JPWO2007142235A1 - Abrasive cloth for precision processing - Google Patents

Abstract

Number of single yarns constituting a single yarn-dispersed non-woven fabric, which is a polishing cloth comprising a multilayer structure sheet of two or more layers in which a single yarn-dispersed non-woven fabric and a support are laminated. The average fiber diameter is 0.1 to 1.7 μm, the surface of the first layer is raised, the maximum height roughness of the surface of the first layer is 70 μm or less, the water absorption speed is 100 to 240 mm, and the compression energy Is a polishing cloth for precision processing, characterized in that is 0.10 to 0.30 gf · cm / cm 2.

Description

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

  In recent years, computers, digital cameras, mobile phones, video and music recording / playback devices, etc. have been improved in performance, size and recording capacity. One of the factors that make these possible is the high-density recording of information, and since hard disks are one of magnetic recording media with a high access speed for data writing and reading and a low capacity unit price, many electronic devices It has been widely used by ordinary households.

  In a general manufacturing method of a hard disk, a desired fine uneven pattern, that is, a texture is processed and formed on the hard disk substrate before coating the magnetic thin film. By processing and forming this texture, there are effects such as suppression of scratches when coming into contact with the magnetic head, prevention of adsorption of the magnetic head to the magnetic disk, increase of magnetic anisotropy, and improvement of information recording density.

  In order to improve the information recording density of hard disks, which have been developed at an accelerated rate in recent years, (1) low flying height of magnetic head, (2) head crash and magnetic field during CSS (contact start and stop) operation It is necessary to further refine the texture for the purpose of suppressing the adsorption of the head, that is, to reduce the surface average roughness (Ra) represented by the average depth of the irregularities on the disk surface. The improvement of is extremely important.

  Conventionally, as a polishing cloth for texture processing of a hard disk substrate, many proposals have been made to improve the polishing performance by reducing the diameter of the fibers constituting the polishing cloth.

  For example, as a conventional texture processing method, a flocked fabric or a woven or knitted fabric is used as a polishing cloth for processing (Japanese Patent Laid-Open No. Hei 6-295432). According to this method, when the fiber is thinned, the abrasive grains uniformly adhere 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 disk surface, and the surface roughness of the disk It is said that this can be reduced. However, since the fiber diameter of the polishing cloth is 3 to 15 μm, there is a limit to improving the processing accuracy, and it has become impossible to cope with the recent increase in capacity of hard disks.

  Recently, in a nonwoven fabric made of sea-island yarn produced by a composite spinning method, after impregnating a polymer elastic body into the nonwoven fabric, an ultrafine fiber is formed by removing sea components with an appropriate solvent, and further, one side or Various proposals have been made to obtain a textured polishing cloth by raising both sides (JP 2002-79472 A, JP 2003-170348 A, JP 2004-130395 A, etc.). It has become the mainstream for polishing cloth. This type of processing abrasive cloth becomes ultrafine fiber with a fiber diameter of 1.9 μm or less by using Umijima yarn, which is much thinner than the fiber diameter of conventional woven or knitted fabric (about 5 μm). The accuracy can be improved.

  However, the above-mentioned method of obtaining ultrafine fibers from a non-woven fabric made of sea-island yarn impregnated with a polymer elastic body by removing the sea component with an appropriate solvent and leaving the island component remains in one sea-island yarn. Since there are single yarns consisting of tens to hundreds of island components, there are fiber bundles that are several tens to several hundred times thicker than the fiber diameter of single yarns of island components (single yarns are biased , A state in which a bundle shape is formed) will be present.

  When such a fiber bundle is present, it becomes difficult to reduce the surface roughness of the polishing layer when used as a textured polishing cloth. That is, it becomes difficult to press the polishing surface against the disc with uniform surface pressure, and there is a limit to reducing the surface roughness of the disc. Further, large concave portions are likely to be generated around the fiber bundle, so that the abrasive grains are likely to aggregate around the fiber bundle, and the aggregated abrasive grains locally grind the disk surface and cause deep scratches. There was a problem that.

  On the other hand, as a textured polishing cloth having no fiber bundle, Japanese Patent Application Laid-Open No. 9-262775 proposes an extra fine thread polishing cloth using split yarn or melt blown nonwoven fabric. According to this proposal, the melt-blown nonwoven fabric constituting the polished surface is maintained in the form by the fusion of the fibers constituting the nonwoven fabric, and is not fixed by the resin, so that the problem of dropping off the resin does not occur. Moreover, since the fibers are unstretched and the fibers themselves are soft, the abrasive particles are not excessively pressed against the disk surface, so that the disk surface is rarely damaged.

  In addition, the fibers constituting the meltblown nonwoven fabric layer are mainly fibers having a fiber diameter of 10 μm or less, and are excellent in retaining fine abrasive particles, so that the disk surface can be uniformly polished to form a fine texture. it can. In addition, since the single yarn is not fixed to a resin such as a polymer elastic body, the fiber has a degree of freedom, so that it is possible to prevent the disk surface from being deeply scratched during surface polishing.

  However, in texture processing, since the back surface of the polishing cloth is pressed with a rubber roll and the polishing surface is pressed against the disk surface, the softness of the entire polishing cloth is important in addition to the softness of the fibers themselves. Moreover, since the melt blown nonwoven fabric with a small fiber diameter has a large specific surface area, the area which contacts a polishing abrasive grain is large, and it is effective for improvement of polishing performance. However, in the case of a melt blown nonwoven fabric made of a hydrophobic thermoplastic resin such as polypropylene or polyester, even if a slurry liquid containing abrasive grains is dropped, the slurry liquid does not diffuse uniformly and the texture processing accuracy is insufficient. There was a problem of becoming. In other words, the polishing cloth disclosed in Japanese Patent Application Laid-Open No. 9-262775 has a limit to improve the texture processing accuracy.

  As described above, with conventional technology, it is difficult to obtain a polishing cloth for texture processing that can sufficiently cope with the recent improvement in information recording density of hard disks, and texture processing that can further improve processing accuracy A polishing cloth for the use is desired.

  An object of the present invention is to provide a polishing cloth for precision processing of a magnetic disk, in particular, a polishing cloth for texture processing having excellent polishing accuracy in texture processing of a hard disk.

In order to improve the information recording density of the hard disk, the present inventors have made extensive studies on the polishing cloth used for precision machining of the hard disk. As a result, in addition to making the single yarn of the polishing layer of the polishing cloth thinner Polishing with a specific three-dimensional structure in which the horizontal direction is single yarn dispersion and the vertical direction has a maximum height roughness of 70 μm or less in the vertical direction, and further has specific water absorption and compression characteristics It has been found that the cloth can dramatically reduce the surface average roughness of the hard disk surface, and has led to the present invention.
That is, the present invention is as follows.

(1) A polishing cloth comprising a multilayer structure sheet of two or more layers in which a single yarn-dispersed nonwoven fabric and a support are laminated, and the single yarn-dispersed nonwoven fabric is used as the first layer of the polishing-side surface layer. The number average fiber diameter of the yarn is 0.1 to 1.7 μm, the surface of the first layer is raised, the maximum height roughness of the surface of the first layer is 70 μm or less, and the water absorption speed is 100 to 240 mm. A polishing cloth for precision processing, wherein the compression energy is 0.10 to 0.30 gf · cm / cm ² .

(2) The polishing cloth for precision processing as described in 1 above, wherein the single yarn dispersed nonwoven fabric is a melt blown nonwoven fabric.
(3) The polishing cloth for precision machining as described in 1 or 2 above, wherein the thickness of the single-layer dispersed nonwoven fabric of the first layer is 100 μm or more.

(4) The fine-fabricated polishing cloth according to any one of (1) to (3) above, wherein the single yarn-dispersed nonwoven fabric used for the first layer has an absorbance with a standard deviation of 0.050 or less.
(5) The precision processing abrasive cloth according to any one of the above items 1 to 4, wherein the single-layer dispersed nonwoven fabric of the first layer is made of polyester fibers, and the crystallinity of the polyester fibers is 35% or more. .

(6) The precision processing polishing cloth as described in any one of 1 to 5 above, wherein the multilayer structure sheet is impregnated with a polymer elastic body.
(7) The polishing cloth for precision processing as described in any one of 1 to 6 above, wherein the polymer elastic body is applied to the multilayer structure sheet at 30 wt% or less.

(8) The precision processing polishing cloth as described in any one of 1 to 7 above, wherein the polymer elastic body is polyurethane.
(9) The precision processing according to any one of 1 to 8 above, wherein the elongation in the longitudinal direction at a load of 1.0 kgf / cm is 4% or less and the elongation in the width direction is 12% or less. Abrasive cloth.

(10) The precision processing abrasive cloth according to any one of 1 to 9, wherein the support is a nonwoven fabric.
(11) The precision processing polishing cloth according to any one of (1) to (10), wherein the support is a laminate in which ultrafine fiber layers having a fiber diameter of 10 μm or less are laminated on both sides of a woven fabric.

Hereinafter, the present invention will be described in detail.
The polishing cloth for precision processing according to the present invention comprises raising a single yarn-dispersed non-woven fabric after subjecting a multilayer structure sheet obtained by laminating a single yarn-dispersed non-woven fabric and a support to hydrophilic treatment so as to achieve a water absorption rate described later. Is obtained.

  In the present invention, single yarn dispersion means that the single yarn does not exist unevenly and does not form a bundle (fiber bundle) in the overall observation, and preferably four single yarns. The state where it is not fixed and is dispersed. Since the single yarn-dispersed nonwoven fabric has no fiber bundle, the fiber dispersibility and smoothness of the first layer of the polished surface are extremely excellent. As a result, the abrasive grains agglomerate when texturing is performed. Since it is easy to press the polishing surface against the disk with a uniform surface pressure, it is suitable as a polishing cloth for precision processing such as texture processing.

  Moreover, before laminating | stacking with a support body, you may hydrophilically process a single yarn dispersion | distribution nonwoven fabric. In addition, when a single yarn dispersion | distribution nonwoven fabric consists of hydrophilic resin and has the water absorption speed mentioned later, it is not necessary to give a hydrophilic process.

  In the present invention, the number average fiber diameter of the single yarn of the single yarn-dispersed nonwoven fabric used for the first layer of the surface layer on the polishing side is 0.1 to 1.7 μm, preferably 0.4 to 1.5 μm, more preferably. Is 0.4 to 1.3 μm. If the number average fiber diameter of the single yarn is less than 0.1 μm, the single yarn strength decreases, so that the force applied during texturing cannot be withstood and the single yarn breaks. Therefore, the abrasive grains are difficult to be fixed, resulting in insufficient grinding force or uneven polishing in texturing. On the other hand, when the number average fiber diameter exceeds 1.7 μm, the density of the raised fibers on the surface layer is reduced, and the coarse and dense spots of the raised fibers are increased, so that the abrasive grains are difficult to be uniformly dispersed, As a result, it becomes difficult to perform highly accurate polishing.

What is required of the polishing cloth for texturing is reduction of the average surface roughness (Ra) represented by the average depth of irregularities on the disk surface as described above. For that purpose, suppression of agglomeration of abrasive grains during texturing and uniform dispersion are important.
The first layer on the polishing side surface is composed of a single yarn-dispersed nonwoven fabric that does not contain fiber bundles, and the number average fiber diameter of the single yarn constituting the single yarn-dispersed nonwoven fabric is 0.1 to 1.7 μm. The requirement is a requirement necessary to uniformly disperse the abrasive grains in the horizontal direction of the precision processing polishing cloth.

  However, the above requirements alone cannot be said to be a precision processing polishing cloth that can sufficiently meet the currently required processing accuracy. This is because the single yarn-dispersed nonwoven fabric used for the first layer on the surface on the polishing side has a lot of irregularities in the vertical direction, and depending on the size of the irregularities, in the texture processing step processed at a constant pressure This is because a portion where the surface of the first layer does not come into uniform contact with the surface of the disk occurs, causing agglomeration and unevenness (non-uniform dispersion) of the abrasive grains, which makes it difficult to perform high-precision polishing. .

  Therefore, it is important to control the three-dimensional abrasive dispersibility together with the requirement to reduce unevenness in the vertical direction and further uniformly disperse the abrasive grains in the horizontal direction of the polishing cloth for precision processing. .

  From such an idea, it is important that the maximum height roughness of the surface of the first layer of the polishing cloth for precision processing of the present invention is 70 μm or less, preferably 50 μm or less, more preferably 40 μm or less. When the thickness exceeds 70 μm, in the texturing process that is processed at a constant pressure, a portion where the surface of the first layer of the polishing cloth does not come into uniform contact with the surface of the disk is generated. It becomes difficult to perform accurate polishing. In addition, the maximum height roughness of the surface of the first layer of the polishing pad can be measured by the method described later.

Moreover, there exists a relationship like the following (1)-(3) about the structure and manufacturing method of the polishing cloth for precision processing, and the maximum height roughness of a polishing layer.
(1) In a nonwoven fabric made of sea-island yarn produced by a composite spinning method, after impregnating the nonwoven fabric with a polymer elastic body, the production method of forming ultrafine fibers by removing sea components with an appropriate solvent is as follows: Not a few fiber bundles remain, and it is difficult to make the maximum height roughness of the polishing layer 70 μm or less due to the influence of the fiber bundle.

  (2) The thickness of the single yarn-dispersed nonwoven fabric that is the polishing-side first layer after the surface finishing process is performed by buffing or the like is preferably 100 μm or more, more preferably 120 to 500 μm. When the thickness is smaller than that, the influence of the support appears on the polishing-side first layer, and the maximum height roughness increases.

  (3) When a nonwoven fabric is used as a support laminated on a single yarn-dispersed nonwoven fabric, the single yarn diameter of the fibers constituting the nonwoven fabric is preferably less than 8.0 μm, more preferably less than 4.0 μm, and even more preferably 3.3 μm. Is less than. As the single yarn diameter of the fiber increases, the unevenness of the nonwoven fabric as the support increases, and the maximum height roughness of the single yarn-dispersed nonwoven fabric of the polishing-side first layer also increases.

  The precision processing abrasive cloth of the present invention has a water absorption rate of 100 to 240 mm, preferably 110 to 200 mm, and more preferably 120 to 180 mm. When the water absorption speed is less than 100 mm, the slurry liquid containing abrasive grains is not sufficiently absorbed by the surface of the polishing cloth during processing, and thus it is difficult to sufficiently hold the abrasive grains. As a result, it becomes difficult to obtain a sufficient grinding amount. On the other hand, if the water absorption speed exceeds 240 mm, the slurry liquid is absorbed in the vertical direction before sufficiently diffusing in the horizontal direction of the polishing cloth, so that it is difficult to uniformly diffuse the abrasive grains. As a result, spots are generated in the abrasive grain distribution, and the spots are the cause, making it difficult to implement a texture with high processing accuracy.

  The method for providing water absorption as described above is not particularly limited, and is a physical surface treatment method such as graft polymerization treatment or plasma treatment, or a surface that is coated with an ion exchange resin or oxide to impart hydrophilicity. Examples thereof include a coating method and a chemical surface treatment method such as sulfonating the surface by concentrated sulfuric acid treatment. Moreover, the method of performing hydrophilic processing using the solution of hydrophilic components, such as surfactant, is also mentioned as a method of providing water absorption.

  Although there are ionic and nonionic surfactants, a nonionic surfactant that does not contain metal ions is preferable in consideration of use as a polishing cloth for precision machining of magnetic disks. Furthermore, it is also preferable to use a hydrophilic resin such as a copolyester of polyethylene terephthalate and polyethylene glycol in order to provide water absorption. The water absorption rate can be measured by the method described later.

The precision processing abrasive cloth of the present invention has a compression energy of 0.10 to 0.30 gf · cm / cm ² , preferably 0.10 to 0.25 gf · cm / cm ² . The compression energy is an index indicating the hardness of the object to be evaluated. The larger the value of the compression energy, the softer the value. When the compression energy is less than 0.10 gf · cm / cm ² , that is, when the polishing cloth is too hard, the surface of the disk substrate is likely to be damaged although the amount of grinding is large. On the other hand, when the compression energy exceeds 0.30 gf · cm / cm ² , that is, when the polishing cloth is too soft, the surface of the substrate is hardly scratched, but there is a problem that the grinding amount is small and the workability is poor.

In order to satisfy both the grinding amount and the texturing accuracy, the compression energy needs to be 0.10 to 0.30 gf · cm / cm ² . The compression energy can be measured by the method described later.

  In order to improve the processing accuracy, it is necessary that the number average fiber diameter of the single yarn-dispersed nonwoven fabric is 0.1 to 1.7 μm. However, it is difficult to satisfy the above compression energy range with an abrasive cloth composed of only a single yarn-dispersed nonwoven fabric having such a number average fiber diameter. This is because, since the fiber diameter is thin, the porosity is small and the cushioning property is poor.

  Therefore, in the present invention, the compression energy can be within an appropriate range by laminating the single yarn-dispersed nonwoven fabric with the support to form a multilayer structure sheet. That is, the compression energy can be adjusted by using the support material, basis weight, thickness, and porosity as adjustment factors. Also, as will be described later, a polymer elastic body can be used as a compression energy adjusting factor. In this way, by adjusting the material of the support, the porosity, etc., as the polishing layer, by providing an appropriate cushioning property that is difficult to achieve with only a single yarn-dispersed nonwoven fabric, it is highly accurate and stable. It became possible to perform smooth polishing.

The polishing-side first layer of the precision processing abrasive cloth of the present invention needs to be raised. Raising has the following three effects.
(1) The surface area in contact with the abrasive grains is increased, and as a result, the gripping ability of the abrasive grains is improved and the grinding amount is improved.

(2) The orientation of the fibers in the first layer on the polishing side is improved, and the fibers contact in the circumferential direction during texturing. As a result, highly accurate polishing can be performed.
(3) Since the contact resistance on the surface of the polishing cloth is reduced, the disk substrate surface is hardly damaged.

  Generally, raising is performed by a method called a buffing method in which buffing paper such as sandpaper is used to rub the surface at a high speed, and it is preferable to apply a surfactant to the surface before buffing. By applying the surfactant, it is possible to reduce the frictional force between the buffing paper and the polishing-side first layer, to prevent the single yarn from being cut, and to improve the fiber orientation.

  The raising length of the polishing-side first layer is preferably 50 to 3000 μm, more preferably 50 to 2000 μm, and still more preferably 50 to 1000 μm. When the raised length is 50 μm or more, the gripping ability of the abrasive grains is sufficient, so that a sufficient amount of grinding can be obtained, and the surface touch is soft, so that the surface of the disk substrate is hardly damaged. Further, if the raised length is 3000 μm or less, the degree of freedom of the fibers is appropriate without being too large, and therefore, the ultrafine fibers of the first layer on the polishing side can easily come into contact with the radial direction of the disk substrate at the time of processing. Yes, the grooves along the circumferential direction can be uniformly provided. Further, since the gripping ability of the abrasive grains is not excessively increased, the surface roughness of the disk substrate can be reduced.

  In the present invention, as the single yarn-dispersed nonwoven fabric of the polishing-side first layer, it is preferable to use a nonwoven fabric with extremely small density of fibers. As the index, the standard deviation of the absorbance of the single yarn-dispersed nonwoven fabric used for the first layer is preferably 0.050 or less. When the standard deviation of the absorbance is 0.050 or less, the fiber dispersibility is good, the single yarn-dispersed non-woven fabric is uniform, and the partial coarse and dense spots are small. It can be carried out. The standard deviation of absorbance can be measured by the method described later.

  In the present invention, examples of the method for producing a single yarn-dispersed nonwoven fabric include a melt blow method and a wet spun lace method. Among these, the melt blow method is suitable as a method for producing a single yarn-dispersed nonwoven fabric used for the first layer because the number average fiber diameter of the single yarn can be easily reduced as compared with other production methods (hereinafter referred to as melt blow method). Nonwoven fabric manufactured by the law is called melt blown nonwoven fabric).

  Further, the melt blown nonwoven fabric suitable as one of the single yarn-dispersed nonwoven fabrics used in the present invention has been devised in terms of single yarn collection conditions so that the standard deviation of absorbance is 0.050 or less, and high-speed gas Manufactured by melt-blowing method with controlled flow and associated flow. As a method for producing a polyester melt blown nonwoven fabric, for example, a nozzle having a nozzle diameter of 0.2 to 0.4 mm and a nozzle pitch of 0.3 to 1.0 mm is used, and the intrinsic viscosity is 0.40 to 0. .75 polyester polymer is heated and melted and fed to a die heated to 250 to 350 ° C.

  Subsequently, the discharge amount per nozzle is discharged from the nozzle at 0.05 to 0.50 g / min, and the gas heated to 280 to 380 ° C. from the vicinity of the opening end of this spinning nozzle is pressure of 0.18 to 0.40 MPa. In order to prevent the single yarn from scattering and agglomerating, the flow of the high-speed gas flow and the accompanying flow is controlled by using a rectifier as described in, for example, Japanese Examined Patent Publication No. 62-12345. The method of collecting and pressing so that it may become the fabric weight, thickness, and bulk density of this may be mentioned.

  In the present invention, it is preferable to use a thermoplastic resin capable of forming fibers as the resin constituting the single yarn-dispersed nonwoven fabric. For example, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene terephthalate copolymer; polyamides such as nylon 6, nylon 66, nylon 12, and polyamide copolymer; polyethylene, polypropylene, polymethyl Polyolefins such as pentene; polyacrylonitriles; vinyl polymers such as polystyrene and polyvinyl chloride; aliphatic polyester polymers such as polylactic acid, lactic acid copolymer and polyglycolic acid; And polymers.

  Non-woven fabric treatment methods include three-dimensional entanglement such as needle punching and water jet treatment, thermal bonding, adhesives, etc. Among them, three-dimensional entanglement due to water jet treatment increases the density of fibers and polishes them. It is preferable from the viewpoint of smoothing the cloth surface.

  In this invention, when the fiber which comprises a single yarn dispersion | distribution nonwoven fabric is polyester, it is preferable that the crystallinity degree of a polyester fiber is 35% or more. If the degree of crystallinity is 35% or more, the single yarn has high strength, so that it can withstand the force applied during texturing, and the single yarn does not break. Therefore, the abrasive grains are easily fixed, a sufficient grinding force can be obtained in the texture processing, and uniform polishing can be performed. Furthermore, depending on conditions such as the abrasive grain and load of the buffing paper, the single yarn is not cut during the buffing process, and the polishing cloth can be easily produced.

  In addition, when the spinning conditions are the same, the polyester fiber tends to decrease in crystallinity as the intrinsic viscosity decreases. However, if the crystallinity is 35% or more, the single-layer dispersed nonwoven fabric of the first layer Good results are also obtained when a polyester with a low intrinsic viscosity is selected to reduce the number average fiber diameter.

  It is preferable to impregnate the polymer elastic body from the viewpoint of controlling the compression energy of the polishing cloth and smoothing the surface of the first layer. In addition, when unevenness of fibers due to insufficient fixation of fibers by resin occurs, depending on the texture processing conditions, processing uniformity may deteriorate, but in such cases, in order to prevent unevenness of fibers It is effective to impregnate the polymer elastic body.

  The polymer elastic body is not particularly limited, but polyurethane is preferable because it can be easily impregnated and has good cushioning properties as an abrasive cloth. As the polyurethane, solvent-based polyurethane, water-based polyurethane, or the like can be used, and water-based polyurethane is preferable because it has a small environmental load and is low in production cost.

  The water-based polyurethane is preferably used in an emulsion, and examples of the polyurethane component include the following. Examples of the polyol component include polyester polyols such as polyethylene adipate glycol and polybutylene adipate glycol; polyether polyols such as polyethylene glycol and polytetramethylene glycol; polycarbonate polyols and the like. Examples of the isocyanate component include aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate; alicyclic diisocyanates such as 4,4′-dicyclohexylmethane diisocyanate; and aliphatic diisocyanates such as hexamethylene diisocyanate. Examples of the chain extender include glycols such as ethylene glycol; diamines such as ethylene diamine, hexamethylene diamine, and 4,4′-dicyclohexylmethane diamine. Moreover, the polyurethane which combined the said various components suitably can be used.

  The content of the polymer elastic body is preferably 30 wt% or less, more preferably 0.5 to 20 wt%, still more preferably 1 to 10 wt% with respect to the polishing cloth, and the polishing cloth depends on the content of the polymer elastic body. The surface condition, cushioning property, hardness, and polishing performance of can be adjusted. When the content of the polymer elastic body is 30 wt% or less, the effect of including the polymer elastic body is sufficiently obtained, and a sufficient amount of grinding and precise control of the grinding become possible, and a good texture processing And productivity.

  In this invention, it is preferable that the thickness of the single yarn dispersion | distribution nonwoven fabric which comprises the polishing cloth for precision processing is 100 micrometers or more, More preferably, it is 120-500 micrometers. In texturing, the polishing cloth is pressed against the disc with a rubber roll or the like from the side opposite to the polishing layer. In that case, when the thickness of the single yarn-dispersed nonwoven fabric is less than 100 μm, there is a concern that the influence of the support appears on the polishing layer side and high-precision processing becomes difficult. In particular, when a nonwoven fabric made of woven fabric or large-diameter fibers is used as the support, the thickness of the single yarn-dispersed nonwoven fabric is preferably 100 μm or more.

  In the polishing cloth of the present invention, the elongation in the longitudinal direction (MD direction) at a load of 1.0 kgf / cm is preferably 4% or less, more preferably 3% or less, and 1.0 kgf / cm. The elongation in the longitudinal direction (CD direction) during loading is preferably 12% or less, and more preferably 9% or less. If the elongation in the MD direction and the elongation in the CD direction are within the above ranges, the polishing cloth can be pressed uniformly and stably on the surface of the disk substrate. Is possible.

  In the polishing cloth of the present invention, it is preferable to buff the polishing-side first layer. As the buffing material, for example, buffing paper of # 100 to # 1000 can be used, and a suitable range can be appropriately selected for the processing speed and the number of times.

  In the present invention, when the polymer elastic body is impregnated, the fibers of the first layer on the polishing side are sufficiently fixed, and buffing paper of # 150 to # 300 having a relatively coarse mesh is used. it can. In addition, when the polymer elastic body is not impregnated, the smoothness of the first layer on the polishing side is increased by performing treatment several times using # 400 to # 600 buffing paper having a relatively fine mesh. Height roughness performance can be improved.

  In the present invention, examples of the support include nonwoven fabrics such as short fiber nonwoven fabrics and long fiber nonwoven fabrics, porous materials, and films. Among these, a nonwoven fabric is desirable because it has a high porosity and is excellent in cushioning properties and is excellent in workability.

  As a method for producing a nonwoven fabric used as a support, for example, after carding, it is formed into a sheet with a cross layer, an air layer, and the like, a needle punch method in which it is entangled with a cloth, a dry spunlace method in which it is entangled with a columnar water stream, Examples thereof include a wet spunlace method in which water is dispersed and formed into a sheet by a papermaking method and then entangled with a columnar water flow, a normal spunbond method, and the like. Especially, it is preferable to use a wet spunlace method from the point that the unevenness | corrugation unevenness and thickness unevenness of the nonwoven fabric obtained are small and it is excellent in the isotropy of a physical property.

  In order to further improve the dimensional stability of the polishing cloth, a method of incorporating a woven fabric is also included. In that case, it is preferable to use a laminate in which ultrafine fiber layers having a fiber diameter of 10 μm or less are laminated on both sides of the woven fabric as the support.

  Since the woven fabric has a large surface roughness, the surface is greatly affected by the surface roughness of the woven fabric when the single-layer dispersed nonwoven fabric of the first polishing side layer is directly laminated on the woven fabric. As a result, the surface roughness of the polishing-side first layer increases, and precise texture processing may be difficult. Moreover, since the fiber diameter of the fiber which comprises a textile fabric and the single yarn dispersion | distribution nonwoven fabric of a grinding | polishing side 1st layer has a big difference, it may become difficult to make both into a nonwoven fabric directly by entanglement. For the above reasons, it is preferable to use a laminate in which ultrafine fiber layers are laminated on both sides of a fabric as a support.

  The polishing cloth for precision processing of the present invention is a single yarn dispersion having a three-dimensional structure in which the single yarn dispersion is in the horizontal direction and the maximum height roughness of the surface of the first layer on the polishing side is 70 μm or less in the vertical direction. By using a nonwoven fabric and having a specific water absorption speed and compression characteristics, it is possible to perform high-precision polishing in hard disk texture processing.

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to the examples. Measurement methods, evaluation methods, etc. are as follows.

(1) Number average fiber diameter (μm)
Ten arbitrary positions on the surface of the single-sided nonwoven fabric of the polishing side first layer were observed with a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.), and an image with a magnification of 3500 times was taken at an acceleration voltage of 20 kV. The diameter of any 10 single yarns per image was measured and this was performed on 10 photos. The measured value of the diameter of 100 single yarns in total was calculated | required, and those arithmetic mean values were made into the number average fiber diameter.

(2) Thickness (mm) of single yarn-dispersed nonwoven fabric of polishing side first layer
The abrasive cloth sample was cut in the cross-sectional direction using an ultramicrotome (ULTRACUT-N: manufactured by REICHERT), observed with a scanning electron microscope (JSM-5510: JEOL Ltd.), and magnification at an acceleration voltage of 20 kV. A 50x image was taken. The thicknesses of arbitrary 10 single yarn-dispersed nonwoven fabrics were measured, and their arithmetic average value was taken as the thickness of the single yarn-dispersed nonwoven fabric.

(3) The basis weight and thickness of the melt blown nonwoven fabric The basis weight (g / m ² ) is measured according to JIS L 1096-1999, and the thickness (mm) is a dial thickness gauge (Peacock: manufactured by Ozaki Mfg. Co., Ltd.). The sample was measured at 20 points, and the average value was used.

(4) Absorbance standard deviation A sample of 25 cm × 18 cm was left in an atmosphere at a temperature of 20 ° C. and a humidity of 60% for 12 hours or more, and then set on the ground total (formation tester FMT-MIII: manufactured by Nomura Corporation). The transmittance of the pixel was measured. From the obtained transmittance, the absorbance and its standard deviation were calculated using a defined absorbance conversion formula.

(5) Maximum height roughness (μm)
After leaving a 4 cm × 10 cm polishing cloth sample in an atmosphere of temperature 20 ° C. and humidity 60% for 12 hours or more, the surface of the single yarn-dispersed nonwoven fabric was measured with a 3D real surface view microscope (VE-9800: manufactured by Keyence Corporation). Observed and imaged at 50x magnification. By analyzing the cross-sectional profile of the obtained image, the maximum height roughness (difference in height between the top and bottom of the roughness curve) of a 2 mm long abrasive cloth sample is measured per measurement. This measurement was performed 10 times. Evaluation was made using the average of the 10 measurements obtained.

(6) Texture processing result (Ra) (nm)
This was performed according to JIS B 0601-1994.
By using an atomic force microscope (Nano Scope IV D3100: manufactured by Digital Instruments), the arithmetic average roughness is measured for 10 arbitrary linear surfaces of the disk substrate sample, and the measured values at 10 positions are averaged. The surface average roughness (Ra) was determined.

(7) Presence / absence of fiber bundle An abrasive cloth sample was cut in a cross-sectional direction using an ultramicrotome (ULTRACUT-N: manufactured by REICHERT), and this was cut with a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.). Observation was performed and an image with an acceleration voltage of 20 kV and a magnification of 500 times was taken. Arbitrary 10 images were observed, and the presence or absence of a fiber bundle in which a single yarn was present in an uneven manner and a bundle shape was confirmed.

(8) Crystallinity (%)
The single yarn-dispersed nonwoven fabric of the polishing side first layer was peeled off from the polishing sheet, and the heat of fusion was measured with a differential scanning calorimeter (DSC-60: manufactured by Shimadzu Corporation) (temperature rising rate was 20 ° C./min, sample) Weight is about 5 mg). When the measured heat of fusion per unit mass is ΔH _m , the crystallinity (Xc) can be calculated from the following equation. Here, ΔH ₀ is the heat of fusion per unit mass of the crystal.
Xc (%) = [ΔH _m / ΔH ₀ ] × 100

(9) Water absorption speed (mm)
According to JIS L 1907-2003, the lower end of the vertically suspended test piece was immersed in water and allowed to stand for a certain time (10 minutes), and then the height of the raised water was measured.

(10) Compressive energy (gf · cm / cm ² )
As a measuring instrument, KES-G5 (manufactured by Kato Tech Co., Ltd.) was used. The test conditions are as follows.

・ SENS (recording sensitivity): 2
・ Type of force meter: 1kg
・ SPEED RANGE: 0.02 mm / sec ・ Pressurized area: 2 cm ²
・ STROKE SET: 5.0
・ Capture interval: 0.5
-Upper limit load: 50 gf / cm ²

  Compression was performed under the above test conditions, and compression energy was obtained from a correlation diagram between pressure and deformation. It means that it is easy to compress, ie, it is soft, so that compression energy is large. It means that it is so hard that compression energy is small.

(11) Elongation (%)
According to JIS L 1096-2003, it measured using the constant-speed expansion | extension type | mold tensile tester (Tensilon RTC-1210A: Co., Ltd. product made by Orientec Co., Ltd.). The test conditions are as follows.
・ Dimensions of test piece: width 2.5 cm, length 20 cm
・ Grip interval: 10cm
・ Tensile speed: 10 cm / min

[Example 1]
Polyethylene terephthalate (hereinafter abbreviated as PET) pellets having an intrinsic viscosity of 0.51 were heated and melted with an extruder and fed into a die heated to 310 ° C. Molten PET is discharged at a discharge rate of 0.20 g / min per nozzle from a nozzle in which nozzles having a diameter of 0.3 mm are arranged in a row at a pitch of 1.0 mm, and the temperature is 365 ° C. from the vicinity of the opening end of the nozzle. The heated air was sprayed at a pressure of 0.24 MPa, and the produced single yarn group was continuously accumulated on a moving collecting surface positioned 60 cm below the spinning nozzle, and wound 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 cut to a length of 5.0 mm were dispersed in water to obtain a papermaking slurry. This slurry was made to produce a paper sheet (A) having a basis weight of 42 g / m ² and a paper sheet (B) having a weight of 17 g / m ² .

100 denier / 48 plain weave fabric having a basis weight 41 g / ^{m 2} made of PET fiber false twist textured yarn of filaments (warp density of 46 per 2.54 cm, weft density of 54 per 2.54 cm, untwisted) papermaking on both sides of the sheet (A) and (B) were laminated | stacked and the papermaking sheet | seat (C) was manufactured.

  After the melt-blown nonwoven fabric obtained above is laminated on the sheet (A) side of the paper-making sheet (C), a multilayer structure is formed by spraying a high-speed water stream and sucking it three-dimensionally while sucking from below so that the static pressure is 20 kPa. A sheet was produced. The high-speed water flow was continuously ejected at a pressure of 3.0 MPa from nozzles having a diameter of 0.2 mm arranged in a line at a pitch of 3.0 mm, and the high-pressure water flow was collided with the sheet at a position 30 mm from the nozzle.

Next, this multilayer structure sheet was impregnated with an aqueous polyether polyurethane emulsion (AP-18: manufactured by Nikka Chemical Co., Ltd.) so as to be 12 wt% with respect to the multilayer structure sheet, and dried with a hot air dryer (130 C. for 3 minutes) to solidify the polyurethane.
Subsequently, a surfactant (Emulgen 120: manufactured by Kao Corporation) was impregnated so as to be 0.5 wt%, and dried with a hot air dryer (130 ° C. × 2 minutes). This processing can improve water absorption.

  Further, a # 240 buffing paper (W54P240: manufactured by Riken Chemical Co., Ltd.) was used to buff the melt blown nonwoven fabric surface, which is the first layer on the polishing side, at a paper speed of 1000 m / min to obtain a polishing cloth for texturing.

The single yarn-dispersed nonwoven fabric, which is the polishing-side first layer of the obtained textured polishing cloth, has a number average fiber diameter of 1.0 μm, a thickness of 160 μm, a maximum height roughness of 42 μm, and a fiber bundle is observed. There wasn't.
The obtained polishing cloth was slit into a width of 38 mm, and a disk substrate obtained by subjecting an aluminum plate to Ni-P plating and polishing treatment was textured under the following conditions.

(Texture processing conditions)
Abrasive grain: Diamond free abrasive grain Abrasive grain average particle diameter: 0.3 μm
Substrate rotation speed: 500rpm
Polishing cloth supply speed: 10 cm / min Traverse condition: amplitude 1 mm, 600 times / min (10 Hz)
The surface average roughness (Ra) of the processed disk substrate was measured and found to be 0.31 nm.

[Example 2]
In the production of the melt blown nonwoven fabric, the basis weight is 60 g / m ² , the thickness is 280 μm, the number average fiber diameter of the single yarn is 0.6 μm, and the absorbance, except that the single hole discharge rate is 0.10 g / min. A melt blown nonwoven fabric having a standard deviation of 0.028 was obtained. Next, using the obtained melt-blown nonwoven fabric, in the same manner as in Example 1, production of a textured polishing cloth and texture processing / Ra measurement were performed.

  The number average fiber diameter of the single yarn constituting the melt blown nonwoven fabric can be reduced to 0.6 μm by reducing the single hole discharge amount to half that of Example 1, and the texture obtained by reducing the diameter of the single yarn The maximum height roughness of the polishing-side first layer surface of the processing polishing cloth can be reduced to 34 μm, and no fiber bundle was observed. It was 0.26 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Example 3]
In the production of the melt blown nonwoven fabric, the weight per unit area was 60 g / m ² , the thickness was 280 μm, and the number average fiber of single yarn, except that nylon 6 (UBE nylon 1011FB: manufactured by Ube Industries) was used as the polymer. A meltblown nonwoven fabric having a diameter of 1.4 μm and a standard deviation of absorbance of 0.038 was obtained. Next, using the obtained melt-blown nonwoven fabric, in the same manner as in Example 1, production of a textured polishing cloth and texture processing / Ra measurement were performed.

  The number average fiber diameter of the single yarn-dispersed nonwoven fabric, which is the polishing-side first layer of the resulting textured polishing cloth, is 1.4 μm, the thickness is 120 μm, the maximum height roughness is 48 μm, and no fiber bundle is observed. It was. It was 0.39 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Example 4]
A melt blown nonwoven fabric obtained in the same manner as in Example 1 and 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 was used. Except for impregnating with ether-based water-based polyurethane emulsion, using # 500 buffing paper (C54P500: manufactured by Riken Chemical Co., Ltd.) and buffing the single yarn-dispersed non-woven fabric surface, which is the first layer on the polishing side, four times at a paper speed of 1000 m / min. In the same manner as in Example 1, production of a textured polishing cloth and texture processing / Ra measurement were performed.

  The number average fiber diameter of the single yarn-dispersed nonwoven fabric, which is the polishing-side first layer of the textured polishing cloth, is 1.0 μm, the thickness is 110 μm, the maximum height roughness is 56 μm, and no fiber bundle is observed. It was. The surface average roughness (Ra) of the textured disk substrate was measured and found to be 0.42 nm.

[Comparative Example 1]
A melt blown nonwoven fabric obtained in the same manner as in Example 1 and 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 was used. Except not impregnating with the ether-based aqueous polyurethane emulsion, the production of the textured polishing cloth and the texture processing / Ra measurement were carried out in the same manner as in Example 1.

  Buffing using a relatively coarse buffing paper without impregnating the polymer elastic body, the smoothness of the polishing layer is poor, and the maximum height roughness of the surface of the single yarn-dispersed nonwoven fabric that is the first layer on the polishing side Was 98 μm, and the maximum height roughness was about twice that of Example 1 impregnated with a polymer elastic body. It was 0.68 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Comparative Example 2]
Using a melt blown nonwoven fabric obtained in the same manner as in Example 1 and 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, a papermaking sheet (A) And (B), except that the single yarn diameter of the short fibers was 10.1 μm, the production of the textured polishing cloth and the texture processing / Ra measurement were carried out in the same manner as in Example 1.
It was 0.61 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Comparative Example 3]
A polyester copolymer polymer (PET obtained by copolymerizing 10 wt% of polyethylene glycol having a molecular weight of 4000) which is easily reduced in alkali was used as a sea component, and regular type PET (inherent viscosity 0.65) was used as an island component. Each of these two polymers was weighed with a gear pump and melt-spun at 290 ° C. using a spout with 100 islands / hole at a ratio of 35 wt% sea component and 65 wt% island component to obtain an undrawn yarn. .

The obtained undrawn yarn was heat-drawn at a temperature of 75 ° C. and a draw ratio of 2.8 times, and heat-set at 130 ° C. )
The obtained sea-island type composite fiber was cut to 5.0 mm and dispersed in water to obtain a papermaking slurry. The slurry was papermaking to produce a papermaking sheet having a basis weight 17g / ^{m 2} (B) and the papermaking sheet basis weight 150g / ^{m 2} (D).

Next, in the same manner as in Example 1, the paper sheet (D) and the paper sheet (B) were laminated on both sides of a plain fabric with a basis weight of 41 g / m ^{2 made} of 100 denier / 48 filament PET fibers, While sucking from below so that the pressure becomes 15 kPa, a high-speed water flow was jetted to make a three-dimensional entanglement to produce a multilayer structure sheet (E). The high-speed water flow was continuously ejected at a pressure of 3.0 MPa from nozzles having a diameter of 0.2 mm arranged in a row at a pitch of 3.0 mm, and the high-pressure water flow was made to collide with the sheet at a position 30 mm from the nozzle.

  The obtained multilayer structure sheet (E) is impregnated with a dimethylformamide (DMF) solution of a solvent-based polyether polyurethane emulsion so that the multilayer structure sheet is 26 wt%, and is immersed in a water bath to solidify the polyurethane. After (wet coagulation), it was dried with a hot air dryer (130 ° C. × 3 minutes). Further, sea components were eluted with a 5 wt% NaOH aqueous solution at 80 ° C. to form ultrafine fibers having a number average fiber diameter of 1.2 μm. In addition, when observed with a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.), the presence of the fiber bundle was confirmed.

Then, using a # 240 buffing paper (W54P240, manufactured by Riken Chemical Co., Ltd.), the surface of the first layer was buffed and raised at a paper speed of 1000 m / min to obtain a polishing cloth for texturing. Because 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 was present despite impregnating the polymer elastic body, The maximum height roughness of the polishing-side first layer of the textured polishing cloth was 120 μm, which was extremely large.
As a result of carrying out texture processing and Ra measurement in the same manner as in Example 1, the surface average roughness (Ra) of the disk substrate after texturing 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 340 ° C. The obtained meltblown 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, a textured polishing cloth was produced and textured and Ra was measured in the same manner as in Example 1. As a result, the surface average roughness (Ra) of the disk substrate after texturing was 0. 0.52 nm.

  Although the maximum height roughness of the surface of the single yarn-dispersed nonwoven fabric that is the first layer on the polishing side is 70 μm or less, the heated air temperature in the production of the meltblown nonwoven fabric was low (implemented at 365 ° C. in Example 1). It is considered that 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, and as a result, the surface average roughness (Ra) of the disk substrate after texturing is increased.

[Comparative Example 5]
A melt blown nonwoven fabric was produced in the same manner as in Example 1 except that the heating air temperature was 315 ° C. and the rectifier was not used. 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, the surface roughness average (Ra) of the disk substrate after texturing was 0 as a result of producing a textural polishing cloth and texturing / Ra measurement in the same manner as in Example 1. It was .65 nm.

[Comparative Example 6]
In the production of the melt blown nonwoven fabric, the weight per unit area was 60 g / m ² , the thickness was 280 μm, and the number average fiber of single yarn, except that nylon 6 (UBE nylon 1011FB: manufactured by Ube Industries) was used as the polymer. A meltblown nonwoven fabric having a diameter of 1.0 μm and a standard deviation of absorbance of 0.032 was obtained.

Using the obtained melt blown nonwoven fabric, a multilayer structure sheet was produced in the same manner as in Example 1. Next, a surfactant was not impregnated, and a dimethylformamide (DMF) solution of a solvent-based polyether polyurethane emulsion was added to the multilayer sheet. Fabrication of a textured polishing cloth and texture processing / Ra measurement were performed in the same manner as in Example 3 except that the structure sheet was impregnated so as to be 11 wt%.
It was 0.58 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Comparative Example 7]
Similar to Example 1 using a melt blown nonwoven fabric obtained in the same manner as in Example 1 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. Thus, a multilayer structure sheet was produced.

Next, the multilayer structure sheet is impregnated with a dimethylformamide (DMF) solution of a solvent-based polycarbonate polyurethane emulsion so that the multilayer structure sheet is 34 wt%, and the polyurethane is solidified by dipping in a water tank (wet coagulation). Then, production of a textured polishing cloth and texture processing / Ra measurement were carried out in the same manner as in Example 1 except that it was dried (130 ° C. × 3 minutes) with a hot air dryer.
It was 0.59 nm when the surface average roughness (Ra) of the disk board | substrate after texture processing was measured.

[Comparative Example 8]
A basis weight of 60 g / m ² , a thickness of 280 μm, a number average fiber diameter of a single yarn of 0.9 μm, and an absorbance standard obtained in the same manner as in Example 1 except that PET pellets having an intrinsic viscosity of 0.39 were used. Using a melt blown nonwoven fabric with a deviation of 0.045, a multilayer structure sheet was produced in the same manner as in Example 1.

  Using the obtained meltblown nonwoven fabric, an attempt was made to produce a textured polishing cloth in the same manner as in Example 1. When the surface of the melt blown nonwoven fabric, which is the first layer on the polishing side, was buffed, many single yarns were cut, and a textured polishing cloth worthy of evaluation could not be produced. When the degree of crystallinity of the single yarn-dispersed nonwoven fabric as the polishing side first layer was measured, it was 27.2%.

[Comparative Example 9]
Similar to Example 1, using a melt blown nonwoven fabric obtained in the same manner as in Example 1 and having a basis weight of 30 g / m ² , a thickness of 140 μm, a single yarn number average fiber diameter of 1.0 μm, and a standard deviation of absorbance of 0.032. Thus, a multilayer structure sheet was produced.
Texture processing and Ra measurement were carried out using the textured polishing cloth comprising this multilayer structure sheet. It was 0.63 nm when the surface average roughness (Ra) of the disk substrate after texturing was measured.
Tables 1 and 2 show the structures and physical properties of the polishing cloths produced in the above Examples and Comparative Examples.

Claims (11)

The number of single yarns constituting a single yarn-dispersed nonwoven fabric, which is a polishing cloth comprising two or more layers of multilayered sheets laminated with a single yarn-dispersed nonwoven fabric and a support. The average fiber diameter is 0.1 to 1.7 μm, the surface of the first layer is raised, the maximum height roughness of the surface of the first layer is 70 μm or less, the water absorption speed is 100 to 240 mm, and the compression energy Is a polishing cloth for precision processing, characterized in that is 0.10 to 0.30 gf · cm / cm ² .   The abrasive cloth for precision processing according to claim 1, wherein the single yarn-dispersed nonwoven fabric is a melt blown nonwoven fabric.   The precision processing abrasive cloth according to claim 1 or 2, wherein the thickness of the single-layered single-fiber dispersed nonwoven fabric is 100 µm or more.   The abrasive cloth for precision processing according to any one of claims 1 to 3, wherein the single yarn-dispersed nonwoven fabric used for the first layer has an absorbance with a standard deviation of 0.050 or less.   The abrasive cloth for precision processing according to any one of claims 1 to 4, wherein the single-layer dispersed nonwoven fabric of the first layer is made of polyester fibers, and the crystallinity of the polyester fibers is 35% or more.   The abrasive cloth for precision processing according to any one of claims 1 to 5, wherein the multilayer structure sheet is impregnated with a polymer elastic body.   The polishing cloth for precision processing according to any one of claims 1 to 6, wherein the polymer elastic body is applied to the multilayer structure sheet at 30 wt% or less.   The abrasive cloth for precision processing according to any one of claims 1 to 7, wherein the polymer elastic body is polyurethane.   The polishing cloth for precision machining according to any one of claims 1 to 8, wherein the elongation in the longitudinal direction at a load of 1.0 kgf / cm is 4% or less and the elongation in the width direction is 12% or less. .   The polishing pad for precision processing according to any one of claims 1 to 9, wherein the support is a nonwoven fabric.   The abrasive cloth for precision processing according to any one of claims 1 to 10, wherein the support is a laminate in which ultrafine fiber layers having a fiber diameter of 10 µm or less are laminated on both surfaces of the woven fabric.