JP2002068774A - GLASS SUITABLE FOR SEALING Fe-Ni-Co BASED ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass suitable for a glass tube for a fluorescent lamp having composition which is substantially free from PbO. SOLUTION: This glass suitable for sealing Fe-Ni-Co based alloy is characterized by having composition containing, by mass, SiO2 of 60-70%, Al2O3 of 1-10%, B2O3 of 10-25%, Li2O+Na2O+K2O of 5-15%, WO3+Sb2O3+Nb2O5 of 0.05-5%, and Bi2O3+CeO2+Fe2O3 of 0.001-5% and having an average coefficient of linear expansion of 48-58×10-7/ deg.C ranging in temperature from 50 deg.C to a glass transition point (Tg).

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 a glass suitable for sealing an Fe—Ni—Co alloy.

[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 current backlight applications such as a pipe diameter of 5 to 0.5 mm and a wall thickness of 0.6 to 0.1 mm, it is difficult to ensure sufficient strength and heat resistance in product reliability, and lead soda-based It has been studied to make a fluorescent lamp using borosilicate hard glass, which has higher thermal and mechanical strength than soft glass, and as a combination of hermetically sealable metal and hard glass,
Fluorescent lamps using Kovar alloy and Kovar sealing glass, which are well known, have been developed and commercialized. Here, “Kovar” is a trade name of Westinghouse Ele. Corp., which indicates an Fe—Ni—Co alloy, and is used to include equivalent products of other companies such as KOV (trade name) manufactured by Toshiba Corporation.

[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 ray solarization resistance and ultraviolet ray cut-off performance, so that these did not cause any problem. Glass for sealing was originally used to seal electronic tubes and electronic components.No measures were taken against the action of ultraviolet rays as a glass material, and the problems of ultraviolet solarization and ultraviolet transmission were avoided. Did not.

For this reason, when the conventional Kovar sealing glass is used for an outer tube for a fluorescent lamp, Al ₂ O ₃ or TiO ₂ which is a component that reflects or absorbs ultraviolet rays is applied to the inner surface of the glass tube.
In addition, measures have been taken such that a fluorescent material is applied thereon to form a multilayer film, and the intensity of ultraviolet rays reaching the glass is reduced. However, such a method
The increase in cost due to the difficulty of coating and the increase in the number of coating steps inevitably accompanies the reduction in the diameter of the glass tube.

In view of the above background, JP-A-8-333132, JP-A-8-333136, and JP-A-9-233136 disclose a glass having a thermal expansion coefficient capable of sealing with a Kovar alloy and having ultraviolet solarization resistance. −110
Japanese Patent No. 467 proposes a glass disclosed. All of these glasses are made of borosilicate glass and PbO, Ti
By adding at least one of O ₂ and Sb ₂ O ₃ , ultraviolet solarization resistance is imparted.

[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, is capable of being sealed with a Kovar alloy, and has a sufficient ultraviolet solarization resistance. An object of the present invention is to provide a glass suitable for use as a fluorescent lamp glass tube that has a harmful ultraviolet ray and has no transmission.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
In the present invention, SiO 2_Two 55-75%, 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 5
15% and WO₃, Sb_Two O_Three, Nb₂O₅, Bi₂O
₃, CeO₂, Fe₂O₃At least two or more
The composition contains 0.05 to 10% of a component, and has a glass transition temperature of 50 ° C.
The average coefficient of linear expansion in the temperature range up to the point (Tg) is 48
~ 58 × 10^-7/ ° C
You.

Further, the present invention provides a method for preparing SiO _{2 by} 55% by mass.
_{70%, 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 5 to 15%, 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, in mass%, SiO _{2 is} 60 to 70%,
_{Al 2 O 3 1~7%, B} 2 O 3 12~24%, ZrO
_{2 0.01~3%, Li 2 O +} Na 2 O + K 2 O 5~
_{15%, 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
To _3%, characterized by containing the _Fe 2 O 3 _0.001~0.05%.

Further, the glass is substantially free of PbO and has the above composition, and is characterized by having an ultraviolet transmittance at a wavelength of 253.7 nm of 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, but if it exceeds 75%, the meltability and workability of the glass deteriorate, and if it is less than 55%, 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 60 to 70%.

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 Kovar 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%, the expansion coefficient is greatly reduced and the viscosity is greatly increased, and it is difficult to seal with Kovar. Also, the content of each component,
Li ₂ O and 0-5% 0 to 8% of Na ₂ O, the K ₂ O
It is preferable to set it to 2 to 12%. 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,
_It is not preferable to add ₂ O exceeding the above upper limit. More preferably, it is 0 to 4.2%. If the value is less than each of the lower limits, the coefficient of expansion is greatly reduced, and the Kovar sealing cannot be performed 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 is 0~3%, _Nb 2 _{O 5} is 0 to 3%, Sb ₂
O ₃ is 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 content of Sb ₂ O ₃ is large, the glass is blackened at the time of thermal processing such as Kovar sealing, which causes a decrease in luminance of the fluorescent lamp, discoloration of emission color, and uneven color. On the other hand, if it is less than the lower limit, the fining effect cannot be obtained, so that the time required for melting and fining the glass 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 5% 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]

Embodiments of the present invention will be described below. The glass of the present invention can be prepared as follows. First, the above composition range, for example, SiO ₂
68%, Al ₂ O ₃ 3.5%, Li ₂ O 1%, Na ₂ O
0.5%, K ₂ O 8.3%, B ₂ O ₃ 18%, WO
₃ 0.2%, Sb ₂ O ₃ 0.3%, ZrO ₂ 0.1
% And Fe ₂ O ₃ 0.01%. This raw material mixture is accommodated in a platinum crucible and heated and melted in an electric furnace. After sufficiently stirring and refining, it is formed into a desired form. In the case where a tube is mass-produced in order to produce a thin tube for a fluorescent lamp or the like, the tube can be melted in a tank furnace and formed without problems by a known tube drawing method such as a danna method or a redraw method.

[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 conventional Kovar sealing glass. In addition, the composition in the table is shown by 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. Using crucible or quartz crucible
Melted at 1450 ° C for 5 hours. 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 coefficient of thermal expansion and the transition point of glass are as follows.
The measurement was performed with a thermomechanical analyzer (TMA) using a sample processed into a cylinder having a length of 20 mm and a length of 20 mm. At this time, the coefficient of thermal expansion is from 50 ° C. to the transition point (T
measuring the average coefficient of linear expansion in the temperature range up to g),
In addition, the average linear expansion coefficient of the Kovar alloy in the same temperature range is described. For Kovar alloys, the expansion curve bends in the second half of the 400 ° C range, so it is necessary to lower the transition point of glass to approximate the expansion curve to Kovar alloy, and to evaluate the sealing properties of glass with Kovar alloy. It is preferable that the thermal expansion coefficient up to this temperature range is equal to or slightly lower than that of the Kovar alloy. Therefore, the coefficient of thermal expansion in a temperature range from 50 ° C. to the transition point (Tg) of each glass including this temperature range was evaluated. If the difference between the thermal expansion coefficients of the glass and the Kovar alloy 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 had an average thermal expansion coefficient of Kovar of 60.9 × 10 ⁻⁷ / ° C.
The value is relatively close to that of the Kovar alloy, and is slightly lower than that of the Kovar alloy.Since the expansion and contraction behaviors below the glass adhesion point are similar, a good and reliable seal with the Kovar alloy is obtained. Adhesion is obtained. It is for this reason that the average linear expansion coefficient of the glass is set to 48 to 58 × 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. For sample No. 19, the transmittance was significantly deteriorated by the irradiation of ultraviolet rays. Sample No. 20 had 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 thermal expansion coefficient suitable for sealing with a Kovar alloy and has excellent ultraviolet solarization resistance. It is suitable as a glass tube used for a fluorescent lamp for a backlight of a display device such as the above. 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.

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Claims (7)

[Claims] 1. An amount of 55 to 75% by weight of SiO ₂ , Al
₂ O ₃ 1 to 10%, B ₂ O ₃ 10 to 25%, ZrO
_{2 0.01~3%, Li 2 O +} Na 2 O + K 2 O 5~
15%, WO ₃ , Sb ₂ O ₃ , Nb ₂ O ₅ , Bi ₂ O
₃ , CeO ₂ , and Fe ₂ O ₃ , containing at least two or more components of 0.05 to 10%, and having an average linear expansion coefficient of 48 in a temperature range from 50 ° C. to a glass transition point (Tg).
~58 × 10 ^{- 7} / wherein the ℃ is Fe-N
Glass suitable for sealing an i-Co alloy. 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 Fe-Ni-C according to claim 1, wherein the Fe-Ni-C is at least one member selected from the group consisting of ₂ O ₃ , CeO ₂ , and Fe ₂ O _3.
Glass suitable for sealing o-based alloys. 3. 55% to 70% by weight of SiO ₂ , 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 5~
_{15%, 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
% Of Fe-N according to claim 2.
Glass suitable for sealing an i-Co alloy. 4. The method according to claim 1, wherein the mass%_Two 60-70%, Al_Two
 O_Three 1-7%, B_Two O_Three12 to 24%, ZrO₂0.0
1-3%, Li_Two O + Na_Two O + K_Two O 5-15%,
WO₃0-3%, Sb_Two O_Three0.05-2%, Nb₂O
₅0-3%, Bi ₂O₃0-5%, CeO₂0-3%,
Fe₂O₃It is characterized by containing 0.001-0.05%
Sealing of the Fe—Ni—Co alloy according to claim 3.
Suitable for glass. 5. The Fe—Ni according to claim 1, wherein the Fe—Ni is substantially free of PbO.
-Glass suitable for sealing a Co-based alloy. 6. The sealing of the Fe—Ni—Co alloy according to claim 1, wherein an ultraviolet transmittance at a wavelength of 253.7 nm and a thickness of 1 mm is 1% or less. Suitable for glass. 7. A glass suitable for sealing an Fe—Ni—Co alloy according to claim 1, which is used as a glass tube for a fluorescent lamp.