JP5912770B2 - Holding pad - Google Patents

Description

The present invention relates to a holding pad, in particular, a soft resin sheet made of polyurethane based elastic resin, as well as have a skin layer on the holding surface side for holding the object to be polished, the interior side of said skin layer, continuous pore diameter of the holding face in portrait in the thickness direction of the soft resin sheet is small bubbles from the surface side opposite to the holding surface communicates with the reticulated and the bubble is communicated with the holding surface via the skin layer The present invention relates to a holding pad provided with a soft resin sheet having a cell structure .

  Conventionally, when performing precision flat surface polishing on semiconductor wafers, interlayer insulation films of semiconductor devices, metal wiring, various recording disks, LCD (liquid crystal display) glass, etc., it was usually attached to a polishing machine. Polishing is performed while holding an object to be polished via a holding pad. As the holding pad, a polyurethane foam formed by a wet film forming method and having an open cell structure is widely used.

  A polyurethane foam by a wet film forming method has a skin layer on the holding surface side for holding an object to be polished, and a large number of bubbles are continuously formed on the inner side of the skin layer. A large number of minute gaps are formed on the holding surface as traces of solvent extraction accompanying the wet film formation, and these many gaps communicate with the internal bubbles through the skin layer. In such a holding pad, since the surface tension of water or the like acts by including water or the like in the minute gap formed on the holding surface, the object to be polished is brought into close contact with the holding object effectively. It can be demonstrated.

  However, under polishing conditions, a large amount of polishing liquid (slurry) is applied around the holding pad, that is, the portion of the holding surface that is not in contact with the object to be polished. The liquid component of the polishing liquid enters the bubbles inside the pad. Furthermore, the entire bubbles of the holding pad may be filled with the liquid component in a short time. In such a state, the liquid component filled with the bubbles is pushed out to the holding surface side by the polishing pressure applied during the polishing process, and there is a possibility that the holding property of the object to be polished is lowered. As a result, the “floating” of the object to be polished occurs on the holding pad, and the flatness of the object to be polished is impaired, and it is difficult to continue the polishing process. Further, if the liquid component of the polishing liquid enters the holding pad, the surface side (back side) of the object to be polished that is in contact with the holding pad is always exposed to the polishing liquid. The surface roughness may be reduced.

  In order to prevent the liquid component of the polishing liquid from penetrating into the holding pad, there has been disclosed a technique for a holding pad to which water repellency is imparted using a water repellent containing 1% or more of a fluorine-based water repellent. (See Patent Document 1). Moreover, the technique of the holding pad which apply | coated the adhesive on the porous sheet | seat and mix | blended the water repellent in the sheet | seat is disclosed (refer patent document 2). Furthermore, a technique of a holding pad in which a two-layer structure is used to prevent the polishing liquid from entering the lower layer and a water repellent is blended in the layer on the object to be polished is disclosed. (See Patent Document 3).

JP-A-9-254027 JP 2005-224888 A JP 2010-274363 A

  However, the fluorine-based water repellent used in Patent Document 1 includes perfluorooctyl sulfate (PFOS), perfluorooctanoate (PFOA), and the like, which are becoming subject to global regulations. In some cases, it is preferable to avoid use. On the other hand, in Patent Document 2, although the object to be polished can be firmly held by the pressure-sensitive adhesive layer coated on the porous sheet, it becomes difficult to remove the object to be polished after the polishing is completed. There is also a risk of damage. Further, in Patent Document 3, the production cost is increased due to the two-layer structure, and the lower layer is an independent foam structure. Therefore, even if the compression rate is increased, the cushioning effect expected as a holding pad, that is, the appropriate sinking and returning. It becomes difficult to get sex.

  An object of the present invention is to provide a holding pad that can prevent the liquid component of the polishing liquid from entering, and can improve the life while ensuring the holdability of an object to be polished.

In order to solve the above problems, the present invention provides a soft resin sheet made of polyurethane based elastic resin, as well as have a skin layer on the holding surface side for holding the workpiece, the internal side of the skin layer In addition, bubbles that are vertically long in the thickness direction of the soft resin sheet and smaller in pore diameter on the holding surface side than the surface side opposite to the holding surface communicate with each other in a mesh pattern, and the bubbles pass through the skin layer. in the holding pad with a soft resin sheet having communicating the open cell structure on the holding surface, the resin portion of the soft resin sheet, the number-average molecular weight of 10,000 or more, and ethylene oxide weight ratio following 50% Resin component containing polyalkylene oxide bonded in a range and acylated cellulose, and the content of the polyalkylene oxide constituting the soft resin sheet In the range of 1 wt% to 8 wt% for, and the content of the acylated cellulose is in the range of 40 to 100 mass% relative to the polyalkylene oxide.

In this case, acylated cellulose is obtained by introducing an acyl group represented by the chemical formula CH ₃ (CH ₂ ) _n CO (n = 0 to 2) into cellulose, and hydroxyl groups per glucose unit constituting cellulose. The average substitution degree of the acyl group with respect to may be in the range of 1 to 3. At this time, it is preferable that the acylated cellulose is soluble in a polar solvent that dissolves the resin component and is hardly soluble or insoluble in water. The polyalkylene oxide can be a copolymer of ethylene oxide and propylene oxide. At this time, the number average molecular weight of the polyalkylene oxide may be 12000 or more. Moreover, it is preferable to make content with respect to the resin component of a polyalkylene oxide into the range of 2 mass%-7 mass%, and make content with respect to the polyalkylene oxide of acylated cellulose into the range of 50 mass%-90 mass%. The A hardness of the soft resin sheet can be in the range of 5 degrees to 20 degrees.

According to the present invention, polyalkylene oxide in the range of 1% by mass to 8% by mass with respect to the resin component constituting the flexible resin sheet made of polyurethane-based elastic resin , and 40% by mass to 100% by mass with respect to the polyalkylene oxide. % Of the acylated cellulose in the resin portion of the soft resin sheet increases the hydrophobicity of the entire soft resin sheet, so that the liquid component of the polishing liquid supplied at the time of the polishing process from the holding surface to the skin layer It is possible to obtain an effect that it is possible to suppress the intrusion into bubbles communicating with each other and to improve the life while ensuring the retention of the object to be polished.

It is sectional drawing which shows typically the holding pad of embodiment to which this invention is applied. It is process drawing which shows the principal part of the manufacturing method of the holding pad of embodiment.

  Hereinafter, embodiments of a holding pad to which the present invention is applied will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, the holding pad 10 of the present embodiment includes a urethane sheet 2 as a soft resin sheet made of polyurethane elastic resin. The urethane sheet 2 is formed by a wet film forming method, and has a holding surface P for holding an object to be polished on one surface side.

  The urethane sheet 2 has a skin layer 2a having a thickness of several μm closest to the holding surface P. Inside the skin layer 2a, a large number of cells (bubbles) 5 are formed in a substantially uniformly dispersed state. The cell 5 is formed in a vertically long and rounded conical shape (longitudinal triangular shape in cross section) in the thickness direction of the urethane sheet 2, and the hole diameter on the holding surface P side is smaller than the surface side opposite to the holding surface P. Has been. That is, the diameter of the cell 5 is reduced on the holding surface P side. The length in the longitudinal direction of the cell 5 varies within the thickness range of the urethane sheet 2. The polyurethane-based elastic resin between the cells 5 is formed in a partition shape so as to define the cells 5, and a plurality of fine holes smaller than the cells 5, not shown, are formed inside. That is, in the urethane sheet 2, the cells 5 and a large number of fine holes (not shown) communicate with each other in a mesh shape, and the resin portion formed in a partition shape has a microporous structure.

  The skin layer 2a has a dense structure formed as a trace of solvent extraction during film formation by a wet film formation method. For this reason, many minute gaps are formed on the surface of the skin layer 2a, that is, the holding surface P. In FIG. 1, the minute gaps in the skin layer 2a are omitted. Further, the minute gap formed on the holding surface P does not substantially allow the passage of the abrasive particles (abrasive grains) contained in the polishing liquid, and it is extremely difficult for only the liquid component of the polishing liquid to permeate. It means a precise gap.

The polyurethane elastic resin portion (between the cells 5) of the urethane sheet 2 contains polyalkylene oxide and acylated cellulose. As the polyalkylene oxide, ethylene oxide (hereinafter abbreviated as EO) bonded in a mass ratio of 50% or less and having a number average molecular weight of 10,000 or more is used. In acylated cellulose, an acyl group represented by the chemical formula CH ₃ (CH ₂ ) _n CO (n = 0 to 2), that is, an acetyl group, a propionyl group, and a butyryl group are introduced into cellulose. The average substitution degree of the acyl group with respect to the hydroxyl group per glucose unit constituting is in the range of 1 to 3. The content of polyalkylene oxide is adjusted to a range of 1 to 8% by mass (wt%) with respect to the polyurethane elastic resin constituting the urethane sheet 2. The acylated cellulose content is adjusted in the range of 40 to 100% by mass with respect to the polyalkylene oxide.

  In this urethane sheet 2, A hardness is adjusted in the range of 5 to 20 degrees. The A hardness can be adjusted by the molecular weight, coagulation value, film forming conditions, etc. of the polyurethane-based elastic resin used. The coagulation value is the same as the gel point, and in this example, the value measured as follows is shown. That is, a polyurethane-based elastic resin solution dissolved in a polar solvent (N, N-dimethylformamide) was prepared so that the polyurethane-based elastic resin was 1% by mass, and 100 g of this polyurethane resin solution was temperature adjusted to 25 ° C. While stirring with a stirrer, a poor solvent (water) at 25 ° C. is dropped. In this case, the amount of poor solvent (unit: ml) required to reach a point where the polyurethane elastic resin gels and the cloudiness of the polyurethane elastic resin solution does not disappear is shown. Moreover, in the urethane sheet 2, since the polyalkylene oxide and the acylated cellulose are contained in the polyurethane-based elastic resin portion, the contact angle with respect to water when a water droplet is dropped on the holding surface P is in the range of 80 to 110 degrees. Show.

  Further, the holding pad 10 has a double-sided tape 7 attached to the surface of the urethane sheet 2 opposite to the holding surface P for attaching the holding pad 10 to the polishing machine. The double-sided tape 7 has, for example, a base material (not shown) of a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), and an acrylic adhesive or the like is provided on both sides of the base material. Adhesive layers (not shown) are respectively formed. The double-sided tape 7 is bonded to the urethane sheet 2 with a pressure-sensitive adhesive layer on one side of the base material, and the pressure-sensitive adhesive layer on the other side (the side opposite to the urethane sheet 2) is covered with the release paper 8. The base material of the double-sided tape 7 also serves as the base material of the holding pad 10.

(Manufacturing)
As shown in FIG. 2, the holding pad 10 is manufactured by preparing a urethane sheet by a wet film forming method and bonding the urethane sheet 2 obtained after the buffing and the double-sided tape 7 together. In the wet film forming method, a polyurethane elastic resin, polyalkylene oxide, acylated cellulose, a preparation step for preparing additives and a polar solvent, a resin solution obtained by dissolving or dispersing components such as a polyurethane elastic resin in a polar solvent A coating process for coating the film-forming substrate in a sheet form, a sheet forming process for solidifying the resin solution in a coagulating liquid to form a sheet-like polyurethane elastic resin, and washing the formed sheet-like polyurethane elastic resin. A urethane sheet is produced through a drying / drying process. Hereinafter, it demonstrates in order of a process.

  In the preparation step, a polyurethane-based elastic resin, a water-miscible polar solvent (good solvent) that can dissolve the polyurethane-based elastic resin, a polyalkylene oxide, acylated cellulose, and an additive are prepared. As the polyurethane-based elastic resin, those having a 100% modulus of 30 MPa or less and a coagulation value of 8 or more are selected from resins such as polyester-based, polyether-based, and polycarbonate-based resins. As the polar solvent, N, N-dimethylformamide (hereinafter abbreviated as DMF), N, N-dimethylacetamide (DMAc), or the like can be used. In this example, DMF is used. As the additive, a pigment such as carbon black for controlling the size and amount (number) of the cells 5 can be used. In addition, you may add auxiliary agents, such as a hydrophilic activator which accelerates | stimulates cell formation, and a hydrophobic activator which stabilizes reproduction | regeneration of a polyurethane-type elastic resin which are conventionally used with the wet film-forming method.

  As the polyalkylene oxide, in this example, a copolymer of EO and propylene oxide (hereinafter abbreviated as PO) is used. In this copolymer, EO is bonded at a mass ratio of 50% or less, PO is bonded at a mass ratio of 20% or more, and the number average molecular weight (Mn) is 10,000 or more. The polymer of only EO has water solubility, whereas the polyalkylene oxide used in this example is bonded with a ratio of EO of 50% or less and PO of 20% or more, and the number average molecular weight is 10,000 or more. It becomes insoluble in water and dissolves in DMF, which is a polar solvent used for dissolving the polyurethane elastic resin.

  Further, as the acylated cellulose, propionylated cellulose in which a propionyl group is introduced into cellulose is used in this example. Propionylated cellulose has an average degree of substitution of propionyl groups with respect to hydroxyl groups per glucose unit constituting the cellulose in the range of 1 to 3, and an average degree of polymerization in the range of 200 to 400. Propionylated cellulose is soluble in a polar solvent that dissolves the polyurethane elastic resin, that is, DMF, and insoluble in water used as a coagulation liquid. In other words, the degree of substitution is adjusted so that the propionylated cellulose to be used can be dissolved in DMF.

  In the application step, first, a resin solution is prepared using each material prepared in the preparation step. At this time, the polyurethane-based elastic resin, polyalkylene oxide and propionylated cellulose are each dissolved in DMF so as to be, for example, 30 wt%, and the respective solutions are mixed so that each component has the above-described content. After dispersing the additive carbon black, a resin solution is prepared by defoaming under reduced pressure. The obtained resin solution is applied substantially uniformly in a sheet form to a belt-shaped film forming substrate by a coating device such as a knife coater at room temperature. At this time, the application thickness (application amount) of the resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. Although a cloth, a nonwoven fabric, etc. can also be used as a film-forming base material, in this example, a PET film is used.

  In the sheet forming step, the resin solution applied to the film forming substrate is continuously guided to a coagulating liquid (water-based coagulating liquid) whose main component is water which is a poor solvent for the polyurethane elastic resin. As the coagulation liquid, polar solvents such as DMF and DMAc can be mixed with water, but in this example, water is used. The resin solution coagulates in the coagulation liquid, and a sheet-like polyurethane elastic resin having an open cell structure is regenerated. At this time, the polyalkylene oxide and propionylated cellulose blended in the resin solution are regenerated while the molecular chain is entangled with the molecular chain of the polyurethane-based elastic resin.

  Here, bubble formation will be described. When the resin solution is guided into the coagulating liquid, first, a film is formed at the interface between the resin solution and the coagulating liquid, and a dense skin layer is formed over the thickness of several μm in the resin immediately adjacent to the film. After that, a cooperative phenomenon between the diffusion of DMF in the resin solution into the coagulation liquid and the intrusion of water in the coagulation liquid into the resin, that is, solvent replacement proceeds through the skin layer to form an open cell urethane sheet. Is done. When the DMF is desolvated from the resin solution and the DMF and the coagulating liquid are replaced, the cells 5 and micropores (not shown) are formed in the polyurethane resin inside the skin layer 2a. A communication hole (not shown) communicating in a shape is formed. At this time, since the PET film of the film formation substrate does not permeate water, desolvation occurs on the surface side (skin layer 2a side) of the resin solution, and cells 5 having a larger film formation substrate side than the surface side are formed. .

  As shown in FIG. 2, in the cleaning / drying process, the sheet-like polyurethane-based elastic resin (hereinafter referred to as a film-forming resin) formed in the sheet-forming process is washed in a cleaning solution such as water to form the film-forming resin. The DMF remaining in is removed and then dried. In this example, a cylinder dryer having a cylinder having a heat source is used for drying the film-forming resin. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The film-forming resin after drying is rolled up.

  In the buffing process, the surface opposite to the skin layer 2a of the film-forming resin dried in the cleaning / drying process, that is, the back surface is subjected to buffing. In a film-forming resin formed by a wet film-forming method, thickness variation occurs when a resin solution is applied or a polyurethane elastic resin is regenerated. By pressing a pressure welding jig having a flat surface on the surface of the film forming resin on the skin layer 2a side, irregularities appear on the back surface side of the film forming resin. This unevenness is removed by buffing. In this example, since the continuously formed film-forming resin has a belt shape, the buffing process is continuously performed while pressing the pressing roller. The urethane sheet 2 formed by buffing the film-forming resin has a uniform thickness.

  In the bonding step, the buffed surface (back surface) side of the urethane sheet 2 and the double-sided tape 7 are bonded together. At this time, the adhesive layer on one side of the double-sided tape 7 and the urethane sheet 2 are bonded together. The pressure-sensitive adhesive layer on the other side of the double-sided tape 7 is left with its surface covered with the release paper 8. Then, after cutting into a desired shape such as a circle and a desired size, an inspection is performed to confirm that there is no adhesion of scratches, dirt, foreign matter, etc., and the holding pad 10 is completed.

  When polishing an object to be polished using the holding pad 10, for example, a single-side polishing machine arranged so that the holding surface plate and the polishing surface plate face each other is used. The holding pad 10 is attached to the holding surface plate, and the polishing pad is attached to the polishing surface plate. When the holding pad 10 is attached to the holding surface plate, the release paper 8 is removed and attached with the exposed adhesive layer. When holding an object to be polished, water is sprayed onto the holding surface P, and the object to be polished is pressed against the holding pad 10 side. The object to be polished comes into close contact with the holding surface P due to the surface tension of water and the like, and is held on the holding platen. A polishing liquid containing abrasive particles is circulated and supplied between the processed surface of the object to be polished and the polishing pad, and the holding object or polishing surface plate is rotated while applying polishing pressure to the object to be polished. (Processed surface) is polished.

<Action etc.>
Next, the operation and the like of the holding pad 10 of this embodiment will be described.

  Here, in order to make the description of the holding pad 10 easy to understand, a conventional holding pad will be described. Conventionally, as the holding pad, a resin sheet having a skin layer formed by a wet film forming method is frequently used. The skin layer is excellent in contact with an object to be polished by having surface flatness, and a large number of minute gaps are formed on the surface as traces of solvent extraction accompanying wet film formation. By including water or the like in the skin layer, the surface tension of water or the like acts, and the object to be polished can be reliably held. However, since a large amount of polishing liquid is applied around the holding pad under polishing conditions, the liquid component of the polishing liquid infiltrates into the bubbles inside the holding pad over time from a minute gap on the holding surface. Since the slurry is acidic or alkaline and contains an oxidizing agent in some cases, when the slurry enters, hydrolysis or oxidative degradation of the polyurethane-based elastic resin occurs. Since the object to be polished is normally adsorbed and held at a fixed position on the holding surface of the holding pad by the surface tension of water or the like, the slurry does not enter from the part where the object to be polished contacts, When the object to be polished sinks into the holding pad, the slurry easily enters from the peripheral portion. For this reason, deterioration may occur from the peripheral portion, and there may be a problem that the holding pad swells due to delamination between the urethane sheet and the base material (double-sided tape) or a crack occurs on the holding surface. In such a case, the adsorptive power is reduced and the flatness of the peripheral portion is likely to be reduced. When the adsorption force decreases, the object to be polished comes off and is damaged, so that the polishing machine must be stopped. In order to restart, not only the polishing pad and holding pad must be replaced, but also all the debris of the object to be polished caught in the circulating slurry must be removed from the slurry circulation line and the polishing machine, The production efficiency is greatly reduced. As described above, when the peripheral part of the holding pad is deteriorated, it is necessary to replace the holding pad before causing damage to the polishing object or lowering the flatness. Short life. In order to prevent the liquid component of the polishing liquid from entering, a fluorine-based water repellent may be added, but it is preferable to avoid using it from environmental considerations. As a result of repeated studies to solve these problems and increase the hydrophobicity of the urethane sheet, the present inventors have found that a surprising effect can be obtained by using polyalkylene oxide and acylated cellulose in combination. It was. According to the recognition of the present inventors, the combined use of polyalkylene oxide and acylated cellulose is a technique that has not been seen in the past.

  In the holding pad 10 of the present embodiment, polyalkylene oxide and propionylated cellulose are contained in the resin portion of the urethane sheet 2. When only propionylated cellulose is included, it is confirmed that although the hydrophobicity is improved, the soft elasticity of the holding pad is impaired, and the hydrophobicity becomes too strong to reduce the retention (adsorption) of the object to be polished. ing. By using a polyalkylene oxide in combination, it is possible to impart hydrophobicity to the holding pad while maintaining the workpiece retention. Thereby, since the hydrophobicity of the whole holding pad is improved, it is possible to prevent the liquid component of the polishing liquid from entering the bubbles inside the holding pad through a minute gap on the holding surface.

  Moreover, in this embodiment, content of polyalkylene oxide is adjusted to the range of 1-8 mass% with respect to a polyurethane-type elastic resin. If an excessive amount of polyalkylene oxide is added, water held between the object to be polished and the holding surface P is repelled when the object to be polished is held, and the elasticity of the polyurethane elastic resin is impaired. Polished matter retention is reduced. By setting the content of the polyalkylene oxide in the above-described range, it is possible to secure the object to be polished while suppressing the liquid component of the polishing liquid from entering the bubbles. Considering that the effect of increasing the hydrophobicity of the urethane sheet 2 and ensuring the retention of the polished object are achieved in a balanced manner, the polyalkylene oxide content is preferably in the range of 2 to 7% by mass. Moreover, when making content of polyalkylene oxide into the ratio with respect to the total solid in a resin solution, although it is based also on the quantity of additives, such as a pigment, what is necessary is just to set it as the range of 1-6 mass% in general.

  Further, polyalkylene oxide having an EO mass ratio of 50% or less is used. When the mass ratio of EO exceeds 50%, the hydrophilicity is increased, and the liquid component of the polishing liquid is liable to enter the cell 5, which is not preferable. By setting the mass ratio of EO within the above-described range, the hydrophobicity of the urethane sheet 2 can be appropriately secured. From the viewpoint of ensuring the hydrophobicity of the urethane sheet 2, the mass ratio of EO is preferably 40% or less. Further, the number average molecular weight of the polyalkylene oxide is limited to 10,000 or more. If the number average molecular weight is less than 10,000, there is a possibility of elution, which is not preferable because the effect cannot be sustained. In order to suppress elution reliably, the number average molecular weight of the polyalkylene oxide is preferably 12000 or more. On the other hand, when the number average molecular weight is too high, the film formability by the wet film formation method may deteriorate. For this reason, when the film formability is taken into consideration, it is preferable that the number average molecular weight of the polyalkylene oxide is approximately 80000 or less.

  Furthermore, in this embodiment, content of propionylated cellulose is adjusted in the range of 40-100 mass% with respect to polyalkylene oxide. If the content of propionylated cellulose is less than 40% by mass with respect to the polyalkylene oxide, the hydrophobicity cannot be increased, and the liquid component of the polishing liquid tends to enter the holding pad, which is not preferable. If an excessive amount of propionylated cellulose is added, when producing a resin solution, the propionylated cellulose and the polyurethane elastic resin may cause phase separation, which may deteriorate the film formability during wet film formation. By setting the content of propionylated cellulose in the above-described range, the urethane sheet 2 can be formed under the conditions of a normal wet film forming method. In consideration of increasing the hydrophobicity of the urethane sheet 2 without deteriorating the film formability, the propionylated cellulose content is preferably in the range of 50 to 90% by mass. When the content of propionylated cellulose is a ratio with respect to the total solid content in the resin solution, it may be generally in the range of 1 to 3% by mass although it depends on the amount of additives such as pigments. Moreover, the substitution degree of the propionyl group in propionylated cellulose is adjusted to the range of 1-3 on average with respect to the hydroxyl group per glucose unit of a cellulose. When the degree of substitution is too low or too high, the solubility in a polar solvent such as DMF deteriorates, which is not preferable. In view of the function of increasing the hydrophobicity of the urethane sheet 2 and the solubility in polar solvents, it is preferable to use those having an average degree of substitution in the range of 1.5 to 2.4.

  Furthermore, in this embodiment, propionylated cellulose having an average degree of polymerization in the range of 200 to 400 and polyalkylene oxide having a number average molecular weight of 10,000 or more are used. For this reason, the urethane sheet 2 is formed while the molecular chains of propionylated cellulose and polyalkylene oxide are entangled with the molecular chains of the polyurethane-based elastic resin during film formation by the wet film formation method. Thereby, even if it is continuously used in the polishing process, the above-described action is exhibited without elution of propionylated cellulose and polyalkylene oxide, so that the life of the holding pad 10 can be improved. Furthermore, in order to increase hydrophobicity by including both polyalkylene oxide and propionylated cellulose, it is possible to infiltrate the liquid components of the polishing liquid without using a relatively low molecular weight fluorine-based water repellent as conventionally used. Can be prevented.

  In the present embodiment, a polyurethane elastic resin having a coagulation value of 8 or more is used for producing the urethane sheet 2. For this reason, at the time of film formation, the affinity between the polyurethane-based elastic resin and water is increased, and the penetration rate of water into the resin solution with respect to elution of DMF into the coagulating liquid is increased. Thereby, the solidification of the resin solution is accelerated, and the obtained urethane sheet 2 has an open cell structure in which the cells 5 are formed. In consideration of exhibiting appropriate subsidence (elasticity) when holding the object to be polished, the coagulation value is preferably in the range of 10-16.

  In the present embodiment, an example in which the mass ratio of PO in the polyalkylene oxide is 20% or more is shown, but the present invention is not limited to this. As the polyalkylene oxide, the above-described effects can be obtained if the mass ratio of EO is 50% or less. When the PO ratio is less than 20%, the hydrophilicity increases, and the liquid component of the polishing liquid easily enters the cell 5. For this reason, in addition to making the mass ratio of EO into the range mentioned above, it is preferable to make the mass ratio of PO 20% or more. In the present embodiment, a copolymer of EO having 2 carbon atoms and PO having 3 carbon atoms is exemplified as the polyalkylene oxide, but the present invention is not limited to this. The polyalkylene oxide may have an EO mass ratio of 50% or less and a number average molecular weight of 10,000 or more, and an alkylene oxide having 4 or more carbon atoms may be bonded thereto.

Further, in this embodiment, as acylated cellulose, propionylation in which the average degree of substitution of propionyl groups with respect to hydroxyl groups per glucose unit constituting cellulose is in the range of 1 to 3 and the average degree of polymerization is in the range of 200 to 400. Although the example using a cellulose was shown, this invention is not restrict | limited to this. As the acylated cellulose, one in which an acyl group represented by the chemical formula CH ₃ (CH ₂ ) _n CO (n = 0 to 2) is introduced into the cellulose can be used. That is, it may be an acetyl group or a butyryl group instead of the propionyl group. In acetylcellulose which introduce | transduced the acetyl group into the cellulose, when the average of substitution degree is the range of 1-3, an acetylation degree (acetylation degree) will be the range of 30-62.5. The degree of acetylation can be adjusted by the acetylation conditions of cellulose. As acetylcellulose, what processed the linter pulp whose alpha-cellulose content is 90 to 97% by the acetic acid method can be used, for example. Such acetyl cellulose can be obtained, for example, by treating wood pulp or linter pulp having an α-cellulose content of 90 to 97% by a conventional method such as a sulfuric acid catalyst method or a methylene chloride method. Diacetyl cellulose or triacetyl cellulose having a degree of 30 to 62.5% and a degree of polymerization of 200 to 4000 is preferable. Considering the solubility in polar solvents (DMF, DMAc, etc.), it is more preferable to use acetylcellulose having an acetylation degree of 45 to 62% and a polymerization degree of 200 to 350. The degree of acetylation represents the percentage by weight of bound acetic acid per unit weight of cellulose. For example, according to ASTM: D-817-91 “Testing Method for Cellulose Acetate”, the method for measuring the degree of acetylation. Can be measured. Furthermore, in the present embodiment, an example is shown in which propionylated cellulose is soluble in DMF used for dissolving polyurethane-based elastic resin and insoluble in water used as a coagulating liquid, but the present invention is not limited thereto. It is not something. The acylated cellulose used in the present invention may be soluble in a polar solvent for dissolving a resin and may be hardly soluble or insoluble in water as a coagulation liquid. If it does in this way, it can melt | dissolve and solidify with a resin component by the wet film-forming method.

  Furthermore, in this embodiment, the polyurethane elastic resin-made urethane sheet 2 produced by the wet film-forming method was illustrated, but this invention is not limited to this. For example, in addition to the polyurethane-based elastic resin, a polyethylene resin or the like can be used, and any resin can be used as long as the skin layer is formed by a wet film forming method. In consideration of use as a holding pad, a resin having moderate elasticity is preferable in order to suppress damage to the object to be polished. In this embodiment, an example in which a polyurethane elastic resin having a 100% modulus of 30 MPa or less is used, but the present invention is not limited to this. By setting the 100% modulus to 30 MPa or less, moderate elasticity is exerted, and when the workpiece is held, it is easily deformed so as to be in close contact with the workpiece. Furthermore, in this embodiment, although the example which sets the coagulation number of a polyurethane-type elastic resin to 8 or more was shown, this invention is not limited to this. A coagulation value of less than 8 may be used, but it is preferable to set the coagulation value to 8 or more in consideration of obtaining the above-described urethane sheet having an open cell structure.

  Furthermore, in this embodiment, the example in which the A hardness of the urethane sheet 2 is in the range of 5 to 20 degrees is shown, but the present invention is not limited to this, and the A hardness is out of this range. It may be. Considering that the object to be polished sinks moderately to the holding pad 10 side and is held securely when holding the object to be polished, the A hardness is preferably set to the above range. More preferably, it is in the range of -15 degrees.

  Furthermore, in the present embodiment, an example is shown in which the surface opposite to the skin layer 2a of the film-forming resin produced by the wet film-forming method is buffed, but the present invention is not limited to this. Absent. For example, if the thickness of the film forming resin by the wet film forming method is uniform, the double-sided tape 7 may be bonded without buffing. Further, in place of the double-sided tape 7, for example, a non-support tape in which only an adhesive is sandwiched between two release papers without having a base material can be used. Further, it is possible to buff the surface on the skin layer 2a side, but if the buffing is performed to the extent that the inner cell 5 is opened, the retention of the object to be polished will be lowered. It is preferable that the buffing is performed to such an extent as not to occur.

  Hereinafter, examples of the holding pad 10 manufactured according to the present embodiment will be described. The holding pad of the comparative example manufactured for comparison is also shown. In addition, when the content of propionylated cellulose (hereinafter abbreviated as PC) is fixed and the content of polyalkylene oxide (hereinafter abbreviated as AO) is changed, the content of AO is fixed and the content of PC When the amount is changed, the ratio of the PC content to the AO content is kept constant, the entire content is changed, the mass ratio of EO in AO is changed, the number average molecular weight of AO is changed, Each case where the type of acyl group in the acylated cellulose is changed will be described.

<When PC content is fixed and AO content is changed>
Example 1
In Example 1, a polyester MDI (diphenylmethane diisocyanate) PU having a 100% modulus of 18 MPa and a coagulation value of 12 was used as a polyurethane elastic resin (hereinafter abbreviated as PU). As AO, a copolymer of EO and PO having a mass ratio of EO of 40% and a number average molecular weight of 12,000 was used. As the PC, those having an average substitution degree of propionyl group of 2 with respect to hydroxyl groups per glucose unit of cellulose were used. Each component was dissolved in DMF such that the solid concentration was 30 wt% to prepare a DMF solution. As shown in Table 1 below, with respect to 100 parts by weight of PU DMF solution, 2.5 parts by weight of AO DMF solution, 1.5 parts by weight of PC DMF solution, 6 parts by weight of carbon black as a pigment, And DMF was mixed by the mixture ratio of 55 weight part, and the resin solution was prepared. The obtained resin solution was applied to a PET film-forming substrate, formed into a sheet by coagulation regeneration, and then the holding pad 10 was manufactured through washing, drying, buffing, and bonding. In the blending ratio of Example 1, the content of AO is 2.5 wt% with respect to PU, and the content of PC is 60.0 wt% with respect to AO. Further, as shown in Table 2 below, since the total solid content in the resin solution is 37.2 parts by weight, the compounding amount of each component with respect to the total solid content is 80.6% for PU, and 2. for AO. 0%, PC 1.2%, and carbon black 16.1%.

(Example 2)
As shown in Table 1, Example 2 was the same as Example 1 except that the blending ratio of AO was 1.5 parts by weight. In the blending ratio of Example 2, the content of AO is 1.5 wt% with respect to PU, and the content of PC is 100.0 wt% with respect to AO. Further, as shown in Table 2, since the total solid content in the resin solution is 36.9 parts by weight, the blending amount of each component with respect to the total solid content is 81.3% PU and 1.2% AO. %, PC is 1.2%, and carbon black is 16.3%.

(Comparative Examples 1 to 4)
As shown in Tables 1 and 2, in Comparative Example 1, a holding pad of Comparative Example 1 was manufactured in the same manner as in Example 1 except that AO and PC were not blended. That is, Comparative Example 1 is a conventional holding pad. In Comparative Example 2, a holding pad in which AO was not blended and PC was blended was produced in the same manner as Example 1 except that AO was not blended. In Comparative Example 3 and Comparative Example 4, a holding pad was produced in the same manner as in Example 1 except that the blending ratio of AO was 7.5 parts by weight and 10.0 parts by weight, respectively.

<When the content of AO is fixed and the content of PC is changed>
(Example 3 to Example 5)
As shown in Table 3 and Table 4 below, in Examples 3 to 5, the mixing ratio of AO was set to 2.5 parts by weight as in Example 1, and the mixing ratio of PC was changed. The holding pad 10 was manufactured in the same manner as in Example 1. The blending ratio of PC was 1.0 part by weight in Example 3, 2.0 parts by weight in Example 4, and 2.5 parts by weight in Example 5. In Tables 3 and 4, the numerical values of Example 1 and Comparative Example 1 are also shown.

(Comparative Example 5 to Comparative Example 7)
As shown in Tables 3 and 4, in Comparative Example 5, except that PC was not blended, a holding pad blended with AO without blending PC was manufactured in the same manner as Example 3. In Comparative Example 6 and Comparative Example 7, a holding pad was produced in the same manner as in Example 3 except that the blending ratio of PC was 0.5 parts by weight and 3.0 parts by weight, respectively.

<When changing the entire content while keeping the ratio of the PC content to the AO content constant>
(Example 6)
As shown in Table 5 and Table 6 below, in Example 6, 5.0 parts by weight of DMF solution of AO and 3.0 parts by weight of DMF solution of PC with respect to 100 parts by weight of PU DMF solution, A resin solution was prepared by mixing 6 parts by weight of carbon black as a pigment and 55 parts by weight of DMF. In Tables 5 and 6, the numerical values of Example 1 and Comparative Example 1 are also shown.

(Comparative Example 8 to Comparative Example 9)
As shown in Tables 5 and 6, in Comparative Example 8, with respect to 100 parts by weight of PU DMF solution, 0.8 parts by weight of AO DMF solution and 0.5 parts by weight of PC DMF solution were used. A holding pad was manufactured in the same manner as in Example 6 except for the above. Comparative Example 9 was held in the same manner as in Example 6 except that 100 parts by weight of PU DMF solution was 10.0 parts by weight of AO DMF solution and 6.0 parts by weight of PC DMF solution. A pad was manufactured.

<When changing the mass ratio of EO in AO>
(Example 7)
As shown in Table 7 and Table 8 below, in Example 7, a holding pad was manufactured in the same manner as in Example 6 except that AO having a mass ratio of EO in the molecule of 0% was used. That is, AO used in Example 7 is polypropylene oxide. In Tables 7 and 8, the numerical values of Example 6 are also shown.

(Comparative Example 10 to Comparative Example 11)
As shown in Tables 7 and 8, in Comparative Examples 10 to 11, a holding pad was manufactured in the same manner as in Example 7 except that AO having a different mass ratio of EO was used. The mass ratio of EO in the used AO is 100 wt% in Comparative Example 10 and 60 wt% in Comparative Example 11. That is, AO used in Comparative Example 10 is polyethylene oxide.

<When the number average molecular weight of AO is changed>
(Comparative Example 12 to Comparative Example 13)
As shown in Tables 9 and 10 below, in Comparative Examples 12 to 13, holding pads were produced in the same manner as in Example 6 except that AOs having different molecular weights were used. The molecular weight of AO used is 2000 in Comparative Example 12 and 7000 in Comparative Example 13. In Tables 9 and 10, the numerical values of Example 6 are also shown.

<When the kind of acyl group in acylated cellulose is changed>
(Example 8 to Example 9)
As shown in Table 11 and Table 12 below, in Examples 8 to 9, acetylated cellulose and butyryl cellulose were used as acylated cellulose (hereinafter abbreviated as AC) in place of PC. A holding pad was manufactured in the same manner as in Example 6 except that. In Tables 11 and 12, the numerical values of Example 6 are also shown.

(Evaluation)
About the holding pad of each Example and the comparative example, the contact angle with respect to the water in a holding surface and the adsorption | suction power of a to-be-polished object were evaluated. The contact angle to water was measured by a droplet method using an automatic contact angle meter (DropMaster 500 manufactured by Kyowa Interface Science Co., Ltd.). That is, distilled water is put into a syringe of an automatic contact angle meter, and under the conditions of a temperature of 20 ° C. and a humidity of 60%, a drop of water is dropped from the injection needle onto the surface of the polishing sheet, and contact is made 10 seconds after dropping. I read the corner. As for the contact angle with respect to water, those in the range of 80 to 110 degrees were judged as acceptable, and those less than 80 degrees and those exceeding 110 degrees were judged as unacceptable. Moreover, the adsorption | suction power of the glass substrate which is a measurement sample measured the vertical direction adsorption | suction power in the following procedures using Tensilon (A & D Co., Ltd. make, Tensilon universal testing machine, RTF-1210). That is, the holding pad was affixed on the test stand through the double-sided tape 7 so that the holding surface P was the upper surface, and the holding surface P was wetted with distilled water. After sufficiently removing the moisture on the holding surface P, a glass substrate (125 mmφ) fixed to the upper surface plate with an adhesive is placed on the holding surface P, and about 4 kgf (39 N) with the glass substrate and its own weight on the upper surface plate. It left still for 1 minute in the state which applied power. The upper surface plate was pulled upward, and the load when the holding pad was detached from the glass substrate was measured. The measurement was performed three times continuously without changing the sample. As for the adsorption power of the object to be polished, a sample obtained by adsorbing a measurement sample with a force of 10 kgf (98 N) or more was determined to be acceptable, and a sample having an adsorption force of less than 10 kgf was determined to be unacceptable.

<When PC content is fixed and AO content is changed>
(Examples 1 to 2, Comparative Examples 1 to 4)
In the comparative example 1 which does not contain AO and PC, water permeability became high and the contact angle was determined to be unacceptable. In addition, the adsorbing force was judged to be unacceptable, and the durability of the holding pad was lowered. In Comparative Example 2 containing only PC without containing AO, the elasticity of the holding pad was lowered, the polishing object retention was insufficient, and the adsorbing power was judged to be unacceptable. Moreover, in Comparative Example 3 and Comparative Example 4, since the PC content with respect to AO is less than 40 wt%, the effect of increasing the hydrophobicity of the holding pad is insufficient, and both the contact angle and the adsorption force are determined to be unacceptable. It was. On the other hand, in the holding pad 10 of Example 1-Example 2, both AO and PC were contained in the range mentioned above, and since hydrophobicity was improved, both a contact angle and adsorption power passed. As a result, it was possible to hold the object to be polished well.

<When the content of AO is fixed and the content of PC is changed>
(Example 3 to Example 5, Comparative Example 5 to Comparative Example 7)
In Comparative Example 5 that does not contain PC and Comparative Example 6 in which the content of PC with respect to AO is less than 40 wt%, the effect of increasing the hydrophobicity of the holding pad is insufficient, and both the contact angle and the adsorption force are judged to be unacceptable. It became. Moreover, in Comparative Example 7 in which the content of PC with respect to AO exceeds 100 wt%, the elasticity of the holding pad was lowered, the retention of the object to be polished was insufficient, and the adsorbing power was judged to be unacceptable. On the other hand, in Examples 3 to 5, the inclusion of AO and PC in the above-described range increases the hydrophobicity, so that both the contact angle and the adsorbing force are determined to be acceptable. The polished product could be held well.

<When changing the entire content while keeping the ratio of the PC content to the AO content constant>
(Example 6, Comparative Examples 8 to 9)
Even if the mass ratio of PC with respect to AO was constant, in Comparative Example 8 in which the content of AO with respect to PU was less than 1% by mass, water immersion was high, and the contact angle was determined to be unacceptable. In addition, the adsorbing force was judged to be unacceptable, and the durability of the holding pad was lowered. On the contrary, in Comparative Example 9 in which the content of AO with respect to PU exceeds 8% by mass, the compatibility between the polyurethane resin, AO and PC was lowered, and the film formation stability was lowered. With such a holding pad, the foamed shape varies and it becomes difficult to flatten the workpiece. On the other hand, in Example 6, the inclusion of AO and PC in the above-described range increased the hydrophobicity, so that both the contact angle and the attractive force were judged to be acceptable, and the object to be polished was good. Was able to hold on.

<When changing the mass ratio of EO in AO>
(Example 7, Comparative Example 10 to Comparative Example 11)
In Comparative Example 10 and Comparative Example 11 containing EO in a proportion exceeding 50% by mass as the structural unit of AO, the wettability of the holding pad was increased, so that the water immersion was increased and the contact angle was determined to be unacceptable. . In addition, the adsorbing force was judged to be unacceptable, and the durability of the holding pad was lowered. On the other hand, in the holding pad 10 of Example 7, the EO ratio is 0% as AO, that is, the inclusion of polypropylene oxide and PC in the above-described range increases the hydrophobicity, thereby bringing about contact. Both the corner and the attractive force were judged to be acceptable, and the object to be polished could be held well.

<When the number average molecular weight of AO is changed>
(Comparative Example 12 to Comparative Example 13)
In Comparative Examples 12 and 13 in which the number average molecular weight of AO is less than 10,000, elution of AO was observed when the holding pad was washed as the molecular weight decreased. For this reason, the water permeability of the holding pad was increased, and it was judged that the adsorbing power of the object to be polished was unacceptable. Therefore, it has been clarified that the elution during use and the decrease in the adsorptive power can be suppressed by setting the number average molecular weight of AO to 10,000 or more.

<When the kind of acyl group in acylated cellulose is changed>
(Example 8 to Example 9)
In Example 8 using acetylated cellulose introduced with an acetyl group as an acyl group of acylated cellulose and Example 9 using butyryl cellulose introduced with a butyryl group, AO and PC were contained in the above-mentioned ranges. As a result, the hydrophobicity was improved, so that it was possible to hold the object to be polished satisfactorily with any of the holding pads 10. Therefore, even if the acyl group of the acylated cellulose is any of acetyl group, propionyl group, and butyryl group, the effect of increasing the hydrophobicity of the holding pad can be obtained if the substitution degree is in the range of 1.5 to 2.4. It became clear.

  Since the present invention provides a holding pad that can prevent the liquid component of the polishing liquid from entering and can improve the life while ensuring the retention of the object to be polished, it contributes to the manufacture and sale of the holding pad. Therefore, it has industrial applicability.

P Holding surface 2 Urethane sheet (soft resin sheet)
2a Skin layer 5 Bubble 10 Holding pad

Claims (7)

A soft resin sheet made of polyurethane based elastic resin, as well as have a skin layer on the holding surface side for holding the object to be polished, the inner side of the skin layer, vertical to the thickness direction of the soft resin sheet in communication with the holding surface side of the pore size of the holding surface opposite to the surface side of the small bubbles is reticulated, and soft resin having a continuous pore structure which bubbles are communicated to the holding surface via the skin layer In the holding pad provided with the sheet, the resin portion of the soft resin sheet has an acylation with a polyalkylene oxide having a number average molecular weight of 10,000 or more and ethylene oxide bonded in a mass ratio of 50% or less. Cellulose is contained, and the content of the polyalkylene oxide is in the range of 1% by mass to 8% by mass with respect to the resin component constituting the soft resin sheet. , Holding pad the content of the acylated cellulose is characterized by a range of 40 to 100 mass% relative to the polyalkylene oxide. In the acylated cellulose, an acyl group represented by the chemical formula CH ₃ (CH ₂ ) _n CO (n = 0 to 2) is introduced into the cellulose, and the acyl with respect to hydroxyl groups per glucose unit constituting the cellulose. The holding pad according to claim 1, wherein the average degree of substitution of the groups is in the range of 1 to 3.   The holding pad according to claim 2, wherein the acylated cellulose is soluble in a polar solvent that dissolves the resin component and is hardly soluble or insoluble in water.   The holding pad according to claim 1, wherein the polyalkylene oxide is a copolymer of ethylene oxide and propylene oxide.   The holding pad according to claim 4, wherein the polyalkylene oxide has a molecular weight of 12,000 or more.   The polyalkylene oxide has a content of 2 to 7% by mass with respect to the resin component, and the acylated cellulose has a content of 50 to 90% by mass with respect to the polyalkylene oxide. The holding pad according to claim 1.   The holding pad according to claim 6, wherein the soft resin sheet has an A hardness in a range of 5 degrees to 20 degrees.

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