JPS6356181B2 - - Google Patents

Description

[Detailed description of the invention]

Tungsten-halogen lamps have been used in the European automobile industry for a long time, and have begun to penetrate the American automobile industry in the past few years. Such lamps have several practical advantages over conventional closed-beam lamps: (1) the light emitted is whiter than that by conventional lamps; (2) they emit as much or more light than conventional lamps; (3) the illuminance remains approximately constant over the life of a tungsten-halogen lamp; and (4) tungsten-halogen lamps have a significantly longer operating life than traditional incandescent lamps. long-
have. However, since tungsten-halogen lamps operate at much higher temperatures than standard lamps (collection zone temperatures can be between 500° and 700°C), the envelopes used in such lamps are not thermally stable at these temperatures. It must be resistant to thermal deformation. The envelope is made of fused silica and 96
% quartz glass composition as raw material.
This is because these components exhibit strain points that are much higher than the lamp operating temperature. However, disadvantageously, these components are very expensive and are not directly applicable to standard mass production techniques. Additionally, these glasses are difficult to mold into lamp specifications and have very low coefficients of thermal expansion, requiring special sealing steps to introduce the leads into the lamp. Accordingly, considerable research has been undertaken to obtain glasses that exhibit melting and forming properties that can be used in the mass production of lamp envelopes, while at the same time exhibiting the physical properties required for that use. This compositional study primarily concerns glasses in alkaline earth aluminosilicate systems. These examples are detailed below. U.S. Patent No. 3,496,401 describes tungsten
It concerns a glass specially designed for use as an envelope in iodine incandescent lamps. The glass has a coefficient of thermal expansion of 30-50×10 ^-7 /°C, a strain point higher than 500°C, and a concentration of 55-70% (expressed as oxide weight percent).
It consists of _SiO2 , 13-25% _{Al2O3 ,} 10-25% alkaline earth metal oxides and _0-10 % _B2O3 .
Alkali metal oxides are preferably absent and in no case exceed a total of 0.1%. Preferred glasses contain BaO,
Contains _{no B2O3} . U.S. Pat. No. 3,798,491 primarily describes (expressed in oxide weight percent) 59-70%
_SiO2 , 10-20% _Al2O3 and _7.4-28 % BaO
The invention relates to the manufacture of tungsten-halogen lamps having a glass envelope consisting of tungsten-halogen lamps.
The coefficient of thermal expansion of the glass is 36 to 40×10 ⁻⁷ /°C. U.S. Pat. No. 3,978,362 primarily (expressed as oxide weight percent) contains 58-63%
_SiO2 , 13-16% _Al2O3 , _14-21 % CaO, 0
Consisting of ~5% MgO and 0-7% BaO,
The present invention relates to a glass envelope for a tungsten-bromine lamp, in which the sum of CaO + MgO + BaO is 19% or more. Preferably _, alkali metal oxides and _B2O3 are absent. The coefficient of thermal expansion of the glass is
48-55×10 ^-7 /°C, and the strain point is higher than 700°C. US Pat. No. 4,060,423 discloses that the liquidus temperature is
1250℃ or less, strain point is 725℃ or more, and thermal expansion coefficient is 42 to 48 × 10 ^-7 /℃, mainly (expressed as oxide weight %), 55 to 68%.
of _SiO2 , 15-18% _Al2O3 , _7-13 % CaO, 6
A glass composition is described which is particularly suitable for the envelope in a tungsten-halogen lamp, consisting of ~16% BaO and trace amounts of incidental impurities, residual fluxing agent and refining agent, respectively. CaO:
The weight ratio of BaO is 0.6:1 to 1:1. Preferred glass compositions are free _of PbO, _B2O3 and alkali metal oxides. US Pat. No. 4,255,198 has a strain point higher than 730℃, a liquidus temperature lower than 1200℃, a liquidus viscosity of 40000 poise or higher, and a thermal expansion coefficient of 43~
48 × 10 ^-7 / °C, mainly (expressed as oxide weight %), 62-64% SiO ₂ , 14-
16% _{Al2O3 ,} 10-13% CaO and 7-9%
A glass for use in a tungsten-halogen lamp envelope is disclosed that is comprised of SrO. Alkali metal oxides must be avoided, MgO and/or BaO may be tolerated up to 5%. U.S. Pat. No. 4,302,250 was filed by Paul S. Danielson on September 8, 1980 and is entitled "Glass Envelope for Tungsten-Halogen Lamps," which has a strain point higher than 750°C; The liquidus temperature is less than 1300℃, the liquidus viscosity is 40000 poise or more, the viscosity is less than 1000 poise at a temperature of 1520℃ or less, and the coefficient of thermal expansion is
42-44 × 10 ^-7 / °C, mainly (expressed in oxide weight), 64-68% SiO ₂ , 11-14
% CaO, 16.5-18.5% _Al2O3 and _3-6 %
of SrO + BaO (0-4% SrO and 0-5%
Comprises glass compositions devised for use as glass envelopes in tungsten-halogen lamps, consisting of BaO).
The molar ratio of SrO:BaO is 2:1 to 1:2. European Patent Application No. 0019850 was filed by Tokyo Shibaura Electric Co., Ltd. on May 21, 1980, claimed priority on May 24, 1979, entitled "Halogen Incandescent Light Bulb" and filed on May 21, 1980. Published on April 10th, the strain point is 675℃ or higher and the coefficient of thermal expansion is
41-48×10 ^-7 /℃, mainly (expressed in terms of oxide), 55-65% SiO ₂ , 15-22%
_Al2O3 , 5-10% CaO, 6-10% _MgO , 3-
6% B ₂ O ₃ and minimal amounts of each accompanying oxide,
A glass composition suitable for use in a tungsten-halogen lamp envelope is included, comprising a residual flux and a residual fining agent. The only example provided is 57
% SiO ₂ , 20% Al ₂ O ₃ , 6% CaO, 8%
It consisted of MgO and 4% _B2O3 , the sum of these components being 95% _. British patent application GB2060602A October 1980
Filed by Carl-Zeiss Stiftung on August 8, 1979.
Claiming priority on October 11, 1981, entitled "Alkali-free sealing glass for molybdenum"
It was published on August 7th, and has a transition temperature of 775° to 810°C and a coefficient of thermal expansion of 46 to 51×10 ^-7 /°C.
Glass compositions suitable for the manufacture of tungsten-halogen lamps are described. The glass can be colorless, or can be made yellowish by adding CeO ₂ +TiO ₂ to the base composition. The maximum ranges listed (expressed as oxide weight percent) are: SiO ₂ 57.00-64.00 Al ₂ O ₃ 12.50-16.50 ZrO ₂ 1.00-5.50 Al ₂ O ₃ +ZrO ₂ 15.00-19.00 CaO 11.50-19.20 BaO 0-6.50 CeO ₂ 0-8.00 TiO ₂ 0-4.50 CaO+BaO+CeO ₂ +TiO ₂ 18.60-25.70 As ₂ O ₃ 0-0.30. Unfortunately, each of the above disclosed glasses has drawbacks. Its major drawback is the inherent difficulty experienced in melting and forming the composition using standard commercial mass production glass forming techniques. Since tungsten-halogen lamp envelopes are typically manufactured from segments of glass tubes, the most desirable glass will be one that exhibits thermal stability and viscosity parameters compatible with the Vello high speed tube drawing process. The main purpose of the present invention is that it can be formed into a tubular shape using the Vero process, and has the following physical properties: a coefficient of thermal expansion (0° to 300°C) of 42 to ⁴⁵ By providing a glass composition suitable for use in high temperature tungsten-halogen lamps, which exhibits a liquidus temperature of 670°C or higher, a liquidus temperature of less than 1150°C, and a liquidus viscosity of greater than 2×10 ⁴ poise. be. The present objective was to obtain a glass composition consisting primarily of _{the following} components ₍ expressed _as weight percent in terms of oxides) _: This can be achieved by using . The total amount of SiO ₂ +Al ₂ O ₃ is important in determining the viscosity, strain point and coefficient of thermal expansion of the composition according to the invention. Generally, for example, when the amount of SiO ₂ +Al ₂ O ₃ is small, the strain point of the glass becomes low. On the other hand, SiO ₂ +
If the Al ₂ O ₃ concentration is very high, the glass will have a high viscosity and will be very difficult to melt. Therefore, the total amount of SiO ₂ +Al ₂ O ₃ will be kept at about 74.5-78%. The weight ratio of SiO ₂ :Al ₂ O ₃ has a considerable influence on the liquidus temperature of the composition according to the invention. For example, if the liquidus temperature is too high, glass cannot be formed into a tube using the Vero process. Therefore,
The weight ratio of SiO ₂ :Al ₂ O ₃ should be about 3.3 to 3.8. The CaO:MgO weight ratio is extremely important regarding the expansion properties of the glass. If this ratio exceeds a certain value, the coefficient of thermal expansion of the composition according to the invention will become too high. Conversely, if this ratio is too low, not only will the coefficient of thermal expansion of the glass fall below the required range, but the liquidus temperature of the glass will rise, which may cause problems during melting. Therefore,
The CaO:MgO weight ratio must be maintained at approximately 1.3-1.8. Finally, the amount of B ₂ O ₃ is carefully controlled to give the glass a sufficiently low viscosity that it melts easily and does not result in expansion. Also,
B ₂ O ₃ also tends to flatten the viscosity-temperature relationship exhibited by glass. However, if the amount of B ₂ O ₃ is too high, the strain point of the glass decreases to an undesirably low value. Conversely, if B ₂ O ₃ is below the minimum value, the liquidus temperature will rise to an unacceptable value. For most ideal lamp operation, the glass should be free of alkali metals, iron, and chlorides. None of these materials are intentionally mixed into the composition. Impurity concentrations in the batch components must be maintained at less than 0.2% alkali metal oxides and less than 0.04% iron oxides. The target composition for the most preferred glass is: Al ₂ O ₃ 17.4±0.2 B ₂ O ₃ 4.5±0.1 CaO 10.9±0.1 MgO 7.8±0.1 SiO ₂ 59.4 (with the remainder ) and has the following physical properties: Strain point 681℃ Coefficient of thermal expansion 42.9×10 ^-7 /℃ Internal liquidus 1126℃ Liquidus viscosity 3.8×10 ⁴ poise. The table reports several glass compositions expressed as weight ratios in terms of oxides, and these compositions have critical characteristics that must be taken care of to produce glasses that satisfy the required physical properties. Useful in indicating compositional parameters. For all practical purposes, the listed ingredients can be considered to be recorded in percent by weight, since each ingredient adds up to 100 or nearly 100. The actual batch components may be oxides or other compounds that convert in appropriate proportions to the required oxides when totally melted. For example, CaCO ₃ can be used as a CaO source. The batch raw material was entirely ball milled to ensure uniform melting and then placed in a platinum crucible.
The crucible is placed in a furnace operated at approximately 1550℃, and
kept in the oven for an hour. Then, remove the crucible from the furnace and pour the melt into a steel mold, approximately 6″ x 6″ x 1/2
A glass plate with dimensions of 2" was formed and the slab was immediately transferred to a lehr kiln operating at 740°C. (The reported composition was melted in a laboratory crucible only, but if necessary For example, it should be understood that larger quantities of glass melt can be processed in commercial crucibles or continuous glass melting equipment.)

Table The table shows the values of some of the physical properties of the glasses of the examples described above, determined according to methods customary in glass technology. The coefficient of thermal expansion is measured over a temperature range of 0° to 300°C and is recorded in units of ×10 ⁻⁷ /°C. The strain point and internal liquidus line are expressed in °C, and the viscosity of glass at the liquidus temperature is expressed in poise.

[Table] It is clearly and fully shown in the above example that the adjustment of the composition is of great importance. That is, Examples 1 to 5 exhibit the required physical property values, whereas Examples 7 to 12, while having approximately the same composition as the glass according to the invention, are outside the specified range and thus their properties Shows no value. Therefore, one or more of the above-mentioned physical properties render the glass according to the invention unsuitable for the required use.

Claims (1)

[Claims] 1. Strain point is 670°C or higher, thermal expansion coefficient (0° to 300°C)
42 to 45 × 10 ^-7 /℃, liquidus temperature is less than 1150℃, viscosity at liquidus temperature is greater than 2 × 10 ⁴ poise, and mainly when expressed as % by weight in terms of oxide, the component : _SiO2 60.0±1.5 _{Al2O3 17.0} ±1.0 _{B2O3 5.0} ±0.8 CaO 11.4±0.8 _MgO 7.5±0.8, the weight ratio of _SiO2 : _Al2O3 is maintained at about 3.3-3.8, A glass envelope for a tungsten-halogen incandescent lamp, characterized in that the weight ratio of CaO:MgO is maintained at about 1.3 to 1.8. 2. The glass according to claim 1, characterized in that it mainly consists of: Al ₂ O ₃ 17.4±0.2 B ₂ O ₃ 4.5±0.1 CaO 10.9±0.1 MgO 7.8±0.1 SiO ₂ 59.4 (remainder) envelope.