JP2012106897A - Glass composition for chemical strengthening - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass composition having excellent heat resistance and excellent ion exchange capability, and capable of being imparted with high strength by a chemical strengthening treatment with ion exchange.SOLUTION: The glass composition contains, by mass, 53-62% SiO, 11-17% AlO, 0-5% LiO, 10-15% NaO, 3-9% KO, 0-4% MgO, 0-4% CaO, 0-6% SrO, 0-5% BaO, 1-4% ZrOand 2-6% TiO.

Description

  The present invention relates to a glass composition having high heat resistance and capable of imparting a larger reinforcing layer to chemical strengthening treatment accompanying ion exchange.

  Since glass has excellent properties such as high surface smoothness and large surface strength, it is widely used for display substrates such as touch panels and color filters.

  However, glass has the disadvantage of being easily broken. As countermeasures, so-called strengthening treatment has been performed by applying compressive stress to the surface by rapid cooling or ion exchange. Among the tempering treatments, the chemical tempering treatment by ion exchange is a tempering treatment suitable for a display substrate material and the like because it is easily tempered even if the thickness of the glass is small compared to other tempering treatments.

  The chemical strengthening treatment gives compressive stress to the glass surface by exchanging ions (generally Na) in the vicinity of the surface of the glass with ions having a larger ion radius. Is naturally influenced by the composition of the glass.

For example, shown in _{mass%, SiO 2 58~65%, Al} 2 O 3 8~15%, Li 2 O 4~10%, Na 2 O 9~13%, ZrO 2 0.5~2%, ZnO A glass for chemical strengthening containing _{2 to} 5% and P ₂ O ₅ 0.5 to 2% is disclosed (see Patent Document 1).

Further, for example, shown in _{mass%, SiO 2 59~68%, Al} 2 O 3 9.5~15%, Li 2 O 0~1%, Na 2 O 3~18%, K 2 O 0~3. 5%, 0~15% MgO, CaO 1~15%, SrO 0~4.5%, BaO 0~1%, ZrO 2 1~10%, TiO 2 0~2%, containing, for chemical strengthening Glass is disclosed (see Patent Document 2).

JP 2000-7372 A JP 2005-15328 A

  Chemically strengthened glass has resistance to scratches on the glass surface due to the size of the strengthening layer, and the resistance to scratches increases as the strengthening layer increases. The reinforcing layer is also correlated with the amount of ion exchange in ion exchange.

Of course, the ease of strengthening and the size of the reinforcing layer are affected by the composition of the glass. For example, the one described in JP-A-2000-7372 requires Li ₂ O, P ₂ O ₅ , and ZnO, and contains a large amount, so that the glass transition point is low and warping tends to occur during strengthening. _Also, poor chemical durability to contain P 2 _{O 5.}

  Moreover, although what is described in Unexamined-Japanese-Patent No. 2005-15328 is CaO, although a claim is wide, in the Example, it is contained in large quantities. In the potassium nitrate solution generally used, it is known that the strengthening ability is remarkably lowered by dissolution of CaO, and it is difficult to say that the composition is suitable for chemical strengthening.

  In view of such conventional technology, the present invention aims to provide a glass composition that is resistant to surface scratches even when used as, for example, glass for a touch panel display, and that can impart a high mechanical strength by chemical strengthening treatment. And

The present invention is shown in _{mass%, SiO 2 53~62%, Al} 2 O 3 11~17%, Na 2 O 10~15%, K 2 O 3~9%, CaO 0~4%, MgO 0 _{~4%, SrO 0~6%, BaO} 0~5%, ZrO 2 1~4%, characterized in that it comprises TiO 2 2 to 5%, of the components.

In the present invention, the ion exchange capacity (ion exchange weight per glass surface area in the chemical strengthening treatment) is 0.2 mg / cm ² or more in the chemical strengthening treatment of the potassium nitrate solution at a temperature 0.9 times the glass strain point. It is a glass composition.

  Moreover, this invention is said glass composition whose glass transition point is 580 degreeC or more.

  Further, according to the present invention, by immersing a glass article containing the above glass composition in a molten salt containing a monovalent cation having an ionic radius larger than the Na ion radius, the Na ion contained in the glass article and the above one. The present invention provides a chemically strengthened article obtained by ion exchange with a valent cation.

  The glass composition of the present invention can obtain a large chemically strengthened layer by chemically strengthening. Further, even when the glass is heated to a high temperature, deformation due to heat hardly occurs.

The glass composition of the present invention is expressed in mass%,
_{SiO 2 53~62%, Al 2 O} 3 11~17%, Na 2 O 10~15%, K 2 O 3~9%, CaO 0~4%, 0~4% MgO, SrO 0~6%, _{BaO 0~5%, ZrO 2 1~4%} , TiO 2 2~5%, preferably made of. A glass composition having this preferred glass composition can be more reliably provided with a large chemical strengthening layer by chemical strengthening treatment.

  The glass composition preferably has a glass transition point of at least 580 ° C. Even if this glass composition is subjected to a high-temperature heat treatment such as heating in a molten salt during chemical strengthening, for example, the glass is not easily deformed.

  According to the chemically strengthened glass article of the present invention, since a large reinforcing layer is formed on the surface of the glass article, the mechanical strength is increased and the glass can be prevented from being broken when an impact is applied from the outside. .

  Furthermore, the chemically tempered glass article of the present invention is resistant to surface scratches, since a large tempered layer is formed on the surface of the glass article, so that there is little deterioration in strength due to scratching from the outside or scratches due to scratching.

  Hereinafter, the reasons for limiting the composition of the glass composition of the present invention will be described. In the following description, all percentages indicating the composition are mass%.

SiO ₂ is a component for forming a glass preferably contains 53 to 62% by mass%. If the SiO ₂ content is less than 53%, the chemical durability is poor. If it exceeds 62%, the melting temperature of the glass becomes high and it becomes difficult to obtain a homogeneous glass.

Al ₂ O ₃ is a component that is the main component of glass like SiO ₂ and is a component that increases the ion exchange rate and improves the water resistance of the glass, and is preferably contained in an amount of 11 to 17% by mass. If Al ₂ O ₃ is less than 11%, it is difficult to obtain the effect. On the other hand, if it exceeds 17%, the viscosity of the glass melt becomes high and it becomes difficult to obtain a homogeneous glass, which is not suitable. More desirably, it is 11 to 15%.

Li ₂ O is a component that improves the strength of the glass by allowing Li ions to be ion exchanged with other cations such as Na ions and K ions in the molten salt. However, when the content is large, there is a drawback that the heat resistance of the glass is impaired. Therefore, the content of Li ₂ O is desirably 5% or less.

Na ₂ O is a component that improves the strength of the glass while improving the strength of the glass by ion exchange of Na ions with other cations such as K ions in the molten salt. If it is 10% or less, the effect is not sufficient and the meltability is poor. On the other hand, if it exceeds 15%, chemical durability deteriorates.

K ₂ O is a component that improves the solubility of glass in the same manner as Na ₂ O, and therefore, 3% or more is preferable. However, normally, chemical strengthening uses potassium nitrate molten salt, so if the content of K ₂ O exceeds 9%, sufficient ion exchange does not occur. Therefore, 9% or less is preferable.

  MgO is a component that lowers the viscosity of the glass and improves the solubility, but in order to increase the devitrification temperature of the glass, it is preferable to contain 0 to 4% by mass.

  CaO, like MgO, is a component that lowers the viscosity of the glass and improves the solubility, but it raises the devitrification temperature of the glass. Therefore, it is preferable to contain 0 to 5% by mass.

  SrO, like MgO and CaO, is a component that lowers the viscosity of the glass and improves the solubility. However, SrO is preferably contained in an amount of 0 to 6% by mass in order to prevent the movement of alkali components in the glass. .

  BaO, like MgO and CaO, is a component that lowers the viscosity of the glass and improves the solubility. However, since BaO hinders the movement of the alkali component in the glass, it is preferably 5% by mass or less.

ZrO ₂ is a component that increases the ion exchange rate and improves the water resistance of the glass, and if it is 1% or less, its effect is not sufficient, and if it exceeds 4%, the melting temperature becomes high. Is preferred.

TiO ₂ is a component that lowers the viscosity of the glass and improves the solubility, but it does not deteriorate the chemical durability as much as the alkali component, so 2% or more is essential, and when the content of TiO ₂ exceeds 5% Since devitrification temperature rises and a moldability is prevented, 2 to 5% by mass is preferable. More preferably, it is 4 to 5%.

It may also contain up to 1% in mass% in total of _{As 2 O 3, Sb 2 O} 3, SnO 2 as a fining agent, if necessary.

Hereinafter, a description will be given based on examples. Glass having the glass composition shown in Examples 1 to 11 of the glass composition of the present invention was prepared by melting experiments, and the melting temperature, working temperature, thermal expansion coefficient, glass transition point, and strain point of the obtained glass were obtained. Table 1 shows the measurement results of devitrification temperature and chemical strengthening ability. Comparative examples are shown in Table 2.

  The glass preparation of Examples 1-10 and Comparative Examples 1-4, and the physical property of the obtained glass were implemented according to the following procedures.

(Production of glass)
Conventional glass materials such as silica, alumina, lithium carbonate, sodium carbonate, potassium carbonate, magnesium oxide, calcium carbonate, strontium carbonate, barium carbonate, titanium oxide, silicic acid so as to have the glass composition shown in Table 1 or Table 2 Glass raw material (batch) was prepared using zirconium. After mixing the prepared batch, the mixture was put into a platinum crucible, heated in an electric furnace at 1600 ° C. for 3 hours, and then stirred twice with a platinum rod. After heating and holding again for 2 hours, it was poured onto a carbon plate at 1500 ° C., immediately put into a 650 ° C. slow cooling furnace, cooled to 550 ° C. in 4 hours, and then allowed to cool in the furnace to obtain a glass block.

(Physical property measurement)
Sample glass is processed into a cylindrical shape having a diameter of 5 mm and a length of 20 mm, and a thermal expansion coefficient of 30 ° C. to 300 ° C. according to JIS R3102, 3103 using a differential thermal dilatometer (Thermoplus manufactured by RIGAKU Corporation, TMA8310). And the glass transition point was measured.

  The high temperature viscosities log η = 2 and 4 were measured using an Opto ball pulling viscometer BVB-13LH.

The bending point was measured using a beam bending viscometer BBVM-900 (manufactured by Opto) to determine the strain point. (Conforms to JIS R3103-2)
After holding at a predetermined temperature for 2 hours using a temperature gradient furnace (manufactured by Eiko), the presence or absence of crystals was confirmed using a polarizing microscope ECLIPSE E600 POL (manufactured by Nikon), and the devitrification temperature was measured.

The ion exchange capacity was defined as the increased weight per glass surface area due to the exchange of Na ⁺ for K ⁺ . The larger the amount of increase, the higher the ion exchange capacity.

  The glass is optically polished to about 40 × 40 × 3 mm, ion-exchanged in potassium nitrate at a temperature 0.9 times the strain point for 4 hours, and the weight (0.1 mg unit) and dimensions before and after the treatment are measured. The increased weight per surface area was calculated.

As shown in Table 1 and Table 2, the glass transition points of Examples 1 to 10 in the present invention are heat resistant at 580 ° C. or higher. In addition, the glass has a chemical strengthening ability of 0.2 mg / cm ² or more and is easy to ion-exchange. If the amount of ion exchange is large, the ion exchange layer from the glass surface to the inside becomes deep and it can be said that the glass is strong against scratches on the surface. .

On the other hand, Comparative Example 1 is a general float glass, but its chemical strengthening ability is as low as 0.06 mg / cm ² and can be said to be a weak glass.
Moreover, although the comparative example 2 is the glass of Example 4 of Unexamined-Japanese-Patent No. 2000-7372, a glass transition point is as low as 450 degreeC and heat resistance is low.
Moreover, although the comparative example 3 is the glass of Example 5 of Unexamined-Japanese-Patent No. 2005-15328, chemical strengthening ability is as few as 0.17 mg / cm < ² >.

Comparative Example 4 has a high BaO content of 8.9% and a low chemical strengthening ability of 0.17 mg / cm ² .

(Industrial applicability)
The present invention provides a glass composition that is resistant to external surface scratches such as scratches on a display substrate such as a touch panel, and that can impart high mechanical strength by chemical strengthening treatment.

Claims (4)

Indicated by mass%
SiO ₂ 53~62%,
Al ₂ O ₃ 11-17%,
Na ₂ O 10-15%,
K ₂ O 3-9%,
CaO 0-4%,
MgO 0-4%,
SrO 0-6%,
BaO 0-5%,
ZrO ₂ 1-4%,
TiO ₂ 2-5%,
A glass composition comprising: The ion exchange capacity (ion exchange weight per glass surface area in the chemical strengthening treatment) is 0.2 mg / cm ² or more in the chemical strengthening treatment of a potassium nitrate solution having a temperature 0.9 times the glass strain point. Glass composition.   The glass composition of Claim 1 or 2 whose glass transition point is 580 degreeC or more.   The glass article containing the glass composition according to any one of claims 1 to 3 is contained in the glass article by immersing the glass article in a molten salt containing a monovalent cation having an ionic radius larger than the Na ion radius. Chemically tempered glass article obtained by ion-exchange of Na ions and the monovalent cations