Silica dispersion and abrasive composition

Abstract

The objective is to provide a silica dispersion that can suppress the adhesion, drying, and aggregation of silica particles to the inner wall of the spout of a storage container, thereby reducing the occurrence of scratches when using an abrasive composition containing the silica dispersion. [Solution] The silica dispersion 1 is stored and / or transported in a state filled in a storage container 2, and contains silica particles 3 and water 4. The storage container 2 comprises a container body 5 into which the silica dispersion 1 can be filled, and a spout 6 whose inner wall portion 7b is formed of an organic polymer material. The ratio of the liquid contact area of ​​the silica dispersion 1 to the total surface area of ​​the inner surface 5a of the storage container 2 filled with the silica dispersion 1 is in the range of 0.950 to 0.999. When the storage container 2 is stored and / or transported, the silica dispersion 1 is in contact with the entire inner wall portion 7b of the spout 6, and a gas phase portion 11 exists in a part between the inner surface 5a of the container body 5 and the silica dispersion 1.

Description

Technical Field

[0001] The present invention relates to silica and an abrasive composition. More specifically, it relates to a silica dispersion stored and / or transported in a filled storage container and an abrasive composition prepared using the silica dispersion.

Background Art

[0002] Conventionally, in memory hard disk drives and the like, for the purpose of increasing the storage capacity and reducing the diameter of magnetic disks, further improvement in the recording density of the magnetic disks has been demanded. Therefore, the flying height of the magnetic head is reduced, and the unit recording area is made smaller to increase the recording density.

[0003] In the manufacture of magnetic disks, a polishing process for polishing the surface of the magnetic disk has been conventionally carried out, and high polishing accuracy in this polishing process, that is, high surface smoothness with the unevenness (surface roughness) of the surface of the magnetic disk after polishing suppressed as much as possible is required. Also, together with high surface smoothness, suppression of the occurrence of undulations on the surface of the magnetic disk and scratches generated during polishing is also required.

[0004] On the other hand, in the semiconductor manufacturing field, the requirements for high integration and high speed are increasing. In particular, in order to achieve high integration of semiconductor substrates, miniaturization that makes the wiring constructed on the semiconductor substrate as thin as possible is required. To meet such requirements, for example, during the semiconductor substrate manufacturing process, it is required to make the depth of focus for exposing the photoresist as shallow as possible. Therefore, high smoothness is required for the substrate surface of the semiconductor substrate as well as the above-described magnetic disk.

[0005] Thus, in order to obtain high surface smoothness on the substrate surface of magnetic disk substrates and semiconductor substrates, it is particularly important to suppress the occurrence of scratches on the polished surface of the workpiece (magnetic disk substrate, etc.). For example, the use of a polishing liquid composition containing colloidal silica has been proposed (see Patent Document 1).

[0006] Furthermore, an attempt has been proposed to reduce the occurrence of scratches on the object to be polished by using a silica dispersion containing the above-mentioned colloidal silica as silica particles as the polishing liquid composition (or abrasive composition), and by performing a filtration treatment such as passing the silica dispersion through a filter equipped with a filtration aid such as diatomaceous earth to remove coarse particles contained in the colloidal silica before using it in the polishing process (see Patent Document 2).

[0007] In this case, when using the polishing liquid composition containing colloidal silica as described above, a commercially available silica dispersion liquid, which has been prepared in advance by stirring and mixing colloidal silica, water, and other additives in a predetermined ratio, is often used. An acid and an oxidizing agent are then added to this silica dispersion liquid to prepare the polishing agent composition, which is then used in the polishing process.

[0008] When silica dispersions are manufactured industrially, they are stored in storage containers after production and transported to their destination in the same state. Therefore, a considerable period of time (for example, several months to about six months) may pass between the time the silica dispersion is manufactured and when it is used as an abrasive composition in the polishing process. As a result, some of the water contained in the stored silica dispersion may evaporate due to the temperature surrounding the storage container. Furthermore, even when the storage container is filled with silica dispersion to near its specified capacity, a gaseous phase portion (gas phase) exists near the spout on the top surface of the container, in contact with the liquid surface of the silica dispersion.

[0009] As a result, the silica dispersion, while stored and / or transported, may adhere to the inner surface of the storage container where it comes into contact with the gas phase, particularly to the inner wall of the spout located on the top surface of the storage container. This can cause water to evaporate from the adhered silica dispersion, leading to the precipitation of silica particles, such as colloidal silica, on the inner wall. Furthermore, the precipitated silica particles may aggregate, resulting in the formation of larger, coarser particles.

[0010] When silica particles and other materials precipitate on the inner wall of the spout in this manner, and the silica dispersion is moved from the storage container to the outside, that is, when attempting to pour the silica dispersion from the outside of the storage container, there is a possibility that coarse particles formed by the aggregation of solid silica particles will be discharged from the storage container along with the liquid silica dispersion. If such a silica dispersion containing coarse particles is used as a raw material for an abrasive composition, the large, hard coarse particles may cause scratches on the surface of the object being polished. In other words, the storage and transport conditions of the silica dispersion could affect the surface quality of the polished surface after the polishing process.

[0011] In response to this, in order to set the filling rate of the abrasive particle dispersion (=silica dispersion) packed into the container higher than usual, the ratio of the contact area of ​​the abrasive particle dispersion to the total area of ​​the inner wall surface inside the container is set to be greater than specified (see Patent Document 3). It has been proposed that this reduces the occurrence of nanoscratch and enables the manufacture of magnetic disk substrates with excellent surface quality. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2002-327170 [Patent Document 2] Japanese Patent Publication No. 2014-124766 [Patent Document 3] Japanese Patent Publication No. 2006-130638 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] However, as shown in Patent Document 3, there were physical limitations to increasing the filling density of the silica dispersion by limiting the ratio of the wetted area to a predetermined range. In other words, in order to prevent the silica dispersion from leaking out of the storage container due to vibrations and temperature changes that occur during storage and / or transport of the storage container, at least a portion of the inner wall of the spout of the storage container had to be in contact with the gas phase.

[0014] Patent Document 3 describes a preferred range for the ratio of the area in contact with the liquid to the total wall surface area inside the container, stating that "from the viewpoint of reducing nano-scratching, the ratio of the area in contact with the liquid to the total wall surface area inside the container is preferably 0.85 or more, more preferably 0.90 or more, and more preferably 0.92 or more. Furthermore, from the viewpoint of preventing the liquid from overflowing from the container due to the volume expansion of the dispersion due to the rise in temperature, it is preferably 0.99 or less, more preferably 0.98 or less, and even more preferably 0.97 or less." (Paragraph 0009).

[0015] Therefore, in view of the above circumstances, the present invention focuses on storage containers used for storing and / or transporting silica dispersions, and in particular limits the ratio of the contact area of ​​the silica dispersion to the inner surface of the storage container (= contact area of ​​the silica dispersion / total surface area of ​​the inner surface of the storage container) to a specific range, and limits the position of the gas phase within the storage container, thereby suppressing the adhesion of the silica dispersion to the inner wall of the spout of the storage container, drying, precipitation of silica particles, and generation of coarse particles due to aggregation of silica particles, and thereby reducing the occurrence of scratches when using an abrasive composition containing the silica dispersion. [Means for solving the problem]

[0016] The inventors of this invention have diligently studied how to achieve both the suppression of the generation of coarse particles due to the aggregation of silica particles and the prevention of leakage of the silica dispersion to the outside. After observing the adhesion of silica particles, including cases where the amount of silica dispersion filled is small and the proportion of the gas phase in the storage container is large, they noticed that agglutinated silica particles and coarse particles were concentrated on the inner wall of the spout, and that there were almost no agglutinated particles or coarse particles on the inner surface of the container body. Based on this, they hypothesized that if there is no gas phase on the inner wall of the spout, then even if there is a gas phase on the inner wall of the container body, agglutinated silica particles and coarse particles are unlikely to be generated, and after further investigation, they arrived at the present invention.

[0017] [1] A silica dispersion liquid that is stored and / or transported in a storage container, comprising silica particles having an average primary particle diameter in the range of 3 to 100 nm and water, wherein the storage container comprises a container body into which the silica dispersion liquid can be filled and a spout portion joined to the container body, the spout portion having at least an inner wall portion formed of an organic polymer material, the ratio of the liquid contact area of ​​the silica dispersion liquid to the total surface area of ​​the inner surface of the storage container filled with the silica dispersion liquid being in the range of 0.950 to 0.999, the silica dispersion liquid coming into contact with the entire inner wall portion of the spout portion when the storage container is stored and / or transported, and a gas phase portion existing in part between the inner surface of the container body and the silica dispersion liquid.

[0018] [2] The silica dispersion according to [1], wherein the silica particles are colloidal silica.

[0019] [3] The silica dispersion liquid according to [1], wherein the organic polymer material is formed of a polyolefin resin material.

[0020] [4] The silica dispersion according to [3], wherein the organic polymer material is polyethylene resin or polypropylene resin.

[0021] [5] The silica dispersion according to [1], wherein the pH value (at 25°C) is in the range of 7 or more and 12 or less.

[0022] [6] The silica dispersion according to [1], wherein the ratio of the liquid contact area is in the range of 0.970 to 0.999.

[0023] [7] An abrasive composition containing the silica dispersion according to any one of [1] to [6], an acid and / or its salt, and an oxidizing agent. [Advantages of the Invention]

[0024] The silica dispersion of the present invention can suppress the precipitation and generation of aggregates and coarse particles of silica particles during storage and / or transportation. By using an abrasive composition using the silica dispersion, scratch reduction can be achieved, and a magnetic disk substrate or semiconductor substrate with an excellent surface state can be obtained. [Brief Description of the Drawings]

[0025] [Figure 1] It is an explanatory view showing a schematic configuration of a storage container filled with the silica dispersion of an embodiment of the present invention. [Figure 2] It is an explanatory view showing a schematic configuration of the pouring outlet portion of the storage container. [Figure 3] It is an explanatory view schematically showing a cross section near the pouring outlet portion of a storage container in a conventional storage form. [Figure 4] It is an explanatory view schematically showing the state of precipitation of silica particles and generation of coarse particles on the inner wall portion of the storage container. [Figure 5] It is an explanatory view schematically showing a storage container in a first storage form. [Figure 6] It is an explanatory view schematically showing a cross section near the pouring outlet portion of a storage container in a first storage form. [Figure 7] It is an explanatory view schematically showing a storage container in a second storage form. [Figure 8] It is an explanatory view schematically showing a cross section near the pouring outlet portion of a storage container in a second storage form. [Figure 9] It is an explanatory view schematically showing a storage container during conversion to a third storage form. [Figure 10] It is an explanatory view schematically showing a storage container in a third storage form. [Figure 11] This is a schematic diagram illustrating a cross-section near the spout of a storage container in the third storage configuration. [Modes for carrying out the invention]

[0026] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. It should be understood that the scope of the present invention also includes modifications, improvements, etc., to the embodiments described below, made in accordance with the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention.

[0027] 1. Silica dispersion A silica dispersion 1 according to one embodiment of the present invention is a dispersion that can be stored and / or transported when filled in a storage container 2 (details of which will be described later), and contains at least silica particles 3 having an average primary particle diameter in the range of 3 to 100 nm and water 4, and is composed of these mixed in a predetermined ratio.

[0028] More specifically, the silica dispersion 1 of this embodiment can use well-known silica particles such as colloidal silica or fumed silica as the silica particles 3. In particular, colloidal silica is preferred to reduce the amount of scratches generated on the surface of the object to be polished when used as an abrasive composition. The silica particles 3 constituting the silica dispersion 1 may be one type or a combination of the above-mentioned colloidal silica or fumed silica.

[0029] Here, colloidal silica, which is suitably used as silica particles 3 in the silica dispersion 1 of this embodiment, can be obtained, for example, by the water glass method, in which an alkali metal silicate salt such as sodium silicate is used as a raw material and particles are grown by a condensation reaction in an aqueous solution; by the alkoxysilane method, in which an alkoxysilane such as tetraethoxysilane is used as a raw material and obtained by a condensation reaction in water containing a water-soluble solvent such as alcohol; or by a method in which metallic silicon and water are reacted in the presence of an alkaline catalyst to produce colloidal silica while generating hydrogen gas.

[0030] On the other hand, fumed silica that can be used as silica particles 3 can be obtained, for example, by a vapor phase method in which volatile silicon compounds such as silicon tetrachloride are used as raw materials and grown by hydrolysis at high temperatures of 1000°C or higher using an oxygen-hydrogen burner. The compositions of these colloidal silica and fumed silica are conventionally known, and they can be used as appropriate.

[0031] The silica particles 3 used in the silica dispersion 1 of this embodiment have an average primary particle diameter (D50) in the range of 3 to 100 nm. In addition, to suppress aggregation of the silica particles 3 themselves, and to make the surface roughness of the workpiece (e.g., magnetic disk, etc.) uniform and reduce scratches generated on the surface of the workpiece (magnetic disk surface, etc.), the silica particles 3 have an average primary particle diameter (D50) in the range of 3 to 100 nm.

[0032] Here, the shape of the silica particles 3 is known to be of various shapes, such as spherical, non-spherical, chain-like, or konpeito-shaped, and is not particularly limited in the silica dispersion of the present invention. In order to reduce the occurrence of scratches described later, it is particularly preferable to use particles that are spherical or close to spherical in shape.

[0033] Furthermore, the ratio of silica particles 3 and water 4 in the silica dispersion 1 is not particularly limited, but for example, the silica concentration in the silica dispersion 1 is in the range of 0.5 to 50% by mass, preferably in the range of 1.0 to 45% by mass.

[0034] Here, although the pH value (at 25°C) of the silica dispersion 1 can be set arbitrarily, it is preferable to set the pH value (at 25°C) to 7 or higher and 12 or lower from the viewpoint of the dispersion stability of the silica particles 3 in the silica dispersion 1. More preferably, it can be set to 8 or higher, and more preferably to 9 or higher.

[0035] On the other hand, from the viewpoint of suppressing the dissolution of silica particles 3 in silica dispersion 1, it is preferable to set the pH value (at 25°C) to 12 or less, more preferably 11 or less.

[0036] As described above, by adjusting the type of silica particles 3, the range of the average primary particle diameter (D50) of the silica particles 3, the shape of the silica particles 3, the silica concentration in the silica dispersion 1, and the pH value (25°C) of the silica dispersion 1 to appropriate ranges, it is possible to create an excellent silica dispersion 1 that is superior in terms of dispersion stability and dissolution suppression of the silica particles 3, and that can suppress the occurrence of scratches when used in an abrasive composition.

[0037] 2.Storage container The storage container 2 used to fill, store, and / or transport the silica dispersion 1 prepared as described above mainly comprises a container body 5 and a spout portion 6 joined to the upper surface of the container body 5, as shown in Figures 1 to 11.

[0038] Here, Figure 1 is an explanatory diagram showing the schematic configuration of a storage container 2 filled with a silica dispersion liquid 1 according to one embodiment of the present invention; Figure 2 is an explanatory diagram showing the schematic configuration of the spout portion 6 of the storage container 2; Figure 3 is an explanatory diagram schematically showing a cross-section near the spout portion 6 of the storage container 2 in conventional storage form D; Figure 4 is an explanatory diagram schematically showing the state of precipitation of silica particles 3 and generation of coarse particles 12 on the inner wall portion 7b of the storage container 2; Figure 5 is an explanatory diagram schematically showing the storage container 2 in first storage form A; and Figure 6 is first storage form Figure 1 is a schematic diagram showing a cross-section near the spout 6 of the storage container 2 in state A, Figure 7 is a schematic diagram showing the storage container 2 in the second storage state B, Figure 8 is a schematic diagram showing a cross-section near the spout 6 of the storage container 2 in the second storage state B, Figure 9 is a schematic diagram showing the storage container 2 in the process of being converted to the third storage state C, Figure 10 is a schematic diagram showing the storage container 2 in the third storage state C, and Figure 11 is a schematic diagram showing a cross-section near the spout 6 of the storage container 2 in the third storage state C. Here, Figures 1 and 3 also illustrate the conventional storage state D, which is a storage state using the conventional storage container 2.

[0039] As shown in Figures 3 and 4, the spout portion 6 of the storage container 2 into which the silica dispersion 1 is filled in this embodiment comprises a substantially cylindrical spout body 7 and a lid portion 10 formed on the inside of the lid (not shown) which has a male threaded portion 8 that protrudes spirally from the outer wall portion 7a of the spout body 7 and a female threaded portion 9 that can be screwed into it. As a result, the lid portion 10 can be fastened and fixed to the spout portion 6 by screwing the female threaded portion 9 of the lid portion 10 into the male threaded portion 8 of the spout portion 6, creating a structure that prevents leakage of the silica dispersion 1 filled inside the container body 5. Consequently, the structure prevents the silica dispersion 1 from leaking out of the storage container 2 during storage and / or transport.

[0040] The storage container 2 in which the silica dispersion 1 is filled is formed entirely of a polyolefin resin material, such as polyethylene resin or polypropylene resin, which is a type of organic polymer material, for the entire spout portion 6. More specifically, the storage container 2 consists of a container body 5 formed by joining multiple translucent, flexible sheets of polyolefin resin material to form a roughly rectangular parallelepiped shape, and a spout portion 6 and a lid portion 10 formed from a white, rigid material made of polyolefin resin material.

[0041] Here, since the container body 5 of the storage container 2 is made of a soft sheet material, the container body 5 itself has the property of being easily deformable under stress. Therefore, when the container body 5 is not filled with silica dispersion liquid 1, it can be stored in a small folded state, while when the container body 5 is filled with silica dispersion liquid 1, it can take on a roughly cubic shape as shown in Figure 1. In other words, the storage container 2 used to fill the silica dispersion liquid 1 in this embodiment can be a so-called "flexible container" whose shape can be arbitrarily changed according to the amount of silica dispersion liquid 1 etc. filled into the container body 5.

[0042] The storage container 2 is not limited to the configuration shown in Figure 1, etc. For example, it may include a container with a corrugated outer shell that further covers the outer surface of the container body formed of the above-mentioned organic polymer material, or a composite container in which the container body is made of a metal material such as a metal can, metal drum, or metal container, and only the spout and lid are made of the organic polymer material (none of which are shown).

[0043] Furthermore, the organic polymer material constituting the spout 6 and the container body 5 of the storage container 2 is not particularly limited, and materials other than the aforementioned polyethylene resin and polypropylene resin, such as polyolefin resins, may be used. However, considering various conditions such as low affinity with silica particles 3, difficulty of silica particles 3 adhering to it, and wide availability on the market, polyethylene resin and polypropylene resin are particularly preferred.

[0044] Polyethylene resins that can be used include low-density polyethylene produced by a high-pressure method using a radical polymerization initiator, and copolymerized linear low-density polyethylene produced by a low-pressure method using a metallocene catalyst.

[0045] On the other hand, examples of polypropylene resins include broad molecular weight distribution polypropylene obtained using a Ziegler-Natta catalyst, or narrow molecular weight distribution polypropylene obtained using a metallocene catalyst.

[0046] These exemplified polyethylene resins and polypropylene resins may be homopolymers or copolymers with different monomers. For example, polyethylene resins include high-density polyethylene homopolymers, ethylene-butene copolymer polyethylene resins, and hexene-based linear low-density polyethylene resins. Polypropylene resins include propylene homopolymers, random copolymers obtained by randomly copolymerizing ethylene, butene, etc., with propylene, and block copolymers obtained by randomly copolymerizing ethylene and propylene after propylene homopolymerization.

[0047] The pouring spout 6 and container body 5 of the storage container 2 can be molded using conventional resin molding methods, such as injection molding, blow molding (hollow molding), sheet molding, and film molding, and any method can be selected depending on the type of organic polymer material used and the shape of the pouring spout. Furthermore, the pouring spout and container body may be formed in a single molding process, or multiple parts may be molded separately and then assembled and joined together.

[0048] The organic polymer material used as the raw material for the container body 5, spout portion 6, and lid portion 10 that constitute the storage container 2 can be polyethylene resin as the main raw material as described above. Additives such as antioxidants, ultraviolet absorbers, antistatic agents, antibacterial agents, fillers, colorants, lubricants, and flame retardants may also be added to this main raw material. Since the composition of these additives is well known in the technical field of resin molding, a detailed explanation will be omitted.

[0049] Furthermore, a mold release agent may be used to facilitate the removal of the pouring spout section 6, which has been molded using a mold.

[0050] 3. Method for storing and / or transporting silica dispersions in storage containers. When filling the container body 5 of the storage container 2 with silica dispersion 1, even if the amount of silica dispersion 1 filled is increased, or air is removed from the empty spaces in the storage container 2 that do not contain silica dispersion 1, the ratio of the contact area (the ratio of the contact area of ​​the silica dispersion 1 to the total surface area of ​​the inner surface 5a of the container body 5 of the storage container 2) can be increased as much as possible, there is a limit to how high this ratio can be. As a result, for example, as shown in Figure 3, a gas phase 11 inevitably exists between the liquid surface 1a of the silica dispersion 1 and the underside 10a of the lid 10 that seals the storage container 2.

[0051] When the silica dispersion 1 is stored or transported in the storage container 2, vibrations may cause the liquid surface 1a to shake, and some of the silica dispersion 1 filled in the container may adhere to the inner wall 7b of the spout 6. Then, as water evaporates from the silica dispersion 1 adhering to the inner wall 7b of the spout 6, silica particles 3 precipitate on the inner wall 7b of the spout 6. At this time, the precipitated silica particles 3 may aggregate, or coarse particles 12 with larger particle sizes may be formed (see Figure 4). Figure 4 is a magnified cross-section of the vicinity of the spout 6 with the lid 10 removed, for the sake of simplicity, and schematically represents the silica particles 3 (aggregated particles) and coarse particles 12 adhering to the inner wall 7b.

[0052] When silica particles 3 and coarse particles 12 have precipitated and formed on the inner wall 7b of the spout 6, and the silica dispersion 1 is discharged from the storage container 2 with the lid 10 removed in order to use it as an abrasive composition, the silica particles 3 and coarse particles 12 that had precipitated and formed on the inner wall 7b of the spout 6 will be discharged from the storage container 2 along with the silica dispersion 1. As a result, there was a possibility that scratches would occur on the surface of the workpiece (magnetic disk, etc.) after polishing due to the influence of the abrasive composition mixed with silica particles 3 and coarse particles 12.

[0053] Therefore, the inventors observed in detail the adhesion status of silica particles 3, including cases where the filling rate of the silica dispersion 1 is low and the proportion of the gas phase 11 in the storage container 2 is large. As a result, they noted that silica particles 3 and coarse particles 12 are mainly concentrated near the inner wall 7b of the spout 6, and that these silica particles 3 etc. are not present in large quantities on the inner surface 5a of the container body 5.

[0054] In other words, by storing and / or transporting a storage container 2 filled with silica dispersion 1 in a state where there is no gas phase 11 between the inner wall 7b of the spout portion 6 and the silica dispersion 1, it is found that even if there are vibrations or temperature changes during storage or transport, aggregation of silica particles 3 and generation of coarse particles 12 become difficult, and useful effects such as reducing the occurrence of scratches can be achieved by using the silica dispersion 1 of the present invention in the abrasive composition.

[0055] In order to prevent the silica dispersion 1 from leaking out of the storage container 2 due to vibration, temperature changes, etc. during storage and / or transport of the storage container 2, a certain amount of gas phase 11 must exist inside the storage container 2. However, based on the above findings, if the storage configuration does not involve the gas phase 11 being located between the inner wall 7b of the spout 6 of the storage container 2 and the silica dispersion 1, in other words, it is sufficient if the gas phase 11 exists between the inner surface 5a of the container body 5 and the silica dispersion 1 (liquid surface 1a).

[0056] Here, when the proportion of the liquid phase portion in the storage container 2 (the proportion of the silica dispersion 1) is expressed as the ratio of the contact area of ​​the silica dispersion 1 to the total surface area inside the storage container 2 (= contact area of ​​the silica dispersion / total surface area of ​​the storage container 2), the ratio of the contact area can be defined as "0.950 to 0.999", preferably "0.970 to 0.999", and even more preferably "0.980 to 0.999".

[0057] By ensuring that the ratio of the contact area of ​​silica dispersion 1 is 0.950 or higher, it is possible to suppress the occurrence of scratches on the surface of the polished workpiece after polishing, even during long-term storage.

[0058] By ensuring that the ratio of the wetted surface area of ​​the silica dispersion 1 is 0.999 or less, leakage of the silica dispersion due to temperature changes during long-term storage or vibrations during transport can be prevented. Furthermore, as already explained, the storage container 2 is preferably a flexible container in order to prevent leakage of the silica dispersion 1 due to temperature changes during long-term storage or vibrations during transport.

[0059] In this specification, "total surface area inside the storage container" means the total surface area of ​​the inner surface (inner wall surface) of the storage container 2 that can be filled with the silica dispersion 1. Specifically, it is defined as the sum of the areas of the inner wall 7b of the spout 6 located inside the storage container 2, the inner surface 5a of the container body 5, and the underside 10a of the lid 10. Furthermore, the liquid contact area means the inner surface of the storage container 2 that comes into contact with the silica dispersion 1 when the storage container 2 is filled with the silica dispersion 1 and left to stand for a sufficient amount of time.

[0060] The total surface area and liquid contact area of ​​the storage container 2 can be calculated using conventional geometric calculations or by unfolding the storage container 2 and directly measuring its dimensions. In such calculations, it is assumed that the inner surface (inner wall surface) of the storage container 2 is formed as a smooth surface overall, and irregularities of less than 1 mm can be ignored. These calculation methods are described in Patent Document 3, which has already been illustrated, and are known in the art to which the present invention belongs.

[0061] In the silica dispersion liquid 1 of this embodiment, a storage configuration in which the gas phase portion 11 does not exist between the inner wall portion 7b of the spout portion 6 of the storage container 2 and the silica dispersion liquid 1 is, for example, to fill the silica dispersion liquid 1 in a so-called "vertical position" with the spout portion 6 of the storage container 2 on the upper side, and then, with the lid portion 10 attached to the spout portion 6 (see Figures 1 and 3), rotate the storage container 2 itself by 90°. This moves the position of the spout portion 6 to the horizontal position of the storage container 2, making it possible to create a "horizontal position" in which the gas phase portion 11 is located higher than the inner wall portion 7b of the spout portion 6 (see Figure 5, first storage configuration A).

[0062] Here, the air constituting the gas phase 11 is lighter than the silica dispersion 1 filled in the storage container 2, and therefore moves to a higher position than the silica dispersion 1. As a result, by changing the storage container 2 from the conventional storage form D (Figure 1) to the first storage form A (Figure 5), the gas phase 11 moves upward inside the container body 5, and the gas phase 11 can exist between a part of the inner surface 5a of the container on the upper side (the side in the conventional storage form D) of the container body 5 and the liquid surface 1a of the silica dispersion 1. In other words, the storage container 2 filled with the silica dispersion 1 can be stored and / or transported in a horizontal position. Note that, for convenience, the term "first storage form A" is used above, but it is not limited to storage; it is also acceptable to transport the storage container 2 filled with the silica dispersion 1 in the state of first storage form A (the same applies hereinafter). At this time, as shown in Figure 6, the area near the spout 6 sealed by the lid 10 is in contact with the silica dispersion 1 on all surfaces, including the underside 10a of the lid 10 and the inner wall 7b of the spout body 7, and there is no gas phase 11.

[0063] As another example, after filling the storage container 2 with the silica dispersion 1 in a so-called "vertical position" with the spout 6 at the top (see Figures 1 and 3), the storage container 2 itself can be rotated 180° to move the position of the spout 6 to the bottom of the storage container 2, resulting in an "inverted position" where the gas phase portion 11 is positioned higher than the inner wall portion 7b of the spout 6 (see Figure 7, second storage form B).

[0064] Similar to the first storage form A, the gas phase portion 11 moves to a position higher than the silica dispersion liquid 1 filled in the storage container 2. Therefore, by changing the storage container 2 from the conventional storage form D (Figure 1) to the second storage form B (Figure 7), the gas phase portion 11 moves upward inside the container body 5, and the gas phase portion 11 can exist between a part of the inner surface 5a of the container on the upper side (bottom side in the conventional storage form D) of the container body 5 and the liquid surface 1a of the silica dispersion liquid 1. In other words, the storage container 2 filled with silica dispersion liquid 1 can be stored and / or transported in an inverted state. At this time, as shown in Figure 8, the vicinity of the spout portion 6 sealed by the lid portion 10 is in contact with the silica dispersion liquid 1 at all points, including the underside 10a of the lid portion 10 and the inner wall portion 7b of the spout body 7, and the gas phase portion 11 does not exist.

[0065] As another example, after filling the storage container 2 with the silica dispersion 1 in a so-called "vertical position" with the spout 6 facing upwards (see Figures 1 and 3), the storage container 2 itself is rotated 90°. This moves the position of the spout 6 to the horizontal position of the storage container 2, allowing the gas phase portion 11 to be positioned higher than the inner wall portion 7b of the spout 6, resulting in a "horizontal position" (see Figure 9, first storage configuration A).

[0066] Then, in this horizontal position, a predetermined pressing force P is applied along a substantially horizontal direction to push the spout portion 6 into the inside of the container body 5, so that the spout portion 6 is embedded in the container body 5 (see Figure 9). This operation can be easily performed because the storage container 2 is a flexible container, as described above.

[0067] Subsequently, the container is returned to a vertical position from a horizontal position with the spout 6 embedded in it, so that the spout 6 is positioned on the upper side of the storage container 2 (see Figure 10, third storage form C). As a result, a gas phase 11 exists between a portion of the inner surface 5a of the container body 5, which is located higher than the spout 6, which is located near the center of the upper surface of the storage container 2, and the silica dispersion 1. In other words, the storage container 2 filled with silica dispersion 1 can be stored and / or transported in a vertical position with the spout 6 embedded in the container body 5. At this time, as shown in Figure 11, the area near the spout 6 sealed by the lid 10 is in contact with the silica dispersion 1 on all surfaces, including the underside 10a of the lid 10 and the inner wall 7b of the spout body 7, and no gas phase 11 exists.

[0068] In the first storage form A, second storage form B, and third storage form C described above, when filling the silica dispersion 1, there is no gas phase 11 between the inner wall 7b of the spout 6 of the storage container 2 and the silica dispersion 1. This suppresses the aggregation of silica particles 3 during storage and / or transport, and reduces the generation of coarse particles 12.

[0069] To explain in more detail, the storage container 2 in this embodiment, into which the silica dispersion is filled, has an inner wall portion 7b of its spout portion 6 that gradually narrows towards the vicinity of the spout. This makes it possible that silica particles 3 may penetrate this portion and have difficulty detaching from the inner wall portion 7b. In other words, it may easily become a starting point for the aggregation of silica particles 3. On the other hand, the inner surface 5a of the container body 5 has an overall flat shape. Even if silica particles 3 adhere to the inner surface 5a, they can easily detach from the point of adhesion, thus reducing the likelihood of aggregation of silica particles 3.

[0070] In addition, as mentioned above, high-density polyethylene is often used as the material forming the inner wall portion 7b of the spout portion 6, while low-density polyethylene is often used as the material forming the container body 5. Here, high-density polyethylene is a hard material with a high degree of crystallinity, while low-density polyethylene is a soft material with a low degree of crystallinity. It is presumed that the difference in the materials forming each part leads to differences in the degree of silica particle adhesion and aggregation.

[0071] 4. Abrasive composition The abrasive composition of this embodiment (not shown) can be prepared using the above-described silica dispersion 1 as the main raw material, and can also contain other components. That is, it can mainly consist of the silica dispersion 1, an acid and / or its salt, and an oxidizing agent.

[0072] As a specific example of an abrasive composition, in the case of an abrasive composition used for polishing nickel-phosphorus plated aluminum magnetic disks, it is preferable to use a silica dispersion whose pH value (at 25°C) has been adjusted to be acidic. For example, the pH value (at 25°C) of the abrasive composition is preferably in the range of 0.1 to 4.0, and more preferably in the range of 0.5 to 3.0.

[0073] The pH value (25°C) of the abrasive composition of this embodiment can be adjusted, for example, by appropriately adding the acids and / or salts shown below. It is preferable to mix the silica dispersion 1 filled in the storage container 2 with the acid and / or salt immediately before using it as an abrasive composition, and in particular, it is preferable to store the acid and / or salt separately in an acid-resistant bottle or the like, different from the silica dispersion 1, until mixing begins.

[0074] Specific examples of acids and / or salts that can be used in the abrasive composition of this embodiment include inorganic acids and / or salts thereof such as nitric acid, sulfuric acid, nitrite, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphate, tripolyphosphate, and amidosulfuric acid, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, Examples include organic phosphonic acids such as ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid, or their salts; aminocarboxylic acids such as glutamic acid and aspartic acid, or their salts; and carboxylic acids such as oxalic acid, nitroacetic acid, and maleic acid, or their salts. In particular, among those listed above, inorganic acids, organic phosphonic acids, or their salts are preferred from the viewpoint of reducing scratches.

[0075] The abrasive composition of this embodiment may further contain an oxidizing agent. Suitable oxidizing agents include peroxides, persulfuric acid or its salts, permanganic acid and its salts, chromic acid and its salts, peroxoacid and its salts, and mixtures of two or more of these oxidizing agents.

[0076] More specifically, examples include hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, metal salts of chromic acid, metal salts of dichromate, persulfuric acid, sodium persulfate, potassium persulfate, ammonium persulfate, peroxolinic acid, and sodium peroxoborate. Among these, hydrogen peroxide, persulfuric acid, and their salts are preferred, and hydrogen peroxide is even more preferred.

[0077] The oxidizing agent content in the abrasive composition of this embodiment is preferably 0.01 to 10.0% by mass. Furthermore, the abrasive composition may contain conventionally known components as needed. For example, it may contain thickeners, dispersants, rust inhibitors, and surfactants.

[0078] The abrasive composition of the embodiment can be used, for example, in a process of polishing a substrate by supplying the abrasive composition between a polishing platen to which a polishing pad is attached and a substrate to be polished, and moving the polishing platen and / or the substrate to be polished under a predetermined polishing pressure.

[0079] Furthermore, examples of materials suitable for polishing with the abrasive composition of this embodiment include metallic materials such as silicon, aluminum, nickel, tungsten, tantalum, and titanium, or metalloids, or alloys thereof, as well as glass, alumina, silicon dioxide, and silicon nitride. In particular, the abrasive composition of this embodiment can be used to polish materials containing metals such as aluminum, nickel, and tungsten, or alloys mainly composed of these metals. For example, it is suitable for polishing nickel-phosphorus plated aluminum alloy substrates and glass substrates such as crystallized glass and tempered glass, and is particularly suitable for polishing nickel-phosphorus plated aluminum alloy substrates.

[0080] Furthermore, in the manufacturing of magnetic disk substrates and the like, if multiple polishing steps are set up, it is preferable to apply the polishing composition of this embodiment to at least the second step and subsequent steps.

[0081] In other words, it is preferable to apply it to a finishing polishing process (final polishing process) aimed at improving surface smoothness by reducing scratches and surface roughness. [Examples]

[0082] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0083] <1> Preparation of silica dispersion The silica dispersions used in Examples 1-8 and Comparative Examples 1-5 were colloidal silica dispersions with an average particle size (D50) of 28 nm, a silica concentration of 30% by mass, and a pH of 10.0 (at 25°C).

[0084] <2> Storage container and filling method for silica dispersion. The storage containers used for the silica dispersions in each example and comparative example are flexible containers with an internal volume of 10L, as shown in Figure 1, with a spout made of high-density polyethylene and a container body made of low-density polyethylene.

[0085] In the above storage container, <1> Twelve kilograms of the prepared silica dispersion were filled into the container, and the air was removed and the lid was attached so that the ratio of the surface area of ​​the silica dispersion to the total surface area inside the storage container was as shown in Tables 1 and 2 below. Details regarding the calculation of the surface area ratio have already been explained and are therefore omitted here.

[0086] <3> How to store a container filled with silica dispersion. <3-1> How to place the storage containers in Examples 1-3 and 6, and Comparative Example 4 After filling with the silica dispersion, the storage container was rotated 90° so that the spout was positioned to the side (side side) and left to stand in a horizontal position (see Figure 5, first storage form A). It was then stored for a predetermined period in a space adjusted to a pre-set storage temperature. During this time, it was visually confirmed that there was no gas phase between the spout of the storage container and the filled silica dispersion while it was standing. In Examples 1-3 and Comparative Example 4, the storage temperature was set to 28°C, and the storage periods were 3 months and 6 months. On the other hand, in Example 6, the storage temperature was set to 45°C, and the storage periods were 7 days and 1 month.

[0087] <3-2> How to place the storage containers in Examples 4 and 7 After filling with the silica dispersion, the storage container was rotated 180° so that the spout was at the bottom (bottom side) and left to stand in an inverted position (see Figure 7, second storage form B). It was then stored for a predetermined period in a space adjusted to a pre-set storage temperature. During this time, it was visually confirmed that there was no gas phase between the spout of the storage container and the filled silica dispersion while it was standing. In Example 4, the storage temperature was set to 28°C, and the storage periods were 3 months and 6 months. On the other hand, in Example 7, the storage temperature was set to 45°C, and the storage periods were 7 days and 1 month.

[0088] <3-3> How to place the storage containers in Examples 5 and 8 After filling with silica dispersion, the storage container was rotated 90° to a horizontal position (see Figure 9, first storage form A) so that the spout was on the side. Then, force was applied to push the spout into the container body, and the container was rotated another 90° so that the spout was on the top (top) of the container, returning it to its original state (see Figure 10, third storage form C). The container was then left to stand and stored for a predetermined period in a space adjusted to a pre-set storage temperature. During this time, it was visually confirmed that there was no gas phase between the spout of the storage container and the silica dispersion while the container was standing. In Example 5, the storage temperature was set to 28°C, and the storage periods were 3 months and 6 months. On the other hand, in Example 8, the storage temperature was set to 45°C, and the storage periods were 7 days and 1 month.

[0089] <3-4> Placement of storage containers in Comparative Examples 1-3 and 5 After filling with silica dispersion, the container was left to stand with the spout positioned at the top (upper surface) of the container (conventional storage configuration D, see Figure 1), and stored for a predetermined period in a space adjusted to a pre-set storage temperature. At this time, a gas phase was observed between the spout of the storage container and the silica dispersion while the container was standing. In Comparative Examples 1 to 3, the storage temperature was set to 28°C, and the storage periods were 3 months and 6 months. On the other hand, in Comparative Example 5, the storage temperature was set to 45°C, and the storage periods were 7 days and 1 month.

[0090] <4> Preparation of abrasive compositions The abrasive compositions used in Examples 1-8 and Comparative Examples 1-5 are prepared by transferring the silica dispersions of each example and comparative example, after standing at their respective storage temperatures and for their respective storage periods, to separate containers, diluting them with pure water to a colloidal silica concentration of 4.0% by mass, and then adding sulfuric acid and hydrogen peroxide to a concentration of 0.8% by mass, thereby adjusting the pH value (at 25°C) to 1.2.

[0091] The results of polishing tests conducted using the abrasive compositions prepared with the silica dispersions of each example and comparative example are shown in Tables 1 and 2.

[0092] [Table 1]

[0093] [Table 2]

[0094] <5> Method for measuring the particle size of colloidal silica The particle size (Heywood diameter) of colloidal silica with an average particle size (D50) of 28 nm used in silica dispersions was measured by taking a field of view at a magnification of 100,000x using a transmission electron microscope (TEM) (JEOL Ltd., Transmission Electron Microscope JEM2000 (200kV)), and analyzing this image using analysis software (Mountec Co., Ltd., Mac-View Ver.4.0) to determine the Heywood diameter (equivalent diameter of the projection area circle). The average particle size of colloidal silica was calculated by analyzing the particle sizes of approximately 2000 colloidal silica particles using the method described above, and determining the particle size at which the cumulative particle size distribution (cumulative volume basis) from the smallest particle size side accounts for 50% using the above analysis software (Mountec Co., Ltd., Mac-View Ver.4.0).

[0095] <6> Polishing conditions Using the abrasive compositions prepared with the silica dispersions of each example and comparative example, a finish polishing test was performed on a roughly polished aluminum alloy magnetic disk substrate with an outer diameter of 97 mm and electroless nickel-phosphorus plating. Polishing machine: Speedfam Co., Ltd. 9B double-sided polishing machine Polishing pad: Pad for P2 manufactured by FILWEL Co., Ltd. Plate rotation speed: Upper plate - 8.3 min -1 Lower surface plate 25.0min -1 Abrasive composition supply rate: 100 ml / min Polishing time: 300 seconds Processing pressure: 11kPa

[0096] <7> Conditions for measuring scratches on the substrate surface after polishing In evaluating the polishing properties of the abrasive compositions prepared using the silica dispersions of each example and comparative example, the number of scratches on the substrate surface was measured using a MicroMAX VMX-4100 manufactured by Vision SciTech Co., Ltd. under the following conditions: tilt angle -5°, magnification 20x. The scratch ratio is a relative value with the number of scratches before filling the storage container set to 1 (reference). The number of scratches before filling the storage container was 0.30 scratches / surface. At this time, 300 scratches were confirmed by observing the back and front surfaces of 10 substrates per batch, totaling 1000 surfaces across 50 batches.

[0097] <8> Consideration First, we will discuss the test results shown in Table 1 (where the storage containers were left standing at a storage temperature of 28°C).

[0098] Comparing Example 1 and Comparative Example 1, the ratio of the surface area in contact with the silica dispersion to the total surface area inside the storage container is 0.990 in both cases. In Example 1, where the storage container was placed horizontally (first storage form A), the scratch ratio after standing for 3 months and 6 months did not increase compared to the test results of polishing tests using the abrasive composition with the silica dispersion before storage (=before filling). In other words, it was found that the silica dispersion was hardly affected by the aggregation of silica particles and coarse particles, and exhibited high polishing performance. On the other hand, in Comparative Example 1, where the storage container was placed vertically, the scratch ratio after 3 months increased compared to before storage, and this value increased further after 6 months.

[0099] Comparing Example 2 and Comparative Example 2, the ratio of the contact area of ​​the silica dispersion to the total inner surface area of ​​the storage container is 0.980 in both cases. In Example 2, where the storage container was placed horizontally (first storage form A), the scratch ratio after standing for 3 months and 6 months did not increase compared to the test results of polishing tests using the abrasive composition with the silica dispersion before storage. In other words, it was found that the silica dispersion was hardly affected by the aggregation of silica particles and coarse particles, and exhibited high polishing performance. On the other hand, in Comparative Example 2, where the storage container was placed vertically, the scratch ratio after 3 months increased compared to before storage, and this value increased further after 6 months.

[0100] Comparing Example 3 and Comparative Example 3, the ratio of the liquid contact area of ​​the silica dispersion to the total inner surface area of ​​the storage container is 0.970 in both cases. In Example 3, where the storage container was placed horizontally (first storage form A), the scratch ratio after standing for 3 months and 6 months did not increase compared to the test results of polishing tests using the abrasive composition with the silica dispersion before storage. In other words, it was found that the silica dispersion was hardly affected by the aggregation of silica particles and coarse particles, and exhibited high polishing performance. On the other hand, in Comparative Example 3, where the storage container was placed vertically, the scratch ratio after 3 months increased compared to before storage, and this value increased further after 6 months.

[0101] In Comparative Example 4, the storage container was placed horizontally, the same as in Examples 1-3 (First Storage Form A), and the ratio of the contact area of ​​the silica dispersion to the total inner surface area of ​​the storage container was 0.830, which deviates from the range of ratios defined in the present invention. In other words, it is a value that is significantly outside the lower limit of the numerical limit range, which is 0.950.

[0102] As a result, unlike the test results of Examples 1-3, an increase in the scratch ratio was observed after standing for 3 and 6 months. This indicates that, in addition to specifying the placement of the storage container, it is essential that the ratio of the surface area in contact with the silica dispersion to the total surface area inside the storage container is at least 0.950 in order for the silica dispersion of the present invention to exert its effects.

[0103] In Examples 4 and 5, the ratio of the wetted surface area of ​​the silica dispersion to the total inner surface area of ​​the storage container is 0.990, similar to Example 1. In Example 4, the storage container was placed upside down (second storage form B), and in Example 5, the storage container was placed in third storage form C. In both Examples 4 and 5, the scratch ratio after standing for 3 months and 6 months did not increase compared to the test results of polishing tests using the abrasive composition with the silica dispersion before storage. In other words, it was found that the silica dispersion was hardly affected by the aggregation of silica particles and coarse particles, and exhibited high polishing performance.

[0104] Next, we will discuss the test results shown in Table 2 (where the storage container was left standing at a storage temperature of 45°C). Note that Examples 6 to 8 and Comparative Example 5 in Table 2 all assume that the ratio of the surface area in contact with the silica dispersion to the total surface area inside the storage container is 0.990.

[0105] In this example, Example 6 uses a horizontal storage container (first storage form A), Example 7 uses an inverted storage container (second storage form B), and Example 8 uses a third storage form C, which is a change from horizontal to vertical storage. In all cases, it was visually confirmed at the time of filling that there was no gas phase between the spout and the silica dispersion. It was shown that the scratch ratio did not increase and there was no decrease in polishing performance after storage periods of 7 days and 1 month.

[0106] On the other hand, in Comparative Example 5, where the storage container was placed vertically as in the conventional method, the scratch ratio after 7 days increased compared to before storage, and after 1 month, that value increased even further.

[0107] As explained above, in both the case where the storage temperature is 28°C as shown in Table 1 and the case where the storage temperature is 45°C as shown in Table 2, a clear difference in the test results of the polishing test occurs depending on the way the storage container is placed (storage method). In other words, the polishing agent composition using the silica dispersion of the present invention does not experience a decrease in polishing performance even after long-term storage, and in particular, it is shown to have a remarkable effect in suppressing the occurrence of scratches that appear on the substrate surface. [Industrial applicability]

[0108] The silica dispersion and abrasive composition using the same of the present invention can be used for polishing various electronic components such as semiconductors, SAW devices, and magnetic recording devices, as well as ceramic components such as oxides. In particular, it can be suitably used for polishing the surface of substrates for magnetic recording media, such as glass magnetic disk substrates and aluminum magnetic disk substrates. In particular, it can be suitably used for polishing aluminum magnetic disk substrates for magnetic recording media in which an electroless nickel-phosphorus plating film has been formed on the surface of an aluminum alloy substrate. [Explanation of Symbols]

[0109] 1: Silica dispersion, 1a: Liquid level, 2: Storage container, 3: Silica particles, 4: Water, 5: Container body, 5a: Inner surface of container, 6: Spout, 7: Spout body, 7a: Outer wall, 7b: Inner wall, 8: Male screw part, 9: Female screw part, 10: Lid, 10a: Underside of lid, 11: Liquid phase, 12: Coarse particles, A: First storage form, B: Second storage form, C: Third storage form, D: Conventional storage form, P: Pressing force.

Claims

1. A silica dispersion liquid that is stored and / or transported in a storage container, Silica particles with an average primary particle diameter in the range of 3 to 100 nm, Water and It contains, The aforementioned storage container is A container body capable of being filled with the silica dispersion, The spout portion is joined to the container body and at least the inner wall portion is made of an organic polymer material. It is equipped with, The ratio of the liquid contact area of ​​the silica dispersion to the total surface area of ​​the inner surface of the storage container filled with the silica dispersion is in the range of 0.950 to 0.

999. A silica dispersion in which the silica dispersion comes into contact with the entire inner wall of the spout when the storage container is stored and / or transported, and a gaseous phase exists in a portion between the inner surface of the container body and the silica dispersion.

2. The silica particles are The silica dispersion according to claim 1, wherein the silica is colloidal silica.

3. The aforementioned organic polymer material is A silica dispersion according to claim 1, formed from a polyolefin resin material.

4. The aforementioned organic polymer material is The silica dispersion according to claim 3, wherein the material is polyethylene resin or polypropylene resin.

5. The silica dispersion according to claim 1, wherein the pH value (at 25°C) is in the range of 7 or more and 12 or less.

6. The silica dispersion according to claim 1, wherein the ratio of the wetted area is in the range of 0.970 to 0.

999.

7. A silica dispersion according to any one of claims 1 to 6, Acids and / or salts thereof, Oxidizing agent and Abrasive composition containing [a specific ingredient / material].

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