JP2007039334A - Glass for sealing tungsten - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass for sealing tungsten which is suitable for a glass pipe for a small-diameter fluorescent lamp used for a light source of a lighting device for a liquid crystal display element, or the like, since the glass can be used for sealing tungsten and also has satisfactory ultraviolet light solarization resistance. <P>SOLUTION: The glass for sealing tungsten has a composition of 73-79% SiO<SB>2</SB>, 12.5-25% B<SB>2</SB>O<SB>3</SB>, 0.5-10% Al<SB>2</SB>O<SB>3</SB>, 1-11% (Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O), 0.01-5% ZrO<SB>2</SB>and 0.05-11% (TiO<SB>2</SB>+PbO+Sb<SB>2</SB>O<SB>3</SB>), with the proviso that 0-5% TiO<SB>2</SB>, 0-10% PbO and 0.1-4% Sb<SB>2</SB>O<SB>3</SB>, and has a linear expansion coefficient of 34×10<SP>-7</SP>/°C to 43×10<SP>-7</SP>/°C in a temperature range of 30°C to 380°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tungsten sealing glass, and more specifically to a tungsten sealing glass used for a glass tube of a small-diameter fluorescent lamp serving as a light source of a lighting device such as a liquid crystal display element.

  Liquid crystal display elements are broadly classified into reflective liquid crystal display elements that use natural light and room illumination light, and transmissive liquid crystal display elements that use backlight light, for example, depending on how the light source is used. Reflective liquid crystal display elements are used for wristwatches and small electronic desk calculators, especially those with low power consumption, but color displays using TFT liquid crystal display elements and high-quality displays such as in-vehicle instruments are required. For such applications, a transmissive liquid crystal display element using a backlight having a fluorescent lamp as a light source is mainly used.

  The light emission principle of the fluorescent lamp for the backlight is the same as that of a general fluorescent lamp for illumination. The mercury gas enclosed by the discharge between the electrodes is excited, and the inner wall surface of the glass tube is irradiated by the ultraviolet rays emitted from the excited gas. The coated phosphor emits visible light. However, the major difference from a general fluorescent lamp is that the glass tube has a small diameter and a small thickness. Conventionally, lead glass soda-based soft glass has been used for the glass tube of this fluorescent lamp because of its ease of processing and past achievements as lighting glass, and inexpensive jumet has been used as the introduced metal.

  However, as the liquid crystal display elements become thinner, lighter, and consume less power, fluorescent lamps for backlights are required to have smaller diameters and thinner walls. In particular, since the mechanical strength is reduced and the heat generation of the lamp is increased, the glass tube needs to have higher strength and lower expansion. In order to improve the light emission efficiency, the frequency of the lighting circuit has been increased. Along with this, a glass tube as an insulator is also required to have a low dielectric loss. For this reason, the conventional lead soda-based soft glass material cannot satisfy these requirements.

  Therefore, it has been studied to manufacture a fluorescent lamp using a borosilicate hard glass, which has higher thermal and mechanical strength than lead soda soft glass and is advantageous in terms of low dielectric loss. As a result, as a combination of hard glass and metal that can be hermetically sealed, conventionally known fluorescent lamps using tungsten sealing glass and tungsten metal have been developed and commercialized.

  However, the glass tube of the above-mentioned fluorescent lamp for backlight uses the borosilicate tungsten sealing glass material generally used for the conventional xenon flash lamp as it is, and this is simply formed into a thin tube and processed Therefore, the glass is discolored (so-called ultraviolet solarization) by ultraviolet rays emitted from excited mercury gas or the like. When the color of the glass is changed, the luminance is lowered and the emission color is shifted, and the liquid crystal display element is deteriorated in quality such as display darkness and color rendering property.

As a countermeasure, the inner surface of the glass tube is coated with Al ₂ O ₃ or TiO ₂ , which is a component that reflects or absorbs ultraviolet rays, and a phosphor is applied on top of it to form a multilayer film. Although some methods have been implemented, such as a weakening of the thickness, this method not only increases the production cost but also makes it difficult to form a homogeneous multilayer film as the diameter is further reduced. Under these circumstances, there is a strong demand for the development of tungsten sealing glass having ultraviolet solarization resistance that can be used as a fluorescent lamp glass tube.

  The present invention has been made in view of the above circumstances, can be sealed with tungsten, and has sufficient ultraviolet solarization resistance, so that it is for a thin fluorescent lamp used for a light source of a lighting device for a liquid crystal display element. An object of the present invention is to provide a glass for sealing tungsten suitable as a glass tube.

That is, the glass for sealing tungsten of the present invention is in a percentage by weight of SiO ₂ 73 to 79%, B ₂ O ₃ 12.5 to 25%, Al ₂ O ₃ 0.5 to 10%, Li ₂ O + Na ₂ O + K _2. O 1-11%, ZrO ₂ 0.01-5%, TiO ₂ + PbO + Sb ₂ O ₃ 0.05-11%, TiO ₂ 0-5%, PbO 0-10%, Sb ₂ O ₃ is 0.1 to 4%, and the linear expansion coefficient in a temperature range of 30 to 380 ° C. is 34 to 43 × 10 ⁻⁷ / ° C.

  The tungsten sealing glass of the present invention is used as a glass tube for a fluorescent lamp.

  The reason why the content of each component constituting the tungsten sealing glass of the present invention is limited as described above is as follows.

SiO ₂ is a main component necessary for constituting the glass skeleton, and its content is 73 to 79%, preferably 73 to 78%. When SiO ₂ is more than 79%, the linear expansion coefficient becomes too low and the solubility is deteriorated, and when it is less than 73%, the chemical durability is deteriorated. Cause a decrease in brightness.

B ₂ O ₃ is a component necessary for improving solubility and adjusting viscosity, and its content is 12.5 to 25%, preferably 14 to 22%. If B ₂ O ₃ is more than 25%, the viscosity will decrease too much, a homogeneous glass will not be obtained by evaporation, and the chemical durability will deteriorate, and if it is less than 12.5%, it will be difficult to dissolve. And the viscosity is too high for tungsten sealing.

Al ₂ O ₃ has a remarkable effect in improving the stability of the glass, and its content is 0.5 to 10%, preferably 1 to 2.2%. When Al ₂ O ₃ is more than 10%, it becomes difficult to melt the glass, and when it is less than 0.5%, the glass tends to be devitrified, and it becomes difficult to produce homogeneous glass and to stably form it.

Li ₂ O is an alkali metal oxide, Na ₂ O, and K ₂ O facilitate dissolution of the glass, a component added to adjust the coefficient of expansion and viscosity, the content is 1 in total 11%, preferably 5.1 to 9%. If the total amount of these components is 11% or more, the expansion coefficient becomes too high, so that it is not suitable for tungsten sealing. Further, if it is less than 1%, the expansion coefficient becomes too small. The content ratio of each component, Li ₂ O 0~4% (preferably _{0~2%), Na 2 O 0~10} % ( preferably _{0~5.9%), K 2 O 0~10} % ( The range of 0 to 4% is preferable. If Li ₂ O is more than 4%, devitrification is likely to deteriorate, and if Na ₂ O is more than 10%, Na ions may contaminate the phosphor in the thermal process during manufacturing of the fluorescent lamp and cause a decrease in luminance. There is sex. If K ₂ O exceeds 10%, the thermal expansion coefficient may become too high.

ZrO ₂ is a component that improves chemical durability, and its content is 0.01 to 5%, preferably 0.1 to 3%. If the amount of ZrO ₂ is more than 5%, the devitrification is deteriorated and the glass becomes non-uniform, the dimensional accuracy is deteriorated, the appearance defect is caused, and a high quality glass cannot be obtained. On the other hand, if it is less than 0.01%, the chemical durability deteriorates. For this reason, when used as a glass tube for a fluorescent lamp, alkali blowing occurs and the phosphor cannot be uniformly applied, and problems such as burns occur.

TiO ₂ , PbO and Sb ₂ O ₃ are all components that impart high ultraviolet solarization resistance to glass, and the total amount thereof is 0.05 to 11%, preferably 0.1 to 5.5%. When the total amount of these components exceeds 11%, the influence of devitrification, evaporation, etc. of the glass becomes strong, and it becomes difficult to obtain a tubular glass having a uniform and good dimensional accuracy. On the other hand, when it is less than 0.05%, there is almost no effect. When TiO ₂ is contained as an essential component, the content of each component is TiO ₂ 0.05 to 5% (preferably 0.1 to 3%), PbO 0 to 10% (preferably 0 to 5.5%). ), Sb ₂ O ₃ 0-4% (preferably 0-1%). When PbO is contained as an essential component, the content of each component is TiO ₂ 0 to 5% (preferably 0 to 2%), PbO 0.05 to 10% (preferably 0.1 to 5.5%), sb ₂ O ₃ 0~4% (preferably 0 to 1% in). When Sb ₂ O ₃ is contained as an essential component, the content of each component is TiO ₂ 0 to 5% (preferably 0 to 2%), PbO 0 to 10% (preferably 0 to 5.5%), A range of Sb ₂ O ₃ 0.1 to 4% (preferably 0.2 to 1%) is suitable. In any case, if the amount of TiO ₂ exceeds a predetermined amount, the glass itself tends to be colored, and the devitrification property deteriorates rapidly, making it difficult to obtain a transparent and homogeneous glass. If PbO exceeds a predetermined amount, the glass itself tends to be colored like TiO _2, and it becomes difficult to obtain a homogeneous glass by evaporating at the time of melting. When Sb ₂ O ₃ exceeds a predetermined amount, it becomes difficult to obtain a homogeneous glass. Further, if PbO or Sb ₂ O ₃ is excessively contained in the glass, the glass is colored brown or black due to thermal processing in the manufacturing process of the fluorescent lamp, which is not preferable.

Furthermore, the borosilicate glass is SrO, BaO, CaO, MgO, ZnO, P ₂ O ₅ , As ₂ O ₃ , SO ₃ , for the purpose of adjusting the viscosity of the glass and improving weather resistance, solubility, and clarity. Appropriate amounts of components such as F ₂ and Cl ₂ can be added.

In the present invention, the reason why the linear expansion coefficient in the temperature range of 30 to 380 ° C. is limited to 34 to 43 × 10 ⁻⁷ / ° C. is that when the linear expansion coefficient is out of this range, there is a mismatch with the expansion coefficient of tungsten metal. This is because slow leaks and cracks are generated and the function as a fluorescent lamp is impaired.

As described above, the glass for sealing tungsten of the present invention has a linear thermal expansion coefficient of 34 to 43 × 10 ⁻⁷ / ° C. suitable for sealing with tungsten metal, and also has excellent ultraviolet solarization resistance. It is suitable as a glass tube material for fluorescent lamps, and in particular for glass tubes for small-diameter fluorescent lamps that serve as light sources for lighting devices for liquid crystal display elements.

  In addition, the glass tube for a thin fluorescent lamp of a lighting device for a liquid crystal display element manufactured using the tungsten sealing glass of the present invention has a high resistance to ultraviolet solarization, so the quality of the liquid crystal display element is deteriorated due to discoloration of the glass. Can be prevented.

  Next, the tungsten sealing glass of the present invention will be described based on examples.

  Tables 1 to 3 show examples of the present invention (sample Nos. 2, 8, 11, and 13) and comparative examples (sample No. 14). Sample No. 1, 3-7, 9, 10 and 12 are reference examples.

  No. shown in the table. Each sample of 1-14 was prepared as follows.

  First, glass materials were prepared so as to have the composition shown in the table, and then melted at 1550 ° C. for 5 hours using a platinum crucible. After melting, the melt is formed into a predetermined shape and processed to produce each glass sample, and the linear expansion coefficient in the temperature range of 30 to 380 ° C. and the spectral transmittance before and after UV irradiation are measured, and each characteristic is measured. Is shown in the table.

As is apparent from the table, No. 1 as an example of the present invention. Each of the samples 2, 8, 11 and 13 has a linear expansion coefficient of 37.5 to 40.1 × 10 ⁻⁷ / ° C., which is close to that of tungsten, and a decrease in transmittance due to ultraviolet irradiation is 1 Since it is almost 0% or less, it can be understood that it has high ultraviolet solarization resistance.

On the other hand, No. as a comparative example. Sample No. 14 had a coefficient of linear expansion of 38.0 × 10 ⁻⁷ / ° C. and showed an expansion that could be sealed with tungsten, but did not contain any of TiO ₂ , PbO, or Sb ₂ O _3. Therefore, the decrease in transmittance due to ultraviolet irradiation was as large as 7% or more, and the ultraviolet solarization resistance was very low.

  The linear expansion coefficient in the table is obtained by measuring an average linear expansion coefficient in a temperature range of 30 to 380 ° C. with a self-recording differential thermal dilatometer after processing the glass into a cylinder having a diameter of about 3 mm and a length of about 50 mm. is there.

  The ultraviolet solarization resistance was evaluated as follows. First, both surfaces of a 1 mm thick plate glass were mirror-polished to obtain a sample. Next, the wavelength of light at which the transmittance of the sample before ultraviolet irradiation showed 80% was measured. Further, after irradiating the sample with ultraviolet light having a main wavelength of 253.7 nm for 60 minutes with a 40 W low-pressure mercury lamp, the transmittance at a wavelength showing a transmittance of 80% is measured again before irradiation, whereby the transmittance by ultraviolet irradiation is measured. Sought to decrease. At this time, the lowering of the transmittance becomes larger as the glass having inferior ultraviolet solarization resistance is reduced. However, it is important that the glass tube for a fluorescent lamp such as a liquid crystal backlight hardly has this reduction.

Claims (12)

Tungsten sealing glass used as a glass tube for a fluorescent lamp, in terms of weight percentage, SiO ₂ 73-79%, B ₂ O ₃ 12.5-25%, Al ₂ O ₃ 0.5-10%, Li ₂ O + Na ₂ O + K ₂ O 1-11%, ZrO ₂ 0.01-5%, TiO ₂ + PbO + Sb ₂ O ₃ 0.05-11%, TiO ₂ 0-5%, PbO 0-10 %, Sb ₂ O ₃ is 0.1 to 4%, and the linear expansion coefficient in the temperature range of 30 to 380 ° C. is 34 to 43 × 10 ⁻⁷ / ° C. In weight _{percent, SiO 2 73~78%, B 2} O 3 14~22%, Al 2 O 3 1~2.2%, Li 2 O + Na 2 O + K 2 O 5.1~9%, ZrO 2 0.1 -3%, TiO ₂ + PbO + Sb ₂ O ₃ 0.1-5.5%, TiO ₂ 0-5%, PbO 0-4.3%, Sb ₂ O ₃ 0.1-4% The glass for sealing tungsten according to claim 1, wherein The tungsten according to claim 1, wherein the content of Li ₂ O is 0 to 4% by weight, the content of Na ₂ O is 0 to 10% by weight, and the content of K ₂ O is 0 to 10% by weight. Glass for sealing. The tungsten sealing material according to claim 1, further comprising at least one selected from SrO, BaO, CaO, MgO, ZnO, P ₂ O ₅ , As ₂ O ₃ , SO ₃ , F ₂ , and Cl _2. Glass.   2. The glass for sealing tungsten according to claim 1, wherein a decrease in transmittance due to ultraviolet irradiation is 1% or less. In weight _{percent, SiO 2 73~79%, B 2} O 3 12.5~25%, Al 2 O 3 0.5~10%, Li 2 O + Na 2 O + K 2 O 1~11%, ZrO 2 0.01 -5%, TiO ₂ + PbO + Sb ₂ O ₃ 0.05-11%, TiO ₂ 0-5%, PbO 0-10%, Sb ₂ O ₃ 0.1-4%, 30 A glass tube for a fluorescent lamp, comprising a glass having a linear expansion coefficient of 34 to 43 × 10 ⁻⁷ / ° C. in a temperature range of ˜380 ° C. In weight _{percent, SiO 2 73~78%, B 2} O 3 14~22%, Al 2 O 3 1~2.2%, Li 2 O + Na 2 O + K 2 O 5.1~9%, ZrO 2 0.1 -3%, TiO ₂ + PbO + Sb ₂ O ₃ 0.1-5.5%, TiO ₂ 0-5%, PbO 0-4.3%, Sb ₂ O ₃ 0.1-4% The glass tube for a fluorescent lamp according to claim 6, wherein the glass tube is made of glass. It is made of glass having a Li ₂ O content of 0 to 4% by weight, a Na ₂ O content of 0 to 10% by weight, and a K ₂ O content of 0 to 10% by weight. 6. Glass tube for fluorescent lamp. Further SrO, BaO, CaO, MgO, ZnO, P 2 O 5, As 2 O 3, SO 3, F 2, in that it consists of glass containing one or more selected from Cl ₂ according to claim 6, wherein Glass tube for fluorescent lamp.   The glass tube for a fluorescent lamp according to claim 6, wherein the glass tube is made of glass whose transmittance is reduced by 1% or less due to ultraviolet irradiation.   7. The glass tube for a fluorescent lamp according to claim 6, which is used for a fluorescent lamp whose introduction metal is tungsten.   The glass tube for a fluorescent lamp according to claim 6, wherein the glass tube is used for a fluorescent lamp as a light source of a liquid crystal backlight.