JP2003170349A - Composition for polishing of substrate for magnetic disc and polishing method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for polishing of a substrate for a magnetic disc capable of maintaining polishing speed at the early stage of polishing work by restraining blinding of a polishing pad in the middle of the polishing work and capable of restraining growth of a surface defect on the substrate for the magnetic disc after the polishing work and a polishing method using it. <P>SOLUTION: The composition for polishing of the substrate for the magnetic disc contains (a) at least one kind of organic acid selected from glycine, glycerin acid, etc., and (b) at least one kind of organic acid selected from glycine, malic acid, etc., and different from the component (a). Or, it contains (e) at least one kind of organic acid selected from a malic acid, glycol acid, etc., and (f) at least one kind of organic acid selected from citric acid, iminodiacetic acid, etc. It is devised to manifest polishing work promoting action and sodimentation restraining action well in balance by containing these organic acid well- combined. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for polishing a magnetic disk substrate used in the manufacture of a magnetic disk used as a storage device of a computer and the like, and a polishing method using the same.

[0002]

2. Description of the Related Art Magnetic disks such as memory hard disks are used in computers and information home appliances. The magnetic disk substrate (hereinafter also referred to as the substrate) used when manufacturing this magnetic disk is
It is manufactured by forming a film such as electroless Ni-P plating on a substrate (blank material) made of a metal material such as aluminum.

In this case, since the plating film is formed along the irregularities on the surface of the blank material such as undulations and scratches which occur when the blank material is manufactured, the undulations and irregularities may remain on the surface of the substrate. is there. In order to remove the undulations and irregularities and smooth the surface of the substrate, the substrate is polished using a polishing composition for a magnetic disk substrate (hereinafter, also simply referred to as a polishing composition). There is.

By the way, with the recent increase in capacity of magnetic disks, the surface quality required for the substrate surface after polishing has become more and more severe, and the surface roughness varies depending on the grade of the magnetic disk. At present, the surface roughness measured by AFM (Digital Instruments, Inc. (USA)), which is a stylus surface roughness meter, reaches Ra = 10 Å or less. Therefore, the accuracy required for the substrate surface after polishing is extremely severe, and a polishing composition that can obtain a smoother polished surface is required.

Further, since the magnetic disk is required to be low in price, the cost is also reduced in the manufacturing process of the substrate. Therefore, the polishing pad does not become clogged during the polishing process of the substrate,
There is a demand for a polishing composition capable of stably polishing a substrate for a long time.

Here, the clogging of the polishing pad means the polishing material in the polishing composition during the polishing process of the substrate and the cutting chips in the waste liquid (the surface material to be polished such as plating removed by the polishing process). ) Is deposited on the surface of the polishing pad.

Conventionally, this type of polishing composition has a structure as shown in JP-A-7-216345 (first conventional structure) and JP-A-2000-1665 (second conventional structure). Things are known. The first conventional polishing composition contains water, an alumina-based abrasive, and a polishing accelerator containing a molybdate and an organic acid. On the other hand, the second conventional composition for polishing contains at least one abrasive selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and manganese dioxide, and water, Further, this composition contains succinic acid or a salt thereof dissolved therein.

All of these conventional polishing compositions have a high polishing rate, and by polishing the substrate with each polishing composition, the surface of the substrate such as fine projections and fine pits is processed. It is possible to suppress the occurrence of defects.

[0009]

However, in these conventional polishing compositions, when polishing a substrate using each polishing composition, when the polishing composition of the substrate is polished There is a problem in that clogging may occur, which lowers the polishing rate, making it difficult to perform polishing under certain conditions.

Further, there has been a problem that irregularities such as pits and minute projections and surface defects such as scratches are likely to occur on the surface of the substrate. Therefore,
Since it is necessary to frequently clean the polishing pad called dressing, the productivity of the substrate is significantly reduced.

The present invention has been made by paying attention to the problems existing in the prior art as described above. The purpose of this is to suppress the clogging of the polishing pad during the polishing process to maintain the polishing rate at the beginning of the polishing process and to suppress the occurrence of surface defects on the magnetic disk substrate after the polishing process. A polishing composition for a magnetic disk substrate and a polishing method using the same.

[0012]

In order to achieve the above object, the polishing composition for a magnetic disk substrate according to the present invention is a polishing composition used in the polishing process of a magnetic disk substrate. (A) Glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, gluconic acid, succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotine At least one organic acid selected from acids, and (b) at least one selected from glycine, malic acid, lactic acid, gluconic acid, tartaric acid, maleic acid, itaconic acid and crotonic acid, and (a)
Containing an organic acid different from (c) at least one abrasive selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide, and (d) water Is.

The composition for polishing a magnetic disk substrate according to the second aspect of the present invention is the same as the first aspect of the present invention.
The organic acid of the component (b) is at least one organic acid selected from glycine, malic acid, lactic acid and gluconic acid.

The composition for polishing a magnetic disk substrate according to the third aspect of the present invention is the composition according to the first or second aspect, wherein the organic acid as the component (a) is malic acid, glycolic acid and It is at least one organic acid selected from succinic acid.

The composition for polishing a magnetic disk substrate according to a fourth aspect of the present invention is the component (a) and the component (b) according to any one of the first to third aspects of the invention.
The content of each is 0.01 to 10% by weight.

A polishing composition for a magnetic disk substrate according to a fifth aspect of the present invention is a polishing composition used in the polishing process for a magnetic disk substrate, comprising (e) glycine, glyceric acid and mandelic acid. , Ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid,
At least one organic acid selected from gluconic acid, succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotinic acid, and (f) citric acid, iminodiacetic acid, malonic acid, oxalic acid, alanine and propionic acid. At least one organic acid selected from (g) at least one abrasive selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide; and (h) water. Is included.

The magnetic disk substrate polishing composition of the invention of claim 6 is the same as that of the invention of claim 5,
The organic acid of the component (f) is at least one organic acid selected from citric acid and iminodiacetic acid.

A polishing composition for a magnetic disk substrate according to a seventh aspect of the present invention is the same as the sixth aspect of the present invention.
The organic acid of component (f) is citric acid. The composition for polishing a magnetic disk substrate according to the invention of claim 8 is the composition according to any one of claims 5 to 7,
The organic acid of the component (e) is at least one organic acid selected from malic acid, glycolic acid and succinic acid.

The composition for polishing a magnetic disk substrate according to the invention of claim 9 is the same as the composition according to any one of claims 5 to 8, wherein the content of the component (e) is 0.
The content of component (f) is 0.01 to 5% by weight, while the content is 01 to 10% by weight.

A polishing composition for a magnetic disk substrate according to a tenth aspect of the present invention is a polishing composition used for polishing a magnetic disk substrate, comprising (i) itaconic acid and (j). Glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, gluconic acid, succinic acid, tartaric acid, maleic acid, crotonic acid, nicotinic acid, citric acid,
At least one organic acid selected from iminodiacetic acid, malonic acid, oxalic acid, alanine and propionic acid,
(K) at least one abrasive selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide;
(L) It contains water.

In the composition for polishing a magnetic disk substrate according to the eleventh aspect of the present invention, in the invention according to the tenth aspect, the organic acid as the component (j) is an organic acid containing at least citric acid.

In the polishing composition for a magnetic disk substrate according to the twelfth aspect of the present invention, in the invention according to the eleventh aspect, the organic acid as the component (j) is an organic acid containing at least succinic acid.

According to a thirteenth aspect of the present invention, there is provided a method for polishing a magnetic disk substrate, which comprises polishing the magnetic disk substrate using the polishing composition according to any one of the first to twelfth aspects. Is.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below.

The magnetic disk substrate polishing composition of the first embodiment includes (a) glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, gluconic acid. At least one organic acid selected from succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotinic acid, and (b) glycine, malic acid, lactic acid, gluconic acid, tartaric acid, maleic acid, itaconic acid and croton An organic acid which is at least one selected from acids and which is different from (a) above, and (c) aluminum oxide, silicon dioxide,
It contains at least one abrasive selected from cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide, and (d) water.

The organic acid as the component (a) is contained as a polishing processing accelerator for promoting the polishing processing of the substrate by the mechanical operation of the polishing material described later by etching the surface of the substrate by a chemical operation. To be done. Specific examples of the organic acid as the component (a) include those mentioned above. Among these, at least one organic acid selected from malic acid, glycolic acid and succinic acid can be obtained because a large polishing rate can be obtained. Is preferred. The organic acid as the component (a) may be contained alone,
You may contain in combination of 2 or more.

Subsequently, the organic acid as the component (b) has a function of the organic acid as the component (a), and also disperses the abrasive in the polishing composition and the cutting chips in the waste liquid by a chemical action, These are contained as a sedimentation inhibitor for suppressing the deposition on the surface of the polishing pad. Specific examples of the organic acid as the component (b) include those mentioned above. Among them, at least selected from glycine, malic acid, lactic acid, and gluconic acid because of high dispersibility of the abrasive and the cutting powder. One organic acid is preferred. The organic acid as the component (b) may be contained alone or in combination of two or more.

The content of each organic acid of component (a) and component (b) is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, most preferably 0.1 to 5% by weight. It is 3% by weight. If it is less than 0.01% by weight, the polishing rate of the polishing composition tends to decrease, and
Even if the content exceeds 5% by weight, the polishing rate is difficult to further improve, and therefore the polishing cost is likely to increase.

Next, the abrasive of the component (c) is contained in order to polish the substrate surface etched by the organic acid of the components (a) and (b) as a processing accelerator by mechanical action. It Specific examples of the abrasive include those mentioned above. Among them, aluminum oxide or silicon dioxide is preferable because it is inexpensive and easily available.

The particle size of the abrasive is such that when the abrasive is aluminum oxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide, a laser diffraction particle size analyzer LS-230 (Coulter, USA )
The average particle size (D50) is preferably 2 μm or less, more preferably 0.01 to 1.
It is 5 μm, most preferably 0.05 to 1.0 μm.

When the abrasive is silicon dioxide, the average particle size (D50) calculated from the specific surface area measured by the BET method is preferably 0.005.
0.5 μm, more preferably 0.01 to 0.3 μm,
Most preferably, it is 0.05 to 0.2 μm.

If the particle size of these abrasives is less than 0.01 μm (aluminum oxide or the like) or less than 0.005 μm (silicon dioxide), the polishing rate will be small, so that it takes a long time to perform a predetermined polishing process, and the substrate is not processed. The outer peripheral portion is more often polished than at least one of the central portion and the inner peripheral portion, so that surface sagging is likely to occur. Further, the consumption of the polishing composition consumed in a predetermined polishing process increases,
Polishing cost tends to increase. On the other hand, when it exceeds 2 μm (aluminum oxide or the like) or 0.5 μm (silicon dioxide), the surface roughness of the substrate after polishing is increased and scratches are easily generated.

Further, the abrasive preferably does not contain coarse particles having a particle size of 5 μm or more in order to suppress the generation of surface defects on the substrate after polishing and to reduce the surface roughness.

The content of the abrasive is preferably 0.1 to 40.
% By weight, more preferably 1 to 30% by weight, most preferably 5 to 25% by weight. If it is less than 0.1% by weight, the mechanical action of the polishing composition is weakened and the polishing rate tends to be low. On the other hand, if the content exceeds 40% by weight, the viscosity of the polishing composition and the waste liquid tends to increase, and the handling tends to be difficult. Further, the polishing pad is apt to be clogged, and the polishing rate is lowered to easily cause surface defects.

Here, the aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide given as specific examples of the abrasive will be further described.

Specific examples of aluminum oxide include α-
Examples include aluminum oxide, δ-aluminum oxide, θ-aluminum oxide, κ-aluminum oxide, amorphous aluminum oxide and the like which are different in form. Among these, α-aluminum oxide or a substance containing α-aluminum oxide as a main component is preferable because of its high hardness. Examples of the method for producing aluminum oxide include a method of sintering an aluminum compound such as aluminum hydroxide and a method of further melting the sintered product.

Subsequently, as a specific example of silicon dioxide,
Examples include colloidal silica, fumed silica, precipitated silica and the like, which have different production methods and properties. Among these, colloidal silica is preferable because it has high hydrophilicity and is less likely to cause surface defects such as scratches. As a method for producing this colloidal silica, for example, there is a method of growing particles of ultrafine particle colloidal silica in which sodium silicate is ion-exchanged, or a method of thermally decomposing an organic silicic acid compound.

The colloidal silica can maintain its colloidal state even at a high concentration by adjusting the pH thereof by adding at least one selected from acids and alkalis or by ion exchange of the colloidal silica.
Commercially available colloidal silica is a monodisperse product,
Examples thereof include particles having some particles bound to each other and having an association ratio, and particles having a high purity with a reduced content of metal impurities.

Specific examples of cerium oxide include trivalent and tetravalent cerium oxides, and hexagonal, equiaxed and face-centered cubic systems from the viewpoint of crystal system. Is mentioned. Further, specific examples of zirconium oxide include those having different forms such as monoclinic system, tetragonal system, and amorphous, and those referred to as fumed zirconia from the manufacturing method. Further, specific examples of the titanium oxide include titanium monoxide, dititanium trioxide, titanium dioxide and the like having different forms, and those referred to as fumed titania from the manufacturing method.

Specific examples of silicon nitride include α-silicon nitride, β-silicon nitride and the like having different forms. Incidentally, it is generally said that α-silicon nitride is easy to obtain fine particles by pulverization, and β-silicon nitride has a high hardness. The method for producing silicon nitride includes a method for reducing silicon oxide and carbon powder in nitrogen gas, a method for directly heating metallic silicon in nitrogen gas, and a method for reacting silicon tetrachloride with ammonia (imide decomposition method). Etc.

Specific examples of silicon carbide include α-silicon carbide, β-silicon carbide and the like which are different in form. Incidentally, GC (green silicon carbide) and C (black silicon carbide) generally used as abrasives are α-silicon carbide. Examples of the method for producing silicon carbide include a method of reducing silicon oxide with carbon and a method of directly reacting metallic silicon with carbon.

When each of these compounds is contained as an abrasive, each compound may contain one kind selected from those having different forms, production methods and properties, or two compounds having different forms, production methods and properties. You may contain it in combination of 1 or more types.

Water is contained as a solvent for the organic acid and a dispersion medium for the abrasive. The water is preferably as free of impurities as possible, and specifically, ion-exchanged water filtered or distilled water is preferable.

The pH of the polishing composition is preferably in the range of 2-7. If the pH is less than 2, a machine used for polishing such as a polishing machine is likely to be corroded. If the pH exceeds 7, the polishing rate of the polishing composition tends to decrease, and the surface roughness of the substrate after polishing may increase or scratches may easily occur. Therefore, when the pH of the polishing composition is less than 2 or exceeds 7, it is preferable to adjust the pH of the polishing composition within the above range by adding an acid or an alkali to the polishing composition.

The polishing composition may further include other additives such as cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and other celluloses, ethanol,
Water-soluble alcohols such as propanol and ethylene glycol, surfactants such as sodium alkylbenzene sulfonate, formalin condensate of naphthalene sulfonic acid, organic polyanion substances such as lignin sulfonate and polyacrylate, water-soluble polyvinyl alcohol, etc. Polymers (emulsifiers), dimethylglyoxime, dithizone, oxine, acetylacetone, glycine, chelating agents such as EDTA, NTA, bactericides such as sodium alginate and potassium hydrogen carbonate, aluminum sulfate, nickel sulfate, aluminum nitrate, nickel nitrate Inorganic salts such as iron nitrate and ammonium molybdate, aqueous processing oils such as higher fatty acid amines, sulfonates, aqueous processing oils containing rust preventives and the like may be contained. The content of these other additional components is
It is determined according to a conventional method for the polishing composition.

The polishing composition is prepared by mixing and dispersing each component other than water in water. Specific examples of the mixing and dispersing include stirring with a blade stirrer, ultrasonic dispersion, shear stirring with a homomixer, and the like. Regarding the mixing order of the components other than water, all of them may be mixed at the same time, or one of them may be mixed later.

Now, a method for producing a memory hard disk as a magnetic disk and a method for polishing a magnetic disk substrate using the polishing composition will be described. When manufacturing a memory hard disk, first, a base film for plating such as electroless Ni-P plating is formed on the surface of a blank material. Next, the surface of the substrate is polished by using the polishing composition. The polishing method and polishing conditions at this time are in accordance with the ordinary method for polishing a substrate. Further, specific examples of the polishing machine used for polishing include a single-sided polishing machine and a double-sided polishing machine, and specific examples of the polishing pad include suede type, non-woven fabric type, woven fabric type, flocked type, and brushed type. Etc.

Specific examples of the substrate to be polished include Ni-P disk, Ni-Fe disk, boron carbide disk, carbon disk and the like. Among these, since they are inexpensive and easily available, Ni-P on which the electroless plating of Ni-P is formed on the surface of a blank material made of aluminum, aluminum alloy, or the like
P discs are particularly preferred.

Then, using a polishing composition such as a fine diamond powder, a processing accelerator, and water, etc., a texture processing composition was used to form concentric lines along the rotation direction of the memory hard disk on the substrate surface. To form a texture. Thus, a memory hard disk is manufactured by forming a magnetic film and a protective film on the surface of the substrate on which the lines are formed.

In recent years, memory hard disks are required to have higher capacities, and therefore it is required to smooth the substrate surface more than ever. Therefore, the polishing process may be performed in two steps.
In the polishing process of the second stage, the polishing process is performed for the purpose of removing waviness of the substrate and surface defects such as large scratches and irregularities on the surface of the substrate which cannot be removed by the final polishing process of the second stage.

On the other hand, in the second polishing process, the surface roughness was adjusted to a desired small surface roughness, and the surface defects generated in the first polishing process or the first polishing process could not be completely removed. Finish polishing is performed for the purpose of removing such surface defects. Also, depending on the case, the polishing process may be 3
It may be performed by subdividing into steps or more. The polishing composition can be used in any of these polishing steps. For example, when used in the first stage polishing process, a polishing composition having a high polishing rate is prepared by increasing the mechanical action by using an abrasive having a relatively large particle size. On the other hand, in the final polishing process from the second stage onward, a polishing composition suitable for the final polishing process is prepared by using an abrasive having a relatively small particle size to suppress the mechanical action and adjust the chemical action. To do.

Further, for the purpose of achieving a high capacity of the memory hard disk, light texture processing is performed in which the streaks formed on the surface of the substrate are made thinner,
In addition, non-textured substrates that are not textured and have no scoring are used to make memory hard disks. The polishing composition can be used in the production of either a substrate having a normal texture or the above-described light texture processing, or a non-texture substrate.

According to the first embodiment described in detail above, the following effects can be obtained. The magnetic disk substrate polishing composition of the first embodiment contains the aforementioned component (a) and component (b). For this reason,
By suppressing the clogging of the polishing pad during the polishing process, it is possible to maintain the polishing rate in the initial stage of the polishing process and to suppress the occurrence of surface defects on the substrate after the polishing process.

This is the organic acid of component (a) and component (b)
By the combination with the organic acid, the polishing process promoting action and the precipitation inhibiting action are exhibited in a well-balanced manner. Therefore,
The abrasive in the polishing composition and the cutting powder in the waste liquid are discharged from the polishing pad in a dispersed state without being deposited on the surface of the polishing pad. Therefore, the polishing rate at the initial stage of polishing processing is maintained even after stacking processing batches.

Furthermore, each organic acid acts on the surface of the abrasive and the cutting powder to suppress the adhesion and scratching of the abrasive and the cutting powder on the surface of the substrate, and the generation of surface defects such as pits and scratches. It is thought to be suppressed. (Second Embodiment) Next, a second embodiment of the present invention will be described. The second embodiment will be described focusing on the points different from the first embodiment.

The magnetic disk substrate polishing composition of the second embodiment includes (e) glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, gluconic acid. , At least one organic acid selected from succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotinic acid, and (f) selected from citric acid, iminodiacetic acid, malonic acid, oxalic acid, alanine and propionic acid. At least one organic acid, and (g) aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide,
It contains at least one abrasive selected from silicon nitride and silicon carbide, and (h) water.

The organic acid as the component (e) corresponds to the above-mentioned component (a).
It is contained for the same function expression as the organic acid. Specific examples of the organic acid as the component (e) include those mentioned above. Among these, at least one organic acid selected from malic acid, glycolic acid and succinic acid can be obtained because a large polishing rate can be obtained. Is preferred. These organic acids of component (e) may be contained alone or in combination of two or more.

The content of each organic acid as the component (e) is preferably 0.01 to 10% by weight, more preferably 0.05.
-5% by weight, most preferably 0.1-3% by weight.
If it is less than 0.01% by weight, the polishing rate of the polishing composition tends to decrease, and if it exceeds 10% by weight,
Since it is difficult to further improve the polishing rate, the polishing cost is likely to increase.

Subsequently, the organic acid as the component (f) is contained for exhibiting the same function as the organic acid as the above-mentioned component (b). Specific examples of the organic acid as the component (f) include the above-mentioned ones. Among them, at least one organic acid selected from citric acid and iminodiacetic acid has a high effect of dispersing abrasives and cutting chips. Acids are preferred, and citric acid is most preferred. These organic acids of component (f) may be contained alone or in combination of two or more.

The content of each organic acid as the component (f) is preferably 0.01 to 5% by weight, more preferably 0.05 to 5% by weight.
It is 3% by weight, most preferably 0.1 to 1% by weight. If it is less than 0.01% by weight, clogging of the polishing pad is likely to occur, and if it exceeds 5% by weight,
Since it is more difficult to suppress the clogging of the polishing pad,
Polishing cost tends to increase. (Third Embodiment) Next, a third embodiment of the present invention will be described. Note that the third embodiment will be described focusing on the points different from the first embodiment.

The magnetic disk substrate polishing composition of the third embodiment includes (i) itaconic acid and (j) glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, Glycolic acid,
At least one organic acid selected from lactic acid, gluconic acid, succinic acid, tartaric acid, maleic acid, crotonic acid, nicotinic acid, citric acid, iminodiacetic acid, malonic acid, oxalic acid, alanine and propionic acid, and (k) Aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide,
It contains at least one abrasive selected from titanium oxide, silicon nitride and silicon carbide, and (l) water.

In addition to the function of the organic acid of the above-mentioned component (b), the itaconic acid of the component (i) improves the dispersibility of the abrasive in the polishing composition by chemical action and the cutting chips in the waste liquid. By doing so, the function of particularly suppressing the clogging of the polishing pad is exhibited.

When the itaconic acid represented by the following formula (1) is dissolved in water, hydrogen ions are dissociated from the carboxyl group to become an itaconic acid ion containing two carboxyl group ions (COO ⁻ ). This itaconic acid ion acts directly on the electric charge of the cutting chips in the waste liquid or acts as a chelating agent to improve the dispersibility by preventing the cutting chips from aggregating, and to improve the performance of the polishing pad. It is considered to suppress clogging.

[0064]

[Chemical 1] The content of itaconic acid is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, and most preferably 0.1 to 1 in order to suppress clogging of the polishing pad.
% By weight. If it is less than 0.01% by weight, the polishing pad is likely to be clogged. On the other hand, even if it exceeds 5% by weight, it is difficult to further suppress the clogging of the polishing pad, so that the polishing cost is likely to increase.

Subsequently, the organic acid as the component (j) is contained for exhibiting the same function as the organic acid as the component (a). The organic acid as the component (j) may be contained alone or in combination of two or more kinds. In addition to the function of the organic acid as the component (a), the organic acid in the polishing composition may be contained. In order to improve the dispersibility of the cutting material in the abrasive and the waste liquid, it is preferable to contain at least citric acid. And in addition to these functions, in order to particularly improve the polishing rate,
It is more preferable to contain at least citric acid and succinic acid.

The citric acid represented by the following formula (2) becomes a citrate ion containing three carboxyl group ions when dissolved in water. And, by preventing the swarf and the like from aggregating by synergistically acting on the swarf and the like with the citrate ion and the above-mentioned itaconic acid ion,
It is considered to improve the dispersion performance.

[0067]

[Chemical 2] In addition, succinic acid represented by the following formula (3) has a higher etching power than other organic acids of the component (j). When the organic acid as the component (j) contains at least citric acid and succinic acid, citric acid and itaconic acid further enhance the etching power of succinic acid, so that the polishing rate can be improved. Conceivable. Therefore, the polishing rate can be further improved as compared with the case where the organic acid as the component (j) does not contain citric acid and succinic acid.

[0068]

[Chemical 3] The content of each organic acid of the component (j) is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, and most preferably 0.1 to 10% by weight in order to improve the polishing rate.
It is 3% by weight. If it is less than 0.01% by weight, the polishing rate tends to decrease. On the other hand, if the content exceeds 10% by weight,
Since it is difficult to further improve the polishing rate, the polishing processing cost tends to increase.

Therefore, since the magnetic disk substrate polishing composition of the third embodiment contains the above-mentioned component (i) and component (j), the polishing pad of It is possible to particularly suppress clogging. Therefore, the pad life of the polishing pad can be improved. Further, it is possible to maintain the polishing rate at the initial stage of the polishing process and to suppress the occurrence of surface defects on the substrate after the polishing process.

The above embodiment may be modified as follows. In the magnetic disk substrate polishing composition of each embodiment, the polishing composition may be prepared as a stock solution having a relatively high concentration and diluted with water when used for polishing. According to this structure, it is possible to improve handleability during storage and transportation.

[0071]

EXAMPLES Next, the above-mentioned embodiment will be described more specifically with reference to Examples and Comparative Examples. (Examples 1 to 33 and Comparative Examples 1 to 15) Examples 1 to 33
Then, each organic acid shown in Table 1 was mixed and dispersed in ion-exchanged water to prepare polishing compositions. On the other hand, Comparative Example 1
In Nos. 15 to 15, each organic acid and each compound shown in Table 2 were mixed and dispersed in ion-exchanged water to prepare polishing compositions. Here, in Comparative Examples 1 to 4, colloidal alumina or ammonium molybdate was added as a compound for the purpose of improving the dispersibility of the polishing composition and the waste liquid and suppressing the generation of surface defects. Further, in the polishing compositions in each row of Tables 1 and 2, 20% by weight of aluminum oxide having an average particle diameter of 0.8 μm was blended as an abrasive so that the total amount of each polishing composition was 100% by weight. Was prepared.

With respect to the polishing compositions in each row of Tables 1 and 2, after measuring the pH and performing the preliminary polishing of the following (1), the following items (2) to (5) were evaluated. In the following (2) to (5), when polishing a substrate, the polishing composition in each row of Table 1 and Table 2 was diluted with 4-fold amount of ion-exchanged water.
The results are shown in Tables 1 and 2.

(1) Preliminary polishing One side of the substrate was preliminarily polished for 5 minutes using the polishing composition in each row of Table 1 and Table 2. The weight of the substrate was measured before and after polishing, and the polishing rate (R ₀ ) calculated from the difference (weight reduction), the specific gravity of the electroless Ni-P plating, the area of the substrate, and the processing time.
Therefore, the substrate for each polishing composition of each example is 1 μm
The processing time required for polishing was calculated. The other conditions for polishing are as follows.

Machine: One-side polishing machine (plate diameter φ300m
m, manufactured by Udagawa Iron and Steel Co., Ltd. Polishing object (substrate): φ3.5 “electroless Ni−
P-plated disc polishing pad: BELLATRIX N0048 (manufactured by Kanebo) Load: 90 g / cm ² Number of revolutions: 100 rpm Polishing composition dilution ratio: 5-fold dilution (polishing composition: deionized water = 1: 4) Polishing composition Material supply rate: 4 cm ³ / min (2) Reduction rate of polishing rate Using the polishing compositions in each row of Tables 1 and 2, 300 substrates were continuously polished. Here, the substrate to be polished was replaced with a new one for each batch, and the processing time in each batch was the processing time obtained in the preliminary polishing in (1) above. The polishing conditions other than the processing time are the same as those in the preliminary polishing.

In the 300th batch, the polishing composition of each row was determined from the weight reduction of the substrate by polishing, the specific gravity of the electroless Ni-P plating, the area of the substrate and the processing time, as in the case of the above-mentioned preliminary polishing. The polishing rate (R ₃₀₀ ) for each was calculated. Then, the polishing rate reduction rate was obtained from the following formula.

[Reduction rate of polishing rate] (%) = [1-R ₃₀₀
/ R ₀ ] × 100 When the polishing rate reduction rate obtained by the above formula is less than 10%, ⊚, 10% or more and less than 20% is ◯, 20% or more and less than 30% is Δ, and 30% or more. The thing was evaluated as x and four steps. In Tables 1 and 2, the "reduction rate of polishing rate" is referred to as "reduction rate".

(3) Dispersibility In the above (2), the waste liquid discharged during 280 to 300 batches was put into a colorimetric tube having an inner diameter of 2.5 cm for 100 cm ³ each.
Each time, the container was shaken to evenly disperse the waste liquid and then allowed to stand, and the bulkiness of the precipitate in the waste liquid after 2 hours was measured. If the ratio of the bulkiness of the precipitate to the liquid height of the entire waste liquid is 60% or more, ◎, 50% or more and 60%
Those with less than 40% were evaluated as ◯, those with 40% or more and less than 50% were evaluated with Δ, and those with less than 40% were evaluated with x.

(4) Clogged Condition of Polishing Pad The surface of the polishing pad after the completion of the continuous polishing process in (2) above was visually observed. The polishing pad surface was not found to be clogged with ◎, and the polishing pad was found to be clogged with only a small portion of the polishing pad, but the level was not a problem.
If the abrasive or cutting powder in the polishing composition was deposited on the surface of the polishing pad and clogging was found on the entire surface of the polishing pad,
It was evaluated. In Tables 1 and 2, the "clogging condition of the polishing pad" is referred to as "clogging".

(5) Surface Defects After the continuous polishing process of (2) above, after washing and drying the substrate of the 300th batch, a differential interference microscope: OPTIPHOT 66 (manufactured by Nikon, eyepiece: 10 times, Objective lens: 5x), and use 1 at 5 mm from the outer and inner peripheral edges of the polished surface.
The circumference was observed to observe the occurrence of pits with a diameter of 10 μm or more. The case where no pit was found was evaluated as ⊚, the case where the pit was found but was not at a level causing a problem was evaluated as ○, and the case where the problematic pit was found was evaluated as ×.

[0080]

[Table 1]

[0081]

[Table 2] As shown in Table 1, in Examples 1 to 33, the polishing rate reduction rate, the dispersibility, the clogging of the polishing pad, and the surface defects were all excellent evaluations. on the other hand,
As shown in Table 2, in Comparative Examples 3 and 4, since the organic acid that acts as a sedimentation inhibitor for the abrasive in the polishing composition and the chips in the waste liquid was not contained, the polishing rate decreased. The rate was over 30%.

In Comparative Examples 5 to 11, since the organic acid is contained alone, the polishing rate decrease rate,
The dispersibility, the clogging of the polishing pad, and the surface defects were low. Further, in Comparative Examples 12 to 15, since the combination of organic acids contained in the polishing composition of each Comparative Example was different from the combination of organic acids contained in the polishing composition of each embodiment, the polishing rate was The evaluation was low in the reduction rate, dispersibility, and clogging of the polishing pad.

With respect to the polishing compositions of Comparative Examples 1, 2 and 11, clogging of the polishing pad due to accumulation of the abrasive in the polishing composition and the cutting chips in the waste liquid on the polishing pad surface was observed. Although not performed, a large amount of the polishing composition and the waste liquid remained on the polishing pad even after the polishing process. Despite the excellent evaluation of dispersibility and clogging of the polishing pad, the rate of decrease in polishing rate was low because the polishing composition and waste liquid remaining on the polishing pad The straight is in a floating state,
It is probable that sufficient processing force was not generated between the polishing pad and the substrate. (Examples 34 to 50 and Comparative Examples 16 to 30) Example 34
In Nos. 50 to 50, the organic acids shown in Table 3 were mixed and dispersed in ion-exchanged water to prepare polishing compositions. On the other hand, in Comparative Examples 16 to 30, each organic acid and each compound shown in Table 4 were mixed and dispersed in ion-exchanged water to prepare polishing compositions. Here, in Comparative Examples 16 to 19, as in Comparative Examples 1 to 4, colloidal alumina or ammonium molybdate was used as a compound for the purpose of improving the dispersibility of the polishing composition and the waste liquid and suppressing the occurrence of surface defects. added. Further, in the polishing compositions in each row of Tables 3 and 4, 20% by weight of aluminum oxide having an average particle diameter of 0.8 μm was blended as an abrasive so that the total amount of each polishing composition was 100% by weight. Was prepared.

With respect to the polishing compositions in each row of Tables 3 and 4, after measuring the pH and performing the preliminary polishing of the following (6), the following items (7) to (10) were evaluated. In the following (7) to (10), when polishing the substrate, the polishing composition in each row of Tables 3 and 4 was diluted with 4-fold amount of ion-exchanged water. The results are shown in Tables 3 and 4.

(6) Preliminary Polishing Using the polishing compositions in each row of Tables 3 and 4, the substrate was polished to 1 μm for each polishing composition of each example in the same manner as in the preparatory polishing in (1) above. The processing time required for processing was calculated. The other conditions for polishing are as follows.

Machine: One-side polishing machine (surface plate diameter φ300 m
m, manufactured by Udagawa Iron and Steel Co., Ltd. Polishing object (substrate): φ3.5 “electroless Ni−
P-plated disc polishing pad: BELLATRIX N0048 (manufactured by Kanebo Ltd.) Load: 150 g / cm ² Number of revolutions: 100 rpm Polishing composition dilution ratio: 5-fold dilution (polishing composition: deionized water = 1: 4) Polishing composition Material supply rate: 3 cm ³ / min (7) Polishing rate reduction rate Using the polishing composition in each row of Tables 3 and 4, the polishing rate reduction of each example was performed in the same manner as the polishing rate reduction rate of (2) above. I asked for the rate. Here, the processing time in each batch is the processing time obtained in the preliminary polishing in (6) above, and the polishing conditions other than the processing time are the same as those in the preliminary polishing in (6) above.

Then, the polishing rate reduction rate of less than 10% is ⊚, 10% or more and less than 20% is ◯, 20% or more and less than 30% is Δ, and 30% or more is x. It was evaluated by. In Tables 3 and 4, the "polishing rate reduction rate" is referred to as "reduction rate".

(8) Dispersibility In the polishing rate reduction rate of (7) above, the dispersibility of each example was evaluated in the same manner as the dispersibility of (3) above.

(9) Clogged Condition of Polishing Pad Clogged condition of the polishing pad on the surface of the polishing pad after the continuous polishing process in (7) above is the same as the clogged condition of the polishing pad in (4) above. Was evaluated. Table 3
Also, in Table 4, the "clogging condition of the polishing pad" is shown as "clogging".

(10) Surface defect After completion of the continuous polishing process in (7) above, (4) above
The surface defects of the substrate were evaluated in the same manner as the surface defects of 1.

[0091]

[Table 3]

[0092]

[Table 4] As shown in Table 3, in Example 34, the dispersibility and the clogging of the polishing pad were excellent. In Examples 35 to 50, the polishing rate reduction rate, dispersibility, clogging of the polishing pad, and surface defects were all excellent evaluations. Furthermore, in Example 47, the polishing rate (R ₀ ) indicating the initial polishing rate was higher than that in the other Examples.

On the other hand, as shown in Table 4, Comparative Examples 16 to 1
In No. 9, since the polishing agent in the polishing composition and the cutting powder in the waste liquid contained no organic acid acting as a precipitation inhibitor, the polishing rate reduction rate was 30% or more. Further, in Comparative Examples 20 to 26, since the organic acid was contained alone, the polishing rate decrease rate, dispersibility, clogging of the polishing pad, or surface defect was low.

Furthermore, in Comparative Examples 27 to 30, the combination of organic acids contained in the polishing composition of each Comparative Example was different from the combination of organic acids contained in the polishing composition of each embodiment. The polishing rate decrease rate, dispersibility, clogging of the polishing pad, and surface defects were low.

[0095]

Since the present invention is constructed as described above, it has the following effects. Claims 1 and 5
According to the polishing composition for a magnetic disk substrate of the invention described in (1) above, by suppressing clogging of the polishing pad during the polishing process, the polishing rate at the initial stage of the polishing process can be maintained and the magnetic disk after the polishing process can be maintained. It is possible to suppress the occurrence of surface defects in the substrate for use.

According to the polishing composition for a magnetic disk substrate of the invention described in claim 2, in addition to the effect of the invention described in claim 1, clogging of the polishing pad during polishing can be further suppressed. You can

According to the polishing composition for a magnetic disk substrate of the invention of claims 3 and 4, in addition to the effect of the invention of claim 1 or 2, the polishing rate is increased. You can

According to the polishing composition for a magnetic disk substrate of the invention described in claim 6, in addition to the effect of the invention described in claim 5, clogging of the polishing pad during polishing can be further suppressed. You can

According to the polishing composition for a magnetic disk substrate of the invention described in claim 7, in addition to the effect of the invention described in claim 6, clogging of the polishing pad during polishing is further suppressed. You can

According to the polishing composition for a magnetic disk substrate of the invention described in claims 8 and 9, in addition to the effect of the invention described in any one of claims 5 to 7, The speed can be increased.

According to the polishing composition for a magnetic disk substrate of the tenth aspect of the present invention, by improving the dispersibility, the clogging of the polishing pad during the polishing process is particularly suppressed, and the polishing at the initial stage of the polishing process is performed. It is possible to maintain the speed and suppress the occurrence of surface defects in the magnetic disk substrate after the polishing process.

According to the polishing composition for a magnetic disk substrate of the invention described in Item 11, in addition to the effect of the invention described in Item 10, the dispersibility can be further improved.
According to the magnetic disk substrate polishing composition of the present invention of claim 12, in addition to the effect of the invention of claim 11, the polishing rate can be increased.

According to the method of polishing a substrate for a magnetic disk of the thirteenth aspect of the present invention, clogging of the polishing pad is suppressed during the polishing process so that the polishing rate at the initial stage of the polishing process is maintained and the polishing process is performed. It is possible to suppress the occurrence of surface defects on the subsequent magnetic disk substrate.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyasu Sugiyama             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted (72) Inventor Toshiki Owaki             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted F term (reference) 3C058 AA07 CB02 CB03 DA02 DA17

Claims (13)

[Claims] 1. A polishing composition for use in polishing a magnetic disk substrate, comprising: (a) glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, At least one organic acid selected from gluconic acid, succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotinic acid, and (b) glycine, malic acid, lactic acid, gluconic acid, tartaric acid, maleic acid, itaconic acid And at least one selected from crotonic acid, and (a)
Containing (c) at least one abrasive selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide; and (d) water. A composition for polishing a substrate for a magnetic disk, comprising: 2. The composition for polishing a magnetic disk substrate according to claim 1, wherein the organic acid as the component (b) is at least one organic acid selected from glycine, malic acid, lactic acid and gluconic acid. 3. The polishing of the magnetic disk substrate according to claim 1 or 2, wherein the organic acid as the component (a) is at least one organic acid selected from malic acid, glycolic acid and succinic acid. Composition. 4. The content of the component (a) and the component (b) is
The composition for polishing a magnetic disk substrate according to claim 1, wherein the composition is 0.01 to 10% by weight, respectively. 5. A polishing composition for use in polishing a magnetic disk substrate, comprising: (e) glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, At least one organic acid selected from gluconic acid, succinic acid, tartaric acid, maleic acid, itaconic acid, crotonic acid and nicotinic acid, and (f) citric acid, iminodiacetic acid, malonic acid, oxalic acid, alanine and propionic acid. At least one organic acid selected from (g) aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide,
A polishing composition for a magnetic disk substrate, comprising (h) water, and at least one abrasive selected from titanium oxide, silicon nitride and silicon carbide. 6. The composition for polishing a magnetic disk substrate according to claim 5, wherein the organic acid as the component (f) is at least one organic acid selected from citric acid and iminodiacetic acid. 7. The composition for polishing a magnetic disk substrate according to claim 6, wherein the organic acid as the component (f) is citric acid. 8. The magnetic disk according to claim 5, wherein the organic acid as the component (e) is at least one organic acid selected from malic acid, glycolic acid and succinic acid. Composition for polishing a substrate. 9. The content of component (e) is 0.01 to 10% by weight, and the content of component (f) is 0.01 to 10.
The composition for polishing a magnetic disk substrate according to any one of claims 5 to 8, which is 5% by weight. 10. A polishing composition for use in polishing a magnetic disk substrate, comprising: (i) itaconic acid;
(J) Glycine, glyceric acid, mandelic acid, ascorbic acid, glutamic acid, glyoxylic acid, malic acid, glycolic acid, lactic acid, gluconic acid, succinic acid, tartaric acid, maleic acid, crotonic acid, nicotinic acid, citric acid, iminodiacetic acid , At least one organic acid selected from malonic acid, oxalic acid, alanine and propionic acid, and (k) at least one selected from aluminum oxide, silicon dioxide, cerium oxide, zirconium oxide, titanium oxide, silicon nitride and silicon carbide. A polishing composition for a magnetic disk substrate, comprising one kind of abrasive and (l) water. 11. The composition for polishing a magnetic disk substrate according to claim 10, wherein the organic acid as the component (j) is an organic acid containing at least citric acid. 12. The composition for polishing a magnetic disk substrate according to claim 11, wherein the organic acid as the component (j) is an organic acid containing at least succinic acid. 13. A method for polishing a magnetic disk substrate, which comprises polishing a magnetic disk substrate using the polishing composition according to claim 1. Description: