JP2012071399A - Holding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a holding material securing holding force to an object to be polished and facilitating removal of the object to be polished.SOLUTION: The holding material 10 includes a polyurethane sheet 2 prepared by a wet coagulation method and a protective layer 5 disposed on a surface of the polyurethane sheet 2. The polyurethane sheet 2 includes a skin layer 2a and a nap layer 2b formed on the inner side from the skin layer 2a. Many vertically long cells 3 are formed along a thickness direction of the polyurethane sheet 2 in the nap layer 2b. The protective layer 5 is formed of a resin having larger acid resistance and alkali resistance as compared with polyurethane resin forming the polyurethane sheet 2. The surface of the protective layer 5 forms a holding surface S for holding the object to be polished. A recess 5a in which the surface of the skin layer 2a is partially exposed is formed on the protective layer 5. The recess 5a is formed so as to be uniform in the holding surface S. The protective layer 5 performs a function for protecting the skin layer 2a.

Description

  The present invention relates to a holding material, and more particularly, to a holding material including a resin sheet made of a soft resin having a skin layer formed by a wet coagulation method and having a number of cells formed on the inner side of the skin layer.

  Conventional glass substrate for liquid crystal display (LCD), glass substrate on which color material films of three primary colors of red (R), green (G), and blue (B) in color filters are formed, flat composed of LCD cells, etc. In panel displays and the like, polishing is performed in the manufacturing process thereof. Generally, in the polishing process, a porous sheet having a skin layer on the surface side by a wet coagulation method and having a large number of cells (foaming) formed therein is provided for the purpose of holding an object to be polished. Retaining material is used. That is, a holding material is used in which a porous sheet (resin holding layer) having a uniform thickness by grinding the back side is bonded to a base material having an adhesive layer and the porous sheet is supported by the base material. Yes.

  When the holding material is used, the object to be polished is held by a composite action such as an adhesion force on the surface of the holding material, an adsorption force due to a surface tension of water or the like. With such a holding material, compared to a template-type holding material having a frame material that is usually used in single-side polishing of semiconductors, side slip of an object to be polished is suppressed during polishing without using a frame material. Can do. Therefore, it is possible to handle a plurality of sizes of objects to be polished in the same process with the same holding material, and the positional accuracy is insufficient in detachment of the objects to be polished in an automated line. Even in such a case, there is an advantage that the object to be polished is hardly damaged.

  On the other hand, in order to improve productivity, the object to be polished tends to be enlarged. For example, glass substrates, which are constituent materials for LCDs, have been increasing in size year by year, and large glass substrates with a side approaching 3 m have been used. Along with the increase in size of the glass substrate, when the glass substrate is removed from the holding material after the polishing process, there is a problem that a force applied to the glass substrate is increased and a crack or the like due to the bending of the glass substrate occurs.

  However, for example, when a holding material is used for polishing a glass substrate, abrasive grains such as cerium oxide contained in the polishing liquid may adhere to the surface of the holding material, and water eluted from the abrasive grains fixed to the holding material. An alkali component such as lanthanum oxide may deteriorate the surface of the skin layer and reduce the retention of the object to be polished. In addition, the deteriorated portion on the surface of the skin layer promotes the penetration of the polishing liquid or the like into the porous sheet and deteriorates the inside of the porous sheet, thereby causing loss of elasticity. In addition, the abrasive grains adhered to the holding material adheres to the glass surface when the polishing process is resumed, and a phenomenon called “glass burn” that cannot be removed even after cleaning after the polishing process occurs. It can have a big impact. In addition to these problems, the skin layer may deteriorate and lose elasticity when it comes into contact with an acid or alkali that chemically degrades the soft resin that is the material of the porous sheet. For this reason, damage to the surface of the skin layer due to friction with the object to be polished becomes significant at the time of polishing, and as a result, the retention of the object to be polished is greatly reduced and the elasticity of the holding material is lost.

  In order to avoid these problems, for example, as a technique for improving the acid resistance and alkali resistance of the holding material, an elastic body technique using vinyl chloride as a material for holding a semiconductor in an air bag type polishing head is disclosed. (See Patent Document 1). In addition, a technique for a holding material using a fiber of polyolefin or polyphenylene sulfide having acid resistance and alkali resistance is disclosed (see Patent Document 2).

JP 2007-324497 A JP 2009-88456 A

  However, in the technique of Patent Document 1, although the object to be polished can be held by a vacuum suction force or surface tension of water, it is difficult to suppress the lateral displacement of the object to be polished, and a template method using a frame material is employed. Will be forced. For this reason, each frame material according to the size of the object to be polished is required, and the object to be polished may be damaged by the contact between the object to be polished and the frame material during the polishing process. Moreover, in the technique of patent document 2, although acid resistance and alkali resistance improve, it becomes difficult to suppress the lateral shift of a to-be-polished object by using a fiber material. For this reason, it must be used as a template-type holding material, and the same problem as in Patent Document 1 occurs. Therefore, it is important to limit the adhesion between the object to be polished and the holding material in order to suppress damage during attachment / detachment even for a large object to be polished, while the holding power rapidly decreases without using a frame material. It is important to ensure a stable holding force over a long period of time.

  An object of the present invention is to provide a holding material that can secure a holding force for an object to be polished and can easily attach and detach the object to be polished.

  In order to solve the above-mentioned problems, the present invention provides a resin sheet made of a soft resin having a skin layer formed by a wet coagulation method and having a plurality of cells formed on the inner side of the skin layer, and the skin layer. A protective layer disposed on the surface, the surface forming a holding surface for holding an object to be polished and protecting the skin layer, wherein the protective layer is made of a soft resin that forms the resin sheet. The holding material is formed of a resin having high acid resistance or alkali resistance, and has holes or grooves formed so as to partially expose the surface of the skin layer.

  In the present invention, since the protective layer is formed of a resin having a higher acid resistance or alkali resistance than the soft resin forming the resin sheet, the resin has a higher resistance to an acidic or alkaline polishing liquid as a whole even if holes or grooves are formed. Since water intrusion into the sheet is suppressed, it is possible to secure a holding force for the object to be polished, and the rigidity on the holding surface is increased by providing a protective layer, and holes or grooves are formed in the protective layer. Thus, since the adhesion force to the object to be polished is limited, the object to be polished can be easily attached and detached.

  In this case, the coverage of the protective layer with respect to the surface of the skin layer can be in the range of 50% to 99%. A hole is formed in the protective layer so as to partially expose the surface of the skin layer, and the hole has a circular shape having a diameter of 2 mm or less and is formed to be uniform in the holding surface. Good. The tensile strength retention ratio before and after immersing the resin constituting the protective layer in a sodium hydroxide aqueous solution having a liquid temperature of 50 ° C. and a pH of 13 for one week can be 80% or more. The tensile strength retention before and after immersing the resin constituting the protective layer in a hydrochloric acid aqueous solution having a liquid temperature of 50 ° C. and a pH of 1.5 for 3 weeks can be 80% or more. The thickness of the protective layer may be in the range of 1 μm to 100 μm, and the thickness of the resin sheet may be in the range of 200 μm to 2000 μm. At this time, the resin sheet may be made of polyurethane resin, and the resin constituting the protective layer may be elastomer.

  According to the present invention, since the protective layer is formed of a resin having a higher acid resistance or alkali resistance than the soft resin forming the resin sheet, even if a hole or a groove is formed, the protective layer as a whole is resistant to an acidic or alkaline polishing liquid. Since the water intrusion into the resin sheet is suppressed and the holding force against the object to be polished can be secured, the rigidity on the holding surface is increased by providing the protective layer, and a hole or groove is formed in the protective layer. As a result, the adhesion to the object to be polished is limited, so that an effect that the object can be easily attached and detached can be obtained.

It is sectional drawing which shows typically the holding material of embodiment to which this invention is applied. It is a top view which shows the formation pattern of the recessed part in the protective layer of a holding material, (A) shows the holding material of embodiment, and the formation pattern formed so that a circular recessed part may disperse | distribute uniformly, (B) is The holding material of another aspect is shown, and the formation pattern in which a grid-like groove is formed as a recess, and (C) shows the holding material of another aspect and the formation pattern in which a concentric groove is formed as a recess. . The positional relationship of a holding material and a to-be-polished object when evaluating the to-be-polished object holding | maintenance property of a holding material is shown typically, (A) is a top view, (B) is sectional drawing.

  Embodiments of a holding material to which the present invention is applied will be described below with reference to the drawings.

<Configuration>
As shown in FIG. 1, the holding material 10 of the present embodiment includes a polyurethane sheet 2 as a polyurethane resin (soft resin) resin sheet manufactured by a wet coagulation method, and a protection disposed on the surface of the polyurethane sheet 2. Layer 5.

  The polyurethane sheet 2 has a skin layer 2a formed at the time of production by a wet coagulation method and having surface flatness, and a nap layer 2b formed on the inner side from the skin layer 2a. In the nap layer 2b, a large number of cells (pores) 3 having a vertically long and rounded conical shape (longitudinal triangular shape in cross section) along the thickness direction (vertical direction in FIG. 1) of the polyurethane sheet 2 are dispersed substantially uniformly. It is formed in a state. The length in the longitudinal direction of the cell 3 varies within the range of the thickness of the polyurethane sheet 2. In the vicinity of the skin layer 2a, a fine cell structure is formed in which a large number of cells 3 having a small length are formed. The cell 3 is formed such that the pore diameter on the skin layer 2a side is smaller than the pore diameter on the surface side opposite to the skin layer 2a (hereinafter, the surface opposite to the skin layer 2a is referred to as the back surface). That is, the diameter of the cell 3 is reduced on the skin layer 2a side from the back side. The polyurethane resin between the cells 3 is formed in a microporous shape in which a large number of micropores (not shown) having a pore diameter smaller than that of the cells 3 are formed. The skin layer 2a, the cells 3 and the fine holes (not shown) communicate with each other in a mesh shape through communication holes (not shown), and the polyurethane sheet 2 has a continuous cell structure as a whole. The thickness of the polyurethane sheet 2 can be adjusted in the range of 200 to 2000 μm, and is adjusted to 800 μm in this example.

  In addition, the protective layer 5 disposed on the surface of the skin layer 2 a is formed of a resin having higher acid resistance and alkali resistance than the polyurethane resin forming the polyurethane sheet 2. For acid resistance, the tensile strength after immersing the resin forming the protective layer 5 in a hydrochloric acid aqueous solution having a liquid temperature of 50 ° C. and pH 1.5 for 3 weeks is A1, and the tensile strength before immersing in the aqueous hydrochloric acid solution is defined as A1. When B1, the tensile strength retention represented by 100 × A1 / B1 is 80% or more. On the other hand, as alkali resistance, when the liquid temperature is 50 ° C. and the tensile strength after immersion in a sodium hydroxide aqueous solution of pH 13 for 1 week is A2, and the tensile strength before immersion in the aqueous sodium hydroxide solution is B2, , 100 × A2 / B2 represents a tensile strength retention of 80% or more. Examples of such resins include elastomers such as rubber materials, and specifically, silicone rubber, fluorine rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile-butadiene rubber, At least one selected from hydrogenated acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, styrene-butadiene rubber, and butadiene rubber can be used. In this example, chloroprene rubber is used as the resin for the protective layer 5. Since the protective layer 5 excellent in acid resistance and alkali resistance is disposed on the surface of the skin layer 2a, the protective layer 5 functions to protect the skin layer 2a.

  The protective layer 5 is formed so as to cover the surface of the skin layer 2a after the production of the polyurethane sheet 2 by the wet coagulation method. The surface of the protective layer 5 forms a holding surface S for holding an object to be polished. In the protective layer 5, a recess 5 a is formed so as to penetrate the thickness of the protective layer 5. That is, since the protective layer 5 is formed on the surface of the skin layer 2a, the surface of the skin layer 2a is partially exposed. Further, since the skin layer 2a is left as it is formed by the wet coagulation method, the cell 3 formed in the nap layer 2b does not form a hole at the position of the holding surface S or the recess 5a. The thickness of the protective layer 5 can be formed in the range of 1 to 100 μm, and is adjusted to 50 μm in this example.

The recess 5a formed in the protective layer 5 can be formed as a hole or a groove, but in this example, it is formed as a circular hole. That is, as shown in FIG. 2A, in this example, the circular concave portions 5a are formed so as to be evenly dispersed. The size of the recess 5a can be adjusted with a diameter of 2 mm or less. The recess 5a is formed at a rate of 1 to 250 pieces / cm ² on the holding surface S. Although the protective layer 5 is formed so as to cover the surface of the skin layer 2a, the coating showing the ratio of the area where the protective layer 5 is formed to the total area of the surface of the skin layer 2a due to the formation of the recess 5a. The rate can be adjusted in the range of 50-99%. For example, if the circular concave portions 5a having a diameter of 1.5 mm are formed at a rate of 3 pieces / cm ² , the coverage is about 95%.

  In the holding material 10, the double-sided tape 7 is bonded to the back side of the polyurethane sheet 2. The double-sided tape 7 has a base material such as a resin film having flexibility. As the substrate, polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene (PE), polypropylene (PP), or the like can be used. In this example, a PET film is used. The base material has an adhesive layer (not shown) in which an adhesive is applied to both sides. As the pressure-sensitive adhesive for the pressure-sensitive adhesive layer, acrylic-based, urethane-based, and epoxy-based pressure-sensitive adhesives can be used. In this example, an acrylic pressure-sensitive adhesive is used. The double-sided tape 7 is bonded to the back surface side of the polyurethane sheet 2 via an adhesive layer on one side, and the adhesive layer on the other side is covered with a release paper 8. In this example, the base material of the double-sided tape 7 also functions to support the entire holding material 10.

<Manufacturing>
The holding material 10 is manufactured by forming a protective layer 5 and a recess 5a on the skin layer 2a side of a polyurethane resin sheet produced by a wet coagulation method, and bonding the double-sided tape 7 together. That is, a preparation process for preparing a resin solution in which a polyurethane resin is dissolved, a sheet formation process for coagulating the resin solution in an aqueous coagulation liquid to form a sheet-like polyurethane resin, and a washing / drying process for washing and drying the polyurethane resin Then, the holding material 10 is manufactured through a protective layer 5, a covering step for forming the recess 5 a by applying an aqueous chloroprene rubber emulsion on the skin layer 2 a side, and a laminating step for bonding to the double-sided tape. Hereinafter, it demonstrates in order of a process.

  In the preparation step, the polyurethane resin is dissolved by mixing the polyurethane resin, a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive. As the organic 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 polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin or the like having a 100% modulus of 20 MPa or less is selected and used, for example, DMF so that the polyurethane resin is 30% by mass (wt%). Dissolve in. As the additive, a pigment such as carbon black for controlling the size and amount (number) of the cells 3, a hydrophilic activator for promoting cell formation, a hydrophobic activator for stabilizing regeneration of the polyurethane resin, and the like are used. it can. The obtained solution is degassed under reduced pressure to prepare a resin solution.

  In the sheet forming step, the resin solution prepared in the preparation step is continuously applied to the film forming substrate, and the resin solution is solidified in an aqueous coagulating liquid to form a sheet-like polyurethane resin. The resin solution is applied to the band-shaped film-forming substrate at a normal temperature by a coating apparatus so as to have a uniform thickness. In this example, a knife coater is used as the coating apparatus, and the coating thickness (coating amount) of the resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. In this example, in order to make the thickness of the polyurethane sheet obtained into the above-mentioned range, the coating thickness is adjusted to a range of 500 to 2000 μm. Although a flexible film, a nonwoven fabric, a woven fabric, or the like can be used as the film forming substrate, in this example, the film forming substrate is described as a PET film.

  The resin solution applied to the film forming substrate is guided into a coagulating liquid (water-based coagulating liquid) whose main component is water, which is a poor solvent for the polyurethane resin. As the coagulation liquid, an organic solvent such as DMF or DMAc can be mixed with water, but in this example, water is used. In the coagulation liquid, first, the skin layer 2a is formed on the surface side of the applied resin solution over a thickness of about several μm. Thereafter, the nap layer 2b is formed by the progress of substitution between the DMF in the resin solution and the coagulating liquid (water), and the polyurethane resin is regenerated into a sheet shape. When the DMF is desolvated from the resin solution and the DMF and the coagulating liquid are replaced, the cells 3 and fine pores (not shown) are formed in the polyurethane resin inside the skin layer 2a, and the skin layers 2a and 3 are not shown. A continuous cell structure is formed in which the micropores are connected in a network. 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 3 having a larger film formation substrate side than the surface side are formed. .

  In the washing / drying step, the regenerated band-like (long sheet-like) polyurethane resin is washed and dried. That is, after the polyurethane resin is peeled from the film forming substrate, it is washed in a cleaning solution such as water to remove DMF remaining in the polyurethane resin. After washing, in this example, the polyurethane resin is dried using a cylinder dryer provided with a cylinder having a heat source inside. When the polyurethane resin passes along the peripheral surface of the cylinder, the polyurethane sheet 2 is obtained by drying.

  When forming the protective layer 5, in this example, a screen printing method using a screen printer is used. In other words, the protective layer 5 is screen-printed on the skin layer 2 a of the polyurethane sheet 2. Specifically, a plate in which a hole pattern is formed in accordance with the formation pattern of the recess 5a is placed on the surface of the dried polyurethane sheet 2 on the skin layer 2a side. Aqueous chloroprene rubber emulsion is poured into the plate and stretched to a uniform thickness with a squeegee. By removing the solvent under a heating atmosphere, the protective layer 5 made of chloroprene rubber is formed, and the concave portion 5 a is formed in the protective layer 5. The thickness of the protective layer 5 can be adjusted by the thickness of the plate and the resin concentration.

  In the laminating step, the surface opposite to the protective layer 5 of the polyurethane sheet 2, that is, the back surface side, and the double-sided tape 7 are bonded together. At this time, the pressure-sensitive adhesive layer on one side of the double-sided tape 7 and the back side of the polyurethane sheet 2 are bonded together. After the polyurethane sheet 2 and the double-sided tape 7 are bonded together, the sheet is cut into a desired size and shape. Then, an inspection such as confirming that there is no adhesion of scratches, dirt, foreign matter, etc. is performed, and the holding material 10 is completed.

  When polishing an object to be polished using the holding material 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. A holding material 10 is attached to the holding surface plate, and a polishing pad is attached to the polishing surface plate. When the holding material 10 is attached to the holding surface plate, the release paper 8 is removed and the exposed adhesive layer is attached. When holding an object to be polished, the object to be polished is brought into contact with the holding surface S and pressed against the holding platen side. The object to be polished is held on the holding surface plate via the holding material 10. A polishing liquid containing abrasive particles is circulated and supplied between the processing surface of the object to be polished and the polishing pad, and the holding surface plate or polishing surface plate is rotated while applying polishing pressure to the object to be polished. Polish the polished object (processed surface).

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

  In the present embodiment, the protective layer 5 is formed on the surface of the skin layer 2 a of the polyurethane sheet 2. In the protective layer 5, chloroprene rubber having higher acid resistance and alkali resistance than polyurethane resin is used. Since the chloroprene rubber forming the protective layer 5 is superior in acid resistance and alkali resistance compared to the polyurethane sheet 2, the protective layer 5 has a recess 5 a, but the protective layer is in contact with the polishing liquid during polishing. 5 can suppress the deterioration of the skin layer 2a as a whole and protect the skin layer 2a. In the conventional holding material that does not have the protective layer 5, the surface of the skin layer deteriorates due to contact with an acidic or alkaline polishing liquid, so that the polishing liquid rapidly infiltrates into the polyurethane sheet, and the object to be polished may fall off. There was a case where breakage and further peeling of the polyurethane sheet and the double-sided tape were caused. On the other hand, in the holding material 10, since the surface of the skin layer 2a is protected by the protective layer 5, it becomes difficult for the polishing liquid to enter the polyurethane sheet 2, and the stable holding property of the object to be polished is ensured for a long time. can do.

Further, the protective layer 5 is formed so that the circular recesses 5 a are uniform in the holding surface S. For this reason, even if air biting occurs between the object to be polished and the holding material 10 when holding the object to be polished, the recess 5a suppresses the storage of air between the holding surface S and the object to be polished. be able to. As a result, the object to be polished can be held flat, and the flatness of the object to be polished can be improved by polishing. In such a holding material 10, since the protective layer 5 of chloroprene rubber is formed on the surface of the skin layer 2a, the rigidity on the holding surface S is increased and the adhesion to the object to be polished, in other words, the holding force is limited. The As a result, even when polishing a large-sized workpiece having an area of 10,000 cm ² or more, it is possible to easily attach and detach the workpiece while ensuring a minimum holding force for the workpiece. Damage due to bending of an object can be suppressed. Furthermore, since the damage to the object to be polished is suppressed, the stoppage of the polishing machine due to the damage to the object to be polished can be reduced, and the efficiency of the polishing process can be improved.

  Furthermore, in this embodiment, since the rapid penetration | invasion of the polishing liquid into the polyurethane sheet 2 which comprises the holding material 10 is suppressed, peeling with the polyurethane sheet 2 and the double-sided tape 7 can be suppressed. For this reason, since the retainability of the object to be polished is stabilized, the occurrence of uneven polishing on the object to be polished can be suppressed. Further, even when the object to be polished is held, since the surface of the object to be polished and the surface of the skin layer 2a partially exposed at the position of the recess 5a are suppressed, damage to the surface of the skin layer 2a is suppressed. can do.

  In the present embodiment, chloroprene rubber having excellent acid resistance and alkali resistance is exemplified as the resin forming the protective layer 5, but the present invention is not limited to this. Any material can be used as long as it has a higher acid resistance or alkali resistance than the polyurethane resin forming the polyurethane sheet 2. That is, it is only necessary to have either acid resistance or alkali resistance, and it may be selected according to an acidic or alkaline polishing liquid. Such materials include silicone rubber, fluoro rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber. , At least one selected from styrene-butadiene rubber and butadiene rubber.

  In the present embodiment, the example in which the coverage of the protective layer 5 on the skin layer 2a is adjusted to a range of 50 to 99% is shown, but the present invention is not limited to this. When the coverage is less than 50%, the surface of the skin layer 2a exposed at the position of the recess 5a may come into contact with the object to be polished, and the protective function of the protective layer 5 with respect to the skin layer 2a becomes insufficient. On the other hand, when the coverage ratio exceeds 99%, it becomes difficult to remove the air bitten between the holding surface S and the object to be polished when the object to be polished is held, and the air is stored. Therefore, the improvement in flatness of the object to be polished by the polishing process is hindered. Further, since the contact area between the holding surface S and the object to be polished becomes large, the object to be polished may be damaged when the object to be polished is removed. Therefore, in consideration of protection of the skin layer 2a and air removal, the coverage is preferably in the range of 50 to 99%.

  Furthermore, in this embodiment, although the example which makes the recessed part 5a circular shape with a diameter of 2 mm or less was shown, this invention is not limited to this. For example, as shown in FIG. 2B, a formation pattern in which lattice-like grooves are formed may be used, or as shown in FIG. 2C, a formation pattern in which concentric grooves are formed may be used. In the formation pattern in which such grooves are formed, in other words, in the pattern in which the non-coated portion of the aqueous chloroprene rubber emulsion forming the protective layer 5 is continuously formed, the retainability to the object to be polished during the polishing process May be reduced. Therefore, in consideration of retention of the object to be polished, it is preferable that the circular concave portions 5a described above are formed so as to be dispersed.

  Furthermore, in this embodiment, although the example which makes the thickness of the protective layer 5 the range of 1-100 micrometers was shown, this invention is not restrict | limited to this. If the thickness of the protective layer 5 is less than 1 μm, it is insufficient to protect the surface of the skin layer 2a. On the contrary, if the thickness exceeds 100 μm, the rigidity of the protective layer 5 itself becomes too high. Adhesion cannot be ensured. In other words, since the thickness of the protective layer 5 affects the rigidity of the holding surface S, the thickness of the protective layer 5 may be adjusted according to the size of the object to be polished. For example, when the thickness of the protective layer 5 is increased, the rigidity becomes high and suitable for a large object to be polished, but a small (small diameter) object to be polished may cause a decrease in retention. Moreover, when the thickness of the protective layer 5 exceeds 100 micrometers, even a 3 m class large-sized to-be-polished object may fall out from a holding material during grinding | polishing process. Therefore, considering the protection of the skin layer 2a and the adhesion to the object to be polished, the thickness of the protective layer 5 is preferably set in the above-described range.

  Furthermore, in this embodiment, although the example which uses a screen printer for formation of the protective layer 5 and the recessed part 5a was shown, this invention is not restrict | limited to this. Any method may be adopted as long as the protective layer 5 is formed to have a uniform thickness and the concave portion 5a can be formed so as to partially expose the surface of the skin layer 2a. Good. An example of such a method is a transfer method using a gravure printing technique.

  Moreover, in this embodiment, although the polyurethane sheet 2 made from a polyurethane resin was illustrated, this invention is not limited to this. For example, a polyethylene resin or the like may be used as long as it has a cell structure in which a skin layer is formed by a wet coagulation method. In addition, for soft resins, the Japanese Industrial Standard (JIS K6900-1994 Plastic-Terminology) states, “Under specified conditions, the elastic modulus in the bending test, or if it is not applicable, the tensile test, Since it is defined as “plastic not larger than 70 MPa”, any material satisfying this condition may be used.

  Further, although not particularly mentioned in the present embodiment, in order to make the thickness of the polyurethane sheet 2 uniform, a buffing process, a slicing process, or the like is performed on the surface opposite to the skin layer 2a of the polyurethane sheet 2, that is, the back surface side. You may do it. For example, when buffing is performed, a pressure welding jig having a flat surface is pressed against the surface of the film-forming resin after drying on the skin layer 2a side, and irregularities appearing on the back side may be removed by buffing or the like. .

  Next, examples of the holding material 10 manufactured according to the present embodiment will be described. In addition, it describes together about the holding material of the comparative example manufactured for the comparison.

Example 1
In Example 1, a polyurethane sheet 2 having a thickness of 800 μm was formed by a wet coagulation method, and an aqueous chloroprene rubber emulsion was applied to the surface of the skin layer 2a to form a protective layer 5 having a thickness of 50 μm. The protective layer 5 has a diameter of 1.5 mm, and the concave portions 5a are formed on the holding surface S side at a rate of 10 pieces / cm ² to manufacture the holding material 10. In this holding material 10, the coverage of the protective layer 5 is about 82%.

(Comparative Example 1)
In Comparative Example 1, a holding material was manufactured in the same manner as in Example 1 except that the protective layer 5 and the recess 5a were not formed. That is, Comparative Example 1 is a holding material having a conventional skin layer 2a.

(Evaluation)
About the holding material of each Example and a comparative example, to-be-polished material holding | maintenance property was evaluated. The retention property of the object to be polished was measured by the following method. As shown in FIG. 3, the holding material 10 is affixed to a surface plate 81 having a substantially flat surface, and a glass plate 82 of 10 cm long × 10 cm wide is placed on the surface (holding surface S) of the holding material 10. In order to reproduce the holding force with the holding material on the large-sized object to be polished at 60 ° C. in the ashing furnace after placing the weight 83 so that a load of 80 gf / cm ² (784 mN / cm ² ) is applied to Adhesion was improved by sufficiently pressing over 2 hours. The glass plate 82 was pulled in the horizontal (horizontal) direction (arrow A direction in FIG. 3), and the peak value (maximum value) of the tensile force when the glass plate 82 was displaced was measured. The measurement was performed 5 times, and the average value was calculated to evaluate the retention.

  In the holding material of Comparative Example 1 in which the protective layer 5 was not formed, the average tensile strength was 890 N in 3 out of 5 measurements, but the glass plate was broken twice and data could be obtained. There wasn't. This is because the holding material of Comparative Example 1 can hold the glass plate, but the adhesion force between the glass plate and the holding material is too large, so that the removal work after polishing becomes difficult and the glass plate is damaged. It is considered a thing. On the other hand, in the holding material 10 of Example 1 in which the protective layer 5 and the recess 5a are formed on the holding surface S side, the holding property is 638N, which is slightly smaller than the holding material of Comparative Example 1, and evaluation of the holding property. Later, the glass plate was not damaged. Therefore, by forming the protective layer 5 and the recess 5 on the holding surface S side, the rigidity on the surface of the holding material is increased and the adhesion to the object to be polished is limited. It was found that the possibility of breakage was reduced when removing.

  Since the present invention provides a holding material that can secure the holding power to the object to be polished and facilitate the attachment and detachment of the object to be polished, it contributes to the manufacture and sale of the holding material. Have sex.

S Holding surface 2 Polyurethane sheet (resin sheet)
2a Skin layer 2b Nap layer 3 Cell 5 Protective layer 5a Recess 10 Holding material

Claims (7)

A resin sheet made of a soft resin having a skin layer formed by a wet coagulation method and having a number of cells formed on the inner side of the skin layer;
A protective layer disposed on the surface of the skin layer, the surface forming a holding surface for holding an object to be polished and protecting the skin layer;
With
The protective layer is formed of a resin having a greater acid resistance or alkali resistance than the soft resin forming the resin sheet, and a hole or a groove is formed so as to partially expose the surface of the skin layer. A holding material characterized by   The holding material according to claim 1, wherein the protective layer has a coverage of 50% to 99% with respect to the surface of the skin layer.   A hole is formed in the protective layer so as to partially expose the surface of the skin layer, and the hole has a circular shape having a diameter of 2 mm or less, and is uniform in the holding surface. The holding material according to claim 2, wherein the holding material is formed.   2. The retention according to claim 1, wherein the resin constituting the protective layer has a tensile strength retention of 80% or more before and after being immersed in an aqueous sodium hydroxide solution having a liquid temperature of 50 ° C. and a pH of 13 for 1 week. Wood.   2. The retention according to claim 1, wherein the resin constituting the protective layer has a tensile strength retention of 80% or more before and after being immersed in an aqueous hydrochloric acid solution having a liquid temperature of 50 ° C. and a pH of 1.5 for 3 weeks. Wood.   2. The holding material according to claim 1, wherein a thickness of the protective layer is in a range of 1 μm to 100 μm, and a thickness of the resin sheet is in a range of 200 μm to 2000 μm.   The holding material according to claim 6, wherein the resin sheet is made of a polyurethane resin, and the resin forming the protective layer is an elastomer.

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