องค์ประกอบของสารขัดสำหรับใช้กับแก้วฟลูออโรฟอสเฟตและวิธีขัดที่ใช้องค์ประกอบของสารขัดสำหรับใช้กับแก้วฟลูออโรฟอสเฟต

Abstract

DEPCT66 จัดให้มีองค์ประกอบของสารขัดสำหรับใช้กับแก้วฟลูออโรฟอสเฟตที่สามารถขัดแก้วฟลูออโร ฟอสเฟตเป็นทางเลือกแทนสารขัดกลุ่มซีเรียมออกไซด์และมีความเร็วในการขัดสูงองค์ประกอบของสาร ขัดสำหรับใช้กับแก้วฟลูออโรฟอสเฟตประกอบด้วยซิลิกาสารประกอบพอลิเมอร์ที่ละลายน้ำได้กรด และ / หรือเกลือของกรดดังกล่าวและน้ำและมีค่าpH(25องศาเซลเซียส)อยู่ในช่วง1.0-9.0นอกจากนี้ซิลิกาดังกล่าว ข้างต้นเป็นซิลิกาในรูปคอลลอยด์มีขนาดอนุภาคเฉลี่ย(D50)ในช่วง10นาโนเมตร-200นาโนเมตร และสามารถใช้พอลิแซ็กคาไรด์และ / หรือพอลิเมอร์ที่มีหน่วยโครงสร้างที่มีที่มาจากเอไมด์ที่ไม่อิ่มตัวเป็น สารประกอบพอลิเมอร์ที่ละลายน้ำได้;

Description

Abrasive composition for fluorophosphate glass and polishing method using the abrasive composition for fluorophosphate glass

[0001] 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 cameras built into smartphones, and a polishing method using the abrasive composition for fluorophosphate glass.

[0002] Conventionally, solid-state imaging devices used in digital cameras, cameras built into smartphones, and the like have spectral sensitivity ranging from the visible region to the near-infrared region around 1200 nm. Therefore, if used as is, it is difficult to obtain good color reproducibility, so the luminosity is corrected by using a near-infrared cut filter glass formed by adding a specific substance with infrared absorption properties.

[0003] 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. While ordinary glass mainly contains silica or silica and alumina, fluorophosphate glass contains substantially no silica and is composed of components optimized for absorbing infrared rays with wavelengths in the near-infrared region.

[0004] To explain in more detail, fluorophosphate glass generally contains phosphorus ions (P ５＋ ) is 15 to 50%, aluminum ions (Al ３＋ ) is 5-30%, calcium ions (Ca ２＋ ) and magnesium ions (Mg ２＋ ) and strontium ions (Sr ２＋ ) and barium ions (Ba ２＋ ) and zinc ions (Zn ２＋ ) in which the total amount of one or more selected from the group consisting of 10 to 40%, lithium ion (Li ＋) and sodium ions (Na ＋ ) and potassium ions (K ＋ ) in a total amount of 5 to 30%, and copper ions (Cu ２＋ ) is 0-20%, and anion % is fluoride ion (F － ) 10 to 50%, and oxygen ions (O ２－ ) is contained in the range of 50 to 90%.

[0005] 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 of the content of each cationic component expressed 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 of the content of each anionic component expressed as a molar percentage corresponds to "anion %".

[0006] The production of near-infrared cut filter glass mainly comprises a melting step in which glass raw materials, such as tripolyphosphate powder, 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 are removed from the glass, a stirring step in which the glass is homogenized, and a shaping step in which the molten glass is poured out and shaped. Known methods include a method in which each of the above steps is performed using a single crucible furnace, or a method in which each step is performed using a continuous furnace having multiple different tanks connected to each other by transport pipes.

[0007] The fluorophosphate glass produced in this way exhibits properties such as a high abrasion resistance and a high thermal expansion coefficient compared to other common optical glasses, making polishing of such fluorophosphate glass difficult.

[0008] Glass materials that are difficult to polish are called "refractory materials" and require careful handling during the processing steps in the glass manufacturing process. That is, the glass materials are soft and the surface is easily scratched, or too hard and difficult to process. In addition to the above-mentioned fluorophosphate glasses, other known glass materials include niobium phosphate-containing high-refractive index, high-dispersion glasses and lanthanum borate-containing high-refractive index, low-dispersion glasses.

[0009] In particular, when the glass material being polished is highly abrasive, the processing accuracy 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.

[0010] Therefore, a method using a cerium oxide-based abrasive containing cerium oxide as a main component has been conventionally 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. Therefore, there has been a demand for an alternative to silica-based abrasives containing silica as a main component, which is inexpensive and can be supplied stably.

[0011] JP 2013-141737 A International Publication No. 2017 / 102826

[0012] However, silica-based abrasives have the problem of lower removal rates than the above-mentioned cerium oxide-based abrasives, and an improvement in such removal rate has been desired.

[0013] In view of the above-described circumstances, an object of the present invention is to provide an abrasive composition for fluorophosphate glass that has a high removal rate and can be used to polish fluorophosphate glass as an alternative to cerium oxide-based abrasives, and a polishing method using the abrasive composition for fluorophosphate glass.

[0014] In order to solve the above-mentioned problems, the inventors of the present application have conducted extensive research into the problem of silica-based abrasives, namely, their low removal rate, and as a result have discovered an abrasive composition for fluorophosphate glass that improves the removal rate of silica-based abrasives and is capable of finishing the fluorophosphate glass surface to an excellent smoothness without generating cloudiness or scratches on the glass surface after polishing, as well as a polishing method using the abrasive composition for fluorophosphate glass, and have thus completed the present invention described below.

[0015] [1] An abrasive composition for fluorophosphate glass, comprising silica, a water-soluble polymer compound, an acid and / or its salt, and water, and having a pH (25°C) value in the range of 1.0 to 9.0.

[0016] [2] The abrasive composition for fluorophosphate glass according to [1], wherein the silica is colloidal silica and has an average particle size (D50) in the range of 10 nm to 200 nm.

[0017] [3] The abrasive composition for fluorophosphate glass according to [1] or [2], wherein the water-soluble polymer compound is a polymer having structural units derived from polysaccharides and / or unsaturated amides.

[0018] [4] The abrasive composition for fluorophosphate glass according to any one of [1] to [3], wherein the acid and / or its salt is an inorganic acid and / or its salt.

[0019] [5] The abrasive composition for fluorophosphate glass according to any one of [1] to [3], wherein the acid and / or its salt is an organic acid and / or its salt.

[0020] [6] The abrasive composition for fluorophosphate glass according to [3], wherein the polymer having a structural unit derived from an unsaturated amide is 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.

[0021] [7] The abrasive composition for fluorophosphate glass according to [4], wherein the inorganic acid and / or its salt is a phosphorus-containing inorganic acid and / or its salt.

[0022] [8] The abrasive composition for fluorophosphate glass according to [5], wherein the organic acid and / or its salt is a chelating compound.

[0023] [9] The abrasive composition for fluorophosphate glass according to [8], wherein the chelating compound is at least one selected from the group consisting of dicarboxylic acids and / or salts thereof, tricarboxylic acids and / or salts thereof, polyaminocarboxylic acid compounds, and phosphonic acid compounds.

[0024]

[10] A polishing method using an abrasive composition for fluorophosphate glass, in which the abrasive composition for fluorophosphate glass according to any one of [1] to [9] above is used to polish fluorophosphate glass.

[0025] The abrasive composition for fluorophosphate glass of the present invention contains silica, a water-soluble polymer compound, an acid and / or its salt, and water. By polishing fluorophosphate glass with the abrasive composition, the polishing rate can be improved and a smooth glass surface free from cloudiness or scratches can be obtained after polishing.

[0026] The following describes embodiments of the present invention. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

[0027] 1. Abrasive Composition for Fluorophosphate Glass The abrasive composition for fluorophosphate glass of this 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.

[0028] 1.1 Silica The silica contained as one component of the polishing compound composition of this embodiment can be fumed silica, wet-process silica, colloidal silica, etc., with colloidal silica being 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 an average particle size (D50) in the range of 20 nm to 150 nm.

[0029] By setting the average particle size (D50) of colloidal silica to 10 nm or more, aggregation of colloidal silica is less likely to occur, and storage stability can be improved. On the other hand, by setting the average particle size (D50) of colloidal silica to 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).

[0030] Colloidal silica may be in any known shape, such as a spherical shape or a confetti-shaped shape (a particle shape having protrusions on the surface), and the primary particles are monodispersed in water to form a colloidal shape.

[0031] The colloidal silica used can be produced by a conventionally known production method, such as the water glass method, which uses an alkali metal silicate such as sodium silicate or potassium silicate as a raw material and grows colloidal silica particles by condensing the raw material in an aqueous solution; the alkoxysilane method, which uses a tetraalkoxysilane such as tetraethoxysilane as a raw material and grows colloidal silica particles by condensing the raw material with an acid or alkali through hydrolysis in a solvent containing a water-soluble organic solvent such as alcohol; or a method of synthesizing colloidal silica by reacting metal silicon with water in the presence of an alkali catalyst. Note that the water glass method is preferred in terms of production cost. The colloidal silica used in the abrasive composition for fluorophosphate glass of this embodiment can be produced by appropriately using these synthesis methods.

[0032] In the polishing compound of this embodiment, the concentration (content) of colloidal silica contained in the polishing compound 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 abrasive particles and of economic efficiency.

[0033] By setting the colloidal silica concentration to 1% by mass or more, the polishing rate can be improved, while by setting the colloidal silica concentration to 50% by mass or less, it is advantageous in terms of economy and also has the advantage that aggregation and gelation are less likely to occur when further adding and compounding abrasives other than colloidal silica and other compounding ingredients.

[0034] 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, or a polymer having structural units derived from an unsaturated amide, and it is preferable to use a polymer having structural units derived from a polysaccharide or an unsaturated amide.

[0035] Furthermore, in the polishing compound of this embodiment, the concentration of the water-soluble polymer compound contained in the polishing compound 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.

[0036] A concentration of the water-soluble polymer compound of 0.0001% by mass or more suppresses clouding and scratches on the substrate surface after polishing, while a concentration of the water-soluble polymer compound of 10.0% by mass or less is not only advantageous from the standpoint of economy but also prevents the abrasive composition for fluorophosphate glass from becoming too viscous.

[0037] Furthermore, examples of polysaccharides used as water-soluble polymer compounds include alginic acid, alginic acid esters, pectinic acid, carboxymethyl cellulose, agar, xanthan gum, chitosan, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and hydroxyethyl cellulose.

[0038] On the other hand, the polymer having a structural unit derived from an unsaturated amide used as a water-soluble polymer compound is preferably a copolymer containing a structural unit derived from an unsaturated amide and a structural unit derived from a carboxyl group-containing vinyl monomer, 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.

[0039] 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) has the same meaning as above.

[0040] Furthermore, the N-substituted (meth)acrylamide may be represented by the following formula (1): ２ = C(R １ )-CONR ２ (R ３ ) ... (1) where R １ is a hydrogen atom or a methyl group, R ２ is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms; R ３ represents a straight or branched alkyl group having 1 to 4 carbon atoms.

[0041] R shown in the above formula (1) ２ or R ３Examples of the linear or branched alkyl group having 1 to 4 carbon atoms in the formula (I) 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.

[0042] Examples of the carboxyl group-containing vinyl monomer 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, etc. In particular, those using (meth)acrylic acid or itaconic acid are preferred.

[0043] Furthermore, the molar ratio of the constituent units derived from the unsaturated amide to 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, more preferably 98:2 to 10:90.

[0044] Furthermore, vinyl monomers other than those mentioned above can also be suitably used. For example, examples of anionic vinyl monomers include organic sulfonic acids such as vinyl sulfonic acid, styrene sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid, as well as alkali metal salts such as sodium salts and potassium salts, and ammonium salts of these various organic acids.

[0045] 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.

[0046] In addition, well-known means can be used to produce a 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.

[0047] To give an example of this, the desired carboxyl group-containing poly(meth)acrylamide can be obtained by charging the various monomers and water described above into a predetermined reaction vessel, adding a radical polymerization initiator, and heating the mixture with stirring.

[0048] In this case, as the radical polymerization initiator, a typical radical polymerization initiator can be used, 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. Furthermore, an azo-based initiator may also be used as the radical polymerization initiator. The amount of such radical polymerization initiator used can be in the range of 0.05% by mass to 2% by mass of the sum of the total amount of vinyl monomers used.

[0049] The weight-average molecular weight of the 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 a value measured using gel permeation chromatography (GPC) in terms of standard polystyrene.

[0050] 1.3 Acid and / or Salt Thereof The acid and / or salt thereof contained as one component of the polishing compound composition of this embodiment is an inorganic acid and / or salt thereof, or an organic acid and / or salt thereof. Note that the acid and / or salt thereof may be a combination of an inorganic acid and / or salt thereof and an organic acid and / or salt thereof.

[0051] 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.

[0052] On the other hand, the organic acid and / or salt thereof may be at least one selected from the group consisting of monocarboxylic acids and / or salts thereof, dicarboxylic acids and / or salts thereof, tricarboxylic acids and / or salts thereof, polyaminocarboxylic acid compounds, and phosphonic acid compounds. More preferably, a chelating compound may be used.

[0053] The chelating compound may be a dicarboxylic acid and / or its salt, a tricarboxylic acid and / or its salt, a polyaminocarboxylic acid compound, a phosphonic acid compound, etc. The dicarboxylic acid and / or its salt may be malic acid, malonic acid, maleic acid, tartaric acid and / or its salt, etc., and the tricarboxylic acid and / or its salt may be citric acid and / or its salt, etc.

[0054] On the other hand, examples of polyaminocarboxylic acid compounds that can be used include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, and their ammonium salts, amine salts, sodium salts, and potassium salts. Examples of phosphonic acid compounds that can be used include diethylenetriaminepentamethylenephosphonic acid, phosphonohydroxyacetic acid, hydroxyethyldimethylenephosphonic acid, aminotrismethylenephosphonic acid, hydroxyethanephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, and their ammonium salts, amine salts, sodium salts, and potassium salts. Among the above chelating compounds, tricarboxylic acids and / or salts thereof, and polyaminocarboxylic acid compounds can be used more preferably.

[0055] The content of the acid and / or its salt in the polishing compound composition for fluorophosphate glass is determined from the viewpoint of adjusting the pH value (25°C) of the polishing compound composition for fluorophosphate glass to a set value, and is preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 8% by mass. By setting the content to 0.01% by mass or more, the polishing rate can be improved. By setting the content to 10% by mass or less, clouding of the substrate surface after polishing can be suppressed.

[0056] 1.4 Water The water contained as one component of the polishing compound composition of this embodiment is used as a medium for dispersing the other components of the polishing compound composition, and preferably used is pure water, ultrapure water, distilled water, etc. In order to smoothly disperse the other components of the polishing compound composition, the polishing compound composition may contain an appropriate amount of an organic medium such as alcohol.

[0057] 1.5 Physical Properties of Polishing Compound Composition The pH value (25°C) of the polishing compound composition of this embodiment is in the range of 1.0 to 9.0, 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 haze on 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.

[0058] 2. Method for Polishing Fluorophosphate Glass When polishing fluorophosphate glass using the abrasive composition of this embodiment, various conventionally known polishing methods can be appropriately selected. For example, a predetermined amount of the abrasive composition is placed in a supply container installed in a polishing machine. The abrasive composition is supplied dropwise from the supply container via a nozzle or tube to a polishing pad attached to the platen of the polishing machine, and the platen is rotated at a predetermined rotational 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.

[0059] The polishing pad can be made of a material commonly used in polishing, such as a nonwoven fabric, polyurethane foam, porous resin, or non-porous resin. Furthermore, in order to facilitate the supply of the abrasive composition to the polishing pad or to ensure that a certain amount of the abrasive composition remains on the polishing pad, the pad surface of the polishing pad may be provided with various grooves, such as a grid-like, concentric circular, or spiral groove.

[0060] 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.

[0061] The experimental examples of Examples 1 to 10 and Comparative Examples 1 to 4 shown below are the results of predetermined polishing tests carried out using abrasive compositions for polishing fluorophosphate glass (compositions 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.

[0062] 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.

[0063] (1) Synthesis of Water-Soluble Polymer Compounds The details of the synthesis procedures for the water-soluble polymer compounds used in Examples 1 to 10 and Comparative Examples 1 to 4 are shown below.

[0064] Synthesis Example 1: A four-neck flask equipped with a thermometer, reflux condenser, and nitrogen inlet tube was charged with 100 parts by mass of acrylamide (95 mol % relative to the total molar amount of vinyl monomers), 6.3 parts by mass (5 mol %) of methacrylic acid, 5.3 parts by mass of isopropyl alcohol, and 400 parts by mass of ion-exchanged water. Oxygen was removed from the reaction system by introducing 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 while 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 completion of polymerization, 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 (25°C) of 7.5 and a polymer concentration of 20%. The resulting water-soluble polymer had a composition of acrylamide / methacrylic acid = 95 / 5 (mol %) and a weight-average molecular weight of 1,400,000.

[0065] 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 amount of vinyl monomers), 5.3 parts by mass (5 mol %) of acrylic acid, 5.3 parts by mass of isopropyl alcohol, and 400 parts by mass of ion-exchanged water. Oxygen was removed from the reaction system by introducing 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 while stirring. The start of polymerization was confirmed by heat generation, and after the reaction liquid temperature reached 90°C, the mixture was maintained at that temperature for 2 hours. After completion of polymerization, 5.5 parts by mass of a 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 (25°C) of 7.5 and a polymer concentration of 20%. The resulting water-soluble polymer had a composition of acrylamide / acrylic acid = 95 / 5 (mol %) and a weight-average molecular weight of 900,000.

[0066] Synthesis Example 3 Acrylic acid homopolymerization was carried out using acrylic acid instead of the acrylamide used in Synthesis Example 2. The resulting water-soluble polymer compound was an acrylic acid homopolymer, and had a weight-average molecular weight of 12,000.

[0067] (2) Preparation of Polishing Compound Composition (Polishing Compound 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 listed in Table 1, and the mixture was stirred and mixed to form a homogenous mixture, which was used in the polishing test as the polishing compound composition of Example 1.

[0068] (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 abrasive composition of Example 1. The other conditions were the same as in Example 1, and the abrasive composition of Example 2 was used in a polishing test.

[0069] (Abrasive Composition of Example 3) 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 abrasive composition of Example 1. The other conditions were the same as in Example 1, and the abrasive composition of Example 3 was used in a polishing test.

[0070] (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 abrasive composition of Example 1. Other conditions were the same as in Example 1, and the abrasive composition of Example 4 was used in the polishing test.

[0071] 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 preparing the abrasive composition of Example 1. The other conditions were the same as in Example 1, and the abrasive composition of Example 5 was used in a polishing test.

[0072] (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 abrasive composition of Example 1. Other conditions were the same as in Example 1, and the abrasive composition of Example 6 was used in a polishing test.

[0073] (Abrasive Composition of Example 7) The concentration of the water-soluble polymer compound used in the preparation of the abrasive composition of Example 1 was changed to 1.5 mass %. Other conditions were the same as in Example 1, and the abrasive composition of Example 7 was used in a polishing test.

[0074] (Abrasive Composition of Example 8) Instead of diammonium ethylenediaminetetraacetate (EDTA 2N) used in preparing the abrasive composition of Example 1, phosphoric acid was used at the concentration shown in Table 1 (the concentration at which the pH value (25°C) was 1.4). Other conditions were the same as in Example 1, and the abrasive composition of Example 8 was used in a polishing test.

[0075] (Abrasive Composition of Example 9) The concentration of diammonium ethylenediaminetetraacetate (EDTA 2N) used in preparing the abrasive composition 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 abrasive composition of Example 9 was used in a polishing test.

[0076] (Abrasive Composition of Example 10) The concentration of phosphoric acid used in preparing the abrasive composition of Example 8 was changed to the concentration (concentration at which the pH value (25°C) was 2.5) shown in Table 1. Other conditions were the same as in Example 8, and the abrasive composition of Example 10 was used in a polishing test.

[0077] (Abrasive 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 the concentration shown in Table 1, and this was used as the abrasive composition of Comparative Example 1 in the polishing test.

[0078] (Abrasive Composition of Comparative Example 2) A commercially available colloidal silica slurry (average particle size (D50) = 40 nm, silica concentration = 40 mass%) and diammonium ethylenediaminetetraacetate (EDTA 2N) 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 abrasive composition of Comparative Example 2.

[0079] (Abrasive Composition of Comparative Example 3) The phosphoric acid used in the preparation of the abrasive composition of Example 8 was replaced with sulfuric acid, and the concentration (concentration at which the pH value (25°C) becomes 0.5) shown in Table 1 was obtained. Other conditions were the same as in Example 8, and the abrasive composition of Comparative Example 3 was used in the polishing test.

[0080] (Abrasive Composition of Comparative Example 4) The diammonium ethylenediaminetetraacetate (EDTA 2N) used in the preparation of the abrasive composition of Example 9 was replaced with tripotassium ethylenediaminetetraacetate (EDTA 3K) so as to have the concentration (concentration giving a pH value (25°C) of 9.5) shown in Table 1. Other conditions were the same as in Example 9, and the abrasive composition of Comparative Example 4 was used in the polishing test.

[0081]

[0082]

[0083] (Particle diameter 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 (Mountech Co., Ltd., Mac-View Ver. 4.0). The average particle diameter of colloidal silica was determined by analyzing the diameters of approximately 2,000 colloidal silica particles using the method described above, and calculating the particle size at which the cumulative particle size distribution (cumulative volume basis) from the small particle size side was 50% using the analysis software (Mountech Co., Ltd., Mac-View Ver. 4.0). This average particle diameter (D50) was calculated.

[0084] (Polishing Conditions) A polishing test using a polishing machine was carried out for the polishing compound compositions of Examples 1 to 10 and Comparative Examples 1 to 4. The polishing conditions for the polishing test were as follows: Polishing machine: double-sided polishing machine (6B-5P-II manufactured by SPEED FAM) Substrate: 3 fluorophosphate glass substrates (76 mm x 76 mm square, 0.9 mm thick) Polishing pad: 2900 W (suede: with XY grooves) Platen rotation speed: 50 rpm Processing pressure: 63 g / cm ２ Processing time: 20 min Abrasive composition supply amount: 200 ml / min (circulation method)

[0085] (Method for Measuring Polishing Rate) The thickness of the substrate before the start of polishing and the thickness of the substrate after polishing were 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 Examples and Comparative Examples, three substrates to be polished were simultaneously polished, and therefore the polishing rate reported is the average value for the three substrates.

[0086] (Method for evaluating fogging on substrate surfaces after polishing) The fogging on the substrate surfaces after polishing was evaluated visually by shining light from a condenser 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 evaluation indicates an overall evaluation of three substrates polished simultaneously. -Fogging evaluation conditions ◯: No fogging △: Partial fogging ×: Full fogging

[0087] (Method for evaluating scratches on substrate surfaces 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 surfaces after polishing. Among the concave defects that occurred on the substrate surface, those with a long-to-short ratio of "5 or more:1" and a width of 5 μm or more were considered scratches. The evaluation was based on the average value per surface for a total of six surfaces of three substrates polished simultaneously. Evaluation conditions for scratches on substrate surfaces ◯: No scratches (0 scratches / substrate surface) △: Slight scratches (1 to 4 scratches / substrate surface) ×: Many scratches (5 or more scratches / substrate surface)

[0088] (Discussion) Compared to the polishing compound composition using cerium oxide abrasive grains in Comparative Example 1, the polishing compound composition using colloidal silica abrasive grains in Comparative Example 2 slightly improved the haze on the substrate surface (fluorophosphate glass surface) after polishing, but the removal 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 removal rate, improved the haze, and improved the scratches compared to Comparative Example 2. In other words, the addition of a water-soluble polymer compound to the polishing compound composition was found to improve the haze and the scratches.

[0089] The polishing compound compositions of Examples 2 to 4 are examples in which the type of water-soluble polymer compound was changed compared to the preparation of the polishing compound composition of Example 1. The polishing compound 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 compound composition of Example 1. On the other hand, the polishing compound composition of Example 6 is an example in which the acid and / or its salt in the preparation of the polishing compound composition of Example 1 was changed from 2N EDTA to 2N citric acid.

[0090] The polishing compound of Example 7 is an example in which the amount of the water-soluble polymer compound added was changed compared to the preparation of the polishing compound of Example 1.

[0091] A comparison of the polishing compound compositions of Examples 8 and 10 with the polishing compound composition of Comparative Example 3 shows that a polishing compound composition having a pH value (25°C) of 1.0 or higher improves the haze and scratches on the surface of the fluorophosphate glass after polishing.

[0092] In addition, a comparison between the polishing compound composition of Example 9 and the polishing compound composition of Comparative Example 4 shows that the pH value (25°C) of the polishing compound composition is 9.0 or less, thereby improving the cloudiness and scratches on the substrate surface after polishing.

[0093] From the above, it has become clear that by using the polishing compound of the present invention to polish fluorophosphate glass, the polishing rate is improved and the occurrence of clouding and scratches on the surface of the fluorophosphate glass after polishing is suppressed.

[0094] 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.