JP2009090454A - Method for producing abrasive cloth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive cloth suitably used in performing finish polishing process to an aluminum alloy substrate used in a magnetic recording disc and a glass substrate with super high precision, which has excellent processing stability in a polishing process and exhibiting excellent conductivity at the time of producing the abrasive cloth. <P>SOLUTION: In a method for producing an abrasive cloth, after superposing fibers capable of forming ultrafine fibers (A) having a single fiber fineness of 1.0×10<SP>-6</SP>to 0.05 dtex on woven fabric to unify them with a punching treatment, a treatment for applying a polymer elastic body, an utrafine fiber forming treatment, and a raising treatment, are carried out, wherein yarns of the woven fabric is the fibers capable of forming ultrafine fibers (B) having a single fiber fineness of less than that of the ultrafine fibers (A). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is excellent in processing stability and dimensional stability when manufacturing a polishing cloth, which can be suitably used when polishing an aluminum alloy substrate used for a magnetic recording disk and a glass substrate with an ultra-high precision finish. The present invention relates to a method for producing an abrasive cloth.

  2. Description of the Related Art In recent years, magnetic recording media such as magnetic disks have a tendency that the flying height of a magnetic head is remarkably reduced with an increase in capacity and storage density. Therefore, if there are protrusions on the magnetic disk surface, the magnetic head and the protrusions come into contact with each other, causing a head crash, and scratching the disk surface. Even a very small protrusion that does not cause a head crash causes an error that occurs when reading and writing information due to contact with the magnetic head.

  Conventionally, the disk surface after slurry grinding with a polishing pad made of hard polyurethane foam or the like has many scratches and minute protrusions and has low smoothness, so that loose abrasive particles are adhered to the surface of the polishing cloth. In addition, processing using a tape-like non-woven fabric or woven fabric is performed to improve smoothness. Specifically, in a state where the aluminum alloy substrate or the glass substrate is continuously rotated, while the tape-like polishing cloth is pressed against the substrate, it is reciprocated in the radial direction of the substrate to continuously run the polishing tape. . At this time, the slurry is supplied between the polishing tape and the substrate, and the free abrasive grains contained in the slurry are held in a state of being finely dispersed in the fibers on the surface of the polishing tape and pressed against the substrate for polishing. ing.

  Recently, as the recording method of magnetic recording disks has shifted from the conventional longitudinal recording method to the perpendicular recording method, there has been an increasing demand for improving the smoothness of the substrate surface. In addition to the slurry grinding used, a cleaning process using no slurry has been performed. When polishing is performed by slurry grinding and / or cleaning using a tape-like polishing cloth, a substrate of 0.2 nm or less is required in order to cope with the recent increase in recording density for rapidly increasing recording capacity. There is a demand for achieving surface roughness and minimizing scratches on the substrate surface called scratch defects.

  In order to reduce the substrate surface roughness, a proposal has been made to obtain cushioning properties by imparting an elastic polymer to the nonwoven fabric in order to minimize the fibers constituting the nonwoven fabric and minimize scratches on the substrate surface ( Patent Documents 1 to 4). Recently, a polishing cloth in which nanofiber-level ultrafine fibers are dispersed on the surface has achieved a reduction in substrate surface roughness to the limit and an improvement in scratch performance (Patent Document 5).

However, due to recent improvements in the accuracy of polishing processing, the shape retention characteristics of the polishing tape have come to be regarded as important. If the polishing tape has insufficient tensile strength at the time of polishing, there is a problem called “necking” in which the tape stretches, and the length and width of the tape polishing surface change, leading to uneven processing. Further, as the constituent fiber fineness decreases, the processing stability at the time of processing for generating ultrafine fibers tends to decrease. To deal with these problems, as a conventional technique for manufacturing artificial leather, a technique in which a nonwoven fabric and a woven or knitted fabric are entangled and integrated with a needle has been mainly used in order to provide the sheet with form stability. However, in the entanglement of the fibers with the needle, it is unavoidable that the fibers constituting the fabric are exposed to the polishing surface due to the hooking of the woven fibers by the needle barb, and the polishing performance is deteriorated. Therefore, a method capable of solving the problem has been desired.
Japanese Patent Laid-Open No. 2001-1252 JP 2002-273650 A JP-A-6-272114 Japanese Patent No. 3457478 JP 2007-144614 A

  An object of the present invention is to provide an aluminum alloy substrate used for a magnetic recording disk and a glass substrate that can be suitably used for polishing with an ultra-high precision finish. An object of the present invention is to provide an abrasive cloth having excellent process passability.

The present invention employs the following means in order to solve such problems. That is,
(1) A fiber capable of generating an ultrafine fiber (A) having an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex and a woven fabric are stacked and entangled and integrated to give an elastic polymer. In the manufacturing method of the polishing cloth that performs the treatment, the ultrafine fiber generation processing and the raising process, the weft of the woven fabric is a fiber capable of generating ultrafine fibers (B) having an average single fiber fineness equal to or less than the ultrafine fibers (A). A method for producing a polishing cloth.

  (2) The method for producing an abrasive cloth according to (1) above, wherein the warp and the weft constituting the woven fabric in the abrasive cloth are strongly twisted yarns in the range of 500 T / m to 4000 T / m.

  (3) The production of the polishing cloth according to (1) or (2), wherein the average single fiber fineness of the warp constituting the woven fabric in the polishing cloth is in the range of 0.3 dtex to 3.0 dtex. Method.

  (4) The method for producing an abrasive cloth according to any one of (1) to (3), wherein the total fineness of the warp and the weft constituting the woven fabric in the abrasive cloth is in the range of 20 dtex to 120 dtex. .

  ADVANTAGE OF THE INVENTION According to this invention, the polishing cloth which is excellent in the process stability at the time of grinding | polishing processing, and the process passability at the time of polishing cloth manufacture can be provided.

In order to solve the above problems, that is, the processing stability during polishing and the process passability during the production of polishing cloth, the present invention provides an ultrafine fiber having an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex (A ) In a method for producing an abrasive cloth, in which an elastic polymer is applied, an ultrafine fiber generation processing process and a raising process are performed after a fiber and a fabric capable of generating) are punched and integrated by entanglement. In addition, it was investigated that an abrasive cloth having the above characteristics can be obtained by using a fiber capable of generating an ultrafine fiber (B) having an average single fiber fineness equal to or less than that of the ultrafine fiber (A).

  The method for producing an abrasive cloth of the present invention can be obtained, for example, by combining the following steps. That is, a process of producing a nonwoven fabric or a web with a composite fiber using a polymer having different solubility in two or more solvents, and a woven fabric using a composite fiber using a polymer having different solubility in two or more solvents as a weft. A step of producing, a step of producing a sheet-like material in which the composite fiber nonwoven fabric or web is entangled by punching the woven fabric, and an elastic polymer is imparted to the sheet-like material, and the elasticity A step of substantially solidifying and solidifying the polymer, a step of raising the surface by applying a raising treatment, and a step of generating ultrafine fibers by dissolving and removing the easily soluble polymer from the composite fiber.

  In the present invention, “woven fabric” means a woven fabric before being entangled and integrated with a nonwoven fabric or web, and “woven fabric in an abrasive cloth” is entangled and integrated and subjected to processing for generating ultrafine fibers. It means that which is a part of the polishing cloth as a reinforcing layer.

Since it is difficult to obtain ultrafine fibers (A) having an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex by direct spinning, in the method for producing an abrasive cloth of the present invention, a composite capable of generating ultrafine fibers is used. After manufacturing a web (nonwoven fabric) from the fibers and intertwining with the woven fabric, it is necessary to go through a process of generating ultrafine fibers from the composite fibers. Similarly, it is difficult to obtain the ultrafine fiber (B) having an average single fiber fineness of the ultrafine fiber (A) or less by direct spinning, so that the woven fabric is composed of wefts using composite fibers capable of generating ultrafine fibers. It is necessary to go through a process of generating ultrafine fibers from this composite fiber.

  In the present invention, the ultrafine fibers (A) and (B) constituting the polishing cloth can be obtained from a sea-island composite fiber, a split composite fiber, or the like, or can be obtained from a polymer alloy fiber. When obtained from a polymer alloy fiber, the polymer alloy fiber that is a precursor of the ultrafine fiber is a sea-island type composite fiber obtained by using a polymer alloy melt obtained by alloying polymers having different solubility in two or more solvents. It is preferable. In this polymer alloy fiber, it is important that the easily soluble polymer forms the sea (matrix) and the hardly soluble polymer forms the island (domain), and the island size is controlled. Here, the island size is a value obtained by observing the cross section of the polymer alloy fiber with a TEM and evaluating it in terms of diameter. The kneading of the polymer to be alloyed is very important and is preferably highly kneaded by a kneading extruder or a stationary kneader. Specifically, the standard for kneading depends on the polymer to be combined, but when using a kneading extruder, it is preferable to use a biaxial extrusion kneader, and when using a static kneader, The number of divisions is preferably 1 million or more.

In order to make the island domain close to a circle, the combination of polymers is also important. It is preferable that the island component polymer and the sea component polymer are incompatible, but it is difficult for the island component polymer to be sufficiently finely dispersed by a combination of simple incompatible polymers. For this reason, it is preferable to optimize the compatibility of the polymer to be combined. One of the indexes for this purpose is the solubility parameter (SP value). Here, the SP value is a parameter that reflects the cohesive strength of substances defined by (evaporation energy / molar volume) ^1/2 , and a polymer alloy having good compatibility can be obtained between those having close SP values. There is. The SP value is known for various polymers, and is described, for example, in “Plastic Data Book”, edited by Asahi Kasei Amidus Corporation / Plastics Editorial Department, page 189. It is preferable that the difference between the SP values of the two polymers is 1 to 9 (MJ / m ³ ) ^{1/2 because} it is easy to achieve both rounding of the island component due to incompatibility and ultrafine dispersion. For example, nylon 6 and polyethylene terephthalate have a SP value difference of about 6 (MJ / m ³ ) ^1/2, which is a preferable example, but nylon 6 and polylactic acid (PLA) also have a SP value difference of 2 ( MJ / m ³ ) ^1/2 , which can be cited as a preferred example. On the other hand, nylon 6 and polyethylene have an SP value difference of about 11 (MJ / m ³ ) ^1/2, which is an unfavorable example.

  Furthermore, the melt viscosity is also important. If the melt viscosity of the polymer that forms the islands is set lower than that of the sea, the island polymer is likely to be deformed by shearing force. From the viewpoint of However, if the island component polymer is excessively low in viscosity, it tends to be seamed and the blend ratio with respect to the whole fiber cannot be increased.

  In the method for producing an abrasive cloth of the present invention, the method for obtaining a nonwoven fabric composed of composite fibers is not particularly limited, but short fiber nonwoven fabrics, long fiber nonwoven fabrics, nonwoven fabrics obtained by papermaking, etc. can be used. The form is not particularly limited.

  The woven fabric used in the present invention is required to be a fiber capable of generating at least an ultrafine fiber (B) having an average single fiber fineness equal to or less than the ultrafine fiber (A) used for the polishing surface. Using the same soluble polymer as the composite fiber that can generate ultrafine fibers on the polished surface, the ultrafine fibers of the nonwoven fabric (polished surface) and the woven fabric (reinforcing layer) can be generated simultaneously during the ultrafine fiber generation processing. And from the viewpoint of cost. Since the warp of the fibers constituting the woven fabric is subjected to a conveying stress at the time of sheet processing, it is difficult to be damaged by the needle in the needle punching process. There is a high possibility that damaged fibers are exposed on the surface of the ultrafine fibers. However, by setting the weft fiber of the woven fabric as a composite fiber capable of generating an ultrafine fiber having an average single fiber fineness of the ultrafine fiber (A) or less, a part of the weft fiber is damaged by the needle barb, so that the entangled integral Even if it is exposed on the surface at the time of forming, after the ultrafine fiber generation treatment, the ultrafine fiber (A) and the ultrafine fiber (B) having an average single fiber fineness below the ultrafine fiber (A) are present on the polished surface. Since it is exposed, the polishing performance is not greatly affected. Moreover, you may use the composite fiber which can generate | occur | produce the ultrafine fiber (B) of the average single fiber fineness below an ultrafine fiber (A) not only for a weft but for a warp.

  For the punching process in which a composite fiber non-woven fabric or web is produced using a composite fiber and integrated with the woven fabric, a normal punching method and its apparatus can be used. However, from the viewpoint of entanglement integration and densification, the needle It is preferable to use a punch method. The felt needle used for the needle punching process and the punching conditions are not particularly limited, and normal equipment and conditions can be used.

  Further, not only the needle punch method but also a known punching method such as a water jet punch method can be used, and these methods can be appropriately combined.

The number of punches in the needle punching process is preferably 500 to 8000 / cm ² from the viewpoint of achieving a dense surface state by highly entangled fibers and fabrics. By setting the number of punching to 500 / cm ² or more, denseness can be obtained, and high-precision finishing can be obtained. By setting the number of punching to 8000 / cm ² or less, deterioration of workability, fiber damage, and strength reduction can be prevented.

  Moreover, when performing a water jet punching process, it is preferable to perform water in the state of a columnar flow. In order to obtain a columnar flow, generally, a method of ejecting from a nozzle having a diameter of 0.05 to 1.0 mm at a pressure of 1 to 60 MPa is suitably used.

  From the viewpoint of densification, the sheet-like material thus obtained is preferably shrunk by dry heat or wet heat, or both, and further densified.

  The method for producing an abrasive cloth of the present invention requires a treatment for imparting an elastic polymer. The elastic polymer is preferably applied before the non-woven fabric and the weft made of the composite fiber are subjected to ultrafine fiber generation processing. Due to the binder effect of the elastic polymer, it is possible to prevent the ultrafine fibers from falling off the polishing cloth and to give the polishing cloth cushioning properties.

  Although there is no particular limitation on the elastic polymer to be used, N, N'-dimethylformamide, dimethyl sulfoxide, or the like can be preferably used as a solvent used for imparting the elastic polymer. Further, as such an elastic polymer, an aqueous polyurethane dispersed as an emulsion in water may be used. The elastic polymer is applied to the non-woven fabric by immersing the non-woven fabric in an elastic polymer solution dissolved in a solvent, and then dried to substantially solidify and solidify the elastic polymer. In drying, you may heat at the temperature which does not impair the performance of a nonwoven fabric and an elastic polymer.

  In the manufacturing method of the polishing cloth of the present invention, it is necessary to raise the surface (polishing surface). The raising treatment of the polishing cloth is not particularly limited, but the buffing treatment is preferable. The buffing treatment here is generally performed by a method of grinding the surface using a sandpaper or a roll sander. In particular, by raising the surface with sandpaper, uniform and dense raising can be formed. Furthermore, in order to form uniform raising on the surface of the polishing pad, it is preferable to reduce the grinding load. In order to reduce the grinding load, it is preferable to appropriately adjust the number of buff stages, sandpaper count, and the like. Among these, it is more preferable that the number of buff stages is multistage buffing of 3 or more stages, and the sandpaper used for each stage is in the range of 150 to 600 in the JIS standard.

  The method of developing ultrafine fibers from a composite fiber, that is, ultrafine fiber generation processing, varies depending on the type of component to be removed (sea component composed of an easily soluble polymer), but if it is a polyolefin such as polyethylene or polystyrene, toluene or In the case of an organic solvent such as trichlorethylene, PLA, or a copolyester, a method of immersing and constricting with an alkaline aqueous solution such as sodium hydroxide can be preferably used. In addition, the ultrafine fiber generation processing in the manufacturing method of the polishing cloth of the present invention may be performed after raising the polishing surface (after raising treatment) or before raising the polishing surface (before raising treatment). May be.

  Moreover, the apparatus used for ultrafine fiber generation processing is not particularly limited, and it is possible to use a known apparatus such as a continuous dyeing machine, a vibro-washer type seawater removal machine, a liquid dyeing machine, a Wins dyeing machine, a jigger dyeing machine or the like. it can. In addition, when the fiber which can generate | occur | produce an ultrafine fiber is a split fiber, it can also be made ultrafine by a physical process.

  In addition, you may give a dyeing process. In principle, the dyeing process is performed after the ultrafine fiber generation processing, but may be performed before the ultrafine fiber generation process when the fiber capable of generating the ultrafine fiber is a split fiber.

  As a method of performing polishing using the polishing cloth obtained by the production method of the present invention, the polishing cloth is cut into a tape of 30 to 50 mm width from the viewpoint of processing efficiency and stability, and polishing is performed. Used as a tape.

  A method of polishing an aluminum alloy magnetic recording disk using the polishing tape and a slurry containing loose abrasive grains is a preferable method. As a polishing condition, a slurry in which high-hardness abrasive grains such as diamond fine particles are dispersed in an aqueous dispersion medium is preferably used. From the viewpoints of retention and dispersibility of the abrasive grains, the abrasive grain size suitable for the ultrafine fibers constituting the polishing cloth obtained by the production method of the present invention is preferably 0.2 μm or less.

  Hereinafter, the polishing cloth obtained by the production method of the present invention will be described in detail.

In the present invention, the ultrafine fibers (A) and (B) refer to fibers having an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex, and in terms of form, the single fibers are dispersed apart. Although it occupies most, it is a general term for all of single fibers that are partially bonded or aggregates of a plurality of single fibers. The fiber length and cross-sectional form are not limited.

  Here, the average value of the single fiber diameter is determined by the following method. That is, the cross section of the polishing cloth containing the ultrafine fibers (A) and (B) is observed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and the ultrafine fibers randomly extracted within the same cross section. The diameters of 50 single fibers (A) and (B) are measured. In the measurement, a cross-sectional photograph of the polishing cloth by TEM or SEM is used to determine the diameter of single fibers using image processing software (WINROOF). This is performed at three locations, and the diameter of a total of 150 single fibers is determined. It is obtained by measuring and calculating an average value. When the ultrafine fiber constituting the polishing cloth has an irregular cross section, the cross sectional area of the single fiber is first measured, and the area is assumed to be the area when the cross section is a circle. The diameter of the single fiber is obtained by calculating the diameter from the area.

  Moreover, the average value of single fiber fineness is calculated | required as follows. First, the diameter of the single fiber is measured in nm to the first decimal place, the average value of 150 is obtained, and the decimal places are rounded off. The average single fiber fineness is calculated from the average single fiber diameter and the polymer density.

In the present invention, the ultrafine fibers (A) and (B) are required to have an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex (corresponding to a single fiber diameter of 10 to 2400 nm). More preferably, it is the range of 1.0 * 10 < ^-5 > -0.01 dtex. In the present invention, the average single fiber fineness of the ultrafine fibers (B) needs to be the same as or less than the average single fiber fineness of the ultrafine fibers (A), but is preferably the same.

  In the present invention, examples of the polymer constituting the ultrafine fibers (A) and (B) include polyesters, polyamides, polyolefins, polyphenylene sulfides (PPS), and the like. Polycondensation polymers represented by polyesters and polyamides have a melting point. Many are more preferable. Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, and potytrimethylene terephthalate. Specific examples of the polyamide include nylon 6, nylon 66, nylon 12, and the like. Further, the polymer may contain additives such as particles, flame retardants, and antistatic agents, and other components may be copolymerized as long as the properties of the polymer are not impaired. Moreover, it is preferable to use the same polymer for the ultrafine fibers (A) and (B) from the viewpoint of influence on the polishing performance.

The polishing cloth obtained by the production method of the present invention has an average single fiber fineness of 0.05 dtex or more in addition to the ultrafine fibers (A) that mainly form the polishing surface from the viewpoint of strength reinforcement and cushioning improvement. You may mix and use the ultra fine fiber which consists of polyamides, such as nylon 6, nylon 66, nylon 12, and copolymer nylon. However, the mixing amount is preferably 30% by weight or less, more preferably 10% by weight or less based on the total fiber weight of the ultrafine fibers (A) from the viewpoint of the smoothness of the surface of the polishing cloth.
In the present invention, as a reinforcing layer, a woven fabric is entangled and integrated with a nonwoven fabric or a web from the viewpoint of suppressing processing unevenness due to tape elongation during polishing and generation of scratch defects.

  In the present invention, the warp and weft constituting the woven fabric in the polishing cloth are preferably strongly twisted yarns having a twist number in the range of 500 T / m to 4000 T / m. The range of 1000 T / m or more and 4000 T / m or less is more preferable, and the range of 2000 T / m or more and 3000 T / m or less is more preferable. It is preferable that the number of twists is 500 T / m or more because fiber damage due to needle punching is suppressed and the product strength is unlikely to decrease. Setting the number of twists to 4000 T / m or less is preferable because it prevents the fibers from becoming hard and suppresses the hardening of the texture. Further, the number of twists of the weft is not particularly limited, but the number of twists similar to the warp is a preferable range.

In the present invention, the average single fiber fineness of the warp fibers constituting the woven fabric in the polishing cloth is preferably in the range of 0.3 dtex or more and 3.0 dtex or less. It is preferable to set it to 0.3 dtex or more because not only sufficient strength can be obtained in the resulting polishing cloth, but also minimum workability can be obtained in punching. Moreover, since it can suppress the unevenness | corrugation of polishing cloth by setting it as 3.0 dtex or less, it is preferable.
Further, the total fineness of the warp and weft constituting the woven fabric in the polishing cloth is preferably in the range of 20 dtex to 120 dtex. By setting it to 20 dtex or more, sufficient strength as an abrasive sheet can be maintained, and setting it to 120 dtex or less is preferable because it can suppress an increase in thickness beyond necessity. As the yarn type, a spun yarn, a filament yarn, a release reel, and the like can be used as appropriate.

  The weaving density of the woven fabric in the polishing cloth is preferably in the range of 10 / cm to 80 / cm for both the warp and the weft. It is preferable that the weave density is 10 pieces / cm or more because misalignment can be suppressed and appropriate dimensional stability can be obtained. By setting it to 80 / cm or less, since the softness | flexibility of the whole polishing sheet is obtained and the fabric weight is suppressed, it is preferable.

  In the present invention, the polishing cloth needs to be provided with an elastic polymer from the viewpoint of cushioning properties. Examples of the elastic polymer include polyurethane, polyurea, polyurethane-polyurea elastomer, polyacrylic resin, acrylonitrile, A butadiene elastomer, a styrene / butadiene elastomer, or the like can be used. Among these, polyurethane elastomers such as polyurethane and polyurethane / polyurea elastomer are preferable.

  Polyurethanes can use polyester-based, polyether-based, polycarbonate-based diols, or copolymers thereof for the polyol component. Moreover, as a diisocyanate component, aromatic diisocyanate, alicyclic isocyanate, aliphatic isocyanate, etc. can be used.

  The weight average molecular weight of the polyurethane is preferably 50,000 to 300,000, more preferably 100,000 to 300,000, and still more preferably 150,000 to 250,000. By setting the weight average molecular weight to 50,000 or more, it is possible to maintain the strength of the obtained sheet-like material and to prevent the ultrafine fibers from falling off. Moreover, by setting it as 300,000 or less, the increase in the viscosity of a polyurethane solution can be suppressed and it can make it easy to impregnate a nonwoven fabric.

  In addition, the elastic polymer preferably uses polyurethane as a main component, but as long as it does not impair the performance and the uniform dispersion state of ultrafine fibers, the binder is an elastomer resin such as polyester, polyamide or polyolefin, acrylic resin, An ethylene-vinyl acetate resin or the like may be included. Furthermore, additives such as a colorant, an antioxidant, an antistatic agent, a dispersant, a softening agent, a coagulation adjusting agent, a flame retardant, an antibacterial agent, and a deodorant may be blended as necessary.

  In the present invention, the content of the elastic polymer in the polishing cloth is preferably 5% by weight or more and 200% by weight or less with respect to the total fiber weight of the polishing cloth. The surface state, cushioning properties, hardness, strength, etc. of the polishing cloth can be appropriately adjusted depending on the content. When the amount is 5% by weight or more, fiber dropping can be reduced, and when the amount is 200% by weight or less, processability and productivity are improved, and a state in which ultrafine fibers are uniformly dispersed on the surface can be obtained. Preferably it is the range of 20-100 weight%, More preferably, it is the range of 30-80 weight%.

When a dimensional change occurs when the polishing cloth obtained by the production method of the present invention is subjected to polishing processing in a tape shape, the substrate surface cannot be uniformly polished. Therefore, from the viewpoint of shape stability of the polishing cloth in the present invention, the total basis weight of the polishing pad is preferably set to 100 to 600 / ^{m 2,} and more preferably set to 150 to 300 g / ^{m 2.} From the same viewpoint, in the present invention, the polishing cloth preferably has a thickness in the range of 0.1 to 10 mm, and more preferably in the range of 0.3 to 2 mm. The density of the polishing cloth is not particularly limited, but a range of 0.1 to 0.9 g / cm ³ is suitable for obtaining uniform workability.

  In order to perform uniform processing without causing necking or the like during polishing, the tensile strength in a wet state of the polishing cloth is preferably 60 N / cm or more, and more preferably 100 N / cm or more. In order to improve the tensile strength in a wet state, the fineness and woven density of the woven fabric and the type and amount of the elastic polymer contained in the polishing cloth may be adjusted.

In the polishing cloth obtained by the production method of the present invention, it is preferable that fibers of a woven fabric having a fineness greater than that of the ultrafine fibers are not exposed on the polishing surface, that is, the ultrafine fiber surface. The number of exposed fabric fibers is preferably 0 to 1/100 cm ² on the polished surface where the ultrafine fibers are present, and more preferably not observed at all. In the method for producing an abrasive cloth of the present invention, as described above, it is possible to generate ultrafine fibers (B) having an average single fiber fineness equal to or less than the average single fiber fineness of the ultrafine fibers (A) on the polished surface on the wefts that are likely to be exposed. Therefore, even if the woven fiber is exposed on the surface, the final fine fiber (B) is equal to or less than the average single fiber fineness of the ground fine fiber (A), which greatly affects the polishing performance. Is not given.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. The evaluation methods used in the examples and the measurement conditions will be described below.

(1) Polymer melt viscosity
The melt viscosity of the polymer was measured with a capillarograph 1B manufactured by Toyo Seiki Seisakusho. The polymer storage time from sample introduction to measurement start was 10 minutes.

(2) Melting point
Using a Perkin Elmaer DSC-7, the peak top temperature indicating the melting of the polymer at 2nd run was taken as the melting point of the polymer. At this time, the rate of temperature increase was 16 ° C./min, and the sample amount was 10 mg.

(3) Weight average molecular weight of PLA Tetrahydrofuran was mixed with the chloroform solution of the sample to obtain a measurement solution, which was measured at 25 ° C. using a gel permeation chromatograph (GPC) Waters 2690 manufactured by Waters, and calculated in terms of polystyrene. . Three points were measured for each sample, and the average value was defined as the weight average molecular weight.

(4) Cross-sectional observation of polishing cloth by TEM The polishing cloth is embedded with an epoxy resin, an ultra-thin section is cut out in the cross-sectional direction, and an ultrafine fiber (A) in the cross-section of the polishing cloth with a transmission electron microscope (TEM). , (B) was observed. Moreover, the metal dyeing | staining was given as needed.
TEM apparatus: H-7100FA type manufactured by Hitachi, Ltd.

(5) Diameter by number average of ultrafine fibers, single fiber fineness A cross section of a polishing cloth containing ultrafine fibers (A) and (B) is observed with a TEM or a scanning electron microscope (SEM). The diameters of 50 single fibers extracted for the purpose were measured. The measurement is to obtain a single fiber diameter and fineness from a cross-sectional photograph of a polishing cloth by TEM or SEM using image processing software (WINROOF). This is performed at three locations, and the diameter of a total of 150 single fibers. It was obtained by measuring. When the ultrafine fiber constituting the polishing cloth has an irregular cross section, the cross sectional area of the single fiber is first measured, and the area is assumed to be the area when the cross section is a circle. The diameter of the single fiber is obtained by calculating the diameter from the area. Moreover, the average value of the single fiber fineness was calculated | required as follows. First, the single fiber diameter is measured in nm to the first decimal place, the average value is obtained, and the decimal places are rounded off. The single fiber fineness was calculated from the single fiber diameter.
SEM apparatus: VE-7800 manufactured by Keyence Corporation.

(6) Vertical tensile strength when wet The vertical tensile strength when wet is in accordance with JIS L 1096 8.12.1 (1999). A 2.5 cm sample was taken and stretched at a tensile rate of 10 cm / min with a constant speed extension type tensile tester at a grip interval (test length) of 10 cm to obtain a load at the time of breaking the sample. After calculating the load per 1 cm width from the obtained value, the load per 1 mm thickness was calculated from the value and used as the tensile strength (unit: N / cm width / mm thickness). The collected sample was immersed in distilled water at 25 ° C. for 60 minutes, and then the moisture on the surface of the sample was wiped lightly and measured by the method described above to measure the vertical tensile strength when wet.

(7) Process passability With regard to the process passability in the ultrafine fiber generation processing by dip-nip processing using a continuous dyeing machine equipped with a steamer, the presence or absence of sheet elongation and wrinkle generation was evaluated. The case where the process passability was good was designated as “◯”, and the case where the sheet was stretched or broken and was difficult to process was designated as “X”.

(8) Number of exposed fibers constituting the fabric on the surface of the ultrafine fiber (polishing surface) Select an arbitrary 10 × 10 cm (100 cm ² ) range on the surface of the ultrafine fiber of the polishing cloth, and maintain the distance from the surface to 30 cm. However, the fibers of the woven fabric having a fineness exceeding the fineness of the ultrafine fibers, which were exposed on the surface of the ultrafine fibers (polished surface), were counted. The measurement was performed at three locations, and the average value was obtained and used as the number of exposed fibers on the surface.

(9) Substrate surface roughness
In accordance with JIS B0601 (2001 edition), using the TMS-2000 surface roughness measuring instrument manufactured by Schmitt Measurement Systems, Inc., any 10 locations on the surface of the disk substrate sample after polishing The average surface roughness was measured, and the substrate surface roughness was calculated by averaging the measured values at 10 locations. The lower the value, the higher the performance. The surface roughness was good at 0.25 nm or less.

(10) Scratch points
Using the Candela 5100 optical surface analyzer as a measurement object on both surfaces of the five substrates after polishing, that is, the total area of the surface of 10 surfaces, a groove having a depth of 3 nm or more was used as a scratch, and the number of scratches was measured. The average value of the measured values was evaluated. The lower the value, the higher the performance. Scratch performance was good at 50 points or less.

[Example 1]
(Nonwoven fabric)
(Polymer alloy chip)
Melt viscosity 310 poise (240 ° C., shear rate 121.6 sec ⁻¹ ), melting point 220 ° C. nylon 6 (40 wt%), weight average molecular weight 120,000, melt viscosity 720 poise (240 ° C., shear rate 121.6 sec ⁻¹ ) Polylactic acid (PLA) having a melting point of 170 ° C. (optical purity of L-lactic acid of 99.5% or more) (60% by weight) was kneaded at 220 ° C. with a biaxial extrusion kneader to obtain a polymer alloy chip.

(Fabric)
The polymer alloy chip was spun from the pores at a spinning temperature of 240 ° C. by the spunbond method, then spun at a spinning speed of 3400 m / min by an ejector, collected on a moving net conveyor, and embossed with a compression rate of 7%. A long fiber nonwoven fabric having a single fiber fineness of 2.0 dtex and a basis weight of 150 g / m ² was obtained by thermocompression bonding with a roll under conditions of a temperature of 80 ° C. and a linear pressure of 10 kg / cm.
An oil agent (SM7060EX: manufactured by Toray Dow Corning Silicone Co., Ltd.) was applied to the nonwoven fabric composed of the polymer alloy fibers by 2% by weight based on the fiber weight.

(fabric)
(Composite fiber filament yarn)
After using the same polymer alloy tip as used for the nonwoven fabric, melting with a pressure melter, using a die with a discharge hole diameter of 0.45 mm, setting the die temperature to 245 ° C., and melt spinning at a spinning speed of 900 m / min By drawing 3.0 times in a liquid bath at 80 ° C., a composite fiber filament yarn having a yarn fineness of 78 dtex and a filament count of 30 was obtained. As a result of observing the cross section of the composite fiber with TEM, the average single fiber fineness of nylon 6 was 2.0 × 10 ⁻⁴ dtex. That is, the composite fiber can generate ultrafine fibers having a single fiber fineness of 0.0002 dtex.

(Weaving)
Weaving density of warp and weft using a twisted yarn having a yarn fineness of 84 dtex, a filament number of 72 and a twist number of 2500 T / m, and a weft yarn obtained by twisting the composite fiber filament yarn to a twist of 1500 T / m. Were woven in a plain fabric of 27 pieces / cm and 27 pieces / cm, respectively.

(Lamination and needle punching)
Using the above non-woven fabric and woven fabric, three sheets of non-woven fabric / one woven fabric / one non-woven fabric were laminated in this order, and 3000 needles / cm ² were needle punched at a barb depth of 60 μm and a needle depth of 7 mm. A sheet in which the woven fabric and the woven fabric were integrated.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
The sheet was impregnated with a polyvinyl alcohol solution having a liquid temperature of about 85 ° C. and a concentration of about 5%, squeezed with a nip roll, provided with 11% by weight of polyvinyl alcohol in solid content with respect to the weight of the sheet fiber, and then dried. Next, it is impregnated with a DMF solution of a polyester / polyether polyurethane having a concentration of about 11%, squeezed with a nip roll, applied with a solid content of 18% by weight of polyurethane, and a liquid temperature of 35 ° C. The polyurethane was coagulated with a 30% DMF aqueous solution, and DMF and polyvinyl alcohol were removed with hot water at about 85 ° C. Then, it was ground and raised with JIS # 180 sandpaper.

(Sea removal treatment)
By using a 35% aqueous sodium hydroxide solution in a continuous dyeing machine for the above raised sheet, dip-nip treatment, steam treatment, water washing, and drying, the PLA, which is a sea component of nonwoven fabric and woven weft, is dried. By elution, ultrafine fibers made of nylon 6 were generated to obtain an abrasive cloth.
In addition, since it integrated with the woven fabric by the needle punch, the process passability at the time of sea removal treatment was favorable.
As a result of analyzing the nylon 6 on the polishing surface in the polishing cloth from the TEM photograph, the average single fiber fineness of the nylon 6 was 2.3 × 10 ⁻⁴ dtex.

(Polishing)
The polishing cloth was used as a tape having a width of 40 mm, and polishing was performed under the following conditions.
After a Ni-P plating treatment is applied to an aluminum substrate, a free abrasive slurry made of diamond crystals having a primary particle diameter of 1 to 10 nm is dropped onto the surface of the polishing cloth using a disk that is polished and controlled to an average surface roughness of 0.3 nm. Then, polishing was carried out for 20 seconds under a tape running speed of 5 cm / min.
The polished disc had a surface roughness of 0.17 nm, a scratch score of 34, and good polishing processability.

[Example 2]
(web)
(raw cotton)
Nylon 6 similar to that used in Example 1 is used as an island component, and PLA similar to that used in Example 1 is used as a sea component. Nylon 6 is melted at 260 ° C. and PLA at 230 ° C. in a pressure melter. Then, using a sea-island type compound base of a polymer inter-array system with 376 islands / hole island at a base temperature of 245 ° C., melt spinning at an island / sea weight ratio of 40/60 at a spinning speed of 1100 m / min. Then, it was stretched, crimped and cut 3.0 times in a liquid bath to obtain a raw material of sea-island type composite fiber having a fineness of 4.6 dtex.

(Web formation)
Using the raw cotton, a laminated web was formed through a card and cross wrapper process.

(fabric)
The same one as used in Example 1 was used.

(Lamination and needle punching)
Using the above web and woven fabric, the woven fabric 1 / web / woven fabric 1 were laminated in this order, and the same needle punching treatment as in Example 1 was performed to produce a sheet having a basis weight of 780 g / m ² and a density of 0.23 g / cm ^3. did.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
The sheet was subjected to hot water shrinkage at 95 ° C., and 10% by weight of polyvinyl alcohol was added to the fiber weight, and then dried. Next, it is impregnated in a DMF solution of a polyester / polyether polyurethane having a concentration of about 11%, squeezed with a nip roll, applied with a solid content of 20% by weight of the fiber, and a liquid temperature of 35 ° C. The polyurethane was coagulated with a 30% DMF aqueous solution, and DMF and polyvinyl alcohol were removed with hot water at about 85 ° C. Then, it cut in half in the thickness direction, and the half-cut surface was ground with JIS # 240 sandpaper and raised.

(Sea removal treatment)
By using a 30% aqueous solution of sodium hydroxide in a continuous dyeing machine for the above raised sheet, dip-nip treatment, steam treatment, water washing, and drying, the PLA which is a sea component of the nonwoven fabric and the woven weft is obtained. By elution, ultrafine fibers made of nylon 6 were generated to obtain an abrasive cloth.
In addition, since it integrated with the woven fabric by the needle punch, the process passability at the time of sea removal treatment was favorable.
As a result of analyzing the nylon 6 on the polishing surface in the polishing cloth from the SEM photograph, the average single fiber fineness of the nylon 6 was 0.005 dtex.

(Polishing)
Polishing was performed in the same manner as in Example 1 using the polishing cloth.
The polished disc had a surface roughness of 0.18 nm, a scratch score of 43, and good workability.

[Example 3]
(Nonwoven fabric)
The same one as used in Example 1 was used.

(fabric)
(Composite fiber filament yarn)
The same one as used in Example 1 was used.

(Weaving)
For both the warp and the weft, the weft density of the warp and the weft was 27 / cm and 27, respectively, in the same manner as in Example 1 except that a twisted yarn having a twist of 1500 T / m was applied to the composite fiber filament yarn. A plain woven fabric of / cm was woven.

(Lamination and needle punching)
Lamination and needle punching were performed in the same manner as in Example 1 except that the above nonwoven fabric and woven fabric were used, and a sheet was produced.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
The sheet was subjected to polyvinyl alcohol application / removal, polyurethane application, and raising treatment in the same manner as in Example 1.

(Sea removal treatment)
The above raised sheet is subjected to alkali treatment using a 2% aqueous sodium hydroxide solution in a jigger dyeing machine, washed with water, and dried, so that PLA, which is a sea component of non-woven fabric and woven warp and weft, is obtained. By elution, ultrafine fibers made of nylon 6 were generated to obtain an abrasive cloth.
In addition, since it integrated with the woven fabric by the needle punch, the process passability at the time of sea removal treatment was favorable.
As a result of analyzing the nylon 6 on the polishing surface in the polishing cloth from a TEM photograph, the average single fiber fineness of the nylon 6 was 0.0002 dtex.

(Polishing)
Polishing was performed in the same manner as in Example 1 using the polishing cloth.
The polished disc had a surface roughness of 0.19 nm, a scratch score of 40, and good workability.

[Example 4]
(Nonwoven fabric)
The same one as used in Example 1 was used.

(fabric)
The same one as used in Example 1 was used.

(Lamination and needle punching)
Using the non-woven fabric and the woven fabric, 4 sheets of 1 woven fabric / 2 non-woven fabrics / 1 woven fabric were laminated in this order, and needle punching was performed in the same manner as in Example 1 so that the nonwoven fabric and the woven fabric were intertwined and integrated. A sheet was produced.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
Polyvinyl alcohol was applied / removed and polyurethane was applied to the sheet in the same manner as in Example 1. Then, it cut in half in the thickness direction, and the cut surface was ground and brushed in the same manner as in Example 1.

(Sea removal treatment)
The above raised sheet is alkali-treated with a 2% aqueous sodium hydroxide solution using a jigger dyeing machine, washed with water, and dried to elute PLA, which is a sea component of the nonwoven fabric and the weft of the fabric. An ultrafine fiber made of nylon 6 was generated to obtain an abrasive cloth.
In addition, since it integrated with the woven fabric by the needle punch, the process passability at the time of sea removal treatment was favorable.
As a result of analyzing the nylon 6 on the polishing surface in the polishing cloth from a TEM photograph, the average single fiber fineness of the nylon 6 was 0.0002 dtex.

(Polishing)
Polishing was performed in the same manner as in Example 1 using the polishing cloth.
The polished disc had a surface roughness of 0.18 nm, a scratch score of 38, and good workability.

[Comparative Example 1]
(Nonwoven fabric)
The same one as used in Example 1 was used.

(fabric)
No fabric was used.

(Needle punch processing)
Needle punching was performed on the nonwoven fabric in the same manner as in Example 1 except that the nonwoven fabric was not laminated.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
Polyvinyl alcohol was applied / removed and polyurethane was applied to the sheet in the same manner as in Example 1. Thereafter, the surface on one side was ground and brushed in the same manner as in Example 1.

(Sea removal treatment)
The brushed sheet was subjected to a sea removal treatment in the same manner as in Example, and sheet elongation occurred during the process, and breakage occurred at the bonded portion. The process passability was very poor.

[Comparative Example 2]
(Nonwoven fabric)
The same one as used in Example 1 was used.

(fabric)
A plain woven fabric having a warp / weft weaving density of 27 / cm and 27 / cm was woven using a strong twisted yarn having a yarn fineness of 84 dtex, a filament number of 72, and a twist number of 2500 T / m as the warp and weft.

(Lamination and needle punching)
Using the above nonwoven fabric and woven fabric, 3 sheets of 1 nonwoven fabric / 1 woven fabric / 1 nonwoven fabric were laminated in this order, and the same needle punching treatment as in Example 1 was performed to prepare a sheet having a basis weight of 540 g / m ² .

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
The sheet was dried in the same manner as in Example 1 after adding 10% by weight of polyvinyl alcohol in solid content. Next, in the same manner as in Example 1, 20% by weight of polyurethane as a solid content with respect to the fiber weight was applied and coagulated, and DMF and polyvinyl alcohol were removed with hot water at about 85 ° C. Then, it was ground and raised with JIS # 180 sandpaper.

(Sea removal treatment)
The brushed sheet was subjected to sea removal treatment in the same manner as in Example 1 to generate ultrafine fibers made of nylon 6 to obtain an abrasive cloth. When the polished surface was observed, exposed portions of woven fibers that were thicker than the ultrafine fibers on the polished surface were found at a frequency of 14 pieces / 100 cm ² .

(Polishing)
Polishing was performed in the same manner as in Example 1 using the polishing cloth.
The polished disc had a surface roughness of 0.23 nm and a scratch score of 174.
Since the fibers of the plain woven fabric were cut by the needle punch, and the fibers of the woven fabric having a large fineness were exposed on the surface of the ultrafine fibers (polished surface), the number of scratches was very large.

[Comparative Example 3]
(web)
(raw cotton)
Nylon 6 similar to that used in Examples 1 and 2 is used as an island component, and PLA similar to that used in Examples 1 and 2 is used as a sea component. The island / sea weight ratio is 40/60, the number of islands is 36, A raw cotton of a sea-island type composite fiber having a fineness of 3.0 dtex was obtained.

(Web formation)
Using the raw cotton, a laminated web was formed through a card and cross wrapper process.

(fabric)
A plain woven fabric having a warp / weft weaving density of 27 / cm and 27 / cm was woven using a strong twisted yarn having a yarn fineness of 84 dtex, a filament number of 72, and a twist of 2500 T / m for the warp and weft (comparative example) 2).

(Lamination and needle punching)
Using the web and the woven fabric, the woven fabric 1 / web / woven fabric 1 were laminated in this order, and the same needle punching treatment as in Examples 1 and 2 was performed to prepare a sheet.

(Polyvinyl alcohol application / removal, polyurethane application, brushing treatment)
The sheet was subjected to hot water shrinkage at 95 ° C., and then 11% by weight of polyvinyl alcohol was added to the fiber weight and then dried. Next, it is impregnated in a DMF solution of a polyester / polyether polyurethane having a concentration of about 11%, squeezed with a nip roll, and 16% by weight of polyurethane with a solid content is given to the fiber weight, and the liquid temperature is 35 ° C. The polyurethane was coagulated with a 30% DMF aqueous solution, and DMF and polyvinyl alcohol were removed with hot water at about 85 ° C. Then, it cut in half in the thickness direction, and the half-cut surface was ground with JIS # 240 sandpaper and raised (similar to Example 2).

(Sea removal treatment)
Using the 30% aqueous solution of sodium hydroxide in the continuous dyeing machine, the above raised sheet is dried after dip-nip treatment, steam treatment, water washing, and the PLA which is the sea component of the nonwoven fabric is eluted. An ultrafine fiber made of nylon 6 was generated to produce an abrasive cloth.
In addition, since it was made to integrate with the textile fabric, the process passage property at the time of alkali treatment was favorable.
As a result of analyzing the nylon 6 on the polishing surface in the polishing cloth from the SEM photograph, the average single fiber fineness of the nylon 6 was 0.08 dtex. Further, when the polished surface was observed, exposed portions of fabric fibers that were thicker than the ultrafine fibers on the polished surface were found at a frequency of 20 pieces / 100 cm ² .

(Polishing)
Polishing was performed in the same manner as in Example 1 using the polishing cloth.
The disk after polishing had a surface roughness of 0.25 nm, a scratch score of 212, a fineness of the ultrafine fibers was thick, and the fabric was exposed on the surface, so that the scratch score was large.

  Table 1 shows the polishing cloths obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and their evaluation results.

  The present invention can provide an abrasive cloth excellent in process passability and dimensional stability during production of the abrasive cloth. Therefore, the present invention can be suitably used as a polishing cloth that can be used particularly when an aluminum alloy substrate and a glass substrate used for a magnetic recording disk are polished with an ultra-high precision finish.

Claims (4)

A fiber capable of generating an ultrafine fiber (A) having an average single fiber fineness of 1.0 × 10 ^{−6 to} 0.05 dtex and a woven fabric are overlapped and tangled and integrated, and then an elastic polymer is applied. In the method for producing a polishing cloth for performing fiber generation processing and raising treatment, the weft of the woven fabric is a fiber capable of generating ultrafine fibers (B) having an average single fiber fineness equal to or less than the ultrafine fibers (A). A method for producing an abrasive cloth.   The method for producing an abrasive cloth according to claim 1, wherein the warp and the weft constituting the woven fabric in the abrasive cloth are strong twisted yarns in the range of 500 T / m to 4000 T / m.   The method for producing an abrasive cloth according to claim 1 or 2, wherein the average single fiber fineness of the warp constituting the fabric in the abrasive cloth is in the range of 0.3 dtex to 3.0 dtex.   The method for producing an abrasive cloth according to any one of claims 1 to 3, wherein the total fineness of warps and wefts constituting the woven fabric in the abrasive cloth is in the range of 20 dtex to 120 dtex.