TW201414687A - Method for producing chemically strengthened glass - Google Patents

Abstract

Provided is a method that is for producing a chemically strengthened glass and that can increase the strength of a cover glass. The method for producing a chemically strengthened glass includes: a chemical strengthening step for chemically strengthening glass; and a post-strengthening etching step for etching the edge and surface of the glass after the chemical strengthening step.

Description

Method for producing chemically strengthened glass

The present invention relates to a method of producing a chemically strengthened glass.

For mobile devices such as smart phones and mobile devices such as PDAs (Personal Digital Assistants), cover glasses are used to protect the display. In recent years, the technology for reducing the size and weight of mobile devices has been demanded, and the weight reduction and thinning of the cover glass have been promoted. In general, if the glass sheet is thinned, the strength is lowered, so that a cover glass having a higher strength than before is required.

As a method of improving the strength of a glass plate, a technique of chemically strengthening a glass plate by an ion exchange method or the like has been developed (for example, Patent Document 1). Patent Document 1 discloses a glass sheet which is formed by compressing a compressive stress layer on the surface of a glass sheet by chemical strengthening to suppress bending or is less likely to be broken, and a method for producing the same.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. Hei 7-223845

Since the cover glass is subjected to a larger stress on the main surface than the outside, it is required to have higher strength and lighter weight, and the inventors have found that the etching can be improved by etching after chemical strengthening or before chemical strengthening. The following ball ring strength or edge strength of the cover glass improves the resistance of the cover glass to cracking.

Accordingly, it is an object of the present invention to provide a method for producing a chemically strengthened glass which can improve the strength of a cover glass.

The present inventors have found that by chemically strengthening a glass plate, the surface of the glass plate (hereinafter referred to as a main surface) and the edge (hereinafter referred to as an end surface) can be etched to improve edge strength and suppress The invention is completed by rupturing the glass and efficiently obtaining a cover glass having an increased strength.

Further, the inventors of the present invention have found that by using a glass having a composition satisfying a specific requirement as one of the preferred aspects of the present invention, the etching rate can be increased to improve the production efficiency. Further, the inventors of the present invention have found that the edge strength of the glass can be further improved by setting the etching amount of the glass to a specific range as one of the preferred aspects of the present invention.

That is, the present invention is as follows.

A method for producing a chemically strengthened glass, comprising a chemical strengthening step of chemically strengthening a glass, and a post-enhancement etching step of etching the surface and the edge of the glass after the chemical strengthening step.

A method for producing a chemically strengthened glass, comprising: a chemical strengthening step of chemically strengthening a glass, and a step of strengthening the etching after etching the surface and the edge of the glass after the chemical strengthening step, the glass is oxidized by The molar percentage of the material reference is SiO ₂ 55-80%, Al ₂ O ₃ 0-20%, B ₂ O ₃ 0-10%, MgO 0-15%, CaO 0-10%, Li ₂ O 0 ~20%, Na ₂ O 0~25%, K ₂ O 0~15%, ZrO ₂ 0~10%, the total content of Li ₂ O and Na ₂ O is 8~25%, using the content of SiO ₂ , The total content of Li ₂ O, Na ₂ O, and K ₂ O is calculated by the following formula, and the content of R ₂ O and ZrO ₂ is 73 or less.

e = SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂

3. The method for producing a chemically strengthened glass according to the above item 2, wherein the glass is The total content of MgO and CaO is 0 to 15%.

4. The method for producing a chemically strengthened glass according to the above item 2, wherein the total content of Li ₂ O, Na ₂ O and K ₂ O in the glass is 25% or less.

5. The method for producing a chemically strengthened glass according to any one of the preceding items, wherein the glass has a Na ₂ O of 0 to 20%, a K ₂ O of 0 to 10%, and a ZrO ₂ of 0 to 5%. .

The method for producing a chemically strengthened glass according to any one of the preceding claims, wherein the glass has a ZrO ₂ of 0 to 2.5%.

A method for producing a chemically strengthened glass, comprising a chemical strengthening step of chemically strengthening a glass, and a post-enhancement etching step of etching the surface and the edge of the glass by 4 μm or more after the chemical strengthening step.

8. The method for producing a chemically strengthened glass according to the above item 7, wherein the glass is a glass plate, and the glass plate is used between the chemical strengthening step and the post-intensification etching step by using an abrasive material having a coarser particle size of 1000 or more. The main surface end grinding step of the fine grinding is performed at the intersection of the main surface and the end surface.

9. The method for producing a chemically strengthened glass according to the above item 7 or 8, wherein the glass is a glass plate, and a surface of the intersection of the main surface and the end surface of the glass plate is included between the chemical strengthening step and the post-intensification etching step. The main surface end grinding step of performing the finish polishing in such a manner that the roughness Ra is 0.1 to 30 μm.

10. The method for producing a chemically strengthened glass according to the above item 8, wherein the surface and the edge of the glass plate are etched by 30 μm or less in the post-enhancement etching step.

The method for producing a chemically strengthened glass according to any one of the preceding claims, wherein the chemically strengthened glass is a chemically strengthened cover glass.

A method for producing a chemically strengthened glass, comprising: a pre-reinforcing etching step of wet etching a surface and an edge of a glass sheet of 7 μm or more, and a chemical strengthening step of chemically strengthening the glass sheet after the etching step.

The method for producing a chemically strengthened glass according to the above item 12, wherein the surface and the edge of the glass sheet are etched by 50 μm or less in the pre-reinforcing etching step.

The method for producing a chemically strengthened glass according to the above item 12 or 13, wherein in the pre-reinforcing etching step, the surface and the edge of the glass plate are etched by 10 to 40 μm.

The method for producing a chemically strengthened glass according to any one of the preceding claims, wherein the surface of the chemically strengthened glass has an arithmetic mean roughness Ra of 1 nm or less.

The method for producing a chemically strengthened glass according to any one of the preceding claims, wherein the glass has an etching rate of 0.50 μm/cm ² /min or more in a 5% aqueous HF solution at 25 ° C.

According to the method for producing a cover glass of the present invention, by chemically strengthening the glass, the surface and the edge of the glass are etched, whereby surface roughness caused by excessive etching can be suppressed and the top end of the crack can be passivated, so that the glass can be efficiently obtained. A cover glass having a high ring strength or edge strength and improved resistance to cracking.

Further, as a first embodiment of the present invention, the glass has a molar percentage of the following oxides, and the glass is made to contain SiO ₂ 55 to 80%, Al ₂ O ₃ 0 to 20%, and B ₂ O ₃ 0~. 10%, MgO 0~15%, CaO 0~10%, Li ₂ O 0~20%, Na ₂ O 0~25%, K ₂ O 0~15%, ZrO ₂ 0~10%, Li ₂ O and The total content of Na ₂ O is 8 to 25%, and the content of SiO _{2 ,} the total content of Li ₂ O, Na ₂ O, and K ₂ O, and the contents of R ₂ O and ZrO _{2 are} calculated by the following formula: The glass is 73 or less, whereby the etching rate can be increased and the time required for the etching process can be shortened, thereby improving the manufacturing efficiency.

e = SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂

Further, as a second embodiment of the present invention, the etching amount of the surface and the edge of the glass in the post-enhancement etching step is set to 4 μm or more, in the case where the glass is a glass plate, even if the edge is not used, especially glass. The mirror-grinding of the intersection of the surface and the edge of the panel further enhances the edge strength of the glass.

1, 10‧‧‧ glass plate

2‧‧‧ Pressing fixture

3‧‧‧Resistance

11‧‧‧Chamfering

12‧‧‧Main surface

13‧‧‧ end face

14‧‧‧Main surface end

D1‧‧‧ thickness of the surface layer

D2‧‧‧ Thickness of the back layer

D‧‧‧ Thickness of glass plate

Maximum residual compressive stress of S1‧‧‧ surface layer

S2‧‧‧ Maximum residual compressive stress on the back layer

S‧‧‧Residual stress of glass plates after chemical strengthening

T‧‧‧ average residual tensile stress

Fig. 1 is a view for explaining four types of fracture modes produced by covering glass.

Fig. 2 is a schematic view showing a thickness direction distribution of residual stress of a glass plate after chemical strengthening.

Fig. 3 is a schematic view for explaining a method of strength test.

Figure 4 is a graph showing the correlation between the composition of the glass for chemical strengthening and the etching rate.

Fig. 5 is a graph showing the correlation between the expression e (SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂ ) representing the composition of the glass and the etching rate.

Figure 6 is a cross-sectional view of a glass sheet for explaining a preferred embodiment of the second embodiment of the present invention.

7(a) and 7(b) are graphs showing the correlation between the amount of etching after strengthening and the ratio of improvement in strength.

Hereinafter, preferred embodiments of the method for producing a chemically strengthened glass of the present invention will be described.

The present invention relates to a method for producing a cover glass comprising a chemical strengthening step of chemically strengthening a glass, and a post-enhancement etching step of etching the surface and edges of the glass after the chemical strengthening step.

[Composition of glass]

Next, the composition of the glass of the present invention will be described using a percentage of the molar percentage unless otherwise specified.

In the first embodiment of the present invention, the composition of the glass is expressed by the molar percentage of the following oxide standard, and contains SiO ₂ 55 to 80%, Al ₂ O ₃ 0 to 20%, and B ₂ O ₃ 0 to 10%. , MgO 0~15%, CaO 0~10%, Li ₂ O 0~20%, Na ₂ O 0~25%, K ₂ O 0~15%, ZrO ₂ 0~10%, Li ₂ O and Na ₂ The total content of O is 8 to 25%, and the above e is 73 or less.

SiO ₂ is a component of the skeleton constituting the glass, and is required to reduce the occurrence of cracks when the damage (indentation) is left on the surface of the glass or to reduce the fracture rate when the indentation is left after chemical strengthening. ingredient. When the SiO _{2 is} less than 55%, the stability or weather resistance or chip resistance of the glass is lowered. The SiO _{2 is} preferably 58% or more, more preferably 60% or more. When SiO ₂ exceeds 80%, the viscosity of the glass increases and the meltability decreases. It is typically 75% or less from the viewpoint of increasing the etching rate.

Although Al ₂ O ₃ is not essential, it is an effective component for improving ion exchange performance and chip resistance, in order to increase the surface compressive stress component, or to reduce the crack generation rate when leaving an indentation. The ingredients. In the case of containing Al ₂ O ₃ , the content thereof is preferably 5% or more. When Al ₂ O ₃ exceeds 20%, the viscosity of the glass becomes high and it becomes difficult to homogenize the melting. Al ₂ O _{3 is} preferably 17% or less, and more typically 13% or less.

Although B ₂ O ₃ is not essential, it may be contained in a range of 10% or less in order to improve the meltability at high temperature or the strength of the glass. When B ₂ O ₃ exceeds 10%, it becomes difficult to obtain a homogeneous glass, and molding of glass becomes difficult, or crack resistance is lowered. More typically it does not contain B ₂ O ₃ .

Although MgO is not essential, it is a component that increases the surface compressive stress or a component that improves the meltability. When it is desired to lower the viscosity at a high temperature and obtain a high surface stress, it is preferably contained in an amount of 1% or more, more preferably 2% or more, and still more preferably 4% or more. Further, when the MgO exceeds 15%, the glass tends to be devitrified, or the change in the surface compressive stress due to the NaNO ₃ concentration in the molten salt of potassium nitrate becomes large, preferably 13% or less.

Although CaO is not essential, it may be contained in a range of 10% or less in order to improve the meltability at a high temperature or to cause devitrification. When CaO exceeds 10%, the ion exchange rate or the resistance to cracking is lowered.

The total content of MgO and CaO is preferably 15% or less. When it exceeds 15%, the ion exchange rate becomes slow, and the time for obtaining the desired stress layer depth becomes too long.

Li ₂ O and Na ₂ O are ion exchange components and must contain at least one component. When the total content of Li ₂ O and Na ₂ O is less than 8%, it becomes difficult to form a desired surface compressive stress layer by ion exchange. When the total of Li ₂ O and Na ₂ O exceeds 25%, the weather resistance is insufficient.

Li ₂ O is a component that forms a surface compressive stress layer by ion exchange or increases the meltability of the glass. In the case of containing Li ₂ O, the content thereof is preferably 9% or more, more preferably 10% or more. When Li ₂ O exceeds 20%, the weather resistance is lowered or cracking is easily caused by the indentation. It is preferably 17% or less.

Na ₂ O is a component that forms a surface compressive stress layer by ion exchange or increases the meltability of the glass. In the case of containing Na ₂ O, the content thereof is preferably 8% or more, more preferably 9% or more. When Na ₂ O exceeds 25%, the weather resistance is lowered or cracking is easily caused by the indentation. It is preferably 20% or less.

Although K ₂ O is not essential, it may be contained in a range of 15% or less in order to increase the ion exchange rate. When more than 15%, it becomes easy to have cracks by the indentation, or potassium nitrate molten salt of NaNO the resulting surface compressive stress change becomes large danger ₃ concentration. K ₂ O is preferably 10% or less, more preferably 6% or less, and is more typically 3% or less. In the case where it is desired to reduce the change in surface compressive stress caused by the concentration of NaNO ₃ in the molten salt of potassium nitrate, it is preferred that K ₂ O is not contained.

Preferably Li ₂ O, Na ₂ O and K ₂ O content of the sum of R ₂ O is 25% or less. When it exceeds 25%, the weather resistance becomes insufficient.

Although ZrO ₂ is not essential, it may be contained in a range of up to 10% in order to lower the viscosity at a high temperature or to increase the surface compressive stress. When ZrO ₂ exceeds 10%, there is a possibility that cracks may occur due to indentation. It is preferably 5% or less, more preferably 2.5% or less.

The glass of the present invention essentially comprises the components described above, but may contain other components within the scope not detracting from the object of the present invention. In the case of containing such a component, it is preferred that the total content of the components is less than 2%, more preferably 1% or less. Following, for the above His components are illustrated illustratively.

In order to increase the meltability at a high temperature of the glass, for example, it is preferable to contain ZnO of at most 2%, preferably 1% or less, and when it is produced by a floating method, it is preferably 0.5% or less. When ZnO exceeds 0.5%, it is reduced by float-forming, which is a defect of the product. More typically, it does not contain ZnO.

By coexisting TiO ₂ with Fe ions present in the glass, the visible light transmittance is lowered and the glass is colored brown. Therefore, even if it is contained, it is preferably 1% or less, and is typically not contained.

SrO may be contained as needed, but since it has a greater effect of lowering the ion exchange rate than MgO and CaO, it is preferably less than 1% even in the case of inclusion. More typically it does not contain SrO.

Since BaO has the largest effect of lowering the ion exchange rate among the alkaline earth metal oxides, it is considered that BaO is not contained, or even if it is contained, the content is preferably less than 1%.

In the case of containing SrO or BaO, the total content of these is preferably 1% or less, more preferably less than 0.3%.

In the case where any one of CaO, SrO, BaO and ZrO _{2 is} contained, it is preferred that the total content of the four components is less than 1.5%. When the total amount is 1.5% or more, the ion exchange rate is lowered, and it is typically 1% or less.

It is also possible to suitably contain SO ₃ , a chloride or a fluoride as a clarifying agent at the time of melting the glass. However, in order to improve the visibility of a display device such as a touch panel, it is preferable to minimize the components mixed in the form of impurities in a raw material such as Fe ₂ O ₃ , NiO or Cr ₂ O ₃ which can be absorbed in the visible light range. The mass percentage is preferably 0.15% or less, more preferably 0.05% or less.

The present inventors analyzed the correlation between e and the etching rate calculated based on the following formula indicating the composition of the glass, and as a result, it was found that there is a correlation as shown in FIG. 5. As shown in FIG. 5, when e exceeds 73, the etching rate becomes less than 0.5 μm/cm ² /min, and the time required for etching of the glass becomes long. Therefore, in the first embodiment of the present invention, the content of each of SiO ₂ , R ₂ O and ZrO ₂ used for the composition of the glass is 73 or less, preferably 72 or less, calculated by the following formula.

e = SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂

As the glass to be subjected to the chemical strengthening treatment, for example, a glass of the following composition is used.

(i) Glass containing 50 to 80% of SiO ₂ , 0 to 25% of Al ₂ O ₃ , 0 to 25% of Na ₂ O, and 0 to 15% of RO, based on the composition expressed by mole %

(ii) SiO ₂ 50~70%, Al ₂ O ₃ 0~25%, Na ₂ O 0~25%, CaO 0~5%, Li ₂ O 0~20%, expressed in % by mole , K ₂ O 0~15%, MgO 0~20%, and ZrO ₂ 0~10% glass

(iii) a composition expressed in mole %, containing 55 to 70% of SiO ₂ , 5 to 20% of Al ₂ O _{3 ,} 5 to 20% of Na ₂ O, 0 to 1% of CaO, and 0 to 10% of K ₂ O, MgO 0~15% and ZrO ₂ 0~5% glass

(iv) a composition expressed in mole %, containing SiO ₂ 60-70%, Al ₂ O ₃ 5-20%, Na ₂ O 5-20%, CaO 0-1%, K ₂ O 0-5%, MgO 0~15% and ZrO ₂ 0~3% glass

(v) a composition expressed by mol%, containing SiO ₂ 60-70%, Al ₂ O ₃ 5-20%, Na ₂ O 5-20%, CaO 0-1%, K ₂ O 0-5%, Glass with MgO 7~15% and ZrO ₂ 0~3%

(vi) a composition expressed in mole %, containing SiO ₂ 60-70%, Al ₂ O ₃ 5-20%, Na ₂ O 5-20%, CaO 0-1%, K ₂ O 0-5%, Glass of MgO 8~15% and ZrO ₂ 0~3%

(vii) SiO ₂ 50~70%, Al ₂ O ₃ 0~25%, Na ₂ O 0~25%, CaO 0~5%, Li ₂ O 0~20%, based on the composition of Moh% , K ₂ O 0~15%, MgO 0~20%, and ZrO ₂ 0~10%, glass without LiO ₂

(viii) a composition expressed by mol%, containing SiO ₂ 60-70%, Al ₂ O ₃ 5-20%, Na ₂ O 5-20%, CaO 0-1%, K ₂ O 0-5%, MgO 0~15% and ZrO ₂ 0~3%, glass without LiO ₂

Hereinafter, the case where the glass is in the form of a plate, that is, the glass is a glass plate, in particular, the cover glass is described. However, the present invention is not limited thereto, and may be, for example, a glass container. The glass plate is produced by a floating method, a melt down method, a slit down method, or a re-drawing method.

Further, the thickness of the glass plate varies depending on the application, and is preferably 0.2 mm to 2.5 mm in the case of covering a glass for use in a mobile phone or the like.

[Chemical strengthening step]

In the chemical strengthening step, the surface of the glass is ion-exchanged to form a surface layer of residual compressive stress. Specifically, alkali metal ions (typically Li ions, Na ions) having a smaller ionic radius on the surface of the glass plate are replaced by ion exchanges with alkali ions having a larger ionic radius by ion exchange at a temperature below the glass transition point ( Typically, it is a Na ion or a K ion with respect to Li ions, and a K ion with respect to a Na ion. Thereby, the compressive stress remains on the surface of the glass, and the strength of the glass is increased.

Fig. 2 is a schematic view showing the thickness direction distribution of the residual stress S of the glass plate after chemical strengthening. In FIG. 2, S1 respectively represents the maximum residual compressive stress of one surface layer (referred to as a surface layer) of the glass sheet, and S2 represents the maximum residual compressive stress of the other surface layer (referred to as a back layer) (normally, S1=S2), D1 represents the thickness of the surface layer, D2 represents the thickness of the back layer, D represents the thickness of the glass sheet, and T represents the average residual tensile stress of the intermediate layer existing between the surface layer and the back layer. Further, the horizontal axis in Fig. 2 indicates the distance in the thickness direction in the case where the surface layer is the reference point (=0).

As shown in FIG. 2, the compressive stress remaining in the surface layer or the back layer tends to gradually decrease from the front surface and the back surface toward the inside. On the other hand, as a reaction between the surface layer and the back layer which form residual compressive stress, a residual stretch is formed between the surface layer and the back layer. The middle layer of force. At this time, the tensile stress remaining in the intermediate layer is substantially constant.

In Fig. 2, S1, S2 (usually S2 = S1), D1, D2 (usually D2 = D1), and T can be adjusted by using enhanced treatment conditions, and those skilled in the art can utilize the concentration or temperature of the treatment liquid for chemical strengthening. Alternatively, the glass for chemical strengthening is immersed in the treatment liquid for adjustment.

The conditions and methods for chemical strengthening are not particularly limited, and well-known methods can be used. The method of chemical strengthening is not particularly limited as long as it can ion-exchange Li ₂ O or Na ₂ O in the glass surface layer with Na ₂ O or K ₂ O in the molten salt. For example, the glass is impregnated. A method of heating potassium nitrate (KNO ₃ ) molten salt.

The conditions of the ion exchange treatment for forming the chemical strengthening layer (surface compressive stress layer) having the desired surface compressive stress on the glass vary depending on the thickness of the glass, but the temperature condition is preferably 520 ° C or lower. Preferably, it is 500 ° C or less, and more preferably 350 ° C or more, more preferably 400 ° C or more.

Further, the time for performing the ion exchange treatment is preferably from 1 to 72 hours, more preferably from 2 to 24 hours. In order to improve productivity, it is preferably 12 hours or less. Examples of the molten salt include KNO ₃ and the like.

Specifically, for example, the glass is typically immersed in a KNO ₃ molten salt at 400 to 500 ° C for 1 to 72 hours. Further, after chemical strengthening, it is preferred to wash with water for the purpose of removing adhering substances such as molten salt adhered to the glass plate.

In order to make the strength-enhancing effect by chemical strengthening effective, it is preferable to have a surface compressive stress layer deeper than the microcrack formed on the glass surface, preferably a surface compressive stress layer produced by chemical strengthening. The depth is 6 μm or more. Further, if the damage exceeding the depth of the surface compressive stress layer is left during use, the glass is broken. Therefore, the surface compressive stress layer is preferably deep, more preferably 10 μm or more, and still more preferably 20 μm or more. Typically it is 30 μm or more.

On the other hand, if the surface compressive stress layer is deep, the internal tensile stress becomes large, and The impact when broken is large. In other words, it is understood that when the internal tensile stress is large, it tends to be scattered and pulverized when the glass is broken. When the depth of the surface compressive stress layer exceeds 70 μm for a glass having a thickness of 1 mm or less, the scattering at the time of crushing becomes remarkable. Therefore, the cover glass of the present invention preferably has a surface compressive stress layer having a depth of 70 μm or less.

The cover glass of the present invention is also suitable for use in a packaged electronic device, for example, in a panel having a high probability of contact damage on the surface, and it is preferable to reduce the depth of the surface compressive stress layer in advance for safety. 60 μm or less, further preferably 50 μm or less, and more typically 40 μm or less.

Further, the surface compressive stress CS (unit: MPa) of the cover glass of the present invention and the thickness DOL (unit: μm) of the compressive stress layer can be measured by measuring birefringence. Further, the depth of the surface compressive stress layer can be measured using an EPMA (electron probe micro analyzer) or the like.

[Fracture of cover glass]

The rupture of the cover glass was classified into four types of fracture modes (1. end face ‧ surface rupture, 2. end face ‧ back rupture, 3. face ‧ back rupture, 4. face ‧ surface rupture) Hereinafter, four types of fracture modes will be described with reference to Fig. 1 .

(1. End face ‧ surface cracking)

End face ‧ Surface rupture, also known as Hertzian rupture (Hertz crack rupture), is generated when a shock is applied to the end face of the cover glass, and a conical fracture surface called a Hertz cone which is generated on the impact face (end face) is used as a starting point. Broken. Regarding the end face ‧ surface rupture, the tolerance can be measured according to the Hertz crack test described below.

(2. End face ‧ back rupture)

When the end surface ‧ the back surface rupture is applied to the end surface of the cover glass, the damage caused by the tensile stress generated by the non-impingement surface (end surface) on the opposite side to the impact surface is generated as a starting point. Regarding the end face ‧ back rupture, the resistance can be measured by the back crack test described below.

(3. Face ‧ back rupture)

When the surface rupture is applied to the main surface of the cover glass, the damage is caused by the damage caused by the tensile stress generated by the non-impact surface (main surface) on the opposite side to the impact surface. Regarding the surface ‧ rupture of the back surface, the tolerance can be measured by the following ball drop test.

(4. Face ‧ surface rupture)

Surface ‧ surface rupture is caused by the impact of the crack that penetrates the compressive stress layer as the starting point and the slow cracking of the glass at a slower speed when the impact is applied to the main surface of the cover glass (hereinafter, this glass is also used) The method of rupture is called slow crack rupture). The slow cracking rupture generally has fewer rupture fragments, most typically one crack extends from the fracture starting point, and the chemically strengthened glass with the touch sensor is broken into two pieces, which is used for mobile phones, personal digital assistants ( A typical rupture visible in the cover glass of a display device having a touch panel function such as a PDA) or a tablet PC (Personal Computer).

[etching step]

The glass for chemical strengthening by ion exchange is preferably a layer (cork) which removes the surface of the glass, or a layer of curved or pitped glass. For example, on the surface of glass, there is generally a crack called Griffith microcrack. In the case where tensile stress is applied to the surface of the glass, stress concentration occurs at the crack, and cracking progresses, resulting in breakage of the glass.

Therefore, in the second embodiment of the present invention, the damage (cracking) on the surface of the chemically strengthened glass or the layer in which the glass is bent or pitped is removed by etching by 4 μm or more, thereby improving Edge strength. The thickness of the layer which etches the surface and the edge of the glass after chemical strengthening is 4 μm or more, preferably 5 μm or more, and more preferably 7 μm or more.

In a second embodiment of the present invention, it is preferred to use an abrasive having a coarser particle size of 1000 (JIS R6001, 1996) or more as a glass plate between the chemical strengthening step and the post-intensification etching step. The main surface end of the intersection of the main surface and the end surface is fine Grinding the main surface end grinding step.

A specific example of a preferred embodiment of the second embodiment will be described using FIG. Fig. 6 is a view showing a cross-sectional view of the glass plate 10. The main surface end portion 14 is an intersection portion between the main surface 12 and the end surface 13 of the glass sheet 10 and belongs to the end surface 13. The end surface 13 is a side portion of the glass sheet 10, and reference numeral 11 in the figure is a chamfered portion.

Since the main surface end portion is highly likely to be the starting point of the fracture, the use of the abrasive having a coarser particle size of No. 1000 (JIS R6001, 1996) or more is included between the chemical strengthening step and the post-intensification etching step. The main surface end grinding step of the main surface end is finely ground, whereby the edge strength of the glass sheet can be improved without mirror polishing the end face of the glass sheet. If grinding is carried out using an abrasive material having a smaller particle size than No. 1000 (JIS R6001, 1996), it enters the so-called mirror-polished area, and the number of grinding steps or time before the fine grinding is increased, and the time of the fine grinding step itself becomes long. And other issues.

Specific examples of the abrasive material having a coarser particle size than No. 1000 (JIS R6001, 1996) include, for example, No. 800 and No. 325.

In the glass sheet 10, chamfering is generally performed as shown in Fig. 6, but the shape of the chamfered portion 11 is not limited, so that a so-called R chamfering (chamfering on a surface having a curvature of a circle) may be performed, or may not be reversed. angle. Fine polishing is generally carried out using a grinding stone, but is not limited thereto, and may be carried out, for example, using a polishing cloth or a polishing slurry. The grinding of the main surface end portion 14 is usually performed simultaneously at the time of grinding of the end surface 13.

Moreover, in the second embodiment of the present invention, it is preferable that the surface roughness Ra of the intersection of the main surface and the end surface of the glass plate is 0.1 to 30 μm between the chemical strengthening step and the post-intensification etching step. The main surface end grinding step of the fine grinding is performed. More preferably, Ra is 0.2 μm or more, and further preferably 10 μm or less. Since the main surface end portion is highly likely to be the starting point of the fracture, the edge strength of the glass sheet can be improved by performing such polishing.

By setting Ra to 0.1 μm or more, it enters the so-called mirror-polished area, although it is produced. The number of grinding steps or the time before the polishing of the fine grinding is increased, and the time of the fine grinding step itself becomes long, but the problem can be prevented. By setting Ra to 30 μm or less, it is possible to reduce the possibility that the end of the main surface becomes the starting point of the fracture.

In the second embodiment, the thickness of the layer which is wet-etched on the surface and the edge of the glass after chemical strengthening is preferably 30 μm or less, more preferably 20 μm or less. By setting it to 30 μm or less, it is possible to prevent the edge bending strength from being lowered when the main surface end portion is polished by the polishing material No. 325 or the like [Fig. 7(b)].

When the finish polishing is performed using the abrasive material No. 325, it is preferably 20 μm or less [Fig. 7(b)]. When fine polishing is performed using the abrasive material of No. 800, it is preferably 7 μm or less [Fig. 7 (a)]. Further, the etching amount is preferably 50% or less, more preferably 30% or less, of the depth of the compressive stress layer. By setting it to 50% or less, the edge bending strength can be prevented from decreasing.

In the second embodiment of the present invention, the chemically strengthened glass is etched by 4 μm or more, and the tip end of the crack can be passivated, and the stress concentration at the crack tip can be reduced, thereby improving the edge strength, thereby suppressing the four kinds of fracture modes. The crack caused by <1. end face ‧ surface rupture>, <2. end face ‧ back rupture>

The edge strength of the cover glass obtained by the production method of the present invention is preferably 400 MPa or more, more preferably 500 MPa or more, still more preferably 600 MPa or more. The edge strength can be measured by a three-point bending test or a four-point bending test in accordance with "JIS R 1601 (2008) Fine Ceramic Bending Strength Test Method".

<1, end face ‧ surface rupture> The rupture strength can be obtained by a Hertz crack test. The Hertz rupture test produces Hertzian stress on the surface of the glass end face by striking the cylindrical end face with a small diameter cylindrical rod of the superhard material, thereby generating a Hertz crack rupture, and the impact energy of the cylindrical rod (impact energy J) = height m × weight kg × 9.8 m / s ² ) The tolerance caused by <1. end face ‧ surface rupture> was measured.

<2. End face ‧ back rupture> The rupture strength can be obtained by a back rupture test. The back rupture test produces impact tensile stress on the back side of the glass end face by striking the glass end face against the cylindrical rod of the super-hard material of the large diameter, thereby generating the end face ‧ back cracker, which can be impacted by the impact energy of the cylindrical rod Energy J = height m × weight kg × 9.8 m / s ² ) The tolerance caused by <2. end face ‧ back rupture> was measured.

In the present invention, the surface and edges of the glass may also be etched prior to chemical strengthening. The thickness of the layer etched on the surface and the edge of the glass before chemical strengthening is preferably 7 μm or more, more preferably 10 μm or more, and still more preferably 15 μm or more. Further, it is preferably 50 μm or less, and more preferably 40 μm or less. By setting the thickness of the layer etched on the surface and the edge of the glass to 10 μm or more before chemical strengthening, the edge strength of the glass can be increased, and the resistance to cracking can be improved. Further, by setting the thickness of the layer to be etched before the chemical strengthening to 50 μm or less, the tip end of the crack can be made passivated, and the edge strength can be further improved.

By etching the chemically strengthened glass to remove the heterogeneous layer containing defects and fine concavities and convexities, the defects which become the starting point of the fracture can be reduced, and the strength of the ball ring can be improved, so that the back surface of the four types of fracture modes can be suppressed. Rupture> causes cracking.

The strength of the spherical ring of the cover glass obtained by the production method of the present invention is preferably 2.0 kN, more preferably 2.2 kN, still more preferably 2.4 kN. By having a ball ring strength of 2.0 kN or more, cracking caused by <3. face ‧ back rupture> can be suppressed. Further, the ball ring strength was measured by the following method in the examples.

<3. Face ‧ Back rupture> The rupture strength can be obtained by the ball drop test. The ball drop test produces a tensile stress by impacting the ball against the back side of the glass, thereby producing a surface ‧ back crack, which can be determined by the falling ball energy (falling ability J = height m × weight kg × 9.8 m / s ² ) 3. Face ‧ back rupture > cause tolerance.

(etching conditions)

In the production method of the present invention, an etching step may be included before both chemical strengthening and chemical strengthening. As the etching solution, a solution containing at least one selected from the group consisting of hydrofluoric acid (HF), hexafluoroantimonic acid, and buffered hydrofluoric acid is preferred, and an etching solution containing hydrofluoric acid is more typically used.

Examples of the etching liquid containing hydrofluoric acid include hydrofluoric acid, an acidic solution containing hydrofluoric acid as a main component, and hydrofluoric acid containing at least one acid selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and fluoroantimonic acid. Mixed acid.

The etching rate is preferably 0.50μm / cm ² / min or more, more preferably 0.60μm / cm ² / min or more, and further preferably 0.70μm / cm ² / min or more. By setting the etching rate to 0.50 μm/cm ² /min or more, the time required for the etching step can be shortened, and the cover glass can be manufactured with higher efficiency. The etching rate can be adjusted by appropriately adjusting the composition of the glass for chemical strengthening, the temperature or concentration of the etching solution, and the like.

The etching temperature is usually preferably from 10 ° C to 60 ° C, more preferably from 20 ° C to 40 ° C. Further, the etching time is usually preferably from 30 seconds to 30 minutes, more preferably from 1 minute to 10 minutes. The conditions of the etching can be appropriately selected depending on the material of the glass substrate to be used so that the reactants are not precipitated.

Since the adhering matter adheres to the surface of the glass plate after etching, it is preferably a glass plate after the cleaning process. The washing method is not particularly limited, and a known method can be used. For example, it can be washed with an aqueous solution such as sulfuric acid, hydrochloric acid or nitric acid in a state where ultrasonic waves are applied.

[other steps]

The method for producing a cover glass of the present invention may also include other steps of removing damage (cracks) or bending or pits of the glass sheet present on the surface of the glass sheet before the step of chemical strengthening. As a method of removing the crack of the surface of the glass plate before the chemical strengthening treatment, a method of polishing the surface of the glass plate may be mentioned in the same manner as the above step of removing the surface heterogeneous layer.

In the case where the surface of the glass plate is ground to remove cracks, the grinding method is not limited as long as the crack existing on the surface of the glass can be removed. For example, a rare earth oxide such as cerium oxide, zirconia, alumina, magnesia, cerium oxide (including colloidal cerium oxide), cerium carbide, manganese oxide, iron oxide, diamond, boron nitride, and zircon may be used. Grinding grain The slurry is subjected to grinding or the like. These abrasive grains may be used alone or in combination of two or more.

In the above-mentioned group of the abrasive grains, in the same manner as the above step of removing the surface heterogeneous layer, the slurry containing the colloidal cerium oxide having an average particle diameter of 80 nm or less is used as the abrasive grains, and the surface of the glass plate can be uniformly polished. It is better to achieve sufficient strength.

Further, a well-known abrasive slurry containing a rare earth oxide such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, cerium oxide, cerium carbide, manganese oxide, iron oxide, diamond, boron nitride or zircon is used. After the material is ground, it is more preferable to use a slurry containing colloidal cerium oxide having an average particle diameter of 80 nm or less as abrasive grains.

[covering glass]

The arithmetic mean roughness Ra of the cover glass of the present invention is preferably 1 nm or less, more preferably 0.7 nm or less, still more preferably 0.5 nm or less, and particularly preferably 0.4 or less. The ball ring strength can be sufficiently increased by the arithmetic mean roughness Ra of 1 nm or less.

The arithmetic mean roughness Ra [JIS B0601 (1994)] extracts only the reference length in the direction of the average line from the roughness curve, and takes the X-axis in the direction of the average line of the extracted portion, in the longitudinal magnification When the Y-axis is taken in the direction and the roughness curve is represented by y=f(x), the value obtained by the following formula is expressed in nanometers (nm).

The arithmetic mean roughness Ra can be measured, for example, using a non-contact surface shape measuring machine (NewView 5032 manufactured by Zygo Corporation).

The method for producing the cover glass varies depending on the application, and is not particularly limited as long as the steps other than the chemical strengthening step and the etching step described above. An example is shown as follows, but the present invention is not limited to this example.

First, the prepared glass plate is formed into a desired size and shape for final completion by steps such as cutting, opening, slitting, grinding, or wire chamfering. At this time, in order to improve the operation of the subsequent steps and to reduce the process cost, the size may be cut to a larger size than expected by the final completion, and after all the processing steps are completed, the desired size and shape are formed.

The formed glass is reinforced by the glass strengthening method of the present invention. A cover glass is produced by printing on a tempered glass, an antireflection coating, a bonding of functional films, and the like.

The cover glass of the present invention can be used for a cover glass for a display such as a mobile phone, a digital camera or a touch panel display.

In the production method of the present invention, the present invention is particularly effective when the mass of the glass is 1.0 kg or more, and is preferable. Further, it is preferable when the size of the glass is 1 m square or more. It is preferable when the thickness of the glass is 0.3 mmt.

The present invention is particularly effective in the case of the above-mentioned quality, size or thickness of the glass because, if the glass becomes large, the size of the surface becomes large, and the length of the edge becomes long, resulting in the possibility of deep damage. It becomes higher, or if the glass becomes heavier, it exerts a greater force on the deeper damage due to the weight of the glass.

Example

Hereinafter, the present invention will be specifically described by way of Examples and the like, but the present invention is not limited by the Examples.

The bottom surface and the top surface in the examples and comparative examples mean a surface (bottom surface) which is in contact with the molten tin and a surface (top surface) on the opposite side when it is formed by the floating method.

In the following examples and comparative examples, the next steps were appropriately combined.

(chemical strengthening)

The plate glass was immersed in a KNO ₃ molten salt, subjected to ion exchange treatment, and then chemically strengthened by cooling to near room temperature. At this time, the temperature of the KNO ₃ molten salt was set to 435 ° C, and the immersion time was set to 4 hours. The obtained chemically strengthened glass was washed with water for the next step.

(yttria grinding)

A cerium oxide having an average particle diameter (d50) of 1 μm was dispersed in water to prepare a slurry as a polishing slurry, and the obtained slab was ground to a thickness of about 3.0 μm using the obtained slurry.

(colloidal cerium oxide grinding)

A colloidal cerium oxide (COMPOL80, manufactured by Fujimi Incorporated) having an average particle diameter (d50) of 80 nm was dispersed in water to prepare a slurry as a polishing slurry, and the plate glass was polished to about 0.2 μm using the obtained slurry.

(etched)

Using a mixed acid of hydrofluoric acid and hydrochloric acid (0.55 mass% of hydrofluoric acid and 5.8 mass% of hydrochloric acid) as an etching liquid, the plate glass was etched at 20 ° C for 5 minutes.

[Example 1]

In Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-3, a flat glass having a longitudinal direction of 50 mm × a lateral direction of 50 mm × a thickness of 1.1 mm obtained by cutting by a floating method was used. The composition of the flat glass used was expressed by mol% of the oxide standard, and was SiO ₂ : 64%, Al ₂ O ₃ : 8%, MgO: 11%, Na ₂ O: 12.5%, and ZrO ₂ : 0.5%.

(Example 1-1)

After the flat glass is reinforced by the above chemical strengthening step, wet etching is performed. The above wet etching is performed on the top surface.

(Example 1-2)

The flat glass is subjected to cerium oxide polishing, and after the flat glass is reinforced by a chemical strengthening step, wet etching is performed. The above cerium oxide polishing and wet etching are performed on the top surface.

(Example 1-3)

After the cerium oxide is polished on the flat glass, the colloidal cerium oxide is ground and used. After the flat glass is reinforced by a chemical strengthening step, wet etching is performed. The above cerium oxide polishing, colloidal cerium oxide polishing, and wet etching are performed on the top surface.

(Examples 1-4)

After the top surface and the bottom surface of the flat glass were wet-etched, the flat glass was strengthened by a chemical strengthening step, and both surfaces were wet-etched again.

(Comparative Example 1-1)

The flat glass is subjected to cerium oxide polishing. The chemical strengthening and chemical strengthening of the flat glass are not performed. The above cerium oxide polishing is performed on the top surface.

(Comparative Example 1-2)

The flat glass is subjected to cerium oxide polishing, and then the flat glass is reinforced by a chemical strengthening step. No chemical strengthening treatment. The above cerium oxide polishing is performed on the top surface.

(Comparative Example 1-3)

The flat glass was reinforced by the above chemical strengthening step, but the treatment before and after the chemical strengthening was not performed.

The conditions of the respective strengthening treatments in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-3 are shown in Table 1.

[Evaluation method]

The evaluation method will be described below. With respect to each of the examples and the comparative examples, the following evaluations were performed on the surfaces subjected to the treatment before and after the chemical strengthening. For Comparative Example 1-3 (without chemical strengthening before and after treatment), the top surface was evaluated.

Ball Ring Test

In the ball on ring (BOR) test, the glass plate 1 was pressed with a press jig 2 made of SUS304 in a state where the glass plate 1 was horizontally placed, and the strength of the glass plate 1 was measured. Fig. 3 is a schematic view for explaining the strength test used in the present invention.

In Fig. 3, on the jig 3 manufactured by SUS304, a glass plate 1 serving as a sample is horizontally disposed. Above the glass plate 1, a pressure treatment for pressurizing the glass plate 1 is provided With 2.

In the embodiment of the present embodiment, the central portion of the glass sheet 1 was pressurized from the upper side of the glass sheet 1 obtained after the examples and the comparative examples. Furthermore, the test conditions are as follows. The thickness of the sample: 1.1 (mm); the descending speed of the press fixture 2: 1.0 (mm/min): At this time, the crushing load (unit: N) at the time of glass breakage was taken as the BOR intensity, and the average value of the 20 measurements was taken as the BOR average intensity.

Falling Ball Test

In the ball drop test, the iron balls were dropped to a glass plate to evaluate the strength of the glass plate. As a specific test method, first, the glass plate obtained in the examples and the comparative examples was mounted on a jig made of SUS304 (a metal plate having a longitudinal direction of a through hole of 40 × 40 mm at the center of 100 × a lateral direction of 100 × a thickness of 10 mm) .

The iron ball (SUS304) having a mass of 230 kg was dropped to the center portion of the glass plate, and the falling ball strength (J) was determined from the height (crushing height) at which the glass was broken. Further, 20 measurements were performed, and the average value of the falling ball strength was taken as the average falling ball strength.

Falling ball strength (J) = mass of iron ball (kg) × gravity acceleration (9.81m/s ² ) × breaking height (m)

Arithmetic Mean Roughness Ra

The surface roughness of the glass substrate was measured using a stylus type surface roughness meter (Multimode V SPM-Nanoscope V controller manufactured by Veeco Co., Ltd.). In addition, the measured value is measured from the surface roughness of any two places of the glass plate, and is represented by the average value.

Edge Strength Test

For the edge strength of the glass substrate, the edge strength was measured by a three-point bending test or a four-point bending test in accordance with "JIS R 1601 (2008) Fine Ceramic Bending Strength Test Method".

The results of the evaluation of the glass obtained by the glass strengthening method of the present invention by the above evaluation method are shown in Table 1.

Further, when the etching amounts of Examples 1-1 to 1-4 were measured by measuring the thickness before and after the etching, they were all 1 μm.

As shown in Table 1, it can be seen that after the chemical strengthening step, the glass-etched glass (Examples 1-1 to 1-4) was compared with the unetched glass (Comparative Examples 1-1 to 1-3), and the ball ring was obtained. The strength is relatively high and the roughness of the surface becomes uniform.

[Embodiment 2]

A plate-shaped glass containing the glass 2A or 2B having the following composition was processed into a shape of 5 mm × 40 mm × 1 mmt, and a surface of 5 mm × 40 mm was mirror-polished using yttrium oxide to prepare a glass test piece. The edge of the glass test piece was chamfered using #600 diamond.

Glass 2A: SiO ₂ : 64.5%, Al ₂ O ₃ : 6%, MgO: 11%, CaO: 0.1%, SrO: 0.1%, Na ₂ O: 12%, K ₂ O: 4%, ZrO ₂ : 2.5 %

Glass 2B: SiO ₂ : 71.3%, Al ₂ O ₃ : 2%, MgO: 10.4%, CaO: 0.3%, Na ₂ O: 10.8%, K ₂ O: 4.6%, ZrO ₂ : 0.5%

20 sheets of the obtained glass test piece were wet-etched for 3 minutes and 12 seconds by an ultrasonic cleaning machine using 5% HF. Thereafter, the glass test piece containing the glass 2A was immersed in a molten salt of 100% of KNO ₃ heated to 425 ° C for 6 hours to carry out chemical strengthening.

The glass test piece containing the chemically strengthened glass 2A had a surface compressive stress of 993 MPa and a surface compressive stress layer of 31 μm. The glass test piece containing the glass 2B was immersed in a molten salt of 100% of KNO ₃ heated to 400 ° C for 7 hours to carry out chemical strengthening. The glass test piece containing the chemically strengthened glass 2B had a surface compressive stress of 648 MPa, and the surface compressive stress layer had a depth of 32 μm. The surface compressive stress and the depth of the surface compressive stress layer were measured using a surface stress meter (FSM-6000LE) manufactured by Ohara.

The glass test piece which has been subjected to the wet etching described above and the glass test piece which was not subjected to the wet etching were respectively subjected to a four-point bending test according to the "JIS R 1601 (2008) Fine Ceramic Bending Strength Test Method" for 20 pieces. Perform an edge strength test. The results are shown in Table 2.

As shown in Table 2, regarding the glass 2A having a faster etching rate than the soda lime glass, the edge strength of the etched glass was improved as compared with the non-etcher (Example 2-1 and Comparative Example 2-1). On the other hand, the glass 2B having a lower etching speed of the soda lime glass hardly improved in strength even when the etching treatment was performed (Example 2-2 and Comparative Example 2-2). From this result, it is understood that the edge strength of the glass is improved by etching, and the higher the etching rate, the more remarkable the improvement in the strength by the etching treatment.

[Example 3]

In order to investigate the correlation between the composition of the glass for chemical strengthening and the etching rate, the glass A to K having the composition shown in Table 3 was reinforced by a chemical strengthening step, and then subjected to wet etching to investigate the etching rate. The results are shown in Tables 4 and 5 and Figures 4 and 5.

As shown in Tables 4 and 5 and FIG. 4, it is understood that the glass plate to be chemically strengthened is represented by mol%, and contains 50 to 70% of SiO ₂ and 0 to 25% of Al ₂ O ₃ . The composition of 0 to 25% of Na ₂ O can set the etching rate to 0.50 μm/cm ² /min or more, thereby improving the productivity of the cover glass.

Moreover, as shown in FIG. 5, it is understood that the e calculated from the following equation as a parameter of the glass composition has an inverse relationship with the etching rate, and when e exceeds 73, the etching rate becomes less than 0.5 μm/cm ² /min.

e = SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂

[Example 4]

The both sides of a float glass plate (0.8 mm thick, size 400 mm × 500 mm) of the glass composition B shown in Table 3 of Example 3 were etched by an etching solution containing HF to remove 100 μm (50 μm per one side). Thereafter, it was immersed in a KNO ₃ molten salt at 400 ° C for 1 hour to carry out chemical strengthening. The surface compressive stress was 700 MPa, and the depth of the surface compressive stress layer was 20 μm.

Thereafter, it was cut into a size of 50 mm × 50 mm using a superhard alloy grinding wheel cutter. Thereafter, the end of the main surface was subjected to a R of 0.2 mm R using a grinding stone of No. 800 or No. 325. Then, etching was performed at an etching rate of 5 μm/min by an etching liquid containing 5% by mass of HF. For the glass plate obtained in this manner, a four-point bending test was performed using a bending test apparatus to evaluate the strength.

The results are shown in Table 6 and Figures 7(a) and (b). Fig. 7(a) shows the results of using No. 800 grinding stone, and Fig. 7(b) shows the result of using No. 325 grinding stone. In FIGS. 7(a) and 7(b), the intensity of each post-enhancement etching amount is divided by the value of the strength at the time of the post-enhancement etching amount of 0 μm as the strength improvement ratio.

As shown in Table 6 and FIG. 7(a) and FIG. 7(b), it is understood that the main surface of the glass plate is used by using an abrasive material having a coarser particle size of 1000 or more between the chemical strengthening step and the post-intensification etching step. The step of fine grinding at the end improves the edge strength of the glass sheet. Further, in the case where the polishing material of No. 325 is used for the etching and the etching is performed for 40 μm, the surface compressive stress layer which is subjected to the chemical strengthening treatment is scraped off by etching to lower the strength.

The present invention has been described in detail with reference to the preferred embodiments thereof. The present application is based on a Japanese patent application filed on Sep. 20, 2012 (Japanese Patent Application No. 2012-207318), the entire disclosure of which is incorporated by reference.

Claims (13)

A method for producing a chemically strengthened glass, comprising a chemical strengthening step of chemically strengthening a glass, and a post-enhancement etching step of etching the surface and the edge of the glass after the chemical strengthening step. A method for producing a chemically strengthened glass, comprising: a chemical strengthening step of chemically strengthening a glass, and a post-enhancement etching step of etching the surface and the edge of the glass after the chemical strengthening step, wherein the glass is based on an oxide The percentage of moles indicates that it contains 55 to 80% of SiO ₂ , 0 to 20% of Al ₂ O _{3 ,} 0 to 10% of B ₂ O ₃ , 0 to 15% of MgO, 0 to 10% of CaO, and 0 to 10% of Li ₂ O. %, Na ₂ O 0~25%, K ₂ O 0~15%, ZrO ₂ 0~10%, the total content of Li ₂ O and Na ₂ O is 8~25%, using the content of SiO ₂ , Li ₂ The total content of O, Na ₂ O and K ₂ O. The content of R ₂ O and ZrO ₂ is calculated by the following formula: e is 73 or less, and e = SiO ₂ + 0.3 × R ₂ O + 0.15 × ZrO ₂ . The method for producing a chemically strengthened glass according to claim 2, wherein the total content of MgO and CaO of the glass is 0 to 15%. The method of manufacturing a glass requested item 2 or 3 of the chemically strengthened glass wherein said Li ₂ O, Na ₂ O and K ₂ O content of the sum of R ₂ O is 25% or less. The method for producing a chemically strengthened glass according to any one of claims 2 to 4, wherein the glass has a Na ₂ O of 0 to 20%, a K ₂ O of 0 to 10%, and a ZrO ₂ of 0 to 5%. The method for producing a chemically strengthened glass according to any one of claims 2 to 5, wherein the glass has a ZrO ₂ of 0 to 2.5%. A method for producing chemically strengthened glass, comprising a chemical strengthening step of chemically strengthening glass, and After the chemical strengthening step, the surface and the edge of the glass are etched by a post-enhancement etching step of 4 μm or more. The method for producing a chemically strengthened glass according to claim 7, wherein the glass is a glass plate, and the main surface of the glass plate is used between the chemical strengthening step and the post-intensification etching step by using an abrasive material having a coarser particle size of 1000 or more. The main surface end grinding step of performing fine grinding with the intersection of the end faces. The method for producing a chemically strengthened glass according to claim 7 or 8, wherein the glass is a glass plate, and the surface roughness Ra of the intersection of the main surface and the end surface of the glass plate is included between the chemical strengthening step and the post-intensification etching step. The main surface end grinding step of performing fine polishing in a manner of 0.1 to 30 μm. The method for producing a chemically strengthened glass according to claim 8 or 9, wherein in the post-enhancement etching step, the surface and the edge of the glass plate are etched by 30 μm or less. The method for producing a chemically strengthened glass according to any one of claims 1 to 10, wherein the chemically strengthened glass is a chemically strengthened cover glass. The method for producing a chemically strengthened glass according to any one of claims 1 to 11, wherein the surface of the chemically strengthened glass has an arithmetic mean roughness Ra of 1 nm or less. The method for producing a chemically strengthened glass according to any one of claims 1 to 12, wherein an etch rate of the glass in a 5% aqueous HF solution at 25 ° C is 0.50 μm/cm ² /min or more.