JP2020166924A - Composition for polishing - Google Patents

Abstract

To provide a composition for polishing a magnetic disk capable of improving a shape of an end portion while maintaining polishing performance such as processability.SOLUTION: A composition for polishing a magnetic disk substrate is provided. This composition for polishing contains silica particles as abrasive grains and water. The composition for polishing further contains a phosphorous ester and at least one selected from phosphoric acid esters having a molecular weight of 150 or more.SELECTED DRAWING: None

Description

The present invention relates to a polishing composition, and more particularly to a magnetic disk substrate polishing composition.

In the manufacture of magnetic disk substrates, polishing (primary polishing) that emphasizes polishing efficiency (for example, polishing rate) is generally performed before the final polishing process that is performed to finish the surface of the final product with high precision. .. For example, a highly accurate surface can be efficiently realized by performing at least primary polishing and final polishing on a disk substrate (Ni-P substrate) plated with nickel phosphorus. In such polishing, silica abrasive grains may be used from the primary polishing stage for the purpose of obtaining higher surface quality. Prior art documents that disclose this type of prior art include Patent Documents 1 to 3.

JP-A-2015-41391 Japanese Unexamined Patent Publication No. 2012-24899 Japanese Unexamined Patent Publication No. 2015-17259

Polishing of a substrate for a magnetic disk is usually performed by pressing a polishing pad against a substrate to be polished and moving both of them relative to each other. Therefore, not only the pressure on the polishing surface (polishing load) but also the force from the side surface is applied to the end portion of the substrate by the amount of the sinking of the polishing pad, and a larger load is applied. Compared to polishing with alumina abrasive grains, polishing with silica abrasive grains is superior in terms of reducing defects such as scratches without residual alumina, and it is easy to obtain high surface quality, but the slurry containing alumina abrasive grains Such processing power cannot be obtained. Therefore, polishing using silica abrasive grains tends to take a long time, and due to the difference in stress between the end portion and the inner peripheral portion described above, the thickness of the substrate end portion is reduced as compared with the inner peripheral portion. .. Such an end shape is called roll-off (also referred to as end face sagging) and is not suitable for recording, so that it can be a limiting factor for increasing the recording capacity of a magnetic disk. For example, in Patent Documents 1 to 3, efforts are made to improve roll-off by devising abrasive grains, complexing agents, polishing pressure, and the like.

However, the conventional roll-off countermeasures as described in Patent Documents 1 to 3 are based on the action on the entire substrate, and do not act selectively on the end portion. Further, if a protective agent is used to reduce the occurrence of roll-off, not only the end portion but also the inner peripheral portion is protected due to the protective action on the entire substrate, and a decrease in workability is unavoidable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composition for polishing a magnetic disk, which can improve the shape of an end portion while maintaining polishing performance such as workability.

According to the present specification, a composition for polishing a magnetic disk substrate is provided. This polishing composition contains silica particles as abrasive grains and water. It also further comprises a phosphite ester and at least one selected from phosphoric acid esters having a molecular weight of 150 or more. By using a phosphite ester or a phosphoric acid ester having a molecular weight of a predetermined value or more in the silica particle-containing polishing composition, the shape of the end portion can be improved while maintaining the polishing performance. In the present specification, the substrate end portion refers to a section (region) of 2 mm from the outer periphery of the substrate toward the inner peripheral direction, and the end shape improvement means prevention or reduction of roll-off in this section. ..

In some preferred embodiments, the polishing composition further comprises hydrogen peroxide as an oxidizing agent. By using hydrogen peroxide as an oxidizing agent, good processability can be preferably exhibited.

；で表される化合物である。ここで、上式（１）中、Ｒ^１およびＲ^２は、それぞれ独立して、水素原子、または、アルキル基、アルケニル基、アルコキシアルキル基、（メタ）アクリル酸アルキルエステル基、（メタ）アクリロイル基、（ポリ）オキシアルキレンアルキルエーテル基、（ポリ）オキシアルキレンアリールエーテル基および芳香族基から選択される有機基である。ただし、Ｒ^１およびＲ^２のうち少なくとも一方は、有機基である。上記の化学構造を有するリン酸エステルを含む研磨用組成物によると、ここに開示される技術による効果が好ましく発揮される。 In some preferred embodiments, the polishing composition comprises the phosphate ester. The phosphoric acid ester has a general formula (1):

It is a compound represented by ;. Here, in the above formula (1), R ¹ and R ² are independently hydrogen atoms, or an alkyl group, an alkenyl group, an alkoxyalkyl group, a (meth) acrylic acid alkyl ester group, and (meth) acryloyl. An organic group selected from a group, a (poly) oxyalkylene alkyl ether group, a (poly) oxyalkylene aryl ether group and an aromatic group. However, at least one of R ¹ and R ² is an organic group. According to the polishing composition containing a phosphoric acid ester having the above chemical structure, the effect of the technique disclosed herein is preferably exhibited.

In the phosphoric acid ester, R ¹ and R ² in the general formula (1) are independently hydrogen atoms or alkyl groups having 3 to 18 carbon atoms, alkenyl groups, and alkoxyalkyl groups. More preferably, it is a compound selected from a (meth) acrylic acid alkyl ester group, a (meth) acryloyl group and a (poly) oxyalkylene alkyl ether group.

In some preferred embodiments, the phosphoric acid ester is preferably a phosphoric acid ester having a monoester ratio of 55 mol% or more. According to the polishing composition containing a phosphoric acid ester having a monoester ratio of 55 mol% or more, a more excellent end shape improving effect tends to be obtained. Such a polishing composition may also have good storage stability.

In some preferred embodiments, the polishing composition comprises, as the silica particles, spherical colloidal silica having an average aspect ratio of less than 1.10 based on SEM (scanning electron microscope) image analysis. According to the polishing composition containing colloidal silica having a high degree of sphericity, it is easy to obtain a substrate surface having high surface quality, but roll-off is likely to occur. In such an embodiment, the effect of the technique disclosed herein (typically the effect of improving the shape of the end) is preferably exhibited.

In some preferred embodiments, the polishing composition comprises, as the silica particles, non-spherical colloidal silica having an average aspect ratio of 1.10 or greater based on SEM image analysis. According to the polishing composition containing colloidal silica having a low sphericality, higher workability can be easily obtained. In the embodiment using such colloidal silica, the effect of the technique disclosed herein (for example, the effect of maintaining processability) is preferably exhibited.

In some preferred embodiments, the silica particles further comprise at least one selected from the group consisting of heat-treated silica particles, condensed silica particles and precipitated silica particles. By using the silica particles (for example, heat-treated silica particles) in combination with the colloidal silica described above, high surface quality and processability can be preferably achieved at the same time. In such a composition, the effect of the technique disclosed herein (for example, the effect of maintaining processability) is preferably exhibited.

In some preferred embodiments, the pH of the polishing composition is in the range of 1-4. By setting the pH in such a range, the effects of the techniques disclosed herein are preferably exhibited.

The polishing composition disclosed herein is suitable as a polishing composition used in the pre-process of the finish polishing step. For example, the polishing composition is suitably used for primary polishing of a magnetic disk substrate. By using the polishing composition disclosed herein before finish polishing and improving the edge shape before finish polishing with good workability, a magnetic disk substrate with improved recording capacity can be produced with high productivity. Obtainable. A preferred example of the magnetic disk substrate is a nickel phosphorus substrate (Ni-P substrate).

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

≪1. First aspect ≫
<1-1. Polishing composition>
(1-1-1. Abrasive grains)
The polishing composition disclosed herein includes silica particles as abrasive grains. The effect of improving the shape of the end portion by the technique disclosed herein is suitably realized in a configuration using a polishing composition containing silica abrasive grains. The silica particles (including all of the silica particles S1, S2, and S3 described later; the same shall apply hereinafter unless otherwise specified) may be various silica particles containing silica as a main component. Here, the silica particles containing silica as a main component refer to particles in which 90% by weight or more, for example, 95% by weight or more, typically 98% by weight or more of the particles are silica. Examples of silica particles that can be used are not particularly limited, and are limited to colloidal silica, condensed silica, precipitated silica (also referred to as precipitated silica), sodium silicate silica, alkoxide silica, fumed silica, dried silica, and explosion. Law silica and the like can be mentioned. Further, silica particles obtained by using the above silica particles as a raw material can also be used. Examples of such silica particles include heat treatment of the above-mentioned raw material silica particles (hereinafter, also referred to as “raw material silica”), heat treatment such as heating, drying, and firing, pressure treatment such as autoclave treatment, crushing, crushing, and the like. Silica particles obtained by applying one or more treatments selected from the mechanical treatment of the above, surface modification, etc. may be contained. Examples of the surface modification include introduction of a functional group and chemical modification such as metal modification. The abrasive grains in the technique disclosed herein may include one of such silica particles alone or in combination of two or more.

Preferable examples of silica particles include colloidal silica. Of these, it is preferable to use colloidal silica synthesized through particle growth in the aqueous phase, such as sodium silicate silica and alkoxide silica. With silica abrasives containing this type of colloidal silica, good surface quality can be suitably achieved. When the silica abrasive grains disclosed herein contain colloidal silica, the colloidal silica contained in the silica abrasive grains may be one kind or two or more kinds having different production conditions and / or physical properties. .. Further, the silica abrasive grains may be composed of one kind or two or more kinds of colloidal silica, and are composed of a combination of colloidal silica and other silica particles, that is, silica particles other than colloidal silica. May be good. In some embodiments, the abrasive grains contained in the polishing composition contain colloidal silica alone. Better surface quality can be achieved by using colloidal silica alone.

The particle shape of colloidal silica is not particularly limited, and may be spherical or non-spherical, for example. Specific examples of the non-spherical shape include a peanut shape, a cocoon shape, a protruding shape, a rugby ball shape, and the like. The peanut shape can be, for example, the shape of a peanut shell. The shape with protrusions can be, for example, a konpeito shape.

As another example of silica particles, for example, silica particles obtained by subjecting raw material silica to heat treatment (hereinafter, also referred to as “heat-treated silica”), specifically heated silica particles, and dried silica. Examples include particles, calcined silica particles, and the like. Here, the heated silica particles are typically obtained through a treatment of holding them in an environment of 60 ° C. or higher and lower than 110 ° C. for a certain period of time or longer, for example, 15 minutes or longer, typically 30 minutes or longer. Silica particles. Further, the dried silica particles are typically in an environment of 110 ° C. or higher and lower than 500 ° C., preferably 300 ° C. or higher and lower than 500 ° C. for a certain period of time or longer, for example, 15 minutes or longer, typically 30 minutes or longer. Silica particles obtained through a holding process. The calcined silica particles (hereinafter, also referred to as "calcined silica") are typically in an environment of 500 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher for a certain period of time or longer, for example, 15. Silica particles obtained through a treatment of holding for minutes or more, typically 30 minutes or more. The silica particles obtained through the process of heat-treating any of the above-mentioned raw material silicas, that is, precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dried silica, explosive silica and the like, are referred to herein. This is a typical example included in the concept of heat-treated silica. When the silica abrasive grains contain heat-treated silica, the heat-treated silica contained in the silica abrasive grains may be one kind or two or more kinds having different production conditions and / or physical properties. Further, the silica particles may be composed of one type or two or more types of heat-treated silica, or may be composed of a combination of heat-treated silica and other silica particles, that is, silica particles that have not been heat-treated. Good.

The technique disclosed herein can also be carried out in an embodiment in which the abrasive grains contained in the polishing composition include heat-treated silica alone or a combination of heat-treated silica and other silica particles. In some preferred embodiments, the silica particles contained in the polishing composition include colloidal silica in combination with heat treated silica. By further containing heat-treated silica particles in addition to colloidal silica, high surface quality can be realized and high workability can be preferably realized.

In the embodiment in which the silica particles contain colloidal silica and heat-treated silica, the content ratio thereof is not particularly limited. From the viewpoint of achieving both workability and surface quality, it is appropriate that the ratio of the heat-treated silica to 100 parts by weight of colloidal silica is about 20 parts by weight or less, preferably about 15 parts by weight or less, and more preferably about 10 parts by weight. It may be less than 7 parts by weight, and may be about 7 parts by weight or less (for example, about 5 parts by weight or less). Further, from the viewpoint of preferably obtaining the effect of using the heat-treated silica, the ratio of the heat-treated silica to 100 parts by weight of the colloidal silica is preferably about 0.1 part by weight or more, preferably about 1 part by weight or more, more preferably. Is about 2 parts by weight or more (for example, about 5 parts by weight or more).

The average primary particle size of the silica particles is not particularly limited, and is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 30 nm or more, and particularly preferably 35 nm or more. Higher workability can be achieved by increasing the average primary particle size. Further, from the viewpoint of obtaining a surface having higher surface quality, the average primary particle diameter is preferably about 300 nm or less, more preferably about 200 nm or less, and may be about 150 nm or less (for example, about 100 nm or less). ..

In the technique disclosed herein, the average primary particle size of the abrasive grains (typically silica particles) means the average particle size obtained based on the BET method. For example, when the abrasive grains are silica abrasive grains (that is, abrasive grains composed of silica particles), the average primary particle diameter of the silica abrasive grains is D1 (nm) from the specific surface area S (m ² / g) measured by the BET method. ) = (6000 / 2.2) / S can be calculated. 2.2 in this formula is the value of the specific gravity of silica, which is the particle size of silica. The specific surface area can be measured, for example, by using a surface area measuring device manufactured by Micromeritex, trade name "Flow Sorb II 2300".

In some embodiments, the silica particles can have a volume average particle diameter of approximately 50 nm or more based on SEM image analysis. From the viewpoint of processability and the like, the volume average particle diameter of the silica particles is preferably about 80 nm or more, more preferably about 100 nm or more, still more preferably about 110 nm or more, and particularly preferably about 140 nm or more. The volume average particle diameter may be, for example, about 160 nm or more, and further may be about 180 nm or more. The volume average particle diameter of the silica particles is preferably about 400 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, still more preferably about 200 nm, from the viewpoint of obtaining a surface having high surface quality. Below, it is particularly preferably about 180 nm or less. The volume average particle diameter may be, for example, about 130 nm or less.

The volume average particle size based on the SEM image analysis in the present specification is specifically obtained by the following method. 50 or more particles contained in the particles to be measured (which may be one type of abrasive particles or a mixture of two or more types of abrasive particles) in one field of view. Observe with SEM images containing particles of. The observation magnification is 25,000 to 50,000 times. A value obtained by 4πr ^3/3 from the radius r of the ideal yen (perfect circle) having an area equal to the projected area of each particle image is calculated as the volume of each particle. Here, the volume is calculated by counting the particles independently dispersed in the polishing composition as one particle regardless of whether they are primary particles or secondary particles. A volume-based cumulative distribution curve is derived from the volume of the predetermined number of particles, and the cumulative frequency of 50% particle diameter (D50) is adopted as the volume average particle diameter (D50). The volume average particle diameter (D50) based on the SEM image analysis can be obtained by using general image analysis software.

Although not particularly limited, the average aspect ratio of the silica particles can be, for example, 1.0 or more. From the viewpoint of workability and the like, in some embodiments, the average aspect ratio may be, for example, 1.02 or more, 1.05 or more, 1.10 or more, or 1.15 or more. Further, from the viewpoint of efficiently improving the surface quality, it is appropriate that the average aspect ratio is 2.50 or less, and may be 2.0 or less, or 1.70 or less in some embodiments. The technique disclosed herein can also be preferably carried out in an embodiment in which the average aspect ratio of the silica particles is 1.50 or less, further 1.30 or less. Here, the average aspect ratio of the silica particles means the average value of the major axis / minor axis ratios of the individual particles constituting the abrasive grains, that is, the number average aspect ratio. Hereinafter, unless otherwise specified, the average aspect ratio in the present specification means the above-mentioned number average aspect ratio.

In the present specification, the average aspect ratio of silica particles can be measured by the following method. That is, using SEM, a predetermined number of silica particles contained in the abrasive grains to be measured are observed in an SEM image containing 50 or more particles in one field of view. Observation is performed at an observation magnification of 10,000 to 50,000 times. The silica particles to be measured may be one type of silica particles or a mixture of two or more types of silica particles. For the silica particles in the SEM image, draw the smallest rectangle circumscribing each particle image. The length of the long side of the rectangle is the value of the major axis, the length of the short side is the value of the minor axis, and the value obtained by dividing the value of the major axis by the value of the minor axis for each particle is calculated as the aspect ratio. That is, the aspect ratio of each particle is obtained as the ratio of the long side / short side of the smallest rectangle circumscribing the particle. The number average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the predetermined number of particles. The number aspect ratio can be obtained by using general image analysis software.
The predetermined number of particles, that is, the number of particles for which the aspect ratio for each particle is calculated, is preferably 1000 or more, and preferably 1500 or more, from the viewpoint of improving measurement accuracy and reproducibility. The upper limit of the predetermined number is not particularly limited. From the viewpoint of measurement efficiency, the predetermined number may be, for example, 5000 or less, or 2500 or less.

In some preferred embodiments, the silica particles include silica particles S1 having an average aspect ratio of 1.10 or higher based on SEM image analysis. By using silica particles S1 having a relatively low sphericality, high workability can be easily obtained. The average aspect ratio of the silica particles S1 is preferably 1.12 or more, more preferably 1.15 or more, still more preferably 1.17 or more (for example, 1.18 or more) from the viewpoint of processability. It is appropriate that the average aspect ratio is about 2.5 or less, and from the viewpoint of surface quality, it is preferably about 2.0 or less, more preferably about 1.5 or less, and further preferably about 1.3 or less ( For example, 1.25 or less). Preferable examples of the silica particles S1 include colloidal silica. The colloidal silica corresponding to the silica particles S1 is also referred to as non-spherical colloidal silica.

In some embodiments, the silica particles S1 may have a volume average particle size of less than 200 nm based on SEM image analysis. By using silica particles S1 having a relatively low sphericality and a relatively small particle size, it is easy to obtain both high workability and high surface quality. From the viewpoint of surface quality, the volume average particle size of the silica particles S1 is preferably less than 180 nm, more preferably less than 160 nm (for example, about 150 nm or less). The volume average particle diameter is preferably about 50 nm or more, and is preferably about 90 nm or more, more preferably about 120 nm or more (for example, about 130 nm or more) from the viewpoint of processability.

The ratio of the silica particles S1 to the entire silica particles (which may be the entire abrasive grains) is not particularly limited. From the viewpoint of processability, the ratio of the silica particles S1 to the total silica particles is preferably about 10% by weight or more, preferably about 20% by weight or more, more preferably about 30% by weight or more, for example, about 30% by weight or more. It may be 40% by weight or more, and may be about 50% by weight or more. Further, in consideration of both workability and surface quality, it is preferable that the silica particles S1 are used in combination with other silica particles (for example, silica particles S2 described later). From such a viewpoint, the ratio of the silica particles S1 to the entire silica particles (which may be the entire abrasive grains) is preferably about 95% by weight or less, preferably about 85% by weight or less, more preferably. Is about 70% by weight or less, more preferably about 65% by weight or less.

In some preferred embodiments, the silica particles include silica particles S2 having an average aspect ratio of less than 1.10 based on SEM image analysis. High surface quality is preferably realized by using silica particles S2 having a relatively high sphericality. Further, in the embodiment containing silica particles having a high degree of sphericality, the effect of improving the shape of the end portion by the technique disclosed herein is preferably exhibited. The average aspect ratio of the silica particles S2 is preferably about 1.08 or less, more preferably about 1.06 or less (for example, less than 1.05) from the viewpoint of surface quality. The average aspect ratio is 1.0 or more, preferably 1.02 or more, and more preferably 1.03 or more from the viewpoint of workability and the like. Preferable examples of the silica particles S2 include colloidal silica. The colloidal silica corresponding to the silica particles S2 is also referred to as spherical colloidal silica.

In some embodiments, the silica particles S2 may have a volume average particle size of less than 200 nm based on SEM image analysis. High surface quality is preferably realized by using silica particles S2 having a relatively high sphericality and a relatively small particle size. Further, in the embodiment including the silica particles S2, the effect of improving the shape of the end portion by the technique disclosed herein is preferably exhibited. From the viewpoint of surface quality, the volume average particle diameter of the silica particles S2 is preferably less than 150 nm, more preferably less than 120 nm, and may be less than 100 nm (for example, about 95 nm or less). The volume average particle diameter is preferably about 30 nm or more, and is preferably about 40 nm or more, more preferably about 50 nm or more (for example, about 60 nm or more) from the viewpoint of processability.

The ratio of the silica particles S2 to the entire silica particles (which may be the entire abrasive grains) is not particularly limited. From the viewpoint of surface quality, the ratio of the silica particles S2 to the entire silica particles may be about 50% by weight or more, for example, 75% by weight or more, and about 90% by weight or more (for example, about 99% by weight). % Or more), typically about 100% by weight. The ratio of the silica particles S2 may be, for example, about 90% by weight or less. When used in combination with other silica particles, it is appropriate, preferably about 60% by weight or less, that the ratio of the silica particles S2 is about 60% by weight or less from the viewpoint of better exerting the effect of the combined use (for example, improvement of workability). It is 50% by weight or less (for example, 45% by weight or less). The lower limit of the ratio of the silica particles S2 is not particularly limited, and for example, it is appropriate to be about 5% by weight or more, preferably about 10% by weight or more, more preferably about 15% by weight or more, for example, 25% by weight. It may be% or more (typically about 30% by weight or more).

In a particularly preferred embodiment, the silica particles S1 and the silica particles S2 are used in combination. By using the silica particles S1 and the silica particles S2 together, it becomes easy to achieve both high surface quality and workability. The content ratio of the silica particles S1 and S2 is not particularly limited. For example, the content ratio (S1 / S2) of the silica particles S1 to the silica particles S2 is appropriately set to about 1/99 or more, preferably 10 /. It is 90 or more, more preferably 30/70 or more, still more preferably 40/60 or more, particularly preferably 50/50 or more, and may be, for example, 60/40 or more. The content ratio (S1 / S2) is preferably 99/1 or less, preferably 90/10 or less, more preferably 80/20 or less, still more preferably 70/30 or less (for example, 65/35). Below).

In some preferred embodiments, the silica particles further include silica particles S3 having an average aspect ratio of 1.10 or more based on SEM image analysis and a volume average particle diameter of 200 nm or more based on SEM image analysis. Workability is improved by including silica particles S3 having a relatively low sphericality and a relatively large particle size. Preferable examples of the silica particles S3 include heat-treated silica (typically calcined silica).

The average aspect ratio of the silica particles S3 is preferably 1.20 or more, more preferably 1.25 or more, still more preferably 1.30 or more, from the viewpoint of processability. It is appropriate that the average aspect ratio is about 2.5 or less, and from the viewpoint of surface quality and the like, it is preferably about 2.0 or less, more preferably about 1.5 or less (for example, 1.4 or less). ..

The volume average particle diameter of the silica particles S3 is preferably about 240 nm or more, more preferably about 280 nm or more, and may be about 300 nm or more from the viewpoint of processability and the like. Further, the volume average particle diameter of the silica particles S3 is preferably about 1000 nm or less, preferably about 700 nm or less, more preferably about 600 nm or less (for example, about 500 nm or less) from the viewpoint of surface quality and the like. ..

From the viewpoint of achieving both workability and surface quality, the silica particles S3 are preferably used in combination with other silica particles (for example, silica particles S1 and S2). In a particularly preferred embodiment, the silica particles S3 are used in combination with the silica particles S1 and the silica particles S2. By using the silica particles S3 in combination with the silica particles S1 and the silica particles S2, workability and surface quality can be compatible at a high level. The ratio of the silica particles S3 to the entire silica particles (which may be the entire abrasive grains) is preferably about 20% by weight or less, preferably about 15% by weight or less, and more preferably about 10% by weight or less. It may be about 7% by weight or less. Further, from the viewpoint of preferably obtaining the effect of using the silica particles S3, it is appropriate that the ratio of the silica particles S3 to the entire silica particles (which may be the entire abrasive grains) is about 0.1% by weight or more. It is preferably about 1% by weight or more, more preferably about 2% by weight or more (for example, about 5% by weight or more).

The polishing composition disclosed herein may contain particles other than the silica particles. As the particles other than the silica particles, any of inorganic particles, organic particles, and organic-inorganic composite particles can be used. Specific examples of the inorganic particles include oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; silicon nitride particles. , Nitride particles such as boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and the like. Examples of the alumina particles include α-alumina, intermediate alumina other than α-alumina, and composites thereof. Intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples thereof include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and composites thereof. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles, poly (meth) acrylic acid particles, polyacrylonitrile particles, and the like. Here, (meth) acrylic acid has the meaning of comprehensively referring to acrylic acid and methacrylic acid. Particles other than these silica particles can be used alone or in combination of two or more.

In the polishing composition disclosed herein, the content of silica particles in the solid content contained in the polishing composition is not particularly limited. The content of the silica particles is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably 50% by weight or more of the total solid content, from the viewpoint of better exerting the effect of the technique disclosed herein. It is 60% by weight or more, more preferably 80% by weight or more, particularly preferably 90% by weight or more, for example 99% by weight or more. In the present specification, the solid content contained in the polishing composition means a residual content after evaporating water from the polishing composition at a temperature at which bound water is not removed, for example, 60 ° C., that is, a non-volatile content. ..

The polishing composition disclosed herein can be preferably carried out in a manner substantially free of alumina particles. Examples of the alumina particles include α-alumina particles. Such a polishing composition prevents quality degradation due to the use of alumina particles. Examples of the quality deterioration referred to here include generation of scratches and dents, residual alumina, and piercing defects of abrasive grains. In the present specification, the term “substantially free of alumina particles” means that the proportion of alumina particles in the total amount of solids contained in the polishing composition is 1% by weight or less, more preferably 0.5% by weight or less, which is typical. It means that it is 0.1% by weight or less. A polishing composition in which the proportion of alumina particles is 0% by weight, that is, a polishing composition containing no alumina particles is particularly preferable. Further, the polishing composition disclosed herein can be preferably carried out in a manner substantially free of α-alumina particles.

The polishing composition disclosed herein can also be preferably carried out in an embodiment that does not substantially contain particles other than silica particles, that is, non-silica particles. Here, the term “substantially free of non-silica particles” means that the proportion of non-silica particles in the total amount of solids contained in the polishing composition is 1% by weight or less, more preferably 0.5% by weight or less, which is typical. It means that it is 0.1% by weight or less. In such an aspect, the application effect of the technique disclosed herein can be suitably exerted.

The content of abrasive grains (typically silica particles) in the polishing composition is not particularly limited, but is typically 0.1% by weight or more, preferably 0.5% by weight or more. It is more preferably 5% by weight or more, more preferably 3% by weight or more, and particularly preferably 5% by weight or more. When a plurality of types of abrasive grains are contained, the above-mentioned content is the total content thereof. Higher workability tends to be obtained by increasing the content of abrasive grains. From the viewpoint of the surface smoothness of the substrate after polishing and the stability of polishing, the content is preferably 30% by weight or less, preferably 25% by weight or less, more preferably 15% by weight or less, still more preferably 10. It is less than% by weight.

(1-1-2. Water)
The polishing composition disclosed herein typically contains, in addition to the abrasive grains as described above, water in which the abrasive grains are dispersed. As the water, ion-exchanged water, pure water, ultrapure water, distilled water and the like can be preferably used. The ion-exchanged water can typically be deionized water.

The polishing composition disclosed herein can be preferably carried out, for example, in a form in which the solid content content is 0.5% by weight to 30.0% by weight. A form in which the solid content is 1.0% by weight to 20.0% by weight is more preferable. The polishing composition can typically be a slurry composition.

(1-1-3. Compound selected from phosphate ester and phosphite ester)
The polishing composition disclosed herein is characterized by containing a phosphoric acid ester having a molecular weight of 150 or more and at least one compound selected from a phosphite ester. By using the above compound in the silica particle-containing polishing composition, the shape of the end portion can be improved while maintaining the polishing performance. The reason can be considered as follows, for example. Normally, a substrate for a magnetic disk is polished by pressing a polishing pad against the substrate to be polished and moving both of them relative to each other. Therefore, the side surface of the substrate is not only the polishing load but also the amount of the sinking of the polishing pad. The force from is applied and a larger load is applied. This causes roll-off. Phosphite esters and phosphoric acid esters with a molecular weight of 150 or more act on the metal surface to exert a lubricating action at the edge of the substrate where the pressure is relatively high during polishing when the force exceeds a certain threshold value, and rolls. It is thought to contribute to the prevention or reduction of off. That is, these compounds do not act on the inner peripheral portion of the substrate, or the action is small and selectively act on the edge portion of the substrate. As a result, it is considered that the polishing performance such as workability is maintained while improving the shape of the end portion. The above mechanism is a consideration of the present inventors based on the experimental results, and the technique disclosed herein is not construed as being limited to the above mechanism.

As the phosphoric acid ester, one having a molecular weight of 150 or more can be used without particular limitation. As the phosphoric acid ester, any of phosphoric acid monoester, phosphoric acid diester, and phosphoric acid triester can be used. One type of phosphoric acid ester can be used alone or two or more types can be used in combination. During polishing, the reactive region (P = O or P-OH) of the phosphoric acid ester is adsorbed on the edge of the substrate, and the substituent (organic group) in the phosphoric acid ester functions as a region for protecting the end. It is thought that. It is considered that the phosphoric acid ester having a molecular weight of a predetermined value or more has a sufficient size for the substituent to protect the end portion and effectively reduces the force from the side surface of the end portion of the substrate. The technology disclosed herein is not construed as being limited to the above mechanism.

From the viewpoint of improving the shape of the end portion, the molecular weight of the phosphoric acid ester may be 180 or more, 200 or more, 220 or more, 250 or more, 300 or more, or 400 or more (for example, 450 or more). .. The upper limit of the molecular weight is typically 1000 or less, preferably 700 or less, more preferably 550 or less, 450 or less, and 350 or less, from the viewpoint of solubility in the polishing composition, handleability, and the like. It may be 270 or less, 210 or less (for example, 170 or less).

The phosphoric acid ester disclosed herein is, for example, a compound represented by the following general formula (1).

上式（１）中、Ｒ^１およびＲ^２は同一であっても互いに異なっていてもよく、いずれも水素原子または有機基である。ただし、Ｒ^１およびＲ^２のうち少なくとも一方は、有機基である。

In the above formula (1), R ¹ and R ² may be the same or different from each other, and both are hydrogen atoms or organic groups. However, at least one of R ¹ and R ² is an organic group.

In some embodiments, in the compound represented by the general formula (1), at least one of R ¹ and R ² is an alkyl group, an alkenyl group, an alkoxyalkyl group, a (meth) acrylic acid alkyl ester group and a (poly) acrylic acid alkyl ester group. ) An organic group selected from an oxyalkylene alkyl ether group, a (poly) oxyalkylene aryl ether group and an aromatic group. The number of carbon atoms constituting the organic group is not particularly limited as long as the molecular weight of the compound is 150 or more, and is appropriate in consideration of edge shape improving property, solubility in a polishing composition, handleability, and the like. Those having a carbon atom number are used. For example, the number of carbon atoms of the alkyl group, the alkenyl group, and the alkoxyalkyl group may be independently 3 or more, preferably 4 or more, 6 or more, or 8 or more. May be good. The aromatic group (eg, aryl group, typically phenyl group) has 6 or more carbon atoms and may be 8 or more carbon atoms. The upper limit of the number of carbon atoms of the alkyl group, the alkenyl group, the alkoxyalkyl group and the aromatic group is independently preferably 24 or less, preferably 18 or less, more preferably 14 or less, still more preferably 12 or less. Especially preferably, it is 8 or less. In the embodiment in which one of R ¹ and R ² is a chain alkyl group, an alkenyl group, or an alkoxy alkyl group, the number of carbon atoms of one of R ¹ and R ² may be 1 or 2.

In some preferred embodiments, the compound represented by the general formula (1) has at least one of R ¹ and R ² being an alkyl group. The above-mentioned alkyl group is not particularly limited, and may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group. It is preferable that at least one of R ¹ and R ² is a chain alkyl group. According to the phosphoric acid ester containing a chain alkyl group, the effect of improving the shape of the end portion can be easily obtained. Specific examples of R ¹ and R ² in this embodiment include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, and the like. Neopentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, Examples thereof include a heptadecyl group, an octadecyl group, a nonadecil group, and an eikosyl group.

In some other preferred embodiments, the compound represented by the general formula (1) has at least one of R ¹ and R ² being an alkoxyalkyl group. In the above alkoxyalkyl group, the number of carbon atoms in the alkoxy moiety is not particularly limited, and may be 1 or more, 2 or more, 4 or more, 10 or less is appropriate, 8 or less, or 6 or less. The number of carbon atoms in the alkyl portion of the alkoxyalkyl group is not particularly limited, and may be 1 or more, 2 or more, 12 or less is appropriate, 8 or less, or 4 or less.

In some other preferred embodiments, in the compound represented by the general formula (1), at least one of R ¹ and R ² is a (meth) acrylic acid alkyl ester group. The number of carbon atoms of the alkyl group constituting the (meth) acrylic acid alkyl ester group is not particularly limited, and may be, for example, 2 or more, 4 or more, 8 or more, 12 or more, or 14 or less. It may be 10 or less, or 6 or less (for example, 4 or less).

In some other preferred embodiments, in the compound represented by the general formula (1), at least one of R ¹ and R ² is a (poly) oxyalkylene alkyl ether group or a (poly) oxyalkylene aryl ether group. is there. The number of carbon atoms of the alkyl group constituting the (poly) oxyalkylene alkyl ether group or the (poly) oxyalkylene aryl ether group is not particularly limited, and is, for example, 2 or more, 4 or more, 8 or more, 12 or more. It may be 24 or less, 18 or less, or 14 or less (for example, 12 or less). The number of repetitions of the oxyalkylene unit of the (poly) oxyalkylene alkyl ether group and the (poly) oxyalkylene aryl ether group is not particularly limited, and is 1 or more, 2 or more is appropriate, 3 or more may be used, and 10 or less. Is appropriate, preferably 8 or less, more preferably 6 or less, for example, 4 or less.

Examples of the phosphoric acid ester include aryl acid phosphates such as monoaryl acid phosphate and diaryl acid phosphate; alkyl acid phosphates such as monoalkyl acid phosphate and dialkyl acid phosphate; alkenyl acid phosphates such as monoalkenyl acid phosphate and dialkenyl acid phosphate; Alkoxyalkyl acid phosphates; hydroxyalkyl (meth) acrylate acid phosphates; monoalkyl phosphates; polyoxyalkylene alkyl ether phosphates; polyoxyalkylene aryl ether phosphates; and the like. These can be used alone or in combination of two or more. Of these, alkyl acid phosphate, alkoxyalkyl acid phosphate, hydroxyalkyl (meth) acrylate acid phosphate, and polyoxyalkylene alkyl ether phosphate are preferred, with alkyl acid phosphate, alkoxyalkyl acid phosphate, and polyoxyalkylene alkyl ether phosphate. More preferred.

Preferable examples of the above phosphate ester include dipropyl acid phosphate, diisopropyl acid phosphate, monobutyl acid phosphate, dibutyl phosphate, mono-2-ethylhexyl acid phosphate, di-2-ethylhexyl acid phosphate, monoisodecyl acid phosphate, and diisodecyl. Alkyl acid phosphates such as acid phosphate; alkoxyalkyl acid phosphates such as butoxyethyl acid phosphate and dibutoxyethyl acid phosphate; hydroxyalkyl (meth) acrylate acid phosphates such as 2-hydroxyethyl (meth) acrylate acid phosphate; polyoxyethylene- 2-Ethylhexyl ether phosphate, polyoxypropylene-2-ethylhexyl ether phosphate, polyoxyethylene octyl ether phosphate, polyoxypropylene octyl ether phosphate, polyoxyethylene decyl ether phosphate, polyoxypropylene Decyl ether phosphate ester, polyoxyethylene lauryl ether phosphate ester, polyoxypropylene lauryl ether phosphate ester, polyoxyethylene tridecyl ether phosphate ester, polyoxypropylene tridecyl ether phosphate ester, polyoxyethylene oleyl ether phosphorus Examples thereof include polyoxyalkylene alkyl ether phosphoric acid esters such as acid esters and polyoxypropylene oleyl ether phosphoric acid esters. These can be used alone or in combination of two or more.

The polishing composition disclosed herein may include a phosphite ester. One type of phosphite ester can be used alone or in combination of two or more types. The molecular weight of the phosphite ester is not particularly limited. This is because the protective function of the phosphite ester is considered to be different from that of the above-mentioned phosphate ester. Specifically, during polishing, the phosphite ester has the same function of the reactive region (P = O) as the above-mentioned phosphate ester, and the ester bond portion (POC) separates the organic group. It is considered that it is adsorbed on the edge of the substrate and finally forms an inorganic acid film. It is considered that the inorganic acid film is arranged at a high density on the edge of the substrate and mainly functions as a protective film against chemical etching, so that the effect is exhibited regardless of the molecular weight of the phosphite ester. It should be noted that the action and effect of the phosphite ester in the technique disclosed herein is not construed as being limited to the above mechanism.

From the viewpoint of improving the shape of the end portion, the molecular weight of the phosphite ester is preferably about 85 or more, preferably 100 or more, more preferably 120 or more, and may be, for example, 150 or more. From the viewpoint of solubility in the polishing composition, handleability, etc., the upper limit of the molecular weight is, for example, 1000 or less, preferably 500 or less, more preferably 300 or less, 200 or less, and 160 or less. It may be.

The phosphite ester disclosed herein is, for example, a compound represented by the following general formula (2).

上式（２）中、Ｒ^３およびＲ^４は同一であっても互いに異なっていてもよく、いずれも水素原子または有機基である。ただし、Ｒ^３およびＲ^４のうち少なくとも一方は、有機基である。

In the above formula (2), R ³ and R ⁴ may be the same or different from each other, and both are hydrogen atoms or organic groups. However, at least one of R ³ and R ⁴ is an organic group.

In some embodiments, the compound represented by the general formula (2) is an organic group in which at least one of R ³ and R ⁴ is selected from an alkyl group and an aromatic group. The number of carbon atoms constituting the organic group is not particularly limited, and one having an appropriate number of carbon atoms is used in consideration of end shape improving property, solubility in a polishing composition, handleability and the like. For example, the number of carbon atoms of the alkyl group is 1 or more, 2 or more is appropriate, and 4 or more may be used. Aromatic groups (eg, aryl groups, typically phenyl groups) have 6 or more carbon atoms. The upper limit of the number of carbon atoms of the alkyl group and the aromatic group is preferably 24 or less, preferably 12 or less, more preferably 8 or less, still more preferably 6 or less, and particularly preferably 4 or less.

In some preferred embodiments, the compound represented by the general formula (2) has at least one of R ³ and R ⁴ being an alkyl group. The above-mentioned alkyl group is not particularly limited, and may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group. It is preferable that at least one of R ³ and R ⁴ is a chain alkyl group. According to the phosphite ester containing a chain alkyl group, the effect of improving the shape of the end portion can be easily obtained. Specific examples of R ³ and R ⁴ in this embodiment include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, and the like. Neopentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, Examples thereof include a heptadecyl group, an octadecyl group, a nonadecil group, and an eikosyl group.

Preferable examples of the phosphite ester are alkylhydrogen phosphites such as dimethylhydrogen phosphite, diethylhydrogen phosphite, diisopropylhydrogen phosphite, dibutylhydrogen phosphite, diisobutylhydrogen phosphite, and bis (2-ethylhexyl) hydrogen phosphite. Arylhydrogen phosphite such as diphenylhydrogen phosphite; and the like. These can be used alone or in combination of two or more. Of these, diethylhydrogen phosphite and dibutylhydrogen phosphite are preferable.

The content (total amount) of the phosphoric acid ester and the phosphite ester having a molecular weight of 150 or more in the polishing composition disclosed herein can be an appropriate amount that achieves both maintenance of processability and improvement of edge shape. It is not limited to a specific range because it may vary depending on the species. The above content can be about 0.001 mM (mmol / L) or more, and about 0.01 mM or more is suitable. From the viewpoint of improving the shape of the end, the above content may be about 0.1 mM or more, about 0.3 mM or more, about 0.5 mM or more, about 1 mM or more, about 2 mM or more, and about. It may be 5 mM or more, and may be approximately 8 mM or more. The upper limit of the content can be, for example, 100 mM or less, and about 30 mM or less (for example, 15 mM or less) is appropriate. From the viewpoint of processability, the above content may be about 10 mM or less, about 7 mM or less, about 3 mM or less, about 1 mM or less, about 0.5 mM or less, or about 0.1 mM or less. ..

Although not particularly limited, in the embodiment in which monoalkyl acid phosphate is used as the phosphoric acid ester in the technique disclosed herein, the content of monoalkyl acid phosphate in the polishing composition is approximately 0.01 to 10 mM (for example,). It is preferably about 0.1 to 5 mM, typically about 0.3 to 1.5 mM). In the embodiment using dialkyl acid phosphate, the content is preferably about 0.1 to 100 mM (for example, about 1 to 30 mM, typically about 5 to 20 mM). In the embodiment using hydroxy (meth) acrylate acid phosphate, the content thereof is preferably about 0.1 to 50 mM (for example, about 1 to 10 mM, typically about 2 to 5 mM). In the embodiment using the (poly) oxyalkylene alkyl ether phosphate, the content thereof is preferably about 0.001 to 15 mM (for example, about 0.01 to 5 mM, typically about 0.02 to 2 mM). .. When the technique disclosed herein is carried out in the form of using a phosphite ester, the content of the phosphite ester is about 0.1 to 50 mM (for example, about 1 to 15 mM, typically about 2 to 10 mM). It is preferable to do so.

(1-1-4. Acid)
The polishing composition disclosed herein preferably contains an acid as a polishing accelerator. As the acid, either an inorganic acid or an organic acid can be used. Examples of the organic acid include organic carboxylic acids, organic phosphonic acids, organic sulfonic acids, amino acids and the like having about 1 to 18 carbon atoms, typically about 1 to 10. The acid may be used alone or in combination of two or more.

Specific examples of the inorganic acid include phosphoric acid (orthric acid), nitrate, sulfuric acid, hydrochloric acid, boric acid, sulfamic acid, phosphinic acid, phosphonic acid, pyrophosphate, tripolyphosphate, tetrapolyphosphate, hexametaphosphate, carbonic acid and fluoride. Hydrogenic acid, sulfite, thiosulfate, chloric acid, perchloric acid, chloric acid, hydroiodic acid, periodic acid, iodic acid, hydrobromic acid, perbromic acid, bromic acid, chromium acid, nitrite, etc. Can be mentioned.

Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, formic acid, acetic acid, propionic acid, Buty acid, adipic acid, oxalic acid, valeric acid, enanthic acid, caproic acid, capric acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid , Crotonic acid, oleic acid, linoleic acid, linolenic acid, ricinolenic acid, methacrylic acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, tartron acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, Organic carboxylic acids such as salicylic acid, isocitrate, methylenesuccinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetate, chloroacetic acid, dichloroacetic acid, trichloroacetic acid; glycine, alanine, glutamic acid, aspartic acid, valine, leucine, isoleucine, Amino acids such as serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine; nicotinic acid; picric acid; picolinic acid; phytic acid, 1-hydroxyethylidene-1,1- Diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1- Hydroxy-1,1-diphosphonic acid, ethanehydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2- Organic phosphonic acids such as dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid, aminopoly (methylenephosphonic acid); methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzene Examples thereof include organic sulfonic acids such as sulfonic acid, p-toluene sulfonic acid, 2-naphthalene sulfonic acid, sulfosuccinic acid, 10-campar sulfonic acid, isethionic acid and taurine.

Examples of preferable acids from the viewpoint of polishing efficiency include phosphoric acid, phosphonic acid, maleic acid, hydrochloric acid, nitrate, sulfuric acid, sulfamic acid, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, methanesulfonic acid and the like. .. Of these, phosphoric acid, phosphonic acid, maleic acid, hydrochloric acid, nitric acid, and sulfuric acid are preferable.

The acid may be used in the form of a salt of the acid. Examples of the salt include metal salts, ammonium salts, alkanolamine salts and the like of the above-mentioned inorganic acids and organic acids. Examples of the metal salt include alkali metal salts such as lithium salt, sodium salt and potassium salt. Examples of the ammonium salt include quaternary ammonium salts such as tetramethylammonium salt and tetraethylammonium salt. Examples of the alkanolamine salt include a monoethanolamine salt, a diethanolamine salt, and a triethanolamine salt.
Specific examples of the salt include alkali metal phosphates and alkali metals such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. Hydrogen phosphate; Alkali metal salt of organic acid exemplified above; Alkali metal salt of diacetate diacetic acid, Alkali metal salt of diethylenetriamine pentaacetic acid, Alkali metal salt of hydroxyethylethylenediamine triacetic acid, Triethylenetetraminehexacetic acid Alkali metal salts; etc. The alkali metal in these alkali metal salts can be, for example, lithium, sodium, potassium and the like.

As the salt that can be contained in the polishing composition disclosed herein, a salt of an inorganic acid, for example, an alkali metal salt or an ammonium salt can be preferably adopted. For example, potassium chloride, sodium chloride, ammonium chloride, potassium nitrate, sodium nitrate, ammonium nitrate, potassium phosphate and the like can be preferably used.

The acid and its salt can be used alone or in combination of two or more (for example, two or three). In some preferred embodiments, an acid and a salt of an acid different from the acid can be used in combination. The acid is preferably an inorganic acid. The salt of the acid is preferably a salt of an inorganic acid.

When the polishing composition contains an acid, the molar concentration of the acid in the polishing composition (in the case of containing a plurality of types of acids, the total molar concentration thereof) is not particularly limited, and is, for example, approximately 0.001 mol / L. The above is appropriate, preferably about 0.01 mol / L or more, more preferably about 0.05 mol / L or more, still more preferably 0.07 mol / L or more, and particularly preferably 0.09 mol. / L or more. In some embodiments, the molar concentration of the acid may be, for example, 0.1 mol / L or higher, typically 0.12 mol / L or higher. Higher processability can be achieved by increasing the molar concentration of acid. From the viewpoint of surface quality after polishing, polishing stability, and the like, the molar concentration of the above acid is preferably about 1.2 mol / L or less, preferably about 1 mol / L or less, and more preferably about 0. It is 8 mol / L or less, more preferably about 0.5 mol / L or less, and particularly preferably about 0.3 mol / L or less (for example, 0.2 mol / L or less).

(1-1-5. Oxidizing agent)
The polishing composition disclosed herein can contain an oxidizing agent. Examples of oxidizing agents are peroxide, nitric acid or its salt, perioic acid or its salt, peroxo acid or its salt, permanganic acid or its salt, chromium acid or its salt, oxygen acid or its salt, metal salts. , Sulfates, etc., but are not limited to these. The oxidizing agent may be used alone or in combination of two or more. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitrate, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfate, ammonium peroxomonosulfate, metal salt peroxo monosulfate, peroxodisulfuric acid, and peroxodisulfuric acid. Ammonium sulfate, peroxodisulfuric acid metal salt, peroxophosphate, peroxosulfuric acid, sodium peroxoborate, perigiic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromic acid, hypoiodic acid, chloric acid, bromic acid, Iodine acid, perioic acid, perchloric acid, hypochloric acid, sodium hypochlorate, calcium hypochlorate, potassium permanganate, metal chromate salt, metal bicarbonate salt, iron chloride, iron sulfate, Examples thereof include iron citrate and iron ammonium sulfate. Preferred oxidizing agents include hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfuric acid, peroxodisulfuric acid and nitric acid. It preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

When the polishing liquid contains an oxidizing agent, the content of the oxidizing agent is preferably 0.05 mol / L or more, more preferably, in consideration of the rate of oxidation of the object to be polished and the processability. It is 0.1 mol / L or more, more preferably 0.15 mol / L or more, and particularly preferably 0.3 mol / L or more. When the polishing composition contains an oxidizing agent, the content thereof is preferably 1 mol / L or less, more preferably 0.8 mol / L or less, still more preferably, from the viewpoint of maintaining surface accuracy. Is 0.6 mol / L or less.

(1-1-6. Basic compounds)
The polishing composition may contain a basic compound, if necessary. Here, the basic compound refers to a compound having a function of raising the pH of the composition by being added to the polishing composition. Examples of basic compounds include alkali metal hydroxides, carbonates and bicarbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogen phosphates, organic acid salts and the like. The basic compound may be used alone or in combination of two or more.

Specific examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide and the like.
Specific examples of carbonates and hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate and the like.
Specific examples of quaternary ammonium or salts thereof include quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; alkali metals of such quaternary ammonium hydroxides. Salt; etc. Examples of the alkali metal salt include sodium salt and potassium salt.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and piperazine anhydride. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.
Specific examples of phosphates and hydrogen phosphates include alkalis such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. Metal salts can be mentioned.
Specific examples of the organic acid salt include potassium citrate, potassium oxalate, potassium tartrate, sodium potassium tartrate, ammonium tartrate and the like.

(1-1-7. Other ingredients)
The polishing composition disclosed herein contains a polishing composition such as a surfactant, a water-soluble polymer, a dispersant, a chelating agent, a preservative, and an antifungal agent, as long as the effects of the present invention are not significantly impaired. If necessary, a known additive that can be used for the product may be further contained.

The surfactant is not particularly limited, and any of an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used. The use of a surfactant can improve the dispersion stability of the polishing composition. The surfactant may be used alone or in combination of two or more. The surfactant is typically be a molecular weight 1 × 10 water-soluble organic compounds of less than ^6.
Specific examples of anionic surfactants include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate ester, alkyl sulfate ester, polyoxyethylene alkyl sulfate, alkyl sulfate, alkylbenzene sulfonic acid, polyoxyethylene sulfosuccinic acid, and alkyl sulfosuccinate. Acid, alkylnaphthalene sulfonic acid, alkyldiphenyl ether disulfonic acid, polyacrylic acid, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonic acid, sodium polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl Examples thereof include ether sodium sulfate and salts thereof.
Other specific examples of anionic surfactants include polyalkylarylsulfonic acid-based compounds such as naphthalenesulfonic acid formaldehyde condensate, methylnaphthalenesulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate, and benzenesulfonic acid formaldehyde condensate. Melamine formalin resin sulfonic acid compound such as melamine sulfonic acid formaldehyde condensate; lignin sulfonic acid compound such as lignin sulfonic acid and modified lignin sulfonic acid; aromatic amino sulfonic acid such as aminoaryl sulfonic acid-phenol-formaldehyde condensate In addition, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonic acid; and salts thereof can be mentioned. As the salt, alkali metal salts such as sodium salt and potassium salt are preferable.
Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, alkyl alkanolamide and the like. ..
Specific examples of the cationic surfactant include alkyltrimethylammonium salt, alkyldimethylammonium salt, alkylbenzyldimethylammonium salt, alkylamine salt and the like.
Specific examples of amphoteric surfactants include alkyl betaine type, fatty acid amide propyl betaine type, alkyl imidazole type, amino acid type, alkyl amine oxide type and the like.

In the polishing composition of the embodiment containing a surfactant, it is appropriate that the content of the surfactant is, for example, 0.0005% by weight or more. The content is preferably 0.001% by weight or more, more preferably 0.002% by weight or more, from the viewpoint of surface smoothness after polishing. Further, from the viewpoint of processability and the like, the content is preferably 3.0% by weight or less, preferably 0.5% by weight or less, for example 0.1% by weight or less.

The polishing composition disclosed herein may contain a water-soluble polymer. By containing a water-soluble polymer, the surface quality after polishing can be improved. Examples of water-soluble polymers include polyalkylarylsulfonic acid-based compounds such as naphthalenesulfonic acid formaldehyde condensate, methylnaphthalenesulfonic acid formaldehyde condensate, and anthracene sulfonic acid formaldehyde; Acid-based compounds; Lignin-sulfonic acid-based compounds such as lignin sulfonic acid and modified lignin sulfonic acid; Aromatic amino sulfonic acid-based compounds such as aminoarylsulfonic acid-phenol-formaldehyde condensate; , Polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylic acid, polyvinyl acetate, polymaleic acid, polyitaconic acid, polyvinyl alcohol, polyglycerin, polyvinylpyrrolidone, isoprene sulfonic acid and acrylic acid Polymers, polyvinylpyrrolidone polyacrylic acid copolymers, polyvinylpyrrolidone vinyl acetate copolymers, diallylamine hydrochloride sulfur dioxide copolymers, carboxymethylcellulose, salts of carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, purulans, chitosan, chitosan salts And so on. The water-soluble polymer may be used alone or in combination of two or more.

In the polishing composition of the embodiment containing the water-soluble polymer, it is appropriate that the content of the water-soluble polymer in the polishing composition is, for example, 0.001% by weight or more. The above content is the total content thereof in the embodiment containing the plurality of water-soluble polymers. The content is preferably 0.003% by weight or more, more preferably 0.005% by weight or more, still more preferably 0.007% by weight or more, from the viewpoint of surface smoothness of the object to be polished after polishing. .. Further, from the viewpoint of workability and the like, the content is preferably 1.0% by weight or less, preferably 0.5% by weight or less, for example 0.1% by weight or less. The technique disclosed herein can also be preferably carried out in a mode in which the polishing composition does not substantially contain a water-soluble polymer.

Examples of dispersants are polycarboxylic acid dispersants such as sodium polycarboxylic acid and ammonium polycarboxylic acid; naphthalene sulfonic acid dispersants such as sodium naphthalene sulfonic acid and ammonium naphthalene sulfonic acid; alkyl sulfonic acid. Examples include system dispersants; polyphosphoric acid dispersants; polyalkylene polyamine dispersants; quaternary ammonium dispersants; alkyl polyamine dispersants; alkylene oxide dispersants; polyhydric alcohol ester dispersants; and the like.

Examples of chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetic acid, and diethylenetriaminepentaacetic acid. , Sodium diethylenetriaminepentaacetate, triethylenetetraminehexacetic acid and sodium triethylenetetraminehexacetate. Examples of organic phosphonic acid-based chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrax (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphone). Acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid , Etan-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphospho Contains succinic acid. Of these, organic phosphonic acid-based chelating agents are more preferable, and among them, ethylenediaminetetrax (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are mentioned. Particularly preferred chelating agents include ethylenediamine tetrakis (methylenephosphonic acid).

Examples of preservatives and fungicides include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters. , Phenoxyethanol and the like.

(1-1-8. pH)
The pH of the polishing composition disclosed herein is not particularly limited. The pH of the polishing composition can be, for example, 12.0 or less, typically 0.5 to 12.0, or 10.0 or less, typically 0.5 to 10.0. Good. From the viewpoint of processability, surface quality, etc., the pH of the polishing composition can be 7.0 or less, for example 0.5 to 7.0, 5.0 or less, typically 1.0 to 1.0. It is more preferably 5.0 or less, and further preferably 1.0 to 4.0 or less. The pH of the polishing composition may be, for example, 3.0 or less, typically 1.0 to 3.0, preferably 1.0 to 2.0, and more preferably 1.0 to 1.8. it can. A pH adjuster such as an organic acid, an inorganic acid, or a basic compound can be contained in the polishing liquid, if necessary, so that the above pH is achieved. The above pH can be preferably applied to a polishing composition for polishing a magnetic disk substrate such as a nickel phosphorus substrate. In particular, it can be preferably applied to a polishing composition for primary polishing.

(1-1-9. Abrasive liquid)
The polishing composition disclosed herein is typically supplied to an object to be polished in the form of a polishing solution containing the composition for polishing, and is used for polishing the object to be polished. The polishing liquid may be prepared by diluting the polishing composition, for example. Here, the dilution is typically a dilution with water. Alternatively, the polishing composition may be used as it is as a polishing liquid. That is, in the concept of the polishing composition in the technique disclosed herein, a polishing liquid (working slurry) supplied to the polishing object and used for polishing the polishing object is diluted and used as the polishing liquid. Both with concentrates are included. Such a polishing composition in the form of a concentrated liquid is advantageous from the viewpoint of convenience and cost reduction in production, distribution, storage and the like. The concentration ratio can be, for example, about 1.5 to 50 times. From the viewpoint of storage stability of the concentrated solution, for example, a concentration ratio of 2 to 20 times, typically 2 to 10 times is appropriate.

(1-1-10. Composition for multi-dosage form polishing)
The polishing composition disclosed herein may be a one-dosage form or a multi-dosage form including a two-dosage form. For example, the constituent components of the polishing composition, typically part A containing a part of the components other than water, and part B containing the remaining components are mixed to polish the object to be polished. It may be configured to be used. The multi-dosage form polishing composition according to some preferred embodiments is composed of Part A containing abrasive grains and Part B containing components other than abrasive grains. Part A containing the abrasive grains may further contain a dispersant. Examples of components other than the abrasive grains contained in Part B include acids, water-soluble polymers and other additives. The compound selected from the phosphite ester and the phosphoric acid ester having a molecular weight of 150 or more can be contained in either or both of parts A and B. Normally, they are stored separately before use and can be mixed during use. The time of use here can typically be the time of polishing the substrate to be polished. At the time of mixing, an oxidizing agent such as hydrogen peroxide may be further mixed. For example, when the oxidizing agent is supplied in the form of an aqueous solution, the aqueous solution can be Part C constituting a multi-dosage polishing composition.

<1-2. Use>
The polishing composition disclosed herein can be preferably applied to polishing, for example, a nickel phosphorus substrate, a glass substrate, a carbon substrate, or the like. Further, the plating material may be a disk substrate having a metal layer or a metal compound layer other than the nickel phosphorus plating layer on the surface of the base disk. Among them, it is suitable as a polishing composition for a nickel-phosphorus-plated substrate having a nickel-phosphorus-plated layer on a base disk made of an aluminum alloy. In such applications, it is particularly meaningful to apply the techniques disclosed herein.

The polishing composition disclosed herein is particularly meaningful in applications that require high polishing efficiency, such as a pre-polishing process in a magnetic disk substrate manufacturing process that requires a highly accurate surface after a finish polishing process. Can be used. When a plurality of pre-polishing steps are provided as a pre-step of the finish polishing step, it can be used in any of the pre-polishing steps, and the same or different polishing compositions can be used in these pre-polishing steps. The polishing composition disclosed herein is suitable, for example, as a polishing composition used in the primary polishing step of a magnetic disk substrate, that is, the first polishing step. Among them, it can be preferably used in the first polishing step after nickel phosphorus plating, that is, the primary polishing step in the manufacturing process of the nickel phosphorus substrate.

The polishing composition disclosed herein polishes a magnetic disk substrate having a surface roughness of about 20 Å to 300 Å as measured by, for example, a laser scan type surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System Inc. Therefore, it is suitable for the purpose of adjusting the surface roughness of the magnetic disk substrate to 10 Å or less. In such applications, it is particularly meaningful to apply the techniques disclosed herein. The surface roughness referred to here means the arithmetic mean roughness (Ra).

<1-3. Polishing method>
The polishing composition disclosed herein can be suitably used for polishing a magnetic disk substrate as an object to be polished, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method of polishing an object to be polished using the polishing composition disclosed herein will be described. Hereinafter, the object to be polished is also referred to as a substrate to be polished.
That is, a polishing liquid (working slurry) containing any of the polishing compositions disclosed herein is prepared. The preparation of the polishing liquid may include preparing the polishing liquid by subjecting the polishing composition to operations such as concentration adjustment and pH adjustment. Examples of the concentration adjustment include dilution. Alternatively, the polishing composition may be used as it is as a polishing liquid.

Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, an object to be polished is set in a general polishing device, and a polishing liquid is supplied to the surface of the object to be polished, that is, the surface to be polished through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the object to be polished to move the two relative to each other. The movement can be, for example, a rotational movement. Polishing of the object to be polished is completed through such a polishing step.

The polishing pad that can be used is not particularly limited. For example, a polishing pad such as a rigid polyurethane foam type, a non-woven fabric type, or a suede type can be used. The suede type may be a buff pad, and typically may be a polishing pad in a non-buffed state (so-called non-buff pad) whose surface is not buffed. Such a suede-type polishing pad (typically a polyurethane polishing pad) is excellent in workability and easily realizes high quality of the substrate surface. The polishing pad used in the technique disclosed herein does not include abrasive grains.

The polishing device used in the polishing step may be a double-sided polishing device that simultaneously polishes both sides of the object to be polished, or a single-sided polishing device that polishes only one side of the object to be polished. When the polishing step is a preliminary polishing step, in some embodiments, a double-sided polishing device can be preferably adopted as the polishing device for performing the polishing step. When the finish polishing step is performed after the primary polishing step, a single-sided polishing device can be preferably adopted as the polishing device for performing the finish polishing step.

The polishing process as described above can be part of the manufacturing process for magnetic disk substrates, such as nickel phosphorus substrates. Therefore, according to this specification, a method for manufacturing a magnetic disk substrate and a method for polishing including the above-mentioned polishing step are provided.

The polishing composition disclosed herein can be preferably used in a pre-polishing step of the object to be polished, for example, a primary polishing step. According to this specification, there is provided a method for producing a magnetic disk substrate and a method for polishing, which comprises a step of performing pre-polishing using any of the above-mentioned polishing compositions. The above method includes a step (1) of supplying the polishing composition disclosed herein to an object to be polished and polishing the object to be polished. The method may include a finish polishing step after the pre-polishing step. The polishing composition used in the finish polishing step is not particularly limited. Therefore, the matters disclosed in this specification include the step (1) of polishing the object to be polished with the polishing composition containing the abrasive grains disclosed herein, and the polishing composition used in the step (1). The method of manufacturing a magnetic disk substrate and the method of polishing include, in this order, a step (2) of polishing an object to be polished with a polishing composition different from that of the above. According to such a manufacturing method, a magnetic disk substrate can be efficiently manufactured.

≪2. Second aspect ≫
<2-1. Polishing composition>
(2-1-1. Abrasive grains)
The polishing composition according to the second aspect contains silica particles as abrasive grains (also referred to as silica particles S; the same shall apply hereinafter unless otherwise specified). Since the abrasive grains contained in the polishing composition according to the second aspect are the same as the abrasive grains contained in the polishing composition according to the first aspect, duplicate description of matters relating to the abrasive grains is omitted. To do.

(2-1-2. Water)
The polishing composition according to the second aspect typically contains, in addition to the abrasive grains as described above, water in which the abrasive grains are dispersed. As the water, ion-exchanged water, pure water, ultrapure water, distilled water and the like can be preferably used. The ion-exchanged water can typically be deionized water.

The polishing composition according to the second aspect can be preferably carried out, for example, in a form in which the solid content content thereof is 0.5% by weight to 30.0% by weight. A form in which the solid content is 1.0% by weight to 20.0% by weight is more preferable. The polishing composition can typically be a slurry composition.

(2-1-3. Compound selected from phosphate ester and phosphite ester)
The polishing composition according to the second aspect is characterized by containing at least one compound selected from a phosphoric acid ester having a molecular weight of 150 or more and a phosphite ester. The compound used in this embodiment (at least one compound selected from a phosphoric acid ester having a molecular weight of 150 or more and a phosphite ester) is the compound described in the first aspect (phosphorus having a molecular weight of 150 or more). Since at least one compound selected from an acid ester and a phosphite ester) can be used, duplicate description will be omitted. Hereinafter, the above-mentioned compound (at least one compound selected from a phosphoric acid ester having a molecular weight of 150 or more and a phosphite ester) according to this embodiment will be described in detail.

The phosphoric acid ester is any one of a phosphoric acid monoester, a phosphoric acid diester, and a phosphoric acid triester. Phosphoric acid monoester is preferable from the viewpoint of improving the shape of the end portion. As the phosphoric acid ester, one selected from phosphoric acid monoester, phosphoric acid diester and phosphoric acid triester can be used alone or in combination of two or more. When the phosphoric acid ester contains two or more kinds of phosphoric acid monoester, phosphoric acid diester, and phosphoric acid triester, the phosphoric acid ester can include, for example, phosphoric acid monoester and phosphoric acid diester. .. When the phosphoric acid ester contains two or more kinds of compounds, the phosphoric acid ester preferably has a high ratio of monoesters. Higher proportions of monoesters tend to improve edge shape and storage stability of the polishing composition. The monoester ratio of the phosphoric acid ester (molar ratio of monoester) can be 30 mol% or more, 40 mol% or more is appropriate, and from the viewpoint of improving the end shape, it is preferably 50 mol% or more. (For example, more than 50 mol%), more preferably 55 mol% or more (for example, more than 55 mol%), still more preferably 60 mol% or more. In some embodiments, the monoester ratio of the phosphate ester is 70 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more (eg, 95-100 mol). %) May be used.

The monoester ratio of the phosphoric acid ester (molar ratio of the monoester) can be obtained by the following method. The general first equivalent acid value, second equivalent acid value, and third equivalent acid value are measured by potentiometric titration, and the contents of phosphoric acid monoester, phosphoric acid diester, and inorganic phosphoric acid are calculated respectively. Furthermore, the number of moles of the phosphoric acid monoester and the phosphoric acid diester is obtained from the calculated molecular weight. The monoester ratio (molar ratio of monoester) can be calculated by (number of moles of phosphoric acid monoester) / (number of moles of phosphoric acid monoester + number of moles of phosphoric acid diester) × 100. The content of the phosphoric acid ester by potentiometric titration can be obtained by adopting the calculation method described in, for example, Japanese Patent Publication No. 58-8746. The examples described later are also measured by the same method.

From the viewpoint of improving the shape of the end portion, the molecular weight of the phosphoric acid ester may be 150 or more, 180 or more, 190 or more, 200 or more, 210 or more, 220 or more, or 230 or more. , 240 or more, 250 or more, 300 or more, 400 or more (for example, 450 or more). The upper limit of the molecular weight is typically 1000 or less, preferably 700 or less, 600 or less, more preferably 550 or less, and 500, from the viewpoint of solubility in the polishing composition, handleability, and the like. It may be less than or equal to 450 or less, 400 or less, 350 or less, 330 or less, 300 or less, 270 or less, 250 or less, 240 or less, 230 or less, 220 or less. It may be 210 or less (for example, 170 or less).

The phosphoric acid ester disclosed herein is, for example, a compound represented by the following general formula (1).

In the above formula (1), R ¹ and R ² may be the same or different from each other, and both are hydrogen atoms or organic groups. However, at least one of R ¹ and R ² is an organic group.

In some preferred embodiments, in the compound, R ¹ and R ² in the general formula (1) are independently hydrogen atoms or alkyl groups, alkenyl groups, alkoxyalkyl groups, (meth) acrylics. It is an organic group selected from an acid alkyl ester group, a (meth) acryloyl group, a (poly) oxyalkylene alkyl ether group, a (poly) oxyalkylene aryl ether group and an aromatic group. The (meth) acryloyl group is used to include both an acryloyl group and a methacryloyl group. The number of carbon atoms constituting the organic group is not particularly limited as long as the molecular weight of the compound is 150 or more, and is appropriate in consideration of edge shape improving property, solubility in a polishing composition, handleability, and the like. Those having a carbon atom number are used. For example, the number of carbon atoms of the organic group may be independently 3 or more, preferably 4 or more, 6 or more, or 8 or more. The aromatic group (eg, aryl group, typically phenyl group) has 6 or more carbon atoms and may be 8 or more carbon atoms. The upper limit of the number of carbon atoms of the organic group is independently, preferably 24 or less, preferably 18 or less, more preferably 14 or less, still more preferably 12 or less, and particularly preferably 8 or less. In the embodiment in which one of R ¹ and R ² is a chain alkyl group, an alkenyl group, or an alkoxy alkyl group, the number of carbon atoms of one of R ¹ and R ² may be 1 or 2.

It is more preferable that at least one of R ¹ and R ^{2 in} the general formula (1) contains an alkyl group, an alkenyl group, an alkoxyalkyl group, a (meth) acryloyl group, and a (poly) oxyalkylene group. , Alkoxyalkyl groups, (meth) acryloyl groups, and (poly) oxyalkylene groups are more preferred. Such compounds tend to exhibit more excellent edge shape improving effects, and the storage stability of the polishing composition also tends to be good or excellent. Examples of such R ¹ and R ² include, for example, an alkoxyalkyl group, a (meth) acryloyl group, and a (poly) oxyalkylene alkyl ether group. Among them, according to the phosphoric acid ester containing an alkoxyalkyl group and a (meth) acryloyl group, it is easy to achieve both an end shape improving effect and storage stability.

In some embodiments, the compound represented by the general formula (1) has at least one of R ¹ and R ² being an alkyl group. The above-mentioned alkyl group is not particularly limited, and may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group. It is preferable that at least one of R ¹ and R ² is a chain alkyl group. According to the phosphoric acid ester containing a chain alkyl group, the effect of improving the shape of the end portion can be easily obtained. The number of carbon atoms of the alkyl group is preferably 3 or more, and is preferably 4 or more, 6 or more, or 8 or more from the viewpoint of improving the shape of the end portion. The upper limit of the number of carbon atoms of the alkyl group is preferably 24 or less, and is preferably 18 or less (for example, 16 or less, 14 or less, further 12 or less), more preferably, from the viewpoint of storage stability of the polishing composition. Is 8 or less, more preferably 7 or less.

In the second aspect, the matters other than the above regarding the phosphoric acid ester having a molecular weight of 150 or more are as described in the first aspect, and thus duplicate description will be omitted.

Since the phosphite ester used in the second aspect is as described in the first aspect, a duplicate description will be omitted.

The phosphite ester and phosphoric acid ester may be in the form of salts.

The content (total amount) of the phosphoric acid ester and the phosphite ester having a molecular weight of 150 or more in the polishing composition according to the second aspect can be as described in the first aspect. In some preferred embodiments, the content of the phosphate ester and phosphite ester having a molecular weight of 150 or more (preferably the content of the phosphoric acid ester) in the polishing composition is 0 from the viewpoint of improving the shape of the end portion. .125 mM (mmol / L) or more, more preferably 0.2 mM or more, still more preferably 1 mM or more, particularly preferably 2.5 mM or more, 3 mM or more, 5 mM or more, 8 mM or more. It may be. In some preferred embodiments, the upper limit of the content is preferably 20 mM or less, preferably 10 mM or less, from the viewpoint of storage stability of the polishing composition.

(2-1-4. Acid)
The polishing composition according to the second aspect preferably contains an acid as a polishing accelerator. Since the acid that can be contained in the polishing composition according to the second aspect is the same as the acid that can be contained in the polishing composition according to the first aspect, matters relating to the acid (including the salt of the acid). , Duplicate description is omitted.

(2-1-5. Oxidizing agent)
The polishing composition according to the second aspect can contain an oxidizing agent. Since the oxidizing agent that can be contained in the polishing composition according to the second aspect is the same as the oxidizing agent that can be contained in the polishing composition according to the first aspect, overlapping explanations regarding matters relating to the oxidizing agent will be given. Omitted.

(2-1-6. Basic compounds)
The polishing composition may contain a basic compound, if necessary. Since the basic compound that can be contained in the polishing composition according to the second aspect is the same as the basic compound that can be contained in the polishing composition according to the first aspect, the matters relating to the basic compound are duplicated. The description to be made is omitted.

(2-1-7. Other ingredients)
The polishing composition according to the second aspect is used for polishing of surfactants, water-soluble polymers, dispersants, chelating agents, preservatives, fungicides, etc., as long as the effects of the present invention are not significantly impaired. Known additives that can be used in the composition may be further contained, if necessary. Since the other components that can be contained in the polishing composition according to the second aspect are the same as the other components that can be contained in the polishing composition according to the first aspect, matters relating to other components are duplicated. The explanation to be done is omitted.

(2-1-8. pH)
The pH of the polishing composition according to the second aspect can be as described in the first aspect. In some preferred embodiments, the pH of the polishing composition is in the range of 1-4 from the viewpoint of processability, end shape improvement and the like. The pH of the polishing composition may be, for example, 3.0 or less, typically 1.0 to 3.0, preferably 1.0 to 2.0, and more preferably 1.0 to 1.8. it can. The above pH can be preferably applied to a polishing composition for polishing a magnetic disk substrate such as a nickel phosphorus substrate. In particular, it can be preferably applied to a polishing composition for primary polishing.

<Other matters>
Other matters (polishing liquid, composition for multi-dosage form polishing, use, polishing method, etc.) of the second aspect can be as described in the first aspect. Here, duplicate description will be omitted.

A combination of the first aspect and the second aspect is also included in the technique disclosed herein. Therefore, the technique disclosed herein can be carried out by appropriately combining the first aspect and the second aspect.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples.

≪Experiment 1≫
<Example 1-1-1-25>
Silica particles S1 (non-spherical colloidal silica, average aspect ratio 1.2, D50 = 150 nm), silica particles S2 (spherical colloidal silica, D50 = 60 nm), and silica particles S3 (baked silica, average aspect ratio 1.3, (D50 = 300 nm), the additives shown in Table 1, 85% phosphoric acid, and 31% hydrogen peroxide solution were mixed with deionized water to prepare the polishing composition according to each example. The content of silica particles S1 in the polishing composition is 40.9 g / L, the content of silica particles S2 is 27.3 g / L, the content of silica particles S3 is 6 g / L, and the content of phosphoric acid is 14. The content of the hydrogen peroxide solution is .7 g / L and the content of the hydrogen peroxide solution is 60 g / L, and the content of the additive is as shown in Table 1. In Table 1, lauryl EO2 acid phosphate is diethylene glycol lauryl ether acid phosphate, and alkyl EO3 acid phosphate is polyoxyethylene (EO3) alkyl ether acid phosphate.

[Disc polishing]
The polishing composition according to each example was used as it was in the polishing liquid, and the object to be polished was polished under the following conditions. As the object to be polished, an aluminum substrate for a hard disk having an electroless nickel phosphorus plating layer on the surface was used. The substrate had a diameter of 3.5 inches, an outer diameter of about 95 mm, an inner diameter of about 25 mm, a donut shape, a thickness of 1.75 mm, and a surface roughness Ra of 130 Å before polishing. The surface roughness Ra is the arithmetic mean roughness of the nickel phosphorus-plated layer measured by a laser scan type surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System Inc.

(Polishing conditions)
Polishing device: Double-sided polishing machine manufactured by System Seiko Co., Ltd., model "9.5B-5P"
Polishing pad: Suede pad manufactured by FILWEL (a pad having a base layer and a surface layer, and the surface layer is made of foamed polyurethane).
Number of substrates to be polished: 15 (3 / carrier x 5 carriers)
Polishing liquid supply rate: 135 mL / min Polishing load: 120 g / cm ²
Upper surface plate rotation speed: 27 rpm
Lower platen rotation speed: 36 rpm
Sun gear (sun gear) rotation speed: 8 rpm
Amount of polishing: Total thickness of about 2.2 μm on both sides of each substrate

[Workability]
The processability (polishing rate) when the substrate to be polished was polished under the above polishing conditions using the polishing composition according to each example was calculated. The workability was determined based on the following formula.
Workability [μm / min] = Weight loss of substrate due to polishing [g] / (Substrate area [cm ² ] x Nickel phosphorus plating density [g / cm ³ ] x Polishing time [min]) x 10 ⁴
The obtained values are converted into relative values when the workability of Example 1-18 is 100, and are shown in the “Workability” column of Table 1. The larger the value, the better the workability.

[End shape]
A non-contact surface shape measuring machine (trade name "NewView5032", manufactured by Zygo) was used for a substrate (a substrate to be polished after polishing) that was polished under the above polishing conditions using the polishing composition according to each example. , PV difference (Peak-Valley difference, maximum height difference) of measurement position coordinates at the edge of the substrate (region with radius 45.5 mm to 47.5 mm) with objective lens magnification 2.5 times and intermediate lens magnification 1.0 times. ) Was measured.
The obtained values are converted into relative values when the measured value of Example 1-18 is set to 100, and are shown in the column of "end shape" in Table 1. The smaller the value, the better the edge shape.

As shown in Table 1, in Examples 1-1 to 1-17 using a composition containing an additive selected from a phosphite ester and a phosphoric acid ester having a molecular weight of 150 or more, no additive was contained. Compared with Example 1-18 (reference example), the workability was maintained well and the end shape was improved. On the other hand, in Examples 1-19 to 1-21 in which the phosphoric acid ester having a molecular weight of less than 150 was used, the effect of improving the end shape was small, and when the amount of the phosphoric acid ester used was increased, the end shape deteriorated. It was a tendency. Further, in Examples 1-22 to 1-25 in which the non-phosphorus additive was used, the end shape was improved, but the processability was lowered. It is considered that the non-phosphorus additive protected not only the edge but also the entire surface of the substrate.
From the above results, by using an additive selected from a phosphite ester and a phosphoric acid ester having a molecular weight of 150 or more in the silica particle-containing polishing composition, the end shape is maintained while maintaining the polishing performance. It turns out that can be improved.

≪Experiment 2≫
<Example 2-1 to 2-33>
Silica particles S1 (non-spherical colloidal silica, average aspect ratio 1.2, D50 = 150 nm), silica particles S2 (spherical colloidal silica, D50 = 60 nm), and silica particles S3 (baked silica, average aspect ratio 1.3, D50 = 300 nm), the additives (phosphoric acid ester, silica ester) shown in Tables 2 to 10, 85% phosphoric acid, and 31% hydrogen peroxide solution are mixed together with deionized water to each example. Such a polishing composition was prepared. The content of silica particles S1 in the polishing composition is 40.9 g / L, the content of silica particles S2 is 27.3 g / L, the content of silica particles S3 is 6 g / L, and the content of phosphoric acid is 14. The content of the hydrogen peroxide solution is .7 g / L and the content of the hydrogen peroxide solution is 60 g / L, and the content of the additive is as shown in Tables 2 to 10. Examples a to e in each example are examples in which the same type of phosphoric acid ester was used in different amounts. The details of the additives are shown in Tables 2 to 10. In Example 2-30, no additives (phosphate ester and phosphite ester) were used. The pH was adjusted to a predetermined value using phosphoric acid or potassium hydroxide. The pH of the polishing composition according to the example not specified in the table was 1.8.

[Storage stability]
2000 g of the polishing composition according to each example was housed in a container having a capacity of 2000 mL, and stored at 23 ° C., 60 ° C., and 70 ° C. for 168 hours, respectively. Polishing compositions stored under each temperature condition (composition for polishing after storage at 23 ° C, composition for polishing after storage at 60 ° C, composition for polishing after storage at 70 ° C) were polished under certain conditions, and each was polished. Storage stability was evaluated by comparing the polishing performance of the polishing composition stored under temperature conditions. The evaluation criteria are as follows.
(Evaluation)
E (Excellent): Within ± 5% rate of change in polishing performance after storage at 70 ° C compared to after storage at 23 ° C G (Good): Within ± 5% rate of change in polishing performance after storage at 60 ° C compared to after storage at 23 ° C A ( Acceptable): Rate of change in polishing performance after storage at 60 ° C compared to after storage at 23 ° C ± 5-10%
P (Poor): The rate of change in polishing performance after storage at 60 ° C with respect to that after storage at 23 ° C was more than 10%, or component separation and aggregation were visually observed.

[Workability]
Using the polishing composition according to each example, the disc was polished in the same manner as in Experiment 1, and the processability was evaluated. The obtained values are converted into relative values when the workability of Example 2-30 is set to 100, and are shown in the “Workability” column of Tables 2-10. The larger the value, the better the workability.

[End shape]
Using the polishing composition according to each example, the disc was polished in the same manner as in Experiment 1, and the PV difference was measured for the polished substrate. The obtained values are converted into relative values when the measured value of Example 2-30 is 100, and are shown in the column of "end shape" in Tables 2 to 10. The smaller the value, the better the edge shape.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. Further, an appropriate combination of the above-described aspects may be included in the scope of the invention for which protection by the patent is sought by the present patent application.

Claims (10)

A composition for polishing a magnetic disk substrate,
Contains silica particles as abrasive grains and water,
A polishing composition further comprising a phosphite ester and at least one selected from a phosphoric acid ester having a molecular weight of 150 or more. The polishing composition according to claim 1, further comprising hydrogen peroxide as an oxidizing agent. Contains the phosphate ester
The phosphoric acid ester has a general formula (1):

(In the above formula (1), R ¹ and R ² are independently hydrogen atoms, or alkyl groups, alkenyl groups, alkoxyalkyl groups, (meth) acrylic acid alkyl ester groups, (meth) acryloyl groups, An organic group selected from a (poly) oxyalkylene alkyl ether group, a (poly) oxyalkylene aryl ether group and an aromatic group, provided that at least one of R ¹ and R ² is an organic group);
The polishing composition according to claim 1 or 2, which is a compound represented by. In the phosphoric acid ester, R ¹ and R ² in the general formula (1) are independently hydrogen atoms or alkyl groups having 3 to 18 carbon atoms, alkenyl groups, and alkoxyalkyl groups. The polishing composition according to claim 3, which is selected from a (meth) acrylic acid alkyl ester group, a (meth) acryloyl group and a (poly) oxyalkylene alkyl ether group. Contains the phosphate ester
The polishing composition according to any one of claims 1 to 4, wherein the phosphoric acid ester has a monoester ratio of 55 mol% or more. The polishing composition according to any one of claims 1 to 5, wherein the silica particles contain spherical colloidal silica having an average aspect ratio of less than 1.10 based on SEM image analysis. The polishing composition according to any one of claims 1 to 6, wherein the silica particles include non-spherical colloidal silica having an average aspect ratio of 1.10 or more based on SEM image analysis. The polishing composition according to claim 6 or 7, wherein the silica particles further include heat-treated silica particles. The polishing composition according to any one of claims 1 to 8, wherein the pH is in the range of 1 to 4. The polishing composition according to any one of claims 1 to 9, which is used in a pre-process of a finish polishing step.