JP2007307654A - Abrasive cloth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive cloth capable of forming a texture mark with excellent acuteness in irregularities, reducing a scratch defect and ridge defect, attaining a high yield ratio, and applying hard disc texture working with high accuracy of surface roughness of 0.3 nm or less on the surface of a substrate. <P>SOLUTION: This abrasive cloth is formed of a sheet-like material composed of non-woven fabric formed by entangling very fine polyamide fiber bundles having the mean fineness of 0.0001-0.05 dtex and a high polymer elastic body mainly composed of polyurethane existing in the internal space of the non-woven fabric, and at least one side of the sheet-like material has a fiber raised surface composed of very fine fibers. The very fine polyamide fiber comprises (1) semiaromatic polyamide composed of an aliphatic dicarboxylic acid and a diamine component wherein 80 mol% or more in the total diamine component is an aromatic diamine, and/or (2) semiaromtic polyamide composed of a dicarboxylic acid component wherein 80 mol% or more in the total dicarboxylic acid component is an aromatic dicarboxylic acid, and an aliphatic alkylene diamine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an abrasive cloth, and more particularly to an abrasive cloth used when texturing an aluminum alloy substrate or a glass substrate used for a hard disk with an ultra-high precision finish.

  In magnetic recording media such as hard disks, demands for higher capacity and higher storage density are increasing due to remarkable technological innovation. For this reason, high precision of various substrate surface processing is required.

  As the capacity increases and the storage density increases, the distance between the hard disk and the magnetic head, that is, the flying height of the magnetic head has been reduced. Recently, a flying height of 5 nm or less is required. When the flying height of the magnetic head is remarkably reduced, if there is a protrusion on the surface of the magnetic disk, the protrusion and the magnetic head come into contact with each other, causing a head crash and causing a scratch on the disk surface. Even a minute protrusion that does not cause a head crash causes an error that occurs when reading and writing information due to contact with the magnetic head. The recording disk has been reduced in size in parallel with the increase in capacity and density, and the motor for rotating the spindle has been reduced in size. For this reason, the torque of the motor is insufficient, causing the trouble that the magnetic head is in close contact with the surface of the recording disk and cannot float.

  As a means for preventing the close contact between the hard disk and the magnetic head, a surface treatment called texture processing is performed to form a substantially concentric fine streak on the substrate surface of the recording disk. Also, by performing this texturing, it becomes possible to improve the coercive force in the recording direction by controlling the direction of crystal growth when forming the metal magnetic layer on the disk substrate, and the magnetic force in the circumferential direction can be improved. The magnetic properties are improved by providing a proper orientation.

  Conventionally, as a texture processing method, slurry grinding is used in which grinding is performed by attaching an aqueous polishing slurry composed of loose abrasive grains to the surface of a polishing cloth. In other words, using a polishing cloth as a tape, while the aluminum alloy substrate or glass substrate is continuously rotated, the polishing tape is pressed against the substrate and reciprocated in the radial direction of the substrate to continuously run the polishing tape. . At that time, the slurry is supplied between the polishing tape and the substrate, the free abrasive grains contained in the slurry are held in a finely dispersed state in the fibers constituting the polishing tape, and contacted with the substrate for polishing. is there.

When performing surface treatment to satisfy the low flying height of the magnetic head by texture processing, the waviness after polishing is lowered in order to cope with the recent increase in recording density for rapid increase in recording capacity, It has been required to form uniform and fine texture marks and extremely reduce the surface roughness of the substrate, and a polishing cloth capable of meeting the demand has been demanded.
In order to reduce the substrate surface roughness in texture processing, many methods using a nonwoven fabric have been proposed because of excellent cushioning properties and smoothness of the substrate surface (see Patent Document 1 and Patent Document 2).

  In particular, for the purpose of improving the smoothness of the surface of the base material and adjusting the contact with the disk substrate surface, various proposals have been made to make the fibers constituting the nonwoven fabric ultrafine and impregnate the nonwoven fabric with a polymer elastic body. For example, in a non-woven fabric formed by entanglement of ultrafine fibers, polyurethane having a specific wet elastic modulus is contained, and on the surface, napped fibers composed of ultrafine fibers having a fineness of 0.03 dtex or less are present. A polishing sheet (see Patent Document 3) has been proposed, and the surface roughness of 0.4 nm is realized by processing using the polishing sheet for texture processing.

  Also, a polishing cloth (see Patent Document 4) made of a non-woven fabric of polyamide ultrafine fibers having an average fineness of 0.001 to 0.1 dtex has been proposed, and this polishing cloth has achieved a surface roughness of 0.28 nm. .

  On the other hand, as the surface roughness is minimized, the allowable range for local flaws having deep valleys on the substrate surface, that is, scratch defects and abnormal protrusions, that is, ridge defects, is becoming narrower. In other words, in order to improve the surface recording density required for hard disks, minimization of unit recording area and low flying height of magnetic heads are increasingly required. In conventional texture processing, it is judged as a scratch defect or a ridge defect. Unscratched scratches and protrusions lead to the occurrence of errors, and these scratches and protrusions are regarded as defects. Therefore, it is necessary to further improve the smoothness and uniformity of the substrate surface.

  Conventionally, the abrasive particles used in the polishing slurry have been diamond particles having a particle size of about 100 nm. In recent years, for the purpose of reducing the disk defects, the diameter of diamond particles has been reduced. For example, Patent Document 5 proposes an aqueous polishing slurry in which cluster particles made of diamond particles having a particle diameter in the range of 1 to 10 nm are used as abrasive particles, and in polishing using a polishing tape made of microfiber, The surface roughness of 0.18 nm and the reduction of abnormal protrusions are realized.

  However, in the texture processing using the conventional polishing cloth described in Patent Documents 1 to 5 and the polishing slurry composed of the small-diameter diamond particles, the diamond particle diameter is small and the grinding force of the abrasive grains itself is reduced. Although it is possible to reduce defects and ridge defects, the textured surface of the substrate surface is formed in an indefinite state, and the final textured surface roughness is small. Due to the lack of sharpness of the irregularities of the marks, it becomes insufficient to control the direction of crystal growth when forming the metal magnetic layer on the disk substrate, and the magnetic orientation in the circumferential direction is lowered. , A new problem that causes errors in hard disk drives, which can cause a significant decrease in electromagnetic conversion characteristics such as resolution and S / N ratio. The have occurred.

  Therefore, recently, in texturing using an aqueous polishing slurry composed of small-diameter diamond particles having a particle size of 10 nm or less, there is a demand for a technique for improving the sharpness of texture marks as well as reducing surface roughness and scratch ridge defects. Therefore, an ultra-high-precision polishing cloth that is the core of this technology is required.

  Here, in order to achieve both the reduction of the surface roughness and scratch ridge defects and the sharpening of the unevenness of the texture marks, the cluster particles composed of small diamond particles having a particle diameter of 10 nm or less were finely dispersed on the surface of the polishing cloth. Since it is necessary to hold the particles firmly with the fibers constituting the surface of the polishing cloth and to increase the pressure of the abrasive grains for grinding, the compatibility with the water-based polishing slurry and the abrasive A polishing cloth is required to increase both the pressing force of the grains.

  Patent Document 6 proposes to use fibers that can be fibrillated such as liquid crystal polyester fibers and aromatic polyamide fibers as abrasive cloth constituent fibers, aiming to increase the pressing of abrasive grains and increase the amount of grinding. Has been. However, when liquid crystal polyester fiber is used for the polishing sheet, the fiber strength in the wet state after dropping the aqueous polishing slurry is high and high grinding power can be obtained, but since the affinity with the aqueous polishing slurry is poor, the locality of the cluster particles Thus, it was impossible to suppress general agglomeration and to prevent the occurrence of scratch defects. In addition, the aromatic polyamide fiber is not specifically exemplified with respect to a specific composition, such as polymer type and mechanical properties of the fiber, and details of the production method. For example, a general-purpose wholly aromatic polyamide fiber ( When using aramid fiber), the fiber polymer itself is hard and high grinding power can be obtained, but the affinity with the water-based polishing slurry cannot be sufficiently increased, resulting in rough cutting as a whole and generation of scratch defects. And processing unevenness could not be suppressed. Further, since the abrasive sheet is made of a single nonwoven fabric, the cushioning property is poor and scratch defects cannot be suppressed.

Therefore, in order to firmly hold the abrasive grains in a finely dispersed state and further improve the pressure, there is a technology that can satisfy all of the high rigidity of the polishing cloth surface fibers and the improvement of the affinity with the aqueous polishing slurry. It has become necessary.
Japanese Patent Laid-Open No. 9-262775 JP-A-9-277175 JP 2002-79472 A JP 2002-273650 A JP 2004-178777 A Japanese Patent Laid-Open No. 10-315142

  Therefore, in view of the background of such prior art, the object of the present invention is to form texture marks with excellent sharpness of irregularities, with few scratch defects and ridge defects, good yield, and surface roughness on the substrate surface. An object of the present invention is to provide an abrasive cloth that can be textured with high accuracy of 0.3 nm or less.

  The present invention employs the following means in order to solve such problems.

  That is, the gist of the polishing cloth of the present invention is that a polyamide ultrafine fiber having an average fineness of 0.0001 to 0.05 dtex and / or a non-woven fabric formed by entanglement of an ultrafine fiber bundle made of the polyamide ultrafine fiber, and polyurethane as a main component A polishing cloth for texturing of a hard disk made of a sheet-like material having at least one raised surface composed of the ultrafine fiber, wherein the polyamide ultrafine fiber comprises (1) aliphatic Fibers composed of a semi-aromatic polyamide comprising a dicarboxylic acid and a diamine component in which at least 80 mol% of the total diamine component is an aromatic diamine and / or (2) at least 80 mol% of the total dicarboxylic acid component is aromatic A fiber made of a semi-aromatic polyamide comprising a dicarboxylic acid component which is a dicarboxylic acid and an aliphatic alkylenediamine. It is a polishing cloth which is characterized in.

  According to the present invention, the napped fibers on the surface of the polishing cloth have excellent affinity with the aqueous polishing slurry used for hard disk texturing, and the fiber rigidity in the wet state after the slurry dripping is high. The abrasive grains are not concentrated locally, but are distributed on the surface of the polishing cloth in a finely dispersed state, and the gripability of the abrasive grains on the fiber surface is high, and the processing pressure per unit particle of the abrasive grains is high, It is possible to form texture marks with excellent sharpness of unevenness, with few scratch defects and ridge defects, good yield, and high precision texture processing with surface roughness of 0.3 nm or less on the substrate surface It is possible to obtain a polishing cloth that can be finished as a processed surface that can cope with higher recording density of a recording disk having excellent electromagnetic conversion characteristics. Kill.

  The inventors of the present invention are concerned with the above-described problems, namely, the sharpening of the textured irregularities, the surface roughness of 0.3 nm or less, the suppression of scratch defects and ridge defects, and the stiffness of napped fibers on the surface of the polishing cloth in the wet state. And the water-based polishing slurry is carefully studied and found that the polymer composition and fineness of the polishing cloth constituent fiber greatly contribute to high-precision texture processing. A semi-aromatic polyamide ultrafine fiber having a fineness of 0.0001 to 0.05 dtex and / or a nonwoven fabric intertwined with an ultrafine fiber bundle made of the polyamide ultrafine fiber and a polymer elastic body mainly composed of polyurethane. As a result, it has been found that such problems can be solved at once.

  The sheet-like material constituting the polishing cloth of the present invention will be described. Specifically, the semi-aromatic polyamide and / or (2) the total dicarboxylic acid in which the ultrafine fiber component is (1) an aliphatic dicarboxylic acid and a diamine component in which 80 mol% of the total diamine component is an aromatic diamine. An ultrafine fiber having an average fineness of 0.0001 to 0.05 dtex, made of a semi-aromatic polyamide composed of a dicarboxylic acid component in which 80 mol% or more of the components is an aromatic dicarboxylic acid and an aliphatic alkylenediamine. Generation fibers are obtained through composite spinning, drawing and crimping. Thereafter, using raw cotton obtained by cutting ultrafine fiber-generating fibers, an entanglement process such as needle punching is performed to create a nonwoven fabric composed of composite fibers. Next, the sea component is dissolved and removed from the composite fiber or peeled / divided by physical and chemical action to give a polymer elastic body mainly composed of polyurethane before and / or after ultrafine fiber formation, The molecular elastic body is substantially solidified and solidified. Next, buffing treatment is performed on the obtained sheet-like material to form a raised surface on the surface of the sheet-like material. The abrasive cloth of the present invention can be achieved by the sheet-like material obtained by the above process.

  Furthermore, the structure and manufacturing method of the polishing cloth of the present invention will be described in detail.

  In the present invention, from the viewpoints of affinity to an aqueous polishing slurry, abrasive pressing force (processing pressure), and surface smoothness, which contributes to improvement in gripping and dispersibility of abrasive grains during hard disk texture processing, ultrafine fibers (1) A semi-aromatic polyamide comprising an aliphatic dicarboxylic acid and a diamine component in which 80 mol% or more of the total diamine component is an aromatic diamine, and (2) 80 mol of the total dicarboxylic acid component. % Or more of a semi-aromatic polyamide comprising a dicarboxylic acid component and an aliphatic alkylenediamine which are aromatic dicarboxylic acids, or (1) a diamine wherein 80 mol% or more of the aliphatic dicarboxylic acid and the total diamine component is an aromatic diamine 80 mol% or more of the semi-aromatic polyamide comprising the components and (2) the total dicarboxylic acid component is the aromatic dicarboxylic acid It is important comprising a carboxylic acid component and an aliphatic alkylenediamine is a mixed polymer of semi-aromatic polyamide. A mode in which the ultrafine fiber made of the semi-aromatic polyamide (1) and the ultrafine fiber made of the semi-aromatic polyamide (2) are also preferable.

  Among them, as the dicarboxylic acid component constituting the semiaromatic polyamide (1), an aliphatic dicarboxylic acid having 6 to 12 carbon atoms is used, and as the diamine component constituting the semiaromatic polyamide (2), It is more preferable to use an aliphatic alkylene diamine having 6 to 12 carbon atoms.

  This is excellent in mechanical properties such as fiber rigidity in the wet state after dropping aqueous slurry in texture processing, that is, tensile / bending, excellent in uniform dispersibility of fibers on the raised surface, and also has high water absorption rate. It is possible to improve the grip and dispersibility of the abrasive grains, and can press the small-diameter diamond particles against the disk surface with a uniform and high processing pressure. This is because it is possible to form texture marks having excellent sharpness.

  In addition, as polyamide types, there are aliphatic polyamides such as nylon 6 and nylon 66 and wholly aromatic polyamides (aramids) in which both the dicarboxylic acid component and the diamine component are aromatic, but aliphatic polyamides are semi-aromatic. Although it has a high water absorption rate and excellent compatibility with water-based polishing slurries compared to the group polyamide, the fiber stiffness is significantly reduced when wet compared to when dry, so the pressing force of the abrasive during texture processing is sufficiently increased. As a result, the uneven shape of the texture mark becomes unclear, which leads to deterioration of electromagnetic conversion characteristics in the hard disk drive, which is not preferable. On the other hand, wholly aromatic polyamide has high fiber stiffness when wet and can increase the pressing force of abrasive grains, but has low water absorption and poor affinity with aqueous polishing slurries. This is not preferable because it causes local agglomeration of the resin and the generation of scratch defects cannot be suppressed.

  Next, the components of the semi-aromatic polyamide used in the present invention will be described in detail.

  First, the aliphatic dicarboxylic acid constituting the semi-aromatic polyamide of (1) includes adipic acid, malonic acid, succinic acid, 2-methyladipic acid, trimethyladipic acid and the like from the viewpoint of strength and processability. Can do. Next, examples of the aromatic diamine include xylenediamine, xylylenediamine, and phenylenediamine from the viewpoints of strength and wear resistance. As xylenediamine, metaxylenediamine is particularly preferable. The content of the aromatic diamine is essentially 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol% with respect to the total diamine component. That is, the semi-aromatic polyamide (1) is preferably a semi-aromatic polyamide comprising an aliphatic dicarboxylic acid and an aromatic diamine. When the aromatic diamine in the diamine component constituting the semi-aromatic polyamide of (1) is less than 80 mol%, the ultrafine fiber has a low tensile / bending rigidity in the wet state, the fiber surface hardness is low, and small-diameter diamond particles Is not preferable because it is insufficient to press against the disk surface with a high processing pressure, and texture marks with sharp corners cannot be sufficiently formed at the tip of the projections and depressions.

  As diamine components other than aromatic diamine components, ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine And aliphatic diamines such as dodecamethylenediamine, and alicyclic diamines such as cyclohexanediamine.

  Examples of the aromatic dicarboxylic acid constituting the semiaromatic polyamide (2) include terephthalic acid, 2,6-naphthalenedicarboxylic acid, and isophthalic acid from the viewpoint of strength and wear resistance. The content of the aromatic dicarboxylic acid is essentially 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 100 mol% with respect to the total dicarboxylic acid component. That is, the semi-aromatic polyamide (2) is preferably a semi-aromatic polyamide comprising an aromatic dicarboxylic acid and an aliphatic alkylene diamine. When the aromatic dicarboxylic acid component in the dicarboxylic acid component constituting the semi-aromatic polyamide of (2) is less than 80 mol%, the tensile / bending rigidity in the wet state of the ultrafine fiber, the fiber surface hardness is low, It is not preferable that the small diameter diamond particles are insufficiently pressed against the disk surface with a high processing pressure, and the textured tip of the concave and convex portions cannot sufficiently form sharp texture marks.

  Examples of dicarboxylic acid components other than the aromatic dicarboxylic acid include aliphatic dicarboxylic acids such as malonic acid, succinic acid, 2-methyladipic acid and trimethyladipic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. An acid etc. can be mentioned.

  Subsequently, as the aliphatic alkylene diamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, Examples thereof include 1,12-dodecanediamine.

  As described above, the polishing cloth of the present invention contains a semi-aromatic polyamide composed of an aliphatic dicarboxylic acid and an aromatic diamine and / or a semi-aromatic polyamide composed of an aromatic dicarboxylic acid and an aliphatic alkylene diamine. Most preferably.

  In addition, as a component of the semi-aromatic polyamide used in the present invention, (1) and (2) are not limited to the dicarboxylic acid component and the diamine component, respectively, as long as the effects of the present invention are not impaired. Two or more kinds of dicarboxylic acid components and diamine components can be used in combination.

  The relative viscosity of sulfuric acid of the semi-aromatic polyamide ultrafine fiber used in the present invention is preferably 2.0 to 3.5, more preferably 2.0 to 3.3. The semi-aromatic polyamide within the range of the relative viscosity of sulfuric acid has excellent spinning and drawing process passability when producing ultrafine fiber-generating fibers and excellent rigidity of the resulting ultrafine fibers. In addition, sulfuric acid relative viscosity can be calculated | required using the following measuring methods. First, components other than the ultrafine fiber component are removed from the polishing cloth of the present invention by dissolution or the like, only the ultrafine fiber is taken out, and 0.25 g of the ultrafine fiber is precisely weighed with a direct balance (0.25 ± 0.005 g). Next, the precisely weighed sample is dissolved in 25 ml of concentrated sulfuric acid to obtain a sample solution. Next, 15 ml of the sample solution was injected into a viscosity tube (with a concentrated sulfuric acid falling time of 100 ± 20 seconds) set in a thermostat heated to 25 ± 0.5 ° C., and then the dropping time of the sample solution Measure. This operation is repeated three times to obtain an average value T. The same operation is repeated three times for concentrated sulfuric acid in which the sample is not dissolved, the average value T0 is determined, and T / T0 is defined as the sulfuric acid relative viscosity.

  It is particularly important that the average fineness of the ultrafine fibers used in the polishing cloth of the present invention is 0.0001 to 0.05 dtex in terms of the density of the napped fibers on the surface of the polishing cloth, the fiber strength, and the gripping ability of the abrasive grains. It is. When it is less than 0.0001 dtex, the fiber strength and rigidity are low, and not only grinding is insufficient, but also the gripability of the abrasive grains is inferior, causing local aggregation of the abrasive grains, and scratch defects are likely to occur. It is not preferable. On the other hand, if it exceeds 0.05 dtex, the density of the napped fibers is inferior, the abrasive grains are not finely dispersed, and the uneven distribution of the abrasive grains on the surface of the polishing cloth is increased. The scratch defect and the ridge defect cannot be suppressed, which is not preferable. In addition, an average fineness says the value measured with the following measuring methods. That is, when a cross section obtained by cutting the polishing cloth in the thickness direction is observed with a scanning electron microscope (SEM) as an observation surface, and an ultrafine fiber bundle exists, the ultrafine fiber fibers constituting one bundle of the ultrafine fiber bundle The diameter is measured, and the fineness is calculated from the specific gravity of the fiber component and the fiber diameter for each ultrafine fiber. The same measurement is performed on a total of five ultrafine fiber bundles, and an average value is calculated using this as a population. The average value is defined as the average fineness. In addition, when a bundle-like ultrafine fiber does not exist, the fiber diameter of 300 ultrafine fibers is measured, and an average value is calculated similarly.

  In order to obtain ultrafine fibers having a desired fineness, it is preferable to use ultrafine fiber generating fibers. The ultra-fine fiber generation type fiber is a sea-island type composite in which two component thermoplastic resins with different solvent solubility are used as sea components and island components, and the sea components are dissolved and removed using a solvent to remove the island components. It is possible to adopt a peelable composite fiber or a multilayer composite fiber in which fibers and two-component thermoplastic resins are alternately arranged in a fiber cross-section radial or layered form and split into ultrafine fibers by separating and separating each component. it can. Among them, the sea-island type composite fiber can give an appropriate gap between the island components by removing the sea component, that is, between the ultra-fine fibers in the fiber bundle, so that the sheet-like material made of the ultra-fine fibers is buffed. And it is preferable because it is excellent in the opening property of the napping when the napped surface is formed.

  For example, (i) a method in which two or more component polymers are blended and spun in a chip state, and (ii) a method in which two or more polymer components are kneaded in advance to form a chip and then spun. (Iii) A method of mixing and spinning two or more polymers in a melted state in a spinning machine pack with a static kneader or the like, and (iv) using a sea-island type compound base such as Japanese Patent Publication No. 44-18369. In addition, a polymer mutual array system in which two components of sea islands are mutually aligned and spun can be used.

  In the present invention, when the ultrafine fiber bundle is present, the fineness CV of the single fiber of the ultrafine fiber constituting the ultrafine fiber bundle is preferably 10% or less. Moreover, although a minimum is not specifically limited, 0.1% or more is preferable. The fineness CV here is a value obtained by dividing the fineness standard deviation of the ultrafine fibers constituting the ultrafine fiber bundle by the average fineness as a percentage (%). The smaller the value, the ultrafine fibers constituting the ultrafine fiber bundle. This shows that the fineness is uniform. When the fineness CV exceeds 10%, uneven distribution of napped fibers due to the difference in rigidity between the low and high fineness fibers on the surface of the polishing cloth occurs, and the uniformity of the abrasive grain dispersion and pressing force is lacking. The scratch defect and the ridge defect cannot be sufficiently suppressed. In order to obtain the desired fineness CV, among the ultrafine fiber generating fibers, the sea-island type composite fiber based on the polymer inter-array system of (iv) is preferable in that ultrafine fibers with uniform fineness can be obtained.

  The cross-sectional shape of the ultra-thin (island) fiber obtained by removing the sea-island composite fiber and the sea component is not particularly limited. For example, a polygon such as a circle, an ellipse, a flat and a triangle, a fan, a cross, Y, H, Examples include X, W, C, and π-type. Further, the number of polymer species used is not particularly limited, but it is preferably 2 to 3 components in consideration of spinning stability, and particularly composed of 2 components of sea 1 component and island 1 component. Is preferred. Moreover, it is preferable that the component ratio at this time is 0.2-0.9 by weight ratio with respect to sea island type composite fiber of an island fiber, More preferably, it is 0.3-0.8. When this component ratio is 0.2 or more, the removal rate of sea components is not too high, productivity is not significantly reduced, and it is preferable in terms of cost. Moreover, it is preferable for the component ratio to be 0.9 or less because the island component fibers are excellent in spreadability and a uniform raised surface can be obtained.

  As the resin constituting the sea component of the sea-island composite fiber, polyethylene, polypropylene, polystyrene, from the point of having chemical properties that are more soluble and degradable than the semi-aromatic polyamide that is a polymer constituting the island component. It is preferable to use a copolymerized polyester, polylactic acid, thermoplastic PVA resin, thermoplastic cellulose resin, or the like containing copolymerized polystyrene, sodium sulfoisophthalic acid or polyethylene glycol as a copolymerization component.

  As the solvent for dissolving the sea component, when the sea component is polyethylene, polypropylene, polystyrene, and copolymer polystyrene, an organic solvent such as toluene or trichloroethylene is used, and when the sea component is a copolymer polyester or polylactic acid, An aqueous alkali solution such as sodium hydroxide can be used. In the case of a thermoplastic PVA resin or a thermoplastic cellulose resin, it can be dissolved in hot water, and the sea-island composite fiber is immersed in the solvent. However, the sea component can be removed by performing the stenosis. In particular, polystyrene, copolymerized polystyrene, polyester, copolymerized polyester, and polylactic acid are preferably used from the viewpoint of increasing the density of surface fibers by high entanglement of fibers when needle punched.

  In the present invention, from the viewpoint of increasing the pressing force of the abrasive grains in the wet state after dropping the aqueous polishing slurry in the texture processing, and improving the sharpness of the unevenness of the texture marks, the initial tension of the semi-aromatic polyamide ultrafine fibers during the wet process The resistance is preferably 10 cN / dtex or more. Further, it is more preferably 15 cN / dtex or more. The higher the initial tensile resistance, the higher the bending resilience when a force is applied in the direction perpendicular to the longitudinal direction of the fiber, so that the substantial processing pressure of the abrasive grains can be increased. Here, the upper limit value is not particularly limited from the viewpoint of rigidity, but it is preferably controlled to 50 cN / dtex or less in consideration of process passability in the spinning and drawing processes. When it is less than 10 cN / dtex, the pressing force of the abrasive grains is insufficient, and not only the uneven shape of the texture marks tends to be unclear, but also the processing pressure of the abrasive grains on the entire disk becomes uneven. This is not preferable because it leads to abnormal surface roughness and uneven processing.

  In order to obtain a desired initial tensile resistance, a semi-aromatic polyamide having the above composition and the relative viscosity of sulfuric acid is used as the ultrafine fiber component, and in order to increase the molecular orientation of the ultrafine fiber component in the spinning and drawing processes, Use the melt-dissolving component of the fiber-generating fiber with a lower viscosity, and set it to a relatively low viscosity relative to the melt viscosity of the ultra-fine fiber component. Using a softening point temperature of the lower temperature side, setting the spinning speed in a range of 800 to 3000 m / min, more preferably in a range of 1000 to 1600 m / min, a draw ratio of 2.7 times or more, Preferably, it is set to 3.0 times or more, and the stretching method is set to multi-stage stretching of two or more stages, and the second stage stretching temperature is set to a high temperature condition with respect to the first stage. It is those that can be achieved.

  The initial tensile resistance of the ultrafine fiber when wet is measured by the following measuring method. First, components other than the ultrafine fiber component are dissolved and removed with an appropriate solvent using 10 ultrafine fiber-generating fibers having the semi-aromatic polyamide obtained through spinning and drawing as the ultrafine fiber component. The obtained ultrafine fiber bundle is immersed in distilled water at 25 ° C. for 30 minutes, and then the surface of the ultrafine fiber bundle is lightly wiped to obtain a wet ultrafine fiber bundle sample. Next, a load-elongation curve is obtained using a constant speed extension type tensile tester (Tensilon) at a test length of 50 mm and a tensile speed of 50 mm / min. Next, in accordance with JIS L 1013 (2005 edition), Section 8.10, the maximum point A (the maximum point of the tangential angle) of the load change with respect to the extension change is obtained from the obtained curve near the origin, and the following formula: Calculate the initial tensile resistance. Tri = P / {(L ′ / L) × F0}, where Tri = initial tensile resistance (cN / dtex), P: load at the maximum point A of contact angle (cN), F0: positive fineness ( dtex), L: trial length (mm), L ′: length of TH (mm) (H is a perpendicular foot from A, and T is an intersection with a horizontal axis of a tangent in A). The same measurement is carried out 5 times, and the average value is defined as the initial tensile resistance (cN / dtex) of the ultrafine fiber when wet.

  The ultrafine fiber-generating fibers thus obtained are entangled to obtain a nonwoven fabric. In order to obtain the nonwoven fabric for constituting the polishing cloth of the present invention, the ultrafine fiber-generating fiber is shortened, a laminated web arranged in the sheet width direction using a card / cross wrapper is formed, and then a needle punch It is preferable to carry out the treatment. In terms of forming a web, a random web or the like can also be used. Moreover, the long fiber nonwoven fabric formed directly from spinning, such as melt blow and spun bond, may be used. However, in particular, in the polishing cloth of the present invention, the long fiber nonwoven fabric is inferior to the short fiber nonwoven fabric in terms of the entanglement between the ultrafine fiber bundles and the denseness of the surface fibers, and the density unevenness of the surface fiber number density is increased. The deviation of the distribution of the abrasive grains is large, and local agglomeration of the abrasive grains may be caused, resulting in the generation of scratches. Therefore, a short fiber nonwoven fabric is preferable to an ultrafine long fiber nonwoven fabric.

The number of punches in the needle punching process is preferably 1000 to 4000 / cm ² from the viewpoint of forming a dense raised surface by high entanglement of fibers. If the number of punching is 1000 / cm ² , the surface fiber is excellent in denseness and a desired high-precision finish can be obtained. If the number of punching is 4000 / cm ² or less, workability is improved. It does not cause deterioration and does not lead to fiber damage or strength reduction. Fiber density of the composite fiber nonwoven fabric sheet after needle punching, from the viewpoint of densification of the surface number of fibers is preferably 0.15~0.4g / cm ^3, with 0.2 to 0.3 g / cm ³ More preferably.

From the viewpoint of densification of the number of surface fibers, the composite fiber nonwoven fabric thus obtained is preferably shrunk by dry heat or wet heat, or both, and further densified.
Next, the ultrafine fiber generating fiber is made into ultrafine fibers. If the ultrafine fiber generating fiber is a sea-island fiber, the sea component may be dissolved and removed with the solvent described above. For the ultra-thinning, a known method and apparatus can be used.

  In addition, after the ultrafine fiber treatment, the intertangling of ultrafine fibers and / or ultrafine fiber bundles is further increased, densification and the openability of the ultrafine fiber bundles are improved, and the smoothness is improved. High-speed fluid flow treatment such as water jet punching treatment, and stagnation treatment using a liquid flow dyeing machine, a Wins dyeing machine, a jigger dyeing machine, a tumbler, a relaxer and the like may be appropriately combined. In the case where the high-speed fluid flow treatment and the stagnation treatment are performed in combination, it is preferable to perform the stagnation treatment after the high-speed fluid flow treatment is performed from the viewpoint of suppressing dimensional variation during the stagnation processing. As the high-speed fluid flow treatment, a water jet punching treatment using a water flow is preferable from the viewpoint of the working environment. When the water jet punching treatment is performed, the water is preferably carried out in a columnar flow state. In order to obtain a columnar flow, generally, a method of ejecting from a nozzle having a diameter of 0.06 to 1.0 mm at a pressure of 1 to 60 MPa is suitably used.

  In the semi-aromatic polyamide ultrafine fiber nonwoven fabric used for the polishing cloth of the present invention, in addition to the semi-aromatic polyamide ultrafine fiber which is the main component, for example, nylon 6 and nylon 66 from the viewpoint of fit to a workpiece and suppression of scratches. Ultrafine fibers made of polyamides such as nylon 12 and copolymer nylon may be mixed and used. From the point of sharpness of the textured irregularities, the mixing amount of the polyamide fibers other than the semi-aromatic polyamide ultrafine fibers is preferably 30% by weight or less, more preferably 10% by weight with respect to the total fiber weight. Hereinafter, it is more preferable to use a smaller amount of 5% by weight or less. Further, from the viewpoint of suppressing scratch defects and ridge defects, the average fineness of the ultrafine fibers made of polyamides other than semi-aromatic polyamide is preferably 0.0001 to 0.05 dtex.

  In the present invention, before and / or after the nonwoven fabric is subjected to the ultrafine fiber treatment, a polymer elastic body mainly composed of polyurethane is applied to form a sheet-like material. Such a polymer elastic body has a role of surface unevenness, a cushion for absorbing vibration, fiber shape maintenance, and the like. It is excellent in the fitting property to the object and the effect of suppressing scratches on the surface of the object to be polished.

  The molecular weight of the polymer diol component of the polyurethane used as the main component of such a polymer elastic body is preferably 500 to 5000, more preferably 1000 to 3000. The diol component as the raw material is polyether diol. Polyester diol, polycarbonate diol, polylactone diol or a copolymer thereof is preferably used. Moreover, as a diisocyanate component, aromatic diisocyanate, alicyclic isocyanate, aliphatic isocyanate, etc. can be used. Among them, in order to improve the fit to the object to be polished and the cushioning property that contributes to the suppression of scratches, the ratio of the polyether diol component in the polymer diol is preferably 60% or more from the viewpoint of flexibility, 70 % Or more is more preferable.

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

  Moreover, it is preferable that the gelation point of a polyurethane is 2.5-6.0 ml from the viewpoint of satisfying the denseness and uniformity of the ultrafine fibers on the raised surface when the buffing treatment is performed. The gel point is more preferably in the range of 3-5 ml. The gelation point of polyurethane refers to stirring of 100 g of N, N′-dimethylformamide (hereinafter abbreviated as DMF) solution of 1% by weight of polyurethane while adding distilled water dropwise to this solution at 25 ± 1 ° C. It is the value of the amount of water dripping when the solidification of the polyurethane starts and becomes slightly cloudy under the temperature conditions of For this reason, it is necessary to use the DMF used for the measurement having a water content of 0.03% or less. The measurement method described above is described on the assumption that the polyurethane DMF solution is transparent. However, when the polyurethane DMF solution is slightly cloudy in advance, the solidification of the polyurethane starts and the degree of cloudiness changes. The amount of water dripping at this time can be regarded as the gel point. When the gel point is less than 2.5 ml, the solidification rate is too high when the polyurethane is wet-coagulated, so the foaming of the polyurethane present in the interior space of the composite fiber nonwoven fabric becomes large and rough, and partly foamed. As a result of defects, when the surface of the sheet is ground by buffing, the length of the raised fibers on the raised surface is uneven, or the distribution of the raised fibers is uneven. In some cases, an evenly dispersed state cannot be obtained, and ultra-high precision finishing cannot be realized. On the other hand, if the gel point exceeds 6.0 ml, the coagulation rate is too slow when the polyurethane is wet coagulated, so that the polyurethane present in the inner space of the composite fiber nonwoven fabric has almost no foaming and is very thick. It exists as a thick, hard polyurethane, and when the sheet surface is ground by buffing, it is difficult to grind polyurethane, the length of napped fibers on the napped surface is very short, and the fiber bundle is not very open. In addition, the uneven density of the surface fiber density increases, which causes local aggregation of the abrasive grains and leads to the generation of scratches.

  The polymer elastic body uses polyurethane as a main component, but as long as it does not impair the performance and the uniform dispersion state of napped fibers as a binder, an elastomer resin such as polyester, polyamide and polyolefin, acrylic resin and ethylene- Vinyl acetate resin and the like may be included, and various additives such as phosphorus-based, halogen-based, inorganic-based flame retardants, phenol-based, sulfur-based, phosphorus-based antioxidants, benzotriazole-based, UV absorbers such as benzophenone, salicylate, cyanoacrylate, oxalic acid anilide, light stabilizers such as hindered amines and benzoates, hydrolysis stabilizers such as polycarbodiimide, plasticizers, antistatic agents, Even if it contains trace amounts of surfactants and coagulation modifiers There.

  As a method for applying such polyurethane to the composite fiber nonwoven fabric, a method of solidifying after applying or impregnating polyurethane can be employed. Among them, from the viewpoint of processability, a method of wet coagulation after impregnating a polyurethane solution into a composite fiber nonwoven fabric is preferably used, and the polyurethane is made into a solution with a solvent such as dimethylformamide. A method of impregnating the polyurethane solution into a nonwoven fabric entangled with a composite fiber and coagulating it in water or an organic solvent aqueous solution, and then dissolving and removing the sea component of the sea-island composite fiber with a solvent that does not dissolve polyurethane (B) ) After applying a polyvinyl alcohol having a saponification degree of preferably 80% or more to a nonwoven fabric entangled with an ultra-fine fiber-generating sea-island composite fiber, the sea component of the sea-island composite fiber is protected after protecting most of the periphery of the fiber. Polyvinyl alcohol is dissolved and removed with a solvent that does not dissolve, and then impregnated with a polyurethane solution and coagulated in water or an organic solvent aqueous solution. After, it can be preferably used a method of removing the polyvinyl alcohol.

  In addition, the shape of the polymer elastic body inside the nonwoven fabric is such that the fibers are not dropped out, and the direction of the napped fibers is uniformly aligned. It is preferable that at least a part of the single fibers located on the outermost periphery of the two are joined. This form can be obtained by the method (B). That is, since the polyvinyl alcohol protects most of the outer periphery of the ultrafine fiber bundle, polyurethane is prevented from entering the inside of the ultrafine fiber bundle, and the outer periphery of the fiber bundle that is not partially protected by polyvinyl alcohol The polyurethane will adhere.

  Since the polymer elastic body partially adheres and restrains the fiber located on the outermost periphery of the ultrafine fiber bundle, the degree of freedom of the napped ultrafine fiber on the napped surface can be controlled appropriately. The directionality of the napped fibers after the treatment can be extremely reduced, that is, it can be adjusted to be aligned in one direction. As a result, the napped fibers are uniformly dispersed, and the unevenness of the fine fibers existing on the napped surface is small and can be uniformly arranged. In this way, the napped fibers are distributed in a dense and uniformly dispersed state, and the structure in which the directionality of the fibers is aligned in one direction improves the dispersibility of the abrasive grains during texturing and polishing. Since the abrasive grain distribution on the cloth surface can be made uniform, scratch defects can be extremely reduced.

  Furthermore, as a form inside the nonwoven fabric of the polymer elastic body, the nail surface was formed after giving the polymer elastic body to the nonwoven fabric from the viewpoint of increasing the slurry retention amount on the surface of the polishing cloth and increasing the linear density of the texture marks. In the sheet-like material, it is preferable that the polymer elastic body is present inside the ultrafine fiber bundle at least near the root of the raised portion of the sheet-like material. This form is obtained by applying a polymer elastic body to a non-woven fabric and forming a raised surface, and (a) impregnating the sheet-like material with a solvent of the polymer elastic body, compressing, and then dissolving the polymer It can be obtained by using a method of resolidifying an elastic body, or (b) a method of recoagulating a dissolved polymer elastic body after applying a solvent of the polymer elastic body to the surface of a sheet-like material. Among these, it is more preferable to carry out the method (b) after forming the napped surface from the viewpoint of achieving both a state in which the napped fibers are densely and uniformly dispersed. Further, after the method (b) is performed, in order to make the distribution of napped fibers more uniform, rubbing treatment or light buffing may be performed using a sandpaper or a roll sander.

  In the polishing cloth of the present invention, cushioning properties and fit properties are important in terms of polishing accuracy, and are controlled and adjusted by the ratio of fine fibers and polymer elastic body and the porosity (which can be seen by the apparent density). The content of the polymer elastic body is preferably 5% by weight to 100% by weight and more preferably 10% by weight to 60% by weight with respect to the total weight of the sheet-like material. The surface state, porosity, cushioning property, hardness, strength, and the like of the polishing cloth can be appropriately adjusted depending on the content. When the content of the polymer elastic body is less than 5%, the fiber drops more, and when it exceeds 100%, the processability and productivity are inferior, and the ultrafine fibers are uniformly dispersed on the surface of the sheet. It is difficult to obtain a raised surface.

  It is particularly important that the polishing cloth of the present invention is composed of an ultrafine fiber nonwoven fabric and a polymer elastic body and has a raised surface made of ultrafine fibers on at least one side. The raised surface is obtained by buffing treatment. As the buffing treatment here, a method of grinding a sheet surface using sandpaper, a roll sander or the like is generally used. In particular, by raising the surface of the sheet using sandpaper, uniform and dense napping can be formed. Furthermore, for the purpose of texturing the substrate surface with an ultra-high precision finish and suppressing scratches, the uniformity and density of the surface fiber distribution on the sheet surface is improved, and the direction of napped fibers is extremely reduced. Therefore, it is preferable to reduce the grinding load. When the grinding load is high, there are many napped fibers that are curly, and the napped fibers are likely to be stuck together in a bundle. In order to reduce the grinding load, it is preferable to appropriately adjust the number of buffs, the sandpaper count, and the like. Among them, the number of buff stages is preferably multistage buffing of 3 or more stages, and the sandpaper used for each stage is preferably in the range of 150 to 600 in JIS regulations.

  In the present invention, the linear density of the number of surface fibers on the raised surface of the polishing cloth is preferably 20/100 μm width or more. The upper limit is not particularly limited, and the larger the value, the better, but it is usually 1000/100 μm width or less. The linear density of the number of surface fibers here is defined as follows. First, the napped surface of the polishing cloth is observed with a scanning electron microscope (SEM) as an observation surface, and 30 points with a width of 100 μm are extracted arbitrarily at intervals of 1 mm in the sheet continuous longitudinal direction. The number of ultrafine fibers present in the outermost layer at each extraction location is measured and taken as the linear density of the number of surface fibers. In addition, an average value using this as a population is calculated. When the linear density of the number of surface fibers is less than 20/100 μm width, the fineness is inferior, the abrasive grains are not finely dispersed, high-precision finishing cannot be achieved, and the fibers on the surface of the polishing cloth Abrasive grains agglomerate in portions where no slag exists, which tends to cause scratches.

In order to satisfy the requirements of the present invention for the linear density of the number of surface fibers, the above-described ultrafine fiber nonwoven fabric and polymer elastic body are used, the method for producing the sheet-like material is adopted, and the fibers of the polishing cloth are used. The apparent density is preferably in the range of 0.2 to 0.5 g / cm ^{3 in} consideration of increasing the density and uniformity of the surface fibers, the retention of the abrasive grains, and the pressing force.

  Further, the water drop absorption time of the polishing cloth of the present invention is preferably 0.1 to 60 seconds. More preferably, it is 0.1-20 seconds, More preferably, it is 0.1-10 seconds. When it exceeds 60 seconds, when the abrasive grains are continuously supplied onto the polishing surface, the polishing surface is slow to become wet, the abrasive grains cannot be sufficiently dispersed, and scratches are likely to increase, resulting in a decrease in polishing accuracy. To do. In addition, when the water absorption time is less than 0.1 seconds, many slurries are removed from the inner layer of the polishing cloth, leading to a decrease in the amount of abrasive grains retained on the surface of the polishing cloth. This is not preferable because the grinding amount tends to be insufficient.

The water droplet absorption time referred to in the present invention uses a FACE / CA-A type contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd., and distilled water is put into a syringe attached to the device, and an injection needle (outer diameter 0.60 mm, One drop of water from an inner diameter of 0.45 mm is dropped on the polishing cloth, and the water drop is observed from the eyepiece of the apparatus, and is calculated by the following formula.
tq (water droplet absorption time) = t2-t1 (seconds)
Here, the time when the water droplet fell on the polishing cloth is defined as t1, and the time when the water droplet is sucked into the polishing cloth as time passes and the water droplet disappears on the surface is defined as t2.

The state of t1 and t2 can be measured visually in the normal case (approximately tq is 10 seconds or more), but when it is very fast or difficult to observe, water droplets start dropping from the injection needle with the aforementioned device. The entire state of the water droplet is video-recorded through the eyepiece of the apparatus until the water droplet is sufficiently absorbed into the polishing cloth. The video image is reproduced, and the water droplet absorption time can be measured from the states of t1 and t2 and the recording time.
In addition, the water absorption time tq is obtained by performing 20 measurements on a sample arbitrarily taken from the product, and taking the average value of the 5 largest data among the 20 measured values (tq). Let the average value be the value of water absorption time.

  Means for making the water droplet absorption time within the scope of the present invention is not particularly limited, and in addition to using a semi-aromatic polyamide fiber excellent in water absorption, it is comprehensively adjusted by the density and fiber fineness of the nonwoven fabric, Furthermore, even if the base material is the same, it is possible and effective by carrying out a hydrophilization processing with a hydrophilic component solution, which is a preferable method. This treatment may be performed at any timing among the above-described production methods, but is preferably easy to adjust the water droplet absorption time, and preferably, after applying the polymer elastic body, before forming the raised surface or Good after. In this case, it is necessary to appropriately adjust the treatment chemical and the applied amount according to the purpose depending on the density and fineness of the base material, the fiber type to be used, and the like.

Here, the hydrophilic component is not particularly limited, but is a compound containing a hydrophilic group such as —OH, —COOH, —NH ₂ , —CONH—, —SO ₃ , —SO ₄ , a derivative thereof, and other surfactants. Is preferably used. Of these, acrylic acid-based, glycol-based, polyvinyl alcohol-based, cellulose-based, urethane-based, hydrophilic group-containing ester-based, nonionic surfactant, cationic surfactant, and the like are more preferable. And after processing by immersion treatment, spraying treatment, coating treatment, etc. using the solution or emulsion aqueous solution, it dries at 80-190 ° C, and adheres. Also, if the water absorption of the entire polishing cloth is increased too much, the abrasive slurry tends to penetrate into the base cloth and the efficiency tends to decrease, so the entire surface is treated with a hydrophilic component treatment agent after a slight water repellent treatment. In addition, a method for suppressing water absorption may be used.

  Moreover, you may perform about provision of a hydrophilic component by addition to a fiber component. For example, as a method for adding to the fiber, there can be used graft polymerization of the hydrophilic component to the fiber, a method of blending the hydrophilic compound fine particles with the fiber component during spinning, adsorption or fixing to the fiber surface, and the like.

  In the present invention, the content of the silicon compound in the polishing cloth is preferably 100 ppm or less, more preferably 50 ppm or less as the weight of silicon element with respect to the total weight of the polishing cloth. When the content is 100 ppm or less, it is preferable because occurrence of peeling of the magnetic film and occurrence of errors in the hard disk drive after sputtering of the magnetic film after texturing can be suppressed.

When the polishing cloth of the present invention is tape-shaped and textured, if the dimensional change occurs, the substrate surface cannot be uniformly polished. From the viewpoint of the form stability of the polishing cloth, the polishing cloth of the present invention it is preferred that the the basis weight is 100 to 400 g / ^{m 2,} and more preferably 150 to 300 g / ^{m 2.} Further, a reinforcing layer may be bonded to one side of the polishing cloth from the viewpoint of suppressing processing unevenness due to tape elongation during texture processing and generation of scratch defects. When the reinforcing layer is provided on the polishing cloth, it is an essential condition that the opposite surface of the sheet-like material to which the reinforcing layer is bonded is a raised surface.

  In addition, as a method for adhering the reinforcing layer to the polishing cloth, any of a thermocompression bonding method, a frame lamination method, and a method of providing an adhesive layer between the reinforcing layer and the sheet-like material may be employed. As the adhesive layer, any material having rubber elasticity such as polyurethane, styrene butadiene rubber (SBR), nitrile butadiene (NBR), polyamino acid, and acrylic adhesive can be used. In view of cost and practicality, an adhesive such as NBR or SBR is preferable. As a method for applying the adhesive, it is applied to a sheet-like material in an emulsion or latex state.

  The reinforcing layer may be a woven or knitted fabric or a non-woven fabric using heat-bonding fibers. However, in order to perform highly accurate texture processing, it is preferable to use a film-like material that is uniform in thickness and physical properties. When woven or knitted fabric or heat-bonded fibers are used for the reinforcing layer, the unevenness of the surface of the reinforcing layer is too large. And the desired surface roughness may not be achieved.

  Since the film-like product is excellent in surface smoothness, highly accurate texture processing can be performed without impairing the smoothness of the polishing cloth surface. Any material having a film shape such as polyolefin, polyester, or polyphenyl sulfide can be used as a material used as a film here, but it is preferable to use a polyester film in consideration of versatility. When providing a reinforcing layer made of a film, balance the thickness with the sheet-like material made of non-woven fabric from the viewpoint of satisfying all of the form stability of the sheet during texture processing, cushioning and fit to the substrate surface. is required. The sheet-like material made of nonwoven fabric is preferably 0.4 mm or more in terms of finished thickness, and more preferably in the range of 0.4 to 2 mm from the viewpoint of productivity. Therefore, the thickness of the film is preferably 20 to 100 μm. If the thickness of the sheet-like material made of non-woven fabric is less than 0.4 mm, the dimensional change during texture processing is large, and a super-high precision finish cannot be performed, so a reinforcing layer is necessary. You may lose your sex. If the thickness of the film layer is less than 20 μm, it is difficult to suppress dimensional changes during texturing, and if it exceeds 100 μm, the rigidity of the entire polishing cloth becomes too high, so that the generation of scratches cannot be suppressed. Therefore, it is not preferable.

  In order to perform texturing using the polishing cloth of the present invention, the polishing cloth is cut into a tape having a width of 30 to 50 mm and used as a texturing tape from the viewpoint of processing efficiency and stability. A method of texturing an aluminum alloy magnetic recording disk or a glass magnetic recording disk using the polishing tape and a slurry containing loose abrasive grains is a preferred method. As a polishing condition, a slurry in which high-hardness abrasive grains such as diamond fine particles are dispersed in an aqueous dispersion medium is preferably used. Among them, the abrasive grains suitable for the ultrafine fibers constituting the polishing cloth of the present invention are composed of single-crystal diamond from the viewpoint of abrasive retention, dispersibility, scratch suppression, and surface roughness reduction, and have a primary particle diameter of single crystal diamond. It is preferably 1 to 20 nm, more preferably 1 to 10 nm. The diamond particles are preferably clustered in order to sharpen the unevenness of the texture marks, and the cluster diameter is preferably 100 to 800 nm, and more preferably 100 to 600 nm.

  In the polishing cloth obtained in the present invention, the napped fibers on the surface of the polishing cloth have excellent affinity with the aqueous polishing slurry used for hard disk texture processing, and the fiber rigidity in the wet state after dropping the slurry is high. In texture processing, the abrasive grains are distributed on the surface of the polishing cloth in a finely dispersed state without locally concentrating, and the gripping ability of the abrasive grains on the fiber surface is high, and the processing pressure per unit particle of the abrasive grains is high The high texture makes it possible to form texture marks with excellent sharpness of irregularities, with few scratch defects and ridge defects, good yield, and high-precision texture processing with a surface roughness of 0.3 nm or less on the substrate surface. A polishing cloth that can be finished as a processed surface that can cope with higher recording density of recording disks with excellent electromagnetic conversion characteristics. Rukoto can.

Hereinafter, although the abrasive cloth of this invention is demonstrated more concretely according to an Example, this invention is not limited to these. The evaluation methods used in the examples and the measurement conditions will be described below.

(1) Relative viscosity of sulfuric acid Components other than the ultrafine fiber component are removed from the polishing cloth by dissolution, etc., only the ultrafine fiber is taken out, and 0.25 g of the ultrafine fiber is precisely weighed with a direct balance (0.25 ± 0.005 g) . Next, the precisely weighed sample is dissolved in 25 ml of concentrated sulfuric acid to obtain a sample solution. Next, 15 ml of the sample solution was injected into a viscosity tube (with a concentrated sulfuric acid falling time of 100 ± 20 seconds) set in a thermostat heated to 25 ± 0.5 ° C., and then the dropping time of the sample solution Measure. This operation is repeated three times to obtain an average value T. The same operation is repeated three times for concentrated sulfuric acid in which the sample is not dissolved, the average value T0 is determined, and T / T0 is defined as the sulfuric acid relative viscosity.

(2) Average fineness and fineness CV
A cross section of the polishing cloth cut in the thickness direction is observed with a scanning electron microscope (SEM) as an observation surface, the fiber diameter of the ultrafine fibers constituting one bundle of bundle fibers is measured, and the fiber component of each ultrafine fiber is measured. The fineness is calculated from the specific gravity and fiber diameter. The same measurement is performed for a total of five bundle fibers, and a standard deviation value and an average value are calculated using the same as a population (if there are no bundle ultrafine fibers, the fiber diameter of 300 ultrafine fibers is measured. , Calculate the average value as well.) The average value was defined as the average fineness, and the value obtained by dividing the standard deviation value by the average value as a percentage (%) was defined as the fineness CV.

(3) Initial tensile resistance of ultrafine fibers when wet First, using 10 ultrafine fiber-generating fibers having an aromatic polyamide obtained through spinning, drawing and crimping as ultrafine fiber components, other than ultrafine fiber components The components are dissolved and removed. The obtained ultrafine fiber bundle is immersed in distilled water at 25 ° C. for 30 minutes, and then the surface of the ultrafine fiber bundle is lightly wiped to obtain a wet ultrafine fiber bundle sample. Next, a load-elongation curve is obtained using a constant speed extension type tensile tester (Tensilon) at a test length of 50 mm and a tensile speed of 50 mm / min. Next, in accordance with JIS L 1013 (2005 edition), Section 8.10, the maximum point A (the maximum point of the tangential angle) of the load change with respect to the extension change is obtained from the obtained curve near the origin, and the following formula: Calculate the initial tensile resistance.
Tri = P / {(L ′ / L) × F0},
Here, Tri = initial tensile resistance (cN / dtex), P: load at the maximum point A of contact angle (cN), F0: positive fineness (dtex), L: trial length (mm), L ′: TH Represents the length (mm) (H is the leg of the perpendicular from A, and T is the intersection of the tangent and the horizontal axis at A).
The same measurement is performed 5 times, and the average value is defined as the initial tensile resistance of the ultrafine fiber when wet.

(4) Linear density of the number of surface fibers The napped surface of the polishing cloth is used as an observation surface and observed with a scanning electron microscope (SEM), and 30 points having a width of 100 μm are extracted at intervals of 1 mm in the sheet continuous longitudinal direction. The number of ultrafine fibers present in the outermost layer at each extraction location was measured, and the average value was defined as the linear density of the number of surface fibers.

(5) Water drop absorption time Using a FACE / CA-A type contact angle measuring device (manufactured by Kyowa Interface Science Co., Ltd.), distilled water is put into a syringe and an injection needle (outer diameter 0.60 mm, inner diameter 0.45 mm). 1 drop of water was dropped on the polishing cloth, the water drop was observed from the eyepiece of the apparatus, and the absorption time (tq) was determined by the following equation.
tq = t2-t1 (seconds)
t1: Time when water drops fell on the polishing cloth t2: Time when water drops are sucked into the polishing cloth and no water drops remain on the surface The condition of t1 and t2 is visually observed in a normal case (approximately tq is 10 seconds or more). However, if it is very fast or difficult to observe, the state from the time when the water droplet starts to drip from the injection needle to the time when the water droplet is sufficiently absorbed in the polishing cloth by the above-mentioned device is measured. It is possible to measure the whole image of the water drop through the lens after taking a video.

  In this way, 20 samples are measured with a sample arbitrarily taken from the product, and the average value of the five largest data among the 20 measured values (tq) is taken. Was the water absorption time value.

(6) Silicon content Sulfuric acid was added to 5 g of the polishing cloth sample, left to stand overnight for carbonization, and then sulfuric acid was volatilized on a hot plate. The obtained carbide was heated in an electric furnace at 550 ° C. for 2 hours to carry out an ashing treatment. The obtained ashed product was melted with sodium carbonate and dissolved in dilute hydrochloric acid to obtain a sample solution. The sample solution was introduced into an ICP emission spectroscopic analyzer, and silicon was quantified.

(7) Substrate Surface Roughness Using an atomic force microscope AFM (NanoScope IIIaAFM Dimension 3000 stage system manufactured by Digital Instruments), an arbitrary 10 for each of both surfaces of 5 disk substrate samples after texturing, that is, a total of 10 surfaces. Extraction points (the observation area per one area is an area of 5 μm in the radial direction × 5 μm in the circumferential direction on the disk surface) are extracted. Next, a cross-sectional profile with one point at each of the 10 locations and a radial direction along the horizontal axis in the thickness direction of the disk is arbitrarily extracted. Each cross-sectional profile obtained is in accordance with JIS B 0601 (2001 edition). The arithmetic average roughness Ra is calculated. The substrate surface roughness was calculated by averaging the measured values of the obtained 10 surfaces × 10 points = total 100 points. The lower the value, the higher the performance.

(8) Scratch score Using the Candela 5100 optical surface analyzer as a measurement object, measure the scratch score using a Candela 5100 optical surface analyzer on both surfaces of 5 textured substrates, that is, the total area of 10 surfaces. And it evaluated by the average value of the measured value of 10 surfaces. The lower the value, the higher the performance.

(9) Number of Ridge Points Using an atomic force microscope AFM (NanoScope IIIaAFM Dimension 3000 stage system manufactured by Digital Instruments), an arbitrary 10 locations on the substrate sample surface after texture processing (the observation area per location is the diameter on the disc surface) (5 μm in the direction × 5 μm in the circumferential direction), the number of protrusions having a height of 5 nm or more was used as a ridge, and the number of the protrusions was measured.

(10) Sharpness of texture mark Using atomic force microscope AFM (NanoScope IIIaAFM Dimension 3000 stage system manufactured by Digital Instruments), the surface of the substrate sample after texture processing was performed under conditions of a scanning speed of 0.5 Hz and a number of pixels of 512 × 128. Three arbitrary locations in the radial direction are extracted (the observation area per location is a region of 1 μm in the radial direction on the disk surface × 0.25 μm in the circumferential direction). Next, a cross-sectional profile with one point at each of the three locations and the radial direction in the horizontal axis in the disc thickness direction is arbitrarily extracted. Next, with respect to the cross-sectional profiles of a total of three points, the shape of all irregularities in the width direction of 1 μm was observed, and the acute angle was evaluated according to the following criteria. In addition, the state in which the tip portion of the unevenness is sharp indicates that the radius of curvature of the tip portion is less than 100 nm, and the gentle curve shape indicates that the radius of curvature of the tip portion is 100 nm or more.
A: The shape of the unevenness is clear, and 90% or more of the tip of the unevenness is pointed.
(Triangle | delta): Although the shape of an unevenness | corrugation is clear, more than 10% and less than 30% of the front-end | tip part of an unevenness | corrugation are gentle curvilinear forms.
X: The shape of unevenness | corrugation is unclear and 30% or more of the front-end | tip part of unevenness | corrugation is a gentle curvilinear shape.

Example 1
(Manufacture of sheet-like materials)
Semiaromatic polyamide: nylon MXD6 (sulfuric acid relative viscosity 2.93), dicarboxylic acid component as adipic acid and diamine component as metaxylenediamine as island component, polystyrene (temperature 220 ° C., orifice size 2.0955 mmφ × 8 mm) as sea component , With a melt index of 15 g / 10 min under a load of 2160 g and a softening point temperature of 60 ° C.), the island / sea After melt spinning at a weight ratio of 40/60 and a spinning speed of 1000 m / min, a two-stage drawing in a liquid bath at a total draw ratio of 3.0 is performed, and after crimping, a sea-island type composite fiber having a single fiber fineness of 4 dtex is obtained. Produced. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing sea components from the sea-island composite fiber with toluene was 17 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and a cross wrapping process, and needle punching is performed at a punch number of 1500 / cm ² , and the basis weight is 650 g / A composite fiber nonwoven fabric of m ² and a density of 0.22 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric is impregnated with 25% by weight of polyurethane (the polymer diol has a ratio of 75 to 25 in the polyether and polyester systems, and the gel point is 3 ml) based on the total weight of the sheet. After the polyurethane was coagulated in water, polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material is cut in half in the thickness direction, a napped paper sheet with a sandpaper count of 240 is subjected to three-stage buffing on the non-sliced surface to form a raised surface to form a raised sheet A product was made. The napped sheet was used as an abrasive cloth, and had a thickness of 0.55 mm, a basis weight of 190 g / m ² , and an apparent fiber density of 0.35 g / cm ³ .

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.05 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20. Further, the linear density of the surface fibers of the polishing cloth was 25/100 μm width, the water droplet absorption time was 4 seconds, and the silicon content was 30 ppm.

(Texture processing)
The abrasive cloth was made into a tape having a width of 40 mm, and textured under the following conditions.

  After a Ni-P plating treatment is applied to an aluminum substrate, a single crystal diamond particle having a primary particle size of 1 to 10 nm and a cluster average size of 150 nm is applied to the surface of the polishing cloth using a polishing process and controlling the average surface roughness to 0.2 nm. The clustered free abrasive slurry was dropped, and polishing was performed for 10 seconds under a tape running speed of 5 cm / min. In the texture processing, both surfaces of each disk were polished under the above conditions.

  The textured disc had a surface roughness of 0.20 nm, a scratch score of 30, and a ridge score of 1. In addition, the acuteness of the texture mark was evaluated as ◯ because the unevenness was clearly formed and the tip of the unevenness was sharp. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

(Example 2)
Using the same island component and sea component as in Example 1, the island / sea weight ratio is 40/60 and the spinning speed is 1200 m through a sea-island type composite base of a polymer inter-array system with 100 islands / hole. After melt-spinning at a rate of 1 min / min, the film was stretched in two stages at a total draw ratio of 3.3 times in a liquid bath, and then crimped to produce a sea-island type composite fiber having a single fiber fineness of 5 dtex. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 24 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and a cross wrapping process, and needle punching is performed at a punch number of 1500 / cm ² , and the basis weight is 650 g / A composite fiber nonwoven fabric of m ² and a density of 0.2 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. The obtained sheet-like material is cut in half in the thickness direction, and then the napped surface is formed by buffing the non-sliced surface with three-stage buffing using an endless sandpaper with a sandpaper count of 240. Was made. The napped sheet was used as an abrasive cloth, and had a thickness of 0.57 mm, a basis weight of 200 g / m ² , and an apparent fiber density of 0.35 g / cm ³ .

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.02 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20.

  The linear density of the surface fibers of the polishing cloth was 37/100 μm width, the water droplet absorption time was 4 seconds, and the silicon content was 30 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.16 nm, a scratch score of 20, and a ridge score of 0. In addition, the acuteness of the texture mark was evaluated as ◯ because the unevenness was clearly formed and the tip of the unevenness was sharp. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

(Example 3)
Using the same island component and sea component as in Example 1, through a sea-island type composite base of a polymer inter-array system with 400 islands / hole, an island / sea weight ratio of 30/70 and a spinning speed of 1000 m After melt spinning at a rate of 1 / min, the film was drawn in two stages at a total draw ratio of 3.0 in a liquid bath, and then crimped to produce a sea-island type composite fiber having a single fiber fineness of 4 dtex. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 18 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and a cross wrapping process, and needle punching is performed with a number of punches of 1500 / cm ^2. A composite fiber nonwoven fabric of m ² and a density of 0.23 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. Using the endless sandpaper whose sandpaper count is 240, the obtained sheet-like material was subjected to three-stage buffing on one side to form a raised surface to produce a raised sheet-like material. The napped sheet was used as an abrasive cloth, and had a thickness of 0.55 mm, a basis weight of 180 g / m ² , and an apparent fiber density of 0.33 g / cm ³ .

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.003 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20.

  Moreover, the linear density of the number of surface fibers of the polishing cloth was 90/100 μm width, the water droplet absorption time was 5 seconds, and the silicon content was 25 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.14 nm, a scratch score of 5, and a ridge score of 0. In addition, the acuteness of the texture mark was evaluated as ◯ because the unevenness was clearly formed and the tip of the unevenness was sharp. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

Example 4
N, N-dimethylformamide was applied to the raised surface of the raised sheet obtained in Example 2 with a gravure roll, re-coagulated in water and dried, and then the raised surface was sandpaper with a sandpaper count of 600. Using an endless sandpaper, a rubbing treatment was performed, and the napped sheet-like material thus obtained was used as an abrasive cloth.

In the polishing cloth, polyurethane was present inside the ultrafine fiber bundle in the vicinity of the root of the napped portion, and had a thickness of 0.55 mm, a basis weight of 190 g / m ² , and an apparent fiber density of 0.35 g / cm ³ .

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.02 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20.

  The linear density of the number of surface fibers of the polishing cloth was 35/100 μm width, the water droplet absorption time was 4 seconds, and the silicon content was 30 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.17 nm, a scratch score of 25, and a ridge score of 0. Further, the acuteness of the texture mark was evaluated as ◯ because the unevenness was clearly formed and the tip of the unevenness was pointed, and the line density of the texture mark was high. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

(Example 5)
The napped sheet-like material obtained in Example 2 was treated with ethylene glycol and decylbenzenesulfonic acid so that 0.5% by weight was given to the total weight of the sheet-like material, did.

The obtained polishing cloth has a thickness of 0.55 mm, a basis weight of 190 g / m ² , an apparent fiber density of 0.35 g / cm ³ , the average fineness of the ultrafine fibers constituting the polishing cloth is 0.02 dtex, and the fineness CV is 8%. The relative viscosity of sulfuric acid was 3.20.

  The linear density of the number of surface fibers of the polishing cloth was 37/100 μm width, the water droplet absorption time was 0.5 seconds, and the silicon content was 35 ppm.

  Using the abrasive cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.19 nm, a scratch score of 10, and a ridge score of 0. Further, the acuteness of the texture mark was evaluated as ◯ because the unevenness was clearly formed and the tip of the unevenness was pointed, and the line density of the texture mark was high. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

(Example 6)
Using the same island component as in Example 1, polystyrene as the sea component (temperature 220 ° C., orifice size 2.0955 mmφ × 8 mm, melt index under load 2160 g is 2 g / 10 min, softening point temperature is 70 ° C. ), And melt melt-spinned at an island / sea weight ratio of 40/60 at a spinning speed of 600 m / min through a sea-island type compound base having a number of islands of 36 islands / hole, and then in a liquid bath. The sea-island type composite fiber having a single fiber fineness of 4 dtex was produced after crimping by 2.5 step and crimping. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 9 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and cross wrapping process, and needle punching is performed at a punch number of 1500 pieces / cm ² , with a basis weight of 670 g / A composite fiber nonwoven fabric with m ² and a density of 0.21 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a thickness of 0.55 mm, a basis weight of 180 g / m ² , and an apparent fiber density of 0.33 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.05 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20.

  The linear density of the surface fibers of the polishing cloth was 25/100 μm width, the water droplet absorption time was 4 seconds, and the silicon content was 35 ppm.

  Using the abrasive cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.20 nm, a scratch score of 35, and a ridge score of 1. The sharpness of the texture marks was clear, although the shape of the unevenness was clear, but the portion where the tip of the unevenness was a gentle curve accounted for about 20% of the whole, and was a Δ evaluation. The substrate on which the magnetic layer was formed after texturing had a good S / N ratio in the hard disk drive test, but several errors occurred.

(Example 7)
Semiaromatic polyamide: copolymer nylon consisting of a dicarboxylic acid component as an island component, adipic acid, 80 mol% of all diamine components consisting of metaxylenediamine and 20 mol% of 1,6-hexanemethylenediamine Island / sea weight ratio through MXD6 (sulfuric acid relative viscosity 2.7), sea component same as in Example 1, using sea island type composite base of 36 islands / hole of polymer islands After melt spinning at 40/60 and a spinning speed of 1200 m / min, one-stage drawing was performed 3.0 times in a liquid bath, and after crimping, sea-island type composite fibers having a single fiber fineness of 4 dtex were produced. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 13 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and cross wrapping process, needle punched at a punch number of 1500 / cm ² , and a basis weight of 720 g / A composite fiber nonwoven fabric of m ² and a density of 0.22 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a diameter of 1.6 mm, a basis weight of 190 g / m ² , and an apparent fiber density of 0.32 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.05 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 2.90.

  Further, the linear density of the number of surface fibers of the polishing cloth was 26/100 μm width, the water droplet absorption time was 5 seconds, and the silicon content was 35 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.18 nm, a scratch score of 22, and a ridge score of 0. The sharpness of the texture mark was evaluated as ○, because the unevenness was clearly formed and the tip of the unevenness was sharp. In addition, the substrate on which the magnetic layer was formed after texturing was excellent in electromagnetic conversion characteristics such as S / N ratio.

(Example 8)
The semi-aromatic polyamide: nylon 6T (sulfuric acid relative viscosity 2.6), in which the dicarboxylic acid component is terephthalic acid and the diamine component is 1,6-hexanemethylenediamine as the island component, and the same component as in Example 1 is used as the sea component Then, after melt spinning at an island / sea weight ratio of 40/60 and a spinning speed of 1200 m / min through a sea-island type compound base of a polymer inter-array system with 36 islands / hole, the total draw ratio in a liquid bath After two-stage drawing at 3.0 times, a sea-island type composite fiber having a single fiber fineness of 4 dtex was produced through crimping. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 25 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and cross wrapping process, and needle punching is performed with a number of punches of 1500 pieces / cm ^2. A composite fiber nonwoven fabric of m ² and a density of 0.2 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a weight of .58 mm, a basis weight of 190 g / m ² , and an apparent fiber density of 0.33 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.05 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 2.75.

  The linear density of the number of surface fibers of the polishing cloth was 23/100 μm width, the water droplet absorption time was 5 seconds, and the silicon content was 35 ppm.

  Using this polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.23 nm, a scratch score of 33, and a ridge score of 1. The sharpness of the texture mark was evaluated as ○, because the unevenness was clearly formed and the tip of the unevenness was sharp. Further, the substrate on which the magnetic layer was formed after texturing was extremely excellent in electromagnetic conversion characteristics such as S / N ratio.

Example 9
A semi-aromatic polyamide: nylon MXD6 (sulfuric acid relative viscosity 2.93) composed of adipic acid as a dicarboxylic acid component and meta-xylenediamine as an island component, and the same as in Example 1 as a sea component, After mixing the chips at a sea weight ratio of 40/60, melt spinning at a spinning speed of 800 m / min, drawing in one step 3.0 times in a liquid bath, crimping, and sea island type with a single fiber fineness of 4 dtex A composite fiber was produced. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 15 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and a cross wrapping process, and needle punching is performed at a punch number of 1500 / cm ² , and the basis weight is 650 g / A composite fiber nonwoven fabric of m ² and a density of 0.23 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, polystyrene as a sea component was dissolved and removed in trichlorethylene, followed by drying to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a diameter of .53 mm, a basis weight of 170 g / m ² , and an apparent fiber density of 0.32 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.005 dtex, the fineness CV was 40%, and the sulfuric acid relative viscosity was 3.10.

  Further, the linear density of the surface fibers of the polishing cloth was 70/100 μm width, the water droplet absorption time was 6 seconds, and the silicon content was 35 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.27 nm and a ridge score of 2. Also, the scratch score was a little as high as 45. The sharpness of the texture mark was evaluated as ○, because the unevenness was clearly formed and the tip of the unevenness was sharp. In addition, the substrate on which the magnetic layer was formed after texturing was excellent in electromagnetic conversion characteristics such as S / N ratio.

(Comparative Example 1)
Using the same island component and sea component as in Example 1, the island / sea weight ratio is 40/60 and the spinning speed is 1200 m through a sea-island type composite base of a polymer inter-array system with 16 islands / hole. After melt spinning at / min, the film was stretched in two stages at a total magnification of 3.0 times in a liquid bath, and then crimped to produce a sea-island composite fiber having a single fiber fineness of 4 dtex. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 20 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and cross wrapping process, and needle punching is performed with a number of punches of 1500 pieces / cm ^2. A composite fiber nonwoven fabric of m ² and a density of 0.23 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, the copolymer polystyrene, which is a sea component, was dissolved and removed in trichlorethylene and dried to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a thickness of .55 mm, a basis weight of 200 g / m ² , and an apparent fiber density of 0.36 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.1 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 3.20.

  The linear density of the number of surface fibers of the polishing cloth was 15/100 μm width, the water droplet absorption time was 5 seconds, and the silicon content was 35 ppm.

  Using the polishing cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.25 nm, a scratch score of 120, and a ridge score of 15, and a textured disc. When the entire processed surface was observed, the surface waviness was large and the texture marks were not uniform. Furthermore, the sharpness of the texture mark was clear because the shape of the unevenness was clear and the tip of the unevenness was pointed, and it was evaluated as ◯, but due to the unevenness of the texture mark, the magnetic layer after texture processing In the hard disk drive test, errors occurred frequently and the electromagnetic conversion characteristics were low.

(Comparative Example 2)
Using the same sea component as in Example 1 and using nylon 6 (sulfuric acid relative viscosity 2.63) as the island component, through the sea-island type compound base of the polymer inter-array system with 36 islands / hole. After melt-spinning at an island / sea weight ratio of 40/60 and a spinning speed of 1200 m / min, one-stage drawing is performed 3.0 times in a liquid bath, and after crimping, a sea-island type composite fiber having a single fiber fineness of 4 dtex is obtained. Produced. The initial tensile resistance when wet of the ultrafine fiber obtained by dissolving and removing the sea component from the composite fiber with toluene was 6 cN / dtex.

Next, using the raw cotton obtained by cutting this sea-island type composite fiber to 51 mm, a laminated web is formed through a card and a cross wrapping process, and needle punching is performed at a punch number of 1500 / cm ² , and the basis weight is 650 g / A composite fiber nonwoven fabric of m ² and a density of 0.22 g / cm ³ was produced. The composite fiber nonwoven fabric was subjected to hot water shrinkage, then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Thereafter, the copolymer polystyrene, which is a sea component, was dissolved and removed in trichlorethylene and dried to obtain an ultrafine fiber nonwoven fabric in which ultrafine fiber bundles were entangled.

Next, the ultrafine fiber nonwoven fabric was impregnated with 25% by weight of the same polyurethane as in Example 1 with respect to the total weight of the sheet to solidify the polyurethane in water, and then the polyvinyl alcohol was dissolved and removed with hot water and dried. After the obtained sheet-like material was cut in half in the thickness direction, a nap surface was formed by buffing the non-sliced surface by three-stage buffing using an endless sandpaper with a sandpaper count of 240. An abrasive cloth having a weight of .58 mm, a basis weight of 180 g / m ² , and an apparent fiber density of 0.31 g / cm ³ was obtained.

  The average fineness of the ultrafine fibers constituting the obtained polishing cloth was 0.05 dtex, the fineness CV was 8%, and the sulfuric acid relative viscosity was 2.95.

  The linear density of the surface fibers of the polishing cloth was 25/100 μm width, the water droplet absorption time was 4 seconds, and the silicon content was 35 ppm.

  Using the abrasive cloth, texturing was performed in the same manner as in Example 1. The textured disc had a surface roughness of 0.15 nm, a scratch score of 20, and a ridge score of 0. The sharpness of the texture mark was unsatisfactory in the shape of the unevenness, and the portion where the tip of the unevenness was a gentle curve accounted for 90% or more, and was evaluated as x. Substrates on which a magnetic layer was formed after texture processing frequently generated errors in the hard disk drive test and had low electromagnetic conversion characteristics.

The polishing cloth for hard disk texture processing of the present invention has high affinity for the napped fibers on the surface of the polishing cloth with the aqueous polishing slurry used for hard disk texturing and high fiber rigidity in the wet state after slurry dropping. Thus, in texture processing, the abrasive grains are distributed on the surface of the polishing cloth in a finely dispersed state without locally concentrating, and the gripping ability of the abrasive grains on the fiber surface is high, and the processing per unit particle of the abrasive grains High pressure can form texture marks with excellent sharpness of irregularities, and there are few scratch defects and ridge defects with good yield, and the surface roughness on the substrate surface is 0.3 nm or less. It can be textured and processed as a processed surface that can cope with higher recording density of recording disks with excellent electromagnetic conversion characteristics. It is possible to obtain a polishing cloth that can gel.

Claims (9)

It is composed of a polyamide ultrafine fiber having an average fineness of 0.0001 to 0.05 dtex and / or a non-woven fabric in which an ultrafine fiber bundle made of the polyamide ultrafine fiber is entangled with a polymer elastic body mainly composed of polyurethane, A polishing cloth comprising a sheet-like material having at least one raised surface composed of the polyamide ultrafine fibers, the polyamide ultrafine fibers comprising (1) at least 80 mol% of the aliphatic dicarboxylic acid and the total diamine component is aromatic A semiaromatic polyamide comprising a diamine component which is a diamine and / or (2) a semiaromatic polyamide comprising a dicarboxylic acid component wherein at least 80 mol% of the total dicarboxylic acid component is an aromatic dicarboxylic acid and an aliphatic alkylenediamine. A polishing cloth comprising:   The semi-aromatic polyamide (1) is a semi-aromatic polyamide comprising an aliphatic dicarboxylic acid and an aromatic diamine, and the semi-aromatic polyamide (2) is a semi-aromatic polyamide comprising an aromatic dicarboxylic acid and an aliphatic alkylene diamine. The abrasive cloth according to claim 1, which is an aromatic polyamide. The polishing cloth according to claim 1 or 2, wherein an initial tensile resistance when the polyamide ultrafine fiber is wet is 10 to 50 cN / dtex. The polishing cloth according to any one of claims 1 to 3, wherein the fineness CV of single fibers of the ultrafine fibers constituting the polyamide ultrafine fiber bundle is 10% or less. The abrasive cloth according to any one of claims 1 to 4, wherein the linear density of the number of surface fibers on the raised surface of the sheet-like material is 20/100 μm width or more and 1000/100 μm width or less. The abrasive cloth according to any one of claims 1 to 5, wherein the polymer elastic body and fibers located on the outermost periphery of the ultrafine fiber bundle are partially joined. The abrasive cloth according to any one of claims 1 to 6, wherein the water droplet absorption time is 0.1 to 60 seconds. The polishing cloth according to any one of claims 1 to 7, wherein the polymer elastic body is present inside the ultrafine fiber bundle at least near the root of the raised portion of the sheet-like material. The polishing cloth according to claim 1, which is used for texture processing of a hard disk.