to obtain the adsorption force. The adsorption force of the object to be polished was evaluated based on the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: The arithmetic mean of the maximum value of the tensile load is 20 kgf or more B: The arithmetic mean of the maximum value of the tensile load is 17 kgf or more and less than 20 kgf C: The arithmetic mean of the maximum value of the tensile load is less than 17 kgf

(Result of evaluation test 2)
In Examples 1 to 3 and Comparative Example 2, the suction force exceeded 20 kgf, showing good suction force. In Comparative Examples 1 and 3, the adsorption force was less than 20 kgf, which was inferior to that of Examples 1 to 3.

(Evaluation test 3: Adsorption sustainability test)
The object to be polished was polished using the holding pads of Examples 1 to 3 and Comparative Examples 1 to 3, and it was confirmed whether or not the slurry had penetrated into the end portion of the object to be polished after polishing. If the slurry is infiltrated, the slurry will enter the back surface of the object to be polished and the object to be polished will float from the holding pad as the polishing process is continued, resulting in damage due to lateral displacement or movement of the object to be polished. Connect. In other words, it is an index showing that the adsorptivity is weak. Therefore, the adsorptivity was evaluated based on the following criteria. The polishing conditions were the same as those in the evaluation test 1. The results are shown in Table 1.
[Evaluation criteria]
A: No slurry penetration C: Slurry penetration

(Result of evaluation test 3)
In Examples 1 to 3 and Comparative Example 2, no penetration of the slurry was observed between the object to be polished and the holding pad, and the adsorptivity was good. On the other hand, in Comparative Example 1 and Comparative Example 3, the penetration of the slurry was confirmed from the end portion.

(Evaluation test 4: Detachability after polishing)
The peelability of the holding pads of Examples 1 to 3 and Comparative Examples 1 to 3 after polishing was evaluated by the following method. The surface opposite to the holding surface of the holding pad cut into a hexagon with an area of 42 cm ² is passed through the adhesive layer of double-sided tape, and the Tensiron Tensile Testing Machine (A & D Co., Ltd., Tensiron Universal Testing Machine) , RTF-1210). After spraying water on the holding surface of the holding pad, the water on the surface was lightly removed with a wiper. Next, a circular glass plate having a thickness of 1 mm and a diameter of 150 mm was placed on the holding surface. It was adsorbed evenly on the entire upper surface of the glass plate ^{so that a load of a surface pressure of 500 g / cm 2} was applied, and the glass plate was pulled at a speed of 10 mm / min at an angle diagonally upward twice with respect to the holding surface. Since the glass plate gradually peeled off from the holding pad, the time from the start of peeling to complete peeling and the tensile load required for peeling were measured. If the time until peeling or the tensile load is too large, the ability to hold the object to be polished is excellent, but it takes time to remove the holding pad, which causes a problem of reduced work efficiency and an excessive load on the object to be polished. Causes problems. Therefore, the holding pad is required to have sufficient holding force and to have peelability to the extent that it does not require more time or tensile load when it is removed. Based on the above, the peelability was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: The time it takes for the glass plate to peel off from the holding pad is 6 seconds or less and the peeling load is 20 kgf or less B: The time it takes for the glass plate to peel off from the holding pad exceeds 6 seconds to 8 seconds or less and the peeling load is Exceeding 20 kgf to 23 kgf or less C: The time it takes for the glass plate to peel off from the holding pad exceeds 8 seconds, or the peeling load exceeds 23 kgf.

(Result of evaluation test 4)
As a result of the peelability evaluation, it was found that the holding pad of Comparative Example 2 took about twice as long as the holding pad of Example 1 to be removed. On the other hand, the holding pads of Examples 1 to 3 and Comparative Examples 1 and 3 had a short time required for peeling from the object to be polished and were excellent in peelability.

As described above, although the holding pads of Comparative Examples 1 and 3 are excellent in peelability, the flatness of the object to be polished is inferior when the object to be polished is held and polished, and the adsorptive power and the long-lasting adsorptive power are not sufficient. There wasn't. Although the holding pad of Comparative Example 2 was excellent in adsorptive power and adsorptive sustainability, it took a very long time to peel off from the object to be polished. In addition, the flatness of the object to be polished was not sufficient when the object to be polished was held and polished, probably because it was caught in air. On the other hand, the holding pad of the present invention is excellent in flatness, adsorptivity (adsorptive force and adsorptive sustainability), and peelability, and can sufficiently hold the object to be polished and can be easily removed after polishing. Moreover, it was excellent in the performance of flattening the object to be polished.

The laminate of the present invention can be used as a holding pad by peeling off the adhesive film at the time of use, and this holding pad has excellent adsorptivity and flatness as compared with the conventional holding pad, and has appropriate peelability. .. Further, since the surface of the holding pad can be protected, the above performance is hardly impaired even if the holding pad is stored without being used for a long period of time. Therefore, the holding pad of the present invention, the laminate used for manufacturing the holding pad, and the manufacturing method thereof are extremely useful in industry.

Claims (11)

A step of preparing a polyurethane sheet having a plurality of tear-shaped bubbles and having a holding surface for holding an object to be polished;
A step of preparing an adhesive film having an adhesive layer on one side of the film; and a step of laminating the adhesive film and the polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet to obtain a laminate.
A method of manufacturing a laminate for use in the manufacture of holding pads, including. The manufacturing method according to claim 1, wherein the adhesive film and the polyurethane sheet are bonded together without heating. The production method according to claim 1 or 2, wherein the peel strength between the adhesive film and the polyurethane sheet is in the range of 0.020 to 0.150 kg / 10 mm. A method for manufacturing a holding pad, which comprises a step of peeling an adhesive film from the laminate obtained by the method according to any one of claims 1 to 3 to obtain a holding pad. A laminate for use in the manufacture of holding pads, comprising a polyurethane sheet having multiple teardrop-shaped bubbles and a holding surface for holding an object to be polished, and an adhesive film having an adhesive layer on one side of the film. There,
The adhesive film is bonded onto a polyurethane sheet so that the adhesive layer of the adhesive film is in contact with the holding surface of the polyurethane sheet, and the films constituting the adhesive film are a polyolefin film and polyvinyl chloride. The laminate selected from a film and a polyester film. The laminate according to claim 5, wherein the adhesive film is peeled off and used as a holding pad. The laminate according to claim 5 or 6, wherein the polyurethane sheet has a skin layer on the holding surface side thereof. One of claims 5 to 7, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is selected from an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a fluororesin-based pressure-sensitive adhesive, a natural rubber-based pressure-sensitive adhesive, and a synthetic rubber-based pressure-sensitive adhesive. The laminate described in the section. The laminate according to any one of claims 5 to 8, wherein the peel strength between the adhesive film and the polyurethane sheet is in the range of 0.020 to 0.150 kg / 10 mm. A holding pad obtained by peeling an adhesive film from the laminate according to any one of claims 5 to 9. A step of preparing a laminate obtained by the method according to any one of claims 1 to 3 or a laminate according to any one of claims 5 to 9;
A step of peeling the adhesive film from the laminate to obtain a holding pad; and a step of polishing the object to be polished with the polishing pad while holding the object to be polished using the holding pad.
A method for polishing an object to be polished, including.

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