JP4373152B2 - Polishing sheet - Google Patents

Description

  The present invention relates to a polishing sheet used for a polishing pad or a back pad, and in particular, surface precision polishing for electronic parts such as liquid crystal glass, glass disk, photomask, silicon wafer, CCD cover glass, or glass, aluminum. The present invention relates to a polishing sheet suitable for disk texture, CMP (chemical mechanical polishing) and the like.

Conventionally, a polishing sheet is based on a nonwoven fabric or a woven fabric made of synthetic fibers and synthetic rubber, or a polyester film, and a polyurethane-based solution is applied to the upper surface thereof, and a porous layer having continuous pores by a wet coagulation method. The surface layer is formed and then ground and removed as necessary (hereinafter, the surface of which is ground is expressed as suede) (see, for example, JP-A-11-335979). Such polishing sheets are already widely used from rough polishing for surface precision polishing for electronic parts such as liquid crystal glass, glass disk, photomask silicon wafer, CCD, and cover glass to polishing pads for finishing. However, in recent years, coupled with the development of measuring equipment for precision polishing surfaces, the quality required by users has increased, and there has been a demand for polishing pads that can perform highly accurate precision polishing.
Japanese Patent Laid-Open No. 11-335979

  In order to improve the performance of a polishing pad that performs precision polishing, it is necessary to improve various accuracies such as pad surface or variation in suede opening diameter and flatness (surface irregularities). As a result of various studies on the solution of these problems from the viewpoint of the pore structure inside the pad, the present inventors have found that the size and distribution of the pores in the polishing sheet greatly affect these various accuracies.

  As shown in FIG. 1, the conventional pore structure of the polishing pad by the wet coagulation method is mainly composed of vertically long, honeycomb-like macropores having a pore diameter of the order of several tens to several hundreds of micrometers, and has a pore diameter of several to several tens of micrometers near the surface layer. It has a non-uniform structure in which the following micropores are formed. In particular, macropores greatly affect the accuracy of the opening diameter of the polishing pad surface and the surface irregularities, and adversely affect the surface of the object to be polished. That is, the conventional polishing pad mainly composed of macropores has large surface irregularities, inferior smoothness, large opening diameter and porosity, and large variation. If the porosity is too large, the contact area (land) with the object to be polished becomes small, and therefore a nonuniform and locally large load is generated on the surface of the object to be polished. As a result, in the initial stage of polishing, fine undulation is likely to occur on the surface of the object to be polished at a pitch corresponding to the opening diameter, and the flatness of the object to be polished is poor and it is difficult to obtain a precise surface shape. . Also, in order to obtain a precise surface finish, the polishing pad needs to be fully adapted to the object to be polished. However, the conventional product has large surface irregularities and poor adhesion to the object to be polished. There was a problem that a lot of time was wasted in starting up the pad, work efficiency was poor, and it was difficult to obtain a product with high flatness.

  The present inventors pay attention to the fact that the pore structure depends on the gel point of the polar solvent-soluble polymer material, and by making the vertically elongated honeycomb-like macropores in the conventional polishing pad into micropores and homogenizing them, The present inventors have found that the various accuracies can be improved and that polishing characteristics such as a high polishing rate and a long life can be improved, and the present invention has been completed.

That is, the abrasive sheet of the present invention, the concentration using a polar solvent in the polymer solution 100cc adjusted to 1% by weight, under stirring with 4-bladed agitator, white turbidity is polymer solution dropwise distilled water When the titration amount (ml) at the beginning is the gel point, the porous layer having continuous pores is an abrasive sheet attached to, embedded in, or laminated on at least a part of the substrate, and the porous layer Is made of a polar solvent-soluble polymer material having a gel point of 6 or more, and the average pore diameter is 30 μm or less (Claim 1).

  In the above, the porosity of the porous layer is preferably 0.3 to 0.8.

  The water absorption rate of the porous layer is preferably 0.1 μl / sec or more (Claim 3).

  As the polar solvent-soluble polymer material, a polyurethane-based resin is suitably used, and its 100% modulus is preferably 5 to 50 MPa (Claim 4).

  The porous layer can be obtained by mixing fine powder in a proportion of 5 to 100 parts by weight with respect to 100 parts by weight of the polar solvent-soluble polymer material.

  Further, a hardening material can be attached to the surface and / or the inside of the porous layer so that the hardness of the porous layer can be 80 ° or more (Claim 6).

  In the polishing sheet of the present invention, by forming the porous layer with a polar solvent-soluble polymer material having a gel point of 6 or more, there is substantially no problem of macropores, and the average pore diameter is 30 μm or less. It can consist of pores. Thereby, the variation in the opening diameter of the porous layer can be reduced and the load on the surface of the object to be polished can be made uniform, so that a precise polished surface can be obtained.

  When the porosity of the porous layer is 0.3 to 0.8, the adhesion to the object to be polished is excellent, and the polishing accuracy and durability are good.

  Further, when the water absorption rate of the porous layer is 0.1 μl / sec or more, the retention of the polishing slurry is improved, thereby shortening the startup time of the polishing pad and improving workability.

  In addition, when a polyurethane resin having a 100% modulus of 5 to 50 MPa is used as the polymer material, the polymer material is particularly excellent in terms of wear resistance, compression recovery, stiffness and the like.

  By mixing fine powder as an additive in the polymer material of the porous layer, microporosity can be easily achieved and the polishing characteristics can be improved.

  Even when a curing material is attached to the surface and / or inside of the porous layer of the polishing sheet, the polishing characteristics and the like can be further improved.

  The porous layer of the polishing sheet of the present invention comprises a polar solvent-soluble polymer material having a gel point of 6 or more as described above as an essential component, and an additive such as fine powder is added thereto as necessary. The pores having an average pore diameter of 30 μm or less are formed.

  A polar solvent-soluble polymer material having a gel point of 6 or more is soluble in a polar solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, N-methylpyrrolidone, etc. Although not particularly limited, examples thereof include acrylics such as polyurethane, polyacrylate, and polyacrylonitrile, vinyls such as polyvinyl chloride, polyvinyl acetate, and polyvinylidene fluoride, epoxy, polysulfone, and poly Examples include ether sulfones, phenols, polystyrenes, polyamides, polyesters, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, fluorines thereof, and silicone derivatives. Among them, polyurethane-based, polysulfone-based, polyacrylonitrile-based, polyvinyl chloride-based, and polyamide-based resins are preferable in terms of wear resistance, compression recovery property, and stiffness, and polyurethane-based resins having a 100% modulus of 5 to 50 MPa are particularly preferable. preferable.

  In the present specification, the gelation point refers to a polymer solution obtained by gradually dropping distilled water into 100 cc of a polymer solution adjusted to a concentration of 1% by weight using a polar solvent while stirring with a four-blade stirrer. Is the numerical value of the titer (ml) when white turbidity starts to appear.

  If the gel point is less than 6, macropores are likely to be generated, and a non-uniform structure in which macropores and micropores are mixed is likely to occur. The gel point is preferably higher in terms of reducing the pores in the abrasive sheet, but if it is too high, the pore-forming ability is likely to be lowered, so that it is usually preferably 15 or less.

  By using a polar solvent-soluble polymer material having a gel point of 6 or more as described above, generation of macropores can be suppressed, and fine and uniform pores having an average pore diameter of 30 μm or less can be easily formed. Become. When the average pore diameter exceeds 30 μm, the variation in the opening diameter increases with the increase in the pore diameter, and a non-uniform load is likely to occur on the surface of the object to be polished due to the decrease in the contact area (land) with the object to be polished. In addition, generation of minute undulation and deterioration of flatness are likely to occur, and it becomes difficult to obtain a precise surface shape. The average pore diameter of the pores is preferably from 0.1 to 20 μm, more preferably from 1 to 10 μm, in terms of surface slurry accuracy, polishing slurry retention, polishing rate, and life. Here, the average pore diameter is expressed as a number average value calculated as an equivalent circle diameter by image analysis of a SEM image (magnification 50 to 500 times) of a longitudinal section of a polishing sheet (porous layer) and binarization processing. Is.

Moreover, it is preferable that the porosity of a porous layer is 0.3-0.8. When the porosity is less than 0.3, the compression rate becomes too low, and the adhesion to the object to be polished is deteriorated. When the porosity exceeds 0.8, the aperture ratio becomes large, so that polishing accuracy, durability, and life are likely to be reduced. Here, the porosity is a value calculated from the following equation using the bulk specific gravity calculated from the thickness of the porous layer and the weight per unit area and the true specific gravity calculated from literature and catalog values;
Porosity = 1- (bulk specific gravity / true specific gravity)

  The water absorption rate of the porous layer is preferably 0.1 μl / sec or more. If it is less than 0.1 μl / sec, the penetration of the polishing slurry into the porous layer will be poor, and it will be difficult to hold the polishing slurry in the pores in the pad. As a result, it becomes difficult for the polishing slurry to intervene between the pad and the object to be polished, the polishing efficiency is lowered, the startup time is lengthened, and the working efficiency and the production efficiency are inferior. Here, the water absorption rate is a value obtained by dividing [amount of dripping water (μl) on the polishing sheet surface (μl)] divided by [a time (second) during which the dripping amount of distilled water is completely absorbed in the polishing sheet]. It is.

  By mixing a fine powder as an additive to the polymer material of the porous layer, microporosity can be facilitated and polishing characteristics can be improved. As such fine powders, in inorganic systems, calcium silicates such as carbon, graphite, calcium carbonate, talc, zonotlite group, metal oxides such as ceria, silica, magnesia, alumina, activated carbon, zeolite, crystalline aluminophosphate type Porous inorganic particles with fine pores in particles such as molecular sieve, silica gel, diatomaceous earth, palygoskite, sepiolite, clay compounds such as montmorillonite, bentonite, smectite, vermiculite, kanemite, aluminum hydroxide, magnesium hydroxide, particle surface is hydrophobic Examples thereof include particles having catalytic activity such as oxidized silica, titania, and manganese oxide. Examples of the organic type include melamine type, acrylic type, and benzoguanamine type condensates or cross-linked products.

  The particle size of the fine powder is preferably 300 mesh pass for Tyler mesh and 1 μm or less in average particle size, more preferably 0.1 μm or less. The fine powder having such a particle size can be prepared using a pulverizer such as a ball mill or an attritor.

  Preferable examples of the fine powder include graphite, ceria, silica, alumina, titania, magnesia and the like.

  As a compounding quantity in the case of using the said fine powder, the ratio of 5-100 weight part by solid content ratio with respect to 100 weight part of polar solvent soluble polymeric materials is preferable. If the amount is less than 5 parts by weight, the effects expected from the use of fine powders such as microporosity, improvement in polishing characteristics such as polishing rate and life cannot be obtained sufficiently. If the amount exceeds 100 parts by weight, the effect of microporosity and polishing properties is obtained, but the proportion of the polymer material is too low, and mechanical strength is reduced and brittleness is likely to occur.

  Further, as additives other than the above fine powders, fine short fibers such as potassium titanate, mineral fiber, ceramic fibers, glass fibers, carbon fibers, activated carbon fibers, whiskers, silicones, fluorocarbons, long chain fatty acid salts , Long-chain amine salt-based water and / or oil repellents, pigments, surfactants, metal salts, isocyanate-based, amine-based cross-linking agents, ketones, alcohols, other polar solvents such as water, xylene And nonpolar solvents such as toluene. Control of micropores becomes easier by mixing these other polar solvents, nonpolar solvents and surfactants and adjusting the mixing ratio.

  Moreover, a hardening | curing material can be attached to the porous layer surface and / or inside of the polishing sheet of the present invention, and the hardness of the porous layer can be increased to 80 ° or more to further improve the polishing characteristics. Examples of such a curing material include thermosetting resins such as melamine, urea, and phenol, polymethyl methacrylate, high styrene SBR, high modulus polyurethane, and cross-linked products thereof. In order to attach these curing materials to the surface and / or inside of the porous layer, these curing materials are made into a liquid state by emulsification or dissolution, and coated on the surface of the porous layer, or impregnated to the inside, and then the curing material. It may be cured by heating or the like according to need.

  As a base material used for the polishing sheet of the present invention, a fabric such as cotton, rayon, polyamide, polyester, polyacrylonitrile, or a woven or non-woven fabric made of a mixture thereof, or impregnated with a resin such as synthetic rubber or polyurethane. Sheets obtained in this manner, or polymer films such as polyester and polyolefin are not limited thereto.

The polishing sheet of the present invention is a slurry in which the polar solvent-soluble polymer material, the polar solvent, and an additive used as necessary are mixed, and is attached to or embedded in at least a part of the substrate by coating or laminating, It is obtained by laminating. Although the adhesion amount of the mixture to the base material is not particularly limited, 20 to 2000 g / m ² in terms of solid content is preferable.

  More specifically, a slurry in which a polymer material is dissolved in a polar solvent and an additive is mixed as necessary is coated or impregnated on a substrate sheet such as a polymer film such as polyester or polyolefin, a nonwoven fabric, or a fabric. Can be produced by forming a continuous porous layer on the surface or inside of the sheet by wet coagulation, washing with water, drying, and grinding the skin layer as necessary. Alternatively, the slurry is coated on a substrate such as a film, a water repellent treatment, a fabric coated with a resin coating, and a continuous porous layer is formed by a wet coagulation method. After washing with water and drying, the porous layer is peeled off, After the obtained porous layer is laminated on a base material such as a nonwoven fabric, a woven fabric, or a film to form a composite, it can be produced by grinding the skin layer as necessary.

  Examples of the method for applying the polar solvent-soluble polymer slurry to the substrate include a roll coater, a knife over roll coater, and a die coater. In addition, as a coagulation liquid for forming a porous layer by a wet coagulation method, a solvent that has an affinity for a polar solvent such as DMF but does not dissolve a polymer material, such as water or a mixed solution of water and a polar solvent. Is used. In particular, in order to form a homogeneous microporous layer, a coagulating liquid having a polar solvent concentration in the range of 10 to 60% by weight is preferable.

  In the polishing sheet of the present invention obtained as described above, pores having an average pore diameter of 30 μm or less were uniformly distributed as shown in the electron micrographs of FIGS. 2 and 3 (partially enlarged photo of FIG. 2). It has a porous layer.

  In order to remove the skin portion of the porous layer, sandpaper, a method of scratching with a needle, a method of making a hole with a needle, a method of partially transferring DMF using a gravure roll and dissolving the skin, etc. are used. be able to.

  Further, the surface of the polishing sheet of the present invention can be subjected to processing such as grooving and embossing as conventionally performed, and the back surface can be subjected to adhesive processing or laminated with a cushioning material or the like. can do.

[Example 1]
A polyurethane film (U-6455D manufactured by Toray Cortex Co., Ltd., 30% solids) dissolved in N, N-dimethylformamide having a gel point of 9 is coated on a polyester film having a thickness of 100 μm, and then wet coagulated. Based on this method, a porous layer was formed, washed with water and dried to obtain a polishing sheet having a thickness of 0.6 mm. The average pore diameter of the pores in the porous layer was 7 μm, and the porosity was 0.65.

[Example 2]
Polyurethane dissolved in N, N-dimethylformamide having a gel point of 14 (U-17204D manufactured by Toray Cortex Co., Ltd., solid content 35%) and dry silica having a primary average particle size of 0.012 μm (Japan) Aerosil Co., Ltd. 200) was mixed at a solid content ratio of 100 parts by weight of the former to 6 parts by weight of the latter to prepare a mixed slurry. After this mixed slurry was coated on a polyester film having a thickness of 100 μm, a porous layer was formed based on a wet coagulation method, washed with water, and dried to obtain a polishing sheet having a thickness of 0.5 mm. The average pore diameter of the pores in the porous layer was 3 μm, and the porosity was 0.54.

[Example 3]
A polyurethane solution (U-5561 manufactured by Toray Cortex Co., Ltd., solid content 25%) dissolved in N, N-dimethylformamide having a gel point of 7 is placed on a polyester nonwoven fabric fixed with a synthetic rubber having a thickness of 1 mm. After coating, a porous layer was formed based on a wet coagulation method, washed with water, and dried to obtain a polishing sheet having a thickness of 2 mm. The average pore diameter of the pores in the porous layer was 20 μm, and the porosity was 0.72. Furthermore, an aqueous solution of melamine resin was impregnated from the surface of the porous layer and dried, so that 50 g / m ² of melamine resin in solid content was attached to the surface and inside of the porous layer.

[Example 4]
Carbon black having 25% solution of polyurethane (U-6455D manufactured by Toray Cortex Co., Ltd., 30% solids) dissolved in N, N-dimethylformamide having a gel point of 9 and 22% by weight solids 20 parts by weight and 10 parts by weight of xylene were mixed to prepare a mixed slurry. After this mixed slurry was coated on a polyester film having a thickness of 100 μm, a porous layer was formed based on a wet coagulation method, washed with water, and dried to obtain a polishing sheet having a thickness of 0.5 mm. The average pore diameter of the pores in the porous layer was 5 μm, and the porosity was 0.48.

[Example 5]
100 parts by weight of 25% solution of polyurethane (U-17204D manufactured by Toray Cortex Co., Ltd., solid content 35%) dissolved in N, N-dimethylformamide having a gel point of 14, 1 part by weight of an anionic surfactant, 20 parts by weight of carbon black and 20 parts by weight of methyl ethyl ketone were mixed to prepare a mixed slurry. After coating this mixed slurry on a polyester film having a thickness of 100 μm, a porous layer was formed based on a wet coagulation method, washed with water, and dried to obtain a polishing sheet having a thickness of 1 mm. The average pore diameter of the pores in the porous layer was 1 μm, and the porosity was 0.6.

[Comparative Example 1]
A polyurethane film (CS-6080D manufactured by Toray Cortex Co., Ltd., 30% solids) dissolved in N, N-dimethylformamide having a gel point of 5 is coated on a polyester film having a thickness of 100 μm, followed by wet coagulation. A porous layer was formed based on the method, washed with water, and dried to obtain a polishing sheet having a thickness of 0.7 mm. The pores in the porous layer had a vertically long shape, an average pore diameter of 120 μm, and a porosity of 0.89.

The polishing sheets obtained in Examples 1 to 5 and Comparative Example 1 were ground and removed from the surface by a 320th sandpaper, the surface roughness was measured according to JIS 1994, and the hardness was measured according to JIS K6301. It was measured. Furthermore, 50 μl of distilled water was dropped on the surface of the polishing sheet, and the time (seconds) during which this distilled water was completely absorbed inside the polishing sheet was measured, and the water absorption rate was determined from the result. The results are shown in Table 1.

  From Table 1, it can be seen that the surface roughness of the polishing sheet of the present invention is an order of magnitude smaller than that of the conventional one, and the surface accuracy is extremely excellent.

  The polishing sheet of the present invention is suitable as a polishing pad or the like for surface precision polishing for electronic parts such as liquid crystal glass, glass disk, photomask, silicon wafer, CCD cover glass, or texture of glass, aluminum disk, CMP, etc. Used.

It is an electron micrograph which shows the pore structure of the porous layer of the conventional polishing sheet. It is an electron micrograph which shows the pore structure of the porous layer of the polishing sheet of this invention. 3 is an electron micrograph showing a part of the pore structure of the porous layer of the polishing sheet of the present invention shown in FIG.

Claims (6)

A porous layer having continuous pores is an abrasive sheet that is attached to, embedded in, or laminated on at least a part of a substrate,
Titration volume (ml) when the polymer solution starts to become cloudy by dripping distilled water into 100 cc of the polymer solution adjusted to 1% by weight with a polar solvent while stirring with a 4-blade stirrer A polishing sheet , wherein the porous layer is made of a polar solvent-soluble polymer material having a gel point of 6 or more, and the average pore diameter is 30 μm or less.   The polishing sheet according to claim 1, wherein the porosity of the porous layer is 0.3 to 0.8.   The abrasive sheet according to claim 1 or 2, wherein the water absorption rate of the porous layer is 0.1 µl / sec or more.   The abrasive sheet according to any one of claims 1 to 3, wherein the polar solvent-soluble polymer material is a polyurethane-based resin and a 100% modulus thereof is 5 to 50 MPa.   The porous layer is formed by mixing fine powder in a proportion of 5 to 100 parts by weight with respect to 100 parts by weight of the polar solvent-soluble polymer material. The polishing sheet according to claim 1.   The abrasive sheet according to any one of claims 1 to 5, wherein a curing material is attached to the surface and / or the inside of the porous layer, and the hardness of the porous layer is 80 ° or more.