TWI410298B - Abrasive cloth for high-precision processing - Google Patents

Abstract

A polishing cloth for precision processing which comprises a multilayered sheet composed of two or more superposed layers comprising a single-yarn-dispersed nonwoven fabric and a support. It is characterized in that the single-yarn-dispersed nonwoven fabric is the first layer, i.e., the outermost layer, on the polishing side, the single yarns constituting the single-yarn-dispersed nonwoven fabric have a number-average fiber diameter of 0.1-1.7 µm, the surface of the first layer has been raised, and the first-layer surface has a maximum height/roughness of 70 µm or less, water absorption rate of 100-240 mm, and compression energy of 0.10-0.30 gf cm/cm<SUP>2</SUP>.

Description

Precision processing abrasive cloth

The present invention relates to a polishing cloth for precision machining of a magnetic disk, and more particularly to a polishing cloth for texture processing of a hard disk (hereinafter referred to as a polishing cloth for texture processing).

In recent years, high performance of computer and digital cameras, mobile phones, video music recording and reproducing equipment. miniaturization. The large capacity of records is developing. One of the main factors that can achieve such a high-density recording of information, one of the magnetic recording media with fast access speed and low unit price, such as writing and reading of hard disk data, is therefore Among many electronic devices, it is also widely used in general households.

In a general manufacturing method of a hard disk, a desired fine concavo-convex pattern, that is, a texture is formed on a hard disk substrate before the magnetic film is coated. By forming the texture by processing, it is possible to obtain an effect of suppressing damage at the time of contact with the magnetic head, preventing the magnetic head from being attracted to the magnetic disk, improving magnetic anisotropy, and improving the information recording density.

In recent years, in order to improve the information recording density of development-advanced hard disks, it is necessary to reduce head damage when (1) low head suspension is suspended, and (2) CSS (contact start and stop) is suppressed. The further miniaturization of the texture for the purpose of magnetic head adsorption, that is, the reduction of the surface average roughness (Ra) represented by the average depth of the unevenness on the surface of the disc, is therefore extremely important.

As a polishing cloth for texture processing of such hard disk substrates, many previous It has been proposed to improve the polishing performance by making the diameter of the fibers constituting the polishing cloth thin.

For example, as a prior art texture processing method, a flocked fabric or a woven fabric is used as a polishing cloth for processing (Japanese Patent Laid-Open No. Hei 6-295432). According to this method, when the fibers are made fine, the abrasive grains are uniformly adhered to the surface of the polishing cloth, and when the polishing cloth is pressed against the disk, the abrasive grains are uniformly pressed against the surface of the disk, so that the disk can be lowered. Surface roughness. However, since the fiber diameter of the polishing cloth is 3 to 15 μm, there is a limit to improvement in processing accuracy, and it is not possible to sufficiently match the capacity of the recent hard disk.

Recently, various proposals have been made to remove a sea terephthalate (polyethylene terephthalate) by a suitable solvent after impregnating a non-woven fabric with a polymer elastomer in a non-woven fabric including a sea-island yarn produced by a composite spinning method. Ethylene phthalate), thereby forming ultrafine fibers, and further, one or both of them are raised, thereby obtaining a polishing cloth for texture processing (Japanese Patent Laid-Open Publication No. 2002-79472, Japanese Patent Laid-Open No. 2003-170348) In the publication, Japanese Laid-Open Patent Publication No. 2004-130395, and the like, and the polishing cloth for texture processing has become the mainstream. Such a polishing cloth for processing uses ultra-fine fibers having a fiber diameter of 1.9 μm or less in a single yarn by using a sea-islanding wire, which is much finer than the fiber diameter (about 5 μm) of the prior knitted fabric, thereby enabling texture processing accuracy. improve.

However, the above method for obtaining ultrafine fibers is obtained by removing the sea component from the non-woven fabric containing the sea-island yarn impregnated with the polymeric elastomer by a suitable solvent, thereby obtaining the ultrafine fiber in one island silk. There are singles containing dozens to hundreds of island components Yarn, therefore, there are many fiber bundles in which the fiber diameter of the single yarn of the coarse island component is several tens to hundreds of times (the single yarn is unevenly present and formed into a bundle shape).

When such a fiber bundle is present, it is difficult to use the polishing cloth for texture processing to reduce the surface roughness of the polishing layer. That is, it is difficult to press the polishing surface against the disc with an equal surface pressure, so that there is a limit to lowering the surface roughness of the disc. Further, there is a problem that it is easy to produce a large concave portion around the fiber bundle, and therefore, the abrasive grains are easily aggregated around the fiber bundle, and the agglomerated abrasive grains locally polish the surface of the disk to make the disk more Deep damage.

On the other hand, as a polishing cloth for texture processing which does not have a fiber bundle, a polishing cloth using a very fine filament of a cut yarn or a melt blown nonwoven fabric is proposed in Japanese Laid-Open Patent Publication No. Hei 9-262775. According to this proposal, the melt-blown nonwoven fabric constituting the polishing surface is held in a state in which the fibers constituting the nonwoven fabric are welded to each other, and is not fixed by the resin. Therefore, there is no problem that the resin is detached. Further, since the fibers are not stretched and the fibers themselves are soft, the abrasive particles are not excessively pressed against the surface of the disc, and therefore, the surface of the disc is rarely damaged to a large extent.

Further, the fibers constituting the melt-blown nonwoven fabric layer are mainly fibers having a fiber diameter of 10 μm or less, and the fine abrasive particles are excellent in retainability, so that the surface of the disc can be uniformly polished to form a fine texture. Further, since the single yarn is not fixed by a resin such as a polymer elastomer, the fiber has a degree of freedom, and therefore, it is possible to prevent the surface of the disc from being deeply damaged when the surface is polished.

However, in the texturing process, the back of the polishing cloth is pressed by a rubber roller The surface is pressed against the surface of the disc. Therefore, in addition to the softness of the fiber itself, the overall softness of the polishing cloth is also important. Further, since the melt-blown nonwoven fabric having a fine fiber diameter has a large specific surface area, the area in contact with the abrasive grains is large, and the polishing performance is improved. However, in the case of a melt-blown nonwoven fabric containing a hydrophobic thermoplastic resin such as polypropylene or polyester, there is a problem that even if the slurry containing the abrasive grains is dropped, the slurry does not uniformly diffuse, and the texture processing accuracy becomes insufficient. In the polishing cloth disclosed in Japanese Laid-Open Patent Publication No. Hei 9-262775, there is a limit in improving the processing accuracy of the texture.

As described above, in the prior art, it is difficult to obtain a polishing cloth for texture processing which can sufficiently satisfy the improvement of the information recording density of a hard disk, and it is eager to obtain a polishing cloth for texture processing which can further improve the processing precision.

It is an object of the present invention to provide a polishing cloth for precision machining of magnetic disks, and more particularly to a polishing cloth for texture processing which is excellent in polishing precision in texture processing of hard disks.

The present inventors have conducted intensive studies on polishing cloths for precision machining of hard disks in order to increase the information recording density of hard disks, and found that in addition to making the single yarn of the polishing layer of the polishing cloth thin, the polishing cloth has a specific three-dimensional structure in which a single yarn is dispersed in a horizontal direction, and a maximum height roughness of the polishing layer in the vertical direction is 70 μm or less, and further, has a specific The abrasive cloth having water absorbability and compression characteristics can diachronically reduce the surface average roughness of the surface of the hard disk, thereby developing the present invention.

That is, the present invention is as follows.

(1) A polishing cloth for precision machining, which comprises a polishing cloth in which two or more layers of a single yarn dispersion nonwoven fabric and a support are laminated, and a single yarn dispersion nonwoven fabric is used as a surface of the polishing side. The first layer, the single yarn constituting the single yarn dispersed non-woven fabric, has an average fiber diameter of 0.1 to 1.7 μm, and the surface of the first layer is raised, and the maximum height roughness of the first layer surface is 70 μm or less, and the water absorption speed is 100~ 240 mm, compression energy is 0.10~0.30 gf. Cm/cm ² .

(2) The polishing cloth for precision machining according to the above 1, wherein the single yarn dispersion nonwoven fabric is a melt blown nonwoven fabric.

(3) The polishing cloth for precision machining according to the above 1 or 2, wherein the single-layered nonwoven fabric of the first layer has a thickness of 100 μm or more.

(4) The polishing cloth for precision machining according to any one of the above 1 to 3, wherein the single yarn dispersion nonwoven fabric used in the first layer has an absorbance with a standard deviation of 0.050 or less.

(5) The polishing cloth for precision machining according to any one of the above 1 to 4, wherein the single-layered nonwoven fabric of the first layer comprises a polyester fiber, and the degree of crystallinity of the polyester fiber is 35% or more.

(6) The polishing cloth for precision machining according to any one of the above 1 to 5, wherein the multilayer structural layer is impregnated with a polymeric elastomer.

(7) The polishing cloth for precision machining according to any one of the above 1 to 6, wherein the multilayer structural layer is provided with a polymer elastomer of 30 wt% or less.

(8) The polishing cloth for precision machining according to any one of the above 1 to 7, wherein the polymer elastic system polyurethane is used.

(9) The polishing cloth for precision machining according to any one of the above 1 to 8, wherein the elongation percentage in the longitudinal direction at a load-bearing weight of 1.0 kgf/cm is 4% or less, and the elongation percentage in the width direction is 12% or less.

(10) The polishing cloth for precision machining according to any one of the above 1 to 9, wherein the support system is non-woven.

(11) The polishing cloth for precision machining according to any one of the above 1 to 10, wherein the support system laminates the ultrafine fibers having a fiber diameter of 10 μm or less on the both sides of the fabric.

Hereinafter, the present invention will be described in detail.

The polishing cloth for precision machining according to the present invention is obtained by subjecting a multilayer structure layer in which a single yarn is dispersed and a support structure to a water-repellent speed to become a water-absorbent speed, and the single-yarn dispersion non-woven fabric is raised. .

In the present invention, the single yarn dispersion means that the single yarn is not unevenly distributed during the entire observation, and is not formed into a bundle (fiber bundle). Preferably, the single yarn is not adhered to four or more. Dispersed state. Since the single-yarn dispersed non-woven fabric does not have a fiber bundle, the first layer of the polished surface is extremely excellent in fiber dispersibility and smoothness, and as a result, the abrasive grains are uniformly aggregated without being aggregated during the texture processing, and further, it is easy Since the polishing surface is pressed against the disk by the uniform surface pressure, it is preferable as a polishing cloth for precision machining such as texturing.

Further, the single-yarn dispersed nonwoven fabric may be subjected to hydrophilic processing before being laminated with the support. Furthermore, when the single yarn dispersion nonwoven fabric contains a hydrophilic resin, When the water absorption speed is as follows, it is not necessary to carry out hydrophilic processing.

In the present invention, the single yarn of the first layer of the surface layer of the polishing side has a single fiber having a number average fiber diameter of 0.1 to 1.7 μm, preferably 0.4 to 1.5 μm, more preferably 0.4 to 1.3 μm. . When the average fiber diameter of the single yarn is less than 0.1 μm, the strength of the single yarn is lowered, so that the force applied during the texture processing cannot be withstood, resulting in breakage of the single yarn. Therefore, it is difficult to fix the abrasive grains, so that the polishing force is insufficient or uneven polishing during the texture processing. On the other hand, when the number average fiber diameter exceeds 1.7 μm, the denseness of the raised fibers of the surface layer is lowered, and the coarse unevenness of the raised fibers becomes large. Therefore, it is difficult to uniformly disperse the abrasive grains, and as a result, it is difficult to carry out high. Precision grinding.

What is required in the polishing cloth for texture processing is to reduce the surface average roughness (Ra) represented by the average depth of the unevenness on the surface of the disc as described above. Therefore, it is important to suppress the aggregation of the abrasive grains during the texture processing and to uniformly disperse.

The above-mentioned constitution is a condition that the first layer including the surface of the polishing side does not contain the fiber bundle, and the single yarn of the single yarn dispersion nonwoven fabric has an average fiber diameter of 0.1 to 1.7 μm. The necessary conditions for uniformly dispersing the abrasive grains in the horizontal direction of the polishing cloth for precision machining.

However, it is not possible to say that the above-mentioned necessary conditions are abrasive cloths for precision machining that correspond to the processing precision required at present. The reason is that the single yarn dispersion non-woven fabric used for the first layer of the surface on the polishing side has many irregularities in the vertical direction, and the first layer is produced in the texture processing step by applying the fixed pressure due to the size of the unevenness. Surface not The portion that is uniformly in contact with the surface of the disc causes agglomeration or unevenness (non-uniform dispersion) of the abrasive grains, making it difficult to perform high-precision polishing.

Therefore, it is important to control the dispersibility of the three-dimensional abrasive grains in accordance with the necessity of reducing the unevenness in the vertical direction and further uniformly dispersing the abrasive grains in the horizontal direction of the polishing cloth for precision machining.

In view of such considerations, it is important that the surface of the first layer of the polishing cloth for precision machining of the present invention has a maximum height roughness of 70 μm or less, preferably 50 μm or less, more preferably 40 μm or less. When it exceeds 70 μm, in the texture processing step of processing by applying a fixed pressure, a portion where the surface of the first layer of the polishing cloth is not uniformly contacted with the surface of the disk is generated, thereby causing aggregation or unevenness of the abrasive grains. It is difficult to perform high precision grinding. Further, the maximum height roughness of the surface of the first layer of the abrasive cloth can be measured by the following method.

Further, the configuration and manufacturing method of the polishing cloth for precision machining and the maximum height roughness of the polishing layer have the following relationships (1) to (3).

(1) In a nonwoven fabric comprising a sea-island yarn produced by a composite spinning method, after the polymer elastomer is impregnated into the nonwoven fabric, the sea component is removed by a suitable solvent to form a method for producing the ultrafine fiber, and the residual method is formed. Many fiber bundles are difficult to make the maximum height roughness of the polishing layer to be 70 μm or less due to the influence of the fiber bundle.

(2) The thickness of the single-yarn dispersed nonwoven fabric as the first layer on the polishing side after surface finishing by polishing or the like is preferably 100 μm or more, more preferably 120 to 500 μm. When the thickness is smaller than the above thickness, the support affects the first layer on the polishing side, and the maximum height roughness becomes large.

(3) When a non-woven fabric is used as a support for laminating a single yarn-dispersed non-woven fabric, the diameter of the single yarn constituting the non-woven fabric is preferably less than 8.0 μm, more preferably less than 4.0 μm, and further preferably Less than 3.3 μm. The larger the single yarn diameter of the fiber, the larger the unevenness of the non-woven fabric as the support, whereby the maximum height roughness of the single-yarn dispersed nonwoven fabric of the first layer on the polishing side also becomes large.

The water-absorbent speed of the polishing cloth for precision machining of the present invention is 100 to 240 mm, preferably 110 to 200 mm, more preferably 120 to 180 mm. When the water absorption speed is less than 100 mm, the slurry containing the abrasive grains is not sufficiently absorbed by the surface of the polishing cloth during the processing. Therefore, it is difficult to sufficiently hold the abrasive grains, and as a result, it is difficult to obtain a sufficient polishing amount. On the other hand, when the water absorption speed exceeds 240 mm, the slurry is absorbed in the vertical direction before being sufficiently diffused in the horizontal direction of the polishing cloth, so that it is difficult to uniformly spread the abrasive grains. As a result, unevenness in the distribution of the abrasive grains occurs, and it is difficult to carry out texture processing with high processing accuracy due to the unevenness.

The method of providing water absorption as described above is not particularly limited, and examples thereof include physical surface treatment methods such as graft polymerization treatment and plasma treatment; and surface coatings which impart hydrophilicity after coating the surface with an ion exchange resin or oxide. Treatment method; chemical surface treatment such as surface sulfonation by treatment with concentrated sulfuric acid. Further, a method of performing hydrophilic processing using a solution of a hydrophilic component such as a surfactant may be mentioned as a method of providing water absorption.

Further, although the surfactant is an ion-based or non-ionic surfactant, it is preferably a non-ionic surfactant which does not contain a metal ion when it is used as a polishing cloth for precision processing of a magnetic disk. Further, polyparaphenylene phthalate can also be used. A hydrophilic resin such as a copolyester of ethylene glycol and polyethylene glycol has a water-repellent property, which is preferable. Further, the water absorption speed can be measured by the following method.

Moreover, the compression energy of the polishing cloth for precision machining of the present invention is 0.10 to 0.30 gf. Cm / cm ² , preferably 0.10 ~ 0.25 gf. Cm/cm ² . The compression energy is an indicator of the hardness of the object to be evaluated, and the larger the compression energy value, the softer the value. When the compression energy is less than 0.10 gf. In the case of cm/cm ² , that is, when the polishing cloth is too hard, the amount of polishing is large, and it is easy to cause damage to the surface of the disk substrate. On the other hand, when the compression energy exceeds 0.30 gf. In the case of cm/cm ² , that is, when the polishing cloth is too soft, it is difficult to cause damage to the surface of the substrate, but there is a problem that the amount of polishing is small and the workability is poor.

In order to satisfy both the grinding amount and the texture processing accuracy, the compression energy must be made 0.10~0.30 gf. Cm/cm ² . Furthermore, the compression energy can be measured by the following method.

In order to improve the processing accuracy, it is necessary to make the number average fiber diameter of the single-yarn dispersed nonwoven fabric 0.1 to 1.7 μm. However, it is difficult to satisfy the above-described range of the compression energy in the case of the polishing cloth composed of the single-fiber-dispersed non-woven fabric of the above-mentioned number-average fiber diameter. The reason is that since the fiber diameter is fine, the void ratio is small and the cushioning property is poor.

Therefore, in the present invention, by laminating a single-yarn dispersion nonwoven fabric and a support to form a multilayer structure layer, the compression energy can be made to be in an appropriate range. That is, the compression energy can be adjusted by setting the raw material, the grammage, the thickness, and the void ratio of the support as adjustment factors. Further, as described below, the polymeric elastomer can also be used as an adjustment factor for the compression energy. So, borrow By adjusting the material, the void ratio, and the like of the support, the polishing layer is provided with an appropriate cushioning property which is difficult to achieve by merely dispersing the nonwoven fabric with a single yarn, whereby stable polishing can be performed with high precision.

It is necessary to fluff the first layer on the polishing side of the polishing cloth for precision machining of the present invention. Making it fluff has the following three effects.

(1) The surface area in contact with the abrasive grains is increased, and as a result, the holding ability of the abrasive grains is improved, and the amount of polishing is increased.

(2) The orientation of the fibers of the first layer on the polishing side is improved, and the fibers are in contact with each other in the circumferential direction during the texture processing. As a result, high-precision polishing can be performed.

(3) The contact resistance of the surface of the polishing cloth becomes small, so that it is difficult to cause deep damage to the surface of the disc substrate.

In general, the raising is carried out by a method called a polishing method in which a polishing paper such as sandpaper is used to rub the surface at a high speed to cause fuzzing, but it is preferred to apply the surfactant to the surface before polishing. By applying the surfactant, the friction between the polishing paper and the first layer on the polishing side can be reduced, and the single yarn can be prevented from being cut, thereby improving the fiber orientation.

The length of the first layer on the polishing side is preferably from 50 to 3000 μm, more preferably from 50 to 2000 μm, and even more preferably from 50 to 1000 μm. When the raising length is 50 μm or more, since the holding ability of the abrasive grains is sufficient, a sufficient polishing amount can be obtained, and since the touch of the surface is soft, the surface of the disk substrate is hardly damaged. Moreover, when the length of the fluffing is 3000 μm or less, the degree of freedom of the fiber is not excessively large, but it is appropriate. Therefore, the ultrafine fibers of the first layer on the polishing side are easily perpendicular to the radial direction of the disc substrate during processing. Touch, and the grooves in the circumferential direction can be uniformly formed. Further, in order to prevent the abrasive grains from being excessively held, the surface roughness of the disc substrate can be made small.

In the present invention, it is preferred to use a nonwoven fabric in which the coarseness of the fibers is extremely small and uneven as the single yarn-dispersed nonwoven fabric of the first layer on the polishing side. As an index thereof, it is preferred that the standard deviation of the absorbance of the single-yarn dispersed nonwoven fabric used in the first layer is 0.050 or less. When the standard deviation of the absorbance is 0.050 or less, the fiber dispersibility is good, the single yarn dispersion non-woven fabric is uniform, and the partial coarseness unevenness is small. Therefore, the abrasive grains are easily dispersed uniformly, and high-precision processing can be performed. Furthermore, the standard deviation of the absorbance can be measured by the following method.

In the present invention, examples of the method for producing the single-yarn dispersed nonwoven fabric include a melt blow method and a wet water needle method. Among them, the melt-blown method tends to make the average fiber diameter of the single yarn thinner than other manufacturing methods, and therefore, the manufacturing method of the single-yarn dispersed nonwoven fabric used as the first layer is preferable (hereinafter, by melt-blown The non-woven fabric manufactured by the law is called melt blown nonwoven fabric).

Further, as a melt blown nonwoven fabric which is preferably one of the single yarn-dispersed nonwoven fabrics used in the present invention, the melt-blown method is used to study the agglutination conditions of the single yarn, and the high-speed airflow and accompanying The flow of the flow is controlled so that the standard deviation of the above absorbance is 0.050 or less. As a manufacturing method of the polyester melt-blown nonwoven fabric, for example, a polyester polymer having an intrinsic viscosity of 0.40 to 0.75 is heated by using a nozzle having a nozzle diameter of 0.2 to 0.4 mm and a nozzle pitch of 0.3 to 1.0 mm. After melting, it is fed into a mold that has been heated to 250 to 350 °C.

Secondly, the following method can be cited: from the vicinity of the open end of the spun, a pressure of 0.18 to 0.40 MPa, which ejects a gas per nozzle of 0.05 to 0.50 g/min and is ejected from a nozzle and heated to 280 to 380 ° C. Further, in order to prevent scattering and agglomeration of a single yarn, for example, use The rectifier disclosed in Japanese Patent Publication No. Sho 62-12345 controls the flow of the high-speed air stream and the accompanying flow, and agglomerates and presses to obtain the desired basis weight, thickness, and bulk density.

In the present invention, it is preferred to use a thermoplastic resin having a fiber forming ability as a resin constituting a single yarn-dispersed nonwoven fabric. For example, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene terephthalate copolymer; nylon 6, Polyamides such as nylon 66, nylon 12, and polyamidamide copolymers; polyolefins such as polyethylene, polypropylene, and polymethylpentene; polyacrylonitriles; and ethylene polymerization such as polystyrene and polyvinyl chloride. Examples: aliphatic polyester polymers such as polylactic acid, lactic acid copolymer, and polyglycolic acid; aliphatic polyester guanamine copolymers.

Examples of the treatment method of the nonwoven fabric include a three-dimensional entanglement such as a needle-drawing treatment or a water-jet treatment, a thermal adhesive, an adhesive, and the like. However, in terms of high density of the fibers and smoothing of the surface of the polishing cloth, water spray is preferred. Handling the three-dimensional symmetry.

In the present invention, when the fiber-based polyester constituting the single yarn-dispersed nonwoven fabric is used, it is preferred that the degree of crystallization of the polyester fiber is 35% or more. When the degree of crystallization is 35% or more, the strength of the single yarn is high, and therefore, the force applied during the texture processing can be withstood, and the single yarn does not break. Therefore, the abrasive grains are easily fixed, a sufficient grinding force can be obtained in the texturing process, and uniform polishing can be performed. Further, by the conditions such as the abrasive grains or the load of the polishing paper, the single yarn is not cut during the polishing process, and the polishing cloth can be easily produced.

Further, when the spinning conditions are the same, the degree of crystallization of the polyester fiber tends to decrease as the inherent viscosity decreases, but when the degree of crystallization is 35% or more, even in order to disperse the single yarn of the first layer Good results can be obtained when the average fiber diameter of the non-woven fabric becomes small, and the polyester having a small inherent viscosity is selected.

From the viewpoint of controlling the compression energy of the polishing cloth and smoothing the surface of the first layer, it is preferred to impregnate the polymeric elastomer. Further, when fiber unevenness due to insufficient fixation of the fibers of the resin occurs, the uniformity of the processing may be deteriorated depending on the texture processing conditions, but in the above case, the polymer elastomer is impregnated to prevent the fiber from being unbalanced. effective.

The polymer elastomer is not particularly limited, but a polyurethane is preferred because it is easy to be impregnated and has good cushioning properties as a polishing cloth. As the polyurethane, a solvent-based polyurethane, an aqueous polyurethane, or the like can be used, and it is preferable from the viewpoint of less environmental load and lower production cost. It is an aqueous polyurethane.

The aqueous polyurethane is preferably used for an emulsion, and as the polyurethane component, the following may be exemplified. Examples of the polyol component include polyester polyols such as polyethylene adipate ethylene glycol and polybutylene adipate glycol; and polyether alcohols such as polyethylene glycol and polybutylene glycol. Polycarbonate polyols, etc. As the isocyanate component, 4,4'-diphenylmethane diiso is mentioned An aromatic diisocyanate such as a cyanate ester; an alicyclic diisocyanate such as 4,4'-dicyclohexylmethane diisocyanate; or an aliphatic diisocyanate such as hexamethylene diisocyanate. Further, examples of the chain extender include ethylene glycols such as ethylene glycol; diamines such as ethylenediamine, hexamethylenediamine, and 4,4'-dicyclohexylmethanediamine. Further, a polyurethane having an appropriate combination of the above various components may be used.

The content of the polymeric elastomer is preferably 30% by weight or less, more preferably 0.5% to 20% by weight, and further preferably 1% to 10% by weight, based on the content of the polymeric elastomer, relative to the polishing cloth. The surface condition, cushioning properties, hardness, and polishing properties of the polishing cloth were adjusted. When the content of the polymeric elastomer is 30% by weight or less, the effect of containing the polymeric elastomer can be sufficiently obtained, and sufficient polishing amount and polishing can be precisely controlled to obtain good texture processability and productivity.

In the present invention, the thickness of the single-yarn dispersed nonwoven fabric constituting the polishing cloth for precision processing is preferably 100 μm or more, more preferably 120 to 500 μm. In the texturing process, the polishing cloth is pressed against the disc from the side opposite to the polishing layer by a rubber roller or the like. At this time, there is a suspense that when the thickness of the single-yarn dispersed nonwoven fabric is less than 100 μm, the support affects the side of the polishing layer, and it is difficult to perform high-precision processing. In particular, it is preferred that when a non-woven fabric comprising a woven fabric or a fiber having a larger diameter is used as the support, the thickness of the single-yarn dispersed nonwoven fabric is 100 μm or more.

The polishing cloth of the present invention preferably has an elongation percentage of 4% or less in the longitudinal direction (MD direction) at a load-bearing weight of 1.0 kgf/cm, more preferably 3%, and more preferably, a load-bearing weight of 1.0 kgf/cm. Elongation of the length direction (CD direction) The percentage is 12% or less, more preferably 9% or less. When the elongation percentage in the MD direction and the elongation percentage in the CD direction are in the above range, the polishing cloth can be uniformly and stably pressed against the surface of the disc substrate, so that a fine and uniform concavo-convex pattern can be processed.

In the polishing cloth of the present invention, it is preferred to polish the first layer on the polishing side. As the polishing material, for example, a polishing paper of #100 to #1000 can be used, and the processing speed and the number of times can be appropriately selected.

In the present invention, when the polymer elastomer is impregnated, the fibers of the first layer on the polishing side are sufficiently fixed, and a #150 to #300 polishing paper having a coarse grain can be used. Further, when the polymer elastomer is not impregnated, the polishing paper of #400 to #600 having a dense texture is used for several times, whereby the smoothness of the first layer on the polishing side can be improved, and the maximum height roughness can be improved. performance.

In the present invention, examples of the support include non-woven fabrics such as short-fiber nonwoven fabrics and long-fiber nonwoven fabrics, porous bodies, and films. Among them, in view of being excellent in cushioning property and processability which are high in void ratio, it is preferable to be non-woven fabric.

Examples of the method for producing the nonwoven fabric used as the support include a method of stratification by cross-layering, a gas layer, or the like, and a needle-tie method of entanglement by card clothing; and entanglement by columnar water flow. The dry water needle method; a wet water needle method in which a fiber is dispersed in an aqueous solution after being layered by a papermaking method, and a cylindrical water flow is used for entanglement; and a usual spunbond method. Among them, it is preferable to use a wet water needle method from the viewpoint that the obtained non-woven fabric has uneven weight unevenness, small thickness unevenness, and excellent isotropy of physical properties.

In order to further improve the dimensional stability of the polishing cloth, it is also mentioned that the fabric is made The method that exists internally. In this case, as the support, it is preferred to use a laminate in which ultrafine fibers having a fiber diameter of 10 μm or less are laminated on both surfaces of the fabric.

The surface roughness of the fabric is large. Therefore, when the single-yarn dispersed non-woven fabric of the first layer on the polishing side is directly laminated on the fabric, the surface is greatly affected by the surface roughness of the fabric. As a result, the surface roughness of the first layer on the polishing side may become large, and it is difficult to perform precise texture processing. Further, the fibers constituting the woven fabric and the fibers of the single-yarn-dispersed nonwoven fabric of the first layer on the polishing side have a large difference in diameter. Therefore, it may be difficult to directly entangle the two to form a nonwoven fabric. For the above reasons, it is preferred to use a laminate in which the ultrafine fibers are laminated on both sides of the woven fabric as a support.

The polishing cloth for precision machining of the present invention uses a three-dimensional structure of a single yarn dispersion nonwoven fabric, that is, a single yarn dispersion in a horizontal direction, and a vertical height direction, a maximum height roughness of a surface of the first layer on the polishing side is 70 μm or less, and has Specific water absorption speed and compression characteristics, thereby enabling high-precision polishing in texture processing of hard disks.

The invention will be further illustrated by the following examples, but the invention is not limited to the examples. Furthermore, the measurement method, the evaluation method, and the like are as follows.

(1) Number average fiber diameter (μm)

Using a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.), the surface of the single yarn of the first layer on the polishing side was observed to be dispersed. Any 10 places, with an acceleration voltage of 20 kV, an image with a magnification of 3500 times. One image measures the diameter of any 10 single yarns, and the above measurement is performed on 10 photographs. The measured values of the total single yarn diameters of 100 were obtained, and the arithmetic mean values were taken as the number average fiber diameter.

(2) Thickness of the single yarn dispersed non-woven fabric of the first layer on the grinding side (mm)

The abrasive cloth sample was cut in the cross-sectional direction using an ultra-thin microtome (manufactured by ULTRACUT-N: manufactured by REICHERT), and observed by a scanning electron microscope (JSM-5510: JEOL Co., Ltd.) to accelerate the voltage by 20 kV. The image with a magnification of 50 times. The thickness of the single-yarn dispersed non-woven fabric of any 10 points was measured, and the arithmetic mean of these was regarded as the thickness of the single-yarn dispersed nonwoven fabric.

(3) The weight and thickness of the melt-blown non-woven fabric

The weight (g/m ² ) is measured in accordance with JIS L 1096-1999, and the thickness (mm) is measured using a dial gauge (peacock: manufactured by Ozaki Co., Ltd.) to measure 20 points of the sample. The average value.

(4) Standard deviation of absorbance

The sample of 25 cm × 18 cm was placed in a gas atmosphere at a temperature of 20 ° C and a humidity of 60% for 12 hours or more, and placed in a blending tester (formation tester-FMT-MIII: manufactured by Nomura Corporation) to measure each pixel. Transmittance. Based on the obtained transmittance, the standard deviation of the absorbance was calculated using the defined absorbance conversion formula.

(5) Maximum height roughness (μm)

After placing a 4 cm × 10 cm abrasive cloth sample in a gas environment with a temperature of 20 ° C and a humidity of 60% for more than 12 hours, use a three-dimensional real surface view. (Three-dimension real surface view) Microscope (VE-9800: manufactured by KEYENCE Co., Ltd.) Observed the surface of a single yarn-dispersed non-woven fabric, and the image was taken at a magnification of 50 times. By analyzing the profile of the obtained image, the maximum height roughness (the difference in height between the top of the mountain and the bottom of the valley of the roughness curve) of the 2 mm length of the cloth sample is measured in one measurement. 10 measurements. The evaluation was performed on the average of the 10 measurements obtained.

(6) Texture processing result (Ra) (nm)

It is carried out in accordance with JIS B 0601-1994.

The atomic force microscope (Nano Scope IV D3100: manufactured by Digital Instruments) was used to measure the arithmetic mean roughness of any linear surface of 10 disc substrate samples, and the measured values at 10 points were averaged to obtain the surface average roughness. Degree (Ra).

(7) Whether or not the fiber bundle is present

The abrasive cloth sample was cut in the cross-sectional direction using an ultra-thin microtome (manufactured by ULTRACUT-N: manufactured by REICHERT), and observed by a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.) to accelerate the voltage 20 kV, an image with a magnification of 500 times. When any 10 images were observed, the single yarns were unevenly distributed, and it was confirmed whether or not the bundles were formed into bundles.

(8) Degree of crystallization (%)

The single yarn dispersion non-woven fabric of the first layer on the polishing side was peeled off from the polishing layer, and the heat of fusion was measured by a differential scanning type calorimeter (DSC-60: manufactured by Shimadzu Corporation) (temperature up rate was 20 ° C / min, sample The weight is about 5 mg). If the measured heat of fusion per unit mass is ΔH _m , the degree of crystallization (Xc) can be calculated according to the following formula. Here, ΔH _o is the heat of fusion per unit mass of the crystal.

Xc(%)=[△H _m /△H _o ]×100

(9) Water absorption speed (mm)

According to JIS L1907-2003, the lower end of the vertically suspended test piece was immersed in water and placed for a fixed time (10 minutes), and the height of the rising water was measured.

(10) Compressed energy (gf.cm/cm ² )

The measuring device used KES-G5 (manufactured by KATO TECH Co., Ltd.). The test conditions are as follows.

. SENS (recording sensitivity): 2

. Dynamometer type: 1 kg

. Rate range: 0.02 mm/sec

. Pressurized area: 2 cm ²

. Stroke setting: 5.0

. Entry interval: 0.5

. Load limit: 50 gf/cm ²

The compression is performed under the above test conditions, and the compression energy is obtained according to the correlation diagram between the pressure and the deformation amount. The greater the compression energy, the easier it is to compress, that is, the softer it means. The smaller the compression energy, the harder it is.

(11) Percent elongation (%)

According to JIS L 1096-2003, using a constant-speed stretch tensile tester (TENSILON RTC-1210A: (share limited) Great Eastern Digital Technology (Manufactured by Orientec) to make measurements. The test conditions are as follows.

. Test piece size: width 2.5 cm, length 20 cm

. Clamping interval: 10 cm

. Stretching speed: 10 cm/min

[Example 1]

The polyethylene terephthalate (hereinafter abbreviated as PET) pellet having an intrinsic viscosity of 0.51 was heated and melted by an extruder, and then fed to a mold which had been heated to 310 °C. The nozzles having a diameter of 0.3 mm are arranged in a row at a pitch of 1.0 mm, and the molten PET is discharged at a discharge amount of 0.20 g/min of each nozzle, and is sprayed at a pressure of 0.24 MPa from the vicinity of the open end of the spun. The air was heated to 365 ° C, and the resulting single yarn group was continuously accumulated on a moving surface of 60 cm below the spinning opening, and rolled up as a melt blown nonwoven fabric.

The obtained melt-blown nonwoven fabric had a basis weight of 60 g/m ² , a thickness of 280 μm, a single yarn number average fiber diameter of 1.0 μm, and a standard deviation of absorbance of 0.032.

On the other hand, a PET fiber having a single yarn diameter of 3.2 μm was produced by a direct spinning method, and short fibers having a length of 5.0 mm were dispersed in water to prepare a pulp for papermaking. The slurry was subjected to papermaking to produce a papermaking layer (A) having a basis weight of 42 g/m ² and a papermaking layer (B) having a basis weight of 17 g/m ² .

A plain fabric with a weight of 41 g/m ^{2 for} a PET fiber false twisted silk containing 100 denier/48 filaments (filament density of 46/2.54 cm, weft density of 54/2.54 cm, no On both sides of the crucible, the papermaking layers (A) and (B) are laminated to produce a papermaking layer (C).

The melt-blown nonwoven fabric obtained as described above was laminated on the layer (A) side of the papermaking layer (C), and then suctioned from below to make a static pressure of 20 kPa, and a high-speed water jet was sprayed to perform three-dimensional entanglement to produce a multilayer structure. Floor. The high-speed water flow was continuously sprayed at a pressure of 3.0 MPa from a nozzle having a diameter of 3.0 mm arranged at a pitch of 3.0 mm, and the high-pressure water flow collided with the layer at a position 30 mm from the nozzle.

Next, a water-based polyether-based polyurethane emulsion (AP-18: manufactured by Rihua Chemical Co., Ltd.) was impregnated into the multilayer structural layer so as to be 12 wt% with respect to the multilayer structural layer. The polyurethane was solidified by drying (130 ° C × 3 minutes) using a hot air dryer.

Next, a surfactant (emulgen 120: manufactured by Kao Co., Ltd.) was impregnated into the multilayer structural layer so as to be 0.5 wt% with respect to the multilayer structural layer, and dried by a hot air dryer (130 ° C × 2 minutes) . By this processing, water absorption can be improved.

Further, using a #240 polishing paper (W54P240: manufactured by Riken Chemical Co., Ltd.), the melt-blown nonwoven fabric surface as the first layer on the polishing side was polished at a paper speed of 1000 m/min to obtain a polishing cloth for texture processing.

The single-yarn dispersed nonwoven fabric as the first layer on the polishing side of the obtained abrasive cloth for texturing had a number average fiber diameter of 1.0 μm, a thickness of 160 μm, and a maximum height roughness of 42 μm, and no fiber bundle was observed.

The obtained polishing cloth was cut at a width of 38 mm and used, and after the Ni-P was plated on the aluminum plate under the following conditions, the disc substrate subjected to the buffing process was subjected to texturing.

(texture processing conditions)

Abrasive grain: diamond free abrasive grain

Average particle size of abrasive particles: 0.3 μm

Number of substrate rotations: 500 rpm

Grinding cloth supply speed: 10 cm / min

Transverse range conditions: amplitude 1 mm, 600 times / minute (10 Hz)

The surface average roughness (Ra) of the processed disc substrate was measured and found to be 0.31 nm.

[Embodiment 2]

In the production of the melt-blown nonwoven fabric, the same as in Example 1, except that the single-hole discharge amount was set to 0.10 g/min, a gram weight of 60 g/m ² , a thickness of 280 μm, and a number average fiber diameter of a single yarn were obtained. A meltblown non-woven fabric of 0.6 μm with a standard deviation of absorbance of 0.028. Next, using the obtained melt-blown nonwoven fabric, the same as in the first embodiment, the production of the polishing cloth for texture processing, and the texture processing. Ra measurement.

By reducing the single-hole discharge amount to one half of the first embodiment, the number of individual yarns constituting the melt-blown nonwoven fabric can be as small as 0.6 μm, and the obtained texture can be processed by the diameter reduction of the single yarn. The maximum height roughness of the surface of the first layer on the side of the polishing side of the polishing cloth was as small as 34 μm, and no fiber bundle was observed. The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.26 nm.

[Example 3]

In the production of the melt-blown nonwoven fabric, in the same manner as in Example 1, except that nylon 6 (UBE nylon 1011FB: manufactured by Ube Industries Co., Ltd.) was used for the polymer, a basis weight of 60 g/m ² and a thickness of 280 were obtained. A melt-blown non-woven fabric of μm, single yarn having an average fiber diameter of 1.4 μm and a standard deviation of absorbance of 0.038. Next, using the obtained melt-blown nonwoven fabric, the same as in the first embodiment, the production of the polishing cloth for texture processing, and the texture processing. Ra measurement.

As the single-yarn dispersed nonwoven fabric of the first layer on the polishing side of the obtained abrasive cloth for texture processing, the number average fiber diameter was 1.4 μm, the thickness was 120 μm, and the maximum height roughness was 48 μm, and no fiber bundle was observed. The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.39 nm.

[Reference Example 4]

A melt-blown nonwoven fabric having a basis weight of 60 g/m ² , a thickness of 280 μm, a number average fiber diameter of a single yarn of 1.0 μm, and a standard deviation of absorbance of 0.032 obtained in the same manner as in Example 1 was used. The aqueous polyurethane emulsion was impregnated into the multilayer structure layer, and the single yarn of the first layer as the polishing side was dispersed at a paper speed of 1000 m/min using a #500 polishing paper (C54P500: manufactured by Riken Chemical Co., Ltd.). In the same manner as in Example 1, except that the non-woven fabric surface was polished four times, the production of the polishing cloth for texture processing and the texture processing were carried out. Ra measurement.

The single-yarn dispersed nonwoven fabric as the first layer on the polishing side of the obtained polishing cloth for texture processing had a number average fiber diameter of 1.0 μm, a thickness of 110 μm, and a maximum height roughness of 56 μm, and no fiber bundle was observed. The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.42 nm.

[Comparative Example 1]

A melt-blown nonwoven fabric having a basis weight of 60 g/m ² , a thickness of 280 μm, a number average fiber diameter of a single yarn of 1.0 μm, and a standard deviation of absorbance of 0.032 obtained in the same manner as in Example 1 was used. In the same manner as in Example 1, except that the aqueous polyurethane emulsion was impregnated into the multilayer structural layer, the production of the polishing cloth for texture processing and the texture processing were carried out. Ra measurement.

It does not contain a dip polymer elastomer and is polished using a coarse-grained polishing paper. Therefore, the smoothness of the polishing layer is poor, and the maximum height roughness of the surface of the single-yarn non-woven fabric as the first layer on the polishing side is 98 μm. Compared with Example 1 impregnated with a polymeric elastomer, it was about 2 times the maximum height roughness. The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.68 nm.

[Comparative Example 2]

Using a melt-blown nonwoven fabric having a basis weight of 60 g/m ² , a thickness of 280 μm, a single yarn number average fiber diameter of 1.0 μm, and a standard deviation of absorbance of 0.032, which is obtained in the same manner as in Example 1, will constitute a papermaking layer ( The production of the polishing cloth for texture processing and the texture processing were carried out in the same manner as in Example 1 except that the single yarn diameter of the short fibers of A) and (B) was 10.1 μm. Ra measurement.

The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.61 nm.

[Comparative Example 3]

A polyester copolymer polymer which is easy to carry out alkali reduction (PET which is copolymerized by 10 wt% of polyethylene glycol having a molecular weight of 4000) is used for the sea component, and a regular type PET (intrinsic viscosity of 0.65) is used for the island component. . Gear pump The two polymers were weighed and melt-spun at 290 ° C at a ratio of 35 wt% of the sea component to 65 wt% of the island component, and the unstretched yarn was obtained at 290 ° C.

The obtained unstretched yarn was thermally extended at a temperature of 75 ° C at a stretching ratio of 2.8 times, and heat set at 130 ° C to obtain an island-in-the-sea type composite fiber (fiber diameter of 14.8 μm) having an island component fiber diameter of 1.2 μm.

The obtained sea-island type composite fiber was cut into 5.0 mm and dispersed in water to prepare a pulp for papermaking. The slurry was subjected to papermaking to produce a papermaking layer (B) having a basis weight of 17 g/m ² and a papermaking layer (D) having a basis weight of 150 g/m ² .

Next, in the same manner as in Example 1, after coating the papermaking layer (D) and the papermaking layer (B) on both sides of the flat fabric having a gram weight of 41 g/m ² containing 100 denier/48 filaments of PET fibers, one side of the papermaking layer (D) and the papermaking layer (B) The multi-layer structure layer (E) was produced by suctioning from below to make the static pressure 15 kPa, and jetting a high-speed water stream to perform three-dimensional entanglement. The high-speed water flow is continuously sprayed at a pressure of 3.0 MPa from a nozzle having a diameter of 3.0 mm arranged at a pitch of 3.0 mm, and the high-pressure water flow collides with the layer at a position 30 mm from the nozzle.

The solvent-based polyether-based polyurethane emulsion dimethylformamide (DMF) solution is impregnated into the obtained multilayer structural layer (E) so as to be opposite to the multilayer structural layer. After 26 wt%, the polyurethane was coagulated (wet-solidified) by immersing in a water tank, and then dried by a hot air dryer (130 ° C × 3 minutes). Further, the sea component was eluted by using a 5 wt% aqueous NaOH solution at 80 ° C to form an ultrafine fiber having a number average fiber diameter of 1.2 μm. Furthermore, when using a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.), it is true. Identify the fiber bundle.

Next, using the #240 polishing paper (manufactured by Riken Chemical Co., Ltd., W54P240), the first layer surface was polished and raised at a paper speed of 1000 m/min to obtain a polishing cloth for texture processing. The number average fiber diameter of the single yarn constituting the nonwoven fabric as the first layer of the polishing layer is 1.2 μm, and the fiber bundle is present regardless of the impregnation of the polymer elastic body. Therefore, the first layer of the polishing side of the polishing cloth for texture processing is The maximum height roughness is 120 μm, which is extremely large.

Texture processing is carried out in the same manner as in Embodiment 1. As a result of Ra measurement, the surface average roughness (Ra) of the textured substrate after the texture processing was 0.84 nm.

[Comparative Example 4]

A melt blown nonwoven fabric was produced in the same manner as in Example 1 except that the heating air temperature was set to 340 °C. The obtained melt-blown nonwoven fabric had a basis weight of 60 g/m ² , a thickness of 280 μm, a single yarn number average fiber diameter of 1.8 μm, and a standard deviation of absorbance of 0.046.

Using this melt-blown nonwoven fabric, in the same manner as in the first embodiment, the production of the polishing cloth for texture processing and the texture processing were carried out. As a result of the Ra measurement, the surface average roughness (Ra) of the textured substrate after the texturing was 0.52 nm.

The maximum height roughness of the surface of the single-yarn non-woven fabric as the first layer on the polishing side is 70 μm or less, but the temperature of the heated air when the melt-blown nonwoven fabric is produced is low (implemented at 365 ° C in Example 1), therefore, melt-blown The number average fiber diameter of the non-woven fabric is increased, and the dispersibility of the abrasive grains in the horizontal direction is deteriorated. As a result, the surface average roughness (Ra) of the disc substrate after the texture processing becomes large.

[Comparative Example 5]

A melt blown nonwoven fabric was produced in the same manner as in Example 1 except that the temperature of the heated air was 315 ° C without using a rectifier. The obtained melt-blown nonwoven fabric had a basis weight of 60 g/m ² , a thickness of 280 μm, a single yarn number average fiber diameter of 2.5 μm, and a standard deviation of absorbance of 0.068.

Using this melt-blown nonwoven fabric, in the same manner as in the first embodiment, the production of the polishing cloth for texture processing and the texture processing were carried out. As a result of Ra measurement, the surface average roughness (Ra) of the textured substrate after the texture processing was 0.65 nm.

[Comparative Example 6]

In the same manner as in Example 1, except that Nylon 6 (UBE Nylon 1011FB: manufactured by Ube Industries Co., Ltd.) was used for the melt-blown nonwoven fabric, a basis weight of 60 g/m ² and a thickness of Melt-blown non-woven fabric of 280 μm, single yarn with an average fiber diameter of 1.0 μm and a standard deviation of absorbance of 0.032.

Using the obtained melt-blown nonwoven fabric, a multilayer structure layer was produced in the same manner as in Example 1, and secondly, a solvent-free polyether-based polyurethane emulsion of dimethylformamide was used. The DMF) solution was prepared in the same manner as in Example 3 except that the solution was 11 wt% with respect to the multilayer structural layer. Ra measurement.

The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.58 nm.

[Comparative Example 7]

A melt-blown nonwoven fabric having a basis weight of 60 g/m ² , a thickness of 280 μm, a number average fiber diameter of a single yarn of 1.0 μm, and a standard deviation of absorbance of 0.032 was obtained in the same manner as in Example 1. , making a multi-layer structure layer.

Next, a solution of a solvent-based polycarbonate-based polyurethane emulsion of dimethylformamide (DMF) was impregnated into the multilayer structural layer so as to be 34 wt% with respect to the multilayer structural layer. The production of the polishing cloth for texture processing was carried out in the same manner as in Example 1 except that the polyurethane was coagulated (wet-solidified) by immersion in a water tank, and then dried by a hot air dryer (130 ° C × 3 minutes). Texture processing. Ra measurement.

The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.59 nm.

[Comparative Example 8]

The grammage was 60 g/m ² , the thickness was 280 μm, the number average fiber diameter of the single yarn was 0.9 μm, and the standard deviation of the absorbance was 0.045, except that the PET pellet having an intrinsic viscosity of 0.39 was used. A melt-blown nonwoven fabric was produced in the same manner as in Example 1 to produce a multilayer structure layer.

Using the obtained melt-blown nonwoven fabric, in the same manner as in Example 1, the production of a polishing cloth for texture processing was attempted. As a result of polishing the melt-blown nonwoven fabric surface as the first layer on the polishing side, a large number of single yarns were cut, and it was impossible to produce a polishing cloth for texture processing which is worthy of evaluation. The result of measuring the degree of crystallization of the single-yarn dispersed nonwoven fabric as the first layer on the polishing side was 27.2%.

[Comparative Example 9]

A melt-blown nonwoven fabric having a basis weight of 30 g/m ² , a thickness of 140 μm, a number average fiber diameter of a single yarn of 1.0 μm, and a standard deviation of absorbance of 0.032 was obtained in the same manner as in Example 1. , making a multi-layer structure layer.

Texture processing is performed using a polishing cloth for texture processing including the multilayer structural layer. Ra measurement. The surface average roughness (Ra) of the textured substrate after the texture processing was measured to be 0.63 nm.

Tables 1 and 2 show the structures and physical properties of the polishing cloth produced in the above Examples and Comparative Examples.

Claims (8)

A polishing cloth for precision machining, which comprises a multilayer structure layer of two or more layers of a melt-blown nonwoven fabric and a support in which a single yarn is dispersed; and the melt-blown nonwoven fabric in which the single yarn is dispersed is set as a polishing side The first layer of the surface layer, the single fiber constituting the single yarn dispersed melt-blown nonwoven fabric has a number average fiber diameter of 0.6 to 1.7 μm, the surface of the first layer is raised, and the surface of the first layer has a maximum height roughness of 70 Μm or less; the multilayer structural layer is impregnated with 0.5~15 wt% or less of polyurethane; water absorption rate is 100-240 mm, and compression energy is 0.10-0.30 gf. cm / cm ^2; and the dispersion of the single yarns is not melt-blown nonwoven fabric comprising ultrafine fiber nonwoven sea component removed using a solvent Haidao Si produced by composite spinning in the form of the. The polishing cloth for precision machining according to claim 1, wherein the melt-blown nonwoven fabric in which the single yarn of the first layer is dispersed has a thickness of 100 μm or more. The polishing cloth for precision machining according to claim 1, wherein the melt-blown nonwoven fabric in which the single yarn of the first layer is dispersed has an absorbance with a standard deviation of 0.050 or less. The polishing cloth for precision machining according to claim 2, wherein the melt-blown nonwoven fabric in which the single yarn of the first layer is dispersed has an absorbance with a standard deviation of 0.050 or less. The polishing cloth for precision machining according to any one of claims 1 to 4, wherein the melt-blown nonwoven fabric in which the single yarn of the first layer is dispersed comprises a polyester fiber, and the degree of crystallization of the polyester fiber is 35% or more. The abrasive cloth for precision machining according to any one of claims 1 to 4, wherein When the weight is 1.0 kgf/cm, the elongation percentage in the longitudinal direction is 4% or less, and the elongation percentage in the width direction is 12% or less. The polishing cloth for precision machining according to any one of claims 1 to 4, wherein the support is a non-woven fabric. The polishing cloth for precision machining according to any one of claims 1 to 4, wherein the support is a laminate in which fine fibers having a fiber diameter of 10 μm or less are laminated on both sides of the fabric.