JP6564638B2 - Polishing composition, magnetic disk substrate manufacturing method, and magnetic disk substrate - Google Patents

Description

  The present invention relates to a polishing composition, a method for producing a magnetic disk substrate using the polishing composition, and a magnetic disk substrate produced by the method.

  Conventionally, a polishing process using a polishing composition is performed on the surface of a material such as a metal, a semimetal, a nonmetal, or an oxide thereof. For example, in a manufacturing process of a polished article that requires a high-precision surface, generally, polishing with a greater emphasis on polishing efficiency (final polishing step) is performed before the final polishing step (finish polishing step) performed to finish the surface accuracy of the final product ( Pre-polishing) is performed. In such a polishing process, for example, in the polishing performed before the final polishing step as in the above-described preliminary polishing, it contributes to the improvement of the surface accuracy in the final polishing step, so it is desirable to realize a good surface state.

  One of the factors that influence the surface accuracy of the object to be polished is the material and properties of the abrasive grains contained in the polishing liquid. For example, a polishing liquid using silica as abrasive grains tends to improve the surface quality (for example, surface smoothness) of the surface to be polished as compared with a polishing liquid using abrasive grains such as alumina having higher hardness. Patent documents 1-4 are mentioned as technical literature about polish technology which uses silica as an abrasive grain.

Japanese Patent Laid-Open No. 2006-026885 JP 2010-016344 A JP 2001-269857 A JP-A-61-136909

  However, generally, a polishing liquid using silica abrasive grains tends to be inferior in polishing efficiency (typically a polishing rate). For example, primary polishing of a magnetic disk substrate (Ni-P substrate) plated with nickel phosphorus is used. When used in polishing that requires a high polishing rate, there is a possibility that such a request cannot be fully met. This invention is made | formed in view of such a situation, Comprising: The polishing composition which can exhibit a high polishing rate using a silica abrasive grain and can achieve favorable surface quality (surface accuracy) is provided. The purpose is to do. Another related object is to provide a method of manufacturing a magnetic disk substrate using such a polishing composition and a magnetic disk substrate manufactured by the method. Still another object is to provide a method for polishing a magnetic disk substrate using the polishing composition.

The polishing composition provided by this specification contains silica abrasive grains, the average primary particle diameter of the silica abrasive grains is 40 nm or more, and the average silanol group density of the silica abrasive grains is 1.25. / Nm ² or less. According to the polishing composition containing such silica abrasive grains, a high polishing rate and good surface accuracy can be achieved at a high level.

In the polishing composition according to a preferred embodiment, the average silanol group density of the silica abrasive grains is 0.5 / nm ² or more. According to such a polishing composition, better surface accuracy tends to be obtained. Therefore, according to the said polishing composition, a high polishing rate and favorable surface precision can be made compatible at a higher level.

  As the silica abrasive grains satisfying the average primary particle diameter and the average silanol group density, silica abrasive grains containing heat-treated silica particles can be preferably employed. According to the polishing composition containing such silica abrasive grains, a high polishing rate and good surface accuracy can be achieved at a higher level.

  The polishing composition disclosed herein preferably has a pH of 5 or less. When the silica abrasive grains satisfying the preferable average primary particle diameter and average silanol group density disclosed herein are used in the polishing composition having such a pH, the effects of the present invention can be suitably exhibited.

  The polishing composition disclosed herein is suitable as a polishing composition used in a pre-process of a final polishing process. For example, the polishing composition can be suitably used for primary polishing of an object to be polished. Since the polishing composition disclosed herein can exhibit a high polishing rate, it is more meaningful to be used in a polishing process that requires high polishing efficiency, such as the primary polishing.

  As a preferable application target of the polishing composition disclosed herein, a magnetic disk substrate is exemplified. Among these, a preferable polishing object is a magnetic disk substrate (Ni-P substrate) on which nickel phosphorus plating is applied. When the polishing composition is applied to the magnetic disk substrate, a high polishing rate can be achieved, and the surface accuracy of the magnetic disk substrate after polishing can be at a suitable level. The polishing composition disclosed herein is particularly suitable for primary polishing of a magnetic disk substrate.

  According to this specification, a method for manufacturing a magnetic disk substrate is also provided. The manufacturing method includes a step (1) of polishing a magnetic disk substrate using any of the polishing compositions disclosed herein. According to this manufacturing method, a magnetic disk substrate having a high-quality surface can be manufactured with high productivity.

  The method of manufacturing the magnetic disk substrate may further include a step (2) of polishing the magnetic disk substrate using a finish polishing composition containing colloidal silica after the step (1). According to this manufacturing method, a magnetic disk substrate having a higher quality surface can be manufactured with high productivity.

  As another aspect of the magnetic disk substrate manufacturing method disclosed herein, a magnetic disk substrate manufactured by the method is provided. Such a magnetic disk substrate is preferable because it has a high-quality surface and can be advantageous in terms of production cost.

  According to this specification, a method for polishing a magnetic disk substrate is further provided. The polishing method is characterized in that any of the polishing compositions disclosed herein is supplied to a magnetic disk substrate to polish the magnetic disk substrate. According to this polishing method, the surface accuracy of the object to be polished can be efficiently increased.

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

<Silica abrasive grains>
The polishing composition disclosed herein contains silica abrasive grains. The silica particles constituting the silica abrasive grains may be various silica particles mainly composed of silica. Here, silica particles containing silica as a main component refer to particles in which 90% by weight or more (usually 95% by weight or more, typically 98% by weight or more) of the particles is silica. Examples of silica particles that can be used include, but are not limited to, precipitated silica, sodium silicate method silica, alkoxide method silica, fumed silica, dry silica, and explosion method silica. Examples of silica particles that can be used further include silica obtained by using the above silica particles (that is, precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dry silica, explosive silica, etc.) as raw materials. Particles. Examples of such silica particles include the above-mentioned raw material silica particles (hereinafter also referred to as “raw silica”), heat treatment such as heating, drying and firing, pressure treatment such as autoclave treatment, pulverization and pulverization ( Includes silica particles obtained by applying one or more treatments selected from mechanical treatment such as crushing), surface modification (for example, introduction of functional groups, chemical modification such as metal modification), etc. obtain. For example, silica particles obtained by applying at least one treatment for lowering the silanol group density of the raw silica (hereinafter referred to as “silanol group density reduction treatment”) to the raw silica can be mentioned. The silica abrasive grains in the technology disclosed herein may contain one kind of such silica particles alone or in combination of two or more kinds.

(Average primary particle size)
The polishing composition disclosed here has an average primary particle size of the silica abrasive grains of 40 nm or more. In the configuration satisfying the average silanol group density described later, according to the polishing composition having an average primary particle size of the silica abrasive grains of 40 nm or more, a high polishing rate and good surface accuracy are achieved at a high level. obtain.

Here, the average primary particle diameter in the present specification refers to an average particle diameter obtained based on the BET method. This average primary particle size (hereinafter sometimes referred to as “D1”) is calculated from the specific surface area S (m ² / g) measured by the BET method according to the formula D1 (nm) = 2727 / S. The The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritex Corporation, a trade name “Flow Sorb II 2300”.

Moreover, in this specification, the average primary particle diameter of silica abrasive grains (hereinafter sometimes referred to as “D1 _AVE ”) is the total silica abrasive grains contained in the polishing composition disclosed herein. Means the average primary particle diameter grasped as a characteristic. That is, when the silica abrasive grains contained in the polishing composition are a mixture of two or more types of silica particles, D1 _AVE is calculated based on the specific surface area of the silica abrasive grains that is the mixture. When the silica abrasive grains contained in the polishing composition are composed of one type of silica particles, the average primary particle diameter D1 and D1 _{AVE of the} silica particles coincide. When the silica abrasive grains contained in the polishing composition are, for example, a mixture of two types of silica particles X and Y, D1 _AVE is a BET method for the silica abrasive grains (that is, a mixture of silica particles X and Y). It can be calculated from the specific surface area measured by In general, at least as a practically sufficient approximate value, the BET specific surface area of each component (here, silica particles X, Y) constituting the silica abrasive grains and the weight of the silica particles X, Y in the silica abrasive grains A value calculated from the ratio can be adopted as D1 _AVE . The same applies when the silica abrasive grains contained in the polishing composition are a mixture of three or more types of silica particles.

In the technology disclosed herein, D1 _AVE is preferably 45 nm or more, and more preferably 50 nm or more. As D1 _AVE increases, the polishing rate tends to improve. From such a viewpoint, in a preferred embodiment, D1 _AVE can be 55 nm or more, may be 60 nm or more, and may be 65 nm or more. The upper limit of D1 _AVE is not particularly limited. From the viewpoint of dispersion stability of the silica abrasive grains, it is usually appropriate to set D1 _AVE to 500 nm or less, preferably from 300 nm or less, more preferably 200 nm or less from the viewpoint of improving the surface accuracy of the surface to be polished. 150 nm or less (for example, 120 nm or less) is more preferable. The technique disclosed here can be preferably implemented, for example, in an embodiment in which D1 _AVE is 40 nm to 200 nm (more preferably 45 nm to 150 nm, still more preferably 50 nm to 120 nm).

The silica abrasive grains in the technology disclosed herein may be composed of one type of silica particles or may be composed of two or more types of silica particles. In a preferred embodiment, the silica abrasive grains contained in the polishing composition can be composed of two or more types of silica particles having different average primary particle diameters D1. This embodiment has an advantage that D1 _AVE can be easily adjusted. For example, it is varied by D1 manufacturing errors and storage conditions of the silica particles used in the preparation of the polishing composition, by adjusting the amount ratio of these silica particles (blend ratio), D1 _AVE of Variation can be suppressed. This is preferable from the viewpoints of productivity and quality stability of the polishing composition. In addition, by using two or more kinds of silica particles in this manner, a polishing composition having both desired D1 _AVE and average silanol group density can be easily obtained.

In the aspect in which the silica abrasive grains contain two or more types of silica particles, D1 of the silica particles for each type is not particularly limited, and the average primary particle diameter (D1 _AVE ) of the silica abrasive grains containing these silica particles is in a desired range. Any diameter can be used. From the viewpoint of dispersion stability and the like, usually, silica particles having D1 of 100 μm or less (typically 50 μm or less, preferably 30 μm or less, for example, 15 μm or less) can be suitably used. From the viewpoint of obtaining a highly accurate polished surface, silica particles having D1 of 10 μm or less (more preferably 5 μm or less, more preferably 3 μm or less, for example, 2 μm or less) are preferable. From the viewpoint of polishing rate and the like, usually, silica particles having D1 of 5 nm or more (preferably 10 nm or more, more preferably 15 nm or more, for example, 20 nm or more) can be suitably used. From the viewpoint of obtaining a higher polishing rate, silica particles having D1 of 30 nm or more (preferably 40 nm or more, for example, 50 nm or more) may be used.

In the technique disclosed herein, the silica abrasive grains include silica particles A and silica particles B, and the average primary particle diameter (D1 _A ) of the silica particles _A is larger than the average primary particle diameter (D1 _B ) of the silica particles B. The embodiment can be preferably implemented. In such embodiments, D1 _A is, for example, than the atmospheric 40nm (typically greater 10μm or less than 40nm is), usually more than 60 nm (e.g. 60Nm～5myuemu) are preferred, and more preferably more than 80 nm (e.g. 80Nm～3myuemu) . D1 _B can be, for example, 1000 nm or less (typically 5 nm to 1000 nm), usually 500 nm or less (for example, 10 nm to 500 nm), and more preferably 300 nm or less (for example, 15 nm to 300 nm). From the viewpoint of obtaining higher surface accuracy, D1 _B may be 200 nm or less (for example, 15 nm to 200 nm), and may be 100 nm or less (for example, 15 nm to 100 nm).

Although not particularly limited, silica particles A and the silica particles B is, D1 _A / D1 _B, for example, 1.2 or more (typically 1.2 to 25) can be chosen to be. By using a combination of silica particles A and B satisfying such D1 _A / D1 _B , a high polishing rate and good surface accuracy tend to be compatible at a higher level. In a preferred embodiment, D1 _A / D1 _B can be 1.5 or more (for example, 1.5 to 20), and is usually 1.8 or more (for example, 1.8 to 15). Yes, and preferably 2.0 or more (typically 2.0 to 10, for example, 2.0 to 8.0).

  In addition, in the polishing composition containing three or more types of silica particles as silica abrasive grains, the two types of silica particles most often contained can be used as silica particles A and B. In this case, the ratio of the total weight of the silica particles A and B to the total weight of the silica abrasive grains is typically more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more. It may be 90% by weight or more, 95% by weight or more, and further 98% by weight or more. Further, the silica abrasive grains in the technology disclosed herein may be silica abrasive grains substantially composed of two types of silica particles A and B.

(Silanol group density)
The polishing composition disclosed herein contains silica abrasive grains, and the average silanol group density of the silica abrasive grains is 1.25 pieces / nm ² or less. Here, the silanol group density means the number of silanol groups per 1 nm ² of the surface area of the silica particles. The silanol group density (hereinafter sometimes referred to as “SD”) is calculated from the specific surface area (BET specific surface area) of silica particles measured by the BET method and the amount of silanol groups measured by titration. The More specifically, the SD of silica particles is measured according to the following silanol group density measurement method.

[Silanol group density measurement method]
A dispersion containing 1% by weight of silica particles is adjusted to pH 3.5 to 3.8 with hydrochloric acid, and then adjusted to pH 4.0 with a 0.1 mol / L aqueous sodium hydroxide solution as a titration sample. . The titration sample is titrated in a pH 4.0 to pH 9.0 range using a 0.1 mol / L sodium hydroxide aqueous solution. From the titration amount and the BET specific surface area of the silica particles, The silanol group density [number / nm ² ] is calculated.

Further, in this specification, the average silanol group density (hereinafter sometimes referred to as “SD _AVE ”) of the silica abrasive grains is the total of the silica abrasive grains contained in the polishing composition disclosed herein. It means silanol group density (SD) which is grasped as a characteristic. When the silica abrasive grains contained in the polishing composition are, for example, a mixture of two types of silica particles X and Y, SD _AVE uses the silica abrasive grains (that is, a mixture of silica particles X and Y) as a measurement sample. It can obtain | require by applying the said silanol group density measuring method. Also, usually, at least as a practically sufficient approximate value, the SD of each component (here, silica particles X and Y) constituting the silica abrasive grains and the weight of the silica particles X and Y in the silica abrasive grains A value calculated from the ratio can be adopted as SD _AVE . The same applies when the silica abrasive grains contained in the polishing composition are a mixture of three or more types of silica particles.

As a result of intensive studies by the present inventors, when the average silanol group density (SD _AVE ) of the silica abrasive grains is set to a predetermined upper limit value or less in a configuration including silica abrasive grains having a D1 _AVE of 40 nm or more, the silica abrasive grains It became clear that efficient polishing was realized in the polishing composition containing. In carrying out the technique disclosed herein, it is not necessary to clarify the reason why the polishing efficiency of the polishing composition is improved by controlling SD _AVE . For example, it is considered as follows. Silanol groups present on the surface of the silica particles form a hydrated layer on the particle surface in the silica dispersion using water as a dispersion medium. The surface of the silica particles on which such a hydrated layer is formed is more effective from the viewpoint of the polishing action on the object to be polished than the base of the silica particles (that is, the central part of the silica particles on which no hydrated layer is formed). The hardness is considered low. When the silanol group density of the silica particles is lowered, the hydrated layer is hardly formed (the hydrated layer is thinned), and the effective hardness of the silica particle surface is relatively increased. Since particles having a high surface hardness tend to exhibit more mechanical polishing action, it is considered that the polishing efficiency is improved.

In the technique disclosed herein, SD _AVE is preferably 1.20 pieces / nm ² or less, and more preferably 1.15 pieces / nm ² or less. When SD _AVE decreases, a higher polishing rate tends to be achieved for D1 _AVE . The lower limit of SD _AVE is not particularly limited, but from the viewpoints of surface accuracy and dispersion stability of the surface to be polished, 0.5 / nm ² or more is usually appropriate, and 0.6 / nm ² or more. It is preferably 0.7 / nm ² or more (for example, 0.8 / nm ² or more).

In a preferred embodiment of the technology disclosed herein, the silica abrasive grains contained in the polishing composition can be configured to include two or more types of silica particles having different SD. This embodiment has an advantage that the SD _AVE can be easily adjusted. For example, even if the SD of each silica particle used in the preparation of the polishing composition varies due to manufacturing errors, storage conditions, etc., by adjusting the ratio of the silica particles used (blend ratio), SD _AVE Variation can be suppressed. This is preferable from the viewpoints of productivity and quality stability of the polishing composition. In addition, by using two or more kinds of silica particles in this way, it becomes easy to obtain a polishing composition that achieves both desired SD _AVE and D1 _AVE .

In the embodiment in which the silica abrasive grains contain two or more types of silica particles, the SD of the silica particles for each type is not particularly limited, and the SD _{AVE of} silica abrasive grains containing these silica particles in an appropriate weight ratio is in the desired range. Any SD can be obtained. From the viewpoint of dispersion stability and the like, usually, silica particles having SD of 0.3 particles / nm ² or more can be preferably used. From the viewpoint of obtaining a polished surface with higher accuracy, SD is 0.4 pieces / nm ² or more (more preferably 0.5 pieces / nm ² or more, for example, 0.6 pieces / nm ² or more, and further 0.7 pieces. / Nm ² or more) can be preferably used. Further, since it is easy to realize the preferred SD _AVE disclosed herein, the SD is usually 10 / nm ² or less (preferably 5 / nm ² or less, more preferably 2.5 / nm ² or less. For example, 2.0 particles / nm ² or less) can be preferably used. From the viewpoint of polishing rate, etc., SD can be preferably used silica particles of 1.5 / nm ² or less (more preferably 1.3 pieces / nm ² or less, for example 1.25 / nm ² or less). SD may be used silica particles of 1.1 pieces / nm ² or less (e.g., 1.0 pieces / nm ² or less).

In the technology disclosed herein, the silica abrasive grains include silica particles K and silica particles L, and the silanol group density (SD _K ) of the silica particles _K is lower than the silanol group density (SD _L ) of the silica particles L. Can be preferably implemented. In such embodiments, SD _K is, for example, less than 1.25 / nm ^2, is usually preferably 1.2 pieces / nm ² or less, preferably 1.1 pieces / nm ² or less, more preferably 1.05 Pieces / nm ² or less. SD _K can be preferably used silica particles K is less than 1.0 pieces / nm ² (eg 0.9 / nm ² or less). The silica particles L, can be suitably used SD _L is, for example, 1.0 pieces / nm ² or more. Polishing composition disclosed herein is preferably implemented in embodiments using silica particles L of SD _L is 1.1 pieces / nm ² or more (e.g., 1.2 pieces / nm ² or more), a high polishing rate And good surface accuracy can be balanced.

  In addition, in the polishing composition containing three or more types of silica particles as silica abrasive grains, the two types of silica particles most often contained can be the silica particles K and L. In this case, the ratio of the total weight of the silica particles K and L to the total weight of the silica abrasive grains is typically more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more. It may be 90% by weight or more, 95% by weight or more, and further 98% by weight or more. Moreover, the silica abrasive grain in the technique disclosed here may be a silica abrasive grain substantially composed of two types of silica particles K and L.

  In the silica particles K and L, the silica particles K may be the silica particles A described above, and the silica particles L may be the silica particles B described above. Further, in the silica particles K and L, the silica particles K may be the silica particles B, and the silica particles L may be the silica particles A. The technique disclosed here can be preferably implemented in an embodiment in which the silica particles K are the silica particles A and the silica particles L are the silica particles B from the viewpoint of material availability.

(Average secondary particle size)
In the polishing composition disclosed herein, the average secondary particle diameter of the silica abrasive grains contained in the polishing composition is not particularly limited. Here, in this specification, the average secondary particle diameter (hereinafter sometimes referred to as “D2”) is the volume-based average particle diameter (50% volume average particle diameter) based on the laser diffraction / scattering method. Point to. The average particle size can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device (model “LA-950”) manufactured by Horiba, Ltd.

Further, in this specification, the average secondary particle diameter of silica abrasive grains (hereinafter sometimes referred to as “D2 _AVE ”) is the total silica abrasive grains contained in the polishing composition disclosed herein. Mean secondary particle diameter grasped as a typical characteristic. From the viewpoint of the polishing rate, D2 _AVE is usually suitably 50 nm or more, preferably 70 nm or more, more preferably 80 nm or more, and further preferably 90 nm or more. In a preferred embodiment, D2 _AVE can be 100 nm or more, 150 nm or more, 250 nm or more, and further 350 nm or more (for example, 450 nm or more). Further, in view of suppressing the polishing rate decreases by number of particles decreases due to agglomeration of abrasive particles, D2 _AVE is preferably 15μm or less, more preferably 13μm or less, more preferably 7μm or less. From the viewpoint of obtaining higher surface accuracy, it is usually advantageous to set D2 _AVE to 5 μm or less (more preferably 3 μm or less, for example, 1 μm or less). The technique disclosed herein can be preferably implemented in an embodiment in which D2 _AVE is, for example, 50 nm to 3 μm (more preferably 70 nm to 1 μm). According to the polishing composition containing silica abrasive grains having such D2 _AVE , a high polishing rate and good surface accuracy are easily achieved at the same time.

(Silica particles)
In the technology disclosed herein, as a suitable example of silica particles that can be used as a constituent of silica abrasive grains, silica particles obtained by applying silanol group density reduction treatment (SD reduction treatment) to raw silica can be cited. It is done. Examples of the SD reduction treatment include heat treatment such as heating, drying and firing, metal modification treatment for bonding metal ions (eg, Al ions, Ti ions, etc.) to silanol groups, and bonding organic acids such as sulfonic acid to silanol groups. Examples include, but are not limited to, organic acid modification treatment.

Silica particles obtained by applying SD reduction treatment to the raw material silica (hereinafter referred to as “low SD silica particles”). ) As an example, silica particles obtained by heat-treating raw material silica (hereinafter also referred to as “heat-treated silica”), specifically, heated silica particles, dried silica particles, and fired silica particles Etc. From the viewpoint of treatment efficiency and the like, it is preferable to perform the heat treatment in a state where a liquid such as water is removed from the silica particles. Here, the heated silica particles are typically obtained through a treatment for holding in an environment of 60 ° C. or higher and lower than 110 ° C. for a predetermined time or longer (for example, 15 minutes or longer, typically 30 minutes or longer). This refers to the produced silica particles. The dried silica particles are typically 110 ° C. or more and less than 500 ° C. (preferably 300 ° C. or more and less than 500 ° C.) for a certain period of time (for example, 15 minutes or more, typically 30 minutes). The above refers to silica particles obtained through the holding treatment. The calcined silica particles (hereinafter also referred to as “calcined silica”) will be described in detail later. Typically, the calcined silica particles are typically at a temperature of 500 ° C. or higher for a predetermined time or longer (for example, 15 minutes or longer, typically Means silica particles obtained through a treatment (hereinafter also referred to as “firing”) for 30 minutes or more. The silica particles obtained through the process of heat-treating any of the above-described raw material silicas (precipitated silica, silica silicate method silica, alkoxide method silica, fumed silica, dry silica, explosive method silica, etc.) It is a typical example included in the concept of silica. In general, silica particles tend to reduce silanol groups on the particle surface by heat treatment. By adjusting the SD of silica particles using this tendency, silica particles useful as a constituent of silica abrasive grains satisfying a desired SD _AVE can be obtained. In addition, since the heat-treated silica can adjust D1 and SD by setting heat treatment conditions, pulverization described later, and a combination thereof, the structure of silica abrasive grains satisfying D1 _AVE and SD _AVE disclosed herein. Suitable as a component. 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. The silica abrasive grains may be composed of one or two or more kinds of heat-treated silica, and contain a combination of heat-treated silica and other silica particles (that is, unheat-treated silica particles). There may be.

  As a raw material (raw material silica) of heat-treated silica, various silica particles can be used as described above. Since suitable SD and D1 are easily obtained by heat treatment, precipitated silica or colloidal silica can be preferably employed as the raw material silica. Of these, precipitated silica is preferred. The technique disclosed here can be preferably implemented in a mode in which the silica abrasive grains contain heat-treated silica derived from precipitated silica.

The temperature when heat-treating the raw material silica is not particularly limited as long as it is lower than the melting point of silica. Usually, it is appropriate to set the heat treatment temperature to 1300 ° C. or lower. From the viewpoint of suppressing excessive growth of silica particles, the heat treatment temperature is usually 1200 ° C. or lower (typically less than 1200 ° C.), and more preferably 1100 ° C. or lower (eg, 1050 ° C. or lower). Moreover, the said heat processing temperature can be 60 degreeC or more, for example, and is good also as 110 degreeC or more. From the viewpoint of efficiently obtaining silica particles that easily contribute to the improvement of the polishing rate, the heat treatment temperature can be, for example, 500 ° C. or higher, usually 600 ° C. or higher, preferably 700 ° C. or higher, More preferably, it is 800 degreeC or more, More preferably, it is 900 degreeC or more (for example, 950 degreeC or more). Silica particles (heat-treated silica) obtained through the process of heat treatment at the temperature described above are likely to be suitable as a constituent of silica abrasive grains satisfying the desired D1 _AVE and SD _AVE disclosed herein. The silica abrasive grains in the polishing composition disclosed herein include, for example, calcined silica obtained by calcining raw material silica at 700 ° C. or higher and lower than 1200 ° C. (more preferably 800 to 1100 ° C., for example, 900 to 1100 ° C.). It is preferable.

  Although it does not specifically limit, the time which heat-processes raw material silica (for example, baking) can be made into 15 minutes or more (typically about 30 minutes to 10 hours), for example, and usually 1 hour or more (typical) 1 hour to 5 hours) is appropriate. By increasing the heat treatment time, the SD of the silica particles tends to decrease. This is advantageous from the viewpoint of the polishing rate. Moreover, in baking, it is in the tendency for the silica particle (baked silica) to be better baked in by making baking time long. From an economic viewpoint, it is usually preferable to set the heat treatment time to about 10 hours or less.

  The atmosphere when heat-treating the raw material silica is not particularly limited. The heat treatment atmosphere can be, for example, an inert gas atmosphere, a reducing gas atmosphere, an oxidizing gas atmosphere (air atmosphere or the like), and the like. Further, the silica particles may be heat-treated in a substantially vacuum state.

  In the technique disclosed herein, when calcined silica is used as the heat-treated silica, the calcined silica can be preferably used after being calcined and crushed. Here, “crushing” in the present specification refers to an operation of loosening and refining what is gathered into a lump of fine particles.

The method for crushing the fired silica particles may be any known method that is conventionally used in this type of field, and is not particularly limited. For example, the crushing can be performed using a crusher such as a bead mill, a ball mill, a roller mill, a hammer mill, a jet mill, or a mortar (the crusher can also be recognized as a pulverizer). Since it is easy to control the degree of crushing (for example, the average primary particle diameter or average secondary particle diameter of the burned silica obtained after crushing), crushing by a bead mill, ball mill or jet mill is preferable. By crushing the silica particles in this manner, the specific surface area of the silica particles increases, and the number of silanol groups per surface area of the silica particles (ie, SD) tends to decrease. Therefore, by appropriately crushing, silica particles (calcined silica) suitable as a constituent of silica abrasive grains satisfying desired D1 _AVE and SD _AVE disclosed herein can be obtained. In addition, the said crushing can be similarly applied to heat-treated silica other than calcined silica (for example, heated silica particles and dried silica particles) as necessary, and exhibits the same effect. obtain.

When heat-treated silica is used as a constituent component of the silica abrasive grains, D1 and SD of the heat-treated silica are not particularly limited as long as the silica abrasive grains containing the heat-treated silica can satisfy the desired D1 _AVE and SD _AVE . Accordingly, the D1 of the heat-treated silica, when used alone (that is, when only one or two or more types of calcined silica are included as silica abrasive grains), the silica abrasive grains D1 _AVE described above, and other silica particles When using together, it can be made the same with D1 of the silica particle for every kind mentioned above, respectively. The heat-treated silica is such that the silica abrasive grains include silica particles A and silica particles B, and the average primary particle diameter (D1 _A ) of the silica particles _A is larger than the average primary particle diameter (D1 _B ) of the silica particles B. The silica particles A can be preferably used. D1 of the heat-treated silica used in such an embodiment can be the same as that of the silica particle A described above.

Similarly, the SD of the heat-treated silica is the same as the SD _{AVE of the} silica abrasive grains described above when used alone, and the SD of the silica particles of each type described above when used in combination with other silica particles. be able to. The heat treatment silica, silica abrasive comprises silica particles K and silica particles L, SD _K is at a lower aspect than SD _L, it can be preferably used as the silica particles K. The SD of the heat-treated silica used in such an embodiment can be the same as that of the silica particle K described above.

Colloidal silica is mentioned as another suitable example of the silica particle which can be used as a structural component of the silica abrasive grain in the technique disclosed here. Of these, colloidal silica synthesized through particle growth in an aqueous phase, such as sodium silicate method silica and alkoxide method silica, is preferably used. According to the silica abrasive grains containing this kind of colloidal silica and satisfying D1 _AVE and SD _AVE disclosed herein, a high polishing rate and good surface accuracy can be suitably achieved. When the silica abrasive grain disclosed here contains colloidal silica, the colloidal silica contained in the silica abrasive grain may be one kind or two or more kinds having different production conditions and / or physical properties. . The silica abrasive grains may be composed of one or more colloidal silicas, and include a combination of colloidal silica and other silica particles (that is, silica particles other than colloidal silica). There may be.

  The particle shape of colloidal silica is not particularly limited, and may be, for example, spherical or non-spherical. Specific examples of the non-spherical shape include a peanut shape (that is, a shape of a peanut shell), a cocoon shape, a shape with a protrusion (for example, a confetti shape), a rugby ball shape, and the like. Although not particularly limited, the average value (average aspect ratio) of the major axis / minor axis ratio of colloidal silica is preferably 1.01 or more, and more preferably 1.05 or more (for example, 1.1 or more). By increasing the average aspect ratio, a higher polishing rate can be achieved. The average aspect ratio of colloidal silica is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing the surface roughness. The technique disclosed herein can be preferably implemented in an embodiment using colloidal silica having an average aspect ratio of less than 1.25 (for example, 1.20 or less, typically less than 1.15).

  The shape (outer shape) and average aspect ratio of colloidal silica can be grasped by, for example, observation with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, using a SEM, a predetermined number (for example, 200) of abrasive particles capable of recognizing the shape of independent particles is the smallest that circumscribes each particle image. Draw a rectangle. For the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (major axis value) by the length of the short side (minor axis value) is the major axis / minor axis ratio (aspect ratio). ). An average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the predetermined number of particles.

When colloidal silica (preferably, colloidal silica synthesized through particle growth in an aqueous phase) is used as a constituent of silica abrasive grains, the silica abrasive grains containing colloidal silica are desired for D1 and SD of colloidal silica. As long as D1 _AVE and SD _AVE can be satisfied, there is no particular limitation. Accordingly, the D1 of colloidal silica is the same as the D1 _{AVE of the} silica abrasive grains described above when used alone and the D1 of the silica particles of each kind described above when used in combination with other silica particles. Can do. The colloidal silica is a mode in which the silica abrasive grains include silica particles A and silica particles B, and the average primary particle diameter (D1 _A ) of the silica particles _A is larger than the average primary particle diameter (D1 _B ) of the silica particles B. The silica particles B can be preferably used. The colloidal silica D1 used in this embodiment can be the same as the silica particle B described above.

Similarly, the SD of colloidal silica is the same as the SD _{AVE of the} silica abrasive grains described above when used alone, and the SD of the silica particles of each type described above when used in combination with other silica particles. be able to. Further, colloidal silica, silica abrasive comprises silica particles K and silica particles L, SD _K is at a lower aspect than SD _L, it can be preferably used as the silica particles L. The SD of the colloidal silica used in such an embodiment can be the same as that of the silica particle L described above.

  Other examples of silica particles that can be suitably used as a constituent of silica abrasive grains in the technology disclosed herein include low-SD silica particles other than fumed silica, explosive silica, and heat-treated silica (that is, raw material silica) In contrast, low-SD silica particles obtained by applying an SD reduction treatment other than heat treatment). These silica particles can be used alone or in combination with other silica particles.

  The technique disclosed here can be preferably implemented in a mode in which the silica abrasive grains contained in the polishing composition contain heat-treated silica alone or in combination with heat-treated silica and other silica particles. Thus, in the aspect in which the silica abrasive grain contains at least heat-treated silica, the content of the heat-treated silica in the silica abrasive grain is not particularly limited. The content of the heat treated silica is preferably 10% by weight or more, more preferably 20% by weight or more (for example, 25% by weight or more), more preferably 40% by weight or more, from the viewpoint of polishing rate. It is. The upper limit of the content of the heat-treated silica in the silica abrasive grains is not particularly limited, and may be substantially 100% by weight (typically 99% by weight or more). From the viewpoint of balancing various performances (for example, polishing rate, waviness of the surface to be polished, etc.), the content of the heat-treated silica in the silica abrasive grains is preferably 90% by weight or less, more preferably 80% by weight or less ( For example, 75% by weight or less), more preferably 60% by weight or less.

For example, as described above, in the embodiment in which the silica abrasive grains include silica particles A and silica particles B, and D1 _A is larger than D1 _B , silica A is heat treated silica and silica B is heat treated silica. It can implement preferably in the aspect which is silica particles other than. In this case, the ratio (W _A / W _B ) between the weight (W _A ) of the silica particles A contained in the silica abrasive grains and the weight (W _B ) of the silica particles B is not particularly limited. The weight ratio (W _A / W _B ) is preferably 0.20 or more, more preferably 0.25 or more, and further preferably 0.30 or more from the viewpoint of the polishing rate. From the viewpoint of obtaining a higher polishing rate, W _A / W _B can be set to 0.50 or more, and may be set to 0.70 or more. Various performance in terms of balancing (eg polishing rate, the surface accuracy of the polished surface after polishing), W A _/ W _B are advantageously be 5.0 or less, usually 4.0 The following is preferable, 3.0 or less is more preferable, and 2.0 or less (for example, 1.5 or less) is more preferable.

The technique disclosed here can be preferably implemented in a mode in which the silica abrasive grains contained in the polishing composition contain a combination of heat-treated silica and colloidal silica. For example, as described above, the silica abrasive grains include silica particles A and silica particles B, and in an embodiment in which D1 _A is larger than D1 _B , silica A is heat-treated silica and silica B is preferably colloidal silica. can do. By using colloidal silica in addition to heat-treated silica, higher surface accuracy can be realized. In addition, colloidal silica (particularly, colloidal silica synthesized through particle growth in the aqueous phase) can contribute to the improvement of surface accuracy, but generally has a tendency that the SD increases as the particle diameter increases, so to some extent. It is difficult to achieve both the above particle size and low SD. By using a combination of heat-treated silica and colloidal silica, D1 _AVE and SD _AVE of the silica abrasive grains can be suitably adjusted, and therefore, a high polishing rate and good surface accuracy can be achieved at a high level at the same time. be able to. In such embodiments, the ratio of the weight _{(W B)} of the heat treatment silica contained in the silica abrasive by weight of the (silica particles A) _{(W A)} and colloidal silica (silica particles _{B) (W A / W B} ) , the above And can be similar. In general, in comparison between sodium silicate colloidal silica and alkoxide colloidal silica having the same particle diameter, alkoxide colloidal silica tends to have higher SD. Accordingly, as the colloidal silica in the technology disclosed herein, sodium silicate colloidal silica can be preferably used rather than alkoxide colloidal silica.

In the technology disclosed herein, the means for adjusting the SD _AVE of the silica abrasive grains is not particularly limited, and various means available to those skilled in the art can be appropriately employed. For example, there are means such as using one type of silica particles having an appropriate SD, selecting two or more types of silica particles having different SDs, and using them at an appropriate blend ratio. Silica particles having various SDs can be obtained depending on selection of types, production conditions, and the like, and one of them can be used alone or in combination of two or more. For example, in the case of heat treated silica (typically calcined silica), the SD of the silica particles obtained can be adjusted by the SD of the raw material silica, the heat treatment temperature of the raw material silica, the heat treatment time, the degree of pulverization, and the like. A person skilled in the art can realize a polishing composition containing silica abrasive grains satisfying a desired SD _AVE by appropriately adopting these means.

The polishing composition disclosed herein can contain particles other than silica particles in addition to silica abrasive grains satisfying such D1 _AVE and SD _AVE . As particles other than silica particles, any of inorganic particles, organic particles, and organic-inorganic composite particles can be used. Specific examples of the inorganic particles include alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, bengara particles, etc .; silicon nitride particles And 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; 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 include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and composites thereof. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid). And polyacrylonitrile particles. These particles other than silica particles can be used singly 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, and still more preferably 60% by weight or more based on the total solid content from the viewpoint of easily exerting the effect of the present invention. (For example, 80% by weight or more). The silica particles may be substantially all (for example, 99% by weight or more) of the solid content contained in the polishing composition. Alternatively, from the viewpoint of easily balancing various performances (for example, polishing rate, surface quality of the surface to be polished, etc.), the content of the silica particles is 90% by weight or less (for example, 80% by weight or less) of the entire solid content. It may be.

  The polishing composition disclosed herein can be preferably implemented in an embodiment that is substantially free of α-alumina abrasive grains. According to such a polishing composition, quality deterioration (for example, generation of scratches and dents, residual alumina, etc.) due to the use of α-alumina abrasive grains is prevented. In the present specification, the fact that predetermined abrasive grains (for example, α-alumina abrasive grains) are substantially not included means that the ratio of the abrasive grains in the total amount of solids contained in the polishing composition is 1% by weight or less. (More preferably 0.5 wt% or less, typically 0.1 wt% or less). A polishing composition in which the proportion of α-alumina abrasive grains is 0% by weight, that is, a polishing composition not containing α-alumina abrasive grains is particularly preferred. In addition, the polishing composition disclosed herein is not limited to α-alumina abrasive grains, and can be preferably practiced in a mode that does not substantially contain alumina abrasive grains.

  The polishing composition disclosed herein can also be preferably implemented in an embodiment that does not substantially contain particles other than silica particles (non-silica particles). Here, “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, typically Is 0.1% by weight or less). In such an aspect, the application effect of the technique disclosed herein can be suitably exhibited.

  When the polishing composition disclosed herein contains a plurality of types of abrasive grains, the number of types of abrasive grains contained in the composition is generally grasped based on the difference in the outer shape of the plurality of types of abrasive grains. can do. The difference in the outer shape of the abrasive grains is, for example, at least one of a difference in average aspect ratio, a difference in average minor diameter, a difference in average particle diameter, a difference in surface shape of particles (for example, the presence or absence of protrusions, and the degree thereof). Can be one. The outer shape of the abrasive grains can be grasped by, for example, SEM (scanning electron microscope) observation. Moreover, each content and content ratio of multiple types of abrasive grain contained in polishing composition can be calculated | required based on the image analysis by SEM observation, for example.

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

  The polishing composition disclosed herein (typically a slurry-like composition) is preferably implemented in a form in which, for example, its non-volatile content (NV) is 5 g / L to 300 g / L. Can be done. A form in which the NV is 10 g / L to 200 g / L is more preferable.

(acid)
The polishing composition disclosed herein can be preferably used in an embodiment containing an acid as a polishing accelerator. Examples of acids that can be suitably used include inorganic acids and organic acids (for example, organic carboxylic acids having 1 to 10 carbon atoms, organic phosphonic acids, organic sulfonic acids, amino acids, etc.). It is not limited. An acid can be used individually by 1 type or in combination of 2 or more types.

Specific examples of the inorganic acid include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, phosphonic acid, boric acid, sulfamic acid and the like.

Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid, acetic acid , Adipic acid, formic acid, oxalic acid, propionic acid, valeric acid, caproic acid, caprylic acid, capric acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, methacrylic acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid Acid, terephthalic acid, glycolic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitric acid, methylene succinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, glycine, alanine, glutamic acid , Aspartic acid, valine, leucine, a Leucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine, nicotinic acid, picolinic acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, isopropyl acid phosphate 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, Tan-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphono Examples include succinic acid, aminopoly (methylenephosphonic acid), methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid.

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

  When an acid is contained in the polishing composition, the content is not particularly limited. The acid content is usually suitably 1 g / L or more, preferably 3 g / L or more, and more preferably 5 g / L or more. If the acid content is too small, the polishing rate tends to be insufficient, which may be undesirable in practice. The acid content is usually suitably 100 g / L or less, preferably 50 g / L or less, more preferably 30 g / L or less (for example 15 g / L or less). When there is too much content of an acid, the surface precision of a grinding | polishing target object will fall easily, and it may be unpreferable practically.

The acid may be used in the form of a salt of the acid. Examples of the salt include metal salts (for example, alkali metal salts such as lithium salt, sodium salt and potassium salt) and ammonium salts (for example, tetramethylammonium salt and tetraethylammonium salt) of the inorganic acids and organic acids described above. Quaternary ammonium salts), alkanolamine salts (for example, monoethanolamine salts, diethanolamine salts, triethanolamine salts) and the like.
Specific examples of the salt include tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate and the like alkali metal phosphates and alkali metals Hydrogen phosphate salt; alkali metal salt of organic acid exemplified above; other alkali metal salt of glutamic acid diacetic acid, alkali metal salt of diethylenetriaminepentaacetic acid, alkali metal salt of hydroxyethylethylenediaminetriacetic acid, triethylenetetramine hexaacetic acid Alkali metal salts; and the like. The alkali metal in these alkali metal salts can be, for example, lithium, sodium, potassium, and the like.

  As a 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 used. For example, potassium chloride, sodium chloride, ammonium chloride, potassium nitrate, sodium nitrate, ammonium nitrate, potassium phosphate and the like can be preferably used.

  An acid and its salt can be used individually by 1 type or in combination of 2 or more types. In a preferred embodiment of the polishing composition disclosed herein, an acid (preferably an inorganic acid) and a salt of an acid different from the acid (preferably a salt of an inorganic acid) can be used in combination.

(Oxidant)
The polishing composition disclosed herein may contain an oxidizing agent as necessary. Examples of the oxidizing agent include peroxide, nitric acid or a salt thereof, peroxo acid or a salt thereof, permanganic acid or a salt thereof, chromic acid or a salt thereof, oxygen acid or a salt thereof, metal salt, sulfuric acid, and the like. However, it is not limited to these. An oxidizing agent can be used individually by 1 type or in combination of 2 or more types. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxodisulfuric acid, ammonium peroxodisulfate, peroxodisulfate metal salt, peroxophosphoric acid, peroxosulfuric acid. , Sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, iodic acid, periodic acid, perchloric acid, hypochlorous acid Examples thereof include acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, iron citrate, and iron iron sulfate. Preferable oxidizing agents include hydrogen peroxide, iron nitrate, peroxodisulfuric acid and nitric acid. It preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

  When the polishing composition contains an oxidizing agent, the content thereof is preferably 1 g / L or more, more preferably 3 g / L or more, further preferably 4 g / L or more, based on the amount of active ingredients. If the content of the oxidizing agent is too small, the rate of oxidizing the object to be polished becomes slow and the polishing rate is lowered, which may be undesirable in practice. Moreover, when an oxidizing agent is included in polishing composition, it is preferable that the content is 30 g / L or less by an active ingredient amount basis, More preferably, it is 15 g / L or less. When there is too much content of an oxidizing agent, the surface precision of a grinding | polishing target object will fall easily, and it may be unpreferable practically.

(Basic compound)
The polishing composition can contain a basic compound as necessary. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. Examples of basic compounds include alkali metal hydroxides, carbonates and hydrogen carbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogen phosphates, organic acid salts and the like. A basic compound can be used individually by 1 type or in combination of 2 or more types.

Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.
Specific examples of the carbonate and bicarbonate include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate and the like.
Specific examples of the quaternary ammonium or a salt thereof include quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide; alkali metals of such quaternary ammonium hydroxides Salt (for example, sodium salt, potassium salt); and the like.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine , 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 are mentioned.
Specific examples of the organic acid salt include potassium citrate, potassium oxalate, potassium tartrate, potassium sodium tartrate, ammonium tartrate and the like.

(Other ingredients)
The polishing composition disclosed herein is a polishing composition such as a surfactant, a water-soluble polymer, a dispersant, a chelating agent, an antiseptic, and an antifungal agent, as long as the effects of the present invention are not significantly hindered. A known additive that can be used in a product (for example, a polishing composition for a magnetic disk substrate such as a Ni-P substrate) may be further contained as necessary.

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 (typically a water-soluble organic compound having a molecular weight of less than 1 × 10 ⁴ ) can improve the dispersion stability of the polishing composition. Surfactant can be used individually by 1 type or in combination of 2 or more types.
Specific examples of the anionic surfactant include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate ester, alkyl sulfate ester, polyoxyethylene alkyl sulfate, alkyl sulfate, alkylbenzene sulfonic acid, alkyl phosphate ester, polyoxyethylene Alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, polyacrylic acid, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, Polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl ether sulfate Sodium, and salts thereof.
Other specific examples of anionic surfactants include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate, benzene sulfonic 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 Compounds such as polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonic acid; and these Etc. The. 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 betaines and alkyl amine oxides.

  In the polishing composition containing the surfactant, it is appropriate that the content of the surfactant is, for example, 0.005 g / L or more. The content is preferably 0.01 g / L or more, more preferably 0.1 g / L or more, from the viewpoint of the smoothness of the surface after polishing. Further, from the viewpoint of polishing rate and the like, the content is suitably 100 g / L or less, preferably 50 g / L or less, for example 10 g / L or less.

  The polishing composition disclosed herein may contain a water-soluble polymer. By containing a water-soluble polymer, the surface accuracy after polishing can be improved. Examples of water-soluble polymers include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate; melamine formalin resin sulfone such as melamine sulfonic acid formaldehyde condensate Acid compounds; lignin sulfonic acid compounds such as lignin sulfonic acid and modified lignin sulfonic acid; aromatic amino sulfonic acid compounds such as aminoaryl sulfonic acid-phenol-formaldehyde condensates; other polyisoprene sulfonic acid, polyvinyl sulfonic acid , Polyallylsulfonic acid, polyisoamylenesulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polymaleic acid, polyitaconic acid, polyvinyl Lucol, polyglycerin, polyvinylpyrrolidone, copolymer of isoprenesulfonic acid and acrylic acid, polyvinylpyrrolidone polyacrylic acid copolymer, polyvinylpyrrolidone vinyl acetate copolymer, diallylamine hydrochloride sulfur dioxide copolymer, carboxymethylcellulose, carboxymethylcellulose Salt, hydroxyethyl cellulose, hydroxypropyl cellulose, pullulan, chitosan, chitosan salts and the like. A water-soluble polymer can be used singly or in combination of two or more.

  In the polishing composition including the water-soluble polymer, the content of the water-soluble polymer in the polishing liquid (in the embodiment including a plurality of water-soluble polymers, the total content thereof) is, for example, 0.01 g. / L or more is appropriate. The content is preferably 0.05 g / L or more, more preferably 0.08 g / L or more, and still more preferably 0.0, from the viewpoint of the surface smoothness of an object to be polished (for example, a magnetic disk substrate) after polishing. 1 g / L or more. Further, from the viewpoint of polishing rate and the like, the content is suitably 10 g / L or less, preferably 5 g / L or less, for example 1 g / L or less. In addition, the technique disclosed here can be preferably implemented even in an embodiment in which the polishing composition does not substantially contain a water-soluble polymer.

  Examples of the dispersing agent include polycarboxylic acid-based dispersants such as polycarboxylic acid sodium salt and polycarboxylic acid ammonium salt; naphthalenesulfonic acid-based dispersants such as naphthalenesulfonic acid sodium salt and naphthalenesulfonic acid ammonium salt; Polydisperse 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 chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic). 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 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-methylphospho Nosuccinic acid is included. Of these, organic phosphonic acid-based chelating agents are more preferable, and ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are particularly preferable. A particularly preferred chelating agent is ethylenediaminetetrakis (methylenephosphonic acid).

  Examples of preservatives and fungicides include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters And phenoxyethanol.

  The polishing composition disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, the liquid A containing a part of the constituent components (typically components other than water) of the polishing composition and the liquid B containing the remaining components are mixed to polish the polishing object. It may be configured to be used.

(Use)
The application target of the technique disclosed here is not particularly limited. The technique disclosed here is a polishing object including polishing of various polishing objects that can be polished by a polishing composition containing silica abrasive grains, and polishing the polishing object using the polishing composition. It can be applied to manufacturing. The material to be polished is silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel or other metals or metalloids or alloys thereof, and thin films used for semiconductor wiring using these materials; quartz Glassy substances such as glass, aluminosilicate glass, and glassy carbon; ceramic materials such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; compound semiconductor substrate materials such as silicon carbide, gallium nitride, and gallium arsenide; A resin material such as a polycarbonate resin, an acrylic resin, an allyl resin, a urethane resin, an epithio resin, and a polyimide resin may be used, but is not limited thereto. Moreover, the grinding | polishing target object comprised with the some material among these may be sufficient.

  The polishing composition disclosed herein is used for polishing various polishing objects requiring a highly accurate surface such as a magnetic disk substrate, a semiconductor substrate such as a silicon wafer, and an optical material such as a lens and a reflection mirror. Can be preferably used. For example, it can be preferably applied to polishing of a magnetic disk substrate (Ni-P substrate) having a nickel phosphorus plating layer on the surface of a base disk. The base disk can be made of, for example, aluminum alloy, glass, glassy carbon, or the like. A disk substrate provided with a metal layer or metal compound layer other than the nickel phosphorus plating layer on the surface of such a base disk may be used. Among these, it is suitable as a polishing composition for a Ni-P substrate having a nickel phosphorous plating layer on a base disk made of aluminum alloy. In such applications, it is particularly meaningful to apply the technology disclosed herein.

  The polishing composition disclosed herein is high in consideration of surface accuracy as in the preliminary polishing step in the manufacturing process of a polished article (for example, a magnetic disk substrate) that requires a high-precision surface after the final polishing step. It can be used particularly meaningfully in applications where polishing efficiency is required. In the case of having a plurality of preliminary polishing steps as a pre-step of the final polishing step, it can be used for any preliminary polishing step, and the same or different polishing composition can be used in these preliminary polishing steps. The polishing composition disclosed here is suitable, for example, as a polishing composition used in a primary polishing step (first polishing step) of an object to be polished. Especially, in the manufacturing process of a Ni-P board | substrate, it can be preferably used in the first grinding | polishing process (primary grinding | polishing process) after nickel phosphorus plating.

  The polishing composition disclosed herein has, for example, a surface roughness (arithmetic average roughness (Ra)) of 20% measured by a laser scan surface roughness meter “TMS-3000WRC” manufactured by Schmitt Measurement System Inc. It is suitable for applications in which a magnetic disk substrate of about ˜300 mm is polished (typically primary polishing) to adjust the surface roughness (arithmetic average roughness (Ra)) of the magnetic disk substrate to 10 mm or less. In such applications, it is particularly meaningful to apply the technology disclosed herein.

(Polishing liquid)
The polishing composition disclosed herein is typically supplied to a polishing object (for example, a magnetic disk substrate) in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. . The polishing liquid can be prepared, for example, by diluting (typically diluting with water) a polishing composition. Or you may use polishing composition as polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein is used as a polishing liquid diluted with a polishing liquid (working slurry) that is supplied to a polishing object and used for polishing the polishing object. Both concentrates are included. Such a polishing composition in the form of a concentrated solution is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration factor can be set to about 1.5 to 50 times, for example. From the viewpoint of the storage stability of the concentrate, a concentration factor of about 2 to 20 times (typically 2 to 10 times) is usually appropriate.

  The content of abrasive grains in the polishing liquid (in the case where plural kinds of abrasive grains are included, the total content thereof) is not particularly limited, but is typically 5 g / L or more and 10 g / L or more. Is preferable, and it is more preferable that it is 30 g / L or more. A higher polishing rate tends to be realized 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 usually suitably 250 g / L or less, preferably 200 g / L or less, more preferably 150 g / L or less, and even more preferably. Is 100 g / L or less.

(PH)
The pH of the polishing composition disclosed herein is not particularly limited. The pH of the polishing composition can be, for example, pH 12.0 or less (typically pH 0.5 to 12.0), and pH 10.0 or less (typically pH 0.5 to 10.0). It is good. In a preferred embodiment, the polishing composition may have a pH of 7.0 or lower (for example, pH 0.5 to 7.0), and a pH of 5.0 or lower (typically pH 1.0 to 5.0). More preferably, the pH is 4.0 or less (for example, pH 1.0 to 4.0). The pH of the polishing composition is, for example, pH 3.0 or less (typically pH 1.0 to 3.0, preferably pH 1.0 to 2.0, more preferably pH 1.0 to 1.8). Can do. If necessary, a pH adjusting agent such as an organic acid or an inorganic acid can be contained so that the above pH is realized in the polishing liquid. The pH can be preferably applied to, for example, a polishing composition for polishing (particularly primary polishing) of a magnetic disk substrate having a nickel phosphorus plating layer.

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

  Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, a polishing object is set in a general polishing apparatus, and a polishing liquid is supplied to the surface (polishing object surface) of the polishing object through a polishing pad of the polishing apparatus. Typically, while supplying the polishing liquid continuously, the polishing pad is pressed against the surface of the object to be polished, and both are relatively moved (for example, rotated). The polishing of the object to be polished is completed through this polishing step.

  The polishing step as described above can be part of a manufacturing process for a substrate (eg, a magnetic disk substrate, typically a Ni-P substrate). Therefore, according to this specification, the manufacturing method of the board | substrate including the said grinding | polishing process is provided.

The polishing composition disclosed herein can be preferably used in a preliminary polishing step (for example, a primary polishing step) of an object to be polished. According to this specification, a method for producing a polished article is provided, which includes a step of performing preliminary polishing using any of the polishing compositions (preliminary polishing composition) described above. This method for manufacturing a polished article may include a final polishing step after the preliminary polishing step. The polishing composition (finish polishing composition) used in the finish polishing step is not particularly limited. For example, a finish polishing composition containing colloidal silica as abrasive grains can be preferably employed. Therefore, the matter disclosed by this specification includes a step of polishing a polishing object with a polishing composition containing silica abrasive grains having D1 _AVE of 40 nm or more and SD _AVE of 1.25 particles / nm ² or less (1 ) And a step (2) of polishing the object to be polished using a final polishing composition containing colloidal silica in this order. According to this manufacturing method, it is possible to efficiently manufacture a polished object with high surface accuracy. The method for producing an abrasive can be preferably applied to the production of a magnetic disk substrate (for example, a magnetic disk substrate having a nickel phosphorus plating layer) and other abrasives.

Thus, in the composition for final polishing containing colloidal silica, D1 _{AVE of the} silica abrasive grain contained in this composition for final polishing is not specifically limited. From the viewpoint of surface accuracy after finish polishing, the D1 _{AVE of the} silica abrasive grains contained in the finish polishing composition is preferably smaller than the D1 _{AVE of the} silica abrasive grains contained in the preliminary polishing composition. The D1 _{AVE of the} silica abrasive grains contained in the finish polishing composition can be, for example, 70 nm or less (typically 5 nm or more and less than 70 nm), and 65 nm or less (typically 5 nm to 65 nm, such as 10 nm to 50 nm. ) Is preferable. In a preferred embodiment, the D1 _{AVE of the} silica abrasive grains contained in the finish polishing composition can be, for example, less than 40 nm (typically 5 nm to less than 40 nm), and 35 nm or less (typically 5 nm to 35 nm). For example, 10 nm to 30 nm). Further, the SD _{AVE of the} silica abrasive grains contained in the final polishing composition is not particularly limited, but is usually about 0.8 to 10 particles / nm ² from the viewpoint of balancing polishing efficiency and surface accuracy in a balanced manner. It is appropriate, and about 1 to 5 pieces / nm ² is preferable.

  In the finish polishing composition containing colloidal silica, the content of colloidal silica is not particularly limited. The content of the colloidal silica is preferably 40% by weight or more, more preferably 50% by weight or more, further preferably 60% by weight or more (for example, 80% by weight) based on the total solid content contained in the finish polishing composition. Above). Colloidal silica may be used for substantially all (for example, 99% by weight or more) of the solid content contained in the polishing composition.

  The finish polishing composition typically contains water in addition to the silica abrasive grains. In addition, the finish polishing composition can contain the same components (acid, oxidizing agent, basic compound, various additives, and the like) as those of the polishing composition described above, if necessary. Although not particularly limited, the pH of the finish polishing composition can be the same as that of the polishing composition described above. The pH of the finish polishing composition can be, for example, pH 12.0 or less (typically pH 0.5 to 12.0), preferably pH 7.0 or less (for example, pH 0.5 to 7.0), The pH is more preferably 5.0 or less (typically pH 1.0 to 5.0), and still more preferably pH 4.0 or less (for example, pH 1.0 to 4.0). In a preferred embodiment, the finish polishing composition has a pH of 3.0 or less (typically pH 1.0 to 3.0, preferably pH 1.0 to 2.0, more preferably pH 1.0 to 1.8. ).

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

In the following examples, the average primary particle diameter (D1) of the silica particles was calculated from the measured value of the specific surface area using a surface area measuring device (trade name “Flow Sorb II 2300”) manufactured by Micromerex. The average secondary particle size (D2) of the silica particles was measured using a laser diffraction / scattering particle size distribution measuring device (model “LA-950”) manufactured by Horiba, Ltd. The silanol group density (SD) of the silica particles was measured according to the silanol group density measurement method described above. Based on D1 and SD of each silica particle and the amount used, the average primary particle diameter (D1 _AVE ) and average silanol group density (SD _AVE ) of the silica abrasive grains contained in each polishing composition were determined.

<Preparation of heat-treated silica>
Raw material silica (precipitated silica having D1 of 146 nm) was heat-treated (fired) for a certain time at 950 ° C. to 1050 ° C. in air atmosphere. The obtained fired product was put into a ball mill and crushed using a ball having a diameter of 3 mm until D2 was about 100 nm to about 500 nm. By adjusting the degree of crushing, three types of silica particles (NC1 to NC3) having different D1 and SD were prepared. NC1 to NC3 are silica particles (fired silica) obtained by firing and crushing raw material silica (precipitated silica). In the preparation of the polishing composition described later, the raw material silica was used as the silica particles NC4, and the fired product obtained by the firing was used as the silica particles NC5 without crushing.

<Preparation of polishing composition>
Example 1
Silica particles NC1, silica particles CS1 (sodium silicate colloidal silica having a D1 of about 34 nm), nitric acid, 31% hydrogen peroxide water, and deionized water are mixed to obtain NC1 of 31 g / L, CS1. Was prepared at 30 g / L, nitric acid (HNO ₃ ) at 8 g / L, and hydrogen peroxide (H ₂ O ₂ ) at 40 g / L.

(Examples 2 and 3)
Polishing compositions according to Examples 2 and 3 were prepared in the same manner as Example 1 except that silica particles NC2 and NC3 were used instead of silica particles NC1, respectively.

Example 4
A polishing composition was prepared in the same manner as in Example 2 except that silica particles CS2 (sodium silicate colloidal silica having D1 of about 63 nm) was used instead of silica particles CS1.

(Example 5)
A polishing composition was prepared in the same manner as in Example 4 except that the content of the silica particles NC2 was changed to 10 g / L.

(Comparative Example 1)
Silica particles NC4, nitric acid, 31% hydrogen peroxide water, and deionized water are mixed to obtain NC4 62 g / L, nitric acid (HNO ₃ ) 8 g / L, hydrogen peroxide (H ₂ O ₂ ). A polishing composition containing 40 g / L was prepared.

(Comparative Example 2)
Silica particle NC5, silica particle CS3 (sodium silicate colloidal silica having a D1 of about 235 nm), nitric acid, 31% hydrogen peroxide water, and deionized water are mixed to obtain NC5 of 31 g / L, CS3. Was prepared at 30 g / L, nitric acid (HNO ₃ ) at 8 g / L, and hydrogen peroxide (H ₂ O ₂ ) at 40 g / L.

(Comparative Examples 3-6)
Comparative Example 1 except that silica particles CS1, CS3, CS4 (sodium silicate colloidal silica with D1 of about 420 nm) and CS5 (alkoxide colloidal silica with D1 of about 96 nm) were used in place of the silica particles NC4. Similarly, polishing compositions according to Comparative Examples 3 to 6 were prepared.

Table 1 shows the composition of the silica abrasive grains, the average primary particle diameter (D1 _AVE ), and the average silanol group density (SD _AVE ) for the polishing composition according to each example.

<Disk polishing>
The polishing composition according to each example was used as it was for the polishing liquid, and the polishing object was polished under the following conditions. As an object to be polished, an aluminum substrate for hard disk having an electroless nickel phosphorus plating layer on the surface was used. The above polishing object (hereinafter also referred to as “Ni-P substrate”) has a diameter of 3.5 inches (a donut shape having an outer diameter of about 95 mm and an inner diameter of about 25 mm) and a thickness of 1.75 mm. The roughness Ra (the arithmetic average roughness of the nickel phosphorus plating layer measured by a laser scan type surface roughness meter “TMS-3000WRC” manufactured by Schmitt Measurement System Inc.) was 130 mm.

[Polishing conditions]
Polishing device: Double-side polishing machine manufactured by System Seiko Co., Ltd., model “9.5B-5P”
Polishing pad: Polyurethane pad manufactured by FILWEL, trade name “CR200”
Number of inserted Ni-P substrates: 15 (5 / carrier x 3 carriers)
Polishing liquid supply rate: 135 mL / min Polishing load: 120 g / cm ²
Upper platen rotation speed: 27rpm
Lower platen rotation speed: 36rpm
Sun gear (sun gear) rotation speed: 8rpm
Polishing amount: about 2.2 μm in total on both sides of each substrate

<Polishing rate>
The polishing rate when the Ni-P substrate was polished under the above polishing conditions using the polishing composition according to each example was calculated. The polishing rate was determined based on the following calculation formula.
Polishing rate [μm / min] = Reduction in weight of substrate by polishing [g] / (Substrate area [cm ² ] × Nickel phosphorus plating density [g / cm ³ ] × Polishing time [min]) × 10 ⁴
The obtained values are shown in the “Polishing Rate” column of Table 1 as relative values converted so that the polishing rate of Comparative Example 1 is 100%.

<Surface accuracy>
Value of arithmetic mean waviness (Wa) measured using “Optiflat II” manufactured by PhaseShift (USA) in the range of radius 20 mm to 44 mm from the center of the Ni-P substrate after polishing under the condition of cutoff value 5 mm Was measured. The obtained measured values are shown in the column of “undulation” in Table 1 as relative values converted so that the measured value for Comparative Example 1 is 100%. A smaller relative value of the waviness means that the long wavelength waviness of the surface to be polished is reduced, that is, the surface accuracy of the surface to be polished is higher.

As apparent from the results shown in Table 1, the polishing compositions of Examples 1 to 5 having D1 _AVE of 40 nm or more and SD _AVE of 1.25 pieces / nm ² or less are as in Comparative Example 2. In comparison with Comparative Example 1 and Comparative Examples 4 to 6, the polishing rate was twice or more higher without causing a significant decrease in surface accuracy (increase in undulation). Further, from comparison between Examples 1 to 5 and Comparative Example 3, it can be seen that even if the SD _{AVE of the} silica abrasive grains is lowered, the polishing rate is not improved in the polishing composition in which D1 _AVE is less than 40 nm. From the above, according to the polishing composition in which D1 _AVE is 40 nm or more and SD _AVE is 1.25 pieces / nm ² or less, high polishing rate and good surface accuracy can be achieved at a high level. It was confirmed.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (8)

A polishing composition used for polishing a magnetic disk substrate having a nickel phosphorus plating layer on its surface,
Containing silica abrasive grains,
Polishing composition whose average primary particle diameter of the said silica abrasive grain is 40 nm or more, and whose average silanol group density of the said silica abrasive grain is 1.25 piece / nm < ² > or less. The polishing composition according to claim 1, wherein an average silanol group density of the silica abrasive grains is 0.5 / nm ² or more.   The polishing composition according to claim 1, wherein the silica abrasive grains include heat-treated silica particles.   The polishing composition according to any one of claims 1 to 3, wherein the pH is 5 or less.   The polishing composition according to any one of claims 1 to 4, which is used in a pre-process of a final polishing process. A method of manufacturing a magnetic disk substrate, comprising:
Comprising the step (1) of polishing a magnetic disk substrate with the polishing composition according to claim 1, any one of 5, the magnetic disk substrate manufacturing method. The method of manufacturing a magnetic disk substrate according to claim 6 , further comprising a step (2) of polishing the magnetic disk substrate using a final polishing composition containing colloidal silica after the step (1). A magnetic disk substrate polishing method, comprising supplying the polishing composition according to any one of claims 1 to 5 to a magnetic disk substrate to polish the magnetic disk substrate.