JP4209275B2 - Polishing fabric and glass disk polishing method using polishing fabric - Google Patents

Description

【００４５】
【発明の効果】
本発明の艶消し剤を含まず、不純物の発生の少ない研磨用織物よりなるテクスチャーテープを使用してガラス基板を研磨テクスチャー加工すれば、ガラス基板の汚染が少なく、ガラス基板の加工量は従来通りで基板の表面粗さは均一で極めて微細であり、磁気高密度化も可能とするものである。
【図面の簡単な説明】
【図１】 代表的複合割繊糸の横断面形態を示す。
【図２】 本発明研磨布よりなるテクスチャーテープの使用状況を示す。
【符号の説明】
１ 基板
２ 基板表面
３ 基板裏面
４，５ テクスチャーテープ
６，７ 押圧ロール
８，９ ノズル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing fabric suitable for finish polishing and texturing of a glass magnetic disk substrate used for a memory hard disk such as a computer.
[0002]
[Prior art]
Memory hard disks, which are one of storage media such as computers, are being developed to increase the storage capacity at the same time as miniaturization. The magnetic disk substrate is a glass or aluminum substrate with parallelism and flatness, and relatively large undulations cannot be completely removed. Even if the film is formed by electroless Ni-P plating The swell remains. In addition, when impurities adhering to the substrate are taken into the electroless Ni—P plating, the plating surface of that portion may rise to form a film.
[0003]
As means for increasing the storage capacity, it is necessary to increase the density of magnetization. In order to increase the density, an anisotropic medium can be formed by orienting the magnetization direction in the circumferential direction, which is the recording direction, by providing concentric disks on the surface of the glass substrate (texture processing). It becomes possible. Patent Document 1 proposes a glass magnetic disk (magnetic storage medium) that can cope with higher recording density and a method for manufacturing the same. As a texture tape used for manufacturing, a processed cloth made of a material selected from the group consisting of urethane, polyester and nylon has been proposed, but in detail, a raised cloth made of ultrafine fibers having a fiber diameter of 10 μm or less. But it only describes what is good. The disclosed content alone is not sufficient to provide a very fine uniform groove on a glass substrate.
[0004]
Contrary to the increase in storage capacity, the area of the substrate is decreasing, the storage density is increasing, and the magnetic force is becoming weaker. Therefore, it is required to minimize the gap between the magnetic head and the magnetic disk substrate. Currently, 0.025 μm or less is required. In addition, the magnetic disk substrate rotates at a high rotational speed of 10,000 rpm or more, and it is necessary to reduce the flatness and surface roughness of the substrate. Patent Document 2 proposes a cleaning fabric that suppresses the generation of impurities during cleaning. However, the fineness of the fibers used is only described as 2 denier or less, and no disclosure is made on the texture processing of the hard disk.
[0005]
The texture processing is performed using an aqueous solution (slurry) of abrasive fine particles such as cerium oxide, silicon dioxide, aluminum oxide, diamond and the like as an abrasive together with a texture tape.
[0006]
[Patent Document 1]
JP 2003-30825 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-25453
[Problems to be solved by the invention]
In the conventional texture processing, if a fine groove is to be formed, the processing speed needs to be extremely slow, and if it is fast, end face sagging occurs along with large scratches. During texture processing, friction may cause the dropping of additives and impurities from the surface of the texture tape fiber, and may cause contamination of the substrate. In addition, impurities contained in the fiber component are liberated during the cleaning process using an organic solvent together, causing contamination.
[0008]
The glass substrate has a high polarity and is particularly likely to adsorb titanium and silicon. When these impurities are adsorbed on the glass substrate, the adhesion between the magnetic film and the substrate is lowered when the magnetic film is formed in the next step. If the glass magnetic disk continues to be used in this state, the magnetic film peels off, making it difficult to read. In the worst case, the magnetic film is sandwiched between the head and the disk, causing a crash. In order to increase the magnetic capacity of a glass magnetic disk substrate, it is necessary to form as many uniform fine grooves as possible in a concentric manner. In order to solve these problems, it is an object of the present invention to provide a high-performance texture tape that can improve the retention of abrasives and trap abrasive particles and suppress the generation and removal of impurities.
[0009]
[Means for Solving the Problems]
In the texture tape of the present invention, the splitting composite fiber formed of polyester and polyamide having a cross-sectional shape having apex angles of three or more places constitutes at least a weft, and the cover factor value of the weft after splitting is 18000 or more And a glass substrate polishing fabric characterized in that the amount of low-molecular-weight impurities generated after a dry heat treatment at 180 ° C. for 30 minutes is 0.1% by weight or less and does not contain any matting agent.
[0010]
In a preferred embodiment of the invention, the polyester constituting the polishing fabric is polyethylene terephthalate and the polyamide is 6 nylon.
[0011]
Furthermore, the present invention is used for texture processing of a magnetic disk substrate in which a woven fabric composed of split fiber composite fibers formed from polyester and polyamide is subjected to weight reduction split using a polymer-soluble solution or split by swelling shrinkage with a solvent. A polishing fabric used.
[0012]
The polishing fabric is particularly suitable for a polishing cloth for texture processing of a glass magnetic disk substrate.
[0013]
The use of the polishing fabric and the abrasive is suitable for the texture processing polishing method for the glass magnetic disk substrate.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below. One of the main constituent elements of the present invention is the cross-sectional shape of the ultrafine fibers of the weft constituting the textured fabric for polishing. It is necessary to have three or more apex angles. It is an important item that the surface roughness of the substrate can be minimized and fine surface defects can be eliminated by the ultrafine fibers having the apex angle, and at the same time, the polishing rate is high and the productivity is high. The flat and polygonal polishing efficiency is good because the surface area of the fiber is larger than that of a fiber having a circular shape or a cross-sectional shape close to it, and the contact area is increased with respect to the surface to be polished. .
[0015]
The polymer constituting the weft of the abrasive fabric is composed of a fiber-forming polyamide and polyester that do not contain any matting agent, and a particularly good combination of hydrophilic and lipophilic polymers. Examples of the polyamide include 4 nylon, 6 nylon, 66 nylon, 12 nylon, 610 nylon, 612 nylon, and copolymer nylon containing them, and 6 nylon and 66 nylon are particularly preferable.
[0016]
As the polyester, polyethylene terephthalate, polybutylene phthalate or those obtained by copolymerizing a small amount of a dibasic acid such as isophthalic acid, sulfoisophthalic acid or adipic acid, or a diol such as trimethylene glycol or polyethylene glycol can be used. Polyethylene terephthalate obtained by copolymerizing terephthalate with sulfoisophthalic acid as an acid component is preferable, and is particularly effective for spinning and drawing operability. The copolymerization ratio of sulfoisophthalic acid is preferably 1.5 mol% or less with respect to the acid component.
[0017]
It is necessary that the polymer constituting the abrasive fabric does not contain any matting agent. Examples of the polymer matting agent include titanium oxide, silicon oxide, zinc oxide, and calcium carbonate. If a matting agent is present on the texture tape surface during the texture processing of the glass substrate, the matting agent is adsorbed on the glass substrate. In the portion where the matting agent is adsorbed, the adhesion between the magnetic film and the glass substrate is lowered during the magnetic film formation in the next step. When such a glass hard disk is used, peeling of the magnetic film occurs and a read error occurs. In the worst case, the peeled magnetic film may be caught between the head and the disk, resulting in a crash.
[0018]
The single fiber fineness of the ultrafine fibers constituting the weft is preferably 0.05 to 0.1 dtex for polyester and 0.02 to 0.05 dtex for polyamide. The finer the fineness, the greater the surface area of the yarn and the greater the retention force of the abrasive particles. However, if the fineness is too small, the strength becomes low, the fiber is cut during use, and waste is generated, which may cause a large scratch (scratch) on the substrate. On the other hand, if the fineness is too large, the scavenging force for polishing dust is reduced, and the polishing dust is left on the substrate, causing scratches and at the same time reducing the magnetic properties.
[0019]
The weft of the texture tape is preferably a combination of different fineness. With a different fineness, the gap of the fabric increases, so that the scavenging power of the polishing debris increases. At the same time, the cushioning property increases and the substrate can be captured accurately, suppressing the occurrence of swell and maintaining the levelness. It becomes easy.
[0020]
In order to improve the polishing effect of the woven fabric, it is preferable that the woven fabric has a certain density, and it is preferable to increase the number of wefts driven and the number of segments after splitting of the split yarn, and the cover factor value (CF) is It is necessary to be 18000 or more. The cover factor value (CF) is represented by CF = (segment fineness dtex) 1/2 × (number of segments / 2.5 cm). If the CF is less than 18000, the denseness of the fabric is inferior, fine grooves cannot be uniformly formed on the substrate, and no increase in magnetization density is observed.
[0021]
Whether or not the matting agent has fallen off is determined by immersing a certain amount of the fabric in distilled water and irradiating with ultrasonic waves for 5 minutes. The presence or absence of a matting agent can be confirmed using a line analysis method.
[0022]
In the polishing fabric of the present invention, the amount of oligomer generated after dry heat treatment at 180 ° C. for 30 minutes is required to be 0.1% by weight or less. A fabric in which oligomers exceed 0.1% by weight when dry heat-treated under the above conditions generates impurities due to frictional heat at the time of polishing or cleaning using a solvent, and cannot exhibit sufficient cleaning ability.
[0023]
The amount (% by weight) of impurities generated after the dry heat treatment is measured as follows. After immersing a certain amount of fabric heat-treated at 180 ° C. for 30 minutes in distilled water and boiling for 30 minutes, the extract is evaporated to dryness, and the residue is weighed to confirm the amount of impurities (% by weight). .
[0024]
A specially prepared raw material polymer is used as a method for obtaining a fiber with a small amount of impurities generated after dry heat treatment. For example, in the case of polyester, a polymer obtained by solid phase polymerization by dry heat treatment in a nitrogen atmosphere or a polymer subjected to hydrothermal treatment may be used. In the case of polyamide, monomers remain inside the polymer as polymerization impurities, and therefore, it may be used after washing with an appropriate liquid and extracting and removing the impurities.
[0025]
The splitting method of the composite yarn is more effective when each polymer is left between each segment than when one polymer is completely dissolved and decomposed to obtain the ultrafine segment of the other polymer. There is a tendency to obtain a dense fabric without large voids and many fine voids. Methods such as partial dissolution / removal of one polymer with a solvent or a decomposing agent, swelling / shrinkage with a swelling agent, deformation / shrinkage by heating, friction or striking with an external force can be used. Preferably, a method using swelling / shrinkage with a solvent (swelling agent), a polyester weight loss with an alkaline aqueous solution, and a weight loss splitting method of a polyamide with an acid are preferable with less residual treatment agent, and it is important that the washing process is sufficiently performed. .
[0026]
The surface of the polishing fabric is alternately arranged without disturbing the arrangement of the single fibers separated from the polyamide and the polyester. By splitting, a minute gap is formed between each single fiber, and at the same time, unevenness between the single fibers is generated on the surface of the fabric due to the difference in shrinkage between polyamide and polyester. The abrasive particles are trapped in the generated recesses, so that the capturing power of the abrasive particles is improved. The surface of the woven fabric is straight and the corners have sharp edges, which increases the polishing speed and improves the trapping power of the abrasive particles, and is different from the rotation direction of the magnetic hard disk substrate formed on the disk substrate by polishing. In order to prevent the magnetic field on the magnetic hard disk substrate from becoming non-uniform due to the direction streaking, it is possible to texture the hard disk substrate after polishing with uniform concentric lines.
[0027]
These lines made it possible to texture a magnetic disk substrate having a uniform surface roughness of 50 nm or less by using a texture tape made of the abrasive fabric of the present invention and abrasive particles. By applying uniform and fine streaks, the magnetic density has been dramatically improved, and the storage capacity has been increased compared to the texture tape using the conventional fabric. The polishing time is the same as that of a texture tape made of a conventional fabric.
[0028]
As the abrasive particles used, diamond, alumina, silicon carbide, zirconia, or the like is used. These particle diameters are preferably 0.05 to 0.3 μm. If this range is exceeded, the surface roughness of the substrate becomes poor and scratches are generated. When the particle size is smaller than this range, the polishing rate becomes very slow and the working efficiency is deteriorated. The abrasive particles are used in the form of an aqueous solution or dispersed and slurried uniformly in the solution. The slurry may contain a dispersant and a polishing accelerator. The used abrasive particles need to be sufficiently removed from the substrate.
[0029]
A weft made of ultrafine fibers constituting an abrasive fabric is formed by splitting a composite split yarn composed of two types of fiber-forming polyamide and polyester. FIG. 1 shows the form of the composite split yarn. a shows a fiber cross-sectional form in which one kind of polymer divides another polymer. “b” shows a cross-sectional form of a fiber in which two kinds of polymers are alternately laminated and have a hollow portion at the center. c shows a fiber cross-sectional form in which two types of polymers are alternately laminated. The composite fiber used in the present invention is preferably a multi-segment hollow annular composite split yarn having a cross-sectional shape of a fiber in which two types of polymers b are alternately laminated and a hollow portion is provided at the center. Multi-divided hollow annular composite split yarn is easy to split, and an ultrafine segment of 0.1 dtex or less is also possible. The spinning method for obtaining these composite split yarns is not limited to any one of the usual spinning drawing method, direct spinning method (SPD), and high-speed spinning (POY) drawing method.
[0030]
The wefts constituting the polishing fabric must be ultrafine fibers containing no matting agent. The warp is not particularly limited, but the fineness of the warp without any matting agent should be thinner than the weft and should not interfere with the surface exposure of the weft. The weft preferably covers 80% or more of the fabric.
[0031]
The weave structure is preferably four or more satin weaves. Covering the entire intersection of the weft and warp (texture point) and covering the entire surface of the fabric with weft, making the surface of the fabric flat by making the surface of the fabric as small and small as possible. At the same time, the surface residue of the polishing dust can be minimized and concealed inside the ultrafine yarn bundle, and the generation of scratches can be reduced. At the same time, it is necessary to eliminate the loss of the matting agent from the abrasive fabric.
[0032]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0033]
Polishing Evaluation Method Evaluation was carried out using the texture processing polishing apparatus shown in FIG. On each of the front and back surfaces 2 and 3 of the substrate 1 that positively rotates in the direction of arrow A, a total of two texture tapes 4 and 5 are driven by each pressing roll 6 and 7 roll pressurizing cylinders. While being pushed, it runs in the direction of the arrow B, and a polishing liquid containing 0.08 μm artificial diamond abrasive grains is supplied from the nozzles 8 and 9 to the textured polished surfaces of the texture tapes 4 and 5 to perform slurry polishing. To be implemented. The texture tapes 4 and 5 are reciprocated (vibrated) in the direction of the arrow C by the reciprocating motion of the pressing rolls 6 and 7, respectively. A textured substrate 1 is formed. The surface roughness Ra (average) of the processed substrate, the presence or absence of scratches, and the processing amount SR were compared.
[0034]
Example 1
1g of low-impurity polyethylene terephthalate (PET) that has been subjected to hydrothermal treatment after solid-state polymerization without any matting agent having an intrinsic viscosity of 0.72 in a 30 ° C orthochlorophenol solution and 25 ° C concentrated sulfuric acid 1/100 ml solution is melt extruded with low impurity 6 nylon (6N) that has been hydrothermally treated without any matting agent and has a PET: 6N ratio of 2: 1 as shown in FIG. As shown in the drawing, a composite split filament yarn in which 6N radial 6N is divided into eight parts is usually spun and drawn to obtain a drawn yarn of 110 dtex / 50f.
[0035]
Five yarn satin fabrics with a weft of 100 T / m S twisted on the composite split yarn and a warp of PET yarn 84 dtex / 36F (200 T / mS twisted additional twist) containing no normal matting agent Was woven. A 20% aqueous solution of benzyl alcohol emulsified with a nonionic surfactant was applied to this raw machine, and the mixture was allowed to stand for 15 minutes to split the weft, washed with 70 ° C. hot water, and dried. The obtained fabric had a warp density of 192 yarns / 2.5 cm and a weft density of 92 yarns / 2.5 cm, consisting of 0.2 dtex PET having three apex angles and 0.6 dtex 6N. It was a woven fabric. The CF value of the weft after splitting was 19700. The fabric was cut into a tape shape in the warp direction and passed through a washing step to obtain a texture tape. Table 1 shows the analysis results of impurities in the obtained texture tape.
[0036]
Example 2
Using a polymer containing no matting agent used in Example 1 as a weft, a composite split yarn of 56 dtex / 25f (Z-twisted twist of 200 T / m) having the same cross-sectional form as in Example 1, Four double satin fabrics were woven using PET yarn 33 dtex / 12F (600 T / mZ twisted additional twist) containing no matting agent. The obtained raw machine was subjected to fiber splitting in a 13 g / l sodium hydroxide aqueous solution at 80 ° C., then washed with hot water at 70 ° C. and dried. The obtained fabric has a warp density of 180 / 2.5 cm and a weft density of 265 / 2.5 cm composed of 0.2 dtex PET having three apex angles and 0.6 dtex of 6N. It was a woven fabric. The CF value of the weft after splitting was 28800.
[0037]
The woven fabric was cut into a tape shape in the warp direction, passed through a washing step with ultrapure water having a specific resistance of 17 MΩ · cm or more in a clean room, and dried to obtain a tape. Table 1 shows the analysis results of impurities in the obtained tape. It had all the performance required as a dry wiping tape for glass hard disk substrates, and it did not contaminate the glass substrates during processing.
[0038]
Example 3
After 30% orthochlorophenol solution copolymerized with 1.5 mol% of sulfoisophthalic acid with respect to the acid component of polyethylene terephthalate does not contain any matting agent having an intrinsic viscosity of 0.70, solid phase polymerization is performed. Water-treated low-impurity copolymerized polyethylene terephthalate (COPET) and 1 g / 100 ml solution in concentrated sulfuric acid at 25 ° C. with a relative viscosity of 2.5. 6 Nylon (6N) was melt-extruded separately, and the ratio of COPET: 6N of 3: 1 was divided into 16 polymers as shown in FIG. A drawn yarn of 56 dtex / 25f was obtained.
[0039]
A yarn obtained by applying a Z twist of 150 T / m to the 32 split hollow annular composite split yarn is used as a weft, and a PET yarn 33 dtex / 12 F (600 T / mZ additional twist) containing no ordinary matting agent is used as a warp. A sheet double satin fabric is woven, processed through the same processing steps as in Example 2, and then split, and is composed of 0.09 dtex COPET having 3-4 apex angles and 0.03 dtex 6N. Fabrics having warp density of 180 yarns / 2.5 cm and weft density of 265 yarns / 2.5 cm were prepared. The CF value of the weft after splitting was 50100. The woven fabric was cut into a tape shape in the warp direction and passed through the same washing process as in Example 2 to obtain a texture tape. Table 1 shows the analysis results of impurities in the obtained texture tape. It had all the performance required as a texture tape for a glass hard disk substrate and did not contaminate the glass substrate during processing.
[0040]
Using the texture polishing machine described above, the glass substrate was polished and textured with the texture tape. The processing amount SR was the same as that of the conventional texture tape, and the average surface roughness Ra of the obtained substrate was very small at 27 nm, and no scratches were observed and there was no polishing dust. Further, it has become possible to increase the magnetic density, which could not be achieved conventionally.
[0041]
Comparative Example 1
A woven fabric similar to that of Example 1 was prepared using PET and 6N used in Example 1 in which 0.3% by weight of titanium oxide was kneaded as a matting agent. A texture tape was produced from the fabric in the same manner as in Example 1. Table 1 shows the analysis results of impurities in the obtained texture tape. Although the performance required as a texture tape for a glass hard disk substrate was satisfied, titanium oxide was observed to fall off and the amount of impurities after heat treatment was as large as 0.3% by weight. Adsorption of titanium oxide was observed even when the glass substrate was actually processed.
[0042]
Comparative Example 2
A woven fabric similar to Example 2 was prepared using PET and 6N used in Example 2 in which 0.3% by weight of titanium oxide was kneaded as a matting agent. A texture tape was produced from the fabric in the same manner as in Example 2. Table 1 shows the analysis results of impurities in the obtained texture tape. The performance required for the texture tape of the glass hard disk substrate was satisfied, and the impurities after heat treatment were as good as 0.1% by weight, but the titanium oxide was removed. Adsorption of titanium oxide was observed even when the glass substrate was actually processed.
[0043]
Comparative Example 3
A woven fabric similar to that in Example 1 was produced using 110 dtex / 96f having a round cross section obtained by normal spinning and drawing processes using PET used in Examples 1 and 2 as the weft. A similar texture tape was produced with the woven fabric without performing the splitting treatment performed in Example 1. The cover factor of the weft is 9450. Table 1 shows the analysis results of impurities in the obtained texture tape. The glass hard disk substrate was textured with the texture tape. Although the processing amount SR was substantially the same as that of the conventional texture tape, the average surface roughness Ra of the obtained substrate was extremely large, and many large scratches were recognized. A lot of polishing debris was also confirmed on the glass substrate.
[0044]
[Table 1]

[0045]
【The invention's effect】
If the glass substrate is polished and textured using a texture tape made of a polishing fabric that does not contain the matting agent of the present invention and generates less impurities, the glass substrate is less contaminated and the processing amount of the glass substrate is the same as before. Thus, the surface roughness of the substrate is uniform and extremely fine, and the magnetic density can be increased.
[Brief description of the drawings]
FIG. 1 shows a cross-sectional form of a representative composite split yarn.
FIG. 2 shows a use situation of a texture tape made of the abrasive cloth of the present invention.
[Explanation of symbols]
1 Substrate 2 Substrate surface 3 Substrate back surface 4, 5 Texture tape 6, 7 Press roll 8, 9 Nozzle

Claims (5)

A splitting composite fiber formed from polyester and polyamide having a cross-sectional shape having apex angles of three or more places constitutes at least a weft, the cover factor value of the weft after splitting is 18000 or more, and 180 ° C., A glass substrate polishing fabric characterized in that the amount of impurities generated after 30 minutes of dry heat treatment is 0.1% by weight or less and contains no matting agent. The polishing fabric according to claim 1, wherein the polyester is polyethylene terephthalate and the polyamide is 6 nylon. The polishing fabric according to any one of claims 1 and 2, wherein the splitting method splits with a solvent. A polishing cloth for texture processing of a glass magnetic disk substrate using the fabric according to any one of claims 1 to 3. A method for polishing a texture of a glass magnetic disk substrate, wherein the polishing cloth according to claim 1 is used.

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