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WO2018062141A1 - Method for producing chemically toughened glass - Google Patents

Method for producing chemically toughened glass Download PDF

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Publication number
WO2018062141A1
WO2018062141A1 PCT/JP2017/034671 JP2017034671W WO2018062141A1 WO 2018062141 A1 WO2018062141 A1 WO 2018062141A1 JP 2017034671 W JP2017034671 W JP 2017034671W WO 2018062141 A1 WO2018062141 A1 WO 2018062141A1
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WO
WIPO (PCT)
Prior art keywords
glass
chemical strengthening
inorganic salt
strength
acid treatment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2017/034671
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French (fr)
Japanese (ja)
Inventor
出 鹿島
祐輔 藤原
洋一 世良
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AGC Inc
Original Assignee
Asahi Glass Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Asahi Glass Co Ltd filed Critical Asahi Glass Co Ltd
Priority to JP2018542579A priority Critical patent/JP6919658B2/en
Priority to KR1020197008010A priority patent/KR102436191B1/en
Priority to CN201780060568.4A priority patent/CN109803938B/en
Publication of WO2018062141A1 publication Critical patent/WO2018062141A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
    • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
    • C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface

Definitions

  • the present invention relates to a method for producing chemically strengthened glass.
  • a thin plate-like cover glass is formed so as to have a wider area than the image display portion in order to enhance display protection and beauty. Is placed in front of the display. Although glass has a high theoretical strength, the strength is greatly reduced due to scratches. Therefore, a chemically strengthened glass with a compressive stress layer formed on the glass surface by ion exchange or the like is used for the cover glass that requires strength. Yes.
  • the cover glass With the demand for weight reduction and thinning of flat panel display devices, it is also required to make the cover glass itself thinner. Accordingly, the cover glass is required to have further strength on the surface in order to satisfy its purpose.
  • Patent Document 1 discloses a method of performing acid treatment and alkali treatment after chemical strengthening with an inorganic salt containing a specific salt.
  • the depth of the compressive stress layer (defined as a depth at which the compressive stress value becomes zero, hereinafter referred to as DOC; Depth of Compression) is increased in order to obtain high strength.
  • DOC Depth of Compression
  • the surface strength is improved by polishing after the chemical strengthening treatment, but the glass surface may be damaged by the polishing, and the surface strength may be lowered. Furthermore, there is a possibility that the warping of the glass increases due to polishing.
  • the present invention does not limit the temperature condition and time for chemical strengthening, and does not weaken the strength of the glass even when chemical strengthening treatment is performed for a long time at a high temperature.
  • a method for producing tempered glass is provided.
  • the present inventors conducted a chemical strengthening step in which the pH of the salt used for chemical strengthening is in a predetermined range and an acid treatment step of acid-treating the glass after the chemical strengthening step.
  • the present invention is completed by finding that a chemically strengthened glass showing a deep DOC and a high surface strength can be obtained even if a chemical strengthening treatment is performed at a high temperature for a long time without limiting the temperature conditions and time for chemical strengthening. It came to.
  • the present invention is as follows. 1. Chemistry in which glass is brought into contact with an inorganic salt having a hydrogen ion index (pH) of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate when ionized into a 10% by mass aqueous solution, and ion exchange is performed. Strengthening process, A method for producing chemically tempered glass, comprising: an acid treatment step in which the glass after the chemical tempering step is contacted with an acidic solution having a hydrogen ion index (pH) of less than 7.0. 2. 2. 2.
  • the method for producing chemically strengthened glass according to 1 or 2 wherein the chemical strengthening step is a step of bringing the glass into contact with the inorganic salt at 400 ° C. or higher for 2 hours or more for ion exchange. 4).
  • the surface strength F (N) measured by the ball-on-ring test under the following conditions is F ⁇ 1000 ⁇ t 2 with respect to the thickness t (mm) of the glass plate. 5.
  • the sphere is lowered at a descending speed of 1 mm / min and loaded onto the center of the ring, and the breaking load (unit N) when the glass plate is broken is defined as BOR strength.
  • the value is the surface strength F (N).
  • the fracture start point of the glass plate is 2 mm or more away from the load point of the sphere, it is excluded from the data for calculating the average value.
  • the glass is chemically strengthened using an inorganic salt having a pH within a predetermined range, so that the Si—O—Si bond of the glass is appropriately adjusted by OH ⁇ in the inorganic salt.
  • an inorganic salt having a pH within a predetermined range so that the Si—O—Si bond of the glass is appropriately adjusted by OH ⁇ in the inorganic salt.
  • the temperature condition and time for chemical strengthening are not limited, and even if chemical strengthening treatment is performed at a high temperature for a long time, deep DOC is exhibited and the surface strength is high. Chemically tempered glass can be easily obtained.
  • FIG. 1 (a) to 1 (d) are schematic views showing a process for producing chemically strengthened glass according to the present invention.
  • FIG. 2 is a schematic diagram for explaining a ball-on-ring test method.
  • FIG. 3A is an AFM image of a glass surface having surface polishing flaws
  • FIG. 3B is an AFM image of a glass surface having no surface polishing flaws.
  • FIG. 4A is a diagram illustrating a state where white clouding is not generated in the glass surface
  • FIG. 4B is a diagram illustrating a state where white clouding is generated in the glass surface.
  • 5A is the stress profile of the chemically strengthened glass obtained in Examples 1 and 3 and Comparative Example 1, FIG.
  • FIG. 5B is the stress profile of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6, and FIG. The stress profile of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11 is shown.
  • 6A and 6B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 1 and 5 and Comparative Examples 1, 4 and 5.
  • FIG. 7A and 7B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6.
  • FIG. 8A and 8B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11.
  • mass% and “wt%”, “mass ppm” and “weight ppm” have the same meaning.
  • ppm when “ppm” is simply described, it indicates “weight ppm”.
  • the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 7.5 or more and 10.5 or less, and an inorganic salt containing at least one of sodium nitrate and potassium nitrate is glass.
  • Na in the glass and K in the inorganic salt are ion-exchanged to form a compressive stress layer on the glass surface, and the surface layer of the compressive stress layer is modified to lower the density. This is a step of forming a low density layer.
  • the inorganic salt has a hydrogen ion index (pH) of 7.5 or more, preferably 8.0 or more, and more preferably 8.5 or more when a 10% by mass aqueous solution is used. Further, the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 10.5 or less, preferably 10.0 or less, and more preferably 9.5 or less.
  • the Si—O—Si bond of the glass is appropriately cut by OH ⁇ in the inorganic salt, and a low-density layer in which the surface layer of the compressive stress layer is modified on the glass surface is formed. can do.
  • the pH of the inorganic salt can be measured at 25 ° C. using a pH meter such as a handy type pH meter D-71S manufactured by Horiba.
  • the inorganic salt preferably contains at least one salt selected from the group consisting of KNO 2 , NaNO 2 , K 2 CO 3 , Na 2 CO 3 , KHCO 3 , NaHCO 3 , KOH or NaOH.
  • the pH of the inorganic salt can be appropriately adjusted depending on the amount.
  • the inorganic salt contains at least one of sodium nitrate and potassium nitrate.
  • the inorganic salt By containing at least one of sodium nitrate and potassium nitrate in the inorganic salt, it becomes a molten state below the strain point of the glass, and handling becomes easy in a general temperature range when chemical strengthening treatment is performed.
  • sodium nitrate in the inorganic salt chemically strengthened glass having a large DOC can be obtained at a CTlimit value or less.
  • the CTlimit value is empirically known to be ⁇ 38.7 ⁇ ln (t) +48.2 [MPa].
  • t represents the plate thickness of the glass, and the unit is mm.
  • the content of sodium nitrate in the inorganic salt is preferably 1% by mass or more, more preferably 5% by mass or more.
  • the content of sodium nitrate in the inorganic salt refers to the sodium concentration of the liquid phase salt in which the inorganic salt is in a liquid state.
  • the content of sodium nitrate in the inorganic salt When the content of sodium nitrate in the inorganic salt is 1% by mass or more, it becomes a molten state below the strain point of the glass, and handling becomes easy in a general temperature range when chemical strengthening treatment is performed.
  • the content of sodium nitrate in the inorganic salt is determined by appropriately adjusting so as to obtain a desired surface compressive stress value (CS, unit is MPa).
  • the inorganic salt may contain other chemical species as long as the effects of the present invention are not impaired.
  • alkali salts such as sodium chloride, potassium chloride, sodium borate and potassium borate
  • examples include chlorides and alkali borates. These may be added alone or in combination of two or more.
  • the content of KNO 2 in the inorganic salt is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and further preferably 0.6% by mass. % Or more. Moreover, 10.0 mass% or less is preferable, More preferably, it is 8.0 mass% or less, More preferably, it is 6.0 mass% or less.
  • the pH of the inorganic salt when the aqueous solution is 10% by mass can be 7.5 or more and 10.5 or less.
  • Examples of the method of bringing the glass into contact with the inorganic salt include a method of applying a paste-like inorganic salt, a method of spraying an aqueous solution of an inorganic salt onto the glass, and a method of immersing the glass in a salt bath of a molten salt heated to a melting point or higher. Although possible, in these, the method of immersing in molten salt is preferable.
  • the glass used in the method of the present invention may contain sodium as long as it contains sodium and has a composition that can be strengthened by molding and chemical strengthening treatment.
  • Specific examples include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.
  • the method for producing the glass is not particularly limited, and a desired glass raw material is charged into a continuous melting furnace, and the glass raw material is heated and melted preferably at 1500 to 1600 ° C., clarified, and then supplied to a molding apparatus. It can be produced by forming into a plate shape and slowly cooling it.
  • various methods can be adopted for forming the glass.
  • various forming methods such as a down draw method (for example, an overflow down draw method, a slot down method, a redraw method, etc.), a float method, a roll out method, and a press method can be adopted.
  • the thickness of the glass is not particularly limited, but is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less in order to effectively perform the chemical strengthening treatment.
  • the shape of the glass used in the method of the present invention is not particularly limited.
  • various shapes of glass such as a flat plate shape having a uniform plate thickness, a shape having a curved surface on at least one of the front surface and the back surface, and a three-dimensional shape having a bent portion can be employed.
  • the glass composition used in the method of the present invention include the following glass compositions.
  • (Viii) expressed in mole percentages on the oxide basis, SiO 2 67-75%, Al 2 O 3 0-4%, Na 2 O 7-15%, K 2 O 1-9%, MgO 6 to 14% and 0 to 1.5% of ZrO 2 , the total content of SiO 2 and Al 2 O 3 is 71 to 75%, the total content of Na 2 O and K 2 O is 12 to Glass which is 20% and contains CaO when its content is less than 1%.
  • the glass is immersed in a molten salt of an inorganic salt in a molten salt bath, and metal ions (Na ions) in the glass are replaced with metal ions (K ions) having a large ionic radius in the molten salt. Done in By this ion exchange, the composition of the glass surface can be changed to form the compressive stress layer 20 having a high density on the glass surface [FIGS. 1 (a) to 1 (b)]. Since compressive stress is generated by increasing the density of the glass surface, the glass can be strengthened.
  • the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 7.5 or more and 10.5 or less, and at least one of sodium nitrate and potassium nitrate is used.
  • the Si—O—Si bond of the glass is appropriately cut by OH ⁇ in the inorganic salt, and the surface layer of the compressive stress layer is modified to reduce the density.
  • the density layer 10 is formed [FIGS. 1B to 1C].
  • the density of the chemically strengthened glass gradually increases from the outer edge of the intermediate layer 30 (bulk) existing in the center of the glass toward the surface of the compressive stress layer. There is no clear boundary between 20 and 20 where the density changes rapidly.
  • the intermediate layer is a layer present in the center of the glass and sandwiched between the compressive stress layers. Unlike the compressive stress layer, this intermediate layer is a layer that is not ion-exchanged.
  • the chemical strengthening step can be performed as follows.
  • the glass is preheated and the molten salt is adjusted to the processing temperature for chemical strengthening.
  • the preheated glass is immersed in the molten salt for a predetermined time, and then the glass is pulled up from the molten salt and allowed to cool.
  • shape processing according to a use, for example, mechanical processing, such as a cutting
  • the preheating temperature of the glass depends on the temperature at which the molten salt is immersed, but is generally preferably 100 ° C. or higher.
  • the temperature at which chemical strengthening is performed is preferably 400 ° C. or higher, more preferably 450 ° C. or higher, and further preferably 470 ° C. or higher from the viewpoint of obtaining chemically strengthened glass having a deep DOC.
  • the upper limit of the temperature at which chemical strengthening is performed is not particularly limited, but typically, the strain point of the glass to be tempered (usually 500 to 600 ° C.) or less is preferable.
  • the immersion time of the glass in the molten salt depends on the chemical strengthening temperature, but is preferably 2 hours or longer, more preferably 4 hours or longer, and even more preferably 8 hours or longer from the viewpoint of obtaining chemically strengthened glass having a deep DOC. It is.
  • the upper limit is not particularly limited, but is usually 48 hours or shorter, and preferably 24 hours or shorter from the viewpoint of productivity.
  • the depth (DOC) of the compressive stress layer formed on the surface layer of the glass after the chemical strengthening step is preferably 35 ⁇ m or more, more preferably 45 ⁇ m or more, and still more preferably. It is 55 ⁇ m or more.
  • the compressive stress value of the chemically strengthened glass produced by the method of the present invention is preferably 100 MPa or more, more preferably 200 MPa or more, and further preferably 300 MPa or more.
  • the upper limit is not particularly limited, but is typically 1200 MPa or less.
  • the depth of the compressive stress layer can be measured using an EPMA (electron probe micro analyzer) or a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho).
  • EPMA electron probe micro analyzer
  • FSM-6000 manufactured by Orihara Seisakusho
  • the thickness of the low density layer is preferably 10 nm or more, and more preferably 20 nm or more from the viewpoint of the glass surface removal amount.
  • the thickness of the low density layer can be controlled by the sodium concentration, temperature or time in the molten salt in the chemical strengthening step.
  • the low-density layer After removing the low-density layer in the acid treatment step, the low-density layer can be further removed by performing an alkali treatment.
  • the density of the low density layer is preferably lower than the density of the region (bulk) deeper than the ion-exchanged compressive stress layer from the viewpoint of glass surface removability.
  • the thickness of the low-density layer is determined from the period ( ⁇ ) measured by the X-ray reflectivity method (X-ray-Reflectometry: XRR).
  • the density of the low density layer is determined by the critical angle ( ⁇ c) measured by XRR.
  • SEM scanning electron microscope
  • the above-described chemical strengthening treatment with an inorganic salt having a hydrogen ion index (pH) of 7.5 to 10.5 and containing at least one of sodium nitrate and potassium nitrate in a 10% by mass aqueous solution.
  • the chemical strengthening treatment described above is a chemical strengthening treatment step in which at least one of the conditions of the inorganic salt composition, hydrogen ion index, chemical strengthening temperature and chemical strengthening time is changed. You may perform several times before and after a process.
  • the glass is cleaned using industrial water, ion exchange water, or the like. Of these, ion-exchanged water is preferred.
  • the washing conditions vary depending on the washing solution used, but when ion-exchanged water is used, washing at 0 to 100 ° C. is preferable because the attached salt is completely removed.
  • the glass cleaned after the chemical strengthening step is further subjected to acid treatment.
  • the acid treatment of glass is performed by bringing the glass into contact with an acidic solution having a hydrogen ion index (pH) of less than 7.0.
  • the solution used for the acid treatment is not particularly limited as long as it is acidic, and may have a pH of less than 7.0.
  • the acid used may be a weak acid or a strong acid. Specifically, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, carbonic acid or citric acid are preferred. These acids may be used alone or in combination.
  • the temperature at which the acid treatment is performed varies depending on the type, concentration, and time of the acid used, but is preferably 100 ° C. or lower. Moreover, 20 degreeC or more is preferable from a viewpoint of making it easy to remove a low density layer.
  • the time for the acid treatment varies depending on the type, concentration and temperature of the acid used, but is preferably 10 seconds to 5 hours from the viewpoint of productivity, and more preferably 1 minute to 2 hours.
  • the concentration of the solution used for the acid treatment varies depending on the type of acid used, the time, and the temperature, but is preferably a concentration with less concern about container corrosion, and specifically 0.1% by mass to 20% by mass.
  • Specific conditions for the acid treatment include, for example, a condition in which the glass after the chemical strengthening step is preferably contacted with a 0.1% by mass to 10% by mass nitric acid aqueous solution at 35 to 75 ° C. for 1 to 15 minutes. Can be mentioned.
  • the acid treatment accelerates the reduction of the density of the glass surface and exposes the surface layer from which part or all of the low density layer has been removed [FIGS. 1 (c) and (d)]. Thereby, a chemically strengthened glass having a significantly improved surface strength is obtained. Further, since the scratches existing on the glass surface are also removed at the same time by removing the low density layer, this point is also considered to contribute to the strength improvement.
  • an alkali treatment may be performed after the acid treatment.
  • the surface strength can be further increased by increasing the removal amount of the low-density layer as compared with the case of only the acid treatment.
  • the solution used for the alkali treatment is not particularly limited as long as it is basic, and may have a pH exceeding 7.0, and a weak base or a strong base may be used. Specifically, a base such as sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate is preferred. These bases may be used alone or in combination.
  • the temperature at which the alkali treatment is performed varies depending on the type, concentration and time of the base used, but is preferably 0 to 100 ° C, more preferably 10 to 80 ° C, and particularly preferably 20 to 60 ° C. If it is this temperature range, there is no possibility that glass will corrode and it is preferable.
  • the alkali treatment time varies depending on the type, concentration and temperature of the base used, it is preferably 10 seconds to 5 hours from the viewpoint of productivity, and more preferably 1 minute to 2 hours.
  • the concentration of the solution used for the alkali treatment varies depending on the type of base used, the time, and the temperature, but is preferably 0.1% by mass to 20% by mass from the viewpoint of glass surface removability.
  • the glass after the acid treatment step is preferably contacted with a 0.1% to 10% by weight sodium hydroxide aqueous solution at 35 to 75 ° C. for 1 to 15 minutes.
  • the condition to make is mentioned.
  • the surface treatment from which the low-density layer is further removed is exposed by the alkali treatment as compared with the glass after the acid treatment step. Thereby, the chemically strengthened glass whose surface strength is further improved is obtained. Moreover, since the flaw which existed on the glass surface is further removed, it is thought that this point contributes to further improvement of surface strength.
  • cleaning process it is preferable to have the same washing
  • the amount of the low density layer to be removed depends on the acid treatment step and at least one of the conditions of the acid treatment step and the alkali treatment step.
  • FIG. 1D shows a mode in which the low density layer 10 is completely removed, a part of the low density layer 10 may be removed and a part may remain. From the viewpoint of improving the strength, the effect can be obtained even if the entire low-density layer is not removed.
  • ⁇ Chemical tempered glass> The surface strength of the chemically strengthened glass produced by the method of the present invention can be evaluated by a ball-on-ring test shown below.
  • the chemically strengthened glass produced according to the present invention preferably satisfies F ⁇ 1000 ⁇ t 2, and more preferably F ⁇ 1200 ⁇ t 2 [wherein F is the BOR strength (N) measured by a ball-on-ring test. And t is the thickness (mm) of the glass plate. ].
  • F is the BOR strength (N) measured by a ball-on-ring test.
  • t is the thickness (mm) of the glass plate. ].
  • FIG. 2 shows a schematic diagram for explaining the ball-on-ring test.
  • a glass plate 1 is used with a pressure jig 2 (hardened steel, diameter 10 mm, mirror finish) made of SUS304 with the glass plate 1 placed horizontally. And the strength of the glass plate 1 is measured.
  • a pressure jig 2 hardened steel, diameter 10 mm, mirror finish
  • a glass plate 1 serving as a sample is horizontally installed on a receiving jig 3 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish).
  • a pressurizing jig 2 for pressurizing the glass plate 1 is installed above the glass plate 1.
  • the central region of the glass plate 1 is pressurized from above the glass plate 1.
  • the test conditions are as follows. Lowering speed of the pressure jig 2: 1.0 (mm / min) At this time, the breaking load (unit N) when the glass plate is broken is defined as BOR strength, and the average value of 20 measurements of the BOR strength is defined as surface strength F (N). However, in the case where the fracture start point of the glass plate is 2 mm or more away from the load point of the sphere, it is excluded from the data for calculating the average value.
  • the depth (DOC) of the compressive stress layer of the chemically strengthened glass produced by the method of the present invention is preferably 35 ⁇ m or more, more preferably 45 ⁇ m or more, and further preferably 55 ⁇ m or more.
  • the thickness of the low-density layer removed by the acid treatment step or the alkali treatment step is about 1000 nm as in the example even if it is large from about 10 nm, so the depth (DOC) of the compressive stress layer is The depth (DOC) formed in the chemical strengthening step and the depth (DOC) after the acid treatment step or the alkali treatment step are substantially the same.
  • the surface compressive stress value (CS) of the chemically strengthened glass produced by the method of the present invention is preferably 100 MPa or more, more preferably 200 MPa or more, and further preferably 300 MPa or more.
  • the upper limit is not particularly limited, but is typically 1200 MPa or less.
  • the compressive stress value can be measured using an EPMA (Electron Probe Micro Analyzer) or a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho).
  • the compressive stress value can be calculated using a stress profile calculation method disclosed in Japanese Unexamined Patent Publication No. 2016-142600.
  • the chemically strengthened glass produced by the method of the present invention has an internal tensile stress (CT) of preferably 72 MPa or less, more preferably 62 MPa or less, and further preferably 52 MPa or less.
  • CT internal tensile stress
  • the lower limit is not particularly limited, but is typically 20 MPa or more.
  • the stress distribution was measured, and the stress distribution was integrated with the thickness to obtain the CT value.
  • the CTlimit value is empirically known to be -38.7 ⁇ ln (t) +48.2 [MPa].
  • t represents the plate thickness of the glass, and the unit is mm.
  • the chemically strengthened glass manufactured by the method of the present invention may be manufactured by performing a polishing step of polishing the glass surface before the chemical strengthening step.
  • polishing in the present invention refers to smoothing by polishing the glass surface using abrasive grains.
  • the presence or absence of polishing flaws that may occur in the polishing process can be determined by surface observation with an AFM (Atomic Force Microscope), and a scratch having a length of 5 ⁇ m or more and a width of 0.1 ⁇ m or more is present in a 10 ⁇ m ⁇ 5 ⁇ m region. When two or more are not present, it can be said that there is no polishing scratch on the surface.
  • FIG. 3A shows a state having surface polishing flaws
  • FIG. 3B shows a state having no surface polishing flaws.
  • the chemically strengthened glass produced by the production method of the present invention has a surface roughness Ra in a measurement range of 10 ⁇ m ⁇ 5 ⁇ m measured by AFM surface observation, preferably 0.2 nm or more, more preferably 0.25 nm or more. is there. Moreover, it is preferably 1.5 nm or less, more preferably 1.2 nm or less.
  • the surface roughness of the chemically tempered glass plate which has not been polished is usually 0.15 nm or more and less than 0.2 nm.
  • the total amount was 100% by mass as KNO 3 .
  • the pH of the inorganic salt is a value measured with a handy type pH meter D-71S manufactured by Horiba, Ltd. at 25 ° C. when the aqueous solution is 10% by mass.
  • a 6 mass% nitric acid aqueous solution was prepared in a beaker, and the temperature was adjusted to 40 ° C. using a water bath.
  • the glass obtained in the chemical strengthening step was immersed in the adjusted aqueous nitric acid solution for 120 seconds, acid-treated, then washed several times with pure water, and then dried by air blowing. The glass thus obtained was subjected to the next step.
  • Alkali treatment process A 4.0 wt% aqueous sodium hydroxide solution was prepared in a beaker, and the temperature was adjusted to 40 ° C. using a water bath. The glass obtained in the acid treatment step was immersed in the prepared sodium hydroxide aqueous solution for 120 seconds, subjected to alkali treatment, then washed several times with pure water, and then dried by air blowing.
  • polishing process cerium oxide having an average particle diameter (d50) of 1 ⁇ m was dispersed in water to prepare a slurry, and the resulting slurry was used to apply a pressure of 0. Under the condition of 1 kPa, both surfaces of the flat glass were polished for a total of about 6 ⁇ m.
  • FIG. 2 is a schematic diagram for explaining the ball-on-ring test used in the present invention.
  • the glass plate 1 aluminosilicate glass A in the following examples
  • the glass plate 1 is pressed using a pressure jig 2 made of SUS304 (hardened steel, diameter 10 mm, mirror finish). The strength of the glass plate 1 was measured.
  • a glass plate 1 serving as a sample is horizontally installed on a receiving jig 3 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish).
  • a pressurizing jig 2 for pressurizing the glass plate 1 is installed above the glass plate 1.
  • the central region of the glass plate 1 was pressurized from above the glass plate 1 obtained in the examples and comparative examples.
  • the test conditions are as follows. Lowering speed of the pressure jig 2: 1.0 (mm / min)
  • the breaking load (unit N) when the glass was broken was defined as the BOR strength
  • the average value of 20 measurements of the BOR strength was defined as the surface strength F (N).
  • the surface strength F (N) depends on the thickness t (mm) of the glass plate.
  • the comparison is made by normalizing (normalizing) the thickness t (mm) of the glass plate.
  • the value normalized (normalized) by the thickness t (mm) of the glass plate was defined as a (unit: N / mm 2 ).
  • the surface compressive stress value (CS) and the depth (DOC, unit: ⁇ m) of the compressive stress layer were measured using a surface stress meter (FSM-6000) manufactured by Orihara Seisakusho.
  • the compressive stress value (CS) and the compressive stress layer depth (DOC) were calculated using the stress profile calculation method disclosed in Japanese Patent Application Laid-Open No. 2016-142600.
  • the tensile stress value (CT, unit MPa) was calculated by measuring the stress distribution using the stress profile calculation method disclosed in Japanese Patent Application Laid-Open No. 2016-142600 and integrating the stress distribution with the thickness.
  • polishing scratches The presence or absence of polishing flaws was determined by surface observation with AFM. When there were no two or more scratches having a length of 5 ⁇ m or more and a width of 0.1 ⁇ m or more in a 10 ⁇ m ⁇ 5 ⁇ m region, the surface was made free of polishing scratches.
  • FIG. 4A is a diagram illustrating a state where white clouding is not generated in the glass surface
  • FIG. 4B is a diagram illustrating a state where white clouding is generated in the glass surface.
  • ⁇ No white clouding occurred in the glass surface.
  • X White cloudiness is generated in the glass surface.
  • a chemical strengthening step in which the glass is brought into contact with an inorganic salt having a pH of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate, and the chemical strengthening step.
  • the chemically tempered glasses of Examples 1 to 12 obtained by the production method of the present invention including the acid treatment step of bringing the latter glass into contact with an acidic solution having a pH of less than 7 and acid-treating were obtained.
  • the chemically tempered glasses of Examples 1 to 12 have higher surface strength even when subjected to chemical tempering treatment at a higher temperature for a longer time than the chemically tempered glasses obtained in Comparative Examples 1 to 11, and the depth of the compressive stress layer ( DOC) is deep and shows a high surface compressive stress value (CS), and there is no occurrence of white haze in the glass surface, which is excellent in appearance quality.
  • Comparative Examples 1 and 2 in which the pH was 7.5 or more and 10.5 or less, and the acid treatment was not performed after the chemical strengthening step in which the glass was brought into contact with an inorganic salt containing at least one of sodium nitrate and potassium nitrate to perform ion exchange.
  • the chemically tempered glasses of 4, 6, 7, 10 and 11 had lower surface strength than the chemically tempered glasses obtained in the examples.
  • white cloudiness occurred in the glass surface.
  • polishing treatment is performed without acid treatment after the chemical strengthening step in which the glass is brought into contact with an inorganic salt containing at least one of sodium nitrate and potassium nitrate having a pH of 7.5 or more and 10.5 or less and subjected to ion exchange.
  • the chemically strengthened glass of Comparative Example 5 had a slightly higher surface strength than the other comparative examples. However, polishing scratches were observed on the glass surface, and the surface strength was low compared to the chemically strengthened glass obtained in the examples.
  • the chemically strengthened glass of Comparative Example 3 which was subjected to acid treatment and alkali treatment after the chemical strengthening step using an inorganic salt having a pH of less than 7.5, and an inorganic salt having a pH of more than 10.5
  • Comparative Example 8 in which acid treatment was performed after using the chemical strengthening step
  • Comparative Example 9 in which acid treatment and alkali treatment were performed after performing the chemical strengthening step using an inorganic salt having a pH of more than 10.5
  • the chemically strengthened glass had lower surface strength than the chemically strengthened glass obtained in the examples, and white cloudiness was generated in the glass surface.
  • FIG. 5A is the stress profile of the chemically strengthened glass obtained in Examples 1 and 3 and Comparative Example 1
  • FIG. 5B is the stress profile of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6
  • FIG. The stress profile of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11 is shown.
  • Example 5A the stress profiles of the chemically tempered glass obtained in Example 1 and Comparative Example 1 were almost the same. Moreover, as shown to FIG. 5B, the stress profile of the chemically strengthened glass obtained in Example 7 and 8 and the comparative example 6 substantially corresponded. Furthermore, as shown in FIG. 5C, the stress profiles of the chemically tempered glasses obtained in Examples 10 and 11 and Comparative Example 11 almost coincided.
  • FIG. 6A and FIG. 6B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 1 and 5 and Comparative Examples 1, 4 and 5. As shown in FIGS. 6A and 6B, the chemically strengthened glasses obtained in Examples 1 and 5 were not subjected to acid treatment after the chemical strengthening step, and Comparative Examples 1 and 4 were not subjected to acid treatment after the chemical strengthening step. The surface strength was remarkably improved as compared with Comparative Example 5 in which the polishing treatment was performed.
  • FIGS. 7A and 7B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6.
  • FIG. 7A and 7B the chemically strengthened glass obtained in Examples 7 and 8 has a significantly improved surface strength as compared with Comparative Example 6 in which acid treatment was not performed after the chemical strengthening step. It was.
  • FIGS. 8A and 8B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11.
  • FIG. 8A and 8B the chemically strengthened glass obtained in Examples 10 and 11 has a significantly improved surface strength compared to Comparative Example 11 in which acid treatment was not performed after the chemical strengthening step. It was.

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Abstract

The present invention provides a method for producing a chemically toughened glass having a deep depth of compression (DOC) and a high surface strength without decreasing the strength of the glass even if the glass has been subjected to a chemical toughening treatment at a high temperature for a long period of time. The present invention relates to a method for producing a chemically toughened glass, which comprises a chemical toughening step wherein a glass is brought into contact with an inorganic salt for ion exchange, said inorganic salt containing at least one of sodium nitrate and potassium nitrate and having a hydrogen ion index (pH) of from 7.5 to 10.5 (inclusive) when formed into a 10% by mass aqueous solution; and an acid treatment step wherein the glass after the chemical toughening step is brought into contact with an acidic solution for an acid treatment, said acidic solution having a hydrogen ion index (pH) of less than 7.0.

Description

化学強化ガラスの製造方法Method for producing chemically strengthened glass

　本発明は化学強化ガラスの製造方法に関する。 The present invention relates to a method for producing chemically strengthened glass.

　デジタルカメラ、携帯電話または携帯情報端末ＰＤＡ（Ｐｅｒｓｏｎａｌ　Ｄｉｇｉｔａｌ　Ａｓｓｉｓｔａｎｔｓ）等のフラットパネルディスプレイ装置において、ディスプレイの保護および美観を高めるために、画像表示部分よりも広い領域となるように薄い板状のカバーガラスをディスプレイの前面に配置することが行われている。ガラスは理論強度が高いものの、傷がつくことで強度が大幅に低下するため、強度が求められるカバーガラスには、イオン交換等によりガラス表面に圧縮応力層を形成した化学強化ガラスが用いられている。 In a flat panel display device such as a digital camera, a mobile phone, or a personal digital assistant PDA (Personal Digital Assistants), a thin plate-like cover glass is formed so as to have a wider area than the image display portion in order to enhance display protection and beauty. Is placed in front of the display. Although glass has a high theoretical strength, the strength is greatly reduced due to scratches. Therefore, a chemically strengthened glass with a compressive stress layer formed on the glass surface by ion exchange or the like is used for the cover glass that requires strength. Yes.

　フラットパネルディスプレイ装置に対する軽量化および薄型化の要求に伴い、カバーガラス自身も薄くすることが要求されている。したがってカバーガラスには、その目的を満たすために表面にさらなる強度が求められる。 With the demand for weight reduction and thinning of flat panel display devices, it is also required to make the cover glass itself thinner. Accordingly, the cover glass is required to have further strength on the surface in order to satisfy its purpose.

　ガラスの強度を向上させる手法の一つとして、特許文献１には、特定の塩を含む無機塩により化学強化の後に酸処理およびアルカリ処理を行う方法が開示されている。 As one of the techniques for improving the strength of glass, Patent Document 1 discloses a method of performing acid treatment and alkali treatment after chemical strengthening with an inorganic salt containing a specific salt.

国際公開第２０１５／００８７６３号International Publication No. 2015/008763

　しかしながら、特許文献１に記載の方法では、高い強度を得るために圧縮応力層の深さ（圧縮応力値がゼロとなる深さと定義、以下、ＤＯＣ；Ｄｅｐｔｈ　ｏｆ　Ｃｏｍｐｒｅｓｓｉｏｎとも略す）を高くすることを目的として高温で長時間化学強化すると、副作用としてガラスの強度が低下するとともに、化学強化の温度条件や時間が制限されるという問題がある。 However, in the method described in Patent Document 1, the depth of the compressive stress layer (defined as a depth at which the compressive stress value becomes zero, hereinafter referred to as DOC; Depth of Compression) is increased in order to obtain high strength. For the purpose of chemical strengthening at a high temperature for a long time, there are problems that the strength of the glass is lowered as a side effect and the temperature condition and time for chemical strengthening are limited.

　また、従来、化学強化処理後に研磨処理することにより、面強度の向上を図っているが、研磨によってガラス表面が傷つき、面強度がかえって低下してしまうおそれがある。さらに、研磨によってガラスの反りが増大するおそれがある。 Conventionally, the surface strength is improved by polishing after the chemical strengthening treatment, but the glass surface may be damaged by the polishing, and the surface strength may be lowered. Furthermore, there is a possibility that the warping of the glass increases due to polishing.

　したがって、本発明は、化学強化の温度条件や時間が制限されることなく、高温で長時間の化学強化処理をしてもガラスの強度を弱めることなく、深いＤＯＣを示すとともに面強度が高い化学強化ガラスを製造する方法を提供する。 Therefore, the present invention does not limit the temperature condition and time for chemical strengthening, and does not weaken the strength of the glass even when chemical strengthening treatment is performed for a long time at a high temperature. A method for producing tempered glass is provided.

　本発明者らは鋭意検討を重ねた結果、化学強化に用いる塩のｐＨを所定の範囲とする化学強化工程と、前記化学強化工程後のガラスを酸処理する酸処理工程とを行うことにより、化学強化の温度条件や時間が制限されることなく、高温で長時間の化学強化処理をしても深いＤＯＣを示すとともに面強度が高い化学強化ガラスが得られることを見出し、本発明を完成するに至った。 As a result of intensive studies, the present inventors conducted a chemical strengthening step in which the pH of the salt used for chemical strengthening is in a predetermined range and an acid treatment step of acid-treating the glass after the chemical strengthening step. The present invention is completed by finding that a chemically strengthened glass showing a deep DOC and a high surface strength can be obtained even if a chemical strengthening treatment is performed at a high temperature for a long time without limiting the temperature conditions and time for chemical strengthening. It came to.

　すなわち本発明は以下の通りである。
１．１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させてイオン交換する化学強化工程と、　
　前記化学強化工程後のガラスを、水素イオン指数（ｐＨ）が７．０未満である酸性の溶液に接触させて酸処理する酸処理工程と、を含む化学強化ガラスの製造方法。
２．前記酸処理工程後のガラスを、水素イオン指数（ｐＨ）が７．０超であるアルカリ性の溶液に接触させてアルカリ処理するアルカリ処理工程をさらに含む前記１に記載の化学強化ガラスの製造方法。
３．前記化学強化工程は、４００℃以上の前記無機塩に前記ガラスを２時間以上接触させてイオン交換する工程である前記１または２に記載の化学強化ガラスの製造方法。
４．前記化学強化工程後のガラスは、深さ３５μｍ以上の圧縮応力層を有する前記１～３のいずれか１に記載の化学強化ガラスの製造方法。
５．前記化学強化工程後のガラスは、ボールオンリング試験により下記条件で測定した面強度Ｆ（Ｎ）が、ガラス板の板厚ｔ（ｍｍ）に対して、Ｆ≧１０００×ｔ２である前記１～４のいずれか１に記載の化学強化ガラスの製造方法。
ボールオンリング試験条件：
　板厚ｔ（ｍｍ）のガラス板を、直径３０ｍｍ、接触部が曲率半径２．５ｍｍの丸みを持つステンレスからなるリング上に配置し、該ガラス板に直径１０ｍｍの鋼からなる球体を接触させた状態で、該球体を下降速度１ｍｍ／ｍｉｎで下降させ該リングの中心に荷重し、ガラス板が破壊された際の破壊荷重（単位Ｎ）をＢＯＲ強度とし、該ＢＯＲ強度の２０回の測定平均値を面強度Ｆ（Ｎ）とする。ただし、ガラス板の破壊起点が、該球体の荷重点から２ｍｍ以上離れている場合は、平均値算出のためのデータより除外する。 That is, the present invention is as follows.
1. Chemistry in which glass is brought into contact with an inorganic salt having a hydrogen ion index (pH) of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate when ionized into a 10% by mass aqueous solution, and ion exchange is performed. Strengthening process,
A method for producing chemically tempered glass, comprising: an acid treatment step in which the glass after the chemical tempering step is contacted with an acidic solution having a hydrogen ion index (pH) of less than 7.0.
2. 2. The method for producing chemically strengthened glass according to 1, further comprising an alkali treatment step in which the glass after the acid treatment step is contacted with an alkaline solution having a hydrogen ion index (pH) of greater than 7.0.
3. 3. The method for producing chemically strengthened glass according to 1 or 2, wherein the chemical strengthening step is a step of bringing the glass into contact with the inorganic salt at 400 ° C. or higher for 2 hours or more for ion exchange.
4). 4. The method for producing chemically strengthened glass according to any one of 1 to 3, wherein the glass after the chemical strengthening step has a compressive stress layer having a depth of 35 μm or more.
5). In the glass after the chemical strengthening step, the surface strength F (N) measured by the ball-on-ring test under the following conditions is F ≧ 1000 × t 2 with respect to the thickness t (mm) of the glass plate. 5. The method for producing chemically tempered glass according to any one of 1 to 4.
Ball-on-ring test conditions:
A glass plate having a thickness of t (mm) was placed on a ring made of stainless steel having a diameter of 30 mm and a contact portion having a radius of curvature of 2.5 mm, and a sphere made of steel having a diameter of 10 mm was brought into contact with the glass plate. In this state, the sphere is lowered at a descending speed of 1 mm / min and loaded onto the center of the ring, and the breaking load (unit N) when the glass plate is broken is defined as BOR strength. The value is the surface strength F (N). However, when the fracture start point of the glass plate is 2 mm or more away from the load point of the sphere, it is excluded from the data for calculating the average value.

　本発明の化学強化ガラスの製造方法においては、ｐＨが所定の範囲である無機塩を用いてガラスを化学強化することにより、無機塩中のＯＨ－によってガラスのＳｉ－Ｏ－Ｓｉ結合が適度に切断され、ガラス表面に圧縮応力層の表層が改質した低密度層が形成される。その後、酸処理することにより該低密度層を均一に除去することができ、研磨処理しなくても、効率的にガラスの面強度を著しく高めることができる。 In the method for producing chemically tempered glass according to the present invention, the glass is chemically strengthened using an inorganic salt having a pH within a predetermined range, so that the Si—O—Si bond of the glass is appropriately adjusted by OH − in the inorganic salt. By cutting, a low-density layer in which the surface layer of the compressive stress layer is modified is formed on the glass surface. Thereafter, the low-density layer can be uniformly removed by acid treatment, and the surface strength of the glass can be effectively increased without polishing.

　したがって、本発明の化学強化ガラスの製造方法によれば、化学強化の温度条件や時間が制限されることなく、高温で長時間の化学強化処理をしても深いＤＯＣを示すとともに面強度が高い化学強化ガラスを簡易に得ることができる。 Therefore, according to the method for producing chemically strengthened glass of the present invention, the temperature condition and time for chemical strengthening are not limited, and even if chemical strengthening treatment is performed at a high temperature for a long time, deep DOC is exhibited and the surface strength is high. Chemically tempered glass can be easily obtained.

図１（ａ）～（ｄ）は、本発明に係る化学強化ガラスの製造工程を表す模式図である。1 (a) to 1 (d) are schematic views showing a process for producing chemically strengthened glass according to the present invention. 図２は、ボールオンリング試験の方法を説明するための概略図である。FIG. 2 is a schematic diagram for explaining a ball-on-ring test method. 図３Ａは表面研磨傷を有するガラス表面のＡＦＭ画像であり、図３Ｂは表面研磨傷を有さないガラス表面のＡＦＭ画像である。FIG. 3A is an AFM image of a glass surface having surface polishing flaws, and FIG. 3B is an AFM image of a glass surface having no surface polishing flaws. 図４Ａはガラス面内に白曇りが発生していない状態を表す図であり、図４Ｂはガラス面内に白曇りが発生している状態を表す図である。FIG. 4A is a diagram illustrating a state where white clouding is not generated in the glass surface, and FIG. 4B is a diagram illustrating a state where white clouding is generated in the glass surface. 図５Ａは実施例１および３並びに比較例１で得られた化学強化ガラスの応力プロファイル、図５Ｂは実施例７および８並びに比較例６で得られた化学強化ガラスの応力プロファイル、図５Ｃは実施例１０および１１並びに比較例１１で得られた化学強化ガラスの応力プロファイルを示す。5A is the stress profile of the chemically strengthened glass obtained in Examples 1 and 3 and Comparative Example 1, FIG. 5B is the stress profile of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6, and FIG. The stress profile of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11 is shown. 図６Ａおよび図６Ｂは、実施例１および５並びに比較例１、４および５で得られた化学強化ガラスの面強度を評価した結果を示す。6A and 6B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 1 and 5 and Comparative Examples 1, 4 and 5. FIG. 図７Ａおよび図７Ｂは、実施例７および８並びに比較例６で得られた化学強化ガラスの面強度を評価した結果を示す。7A and 7B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6. FIG. 図８Ａおよび図８Ｂは、実施例１０および１１並びに比較例１１で得られた化学強化ガラスの面強度を評価した結果を示す。8A and 8B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11. FIG.

　以下、本発明を詳細に説明するが、本発明は以下の実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲において、任意に変形して実施することができる。 Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention.

　ここで、本明細書において“質量％”と“重量％”、“質量ｐｐｍ”と“重量ｐｐｍ”とは、それぞれ同義である。また、単に“ｐｐｍ”と記載した場合は、“重量ｐｐｍ”のことを示す。 Here, in the present specification, “mass%” and “wt%”, “mass ppm” and “weight ppm” have the same meaning. In addition, when “ppm” is simply described, it indicates “weight ppm”.

　又、本明細書において数値範囲を示す「～」とは、その前後に記載された数値を下限値及び上限値として含む意味で使用され、特段の定めがない限り、以下本明細書において「～」は、同様の意味をもって使用される。 In the present specification, “to” indicating a numerical range is used to mean that the numerical values described before and after it are used as a lower limit and an upper limit, and unless otherwise specified, hereinafter “to” "Is used with the same meaning.

＜化学強化ガラスの製造方法＞
　本発明に係る化学強化ガラスを製造する方法（以下、本発明の方法ともいう。）の一態様を以下に説明するが、本発明はこれに限定されない。なお、特に言及しない限り、ガラスの組成は酸化物基準のモル百分率で表記する。 <Method for producing chemically strengthened glass>
One embodiment of the method for producing chemically tempered glass according to the present invention (hereinafter also referred to as the method of the present invention) will be described below, but the present invention is not limited thereto. Unless otherwise specified, the glass composition is expressed as a molar percentage based on oxide.

（化学強化工程）
　本発明の方法における化学強化工程は、１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させて、前記ガラス中のＮａと前記無機塩中のＫとをイオン交換してガラス表面に圧縮応力層を形成し、さらに該圧縮応力層の表層が改質して低密度化された低密度層を形成する工程である。 (Chemical strengthening process)
In the chemical strengthening step in the method of the present invention, the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 7.5 or more and 10.5 or less, and an inorganic salt containing at least one of sodium nitrate and potassium nitrate is glass. , And Na in the glass and K in the inorganic salt are ion-exchanged to form a compressive stress layer on the glass surface, and the surface layer of the compressive stress layer is modified to lower the density. This is a step of forming a low density layer.

　無機塩は、１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上であり、好ましくは８．０以上であり、より好ましくは８．５以上である。また、１０質量％水溶液としたときの水素イオン指数（ｐＨ）が１０．５以下であり、好ましくは１０．０以下であり、より好ましくは９．５以下である。 The inorganic salt has a hydrogen ion index (pH) of 7.5 or more, preferably 8.0 or more, and more preferably 8.5 or more when a 10% by mass aqueous solution is used. Further, the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 10.5 or less, preferably 10.0 or less, and more preferably 9.5 or less.

　無機塩のｐＨを前記範囲とすることで、無機塩中のＯＨ－によってガラスのＳｉ－Ｏ－Ｓｉ結合を適度に切断し、ガラス表面に圧縮応力層の表層が改質した低密度層を形成することができる。無機塩のｐＨは、２５℃にて、堀場製作所製ハンディータイプｐＨメーターＤ－７１Ｓ等のｐＨメーターを用いて測定することができる。 By setting the pH of the inorganic salt within the above range, the Si—O—Si bond of the glass is appropriately cut by OH − in the inorganic salt, and a low-density layer in which the surface layer of the compressive stress layer is modified on the glass surface is formed. can do. The pH of the inorganic salt can be measured at 25 ° C. using a pH meter such as a handy type pH meter D-71S manufactured by Horiba.

　無機塩は、ＫＮＯ２、ＮａＮＯ２、Ｋ２ＣＯ３、Ｎａ２ＣＯ３、ＫＨＣＯ３、ＮａＨＣＯ３、ＫＯＨまたはＮａＯＨからなる群より選ばれる少なくとも一種の塩を含有することが好ましく、上記塩の含有量により、無機塩のｐＨを適宜調整することがきる。 The inorganic salt preferably contains at least one salt selected from the group consisting of KNO 2 , NaNO 2 , K 2 CO 3 , Na 2 CO 3 , KHCO 3 , NaHCO 3 , KOH or NaOH. The pH of the inorganic salt can be appropriately adjusted depending on the amount.

　無機塩は硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む。無機塩に硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含有することで、ガラスの歪点以下で溶融状態となり、かつ化学強化処理を施すときの一般的な温度領域においてハンドリングが容易となる。無機塩に硝酸ナトリウムを含むことで、ＣＴｌｉｍｉｔ値以下で、ＤＯＣが大きな化学強化ガラスを得られる。なお、ＣＴｌｉｍｉｔ値は、経験的に－３８．７×ｌｎ（ｔ）＋４８．２［ＭＰａ］であることが知られている。ここで、ｔはガラスの板厚を表し、単位はｍｍである。 The inorganic salt contains at least one of sodium nitrate and potassium nitrate. By containing at least one of sodium nitrate and potassium nitrate in the inorganic salt, it becomes a molten state below the strain point of the glass, and handling becomes easy in a general temperature range when chemical strengthening treatment is performed. By including sodium nitrate in the inorganic salt, chemically strengthened glass having a large DOC can be obtained at a CTlimit value or less. The CTlimit value is empirically known to be −38.7 × ln (t) +48.2 [MPa]. Here, t represents the plate thickness of the glass, and the unit is mm.

　無機塩における硝酸ナトリウムの含有量は１質量％以上が好ましく、より好ましくは５質量％以上である。ここで、無機塩における硝酸ナトリウムの含有量は、無機塩が液体状態の液相塩のナトリウム濃度をいう。なお、無機塩における硝酸ナトリウムの含有量の上限としては特に制限はない。 The content of sodium nitrate in the inorganic salt is preferably 1% by mass or more, more preferably 5% by mass or more. Here, the content of sodium nitrate in the inorganic salt refers to the sodium concentration of the liquid phase salt in which the inorganic salt is in a liquid state. In addition, there is no restriction | limiting in particular as an upper limit of content of sodium nitrate in inorganic salt.

　無機塩における硝酸ナトリウムの含有量が１質量％以上であることで、ガラスの歪点以下で溶融状態となり、且つ化学強化処理を施すときの一般的な温度領域においてハンドリングが容易となる。無機塩における硝酸ナトリウムの含有量は、所望の表面圧縮応力値（ＣＳ、単位はＭＰａ）が得られるよう適宜調整して決められる。 When the content of sodium nitrate in the inorganic salt is 1% by mass or more, it becomes a molten state below the strain point of the glass, and handling becomes easy in a general temperature range when chemical strengthening treatment is performed. The content of sodium nitrate in the inorganic salt is determined by appropriately adjusting so as to obtain a desired surface compressive stress value (CS, unit is MPa).

　無機塩は、硝酸ナトリウムまたは硝酸カリウムの他に、本発明の効果を阻害しない範囲で他の化学種を含んでいてもよく、例えば、塩化ナトリウム、塩化カリウム、ホウ酸ナトリウムおよびホウ酸カリウム等のアルカリ塩化塩並びにアルカリホウ酸塩などが挙げられる。これらは単独で添加しても、複数種を組み合わせて添加してもよい。 In addition to sodium nitrate or potassium nitrate, the inorganic salt may contain other chemical species as long as the effects of the present invention are not impaired. For example, alkali salts such as sodium chloride, potassium chloride, sodium borate and potassium borate Examples include chlorides and alkali borates. These may be added alone or in combination of two or more.

　上記無機塩にＫＮＯ２を含有する場合は、無機塩におけるＫＮＯ２の含有量は、０．２質量％以上が好ましく、より好ましくは０．４質量％以上であり、さらに好ましくは０．６質量％以上である。また、１０．０質量％以下が好ましく、より好ましくは８．０質量％以下であり、さらに好ましくは６．０質量％以下である。ＫＮＯ２の含有量を前記範囲とすることにより、１０質量％水溶液としたときの無機塩のｐＨを７．５以上１０．５以下にできる。 When KNO 2 is contained in the inorganic salt, the content of KNO 2 in the inorganic salt is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and further preferably 0.6% by mass. % Or more. Moreover, 10.0 mass% or less is preferable, More preferably, it is 8.0 mass% or less, More preferably, it is 6.0 mass% or less. By setting the content of KNO 2 in the above range, the pH of the inorganic salt when the aqueous solution is 10% by mass can be 7.5 or more and 10.5 or less.

　無機塩にガラスを接触させる方法としては、ペースト状の無機塩を塗布する方法、無機塩の水溶液をガラスに噴射する方法、融点以上に加熱した溶融塩の塩浴にガラスを浸漬させる方法などが可能であるが、これらの中では、溶融塩に浸漬させる方法が好ましい。 Examples of the method of bringing the glass into contact with the inorganic salt include a method of applying a paste-like inorganic salt, a method of spraying an aqueous solution of an inorganic salt onto the glass, and a method of immersing the glass in a salt bath of a molten salt heated to a melting point or higher. Although possible, in these, the method of immersing in molten salt is preferable.

　本発明の方法で使用されるガラスは、ナトリウムを含んでいればよく、成形、化学強化処理による強化が可能な組成を有するものである限り、種々の組成のものを使用することができる。具体的には、例えば、アルミノシリケートガラス、ソーダライムガラス、ボロシリケートガラス、鉛ガラス、アルカリバリウムガラスおよびアルミノボロシリケートガラス等が挙げられる。 The glass used in the method of the present invention may contain sodium as long as it contains sodium and has a composition that can be strengthened by molding and chemical strengthening treatment. Specific examples include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

　ガラスの製造方法は特に限定されず、所望のガラス原料を連続溶融炉に投入し、ガラス原料を好ましくは１５００～１６００℃で加熱溶融し、清澄した後、成形装置に供給した上で溶融ガラスを板状に成形し、徐冷することにより製造できる。 The method for producing the glass is not particularly limited, and a desired glass raw material is charged into a continuous melting furnace, and the glass raw material is heated and melted preferably at 1500 to 1600 ° C., clarified, and then supplied to a molding apparatus. It can be produced by forming into a plate shape and slowly cooling it.

　なお、ガラスの成形には種々の方法を採用できる。例えば、ダウンドロー法（例えば、オーバーフローダウンドロー法、スロットダウン法およびリドロー法等）、フロート法、ロールアウト法およびプレス法等の様々な成形方法を採用できる。 In addition, various methods can be adopted for forming the glass. For example, various forming methods such as a down draw method (for example, an overflow down draw method, a slot down method, a redraw method, etc.), a float method, a roll out method, and a press method can be adopted.

　ガラスの厚みは、特に制限されないが、化学強化処理を効果的に行うために、３ｍｍ以下が好ましく、より好ましくは２ｍｍ以下であり、さらに好ましくは１ｍｍ以下である。 The thickness of the glass is not particularly limited, but is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less in order to effectively perform the chemical strengthening treatment.

　また、本発明の方法で使用されるガラスの形状は特に限定されない。例えば、均一な板厚を有する平板形状、表面と裏面のうち少なくとも一方に曲面を有する形状および屈曲部等を有する立体的な形状等の様々な形状のガラスを採用できる。 Further, the shape of the glass used in the method of the present invention is not particularly limited. For example, various shapes of glass such as a flat plate shape having a uniform plate thickness, a shape having a curved surface on at least one of the front surface and the back surface, and a three-dimensional shape having a bent portion can be employed.

　本発明の方法で使用されるガラスの組成の具体例としては、例えば、以下のガラスの組成が挙げられる。
（ｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を５６～７２％、Ａｌ２Ｏ３を５～１８％、Ｂ２Ｏ３を０～１５％、Ｐ２Ｏ５を０．１～１０％含有し、Ｎａ２ＯおよびＫ２Ｏの含有量の合計が３～３０％であるガラス。
（ｉｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を５５．５～８０％、Ａｌ２Ｏ３を１２～２０％、Ｎａ２Ｏを８～２５％、Ｐ２Ｏ５を２．５％以上、アルカリ土類金属ＲＯ（ＲＯはＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯである）を１％以上含有するガラス。
（ｉｉｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を５７～７６．５％、Ａｌ２Ｏ３を１２～１８％、Ｎａ２Ｏを８～２５％、Ｐ２Ｏ５を２．５～１０％、アルカリ土類金属ＲＯを１％以上含有するガラス。
（ｉｖ）酸化物基準のモル百分率表示で、ＳｉＯ２を５６～７２％、Ａｌ２Ｏ３を８～２０％、Ｂ２Ｏ３を３～２０％、Ｎａ２Ｏを８～２５％、Ｋ２Ｏを０～５％、ＭｇＯを０～１５％、ＣａＯを０～１５％、ＳｒＯ２を０～１５％、ＢａＯを０～１５％およびＺｒＯ２を０～８％を含有するガラス。
（ｖ）酸化物基準のモル百分率表示で、ＳｉＯ２を５０～８０％、Ａｌ２Ｏ３を２～２５％、Ｌｉ２Ｏを０～１０％、Ｎａ２Ｏを０～１８％、Ｋ２Ｏを０～１０％、ＭｇＯを０～１５％、ＣａＯを０～５％およびＺｒＯ２を０～５％を含有するガラス。
（ｖｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を５０～７４％、Ａｌ２Ｏ３を１～１０％、Ｎａ２Ｏを６～１４％、Ｋ２Ｏを３～１１％、ＭｇＯを２～１５％、ＣａＯを０～６％およびＺｒＯ２を０～５％含有し、ＳｉＯ２およびＡｌ２Ｏ３の含有量の合計が７５％以下、Ｎａ２ＯおよびＫ２Ｏの含有量の合計が１２～２５％、ＭｇＯおよびＣａＯの含有量の合計が７～１５％であるガラス。
（ｖｉｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を６８～８０％、Ａｌ２Ｏ３を４～１０％、Ｎａ２Ｏを５～１５％、Ｋ２Ｏを０～１％、ＭｇＯを４～１５％およびＺｒＯ２を０～１％含有するガラス。
（ｖｉｉｉ）酸化物基準のモル百分率表示で、ＳｉＯ２を６７～７５％、Ａｌ２Ｏ３を０～４％、Ｎａ２Ｏを７～１５％、Ｋ２Ｏを１～９％、ＭｇＯを６～１４％およびＺｒＯ２を０～１．５％含有し、ＳｉＯ２およびＡｌ２Ｏ３の含有量の合計が７１～７５％、Ｎａ２ＯおよびＫ２Ｏの含有量の合計が１２～２０％であり、ＣａＯを含有する場合その含有量が１％未満であるガラス。
（ｉｘ）酸化物基準の質量％表示で、ＳｉＯ２を６５～７５％、Ａｌ２Ｏ３を０．１～５％、ＭｇＯを１～６％、ＣａＯを１～１５％含有し、Ｎａ２Ｏ＋Ｋ２Ｏが１０～１８％であるガラス。
（ｘ）酸化物基準の質量％表示で、ＳｉＯ２を６０～７２％、Ａｌ２Ｏ３を１～１０％、ＭｇＯを５～１２％、ＣａＯを０．１～５％、Ｎａ２Ｏを１３～１９％、Ｋ２Ｏを０～５％含有し、ＲＯ／（ＲＯ＋Ｒ２Ｏ）が０．２０以上、０．４２以下（式中、ＲＯとはアルカリ土類金属酸化物、Ｒ２Ｏはアルカリ金属酸化物を示す）であるガラス。 Specific examples of the glass composition used in the method of the present invention include the following glass compositions.
(I) Oxide-based molar percentage display, SiO 2 56-72%, Al 2 O 3 5-18%, B 2 O 3 0-15%, P 2 O 5 0.1-10 %, And the total content of Na 2 O and K 2 O is 3 to 30%.
(Ii) 55.5 to 80% of SiO 2 , 12 to 20% of Al 2 O 3 , 8 to 25% of Na 2 O and 2.5% of P 2 O 5 in terms of mole percentage based on oxide The glass containing 1% or more of the alkaline earth metal RO (RO is MgO + CaO + SrO + BaO).
(Iii) Expressing mole percentage on oxide basis, SiO 2 is 57-76.5%, Al 2 O 3 is 12-18%, Na 2 O is 8-25%, P 2 O 5 is 2.5-2.5%. Glass containing 10%, alkaline earth metal RO 1% or more.
(Iv) Oxide-based mole percentage, SiO 2 56-72%, Al 2 O 3 8-20%, B 2 O 3 3-20%, Na 2 O 8-25%, K the 2 O 0 ~ 5%, the MgO 0 ~ 15%, the CaO 0 ~ 15%, the SrO 2 0 ~ 15%, glass BaO 0 ~ 15% and a ZrO 2 containing 0-8%.
(V) SiO 2 50-50%, Al 2 O 3 2-25%, Li 2 O 0-10%, Na 2 O 0-18%, K 2 , expressed as mole percentages based on oxide. Glass containing 0-10% O, 0-15% MgO, 0-5% CaO and 0-5% ZrO 2 .
(Vi) Oxide-based molar percentage display, SiO 2 50-74%, Al 2 O 3 1-10%, Na 2 O 6-14%, K 2 O 3-11%, MgO 2 to 15%, CaO 0 to 6% and ZrO 2 0 to 5%, the total content of SiO 2 and Al 2 O 3 is 75% or less, the content of Na 2 O and K 2 O Glass whose total is 12 to 25% and whose total content of MgO and CaO is 7 to 15%.
(Vii) SiO 2 68 to 80%, Al 2 O 3 4 to 10%, Na 2 O 5 to 15%, K 2 O 0 to 1%, MgO Glass containing 4-15% and 0-1% ZrO 2 .
(Viii) expressed in mole percentages on the oxide basis, SiO 2 67-75%, Al 2 O 3 0-4%, Na 2 O 7-15%, K 2 O 1-9%, MgO 6 to 14% and 0 to 1.5% of ZrO 2 , the total content of SiO 2 and Al 2 O 3 is 71 to 75%, the total content of Na 2 O and K 2 O is 12 to Glass which is 20% and contains CaO when its content is less than 1%.
(Ix) SiO 2 65 to 75%, Al 2 O 3 0.1 to 5%, MgO 1 to 6%, CaO 1 to 15%, and Na 2 Glass with O + K 2 O of 10-18%.
(X) SiO 2 60 to 72%, Al 2 O 3 1 to 10%, MgO 5 to 12%, CaO 0.1 to 5%, Na 2 O 13 to 19%, 0 to 5% of K 2 O, RO / (RO + R 2 O) is 0.20 or more and 0.42 or less (wherein RO is an alkaline earth metal oxide, R 2 O Is an alkali metal oxide).

　化学強化処理は、溶融塩浴内でガラスを無機塩の溶融塩に浸漬し、ガラス中の金属イオン（Ｎａイオン）を、溶融塩中のイオン半径の大きな金属イオン（Ｋイオン）と置換することで行われる。このイオン交換によってガラス表面の組成を変化させ、ガラス表面が高密度化した圧縮応力層２０を形成できる［図１（ａ）～（ｂ）］。このガラス表面の高密度化によって圧縮応力が発生することから、ガラスを強化ができる。 In the chemical strengthening treatment, the glass is immersed in a molten salt of an inorganic salt in a molten salt bath, and metal ions (Na ions) in the glass are replaced with metal ions (K ions) having a large ionic radius in the molten salt. Done in By this ion exchange, the composition of the glass surface can be changed to form the compressive stress layer 20 having a high density on the glass surface [FIGS. 1 (a) to 1 (b)]. Since compressive stress is generated by increasing the density of the glass surface, the glass can be strengthened.

　本発明の方法における化学強化工程では、化学強化するとき、１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩を用いて化学強化処理することにより、無機塩中のＯＨ－によってガラスのＳｉ－Ｏ－Ｓｉ結合が適度に切断され、圧縮応力層の表層が改質して低密度化された低密度層１０を形成する［図１（ｂ）～（ｃ）］。 In the chemical strengthening step in the method of the present invention, when the chemical strengthening is performed, the hydrogen ion index (pH) when the aqueous solution is 10% by mass is 7.5 or more and 10.5 or less, and at least one of sodium nitrate and potassium nitrate is used. By carrying out chemical strengthening treatment using the inorganic salt contained, the Si—O—Si bond of the glass is appropriately cut by OH − in the inorganic salt, and the surface layer of the compressive stress layer is modified to reduce the density. The density layer 10 is formed [FIGS. 1B to 1C].

　なお実際には、化学強化ガラスの密度は、ガラスの中心に存在する中間層３０（バルク）の外縁から圧縮応力層表面に向かって徐々に高密度化してくるため、中間層３０と圧縮応力層２０との間には、密度が急激に変化する明確な境界はない。ここで中間層とは、ガラス中心部に存在し、圧縮応力層に挟まれる層を表す。この中間層は圧縮応力層とは異なり、イオン交換がされていない層である。 Actually, the density of the chemically strengthened glass gradually increases from the outer edge of the intermediate layer 30 (bulk) existing in the center of the glass toward the surface of the compressive stress layer. There is no clear boundary between 20 and 20 where the density changes rapidly. Here, the intermediate layer is a layer present in the center of the glass and sandwiched between the compressive stress layers. Unlike the compressive stress layer, this intermediate layer is a layer that is not ion-exchanged.

　化学強化工程は、具体的には、次のように行うことができる。化学強化工程では、ガラスを予熱し、溶融塩を化学強化の処理温度に調整する。次いで予熱したガラスを溶融塩中に所定の時間浸漬した後、ガラスを溶融塩中から引き上げて、放冷する。なお、ガラスには、化学強化処理の前に用途に応じた形状加工、例えば、切断、端面加工および穴あけ加工などの機械的加工を行うことが好ましい。 Specifically, the chemical strengthening step can be performed as follows. In the chemical strengthening step, the glass is preheated and the molten salt is adjusted to the processing temperature for chemical strengthening. Next, the preheated glass is immersed in the molten salt for a predetermined time, and then the glass is pulled up from the molten salt and allowed to cool. In addition, it is preferable to perform shape processing according to a use, for example, mechanical processing, such as a cutting | disconnection, an end surface processing, and a drilling process, before a chemical strengthening process to glass.

　ガラスの予熱温度は、溶融塩を浸漬する温度に依存するが、一般に１００℃以上が好ましい。 The preheating temperature of the glass depends on the temperature at which the molten salt is immersed, but is generally preferably 100 ° C. or higher.

　化学強化を行う温度は、深いＤＯＣを備えた化学強化ガラスを得る観点から、４００℃以上が好ましく、より好ましくは４５０℃以上であり、さらに好ましくは４７０℃以上である。化学強化を行う温度の上限は特に制限されないが典型的には、被強化ガラスの歪点（通常５００～６００℃）以下が好ましい。 The temperature at which chemical strengthening is performed is preferably 400 ° C. or higher, more preferably 450 ° C. or higher, and further preferably 470 ° C. or higher from the viewpoint of obtaining chemically strengthened glass having a deep DOC. The upper limit of the temperature at which chemical strengthening is performed is not particularly limited, but typically, the strain point of the glass to be tempered (usually 500 to 600 ° C.) or less is preferable.

　ガラスの溶融塩への浸漬時間は、化学強化温度によるが、深いＤＯＣを備えた化学強化ガラスを得る観点から、２時間以上が好ましく、より好ましくは４時間以上であり、さらに好ましくは８時間以上である。上限は特に制限されないが、通常４８時間以下であり、２４時間以下であると生産性の観点より好ましい。 The immersion time of the glass in the molten salt depends on the chemical strengthening temperature, but is preferably 2 hours or longer, more preferably 4 hours or longer, and even more preferably 8 hours or longer from the viewpoint of obtaining chemically strengthened glass having a deep DOC. It is. The upper limit is not particularly limited, but is usually 48 hours or shorter, and preferably 24 hours or shorter from the viewpoint of productivity.

　化学強化工程後のガラスの表層に形成される圧縮応力層の深さ（ＤＯＣ）は、ガラスに十分な強度を付与する観点から、３５μｍ以上が好ましく、より好ましくは４５μｍ以上であり、さらに好ましくは５５μｍ以上である。 From the viewpoint of imparting sufficient strength to the glass, the depth (DOC) of the compressive stress layer formed on the surface layer of the glass after the chemical strengthening step is preferably 35 μm or more, more preferably 45 μm or more, and still more preferably. It is 55 μm or more.

　本発明の方法により製造される化学強化ガラスの圧縮応力値は、１００ＭＰａ以上が好ましく、より好ましくは２００ＭＰａ以上であり、さらに好ましくは３００ＭＰａ以上である。また上限は特に制限されないが、典型的には１２００ＭＰａ以下である。 The compressive stress value of the chemically strengthened glass produced by the method of the present invention is preferably 100 MPa or more, more preferably 200 MPa or more, and further preferably 300 MPa or more. The upper limit is not particularly limited, but is typically 1200 MPa or less.

　圧縮応力層の深さは、ＥＰＭＡ（ｅｌｅｃｔｒｏｎ　ｐｒｏｂｅ　ｍｉｃｒｏ　ａｎａｌｙｚｅｒ）または表面応力計（例えば、折原製作所製ＦＳＭ－６０００）等を用いて測定できる。 The depth of the compressive stress layer can be measured using an EPMA (electron probe micro analyzer) or a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho).

　低密度層は、後述する酸処理工程により除去されるため、低密度層が厚いほどガラス表面が除去されやすい。したがって低密度層の厚みはガラス表面除去量の観点から１０ｎｍ以上が好ましく、２０ｎｍ以上がより好ましい。低密度層の厚みは化学強化工程における溶融塩中のナトリウム濃度、温度または時間等により制御できる。 Since the low density layer is removed by an acid treatment step described later, the thicker the low density layer, the easier the glass surface is removed. Therefore, the thickness of the low density layer is preferably 10 nm or more, and more preferably 20 nm or more from the viewpoint of the glass surface removal amount. The thickness of the low density layer can be controlled by the sodium concentration, temperature or time in the molten salt in the chemical strengthening step.

　酸処理工程で低密度層を除去した後、アルカリ処理を行うことによって、更に低密度層を除去できる。 After removing the low-density layer in the acid treatment step, the low-density layer can be further removed by performing an alkali treatment.

　低密度層の密度はガラス表面除去性の観点から、イオン交換された圧縮応力層よりも深い領域（バルク）の密度に比べて低いことが好ましい。 The density of the low density layer is preferably lower than the density of the region (bulk) deeper than the ion-exchanged compressive stress layer from the viewpoint of glass surface removability.

　低密度層の厚みはＸ線反射率法（Ｘ－ｒａｙ－Ｒｅｆｌｅｃｔｏｍｅｔｒｙ：ＸＲＲ）によって測定した周期（Δθ）から求められる。低密度層の密度はＸＲＲによって測定した臨界角（θｃ）により求められる。なお、簡易的には走査型電子顕微鏡（ＳＥＭ）でガラスの断面を観察することによって、低密度層の形成と層の厚みを確認することも可能である。 The thickness of the low-density layer is determined from the period (Δθ) measured by the X-ray reflectivity method (X-ray-Reflectometry: XRR). The density of the low density layer is determined by the critical angle (θc) measured by XRR. In addition, it is also possible to confirm the formation of the low density layer and the thickness of the layer by simply observing a cross section of the glass with a scanning electron microscope (SEM).

　化学強化工程においては、１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩による上記した化学強化処理と組み合わせて、上記した化学強化処理と、無機塩の組成、水素イオン指数、化学強化する温度および化学強化する時間の条件のうち少なくとも一つの条件を変更した化学強化処理工程を上記した化学強化処理工程の前後に複数回行ってもよい。 In the chemical strengthening step, the above-described chemical strengthening treatment with an inorganic salt having a hydrogen ion index (pH) of 7.5 to 10.5 and containing at least one of sodium nitrate and potassium nitrate in a 10% by mass aqueous solution. In combination with the above-described chemical strengthening treatment, the chemical strengthening treatment described above is a chemical strengthening treatment step in which at least one of the conditions of the inorganic salt composition, hydrogen ion index, chemical strengthening temperature and chemical strengthening time is changed. You may perform several times before and after a process.

　化学強化工程後は工水、イオン交換水等を用いてガラスの洗浄を行う。中でもイオン交換水が好ましい。洗浄の条件は用いる洗浄液によっても異なるが、イオン交換水を用いる場合には０～１００℃で洗浄すると付着した塩を完全に除去させる点から好ましい。 After the chemical strengthening process, the glass is cleaned using industrial water, ion exchange water, or the like. Of these, ion-exchanged water is preferred. The washing conditions vary depending on the washing solution used, but when ion-exchanged water is used, washing at 0 to 100 ° C. is preferable because the attached salt is completely removed.

（酸処理工程）
　酸処理工程では、化学強化工程後に洗浄したガラスに対して、さらに酸処理を行う。ガラスの酸処理は、水素イオン指数（ｐＨ）が７．０未満である酸性の溶液中にガラスを接触させることによって行う。 (Acid treatment process)
In the acid treatment step, the glass cleaned after the chemical strengthening step is further subjected to acid treatment. The acid treatment of glass is performed by bringing the glass into contact with an acidic solution having a hydrogen ion index (pH) of less than 7.0.

　酸処理に用いる溶液は酸性であれば特に制限されずｐＨ７．０未満であればよく、用いられる酸が弱酸であっても強酸であってもよい。具体的には、塩酸、硝酸、硫酸、リン酸、酢酸、シュウ酸、炭酸またはクエン酸等の酸が好ましい。これらの酸は単独で用いても、複数を組み合わせて用いてもよい。 The solution used for the acid treatment is not particularly limited as long as it is acidic, and may have a pH of less than 7.0. The acid used may be a weak acid or a strong acid. Specifically, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, carbonic acid or citric acid are preferred. These acids may be used alone or in combination.

　酸処理を行う温度は、用いる酸の種類や濃度、時間によっても異なるが、１００℃以下が好ましい。また、低密度層を除去しやすくする観点から、２０℃以上が好ましい。酸処理を行う時間は、用いる酸の種類や濃度、温度によっても異なるものの、１０秒～５時間が生産性の点から好ましく、１分～２時間がより好ましい。 The temperature at which the acid treatment is performed varies depending on the type, concentration, and time of the acid used, but is preferably 100 ° C. or lower. Moreover, 20 degreeC or more is preferable from a viewpoint of making it easy to remove a low density layer. The time for the acid treatment varies depending on the type, concentration and temperature of the acid used, but is preferably 10 seconds to 5 hours from the viewpoint of productivity, and more preferably 1 minute to 2 hours.

　酸処理を行う溶液の濃度は、用いる酸の種類や時間、温度によって異なるものの、容器腐食の懸念が少ない濃度が好ましく、具体的には０．１質量％～２０質量％が好ましい。 The concentration of the solution used for the acid treatment varies depending on the type of acid used, the time, and the temperature, but is preferably a concentration with less concern about container corrosion, and specifically 0.1% by mass to 20% by mass.

　酸処理の条件としては、具体的には、例えば、化学強化工程後のガラスを好ましくは、３５～７５℃の０．１質量％～１０質量％硝酸水溶液に、１～１５分間接触させる条件が挙げられる。 Specific conditions for the acid treatment include, for example, a condition in which the glass after the chemical strengthening step is preferably contacted with a 0.1% by mass to 10% by mass nitric acid aqueous solution at 35 to 75 ° C. for 1 to 15 minutes. Can be mentioned.

　上記酸処理により、ガラス表面の低密度化が加速され、低密度層の一部又は全部が除去された表層が露出する［図１（ｃ）および（ｄ）］。これにより面強度が顕著に向上した化学強化ガラスが得られる。さらに、低密度層が除去されることでガラス表面に存在していた傷も同時に除去されるので、この点も強度向上に寄与すると考えられる。 The acid treatment accelerates the reduction of the density of the glass surface and exposes the surface layer from which part or all of the low density layer has been removed [FIGS. 1 (c) and (d)]. Thereby, a chemically strengthened glass having a significantly improved surface strength is obtained. Further, since the scratches existing on the glass surface are also removed at the same time by removing the low density layer, this point is also considered to contribute to the strength improvement.

（アルカリ処理工程）
　本発明の方法では、酸処理後に続いてアルカリ処理を行ってもよい。アルカリ処理を行うことにより、酸処理のみの場合と比較して、低密度層の除去量を増加させて面強度をさらに高められる。 (Alkali treatment process)
In the method of the present invention, an alkali treatment may be performed after the acid treatment. By performing the alkali treatment, the surface strength can be further increased by increasing the removal amount of the low-density layer as compared with the case of only the acid treatment.

　アルカリ処理に用いる溶液は塩基性であれば特に制限されずｐＨ７．０超であればよく、弱塩基を用いても強塩基を用いてもよい。具体的には、水酸化ナトリウム、水酸化カリウム、炭酸カリウムまたは炭酸ナトリウム等の塩基が好ましい。これらの塩基は単独で用いても、複数を組み合わせて用いてもよい。 The solution used for the alkali treatment is not particularly limited as long as it is basic, and may have a pH exceeding 7.0, and a weak base or a strong base may be used. Specifically, a base such as sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate is preferred. These bases may be used alone or in combination.

　アルカリ処理を行う温度は、用いる塩基の種類や濃度、時間によっても異なるが、０～１００℃が好ましく、１０～８０℃がより好ましく、２０～６０℃が特に好ましい。かかる温度範囲であればガラスが腐食するおそれがなく好ましい。 The temperature at which the alkali treatment is performed varies depending on the type, concentration and time of the base used, but is preferably 0 to 100 ° C, more preferably 10 to 80 ° C, and particularly preferably 20 to 60 ° C. If it is this temperature range, there is no possibility that glass will corrode and it is preferable.

　アルカリ処理を行う時間は、用いる塩基の種類や濃度、温度によっても異なるものの、１０秒間～５時間が生産性の点から好ましく、１分間～２時間がより好ましい。アルカリ処理を行う溶液の濃度は、用いる塩基の種類や時間、温度によって異なるものの、ガラス表面除去性の観点から０．１質量％～２０質量％が好ましい。 Although the alkali treatment time varies depending on the type, concentration and temperature of the base used, it is preferably 10 seconds to 5 hours from the viewpoint of productivity, and more preferably 1 minute to 2 hours. The concentration of the solution used for the alkali treatment varies depending on the type of base used, the time, and the temperature, but is preferably 0.1% by mass to 20% by mass from the viewpoint of glass surface removability.

　アルカリ処理の条件としては、具体的には、例えば、酸処理工程後のガラスを好ましくは、３５～７５℃の０．１質量％～１０％質量％水酸化ナトリウム水溶液に、１～１５分間接触させる条件が挙げられる。 As the conditions for the alkali treatment, specifically, for example, the glass after the acid treatment step is preferably contacted with a 0.1% to 10% by weight sodium hydroxide aqueous solution at 35 to 75 ° C. for 1 to 15 minutes. The condition to make is mentioned.

　上記アルカリ処理により、酸処理工程後のガラスと比較して、低密度層がさらに除去された表層が露出する。これにより面強度がさらに向上した化学強化ガラスが得られる。また、ガラス表面に存在していた傷もさらに除去されるので、この点もさらなる面強度向上に寄与すると考えられる。 The surface treatment from which the low-density layer is further removed is exposed by the alkali treatment as compared with the glass after the acid treatment step. Thereby, the chemically strengthened glass whose surface strength is further improved is obtained. Moreover, since the flaw which existed on the glass surface is further removed, it is thought that this point contributes to further improvement of surface strength.

　なお、上記酸処理工程およびアルカリ処理工程の間や、アルカリ処理工程の終了後に、化学強化工程後の洗浄工程と同様の洗浄工程を有することが好ましい。 In addition, it is preferable to have the same washing | cleaning process as the washing | cleaning process after a chemical strengthening process between the said acid treatment process and an alkali treatment process, or after completion | finish of an alkali treatment process.

　なお、除去される低密度層の量は、酸処理工程、並びに酸処理工程およびアルカリ処理工程の少なくとも一方の条件による。図１（ｄ）には、低密度層１０が全て除去された態様を示すが、低密度層１０の一部が除去され一部が残存していてもよい。強度向上の観点からは、低密度層の全部が取り除かれずとも効果が得られる。 Note that the amount of the low density layer to be removed depends on the acid treatment step and at least one of the conditions of the acid treatment step and the alkali treatment step. Although FIG. 1D shows a mode in which the low density layer 10 is completely removed, a part of the low density layer 10 may be removed and a part may remain. From the viewpoint of improving the strength, the effect can be obtained even if the entire low-density layer is not removed.

＜化学強化ガラス＞
　本発明の方法により製造される化学強化ガラスの面強度は、下記に示すボールオンリング試験により評価できる。 <Chemical tempered glass>
The surface strength of the chemically strengthened glass produced by the method of the present invention can be evaluated by a ball-on-ring test shown below.

（ボールオンリング試験）
　ガラス板を直径３０ｍｍ、接触部が曲率半径２．５ｍｍの丸みを持つステンレスからなるリング上に配置し、該ガラス板に直径１０ｍｍの鋼からなる球体を接触させた状態で、該球体を静的荷重条件下で該リングの中心に荷重するボールオンリング［Ｂａｌｌ　ｏｎ　Ｒｉｎｇ（ＢＯＲ）］試験により測定したＢＯＲ強度Ｆ（Ｎ）で評価する。 (Ball-on-ring test)
The glass plate is placed on a ring made of stainless steel having a diameter of 30 mm and the contact portion is rounded with a radius of curvature of 2.5 mm. The BOR strength F (N) measured by a ball-on-ring (Ball on Ring (BOR)) test is applied to the center of the ring under load conditions.

　本発明により製造された化学強化ガラスは、Ｆ≧１０００×ｔ２を満たすことが好ましく、Ｆ≧１２００×ｔ２がより好ましい［式中、Ｆはボールオンリング試験により測定したＢＯＲ強度（Ｎ）であり、ｔはガラス板の板厚（ｍｍ）である。］。ＢＯＲ強度Ｆ（Ｎ）がかかる範囲であることにより、薄板化した場合にも優れた強度を示す。 The chemically strengthened glass produced according to the present invention preferably satisfies F ≧ 1000 × t 2, and more preferably F ≧ 1200 × t 2 [wherein F is the BOR strength (N) measured by a ball-on-ring test. And t is the thickness (mm) of the glass plate. ]. When the BOR strength F (N) is within this range, excellent strength is exhibited even when the plate is thinned.

　図２に、ボールオンリング試験を説明するための概略図を示す。ボールオンリング［Ｂａｌｌ　ｏｎ　Ｒｉｎｇ（ＢＯＲ）］試験では、ガラス板１を水平に載置した状態で、ＳＵＳ３０４製の加圧治具２（焼入れ鋼、直径１０ｍｍ、鏡面仕上げ）を用いてガラス板１を加圧し、ガラス板１の強度を測定する。 FIG. 2 shows a schematic diagram for explaining the ball-on-ring test. In a ball-on-ring (Ball on Ring (BOR)) test, a glass plate 1 is used with a pressure jig 2 (hardened steel, diameter 10 mm, mirror finish) made of SUS304 with the glass plate 1 placed horizontally. And the strength of the glass plate 1 is measured.

　図２において、ＳＵＳ３０４製の受け治具３（直径３０ｍｍ、接触部の曲率Ｒ２．５ｍｍ、接触部は焼入れ鋼、鏡面仕上げ）の上に、サンプルとなるガラス板１が水平に設置されている。ガラス板１の上方には、ガラス板１を加圧するための、加圧治具２が設置されている。本実施の形態においては、ガラス板１の上方から、ガラス板１の中央領域を加圧する。 In FIG. 2, a glass plate 1 serving as a sample is horizontally installed on a receiving jig 3 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish). Above the glass plate 1, a pressurizing jig 2 for pressurizing the glass plate 1 is installed. In the present embodiment, the central region of the glass plate 1 is pressurized from above the glass plate 1.

　なお、試験条件は下記の通りである。
加圧治具２の下降速度：１．０（ｍｍ／ｍｉｎ）
　この時、ガラス板が破壊された際の、破壊荷重（単位Ｎ）をＢＯＲ強度とし、該ＢＯＲ強度の２０回の測定の平均値を面強度Ｆ（Ｎ）とする。ただし、ガラス板の破壊起点が該球体の荷重点から２ｍｍ以上離れている場合は、平均値算出のためのデータより除外する。 The test conditions are as follows.
Lowering speed of the pressure jig 2: 1.0 (mm / min)
At this time, the breaking load (unit N) when the glass plate is broken is defined as BOR strength, and the average value of 20 measurements of the BOR strength is defined as surface strength F (N). However, in the case where the fracture start point of the glass plate is 2 mm or more away from the load point of the sphere, it is excluded from the data for calculating the average value.

　本発明の方法により製造される化学強化ガラスの圧縮応力層の深さ（ＤＯＣ）は、３５μｍ以上が好ましく、より好ましくは４５μｍ以上であり、さらに好ましくは５５μｍ以上である。 The depth (DOC) of the compressive stress layer of the chemically strengthened glass produced by the method of the present invention is preferably 35 μm or more, more preferably 45 μm or more, and further preferably 55 μm or more.

　酸処理工程やアルカリ処理工程によって、除去される低密度層の厚さは上記のとおり、１０ｎｍ程度から大きくても実施例のとおり１０００ｎｍ程度であるため、圧縮応力層の深さ（ＤＯＣ）は、化学強化工程において形成された深さ（ＤＯＣ）と、酸処理工程やアルカリ処理工程の後の深さ（ＤＯＣ）は、略同一である。 As described above, the thickness of the low-density layer removed by the acid treatment step or the alkali treatment step is about 1000 nm as in the example even if it is large from about 10 nm, so the depth (DOC) of the compressive stress layer is The depth (DOC) formed in the chemical strengthening step and the depth (DOC) after the acid treatment step or the alkali treatment step are substantially the same.

　本発明の方法により製造される化学強化ガラスの表面圧縮応力値（ＣＳ）は、１００ＭＰａ以上が好ましく、より好ましくは２００ＭＰａ以上であり、さらに好ましくは３００ＭＰａ以上である。また上限は特に制限されないが、典型的には１２００ＭＰａ以下である。 The surface compressive stress value (CS) of the chemically strengthened glass produced by the method of the present invention is preferably 100 MPa or more, more preferably 200 MPa or more, and further preferably 300 MPa or more. The upper limit is not particularly limited, but is typically 1200 MPa or less.

　圧縮応力値は、ＥＰＭＡ（Ｅｌｅｃｔｒｏｎ　Ｐｒｏｂｅ　Ｍｉｃｒｏ　Ａｎａｌｙｚｅｒ）または表面応力計（例えば、折原製作所製ＦＳＭ－６０００）等を用いて測定できる。圧縮応力値は、日本国特開２０１６－１４２６００号公報に開示される応力プロファイル算出方法を用いて算出できる。 The compressive stress value can be measured using an EPMA (Electron Probe Micro Analyzer) or a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho). The compressive stress value can be calculated using a stress profile calculation method disclosed in Japanese Unexamined Patent Publication No. 2016-142600.

　本発明の方法により製造される化学強化ガラスは、内部引張応力（ＣＴ）が、７２ＭＰａ以下が好ましく、より好ましくは６２ＭＰａ以下であり、さらに好ましくは５２ＭＰａ以下である。また下限は特に制限されないが、典型的には２０ＭＰａ以上である。応力分布を測定し、その応力分布を厚みで積分し、ＣＴ値を求めた。 The chemically strengthened glass produced by the method of the present invention has an internal tensile stress (CT) of preferably 72 MPa or less, more preferably 62 MPa or less, and further preferably 52 MPa or less. The lower limit is not particularly limited, but is typically 20 MPa or more. The stress distribution was measured, and the stress distribution was integrated with the thickness to obtain the CT value.

　また、ＣＴｌｉｍｉｔ値は、経験的に－３８．７×ｌｎ（ｔ）＋４８．２［ＭＰａ］であることが知られている。ここで、ｔはガラスの板厚を表し、単位はｍｍである。 The CTlimit value is empirically known to be -38.7 × ln (t) +48.2 [MPa]. Here, t represents the plate thickness of the glass, and the unit is mm.

　本発明の方法により製造される化学強化ガラスは、化学強化工程の前にガラス表面を研磨する研磨工程が行われて製造されてもよい。ここで、本発明における研磨とは、砥粒を用いてガラス表面を削ることにより平滑化することをいう。 The chemically strengthened glass manufactured by the method of the present invention may be manufactured by performing a polishing step of polishing the glass surface before the chemical strengthening step. Here, the term “polishing” in the present invention refers to smoothing by polishing the glass surface using abrasive grains.

　また、研磨工程により発生し得る研磨傷の有無はＡＦＭ（Ａｔｏｍｉｃ　Ｆｏｒｃｅ　Ｍｉｃｒｏｓｃｏｐｅ；原子間力顕微鏡）による表面観察によって判別でき、１０μｍ×５μｍ領域内に長さ５μｍ以上、幅０．１μｍ以上のスクラッチが２本以上存在しないという場合に、表面に研磨傷がない状態ということができる。図３Ａに表面研磨傷を有する状態を、図３Ｂに表面研磨傷を有さない状態をそれぞれ示す。 Also, the presence or absence of polishing flaws that may occur in the polishing process can be determined by surface observation with an AFM (Atomic Force Microscope), and a scratch having a length of 5 μm or more and a width of 0.1 μm or more is present in a 10 μm × 5 μm region. When two or more are not present, it can be said that there is no polishing scratch on the surface. FIG. 3A shows a state having surface polishing flaws, and FIG. 3B shows a state having no surface polishing flaws.

　本発明の製造方法により製造された化学強化ガラスは、ＡＦＭ表面観察によって測定される測定範囲１０μｍ×５μｍにおける表面粗さＲａが、好ましくは０．２ｎｍ以上であり、より好ましくは０．２５ｎｍ以上である。また、好ましくは１．５ｎｍ以下であり、より好ましくは１．２ｎｍ以下である。なお、従来の研磨していない化学強化ガラス板の表面粗さは通常０．１５ｎｍ以上、０．２ｎｍ未満である。 The chemically strengthened glass produced by the production method of the present invention has a surface roughness Ra in a measurement range of 10 μm × 5 μm measured by AFM surface observation, preferably 0.2 nm or more, more preferably 0.25 nm or more. is there. Moreover, it is preferably 1.5 nm or less, more preferably 1.2 nm or less. In addition, the surface roughness of the chemically tempered glass plate which has not been polished is usually 0.15 nm or more and less than 0.2 nm.

　以下に実施例および比較例を挙げ、本発明を具体的に説明するが、本発明はこれらに限定されない。 Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited thereto.

［化学強化ガラスの作製］
　下記に示す条件により、化学強化工程を行った後、酸処理工程、アルカリ処理工程および研磨工程の順に行い、化学強化ガラスを作製した。なお、各実施例および比較例について、各工程の有無を表１および２に示す。 [Production of chemically strengthened glass]
After performing the chemical strengthening step under the conditions shown below, an acid treatment step, an alkali treatment step, and a polishing step were performed in this order to produce a chemically strengthened glass. In addition, about each Example and a comparative example, the presence or absence of each process is shown in Table 1 and 2.

（化学強化工程）
　表１および２に示す組成およびｐＨとなるようにＳＵＳ製のカップに無機塩の材料を加え、マントルヒーターで表１および２に示す温度となるまで加熱して溶融塩を調製した。平面視で５０ｍｍ×５０ｍｍであり、表１および２に示す板厚のアルミノシリケートガラスＡ～Ｃを用意し、２００～４００℃に予熱した後、表１および２に示す条件でイオン交換処理した後、室温付近まで冷却することにより化学強化工程を行った。得られた化学強化ガラスは水洗いし、次の工程に供した。なお、無機塩の組成について、表１および２に示す組成の他はＫＮＯ３として合計１００質量％とした。また、無機塩のｐＨは、１０質量％水溶液としたときのｐＨを２５℃にて堀場製作所製ハンディータイプｐＨメーターＤ－７１Ｓにより測定した値である。 (Chemical strengthening process)
An inorganic salt material was added to a SUS cup so as to have the composition and pH shown in Tables 1 and 2, and the mixture was heated with a mantle heater to the temperature shown in Tables 1 and 2 to prepare a molten salt. Aluminosilicate glasses A to C having a thickness of 50 mm × 50 mm in plan view and having thicknesses shown in Tables 1 and 2 were prepared, preheated to 200 to 400 ° C., and then subjected to ion exchange treatment under the conditions shown in Tables 1 and 2. The chemical strengthening step was performed by cooling to near room temperature. The obtained chemically strengthened glass was washed with water and subjected to the next step. In addition, about the composition of the inorganic salt, in addition to the compositions shown in Tables 1 and 2, the total amount was 100% by mass as KNO 3 . The pH of the inorganic salt is a value measured with a handy type pH meter D-71S manufactured by Horiba, Ltd. at 25 ° C. when the aqueous solution is 10% by mass.

（酸処理工程）
　６質量％の硝酸水溶液をビーカーに用意し、ウォーターバスを用いて４０℃に温度調整を行った。前記化学強化工程で得られたガラスを、調整した硝酸水溶液中に１２０秒間浸漬させ、酸処理を行い、その後純水で数回洗浄した後、エアブローにより乾燥した。こうして得られたガラスを次の工程に供した。 (Acid treatment process)
A 6 mass% nitric acid aqueous solution was prepared in a beaker, and the temperature was adjusted to 40 ° C. using a water bath. The glass obtained in the chemical strengthening step was immersed in the adjusted aqueous nitric acid solution for 120 seconds, acid-treated, then washed several times with pure water, and then dried by air blowing. The glass thus obtained was subjected to the next step.

（アルカリ処理工程）
　４．０重量％の水酸化ナトリウム水溶液をビーカーに用意し、ウォーターバスを用いて４０℃に温度調整を行った。酸処理工程で得られたガラスを、調整した水酸化ナトリウム水溶液中に１２０秒間浸漬させ、アルカリ処理を行い、その後純水で数回洗浄した後、エアブローにより乾燥した。 (Alkali treatment process)
A 4.0 wt% aqueous sodium hydroxide solution was prepared in a beaker, and the temperature was adjusted to 40 ° C. using a water bath. The glass obtained in the acid treatment step was immersed in the prepared sodium hydroxide aqueous solution for 120 seconds, subjected to alkali treatment, then washed several times with pure water, and then dried by air blowing.

（研磨工程）
　研磨スラリーとして、平均粒子直径（ｄ５０）が１μｍの酸化セリウムを水に分散させてスラリーを作製し、得られたスラリーを用いて、硬度（ショアＡ硬度）が７４の不織布研磨パッドにより圧力０．１ｋＰａの条件で、平板ガラスの両面を合計約６μｍ研磨した。 (Polishing process)
As a polishing slurry, cerium oxide having an average particle diameter (d50) of 1 μm was dispersed in water to prepare a slurry, and the resulting slurry was used to apply a pressure of 0. Under the condition of 1 kPa, both surfaces of the flat glass were polished for a total of about 6 μm.

＜評価方法＞
　本実施例における各種評価は以下に示す分析方法により行った。 <Evaluation method>
Various evaluations in this example were performed by the following analysis methods.

（表面除去量）
　ガラスの除去量の厚みは、薬液処理（酸処理およびアルカリ処理）前後の重量を分析用電子天秤（ＨＲ－２０２ｉ；ＡＮＤ製）により測定し、次の式を用いて厚み換算することにより求めた。
　（片面あたりの除去量の厚み）＝［（処理前重量）－（処理後重量）］／（ガラス比重）／処理面積／２　　
　このとき、硝材（ガラスＡ、ガラスＢおよびガラスＣ）のガラス比重は次のとおりであり、これら値を用いて計算した。
　ガラスＡ：２．４２（ｇ／ｃｍ３）
　ガラスＢ：２．４８（ｇ／ｃｍ３）
　ガラスＣ：２．３９（ｇ／ｃｍ３） (Surface removal amount)
The thickness of the glass removal amount was determined by measuring the weight before and after chemical treatment (acid treatment and alkali treatment) with an analytical electronic balance (HR-202i; manufactured by AND) and converting the thickness using the following equation. .
(Thickness of removal amount per side) = [(weight before treatment) − (weight after treatment)] / (specific gravity of glass) / treatment area / 2
At this time, the glass specific gravity of the glass material (glass A, glass B, and glass C) is as follows, and it calculated using these values.
Glass A: 2.42 (g / cm 3 )
Glass B: 2.48 (g / cm 3 )
Glass C: 2.39 (g / cm 3 )

（面強度）
　ガラス面強度はボールオンリング試験により測定した。図２に、本発明で用いたボールオンリング試験を説明するための概略図を示す。ガラス板１（以下の実施例ではアルミノシリケートガラスＡ）を水平に載置した状態で、ＳＵＳ３０４製の加圧治具２（焼入れ鋼、直径１０ｍｍ、鏡面仕上げ）を用いてガラス板１を加圧し、ガラス板１の強度を測定した。 (Area strength)
The glass surface strength was measured by a ball-on-ring test. FIG. 2 is a schematic diagram for explaining the ball-on-ring test used in the present invention. With the glass plate 1 (aluminosilicate glass A in the following examples) placed horizontally, the glass plate 1 is pressed using a pressure jig 2 made of SUS304 (hardened steel, diameter 10 mm, mirror finish). The strength of the glass plate 1 was measured.

　図２において、ＳＵＳ３０４製の受け治具３（直径３０ｍｍ、接触部の曲率Ｒ２．５ｍｍ、接触部は焼入れ鋼、鏡面仕上げ）の上に、サンプルとなるガラス板１が水平に設置されている。ガラス板１の上方には、ガラス板１を加圧するための、加圧治具２が設置されている。 In FIG. 2, a glass plate 1 serving as a sample is horizontally installed on a receiving jig 3 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish). Above the glass plate 1, a pressurizing jig 2 for pressurizing the glass plate 1 is installed.

　実施例及び比較例により得られたガラス板１の上方から、ガラス板１の中央領域を加圧した。なお、試験条件は下記の通りである。
加圧治具２の下降速度：１．０（ｍｍ／ｍｉｎ）
　この時、ガラスが破壊された際の、破壊荷重（単位Ｎ）をＢＯＲ強度とし、該ＢＯＲ強度の２０回の測定の平均値を面強度Ｆ（Ｎ）とした。ただし、ガラス板の破壊起点が該球体（加圧冶具）の荷重点から２ｍｍ以上離れていた場合は、平均値算出のためのデータより除外した。
　面強度Ｆ（Ｎ）は、ガラス板の板厚ｔ（ｍｍ）に依存する、そのためここでは、ガラス板の板厚ｔ（ｍｍ）により規格化（正規化）することにより比較をする。ガラス板の板厚ｔ（ｍｍ）により規格化（正規化）した値をａ（単位Ｎ／ｍｍ２）とした。ａ値は、式：ａ＝Ｆ／ｔ２にて算出される。 The central region of the glass plate 1 was pressurized from above the glass plate 1 obtained in the examples and comparative examples. The test conditions are as follows.
Lowering speed of the pressure jig 2: 1.0 (mm / min)
At this time, the breaking load (unit N) when the glass was broken was defined as the BOR strength, and the average value of 20 measurements of the BOR strength was defined as the surface strength F (N). However, when the fracture origin of the glass plate was 2 mm or more away from the load point of the sphere (pressure jig), it was excluded from the data for calculating the average value.
The surface strength F (N) depends on the thickness t (mm) of the glass plate. Therefore, here, the comparison is made by normalizing (normalizing) the thickness t (mm) of the glass plate. The value normalized (normalized) by the thickness t (mm) of the glass plate was defined as a (unit: N / mm 2 ). The a value is calculated by the formula: a = F / t 2 .

（表面圧縮応力・圧縮応力層の深さ）
　表面圧縮応力値（ＣＳ）および圧縮応力層の深さ（ＤＯＣ、単位はμｍ）は、折原製作所社製表面応力計（ＦＳＭ－６０００）を用いて測定した。圧縮応力値（ＣＳ）および圧縮応力層の深さ（ＤＯＣ）は、日本国特開２０１６－１４２６００号公報に開示される応力プロファイル算出方法を用いて算出した。 (Surface compressive stress / depth of compressive stress layer)
The surface compressive stress value (CS) and the depth (DOC, unit: μm) of the compressive stress layer were measured using a surface stress meter (FSM-6000) manufactured by Orihara Seisakusho. The compressive stress value (CS) and the compressive stress layer depth (DOC) were calculated using the stress profile calculation method disclosed in Japanese Patent Application Laid-Open No. 2016-142600.

（引張応力）
　引張応力値（ＣＴ、単位ＭＰａ）は、日本国特開２０１６－１４２６００号公報に開示される応力プロファイル算出方法を用いて、応力分布を測定し、その応力分布を厚みで積分し、算出した。 (Tensile stress)
The tensile stress value (CT, unit MPa) was calculated by measuring the stress distribution using the stress profile calculation method disclosed in Japanese Patent Application Laid-Open No. 2016-142600 and integrating the stress distribution with the thickness.

（研磨傷）
　研磨傷の有無はＡＦＭによる表面観察によって判別した。１０μｍ×５μｍ領域内に長さ５μｍ以上、幅０．１μｍ以上のスクラッチが２本以上存在しないという場合に、表面に研磨傷がない状態とした。 (Polishing scratches)
The presence or absence of polishing flaws was determined by surface observation with AFM. When there were no two or more scratches having a length of 5 μm or more and a width of 0.1 μm or more in a 10 μm × 5 μm region, the surface was made free of polishing scratches.

（外観品質）
　高輝度光源下で照度１０００００Ｌｕｘとなる条件で外観を観察し、下記評価基準により外観品質を評価した。図４Ａはガラス面内に白曇りが発生していない状態を表す図であり、図４Ｂはガラス面内に白曇りが発生している状態を表す図である。
○：ガラス面内に白曇りが発生していない。
×：ガラス面内に白曇りが発生している。 (Appearance quality)
The appearance was observed under the condition of an illuminance of 100,000 Lux under a high-intensity light source, and the appearance quality was evaluated according to the following evaluation criteria. FIG. 4A is a diagram illustrating a state where white clouding is not generated in the glass surface, and FIG. 4B is a diagram illustrating a state where white clouding is generated in the glass surface.
○: No white clouding occurred in the glass surface.
X: White cloudiness is generated in the glass surface.

　得られた結果を表１および２、並びに図５～８に示す。 The results obtained are shown in Tables 1 and 2 and FIGS.

Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

　表１に示すように、ｐＨが７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させてイオン交換する化学強化工程と、前記化学強化工程後のガラスを、ｐＨが７未満である酸性の溶液に接触させて酸処理する酸処理工程を含む本発明の製造方法により得られた実施例１～１２の化学強化ガラスを得た。実施例１～１２の化学強化ガラスは、比較例１～１１で得られた化学強化ガラスに比べ、高温で長時間の化学強化処理をしても面強度が高く、圧縮応力層の深さ（ＤＯＣ）が深く、および、高い表面圧縮応力値（ＣＳ）を示すとともに、ガラス面内に白曇りの発生が無く外観品質においても優れている。 As shown in Table 1, a chemical strengthening step in which the glass is brought into contact with an inorganic salt having a pH of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate, and the chemical strengthening step. The chemically tempered glasses of Examples 1 to 12 obtained by the production method of the present invention including the acid treatment step of bringing the latter glass into contact with an acidic solution having a pH of less than 7 and acid-treating were obtained. The chemically tempered glasses of Examples 1 to 12 have higher surface strength even when subjected to chemical tempering treatment at a higher temperature for a longer time than the chemically tempered glasses obtained in Comparative Examples 1 to 11, and the depth of the compressive stress layer ( DOC) is deep and shows a high surface compressive stress value (CS), and there is no occurrence of white haze in the glass surface, which is excellent in appearance quality.

　ｐＨが７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させてイオン交換する化学強化工程後に酸処理を行わなかった比較例１、２、４、６、７、１０および１１の化学強化ガラスは、実施例で得られた化学強化ガラスと比較して面強度が低かった。また、比較例１、２、４、８および９の化学強化ガラスは、ガラス面内に白曇りが発生していた。 Comparative Examples 1 and 2 in which the pH was 7.5 or more and 10.5 or less, and the acid treatment was not performed after the chemical strengthening step in which the glass was brought into contact with an inorganic salt containing at least one of sodium nitrate and potassium nitrate to perform ion exchange. The chemically tempered glasses of 4, 6, 7, 10 and 11 had lower surface strength than the chemically tempered glasses obtained in the examples. In the chemically strengthened glasses of Comparative Examples 1, 2, 4, 8 and 9, white cloudiness occurred in the glass surface.

　また、ｐＨが７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させてイオン交換する化学強化工程後に酸処理を行わずに研磨処理を行った比較例５の化学強化ガラスは、面強度が他の比較例と比較してやや高くなった。しかし、研磨傷がガラス表面に観察され、実施例で得られた化学強化ガラスと比較して面強度が低かった。 In addition, polishing treatment is performed without acid treatment after the chemical strengthening step in which the glass is brought into contact with an inorganic salt containing at least one of sodium nitrate and potassium nitrate having a pH of 7.5 or more and 10.5 or less and subjected to ion exchange. Further, the chemically strengthened glass of Comparative Example 5 had a slightly higher surface strength than the other comparative examples. However, polishing scratches were observed on the glass surface, and the surface strength was low compared to the chemically strengthened glass obtained in the examples.

　また、ｐＨが７．５未満である無機塩を用いて化学強化工程後を行った後に酸処理およびアルカリ処理を行った比較例３の化学強化ガラス、ｐＨが１０．５超である無機塩を用いて化学強化工程を行った後に酸処理を行った比較例８およびｐＨが１０．５超である無機塩を用いて化学強化工程を行った後に酸処理およびアルカリ処理を行った比較例９の化学強化ガラスは、実施例で得られた化学強化ガラスと比較して面強度が低く、ガラス面内に白曇りが発生していた。 In addition, the chemically strengthened glass of Comparative Example 3, which was subjected to acid treatment and alkali treatment after the chemical strengthening step using an inorganic salt having a pH of less than 7.5, and an inorganic salt having a pH of more than 10.5 Comparative Example 8 in which acid treatment was performed after using the chemical strengthening step, and Comparative Example 9 in which acid treatment and alkali treatment were performed after performing the chemical strengthening step using an inorganic salt having a pH of more than 10.5 The chemically strengthened glass had lower surface strength than the chemically strengthened glass obtained in the examples, and white cloudiness was generated in the glass surface.

　図５Ａは実施例１および３並びに比較例１で得られた化学強化ガラスの応力プロファイル、図５Ｂは実施例７および８並びに比較例６で得られた化学強化ガラスの応力プロファイル、図５Ｃは実施例１０および１１並びに比較例１１で得られた化学強化ガラスの応力プロファイルを示す。 5A is the stress profile of the chemically strengthened glass obtained in Examples 1 and 3 and Comparative Example 1, FIG. 5B is the stress profile of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6, and FIG. The stress profile of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11 is shown.

　図５Ａに示すように、実施例１および比較例１で得られた化学強化ガラスの応力プロファイルは概ね一致していた。また、図５Ｂに示すように、実施例７および８並びに比較例６で得られた化学強化ガラスの応力プロファイルは概ね一致していた。さらに、図５Ｃに示すように、実施例１０および１１並びに比較例１１で得られた化学強化ガラスの応力プロファイルは概ね一致していた。 As shown in FIG. 5A, the stress profiles of the chemically tempered glass obtained in Example 1 and Comparative Example 1 were almost the same. Moreover, as shown to FIG. 5B, the stress profile of the chemically strengthened glass obtained in Example 7 and 8 and the comparative example 6 substantially corresponded. Furthermore, as shown in FIG. 5C, the stress profiles of the chemically tempered glasses obtained in Examples 10 and 11 and Comparative Example 11 almost coincided.

　図６Ａおよび図６Ｂは、実施例１および５並びに比較例１、４および５で得られた化学強化ガラスの面強度を評価した結果を示す。図６Ａおよび図６Ｂに示すように、実施例１および５で得られた化学強化ガラスは、化学強化工程後に酸処理を行わなかった比較例１および４並びに化学強化工程後に酸処理を行わずに研磨処理を行った比較例５と比較して、面強度が顕著に向上していた。 FIG. 6A and FIG. 6B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 1 and 5 and Comparative Examples 1, 4 and 5. As shown in FIGS. 6A and 6B, the chemically strengthened glasses obtained in Examples 1 and 5 were not subjected to acid treatment after the chemical strengthening step, and Comparative Examples 1 and 4 were not subjected to acid treatment after the chemical strengthening step. The surface strength was remarkably improved as compared with Comparative Example 5 in which the polishing treatment was performed.

　図７Ａおよび図７Ｂは、実施例７および８並びに比較例６で得られた化学強化ガラスの面強度を評価した結果を示す。図７Ａおよび図７Ｂに示すように、実施例７および８で得られた化学強化ガラスは、化学強化工程後に酸処理を行わなかった比較例６と比較して、面強度が顕著に向上していた。 7A and 7B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 7 and 8 and Comparative Example 6. FIG. As shown in FIGS. 7A and 7B, the chemically strengthened glass obtained in Examples 7 and 8 has a significantly improved surface strength as compared with Comparative Example 6 in which acid treatment was not performed after the chemical strengthening step. It was.

　図８Ａおよび図８Ｂは、実施例１０および１１並びに比較例１１で得られた化学強化ガラスの面強度を評価した結果を示す。図８Ａおよび図８Ｂに示すように、実施例１０および１１で得られた化学強化ガラスは、化学強化工程後に酸処理を行わなかった比較例１１と比較して、面強度が顕著に向上していた。 8A and 8B show the results of evaluating the surface strength of the chemically strengthened glass obtained in Examples 10 and 11 and Comparative Example 11. FIG. As shown in FIGS. 8A and 8B, the chemically strengthened glass obtained in Examples 10 and 11 has a significantly improved surface strength compared to Comparative Example 11 in which acid treatment was not performed after the chemical strengthening step. It was.

　これらの結果から、ｐＨが７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩を用いた化学強化工程後に酸処理を行うことにより、高温で長時間の化学強化処理をしてもガラスの強度を弱めることがなく、深いＤＯＣを示すとともに面強度が高い化学強化ガラスが得られる。 From these results, by performing an acid treatment after the chemical strengthening step using an inorganic salt having a pH of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate, Even if the tempering treatment is performed, the strength of the glass is not weakened, and a chemically tempered glass having a deep DOC and a high surface strength can be obtained.

　本発明を特定の態様を参照して詳細に説明したが、本発明の精神と範囲を離れることなく様々な変更および修正が可能であることは、当業者にとって明らかである。なお、本出願は、２０１６年９月３０日付けで出願された日本特許出願（特願２０１６－１９３９７２号）に基づいており、その全体が引用により援用される。また、ここに引用されるすべての参照は全体として取り込まれる。 Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Note that this application is based on a Japanese patent application filed on September 30, 2016 (Japanese Patent Application No. 2016-193972), which is incorporated by reference in its entirety. Also, all references cited herein are incorporated as a whole.

１０　低密度層
２０　圧縮応力層
３０　中間層
１　ガラス板
２　加圧治具
３　受け治具 10 Low Density Layer 20 Compressive Stress Layer 30 Intermediate Layer 1 Glass Plate 2 Pressure Jig 3 Receiving Jig

Claims (5)

　１０質量％水溶液としたときの水素イオン指数（ｐＨ）が７．５以上１０．５以下であり、且つ硝酸ナトリウムおよび硝酸カリウムの少なくとも一方を含む無機塩にガラスを接触させてイオン交換する化学強化工程と、
　前記化学強化工程後のガラスを、水素イオン指数（ｐＨ）が７．０未満である酸性の溶液に接触させて酸処理する酸処理工程と、を含む化学強化ガラスの製造方法。 A chemical strengthening step in which a glass is brought into contact with an inorganic salt having a hydrogen ion index (pH) of 7.5 or more and 10.5 or less and containing at least one of sodium nitrate and potassium nitrate when the aqueous solution is 10% by mass, and ion exchange is performed. When,
A method for producing chemically tempered glass, comprising: an acid treatment step in which the glass after the chemical tempering step is contacted with an acidic solution having a hydrogen ion index (pH) of less than 7.0. 　前記酸処理工程後のガラスを、水素イオン指数（ｐＨ）が７．０超であるアルカリ性の溶液に接触させてアルカリ処理するアルカリ処理工程をさらに含む請求項１に記載の化学強化ガラスの製造方法。 The method for producing chemically tempered glass according to claim 1, further comprising an alkali treatment step of contacting the glass after the acid treatment step with an alkaline solution having a hydrogen ion index (pH) of more than 7.0 to perform an alkali treatment. . 　前記化学強化工程は、４００℃以上の前記無機塩に前記ガラスを２時間以上接触させてイオン交換する工程である請求項１または２に記載の化学強化ガラスの製造方法。 The method for producing chemically tempered glass according to claim 1 or 2, wherein the chemical tempering step is a step of ion exchange by bringing the glass into contact with the inorganic salt at 400 ° C or higher for 2 hours or more. 　前記化学強化工程後のガラスは、深さ３５μｍ以上の圧縮応力層を有する請求項１～３のいずれか１項に記載の化学強化ガラスの製造方法。 The method for producing chemically tempered glass according to any one of claims 1 to 3, wherein the glass after the chemical tempering step has a compressive stress layer having a depth of 35 µm or more. 　前記化学強化工程後のガラスは、ボールオンリング試験により下記条件で測定した面強度Ｆ（Ｎ）が、ガラス板の板厚ｔ（ｍｍ）に対して、Ｆ≧１０００×ｔ２である請求項１～４のいずれか１項に記載の化学強化ガラスの製造方法。
ボールオンリング試験条件：
　板厚ｔ（ｍｍ）のガラス板を、直径３０ｍｍ、接触部が曲率半径２．５ｍｍの丸みを持つステンレスからなるリング上に配置し、該ガラス板に直径１０ｍｍの鋼からなる球体を接触させた状態で、該球体を下降速度１ｍｍ／ｍｉｎで下降させ該リングの中心に荷重し、ガラス板が破壊された際の破壊荷重（単位Ｎ）をＢＯＲ強度とし、該ＢＯＲ強度の２０回の測定平均値を面強度Ｆ（Ｎ）とする。ただし、ガラス板の破壊起点が、該球体の荷重点から２ｍｍ以上離れている場合は、平均値算出のためのデータより除外する。 The glass after the chemical strengthening step has a surface strength F (N) measured under the following conditions by a ball-on-ring test, and F ≧ 1000 × t 2 with respect to a thickness t (mm) of the glass plate. 5. The method for producing chemically tempered glass according to any one of 1 to 4.
Ball-on-ring test conditions:
A glass plate having a thickness of t (mm) was placed on a ring made of stainless steel having a diameter of 30 mm and a contact portion having a radius of curvature of 2.5 mm, and a sphere made of steel having a diameter of 10 mm was brought into contact with the glass plate. In this state, the sphere is lowered at a descending speed of 1 mm / min and loaded onto the center of the ring, and the breaking load (unit N) when the glass plate is broken is defined as BOR strength. The value is the surface strength F (N). However, when the fracture start point of the glass plate is 2 mm or more away from the load point of the sphere, it is excluded from the data for calculating the average value.
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