阅读说明：本技术 强化玻璃及强化用玻璃 (Tempered glass and glass for tempering ) 是由 市丸智宪 于 2019-02-04 设计创作，主要内容包括：本发明的强化玻璃的特征在于,在表面具有压缩应力层,作为玻璃组成,以质量％计含有SiO<Sub>2</Sub>40～70％、Al<Sub>2</Sub>O<Sub>3</Sub>10～30％、B<Sub>2</Sub>O<Sub>3</Sub>0～3％、Na<Sub>2</Sub>O 5～25％、K<Sub>2</Sub>O 1～5.5％、MgO 0.1～5.5％、P<Sub>2</Sub>O<Sub>5</Sub>2～10％,由0.41×[SiO<Sub>2</Sub>]+2.17×[Al<Sub>2</Sub>O<Sub>3</Sub>]-5.28×[B<Sub>2</Sub>O<Sub>3</Sub>]-0.54×[Na<Sub>2</Sub>O]-0.04×[K<Sub>2</Sub>O]-3.29×[MgO]+5.09×[P<Sub>2</Sub>O<Sub>5</Sub>]表示的X值为70以上。(The tempered glass of the present invention has a compressive stress layer on the surface, and contains SiO in mass% as a glass composition 2 40～70％、Al 2 O 3 10～30％、B 2 O 3 0～3％、Na 2 O 5～25％、K 2 O 1～5.5％、MgO 0.1～5.5％、P 2 O 5 2 to 10% of a composition consisting of 0.41X SiO 2 ]+2.17×[Al 2 O 3 ]‑5.28×[B 2 O 3 ]‑0.54×[Na 2 O]‑0.04×[K 2 O]‑3.29×[MgO]+5.09×[P 2 O 5 ]Value of X shownIs 70 or more.)

1. A tempered glass having a compressive stress layer on its surface,

the glass composition contains SiO in mass%₂40％～70％、Al₂O₃10％～30％、B₂O₃0％～3％、Na₂O 5％～25％、K₂O 1％～5.5％、MgO 0.1％～5.5％、P₂O₅2％～10％，

From 0.41 × [ SiO ]₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more.

2. The tempered glass according to claim 1, wherein the glass composition contains SiO in mass%₂40％～70％、Al₂O₃10％～30％、B₂O₃0％～3％、Na₂O 7％～20％、K₂O 1.5％～5.5％、MgO0.5％～5.5％、P₂O₅2％～8％。

3. The strengthened glass according to claim 1 or 2, as glassA glass composition containing SiO in mass%₂45％～65％、Al₂O₃15％～25％、B₂O₃0％～2％、Na₂O 10％～18％、K₂O 2％～5％、MgO 1％～4％、P₂O₅2％～7％。

4. The strengthened glass according to any one of claims 1 to 3, wherein the glass is composed of-5.40 × [ SiO ]₂]+9.69×[Al₂O₃]+18.08×[B₂O₃]+2.87×[Na₂O]+18.25×[K₂O]-5.79×[MgO]-2.89×[P₂O₅]The Y value is 30 or less.

5. The strengthened glass according to any one of claims 1 to 4, wherein the Vickers hardness value is 630 or greater.

6. The tempered glass of any one of claims 1-5, wherein the tempered glass is used as a cover glass for a cellular phone.

7. A glass for strengthening, characterized by comprising SiO in a mass% as a glass composition₂40％～70％、Al₂O₃10％～30％、B₂O₃0％～3％、Na₂O 5％～25％、K₂O 1％～5.5％、MgO 0.1％～5.5％、P₂O₅2％～10％，

From 0.41 × [ SiO ]₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more.

8. A glass for strengthening, characterized by comprising SiO in a mass% as a glass composition₂40％～60％、Al₂O₃13％～26％、B₂O₃0％～1.8％、Na₂O 8％～25％、K₂O 0.01％～5.5％、MgO 0％～5.5％、P₂O₅2.1％～8.5％、CaO+SrO+BaO 0％～2.5％，

From 0.41 × [ SiO ]₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more.

9. The reinforcing glass according to claim 7 or 8, wherein the phase separation occurrence viscosity is 10^5.5dPas or more.

Technical Field

The present invention relates to a tempered glass and a glass for tempering, and more particularly to a tempered glass and a glass for tempering suitable for a cover glass of a mobile phone, a PDA (mobile terminal), and the like.

Background

Devices such as portable phones, digital cameras, PDAs, touch panel displays, large televisions, and contactless power supplies are becoming increasingly popular.

In these applications, strengthened glass subjected to ion exchange treatment is used (see patent document 1 and non-patent document 1).

In recent years, the use of tempered glass for exterior parts of digital signage, mice, smartphones, and the like has been increasing.

The main required properties of the tempered glass include (1) high mechanical strength, (2) high scratch resistance, (3) light weight, and (4) low cost. In particular, in applications to smart phones, there are demands for a thin profile and high drop impact strength.

Disclosure of Invention

Problems to be solved by the invention

As a method for improving the drop impact strength, it is effective to increase the stress depth of the tempered glass.

However, in the conventional tempered glass, when the stress depth is increased, the ion exchange time becomes extremely long, and the production efficiency is significantly lowered.

Therefore, patent document 2 proposes to include P in the glass composition in order to increase the ion exchange rate₂O₅Glass for strengthening (containing P)₂O₅Glass of (d). However, the compound contains P₂O₅The glass of (2) has a problem of low acid resistance. In addition, the P-containing compound₂O₅When the glass of (2) is exposed to a high temperature during production, it is separated into phases to cause cloudiness, which tends to lower the visibility.

The present invention has been made in view of the above circumstances, and has the technical subjects of: the invention comprises P in the glass composition₂O₅The tempered glass and the tempered glass have high ion exchange speed, good acid resistance and are less likely to cause phase separation.

Means for solving the problems

The present inventors have conducted various studies and, as a result, have found that: the above technical problem can be solved by strictly limiting the glass composition, and the present invention has been made. That is, the tempered glass of the present invention has a compressive stress layer on the surface, and contains SiO in mass% as a glass composition₂40～70％、Al₂O₃10～30％、B₂O₃0～3％、Na₂O 5～25％、K₂O 1～5.5％、MgO 0.1～5.5％、P₂O₅2 to 10% of a composition consisting of 0.41X SiO₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more. Here, are each [ SiO ]₂]Represents SiO₂(content (mass%), [ Al₂O₃]Represents Al₂O₃(amount (mass%), [ B₂O₃]Is represented by B₂O₃(iii) content (mass%), [ Na₂O]Represents Na₂O content (% by mass) and [ K ]₂O]Represents K₂O content (mass%), [ MgO]Represents the MgO content (% by mass), [ P ]₂O₅]Represents P₂O₅Content (mass%) of (c).

In addition, for the tempered glass of the present invention, it is preferable that: the glass composition contains SiO in mass%₂40～70％、Al₂O₃10～30％、B₂O₃0～3％、Na₂O 7～20％、K₂O 1.5～5.5％、MgO 0.5～5.5％、P₂O₅2～8％。

In addition, for the tempered glass of the present invention, it is preferable that: the glass composition contains SiO in mass%₂45～65％、Al₂O₃15～25％、B₂O₃0～2％、Na₂O 10～18％、K₂O 2～5％、MgO 1～4％、P₂O₅2～7％。

Further, it is preferable that the tempered glass of the present invention has a composition of-5.40 × [ SiO ]₂]+9.69×[Al₂O₃]+18.08×[B₂O₃]+2.87×[Na₂O]+18.25×[K₂O]-5.79×[MgO]-2.89×[P₂O₅]The Y value is 30 or less.

Further, the tempered glass of the present invention preferably has a vickers hardness value of 630 or more. Here, the "Vickers hardness" is a value measured in accordance with JIS Z2244-1992 by pressing into a Vickers indenter with a Vickers hardness tester at a load of 100gf, and is an average value measured 10 times.

The tempered glass of the present invention is preferably used for a cover glass of a mobile phone.

The glass for strengthening of the present invention is characterized by containing SiO in mass% as a glass composition₂40～70％、Al₂O₃10～30％、B₂O₃0～3％、Na₂O 5～25％、K₂O 1～5.5％、MgO 0.1％～5.5％、P₂O₅2 to 10% of a composition consisting of 0.41X SiO₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more.

The glass for strengthening of the present invention is characterized by containing SiO in mass% as a glass composition₂40～60％、Al₂O₃13～26％、B₂O₃0～1.8％、Na₂O 8～25％、K₂O 0.01～5.5％、MgO 0％～5.5％、P₂O₅2.1 to 8.5% of CaO + SrO + BaO, 0 to 2.5% of CaO + SrO + BaO, and made of 0.41 x [ SiO ]₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more. Here, "CaO"+ SrO + BaO "refers to the total amount of CaO, SrO, and BaO.

Further, it is preferable that the phase separation viscosity of the glass for reinforcing of the present invention is 10^5.5dPas or more. Here, the "phase separation occurrence viscosity" refers to a value obtained by measuring the viscosity of glass at a phase separation occurrence temperature by the platinum ball pulling method. "phase separation onset temperature" means: the glass powder which passed through a standard sieve of 30 mesh (500 μm) and remained in 50 mesh (300 μm) was put into a platinum boat and kept in a temperature gradient furnace for 24 hours, and then the platinum boat was taken out, and the highest temperature of cloudiness due to phase separation inside the glass was visually recognized.

Detailed Description

The tempered glass (glass for tempering) of the present invention is characterized by containing SiO in terms of mass% as a glass composition₂40～70％、Al₂O₃10～30％、B₂O₃0～3％、Na₂O 5～25％、K₂O 0.01～5.5％、MgO 0～5.5％、P₂O₅2 to 10% of a composition consisting of 0.41X SiO₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]The X value represented is 70 or more. The reason why the content ranges of the respective components in the tempered glass (glass for tempering) of the present invention are limited is shown below. In the description of the content range of each component,% expression means mass% unless otherwise specified.

SiO₂Is a component used to form the network of the glass. If SiO₂When the content of (b) is too small, vitrification becomes difficult and acid resistance is liable to decrease. Thus, SiO₂The preferable lower limit range of (b) is 40% or more, 40.5% or more, 41% or more, 41.5% or more, 42% or more, 42.5% or more, 43% or more, 44% or more, 45% or more, 46% or more, 47% or more, 48% or more, 49% or more, particularly 50% or more. On the other hand, if SiO₂When the content of (A) is too large, the meltability and moldability are liable to be lowered, and the thermal expansion coefficient is too low, whereby it becomes difficult to match the peripheral materialThe coefficient of thermal expansion of the material. Thus, SiO₂The preferable upper limit range of (b) is 70% or less, 68% or less, 65% or less, 62% or less, 60% or less, 58% or less, 57% or less, 56% or less, 55% or less, particularly 54% or less.

Al₂O₃Is a component for increasing the ion exchange rate and is a component for increasing the Young's modulus and increasing the Vickers hardness. Further, the viscosity of the phase separation is increased. Al (Al)₂O₃The content of (A) is 10-30%. If Al is present₂O₃When the content (b) is too small, the ion exchange rate and Young's modulus are liable to decrease. Thus, Al₂O₃The preferable lower limit range of (b) is 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 14.5% or more, 15% or more, 15.5% or more, 16% or more, 16.5% or more, 17% or more, 17.5% or more, 18% or more, 18.5% or more, 19% or more, particularly 19.5% or more. On the other hand, if Al₂O₃When the content of (b) is too large, devitrified crystals are likely to precipitate in the glass, and it becomes difficult to form a sheet by an overflow down-draw method or the like. In particular, when an alumina refractory is used as the formed refractory and plate-shaped forming is performed by the overflow downdraw method, devitrified crystals of spinel are likely to precipitate at the interface with the alumina refractory. In addition, acid resistance is also reduced, and thus it becomes difficult to apply to an acid treatment process. Further, the high-temperature viscosity becomes high, and the meltability tends to be low. Thus, Al₂O₃The preferable upper limit range of (b) is 30% or less, 28% or less, 26% or less, 25% or less, 24% or less, 23.5% or less, 23% or less, 22.5% or less, 22% or less, 21.5% or less, particularly 21% or less.

B₂O₃Is a component for reducing high-temperature viscosity and density and improving resistance to devitrification. However, if B₂O₃If the content (c) is too large, the ion exchange rate (particularly, the stress depth) tends to be lowered. Further, the glass surface is colored by ion exchange, which is called scorch, or the acid resistance and water resistance are easily lowered. Thus, B₂O₃The preferable range of (B) is 0 to 3%, 0 to 2.5%, 0 to 2%, 0 to 1.9%, 0 to 1.8%, 0 to 1.7%, 0 to 1.6%, 0 to 1.5%, 0 to 1.3%, particularly 0% or more and less than 1%.

Na₂O is an ion exchange component, and is a component that lowers the high-temperature viscosity to improve the meltability and moldability. In addition, Na₂O is also a component for improving devitrification resistance and reaction devitrification with a formed refractory, particularly an alumina refractory. If Na₂When the content of O is too small, the meltability is lowered, the thermal expansion coefficient is too low, or the ion exchange rate is liable to be lowered. Thus, Na₂The preferable lower limit range of O is 5% or more, 7% or more, 8% or more, 8.5% or more, 9% or more, 9.5% or more, 10% or more, 11% or more, 12% or more, particularly 12.5% or more. On the other hand, if Na₂When the content of O is too large, the viscosity of the resulting phase separation tends to be low. Further, the acid resistance may be lowered, or the compositional balance of the glass composition may be lost, whereby the devitrification resistance may be lowered. Thus, Na₂The preferable upper limit range of O is 25% or less, 22% or less, 20% or less, 19.5% or less, 19% or less, 18% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, particularly 15% or less.

K₂O is a component for improving the meltability and moldability by lowering the high-temperature viscosity. Further, it is also a component for improving the devitrification resistance or increasing the vickers hardness. However, if K₂When the content of O is too large, the viscosity of the resulting phase separation tends to be low. Further, the acid resistance is lowered, or the compositional balance of the glass composition is lost, and the devitrification resistance tends to be lowered. Thus, K₂The lower limit of O is preferably 0.01% or more, 0.02% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, 2, 5% or more, 3% or more, particularly 3.5% or more, and the upper limit is preferably 5.5% or less, 5% or less, particularly less than 4.5%.

MgO is a component for improving meltability and moldability by lowering high-temperature viscosity. Further, it is also a component for improving young's modulus, increasing vickers hardness, or improving acid resistance. Accordingly, the preferable lower limit range of MgO is 0% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, and particularly 2% or more. However, if the content of MgO is too large, the ion exchange rate tends to be decreased, and the glass tends to be devitrified. In particular, when an alumina refractory is used as a formed refractory and plate-shaped forming is performed by the overflow downdraw method, devitrified crystals of spinel are likely to precipitate at the interface with the alumina refractory. Accordingly, the preferable upper limit range of MgO is 5.5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, and particularly 2.5% or less.

P₂O₅Is a component for increasing the ion exchange rate while maintaining the compression stress value. Thus, P₂O₅The preferable lower limit range of (b) is 2% or more, 2.1% or more, 2.5% or more, 3% or more, 4% or more, particularly 4.5% or more. However, if P₂O₅When the content of (b) is too large, cloudiness due to phase separation occurs in the glass, or the water resistance is liable to be lowered. Thus, P₂O₅The preferable upper limit range of (b) is 10% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.5% or less, 6.3% or less, 6% or less, 5.9% or less, 5.7% or less, 5.5% or less, 5.3% or less, 5.1% or less, particularly 5% or less.

The above-mentioned X value has a strong correlation with the ion exchange rate, and the larger the X value is, the faster the ion exchange rate becomes. The preferable range of the X value is 70 or more, 70.5 or more, 71 or more, 71.5 or more, 72 or more, 72.5 or more, 73 to 90, 74 to 87, particularly 75 to 85.

The Y value has a strong correlation with acid resistance, and the smaller the Y value, the more the acid resistance is improved. The preferable range of the Y value is 30 or less, 27 or less, 25 or less, 23 or less, 20 or less, 17 or less, 15 or less, particularly-15 to 10.

Mass ratio K₂O/P₂O₅Preferably 0.7 to 1.3, in particular 0.75 to 1.25. In addition, K₂O-P₂O₅Preferably-2 to 2, -1.5 to 1.5, especially-1 to 1. If the setting is made as described above, it becomes easy to improve both the ion exchange rate and the acid resistance. Note that "K" is₂O/P₂O₅"means K₂O content divided by P₂O₅The content of (b). ' K₂O-P₂O₅"means from K₂P is subtracted from the O content (% by mass)₂O₅The content (mass%) of (c).

In addition to the above components, for example, the following components may be added.

Li₂O is an ion exchange component, and is a component that lowers the high-temperature viscosity to improve the meltability and moldability. Or a component for increasing the young's modulus. In addition, Li₂O is a component that dissolves during the ion exchange treatment and deteriorates the ion exchange solution. Thus, Li₂The preferable content of O is 0 to 2%, 0 to 1.7%, 0 to 1.5%, 0 to 1%, 0% or more and less than 1%, 0 to 0.5%, 0 to 0.3%, 0 to 0.1%, particularly 0 to 0.05%.

CaO is a component having a greater effect than other components, namely, an effect of improving meltability and moldability by lowering high-temperature viscosity without accompanying a decrease in devitrification resistance, or an effect of improving strain point and young's modulus. However, if the content of CaO is too large, the ion exchange rate decreases or the ion exchange solution is easily deteriorated. Therefore, the preferable content of CaO is 0 to 6%, 0 to 5%, 0 to 4%, 0 to 3.5%, 0 to 3%, 0 to 2%, 0 to 1%, and particularly 0 to 0.5%.

SrO and BaO are components for improving meltability, moldability, or strain point and young's modulus by lowering high-temperature viscosity, and when the content thereof is too large, the ion exchange rate is lowered, the density and thermal expansion coefficient are increased, or devitrification is likely to occur in the glass. Thus, the preferable content of SrO and BaO is 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, particularly 0% or more and less than 0.1%, respectively.

The total amount of CaO, SrO and BaO is preferably 0 to 5%, 0 to 2.5%, 0 to 2%, 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, particularly 0% or more and less than 0.1%. If the total amount of CaO, SrO and BaO is too large, the ion exchange rate tends to decrease.

ZnO is a component for increasing the ion exchange rate, and particularly has a large effect of increasing the compression stress value. Further, the viscosity at high temperature is reduced without reducing the viscosity at low temperature. However, when the content of ZnO is too large, the glass tends to be phase-separated, the devitrification resistance tends to be low, the density tends to be high, or the stress depth tends to be small. Thus, the preferable content of ZnO is 0 to 6%, 0 to 3%, particularly 0 to 1%.

TiO₂The component is a component for increasing the ion exchange rate and for reducing the high-temperature viscosity, but if the content is too large, the glass is colored or easily devitrified. Thus, TiO₂The content of (B) is 0 to 4.5%, 0% or more but less than 1%, 0 to 0.5%, particularly 0 to 0.3%.

ZrO₂Is a component for remarkably increasing the ion exchange rate and is a component for increasing the viscosity and strain point in the vicinity of the viscosity of the liquid phase, but if the content is too large, the resistance to devitrification may be remarkably reduced and the density may be excessively high. Thereby, ZrO₂The preferable content is 0 to 5%, 0 to 4%, 0 to 3%, 0 to 2%, particularly 0% or more and less than 1%.

As the fining agent, SnO is preferably introduced₂、SO₃、Cl、CeO₂Group (preferably SnO)₂、SO₃And Cl) is used. SnO₂+SO₃The preferable content of + Cl is 0.01-3%, 0.05-3%, 0.1-3%, especially 0.2-3%. Note that "SnO₂+SO₃+ Cl "is SnO₂、SO₃And the total amount of Cl.

Fe₂O₃Is an impurity component derived from a raw material, and is a component that absorbs ultraviolet light having an adverse effect on human eyes. However, if Fe₂O₃When the content of (B) is too large, the glass is coloredAnd (4) color enhancement. Thus, Fe₂O₃Preferred contents of (B) are below 1000ppm (0.1%), below 800ppm, below 600ppm, below 400ppm, below 300ppm, below 250ppm, below 200ppm, below 150ppm, in particular below 100 ppm.

Nd₂O₃、La₂O₃Etc. rare earth oxides are components for improving the young's modulus. However, the cost of the raw material itself is high, and the devitrification resistance is liable to decrease when a large amount of the raw material is added. Accordingly, the content of the rare earth oxide is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly 0.1% or less.

From the viewpoint of environment, it is preferable that the glass composition does not substantially contain As₂O₃、5b₂O₃、PbO、F、Bi₂O₃. The main point of "not substantially containing … …" is that although an explicit component is not positively added as a glass component, the mixing at the level of an impurity amount is allowed, specifically, the content of the explicit component is less than 0.05%.

The tempered glass (glass for tempering) of the present invention preferably has the following characteristics, for example.

The density is preferably 2.6g/cm³2.55g/cm below³2.50g/cm below³2.48g/cm below³Below, in particular 2.46g/cm³The following. The lower the density, the lighter the tempered glass can be.

The thermal expansion coefficient is preferably 65 to 115 x 10^-7/℃、75～115×10^-7/℃、90～110×10^-7/° C, in particular 95-105 × 10^-7V. C. If the thermal expansion coefficient is limited to the above range, the glass is less likely to be damaged by thermal shock, and therefore, the time required for preheating before the ion exchange treatment and annealing after the ion exchange treatment can be shortened. As a result, the manufacturing cost of the tempered glass can be reduced. Further, it becomes easy to match the thermal expansion coefficient of the peripheral member such as metal or organic adhesive, and peeling of the peripheral member can be prevented. Here, the "coefficient of thermal expansion" means 30 to 380 ℃ measured by using an dilatometerA value obtained by averaging the thermal expansion coefficients in the temperature range of (a).

The strain point is preferably 550 ℃ or higher, 580 ℃ or higher, 590 ℃ or higher, 600 ℃ or higher, 610 ℃ or higher, 615 ℃ or higher, particularly 620 ℃ or higher. The higher the strain point, the more difficult the ion exchange characteristics become due to KNO₃The temperature of the molten salt changes. In particular, even when the thickness is reduced, it becomes easy to strictly control the in-plane ion exchange characteristics.

High temperature viscosity 10^4.0The temperature at dPa · s is preferably 1400 ℃ or lower. High temperature viscosity 10^4.0As the temperature at dpas is lower, the load on the forming equipment is reduced, and the life of the forming equipment is prolonged, and as a result, the production cost of the tempered glass can be easily reduced. Note that "10" is^4.0The "temperature at dPa · s" can be measured by, for example, a platinum ball pulling method.

High temperature viscosity 10^2.5The temperature at dPa · s is preferably 1650 ℃ or lower, 1620 ℃ or lower, particularly 1600 ℃ or lower. High temperature viscosity 10^2.5The lower the temperature at dpas, the lower the melting temperature, the more the low-temperature melting becomes possible, and the load on glass production facilities such as a melting furnace is reduced and the bubble quality is easily improved. Thus, high temperature viscosity 10^2.5The lower the temperature at dPa · s, the easier it becomes to reduce the production cost of the tempered glass. Note that "10" is^2.5The "temperature at dPa · s" can be measured by, for example, a platinum ball pulling method.

Viscosity at high temperature 10^4.0dPa·s、10^2.5When the temperature at dPa · s is increased, the alkali metal oxide, the alkaline earth metal oxide, and B are added₂O₃、ZnO、TiO₂Or by reducing SiO₂、Al₂O₃The amount of (b) becomes liable to decrease.

The vickers hardness is preferably 630 or more, 640 or more, 650 or more, 660 or more, 670 or more, 675 or more, 680 or more, 685 or more, and particularly 690 or more. If the vickers hardness is too low, the scratch resistance is likely to be lowered. The Vickers hardness is based on Al₂O₃Increase in amount of MgOAnd thus becomes easy to rise.

The phase separation viscosity is preferably 10^4.0dpa s or more, 10^4.4dpa s or more, 10^4.8dpa s or more, 10^5.010 dPas or more^5.3dPas or more, particularly 10^5.5dPas or more. If the viscosity of the separated phase is too low, it becomes difficult to perform plate-like molding by the overflow downdraw method.

When the glass is immersed in 5 mass% hydrochloric acid at 80 ℃ for 24 hours with shaking, the amount of mass loss per unit surface area of the glass is preferably 30mg/cm²Below, 25mg/cm²Below, 20mg/cm²Below, 15mg/cm²Below, in particular 10mg/cm²The following. If the amount of the mass reduction is too large, the glass is likely to be deteriorated in the acid treatment process of the device.

The tempered glass of the present invention has a compressive stress layer on the surface. The compressive stress value of the compressive stress layer is preferably 300MPa or more, 400MPa or more, 500MPa or more, 600MPa or more, 700MPa or more, 800MPa or more, 900MPa or more, and particularly 950MPa or more. The larger the compression stress value is, the higher the mechanical strength of the tempered glass becomes. On the other hand, if a very large compressive stress is formed on the surface, the tensile stress in the strengthened glass becomes extremely high, and the dimensional change before and after the ion exchange treatment may become large. Accordingly, the compressive stress value of the compressive stress layer is preferably 1500MPa or less, 1300MPa or less, 1200MPa or less, and particularly 1100MPa or less.

The stress depth is preferably 50 μm or more, 55 μm or more, 60 μm or more, 65 μm or more, 70 μm or more, 75 μm or more, particularly 80 μm or more. As the stress depth increases, even if deep damage occurs in the tempered glass, the tempered glass is less likely to break and variation in mechanical strength is reduced. On the other hand, the larger the stress depth, the larger the dimensional change before and after the ion exchange treatment becomes. Thus, the stress depth is preferably 120 μm or less, 115 μm or less, particularly 110 μm or less.

The internal tensile stress value is preferably 150MPa or less, 140MPa or less, 130MPa or less, 120PMa or less, 110MPa or less, 100MPa or less, 90MPa or less, 80MPa or less, particularly 70MPa or less. If the internal tensile stress value is too high, the tempered glass tends to break by itself due to physical impact or the like. On the other hand, if the internal tensile stress value is too low, it becomes difficult to ensure the mechanical strength of the tempered glass. The internal tensile stress value is preferably 5MPa or more, 15MPa or more, 20MPa or more, 25MPa or more, and particularly 30MPa or more. The internal tensile stress can be calculated by the following equation 1.

[ mathematical formula 1]

Internal tensile stress value (compressive stress value x stress depth)/(sheet thickness-2 x stress depth)

The glass for strengthening of the present invention is characterized by containing SiO in mass% as a glass composition₂40～70％、Al₂O₃10～30％、B₂O₃0～3％、Na₂O 5～25％、K₂O 1～5.5％、MgO 0.1％～5.5％、P₂O₅2 to 10% of a composition consisting of 0.41X SiO₂]+2.17×[Al₂O₃]-5.28×[B₂O₃]-0.54×[Na₂O]-0.04×[K₂O]-3.29×[MgO]+5.09×[P₂O₅]X represents a value of 70 or more; further, the composition is characterized by containing SiO in mass%₂40～60％、Al₂O₃13～26％、B₂O₃0～1.8％、Na₂O 8～25％、K₂O 0.01～5.5％、MgO 0％～5.5％、P₂O₅2.1-8.5%, CaO + SrO + BaO 0-2.5%, and X is above 70%. The technical features of the tempered glass of the present invention are common to those of the tempered glass of the present invention, and a detailed description thereof will be omitted.

The glass for strengthening of the present invention can be produced as follows. Preferably: first, a glass raw material prepared so as to have a desired glass composition is charged into a continuous melting furnace, heated and melted at 1500 to 1700 ℃, and clarified, and then the molten glass is supplied to a forming apparatus, further subjected to sheet-like forming, and cooled. A known method can be used for cutting the sheet-like material into a predetermined size after the sheet-like material is formed.

In the forming of the molten glass, it is preferable to cool the molten glass at a cooling rate of 3 ℃/min or more and less than 1000 ℃/min in a temperature region between the annealing point and the strain point of the molten glass, and the cooling rate is preferably 10 ℃/min or more, 20 ℃/min or more, 30 ℃/min or more, particularly 50 ℃/min or more, and is preferably less than 1000 ℃/min, less than 500 ℃/min, particularly less than 300 ℃/min. If the cooling rate is too high, the structure of the glass becomes coarse, and it becomes difficult to increase the vickers hardness after the ion exchange treatment. On the other hand, if the cooling rate is too low, the production efficiency of the glass for reinforcement is lowered. After the molten glass is formed into a plate shape, a separate step of heating the reinforcing glass and cooling the glass at the cooling rate may be provided.

As a method for forming a molten glass into a sheet shape, an overflow down-draw method is preferably employed. The overflow down-draw method is a method that can produce high-quality glass sheets in large quantities and can also easily produce large-sized glass sheets. In addition, in the overflow down-draw method, alumina and zirconia are used as the formed refractory, and the glass plate for reinforcement of the present invention has good compatibility with alumina and zirconia, particularly alumina, and therefore, is less likely to react with these formed bodies to generate bubbles, pits, and the like.

In addition to the overflow downdraw process, various forming methods may be used. For example, a forming method such as a float method, a down-draw method (slit down-draw method, redraw method, or the like), a rolling method, or a pressing method can be used.

The tempered glass of the present invention can be produced by subjecting a glass for tempering to ion exchange treatment. The conditions of the ion exchange treatment are not particularly limited, and the optimum conditions may be selected in consideration of the viscosity characteristics, the application, the thickness, the internal tensile stress, the dimensional change, and the like of the glass. In particular, if KNO is used₃The K ions in the molten salt are ion-exchanged with the Na component in the glass, whereby the compressive stress layer on the surface can be efficiently formed.

The number of ion exchange treatments is not particularly limited, and may be carried out once or more. In the case of performing the ion exchange treatment a plurality of times, the number of times of the ion exchange treatment is preferably 2 times. This can increase the stress depth and reduce the total amount of tensile stress accumulated in the glass.