JP2013071878A - Antibacterial glass, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide antibacterial glass having strength and visibility which are utilizable as cover glass for a touch panel display.SOLUTION: There is disclosed antibacterial glass having an antibacterial material in a surface layer, the antibacterial glass has in the surface layer, a silver ion diffusion layer within the depth of 30 μm from the glass surface, and a compression layer having the thickness of ≥15 μm in the depth direction from the glass surface, wherein the surface compression stress is ≥480 MPa, and, in the surface layer, the ratio (Ag/K) between the X-ray intensity (K) of potassium and the X-ray intensity (Ag) of silver measured by X-ray fluorescence analysis is 0.0005-0.5.

Description

  The present invention relates to an antibacterial glass, and particularly relates to an antibacterial glass subjected to a chemical strengthening treatment.

  At present, various bacteria live in the environment where we live. The presence of bacteria can be problematic for people with low resistance, such as sick people, children, and the elderly. In recent years, hospital infections in medical facilities and the presence of highly infectious bacteria have become a problem, and antibacterial effects (such as bactericidal action and bacterial growth inhibitory action) with antibacterial agents have attracted attention as countermeasures.

  Known antibacterial agents include organic synthetic antibacterial agents including imidar derivatives, natural antibacterial agents such as wasabi, metal antibacterial agents such as silver and copper, and oxide antibacterial agents such as titanium oxide. In particular, silver, copper, zinc, and products containing these metal ions, particularly silver and silver ions, used for the metal antibacterial agents mentioned above, have a history of history, are friendly to the global environment, and are safe. It is said to be expensive. A large number of techniques relating to the article provided with the antibacterial agent and a method for producing the article have been disclosed, and for example, all items such as clothing, kitchenware, and home appliances have been put into practical use.

  On the other hand, in recent years, mobile devices such as mobile phones, display devices with touch panel displays such as ticket machines and bank ATMs, etc. have become widespread, and opportunities to use these devices are increasing. In particular, devices such as the above-described mobile terminals and touch panel displays employ a cover glass to prevent the display surface from being damaged. The above-mentioned cover glass is directly touched by human hands, and since it is placed in various usage environments such as outdoor use and use by unspecified number of people, consideration for hygiene is required. It has been studied to impart antibacterial properties.

  As a method for imparting antibacterial properties to a glass article, a method of immersing in a solution or molten salt containing silver and diffusing silver from the surface of the glass article to the inside of the surface layer by ion exchange or the like can be mentioned. For example, a bactericidal glass (Patent Document 1) in which sodium ions contained in glass are replaced with silver ions exhibiting a bactericidal action is disclosed.

  Further, as a cover glass used for the above-described display or the like, it is expected to use a glass that has been chemically strengthened for the purpose of preventing the glass from being damaged. For example, an antibacterial glass (for example, Patent Documents 2 and 3) in which sodium ions contained in the antibacterial glass are replaced with silver ions or the like exhibiting an antibacterial effect and the glass is chemically strengthened is disclosed.

  In Patent Document 2, since the glass is a general soda lime glass, the strength is insufficient even when the chemical strengthening treatment is performed, and the antibacterial substance exists as a reduced and stabilized metal. For this reason, it was assumed that the glass was colored, and its practicality as a cover glass was insufficient.

In Patent Document 3, the surface compressive stress of glass is 250 MPa or more and has antibacterial properties. According to Patent Document 3, the antibacterial effect is insufficient unless the amount of silver at a depth of 40 μm from the surface diffuses to 0.2 μg / cm ² or more.

JP 04-338138 A Japanese Patent Laid-Open No. 11-228186 JP 2011-133800 A

  The antibacterial glass using silver as the antibacterial agent described above needs to carry silver at least near the surface of the glass in order to exhibit an antibacterial function. However, when chemical strengthening treatment is performed for use as the cover glass described above, silver easily diffuses into the glass due to its characteristics, so there is a problem that silver on the glass surface diffuses into the glass and impairs antibacterial properties. It was. Furthermore, when the amount of silver to be diffused is excessive, a colloidal substance derived from silver is formed to cause coloring, resulting in a problem that visibility of the display is lowered.

  An object of the present invention is to supply antibacterial glass having strength and visibility that can be used as a cover glass of a touch panel display.

  The present invention is an antibacterial glass having an antibacterial substance on the surface layer, and the antibacterial glass has a silver ion diffusion layer within a depth of 30 μm from the glass surface and a thickness of 15 μm or more in the depth direction from the glass surface. And an antibacterial glass characterized by having a surface compressive stress of 480 MPa or more.

  The “surface layer” here refers to a region from the glass surface to a depth of 100 μm, and the surface layer has the diffusion layer and the compression layer. Further, the surface layer has a region where alkali ions are ion-exchanged by the chemical strengthening treatment.

  The diffusion layer is a region where silver ions are diffused, and is formed within a depth of 30 μm from the glass surface. In the diffusion layer, it is preferable to carry a large amount of silver ions on the glass surface because it can effectively exhibit antibacterial properties.

  The compression layer is a layer in which a surface compression stress is generated by ion exchange of an alkali component contained in a glass surface layer with an alkali ion having a larger ion radius, and a thickness of 15 μm or more in the depth direction from the glass surface. Formed to be. In the present invention, main alkali ions to be ion-exchanged are sodium ions and potassium ions, and sodium ions contained in the glass surface layer are exchanged with potassium ions in the strengthening salt bath for chemical strengthening treatment.

  The antibacterial glass of the present invention contains potassium ions in the surface layer of the antibacterial glass, and the ratio between the X-ray intensity (K) of potassium and the X-ray intensity (Ag) of silver measured by fluorescent X-ray analysis. (Ag / K) is 0.0005 to 0.5.

  In the glass surface layer, the diffusion layer and the compression layer have at least overlapping regions, and at least a part of diffused silver ions and ion-exchanged potassium ions are mixed. When the amount of silver ions to diffuse increases, the amount of potassium ions taken in by ion exchange tends to decrease. Therefore, the Ag / K is preferably 0.0005 to 0.5.

In antimicrobial glass of the present invention, the glass portion excluding the surface layer, in substantially _{wt%, SiO 2: 50~75, Al} 2 O 3: 3~20, B 2 O 3: 0~10, Na ₂ O: 5 to 20, K ₂ O: 0 to 10, MgO: 0 to 10, CaO: 0 to 10, SrO: 0 to 5, BaO: 0 to 5, ZrO ₂ : 0 to 5, TiO ₂ : It is a glass composition which consists of 0-10 and SnO: 0-3.

  The antibacterial glass of the present invention is characterized in that the surface layer has a compression layer having a thickness of 60 to 95 μm in the depth direction from the glass surface.

  The antibacterial glass of the present invention is characterized in that the surface layer has a compression layer having a thickness of 15 to 60 μm in the depth direction from the glass surface.

The present invention is a method for producing antimicrobial glass, substantially _{wt%, SiO 2: 50~75, Al} 2 O 3: 3~20, B 2 O 3: 0~10, Na 2 O _{: 5~20, K 2 O: 0~10} , MgO: 0~10, CaO: 0~10, SrO: 0~5, BaO: 0~5, ZrO 2: 0~5, TiO 2: 0~10 A glass composition comprising SnO: 0 to 3 in a strengthened salt bath of a mixed molten salt containing potassium ions and silver ions, wherein the strengthened salt bath contains silver with respect to the potassium compound. It is a strengthening salt bath in which a compound is added and mixed at 0.0001 to 0.5% by mass.

  The present invention makes it possible to obtain antibacterial glass having strength and visibility that can be used as a cover glass for a touch panel display.

The cross-sectional schematic of the antibacterial glass of this invention. Ag profile of Example 6 from glass surface to depth direction.

  The present invention is an antibacterial glass that achieves both strengthening of glass and imparting antibacterial properties and does not impair the visible light transmittance.

  That is, as shown in FIG. 1, the present invention is an antibacterial glass 1 having an antibacterial substance on a surface layer 2, and the antibacterial glass 1 is a diffusion layer of silver ions within a depth of 30 μm from the glass surface in the surface layer 2. 3 and a compression layer 4 having a thickness of 15 μm or more in the depth direction from the glass surface, and the surface compression stress is 480 MPa or more.

  The silver ion diffusion layer 3 is formed by diffusing silver ions in the depth direction from the glass surface. The diffusion distance of silver ions is 30 μm or less from the surface, and preferably 20 μm or less. If this diffusion distance exceeds 30 μm, the amount of wasted silver ions that do not contribute to antibacterial properties may increase.

  In the compression layer 4 of the present invention, the surface of the glass composition is brought into contact with a mixed molten salt containing potassium ions and silver ions, and the sodium ions on the surface of the glass composition and the potassium ions in the mixed molten salt It is formed by causing ion exchange between them.

  In the surface layer 2 after immersion in the molten salt, the ratio (K / Na) of potassium X-ray intensity (K) and sodium X-ray intensity (Na) measured by fluorescent X-ray analysis is 150 or more, more preferably. It is preferable to form the compressed layer 4 so as to be 200 or more. When K / Na is less than 150, ion exchange between sodium ions in the glass composition and potassium ions in the molten salt is insufficient, and it is difficult to obtain a desired strength.

  The antibacterial glass 1 of the present invention has a surface compressive stress of 480 MPa or more by the above-described chemical strengthening treatment. In addition, the surface compressive stress of this invention shall point out the numerical value measured using the photoelastic method using surface stress meter FSM-60V (made by Toshiba Glass). In general, glass is weak against the tensile stress of the surface and is broken by applying the stress. However, by forming a compressive stress on the surface, the resistance to the tensile stress can be increased. That is, the higher the surface compressive stress value, the higher the mechanical strength. Therefore, the surface compressive stress may be 480 MPa or more, preferably 500 MPa or more. Further, the upper limit is not particularly limited, but in an industrial production process, if mechanical strength is high, it may be difficult to process, so 900 MPa or less may be preferable.

  One of the preferred embodiments of the present invention is an antibacterial glass having a compression layer 4 having a surface compressive stress of 480 MPa or more and a thickness of 60 to 95 μm in the depth direction from the glass surface. In addition, the thickness of the compression layer of this invention shall point out the numerical value measured using the photoelastic method using the surface stress meter FSM-60V (made by Toshiba Glass). If the scratch enters deeply beyond the compression layer 4, the glass is easily broken. Therefore, when the thickness of the compression layer 4 is in the above range, it is possible to make it difficult for the glass to break down due to scratching. .

  One of the preferred embodiments of the present invention is antibacterial glass having a compression layer 4 having a surface compression stress of 480 MPa or more and a thickness of 15 or more and less than 60 μm in the depth direction from the glass surface. As described above, when the thickness of the compression layer 4 is in the above range, the fracture strength is likely to be reduced due to the scratch of the compression layer 4, but on the other hand, it is easy to perform processing such as cutting. For example, when it is used for a small mobile terminal such as a mobile phone, it is easy to process and cut it into a desired size after performing chemical strengthening treatment on the glass for the cover. Is possible.

  If the thickness of the compression layer 4 is less than 15 μm, the strength required for chemically strengthened glass is insufficient, and the glass may be damaged.

  The visible light transmittance of the antibacterial glass of the present invention is preferably 80% or more, and more preferably 85% or more. If the visible light transmittance is less than 80%, the visibility is insufficient for use in a display or the like, which may cause a reduction in luminance.

  The surface layer 2 has a ratio (Ag / K) of potassium X-ray intensity (K) and silver X-ray intensity (Ag) measured by X-ray fluorescence analysis of 0.0005 or more, 0.5 Or less, more preferably 0.0005 or more and 0.005 or less.

In antimicrobial glass of the present invention, the glass portion excluding the surface layer 2 is substantially _{wt%, SiO 2: 50~75, Al} 2 O 3: 3~20, B 2 O 3: 0~10, Na ₂ O: 5 to 20, K ₂ O: 0 to 10, MgO: 0 to 10, CaO: 0 to 10, SrO: 0 to 5, BaO: 0 to 5, ZrO ₂ : 0 to 5, TiO ₂ : It is a glass composition composed of 0 to 10, SnO: 0 to 3, and the composition is determined so that the strain point is 400 to 600 ° C.

  The antibacterial glass of the present invention uses the above glass composition, and immerses the surface of the glass composition in a tempered salt bath containing a mixed molten salt containing silver ions and potassium ions. The surface layer 2 is preferably obtained by applying the above. Moreover, the glass part except this glass surface layer consists of said glass composition.

In the glass composition, SiO ₂ is a main component, and if it is less than 50% by mass, the strength is lowered and the chemical durability of the glass composition is deteriorated. On the other hand, if it exceeds 75%, the high-temperature viscosity of the glass melt becomes high, and glass molding becomes difficult. Accordingly, the content is 50 to 75%, preferably 50 to 72%.

Al ₂ O ₃ is a component that forms a glass network structure like SiO _2, and therefore increases the potential strength of the glass composition. Further, the glass composition containing Al ₂ O ₃ is easily ion-exchanged, and the compression layer 4 and the silver diffusion layer 3 are easily formed on the surface layer 2. Further, it is preferably used in order to make silver easily exist in a silver ion state. If less than 3% by mass, it becomes difficult to exchange ions, so the strength after chemical strengthening may be insufficient. On the other hand, if it exceeds 20%, the high-temperature viscosity of the glass melt increases and devitrification tends to occur. Since it increases, glass molding may become difficult.

Although B ₂ O ₃ is not an essential component, it has an action of lowering the viscosity of the molten glass at the time of melting the glass and has an action of reducing the tendency of devitrification, so it is contained in the glass composition up to 10% by mass or less. May be.

Since Na ₂ O is indispensable for chemical strengthening treatment, it is contained in the glass composition of the present invention. When the mass% is less than 5%, ion exchange becomes insufficient. On the other hand, when it exceeds 20%, the chemical durability of the glass composition is deteriorated and the weather resistance is deteriorated. Accordingly, it should contain 5 to 20%, preferably 5 to 18%.

K ₂ O is a component that acts as a flux when melting glass together with Na ₂ O. On the other hand, sodium ion migration is suppressed by the mixed alkali effect with Na ₂ O to make it difficult to exchange ions. If it exceeds 10% by mass%, it becomes difficult to exchange ions. Therefore, it is desirable that the glass composition contains 10% or less.

In addition, by in mole percent _{(Na 2 O + K 2 O} ) / Al 2 O 3 and from 0.7 to 10.0, sodium ions in the glass composition is a potassium ion and a silver ion in the mixed molten salt Since the ion exchange is easy to occur and the silver ions after the ion exchange are easily present in an ion state, the strength of the antibacterial glass is improved and the silver ions are easily supported. Therefore, (Na ₂ O + K ₂ O) / Al ₂ O ₃ is 0.7 to 10.0, preferably 1.0 to 9.0, and more preferably 1.0 to 8.5.

  MgO is not an essential component, and it is difficult to perform ion exchange by suppressing the movement of sodium ions. Therefore, if it is contained in the glass composition, it is desirable that the content be 10% by mass or less.

  CaO is not an essential component, but has the effect of lowering the viscosity of the molten glass during glass melting. However, in order to suppress the movement of sodium ions and make it difficult to exchange ions, if it is contained in the glass composition, the content is preferably 10% by mass or less.

  SrO and BaO have the effect of reducing the high-temperature viscosity of the glass melt in the coexistence with CaO and suppressing the occurrence of devitrification. It is desirable to make it contain in a glass composition in the range below mass%.

ZrO ₂ has an effect of improving the strength of the glass composition, but it is preferably contained in an amount of 5% by mass or less in order to suppress the movement of sodium ions and make it difficult to exchange ions.

TiO ₂ has the effect of improving the strength of the glass composition and lowering the viscosity of the molten glass at the time of melting the glass. However, in order to suppress the movement of sodium ions and make it difficult to exchange ions, it is 10% by mass or less. It is preferable to make it contain in the range.

  SnO contributes to the dissolution, clarification, and improvement of moldability of the glass. However, if it is excessive, the glass composition is colored, and the antibacterial substance is easily reduced. Therefore, SnO is preferably contained at 3% by mass or less.

Although the glass composition of the preferable aspect of this invention consists of said component substantially, in the range which does not impair the objective of this invention, you may contain other components to 10% by mass. , For example, _Li 2 O, ZnO or the like or _P 2 _{O 5} and may contain up to 10 wt% for improved dissolution of the glass. Further, refining, for molding for improved _SO 3, _Cl, F, and _{Sb 2 O 3, As 2 O} 3 or the like may be contained up to 1% by weight. Further, when the desired antibacterial glass is colored, Fe ₂ O ₃ , CoO, NiO, CeO _{2 and the} like may be contained up to 1% by mass for coloring.

  The antibacterial glass of the present invention is preferably formed by a general glass forming method such as a float method, a roll-out method, or a down-draw method, particularly by the down-draw method or the roll-out method. It is preferable. Further, the glass surface may be formed by the above-described forming method, or may be imparted with anti-glare functionality by roughening the surface using hydrofluoric acid etching or the like.

  When the glass composition molded by the above molding method is used for a display, it is preferably molded into a plate shape. Further, the glass composition formed into a plate shape may be deformed such as bending.

  When chemically strengthening a glass composition, the glass composition is immersed in a strengthened salt bath containing a mixed molten salt. At this time, the mixed molten salt is 0.0001 to 0.5 mass%, preferably 0.0001 to 0.1 mass%, more preferably 0.0001 to 0.05 mass% of the silver compound with respect to the potassium compound. It is desirable to use a mixture in%. If it is less than 0.0001% by mass, the antibacterial property is insufficient, while if it is 0.5% by mass or more, colloidal color development is likely to occur after immersion.

  Moreover, when immersed in said reinforced salt bath, it is preferable that immersion temperature shall be the temperature of the strain point x0.7 of glass-the strain point of glass x1.1, and immersion time is 0.5-10. Time is preferred. If the immersion temperature is out of the above range, the inorganic salt in the mixed molten salt may be adversely affected or ion exchange may be insufficient. On the other hand, if the immersion time exceeds 10 hours, the compression layer 4 is generated. The compressive stress is relaxed by heat, and as a result, the compressive stress is impaired and the strength of the antibacterial glass may be lowered. If the immersion time is less than 0.5 hours, ion exchange becomes insufficient.

  Examples of the potassium compound include potassium nitrate, potassium chloride, potassium sulfate, potassium hydroxide, and the like. Among these, potassium nitrate is preferably used. In addition to potassium, other alkali (lithium, sodium, rubidium, cesium) compounds may be mixed in the strengthened salt bath within a range of 10% by mass or less as long as ion exchange is not inhibited.

  Examples of the silver compound include silver nitrate and silver chloride, and silver nitrate is preferably used. In addition, examples of antibacterial substances other than silver include copper and zinc, and copper nitrate, copper chloride, copper sulfate, zinc nitrate, zinc chloride, zinc sulfate and the like as long as they do not inhibit the ion exchange of silver and potassium. May be contained in the reinforced salt bath.

  In order to facilitate the exchange of ions with sodium ions in the glass composition and potassium ions and silver in the mixed molten salt, or in order to prevent thermal cracking in the reinforced salt bath, before soaking in the reinforced salt bath It is preferable to preheat the glass composition with an electric furnace or the like. In addition, in the step of removing from the reinforced salt bath after immersion in the reinforced salt bath, it is desirable to slowly cool it with a slow cooling furnace or the like in order to prevent thermal cracking due to rapid cooling.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to this.

  Examples of the present invention and comparative examples are described below. Table 1 shows the composition of each glass composition, and Table 2 shows the evaluation results. Each sample used in Examples and Comparative Examples was produced as follows.

Oxidized silicon dioxide as SiO ₂ source, aluminum oxide as Al ₂ O ₃ source, boric acid as B ₂ O ₅ source, sodium carbonate as Na ₂ O source, potassium carbonate as K ₂ O source, and MgO source Magnesium, calcium carbonate as the CaO source, strontium carbonate as the SrO source, barium carbonate as the BaO source, zirconium oxide as the ZrO ₂ source, titanium oxide as the TiO ₂ source, and tin oxide as the SnO ₂ source, respectively. These were prepared as much as possible in the composition shown in Table 1, and then put into a platinum crucible, and heated and melted in an electric heating furnace at 1300 to 1650 ° C. for about 6 hours to obtain molten glass. The obtained molten glass was poured into a mold to form a block shape, transferred into an electric furnace maintained above the glass transition point, and gradually cooled to obtain a glass composition.

The obtained glass composition block was cut and processed into a glass plate of 50 mm × 50 mm × 3 mm and subjected to chemical strengthening under the conditions described in Table 2. Potassium nitrate and silver nitrate were used as mixed molten salts in the reinforced salt bath. After performing chemical strengthening treatment according to the immersion temperature and immersion time described in Table 2, the sample was taken out, washed with running water, and dried at room temperature to obtain a sample.

  About the obtained sample, surface Na density | concentration, K density | concentration and Ag density | concentration, visible light transmittance | permeability, surface compressive stress, and the antimicrobial effect were investigated, respectively.

  Each surface concentration of Na, K, and Ag was measured using a fluorescent X-ray analyzer ZSX Primux II (manufactured by RIGAKU). At 50 kV-60 mA, the X-ray intensities of Na (measurement line Kα, target Rh, slit S4), K (measurement line Kα, target Rh, slit S4), and Ag (measurement line Lα, target Rh, slit S2) are measured. Each X-ray intensity ratio (Ag / K, K / Na) was calculated. Na was measured to have a depth of about 5 μm from the surface, K was about 50 μm, and Ag was about 5 μm.

  The diffusion distance of silver ions was determined from the Ag profile (for example, FIG. 2) in the depth direction from the glass surface obtained using EPMA JXA-8600 (manufactured by JEOL). In addition, the value deducted from the obtained Ag profile was used for the Ag profile of the glass plate before a chemical strengthening process as noise.

  The visible light transmittance was measured according to JIS R3106 and JIS Z8729 using a self-recording spectrophotometer U4000 type (manufactured by Hitachi, Ltd.).

  The surface compressive stress and the thickness of the compressed layer were measured using a photoelastic method using a surface stress meter FSM-60V (manufactured by Toshiba Glass).

  The antibacterial effect was evaluated using Escherichia coli as a bacterial species with reference to JIS Z2801. The logarithm log (A / B) is more than 2.0 for the viable cell count A after 24 hours and the viable cell count B after 24 hours of diffusing silver ions on the glass surface layer where silver ions are not diffused. If it is large, it has an antibacterial effect.

  As described above, from the examples and comparative examples, it was revealed that the present invention is an antibacterial glass that achieves a surface compressive stress of 500 MPa or more and a visible light transmittance of 85% or more without impairing the antibacterial properties.

1 Antibacterial glass 2 Surface layer 3 Diffusion layer 4 Compression layer

Claims (7)

An antibacterial glass having an antibacterial substance on a surface layer, wherein the antibacterial glass has a silver ion diffusion layer within a depth of 30 μm from the glass surface, and a compressed layer having a thickness of 15 μm or more in the depth direction from the glass surface. An antibacterial glass characterized by having a surface compressive stress of 480 MPa or more. In the surface layer of the antibacterial glass, the surface layer contains potassium ions, and the ratio (Ag / K) of potassium X-ray intensity (K) and silver X-ray intensity (Ag) measured by fluorescent X-ray analysis The antibacterial glass according to claim 1, wherein is 0.0005 to 0.5. In the antibacterial glass, the glass portion excluding the surface layer is substantially mass%,
SiO _2: 50~75,
Al ₂ O _3: 3~20,
B ₂ O ₃ : 0 to 10,
Na ₂ O: 5~20,
K ₂ O: 0~10,
MgO: 0 to 10,
CaO: 0 to 10,
SrO: 0 to 5,
BaO: 0 to 5,
ZrO ₂ : 0 to 5,
TiO _2: 0~10,
SnO: 0 to 3,
The antibacterial glass according to claim 1, wherein the antibacterial glass is a glass composition comprising: The antibacterial glass according to any one of claims 1 to 3, wherein a surface layer of the antibacterial glass has a compression layer having a thickness of 60 to 95 µm in a depth direction from the glass surface. The antibacterial glass according to any one of claims 1 to 3, wherein a surface layer of the antibacterial glass has a compressed layer having a thickness of 15 to 60 µm in a depth direction from the glass surface. It is a manufacturing method of the antibacterial glass of any one of Claims 1 thru | or 5, Comprising: In mass% substantially,
SiO _2: 50~75,
Al ₂ O _3: 3~20,
B ₂ O ₃ : 0 to 10,
Na ₂ O: 5~20,
K ₂ O: 0~10,
MgO: 0 to 10,
CaO: 0 to 10,
SrO: 0 to 5,
BaO: 0 to 5,
ZrO ₂ : 0 to 5,
TiO _2: 0~10,
SnO: 0 to 3,
A glass composition comprising a step of immersing the glass composition in a strengthened salt bath of a mixed molten salt containing potassium ions and silver ions, wherein the strengthened salt bath contains 0.0001 to 0 silver compounds relative to potassium compounds. A method for producing antibacterial glass, which is a strengthened salt bath added and mixed at 5% by mass. A cover glass for a display, wherein the antibacterial glass according to any one of claims 1 to 5 is used.

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