JP2002060241A - Glass for sealing tungsten - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide glass having a composition substantially containing no PbO and suitable for the glass tube for a fluorescent lamp. SOLUTION: The glass has the composition of, by mass %, 70 to 80% SiO2, 1 to 10% Al2O3, 10 to 25% B2O3, 3 to 10% Li2O+Na2O+K2O, 0 to 3% WO3, 0.05 to 2% Sb2O3, 0 to 3% Nb2O5, 0 to 5% Bi2O3, 0 to 3% CeO2 and 0.001 to 0.05% Fe2O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition mainly used as a glass tube for a fluorescent lamp, and more particularly, to a glass composition used for a backlight of a display device such as a liquid crystal display (hereinafter sometimes referred to as an LCD). And glass suitable for sealing tungsten.

[0002]

2. Description of the Related Art In recent years, LCDs have been widely used as key devices for multimedia-related equipment. However, as their applications have expanded, weight reduction, thickness reduction, high luminance, and low power consumption have been demanded. ing. In particular, a display for a personal computer, a display device for a vehicle, a portable information terminal, and the like are required to have high-quality display quality. On the other hand, since the liquid crystal display element itself does not emit light, a transmissive liquid crystal display element using a backlight using a fluorescent lamp as a light source is used in the above-mentioned applications.

[0003] As described above, LCDs are required to be lighter, thinner, have higher luminance, and have lower power consumption.
Similarly, the backlight is smaller and lighter, has higher brightness,
Low power consumption is required, and fluorescent lamps for backlights are becoming thinner and thinner.

However, the thinning and thinning of fluorescent lamps are
This results in a decrease in mechanical strength and an increase in the temperature of the electrode due to an increase in the amount of heat generated. For this reason, a glass tube used for a fluorescent lamp for a backlight is required to have a higher strength and a lower expansion property.

Conventionally, lead-soda-based soft glass which has a proven track record as illumination glass and is excellent in workability has been used for the glass tube of this kind of fluorescent lamp. However, in the current backlight applications with a tube diameter of 5 mm or less and a wall thickness of 0.6 mm or less, it is difficult to secure sufficient strength and heat resistance in product reliability, and it is more thermally stable than lead soda-based soft glass. Considering the manufacture of fluorescent lamps using borosilicate hard glass with high mechanical strength, tungsten as a combination of metal and hard glass that can be hermetically sealed is conventionally known as a sealed wire for light bulbs and the like. And a fluorescent lamp using tungsten sealing glass have been developed and commercialized.

[0006]

The light emission principle of a fluorescent lamp for a backlight is the same as that of a fluorescent lamp for general lighting. Mercury vapor or xenon gas excited by discharge between electrodes in a fluorescent tube emits 253.7 nm ultraviolet rays. This is because the phosphor applied to the inner wall surface of the tube emits light.
However, it is known that ultraviolet rays have a function of causing discoloration of glass, and a glass in which no measures are taken against ultraviolet rays causes a discoloration action called solarization by irradiation with ultraviolet rays. When solarization occurs in the fluorescent tube glass, the resulting reduction in lamp brightness,
The color of the emitted light is changed, and the display quality of the backlight is reduced, for example, the display on the LCD becomes dark or the display color becomes unclear. In addition, when ultraviolet rays pass through the backlight glass tube and are emitted to the outside of the tube, the deterioration of the material of the resin parts and the like inside the LCD display device is promoted, the display quality is deteriorated due to coloring of the light diffusion film, and the product life is shortened. However, there is a problem that the reliability is reduced.

[0007] In the above-mentioned lead soda-based glass, lead contained as a glass component had ultraviolet-solarization resistance and ultraviolet-cutting performance, so that these did not cause any problem. Glass for sealing was originally used for sealing electronic tubes and electronic components, and no action was taken as a glass material against the effects of ultraviolet rays.
The problem of UV transmission was inevitable.

For this reason, when conventional tungsten sealing glass is used for an outer tube for a fluorescent lamp, Al ₂ O ₃ or Ti, which is a component that reflects or absorbs ultraviolet rays, is applied to the inner surface of the glass tube.
Measures have been taken to coat O ₂ , apply a phosphor thereon, form a multilayer film, and reduce the intensity of ultraviolet light reaching the glass. However, such a method inevitably increases the cost due to the difficulty in coating due to the reduction in the diameter of the glass tube and the increase in the number of coating steps.

In view of the above background, Japanese Patent Application Laid-Open No. 9-77529 proposes a glass having a thermal expansion coefficient capable of sealing with tungsten and having ultraviolet solarization resistance. All of these glasses are obtained by adding at least one of PbO, TiO ₂ , and Sb ₂ O ₃ to borosilicate glass to have ultraviolet solarization resistance.

[0010] These glasses solve the problem of solarization due to ultraviolet rays, but all of the glasses allow the inclusion of PbO, an environmentally harmful substance, and are not preferred from the viewpoint of environmental protection. In addition, when used as a fluorescent lamp, consideration for ultraviolet cut is not sufficient. Depending on the combination and content of the above-mentioned components for imparting ultraviolet solarization resistance, harmful ultraviolet rays of 253.7 nm emitted from excited mercury or the like are transmitted. However, the interior parts may be deteriorated.

The present invention has been made in view of the above-mentioned circumstances, and has a composition which does not substantially contain PbO, has a sealing property with tungsten, and has a sufficient ultraviolet solarization resistance. Another object of the present invention is to provide a glass suitable for a fluorescent lamp glass tube that does not transmit harmful ultraviolet rays.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
In the present invention, SiO 2_Two 70-80%, Al_Two
O_Three 1-10%, B_Two O_Three 10-25%, ZrO
₂0.01 to 3%, Li_Two O + Na_Two O + K_Two O 3 ~
10% and WO₃, Sb_Two O_Three, Nb₂O₅, Bi₂O
₃, CeO₂, Fe₂O₃At least two or more
0.05% to 300 ° C
The average linear expansion coefficient in the temperature range is 36 to 45 × 10
^-7/ ° C.

[0013] The present invention, in mass%, SiO ₂ 70 to
_{80%, Al 2 O 3 1~10} %, B 2 O 3 10~25
%, ZrO ₂ 0.01-3%, Li ₂ O + Na ₂ O +
K ₂ O 3 to 10%, WO ₃ + Sb ₂ O ₃ + Nb ₂ O ₅ ,
_{0.05~5%, Bi 2 O 3 +} CeO 2 + Fe 2 O
₃ 0.001 to 5%.

Further, it is characterized in that it contains substantially no PbO.

Further, the glass having the above composition is characterized in that the ultraviolet transmittance at a wavelength of 253.7 nm and a thickness of 1 mm is 1% or less.

Further, the present invention is characterized in that it is used as a glass tube for a fluorescent lamp.

Next, the reason why the content of each component constituting the glass of the present invention is limited as described above will be described.

SiO ₂ is a glass network-forming component. If it exceeds 80%, the meltability and workability of the glass deteriorate, and if it is less than 70%, the chemical durability of the glass decreases.
A decrease in chemical durability causes weathering, burns, and the like, and causes a decrease in luminance of the fluorescent lamp and uneven color. Preferably it is 73-78%.

Al ₂ O ₃ has an effect of improving the chemical durability of the glass, but if it exceeds 10%, there is a problem in meltability such as generation of striae. It causes devitrification. On the other hand, if it is less than 1%, phase separation occurs, which causes a problem in moldability and also causes a decrease in chemical durability of the glass. Preferably, it is in the range of 1 to 7%.

B ₂ O ₃ is a component used for the purpose of improving the meltability and adjusting the viscosity. However, if it exceeds 25%, the chemical durability of the glass is reduced, and weathering is caused by long-term use. If B ₂ O ₃ is less than 10%, problems such as deterioration of meltability and deterioration of sealing property with tungsten due to an increase in viscosity occur. Preferably it is 12 to 24%.

ZrO ₂ can be expected to be effective for improving the chemical durability of the glass and for suppressing the phase separation. However, if the content is less than 0.01%, the effect is not sufficient. It is not preferred because it tends to be non-uniform and causes variations in wall thickness and dimensional accuracy when formed into a thin tube. Particularly, in borosilicate glass, Fe ₂ O ₃ , W
In the case where the glass contains components which may give coloring to the glass, such as O ₃ , Nb ₂ O ₅ , Bi ₂ O ₃ , and CeO ₂ , when a phase separation occurs in the glass in the melt molding step, the phase separation portion starts. In the present invention, it is a necessary component for preventing coloration of glass.

Li ₂ O, Na ₂ O and K ₂ O are components used as fluxes to improve the melting property of glass and to adjust the viscosity and the coefficient of thermal expansion. Exceeds 15%, the thermal expansion coefficient becomes too large, and the chemical durability deteriorates. On the other hand, if it is less than 5%, sealing with tungsten becomes difficult with a large decrease in expansion coefficient and a large increase in viscosity. The content of each component is as follows: Li ₂ O: 0 to 3%, Na ₂ O: 0 to 5%, K ₂ O
Is preferably 2 to 8%. If the respective contents exceed the respective upper limit values, the coefficient of thermal expansion becomes too large or the chemical durability is deteriorated. It is also known that Na ₂ O reacts with mercury to form amalgam during the operation of a fluorescent lamp, and excess Na ₂ O in glass reduces the amount of mercury that works effectively in a fluorescent lamp. From the environmental point of view of reducing mercury consumption
Addition of a ₂ O exceeding the above upper limit is not preferred. If the amount is less than each of the lower limits, the coefficient of expansion is significantly reduced, and the sealing is not possible due to a large increase in viscosity.

WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅ , Bi ₂
O ₃ , CeO ₂ , and Fe ₂ O ₃ are added for the purpose of imparting ultraviolet solarization resistance and ultraviolet cut performance.
If the total amount exceeds 10%, the glass is liable to be devitrified and the homogeneity is deteriorated, and the batch cost is extremely increased, which is not preferable from an economic viewpoint.
If it is less than 0.05%, characteristics such as ultraviolet solarization resistance and ultraviolet cut performance cannot be sufficiently obtained. The addition amount of these components is preferably 0.05 to 5
%, More preferably in the range of 0.1 to 3%.

WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅ , Bi ₂
Among O ₃ and CeO ₂ , WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅
Has a particularly strong effect of suppressing solarization caused by ultraviolet rays, and Bi ₂ O ₃ , CeO ₂ , and Fe ₂ O ₃ have remarkable ultraviolet absorption, so that WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅ ,
Bi ₂ O _3, the case of adding two or more components from among CeO _2, WO 3, and one or more selected from _{Sb 2 O 3, Nb 2 O} 5, Bi 2 O 3, CeO 2, Fe 2 It is desirable to use in combination with at least one of O ₃ .

The preferred content of each of these components is as follows:
The total amount of WO ₃ , Sb ₂ O ₃ and Nb ₂ O ₅ is 0.05 to 5
% WO ₃ 0 to 3% _Nb 2 _{O 5} is 0-3%, preferably WO ₃ and _Nb 2 _O at least one 0.05 to 3% of the _5, Sb ₂ O ₃ 0.05 To 2%, more preferably 0.1 to 1%. Sb ₂ O ₃ is suitably used in the present invention because it has a function of clarifying glass as well as imparting ultraviolet solarization resistance. However,
When the Sb ₂ O ₃ content is increased, the glass is blackened at the time of thermal processing such as tungsten sealing, which causes a decrease in luminance of the fluorescent lamp, discoloration of luminescent color, and uneven color. In addition, if it is less than the lower limit, the fining effect cannot be obtained,
Refining time increases.

Bi ₂ O ₃ , CeO ₂ , and Fe ₂ O ₃ are effective in cutting ultraviolet rays, and the total amount of these components is 0.001.
-5% can be added. The total amount of these components is 5%
If the content exceeds 0.005%, the devitrification becomes strong and the glass is colored, which is not preferable. If the content is less than 0.001%, a remarkable ultraviolet ray cutting effect is not recognized. The allowable content of each component alone is as follows: Bi ₂ O ₃ is 0 to 5%, preferably 0.02 to
5%, CeO ₂ is 0~3%, _Fe 2 _{O 3} is 0 to 0.05
%, Preferably 0.003 to 0.03%. Especially F
It is necessary to note that e ₂ O ₃ is effective in cutting ultraviolet rays when it is used in a small amount, but when it exceeds the upper limit value, the negative effect is exerted on ultraviolet solarization resistance.

Further, in order to effectively exhibit the action of the components added for the purpose of imparting the ultraviolet solarization resistance and the ultraviolet cut performance, and to prevent unnecessary coloring of the glass, the glass is melted by reduction fining. In this case, it is preferable to selectively use WO ₃ , Nb ₂ O ₅ , and Bi ₂ O _3. If the glass is melted by oxidizing and refining, Sb ₂ O ₃ , CeO ₂ , and Bi ₂ O _{3 are used.} Is preferably used selectively.

There is no particular limitation on the fining agent used for melting the glass of the present invention. In addition to Sb ₂ O ₃ , commonly used NaCl, Na ₂ SO _{4 and the} like can be used.

Further, ZnO, CaO, MgO, Sr is used for the purpose of improving the weather resistance, melting property, devitrification property, etc. of the glass.
_{O, ZrO 2, P 2 O} 5, F - is also possible to add a component such as within a range not to impair the desired properties of the present invention.

Further, as described above, the glass of the present invention is LC
When used in a backlight fluorescent lamp such as a D display device, when ultraviolet rays are transmitted through a glass tube and emitted outside the tube,
In order to promote the deterioration of the material of the resin parts and the like inside the LCD display device and to shorten the product life and reliability, in the present invention, the above-mentioned composition is used to give the ultraviolet ray cut characteristics, and the glass is optically polished to a thickness of 1 mm. Wavelength 2
The ultraviolet transmittance at 53.7 nm is set to 1% or less. Although the glass thickness of an actual fluorescent lamp is even thinner, practically no problem occurs if the transmission of ultraviolet rays is suppressed to this extent. If a higher quality level is desired without affecting the transmission of visible light, the thickness is 1 mm.
To 0.1% or less.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
Will be explained. The glass of the present invention is prepared as follows.
be able to. First, the above composition range, for example, SiO 2_Two
73%, Al_TwoO_Three3.5%, Li_TwoO 0.3%, Na
_TwoO 1.0%, K_TwoO 5.0%, B_TwoO_Three 16%, WO₃
0.2%, Sb₂O₃0.3%, ZrO₂0.2%,
Fe₂O ₃0.01%, CeO₂To be 0.5%
Weigh and mix the raw materials. This raw material mixture is placed in a platinum crucible.
And heat and melt in an electric furnace. Mix well and clean
After clarification, it is shaped into the desired form. For fluorescent lamps
When mass-producing into a tube to create a thin tube
Is melted in a tank furnace, and is
It can be formed without problems by the known pipe drawing method
You.

[0032]

Next, the glass of the present invention will be described in detail based on examples. Tables 1 and 2 show Examples and Comparative Examples of the present invention. Sample No. Nos. 1 to 18 are examples of the present invention. 19 and 20 are comparative examples showing a conventional glass for sealing tungsten. In addition, the composition in a table | surface is shown by the mass%. The glasses described in the table were prepared by weighing and mixing raw material powders such as silica sand, carbonates, nitrates, and hydroxides of each metal so as to have the oxide composition shown in the table, and platinum by a fining method selected according to the respective components. Melting was performed at 1450 ° C. for 5 hours using a crucible or a quartz crucible. Thereafter, the sufficiently stirred and clarified glass was allowed to flow into a rectangular frame, and after slow cooling, a sample processed into a desired shape was prepared according to the following evaluation items. In the case of oxidizing fining, Sb ₂ O ₃ was used as a fining agent, and in the case of reducing fining, NaCl was used as a fining agent.

Explaining the items shown in the table, the thermal expansion coefficient is a value obtained by measuring the average linear expansion coefficient at 0 to 300 ° C. by the JIS method. In order to evaluate the sealing property of glass with tungsten, it is preferable that the coefficient of thermal expansion of glass is equal to or slightly lower than that of tungsten. If the difference between the coefficients of thermal expansion of glass and tungsten is large, it causes leakage or cracks from the sealing portion, and cannot be used for fluorescent lamps.

The degree of deterioration of the transmittance by the ultraviolet solarization resistance test was determined by cutting each glass sample into a plate having a side of 30 mm square and performing optical polishing on both sides so as to have a thickness of 1 mm. 400P) to 20
After irradiating with ultraviolet light for 300 hours at a position of cm, the transmittance at a wavelength of 400 nm was measured and indicated by the degree of deterioration from the initial transmittance before irradiation with ultraviolet light. The degree of deterioration (%) = [(initial transmittance—transmittance after ultraviolet irradiation) / initial transmittance] × 100.

In addition, the measured values of the transmittance at a wavelength of 253.7 nm in the sample before being subjected to the ultraviolet solarization resistance test are also shown.

[0036]

[Table 1]

[0037]

[Table 2]

As is clear from the table, the No. 1 example of the present invention was used. Each of the samples Nos. 1 to 18 has a coefficient of thermal expansion of 45 × 10 ⁻⁷ / ° C., which is the average coefficient of thermal expansion of tungsten.
The value is relatively close to and slightly lower than that of tungsten, and the expansion and shrinkage behavior below the glass adhesion point is similar, so good and reliable sealing with tungsten Is obtained. It is for this reason that the average linear expansion coefficient of the glass is set to 36 to 45 × 10 ⁻⁷ / ° C. in the present invention. Further, the transmittance at a wavelength of 253.7 nm is extremely low, and hardly transmits harmful ultraviolet rays. Further, the transmittance deterioration due to the ultraviolet irradiation was suppressed to 0.2% or less, and it had an extremely high ultraviolet solarization resistance.

On the other hand, in Comparative Example No. 19, 20
The sample No. had a large deterioration in transmittance due to ultraviolet irradiation, and a high transmittance at a wavelength of 253.7 nm.

Further, since the glass tube for a fluorescent lamp according to the embodiment of the present invention does not contain PbO which is an environmentally harmful substance, it also contributes to a reduction in environmental load.

Although the glass according to the present invention is suitable as a glass tube for a fluorescent lamp as described in detail above, the glass is not limited to this, and is excellent in ultraviolet ray cutting property and visible light transmittance. Since it has an ultraviolet cut filter and a high ultraviolet solarization resistance, it can be used for an envelope of a light source that emits ultraviolet light such as a mercury lamp.

[0042]

As described above, the glass of the present invention has a coefficient of thermal expansion suitable for sealing with tungsten and has excellent ultraviolet solarization resistance, so that glass tubes for fluorescent lamps, especially liquid crystal displays, etc. It is suitable as a glass tube used for a fluorescent lamp for backlight of a display device. Also, since it does not substantially contain a lead component, it contributes to reduction of environmental load.

Further, since the glass of the present invention is also excellent in ultraviolet ray cut properties, even when used for a backlight fluorescent lamp of a display device such as a liquid crystal display, it deteriorates the material of resin parts and the like inside the display device. Without
Improve the reliability of a display device.

Furthermore, since the glass tube for a fluorescent lamp manufactured using the glass of the present invention has high resistance to ultraviolet solarization, deterioration of display quality of a liquid crystal display or the like due to discoloration of the glass can be prevented.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G062 AA08 AA09 BB05 DA07 DB03 DC04 DD01 DE01 DF01 EA01 EA02 EA03 EA10 EB01 EB02 EB03 EC01 EC02 EC03 ED01 EE01 EF01 EG01 FA01 FB01 FC02 FC03 FD01 FF01 F01 FF01 F01 FG01 FL02 FL03 GA01 GA02 GA03 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH08 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 NN11 NN11 NN10 NN11 NN11 NN10

Claims (7)

[Claims] 1. The composition according to claim 1, wherein the content of SiO _{2 is} 70 to 80% by mass,
₂ O ₃ 1 to 10%, B ₂ O ₃ 10 to 25%, ZrO
₂ 0.01 to 3%, Li ₂ O + Na ₂ O + K ₂ O 3 to
10%, WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅ , Bi ₂ O
₃ , containing at least two or more components of 0.05 to 10% of CeO ₂ and Fe ₂ O ₃ , and having an average linear expansion coefficient of 36 to 45 × 10 in a temperature range from 0 ° C. to 300 ° C.
^-7 / ° C., a glass for sealing tungsten. 2. The method according to claim 2, wherein the two or more components are WO ₃ , Sb ₂
At least one selected from O ₃ and Nb ₂ O ₅ and Bi
_{2. The} glass for sealing tungsten according to claim 1, wherein the glass is one or more selected from ₂ O ₃ , CeO ₂ , and Fe ₂ O ₃ . 3. 70% to 80% by weight of SiO ₂ , Al _{2
O 3 1~10%, B 2 O} 3 10~25%, ZrO
₂ 0.01 to 3%, Li ₂ O + Na ₂ O + K ₂ O 3 to
_{10%, WO 3 + Sb 2} O 3 + Nb 2 O 5 0.05~5
_{%, Bi 2 O 3 + CeO} 2 + Fe 2 O 3 0.001~5
%. 3. The glass for sealing tungsten according to claim 2, wherein 4. 70% to 80% by weight of SiO ₂ , Al _{2
O 3 1~10%, B 2 O} 3 10~25%, ZrO
₂ 0.01 to 3%, Li ₂ O + Na ₂ O + K ₂ O 3 to
_{10%, WO 3 0~3%,} Sb 2 O 3 0.05~2%,
_{Nb 2 O 5 0~3%, Bi} 2 O 3 0~5%, CeO 2 0
_3%, according to claim 3 tungsten sealing glass according to characterized in that it contains _Fe 2 O 3 0.001 to 0.05%. 5. The glass for sealing tungsten according to claim 1, which is substantially free of PbO. 6. The glass for sealing tungsten according to claim 1, wherein an ultraviolet transmittance at a thickness of 1 mm at a wavelength of 253.7 nm is 1% or less. 7. The glass for sealing tungsten according to claim 1, which is used as a glass tube for a fluorescent lamp.