CN112694255A - Low-phosphorus alkali-free glass easy to melt, decompress and clarify and suitable for float forming - Google Patents

Abstract

The invention relates to low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming, and is characterized by being prepared from the following raw materials in percentage by mol: 63.5-64 mol% SiO₂2-3 mol% of GeO₂0.1-0.2 mol% of P₂O₅11-12 mol% of Al₂O₃0.1 to 0.4 mol% of ZrO₂5-6 mol% of B₂O₃3 to 4mol percent of MgO, 4.5 to 5mol percent of CaO, 4 to 4.5mol percent of SrO, 2.9 to 3.6mol percent of BaO and 0.1 to 0.5mol percent of SrF₂And 0.1-0.5mol% of CaCl₂. The invention has the beneficial effects that: the melting temperature of the glass is reduced to < 1638 ℃ from 1638-1665 ℃; the surface tension is reduced from 330 to 350mN/m to 310 to 328mN/m, and the glass is easier to melt at low temperature and clarify under reduced pressure; the glass meets the use requirement of electronic information display, simultaneously improves the thermal stability of the glass, and reduces the thermal shrinkage rate from 3.8-3.9ppm to 2.8-3.2 ppm; the prepared glass can be applied to the fields of electronic information display, high-end touch control and the like.

Description

Low-phosphorus alkali-free glass easy to melt, decompress and clarify and suitable for float forming

Technical Field

The invention relates to the field of glass manufacturing, in particular to low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming.

Background

At present, the base plate glass of the alkali-free silicate glass such as TFT-LCD, LTPS-LCD and the like is mainly alkali-free aluminosilicate glass, and the alkali-free aluminosilicate glass has the characteristic of high viscosity due to the fact that the formula contains more aluminum oxide (10-13 mol.%) and calcium oxide (4-5 mol.%) and the surface tension of the glass is high (about 20% higher than that of the common soda-lime glass) under the same temperature condition.

In the float process, molten glass is flattened and cooled on a horizontal plane by utilizing gravity, but the alkali-free aluminosilicate glass has high viscosity (the melting temperature 1650-; this aspect affects the properties of the glass; on the other hand, since the density is not uniform, the glass is easily warped when subjected to the strengthening treatment in the downstream processing plant, so that the processing yield of the float glass is lower than that of the overflow glass.

If the viscosity of the molten glass is reduced simply by increasing the temperature, the product cost is increased, and the requirement on equipment is higher, so that the problem of viscosity is not solved simply by increasing the temperature, and the material formula is considered comprehensively. The existing alkali-free glass plate still has the need of greatly improving the thermal stability (thermal expansion and thermal contraction), but along with the improvement of the performance, the high-temperature viscosity and the surface tension of the glass are greatly increased, the glass forming stability is reduced, and the requirements of clarification and forming production processes are difficult to meet.

The glass batch proposed in patent publication No. CN108483900A, namely, "a low-phosphorus alkali-free glass batch suitable for float molding", has the advantages that the surface tension of the molten glass is reduced, the density uniformity of the product is improved, but the melting and clarifying temperature is higher (up to 1638-1665 ℃ in the embodiment), which means the implementation difficulty is increased for the industrial production, and the product cost is correspondingly increased; meanwhile, the surface tension of the molten glass is measured to be higher than 330mN/m according to melting of the batch materials, which is not beneficial to carrying out decompression clarification operation.

Disclosure of Invention

The invention aims to solve the problems of difficult implementation and high cost in industrial production of the low-phosphorus alkali-free glass batch suitable for float forming disclosed in the patent publication No. CN108483900A, and provides low-phosphorus alkali-free glass which is easy to melt and refine under reduced pressure and is suitable for float forming.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming is characterized by being prepared from the following raw materials in percentage by mole:

63.5-64 mol% SiO₂2-3 mol% of GeO₂0.1-0.2 mol% of P₂O₅11-12 mol% of Al₂O₃0.1 to 0.4 mol% of ZrO₂5-6 mol% of B₂O₃，3-4mol%MgO, 4.5-5 mol% CaO, 4-4.5 mol% SrO, 2.9-3.6 mol% BaO, 0.1-0.5mol% SrF₂And 0.1-0.5mol% of CaCl₂。

Further, in the above-mentioned low-phosphorus alkali-free glass (GeO)₂+P₂O₅)/SiO₂The molar ratio of (A) to (B) is 0.03 to 0.05.

Further, CaCl in the low-phosphorus alkali-free glass₂And SrF₂Is 1: 1.

The low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming is characterized by comprising the following steps: weighing the raw materials according to the proportion, mixing, melting and clarifying under the reduced pressure condition of 300-500 mbar, and then sequentially molding and annealing.

The invention adjusts GeO₂And P₂O₅The content of the component (B) is controlled within a specific range (molar content (GeO)₂+P₂O₅)/SiO₂0.03-0.05), the structure of the glass network is further relaxed, the compactness of the original glass network is reduced, and the melting temperature (less than 1638 ℃) and the forming difficulty of the glass are reduced; in the adjustment of GeO₂And P₂O₅The content reduces the compactness of the glass network, and simultaneously, the content of other glass components is correspondingly adjusted, so that each performance index of the glass can be maintained at the level meeting the use requirement of electronic information display (such as strain point is more than 650 ℃, annealing point is more than 715 ℃, softening point is more than 950 ℃, thermal expansion coefficient is more than 3.6E-6/DEG C, transmittance is more than 90.5%, Young modulus is more than 72GPa and the like);

in addition, the invention also introduces 0.1-0.5mol percent of SrF₂And 0.1-0.5mol% of CaCl₂The surface tension of the glass is reduced to 310-328 mN/m, and bubbles in the molten glass are easily discharged under the decompression condition within the surface tension value, so that decompression clarification is facilitated.

The invention has the beneficial effects that:

1. the melting temperature of the glass is reduced to < 1638 ℃ from 1638-1665 ℃; the surface tension (1600 ℃) of the glass is reduced to 310-328 mN/m from the original 330-350 mN/m, so that the glass is easier to melt at low temperature and clarify under reduced pressure;

2. the glass prepared by the invention meets the use requirement of electronic information display, and simultaneously improves the thermal stability of the glass, particularly the thermal shrinkage rate of the glass (reduced from 3.8-3.9ppm to 2.8-3.2 ppm); the prepared glass can be applied to the fields of electronic information display, high-end touch control and the like;

3. due to the reduction of the melting temperature, the unit energy consumption of melting glass is reduced by about 10 percent, and the embodiment can be seen.

Drawings

FIG. 1 is a graph showing the fining effect of the molten glass at 0.1MPa in example 1;

FIG. 2 is a graph showing the clarifying effect of the molten glass at 0.05MPa in example 1;

FIG. 3 is a graph showing the clarifying effect of the molten glass at 0.03MPa in example 1;

FIG. 4 is a graph showing the fining effect of the molten glass at 0.1MPa in example 2;

FIG. 5 is a graph showing the clarifying effect of the molten glass at 0.05MPa in example 2;

FIG. 6 is a graph showing the clarifying effect of molten glass at 0.03MPa in example 2;

FIG. 7 is a graph showing the fining effect of the molten glass at 0.1MPa in example 3;

FIG. 8 is a graph showing the clarifying effect of the molten glass at 0.05MPa in example 3;

FIG. 9 is a graph showing the effect of clarifying the molten glass at 0.03MPa in example 3.

Detailed Description

The low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming comprises the following specific implementation steps.

Examples

Uniformly mixing the raw materials according to the following table 1, then carrying out reduced pressure melting (4-6 h) and clarification in an atmosphere furnace under the reduced pressure condition of 300-500 mbar, and then sequentially carrying out forming and annealing (3-7 h); the alkali-free glass is tested for density, linear thermal expansion coefficient, strain point, elastic modulus and other data, and the test results are listed in table 1.

According to the invention, the glass can be further subjected to mechanical processing treatment as required after the annealing. The mechanical processing treatment in the present invention is not particularly limited, and various mechanical processing methods commonly used in the art may be used, and for example, the product obtained by the annealing treatment may be cut, ground, polished, and the like.

Table 1 examples 1-3 and comparative example 1 data:

FIGS. 1 to 3, 4 to 6, and 7 to 9 show the clarifying effect of the molten glass under the condition of gradual pressure reduction in examples 1 to 3, and it can be seen from the figure that the number of bubbles in the molten glass gradually decreases with the decrease of the air pressure, indicating a good pressure reduction clarifying effect.

Claims (4)

1. The low-phosphorus alkali-free glass which is easy to melt, easy to reduce pressure and clarify and suitable for float forming is characterized by being prepared from the following raw materials in percentage by mole:

63.5-64 mol% SiO₂2-3 mol% of GeO₂0.1-0.2 mol% of P₂O₅11-12 mol% of Al₂O₃0.1 to 0.4 mol% of ZrO₂5-6 mol% of B₂O₃3 to 4mol percent of MgO, 4.5 to 5mol percent of CaO, 4 to 4.5mol percent of SrO, 2.9 to 3.6mol percent of BaO and 0.1 to 0.5mol percent of SrF₂And 0.1-0.5mol% of CaCl₂。

2. The fusible, pressure-reducing and clarifying low-phosphorus alkali-free glass suitable for float forming according to claim 1, wherein: CaCl in low-phosphorus alkali-free glass₂And SrF₂Is 1: 1.

3. The fusible, pressure-reducing and fining low-phosphorus alkali-free glass suitable for float forming according to claim 1 or 2, wherein: low phosphorus alkali-free glass (GeO)₂+P₂O₅)/SiO₂The molar ratio of (A) to (B) is 0.03 to 0.05.

4. The method for preparing the easily meltable, pressure-reducing and clarifying low-phosphorus alkali-free glass suitable for float forming according to claim 1 or 2, which is characterized by comprising the following steps: weighing the raw materials according to the proportion, mixing, melting and clarifying under the reduced pressure condition of 300-500 mbar, and then sequentially molding and annealing.

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