JP2019064852A - Silica dispersion liquid, polishing slurry, and kit for preparing polishing slurry - Google Patents

Abstract

To provide a silica dispersion liquid suitable as a constituent of polishing slurry, which is excellent in antiseptic properties and may be compatible with polishing performance.SOLUTION: A silica dispersion liquid contains silica particles, an organic antiseptic agent, and water. When the carbon weight of the organic antiseptic agent contained in the silica dispersion liquid is expressed by W0, and the carbon weight of the organic antiseptic agent contained in a supernatant obtained by subjecting the silica dispersion liquid to centrifugal separation treatment to precipitate the silica particles is expressed by W1, the adsorption index α of the silica dispersion liquid is 5 or less, measured by the following formula: α=[(W0-W1)/W0]×100.SELECTED DRAWING: None

Description

  The present invention relates to a silica dispersion, a polishing slurry containing the silica dispersion, and a kit for preparing a polishing slurry containing the silica dispersion as a component.

  Polishing using a polishing slurry is performed on the surface of materials such as metals, semimetals, nonmetals, and oxides thereof. As the above-mentioned polishing slurry, generally used is one in which abrasive grains according to the material of the object to be polished and the purpose of polishing are dispersed in a liquid medium mainly composed of water. For example, as an object to be polished for a hard disk, there is a magnetic disk substrate or a glass substrate having a nickel phosphorus plating layer. There are cases in which alumina or silica is used in the rough polishing process and silica is used in the precision polishing process as abrasive grains of a polishing slurry for magnetic disk substrates having a nickel phosphorus plating layer. There are cases where ceria, zirconia or silica is used in the rough polishing process and silica is used in the precision polishing process as abrasive grains of the polishing slurry for glass substrate. Such an abrasive slurry is an abrasive particle dispersion in which abrasive particles having a high concentration are dispersed in water as compared to the abrasive slurry (working slurry) supplied to the object to be polished (workpiece) for the convenience of distribution and storage, and It may be provided separately from the abrasive particle dispersion and other components used for preparation of the polishing slurry. For example, a polishing slurry using silica particles as abrasive grains can be suitably prepared by mixing the silica dispersion liquid as the abrasive grain dispersion liquid with other components.

  A preservative may be added to the abrasive grain dispersion in order to prevent decay during distribution or storage. For example, Patent Documents 1 and 2 disclose a silica dispersion containing an organic preservative having a specific structure. Patent Document 3 describes that an aqueous solution of an additive may contain an antiseptic, and Patent Document 4 describes that an abrasive composition may contain an antiseptic, but these Patent Documents There is no specific disclosure of the inclusion of an organic preservative in the silica dispersion. Patent Document 5 is a document relating to a polishing composition containing alumina and a preservative, and does not disclose a silica dispersion containing an organic preservative.

JP, 2016-124743, A JP, 2016-124977, A JP, 2016-127268, A Unexamined-Japanese-Patent No. 2017-11220 Unexamined-Japanese-Patent No. 2006-176733

  As a result of examining the preservation of the silica dispersion which can be used for preparation of polishing slurry in detail, the present inventors appropriately exhibit the preservation performance by the use of the organic preservative in the techniques described in Patent Documents 1 and 2 I found that I might not be. It would be beneficial if techniques were provided to more effectively preserve silica dispersions using organic preservatives.

  The present invention has been made in view of the above circumstances, and is a silica suitable as a constituent component of a polishing slurry which exhibits good preservative performance by efficiently using an organic preservative, and is compatible with polishing performance. The purpose is to provide a dispersion. Another related objective is to provide an abrasive slurry and a kit for preparing the abrasive slurry, which contain such a silica dispersion.

  The inventors of the present invention, in a silica dispersion containing silica particles and an organic preservative, the distribution ratio of the organic preservative in the liquid phase of the silica dispersion and on the silica particles is the constitution of the silica dispersion. We focused on the differences depending on the And it discovered that the said subject could be solved by controlling the distribution ratio of the said organic preservative appropriately, and completed this invention.

The silica dispersion provided by this specification comprises silica particles, an organic preservative and water. The above-mentioned silica dispersion liquid contains carbon weight W0 of the above-mentioned organic preservative contained in the above-mentioned silica dispersion, and the above-mentioned organic preservative contained in the supernatant obtained by subjecting the above-mentioned silica dispersion to centrifugal separation treatment. From the carbon weight W1, the following equation:
Adsorption index α = [(W0−W1) / W0] × 100;
Is characterized by the adsorption index .alpha.

  The fact that the adsorption index α is smaller means that the proportion of the organic preservative that precipitates together with the silica particles by the above-mentioned centrifugation is low among the organic preservatives contained in the above silica dispersion, that is, in the liquid phase of the above silica dispersion. Means that the proportion of organic preservatives present in is higher. Therefore, according to the silica dispersion in which the adsorption index is suppressed to 5 or less, the organic preservative contained in the silica dispersion can be efficiently used to exert a good preservative effect. Such silica dispersions may be suitable as components of polishing slurries that exhibit good preservative properties and are compatible with polishing performance. For example, it may be less likely to cause a decrease in polishing rate or deterioration in cleanliness resulting from the use of an organic preservative, or defects due to aggregation of silica particles in the process of preparing the polishing slurry. In order to realize the preservation of the silica dispersion with an organic preservative having a high adsorption index α, it is necessary to increase the amount of the organic preservative added, which makes it difficult to achieve both the above-mentioned polishing performance and cost and environment. It is not preferable from the viewpoint of load.

  In the silica dispersion disclosed herein, the concentration of the silica particles is preferably 15% by weight or more. Hereinafter, the concentration of silica particles is also referred to as “silica concentration” for short. In silica dispersions with high silica concentration, the organic preservative present on the silica particles tends to be a factor that causes the aggregation of the silica particles. Therefore, it is particularly significant to suppress the adsorption index α of the silica dispersion to 5 or less.

  The silica dispersion disclosed herein preferably has a pH of 2.0 to 12.0. A silica dispersion having such a pH is more susceptible to decay as compared to a more acidic or more alkaline silica dispersion, and therefore, the application of the technology disclosed herein is significant.

In some embodiments of the silica dispersion disclosed herein, the adsorption amount to the silica particles of the organic preservative is preferably not more than a surface area 1 m ² per 5μg of the silica particles. The small adsorption amount of the organic preservative per surface area of the silica particles is used as a constituent component of the polishing slurry from the viewpoint of suppression of deterioration of the polishing rate, suppression of deterioration of cleanliness and suppression of defects caused by aggregation of the silica particles. It can be advantageous.

  In some embodiments of the silica dispersion disclosed herein, the concentration of the organic preservative may be 0.1 wt% or less. Limiting the concentration of the organic preservative to 0.1% by weight or less may be advantageous from the viewpoint of suppressing the lowering of the polishing rate, suppressing the deterioration of the cleanliness, suppressing the defects, reducing the cost, and reducing the environmental load. The silica dispersion disclosed herein can effectively utilize the organic preservative in the silica dispersion when the adsorption index α is 5 or less. Therefore, compared to a silica dispersion having an adsorption index α of greater than 5, it may exhibit good preservative even at lower organic preservative concentrations.

  It is preferable that the BET diameter of the said silica particle of the silica dispersion liquid disclosed here is 10 nm or more. Such silica particles can be preferably used as an abrasive component of a polishing slurry in which the polishing rate is important. Therefore, there is great significance in achieving both the suppression of the decrease in the polishing rate and the good preservative effect by applying the technology disclosed herein.

As the above-mentioned organic preservative, the following conditions:
(A) contains a nitrogen atom having a non-covalent electron pair; and (B) has a π bond between the nitrogen atom and its α-position atom, or between the α-position atom and the β-position atom;
The compound which has a structural part which satisfy | fills can be used preferably. The technology disclosed herein can be suitably practiced using an organic preservative that satisfies the above conditions (A) and (B).

  The silica dispersion disclosed herein can be preferably used to prepare a polishing slurry. In particular, by mixing at least the pH adjusting agent and the above-mentioned silica dispersion, the present invention can be applied to the use of preparing a polishing slurry having a different pH from that of the above-mentioned silica dispersion before the mixing. The state of adsorption of the organic preservative onto the silica particles can vary with pH. The fluctuation of the adsorption state can be a factor causing aggregation of silica particles. According to the silica dispersion having a low distribution ratio of the organic preservative onto the silica particles, that is, the silica dispersion having a small adsorption index α, it is possible to achieve both the good preservative effect of the silica dispersion and the dispersion stability against pH fluctuation. It is easy to do.

  The silica dispersion disclosed herein can be applied, for example, as a silica dispersion for mixing with an acid to prepare a polishing slurry. This specification can provide an abrasive slurry comprising any of the silica dispersions disclosed herein and an acid. Such a polishing slurry can be excellent in the preservative effect of the silica dispersion and can exhibit a favorable polishing rate.

  Preferred applications of the polishing slurry disclosed herein include applications for polishing magnetic disk substrates. Above all, it is useful for polishing a glass substrate or a magnetic disk substrate having a nickel phosphorus plating layer on the surface. Hereinafter, the magnetic disk substrate having a nickel phosphorus plating layer on its surface is also abbreviated as "Ni-P substrate". The polishing slurry disclosed herein can be preferably used, for example, for polishing a magnetic disk substrate.

  According to this specification, it is possible to provide a kit for preparing an abrasive slurry, which comprises, for example, a first composition comprising any of the silica dispersions disclosed herein, and a second composition containing at least an acid. . In the kit, the first composition and the second composition are stored separately from each other. The polishing slurry preparation kit configured as described above is excellent in the preservative property of the first composition during distribution and storage of the kit, and has a good polishing rate in the polishing slurry prepared using the kit. It can be demonstrated.

  Hereinafter, preferred embodiments of the present invention will be described. The matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as the design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field. In the specification, "weight" and "mass" are used interchangeably.

Silica dispersion
(Adsorption index α)
The silica dispersion disclosed by this specification comprises silica particles, an organic preservative and water. The adsorption index α of the silica dispersion is 5 or less. Here, the adsorption index α is determined by using the carbon weight W0 of the organic preservative contained in the silica dispersion and the organic preservative contained in the supernatant obtained by subjecting the silica dispersion to a centrifugal separation treatment. From the carbon weight W1 of the agent, the following formula:
Adsorption index α = [(W0−W1) / W0] × 100;
Calculated by The centrifugation can be performed at room temperature (20 to 30 ° C., for example, 25 ° C.) under conditions that allow the silica particles to precipitate, and can be performed, for example, under the conditions described in the examples described later. The carbon weight W1 of the organic preservative contained in the supernatant can be determined, for example, by measuring the total organic carbon content (TOC) of the supernatant and based on the measurement result. In addition, carbon weight W0 of the organic preservative contained in the silica dispersion is prepared by mixing an organic preservative of the same type as the organic preservative contained in the silica dispersion into pure water at equal concentration to prepare a preservative diluted aqueous solution Similarly, TOC can be measured and determined based on the measured value. Specifically, W1 and W0 can be calculated by the following equations.

W1 = [TOC1 × Vu]
W0 = [TOC0 × Vs]
Vs = Ws / ρs
Vu = Vs− (W _silica / ρ _silica )
TOC 1: TOC measured on the supernatant of the silica dispersion (mg / l)
TOC 0: TOC (mg / l) of preservative diluted aqueous solution diluted to the same concentration as preservative of silica dispersion
Vu: volume of supernatant of silica dispersion (ml)
Vs: Volume of silica dispersion (ml)
Ws: mass of silica dispersion (g)
ss: density of silica dispersion (g / ml)
W _silica : mass of silica (g)
sil _silica : density of silica (typically 2.2 g / ml is used)

  The measurement of TOC can be performed, for example, using a total organic carbon meter manufactured by Shimadzu Corporation (a combustion catalyst oxidation system, model “TOC-5000A”) or the like. More specifically, for example, the adsorption index α of the silica dispersion can be determined by the procedure described in the examples to be described later. When the silica dispersion to be measured contains an organic compound other than the organic preservative, for example, prepare a reference solution of a composition obtained by removing the organic preservative from the silica dispersion, and centrifuge the reference solution to separate it. The TOC of the organic preservative can be determined by measuring the TOC of the obtained supernatant and correcting the TOC of the supernatant of the silica dispersion to be measured using the TOC of the supernatant of the reference solution.

  According to the silica dispersion having an adsorption index α of 5 or less, the organic preservative contained in the silica dispersion can be efficiently used to exert a good preservative effect. Such a silica dispersion is preferable in the polishing slurry prepared using the silica dispersion, since it is easy to suppress a negative effect due to the presence of an organic preservative, for example, a decrease in polishing rate.

  In some embodiments of the silica dispersion disclosed herein, the adsorption index α may be, for example, 4.5 or less, 4 or less, or 3.5 or less. The decrease in the adsorption index α tends to further increase the utilization efficiency of the organic preservative contained in the silica dispersion. The fact that the adsorption index α of the silica dispersion is small is compatible with the polishing performance such as suppression of lowering of the polishing rate, suppression of deterioration of cleanliness, improvement of aggregation preventing property against pH change such as mixing with acid, and suppression of defects due to aggregation. In terms of cost and environmental impact, it can be advantageous. The technique disclosed herein can also be suitably practiced in the form of a silica dispersion having an adsorption index α of 3.0 or less, 2.5 or less, 1.5 or less, or 1.0 or less. The lower limit of the adsorption index α is not particularly limited, and may be, for example, 0. The adsorption index α is determined, for example, by selecting the type and concentration of the organic preservative contained in the silica dispersion, selecting the type, shape and concentration of the silica particles contained in the silica dispersion, selecting the pH of the silica dispersion, etc. It can be adjusted.

(Silica particles)
The type, properties, etc. of the silica particles are not particularly limited, and can be appropriately selected so that a desired adsorption index α can be obtained in the silica dispersion containing the silica particles, according to the purpose of use, mode of use, etc. The term "silica particles" as used herein refers to particles containing silica as a main component, and in addition to particles substantially consisting of silica, for example, 90 wt% or more, 95 wt% or more, or 98 wt% or more of the particles It may include particles consisting of silica.

  Examples of silica particles that can be used include, but are not limited to, colloidal silica, precipitated silica, sodium silicate method silica, alkoxide method silica, fumed silica, dry silica, detonation silica and the like. Examples of silica particles that can be used further include silica particles obtained using the above-mentioned silica particles as a raw material. Examples of such silica particles include silica particles of the above-mentioned raw material (hereinafter also referred to as "raw material silica"), heat treatment such as heating, drying, and calcination, pressure treatment such as autoclave treatment, crushing and crushing, etc. And silica particles obtained by applying one or more treatments selected from mechanical treatment, surface modification and the like. The surface modification includes, for example, introduction of a functional group, and chemical modification such as metal modification. The silica dispersion disclosed herein may contain one of such silica particles alone or in combination of two or more.

  Colloidal silica is mentioned as a suitable example of the silica particle which can be used as a component of the silica dispersion liquid indicated here. Among them, use of colloidal silica synthesized through particle growth in an aqueous phase, such as sodium silicate silica and alkoxide silica, is preferable. According to the silica dispersion containing colloidal silica of this type, a polishing slurry which achieves both a high polishing rate and a good surface accuracy can be suitably achieved. When the silica dispersion liquid disclosed herein contains colloidal silica, the colloidal silica may be one kind, and may be two or more kinds different in production conditions and / or physical properties. The silica dispersion may contain only one or two or more types of colloidal silica as silica particles, and may include colloidal silica in combination with other silica particles, that is, silica particles other than colloidal silica. It may be a configuration. The silica dispersion liquid which concerns on one preferable aspect contains only 1 type, or 2 or more types of colloidal silica as a silica particle. By using only colloidal silica as the silica particles, better surface accuracy (e.g., a surface with reduced undulation) can be realized while maintaining a high polishing rate.

  The particle shape of the colloidal silica is not particularly limited, and may be, for example, spherical or non-spherical. Specific examples of the non-spherical shape include peanut shape, bowl shape, protrusion shape, rugby ball shape and the like. The peanut shape may be, for example, the shape of a peanut shell. The projecting shape may be, for example, a gourd sugar shape.

  As another example of the silica particles, for example, silica particles obtained by subjecting raw material silica to a heat treatment (hereinafter also referred to as "heat-treated silica"), specifically heated silica particles, dried silica Particles, calcined silica particles, etc. may be mentioned. Here, the heated silica particles are typically obtained through a process of holding for a certain time or more, for example, 15 minutes or more, typically 30 minutes or more, under an environment of 60 ° C. or more and less than 110 ° C. Mean silica particles. In addition, the dried silica particles are typically at least 110 ° C. and less than 500 ° C., preferably at least 300 ° C. and less than 500 ° C., for a fixed time or more, for example, 15 minutes or more, typically 30 minutes or more It refers to silica particles obtained through holding treatment. And, the calcined silica particles (hereinafter also referred to as “calcined silica”) are typically 500 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher, for a predetermined time or more, for example 15 This refers to silica particles obtained through treatment for holding for more than a minute, typically 30 minutes or more. Silica particles obtained through the heat treatment of any of the above-mentioned starting silicas, ie precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dry silica, explosive silica etc. It is a typical example included in the concept of heat-treated silica. When the silica dispersion contains heat-treated silica, the heat-treated silica may be one kind, and may be two or more kinds different in production conditions and / or physical properties. In addition, the above-mentioned silica dispersion liquid may be configured to contain only one or two or more types of heat-treated silica as silica particles, and a combination of heat-treated silica and other silica particles, that is, silica particles not subjected to heat treatment The configuration may be included. In such an embodiment, the proportion of thermally treated silica in the entire silica particles contained in the silica dispersion is not particularly limited, and may be, for example, 10 to 90% by weight, 20 to 80% by weight, or 30 to 70% by weight. The silica particles used in combination with the heat treated silica may be, for example, colloidal silica. Higher surface accuracy may be realized by using a silica dispersion containing colloidal silica in addition to heat treated silica.

  In the technology disclosed herein, the BET diameter of the silica particles is not particularly limited as long as a desired adsorption index α can be obtained in the silica dispersion containing the silica particles, and is selected according to the purpose of use of the silica dispersion, etc. It can. The BET diameter of the silica particles may be, for example, about 10 nm to 500 nm. From the viewpoint of polishing efficiency and the like, in some embodiments, the BET diameter may be, for example, 15 nm or more, and may be 20 nm or more. The polishing rate tends to be improved by the increase of the BET diameter. In addition, in a silica dispersion having a similar silica concentration, the adsorption index α tends to generally decrease as the BET diameter increases. The technology disclosed herein can also be suitably implemented in an embodiment in which the BET diameter of the silica particles is 25 nm or more, 30 nm or more, or 40 nm or more. On the other hand, from the viewpoint of enhancing the surface accuracy of the substrate surface after polishing, the BET diameter is usually 300 nm or less, 200 nm or less, 150 nm or less, or 120 nm or less. In the process where surface precision of the surface of the substrate after polishing is required, the BET diameter of the smaller silica particles is suitably implemented, and may be 50 nm or less. In a silica dispersion having a similar silica concentration, when the BET diameter decreases, the difficulty disclosed in obtaining a good preservative effect while suppressing the decrease in the polishing rate tends to increase, so the technique disclosed herein is applied. The significance of In some embodiments, the BET diameter may be, for example, 100 nm or less, 80 nm or less, or 60 nm or less. The above-described BET diameter can be applied to, for example, a silica dispersion used to prepare a polishing slurry. Among them, the present invention can be preferably applied to a silica dispersion used for preparing a polishing slurry of a magnetic disk substrate such as a Ni-P substrate or a glass substrate. Among the silica dispersions used for the polishing slurry to which particles having a large BET diameter are applied among the above, a silica dispersion to which, for example, abrasive grains having a BET diameter of 25 nm or more is applied can be preferably applied particularly for primary polishing.

Here, the BET diameter is defined as BET diameter (nm) = 6000 / (true density (g / cm ³ ) × BET value (m ² / g)) from the specific surface area (BET value) measured by the BET method. It refers to the particle size calculated by the formula. It is also called a specific surface area converted particle diameter. For example, in the case of silica particles, the value of the true density of silica is 2.2, and the BET diameter can be calculated by the equation of BET diameter (nm) = 2727 / BET value (m ² / g). The measurement of the specific surface area can be performed, for example, using a surface area measurement device manufactured by Micromeritex, trade name "Flow Sorb II 2300".

  The silica concentration of the silica dispersion disclosed herein is not particularly limited, and may be, for example, about 5% by weight to 70% by weight. Since the distribution and storage of the silica dispersion can be compact, the concentration of the silica is usually 10% by weight, preferably 15% by weight or more. In the case of a silica dispersion having a high concentration of silica, the organic preservative present on the silica particles tends to trigger a dispersion failure such as aggregation. Therefore, it is particularly significant to apply the technology disclosed herein to suppress the adsorption index α. From such viewpoints, in some preferred embodiments, the silica concentration may be 20% by weight or more, and 23% by weight or more. On the other hand, from the viewpoint of preparation easiness of preparation and dispersion stability of the polishing slurry containing the silica dispersion, the above-mentioned silica concentration is usually 50 wt% or less, 40 wt% or less, 35 wt%. % Or less, or 30 wt.% Or less. Since a silica dispersion having a low silica concentration has a lower dilution ratio when preparing a polishing slurry from the silica dispersion than a silica dispersion having a higher silica concentration, the organic preservative derived from the silica dispersion is The effect on the performance of the polishing slurry, such as the polishing rate, can be significant. Therefore, there is great significance in efficiently using the organic preservative contained in the silica dispersion by using the technology disclosed herein.

(Organic preservative)
The type of the organic preservative to be contained in the silica dispersion is not particularly limited, and among various organic preservatives known to be able to exert the preservative effect, the adsorption index α of the silica dispersion may be 5 or less. Materials can be selected and used. Nonlimiting examples of the organic preservatives mentioned here include imidazole compounds, guanidine compounds, triazole compounds, isothiazoline compounds, nitro alcohol compounds, dithiol compounds, thiophene compounds, haloacetylene compounds, phthalimides It is possible to include a compound, a haloalkylthio compound, a pyrithione compound, a phenylurea compound, a triazine compound, a quinolone compound, a quaternary ammonium salt compound and the like. For example, one or two or more compounds selected from the group consisting of imidazole compounds and guanidine compounds can be used. Examples of the imidazole compounds include benzimidazole, thiabendazole, fuberidazole, mebendazole, albendazole, fenbendazole, flubendazole, oxfendazole, oxybendazole, perbendazole, cambendazole, luxabendazole, lycobendazole, etc. And benzimidazole compounds. Examples of guanidine compounds include polyalkylene biguanidines such as polyhexamethylene biguanidine, polyalkylene guanidines such as polyhexamethylene guanidine, 1,6-di- (4'-chlorophenyl diguanide) -hexane, dodecyl guanidine And salts thereof, and the like. The salt may be, for example, hydrochloride or phosphate. Organic preservatives can be used singly or in combination of two or more.

In some embodiments of the silica dispersion disclosed herein, the above-mentioned organic preservatives have the following conditions:
(A) contains a nitrogen atom having a non-covalent electron pair; and (B) has a π bond between the nitrogen atom and its α-position atom, or between the α-position atom and the β-position atom;
The compound which has a structural part which satisfy | fills can be used preferably. According to an organic preservative having such a structural part, a silica dispersion suitable for use as a component of a polishing slurry which has a small adsorption index α, exhibits good preservative properties, and is compatible with polishing performance, for example, It is easy to obtain a silica dispersion which is less likely to cause defects such as a decrease in polishing rate and deterioration in cleanliness resulting from the use of an organic preservative, and aggregation of silica particles in the process of preparing the polishing slurry.

  As an organic preservative having a structural moiety satisfying the above (A) and (B), for example, a compound represented by the following general formula (I) or (II) can be adopted.

  In each of the above general formulas (I) and (II), R 1, R 2 and R 3 are any groups satisfying valency, and two or more of R 1, R 2 and R 3 together form a ring structure You may form. The above arbitrary group is, for example, a linear or branched hydrocarbon group such as an alkyl group or an alkylene group; a hydrocarbon group containing a cyclic structure such as a cycloalkyl group, an aryl group or an arylalkyl group; A linear or branched organic group containing an organic group containing a heterocyclic structure; an atom that can be accepted according to valency, such as a hydrogen atom, an oxygen atom, a sulfur atom, a halogen atom, etc .; an amino group, a monoalkylamino group, It may be an optionally substituted amino group such as a dialkylamino group; an optionally substituted imino group such as an imino group and an alkylimino group;

Although not wishing to be bound by theory, an organic preservative having a structural moiety satisfying the above (A) and (B) (for example, an organic preservative represented by the above general formula (I) or (II) The reason why the preferred result is obtained is considered as follows, for example. That is, for example, as in the above general formula (I), a structure containing a nitrogen atom having an unshared electron pair and having a π bond between the α-position atom (preferably carbon atom) and the β-position atom of the nitrogen atom In a compound having a moiety, the noncovalent electron pair on the nitrogen atom is subject to a resonance effect. Further, in a compound having a π bond between a nitrogen atom and its α-position atom (preferably a carbon atom) as in the above general formula (II), a proton is bonded to the noncovalent electron pair on the nitrogen atom When the nitrogen atom is charged with a cationic charge, electrons on the π bond between the nitrogen atom and the α-position atom delocalize the charge. As a result, the property that the noncovalent electron pair is localized or isolated on the nitrogen atom is weakened.
In general, the non-covalent electron pair on the nitrogen atom can contribute to the formation of a hydrogen bond with the silanol group present on the surface of the silica particle. As described above, according to the organic preservative having a structure capable of delocalizing the noncovalent electron pair on the nitrogen atom, the adsorption of the organic preservative onto the silica particles is weakened, and a silica dispersion having a low adsorption index α is obtained. It will be easier. As a result, by effectively using the organic preservative in the silica dispersion, it is possible to realize a silica dispersion suitable for use as a component of a polishing slurry that exhibits good preservative properties and is compatible with polishing performance. It is considered to be However, the present invention is not limited to this mechanism.

Preferred organic preservatives include thiabendazole, thiabendazole having a hydrocarbon group of 1 to 6 or 1 to 3 carbon atoms as a substituent, one or more hetero atoms selected from the group consisting of N, O and S. Thiabendazole-based compounds such as thiabendazole having an organic group having 1 to 6 or 1 to 3 carbon atoms as a substituent; poly C _1-8 alkylene biguanidine, poly C _1-8 alkylene alkylene guanidine, hydrochlorides thereof or phosphorus And guanidine compounds such as acid salts and the like; In the guanidine type compound, "C _1-8 alkylene" represents an alkylene group having 1 to 8 carbon atoms. A linear alkylene group having 4 to 8 carbon atoms is preferred, and a hexamethylene group is particularly preferred. In some embodiments of the silica dispersion disclosed herein, the above organic preservatives of chemical structure that do not contain oxygen atoms may be preferably employed.

  The concentration of the organic preservative is not particularly limited, and may be selected according to the type of organic preservative and the use of the silica dispersion. The concentration of the organic preservative may be, for example, about 0.0001% by weight to 1% by weight. The concentration of the organic preservative may be, for example, 0.5% by weight or less, in some preferred embodiments, from the viewpoint of suppression of polishing rate reduction and prevention of aggregation against mixing with an acid. % Or less, or 0.05 wt.% Or less. The silica dispersion disclosed herein can be suitably carried out even in an embodiment in which the concentration of the organic preservative is 0.02% by weight or less, 0.01% by weight or less, or 0.005% by weight or less. Good preservative can be exhibited even at organic preservative concentrations. The lower limit of the concentration of the organic preservative is not particularly limited, and can be set to obtain a desired preservative. In some embodiments, the organic preservative concentration may be, for example, 0.0005 wt% or more, and may be 0.001 wt% or more. From the viewpoint of suitably expressing the preservative action by the organic preservative, the compounding amount may be added according to various preservatives and the target bacterial species, at least the addition amount close to the general index MIC (minimum growth inhibition concentration) Preferably, the above concentration is exemplified. In addition, when the lower limit of the organic preservative concentration is increased, the significance of suppressing the adsorption index α tends to be further increased.

(Adsorption amount per surface area)
Silica dispersion disclosed herein, an organic preservative adsorption amount of surface area 1 m ² per silica particles contained in the silica dispersion (hereinafter referred to as "surface area per adsorption".) Is, for example, may be less than 10μg . The adsorption amount per surface area can be calculated based on the carbon weight W0 of the organic preservative contained in the silica dispersion, the surface area of the silica particles contained in the silica dispersion, and the adsorption index α of the silica dispersion. . In some embodiments, the adsorption amount per surface area may be, for example, 5 μg / m ² or less, 2 μg / m ² or less, or 1 μg / m ² or less. The low adsorption amount per surface area can be advantageous from the viewpoint of suppressing the decrease in polishing rate resulting from the use of the organic preservative. In addition, the suppression of the amount of adsorption per surface area tends to increase the resistance to pH changes such as mixing of acids and to improve the aggregation preventing property of the silica particles. The lower limit of the adsorption amount per surface area is not particularly limited, and may be substantially 0 μg / m ² .

(water)
As water contained in the silica dispersion liquid, ion exchange water, distilled water, pure water, ultra pure water, reverse osmosis water, filtered water, industrial water, etc. can be used. For example, ion exchange water, pure water, Ultrapure water, distilled water and the like can be preferably used. Ion exchange water can typically be deionized water.

(PH of silica dispersion)
The pH of the silica dispersion is not particularly limited, and may be selected according to the application of the silica dispersion. The pH of the silica dispersion may be selected, for example, from the range of 2.0 to 12.5. In some embodiments, the pH of the silica dispersion may be, for example, 5.0 or more, 7.0 or more, 8.0 or more, 9.0 or more, It is also good. When the pH of the silica dispersion increases, the dispersion stability of the silica dispersion tends to improve. Further, from the viewpoint of preventing the dissolution of the silica particles, the pH of the silica dispersion is usually 12.0 or less, preferably 11.0 or less, and preferably 10.5 or less. For example, it may be 10.0 or less. The pH of the silica dispersion can be adjusted by adding a pH adjusting agent as needed. As the pH adjuster, basic compounds and acids exemplified as being usable for the polishing slurry described later can be used singly or in combination of two or more. In some embodiments, an inorganic basic compound such as potassium hydroxide can be preferably employed as the pH adjuster.
In the technique disclosed herein, the pH of the silica dispersion can be grasped by putting a glass electrode into a liquid to be measured and measuring it after calibration at three points using a pH meter. Standard buffers include, for example, phthalate pH buffer: pH 4.01 (25 ° C.), neutral phosphate pH buffer: pH 6.86 (25 ° C.), carbonate pH buffer: pH 1 0.01 (25) ° C).

  In addition, the silica dispersion disclosed herein prepares a polishing slurry (for example, a polishing slurry for a magnetic disk substrate such as a Ni-P substrate or a glass substrate) to the extent that the effects of the present invention are not significantly impaired. If necessary, known additives which can be used for the dispersion of silica for the purpose can be contained. Examples of such additives may include dispersants, surfactants, water soluble polymers, chelating agents, and the like.

<Abrasive slurry>
The silica dispersion disclosed herein can be preferably used for preparation of polishing slurry. The polishing slurry prepared using the above-mentioned silica dispersion can be grasped as a polishing slurry which contains this silica dispersion as a component. The polishing slurry contains, as necessary, one or more of the components exemplified below as a component derived from the silica dispersion or as a component newly mixed with the silica dispersion, for example. obtain.

(acid)
The polishing slurry can contain an acid as a polishing accelerator. As the acid, both inorganic acids and organic acids can be used. An acid can be used individually by 1 type or in combination of 2 or more types.

  Specific examples of inorganic acids include phosphoric acid (orthophosphoric acid), nitric acid, sulfuric acid, hydrochloric acid, boric acid, sulfamic acid, phosphinic acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, carbonic acid, fluorinated acid Hydrogen acid, sulfurous acid, thiosulfuric acid, chloric acid, perchloric acid, chlorous acid, hydroiodic acid, periodic acid, iodic acid, hydrobromic acid, perbromic acid, bromic acid, chromic acid, nitrous acid, etc. It can be mentioned.

  Examples of organic acids include organic carboxylic acids, organic phosphonic acids, organic sulfonic acids, amino acids 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, formic acid, acetic acid, propionic acid, Butyric acid, adipic acid, oxalic acid, valeric acid, enanthate, caproic acid, caprylic acid, pelargonic acid, capric acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid , Crotonic acid, oleic acid, linoleic acid, linolenic acid, licinolenic acid, methacrylic acid, glutaric acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, thalthronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, Salicylic acid, isocitric acid, methylene succinic acid, gallic acid, Organic carboxylic acids such as skorbic acid, nitroacetic acid, oxaloacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid; glycine, alanine, glutamic acid, aspartic acid, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, Amino acids such as tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine, etc .; nicotinic acid; picric 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 (methylene phosphonic acid), ethylene diamine tetra (methylene phosphonic acid), diethylene acid Amine penta (methylene phosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane hydroxy-1,1,2-triphosphonic acid Acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methyl Organic phosphonic acids such as phosphonosuccinic acid, aminopoly (methylene phosphonic acid); methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 2-naphthalenesulfonic acid, sulfosuccinic acid, 10 -Organic sulfonic acids such as camphor sulfonic acid, isethionic acid and taurine; It is. As the organic acid, one having about 1 to 18 carbon atoms, for example, about 1 to 10 carbon atoms can be preferably employed.

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

The acid may be used in the form of a salt of the acid. Examples of the salt include metal salts, ammonium salts and alkanolamine salts of the above-mentioned inorganic acids and organic acids. Examples of the metal salt include alkali metal salts such as lithium salt, sodium salt and potassium salt. Examples of the ammonium salt include quaternary ammonium salts such as tetramethyl ammonium salt and tetraethyl ammonium salt. As an alkanolamine salt, a monoethanolamine salt, a diethanolamine salt, a triethanolamine salt is mentioned, for example.
Specific examples of the salt include alkali metal phosphates and alkali metals such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate and the like Hydrogen phosphate; alkali metal salts of organic acids exemplified above; other, alkali metal salts of glutamic acid diacetic acid, alkali metal salts of diethylene triamine pentaacetic acid, alkali metal salts of hydroxyethyl ethylenediamine triacetic acid, triethylene tetramine 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 included in the polishing slurry disclosed herein, salts of inorganic acids such as alkali metal salts and ammonium salts can be preferably employed. 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 some embodiments, an acid and a salt of an acid different from the acid can be used in combination. The acid is preferably an inorganic acid. The salts of acids different from the above acids are preferably salts of inorganic acids.

  When the polishing slurry contains an acid, its content is not particularly limited. The content of the acid is usually 0.1% by weight or more, preferably 0.3% by weight or more, and more preferably 0.5% by weight or more, for example, 1.0% by weight or more. If the content of the acid is too small, the polishing rate tends to be insufficient, which may be undesirable in practice. The content of the acid is usually 20.0% by weight or less, preferably 10.0% by weight or less, and more preferably 5.0% by weight or less, for example 3.0% by weight or less. If the content of the acid is too large, the surface accuracy of the object to be polished tends to be reduced, which may be undesirable in practice.

(Oxidant)
The polishing slurry disclosed herein can contain an oxidizing agent as needed. Examples of oxidizing agents include peroxides, nitric acid or salts thereof, periodic acid or salts thereof, peroxy acids or salts thereof, permanganic acid or salts thereof, chromic acid or salts thereof, oxygen acid or salts thereof, metal salts And sulfuric acid, etc., but not limited thereto. 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, peroxymonosulfuric acid, ammonium peroxomonosulfate, metal salt of peroxomonosulfuric acid, peroxodisulfuric acid, peroxodisulfuric acid Ammonium sulfate, metal peroxodisulfate, peroxophosphoric acid, peroxosulfuric acid, sodium perborate, perforic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromous acid, hypoiodic acid, chloric acid, bromic acid, Iodic acid, periodic acid, perchloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal salts of chromate, metal salts of dichromate, iron chloride, iron sulfate, Examples include iron citrate and ammonium iron sulfate. Examples of preferable oxidizing agents include hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfuric acid, peroxodisulfuric acid and nitric acid. It is preferable to include at least hydrogen peroxide, and more preferable to be composed of hydrogen peroxide.

  When the polishing slurry contains an oxidizing agent, the content may be 0.01% by weight or more based on the amount of the active ingredient, usually 0.1% by weight or more, and preferably 0.3% by weight or more. And may be 0.4% by weight or more. If the content of the oxidizing agent is too small, the rate at which the object to be polished is oxidized becomes slow, and the polishing rate decreases, which may be undesirable in practice. In addition, when the content of the oxidizing agent is too large, the surface accuracy of the object to be polished is likely to be lowered, which may be undesirable in practice. From this point of view, the content of the oxidizing agent is usually 15% by weight or less based on the amount of the active ingredient, and may be 10% by weight or less, 5% by weight or less, or 3% by weight or less. In some embodiments, the content of the oxidizing agent in the polishing slurry may be, for example, 2 wt% or less, and may be 1.5 wt% or less.

(Basic compound)
The polishing slurry can contain a basic compound as required. Here, the basic compound refers to a compound having a function of increasing pH by addition. Examples of the basic compound include alkali metal hydroxides, carbonates and hydrogencarbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogenphosphates, organic acid salts and the like. The basic compounds can be used alone or in combination of two or more.

Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.
Specific examples of carbonates and hydrogencarbonates include ammonium hydrogencarbonate, ammonium carbonate, potassium hydrogencarbonate, potassium carbonate, sodium hydrogencarbonate, sodium carbonate and the like.
Specific examples of the quaternary ammonium or salts thereof include quaternary ammonium hydroxides such as tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide and tetrabutyl ammonium hydroxide; alkali metals of such quaternary ammonium hydroxides Salt; and the like. Examples of the alkali metal salt include sodium salt and potassium salt.
Specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine And piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methyl piperazine, guanidine, azoles such as imidazole and triazole, and the like.
Specific examples of phosphate and hydrogen phosphate 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 slurry disclosed herein can be any known additive that can be used in the polishing slurry, such as a surfactant, a water-soluble polymer, a dispersing agent, and a chelating agent, to the extent that the effects of the present invention are not significantly impaired. You may further contain as needed.

The surfactant is not particularly limited, and any of anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants can be used. The use of a surfactant can improve the dispersion stability of the polishing slurry. The surfactant may be used alone or in combination of two or more. The surfactant may typically be a water soluble organic compound having a molecular weight of less than 1 × 10 ⁴ .
Specific examples of the anionic surfactant include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate, alkyl sulfate, polyoxyethylene alkyl sulfate, alkyl sulfate, alkyl benzene sulfonic acid, alkyl phosphate, 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 dodecyl benzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, Polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl ether sulfur Sodium, and salts thereof.
Other specific examples of the anionic surfactant include polyalkyl aryl 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 and the like Melamine formalin resin sulfonic acid type compounds such as melamine sulfonic acid formaldehyde condensate; lignin sulfonic acid type compounds such as lignin sulfonic acid and denatured lignin sulfonic acid; aromatic amino sulfonic acid such as aminoaryl sulfonic acid-phenol-formaldehyde condensate Other compounds, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonic acid; Etc. The. As the salt, alkali metal salts such as sodium salt and potassium salt are preferable.
Specific examples of nonionic surfactants 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 alkyl trimethyl ammonium salts, alkyl dimethyl ammonium salts, alkyl benzyl dimethyl ammonium salts, alkyl amine salts and the like.
Specific examples of the amphoteric surfactant include alkyl betaine type, fatty acid amidopropyl betaine type, alkyl imidazole type, amino acid type, alkyl amine oxide type and the like.

  In the polishing slurry of the embodiment including the surfactant, the content of the surfactant is suitably, for example, 0.0005% by weight or more. The content is preferably 0.001% by weight or more, more preferably 0.002% by weight or more, from the viewpoint of surface smoothness and the like after polishing. Further, from the viewpoint of polishing rate and the like, the content is suitably 3.0% by weight or less, preferably 0.5% by weight or less, for example, 0.1% by weight or less.

  The polishing slurry disclosed herein may contain a water-soluble polymer. By including a water-soluble polymer, the surface accuracy after polishing can be improved. Examples of the water-soluble polymer include naphthalene sulfonic acid formaldehyde condensates, methyl naphthalene sulfonic acid formaldehyde condensates, polyalkyl aryl sulfonic acid compounds such as anthracene sulfonic acid formaldehyde; melamine formalin resin sulfones such as melamine sulfonic acid formaldehyde condensates Acid compounds; lignin sulfonic acid compounds such as lignin sulfonic acid and denatured lignin sulfonic acid; aromatic amino sulfonic acid compounds such as aminoaryl sulfonic acid-phenol-formaldehyde condensate; and others, polyisoprene sulfonic acid, polyvinyl sulfonic acid , Polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polymaleic acid, polyitaconic acid, polyvinyl Rubol, polyglycerin, polyvinyl pyrrolidone, copolymer of isoprene sulfonic acid and acrylic acid, polyvinyl pyrrolidone polyacrylic acid copolymer, polyvinyl pyrrolidone vinyl acetate copolymer, diallylamine hydrochloride sulfur dioxide copolymer, carboxymethyl cellulose, carboxymethyl cellulose Salts of hydroxyethyl cellulose, hydroxypropyl cellulose, pullulan, chitosan, chitosan salts and the like. The water-soluble polymers can be used alone or in combination of two or more.

  In the polishing slurry of the embodiment containing the water-soluble polymer, it is suitable that the content of the water-soluble polymer in the polishing slurry is, for example, 0.001% by weight or more. The said content is those total content in the aspect containing several water-soluble polymer. The content is preferably 0.003% by weight or more, more preferably 0.005% by weight or more, and still more preferably 0.007% by weight or more from the viewpoint of surface smoothness and the like of the object to be polished after polishing. . Further, from the viewpoint of polishing rate etc., the content is suitably 1.0 wt% or less, preferably 0.5 wt% or less, for example 0.1 wt% or less. In addition, the technique disclosed here can be preferably implemented also in the aspect which polishing slurry does not contain a water-soluble polymer substantially.

  Examples of the dispersant 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; alkylsulfonic acid Poly system based dispersing agent; poly phosphoric acid based dispersing agent; polyalkylene polyamine based dispersing agent; quaternary ammonium based dispersing agent; alkyl polyamine based dispersing agent; alkylene oxide based dispersing agent; polyhydric alcohol ester based dispersing agent;

  Examples of chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, ammonium hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid Sodium diethylene triamine pentaacetate, triethylene tetramine hexaacetic acid and sodium triethylene tetramine hexaacetate. Examples of organic phosphonic acid type chelating agents include 2-aminoethyl phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylene phosphonic acid), ethylene diamine tetrakis (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) 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-methylphosphorus Includes nosuccinic acid. Among these, organic phosphonic acid type chelating agents are more preferable, and ethylenediamine tetrakis (methylene phosphonic acid) and diethylene triamine penta (methylene phosphonic acid) are mentioned as preferable one among them. Particularly preferred chelating agents include ethylenediamine tetrakis (methylene phosphonic acid).

  The polishing slurry disclosed herein may contain particles other than silica particles, as long as the effects of the present invention are not significantly impaired. 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, oxide particles such as bengara particles; 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; and the like. Examples of the alumina particles include α-alumina, intermediate alumina other than α-alumina, and composites thereof. Intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and composites of these. Specific examples of the organic particles include poly (methyl methacrylate) (PMMA) particles, poly (meth) acrylic acid particles, and polyacrylonitrile particles. Here, (meth) acrylic acid is a meaning that generally refers to acrylic acid and methacrylic acid. Particles other than these silica particles can be used individually by 1 type or in combination of 2 or more types.

  The polishing slurry disclosed herein can be preferably practiced in a manner substantially free of alumina particles. As an alumina particle, an alpha alumina particle is mentioned, for example. Such polishing slurry prevents the deterioration of quality due to the use of alumina particles. As the quality deterioration mentioned here, for example, generation of scratches and depressions, residual of alumina, puncture defects of alumina particles and the like can be mentioned. In the present specification, “substantially free of alumina particles” means that the ratio of alumina particles is 1% by weight or less, more preferably 0.5% by weight or less, based on the total particles contained in the polishing slurry. It means that it is 0.1 weight% or less. Particular preference is given to polishing slurries in which the proportion of alumina particles is 0% by weight, ie polishing slurries which do not contain alumina particles. In addition, the polishing slurry disclosed herein can be preferably carried out in a manner substantially free of α-alumina particles.

  The polishing slurry disclosed herein can also be preferably carried out in an embodiment substantially free of particles other than silica particles, that is, non-silica particles. Here, “substantially free of non-silica particles” means that the proportion of non-silica particles is 1% by weight or less, more preferably 0.5% by weight or less, based on the total particles contained in the polishing slurry. .1 weight percent or less. In such an embodiment, the application effect of the technology disclosed herein can be suitably exhibited.

  The silica concentration in the polishing slurry is not particularly limited. The above silica concentration is typically 0.1% by weight or more, preferably 0.5% by weight or more, and more preferably 1% by weight or more. In some embodiments, the silica concentration may be, for example, 2 wt% or more, 3 wt% or more, or 4 wt% or more. Higher silica rates tend to achieve higher polishing rates. On the other hand, from the viewpoint of the stability of the polishing slurry and the stability of the polishing, the silica concentration is usually 30% by weight or less, preferably 25% by weight or less, more preferably 15% by weight or less, more preferably It is 10% by weight or less.

(PH of polishing slurry)
The pH of the polishing slurry is not particularly limited. The pH may be, for example, 12.0 or less, or 10.0 or less. The pH of the polishing slurry may be, for example, 7.0 or less, preferably 5.0 or less, more preferably 4.0 or less, and 3.0 or less from the viewpoint of polishing rate, surface accuracy, etc. It is also good. The pH of the polishing slurry may be, for example, 0.5 or more, or 1.0 or more from the viewpoint of, for example, suppressing damage to the polishing apparatus. In some embodiments, the pH of the polishing slurry may be, for example, in the range of 0.5 to 3.0, may be in the range of 1.0 to 2.0, and may be in the range of 1.0 to 1.8. . A pH adjuster such as an organic acid, an inorganic acid, a basic compound and the like can be contained as necessary so that the above pH is realized in the polishing slurry (working slurry) supplied to the object to be polished. The above pH can be preferably applied to, for example, a polishing slurry used for polishing a nickel phosphorus substrate. In particular, it can be preferably applied to a polishing slurry for primary polishing of a nickel phosphorus substrate.
The pH of the polishing slurry used for polishing the glass magnetic disk substrate may be, for example, 1.5 or more, 2.0 or more, or 2.5 or more. The pH of the polishing slurry may be, for example, about 1.5 to 5.5, about 2.5 to 4.3, or about 2.5 to 4.0. In particular, it can be preferably applied to a polishing slurry for primary polishing of a glass magnetic disk substrate.
In the technique disclosed herein, the pH of the polishing slurry can be grasped by putting a glass electrode into a liquid to be measured and measuring it after calibration at three points using a pH meter. Standard buffers include, for example, borate pH buffer: pH 1.68 (25 ° C.), phthalate pH buffer: pH 4.01 (25 ° C.), neutral phosphate pH buffer: pH 6.86 (25) ° C).

The silica dispersion disclosed herein can be used to prepare a polishing slurry having a lower pH than the silica dispersion. That is, when the pH of the above-mentioned silica dispersion is pH _D and the pH of the polishing slurry prepared using this silica dispersion is pH _S , it is used to prepare a polishing slurry satisfying pH _S <pH _D. obtain. Such polishing slurry can usually be prepared by mixing the above-mentioned silica dispersion with at least an acid. The silica dispersion disclosed herein has a composition containing an effective amount of an organic preservative, and since the adsorption index α is 5 or less, aggregation of silica particles is caused even if the pH is lowered by mixing with an acid. It is hard to occur. The silica dispersion disclosed herein can be preferably used in an embodiment in which the difference between pH _D and pH _S (pH _D- pH _S ) is 1.0 or more, more preferably 2.0 or more. In some embodiments, pH _D- pH _S may be, for example, 3.0 or more, 4.0 or more, or 5.0 or more. The pH upper limit of the _{D-pH S} is not particularly limited, usually is suitably 11 or less, preferably 10 or less.

  The polishing slurry disclosed herein may be of one-part type or multi-part type including two-part type. For example, a polishing slurry may be prepared by mixing part A containing the silica dispersion, part B containing water and components other than silica particles among the components contained in the polishing slurry, and water. It can be configured.

  The silica dispersion disclosed herein can be preferably used as a component of a polishing slurry preparation kit. Especially, it is suitable as a component of the kit for mixing the said silica dispersion liquid and an acid, and preparing polishing slurry. Such a kit can comprise at least a first composition comprising any of the silica dispersions disclosed herein and a second composition comprising at least an acid. Here, the first composition and the second composition are preferably stored separately from each other.

  The polishing slurry containing the silica dispersion disclosed herein can be preferably applied, for example, to polishing a nickel phosphorus substrate, a glass substrate, a carbon substrate, and the like. In addition, as a plating material, a disk substrate provided with a metal layer or a metal compound layer other than the nickel phosphorus plating layer on the surface of the base disk may be used. Among them, it is suitable as a polishing slurry for a nickel phosphorous plated 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 techniques disclosed herein.

  The polishing slurry disclosed herein can be used particularly effectively in applications where high polishing efficiency is required. One preferred example of such an application is a preliminary polishing step which is carried out as a step prior to the above-mentioned finish polishing step in the process of manufacturing a magnetic disk substrate which requires a highly accurate surface after the finish polishing step. If there are multiple pre-polishing steps prior to the final polishing step, they can be used in any of the pre-polishing steps, and the same or different polishing slurries can be used in these pre-polishing steps. The polishing slurry disclosed herein is suitable, for example, as a polishing slurry used in the primary polishing step of the magnetic disk substrate, ie, the first polishing step. In particular, in the process of manufacturing a nickel phosphorus substrate, it can be preferably used in the first polishing step after the nickel phosphorus plating, ie, the primary polishing step.

  The polishing slurry disclosed herein is, for example, a magnetic disk substrate having a surface roughness of about 20 Å to 300 Å as measured by a laser scanning type surface roughness meter “TMS-3000 WRC” manufactured by Schmitt Measurement System Inc. The present invention is suitable for use in adjusting the surface roughness of the magnetic disk substrate to 10 Å or less. In such applications, it is particularly meaningful to apply the techniques disclosed herein. The surface roughness as used herein refers to arithmetic mean roughness (Ra).

  The polishing slurry disclosed herein can be suitably used for polishing an object to be polished, for example, in a mode including the following operations. That is, a polishing slurry (working slurry) having a composition containing any of the silica dispersions disclosed herein is prepared. Then, the polishing slurry is supplied to the object to be polished and polished by a conventional method. For example, the object to be polished is set in a general polishing apparatus, and the polishing slurry is supplied to the surface of the object to be polished, ie, the surface to be polished, through the polishing pad of the polishing apparatus. Typically, while the polishing slurry is continuously supplied, the polishing pad is pressed against the surface of the object to be moved relative to each other. The movement may be, for example, rotational movement. Polishing of the object to be polished is completed through this polishing process.

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

  The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown.

Experimental Example 1
<Preparation of Silica Dispersion>
Example 1
A silica dispersion liquid was prepared, containing silica particles (colloidal silica) with a BET diameter of 50 nm in water at a concentration of 25% by weight, and further containing thiabendazole as an organic preservative at a concentration of 0.0035% by weight.
(Examples 2 to 4 and Comparative Examples 1 to 7)
The silica dispersions according to Examples 2 to 4 and Comparative Examples 1 to 7 are prepared in the same manner as in Example 1 except that the type and concentration of the organic preservative to be contained in the silica dispersion are changed as shown in Table 1. did.
In addition, as for pH of the silica dispersion liquid which concerns on Examples 1-4 and Comparative Examples 1-7, all were adjusted to about 9.0 using potassium hydroxide (KOH).
In addition, the organic preservative concentration of the silica dispersion according to each example was set by the following method. Specifically, a fungus liquid of Fusarium spp. Is inoculated so as to be 1 × 10 ⁴ CFU / mL in 10 mL of pure water to which an organic preservative is added at an arbitrary concentration, and left at room temperature for 15 hours, 0.1 mL of the solution was collected, applied to Komada medium, and cultured at 30 ° C. for 3 days to give a concentration at which no colony was observed.

<Evaluation>
(Measurement of adsorption index α)
The adsorption index α of the silica dispersion according to each example was measured by the following procedure, and the results are shown in Table 1.
That is, a predetermined volume of 100 mL or more (here, about 30 mL) was fractionated from the silica dispersion according to each example, and the volume and weight at 25 ° C. were recorded. This silica dispersion was subjected to a centrifuge manufactured by Beckman Coulter, type "Avanti HP-30I", using a rotor "JA-30.50", at a temperature of 25.degree. C. for 60 minutes at 26,000 rpm. The silica particles were sedimented by centrifugation under the conditions. The supernatant was collected, and the total organic carbon content (TOC) of the supernatant was measured using a total organic carbon meter manufactured by Shimadzu Corporation (a combustion catalyst oxidation system, type “TOC-5000A”). From the results, the carbon weight W1 of the organic preservative contained in the above supernatant was determined. In addition, an organic preservative of the same type as the organic preservative contained in the silica dispersion is mixed with pure water at an equal concentration to prepare a preservative-diluted aqueous solution, TOC is similarly measured, and carbon weight based on the measured value I asked for W0. Specifically, the carbon weight W0 and the carbon weight W1 were determined based on the following formula.

W1 = [TOC1 × Vu]
W0 = [TOC0 × Vs]
Vs = Ws / ρs
Vu = Vs− (W _silica / ρ _silica )
TOC 1: TOC measured on the supernatant of the silica dispersion (mg / l)
TOC 0: TOC (mg / l) of preservative diluted aqueous solution diluted to the same concentration as preservative of silica dispersion
Vu: volume of supernatant of silica dispersion (ml)
Vs: Volume of silica dispersion (ml)
Ws: mass of silica dispersion (g)
ss: density of silica dispersion (g / ml)
W _silica : mass of silica (g)
sil _silica : density of silica (here, 2.2 g / ml was used)

From the carbon weight W0 of the organic preservative contained in the silica dispersion and the carbon weight W1 of the organic preservative contained in the supernatant, the adsorption index α was calculated by the following equation.
Adsorption index α = [(W0−W1) / W0] × 100;

In addition, the adsorption index α of the organic preservative contained in the above silica dispersion, the concentration Ca (mass%) of the organic preservative, BET value Sa (m ² / g) of silica particles contained in the silica dispersion, and silica The organic preservative adsorption amount [μg / m ² ] per surface area of the silica particles was calculated from the concentration Cs (mass%) of the particles according to the following equation.
Organic preservative adsorption amount [μg / m ² ] = [(α / 100) * (Ca / 100) * 10 ⁶ ] / [Sa * (Cs / 100)]

(Antiseptic evaluation of silica dispersion)
The silica dispersion according to each example was subjected to a centrifugation treatment under the same conditions as the measurement of the adsorption index α, and a supernatant was collected. Inoculate 10 mL of this supernatant with a fungus liquid of Fusarium to 1 × 10 ⁴ CFU / mL and allow to stand at room temperature for 15 hours, then collect 0.1 mL and apply to Komada medium, 30 Culturing was carried out for 3 days. As a result, when no colony was observed, it was evaluated as "preservative good" and indicated as "G" (Good) in Table 1. When a colony was observed, it evaluated as "poor antiseptic | preservative property", and displayed it as "P" (Poor) in Table 1.

(Preparation of polishing slurry)
The silica dispersion according to each example is mixed with phosphoric acid, hydrogen peroxide, and water for dilution to obtain a silica having a concentration of 0.176 times (ie, 4.4% by weight) the concentration in the silica dispersion. Particles, an organic preservative having a concentration of 0.176 times the concentration in the silica dispersion (for example, 0.000616% by weight in Example 1), 1% by weight of phosphoric acid, and 1% by weight of peroxide A polishing slurry containing hydrogen and was prepared. The pH of the polishing slurry according to each example was in the range of 1.3 to 1.8.

(Abrasion test)
An object to be polished was polished using the above-mentioned polishing slurry under the following conditions. As an object to be polished, an aluminum substrate for a hard disk provided with an electroless nickel phosphorus plating layer on the surface was used. The substrate has a diameter of 3.5 inches, an outer diameter of about 95 mm, an inner diameter of about 25 mm, a donut shape, a thickness of 1.75 mm, and the specific gravity of the nickel phosphorus plating layer is about 7.9. The surface roughness Ra before polishing of the layer was 130 Å. The surface roughness Ra is an arithmetic mean roughness of the nickel phosphorus plating layer measured by a laser scan type surface roughness meter “TMS-3000 WRC” manufactured by Schmitt Measurement System Inc.

[Polishing conditions]
Polishing system: Double side polishing machine manufactured by System Seiko Co., Ltd., model "9.5 B-5 P"
Polishing pad: Polyurethane pad manufactured by FILWEL, trade name "CR200", grooved Number of polishing objects inserted: 15 sheets (3 sheets / carrier x 5 carriers)
Polishing slurry supply rate: 135 mL / min Polishing load: 120 g / cm ²
Upper surface plate rotation speed: 27 rpm
Lower surface plate rotation speed: 36 rpm
Sun gear (sun gear) speed: 8 rpm
Polishing time: 5 minutes

The polishing rate in the above-mentioned polishing test was calculated based on the following formula.
Polishing rate [μm / min] = weight loss of substrate due to polishing [g] / (area of substrate [cm ² ] × density of nickel phosphorus plating layer [g / cm ³ ] × polishing time [min]) × 10 ⁴
The obtained value is converted to a relative value (relative polishing rate) where the polishing rate in Example 1 is 100, and when the relative polishing rate is 90 or more and 110 or less, “A”, and the relative polishing rate is 80 When the relative polishing rate was less than 80, it was evaluated as "C". The results are shown in Table 1.

  As shown in Table 1, the silica dispersions of Examples 1 to 4 in which the adsorption index α is 5 or less are lower than the silica dispersions of Comparative Examples 1, 2, 4 to 7 in which the adsorption index α is larger. It was confirmed that the polishing rate of the polishing slurry prepared using each of the silica dispersions was substantially equal, but clearly superior in terms of the preservative property of the silica dispersion.

Experimental Example 2
<Preparation of Silica Dispersion>
(Example 5)
A silica dispersion liquid according to Example 5 was prepared in the same manner as Example 1 except that silica particles (colloidal silica) having a BET diameter of 91 nm were used.
(Example 6)
A silica dispersion liquid according to Example 6 was prepared in the same manner as in Example 1 except that the concentration of the silica particles was changed to 15% by weight.
In addition, as for pH of the silica dispersion liquid which concerns on Example 5, 6, all were adjusted to about 9.0 using potassium hydroxide (KOH).

<Evaluation>
In the same manner as in Experimental Example 1, the adsorption index α of the silica dispersion according to Examples 5 and 6 was measured, and the preservative property of the supernatant was evaluated.

  The silica dispersion according to Example 5 is mixed with phosphoric acid, hydrogen peroxide, and water for dilution to a concentration of 0.176 times (ie, 4.4% by weight) the concentration in the above silica dispersion. A polishing slurry was prepared comprising silica particles, an organic preservative having a concentration of 0.176 times the concentration in the silica dispersion, 1% by weight of phosphoric acid, and 1% by weight of hydrogen peroxide. In addition, the silica dispersion according to Example 6 is mixed with phosphoric acid, hydrogen peroxide, and water for dilution to give a concentration of 0.176 times the concentration in the above silica dispersion (that is, 2.6% by weight). ), And an organic preservative having a concentration of 0.176 times the concentration in the above silica dispersion, 1 wt% of phosphoric acid, and 1 wt% of hydrogen peroxide were prepared. . The pH of the polishing slurry according to each example was in the range of 1.3 to 1.8.

  Using these polishing slurries, a polishing test was conducted in the same manner as in Experimental Example 1 to determine the polishing rate. The obtained results were converted into relative polishing rates in the same manner as in Experimental Example 1, and the results are shown in Table 2 according to the same evaluation criteria. In Table 2, the results of Experimental Example 1 are shown again for the convenience of comparison.

  As shown in Table 2, even in Examples 5 and 6 in which the BET diameter and concentration of the silica particles are different from those in Example 1, by setting the adsorption index α to 5 or less, it is possible to suppress the decrease in the polishing rate and to be good. It was confirmed that a silica dispersion having antiseptic properties was obtained.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

Claims (10)

A silica dispersion comprising silica particles, an organic preservative, and water,
From the carbon weight W0 of the organic preservative contained in the silica dispersion and the carbon weight W1 of the organic preservative contained in the supernatant obtained by subjecting the silica dispersion to a centrifugal separation treatment, The following equation:
Adsorption index α = [(W0−W1) / W0] × 100;
The silica dispersion liquid whose adsorption index alpha calculated by is 5 or less.   The silica dispersion according to claim 1, wherein the concentration of the silica particles is 20% by weight or more, and the pH of the silica dispersion is 2.0 to 12.0. The adsorption amount to the silica particles of the organic preservative is less surface area 1 m ² per 5μg of the silica particles, the silica dispersion according to claim 1 or 2.   The silica dispersion according to any one of claims 1 to 3, wherein the concentration of the organic preservative is 0.1 wt% or less.   The silica dispersion liquid as described in any one of Claims 1-4 whose BET diameter of the said silica particle is 10 nm or more. As said organic preservative, the following conditions:
Comprising a nitrogen atom having a non-covalent electron pair; and having a π bond between the nitrogen atom and its alpha atom or between the alpha and beta atoms;
The silica dispersion liquid as described in any one of Claim 1 to 5 containing the compound which has a structural part which satisfy | fills.   The silica dispersion according to any one of claims 1 to 6, which is used to prepare a polishing slurry by mixing with an acid.   A polishing slurry comprising the silica dispersion according to any one of claims 1 to 7 and an acid.   The polishing slurry according to claim 8, used for polishing a nickel phosphorus plated hard disk substrate. A first composition comprising the silica dispersion according to any one of claims 1 to 7;
A second composition comprising at least an acid,
Including
A polishing slurry preparation kit, wherein the first composition and the second composition are stored separately from each other.