TWI575131B - Polishing cloth and method for producing the same - Google Patents

Description

Abrasive cloth and method of manufacturing same

The present invention relates to a polishing cloth suitable for use in performing ultra-high-precision polishing processing and/or cleaning processing on a substrate such as an aluminum alloy substrate or a glass substrate used for a magnetic recording disk or the like, and a method for producing the same.

The magnetic recording disc is required to be smoothed up to the surface limit of the disc with the recent high memory density. In recent years, recording methods for magnetic recording discs have become mainstream with vertical recording media in which the easy magnetization axis in the magnetic film is aligned in the vertical direction. Therefore, when the substrate before the formation of the magnetic layer is uneven or damaged, the magnetization axis may be inclined after the magnetic film is formed and become an abnormal portion. In the above-described problem, the surface of the disk before the formation of the magnetic film is required to have a surface roughness of the substrate of 0.2 nm or less, and the damage of the surface of the substrate called the scratch defect is minimized. Further, in the recording method developed after the vertical recording medium, the requirements for the substrate before the magnetic layer is formed are smoothed up to the limit as described above.

Heretofore, the surface treatment for satisfying the low floating of the magnetic head has been carried out by slurry polishing and/or cleaning processing using a belt polishing cloth. In this case, in order to cope with the high recording density for the recent high recording capacity, it is required to achieve a substrate surface roughness of 0.2 nm or less, and the damage of the surface of the substrate called the scratch defect is extremely small, and it is expected to be compatible. The abrasive cloth required for this.

Conventionally, in order to reduce the surface roughness of the substrate, the fibers constituting the non-woven fabric of the polishing cloth are extremely thinned, and the damage to the surface of the substrate is extremely reduced, and in order to have cushioning properties, a non-woven fabric impregnated with a polishing cloth is proposed. Elastomer proposal. For example, a non-woven fabric composed of an ultrafine fiber having a single fiber diameter of 0.05 to 2.0 μm, and a polishing cloth containing a polymer elastomer containing a polyurethane as a main component have been proposed (see Patent Documents 1 and 2). In this proposal, a surface roughness of about 0.2 nm is achieved.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-83093

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-214205

However, the smoothness required for the magnetic recording disc of the vertical recording type, that is, the suppression system with less scratches is further improved. Further, in the proposals of these prior art, only general needle punching conditions common to all artificial leathers composed of non-woven fabrics are described. That is, the optimum conditions for the construction of the surface fiber velvet portion of the surface of the cloth are required, and the setting of the general acupuncture conditions for obtaining a surface capable of maintaining sufficient dispersibility is required.

Therefore, in view of the above-described problems of the prior art, it is an object of the present invention to provide a high-performance polishing which is less scratch-resistant and has a higher-precision polishing process than a polishing cloth composed of ultrafine fibers in a polishing process. cloth.

Another object of the present invention is to provide a method of efficiently producing the above-mentioned abrasive cloth.

In order to solve the above problems, the polishing cloth of the present invention is mainly composed of a non-woven fabric and a polymer elastic body in which ultrafine fiber bundles obtained by converging ultrafine fibers having an average single fiber diameter of 0.05 to 2.0 μm are intertwined with each other. The polishing cloth is characterized in that the average size of the ultrafine fiber bundle of the surface fiber velvet portion formed of the ultrafine fiber bundle of the nonwoven fabric in the width direction is 50 to 180 μm.

According to a preferred embodiment of the polishing cloth of the present invention, the ultrafine fiber bundle of the surface fiber velvet portion has an average size in the width direction of 50 to 120 μm.

In a preferred embodiment of the polishing cloth of the present invention, the polishing cloth has a surface roughness of 5 to 18 μm.

In a preferred embodiment of the polishing cloth of the present invention, the ultrafine fibers have a CV value of from 1 to 30%.

Further, the method for producing a polishing cloth of the present invention is a method for producing a polishing cloth obtained by combining at least the following steps (1) to (5), characterized in that it is carried by a needle punching in the following step (2). The number of the island-type composite fibers which can be extremely finely fibrillated is set to 3 to 6 strips/1 barb:

(1) a step of producing a finely fibrillated sea-island type composite fiber with an average single fiber fineness of 0.05 to 2.0 μm;

(2) using the sea-island type composite fiber, a step of forming a fiber web by crimping and cross-rolling, and forming a fiber web by needle punching;

(3) a step of imparting 10 to 200% by mass of the ultrafine fiber mass of the non-woven fabric to the ultra-fine polymer elastomer;

(4) at least a step of performing a polishing treatment on one side; and

(5) A step of subjecting the sea-island type composite fiber to an ultrafine treatment.

In a preferred embodiment of the method for producing a polishing cloth according to the present invention, the number of the extremely fine-fiber-formed island-in-the-sea composite fibers to be carried by the needle punching in the step (2) is 3 to 4 strips per 1 barb.

According to the present invention, compared with the conventional polishing cloth, it is possible to obtain a polishing cloth having a small smoothness of the ultrafine fiber bundle of the surface fiber pile portion composed of the ultrafine fiber bundle and having excellent smoothness. Therefore, it is possible to obtain a high-performance polishing which can reduce the surface roughness of the scratch and the object to be polished in the polishing process using the slurry of the strip-shaped polishing cloth on the surface of the substrate of the recording disk and/or the use of the slurry. cloth.

The polishing cloth of the present invention is suitably used when the aluminum alloy substrate or the glass substrate used for the magnetic disk is polished by a highly precise finished product and/or subjected to a cleaning process.

According to the production method of the present invention, the above-mentioned polishing cloth can be efficiently produced.

[Formation for implementing the invention]

Next, the polishing cloth of the present invention and the method for producing the same will be described with respect to the embodiment for carrying out the invention.

The present inventors have focused on the above-mentioned problems, that is, to reduce the scratching disadvantage of the surface of the substrate and the surface roughness of the object to be polished, and to emphasize the structure of the surface fiber velvet portion composed of the ultrafine fiber bundle on the surface of the polishing cloth. The size and surface smoothness of the portion in which the ultrafine fibers composed of the ultrafine fiber bundles are substantially uniformly aligned in the longitudinal direction and aligned in a single direction are carefully studied. Next, it was found that the compactness and dispersibility on the surface of the polishing cloth contributed greatly to the high-precision slurry polishing and/or cleaning process.

As a result, it has been studied to form a non-woven fabric constituting a polishing cloth into a non-woven fabric in which extremely fine fiber bundles which are bundled by ultrafine fibers having an average single fiber diameter of 0.05 to 2.0 μm are intertwined, and a fine fiber bundle on the surface of the polishing cloth is formed. The non-woven fabric having a width of 50 to 180 μm in the width direction formed by the ultrafine fiber bundle having the structure of the surface fiber velvet portion can solve the above problem at a time.

It is extremely important that the ultrafine fibers used in the present invention have an average single fiber diameter of 0.05 to 2.0 μm from the viewpoint of the compactness of the surface fibers of the polishing cloth, the fiber strength, and the gripability of the abrasive grains. By forming the average single fiber diameter to 2.0 μm or less, the surface roughness of the object to be polished can be reduced. On the other hand, by setting the average single fiber diameter to 0.05 μm or more, the fiber strength and rigidity can be maintained, so that the polishing can be performed efficiently.

Examples of the polymer forming the ultrafine fibers used in the present invention include polyester, polyamine, polyolefin, and polyphenylene sulfide (PPS). Most of the polycondensation-based polymers represented by the polyester or the polyamine are those having a high melting point and are excellent in heat resistance to heat generated during polishing, and these are suitable for use. Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. Further, specific examples of the polyamines include nylon 6, nylon 66, and nylon 12.

Further, the polymer constituting the ultrafine fibers may copolymerize other copolymerization components, and may further contain additives such as particles, a flame retardant, and an antistatic agent. Examples of the other copolymerization component include sodium 5-isophthalate sulfonate, 3-hydroxybutyric acid, nylon 6, nylon 66, and nylon 12. Further, examples of the particles include titanium oxide. Further, examples of the flame retardant include an organic flame retardant or an inorganic flame retardant. The antistatic agent may, for example, be an alcohol-based antistatic agent.

The non-woven fabric which is a fiber intertwined body used as the polishing cloth of the present invention is suitably used for performing a needle punch or a waterjet punch after forming a laminated fiber web by using a crimped fiber and crimping a short fiber. Short fibers are not woven. Further, a long-fiber non-woven fabric obtained by a spunbond method or a melt-blown method, a non-woven fabric obtained by a papermaking method, or the like can be suitably used. Among them, the short fiber non-woven fabric or the spunbonded non-woven fabric can be obtained by needle punching to obtain a form of an ultrafine fiber bundle as described later, and thus is suitable for use.

In the polishing cloth of the present invention, it is necessary to form a nonwoven fabric as a nonwoven fabric in which the fibers are intertwined. By blending the fibers with the polymer elastomer, the bonding effect of the polymer elastomer prevents the ultrafine fibers from falling off the polishing cloth, and a uniform pile can be formed at the time of raising. Further, by including the polymer elastic body as the nonwoven fabric as the intertwined fiber, the cushioning property of the polishing cloth can be imparted, and the scratching disadvantage of the surface of the substrate to be polished by the polishing can be further reduced.

As the polymeric elastomer used in the present invention, for example, polyurethane, polyurea, polyurethane-polyurea elastomer, polyacrylic acid, acrylonitrile-butadiene elastomer, and benzene can be used. Ethylene-butadiene elastomer, and the like. Among them, a polyurethane-based elastomer such as a polyurethane and a polyurethane-polyurea elastomer is preferably used.

The weight average molecular weight of the polymer diol component of the polyurethane used as the main component of the polymer elastomer is preferably from 500 to 5,000, more preferably from 1,000 to 3,000. By setting the weight average molecular weight to 500 or more, preferably 1,000 or more, the strength of the polishing cloth can be maintained, and the ultrafine fibers can be prevented from falling off. Further, by setting the weight average molecular weight to 5,000 or less, preferably 3,000 or less, the viscosity of the polyurethane solution can be suppressed from increasing, and the polyurethane impregnation of the ultrafine fiber layer can be easily performed.

Further, as the diol component of the raw material of the polyurethane, a polyether diol, a polyester diol, a polycarbonate diol, a polylactone diol, and the like are preferably used.

Further, as the diisocyanate component of the raw material of the polyurethane, an aromatic diisocyanate, an alicyclic isocyanate, an aliphatic isocyanate or the like can be used. In addition, in order to improve the suitability of the object to be polished and the cushioning property which contributes to the suppression of damage, the ratio of the polyether diol component in the polymer diol is 60% by mass or more from the viewpoint of flexibility. Preferably, it is preferably 70% by mass or more.

The weight average molecular weight of the polyurethane used in the present invention is preferably from 100,000 to 300,000, preferably from 150,000 to 250,000. By setting the weight average molecular weight of the polyurethane to 100,000 or more, the strength of the obtained polishing cloth can be maintained, and the fine fibers on the pile surface can be prevented from falling off. Further, by setting the weight average molecular weight of the polyurethane to 300,000 or less, it is possible to suppress the increase in the viscosity of the polyurethane solution and facilitate the impregnation of the nonwoven fabric.

Further, from the viewpoint of satisfying the compactness and distribution uniformity of the ultrafine fibers on the surface of the polishing cloth, the gelation point of the polyurethane is preferably in the range of 2.5 to 6.0 ml. The gelation point is more preferably in the range of 3.0 to 5.0 ml.

The gelation point of the polyurethane means 100 g of a solution of N,N'-dimethylformamide (hereinafter sometimes abbreviated as DMF) with a concentration of 1 mass% of the polyurethane being stirred, and the solution is in the solution. The value of the amount of water droplets when the distilled water was dropped and the polyurethane began to solidify at a temperature of 25 ± 1 ° C and was slightly cloudy. Therefore, it is necessary to use a moisture content of 0.03% or less for the DMF used in the measurement of the gelation point. The method for measuring the gelation point is described before the transparency of the polyurethane DMF solution is used. However, if the polyurethane DMF solution is slightly turbid in advance, the polyurethane can be solidified to make it cloudy. The amount of water drop when the degree is changed is regarded as the gelation point.

If the gelation point is less than 2.5 ml, when the polyurethane is wet-solidified, since the solidification rate is too fast, the foaming of the polyurethane present in the inner space of the nonwoven fabric becomes large and rough. The situation of the person. Further, if the gelation point is less than 2.5 ml, a part of the foaming failure may occur, and when the surface of the sheet is polished by the polishing treatment described later, the length of the fine fibers of the pile surface may be stained, or The distribution of the pile fibers is deviated, and it is impossible to obtain a state in which the abrasive grains are uniformly dispersed in the pile surface, and there is a case where the finished product of ultra high precision cannot be realized.

On the other hand, if the gelation point exceeds 6.0 ml, when the polyurethane is wet-solidified, since the solidification rate is too slow, almost no foaming is observed in the polyurethane present in the inner space of the nonwoven fabric. There will be cases where there is a very thick and hard polyurethane. Therefore, when the surface of the sheet to be polished is polished, it is difficult to polish the polyurethane, the length of the fine fibers of the pile surface is very short, and the fiber bundle is poor in fiber opening, and the surface fiber is The coarseness of the strip density will become larger. Therefore, the abrasive grains are locally agglomerated, and there is a case where the disadvantage of occurrence of scratches is caused.

Further, in the present invention, as the polymer elastomer, it is preferred to use a polyurethane as a main component, and thus it is also possible to prevent the performance of the adhesive or the uniform dispersion state of the velvet fibers as a binder. May contain other resins. Examples of the other resin include an elastomer resin such as a polyester resin, a polyamide amine resin, and a polyolefin resin, an acrylic resin, and an ethylene-vinyl acetate resin.

Further, the polymeric elastomer may contain a small amount of various additives such as a phosphorus-based, halogen-based or inorganic-based flame retardant; phenolic, sulfur-based, phosphorus-based antioxidants; benzotriazole-based, diphenyl-based a UV absorber such as a ketone-based, a salicylate-based, a cyanoacrylate-based or an Oxalic acid anilide; a hindered amine-based and a benzoate-based light stabilizer; Hydrolysis-resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, surfactants, and coagulation modifiers.

In addition, in the form of the inside of the non-woven fabric of the polymer elastic body, the outermost circumference of the fiber bundle composed of the ultrafine fibers is obtained from the viewpoint of less detachment of the fibers and uniform alignment of the directionality of the velvet fibers. A state in which at least a part of the fibers are joined is a preferred embodiment.

This form can be obtained by the method of (B) mentioned later. That is, the polyvinyl alcohol protects most of the outer periphery of the ultrafine fiber bundle, thereby preventing the polyurethane from intruding into the fiber bundle of the ultrafine fiber, and adhering the polyamine to the outer peripheral portion of the fiber bundle partially protected by the polyvinyl alcohol. Acid ester.

The polymer elastomer is partially adhered to and restrains the fibers located at the outermost periphery of the ultrafine fiber bundle, whereby the degree of freedom of the fine pile fibers on the pile surface can be appropriately controlled. As a result, the free directivity of the velvet fibers after the polishing treatment becomes extremely small. That is, the pile fibers can be adjusted to be aligned in a single direction. Thereby, it is formed in a state in which the pile fibers are uniformly aligned in a single direction, and it is possible to form a state in which the density of the ultrafine fibers existing on the pile surface is small and the ultrafine fibers are uniformly arranged. As described above, it is possible to form a configuration in which the pile fibers are distributed in a state of being dense and uniformly aligned in a single direction, and the directivity of the fibers is aligned in a single direction. By forming the structure as described above, the dispersibility of the abrasive grains during the polishing process can be improved, and the distribution of the abrasive grains on the surface of the polishing cloth can be made uniform, so that the scratching disadvantage can be extremely reduced.

In the polishing cloth of the present invention, cushioning properties and suitability are very important in polishing precision. These cushioning properties and suitability can be controlled and adjusted by the ratio of the ultrafine fibers to the polymeric elastomer or the void ratio (known from the apparent density).

In the polishing cloth of the present invention, the total mass of the ultrafine fibers and the polymer elastic system relative to the polishing cloth is preferably from 50 to 100% by mass, preferably from 80 to 100% by mass. The total weight of the ultrafine fibers relative to the polishing cloth is preferably from 40 to 90% by mass, more preferably from 50 to 80% by mass. The content of the polymeric elastomer is preferably from 10 to 50% by mass, preferably from 10 to 40% by mass, based on the total mass of the polishing cloth. The surface state, the void ratio, the cushioning property, the hardness, the strength, and the like of the polishing cloth can be appropriately adjusted by the content of the polymeric elastomer. When the content of the polymeric elastomer exceeds 50% by mass, workability and productivity are inferior, and it is difficult to obtain a velvet surface in which fine fibers are uniformly dispersed on the surface of the sheet. Therefore, there is a possibility that the occurrence of scratch defects at the time of slurry polishing processing cannot be completely suppressed. On the other hand, when the content of the polymeric elastomer is less than 10% by mass, the strength of the polishing cloth is lowered, and the polishing cloth is easily deformed during the slurry polishing process, which is not preferable. Further, the polishing cloth of the present invention may contain a reinforcing material such as a woven fabric as a component other than the ultrafine fibers and the polymeric elastomer.

In the polishing cloth of the present invention, it is extremely important that at least one side of the polishing cloth is a pile surface composed of ultrafine fibers from the viewpoint of the denseness and dispersibility of the ultrafine fibers on the surface of the polishing cloth.

Fig. 1 is a SEM magnification (40 magnification) photograph showing an example of a structure of a surface fiber velvet portion formed by an ultrafine fiber bundle on the surface of the polishing cloth of the present invention.

As shown in Fig. 1, the pile surface of the polishing cloth is formed by a structure including a surface fiber velvet portion composed of a bundle of ultrafine fibers. The surface fiber velvet portion is indicated by the square shape of Fig. 1. In the present invention, in the square shape shown in Fig. 1, the direction of the ultrafine fiber bundle (the width direction of the fiber bundle) is the transverse direction of the structure of the surface fiber velvet portion, and the length direction of the ultrafine fiber bundle of the ultrafine fiber bundle is the surface fiber. The length direction of the structure of the velvet portion. As a form of the structure of the surface fiber velvet portion, the ultrafine fibers can be uniformly aligned, and the ultrafine fibers can be slightly separated from each other, or partially bonded or agglomerated.

Here, the term "bonding" means a chemical reaction or a physical fusion, and the aggregation refers to an intermolecular force such as hydrogen bonding.

In the polishing cloth of the present invention, the average size of the ultrafine fiber bundle of the structure of the surface fiber velvet portion in the width direction is in the range of 50 to 180 μm, preferably in the range of 50 to 120 μm. When the average size of the ultrafine fiber bundle of the structure of the surface fiber velvet portion is 180 μm or less, the ultrafine fiber bundles of the surface fiber velvet portion do not overlap each other, and the surface of the polishing cloth becomes small and uneven, and is used for polishing. When it is difficult to cause scratches on the object to be polished, the surface roughness of the object to be polished can be reduced. In addition, when the average size of the ultrafine fiber bundles in the width direction of the surface fiber pile portion is 50 μm or more, the amount of the ultrafine fibers present on the surface of the polishing cloth increases, and the surface coverage becomes high, which is a preferred embodiment.

The average length of the ultrafine fiber bundle of the structure of the surface of the polishing cloth-based fiber of the present invention is preferably from 100 μm to 500 μm. The longitudinal direction of the ultrafine fiber bundle is the longitudinal direction of the ultrafine fibers, and corresponds to the longitudinal direction of the rectangle in Fig. 1 . When the average length in the longitudinal direction of the structure of the surface fiber pile portion is 500 μm or less, the ultrafine fiber bundles are less likely to overlap each other, and the surface unevenness of the polishing cloth is small, and it is difficult to cause scratches on the object to be polished when used for polishing. The surface roughness of the cloth to be polished can be reduced. Further, when the average size in the longitudinal direction is 100 μm or more, the amount of the ultrafine fibers present on the surface is increased, and the surface coverage is high, which is a preferred embodiment.

The polishing cloth of the present invention preferably has a surface roughness of 5 to 18 μm. The surface roughness is preferably from 5 to 15 μm, more preferably from 5 to 8 μm. When the surface roughness is more than 5 μm, it is preferable from the viewpoint of the abrasive grain retainability and dispersibility at the time of slurry polishing. Further, when the surface roughness is less than 18 μm, it is less likely to cause scratching of the object to be polished during polishing, and the surface roughness of the object to be polished can be reduced.

The polishing cloth of the present invention is formed into a belt shape, and when the slurry is polished and cleaned, the surface of the substrate cannot be uniformly polished if the size changes. Therefore, the polishing cloth of the present invention preferably has a basis weight of from 100 to 400 g/m ² and a basis weight of from 150 to 300 g/m ^{2 in} view of the form stability of the polishing cloth.

Next, a method of producing the polishing cloth of the present invention will be described.

The polishing cloth of the present invention is suitably obtained by combining at least the following steps (1) to (5). At this time, in order to achieve the surface fiber velvet portion of the polishing cloth of the present invention, the number of extremely fine fiber-type island-in-the-sea composite fibers to be carried by the needle punching in the following step (2) is 3 to 6 The /1 barb is extremely important.

(1) a step of producing a finely fibrillated sea-island type composite fiber having an average single fiber fineness of 0.05 to 2.0 μm;

(2) using the sea-island type composite fiber, the step of laminating the fiber web by crimping and cross-rolling, and obtaining a non-woven fabric by needle punching;

(3) a step of imparting 10 to 200% by mass of the polymer elastic body to the ultrafine fiber after the extremely finer nonwoven fabric;

(4) at least a step of performing a polishing treatment on one side; and

(5) A step of subjecting the sea-island type composite fiber to an ultrafine treatment.

In order to obtain a nonwoven fabric-like intertwined body in which the ultrafine fiber bundles are entangled with each other, an ultrafine fiber-generating fiber such as an island-in-sea type composite fiber can be used. Although it is not easy to directly manufacture the fiber intertwined body from the ultrafine fibers, the interfiber-entangled body can be produced from the ultrafine fiber-generating fiber, and the sea-island type composite fiber in the intertwined body of the fiber produces the ultrafine fibers, thereby obtaining the extremely fine fiber bundles intertwined with each other. The fibers are intertwined with each other.

In the conjugate fiber which can be extremely fibrillated, (a) a thermoplastic resin having two components having different solvent solubility can be used as a sea component and an island component, and the sea component can be dissolved and removed by using a solvent or the like to thereby form an island component. An island-in-sea type composite fiber formed into an ultrafine fiber; (b) a two-component thermoplastic resin is alternately arranged in a radial or multi-layered fiber cross section, and each component is peeled and divided, whereby the fiber is a peeling type composite of ultrafine fibers. Fiber, etc.

In the sea-island type composite fiber, an island-in-sea type composite fiber in which a sea-in-sea composite metal cover is used and two components of a sea component and an island component are arranged to each other, and a sea-island composite fiber is mixed with two components of an island component. Spinning mixed spinning fibers, etc. Among them, it is preferable to use an island-in-sea type composite fiber from the viewpoint of obtaining a fine fiber of uniform fineness and obtaining a very fine fiber of a sufficient length and contributing to the strength of the sheet.

As the sea component of the sea-island type composite fiber, a copolymerized polyester obtained by copolymerizing polyethylene, polypropylene, polystyrene, sodium sulfonate dibenzoic acid or polyethylene glycol, or polylactic acid can be used.

The dissolution and removal of the sea component can also be carried out at any timing and step after the application of the elastic polymer, after the application, and after the raising treatment.

In order to obtain a fiber intertwined body such as a non-woven fabric, as described above, a method of twisting the webs by needle punching or water jet acupuncture, a spinning adhesive method, a melt blow method, a papermaking method, etc. may be employed. . In the form of the ultrafine fiber bundle as described above, it is preferred to use a method such as treatment by needle punching or water jet acupuncture.

The number of needle punched needles is preferably from 2,000 to 8,000 pieces/cm ² , preferably from 3,000 to 5,000 pieces, from the viewpoint of formation of a dense pile surface by high intertwining of fibers. /cm ² . When the number of the needle punches is 2,000 pieces/cm ² or more, the surface fibers are excellent in compactness, and a desired high-precision finished product can be obtained. Further, when the number of the needle punches is 8,000 pieces/cm ² or less, the workability is not deteriorated, and there is no possibility of causing fiber damage or strength reduction.

The fiber density of the non-woven fabric after needle punching is preferably 0.15 to 0.4 g/cm ³ , more preferably 0.2 to 0.3 g/cm ³ from the viewpoint of densification of the number of surface fibers.

The structure of the surface fiber velvet portion must have an average size in the width direction of 50 to 180 μm, and an average size of 50 to 120 μm. Therefore, it is extremely important that the number of the conjugate fibers such as the ultrafine fiber-generating fibers brought in by one needle punching is 3 to 6 strips per 1 barb, and the number of the conjugate fibers is preferably 3 to 4 strips per 1 barb. .

The number of the composite fibers such as the extremely fine fiber-reinforced composite fiber stuck to the barb is determined by the shape of the barb and the diameter of the composite fiber. Here, the idea of the number of the extremely fine fiber-bonded composite fibers stuck to the barbs will be described using FIG.

That is, the angle formed by the end of the barb (α in Fig. 2) is assumed to be the apex angle, from the end of the barb (B of Fig. 2) to the front end of the barb (A of Fig. 2). An equilateral triangle on one side. The composite fibers are finely packed and aligned by the end of the equilateral triangle (the end of the barb). Regarding the extremely fine fiber-reinforced composite fiber in which the equilateral triangle is protruded, the case where the area ratio of the composite fiber in the equilateral triangle is 50% or more is regarded as the extremely fine fiber-bonded composite fiber to be carried. The total number of these items is defined as the number of entries.

Therefore, in the invention of the present invention, among the steps (1) to (5) of the polishing cloth, the needling step of the step (2) is before the step of performing the miniaturization treatment on the non-woven fabric of the step (5). Extremely important.

Further, the needle used in the needling step preferably has a barb number of 1 to 3, a barb shape of a kick up of 0 to 50 μm, a lower cut angle of 0 to 40°, and a neck depth (throat). Depth) 40 to 80 μm, and the neck length (throat length) is 0.5 to 1.0 mm.

The nonwoven fabric containing the elastic polymer obtained as described above is preferably formed by shrinking by dry heat or moist heat or both, from the viewpoint of densification of the number of surface fibers.

In the polishing cloth of the present invention, it is extremely important that the nonwoven fabric obtained by winding the above-mentioned ultrafine fiber bundles as a main body.

In the polishing cloth of the present invention, from the viewpoint of the suitability for the object to be polished and the damage suppressing effect on the surface of the object to be polished, it is preferred to make the nonwoven fabric before and/or after the ultrafine fiberizing treatment. It imparts a polymeric elastomer containing a polyurethane as a main component. The polymer elastic system as described above has a function of buffering or fiber form retention for surface unevenness or vibration absorption. In other words, the polymer elastic body is filled in the inner space of the nonwoven fabric and integrated, whereby the suitability for the object to be polished and the damage suppressing effect on the surface of the object to be polished are excellent.

In the method of imparting a non-woven fabric to a polymeric elastomer such as the above-described polyurethane, a method of applying a polymeric elastomer to a nonwoven fabric or coagulation after impregnation may be employed. Among them, from the viewpoint of workability, it is preferred to use a method in which a polymer elastomer solution is impregnated in a nonwoven fabric and then wet-solidified.

For example, a polyurethane used as a polymer elastomer is formed into a solution by a solvent such as dimethylformamide, and (A) impregnated with a non-woven fabric in which extremely fine fiber-bonded composite fibers are entangled with each other. a method in which a polyurethane solution is solidified in water or an aqueous solution of an organic solvent, and the polymer component is removed by dissolving the extremely fine fiber-formed composite fiber, and is dissolved and removed without dissolving the solvent of the polyurethane. . Or preferably, (B) a polyvinyl alcohol having a degree of alkalinity of preferably 80% or more is provided in a non-woven fabric in which the extremely fine fiber-reinforced composite fibers are intertwined, and is extremely finely fiberized after protecting most of the fibers. Dissolving the composite fiber to remove the polymer component, dissolving and removing it in a solvent that does not dissolve the polyvinyl alcohol, and then, the solution impregnated with the polyurethane is solidified in water or an aqueous solution of an organic solvent, and then the polyvinyl alcohol is removed. Method etc.

In the raising treatment of the surface of the nonwoven fabric obtained as described above, it can be suitably carried out by polishing using sandpaper or roller sand or the like. In particular, by using sandpaper, a uniform and dense pile can be formed on the surface of the nonwoven fabric.

In addition, the surface of the substrate is subjected to slurry polishing and cleaning with an ultra-high-precision finished product, and the disadvantage of scratching is suppressed, so that the uniformity and compactness of the surface fiber distribution on the surface are improved, and the direction of the pile fiber is extremely reduced. Sex, to reduce the grinding load even better. In a state where the polishing load is high, it is easy to form a pile of pile-like fibers, and the pile fibers are in a bundled state. In order to reduce the grinding load, it is preferred to appropriately adjust the number of polishing segments or the number of sandpaper. Among them, the number of polishing stages is preferably three or more stages of polishing, and the number of sandpaper used in each stage is set to the range of 150 to 600 specified by JIS.

In the method of appropriately performing slurry polishing and cleaning using the polishing cloth of the present invention, the polishing cloth is cut into a strip shape of 30 to 50 mm wide and used as a slurry from the viewpoint of processing efficiency and stability. It is preferred to use a tape for material grinding and cleaning. In the present invention, a method of polishing and cleaning a slurry of an aluminum alloy magnetic recording disk or a glass magnetic recording disk using a polishing tape as shown above and a slurry containing free abrasive grains is a more suitable method. .

In terms of polishing conditions, the slurry is preferably one in which a high-hardness abrasive grain such as diamond fine particles is dispersed in an aqueous dispersion medium. Among them, the abrasive grains suitable for the ultrafine fibers constituting the polishing cloth of the present invention are composed of single crystal diamonds from the viewpoints of suppression of the retention of the abrasive grains, dispersibility, and scratch resistance, and reduction in surface roughness. The secondary particle diameter is preferably 1 to 20 nm, and preferably 1 to 10 nm.

That is, the polishing cloth of the present invention is suitably used when the aluminum alloy substrate or the glass substrate used for the magnetic disk is polished by a highly precise finished product or subjected to a cleaning process.

[Examples]

Next, the polishing cloth of the present invention and the method for producing the same will be described more specifically by way of examples, but the invention is not limited thereto. Further, the evaluation method used in the examples and the evaluation conditions thereof are as follows.

(1) The melting point of the polymer

Using a DSC-7 manufactured by Perkin Elmaer Co., Ltd., in the second run, the peak temperature indicating the melting of the polymer was taken as the melting point of the polymer. The rate of temperature rise at this time was 16 ° C / min, and the amount of the sample was 10 mg.

(2) Melt flow rate (MFR) of the polymer

4 to 5 g of the sample pellets were placed in a sleeve of an MFR meter electric furnace, and a resin which was extruded in 10 minutes was measured under a load of 2160 gf and a temperature of 285 ° C using a melt index meter (S101) manufactured by Toyo Seiki Co., Ltd. Quantity (g). The same measurement was repeated three times, and the average value was set to MFR.

(3) Number of composite fibers brought in acupuncture

Fig. 2 is a schematic view for explaining a relationship between a needle and a conjugate fiber at the time of needling, and a method for estimating the number of conjugated fibers to be taken at the time of needling. The method of estimating the number of the conjugated fibers in the needle punching will be described using the pattern of the needle and the composite fiber shown in Fig. 2 . First, a point D having the same length as the length of the tip end of the barb (A of FIG. 2) and the end of the barb (B of FIG. 2) is obtained on the BC of FIG. Next, the front ends A and D of the barbs of Fig. 2 are connected by line segments, and an equilateral triangle BAD of BA = BD is produced. Within the equilateral triangle, the composite fibers are finely packed and arranged. Regarding the composite fiber which is arranged by the equilateral triangle BAD, the area ratio of the composite fiber in the equilateral triangle BAD is 50% or more, and the composite fiber which can be carried in is considered as the total number of the composite fibers. Defined as the number of entries.

(4) Average fiber diameter and fiber diameter CV

The cross section of the polishing cloth cut in the thickness direction was used as an observation surface, and observation was performed by a scanning electron microscope (SEM) at a magnification of 5000 times, and the diameter of 50 single fibers randomly extracted was measured. The measurement was carried out at three locations, and the total diameter of 150 single fibers was measured, and the average value and standard deviation value of the parent were calculated. The average value is defined as the average fiber diameter, and the value obtained by dividing the standard deviation value by the average value is expressed as a percentage (%) as the fiber diameter CV.

(5) Determination of the structural dimensions of the surface fiber velvet portion

As shown in Fig. 1, the surface of the polishing cloth is used as the observation surface, and the SEM is observed at a magnification of 40 times, and the ultrafine fiber bundle formed by the arrangement of the ultrafine fibers existing on the surface is defined as the surface fiber velvet. Part of the construction. The structure of 50 surface fiber pile portions was randomly extracted, and the width direction and the length direction of the extracted 50 surface fiber pile structures were measured, and the average values were calculated.

(6) Determination of surface roughness of abrasive cloth

The surface roughness of the surface of the polishing cloth was measured using a surface roughness measuring device SE-40C with a surface roughness measuring device SE-40C of 2.5 mm, an evaluation length of 12.5 mm, and an evaluation speed of 0.5 m/s. The average value was calculated by measuring the piles three times in the direction of the weaving.

(7) Grinding by grinding cloth

The abrasive cloth was formed into a tape of 30 mm width. For the object to be polished, a glass substrate made of amorphous glass made of KMG Co., Ltd. whose surface roughness is controlled to 0.3 nm or less is used. A primary particle diameter 5 nm single crystal diamond particle was collected into a slurry having a concentration of 0.01% of free abrasive grains having an average diameter of 80 nm, and dropped onto the surface of the polishing cloth at 50 ml/min. Further, the winding speed of the tape was 70 mm/min, the number of rotations of the disk was 600 rpm, the wobble was set to 100 times/min, the pressing pressure was set to 1.5 kgf, and the grinding was performed for 15 seconds. This step is performed for both sides of each disc.

(8) Surface roughness of the substrate to be polished

The measurement was carried out in a tapping mode using "AFM NanoScope" (registered trademark) IIIa manufactured by Veeco Co., Ltd. The observation field on the substrate was set to 10 μm × 10 μm, and any one point on the substrate was measured, and the average value of any three points was defined as the surface roughness (Ra). The surface roughness of the substrate was 2.0 nm or less, and the polishing performance was good.

(9) Number of scratches on the object to be polished

The surface of the five substrates after the polishing, that is, the entire surface of the surface of the gauge 10 was used as a measurement target, and the number of scratches was measured by using an optical surface analyzer (Candela 6100) as a scratch having a depth of 2 nm or more. The average of the measured values of the surface is evaluated. The lower the value, the higher the performance. The number of scratches is 20 or less, and the polishing performance is good.

[Example 1] (raw cotton) (sea composition and island composition)

Using nylon 6 having a melting point of 220 ° C and an MFR of 10.5 as an island component, a copolymerized polystyrene (co-PSt) having a melting point of 53 ° C and a MFR of 12 of 2-ethylhexyl acrylate was subjected to 22 mol% copolymerization. Sea ingredients.

(spinning/extension)

Using the above-mentioned sea component and island component, a sea-island composite metal cover of 376 islands/hole was used, with a spinning temperature of 285 ° C, an island/sea mass ratio of 40/60, a discharge amount of 1.7 g/min, a hole, and a spinning speed of 1200 m/ Minutes, the island composite fiber was melt spun. Then, it was extended to 3.0 times in an oil bath for spinning at a temperature of 85 ° C, and was crimped by a plug-in type crimper to perform cutting, and the sea-island type having a fineness of 6.5 dtex and a fiber length of 51 mm was obtained. Raw cotton of composite fibers.

(non-woven fabric composed of extremely fine fiber composite fibers)

The raw cotton of the sea-island type composite fiber is used to form a laminated fiber web via a crimping and cross-rolling step. Next, the obtained laminated fiber web was subjected to a needle punching machine with a needle having a needle neck depth of 60 μm, an upper bend of 0 μm, a lower cut angle of 4°, and a neck length of 0.9 mm, with a needle depth of 8 mm and a needle punching number of 3,200. /cm ² was needle-punched to produce a non-woven fabric composed of sea-island type composite fibers having a basis weight of 800 g/m ² and an apparent density of 0.190 g/cm ³ . The number of strips of the island-in-the-sea composite fiber by needle punching is 3/1 barb.

(grinding cloth)

The non-woven fabric composed of the above-described sea-island type composite fiber was subjected to hot water shrinkage treatment, and then impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. Then, in the trichloroethylene, the sea-component co-PST is dissolved and removed, and dried to obtain an ultrafine fiber nonwoven fabric in which extremely fine fiber bundles are entangled with each other.

In the nonwoven fabric obtained as described above, the polymer diol was a polyurethane having a polyether content of 75% by mass and a polyester based product of 25% by mass (the gelatinization point was 4.2 ml), and the fiber mass was imparted in a solid form. 20% by mass, the polyurethane was solidified in a 30% DMF aqueous solution at a liquid temperature of 35 ° C, and DMF and polyvinyl alcohol were removed by hot water at a temperature of about 85 ° C. Thereafter, the half-cut was performed in the thickness direction by a half-cutting machine having a band knife, and the non-semi-cut surface was polished in three stages using a sandpaper of JIS #240, and a pile was formed to form a polishing cloth.

In the obtained polishing cloth, the ultrafine fibers had an average single fiber diameter of 0.72 μm, a fiber diameter of 7.0%, a thickness of 0.5 mm, a basis weight of 180 g/m ² and an apparent density of 0.36 g/cm ³ . As a result of evaluating the polishing performance using the obtained polishing cloth, the surface roughness and the number of scratches of the substrate were all satisfied, and the surface after polishing was also high in uniformity. The results are shown in Table 1.

[Embodiment 2] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

Using the above-mentioned sea component and island component, a 200 island/hole island-type composite metal cover was used, with a spinning temperature of 285 ° C, an island/sea mass ratio of 40/60, a discharge amount of 0.9 g/min, a hole, and a spinning speed of 1200 m/ The island-type composite fiber was melt-spun in a minute condition. Then, it was extended to 3.0 times in the oil bath for spinning, and was crimped and cut by a plug-in type crimper to obtain a sea-island type having a fineness of 5.2 dtex and a fiber length of 51 mm. Raw cotton of composite fibers.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 1, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 680 g/m ² and an apparent density of 0.224 g/cm ³ was produced.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average single fiber diameter of 1.53 μm, a fiber diameter of 5.8%, a thickness of 0.51 mm, a basis weight of 186 g/m ² and an apparent density of 0.365 g/cm ³ . The results are shown in Table 1.

[Example 3] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 1.

(non-woven fabric composed of extremely fine fiber composite fibers)

A base weight of 800 g/m ² and an apparent density of 0.190 g/cm ³ were produced in the same manner as in Example 1 except that a needle having a neck depth of 60 μm, a 10 μm upper bend, a lower cut angle of 27°, and a neck length of 0.8 mm was used. The ultrafine fiber-forming fibers are not woven.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1.

In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.72 μm, a fiber diameter of 7.0%, a thickness of 0.49 mm, a basis weight of 175 g/m ² and an apparent density of 0.357 g/cm ³ . The results are shown in Table 1.

[Example 4] (raw cotton)

The sea component and the island component were used in the same manner as in the user of Example 2.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 2.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 3, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 680 g/m ² and an apparent density of 0.224 g/cm ³ was produced.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1.

In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 1.53 μm, a fiber diameter of 5.8%, a thickness of 0.5 mm, a basis weight of 180 g/m ² and an apparent density of 0.360 g/cm ³ . The results are shown in Table 1.

[Example 5] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

Using the above-mentioned sea component and island component, an island-type composite metal cover of 800 islands/hole is used, with a spinning temperature of 285 ° C, an island/sea mass ratio of 30/70, a discharge amount of 2.1 g/min, a hole, and a spinning speed of 1200 m. The island-in-the-sea composite fiber was melt-spun under the condition of /min. Subsequently, it was extended to 3.0 times in a liquid bath at a temperature of 85 ° C, and crimped by a plug-in type crimping machine to perform dicing, thereby obtaining a raw cotton of a sea-island type composite fiber having a fineness of 12.1 dtex and a fiber length of 51 mm.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 3, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 680 g/m ² and an apparent density of 0.224 g/cm ³ was produced.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 3.

In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.50 μm, a fiber diameter of 7.7%, a thickness of 0.48 mm, a basis weight of 175 g/m ² and an apparent density of 0.365 g/cm ³ . The results are shown in Table 1.

[Embodiment 6] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

In the so-called hybrid spinning method in which the sea-island type composite fiber is melt-spun at a spinning temperature of 285 ° C, the sea component is mixed with the island component by 50% by weight, and an island having about 1,000 island components is disposed in the sea component. The composite fiber was melt-spun at a spinning speed of 1200 m/min. Then, it was extended to 3.0 times in an oil bath for spinning at a temperature of 85 ° C, and was crimped by a plug-in type crimper to perform cutting, and the sea-island type having a fineness of 11.6 dtex and a fiber length of 51 mm was obtained. Raw cotton of composite fibers.

(non-woven fabric composed of extremely fine fiber composite fibers)

A non-woven fabric composed of sea-island type composite fibers was obtained in the same manner as in Example 1 except that the sandpaper of JIS #320 was used.

(grinding cloth)

After the non-woven fabric composed of the above-described sea-island type composite fiber was shredded by hot water, it was impregnated with a 12% aqueous solution of polyvinyl alcohol and dried. In the nonwoven fabric, the polymer diol is a polyurethane composed of a polyether-based 75 mass% and a polyester-based 25 mass%, and the fiber mass is 20% by mass based on the solid content, and the liquid temperature is 35° C. The aqueous solution of %DMF solidifies the polyurethane and removes DMF with hot water at a temperature of about 85 °C. Thereafter, the sea component co-PST was dissolved and dissolved in trichloroethylene, and dried to obtain an ultrafine fiber nonwoven fabric composed of an ultrafine fiber bundle and a polyurethane.

Thereafter, the obtained ultrafine fiber nonwoven fabric was half-cut in the thickness direction by a semi-cutting machine having a jointless belt knife, and the semi-finished surface was polished in three stages using JIS #320 sandpaper to form a pile fabric. Grinding cloth.

In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.72 μm, a fiber diameter of 32.3%, a thickness of 0.55 mm, a basis weight of 180 g/m ² and an apparent density of 0.327 g/cm ³ . The results are shown in Table 1.

[Embodiment 7] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 5.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 5.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 3, a nonwoven fabric composed of sea-island type composite fibers was obtained.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 5. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.72 μm, a fiber diameter of 32.3%, a thickness of 0.5 mm, a basis weight of 190 g/m ² and an apparent density of 0.380 g/cm ³ . The results are shown in Table 1.

[Embodiment 8] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

An island having a single fiber fineness of 2.2 dtex and a fiber length of 51 mm was obtained in the same manner as in Example 1 except that the sea-island composite metal cover having an island number of 600 islands/hole was used and the discharge amount was 1.0 g/min. Raw cotton of composite fiber.

(non-woven fabric composed of extremely fine fiber composite fibers)

A non-woven fabric composed of sea-island type composite fibers was obtained in the same manner as in Example 6.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.35 μm, a fiber diameter of 6.2%, a thickness of 0.5 mm, a basis weight of 177 g/m ² and an apparent density of 0.354 g/cm ³ . The results are shown in Table 1.

[Embodiment 9] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

A denier of 6.8 dtex and a fiber length were obtained in the same manner as in Example 1 except that the island-type composite metal lid of 448 islands/hole was used, and the island/sea mass ratio was 50/50 and the discharge amount was 2.0/min. Raw cotton of 51mm island-type composite fiber.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 1, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 680 g/m ² and an apparent density of 0.224 g/cm ³ was produced. The number of strips of the island-in-the-sea composite fiber by needle punching is 3/1 barb.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.52 μm, a fiber diameter of 5.5%, a thickness of 0.5 mm, a basis weight of 180 g/m ² and an apparent density of 0.36 g/cm ³ . As a result of evaluating the polishing performance using the obtained polishing cloth, the surface roughness and the number of scratches of the substrate were all satisfied, and the surface after polishing was also high in uniformity. The results are shown in Table 1.

[Embodiment 10] (raw cotton) (sea composition and island composition)

Polyethylene terephthalate having a melting point of 260 ° C and an MFR of 46.5 was used as an island component, and a polystyrene having a melting point of 85 ° C and an MFR of 117 was used as a sea component.

(spinning/extension)

A denier of 2.5 dtex and a fiber length were obtained in the same manner as in Example 1 except that the island-type composite metal lid of 200 islands/hole was used, and the island/sea mass ratio was 50/50 and the discharge amount was 1.0/min. Raw cotton of 51mm island-type composite fiber.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 1, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 650 g/m ² and an apparent density of 0.224 g/cm ³ was produced. The number of strips of the island-in-the-sea composite fiber by needle punching is 4/1 barb.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.75 μm, a fiber diameter of 6.8%, a thickness of 0.5 mm, a basis weight of 190 g/m ² and an apparent density of 0.38 g/cm ³ . As a result of evaluating the polishing performance using the obtained polishing cloth, the surface roughness and the number of scratches of the substrate were all satisfied, and the surface after polishing was also high in uniformity. The results are shown in Table 1.

[Example 11] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 11.

(spinning/extension)

A denier of 4.1 dtex and a fiber length were obtained in the same manner as in Example 1 except that the island-in-sea composite metal lid of 200 islands/hole was used, and the island/sea mass ratio was 50/50 and the discharge amount was 1.6/min. Raw cotton of 51mm island-type composite fiber.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 1, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 650 g/m ² and an apparent density of 0.224 g/cm ³ was produced. The number of strips of the island-in-the-sea composite fiber by needle punching is 3/1 barb.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.94 μm, a fiber diameter of CV of 5.2%, a thickness of 0.5 mm, a basis weight of 190 g/m ² and an apparent density of 0.38 g/cm ³ . As a result of evaluating the polishing performance using the obtained polishing cloth, the surface roughness and the number of scratches of the substrate were all satisfied, and the surface after polishing was also high in uniformity. The results are shown in Table 1.

[Comparative Example 1] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 1.

(non-woven fabric composed of extremely fine fiber composite fibers)

A base weight of 870 g/m ² and an apparent density of 0.220 g/cm were produced in the same manner as in Example 1 except that a needle having a neck depth of 65 μm, a 10 μm upper bend, a lower cut angle of 35°, and a neck length of 0.9 μm was used. A non-woven fabric composed of ^three island-type composite fibers.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.72 μm, a fiber diameter of 7.0%, a thickness of 0.51 mm, a basis weight of 180 g/m ² and an apparent density of 0.360 g/cm ³ . The results of the evaluation of the polishing performance were carried out using the obtained polishing cloth, and the surface roughness and the number of scratches of the substrate were not satisfactory. The results are shown in Table 2.

[Comparative Example 2] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 2.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 2.

(non-woven fabric composed of extremely fine fiber composite fibers)

A nonwoven fabric composed of sea-island type composite fibers was obtained in the same manner as in Comparative Example 1.

(grinding cloth) [Comparative Example 3]

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 1.53 μm, a fiber diameter of 5.8%, a thickness of 0.51 mm, a basis weight of 180 g/m ² and an apparent density of 0.353 g/cm ³ . The results are shown in Table 2.

(sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 1.

(spinning/extension)

Using the sea component/island component described above, a sea-island composite metal cover of 36 islands/hole is used, with a spinning temperature of 285 ° C, an island/sea mass ratio of 50/50, a discharge amount of 1.5 g/min, a hole, and a spinning speed of 1000 m/ Melt spinning is carried out in minutes. Then, it was extended to 3.0 times in an oil bath for spinning at a temperature of 85 ° C, and was crimped by a plug-in type crimper to perform cutting, and an island having a fineness of 3.8 dtex and a fiber length of 51 mm was obtained. Raw cotton of composite fiber.

(non-woven fabric composed of extremely fine fiber composite fibers)

A nonwoven fabric composed of sea-island type composite fibers was obtained in the same manner as in Comparative Example 1.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 6. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 3.73 μm, a fiber diameter of 6.9%, a thickness of 0.53 mm, a basis weight of 184 g/m ² and an apparent density of 0.347 g/cm ³ . The results are shown in Table 2.

[Comparative Example 4] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Example 5.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 5.

(non-woven fabric composed of extremely fine fiber composite fibers)

A base weight of 660 G/m ² and an apparent density of 0.188 g/cm ^{3 were} produced in the same manner as in Example 1 except that a needle having a neck depth of 40 μm, a top bend of 0 μm, a lower cut angle of 2°, and a neck length of 0.8 mm was used. Non-woven fabric composed of island-type composite fibers.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1. In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 0.50 μm, a fiber diameter of 7.7%, a thickness of 0.52 mm, a basis weight of 162 g/m ² and an apparent density of 0.311 g/cm ³ . The results are shown in Table 2.

[Comparative Example 5] (raw cotton) (sea composition and island composition)

The sea component and the island component were used in the same manner as in the user of Comparative Example 3.

(spinning/extension)

The spinning and the stretching were carried out in the same manner as in Example 3.

(non-woven fabric composed of extremely fine fiber composite fibers)

In the same manner as in Example 1, a non-woven fabric composed of sea-island type composite fibers having a basis weight of 640 g/m ² and an apparent density of 0.196 g/cm ³ was produced.

(grinding cloth)

A polishing cloth was obtained in the same manner as in Example 1.

In the obtained polishing cloth, the ultrafine fibers had an average fiber diameter of 3.73 μm, a fiber diameter of 6.8%, a thickness of 0.51 mm, a basis weight of 192 g/m ² and an apparent density of 0.376 g/cm ³ . The results are shown in Table 2.

A. . . Front end of the barb

B. . . The end of the barb

C. . . B to any point in the direction of the front end of the needle (where the point satisfying BC>BA)

D. . . Located on BC, the same length as BA

Fig. 1 is a SEM magnification (40 magnification) photograph showing an example of the surface of the polishing cloth of the present invention.

Fig. 2 is a schematic view showing the relationship between the needle and the conjugate fiber at the time of needling, and a method for estimating the number of conjugated fibers brought in the needle punching.

Claims (7)

A polishing cloth comprising a non-woven fabric and a polymer elastic body in which an ultrafine fiber bundle composed of ultrafine fibers having an average single fiber diameter of 0.05 to 2.0 μm is intertwined with each other, and is characterized in that: The average size of the ultrafine fiber bundle of the surface fiber velvet portion formed of the non-woven fabric of the ultrafine fiber bundle in the width direction is 50 to 180 μm, and a part of the polymer elastic body is not present inside the fiber bundle. The abrasive cloth of claim 1, wherein the ultrafine fiber bundle of the surface fiber velvet portion has an average size in the width direction of 50 to 120 μm. The abrasive cloth of claim 2, wherein the polishing cloth has a surface roughness of 5 to 18 μm. The abrasive cloth of claim 1, wherein the polishing cloth has a surface roughness of 5 to 18 μm. The abrasive cloth of any one of claims 1 to 4, wherein the ultrafine fibers have a CV value of 1 to 30%. A method for producing a polishing cloth, which is a method for manufacturing at least a polishing cloth obtained by the following steps (1) to (5), characterized in that the needle punched by the following step (2) is extremely fine The number of fibrillated island-in-the-sea composite fibers is set to 3-6 strips/1 barbs: (1) a step of producing extremely fine fiberized island-in-the-sea composite fibers with an average single fiber fineness of 0.05 to 2.0 μm; (2) Using the sea-island type composite fiber, a step of forming a fiber web by crimping and cross-rolling, and obtaining a non-woven fabric by needling; (3) The polyvinyl alcohol having a degree of alkalinity of 80% or more is imparted to the nonwoven fabric, and after the majority of the periphery of the protective fiber, the polymer component of the extremely fine fiber-bonded composite fiber is removed to dissolve the polyethylene. The solvent of the alcohol is dissolved and removed, and then the polymer elastomer solution is impregnated and solidified in water or an aqueous solution of an organic solvent, and then the polyvinyl alcohol is removed, and the mass of the ultrafine fibers after the ultrafine refining of the polymer elastomer is imparted to 10 a step of ~200% by mass; (4) a step of performing a polishing treatment on at least one side; and (5) a step of performing an ultrafine treatment on the sea-island type composite fiber. The method for producing a polishing cloth according to claim 6, wherein the number of the sea-island type composite fibers brought in by the needling is 3 to 4 pieces/1 barb.