JP7619796B2 - Polishing composition for fluorophosphate glass, and polishing method using the polishing composition for fluorophosphate glass - Google Patents

Description

The present invention relates to an abrasive composition for fluorophosphate glass, and a polishing method using the abrasive composition for fluorophosphate glass. More specifically, the present invention relates to an abrasive composition for fluorophosphate glass for polishing fluorophosphate glass that is suitable for use in the lenses of digital cameras and the lenses of cameras built into smartphones, and a polishing method using the abrasive composition for fluorophosphate glass.

Conventionally, solid-state imaging devices used in digital cameras and cameras built into smartphones have spectral sensitivity that ranges from the visible region to the near-infrared region around 1200 nm. Therefore, it is difficult to obtain good color reproduction when used as is, so the visibility is corrected by using near-infrared cut filter glass formed by adding a specific substance with infrared absorbing properties.

Optical glass made by adding copper oxide to fluorophosphate glass has been developed and used as a near-infrared cut filter glass, because it has the property of selectively absorbing infrared rays with wavelengths in the near-infrared region and has high weather resistance. Ordinary glass mainly contains silica components or silica and alumina components, but fluorophosphate glass contains virtually no silica components and is composed of components optimized to absorb infrared rays with wavelengths in the near-infrared region.

More specifically, fluorophosphate glass generally contains, as cationic percentages, 15-50% phosphorus ions (P ⁵⁺ ), 5-30% aluminum ions (Al ³⁺ ), 10-40% total of one or more ions selected from calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ), strontium ions (Sr ²⁺ ), barium ions (Ba ²⁺ ), and zinc ions (Zn ²⁺ ), 5-30% total of one or more ions selected from lithium ions (Li ⁺ ), sodium ions (Na ⁺ ), and potassium ions (K ⁺ ), and 0-20% copper ions (Cu ²⁺ ). As anionic percentages, 10-50% fluorine ions (F ⁻ ), and 50-90% oxygen ions (O ²⁻ ) are contained.

Here, "cation %" and "anion %" are defined as the units shown below. That is, when the constituent components of fluorophosphate glass are divided into cationic components and anionic components, and the total content of all cationic components contained in the fluorophosphate glass is taken as 100 mol%, the unit expressing the content of each cationic component as a molar percentage corresponds to "cation %". On the other hand, when the total content of all anionic components contained in the fluorophosphate glass is taken as 100 mol%, the unit expressing the content of each anionic component as a molar percentage corresponds to "anionic %".

The production of near-infrared cut filter glass is mainly composed of a melting step in which glass raw materials such as a phosphoric acid raw material such as tripolyphosphate powder or orthophosphoric acid, a fluoride raw material, and a copper oxide raw material are melted at a temperature of 600° C. to 1000° C. for 2 to 80 hours, a fining step in which bubbles in the glass are removed, a stirring step in which the glass is homogenized, and a forming step in which the molten glass is poured out and shaped. Methods in which each of the above steps is performed using one crucible furnace, or a method in which each step is performed using a continuous furnace having different tanks for carrying out each step and the tanks are connected to each other by transport pipes, etc., are known.

The fluorophosphate glass produced in this way exhibits properties that are more susceptible to wear and have a higher coefficient of thermal expansion than other common optical glasses. This makes polishing such fluorophosphate glass difficult.

Glass materials that are difficult to polish are called resistant glass materials, and require careful handling during the processing steps in the glass manufacturing process. In other words, the glass material is soft and the surface is easily scratched, or too hard and difficult to process. In addition to the above-mentioned fluorophosphate glass, other known examples include niobium phosphate-containing high refractive index, high dispersion glass and lanthanum borate-containing high refractive index, low dispersion glass.

In particular, when the glass material being polished is highly abrasive, the processing precision decreases and scratches caused during polishing tend to remain on the glass surface. Therefore, when polishing fluorophosphate glass, special care must be taken in selecting the abrasive and setting the polishing conditions compared to general optical glass.

For this reason, a method of using a cerium oxide-based abrasive containing cerium oxide as the main component has been used to polish fluorophosphate glass (see Patent Documents 1 and 2). However, cerium is a rare metal, and there have been concerns about its supply due to resource depletion and rising cerium prices. For this reason, there has been a demand for an alternative to silica-based abrasives containing silica as the main component, which is inexpensive and can be supplied stably.

JP 2013-141737 A International Publication No. 2017/102826

However, silica-based abrasives have the problem of having a slower polishing rate than the cerium oxide-based abrasives mentioned above, and there was hope for an improvement in this polishing rate.

In view of the above, the present invention aims to provide an abrasive composition for fluorophosphate glass that has a high polishing rate and can be used to polish fluorophosphate glass as an alternative to cerium oxide-based abrasives, and a polishing method that uses the abrasive composition for fluorophosphate glass.

In order to solve the above problems, the inventors of the present application have conducted extensive research into the issue of silica-based abrasives, which has a low polishing rate. As a result, they have discovered an abrasive composition for fluorophosphate glass that improves the polishing rate of silica-based abrasives and can produce a glass surface with excellent smoothness without causing any cloudiness or scratches on the glass surface of the fluorophosphate glass after polishing, as well as a polishing method using the abrasive composition for fluorophosphate glass, and have completed the present invention described below.

[1] An abrasive composition for fluorophosphate glass, comprising silica, a water-soluble polymeric compound, an acid and/or a salt thereof, and water, wherein the water-soluble polymeric compound is a polymer having structural units derived from a polysaccharide and/or an unsaturated amide, and having a pH (25°C) value in the range of 1.0 to 9.0.

[2] The abrasive composition for fluorophosphate glass described in [1], in which the silica is colloidal silica and has an average particle size (D50) in the range of 10 nm to 200 nm.

[ 3 ] The abrasive composition for fluorophosphates glass according to the above [1] or [ 2 ], wherein the acid and/or its salt is an inorganic acid and/or its salt.

[ 4 ] The abrasive composition for fluorophosphates glass according to the above [1] or [ 2] , wherein the acid and/or its salt is an organic acid and/or its salt.

[ 5 ] The abrasive composition for fluorophosphate glass according to [1], wherein the polymer having a constitutional unit derived from an unsaturated amide is a copolymer containing a constitutional unit derived from (meth)acrylamide and/or an N -substituted (meth)acrylamide and a constitutional unit derived from (meth)acrylic acid and/or a salt thereof.

[ 6 ] The abrasive composition for fluorophosphates glass according to [ 3 ], wherein the inorganic acid and/or its salt is a phosphorus-containing inorganic acid and/or its salt.

[ 7 ] The abrasive composition for fluorophosphates glass according to [ 4 ], wherein the organic acid and/or its salt is a chelating compound.

[8] The abrasive composition for fluorophosphate glass according to [ 7 ], wherein the chelating compound is at least one selected from the group consisting of dicarboxylic acids and/or their salts, tricarboxylic acids and / or their salts, polyaminocarboxylic acid compounds, and phosphonic acid compounds.

[ 9 ] A polishing method using an abrasive composition for fluorophosphates glass according to any one of [1] to [ 8 ] above, for polishing fluorophosphates glass.

The polishing composition for fluorophosphate glass of the present invention contains silica, a water-soluble polymeric compound, an acid and/or its salt, and water. By polishing fluorophosphate glass, the polishing speed can be improved, and a smooth glass surface without cloudiness or scratches can be obtained after polishing.

The following describes the embodiments of the present invention. The present invention is not limited to the following embodiments, and changes, modifications, and improvements may be made without departing from the scope of the invention.

1. Abrasive Composition for Fluorophosphates Glass The abrasive composition for fluorophosphates glass of the present embodiment (hereinafter simply referred to as the "abrasive composition") contains silica, a water-soluble polymer compound, an acid and/or a salt thereof, and water.

1.1 Silica The silica contained as one component of the polishing compound composition of this embodiment may be fumed silica, wet-process silica, colloidal silica, etc., and colloidal silica is particularly preferred. Furthermore, the colloidal silica preferably has an average particle size (D50) in the range of 10 nm to 200 nm, and more preferably has an average particle size (D50) in the range of 20 nm to 150 nm.

By making the average particle size (D50) of colloidal silica 10 nm or more, the aggregation of colloidal silica is less likely to occur, and storage stability can be improved. On the other hand, by making the average particle size (D50) of colloidal silica 200 nm or less, the smoothness of the glass surface after polishing can be improved, and the occurrence of cloudiness and scratches can be suppressed. Here, the average particle size (D50) of colloidal silica is calculated by analysis based on the results of observation using a transmission electron microscope (TEM) (details will be described later).

Colloidal silica can be of any known shape, such as spherical or confetti-shaped (particulate with protrusions on the surface), and the primary particles are monodispersed in water to form a colloid.

The colloidal silica used can be manufactured by a conventionally known manufacturing method, for example, the water glass method, in which an alkali metal silicate such as sodium silicate or potassium silicate is used as a raw material and the raw material is subjected to a condensation reaction in an aqueous solution to grow colloidal silica particles, the alkoxysilane method, in which a tetraalkoxysilane such as tetraethoxysilane is used as a raw material and the raw material is subjected to a condensation reaction by hydrolysis with an acid or alkali in a solvent containing a water-soluble organic solvent such as alcohol to grow colloidal silica particles, or a method of synthesizing colloidal silica by reacting metal silicon with water in the presence of an alkali catalyst. The water glass method can be preferably used in terms of manufacturing costs. The colloidal silica used in the abrasive composition for fluorophosphate glass of this embodiment can be manufactured by appropriately using these synthesis methods, etc.

In the polishing composition of this embodiment, the concentration (content) of colloidal silica contained in the polishing composition is preferably in the range of 1% by mass to 50% by mass, and more preferably in the range of 2% by mass to 45% by mass, from the viewpoints of ensuring a stable dispersion state of the polishing particles and of economic efficiency.

By setting the colloidal silica concentration to 1% by mass or more, the polishing speed can be improved. On the other hand, by setting the colloidal silica concentration to 50% by mass or less, it is advantageous in terms of economy, and has the advantage that aggregation and gelation are less likely to occur when further adding and blending abrasives other than colloidal silica and other compounding agents.

1.2 Water-soluble polymer compound The water-soluble polymer compound contained as one component of the polishing compound composition of this embodiment may be a polysaccharide, an acrylic acid polymer, a methacrylic acid polymer, a polymer having a structural unit derived from an unsaturated amide, or the like. It is preferable to use a polymer having a structural unit derived from a polysaccharide or an unsaturated amide.

Furthermore, in the polishing composition of this embodiment, the concentration of the water-soluble polymer compound contained in the polishing composition is preferably in the range of 0.0001% by mass to 10.0% by mass, and more preferably in the range of 0.001% by mass to 5.0% by mass.

By setting the concentration of the water-soluble polymer compound to 0.0001% by mass or more, clouding and scratches on the substrate surface after polishing are suppressed. By setting the concentration of the water-soluble polymer compound to 10.0% by mass or less, not only is it advantageous in terms of economy, but it also makes it possible to prevent the fluorophosphate glass polishing compound composition from becoming too viscous.

Furthermore, examples of polysaccharides used as water-soluble polymer compounds include alginic acid, alginic acid esters, pectic acid, carboxymethylcellulose, agar, xanthan gum, chitosan, methylcellulose, ethylcellulose, hydroxypropylcellulose, and hydroxyethylcellulose.

On the other hand, as a polymer having a structural unit derived from an unsaturated amide used as a water-soluble polymer compound, a copolymer containing a structural unit derived from an unsaturated amide and a structural unit derived from a carboxyl group-containing vinyl monomer is preferable, and more preferably, a copolymer containing a structural unit derived from (meth)acrylamide and/or an N-substituted (meth)acrylamide and a structural unit derived from (meth)acrylic acid and/or a salt thereof can be mentioned.

Here, (meth)acrylamide refers to acrylamide and/or methacrylamide, and (meth)acrylic acid refers to acrylic acid and/or methacrylic acid. Hereinafter, in this specification, (meth) will have the same meaning as above.

Furthermore, the N-substituted (meth)acrylamide is represented by the following formula (1):

CH ₂ =C(R ¹ )-CONR ² (R ³ )...(1)

It is a compound that can be generally represented as:
Here, ^R1 represents a hydrogen atom or a methyl group, ^R2 represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and ^R3 represents a linear or branched alkyl group having 1 to 4 carbon atoms.

Examples of the linear or branched alkyl group having 1 to 4 carbon atoms in R ² or R ³ shown in the above formula (1) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, and a t-butyl group, while specific examples of the N-substituted (meth)acrylamide include N,N-dimethyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-n-propyl(meth)acrylamide, N-i-propyl(meth)acrylamide, N-n-butyl(meth)acrylamide, N-i-butyl(meth)acrylamide, N-s-butyl(meth)acrylamide, and N-t-butyl(meth)acrylamide.

Examples of carboxyl group-containing vinyl monomers include monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and (meth)acrylic carboxylic acid, dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid, and alkali metal salts such as sodium salts and potassium salts of these various organic acids, and ammonium salts. In particular, those using (meth)acrylic acid or itaconic acid are preferred.

Furthermore, the ratio of the constituent units derived from the unsaturated amide and the constituent units derived from the carboxyl group-containing vinyl monomer in the copolymer is preferably in the range of 99:1 to 10:90 in molar ratio, more preferably in the range of 98:2 to 10:90.

Furthermore, vinyl monomers other than those mentioned above can also be suitably used. For example, anionic vinyl monomers include organic sulfonic acids such as vinyl sulfonic acid, styrene sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid, or alkali metal salts such as sodium salts and potassium salts of these various organic acids, or ammonium salts.

Further examples of nonionic vinyl monomers include carboxyl group-containing vinyl monomers or alkyl esters of the above-mentioned anionic vinyl monomers, acrylonitrile, styrene, divinylbenzene, vinyl acetate, methyl vinyl ether, and N-vinylpyrrolidone.

In addition, known methods can be used to produce carboxyl group-containing poly(meth)acrylamide obtained by copolymerizing (meth)acrylamide and/or N-substituted (meth)acrylamide, a carboxyl group-containing vinyl monomer, and, if necessary, a vinyl monomer other than those mentioned above.

To give an example of this, the desired carboxyl group-containing poly(meth)acrylamide can be obtained by charging the various monomers and water mentioned above into a specified reaction vessel, adding a radical polymerization initiator, and heating with stirring.

In this case, as the radical polymerization initiator, a typical radical polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate, or a redox-based polymerization initiator in the form of a combination of these with a reducing agent such as sodium hydrogen sulfite, can be used. Furthermore, an azo-based initiator may be used as the radical polymerization initiator. The amount of such a radical polymerization initiator used can be in the range of 0.05% to 2% by mass of the sum of the total amount of vinyl monomers used.

The weight average molecular weight of a polymer having structural units derived from an unsaturated amide is usually about 1,000 to 10,000,000, preferably 10,000 to 5,000,000, and more preferably 100,000 to 3,000,000. The weight average molecular weight is the value measured using GPC (gel permeation chromatography) in terms of standard polystyrene.

1.3 Acid and/or Salt Thereof The acid and/or salt thereof contained as one component of the polishing compound composition of the present embodiment is an inorganic acid and/or salt thereof, or an organic acid and/or salt thereof. As the acid and/or salt thereof, an inorganic acid and/or salt thereof and an organic acid and/or salt thereof may be used in combination.

Examples of inorganic acids and/or salts thereof include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, phosphonic acid, phosphinic acid, tripolyphosphoric acid, pyrophosphoric acid, and/or salts thereof. More preferably, phosphorus-containing inorganic acids and/or salts thereof can be used, and particularly preferably, phosphoric acid, phosphonic acid, phosphinic acid, tripolyphosphoric acid, pyrophosphoric acid, and/or salts thereof can be used.

On the other hand, as the organic acid and/or its salt, at least one selected from the group consisting of monocarboxylic acid and/or its salt, dicarboxylic acid and/or its salt, tricarboxylic acid and/or its salt, polyaminocarboxylic acid compounds, and phosphonic acid compounds can be used. More preferably, a chelating compound can be used.

As the chelating compound, dicarboxylic acid and/or its salt, tricarboxylic acid and/or its salt, polyaminocarboxylic acid compound, phosphonic acid compound, etc. can be used. As the dicarboxylic acid and/or its salt, malic acid, malonic acid, maleic acid, tartaric acid and/or its salt, etc. can be used, and as the tricarboxylic acid and/or its salt, citric acid and/or its salt, etc. can be used.

On the other hand, as polyaminocarboxylic acid compounds, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, and their ammonium salts, amine salts, sodium salts, potassium salts, etc. can be used. As phosphonic acid compounds, diethylenetriaminepentamethylenephosphonic acid, phosphonohydroxyacetic acid, hydroxyethyldimethylenephosphonic acid, aminotrismethylenephosphonic acid, hydroxyethanephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, and their ammonium salts, amine salts, sodium salts, potassium salts, etc. can be used. Among the above chelating compounds, tricarboxylic acids and/or their salts, and polyaminocarboxylic acid compounds, etc. can be used more preferably.

The content of acid and/or its salt in the polishing composition for fluorophosphate glass is determined from the viewpoint of adjusting the pH value (25°C) of the polishing composition for fluorophosphate glass to a set value, and is preferably 0.01% to 10% by mass, and more preferably 0.05% to 8% by mass. By making it 0.01% by mass or more, the polishing speed can be improved. By making it 10% by mass or less, clouding of the substrate surface after polishing can be suppressed.

1.4 Water The water contained as one component of the polishing compound composition of the present embodiment is used as a medium for dispersing other components of the polishing compound composition, and preferably used is pure water, ultrapure water, distilled water, etc. In order to smoothly disperse other components of the polishing compound composition, the polishing compound composition may contain an appropriate amount of an organic medium such as alcohol.

1.5 Physical Properties of Polishing Compound The pH value (25°C) of the polishing compound composition of this embodiment is in the range of 1.0 to 9.0, and preferably in the range of 2.0 to 8.0. If the pH value (25°C) is less than 1.0, there is a concern that the cloudiness of the substrate surface after the polishing step may worsen, and if the pH value (25°C) is more than 9.0, there is a concern that the polishing rate may decrease. Here, the pH value (25°C) refers to the pH value at 25°C.

2. Method for polishing fluorophosphate glass When polishing fluorophosphate glass using the polishing agent composition of this embodiment, various polishing methods well known in the art can be appropriately selected. For example, a predetermined amount of the polishing agent composition is put into a supply container installed in a polishing machine. The polishing agent composition is dripped and supplied from the supply container through a nozzle or tube to a polishing pad attached on a platen of the polishing machine, and the platen is rotated at a predetermined rotation speed while pressing the polishing surface of the object to be polished against the polishing pad, thereby polishing the polishing surface of the object to be polished.

The polishing pad may be made of nonwoven fabric, polyurethane foam, porous resin, nonporous resin, or the like that are commonly used in polishing. Furthermore, in order to facilitate the supply of the polishing agent composition to the polishing pad or to ensure that a certain amount of the polishing agent composition remains on the polishing pad, the pad surface of the polishing pad may be provided with various grooves, such as a lattice, concentric circle, or spiral groove.

The present invention will be further explained below based on examples, but the present invention is not limited to these examples. In addition to the following examples, various modifications and improvements can be made to the present invention based on the knowledge of those skilled in the art, as long as they do not deviate from the spirit of the present invention.

The experimental examples of Examples 1 , 2 , 4 to 10 , Reference Example 1 , and Comparative Examples 1 to 4 shown below are the results of predetermined polishing tests carried out using a polishing agent composition for polishing fluorophosphate glass (composition for polishing fluorophosphate glass) containing the materials and additive amounts shown in Table 1. Furthermore, the results of the polishing tests are shown in Table 2.

In Tables 1 and 2, "AM" stands for acrylamide, "MAA" for methacrylic acid, "AA" for acrylic acid, "EDTA2N" for diammonium ethylenediaminetetraacetate, "EDTA3K" for tripotassium ethylenediaminetetraacetate, and "citric acid 2N" for diammonium hydrogen citrate. MW is an abbreviation for weight average molecular weight.

(1) Synthesis of Water-Soluble Polymer Compounds The details of the synthesis procedures for the water-soluble polymer compounds used in Examples 1 , 2, 4 to 10 , Reference Example 1 and Comparative Examples 1 to 4 are shown below.

(Synthesis Example 1)
A four-neck flask equipped with a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 100 parts by mass of acrylamide (95 mol% relative to the total molar sum of vinyl monomers), 6.3 parts by mass of methacrylic acid (5 mol%), 5.3 parts by mass of isopropyl alcohol, and 400 parts by mass of ion-exchanged water, and oxygen in the reaction system was removed through nitrogen gas. The reaction system was adjusted to 40°C, and 0.3 parts by mass of ammonium persulfate and 0.2 parts by mass of sodium hydrogen sulfite were added as polymerization initiators under stirring. The start of polymerization was confirmed by heat generation, and after the reaction liquid temperature reached 90°C, the temperature was maintained for 2 hours. After the polymerization was completed, 5.5 parts by mass of 48% aqueous sodium hydroxide solution and 11 parts by mass of ion-exchanged water were added to obtain a carboxyl group-containing polyacrylamide aqueous solution with a pH value (25°C) of 7.5 and a polymer concentration of 20%. The composition of the obtained water-soluble polymer compound was acrylamide/methacrylic acid = 95/5 (mol%), and the weight average molecular weight was 1,400,000.

(Synthesis Example 2)
A four-neck flask equipped with a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 100 parts by mass of acrylamide (95 mol% relative to the total molar sum of vinyl monomers), 5.3 parts by mass of acrylic acid (5 mol%), 5.3 parts by mass of isopropyl alcohol, and 400 parts by mass of ion-exchanged water, and oxygen in the reaction system was removed through nitrogen gas. The reaction system was adjusted to 40°C, and 0.3 parts by mass of ammonium persulfate and 0.2 parts by mass of sodium hydrogen sulfite were added as polymerization initiators under stirring. The start of polymerization was confirmed by heat generation, and after the reaction liquid temperature reached 90°C, the mixture was kept warm for 2 hours. After the polymerization was completed, 5.5 parts by mass of 48% aqueous sodium hydroxide solution and 11 parts by mass of ion-exchanged water were added to obtain a carboxyl group-containing aqueous polyacrylamide solution with a pH value (25°C) of 7.5 and a polymer concentration of 20%. The composition of the obtained water-soluble polymer compound was acrylamide/acrylic acid = 95/5 (mol%), and the weight average molecular weight was 900,000.

(Synthesis Example 3)
Homopolymerization of acrylic acid was carried out using acrylic acid instead of the acrylamide used in Synthesis Example 2. The resulting water-soluble polymer was an acrylic acid homopolymer and had a weight average molecular weight of 12,000.

(2) Preparation of abrasive composition (abrasive composition of Example 1)
A commercially available colloidal silica slurry (average particle size (D50) = 40 nm, silica concentration = 40 mass%), the water-soluble polymer compound synthesized in Synthesis Example 1, and diammonium ethylenediaminetetraacetate (EDTA2N) were added while diluting with pure water to the concentrations shown in Table 1, and the mixture was stirred and mixed to homogenize, and used as the polishing compound composition of Example 1 in the polishing test.

(Abrasive composition of Example 2)
The water-soluble polymer compound synthesized in Synthesis Example 2 was used in place of the water-soluble polymer compound of Synthesis Example 1 used in the preparation of the polishing composition of Example 1. The other conditions were the same as in Example 1, and the polishing composition of Example 2 was used in the polishing test.

(Abrasive composition of Reference Example 1 )
The water-soluble polymer compound synthesized in Synthesis Example 3 was used in place of the water-soluble polymer compound of Synthesis Example 1 used in the preparation of the polishing compound of Example 1. The other conditions were the same as in Example 1, and the polishing compound was used in the polishing test as the polishing compound of Reference Example 1 .

(Abrasive composition of Example 4)
A propylene glycol alginate was used in place of the water-soluble polymer compound of Synthesis Example 1 used in the preparation of the polishing composition of Example 1. The other conditions were the same as in Example 1, and the polishing composition of Example 4 was used in the polishing test.

(Abrasive composition of Example 5)
A colloidal silica slurry having an average particle size (D50) of 110 nm and a silica concentration of 40 mass% was used instead of the commercially available colloidal silica slurry (average particle size (D50) of 40 nm, silica concentration of 40 mass%) used in the preparation of the polishing composition of Example 1. The other conditions were the same as in Example 1, and the composition was used in the polishing test as the polishing composition of Example 5.

(Abrasive composition of Example 6)
Diammonium hydrogen citrate (citric acid 2N) was used instead of diammonium ethylenediaminetetraacetate (EDTA 2N) used in the preparation of the polishing compound of Example 1. The other conditions were the same as in Example 1, and the polishing compound of Example 6 was used in the polishing test.

(Abrasive composition of Example 7)
The concentration of the water-soluble polymer compound used in the preparation of the polishing compound of Example 1 was changed to 1.5 mass %. Other conditions were the same as in Example 1, and the polishing compound of Example 7 was used in the polishing test.

(Abrasive composition of Example 8)
Instead of diammonium ethylenediaminetetraacetate (EDTA 2N) used in the preparation of the polishing compound of Example 1, phosphoric acid was used at the concentration (concentration at which the pH value (25° C.) was 1.4) shown in Table 1. Other conditions were the same as in Example 1, and the polishing compound of Example 8 was used in the polishing test.

(Abrasive composition of Example 9)
The concentration of diammonium ethylenediaminetetraacetate (EDTA2N) used in the preparation of the polishing compound of Example 1 was changed to the concentration (concentration at which the pH value (25° C.) was 8.5) shown in Table 1. Other conditions were the same as in Example 1, and the polishing compound of Example 9 was used in the polishing test.

(Abrasive composition of Example 10)
The concentration of phosphoric acid used in the preparation of the polishing compound of Example 8 was changed to the concentration shown in Table 1 (the concentration at which the pH value (25° C.) was 2.5). Other conditions were the same as in Example 8, and the polishing compound of Example 10 was used in the polishing test.

(Polishing composition of Comparative Example 1)
A commercially available cerium oxide slurry (average particle size = 300 nm, solid concentration = 20 mass %) was diluted with pure water to prepare a concentration shown in Table 1, and used as the polishing compound composition of Comparative Example 1 in the polishing test.

(Polishing composition of Comparative Example 2)
A commercially available colloidal silica slurry (average particle size (D50) = 40 nm, silica concentration = 40 mass%) and diammonium ethylenediaminetetraacetate (EDTA2N) were added while diluting with pure water to the concentrations shown in Table 1, and the mixture was stirred and mixed to homogenize. This was used in the polishing test as the polishing compound composition of Comparative Example 2.

(Polishing composition of Comparative Example 3)
The phosphoric acid used in the preparation of the polishing compound of Example 8 was replaced with sulfuric acid so as to have the concentration (concentration giving a pH value (25° C.) of 0.5) shown in Table 1. Other conditions were the same as in Example 8, and the polishing compound of Comparative Example 3 was used in the polishing test.

(Polishing composition of Comparative Example 4)
The diammonium ethylenediaminetetraacetate (EDTA2N) used in the preparation of the polishing compound of Example 9 was replaced with tripotassium ethylenediaminetetraacetate (EDTA3K) so as to have the concentration (concentration at which the pH value (25° C.) becomes 9.5) shown in Table 1. The other conditions were the same as those of Example 9, and the polishing compound of Comparative Example 4 was used in the polishing test.

(Particle size of colloidal silica)
The particle diameter (Heywood diameter) of colloidal silica was measured as the Heywood diameter (diameter equivalent to a circle with a projected area) by taking a photograph of the field of view at a magnification of 100,000 times using a transmission electron microscope (TEM) (JEOL Ltd., transmission electron microscope JEM2000FX (200 kV)) and analyzing the photograph using analysis software (Mountec Co., Ltd., Mac-View Ver. 4.0). The average particle diameter of colloidal silica is the average particle diameter (D50) calculated by analyzing the diameters of about 2,000 colloidal silica particles using the above-mentioned method, and calculating the particle diameter at which the cumulative particle diameter distribution (accumulated volume basis) from the small particle diameter side is 50% using the above-mentioned analysis software (Mountec Co., Ltd., Mac-View Ver. 4.0).

(Polishing conditions)
A polishing test using a polishing device was carried out for the polishing compound compositions of Examples 1 , 2, 4 to 10 , Reference Example 1 and Comparative Examples 1 to 4. The polishing conditions for the polishing test were as follows.
Polishing machine: Double-sided polishing machine (SPEED FAM 6B-5P-II)
Substrate: Fluorophosphate glass substrate x 3
(76mm x 76mm square, thickness 0.9mm)
Polishing pad: 2900W (suede: with XY grooves)
Rotation speed of the platen: 50 rpm
Processing pressure: 63g/ ^cm2
Processing time: 20min
Amount of polishing compound supplied: 200 ml/min (circulation method)

(Method of Measuring Polishing Rate)
The thickness of the substrate before and after polishing was measured using a micrometer (manufactured by Mitutoyo Corporation, measurement accuracy: 1 μm), and the polishing rate (μm/min) was measured based on this. Note that, for each of the polishing compound compositions of the Examples , Reference Example 1 , and Comparative Example, three substrates to be polished were polished simultaneously, and therefore the polishing rate reported is the average value for the three substrates.

(Method for evaluating haze on substrate surface after polishing)
The cloudiness of the substrate surface after polishing was judged visually by shining light from a focusing lamp (ECO LIGHT 30,000 Lux, manufactured by Nagata Seisakusho Co., Ltd.) on the substrate surface and observing the reflected light based on the following evaluation conditions. The judgment shows the overall judgment for three substrates polished at the same time.
- Clouding evaluation conditions: 〇: No clouding △: Partial clouding ×: Full clouding

(Method of Evaluating Scratches on the Substrate Surface after Polishing)
An ultrafine defect high-speed visualization macro inspection device (W-SCOPE WUV, manufactured by Wacom Electronics Co., Ltd.) was used to evaluate scratches on the substrate surface after polishing. Among the concave defects occurring on the substrate surface, those with a long/short ratio of "5 or more:1" and a width of 5 μm or more were considered scratches. The judgment was based on the average value per surface for a total of six surfaces of three substrates polished at the same time.
・Evaluation conditions for scratches on the substrate surface 〇: No scratches (0 scratches/substrate surface)
△: Slightly scratched (1 to 4 scratches per board surface)
×: Many scratches (5 or more per board surface)

(Discussion)
Compared with the polishing compound using cerium oxide abrasive grains in Comparative Example 1, the polishing compound using colloidal silica abrasive grains in Comparative Example 2 slightly improved the haze on the substrate surface (fluorophosphate glass surface) after polishing, but the polishing rate was low and scratches on the substrate surface were not improved. On the other hand, Example 1, in which a water-soluble polymer compound was added to the polishing compound composition of Comparative Example 2, improved the polishing rate, improved the haze, and improved the scratches compared to Comparative Example 2. That is, the addition of a water-soluble polymer compound to the polishing compound composition improved the haze and improved the scratches.

The polishing compositions of Examples 2 and 4 and Reference Example 1 are examples in which the type of water-soluble polymer compound was changed compared to the preparation of the polishing composition of Example 1. The polishing composition of Example 5 is an example in which colloidal silica abrasive grains having a different average particle size (D50) were used compared to the preparation of the polishing composition of Example 1. On the other hand, the polishing composition of Example 6 is an example in which the acid and/or its salt in the preparation of the polishing composition of Example 1 was changed from 2N EDTA to 2N citric acid.

The polishing composition of Example 7 is an example in which the amount of water-soluble polymer compound added was changed compared to the preparation of the polishing composition of Example 1.

Comparing the polishing compositions of Examples 8 and 10 with the polishing composition of Comparative Example 3, it can be seen that the pH value (25°C) of the polishing composition is 1.0 or higher, which improves the cloudiness and scratches on the surface of the fluorophosphate glass after polishing.

In addition, a comparison between the polishing composition of Example 9 and the polishing composition of Comparative Example 4 shows that the pH value (25°C) of the polishing composition is 9.0 or less, which improves the cloudiness and scratches on the substrate surface after polishing.

From the above, it has become clear that by using the polishing composition of the present invention to polish fluorophosphate glass, the polishing speed is improved and the occurrence of clouding and scratches on the surface of the fluorophosphate glass after polishing is suppressed.

The polishing composition of the present invention (polishing composition for fluorophosphate glass) can be suitably used for polishing fluorophosphate glass used in the lenses of digital cameras or the camera parts built into smartphones.

Claims (9)

Silica and
A water-soluble polymer compound,
an acid and/or a salt thereof;
and water,
The water-soluble polymer compound is
A polymer having structural units derived from a polysaccharide and/or an unsaturated amide,
An abrasive composition for fluorophosphate glass, having a pH (25° C.) value in the range of 1.0 to 9.0. The silica is
Colloidal silica,
The average particle size (D50) is
2. The abrasive composition for fluorophosphates glass according to claim 1, wherein the particle size is in the range of 10 nm to 200 nm. The acid and/or its salt is
3. The abrasive composition for fluorophosphates glass according to claim 1, which is an inorganic acid and/or a salt thereof . The acid and/or its salt is
3. The abrasive composition for fluorophosphates glass according to claim 1, which is an organic acid and/or a salt thereof. The polymer having a structural unit derived from an unsaturated amide is
A structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide;
A structural unit derived from (meth)acrylic acid and/or a salt thereof;
Contains
The abrasive composition for fluorophosphates glass according to claim 1 . The inorganic acid and/or its salt is
4. The abrasive composition for fluorophosphates glass according to claim 3, which is a phosphorus-containing inorganic acid and/or a salt thereof . The organic acid and/or its salt is
5. The abrasive composition for fluorophosphates glass according to claim 4, which is a chelating compound . The chelating compound is
8. The polishing composition for fluorophosphate glass according to claim 7, which is at least one selected from the group consisting of dicarboxylic acids and/or their salts, tricarboxylic acids and/or their salts, polyaminocarboxylic acid compounds, and phosphonic acid compounds . A polishing method using the abrasive composition for fluorophosphates glass according to any one of claims 1 to 8, which comprises polishing fluorophosphates glass.