JP2002273650A - Abrasive cloth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive cloth with excellent fitting property to an abrasive material, capable of grinding a work to be ground without any damages, and with small irregularities of fuzz density of the surface of the abrasive cloth. SOLUTION: This abrasive cloth is formed of nonwoven fabric of polyamide very thin and short fibers of 0.001-0.1 dtex in mean fineness, the number of the very thin and short fibers is >=2×10<6> pieces/cm<3> . After preparing normalized image from surface image data captured from a stereoscopic microscope at the magnification of 25 by using an image processor, the image is binarized at the threshold 100, and the surface roughness index obtained by measuring the area of white parts by the pixel unit (1 pixel =(square) 5.6 μm) is 1,000-10,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing cloth used for polishing an aluminum alloy substrate (hereinafter abbreviated as "Al substrate") used for a recording disk or the like with ultra-high precision finishing. .

[0002]

2. Description of the Related Art In recent years, in a magnetic recording medium such as a recording disk, the space between the recording disk and the magnetic head, that is, the flying height of the magnetic head has been reduced with the increase in capacity and density. Requires a thickness of 0.05 μm or less. When the flying height of the magnetic head becomes extremely small, if there are protrusions on the surface of the magnetic disk, the protrusions and the magnetic head come into contact with each other, causing a head crash and causing a scratch on the disk surface. In addition, even a minute protrusion that does not lead to a head crash may cause an error that occurs when reading or writing information due to contact with the magnetic head. As recording disks have been reduced in size in parallel with higher capacity and higher density, motors for rotating the spindle and the like have also been reduced in size.
For this reason, the torque of the motor is insufficient, and the magnetic head comes into close contact with the recording disk surface, causing a problem that the magnetic head does not fly. As means for preventing the close contact between the recording disk and the magnetic head, a surface treatment called texture processing for forming fine striations on the substrate surface of the recording disk is performed.

[0003] Conventionally, as a texture processing method,
Slurry grinding or the like in which a slurry of loose abrasive grains is adhered to a polishing cloth surface to perform grinding is used. However, when performing surface treatment to satisfy the low flying height of the magnetic head by texture processing, in order to cope with recent rapid increase in recording density due to rapid increase in recording capacity, undulation after polishing is reduced. However, it is required that the surface roughness of the substrate be extremely small, and a polishing cloth that can meet the demand is required.

As a polishing cloth used for texture processing for polishing an Al substrate or the like used for a recording disk or the like with ultra-high precision finishing, a woven fabric made of ultrafine fibers, a foamed polyurethane sheet, and the like have been conventionally used. However, in texture processing, it was not possible to obtain a substrate surface roughness capable of coping with high recording density.

[0005] In recent years, artificial raised hair made of a microfiber non-woven fabric and a polymer elastic material having dense fluff has been used as a polishing cloth in recent years. However, it is extremely difficult to perform such highly accurate texture processing. It is in.

[0006]

The conventional polishing cloth has a non-uniform uneven surface, has a large unevenness in fluff density, and is inferior in denseness. Therefore, after polishing, the surface condition of the polishing cloth is reflected, and the recording disk substrate, which is the object to be polished, has a large undulation and a large substrate surface roughness, and the recording density has been increased to increase the recording capacity of the recording disk. Could not respond to. Further, at the time of polishing, scratches on the substrate surface due to large unevenness of fluff density on the polishing cloth surface, that is, so-called scratches, are a serious problem that extremely lowers productivity.

In view of the problems of the conventional polishing cloth, the present invention is excellent in fitting property to an abrasive, can be polished without scratching the object to be polished, and has uneven density of fluff on the surface of the polishing cloth. Is intended to provide a small polishing cloth.

[0008]

The present invention employs the following means in order to solve the above-mentioned problems.

That is, the polishing cloth of the present invention is composed of a polyamide ultrafine short fiber nonwoven fabric having an average fineness of 0.001 to 0.1 dtex, and the number of the ultrafine short fibers is 2 × 10 ⁶ / c.
m ³ or more, at a magnification of 25 times, after creating a normalized image from surface image data captured using an image processing device from a stereomicroscope, perform a binarization process at a threshold of 100,
The surface roughness index obtained by measuring the area of the white portion in pixel units (1 pixel = □ 5.6 μm) is 1000 to 10000
It is characterized by being.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The object of the present invention is to achieve the above object, that is, it has excellent fit to abrasives, can be polished without scratching the object to be polished, and has small unevenness in the fluff density on the polishing cloth surface. The present inventors have conducted intensive studies on the polishing cloth, and have made a nonwoven fabric of polyamide ultrafine short fibers satisfying a specific surface roughness index. As a result, they have sought to solve these problems at once.

That is, the cause of the large undulation and large surface roughness of the object to be polished is that the surface roughness index of the surface of the polishing cloth is uneven, and the fineness of the surface fiber is inferior. Heading, on the other hand, average fineness 0.001
The number of ultrafine short fibers of 0.1 dtex is 2 × 10 ⁶ fibers / cm ³
When the polyamide ultra-fine short fiber nonwoven fabric described above is configured and the surface roughness index is controlled to 1,000 to 10,000, the surface roughness of the recording disk substrate which is the object to be polished is extremely small, and the textured surface with excellent precision is obtained. It has been determined that it can be provided with high productivity.

More specifically, the polishing cloth of the present invention is constituted by a nonwoven fabric made of the ultrafine short polyamide fibers. That is, sea-island composite spinning using a polyamide as an island component, the cut raw cotton is entangled to form a nonwoven fabric, and then at least one component of the composite fiber in the nonwoven fabric is dissolved or removed, or a physical or chemical action is performed. By peeling, dividing, and ultrafine-thinning to an average fineness of 0.001 to 0.1 dtex, then applying a polymer elastic body, substantially solidifying and solidifying the polymer elastic body, and then performing a raising treatment. It has been clarified that a dense raised surface can be formed to provide a polishing cloth having the characteristic surface roughness index described above.

As the fiber entangled body of the composite fiber used in the present invention, the composite fiber is shortened to form a web using a card / cloth wrapper or a random web, and then a needle punching process or a water jet punching process is performed. The short fiber nonwoven fabric formed into a sheet by performing the entanglement treatment is preferably used.
Among them, the short-fiber nonwoven fabric that has been subjected to needle punching is used to increase the fiber density by forming a high degree of entanglement of the fibers (formation of a dense raised surface)
In this case, the number of punching is preferably from 1000 to 350 from the viewpoint of densely orienting the fibers in the vertical direction of the sheet surface (forming a dense raised surface).
0 / cm ² , preferably from 1500 to 350
More preferably, the number is 0 / cm ² . 1000 /
If it is less than cm ² , the denseness of the nap fiber is inferior, and if it exceeds 3500 fibers / cm ² , it is not preferable from the viewpoint of processability.

In terms of forming a web, a long-fiber non-woven fabric directly formed by spinning such as melt blown or spun bond may be used. Particularly, in the case of a polishing cloth, entanglement of ultrafine fibers and densification of nap fibers are considered. The ultrafine long-fiber nonwoven fabric cannot be used as a polishing cloth, since its properties are remarkably inferior to that of the short-fiber nonwoven fabric and the unevenness of fluff density becomes too large. In other words, the short-fiber non-woven fabric has dense fibers (short-fiber ends, that is, naps) in the vertical direction of the cloth and is densely present. However, since the contact between the fiber ends and the abrasive is polished, uniform polishing can be achieved. However, in a long-fiber nonwoven fabric, the probability that the fiber side surface and the surface of the material to be polished come into contact with each other is extremely high. Therefore, the polishing is uneven and the polishing is likely to be uneven.

The parameter of the surface roughness index in the present invention is the density of such fibers (short fiber ends, ie, naps),
It is the most suitable and adopted as an index that simply indicates the degree of density.

The surface roughness index of the polishing cloth of the present invention is 10 from the viewpoint of the surface roughness of the object to be polished and the productivity.
In the range of 00 to 10000, preferably 1000 to 500
It is important that the range be zero. Surface roughness index of 10
If it exceeds 000, the surface roughness of the object to be polished increases, and scratches on the surface of the object to be polished are easily generated. On the other hand, if it is less than 1000, the fluff on the surface of the polishing cloth is extremely small, so that agglomeration of free abrasive grains occurs, and scratches on the surface of the object to be polished tend to occur, which is not preferable.

The polyamide ultrafine short fiber nonwoven fabric according to the present invention comprises a polishing cloth selectively using polyamide from the viewpoint of abrasion resistance and anti-shattering property, and further has excellent fit to abrasives. It has excellent functions as a material that can be polished without scratching the object to be polished.

Such a polyamide ultra-fine short fiber nonwoven fabric is, for example, a sea-island composite fiber in which a polyamide is arranged in an island component. That is, as such polyamide, for example, nylon 6, nylon 66,
Nylon 12, copolymer nylon and the like are used. As the polymer constituting the sea component to be separated and dissolved or separated by physical action or chemical action of the composite fiber, the above-mentioned polyamides, polyesters, polyethylene, polystyrene, copolymer polystyrene, polyolefins such as polypropylene, etc. Can be used. From among these, the sea component and the island component may be selected and combined in consideration of the cross-sectional formability, spinnability, stretchability, etc. of the ultrafine short fiber, but particularly high entanglement of the fiber when needle punched. As the sea component, polystyrene and copolymerized polystyrene are preferably used from the viewpoint of satisfying the densification of the fibers (naps) by the formation.

In the present invention, it is preferable to subject the nonwoven fabric sheet to hot water shrinkage before performing the ultrafine fiber treatment in order to increase the denseness of the polyamide ultrafine short fibers. To obtain uniform and high shrinkage, the sea component is polystyrene,
It is preferably copolymerized polystyrene, and from the viewpoint of achieving both compactness and productivity, the component weight ratio is preferably 40 to 80% with respect to the total weight, and 50 to 7%.
More preferably, it is 0%.

In the present invention, it is particularly important that the average fineness of the ultrafine short fibers after dissolving and removing the above-mentioned conjugate fibers or peeling and splitting by the physical and chemical actions is 0.001 to 0.1 dtex. . 0.01 to 0.1 dte from the viewpoint of the fit to the workpiece and the retention of the abrasive grains
It is preferably x. In the known sea-island composite spinning,
Depending on the die structure, less than 0.001 dtex is possible, but the die structure is complicated and the spinnability is extremely low.

In addition, if a mixed spinning of a chip blend, a polymer blend, or the like is used, ultrafine short fibers of less than 0.001 dtex can be easily obtained. However, compared to ultrafine short fibers obtained by composite spinning using a sea-island type mouthpiece, Since it is easy to become a bundle state in which ultrafine short fibers are partially adhered to each other, and the uniform dispersibility of the fibers is inferior, the surface roughness of the polishing cloth increases, and the unevenness of the fluff density is large, and the fluff is rough. Agglomeration of the abrasive grains is likely to occur in such portions, and scratches are likely to occur. On the other hand, in the conjugate spinning using the sea-island type conjugate fiber spinneret, an ultra-fine short fiber non-woven fabric is formed because the dispersion of the fiber diameter of the obtained ultra-fine short fiber and the dispersion of the distance between the fibers in the ultra-fine short fiber bundle are small. It is excellent in the uniform dispersibility of the surface fibers at the time of polishing, the surface roughness index of the polishing pad can be suppressed to a small value, and the surface roughness of the object to be polished can be reduced and the scratch can be suppressed. Further, the number of islands in the conjugate single fiber is preferably from 50 to 500,
More preferably, it is 500.

When the number of islands is less than 50, the inter-fiber distance in the ultra-short fiber bundle becomes large, and the fineness of the surface fibers when forming the ultra-short fiber non-woven fabric is inferior. Is not preferred because it cannot be kept small. If the number of islands exceeds 500, the die structure becomes complicated and the die workability and spinnability become extremely low. If it is less than 0.001 dtex, the fiber strength is low and the retention of the free abrasive grains in the slurry is poor, so that the free abrasive grains are likely to aggregate and scratch, which is not preferable. On the other hand, if it exceeds 0.1 dtex, the density of the nap on the polishing cloth surface is inferior, which is not preferable. The cross sections of the conjugate fiber and the ultrafine short fiber are not particularly limited.

[0023] Such a polyamide ultrafine short fiber nonwoven fabric includes:
In addition to the main polyamide, for example, polyethylene terephthalate, copolymerized polyethylene terephthalate,
Polybutylene terephthalate, polyesters such as copolymerized polybutylene terephthalate, polypropylene terephthalate, copolymerized polypropylene terephthalate, etc. can be used as a mixture. In view of the above, the mixing amount is preferably 30% by weight or less, and more preferably 10% by weight or less, which is more preferably used.

In the present invention, it is particularly important that the number of ultrafine short fibers constituting the polishing cloth is 2 × 10 ⁶ fibers / cm ³ or more. The number of ultra-fine short fibers is 2 × 10 ⁶ fibers / cm ³
If it is less than 1, the fineness of the fiber (nap) is inferior, so that the surface roughness of the object to be polished cannot be reduced, which is not preferable.

As a method for producing such ultrafine short fibers, ultrafine short fibers can be produced by removing the polymer of at least one component of the conjugate fibers or exfoliating them from each other. In particular, at least one of said composite fibers
When removing the component polymer, there are various methods such as a method of extracting with a solvent, a method of thermal decomposition,
A method of extracting with a solvent is preferable, and a method of extracting before or after imparting a polymer elastic body can be preferably used.

The polishing cloth of the present invention is preferably made of a polyamide ultrafine short fiber non-woven fabric containing an elastic polymer. The one integrated with such a polymer elastic body is preferable from the viewpoint of fitting property to the object to be polished and suppressing scratches on the object to be polished. As such a polymer elastic body, polyurethane elastomer, acrylonitrile, butadiene rubber, natural rubber, polyvinyl chloride and the like can be used. Among them, polyurethane elastomers are preferred from the viewpoint of processability in the process of the present invention. As a method for applying such a polymer elastic body, various methods such as a method of solidifying after applying or impregnating the polymer elastic body, or a method of applying or impregnating and drying and fixing in the form of an emulsion or latex may be employed. it can.

Next, the polyamide ultra-fine short fiber nonwoven fabric is raised. The raising process here may be a suede-like finish with at least one surface raised. The raising process is generally performed using a needle cloth or sandpaper. In particular, after applying the polymer elastic body, the surface can be raised by using sandpaper, so that uniform and good nap can be formed.

The polishing cloth obtained by the present invention can provide a recording disk substrate having a highly polished surface with extremely small surface roughness and excellent precision with high productivity.

Here, the term "surface roughness index" means that the distribution of each fiber constituting the polishing cloth surface is uniformly dispersed. In order to quantify the surface roughness of this polishing cloth, a surface roughness index was defined by the following procedure.

That is, the surface roughness index is calculated by a magnification of 25.
At normal magnification, a normalized image was created from the surface image data captured from the stereomicroscope using an image processing device, and then a threshold 1
This is obtained by performing a binarization process at 00 and measuring the area of the white portion in pixel units (1 pixel = 5.6 μm).

Specifically, first, a polishing cloth sample (30
(Approximately 30 mm) is set in a stereo microscope, and the image data is taken into an image processing apparatus at a magnification of 25 times. Next, the average image data value profile f (x) in the vertical direction and the average image data value profile g in the horizontal direction of the original image are obtained.
(Y) is obtained, and an average image is created from the average value of the image data values f (xi) and g (yi) at the pixel position (xi, yi). Next, a subtraction operation is performed on the average image with the image data value of the pixel at the same position in the original image, and the data after the operation is amplified at a fixed magnification and offset is added to create a normalized image. Since the light and darkness due to the unevenness on the sheet surface in the original image is periodically distributed throughout the image, the light and darkness due to the unevenness has almost no effect on the average image data profile in the vertical and horizontal directions. Only information on unevenness is included. By subtracting the original image and the average image, the normalized image after the calculation includes only the information of the light and dark due to the unevenness of the sheet surface, that is, the density of the fluff on the polishing cloth surface.

Next, a threshold value of 100 is applied to the normalized image.
The above grayscale values are converted to white, and grayscale values less than the threshold value 100 are converted to black to create a binary image (white = 255, black = 0). Here, white indicates a portion where the fuzz density is low on the polishing cloth surface, and black indicates a portion where the fuzz density is high on the polishing cloth surface. With respect to the obtained binary image, the area of the white portion was measured in pixel units (1 pixel = □ 5.6 μm), and the measured value of the area was defined as the surface roughness index.

The surface roughness index obtained in this manner shows a smaller value when the fuzz density on the polishing cloth surface is uniform and dense, and a larger value when there are many portions where the fuzz density is uneven and rough. Is shown. Further, when the fuzz density is extremely low, the value shows an extremely small value.

The polishing cloth of the present invention comprises, for example, spinning a composite fiber capable of forming ultrafine fibers to 0.001 to 0.1 dtex using a sea-island type die having 50 to 500 islands using polyamide as an island component. After drawing, crimping, and cutting, the short fibers are formed into short fibers. The short fibers are formed into a web sheet using a carding machine, a cross wrapper, and then subjected to a fiber entanglement process that combines needle punching. The fiber nonwoven fabric can be obtained by subjecting the fiber nonwoven fabric to an ultrafine fiber treatment, an elastic polymer imparting treatment, a slicing and a buffing treatment, and setting the number of ultrafine short fibers to 2 × 10 ⁶ / cm ³ or more.

In particular, after the normalized image is created from the surface image data captured by the stereoscopic microscope using the image processing device at the aforementioned magnification of 25, the binarization process is performed with the threshold value 100, and the white portion is processed. Area is pixel unit (1 pixel = □ 5.6
μm) and a surface roughness index of 1000 to
As described above, the number of the ultrafine short fibers constituting the polishing pad is set to 2 × 10 ⁶ fibers / cm ^{3 in} order to make it 10,000.
Processing to satisfy the conditions described above,
In order to increase the compactness of the polyamide ultra-short fibers, the non-woven fabric sheet is subjected to hot water shrinkage treatment before the ultra-fine fiberization treatment, and even in this case, specifically, in order to obtain uniform and high shrinkage, It is important to use polystyrene or copolymer polystyrene as a component, or to use a composite fiber having a weight ratio of preferably 40 to 80%, more preferably 50 to 70% with respect to the total weight in order to increase the density. It is. Furthermore, it is also important to use an average fineness of the ultra-fine short fibers after dissolving or removing the conjugate fibers or by physical or chemical action, and after splitting, in the range of 0.001 to 0.1 dtex. . When it is too fine, that is, when a mixed spinning of a chip blend, a polymer blend, or the like is used, a very thin ultrafine short fiber of less than 0.001 dtex can be easily obtained. , Compared to the ultra-fine short fibers obtained by composite spinning using a sea-island type die, it is easy to be in a bundle shape where the ultra-fine short fibers are bonded together, and the uniform dispersion of the fibers is inferior. Since the roughness increases and the unevenness of the fluff density increases, it can be said that the method is not suitable as a method for manufacturing the polishing cloth of the present invention.
In the composite spinning using the sea-island type spinneret, the dispersion of the surface fibers when forming the ultrafine short fiber non-woven fabric is small because the dispersion of the ultrafine short fibers in the fiber diameter and the dispersion between the fibers in the ultrafine short fiber bundle are small. The surface roughness index of the polishing cloth can be kept small, the surface roughness of the object to be polished can be reduced, and the scratch can be suppressed. Is preferably from 50 to 500, and more preferably from 70 to 500. When the number of islands is less than 50, the inter-fiber distance in the ultra-short fiber bundle becomes large, the fineness of the surface fibers when forming the ultra-short fiber nonwoven fabric is inferior, and the surface roughness of the object to be polished is suppressed to a small value. It is difficult and undesirable.

Thus, it is possible to provide a recording disk substrate having a textured surface with extremely small surface roughness and excellent precision with high productivity.

[0037]

Next, the present invention will be described in more detail by way of examples. <Texture processing test> The polishing cloth was mounted on a texture processing machine, and 3.5 inches using a slurry (0.20% by weight of a diamond crystal having an average particle diameter of 0.2 µm and an aqueous dispersion medium) was used. The Al substrate is polished for 30 seconds. The polishing conditions are as follows. Disk rotation speed 500 rpm Slurry supply amount 10 ml / min Processing pressure 1.2 kg / cm ² <Evaluation of surface roughness of polished object> The surface roughness of a 3.5-inch Al substrate as a polished object was measured using a surface roughness measuring instrument TMS2000.
The substrate surface roughness Ra (angstrom) is measured using a gygo (manufactured by Zygo), and evaluated according to the following criteria.

○: Less than 4 Å, good.

×: 4 Å or more, defective. <Surface Roughness Index> The surface roughness index was calculated at a magnification of 25 by creating a normalized image from surface image data captured by a stereoscopic microscope using an image processing apparatus,
After performing the binarization process, the area of the white portion is determined in pixel units (1 pixel = □
(5.6 μm). Example 1 Composite spinning was performed using nylon 6 as an island component and copolymerized polystyrene as a sea component using a sea-island type die at a component ratio of 30/70, with 70 islands, a composite fineness of 4.4 dtex, and an island component fineness of 0. A raw cotton of sea-island composite fiber having a length of .02 dtex and a fiber length of 51 mm is formed.

Using the raw cotton of the sea-island type conjugate fiber, a laminated web was formed through a card and cross-wrapper process, and then a needle punch of 100 / cm ² was performed with a pre-punch to form a nonwoven fabric.

Next, from the top and bottom of this nonwoven fabric sheet, 30
Needle punching with the number of needles of 00 needles / cm ²
A nonwoven fabric having a fiber density of ² g / m ² and a fiber density of 0.230 g / cm ³ was formed. The nonwoven fabric sheet is made into an ultrafine fiber, and then impregnated with polyurethane. After solidifying the polyurethane in water, the sheet is buffed to form naps, and the present invention has a thickness of 0.6 mm and a basis weight of 204 g / m ² . Was obtained. The number of ultrafine short fibers in the polishing cloth was 1 × 10
^{There were 7} lines / cm ³ .

The obtained polishing pad had dense and uniform fluff on the surface, and had a surface roughness index of 3668 (pixels).

Using this polishing cloth, the object to be polished, Al
When the substrate was textured, no scratch (scratch) was generated on the substrate surface, and the substrate surface roughness Ra was evaluated as 3 Å and ○. Comparative Example 1 Polyamide was used as an island component and copolymer polystyrene was used as a sea component, and chips were mixed at a component ratio of 32/68. The resulting mixture was melt-spun, and the number of islands was 1,800, the composite fineness was 5.0 dtex, the island component fineness was 0.0009 dtex, and the fiber was A 51 mm long composite fiber raw cotton is formed. Using raw cotton of the composite fiber, a card, a laminated web is formed through a cross wrapper process,
Next, needle punching of 100 needles / cm ² was performed with a pre-punch to form a nonwoven fabric.

Next, from the top and bottom of the nonwoven fabric sheet, 3000 pieces /
Needle punch with the number of needles of cm ^2
Two nonwoven fabrics were formed. The sheet was converted to ultrafine fibers and coagulated with polyurethane in water. Then, the sheet was buffed to form nap, and had a thickness of 0.6 mm and a basis weight of 198 g /
An abrasive cloth of m ² was obtained. The number of ultrafine short fibers in the polishing cloth was 1 × 10 ⁸ fibers / cm ³ .

The obtained polishing pad had a non-uniform fuzz on the surface, and had a surface roughness index of 21,000 (pixels). When texture processing was performed on the Al substrate as the object to be polished using the polishing cloth, a scratch (scratch) was generated on the substrate surface, and the substrate surface roughness Ra was evaluated as 7 Å, which was evaluated as x. Comparative Example 2 Nylon 6 was used as an island component and copolymerized polystyrene was used as a sea component, and composite spinning was performed using a sea-island type die at a component ratio of 30/70. The number of islands was 70, the composite fineness was 4.4 dtex, and the island component fineness was 0. A raw cotton of sea-island composite fiber having a length of .02 dtex and a fiber length of 51 mm is formed. Using the raw cotton of the sea-island type composite fiber, a laminated web was formed through a card and a cross wrapper process, and then a needle punch of 100 / cm ² was performed with a prepunch to form a nonwoven fabric.

Next, from the top and bottom of the nonwoven fabric sheet, 3000 pieces /
Needle punch with the number of needles of cm ^2
Two nonwoven fabrics were formed. This sheet was converted into ultrafine fibers and coagulated with polyurethane in water. The sheet was not subjected to buffing and was not in a raised state, to obtain a polishing cloth having a thickness of 0.7 mm and a basis weight of 240 g / m ² . The number of ultrafine short fibers in the polishing cloth was 1 × 10 ⁷ / cm ³ .

The obtained polishing cloth has no fluff on the surface,
The surface roughness index was 900 (pixels). When texture processing is performed on an Al substrate, which is an object to be polished, using the polishing cloth, a scratch (scratch) on the substrate surface occurs, and the polishing cannot be performed, and the substrate surface roughness Ra cannot be evaluated. Met. Comparative Example 3 Using polyester as an island component, polystyrene as a sea component, and compound spinning using a sea-island type die at a component ratio of 55/45, 36 islands, a composite fineness of 2.8 dtex, an island component fineness of 0.04 dtex, The raw cotton of the sea-island composite fiber having a fiber length of 51 mm is formed.

Using the raw cotton of the sea-island type conjugate fiber, a laminated web was formed through a card and a cross wrapper process, and then a needle punch of 100 / cm ² was performed with a prepunch to form a nonwoven fabric.

Next, from the top and bottom of this nonwoven fabric sheet, 30
Needle punching with the number of needles of 00 needles / cm ²
A nonwoven fabric having 0 g / m ² and a fiber density of 0.230 g / cm ³ was formed. This non-woven fabric sheet is made into ultrafine fibers, and then impregnated with polyurethane. After solidifying the polyurethane in water, the sheet is buffed to form nap, and the present invention has a thickness of 0.6 mm and a basis weight of 170 g / m ² . Was obtained. The density of the ultrafine short fibers in the polishing cloth was 0.23.
g / cm ³ , and the number of ultrafine short fibers was 5 × 10 ⁶ fibers / cm ³ .

The obtained polishing pad had dense and uniform fluff on the surface, and had a surface roughness index of 5000 (pixels).

Using this polishing cloth, the object to be polished, Al
When the substrate was textured, no scratch (scratch) was generated on the substrate surface, and the substrate surface roughness Ra was evaluated as 8 Å and x. Comparative Example 4 Composite spinning was performed using a sea-island type die at a component ratio of 45/55 using polyamide as the island component and copolymerized polystyrene as the sea component, resulting in 16 islands, a composite fineness of 4.4 dtex, and an island component fineness of 0.12 dtex. To form raw cotton of sea-island composite fibers having a fiber length of 51 mm.

Using the raw cotton of this sea-island type composite fiber, a laminated web was formed through a card and cross-wrapper process, and then a needle punch of 100 pieces / cm ² was performed with a pre-punch to form a nonwoven fabric.

Next, from the top and bottom of this nonwoven fabric sheet, 35
Needle punching with the number of needles of 00 needles / cm ²
A nonwoven fabric having 0 g / m ² and a fiber density of 0.250 g / cm ³ was formed. The nonwoven sheet was microfine fiber formation, followed after impregnation with polyurethane, after coagulating the polyurethane in water, the sheet to form a napped subjected buffing machine, thickness 0.6 mm, the present invention having a basis weight of 200 g / m ² Was obtained. The number of ultrafine short fibers in the polishing cloth was 2 × 1
0 was ^six / cm ^3.

The surface roughness index of the obtained polishing pad was 7,000.
(Pixel).

Using this polishing cloth, the object to be polished, Al
When the substrate was textured, no scratch was generated on the substrate surface, and the substrate surface roughness Ra was evaluated as 6 Å and x. Comparative Example 5 Composite spinning was performed using a sea-island type die at a component ratio of 40/60 using polyamide as the island component and copolymerized polystyrene as the sea component, 16 islands, a composite fineness of 3.8 dtex, and an island fineness of 0.09 dtex. To form raw cotton of sea-island composite fibers having a fiber length of 51 mm.

Using the raw cotton of the sea-island type conjugate fiber, a laminated web was formed through a card and a cross wrapper process, and then a needle punch of 100 / cm ² was performed with a prepunch to form a nonwoven fabric.

Next, from the top and bottom of this nonwoven fabric sheet, 50
Needle punch with 0 needles / cm ²
g / m ² and a nonwoven fabric having a fiber density of 0.140 g / cm ² . This non-woven fabric sheet is made into an ultrafine fiber, and then impregnated with polyurethane.After solidifying the polyurethane in water, the sheet is buffed to form naps,
A polishing cloth of the present invention having a thickness of 0.6 mm and a basis weight of 130 g / m ² was obtained. The number of ultrafine short fibers in the polishing cloth was 1 × 10 ⁶ fibers / cm ³ .

The surface roughness index of the obtained polishing pad was 8,000.
(Pixel).

Using this polishing cloth, the object to be polished, Al
When the substrate was textured, no scratch (scratch) was generated on the substrate surface, and the substrate surface roughness Ra was evaluated as 8 Å and x.

[0060]

According to the present invention, since the surface is excellent in smoothness and smoothness, when texture processing is performed on an Al substrate or the like, the surface of the object to be polished has low undulation and the substrate surface roughness is extremely small. In addition to a good polishing state, scratches on the substrate surface are not generated, productivity is remarkably improved, and it is possible to cope with a high recording density for rapidly increasing the recording capacity of a recording disk. Texture processing can be finished as a processed surface with extremely small surface roughness and excellent precision.

Claims (6)

[Claims] 1. A nonwoven fabric of polyamide ultrafine short fibers having an average fineness of 0.001 to 0.1 dtex, wherein the number of ultrafine short fibers is 2 × 10 ⁶ fibers / cm ³ or more.
After creating a normalized image from the surface image data captured from the stereoscopic microscope using an image processing device, a binarization process is performed using a threshold value of 100, and the area of the white portion is determined in pixel units (1 pixel =
□ 5.6 μm) and the surface roughness index obtained by measurement is 1
A polishing cloth characterized by being 000 to 10,000. 2. The polishing cloth according to claim 1, wherein said surface roughness index is from 1,000 to 5,000. 3. The ultrafine short polyamide fiber has an average fineness of 0.1.
2. The polishing cloth according to claim 1, wherein the polishing cloth has a density of from 0.01 to 0.1 dtex. 4. The polyamide ultrafine short fiber is composite-spun using a sea-island type die with polyamide as an island component, and
Claims 1 to 1 are configured by desealing or splitting.
3. The polishing cloth according to any one of 3. 5. The polishing cloth according to claim 1, wherein said polishing cloth contains an elastic polymer. 6. The polishing cloth according to claim 5, wherein said elastic polymer is a polyurethane elastomer.