JPH0640739A - Alkali-free glass - Google Patents

Abstract

PURPOSE:To provide an alkali-free glass excellent in heat resistance, chemical resistance and optical homogeneity, used frequently as a stock for electronic parts in the electronic industry and easy to mold into a sheet by electromelting especially by direct supply of electric current and floating. CONSTITUTION:This alkali-free glass consists of, by weight, 57-59% SiO2, 11-12% Al2O3, 7-9% B2O3, 0.1-0.5% ZrO2, 21-23%, in total, of 10-12% CaO, 0.8-2% MgO and 8-11% BaO and 0.1-0.5% F2. This glass does not practically contain alkali metal oxides, PbO, ZnO, TiO2, As2O3 or Sb2O3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent heat resistance, chemical resistance and optical homogeneity, and is widely used, for example, as a material for electronic parts in the field of electronic industry. In particular, electric melting by a direct current method and molding by a float method. The present invention relates to alkali-free glass that is easy to plate.

[0002]

2. Description of the Related Art In recent years, as a transparent substrate for a display or the like, an alkali-free glass substrate in which a thin film of metal or metal oxide is formed on the surface of glass has been used.

These non-alkali glass substrates are required to have the following characteristics from the viewpoints of use as an electronic component material and manufacturing. That is, a heat treatment at a high temperature is performed in the film forming process on a glass substrate, but the heat resistance is high enough to withstand it, and the thin film formed on the substrate is etched by a chemical solution such as acid or alkali in the patterning process. However, chemical resistance is required so that the substrate glass itself is not corroded, and if bubbles, phase separations, or striae are present in the glass, optical homogeneity is required because it becomes an optical defect of a display or the like.

In addition, for industrial production, it must be easy to melt and easy to mold, and in particular, electric melting by the direct energization method that can be continuously melted with little pollution by atmosphere, furnace material, etc., It is desired that the glass composition has excellent surface smoothness and is suitable for continuous molding by the float molding.

Conventionally, the composition consists of SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ system
Glass containing components such as CaO or BaO is known. Japanese Patent Laid-Open No. 63-74935 discloses SiO ₂ --Al ₂ O ₃ --B ₂
A glass composition suitable for an electronic material substrate containing CaO, BaO, etc. in the O ₃ system and not containing MgO has been disclosed, but since it does not contain ZrO ₂ , it has poor chemical resistance such as acid resistance and hydrofluoric acid resistance, and glass. There is a problem in that it does not contain MgO which does not significantly increase the coefficient of thermal expansion of glass unlike other divalent components, by suppressing devitrification during melt molding and facilitating glass molding.

Japanese Patent Application No. 1-311289, filed by the applicant of the present invention, discloses that SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ system contains a specific amount of MgO, CaO, BaO, and ZrO ₂ and is alkali metal oxidized. We have proposed a non-alkali glass that does not contain a volatile component, a reactive component with an electrode for electric current melting, a reactive component with a reducing atmosphere, and a volatile component. The alkali-free glass is excellent in heat resistance, acid resistance, etc. and can be mass-produced by the float molding, but has a high temperature viscosity as compared with the soda-lime glass which is suitably used for the float molding. However, it is inferior in foam breakage, homogeneity, flatness of glass plate, etc., and it is difficult to operate for that amount, or it is necessary to operate at a higher temperature.

The present invention relates to the improvement of the technique proposed by the present applicant, and is excellent in heat resistance and acid resistance. Particularly, glass melt molding, electric melting by direct current method, continuous molding by float method are extremely preferable. An object is to provide an easy alkali-free glass having optical homogeneity.

[0008]

According to the present invention, SiO ₂ 57 to 59, Al ₂ O ₃ 11 to 12, B ₂ O ₃ 7 to 9 and ZrO ₂ 0.1 are expressed in weight percent.
~ 0.5, CaO 10 ~ 12, MgO 0.8 ~ 2, BaO 8 ~ 11, F ₂
0.1 to 0.5, with CaO, MgO and BaO totaling 21 to 23, consisting essentially of alkali metal oxides and PbO, ZnO
And alkali-free glass containing no TiO ₂ , As ₂ O ₃ and Sb ₂ O ₃ .

In the present invention, SiO ₂ is the main component of glass, and if it is less than 57%, the acid resistance and hydrofluoric acid resistance of the glass decrease. When it exceeds 59%, the high temperature viscosity of the glass melt becomes high, resulting in poor meltability and an increase in the devitrification tendency of the glass.
O ₂ type crystals tend to precipitate. Therefore, the range of 57 to 59% is preferable.

Al ₂ O ₃ has a function of suppressing the generation of phase separation of SiO ₂ system and B ₂ O ₃ -RO system and homogenizing it, but if it is less than 11%, the function is insufficient, and 12%. If it exceeds, the meltability deteriorates,
In addition, the devitrification tendency increases, and SiO ₂ —Al ₂ O ₃ —CaO (—MgO) -based crystals tend to precipitate. In addition, the acid resistance of the glass decreases. Therefore, the range of 11 to 12% is preferable.

B ₂ O ₃ lowers the high temperature viscosity of the glass melt and improves the meltability. Further, the glass containing this exhibits durability against hydrofluoric acid. If it is less than 7%, their effects are small,
If it exceeds 9%, the heat resistance of the glass decreases and the acid resistance also decreases. Therefore, the range of 7-9% is preferable.

ZrO ₂ itself has a higher melting point than SiO ₂ ,
Eutectic at low temperature due to coexistence of CaO, MgO and BaO. It also improves the heat resistance, acid resistance and alkali resistance of the glass.
However, if less than 0.1%, these effects are not sufficiently obtained, and
If it exceeds 5%, the viscosity at high temperature tends to increase, striae are likely to occur, and ZrO ₂ system devitrification is likely to occur to deteriorate the meltability. Therefore 0.1
It is preferably in the range of 0.5%.

The above SiO₂, B₂O₃, Al₂O₃ And ZrO₂Acid such as
Or neutral oxides, especially SiO₂, Al ₂O₃ , ZrO₂As opposed to
Basic oxides such as CaO, MgO, and BaO described below are
To coexist and act as a solvent when melting glass
This facilitates melting. That is, CaO is a glass melt
Lowers high temperature viscosity, improves meltability, and reduces devitrification tendency
Suppress. If less than 10%, those effects are insufficient,
If it exceeds 12%, the heat resistance of the glass decreases, and
Phase easily occurs. Therefore, the range is 10-12%.
It

MgO improves meltability without increasing the coefficient of thermal expansion of glass and is effective in suppressing devitrification, but 0.8%
If it is less than 2%, the effect is small, and if it exceeds 2%, white turbidity is likely to occur due to pitting corrosion by the hydrofluoric acid type liquid, and SiO ₂ -Al ₂ O ₃
-MgO-based crystals tend to precipitate and the glass tends to devitrify. Therefore, the range is 0.8 to 2%.

BaO improves the meltability in the presence of CaO and suppresses the devitrification tendency of the glass, but if it is less than 8%, its effect is insufficient. If it exceeds 11%, the acid resistance of the glass decreases, and the high temperature viscosity of the glass melt increases, resulting in poor meltability. Therefore, the range of 8 to 11% is preferable.

F ₂ is introduced as CaF ₂ , MgF _2, etc.
The majority of the components evaporate in the melting stage, but in this system, F
The effect is that the minute content of the glass melt lowers the viscosity and surface tension of the glass melt, melts, and exerts a great effect on clarity, and as a result, a glass molded product with extremely few defects can be obtained. If the amount is less than 0.1 wt%, the effect is small, and if it exceeds 0.5 wt%, there is a problem in erosion of the furnace material, and therefore the range of 0.1 to 0.5 wt% is recommended.

Further, within the above composition range, CaO +
By adjusting the MgO + BaO content to 21-23%, while maintaining the meltability of the glass in a favorable range, the viscosity-temperature gradient is moderated to improve moldability, excellent heat resistance, acid resistance, etc., and devitrification tendency. It is possible to obtain a non-alkali glass having a small size.
When CaO + MgO + BaO exceeds 23%, the meltability is improved, but the acid resistance and moldability are particularly poor. If it is less than 21%, the acid resistance is improved but the meltability is deteriorated, the devitrification tendency is increased, and the electric resistance during melting is increased, which is not suitable for electric melting. Therefore, the range is 21 to 23%.

In the present invention, the alkali metal oxide lowers the heat resistance of the glass, and in particular, when forming a metal thin film or the like on glass as a raw material for electronic parts, alkali metal ions deteriorate the surface seeping film property, and therefore, substantially. Must not exist.

Further, in order to enable electric fusion by direct current application, it is necessary to avoid reacting with a commonly used electrode such as molybdenum to form a eutectic body, and thus, to obtain PbO having reactivity. , ZnO and As ₂ O ₃ as fining agent,
It must not contain Sb ₂ O ₃ .

Further, in order to facilitate mass production by the float molding and to prevent volatilization in a reducing atmosphere such as nitrogen and hydrogen and not coloring the glass, volatile components such as PbO and ZnO and TiO ₂ , As and Reactive coloring components such as ₂ O ₃ and Sb ₂ O ₃ should not be contained substantially.

It should be noted that the reactive components with the above-mentioned alkali metal oxide and the electrode for electric current melting, the reaction with the reducing atmosphere, the volatile components and the trace amounts of SrO, Fe ₂ O ₃ , MnO ₂ , SO _{3 and} other impurities. Inclusion does not hinder the invention.

[0022]

Example: A zirconia-made refractory crucible was filled with a compounding material consisting of silica sand, aluminum hydroxide, boric acid, calcium carbonate, barium carbonate, zinc white, titanium oxide, zircon sand, and magnesium carbonate, and heated at 1550 ° C. in an electric furnace at about 1550 ° C. It was heated and melted in 5 hours. Next, the molten glass was poured into a mold, held in a nitrogen gas and hydrogen gas atmosphere furnace to form a glass block having a size of about 300 □ × 35 mm, and gradually cooled. For these glass samples, the components were analyzed for high temperature viscosity (temperature of 10 ² poise),
Acid resistance was measured. In addition, undissolved with the naked eye and under the mirror,
The presence or absence of residual bubbles, striae, phase separation, etc. was observed, and the colored state was also observed. The results are shown in Table 1.

[0023]

[Table 1]

The high temperature viscosity was measured by the sphere pulling method. The acid resistance was measured by immersing the sample in 1 / 100N nitric acid at 95 ℃ for 20 hours and then measuring the weight loss. In Table 1, Examples No. 1 to No. 5 are the glasses according to the present invention, which are excellent in melting, homogeneity, and clarification. Although not shown, the strain point exceeds 600 ° C. and the heat resistance is excellent. 10 ²
The Poise temperature, that is, the melting equivalent temperature is around 1500 ° C, and it is easy to melt in industrial production. The acid loss resistance was 0.2 or less, and no turbid white turbidity was visually observed.

On the other hand, in Comparative Examples NO.1 to NO.5, coloring and phase separation are observed, 10 ² Poise temperature exceeds 1550 ° C., melting is not easy, homogeneous melting and clarity are poor. There is nothing that can satisfy all of the displayed items.

[0026]

The alkali-free glass of the present invention has heat resistance,
Since it has excellent acid resistance, it is suitable as a glass substrate for forming a thin film of metal or metal oxide on the glass surface and etching the thin film to form a pattern. Since it is excellent in moldability and moldability by the float method, it is possible to continuously manufacture homogeneous glass without phase separation, coloring, etc. at low cost, and it is suitable for mass production.

Claims (1)

[Claims] 1. SiO ₂ 57-59, Al ₂ O ₃ 11-
12, B ₂ O ₃ 7-9, ZrO ₂ 0.1-0.5, CaO 10-12, MgO 0.
8 ~2, BaO 8 ~11, F 2 0.1~0.5, however CaO, MgO
And BaO 21 to 23 in total, which is substantially free of alkali metal oxides and PbO ₂ , ZnO ₂ , TiO ₂ , As ₂ O ₃ and Sb ₂ O ₃ .