JP2856783B2 - Polishing tool - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a polishing tool that can be used in the field of precision polishing, especially texturing of a hard disk.

(Prior art) Conventional polishing tool is polyethylene terephthalate (PET)
On the film, there is one in which a coating material in which an abrasive powder such as a fused alumina powder is dispersed in a binder resin is applied to form a continuous or discontinuous abrasive layer.As the abrasive, diamond, alumina, Powders such as silicon carbide, iron oxide, and chromium oxide are used. In particular, a textured surface of a magnetic hard disk requires a polished surface having a uniform width and depth.

However, the conventionally manufactured polishing tape for texturing a hard disk has a polishing layer having a multilayer structure, and a uniform surface structure in which particles are in close contact with each other or a paint as shown in FIGS. It has a Benard cell structure caused by shrinkage during drying. However, when viewed microscopically, the surface is never uniform, and agglomerates of abrasive particles protrude from the surface of the polishing layer in many places, and there are concave holes in the center of the cell, Since the portions are groove-shaped, the cohesive force of the coating film is weakened, and the coated films fall off as agglomerates during polishing, resulting in deep scratches and scratches. Furthermore, since the coating film of the Benard cell structure has low strength, the coating film is crushed by the tape tension when wound in a tape shape, and the coating film structure is considerably different at the beginning and end of the winding, and the polishing characteristics are different, so that the tape is different from the beginning of the tape. There is a problem that the polished surface varies from the end of the winding.
Agglomerates are also likely to fall off from the tape edge, which also causes scratches.

In the case of a polishing method in which the surface structure of a polishing tape is directly transferred as a polishing surface, such as texturing of a hard disk, uniformity of the polishing surface of a polishing film is most important. However, it is difficult to obtain surface uniformity with a conventional multi-layer polishing film having a Benard cell structure.

In particular, as it has recently become necessary to increase the recording density by finishing the surface of the hard disk as precisely as possible, the surface roughness of the texturing surface has been reduced to 20%.
It must be controlled within the range of ~ 100ÅRa (the lower limit is the surface roughness required to prevent the magnetic head from sticking to the hard disk when the magnetic head starts running). Scratches need to be further suppressed on such smooth surfaces. For this purpose, no agglomerates should be present on the surface of the polishing film.

To solve this problem, the present inventor has previously filed Japanese Patent Application No.
No. 58392 (filed on Mar. 14, 1988) proposed a polishing film having a single-layer structure abrasive layer. Briefly, the abrasive film is obtained by uniformly dispersing and adhering abrasive particles as substantially single-layered and discrete particles on a base (substrate) such as a polyester film, and thereby using the abrasive particles. It is possible to manufacture a polished surface having substantially only the roughness according to the average particle size and the particle size distribution of the abrasive to be polished. That is, the surface polished by the polishing tool has uniform polishing streaks without any abnormal scratches. The polishing tool is
Since the surface density of the abrasive particles is low and the contact area between the polishing layer and the surface to be polished is small, even under the same pressure, the polishing grooves (texturing Grooves) become deeper, and the friction with the object to be polished is reduced, so that the sharpness is improved and the finished surface condition is improved. Further, since there is a gap between the abrasive particles, the gap between the particles acts as a chip pocket, so that clogging can be prevented and the durability is improved.

However, it was found that the polishing tool described in Japanese Patent Application No. 63-58392 had insufficient polishing efficiency.

(Object of the Invention) An object of the present invention is to provide a surface to be polished, particularly a surface roughness of a texturing surface of a hard disk, within a range of 20 to 100 ° Ra, and to give a deep scratch, a discontinuous line or a damage such as a scratch. An object of the present invention is to provide a polishing tool such as a polishing film which facilitates control of processing (polishing width, polishing depth) of a hard disk without using the same.

(Summary of the Invention) The present invention has a coating film in which abrasive particles are dispersed in a binder resin, and has only one or less superimposed particles per 100 particles on a base, and an abrasive particle concentration of 50% or more per unit area ( A polishing tool for texturing a magnetic disk, characterized in that a polishing layer formed by bonding with a substantially single-layer structure is formed in an area occupancy ratio.

According to the polishing tool of the present invention, the average particle diameter of the abrasive used, having substantially only the surface roughness according to the particle size distribution,
Not only enables the formation of a polished surface with no abnormal scratches and a uniform polishing streak, but also increases the extreme pressure applied to each particle to increase polishing efficiency, and furthermore, because it has no Benard structure, pressure Therefore, constant polishing characteristics can be achieved at all times. For example, even if the polishing tool of the present invention is formed in a long tape shape, the effects of the tape tension and the winding pressure are small and the polishing characteristics are not changed at any portion, and therefore, the advantage that the labor required for tape replacement is reduced is obtained.

Since the polishing tool of the present invention has a much higher abrasive particle surface density than the polishing tool of the above-mentioned patent application, the polishing efficiency is high, but since the single-layer structure is maintained, the polishing particles still have Since there is a gap, the gap between the particles acts as a chip pocket to prevent clogging and improve durability.

In particular an average particle diameter (D ₅₀₎ of the abrasive particles are obtained good polishing effect of a certain the time stability in the range of 1 to 6 m. This time stability is important for always obtaining a certain texturing effect.

(Detailed Description of the Invention) In the above-mentioned Japanese Patent Application No. 63-58392 (Japanese Patent Application Laid-Open No. 1-234169), it was pointed out that it is important that the abrasive particles have a single-layer structure. Most important. However, in that application, it is believed that the abrasive particles should be as discrete as possible. This is because when the abrasive particles were close together, the number of superimposed particles would be correspondingly increased to increase polishing flaws. However, the present inventor has found from subsequent studies that if the method of applying the mixture of the abrasive particles and the binder to the substrate is appropriate, there is a method capable of maintaining the single-layer structure even when the abrasive particles contact each other. Was found, and the present invention was able to be led.

FIGS. 3 and 4 are a plan view and a cross-sectional view, respectively, showing a part of the uniform application type polishing tool of the present invention. FIGS. 5 and 6 show the non-uniform application type polishing tool of the present invention. It is a top view and a sectional view. These polishing tools are preferably made of plastic film, nonwoven fabric, metal foil, metal plate, glass plate, etc.
25-50 μm polyethylene terephthalate film (PE
T) A coating material obtained by dispersing abrasive particles 2 in a binder resin 3 on a base 1 in such a manner that the abrasive layer is substantially a single layer and the abrasive particles are brought into contact in the in-plane direction as much as possible. It has a structure formed by applying so that abrasive particles are present at a high density. Here, a single layer means that there is substantially no superposition of particles, and preferably two or more superposed portions of particles are suppressed to 1 or less per 100 particles, more preferably 1 or less per 1000 particles. . This allows
Probability of generation of scratches (deeper and / or wider scratches) or scratches different from normal polishing streaks due to single particles with respect to the surface roughness of the polished surface of the object to be polished determined by the average particle size of the abrasive particles Is greatly reduced, and high-precision polishing can be achieved. What must be avoided in the present invention is that the abrasive particles overlap one another up and down to form abnormal protrusions.

Such a single-layer abrasive layer can be relatively easily formed by adjusting appropriate polymer binders, solvents, dispersants, their mixing ratios, coating means, coating amounts, etc. without using a special method. It turns out that it can be realized. The uniform abrasive distribution shown in FIGS. 3 and 4 or the non-uniform abrasive distribution shown in FIGS. 5 and 6 can be realized by adjusting the above-mentioned factors. In any case, it is important that the abrasive particles have a high density as they come into contact with each other, and it is not a superposition whether the abrasive particles have a uniform distribution or a non-uniform distribution.

The base can be processed into an arbitrary shape such as a tape, a sheet, and a disk.

Examples of the abrasive include diamond, CBN, silicone carbide, single crystal alumina, pulverized fused alumina, chromium oxide, iron oxide, cerium oxide, and the like, and particularly preferred is fused alumina and diamond. Fused alumina is particularly preferred for texturing aluminum plates or metal plates with plated surfaces, but for texturing magnetic recording media with a magnetic recording layer applied to a thin glass substrate, use harder, for example, diamond. I knew I needed to.

The abrasive preferably has an average particle diameter (D ₅₀ ) of 1 to 12 μm, preferably 1 to 6 μm. Expressing the texturing depth of the hard disk as surface roughness Ra
Although it depends on the flexibility of the base, an average particle diameter in this range is required to make the range of 0 °. If the base is flexible, the particle size of the abrasive may be large, but if the base lacks flexibility, an abrasive having a small particle size is required.

As the binder resin, a thermosetting resin and a thermoplastic resin can be used. As the thermosetting resin, polyester or acrylic polyol urethane resin, chlorinated polypropylene-modified acrylic polyol urethane resin, acrylic
Chelate curable resin, epoxy or epoxy pendant acrylic resin + amine pendant acrylic resin, polyorganosiloxane resin, various UV curable resins, urethane oil resin, moisture-curable polyurethane resin, fluorine resin, etc. Those in which the curing reaction proceeds are suitable.

As the thermoplastic resin, pure acrylic resin, vinyl chloride resin, nitrocellulose resin, nitrocellulose
Acrylic resin, deformed acrylic resin, alkyd,
Polyolefin resins, polyester resins, urethane elastomers such as rubber resins, nitrile rubber, silicone rubber, ethylene vinyl acetate rubber, fluororubber resins, other water-soluble resins, and emulsion resins are used.
As the base film substrate, a plastic film such as polyethylene terephthalate, polyimide, polycarbonate, a film obtained by treating the surface thereof, a synthetic paper, a nonwoven fabric, a metal foil, or the like is used.

(Manufacturing Method of Polishing Tool) The abrasive particles are mixed with a binder resin and a solvent, then adjusted to an appropriate coating thickness by an appropriate coating means according to the particle size distribution of the abrasive particles, and applied to a substrate such as a film.

For example, a Meyer bar coater, a gravure coder, a reverse roll coater, a knife coater and the like can be used.

The coating thus obtained is fixed to the substrate by a drying or curing treatment.

3 and 4 show a polishing layer having a single layer structure with a uniform distribution of abrasive particles.

5 and 6 show a single-layer polishing layer having a non-uniform distribution of abrasive particles.

The polishing layer having a single layer structure of the uniform abrasive particles and the non-uniform abrasive particles was adjusted by the ratio of the dispersant in the binder resin.

 Next, examples of the present invention will be described.

Example 1 This example is an example in which a thermoplastic resin was used as a binder resin of a polishing layer in order to experimentally produce a polishing film according to the present invention. First, a coating solution having a composition shown in Table 1 was prepared. Was done.

As the abrasive particles, various types of meshes having different average particle diameters using pulverized powder of fused alumina WA were used. The abrasive particles used were as follows.

_{WA2500 (D 50 = 6.0μm) WA3000} (D 50 = 4.5μm) WA4000 (D 50 = 3.0μm) WA6000 (D 50 = 2.0μm) A coating liquid having a composition shown in Table 1 (polyester resin is V200 manufactured by Toyobo Co., Ltd.) is applied on a 25 μm-thick polyethylene terephthalate film with a gravure roll coater at an application thickness corresponding to various particle sizes, and the solvent is dried. Then, it was slit into a predetermined width, processed into a tape shape, and subjected to texturing polishing of a nickel-plated substrate for a hard disk. Table 2 and Table 3
Represents the measurement results of the surface roughness of the uniform distribution type and the non-uniform distribution type polishing tape. Average of all several samples. The polishing tapes of the uniform distribution type and the non-uniform distribution type have almost the same surface roughness as long as they have a single layer structure, and the average particle diameter (D ₅₀ ) of the particles used and the surface roughness difference Rz are almost equal.
Takes a value smaller than the maximum particle size of the abrasive. The uniform distribution type polishing tape has a structure in which abrasive particles are uniformly distributed on a single layer to a base by a dispersant. A non-uniform polishing tape has a structure in which abrasive particles are present in a single layer on a base, but relatively large particles are aggregated, and fine particles fill gaps in the aggregate.

In the table, Ra, Rz, and Rmax represent surface roughness according to JIS standards.

Next, when a micrograph of the cut surface of the above-mentioned polishing tape was observed, the superposition of the abrasive particles was 1 or less per 100 in all the polishing tapes.

Comparative Example 1 Using the abrasive particles used in Example 1, a hard disk was subjected to texturing polishing using a multilayer high-density type abrasive tape having a Benard cell structure manufactured by an ordinary method, and the present invention was applied thereto. The comparison was made with the polishing tape of Example. When the hard disk was subjected to texturing with the polishing tape of the example under such a condition that a polishing surface as shown in Table 4 was obtained using this polishing tape,
The results of Tables 5 and 6 were obtained.

In the table, the abnormal number indicates the number of conspicuously-sized scuffs, and the number of scratches indicates the number of streaks larger than a normal polishing streak.

As is clear from the above table, it can be seen that the polishing tape having the polishing layer of the single-layer structure of the present invention provides a surface to be polished consisting of only ordinary polishing streaks.

Next, in the polishing tests of Tables 4, 5, and 6, changes over time in polishing time and surface roughness were examined. The result is the average of several samples. The results are shown in the graph of FIG. As is clear from the figure, the conventional product reaches a certain surface roughness in about 30 seconds, while the product of the present invention reaches the target surface roughness in about two-thirds of the time.

Example 2 Next, the amount of the abrasive coating material of Example 1 applied per unit area was changed in a stepwise manner in order to examine how much the superimposed particles were allowed. Sections were taken of those showing minimal scratches and observed under a microscope, and found to be usable for hard disk texturing when the average was less than one per hundred.

FIG. 8 shows the relationship between the number of scratches (relative value) and the number of superposed particles per unit area. From the figure, it was confirmed that scratches disappeared when the number of superimposed particles was reduced by one per 100 particles.

Example 3 In this example, a thermosetting resin was used as a binder resin of a polishing layer, and diamond was used as a polishing material. First, a coating liquid having a composition shown in Table 7 was prepared. .

Diamond particles were used as abrasive particles,
Two different ones, 6 microns and 6-12 microns, were used. In this example, the particle diameter is not an average diameter, but represents a powder having an extremely sharp particle size distribution, which means that particles substantially outside this range do not exist.

A gravure roll coater was used to apply a coating liquid having the composition shown in Table 1 (a thermosetting resin used was a polyurethane prepolymer (manufactured by Nippon Polyurethane Co., Ltd.). 25 μm
On a polyethylene terephthalate film with a thickness of 3 mm, applying a coating thickness according to various particle diameters, drying the solvent, heat curing,
It was slit into a predetermined width and processed into a tape shape. The particles had a substantially uniform distribution type single layer structure in which a large number of particles partially contacted each other.

Next, when a micrograph of the cut surface of the polishing tape was observed, the superposition of the abrasive particles was not more than 1 per 1000 particles in all the polishing tapes.

Next, these polishing tapes were subjected to texturing polishing of a 3.5-inch glass disk substrate for a hard disk. As processing conditions, while applying a certain pressure to the polishing tape and flowing the polishing liquid, at a feed rate of the polishing tape of 150 mm / min,
The polishing test was performed by changing the number of revolutions, the polishing time, and the frequency of the disk space spindle (the frequency when the polishing tape was vibrated between the inner edge and the outer edge of the polished surface of the disk). None of the samples scratched. Table 8 shows the results of measuring the surface roughness. The measurement was performed on the center of the disk (the middle circle between the inner and outer peripheral surfaces).

From the above table, the values of Ra are all 100 ° or less even after a polishing time of 60 seconds, so that they can be used for texturing suitable as a polishing tool of the present invention. Also from the table, the surface roughness Ra depends on time
Gradually increases, but at a particle diameter of 4 to 6 μ, the particle diameter is
For a particle size of ~ 12μ, the particle size is 80μ or less, and can be used properly depending on the required texturing.

Example 4 Next, an abrasive was applied to a polyethylene terephthalate base having a thickness of 25 μm and 50 μm in the same manner as in Example 3 to produce a thermosetting polishing tape, and other polishing experiments were performed using these. Was. The polishing tape was polished without vibration. No scratch occurred in any case. The measurement results of the surface roughness are shown in the graphs of FIGS. These figures respectively show the relationship between the polishing time and the surface roughness ÅRa of the polished surface at the center, inner circumference, and outer circumference of the disk. From these figures, it can be seen that when the base is thin, the stability of the surface roughness can be obtained for a relatively long time even when the abrasive has a particle diameter of 6 to 12 μm, but when the base is thick, an abrasive having a too large particle diameter is inappropriate. You can see that. Conversely, it can be seen that when the base is thin and the particle size of the abrasive is small, the stability of the surface roughness can be obtained. Texturing less than Ra100Å base thickness 50
It cannot be obtained with a combination of μm and a particle size of the abrasive of 6 to 12 μm, but is obtained in other cases.

(Operation and Effect) As described above, according to the present invention, the following operation and effect can be achieved.

1) Since the abrasive particles are adhered to the base in a state where the abrasive particles are substantially a single layer and are dispersed as uniformly as possible in the resin, the abrasive tape has a surface roughness according to the particle size distribution and shape of the abrasive particles. And the control of the shape of the work surface is facilitated.

2) Since the abrasive particles have a single-layer structure, there is no portion that falls off as an agglomerate during polishing as compared with a conventional polishing tool, so that damages such as deep scratches and scratches and discontinuous lines are given. It became possible to obtain a uniform texturing without any.

3) On the surface of the conventional Benard cell structure, when a tape-shaped polishing tool is used as a slit in the form of a tape, the coating is crushed due to fluctuations in tape tension and winding pressure, and the surface state changes between the beginning and end of the winding. However, with the single-layer structure of the present invention, the same polished surface can always be obtained without such a problem. Since there is no change in the polishing surface due to the other tape tension, the length of the polishing tool can be increased, the time for exchanging the polishing tool can be shortened, and the working efficiency can be increased.

4) In a conventional tape-shaped polishing tool having a Benard cell structure, the abrasive aggregates easily fall off from the tape edge and cause scratching. However, in the polishing tool of the present invention, there is no such a problem because the aggregates do not exist. .

5) Despite the fact that the polishing layer of the polishing tool of the present invention has a single-layer structure, the particles are in a dense state in which they come into contact with each other in the in-plane direction. The polishing efficiency is higher than the layer structure, and the polishing time can be reduced.

[Brief description of the drawings]

1 is a plan view showing an outline of a conventional polishing tool, FIG. 2 is a sectional view thereof, FIG. 3 is a plan view of a polishing tool according to an embodiment of the present invention, FIG. Is a plan view of a polishing tool according to another embodiment of the present invention, FIG. 6 is a cross-sectional view, FIG. 7 is a graph showing the relationship between polishing time and surface roughness of the polishing tool of the present invention and a conventional polishing tool, and FIG. A graph showing the relationship between the number of scratches (relative value) and the number of superimposed particles per unit area, and FIG.
10 and 11 are graphs showing the relationship between the polishing time and the surface roughness of the central portion, the inner peripheral portion and the outer peripheral portion of the surface to be polished, respectively.

Continuation of the front page (56) References JP-A-63-169270 (JP, A) JP-A-63-185579 (JP, A) JP-A-1-205978 (JP, A) JP-A-62-94271 (JP) , A) Actual opening 621-253053 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24D 11/00

Claims (4)

(57) [Claims] 1. A coating film in which abrasive particles are dispersed in a binder resin has only one or less superimposed particles per 100 particles on a base and an abrasive particle concentration of 50% or more per unit area (area occupancy). A polishing tool for texturing a magnetic disk, characterized in that a polishing layer formed by bonding with a substantially single-layer structure is formed. 2. The polishing tool according to claim 1, which is used with abrasive particles having an average particle diameter (D ₅₀ ) of 1 to 6 μm. 3. The polishing tool according to claim 1, wherein the abrasive particles are uniformly applied on the base. 4. The polishing tool according to claim 1, wherein the abrasive particles are unevenly applied on the base.