JP2008103012A - Polishing knit fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing knit fabric for texture polishing of a magnetic recording disk which can regulate micro undulation while keeping sufficient processing rate and uniformity of texture traces. <P>SOLUTION: The polishing knit fabric is composed by combining an ultrafine fiber whose single yarn fineness is equal to or less than one dtex and a thick fineness fiber whose single yarn fineness is equal to or more than four times of the ultrafine fiber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides high precision polishing used for finishing of recording media and integrated circuit boards, surface polishing using abrasive grains, and further on the surface of a disk substrate in the manufacturing process of magnetic recording disks such as aluminum and glass substrates. The present invention relates to a polishing knitted fabric that can be used for texturing with an order groove.

  In recent years, energetic technological development has been carried out on recording media such as optical disks and magnetic disks, and integrated circuit boards, but the demand for higher capacity and higher recording density is still the most important issue in this field. ing. The higher the performance, the higher the accuracy of various substrate surface processing. For example, in a magnetic disk for a hard disk, a glass or aluminum substrate is used as a disk substrate, but in general, a pre-processing called a polishing process and a texture process before forming a magnetic thin film layer by a sputtering method. There is a post-processing called. Polishing is a process for improving surface waviness and unevenness on the substrate surface and smoothing the surface.

  On the other hand, texturing is a process in which a large number of fine grooves (hereinafter referred to as texture marks) having a groove depth of nearly angstrom order are formed on the substrate surface smoothed in the previous step, as shown in FIG. Texture processing equipment is used.

  In FIG. 1, 1 is a substrate, 2 is a rubber roller, 3 is a supply reel, 4 is a collection reel, 5 is a supply nozzle, F is a polishing tape, and texturing includes fine particles having an average particle size of submicron or less. A free abrasive method is generally used in which abrasive slurry is supplied between the polishing tape F and the magnetic disk substrate 1 and the disk substrate 1 is rotated and polished with fine particles in the abrasive slurry dispersed on the polishing tape F. It is.

The purpose of texturing is
(1) In the case of the longitudinal magnetic recording method, improving magnetic recording characteristics by giving magnetic anisotropy,
(2) In the case of perpendicular magnetic recording, reducing the difference in surface roughness between products, or reducing the average surface roughness (hereinafter referred to as Ra),
(3) In a hard disk device (hereinafter referred to as HDD) using a contact start and stop (CSS) method, preventing the magnetic head and the magnetic disk surface from being attracted when not operating;
(4) In an HDD using a ramp load system in which the magnetic head is moved from above the magnetic disk during non-operation, preventing the lubricant from being sucked from the magnetic disk to the magnetic head;
(5) And, in all methods, removing harmful convex defects on the surface,
Etc.

  The HDD is required to improve the recording density year by year. For this purpose, it is important to reduce the flying height of the head. Currently, the head flying height is about 15 nm or less. In order to achieve this flying height, it is necessary to reduce the average surface waviness (Wa) of the surface.

  This Wa is formed in a polishing process stage (substrate smoothing polishing stage) before texture processing. Since this polishing process is performed by batch processing of a plurality of sheets, it has periodicity in a direction unrelated to the circumferential direction. When the minute waviness is large, the flying height of the magnetic head varies, and the recording characteristics deteriorate. If the degree is further worse, the flying stability is impaired, and the magnetic head and the magnetic disk come into contact with each other, resulting in damage to the HDD. In addition to the problem that micro waviness is further increased by texture processing in the next stage, in addition to improving recording density, there is a reduction in the diameter of magnetic disks and the expansion of the usage environment. It has become an important required characteristic.

  The factors that determine Wa in the texturing process are abrasive slurry, polishing tape, and equipment processing conditions (abrasive slurry supply rate, disk rotation speed, pressure to press the polishing tape against the disk, polishing tape feed speed, processing time) Of these, the abrasive tape contributes the most to the properties. In addition, the uniformity of the depth and height of the grooves is important for the texture marks formed on the surface.

  As a specific index for evaluating the required textured surface, Ra value after texture processing and Wa value are important. The Ra value is set to an appropriate value that satisfies all the characteristics. A typical Ra value is 4 angstroms or less, and since it is necessary to reduce the flying height in order to realize an improvement in recording density, a value of 3 angstroms or less is currently required. For the measurement of Ra value, an atomic force microscope (hereinafter referred to as AFM) having high measurement resolution is used.

  On the other hand, the Wa value increases after processing in comparison between before and after texture processing because a periodic component is added by texture processing, but it is preferable that the increase amount (ΔWa) is smaller in terms of characteristics. For the Wa value measurement, an optical measuring instrument or a stylus measuring instrument is used, but a non-contact measuring instrument is often used because it is simple.

  In response to such a demand for low minute waviness, for example, in a smooth polishing step before texturing in a glass disk substrate, first polishing with a cerium oxide-containing slurry and then polishing with colloidal silica before the texturing step. A method of reducing the micro waviness of the disk substrate is disclosed (Patent Document 1).

  In addition, a method is disclosed in which a correlation formula composed of the number of rotations of the disk substrate and the oscillation frequency of the disk is defined in the texture processing step, and a numerical range obtained from the correlation formula is defined (Patent Document 2).

  However, no matter how much the fine waviness can be reduced in the smooth polishing step before texturing as in the former, the fine waviness may recur or increase further in the texture step as described above, which is not an effective method. Moreover, even if the conditions at the time of texturing can be optimized as in the latter case, there is a drawback that the expected effect cannot be obtained depending on the properties of the polishing tape (texture tape) and the polishing slurry used.

  On the other hand, paying attention to the polishing tape (texture tape) used at the time of texturing, as a method of achieving the reduction of micro waviness, the fiber bundle in a woven tape or a knitted tape woven with a plastic fiber bundle having a diameter of 8 μm or less A method is disclosed in which a tape having a discontinuous or stitched discontinuity in the longitudinal direction of the tape is used (Patent Documents 3 and 4).

  Here, the woven fabric is a fabric in which warp yarns (or warp yarn bundles) and weft yarns (or weft yarn bundles) are arranged at right angles and crossed up and down, while knitted fabric is yarn. A loop is formed with (or a yarn bundle), and a fabric is formed by repeating the formation of a loop by passing a yarn (or a yarn bundle) through the loop.

However, when the polishing tape is a woven fabric as in these cases, the weft yarn is pressed more than necessary on the disk substrate surface due to the influence of the warp yarn bundle located on the back side of the weft yarn bundle that contributes to actual polishing. For this reason, there is a drawback that micro swell is generated. On the other hand, when the abrasive tape is a knitted fabric, the involvement of warp yarn such as woven fabric can be excluded, but the problem of tape elongation and deformation due to the inherent elasticity of the knitted fabric is a problem during actual texturing. The degree of freedom of the fiber bundle on the surface of the knitted fabric is much larger than that of the woven fabric, resulting in a macro soft surface. As a result, the occurrence of waviness can be suppressed, but other texture characteristics such as surface roughness ( Ra) was too small and the processing rate was very low.
JP 2003-187421 A Republished patent WO2004-059619 Japanese Patent Laid-Open No. 10-241156 JP-A-6-295432

  The present invention provides a polishing knitted fabric capable of reducing a sufficient processing rate, uniformity of texture marks, and fine waviness particularly in texture processing of a magnetic disk or the like.

The present invention has the following configuration in order to solve the above problems.
That is, the present invention is an abrasive knitted fabric composed of a composite yarn composed of ultrafine fibers having a single yarn fineness of 1 dtex or less and thick fine fibers having a single yarn fineness of 4 times or more of the ultrafine fibers.

  According to the present invention, it is possible to suppress the elongation and deformation of the tape due to the size of stretch characteristic peculiar to the knitted fabric.For example, in the texturing of a magnetic disk for a hard disk, the processing rate sufficient for practical use, the uniformity of texture marks, A polishing knitted fabric that can reduce microwaviness while maintaining sharpness can be obtained.

Hereinafter, the present invention will be described in detail.
The polishing knitted fabric of the present invention can be used for various applications that require surface polishing processing and removal of surface dirt, such as semiconductor-related materials such as recording media and integrated circuit boards, optical products, jewelry, etc. Since it is suitable as a polishing knitted fabric for texture processing of a magnetic recording disk substrate, the following description will be focused mainly on the texture processing.

  The material constituting the abrasive knitted fabric of the present invention is a knitted fabric composed of composite yarns composed of ultrafine fibers having a single yarn fineness of 1 dtex or less and thick fine fibers having a single yarn fineness of 4 times or more of the ultrafine fibers.

  The ultrafine fibers and thick fine fibers are preferably made of polyester, but may be other synthetic fibers such as polyamide. When both ultrafine fibers and thick fibers are polyester, there is no problem even if polyamide or carbon fiber is contained in a small amount within 10%. The properties of the fibers may be either filament fibers (continuous fibers) or short fibers (staple fibers) for both ultrafine fibers and thick fibers, but the filaments are less likely to generate fiber waste. Basically it is a fiber.

  The single yarn fineness of the ultrafine fibers is 1 dtex or less, and those in the range of 0.001 to 1 dtex are preferable. Furthermore, the thing of the range of 0.01-0.1 dtex is preferable. When the single yarn fineness of the ultrafine fiber exceeds 1 dtex, the abrasive particles in the polishing slurry cannot be efficiently captured on the surface of the knitted fabric, the polishing rate is low, or the texture marks are not sharp, and further fine The swell may increase. In addition, when the single yarn fineness of the ultrafine fiber is less than 0.001 dtex, the processing rate is drastically lowered, and Ra may become extremely small texture marks.

  The single yarn fineness of the thick fineness fiber needs to be at least 4 times higher than the single yarn fineness of the ultrafine fiber used. More preferably, it is 10 times or more, and more preferably 50 times or more. When the single yarn fineness of the thick fine fiber is less than 4 times the single yarn fineness of the ultrafine fiber, the knitted fabric will be composed of only thin fibers, and the texture will be firm and free from lumps. In some cases, there is a problem that the fabric is stretched or deformed due to the stretchability characteristic of the knitted fabric.

  Further, the single yarn fineness of the thick fineness fiber is preferably 4 times or more higher than the single yarn fineness of the ultrafine fiber used, and the single yarn fineness is preferably 1 dtex or more. More preferably, it is 3 dtex or more. If the single yarn fineness of the thick fineness fiber is less than 1 dtex, the knitted fabric will be composed of only thin fibers, and the texture will not be stiff and waisty. In some cases, the fabric may be stretched or deformed due to the size of the stretch.

  The upper limit of the single yarn fineness of the thick fine fiber is preferably up to about 5000 times the single yarn fineness of the ultrafine fiber, more preferably up to about 2000 times. Moreover, as a specific single yarn fineness, 30 dtex or less is preferable, More preferably, it is 20 dtex or less. The reason for this is that if the single yarn fineness difference between the single yarn fineness of the thick fineness fiber and the ultrafine fiber is very large, irregularities will be generated on the surface of the knitted fabric. This is because the processed surface cannot be uniformly contacted with the disk substrate, resulting in non-uniform texture marks, which cannot reduce microwaviness, and also causes scratches.

In the present invention, the composite ratio of the ultrafine fibers and the thick fine fibers is important, and the weight percentage of the fine fibers with respect to the total weight of the abrasive knitted fabric is at least occupied by the fine fibers with respect to the gross weight of the abrasive knitted fabric. Preferably it is higher than% by weight. From the viewpoint of the bulkiness, texture, and polishing characteristics of the fabric, the ultrafine fibers are preferably contained in an amount of 50 to 80% by weight, more preferably 60 to 70% by weight, based on the total weight of the knitted fabric for polishing. More preferred.

  Basically, thick fine fibers occupy the remaining part. However, there is no problem even if anti-static fibers such as carbon fibers are included as necessary.

  The thick fine fibers are preferably raw yarn (non-processed yarn) that has not been temporarily twisted. Moreover, the thick fine fiber has a higher shrinkage property than the ultrafine fiber in a state before the heat treatment. The shrinkage rate is not particularly limited, but the important thing is that the shrinkage property to heat is larger than that of the ultrafine fiber. The fine fiber should have a shrinkage of 10 to 25% while the boiling water shrinkage of the ultrafine fiber is 4 to 8%. In particular, those having a shrinkage rate 4 to 8% larger than the boiling water shrinkage rate of the ultrafine fibers are more preferable.

  In other words, the heat treatment causes the fine fibers to contract more than the ultrafine fibers to form the inside of the knitted fiber bundle. By having this shrinkage difference, after heat treatment, the thick fine fibers relatively form the inner layer part of the yarn (inner layer part of the knitted fabric), and the ultrafine fibers form the outer layer part of the yarn (surface layer part of the knitted fabric) relatively. Will do. Further, before the heat treatment, the difference in yarn length between the two is preferably such that the ultrafine fiber is 3% or more longer than the thick fiber.

  Furthermore, it is preferable that the ultrafine fiber is given a crimp by temporary twisting. Because of this temporary twisting, the single fiber array that is originally straight is disturbed, and the bulkiness of the knitted surface is increased, so that the surface fiber layer exhibits an appropriate cushioning property during texture processing. This is effective in reducing the occurrence of scratches and scratches.

  As an index that specifically indicates the cushioning property of the polishing knitted fabric, there are compression energy and compression recovery energy of the fabric.

The compression energy and compression recovery energy refer to the compression energy and compression recovery energy of the fabric per cm ² measured by an automated compression tester KESFB3 manufactured by Kato Tech Co., Ltd.

The compression pressure P applied to the fabric increased from 0 gf / cm ² up to 50 gf / cm ^2, followed by reducing the compressive force from 50 gf / cm ² to 0 gf / cm ² to measure the change in thickness therebetween the fabric. When the thickness at the compression pressure P = 0.5 gf / cm ² when the compression pressure is increased is T ₀ and the thickness at the compression pressure P = 50 gf / cm ² is T _m , the compression energy WC is the compression pressure when the compression force is increased. It is a value obtained by integrating the value of P = P (T) from T = T ₀ to T _m , and corresponds to the area under the curve P = P (T) in the section from T ₀ to T _m . On the other hand, the compression recovery energy WC ′ is a value obtained by integrating the value of the compression pressure P = P ′ (T) when the compression force is decreased from T = T ₀ to T _m , and the curve P = in the section from T ₀ to T _m This corresponds to the area under P ′ (T). FIG. 2 shows an example of the relationship between pressure and thickness in a compression cycle (when compression is increased and when compression is decreased) used to calculate compression energy and compression recovery energy using an automated compression tester KESFB3 manufactured by Kato Tech Co., Ltd. It was shown to.

  A larger value of the compression energy and a larger value of the compression recovery energy have a higher cushioning property of the fabric, that is, it is more effective for reducing micro-waviness and reducing the occurrence of scratches.

In the polishing knitted fabric of the present invention, the compression energy, which is an index of the cushioning property, is 0.10 gf · cm / cm ² or more, preferably 0.12 gf · cm / cm ² or more. The compression recovery energy is 0.05 gf · cm / cm ² or more, more preferably 0.06 gf · cm / cm ² or more. The upper limit of each of these values, the compression energy 3.00gf · cm / cm ^2, compression recovery energy is 1.50gf · cm / cm ^2. The compression energy and the compression recovery energy are not particularly limited. However, in the present invention, as described above, the ultrafine fiber having a single yarn fineness of 1 dtex or less and the single yarn fineness of the ultrafine fiber are not particularly limited. By forming a knitted fabric using a thick fine fiber having a single yarn fineness of 4 times or more of the above and having a shrinkage ratio in heat treatment larger than that of the ultrafine fiber, the thick fine fiber forms the inner layer portion of the knitted fabric after heat treatment. However, it can be realized by forming the surface layer portion of the yarn with the ultrafine fiber, or by applying a temporary twisting process when the yarn is manufactured, and applying a crimp to the ultrafine fiber by the temporary twisting process.

  In the present invention, the low-shrinking ultrafine fibers and the high-shrinking thick fine fibers that have been temporarily twisted as described above are subjected to a fluid entanglement process, and both are entangled and combined. Preferably, the composite yarn is integrated by entanglement without being twisted, so that after the shrinkage treatment, the ultrafine fibers appear with a bulge on the surface and the texture becomes extremely soft.

  The density of the knitted fabric is preferably a high density of 25,000 fibers / in or more for both the fine and fine fibers. More preferably, the density is 30000 to 50000 / in. For example, if a composite yarn composed of 650 filaments of ultrafine fibers of 80 denier and thick fibers is 60 / in, it is composed of 39000 / in single fibers. Here, if it is less than 25000 pieces / in, the knitted fabric is soft and has no waist, and adverse effects occur during texturing. From the standpoint of polishing characteristics, the greater the number of fibers, the better. However, there is no fiber with an infinitely large density in terms of texture, workability, and the degree of clearance between yarns.

  Furthermore, by imparting disorder to the arrangement of the single fibers constituting the knitted fabric, the knitted fabric has no polishing direction during texture processing, and is effective in reducing microwaviness. In order to impart this arrangement disorder, the surface of the knitted fabric can be obtained by water jet processing. By water jet processing the surface of the knitted fabric, the single fibers constituting the knitting yarn are disturbed, a part of the surface ultrafine fibers are entangled with the thick fine fibers toward the inside of the yarn, and the direction of the stitches becomes random, Density meter: The knitting density cannot be read with a renometer, or the knitting surface becomes very difficult to read, and the surface of the knitted fabric changes to a chamois tone.

  The polishing knitted fabric of the present invention has good dimensional stability despite the knitted fabric. That is, the shrinkage rate by dry heat treatment at 160 ° C. is 5% or less, and the shrinkage rate by washing is 5% or less. Preferably both are 3% or less.

  Although the knitted fabric usually has a large shrinkage due to heat and it has been difficult to keep it below 5%, the knitted fabric of the present invention has a shrinkage due to dry heat treatment at 160 ° C. and a shrinkage due to washing of 5% or less. By using a knitted fabric, it is possible to obtain a knitted fabric that is excellent in dimensional stability and that does not easily fray the cut surface, although the knitted fabric is entangled between fibers.

Next, an example of the manufacturing method of the abrasive knitted fabric of the present invention will be described.
The abrasive knitted fabric of the present invention is a low-shrinkage polyester composite fiber filament temporary twisted yarn (A) having a sea-island structure with an island component of 1 dtex or less, which is an ultrafine fiber precursor, and a high-shrinkage polyester with high-fineness fibers. A knitted fabric obtained by aligning filament raw yarn (B) and knitting a composite yarn fluid-entangled with an air nozzle by an interlock method using a circular knitting machine is used as a raw machine, and this raw machine is subjected to hot water treatment to remove sea components. By removing this sea component, ultrafine fibers of 1 dtex or less can be obtained. Removal of sea components is effective in the presence of alkali, and sodium hydroxide is usually used.

  It is also possible to use peelable split fibers instead of sea-island structure composite fibers. As the temporary twisting process, a normal Woolley process can be used.

  Any method may be used for making the knitted fabric, but the circular knitting method is effective in productivity and prevention of fraying of cutting.

  The method of entanglement of ultrafine fibers is achieved by a composite of fluid twisting of the temporary twisted ultrafine fibers and high shrinkage raw yarn of the present invention, but further entanglement is further promoted by water jet processing.

  The fine fiber lifts the ultrafine fiber by shrinkage treatment by heat treatment, and further, the water pressure by water jet processing causes 1% to 3% shrinkage, and at the same time, the single fiber constituting the knitting yarn is disturbed, and the surface of the ultrafine fiber is While the portion is intertwined with the thick fine fibers toward the inside of the yarn, the directionality of the stitches becomes random and difficult to see.

That is, when the fabric after sea removal is sprayed with 50 to 100 kg / cm ² of fluid from the small holes onto the surface of the fabric, the ultrafine fibers existing in the vicinity of the surface within the fabric are separated almost one by one. The form which floats on the fabric surface is shown. The reason why the ultrafine fibers selectively float on the surface of the fabric is due to the action of thick fine fibers having a shrinkage ratio larger than that of the ultrafine fibers. That is, by performing water jet processing, the fibers are disturbed in arrangement and become a random arrangement. High shrinkage yarns having a large single yarn fineness selectively form an inner layer portion, and ultrafine fibers having a small single yarn fineness form a surface layer portion. It is possible to form a polishing knitted fabric having a volume feeling.

  As described above, the polishing knitted fabric of the present invention can reduce micro-waviness which is a problem particularly as a texture processing material for a magnetic disk substrate for a hard disk, and has a processing rate sufficient for practical use and uniform texture marks. It is possible to realize excellent texture characteristics that have both properties.

Hereinafter, the present invention will be specifically described by way of examples.
[1] Measurement of dry heat shrinkage and washing shrinkage of fabric The dry heat shrinkage at 160 ° C. was measured according to JIS L1042. However, the dry heat treatment temperature and time were set to 160 ° C. × 3 minutes and suspended in a vertical direction in a hot air dryer.
The measurement of the washing shrinkage was carried out by the method described in JIS L0217, 40 ° C. × 25 minutes and rinsing 10 minutes.

[2] Measurement of Boiling Water Shrinkage of Fiber The test fiber (yarn) was wound 10 times with a casserole machine, the test length a was measured by applying a load of 0.09 g / dtex, and 15% in boiling water at 100 ° C. After heat-treating for a minute and air-drying for 8 hours or longer, a load of 0.9 g / dtex was applied, the test length b was measured, and the boiling water shrinkage was calculated from the following equation.
Boiling water shrinkage ratio (%) = [(ab) / a] × 100

[3] Magnetic disk substrate texture processing and evaluation for HD (1) Magnetic disk substrate texture processing for HD A magnetic disk for HD using a polishing knitted fabric (or woven fabric) cut into a 38 mm width into a polishing tape As the substrate, a 2.5-inch glass substrate (outer diameter 65 mm, inner diameter 20 mm, plate thickness 0.635 mm) subjected to polishing before the texture process was used. A texture processing machine as shown in FIG. 1 was used for texture processing, and in processing tape evaluation, both sides were processed simultaneously, and two substrates were processed and evaluated.

The texture processing conditions are as follows.
Device name EDC1800 (manufactured by EDC)
Abrasive slurry supply rate 7.5ml / min
Disk rotation speed 400rpm
Abrasive tape pressing force 5.5 pounds (2.5 kg)
Tape tension 5.0 pounds (2.3 kg)
Pressing roller hardness 45duro
Roller size outer diameter 51mm
Abrasive tape feed speed 75 mm / min
Machining time 15 seconds Oscillation width 0.8mm
Oscillation frequency 8Hz

  The processing slurry is composed of 0.05% by weight of cluster particles (average particle size: 0.11 micrometer), 1% by weight of additive (surfactant of glycol compound), and 98.95% by weight of pure water. It was used.

(2) Magnetic disk substrate evaluation method after texture processing The following items were evaluated for the obtained magnetic disk substrate after texture processing.

(A) Average surface roughness (Ra)
The average surface roughness (Ra) of the textured magnetic disk substrate surface (4 surfaces in total) was measured, and the average value was obtained. Here, the surface arithmetic average roughness (Ra value) was measured using an atomic force microscope (AFM) by measuring an area of 5 micrometers in length and width on the textured surface and correcting the inclination of this range. Ra value was calculated from the height data. The measurement sample was fixed so that the texture line was perpendicular to the horizontal direction in the measurement range. As a measuring device, Dimension 3100 manufactured by Veeco was used. The reason for using AFM is that the resolution is higher than that of a stylus type surface roughness meter and an optical surface roughness meter.

  Using AFM, the average surface roughness (Ra) of the surface of the magnetic disk substrate (4 surfaces in total) after texturing was measured, and the average value was obtained. Ra is 4.3 (Ang) or more and 4.6 Angstrom or less A (good), and out of this range is C (bad).

(B) Microwaviness (Wa) and microwaviness increase (ΔWa)
For the fine waviness (Wa value), a white light interference type shape measuring device was used. The measuring instrument used was New View 5000 manufactured by Zygo. The measurement range was 0.66 mm in length and 0.88 mm in width, and the measurement sample was fixed so that the texture line was perpendicular to the measurement range. From the measurement results, a filtering process for capturing only frequency components in the range of 0.05 mm to 0.50 mm was performed, and this fluctuation component was defined as a Wa value.
Wa (before texture processing): Wa of the glass substrate before texture processing
Wa (after texture processing): Glass substrate Wa after texture processing
ΔWa: Wa (after texture processing) -Wa (before texture processing)

  ΔWa was evaluated as C at 0.4 angstroms or more, B (average) less than 0.2 angstroms at 0.2 angstroms or more, and A as less than 0.2 angstroms. Here, the meaning of evaluation “A” is a good characteristic that the flying height of the magnetic head does not fluctuate, and the meaning of evaluation “B” is inferior to “A” in that the flying height of the magnetic head fluctuates. The meaning of “C”, which is a level that can be practically endured, is the level at which the flying stability of the magnetic head is impaired and the flying height fluctuates and the recording characteristics deteriorate.

(C) Processing rate The weight of the magnetic disk substrate to be processed is measured in advance with an electronic balance. Since the texture processing needs to measure the weight change stably, the texture processing is longer than the normal conditions, and is 300 seconds corresponding to 20 times the normal processing. After the texture processing, precision cleaning is performed to remove the adhering components such as slurry and water remaining on the surface of the magnetic disk substrate, followed by drying. Furthermore, in order to realize that the water remaining on the surface is sufficiently dried, the magnetic disk substrate was placed for 3 hours in a place where particles in the atmosphere, such as a clean bench, are difficult to adhere. The weight of the magnetic disk substrate after processing was performed in the same manner as before processing.

  The weight change before and after this was defined as the processing rate (unit: mg). The measurement processed and measured 2 sheets and calculated | required the average value.

  When the processing rate is 4 mg or more, (1) the removal of harmful convex defects on the disk surface can be sufficiently achieved, and (2) magnetic anisotropy is effectively provided in the case of the longitudinal magnetic recording system. This is a preferable characteristic. On the other hand, when the amount is less than 0.2 mg, the characteristics (1) and (2) are not sufficiently achieved. Therefore, 0.4 mg or more was evaluated as A, less than 0.4 mg as 0.2 mg or more as B, and less than 0.2 mg as C.

Example 1
66 dtex, 9 filaments as ultrafine fiber, [70 islands / filaments: manufactured by Toray Industries, Inc.] sea island type polyester, island component is polyethylene terephthalate, sea component is polyester acid component, terephthalic acid and 5-sodium sulfoisophthalic acid Fibers made of a polymer and an alkaline hot water soluble polyester (the ratio of sea islands is 20/80. Therefore, the single yarn fineness of the island component fibers after removal of the sea components was calculated to be 0.084 dtex). The boiling water shrinkage of this yarn was 5.8%. As the fine fiber, 33 dtex, 6-filament polyester yarn (manufactured by Toray Industries, Inc.) was used. The single yarn fineness of this yarn was 5.5 dtex, and the boiling water shrinkage was 21.2%. On the other hand, the ultra fine fiber is temporarily twisted (temporary twist number: 3000 T / m, temperature: 180 ° C.) without sea removal, and is entangled with the thick fine fiber and air entangled (overfeed rate of ultra fine yarn: 2%, air pressure : 3 kg / cm ² ) to obtain a composite yarn. Furthermore, a circular knitting machine (32G, 38 inches) was used to form a raw machine by knitting using an interlock method.

This raw machine was once heat-treated at 130 ° C. for 20 minutes, and further treated at 80 ° C. for 30 minutes in the presence of 1% sodium hydroxide to completely remove sea components. Next, it dye | stained by the normal method, and it water-jet-processed with the pressure of 100 kg / cm < ² > from the surface. Thereafter, heat setting was performed at 135 ° C., and the number of wells and courses was set to 60 / in. The single yarn fineness of the ultrafine fiber of the obtained knitted fabric is finally 0.07 dtex by measuring the relationship between the length and the weight, and the proportion of the ultrafine fiber in the knitted fabric is 65% by weight, mainly composed of the ultrafine fiber. The monofilament was a high-density knitted fabric of about 35,000 pieces / in or more in both the well course. The basis weight was 210 g / m ² , and the shrinkage was 68% in width and 72% in length with respect to the raw machine. However, the product was a knitted knitting for dimensional stability with a dry heat shrinkage at 160 ° C. of 1.6% and a laundry shrinkage of 2%.

When the cloth physical properties of the obtained knitted fabric were calculated by an automated compression tester KESFB3 manufactured by Kato Tech Co., Ltd., the compression energy was 0.150 gf · cm / cm ² and the compression recovery energy was 0.072 gf · cm / cm ² . there were. When the texture was processed using the obtained knitted fabric, the processing rate was 0.4 mg, the surface roughness (Ra) was 4.4 angstroms, and Wa (before texture processing) was 1.10 angstroms, while Wa (textured processing). After) was 1.22 angstroms, and ΔWa was 0.12 angstroms, and the increase in fine waviness after texturing was significantly suppressed compared to the comparative example. The evaluation results of Example 1 are summarized in Table 1.

Comparative Example 1
Using 56 dtex, 18 filament polyester long fiber (single yarn fineness 3.1 dtex) for warp yarn, 135 dtex, 18 filament sea-island type composite fiber (70 islands / filament for weft yarn. The single fiber fineness of the component fiber is 0.086 dtex), and the island component is polyethylene terephthalate and the sea component is an acid component of the polyester, which is an alkaline hot water soluble polyester composed of a copolymer of terephthalic acid and 5-sodium sulfoisophthalic acid. The resulting fiber (the ratio of sea islands is 20/80) was used by laying two yarns (temporary twisting number: 300 T / m, temperature: 180 ° C.) by pulling two yarns together, and woven a five-back satin fabric.

  The fabric density was 137 pieces / inch for the vertical and 119 pieces / inch for the horizontal, and this was used as a living machine.

This raw machine was once treated with hot water at 130 ° C. for 20 minutes, and then further treated at 80 ° C. for 60 minutes in the presence of 1% sodium hydroxide to completely remove sea components. Next, it was washed with hot water and then dried to finish. The single yarn fineness of the ultrafine fiber was finally 0.07 dtex by measuring the relationship between length and weight. When the physical properties of the obtained woven fabric were calculated by an automated compression tester KESFB3 manufactured by Kato Tech Co., Ltd., the compression energy was 0.096 gf · cm / cm ² and the compression recovery energy was 0.047 gf · cm / cm ² . there were.

When the texture was processed using the obtained woven fabric, the processing rate was 0.5 mg, the surface roughness (Ra) was 4.5 angstroms, and Wa (before texture) was 1.10 angstroms, while Wa (after texture). Was 1.55 angstroms and ΔWa was 0.45 angstroms, and micro-waviness increased after texturing.
The evaluation results of Comparative Example 1 are also summarized in Table 1.

FIG. 1 illustrates a step of texturing using the abrasive knitted fabric of the present invention, (A) is a front view, and (B) is a side view. FIG. 2 is an example of a relationship diagram between applied pressure and fabric thickness in a compression cycle in a compression test.

Explanation of symbols

1: Substrate 2: Rubber roller 3: Supply reel 4: Collection reel 5: Supply nozzle F: Polishing tape

Claims (11)

  A polishing knitted fabric comprising a composite yarn comprising ultrafine fibers having a single yarn fineness of 1 dtex or less and thick fine fibers having a single yarn fineness of 4 times or more of the ultrafine fibers.   The knitting for polishing according to claim 1, wherein the single yarn fineness of the thick fine fiber is 10 times or more of the single yarn fineness of the ultrafine fiber.    The polishing knitted fabric according to claim 1 or 2, wherein the single yarn fineness of the ultrafine fiber is 0.01 to 0.1 dtex.   The abrasive knitted fabric according to any one of claims 1 to 3, wherein the ultrafine fiber is contained in an amount of 50 to 80% by weight (ratio to the total weight of the abrasive knitted fabric). The abrasive knitted fabric according to any one of claims 1 to 4, wherein the compression energy is 0.10 gf · cm / cm ² or more. The abrasive knitted fabric according to any one of claims 1 to 5, wherein the compression recovery energy is 0.05 gf · cm / cm ² or more.   The knitted fabric for polishing according to any one of claims 1 to 6, wherein the ultrafine fibers are knitted by being used at 25000 pieces / in or more for both the well and the course.   The polishing knitted fabric according to any one of claims 1 to 7, wherein a dry heat shrinkage rate at 160 ° C is 5% or less and a washing shrinkage rate is 5% or less.   The knitted structure for polishing according to any one of claims 1 to 8, wherein the knitted structure is a circular knitting.   The abrasive knitted fabric according to any one of claims 1 to 9, wherein the ultrafine fibers and the thick fine fibers are made of polyester.   A method of manufacturing a magnetic disk substrate, comprising polishing the magnetic disk substrate using the polishing knitted fabric according to any one of claims 1 to 10.

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