Glass plate manufacturing method

Abstract

A glass plate (glass plate for cover glass) having a low impurity concentration is manufactured using an article cullet. A step of melting a glass raw material and cullet to produce a glass plate is repeated. The glass plate is further processed into a glass article. The glass article is a display cover glass having the glass plate and a coating layer disposed on the surface of the glass plate. Glass plate cullet, which is cullet of the glass plate, and article cullet, which is cullet of the glass article, are used as the cullet. The impurity concentration of the glass plate cullet and / or the impurity concentration of the article cullet is determined according to at least one of the impurity concentration of the glass plate cullet and the impurity concentration of the article cullet. At least one of the mixing ratio of the glass raw material, the mixing ratio of the glass cullet, the mixing ratio of the article cullet, the impurity concentration of the glass raw material, the impurity concentration of the glass cullet, and the impurity concentration of the article cullet is adjusted.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a glass sheet. Background Art

[0002] Patent Document 1 states that "a glass raw material composition and, as required, cullet having the same glass composition as the target molten glass are continuously charged into a melting furnace and heated to about 1600° C. to about 1700° C. to melt, thereby forming molten glass" (paragraph

[0025] ).

[0003] In addition, Patent Document 1 states that "after the molten glass obtained in the above-mentioned melting step is formed into a target shape in a forming step, it is slowly cooled in a slow cooling step as needed, and then, in a post-processing step, post-processing is performed by known methods such as cutting and grinding as needed to obtain a glass article" (paragraph

[0026] ).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 088503 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Examples of the glass article include protective glass for displays in which a coating layer (antifouling film, antireflection film, printed portion, etc.) is disposed on the surface of a glass plate.

[0009] The cullet (article cullet) obtained by pulverizing a display protective glass as such a glass article contains more impurities derived from the coating layer and the like than the cullet of a glass plate (glass plate cullet).

[0010] A glass plate used as a cover glass for a display (hereinafter also referred to as a “glass plate for a cover glass”) is required to have a high quality level, and, for example, a lower impurity concentration than conventional soda-lime glass.

[0011] Therefore, in the production of the glass plate for protection glass, glass plate cullets are used, and cullets containing many impurities are not used.

[0012] However, in recent years, from the viewpoint of cost reduction, etc., studies have been conducted on using cullet in the production of a glass plate for a protective glass.

[0013] The present invention has been made in view of the above problems, and an object of the present invention is to manufacture a glass plate (glass plate for protective glass) having a low impurity concentration using article cullet.

[0014] Means used to solve problems

[0015] The present inventors have conducted intensive studies and have found that the above-mentioned object can be achieved by adopting the following configuration, thereby completing the present invention.

[0016] That is, the present invention provides the following [1] to

[15] .

[0017] [1] A method for manufacturing a glass plate, the method comprising repeatedly performing a step of melting glass raw materials and cullet to manufacture a glass plate, wherein the glass plate is further processed to become a glass article, the glass article being a protective glass for a display having the glass plate and a coating layer disposed on a surface of the glass plate, wherein the cullet comprises glass plate cullet as cullet of the glass plate and article cullet as cullet of the glass article, and wherein at least any one of a mixing ratio of the glass raw materials, a mixing ratio of the glass plate cullet, a mixing ratio of the article cullet, an impurity concentration of the glass raw materials, an impurity concentration of the glass plate cullet, and an impurity concentration of the article cullet is adjusted based on at least any one of an impurity concentration of the glass plate cullet and an impurity concentration of the article cullet.

[0018] [2] The method for manufacturing a glass plate according to [1] above, wherein the impurity concentration of the cullet is reduced by subjecting the cullet to a treatment A for removing matter adhering to the outside of the glass plate, i.e., matter adhering outside the glass.

[0019] [3] The method for manufacturing a glass plate according to [2] above, wherein the external deposits on the cullet contain at least one element selected from the group consisting of Fe, Ti, Co, Ni, Cr, Mo, Mg, Cu and Nb as impurities.

[0020] [4] The method for producing a glass plate according to any one of [1] to [3] above, wherein the mixing ratio of the cullet is 2% by mass or more.

[0021] [5] The method for producing a glass plate according to any one of [1] to [3] above, wherein the mixing ratio of the cullet is 8% by mass or more.

[0022] [6] The method for manufacturing a glass plate according to [2] or [3] above, wherein the treatment A reduces the amount of the external deposits on the cullet by 50% by mass or more.

[0023] [7] The method for manufacturing a glass plate according to any one of [1] to [3] above, wherein the impurity concentration of the glass plate cullet is reduced by subjecting the glass plate cullet to a treatment A for removing matter attached to the outside of the glass plate, i.e., matter attached outside the glass.

[0024] [8] The method for manufacturing a glass sheet according to [7] above, wherein the external glass deposits of the glass sheet cullet contain Fe as an impurity.

[0025] [9] The method for manufacturing a glass sheet according to any one of [1] to [3] above, wherein the impurity concentration of the glass sheet at time n is set to P n When the maximum concentration of impurities in the glass sheet is expressed by the following formula (6): ∞ Less than the specified value,

[0026]

[0027] In the above formula (6), CR B : Impurity concentration of the glass raw material, CR i : The impurity concentration of the entire glass plate cullet, CR e : The impurity concentration of the entire cullet, MR B : The mixing ratio of the glass raw materials, MR i : The mixing ratio of the glass plate cullet, MR e : The mixing ratio of the broken glass of the article, E1: a value greater than 0 to less than or equal to 1, E2: a value greater than 0 to less than or equal to 1, E3: a value greater than 0 to less than or equal to 1, CR B , CR i and CR e The unit of impurity concentration is expressed in ppm by mass.

[0028]

[10] The method for manufacturing a glass sheet according to [9] above, wherein in the formula (6), E1, E2 and E3 are each in the range of 0.7 to 1.

[0029]

[11] The method for manufacturing a glass sheet according to [9] above, wherein in formula (6), E1 is E i ×E e , E2 is E e ×E B , E3 is E i ×E B , E B The residual rate of the glass raw material when it is melted is i The residual rate of the cullet when the glass plate is melted, E eIt is the residual rate of the cullet when the object is melted.

[0030]

[12] The method for manufacturing a glass sheet according to any one of [1] to [3] above, wherein the impurity concentration of the glass sheet at time n is set to P n When the maximum concentration of impurities in the glass sheet is expressed by the following formula (6): ∞ Less than the specified value,

[0031]

[0032] In the above formula (6), CR B : Impurity concentration of the glass raw material, CR i : The impurity concentration of the deposits attached to the outside of the glass plate in the glass plate cullet, that is, the impurity concentration of the deposits outside the glass, CR e : The impurity concentration of the deposits attached to the outside of the glass plate in the cullet, that is, the impurity concentration of the deposits outside the glass, MR B : The mixing ratio of the glass raw materials, MR i : The mixing ratio of the glass plate cullet, MR e :The mixing ratio of the broken glass of the above items, E1:E i ×E e , E2:E e ×E B , E3:E i ×E B , E B : The residual rate when the glass raw material is melted, E i : The residual rate when the cullet of the glass plate is melted, E e : The residual rate when the cullet of the article is melted, CR B , CR i and CR e The unit of impurity concentration is expressed in ppm by mass.

[0033]

[13] The method for manufacturing a glass sheet according to

[12] above, wherein in the formula (6), E1, E2 and E3 are each in the range of 0.7 to 1.

[0034]

[14] The method for producing a glass plate according to any one of [1] to [3] above, wherein the coating layer includes at least one selected from the group consisting of an antifouling film, an antireflection film, and a printed portion.

[0035]

[15] The method for producing a glass plate according to any one of [1] to [3] above, wherein the glass plate is a glass plate subjected to a chemical strengthening treatment.

[0036] Effects of the Invention

[0037] According to the present invention, a glass plate (glass plate for protective glass) having a low impurity concentration can be produced using article cullet. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flowchart showing the production process of a glass plate and a glass product (cover glass for a display). DETAILED DESCRIPTION

[0039] Hereinafter, preferred embodiments of the present invention will be described.

[0040] However, the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the gist of the present invention.

[0041] The composition of each component is determined using a known measurement method, specifically, by using, for example, X-ray fluorescence (XRF) analysis and ICP (inductively coupled plasma) emission spectrometry alone or in combination.

[0042] [Method for manufacturing glass plate]

[0043] The method for producing a glass plate according to the present embodiment (hereinafter also referred to as “the present production method”) repeatedly performs the steps of melting glass raw materials and cullet to produce a glass plate.

[0044] <Glass Raw Materials>

[0045] Examples of the glass raw material include a silicon source, an aluminum source, an alkali metal source, and an alkaline earth metal source.

[0046] The silicon source is a compound that becomes SiO2 by melting, and an example thereof is silica sand.

[0047] The aluminum source is a compound that becomes Al2O3 by melting, and an example thereof is aluminum oxide.

[0048] The alkali metal source is a compound that becomes Li2O, Na2O or K2O by melting, and examples thereof include carbonates, sulfates, nitrates, oxides, hydroxides, chlorides and fluorides of alkali metals.

[0049] The alkaline earth metal source is a compound that becomes MgO, CaO, SrO or BaO by melting, and examples thereof include carbonates, sulfates, nitrates, oxides, hydroxides, chlorides and fluorides of alkaline earth metals. Composite carbonates such as dolomite and composite oxides such as calcined dolomite may also be used.

[0050] Examples of other glass raw materials include tin oxide, titanium oxide, zirconium oxide, zircon, cerium oxide, antimony oxide, iron oxide, cobalt oxide, chromium oxide, copper oxide, nickel oxide, and yttrium oxide.

[0051] Each glass raw material may be used alone or in combination of two or more.

[0052] The particle size of each glass raw material is not particularly limited and can be appropriately selected.

[0053] <Broken Glass>

[0054] Cullet is glass scraps discharged during the glass manufacturing process.

[0055] In the present production method, as described later, as the cullets, glass plate cullets as cullets of glass plates and article cullets as cullets of glass articles (cover glass for displays) are used.

[0056] <Melting and Forming>

[0057] The method for melting the glass raw material and the cullet is not particularly limited, and a conventionally known method can be adopted, but a method of placing the glass raw material and the cullet in a melting furnace and melting them is preferred.

[0058] The type of the melting furnace is not particularly limited, and may be a batch type or a continuous type.

[0059] For example, according to the target glass composition, glass raw materials and cullet are continuously charged into a melting furnace, heated to a temperature of about 1600° C. to about 1700° C. to melt, thereby obtaining molten glass.

[0060] Next, the obtained molten glass is formed into a desired shape and then slowly cooled as necessary, and then arbitrarily subjected to post-processing such as cutting and grinding according to a known method.

[0061] For example, molten glass is formed into a plate shape by a known method such as a float method, a down-draw method, or a fusion method, and then slowly cooled as necessary to obtain a glass plate.

[0062] <Glass Plate>

[0063] The glass plate is a glass plate for protecting glass.

[0064] The thickness of the glass plate is, for example, not less than 0.1 mm and not more than 5 mm.

[0065] The size of the glass plate is appropriately selected depending on the intended use.

[0066] The glass composition of the glass plate obtained by shaping the molten glass is basically the same as the glass composition of the molten glass, and is preferably a glass composition that can be strengthened by a chemical strengthening treatment.

[0067] Chemical strengthening treatment

[0068] The glass plate is preferably subjected to chemical strengthening treatment.

[0069] The chemical strengthening treatment method can adopt a conventionally known method, for example, ion exchange is performed on the main surface of the glass plate to form a surface layer with residual compressive stress. Specifically, at a temperature below the glass transition temperature, the alkali metal ions (such as Li ions and / or Na ions) with a small ion radius contained in the glass near the main surface of the glass plate are replaced with alkali metal ions (such as Na ions and / or K ions) with a larger ion radius. As a result, compressive stress remains on the main surface of the glass plate, and the strength of the glass plate is improved.

[0070] The surface compressive stress (CS) and the depth of the surface compressive stress layer (DOL) of the glass plate after the chemical strengthening treatment can be adjusted appropriately. The CS is preferably 300 MPa or more, and the DOL is preferably 10 μm or more.

[0071] <Glass products: Protective glass for displays>

[0072] The glass sheets are further processed to become glass objects.

[0073] The glass article is a protective glass for a display having a glass plate and a coating layer disposed on a surface of the glass plate.

[0074] The cover glass for a display is a member for protecting the display portion in various displays such as a liquid crystal display (LCD) and an organic EL display (OLED).

[0075] "coating"

[0076] As the coating layer, for example, at least one selected from the group consisting of an antifouling film, an antireflection film, and a printed portion can be cited.

[0077] (Anti-fouling film)

[0078] The anti-fouling film easily removes dirt (human fingerprints, etc.).

[0079] As a method for forming the antifouling film, any of dry methods such as vacuum evaporation, ion beam assisted evaporation, ion plating, sputtering, and plasma CVD; and wet methods such as spin coating, dip coating, casting, slit coating, and spraying can be used.

[0080] The constituent material of the antifouling film can be appropriately selected from materials capable of imparting antifouling properties, water repellency, and oil repellency. Specifically, fluorine-containing organosilicon compounds can be mentioned.

[0081] As the fluorine-containing organosilicon compound, for example, an organosilicon compound having at least one group selected from the group consisting of a polyfluoropolyether group, a polyfluoroalkylene group and a polyfluoroalkyl group can be appropriately cited. The polyfluoropolyether group refers to a monovalent or divalent group having a structure in which a polyfluoroalkylene group and a polyfluoroalkylene group are bonded via an etheric oxygen atom. The polyfluoroalkylene group and the polyfluoroalkyl group can be a perfluoroalkylene group and a perfluoroalkyl group, respectively.

[0082] The thickness of the antifouling film is preferably 2 nm or more, more preferably 4 nm or more. On the other hand, the thickness of the antifouling film is preferably 20 nm or less, more preferably 15 nm or less, and further preferably 10 nm or less.

[0083] (Anti-reflection film)

[0084] The anti-reflection film is a film that suppresses reflection of light, and has a structure in which, for example, a high refractive index layer and a low refractive index layer are stacked.

[0085] The high refractive index layer is, for example, a layer having a refractive index of 1.9 or more at a wavelength of 550 nm, and the low refractive index layer is, for example, a layer having a refractive index of 1.6 or less at a wavelength of 550 nm.

[0086] The anti-reflection film can be a structure having 1 high refractive index layer and 1 low refractive index layer respectively, or can be a structure having more than 2 layers respectively. In the case of a structure comprising more than 2 high refractive index layers and more than 2 low refractive index layers, it is preferred that the high refractive index layer and the low refractive index layer are alternately stacked.

[0087] The materials of the high refractive index layer and the low refractive index layer are selected in consideration of the required degree of anti-reflection, productivity, and the like.

[0088] As materials constituting the high refractive index layer, for example, materials containing elements such as Nb, Ti, Zr, Ta, Si, etc., as specific examples, niobium oxide (Nb2O5), titanium oxide (TiO2), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), silicon nitride, etc. can be listed.

[0089] As materials constituting the low refractive index layer, for example, materials containing Si can be listed, and specific examples thereof include silicon oxide (SiO2), mixed oxides of Si and Sn, mixed oxides of Si and Zr, and mixed oxides of Si and Al.

[0090] As a method for forming an antireflection film (high refractive index layer and low refractive index layer), for example, conventionally known methods using magnetron sputtering, pulse sputtering, AC sputtering, digital sputtering, etc. can be cited. For example, a glass plate is arranged in a chamber filled with a mixed gas atmosphere of an inert gas and oxygen, and each layer is formed using a target containing a desired element.

[0091] The thickness of the anti-reflection film is, for example, 100 nm to 300 nm.

[0092] (Printing Department)

[0093] The printed portion is formed in a frame shape on the surface of the glass plate to shield wiring and the like of the display device.

[0094] The printed portion is formed by printing colored ink on a glass plate.

[0095] Examples of the printing method include a bar coating method, a reverse coating method, a gravure coating method, a die coating method, a roll coating method, and a screen coating method.

[0096] Examples of the color ink include organic inks containing a coloring material such as a dye or a pigment and an organic resin. The color ink is often black or white, but the color is not particularly limited.

[0097] The dye or pigment can be used without particular limitation.

[0098] Examples of organic resins include homopolymers such as epoxy resins, acrylic resins, polyethylene terephthalate, polyethersulfone, polyarylate, polycarbonate, transparent ABS resin, phenolic resin, acrylonitrile-butadiene-styrene resin, polyurethane, polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, polyetheretherketone, polyethylene, polyester, polypropylene, polyamide, and polyimide; copolymers of monomers of these resins with copolymerizable monomers; and the like.

[0099] The thickness of the printed portion is preferably 2 μm or more, more preferably 4 μm or more. On the other hand, the thickness of the printed portion is preferably 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less.

[0100] <Impurities and recovery concentration>

[0101] based on Figure 1 The present production method will be described in more detail.

[0102] Figure 1 This is a flowchart showing the production process of a glass plate and a glass product (cover glass for a display).

[0103] As described above, in the present production method, glass plate cullet (cullet of glass plate) and article cullet (cullet of glass article) are used in addition to glass raw materials.

[0104] like Figure 1 As shown, in the case where the production of glass sheets and the production of glass articles are repeated, a portion of the produced glass articles enters into the glass sheets produced next as article cullets.

[0105] Here, the deposits attached to the outside of the glass plate are referred to as "glass external deposits".

[0106] The deposits deposited on the glass contain elements that may become impurities in the glass sheet.

[0107] For example, a glass plate is conveyed for use in the manufacture of glass products, but iron powder may adhere to the outside of the glass plate during this process. This iron powder is "glass external adhesion."

[0108] The iron powder as the external attachment of the glass contains iron (Fe).

[0109] That is, the glass external deposits of the glass plate cullet contain Fe as an impurity.

[0110] In addition, coatings (antifouling films, antireflection films, printed parts, etc.) disposed on the outside of glass plates in glass articles are also "external deposits on glass".

[0111] For example, a coating layer (printed portion) as an external deposit on the glass contains titanium (Ti), cobalt (Co), nickel (Ni), and the like.

[0112] In addition, the coating (anti-reflection film) as an external attachment of the glass contains niobium (Nb), for example.

[0113] In addition, the coating as a glass outer attachment may contain chromium (Cr), molybdenum (Mo), magnesium (Mg), and copper (Cu).

[0114] Therefore, the glass external attachments of the cullet contain Ti, Co, Ni, Cr, Mo, Mg, Cu, and Nb in addition to Fe.

[0115] That is, the glass deposits of the cullet contain at least one element selected from the group consisting of Fe, Ti, Co, Ni, Cr, Mo, Mg, Cu and Nb (hereinafter referred to as "Group G") as impurities. The glass deposits of the cullet may contain at least two elements selected from Group G.

[0116] For example, the coating as the external deposit of the glass is removed by performing a treatment such as cutting the surface of the glass article during the process of the glass article becoming the cullet (hereinafter referred to as "treatment A"). That is, treatment A is a treatment to remove the external deposit of the glass, which will be described in detail later.

[0117] Treatment A is also performed while the glass plate is being converted into glass plate cullets, thereby removing iron powder as a substance adhering to the outside of the glass.

[0118] However, due to reasons such as insufficient treatment A, foreign matter attached to the cullets (glass plate cullets and article cullets) may not be completely removed.

[0119] In this case, foreign matter in the glass external deposits in the cullet (hereinafter referred to as "glass external deposits") is melted together with the glass portion of the cullet, and enters the interior of the glass plate to be manufactured later.

[0120] Foreign matter that has entered the interior of a glass plate is referred to as “foreign matter within the glass”.

[0121] Unlike impurities outside the glass, impurities inside the glass are basically not removed even if treatment A is performed.

[0122] When the production of glass sheets and glass articles is repeated, the concentration of impurities in the glass of the produced glass sheets gradually increases. For convenience, this is referred to as recovery concentration.

[0123] The influence of recovery concentration is particularly significant when using cullet containing a large amount of impurities (impurities outside the glass).

[0124] Therefore, in the present manufacturing method, based on at least any one of the impurity concentrations of the glass plate cullets and the impurity concentrations of the article cullets (preferably the impurity concentrations of the article cullets), the mixing ratio of the glass raw materials, the mixing ratio of the glass plate cullets, the mixing ratio of the article cullets, the impurity concentrations of the glass raw materials, the impurity concentrations of the glass plate cullets, and the impurity concentrations of the article cullets are adjusted.

[0125] Thus, even when using cullet (particularly article cullet) containing many impurities (impurities outside the glass), a glass plate (glass plate for protective glass) containing a low concentration of impurities (impurities inside the glass) can be manufactured.

[0126] For example, when the concentration of impurities (impurities inside the glass) in the manufactured glass sheet is higher than a predetermined value, the concentration of impurities (impurities outside the glass) in the used cullet is reduced by subjecting the used cullet to treatment A.

[0127] In addition, the concentration of impurities (external impurities in the glass) in the glass plate cullet to be used may be reduced by subjecting the glass plate cullet to the treatment A.

[0128] <P ∞ >

[0129] Hereinafter, the present production method will be described in further detail.

[0130] Here, the concentration P of impurities (impurities in the glass) in the glass sheet at time n is n , find the maximum concentration P of impurities in the glass plate (impurities in the glass) ∞ (The concentration P at n=∞ n ).

[0131] First, the concentration P of impurities (impurities in the glass) in the glass plate at time n+1 is n+1 It is represented by the following formula (1).

[0132]

[0133] The first to third terms on the right side of the above formula (1) have the following meanings.

[0134] The first item: the impurity content of glass raw materials.

[0135] Item 2: The amount of impurities in glass plates and broken glass.

[0136] Item 3: The amount of broken glass in the item.

[0137] In the above formula (1), the parameters are as follows. Figure 1 .

[0138] P: Concentration of impurities in the glass plate (impurities in the glass) [ppm by mass].

[0139] B: Impurity concentration of glass raw material [ppm by mass].

[0140] A i : Concentration of impurities in glass of glass plate cullet [mass ppm].

[0141] A e : Concentration of impurities in glass of the article cullet [mass ppm].

[0142] X i : The concentration of impurities in the glass external attachment when the glass plate cullet is a glass plate [mass ppm].

[0143] X e : The concentration of impurities in the external attachments of glass when the cullet is a glass article [mass ppm].

[0144] R i : The residual rate of glass external attachments of broken glass on glass plates.

[0145] R e : The residual rate of glass external attachments of broken glass objects.

[0146] Assuming that the glass plate is directly used as glass plate cullet, R i =1 (100% by mass). When 30% by mass of the glass external deposits are removed by treatment A, R i It is 0.7 (70 mass %).

[0147] Likewise, in the case of glass items being used directly as cullet, R e=1 (100 mass %). When 30 mass % of the glass external deposits are removed by treatment A, R i It is 0.7 (70 mass %).

[0148] MR B : Mixing ratio of glass raw materials.

[0149] MR i : The mixing ratio of glass plate and broken glass.

[0150] MR e : The mix ratio of the item's broken glass.

[0151] MR B , MR i and MR e The total is 1 (MR B +MR i +MR e =1).

[0152] E B : The residual ratio when the glass raw materials are melted.

[0153] E i : The residual rate of cullet when melting the glass plate.

[0154] E e : The residual rate when the cullet is melted.

[0155] For example, when 10% by mass of a certain sample volatilizes during melting, the residual ratio (residual ratio during melting) is 0.9.

[0156] R i ×X i It refers to the concentration of impurities outside the glass of the glass plate and the cullet.

[0157] A i +R i ×X i It refers to the concentration of impurities in the broken glass of the glass plate (impurities inside the glass + impurities outside the glass).

[0158] R e ×X e It refers to the concentration of impurities outside the glass of broken glass.

[0159] A e +R e ×X e It refers to the concentration of impurities in broken glass (impurities inside the glass + impurities outside the glass).

[0160] Here, the concentration A of impurities in the glass of the glass plate cullet is i, and the concentration of impurities in the glass of the broken glass e The concentration of impurities in the glass of the glass plate at time n is P n Therefore, the above formula (1) is transformed to obtain the following formula (2).

[0161]

[0162] When the above formula (2) is transformed, the recursive formula of the following formula (3) is obtained.

[0163]

[0164] The solution of the recursive formula of the above formula (3) is shown in the following formula (4).

[0165]

[0166] According to the above formula (4), the maximum concentration of impurities in the glass of the glass plate is ∞ It is represented by the following formula (5).

[0167]

[0168] It should be noted that this was first manufactured only from glass raw materials, so MR B =1, by P1=B / E B express.

[0169] Furthermore, the above formula (5) is rearranged.

[0170] First, let E i ×E e =E1, E e ×E B =E2, E i ×E B = E3, the numerator on the right side of the above formula (5) becomes

[0171]

[0172] Next, the denominator on the right side of equation (5) becomes

[0173]

[0174] That is, when the above formula (5) is rearranged, it is expressed by the following formula (6).

[0175]

[0176] In the above formula (6),

[0177] CR B (=B): Concentration of impurities in glass raw material [ppm by mass].

[0178] CR i (=R i ×X i ): Concentration of extra-glass impurities (impurities in the extra-glass attachments) in the glass plate cullet [mass ppm].

[0179] CR e (=R e ×X e ): Concentration of extra-glass impurities (impurities in the glass external attachments) in the cullet [mass ppm].

[0180] MR B : Mixing ratio of glass raw materials.

[0181] MR i : The mixing ratio of glass plate and broken glass.

[0182] MR e : The mix ratio of the item's broken glass.

[0183] E1:E i ×E e .

[0184] E2:E e ×E B .

[0185] E3:E i ×E B .

[0186] E B : Residual rate when glass raw materials are melted.

[0187] E i : The residual rate of cullet when melting the glass plate.

[0188] E e : The residual rate when the cullet is melted.

[0189] Each of E1, E2 and E3 is, for example, a numerical value greater than 0 to 1 or less, and preferably a numerical value in the range of 0.7 to 1.

[0190] So that such P ∞ Adjust each parameter in a way that it is less than the specified value.

[0191] For example, regarding a certain impurity, ∞ The case where the concentration was suppressed to less than 360 mass ppm was studied.

[0192] In Examples 1 and 2 shown in Table 1 below, R e (The residual rate of the glass external attachment of the broken glass articles) is different from each other.

[0193]

[0194] As shown in Table 1 above, in R e In Example 1, where the concentration P1 is 0.02 (2 mass %), although the first concentration P1 and the second concentration P2 are less than 360 mass ppm, the maximum concentration P ∞ The content was 365.7 mass ppm and was not suppressed to less than 360 mass ppm.

[0195] It can be seen that in the conventional manufacture of glass sheets (Example 1), sometimes the influence of recovery concentration causes undesirable conditions (recorded as "×" in the "Long-term management" column in Table 1 above, "×" means that P ∞ Suppressed to less than 360 mass ppm).

[0196] Therefore, in Example 2, for example, the conditions of the treatment A described later are changed for the cullet used, and the external attachments of the glass are further removed compared with Example 1, thereby R e Thus, not only the values ​​of the initial concentration P1 and the second concentration P2, but also the maximum concentration P ∞ The concentration of P was also reduced to 351.4 mass ppm, which was suppressed to less than 360 mass ppm (in the column of "Long-term management" in Table 1 above, "○" indicates that P ∞ Suppressed to less than 360 mass ppm).

[0197] It can be seen that by calculating the maximum concentration P of impurities in the glass plate ∞ , and the calculated P ∞ Adjusting various parameters in a way that is less than the specified value can suppress the impact of recovery concentration for a long time.

[0198] It should be noted that in the example of Table 1 above, by changing the residual rate of the glass outer attachment of the cullet (R e ) as a parameter, and changed the impurity concentration of the item cullet (A e +R e ×X e ), but is not limited to them.

[0199] Examples of parameters that can be changed include the mixing ratio of glass raw materials (MR B ), glass plate cullet mixing ratio (MR i ), the mixing ratio of broken glass (MR e ), the concentration of impurities in glass raw materials (B), the concentration of impurities in glass plate cullet (A i +R i ×X i), and the concentration of impurities in the cullet (A e +R e ×X e ).

[0200] It should be noted that, in the example of Table 1, by subjecting the article cullet to the treatment A, the amount of foreign matter attached to the article cullet was reduced by 50% by mass.

[0201] The reduction rate of the deposits on the glass surface by the treatment A is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more.

[0202] In addition, from the perspective of cost reduction, MR e (The mixing ratio of the cullet in the article) is higher, specifically, preferably 0.02 (2 mass %) or more, and more preferably 0.08 (8 mass %) or more. e A value of 0.1 (10% by mass) is preferred.

[0203] It should be noted that when calculating P represented by the above formula (6) ∞ When the actual CR is measured i and CR e It's quite difficult.

[0204] Therefore, it can also replace R i ×X i And use A i +R i ×X i As CR i Similarly, R e ×X e And use A e +R e ×X e As CR e .

[0205] In this case, CR i Refers to the impurity concentration of the entire glass plate cullet, CR e Refers to the impurity concentration of the entire glass fragment.

[0206] By this substitution, P ∞ The value of increases, so the P ∞ It is safer to control the value to be smaller than the specified value.

[0207] About E B 、E i and E e (Furthermore, their products are E1, E2 and E3), and the measured values ​​can be used or they can be taken as parameters.

[0208] In this case as well, as described above, each of E1, E2, and E3 is, for example, a numerical value greater than 0 to 1 or less, and preferably a numerical value in the range of 0.7 to 1.

[0209] <Processing A>

[0210] As the treatment A, for example, there can be mentioned a treatment of simultaneously performing surface removal of a sample and particle size adjustment.

[0211] In this case, specifically, for example, a commercially available crushing device (product name: micro classifier, manufactured by Donico Inter) is preferably used.

[0212] In the micro-classifier, multiple rotors rotate, and the input samples rub against each other through the force of the rotors and the wind from the rotors. According to the principle of air sorting, only the part below the specified size is rolled up. In this way, the surface removal of the sample and the particle size adjustment are carried out at the same time.

[0213] As the treatment A, for example, there can be mentioned other than this a sandblasting treatment and an acid treatment.

[0214] Sandblasting is a process in which abrasive materials (abrasive materials) such as steel grains and sand are blasted onto the surface of a sample using compressed air, thereby removing at least a portion of the surface of the sample.

[0215] In the acid treatment, specifically, an aqueous solution containing an acid is used as an etching solution to etch the sample, thereby dissolving the surface of the sample. In other words, at least a portion of the surface of the sample is removed.

[0216] Examples of the acid contained in the etching solution include hydrofluoric acid (HF), sulfuric acid, nitric acid, hydrochloric acid, and hexafluorosilicic acid, and hydrofluoric acid is preferred.

[0217] The etching method is not particularly limited, but for example, a method of immersing a sample in an etching solution is preferred.

[0218] Conditions such as the acid content in the etching solution, the temperature of the etching solution, and the immersion time in the etching solution (etching time) can be adjusted appropriately.

[0219] When the external deposits on the glass are, for example, iron powder (iron powder attached to the outside of the glass plate during the conveyance of the glass plate), the process A may be a process of removing the iron powder using a known magnetic separator or metal detector.

[0220] It should be noted that when the treatment A is understood as a treatment for reducing the amount of deposits attached to the outside of the glass, the treatment A is not limited to the above-mentioned treatment.

[0221] For example, processing A can also be done by converting R e(Residual rate of glass external attachments of cullet) High cullet a and R e Low item broken glass b (wherein, item broken glass b A e and X e Mixed with the same item as glass cullet a), thereby reducing R e In Figure 1 In the example, process A is described in two places, and the two processes A may be different processes.

[0222] It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2022-106958 filed on July 1, 2022 are incorporated herein by reference in the disclosure of the present invention.

Claims

1. A method for producing a glass plate, the method comprising repeatedly performing a step of melting glass raw materials and cullet to produce a glass plate, wherein: The glass sheet is further processed to become a glass article, The glass article is a protective glass for a display having the glass plate and a coating layer disposed on a surface of the glass plate. As the cullet, glass plate cullet as cullet of the glass plate and article cullet as cullet of the glass article are used. At least any one of the mixing ratio of the glass raw materials, the mixing ratio of the glass plate cullets, the mixing ratio of the article cullets, the impurity concentration of the glass raw materials, the impurity concentration of the glass plate cullets, and the impurity concentration of the article cullets is adjusted based on at least any one of the impurity concentration of the glass plate cullets and the impurity concentration of the article cullets.

2. The method for manufacturing a glass plate according to claim 1, wherein: The impurity concentration of the article cullet is reduced by subjecting the article cullet to a treatment A for removing the deposits attached to the outside of the glass plate, that is, the deposits outside the glass.

3. The method for manufacturing a glass plate according to claim 2, wherein: The glass external deposits of the cullet contain at least one element selected from the group consisting of Fe, Ti, Co, Ni, Cr, Mo, Mg, Cu and Nb as impurities.

4. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The mixing ratio of the cullet in the article is 2% by mass or more.

5. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The mixing ratio of the cullet in the article is 8% by mass or more.

6. The method for manufacturing a glass plate according to claim 2 or 3, wherein: By performing the treatment A, the external deposits on the cullet of the article are reduced by 50% by mass or more.

7. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The impurity concentration of the glass plate cullet is reduced by subjecting the glass plate cullet to a treatment A for removing the deposits attached to the outside of the glass plate, that is, the deposits outside the glass.

8. The method for manufacturing a glass plate according to claim 7, wherein: The glass external deposits of the glass plate cullet contain Fe as an impurity.

9. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The impurity concentration of the glass plate at time n is set to P n When the maximum concentration of impurities in the glass sheet is expressed by the following formula (6): ∞ Less than the specified value, ， In the above formula (6), CR B : Impurity concentration of the glass raw material, CR i : The impurity concentration of the entire glass plate cullet, CR e : The impurity concentration of the entire cullet, MR B : The mixing ratio of the glass raw materials, MR i : The mixing ratio of the glass plate cullet, MR e : The mixing ratio of the broken glass of the article, E1: a value greater than 0 to less than or equal to 1, E2: a value greater than 0 to less than or equal to 1, E3: a value greater than 0 to less than or equal to 1, CR B , CR i and CR e The unit of impurity concentration is expressed in ppm by mass.

10. The method for manufacturing a glass plate according to claim 9, wherein: In the formula (6), E1, E2 and E3 are each in the range of 0.7 to 1.

11. The method for manufacturing a glass plate according to claim 9, wherein: In formula (6), E1 is E i ×E e , E2 is E e ×E B , E3 is E i ×E B , E B The residual rate of the glass raw material when it is melted is i The residual rate of the cullet when the glass plate is melted, E e It is the residual rate of the cullet when the object is melted.

12. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The impurity concentration of the glass plate at time n is set to P n When the maximum concentration of impurities in the glass sheet is expressed by the following formula (6): ∞ Less than the specified value, ， In the above formula (6), CR B : Impurity concentration of the glass raw material, CR i : The impurity concentration of the deposits attached to the outside of the glass plate in the glass plate cullet, that is, the impurity concentration of the deposits outside the glass, CR e : The impurity concentration of the deposits attached to the outside of the glass plate in the cullet, that is, the impurity concentration of the deposits outside the glass, MR B : The mixing ratio of the glass raw materials, MR i : The mixing ratio of the glass plate cullet, MR e :The mixing ratio of the broken glass of the above items, E1:E i ×E e , E2:E e ×E B , E3:E i ×E B , E B : The residual rate when the glass raw material is melted, E i : The residual rate when the cullet of the glass plate is melted, E e : The residual rate when the cullet of the article is melted, CR B , CR i and CR e The unit of impurity concentration is expressed in ppm by mass.

13. The method for manufacturing a glass plate according to claim 12, wherein: In the formula (6), E1, E2 and E3 are each in the range of 0.7 to 1.

14. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The coating layer includes at least one selected from the group consisting of an antifouling film, an antireflection film, and a printed portion.

15. The method for producing a glass plate according to any one of claims 1 to 3, wherein: The glass plate is a glass plate subjected to chemical strengthening treatment.

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