JP5341447B2 - Textured polishing cloth - Google Patents

Description

  The present invention relates to an abrasive cloth used in a texture process of a hard disk manufacturing process.

  2. Description of the Related Art In recent years, magnetic recording media such as magnetic disks have a tendency that the flying height of a magnetic head is remarkably lowered with an increase in capacity and recording density. For this reason, if protrusions are present on the surface of the magnetic disk (if the surface roughness is not sufficiently small), the magnetic head and the protrusions come into contact with each other, causing a head crash and scratching on the disk surface. Further, even a minute protrusion that does not cause a head crash leads to an error that occurs when reading and writing information due to contact with the magnetic head.

  The smoothing of a normal magnetic disk substrate is performed by polishing with hard and soft polyurethane pads and texture with ultrafine fiber nonwoven fabric. Texture processing is an important process that removes protrusions that cannot be removed only by polishing and improves the smoothness of the substrate. Therefore, the polishing cloth for texturing needs to have a grindability that can remove the fine protrusions.

However, if the grinding force of the textured polishing cloth is too large, scratches (scratches) may be formed on the disk surface. This scratch may also cause an error in reading and writing information, and becomes a major defect particularly in a perpendicular magnetic recording type hard disk that has become mainstream in recent years.
In an accelerated development of hard disks, in order to improve information recording density, it is possible to remove protrusions that cause errors without forming scratches, smooth the substrate surface, and reduce surface roughness. Such improvement in polishing accuracy is extremely important.

For this reason, conventionally, as a polishing cloth for texturing, a polishing cloth composed of a superfine fiber entangled nonwoven fabric made of polyester or polyamide having an average fineness of 0.03 dtex or less and a napped artificial leather-like material made of a polymer elastic body has been proposed. Therefore, high-precision finishing and stable texture processing are performed (for example, see Patent Document 1).
However, when polyester or polyamide is used as the material of the ultrafine fiber, even when trying to suppress the scratch by making the fiber ultrafine, the hardness (softness) of the polishing cloth when wet and the modulus when wet of the fiber are large, There was a limit to the suppression of scratches.

On the other hand, there has been proposed a polishing pad that improves the retention of the polishing slurry and improves the polishing accuracy by supporting 20 to 90 wt% of the hydrophilic polymer on the sheet composed of hydrophilic fibers ( For example, see Patent Document 2).
However, Patent Document 2 does not mention the relationship between the fiber diameter of the hydrophilic fiber used for the polishing pad, the hardness of the polishing pad when wet, and the polishing characteristics. The main application of the polishing pad described in Patent Document 2 is CMP polishing, which differs from the polishing in the texture process not only in the field of application but also in the polishing mechanism.

JP 2002-79472 A Japanese Patent Laid-Open No. 2002-11552

  An object of the present invention is to provide a polishing cloth for high-precision processing of a magnetic disk, and in particular, has a grinding performance capable of sufficiently reducing surface roughness in a texture process of a hard disk manufacturing process. An object of the present invention is to provide a textured polishing cloth with excellent polishing accuracy that does not generate scratches.

  As a result of intensive studies on the polishing cloth used for texturing in the hard disk manufacturing process, the present inventors have obtained the following findings (i) to (iv).

(I) An excessive contact pressure, which is one of the main causes of scratches, is suppressed by arranging cellulose fibers having excellent wet flexibility on the polishing surface and reducing the hardness of the polishing cloth when wet. Since the non-woven fabric is soft and has no stiffness, it is excellent in fit to small irregularities and phase follow-up, and it is possible to suppress the occurrence of scratches.
(Ii) Cellulose fibers with excellent water retention are arranged on the polishing surface, and the abrasive slurry absorption is increased to increase the amount of abrasive grains present in the polishing layer. A sufficient amount of grinding can be obtained even if is small.

(Iii) Dispersion of cellulose fibers excellent in slurry diffusibility on the polished surface, and slurry containing dripped abrasive grains uniformly diffuses in the in-plane direction, preventing agglomeration of abrasive grains and suppressing scratches. Is possible.
(Iv) Since the cellulose fiber on the polished surface is hydroentangled and bonded and integrated as a nonwoven fabric, it has excellent surface wear resistance and excellent polishing durability.

Furthermore, it has been found that the polishing cloth produced based on these findings has a sufficient amount of grinding and less scratches than the conventional polishing cloth, and has completed the present invention.
That is, the present invention is as follows.

1. A polishing cloth comprising a nonwoven fabric containing cellulose fibers as a constituent element, cellulose fibers having an average fiber diameter of 20 μm or less are present on one surface of the polishing cloth, the water retention of the nonwoven fabric is 400% or more, and the water absorption rate A textured polishing cloth characterized by having a hardness of 160 mm / 10 min or more and a C hardness when the polishing cloth is wet of 40 degrees or less.
2. 2. The textured polishing cloth according to the item 1, wherein the nonwoven fabric has a cellulose fiber content of 50 wt% or more and is hydroentangled.

3. 3. The textured polishing cloth according to 1 or 2 above, wherein the cellulose fiber is a regenerated cellulose fiber.
4). 4. The nonwoven fabric according to any one of the above items 1 to 3, wherein the nonwoven fabric is composed of at least two or more laminated nonwoven fabrics, and the nonwoven fabric layer having the smallest average fiber diameter is in the first layer on the polishing side surface. Textured polishing cloth.

5. The textured polishing cloth according to any one of the above items 1 to 4, wherein the nonwoven fabric has a basis weight of 70 to 300 g / m ² and a bulk density of 0.15 to 0.30 g / cm ³ .
6). The textured polishing cloth according to any one of 1 to 5 above, wherein the nonwoven fabric has a porosity of 75 to 90%.

7). 7. The textured polishing cloth according to any one of 1 to 6 above, wherein the breaking strength in the longitudinal direction is 3.0 kgf / cm or more and the breaking elongation is 35% or less.
8). The textured polishing cloth according to any one of the above 1 to 7, wherein a base material in which the abrasive slurry is impermeable is bonded to the nonwoven fabric.

Hereinafter, the present invention will be described in detail.
The greatest feature of the polishing cloth of the present invention is that the surface polishing layer is composed of a nonwoven fabric containing cellulose fibers.

  Compared to polyester fibers and polyamide fibers that are mainly used in conventional abrasive cloths, cellulose fibers are superior in liquid absorbency and water absorption, and have a characteristic of low modulus when wet. It is suitable as a material for the polishing layer due to the mechanism of the polishing. Further, unlike polyester fibers and polyamide fibers, cellulose fibers have a feature of having minute irregularities on the surface. This minute unevenness becomes an adsorption seat for abrasive grains, and it becomes possible to grip many abrasive grains. For these reasons, it is preferable to use a nonwoven fabric containing cellulose fibers for the surface polishing layer.

  In the present invention, the cellulose fiber may be either a short fiber or a long fiber of cellulose. In addition, regenerated cellulose fibers are preferable from the viewpoint of being thin and uniform and from the viewpoint that a large amount of moisture can be contained in the amorphous region because of low crystallinity. Furthermore, regenerated cellulose continuous long fibers are most preferable from the viewpoint that the possibility of fiber dropping during polishing that may cause scratches is small.

  The abrasive cloth of the present invention comprises a nonwoven fabric containing cellulose fibers as a constituent element, and cellulose fibers having an average fiber diameter of 20 μm or less are present on one surface of the abrasive cloth. The average fiber diameter of the cellulose fibers is preferably 12 μm or less, more preferably 5 μm or less. As the average fiber diameter is smaller, the gap between the cellulose fibers present on the surface of the polishing cloth is reduced, and it becomes possible to prevent agglomeration of abrasive grains and to suppress scratches. When the average fiber diameter exceeds 20 μm, the fiber gap becomes large, and as a result, it becomes difficult to suppress scratches.

Further, the production of a nonwoven fabric containing large-diameter cellulose fibers is superior in productivity to the production of a nonwoven fabric containing small-diameter cellulose fibers. Therefore, a non-woven fabric having a structure of two or more layers obtained by laminating a non-woven fabric containing cellulose fibers having a small diameter (for example, 5 μm or less) and cellulose fibers having a large diameter (for example, 10 μm or more) by hydroentanglement is used. Thus, it is possible to reduce scratches while having high productivity.
Thus, when the nonwoven fabric containing a cellulose fiber consists of a laminated nonwoven fabric of at least 2 layers, it is preferable that the nonwoven fabric layer with the smallest average fiber diameter exists in the 1st layer of the surface by the side of grinding | polishing.

  Examples of the method for producing a nonwoven fabric containing cellulose fibers used in the present invention include a spunlace method and a wet spunbond method. Taking the spunlace method as an example, short fibers of cellulose short fibers and other components (for example, PET, Nylon 6) are mixed in a papermaking slurry at an arbitrary ratio, and the nonwoven fabric containing cellulose fibers is made by papermaking and hydroentanglement. Can be produced. By hydroentangling, the fibers are entangled three-dimensionally and entangled and integrated as a nonwoven fabric, so that the nonwoven fabric has excellent surface wear resistance and excellent polishing durability.

  The cellulose fiber content can be arbitrarily set at the time of making the papermaking slurry. In order to utilize the characteristics of the cellulose fiber in the polishing cloth, the cellulose fiber content is preferably 50 wt% or more, more Preferably it is 80 wt% or more, and 100 wt% is particularly preferable.

Moreover, since the regenerated cellulose fiber nonwoven fabric can be integrated by hydroentangling using a wet spunbond method, the fibers constituting the nonwoven fabric can be integrated by self-adhesion of the fiber itself.
The regenerated cellulose fiber nonwoven fabric obtained by hydroentanglement using the wet spunbond method is excellent in abrasion resistance, so that there is little possibility of fiber dropping during polishing, which can cause scratches, and a binder. Therefore, there is an advantage that the possibility that foreign matters are generated from the polishing cloth during polishing is small.

In the present invention, the nonwoven fabric containing cellulose fibers has a water retention rate of 400% or more, preferably 450% or more, and particularly preferably 500% or more. The higher the water retention rate, the better.
A conventional polishing cloth made of polyester fiber or polyamide fiber has a water retention rate of 200 to 250% at most even when it is made hydrophilic by the addition of a surfactant, etc., but is made of a nonwoven fabric containing the cellulose fiber of the present invention. Since the polishing cloth can retain water at least 4 to 5 times its own weight, it can contain a large amount of abrasive slurry.

  Moreover, in the polishing cloth comprised from the conventional polyester fiber and polyamide fiber, when the supply amount of abrasive slurry is large, the abrasive slurry falls from both ends of the polishing cloth, but the polishing cloth of the present invention has a high water retention rate. Therefore, it is difficult for the abrasive slurry to sag. Therefore, compared with the conventional polishing cloth, the abrasive grains can be effectively applied to the polishing process.

  In the present invention, the nonwoven fabric containing cellulose fibers has a water absorption rate of 160 mm / 10 min or more, preferably 180 mm / 10 min or more. The higher the water absorption rate, the better. The water absorption rate is an index indicating the diffusibility of the dripping slurry. If the water absorption rate is 160 mm / 10 min or more, the slurry liquid containing abrasive grains dropped on the polishing cloth immediately before contacting the substrate is It becomes easy to quickly and uniformly diffuse in the in-plane direction, and agglomeration of abrasive grains can be prevented. As a result, it is possible to suppress the occurrence of scratches, and at the same time improve the polishing accuracy.

In the present invention, a nonwoven fabric containing cellulose fibers is preferably basis weight is 70~300g / ^{m 2,} more preferably from 80~250g / ^{m 2.} Further, the bulk density is preferably 0.15 to 0.30 g / cm ³ , more preferably 0.18 to 0.30 g / cm ³ , and particularly preferably 0.20 to 0.28 g / cm ^3. It is. When the basis weight and the bulk density are in the above ranges, the strength, dimensional stability, and water retention rate as a nonwoven fabric constituting the polishing cloth can be sufficiently obtained.

  In the present invention, the nonwoven fabric containing cellulose fibers preferably has a porosity of 70 to 90%, more preferably 75 to 90%, and particularly preferably 80 to 90%. When the porosity is in the above range, the liquid retention of the slurry is increased, and coupled with the high water absorption of the cellulose fiber itself, it is possible to hold a large amount of abrasive grains in the polishing layer, resulting in a sufficient amount of grinding. Can have.

  The abrasive cloth of the present invention has a C hardness when wet of 40 degrees or less, preferably 35 degrees or less. If the C hardness when wet is 40 degrees or less, the cushioning property is large, so it is possible to suppress excessive contact pressure, which is one of the main causes of scratches, and to reduce the occurrence of scratches, Since contact pressure can be dispersed, unevenness in contact pressure can be reduced and polishing accuracy can be improved.

  Although the contact pressure can be adjusted depending on the polishing process conditions, a certain level of contact pressure is necessary to stably perform the polishing process. Therefore, since there is a limit in suppressing the generation of scratches only by adjusting the load when pressing the polishing cloth against the substrate, the hardness of the polishing cloth when wet is important. By using a polishing cloth having a C hardness of 40 degrees or less when wet, it is difficult for scratches to occur even when the load is increased, and the processing accuracy can be increased.

  The abrasive cloth of the present invention preferably has a breaking strength in the longitudinal direction of the abrasive cloth of 3.0 kgf / cm or more, more preferably 4.5 kgf / cm or more. Further, the breaking elongation is preferably 35% or less. When the breaking strength and breaking elongation are in the above ranges, the polishing cloth can be pressed uniformly and stably on the surface of the disk substrate, and as a result, the occurrence of scratches can be suppressed. . Then, as a method for bringing the breaking strength and breaking elongation to the above ranges, a method of bonding an SMS (spunbond / meltblown / spunbond laminate) nonwoven fabric or film having excellent dimensional stability to a nonwoven fabric containing cellulose fibers. Is mentioned.

  In the present invention, as a preferred embodiment for increasing the amount of grinding, an abrasive cloth in which a base material in which the abrasive slurry is impermeable is bonded to a nonwoven fabric containing cellulose fibers can be mentioned. By suppressing the permeation of the abrasive slurry, it becomes possible to hold more abrasive grains in the polishing layer, and the number of abrasive grains that come into contact with the substrate during polishing increases, resulting in an increase in the amount of grinding. . In addition, by suppressing the permeation of the abrasive slurry, the same amount of grinding can be obtained even with a small amount of the abrasive slurry. Therefore, when an expensive diamond slurry is used, the amount used is reduced and the cost is reduced. It becomes possible.

Examples of the base material in which the abrasive slurry is impermeable include a film having no hydrophilicity and a foamed sheet composed of independent holes. As a specific example of a preferable substrate, the foamed sheet preferably has a thickness of 0.2 to 1.5 mm, more preferably 0.8 mm, from the viewpoint of easily adjusting the C hardness when wet to the above range. It is preferably ⁴ to 1.2 mm, and the bulk density is preferably 50 to 200 kg / m ³ , more preferably 60 to 120 kg / m ³ .

  The polishing cloth of the present invention can be patterned on the surface of the polishing cloth according to the purpose. For example, when it is desired to increase the grinding amount, a recess for gripping the slurry is formed on the surface, or in order to further suppress scratching, a groove for discharging scraps and excess abrasive grains is formed. It may be formed on the surface.

  As a patterning method, a method using a high-pressure water stream is preferable because it can be carried out simultaneously with the entanglement of the nonwoven fabric. When buffing for the purpose of smoothing the polishing surface, which is generally performed, there is a possibility that not only a small amount of fiber waste will be generated, or because the fibers are oriented in the longitudinal direction, Sufficient care is required because there is a risk of polishing streaks in the circumferential direction.

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

(1) Average fiber diameter (μm)
The surface of the polishing cloth sample was observed with a scanning electron microscope (JSM-5610: manufactured by JEOL Ltd.), an image with an acceleration voltage of 10 kV and a magnification of 1000 times was taken, and the diameters of 50 arbitrary fibers were measured. Was the average fiber diameter of the cellulose fibers.

(2) Water retention rate (%)
Three test pieces having a length of 100 mm and a width of 20 mm were taken with the longitudinal direction of the polishing cloth as the vertical direction, and the mass (W1) of the test piece was measured.
The test piece is immersed in water (distilled water (manufactured by Wako Pure Chemical Industries, Ltd.)) for 20 minutes, then taken out and suspended to remove water drops sufficiently (for 10 minutes at room temperature), and immediately the mass of the test piece (W2 ) Was measured, and the water retention rate was calculated by the following equation.

(3) C hardness (degree) when wet
After dipping in water, three polishing cloth samples left at room temperature for 1 minute are stacked and placed on a flat surface having a surface hardness of 95 degrees C or more, and in accordance with JIS standard (hardness test) K6253, durometer -Using type C (actually, Asker C hardness meter manufactured by Kobunshi Keiki Co., Ltd.), 5 points were measured at room temperature, and the arithmetic average value was defined as C hardness when wet.

(4) Water absorption rate (mm / 10 min)
The bottom end of the vertically suspended test piece was immersed in water and allowed to stand at room temperature for a certain time (10 minutes), and then the height of the raised water was measured (JIS L 1907-2003: Bayrec method).

(5) Weight per unit area (g / m ² )
Taking the longitudinal direction of the polishing cloth as the vertical direction, five test pieces each having a length of 250 mm and a width of 20 mm are collected, and the mass of the nonwoven fabric is measured with a precision balance capable of weighing up to 1 mg. The measured value obtained was arithmetically averaged and divided by the area of the test piece to calculate the basis weight, which is the mass per 1 m ² .

(6) Bulk density (g / cm ³ )
Using a dial thickness gauge (Peacock H type, manufactured by Ozaki Seisakusho Co., Ltd.), the thickness of the nonwoven fabric was measured at five points in the longitudinal direction of the polishing cloth, and the obtained measurement was arithmetically averaged to obtain the thickness of the nonwoven fabric. It was. The bulk density was calculated by dividing the basis weight obtained above by the thickness.

(7) Porosity (%)
The porosity of the nonwoven fabric was determined by the following formula. The density of the cellulose fiber was 1.50 g / cm ³ .

(8) Breaking strength (kgf / cm) and breaking elongation (%)
The measurement was performed using a constant speed extension type tensile tester (Tensilon RTC-1210A, manufactured by Orientec Co., Ltd.). The test conditions are as follows (JIS L 1096-2003).
・ Dimensions of test piece: (width) 2.5 cm, (length) 20 cm
・ Grip interval: 10cm
・ Tensile speed: 10 cm / min

(9) Polishing conditions ・ Abrasive grains: Diamond free abrasive grains (average particle diameter: 0.1 μm)
・ Slurry supply amount: 20 cc / min ・ Slurry concentration: 10 cc / 5 liters ・ Substrate rotation speed: 150 rpm
Polishing cloth supply speed: 3 cm / min Polishing time: 30 seconds / sheet Traverse conditions: amplitude 1 mm, 83 times / min Contact pressure: 0.5 kgf

(10) Surface roughness (Å)
In accordance with JIS B 0601-1994, the roughness of an arbitrary linear surface of a disk substrate sample was measured using an atomic force microscope (Nano Scope IV D3100: manufactured by Digital Instruments). The surface average roughness was determined by arithmetically averaging the measured values at 10 locations.

(11) Scratches (pieces / piece)
The number of scratches of 10 substrates was measured using Micro-MAX VMX-4100Napier (manufactured by Vision Cytec Co., Ltd.), and the arithmetic average value thereof was determined.

[Example 1]
Cotton linter was dissolved with a copper ammonia solution to prepare a spinning dope having a cellulose concentration of 10 wt%. The stock solution was extruded at a rate of 8.1 cc / cm ² · min per unit area of the spinneret from a rectangular spinneret having a stock solution discharge hole diameter of 0.6 mm and 110 pieces / cm ² . The extruded stock solution was introduced into a rectangular single-stage funnel together with spinning water and stretched simultaneously with coagulation by deammonium.

The spinning water temperature at this time was 45 ° C., the spinning water flow rate per unit area of the spinneret was 400 cc / cm ² · min, and the speed of the coagulated yarn was 80 m / min. The net was vibrated in a direction perpendicular to the net traveling direction while being shaken off onto a net having a mesh structure through which the solidified fibers could pass. The net speed at this time was 44 m / min, the vibration width was 4% with respect to the spinneret width, and the number of vibrations was 98 times / min.

  Four layers of webs spun under the same conditions were stacked on the obtained one-layer web, and finally a five-layer cellulose continuous continuous fiber web was obtained. The obtained cellulose continuous long fiber web was regenerated with dilute sulfuric acid, washed with water, and then obtained 8 sheets of the regenerated cellulose continuous long fiber web (A) were stacked. After that, cylinder drying was performed at 100 ° C. to obtain a regenerated cellulose continuous long fiber nonwoven fabric.

  The obtained nonwoven fabric was slit into a tape having a width of 38 mm, and this was used as a polishing cloth. Under the above-described polishing conditions, 10 substrates subjected to polishing processing after Ni-P plating on an aluminum plate were polished. Table 1 shows the structure, physical properties, and evaluation results of the polishing performance of the polishing cloth.

[Example 2]
Four regenerated cellulose continuous long fiber webs (A) obtained in Example 1 were entangled with a high pressure water flow of 3 MPa on a 70 mesh sheet, followed by cylinder drying at 100 ° C. to obtain a regenerated cellulose continuous length. A fiber nonwoven fabric was obtained.

The obtained regenerated cellulose continuous long-fiber non-woven fabric is made into a foam sheet (trade name “Softlon S # 1001” manufactured by Sekisui Chemical Co., Ltd., thickness 1.0 mm, bulk density 100 kg / m ³ ) as a base material, polyolefin A laminate-type polishing cloth was prepared by bonding with an adhesive (trade name “HYPAT”: manufactured by Teru Chemical Co., Ltd.).
The obtained polishing cloth was slit into a 38 mm-wide tape and polished in the same manner as in Example 1 to evaluate the polishing performance. The results are shown in Table 1.

[Example 3]
A regenerated cellulose continuous long fiber web (B) was obtained in the same manner as in Example 1 except that the diameter of the stock solution discharge hole was changed to 0.3 mm.
The obtained regenerated cellulose continuous long fiber web (B) and the regenerated cellulose continuous long fiber web (A) obtained in Example 1 were each overlapped in a total of 4 sheets and entangled in the same manner as in Example 1. A regenerated cellulose continuous long fiber nonwoven fabric was produced.

  The foamed sheet used in Example 2 was adhered so that the thin web (B) was the first layer on the surface on the polishing side to produce a laminated type polishing cloth. Using this polishing cloth, polishing was performed in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1.

[Comparative Example 1]
A regenerated cellulose continuous long-fiber nonwoven fabric was prepared in the same manner as in Example 1 except that the diameter of the stock solution discharge hole was changed to 1.0 mm, and polishing processing and polishing performance evaluation were performed. The results are shown in Table 1.

[Comparative Example 2]
A regenerated cellulose continuous long fiber nonwoven fabric was produced in the same manner as in Example 1 except that the regenerated cellulose continuous long fiber web (A) obtained in Example 1 was used and the number of laminated layers of the web (A) was changed to 2. did. When this nonwoven fabric was used as a polishing cloth and polishing was performed, the polishing performance was not able to be evaluated because the polishing cloth was stretched and filled during processing.

[Comparative Example 3]
The regenerated cellulose continuous long-fiber nonwoven fabric obtained in Comparative Example 2 was adhered to a PET film (thickness 0.2 mm) as a base material using an adhesive for polyester to produce a laminate-type polishing cloth. Using this polishing cloth, polishing was performed in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1.

[Comparative Example 4]
Polyester copolymer polymer (PET copolymerized with 10% polyethylene glycol with a molecular weight of 4000) is easily used for sea component, and polyamide (6 nylon) resin is used for island component, and these two polymers are measured with gear pumps. Then, an undrawn yarn was obtained by melt spinning at 290 ° C. using a spout with a sea component of 35 wt% and an island component of 65 wt% using 100 islands / hole.

  The obtained undrawn yarn was heat drawn at a temperature of 75 ° C. and a draw ratio of 2.8 times, and heat-set at 130 ° C. to obtain a sea-island fiber having a composite fiber diameter of 14.8 μm and an island component fiber diameter of 1.2 μm. Obtained. The obtained sea-island fiber was stapled, and an ultrafine fiber nonwoven fabric was produced from the staple fiber by a series of steps of card, cross wrap and needle punch.

The sea component was removed from the nonwoven fabric with an aqueous alkaline solution to obtain a polyamide (6 nylon) nonwoven fabric. Next, after impregnating the obtained non-woven fabric with a dimethylformamide (DMF) solution of a polyether solvent-based polyurethane emulsion so as to be 30 wt% with respect to the weight of the non-woven fabric sheet, wet coagulation is performed, and the surface is sandpaper. By buffing, an abrasive cloth having a smooth surface was obtained.
Using this polishing cloth, polishing processing and polishing performance evaluation were carried out in the same manner as in Example 1. The results are shown in Table 1.

  As can be seen from Table 1, the polishing cloths produced in Examples 1 to 3 were able to achieve scratch suppression as well as smoothing, and were suppressed to a practical range for the use of texture processing in the hard disk manufacturing process. I understand that

Claims (6)

A polishing cloth comprising a nonwoven fabric containing cellulose fibers as a constituent element, cellulose fibers having an average fiber diameter of 20 μm or less are present on one surface of the polishing cloth, the water retention of the nonwoven fabric is 400% or more, and the water absorption rate is a but 160 mm / 10 min or more, C hardness of wet of the polishing cloth Ri der 40 degrees or less, the porosity of the nonwoven fabric is Ri 75-90% der, and breaking in the longitudinal direction of the polishing cloth A textured abrasive cloth having a strength of 3.0 kgf / cm or more and a breaking elongation of 35% or less .   The textured polishing cloth according to claim 1, wherein the content of cellulose fibers in the nonwoven fabric is 50 wt% or more and hydroentangled.   The textured polishing cloth according to claim 1 or 2, wherein the cellulose fibers are regenerated cellulose fibers.   The texture according to any one of claims 1 to 3, wherein the nonwoven fabric is made of a laminated nonwoven fabric of at least two layers, and the nonwoven fabric layer having the smallest average fiber diameter is in the first layer on the surface on the polishing side. Processing polishing cloth. The textured polishing cloth according to any one of claims 1 to 4, wherein the nonwoven fabric has a basis weight of 70 to 300 g / m ² and a bulk density of 0.15 to 0.30 g / cm ³ . The textured polishing cloth according to any one of claims 1 to 5 , wherein a base material in which the abrasive slurry is impermeable is bonded to the nonwoven fabric.