JP4880922B2 - Disc processing base fabric - Google Patents

Description

  The present invention relates to a disk processing base fabric and a method for manufacturing the same, and more particularly to a disk processing base fabric used for manufacturing a magnetic recording medium and similar materials that require high-precision finishing and a method for manufacturing the same.

  In recent years, with the development of information processing technologies such as computers, high-precision surface finishing is required for magnetic recording media and silicon wafers. For example, when manufacturing a hard disk or the like of a magnetic recording medium, a process of smoothing the surface of a base such as aluminum or glass is performed. However, there is an increasing demand for a disk processing base fabric used there. Also, as a kind of polishing method, surface processing called “texturing” using a slurry in which abrasive grains are dispersed and a polishing base fabric to form fine grooves on the disk surface is increasing. Therefore, there is a demand for a polishing base fabric for polishing that is optimal for increasing the capacity and increasing the density.

  As such a disk processing base fabric, a sheet-like material using fibers that easily hold the slurry is widely used, but when such a normal base fabric is used, the slurry used for polishing is the inside of the base fabric. There was a problem that the polishing efficiency on the surface of the base fabric was lowered due to the large amount of penetration.

Therefore, in Patent Document 1, for example, one surface has a hydrophilic layer having a thickness of 500 μm or less, the water absorption height on one side is 20 mm / hour or more, and the water absorption height on the opposite side is 5 mm / hour or less. An abrasive base fabric is proposed. At present, however, higher accuracy and higher efficiency are required. However, since this base fabric is basically water-repellent as a whole, the slurry existing on the back side cannot be fully used effectively and the processing rate is increased. There was no problem. There is also a problem that the effect is not sufficient due to the difference between the behavior of the slurry used for processing and the behavior of water.
JP 2003-170347 A

  An object of the present invention is to provide a disk processing base fabric that can obtain high accuracy and high efficiency during processing, and a method for manufacturing the same.

The disk processing base fabric of the present invention is a sheet-like material containing fibers, the processing use surface has very fine fiber napping, and the liquid absorption time of the droplet on the processing use surface is 10 to 60 seconds / 15 μl. The liquid absorption time of the droplets on the back surface, which is a non-use surface, is 0.001 to 5 seconds / 15 μl. Furthermore, the water absorption time of the droplets on the working surface is 5 times or more of the liquid absorption time on the back surface, the fibers are ultrafine fibers of 0.1 dtex or less , the sheet-like material Is preferably composed of a fiber and a polymer elastic body.

Another method for producing a disk processing base fabric according to the present invention comprises a water repellent agent on one surface of a sheet-like material that contains fibers, the processing surface has ultrafine fibers, and the entire layer is hydrophilic. A solution containing 10 to 150 g / m ^{2 is} applied .

  ADVANTAGE OF THE INVENTION According to this invention, the base fabric for disk processing from which high precision and high efficiency are obtained at the time of a process, and its manufacturing method are provided.

Hereinafter, the present invention will be described in detail.
The base fabric for disk processing of the present invention is a sheet-like material containing fibers. In order to uniformly polish at this time, it is preferable to use a synthetic fiber as the fiber, and more specific examples include polyamide fibers such as nylon 6, nylon 6, 6, nylon 12, or polyethylene terephthalate, polybutylene terephthalate, etc. A polyester fiber etc. can be mentioned. In particular, when a polyamide fiber such as nylon is used, the modulus is low and scratch scratches are less likely to occur during polishing.

  The fineness of the fiber is preferably an ultrafine fiber of 0.1 dtex or less, and more preferably 0.0001 to 0.1 dtex. When the fineness is small, the strength of the ultrafine fibers tends to decrease, and the surface strength during polishing and the strength as a fibrous base material tend to decrease. If the fineness is too large, the substrate to be polished tends to be damaged during the polishing step. Furthermore, the disk processing base fabric of the present invention preferably has napped surfaces. In particular, when the napping is made of ultrafine fibers, it is easy to control the hydrophilicity and is optimal.

  The disk processing base fabric of the present invention is composed of a so-called fibrous base material containing fibers, and the fibrous base material may be a woven or knitted fabric or a non-woven fabric made of only fibers. The material preferably contains an elastic polymer, and most preferably a fibrous base material composed of ultrafine fibers and an elastic polymer. Furthermore, it is preferable that the fibrous base material is constituted by a fiber bundle in which ultrafine fibers are converged. When the fibrous base material is composed of a fiber bundle made of such ultrafine fibers and an elastic polymer, the elastic polymer is mainly present outside the fiber bundle inside the base material. It is preferable that no elastic polymer is present inside. The base fabric for polishing tends to be flexible and the occurrence of polishing flaws tends to be suppressed.

  Examples of the elastic polymer that can be used for the fibrous base material include polyurethane resins, polyurethane / polyurea resins, polyacrylic acid resins, polystyrene / butadiene resins, and polyacrylonitrile / butadiene resins. In view of wear resistance, hydrolysis resistance, etc., polyurethane resins are preferred. In particular, when the slurry of the abrasive grains is alkaline or acidic and is accompanied by hydrolysis degradation of the polyurethane-based resin, it is preferably an ether-based or carbonate-based polyurethane. Further, it is preferable that the fibrous base material contains a high-molecular elastic polymer in the range of 5 to 95% by weight, more preferably in the range of 10 to 50%, and most preferably in the range of 20 to 40%. preferable. Furthermore, it is preferable that the elastic polymer is porous by a wet coagulation method or the like in order to hold the abrasive grains and polish without causing defects such as scratches.

Now, the disk processing base fabric of the present invention is a sheet-like material containing fibers as described above, and the liquid absorption time of the droplet on the processing and use surface is 10 to 60 seconds / 15 μl, and the non-use surface. It is essential that the liquid absorption time of a droplet on a certain back surface is 0.001 to 5 seconds / 15 μl. Furthermore, it is preferable that the liquid absorption time of the liquid droplet on the working surface is 15 to 50 seconds / 15 μl, and the liquid absorption time of the liquid droplet on the back surface is preferably 0.01 to 2 seconds / 15 μl. Moreover, it is preferable that the liquid absorption time of the droplet on the processing and use surface is 5 times or more of the liquid absorption time on the back surface. In the present invention, the droplets are preferably not a water but a 10% isopropyl alcohol aqueous solution that exhibits properties close to that of the working fluid used for processing and the droplets of the slurry, for example, surface tension. And as for the water absorption time when purified water is used instead of droplets, it is preferable that a droplet of 15 μl of purified water is not absorbed for 600 seconds or more on the processing use surface, and the water absorption time is 0.01 to 5 on the back side. Preferably it is sec / 15 μl.
Here, the liquid absorption time of the liquid droplets is measured by measuring the time taken to drop 15 μl (1 drop) of liquid droplets from a height of 2 cm above the base fabric and completing the liquid absorption on the base fabric, and the unit is seconds / 15 μl. It is represented by.

  In the disk processing base fabric of the present invention, the liquid absorption speed of the liquid droplets is different between the processing use surface and the back surface, which is a non-processing surface. The processing efficiency of the processing liquid is further improved by staying on the disk surface slightly and uniformly and applying pressure from the back of the base fabric with a back roll or the like during processing.

  The shape of the disk processing base fabric of the present invention is preferably uniform in the length direction and the width direction. The width of the base fabric for disk processing is preferably 5 to 300 mm, more preferably 7 to 200 mm, and the length direction is preferably a tape shape longer than the width direction. The thickness is preferably 0.3 to 1.2 mm. If the thickness is less than 0.3 mm, the strength tends to be insufficient. If the thickness is 1.2 mm or more, the workability tends to decrease. In order to optimize the thickness or increase the productivity, it is also a good method to once manufacture a thick base fabric and slice it to a predetermined thickness.

Such a disc processing base fabric of the present invention can be obtained by another method of manufacturing a disc processing base fabric of the present invention. That is, a manufacturing method comprises the fibers and all the layers to the solution 10 to 150 g / m ² coating containing water repellent processing use surface of the sheet-like material exhibits hydrophilicity. At this time, the water repellent is most preferably a fluorine-based water repellent.

  The sheet-like material used in the present invention is particularly preferably a fibrous base material having napped fibers made of ultrafine fibers and made of fibers and an elastic polymer. It can manufacture by the method of. That is, a non-woven fabric is first made from ultrafine fiber-forming fibers. Examples of the ultrafine fiber formable fiber include a method of extracting and removing one component after forming a fiber by a known spinning method using two or more types of fiber-forming polymers having different solvent solubility. The necessary strength can be given to the fiber by drawing. Of these, the nylon 6 / polyethylene combination is preferred because it is easy to produce industrially. The obtained fiber is processed into a nonwoven fabric by needle punching or the like. At this time, it is preferable to calender the nonwoven fabric to increase the smoothness of the nonwoven fabric surface and the nonwoven fabric internal density. Next, a fibrous base material composed of ultrafine fibers is obtained by filling the resulting nonwoven fabric with a polymer elastic polymer by a conventionally known method and then ultrafinening the ultrafine fiber-forming fibers in the base material. can get. By raising the surface of the fibrous base material with sandpaper or the like, napped fibers made of ultrafine fibers are formed.

  The sheet-like material used in the production method of the present invention has hydrophilicity in all layers. For example, this is a sheet-like material that has been previously dipped in a solution containing a hydrophilic agent and dried. Preferably there is. It is effective to use an anionic or nonionic penetrant as the hydrophilic agent used in advance. Specific examples of anionic penetrants include dioctyl sulfosuccinate / sodium salt, dodecyl diphenyl ether disulfonic acid / sodium salt, dodecyl benzene sulfonic acid / sodium salt, naphthalene sulfonic acid / sodium salt, etc. Secondary lauryl alcohol / ethoxylate, ethylene oxide adduct of dodecyl alcohol, ethylene oxide-added alkylphenyl ether, and the like. The amount of treatment varies depending on the agent used, but is in the range of 0.01 to 5% by weight with respect to the base fabric.

  In the production method of the present invention, it is essential to apply a solution containing a water repellent to one surface of the sheet-like material. Moreover, it is preferable that the coating method of the solution containing a water repellent is gravure coating. More specifically, it is preferable to form a strongly water-repellent layer thinly in the range of 5 to 300 μm only on the surface side, and the treatment method is preferably applied 1 to 4 times with a 70 to 200 mesh gravure roll. . Moreover, it is preferable to process by the compression of 50 to 90% with respect to the thickness of the base fabric to process the clearance of the gravure roll and back roll at this time. More preferably, it is 60 to 80% of range. At this time, if the processing is performed under the condition of 50% or less, the penetration of the water repellent becomes too large at the time of processing, and the water repellent does not stay on the processed surface and the surface tends to make it difficult to obtain the desired performance. On the other hand, if it is 90% or more, processing irregularities of the water repellent agent occur, and stable processing by the obtained disk processing base fabric tends to be difficult.

  The processing method using the disk processing base fabric of the present invention thus obtained is a method capable of obtaining a disk excellent in accuracy and processing speed. The processing is preferably used particularly in texture processing of the magnetic recording substrate and cleaning processing performed thereafter. For example, the texture processing when manufacturing a hard disk is performed with a slurry in which abrasive grains are dispersed using the disk processing base fabric of the present invention. The abrasive abrasive slurry used with the disk processing fabric is aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, silicon nitride, single or polycrystalline diamond, etc., each having a particle size of about 0.05 to 0.5 μm. Are preferably used. Further, in the cleaning process performed after texturing, the surface of the hard disk obtained by texturing using abrasive grains is brushed with the polishing base cloth of the present invention with water and chemicals added as necessary. As a result, the abrasive grains and various debris remaining on the hard disk surface can be effectively removed, and the production efficiency can be greatly improved.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each measuring method was based on the following method.
(1) Liquid absorption time Seven samples for measurement cut to 50 mm × 50 mm are prepared, and left in a desiccator at a temperature of 20 ° C. and a humidity of 60% for 12 hours or more to obtain a test piece. One drop (15 μl) of a droplet is dropped from a height of 2 cm on a test piece placed on a flat surface in a room maintained at a temperature of 20 ° C. and a humidity of 60% with a micropipette. The time from dripping to completion of liquid absorption on the base fabric was measured. The measurement is performed once for each measurement sample, and a total of seven measurements are performed on all seven samples. The average of 5 results excluding the shortest time and longest time of the measured values obtained was obtained as the liquid absorption speed of the droplets, and the unit was expressed in seconds / 15 ml. As droplets, an isopropyl alcohol (IPA) aqueous solution having a weight ratio of 10% and purified water were used.

[Example 1]
Manufacture of ultrafine fibers Nylon-6 and polyethylene are mixed at a weight ratio of 50:50 in the form of chips and melt-spun by an extruder, and a sea-island cross-section mixed fiber in which polyethylene is a sea component is spun, drawn, crimped, Cut to produce a short fiber having a fineness of 8 dtex and a length of 51 mm. Polyethylene, which is the sea component of the obtained fiber, was dissolved and removed to make ultrafine fibers, and the cross section of an arbitrary fiber bundle was magnified and observed 2000 times with an electron micrograph, and the fiber calculated from the average diameter of the island component The average fineness was 0.0052 dtex.

Preparation of a base fabric for disk processing The above-mentioned short fibers before being thinned are laminated using a card and a cross layer, and a non-woven fabric is formed by needle punching with a needle density of 1400 / cm ² using a 3 barb needle needle. Created. The obtained nonwoven fabric had a basis weight of 570 g / m ² and a thickness of 2.5 mm. The nonwoven fabric was heated with a dryer at 150 ° C., and cooled and niped with a metal roll at 30 ° C. to be fixed. The basis weight of the nip-treated non-woven fabric was 560 g / m ² and thickness 1.9 mm.

The nonwoven fabric after the nip treatment is impregnated with 1060 g / m ² of a DMF solution having a polyether ester polyurethane concentration of 14% and a silicone coagulation regulator added, and the nonwoven fabric surface is squeezed to 70% of the substrate thickness. Then, after removing the excess polyurethane resin, it was solidified in a water bath of 10% dimethylformamide (hereinafter referred to as DMF) aqueous solution to form a porous polymer elastic body, and dried at 140 ° C. Thereafter, dip and nip were repeated with toluene at 80 ° C. to extract polyethylene. The obtained substrate made of ultrafine fibers had a basis weight of 445 g / m ² . The DMF solution is applied to the substrate surface in two rolls with 200 mesh and gravure, dried, polished with 320 mesh sandpaper, and further polished with 400 mesh sandpaper in the reverse direction to raise the substrate surface. A napped base material whose surface was covered with many napped fibers was obtained.

Dicotyl sulfosuccinate sodium salt as a hydrophilic agent is immersed in this napped base material in a solution of 5% active ingredient so as to give a fixed amount of 3% by weight, and dried after nip to obtain a hydrophilic base material for all layers. It was. Applying 70 g / m ^{2 of} 70% gravure roll with a 10% active ingredient fluorine-based water repellent to the surface side of the base material twice, and treating the clearance with the backup roll as 80% of the base material thickness. A strong water-repellent layer was molded only on the surface side so as to be in the range of 200 μm to obtain a base fabric.

  The time required for the 15 μl of purified water droplets to be absorbed on the processed surface of the base fabric obtained here was measured, but even if it was left for 600 seconds or longer, there was no sign of infiltration. When it was actually allowed to stand overnight, it did not penetrate into the substrate until the droplets were dried. Furthermore, the liquid absorption time of a 10% IPA aqueous solution droplet on this surface was 25 seconds / 15 μl. On the other hand, the water absorption time of the purified water on the back surface side was 2 seconds / 15 μl, and the liquid absorption time of the 10% IPA aqueous solution was 0.5 seconds / 15 μl. The base fabric was slit to 3.5 cm to obtain a disk processing base fabric suitable for texture processing of an aluminum hard disk.

  Using the disk processing base fabric, texturing was carried out using a slurry containing 0.07 μm polycrystalline diamond abrasive grains in an abrasive and containing an anionic dispersant. The surface roughness of the disk after texturing is good at Ra = 2.40 mm, and texturing is performed with very few defects such as scratches, and the peak count during processing is as high as 2700, which is highly efficient. The amount of slurry used was small, and the magnetic properties of the obtained disk were very good at 18.8.

[Comparative Example 1]
A napped base material was obtained in the same manner as in Example 1.
This napped base material was dipped in a solution containing 5% of an active ingredient of a fluorine-based water repellent, nipped, and then dried, so that the weight ratio of the water repellent to the base material was 3%. A full-layer water-repellent substrate was obtained. The substrate surface is treated with 10% active ingredient dioctylsulfosuccinate / sodium salt aqueous solution twice with a 110 mesh gravure roll, and the clearance with the backup roll is set to 80% of the substrate thickness to make the substrate hydrophilic. A base fabric was obtained in which a strong layer was molded on the back side only in the range of 150 μm.

  The time required for the 15 μl of purified water droplets to be absorbed on the processed surface of the base fabric obtained here was measured, but even if it was left for 600 seconds or longer, there was no sign of infiltration. When it was actually allowed to stand overnight, it did not penetrate into the substrate until the droplets were dried. Furthermore, the liquid absorption time of the 10% IPA aqueous solution droplet on this surface was 123 sec / 15 μl. On the other hand, the water absorption time of the purified water on the back surface side was 5 seconds / 15 μl, and the liquid absorption time of the 10% IPA aqueous solution was 4 seconds / 15 μl. The base fabric was slit to 3.5 cm to obtain a processing base fabric.

  Using the base fabric, texturing was performed using a slurry containing an anionic dispersant containing 0.07 μm polycrystalline diamond abrasive grains in the abrasive. During processing, the slurry was repelled on the base fabric, and uniform processing was difficult. Although the surface average roughness Ra of the textured disk was 1.82 mm and it was good with few defects such as scratches, the peak count at the time of processing was 1800 and the efficiency was poor, and the amount of slurry used was It was consumed very much and became inefficient. Further, the magnetic characteristics of the finally obtained disk were as low as 14.5.

[Comparative Example 2]
A napped base material was obtained in the same manner as in Example 1.
In this napped base material, dioctylsulfosuccinate sodium salt as a hydrophilic agent was immersed in a solution of 5% active ingredient so as to give a fixed amount of 3% by weight as in Example 1, and dried after nip to dry all layers. A hydrophilic base material was obtained and, unlike Example 1, a base fabric was obtained without applying a water repellent.

  The time required for the 15 μl of purified water droplets to be absorbed on the processed surface of the base fabric obtained here was 47 seconds. Further, the water absorption rate of the 10% IPA aqueous solution on this surface was 5 seconds / 15 μl. On the other hand, the water absorption time of the purified water on the back surface side was 4.5 seconds / 15 μl, and the liquid absorption time of the 10% IPA aqueous solution was 3 seconds / 15 μl. The base fabric was slit to 3.5 cm to obtain a processing base fabric.

  Using the base fabric, texturing was carried out using a polishing agent containing 0.07 μm polycrystalline diamond abrasive grains and an anionic dispersant. The surface roughness Ra of the disk after texture processing was 1.77 mm, and defects such as scratches were good, but the peak count during processing was 1900 and the efficiency was poor, and the amount of slurry used was large. The magnetic characteristics of the finally obtained disk were 17.8 normal values.

[Comparative Example 3]
A napped substrate was obtained in the same manner as in Comparative Example 1 (Example 1).
This napped base material was dipped in a solution containing 5% of an active ingredient of a fluorine-based water repellent as in Comparative Example 1, nipped and dried, and the weight ratio of the water repellent to the base was 3%. An all-layer water-repellent substrate having a fixed amount was obtained and used as a base fabric without applying a hydrophilic agent unlike Comparative Example 1.

  The time required for the 15 μl of purified water droplets to be absorbed on the processed surface of the base fabric obtained here was measured, but even if it was left for 600 seconds or longer, there was no sign of infiltration. When it was actually allowed to stand overnight, it did not penetrate into the substrate until the droplets were dried. Further, the liquid absorption speed of the 10% IPA aqueous solution droplet on this surface was 150 seconds / 15 μl. On the other hand, on the back side, the time required for supplying 15 μl of purified water droplets was measured, but even if left for 600 seconds or longer, there was no sign of infiltration. When it was actually allowed to stand overnight, it did not penetrate into the substrate until the droplets were dried. Furthermore, the liquid absorption time of the 10% IPA aqueous solution droplets on this surface was 97 seconds / 15 μl. The base fabric was slit to 3.5 cm to obtain a processing base fabric.

  Texturing was carried out using the base fabric and the abrasive containing 0.07 μm polycrystalline diamond abrasive grains and containing an anionic dispersant, but the processed surface has strong water repellency. Therefore, the slurry was repelled on the surface of the base fabric and became non-uniform and could not be processed.

Claims (4)

A sheet-like material containing fibers, the processing use surface has very fine fiber napping, and the liquid absorption time (10% isopropyl alcohol aqueous solution) on the processing use surface is 10 to 60 seconds / 15 μl, A base fabric for disk processing, wherein the liquid absorption time of a droplet (10% isopropyl alcohol aqueous solution) on the back surface as a use surface is 0.001 to 5 seconds / 15 μl.   2. The disk processing base fabric according to claim 1, wherein the water absorption time of the liquid droplets on the processing use surface is at least five times the liquid droplet absorption time on the back surface.   The base fabric for disk processing according to claim 1 or 2, wherein the fibers are ultrafine fibers of 0.1 dtex or less.   The base fabric for disk processing according to any one of claims 1 to 3, wherein the sheet-like material is made of a fiber and a polymer elastic body.