JP2003040644A - Glass composition for lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-free glass composition for lighting having an excellent thermal processability and an excellent electrical isolation and weathering resistance and. SOLUTION: The composition is as follows in mass percentage, SiO2 is 60-75%, Al2 O3 is 1-4%, Na2 O is 3-8%, K2 O is 1-7%, Li2 O is 1.5-3%, Li2 O+Na2 O+ K2 O is 5-15%, CaO is 0-3%, MgO is 0-2%, BaO is 4.1-6.5%, SrO is 0.5-10%, MgO+CaO+BaO+SrO is 4.5-16%, B2 O3 is 0-3%, ZrO2 is 0-3% and TiO2 is 0.2-3%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition for lighting used in fluorescent lamps, incandescent lamps, etc., and substantially frees lead as a component from the glass for a long period of time (weathering). The present invention relates to a glass composition for lighting that is unlikely to occur.

[0002]

2. Description of the Related Art Conventionally, a stem portion that seals an introduction gland in a fluorescent lamp or an incandescent light bulb has an electric resistance sufficient to prevent generation of a leak current, and is heat-treated to soften at a relatively low temperature. Lead-based glass containing 20 to 30 mass% of PbO has been used because of its good properties.

However, lead is a toxic substance, and the volatilization of the lead component during the melting and processing of the lead-based glass and the scattering from the raw materials adversely affect the worker, and the emission and use into the atmosphere from the manufacturing process. Since it is feared that the diffusion of used products will cause environmental pollution, in recent years, development of alternative glass compositions containing no lead has been promoted also in the field of glass products.

Similarly, from the viewpoint of environmental protection, the development of a glass capable of reducing the amount of mercury enclosed in a fluorescent lamp is under way. The amount of mercury in the fluorescent lamp is pre-filled in more than necessary amount because it is expected that mercury will be consumed when the lamp is lit. Mercury is consumed by reacting the sodium component in the glass with mercury.
It has been found to occur by forming an amalgam.

Illumination glasses which do not contain lead are disclosed in, for example, JP-A-6-206737 and JP-A-9-12.
For example, the one described in Japanese Patent No. 3332 is available. JP-A-6-
The glass described in Japanese Patent No. 206737 is a barium silicate glass having a BaO content of 7 to 11% by weight and having an electric insulation property equivalent to that of lead glass.
The glass described in Japanese Patent No. 2332 is one in which the BaO content of barium silicate glass is suppressed to improve the devitrification property, and the tube forming by the Danner method is facilitated.

[0006] Further, as a glass for lighting in which the sodium component is reduced in order to reduce the consumption of mercury, for example, Table 1
There is one described in Japanese Patent Laid-Open No. 1-509514. This glass has a Na ₂ O content of almost 0, but instead of this, Li ₂ O is 0.5 to 4% and K ₂ O is 1%.
The viscosity of glass is lowered by containing it at a relatively high rate of 0 to 15%.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The barium silicate glass disclosed in Japanese Patent No. 737 has a problem that devitrified substances are likely to be formed when the tube is formed by the Danner method, as pointed out in Japanese Patent Application Laid-Open No. 9-12332. Further, when glass containing BaO at a high rate, the furnace material is severely corroded during melting, which shortens the life of the melting furnace and causes problems such as defective spots due to the eroded refractory.

On the other hand, in order to suppress the erosion of the furnace material by BaO, a means for increasing the amount of SrO having the same electrical characteristics as BaO, instead of BaO, as in the glass disclosed in Japanese Patent Laid-Open No. 9-12332. However, increasing the SrO content increases the devitrification tendency and increases the raw material cost.

The soda-free glass disclosed in JP-A-11-509514 is an expensive raw material, Li.
_Since it is necessary to use a large amount of ₂ O and K ₂ O,
This inevitably increases the product price, which is not desirable from an economic point of view. Further, this glass is based on the above-mentioned JP-A-6-206737.
Since BaO is contained at a relatively high rate like the glass disclosed in the publication, the problems of devitrification generation and furnace material erosion are still included.

Further, it has been found that in these glasses, deterioration of the glass surface due to the influence of moisture in the atmosphere, etc., in particular, white clouding called weathering is more likely to occur than lead-containing glass that has been conventionally used. . Weathering appears as a cloudy change on the glass surface during storage of the semi-finished product or use of the product, and is therefore extremely unsuitable as a glass for lighting.

The present invention has been made in view of the above circumstances, and is substantially free of lead, while maintaining the excellent heat workability and electric insulation required for lighting glass, It is an object of the present invention to provide a glass composition for lighting which hardly causes devitrification and has less surface deterioration due to weathering.

[0012]

In order to achieve the above-mentioned object, the present invention has a mass percentage of SiO ₂ 60 to 75%,
Al ₂ O ₃ 1 to 4%, Na ₂ O 3 to 8%, K ₂ O 1 to
7%, Li ₂ O 1.5 to 3%, Li ₂ O + Na ₂ O +
K ₂ O 5-15%, CaO 0-3%, MgO 0-2
%, BaO 4.1 to 6.5%, SrO 0.5 to 10
%, MgO + CaO + BaO + SrO4.5-16%,
B ₂ O ₃ 0 to 3%, ZrO ₂ 0 to 3%, TiO ₂ 0.
It is characterized by containing 2-3%.

Next, the function of the components constituting the glass of the present invention and the reason why the content is limited as described above will be explained.

SiO ₂ is a glass network-forming component, but if it is less than 60%, the chemical durability of the glass tends to be low.
If it exceeds 75%, the meltability and processability of glass deteriorate.

Al ₂ O ₃ has the effect of improving the chemical durability of the glass, but if it is less than 1%, phase separation occurs in the glass and molding is difficult, and if it exceeds 5%, striae occur and homogeneity occurs. Glass cannot be obtained, and devitrification becomes stronger.

Li ₂ O, Na ₂ O and K ₂ O act as a flux to improve the meltability of the glass. At the same time, it has the effect of adjusting the thermal expansion coefficient of the glass, but the total amount of these is 5%.
If it is less than 1, the viscosity becomes high, the meltability deteriorates, and the coefficient of thermal expansion becomes too low. Further, if the total amount exceeds 15%, the chemical durability is lowered and the thermal expansion coefficient becomes too high, which is not preferable. In addition, since these alkali metal oxides produce a mixed alkali effect when they coexist and enhance the electric insulating property, it is preferable to add them in a mixed manner, not alone. Further, Na ₂ O and K ₂ O are not effective in adjusting the coefficient of thermal expansion of the glass when the content is less than the lower limit, respectively, and the coefficient of thermal expansion becomes too high when the content exceeds the upper limit.
It is not preferable from the viewpoint of reducing the amount of mercury used in fluorescent lamps. Particularly, the upper limit of the Na ₂ O content is preferably 6.5% or less. When Li ₂ O is less than the above lower limit value, it is unavoidable to increase the amount of Na ₂ O and K ₂ O added in order to obtain good meltability and heat processability, which lowers the chemical durability and reduces the sodium component. It is not preferable because it goes against the idea. If Li ₂ O exceeds 3%, the thermal expansion coefficient becomes too high, which is not preferable.

BaO is a component which imparts a high electric insulating property to glass, but if it is less than 4%, the desired electric insulating property cannot be obtained, and if it exceeds 6.5%, the erosion of the melting furnace material becomes remarkable, and the product is The number of defective spots inside increases. Preferably 4.5-
It is 6.5%.

Like BaO, SrO contributes to the electrical insulation of glass, but if it is less than 0.5%, the desired electrical insulation cannot be obtained, and if it exceeds 10%, the devitrification tendency increases and the raw material cost rises. To do. Preferably, the upper limit is 8%.

MgO and CaO each have the effect of improving the chemical durability of the glass when added up to the above upper limits, but if added over the respective upper limits, the glass tends to devitrify, which is not preferable.

MgO, CaO, BaO and SrO have a function of enhancing the electrical insulating property of the glass as a whole, but if the total amount of these is less than 4.5%, the effect is insufficient as a glass for lighting, and 16%. If it exceeds, the tendency of glass to crystallize increases. The lower limit is preferably 5% or more.

A small amount of B ₂ O ₃ has the effect of improving the meltability, but if it is added in excess of 3%, the chemical durability of the glass deteriorates and weathering occurs on the surface during long-term use.

ZrO ₂ has the effect of improving the chemical durability of glass, but if it exceeds 3%, the meltability will deteriorate.
ZrO ₂ is effective in a small amount, but on the other hand, it is likely to cause defects in the appearance of glass. Therefore, the range is preferably 0.01-3%.

A small amount of TiO ₂ has the effect of suppressing solarization due to ultraviolet rays, and increasing the amount of TiO ₂ has the effect of improving chemical durability, but if its content exceeds 3%, appearance defects due to coloring of the glass occur. Easier to do. If TiO ₂ alone improves the weather resistance, 1.5
The range is up to 3%.

Since both ZrO ₂ and TiO ₂ are components that impart resistance to surface deterioration of glass, it is preferable to add them together, but if their total amount is less than 0.5%, the effect is expected. If it exceeds 5%, the meltability and appearance quality will be impaired. Preferably 0.5%
The range is 3%.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The glass of the present invention can be manufactured as follows. First, the above composition range, for example, SiO
₂ 65.0%, Al ₂ O ₃ 3.5%, Na ₂ O 7.0
%, K ₂ O 5.5%, Li ₂ O 1.5%, CaO
2.0%, MgO 1.0%, BaO 6.0%, SrO
The raw materials are weighed and mixed so as to be 5.0%, B ₂ O ₃ 2.0%, and TiO ₂ 0.5%. This raw material mixture is placed in a platinum crucible and heated and melted in an electric furnace. After stirring and clarification, it is molded into a desired form. In the case of mass production molding into a tubular shape for producing an illumination stem, an exhaust pipe, etc., it can be molded without problems by melting in a tank furnace and using a known tube drawing molding method such as the Danner method.

[0026]

EXAMPLES Further, the glass composition for illumination of the present invention will be described in detail with reference to Examples. Table 1 shows examples of the present invention and conventional examples. The composition in the table is expressed by mass%, and each sample was melted in a platinum crucible and cast into a mold in the same manner as in the above-mentioned embodiment to obtain samples for measuring various properties shown in Table 1.
As described in the table, a small amount of auxiliary components such as a fining agent may be added as long as the desired characteristics are not impaired.

Explaining the items in the table, the average coefficient of thermal expansion is 10 times the average coefficient of thermal expansion at 0 to 300 ° C.
^-7 K ^-1 , and the electric resistance is a measured value at 100 ° C by log ρ (Ω-cm). Further, Tg is a transition temperature, which is a temperature at which the glass has a viscosity η = 10 ^13.3 dPa · s,
Ts is the softening temperature, the viscosity of the glass η = 10 ^7.65 dPa ·
The temperature is s.

The weathering resistance is determined by cutting each sample glass into a plate shape, polishing the plate surface, and storing the sample glass in a constant temperature and humidity chamber kept at a temperature of 60 ° C. and a humidity of 95% and holding it for 500 hours. The results of visual evaluation of the degree of deterioration of the state are shown. In the table, “◎” indicates almost no change from the initial state, “○” indicates slight deterioration (white cloudiness),
“△” indicates that there was a white deterioration due to moderate deterioration,
“X” represents that the glass surface was deteriorated over a wide area like a white film.

[0029]

【table 1】

[0030]

【table 1】

As is apparent from Table 1, No. 1 which is an embodiment of the present invention. Glasses 1 to 10 have an average coefficient of thermal expansion that is substantially the same as that of soda lime glass generally used for electric bulbs and fluorescent lamps, and can be well welded to these glass parts, and also have an electrical resistance. It is a sufficiently high value. Further, it has a low softening temperature and excellent heat processability. Also,
No devitrification was observed in the glass of the present invention through the steps such as melting and casting.

Regarding weathering, although it can be said that the occurrence of weathering is not absent even in the embodiment of the present invention, even if it occurs, the degree thereof is mild and N described as a comparative example.
o. It exhibited a performance equivalent to that of the 12 lead glass. On the other hand, the conventional example No. containing no ZrO ₂ or TiO ₂ . 11
The average thermal expansion coefficient, electric resistance, and Tg and Ts of the glass of No. 3 were the same as those of the examples of the present invention, but the degree of weathering was strong and the entire surface was clouded.

Before the weathering resistance test, the wavelength 4
The spectral transmittance at 00 nm was measured and the temperature 60
500 in a constant temperature and humidity chamber kept at ℃ and 95% humidity
When the spectral transmittance at a wavelength of 400 nm was measured again after a lapse of time and the reduction rates were compared, conventional example No. 1
While the glass of No. 1 showed a decrease of about 20%,
In the example of the present invention, it was suppressed to 10% or less.

[0034]

INDUSTRIAL APPLICABILITY As described above, the glass of the present invention has substantially the same excellent electrical insulation and heat resistance as the lead-based glass used for lighting, although it does not substantially contain lead. It has workability and does not cause environmental problems due to lead. Also,
Since the sodium component in the glass has been reduced, it also contributes to a reduction in the amount of mercury enclosed when used in fluorescent lamps. Furthermore, since it has excellent weldability with soda lime glass, it is suitable as lighting glass. Moreover, since weathering is unlikely to occur, there is an advantage that it can provide the same quality for long-term storage and use.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G062 AA03 BB01 DA06 DB03 DC01                       DC02 DC03 DD01 DE01 DF01                       EA03 EB03 EC03 ED01 ED02                       ED03 EE01 EE02 EE03 EF02                       EF03 EG03 FA01 FB02 FC01                       FC02 FC03 FD01 FE01 FF01                       FG01 FH01 FJ01 FK01 FL01                       GA01 GB01 GC01 GD01 GE01                       HH01 HH03 HH05 HH07 HH09                       HH11 HH13 HH15 HH17 HH20                       JJ01 JJ03 JJ05 JJ07 JJ10                       KK01 KK03 KK05 KK07 KK10                       MM24 NN29 NN40                 5C043 EB15

Claims (2)

[Claims] 1. A mass percentage of SiO 2₂ 60-75%,
Al₂ O₃ 1-4%, Na₂O 3-8%, K₂O 1-
7%, Li₂O 1.5-3%, Li₂O + Na₂ O + K
₂O 5-15%, CaO 0-3%, MgO 0-2
%, BaO 4.1 to 6.5%, SrO 0.5 to 10
%, MgO + CaO + BaO + SrO4.5-16%,
B₂O₃0-3%, ZrO₂0-3%, TiO_Two 0.
A glass composition for lighting, containing 2-3%
Stuff. 2. A TiO ₂ content of 1.
The glass composition for lighting according to claim 1, which is 5 to 3%.