JP4187002B2 - Envelope for small fluorescent lamp and small fluorescent lamp - Google Patents

Description

  The present invention includes Kovar (= Fe-Ni-Co alloy under the trade name of Westinghouse Ele. Corp. In this application, KV-2 manufactured by Sumitomo Special Metals, KOV manufactured by Toshiba, etc.) The present invention relates to an envelope of a small-diameter fluorescent lamp using the introduced metal and a small-diameter fluorescent lamp using this.

  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 lighting fluorescent lamp. The envelope made of tubular glass is excited by the mercury gas enclosed by the discharge between the electrodes and the ultraviolet rays emitted from the excited gas. The phosphor applied to the inner wall surface of the vessel emits visible light. However, the major difference from a general fluorescent lamp is that the outer diameter of the envelope is small and the wall thickness is thin. Conventionally, lead fluorescent soda-based soft glass has been used for the envelope 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.

  By the way, as the liquid crystal display element becomes thinner, lighter, and consumes 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 tubular glass as the envelope is required to have higher strength and lower expansion. Further, in order to improve the light emission efficiency, the frequency of the lighting circuit has been increased, and accordingly, the dielectric glass is required to have a low dielectric loss. However, the conventional lead soda-based soft glass material cannot satisfy these requirements.

  Therefore, it has been studied to produce a fluorescent lamp envelope using borosilicate hard glass, which has higher thermal and mechanical strength than lead soda-based soft glass and is advantageous in terms of low dielectric loss. It was. As a result, as a combination of hard glass and metal that can be hermetically sealed, a Kovar sealing glass conventionally known for an envelope and a fluorescent lamp using Kovar as an introduction metal have been developed and commercialized.

  However, the envelope of the fluorescent lamp described above uses a conventional borosilicate Kovar sealing glass material that is generally used as a hermetic seal or lens for electronic parts such as conventional electron tubes and photocaps. Is simply formed into a thin tube and processed, so that when it is lit for a long time, there arises a problem that the glass is discolored (so-called ultraviolet solarization) by ultraviolet rays emitted from the excited mercury gas. 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. However, in this method, not only is the production cost increased, but also a thin tube with a small diameter such as an outer diameter of 5.2 mm or less and a wall thickness of 0.6 mm or less is used. For glass, it becomes difficult to form a homogeneous multilayer film. Under such circumstances, there is a strong demand for the development of envelopes for small-diameter fluorescent lamps that have UV-resistant solarization properties.

  The present invention has been made in view of the above circumstances, and an envelope for a small-diameter fluorescent lamp capable of producing a small-diameter fluorescent lamp excellent in solarization resistance using Kovar as an introduction metal, and using this It aims at providing the produced small diameter fluorescent lamp.

Thin fluorescent lamp envelope of the present invention, in% by _{weight, SiO 2 55~73%, B 2} O 3 10~25%, Al 2 O 3 1~10%, Li 2 O + Na 2 O + K 2 O 4 _{~16%, ZrO 2 0~5%,} Sb 2 O 3 containing 0.1 to 4%, the linear expansion coefficient at 30 to 380 ° C. is ^{43~55 × 10 -7 / ℃ (43} × 10 -7 / ℃ It is characterized by being made of tubular glass having an outer diameter of 5.2 mm or less and a wall thickness of 0.6 mm or less, which is made of borosilicate glass.

In addition, according to the method of manufacturing the envelope for a small fluorescent lamp of the present invention, in a small fluorescent lamp using Kovar as an introduction metal , SiO ₂ 55 to 73%, B ₂ O ₃ 10 by weight as the envelope. ˜25%, Al ₂ O ₃ 1-10%, Li ₂ O + Na ₂ O + K ₂ O 4-16%, ZrO ₂ 0-5%, Sb ₂ O ₃ 0.1-4% , at 30-380 ° C. After preparing a glass raw material so as to be a borosilicate glass having a linear expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C. (excluding 43 × 10 ⁻⁷ / ° C.), it is put into a melting furnace and vitrified. It is formed into a tubular shape.

In the present invention, the envelope is made of borosilicate glass containing Sb ₂ O ₃ in the glass composition for the following reason. In other words, borosilicate glass has higher mechanical strength and lower expansion than lead soda-based soft glass, so it has excellent heat resistance and low dielectric loss, and it is easy to make fluorescent lamps thinner and thinner. Further, when Sb ₂ O ₃ is contained in the glass, the resistance to ultraviolet solarization is high, and coloring does not easily occur even when exposed to ultraviolet rays generated inside the fluorescent lamp for a long time.

The reason why the linear expansion coefficient of the borosilicate glass is limited to 43 to 55 × 10 ⁻⁷ / ° C. (30 to 380 ° C.) is that when the linear expansion coefficient is out of this range, the introduced metal is Kovar and the expansion coefficient. This is because they do not match, and slow leaks and cracks occur, impairing the function as a fluorescent lamp.

  The tubular envelope made of the borosilicate glass described above has a size of an outer diameter of 5.2 mm or less, preferably 3.5 mm or less, and a wall thickness of 0.6 mm or less, preferably 0.5 mm or less. If the outer diameter and the wall thickness are larger than this, it is not possible to meet the demands for reducing the diameter of a thin fluorescent lamp for an illuminating device such as a backlight due to the reduction in thickness and weight of the liquid crystal display element.

The tubular borosilicate glass constituting the envelope is SiO ₂ 55 to 73%, B ₂ O ₃ 10 to 25%, Al ₂ O ₃ 1 to 10%, Li ₂ O + Na ₂ O + K ₂ O by weight percentage. 4~16%, ZrO ₂ 0~5%, those having a composition of Sb ₂ O ₃ 0.1~4% is preferred.

  The reason why the content of each component is limited as described above is as follows.

SiO ₂ is a main component necessary for constituting a glass skeleton, and its content is 55 to 73%, preferably 61 to 72%. If SiO ₂ is more than 73%, the coefficient of linear expansion becomes too low and the solubility tends to deteriorate. If it is less than 55%, the chemical durability tends to deteriorate. When it becomes impossible to apply uniformly and burns or the like occur, it causes a decrease in the luminance of the fluorescent lamp.

B ₂ O ₃ is a component necessary for improving solubility and adjusting viscosity, and its content is 10 to 25%, preferably 15.2 to 24%. When B ₂ O ₃ is less than 10%, dissolution becomes difficult and the viscosity becomes too high for Kovar sealing. On the other hand, when it exceeds 25%, there are problems that the viscosity is excessively lowered, a homogeneous glass cannot be obtained by evaporation, and the chemical durability is deteriorated.

Al ₂ O ₃ has a significant effect on improving the stability of the glass, and its content is 1 to 10%, preferably 1 to 4.9%. If Al ₂ O ₃ is more than 10%, it is difficult to melt the glass, and if it is less than 1%, 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 4 in total 16%, preferably 5.1-13%. If the total amount of these components is 16% or more, the expansion coefficient becomes too high, the viscosity is too low to be suitable for Kovar sealing, and the chemical durability is greatly reduced. The coefficient is too small. The content ratio of each component, Li ₂ O 0~4% (preferably _{0~3%), Na 2 O 0~4.3} % ( preferably 0~3.9%), K ₂ O 0~15 % (Preferably 0 to 13%) is suitable. If Li ₂ O is more than 4%, devitrification tends to deteriorate and the coefficient of thermal expansion becomes too high. If Na ₂ O is more than 4.3%, Na ions are phosphor in the thermal process during the production of the fluorescent lamp. May cause a decrease in luminance, or the thermal expansion coefficient may become too high. If K ₂ O exceeds 15%, the thermal expansion coefficient may become too high.

ZrO ₂ is a component that improves chemical durability and prevents alkali blowing and burns, and its content is 0 to 5%, preferably 0.01 to 3%. If ZrO ₂ is more than 5%, devitrification is deteriorated and the glass becomes non-uniform, resulting in poor dimensional accuracy and appearance defects, making it difficult to obtain high-quality glass.

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%), A range of 0 to 4% (preferably 0 to 1%) of Sb ₂ O ₃ is suitable. 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%), Sb ₂ O _{3 is} 0.1 to 4% (preferably 0.2 to 1%). 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. Sb ₂ O ₃ is difficult to obtain a homogeneous glass exceeds a predetermined amount. Further, if PbO or Sb ₂ O ₃ is excessively contained in the glass, the glass is colored brown or black by heat processing in the manufacturing process of the fluorescent lamp, and the appearance quality is deteriorated. Moreover, coloring in the effective light emitting portion is not preferable because it directly leads to a decrease in luminance.

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.

As described above, the envelope for a thin fluorescent lamp of the present invention is composed of borosilicate glass having high mechanical strength and heat resistance and low dielectric loss, so that the fluorescent lamp can be made thinner and thinner. Can respond. Moreover, it has a linear thermal expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C., and can be used for a fluorescent lamp using Kovar as an introduction metal. Moreover, since it is excellent in solarization resistance, it is difficult to cause ultraviolet coloring. Therefore, it is suitable as an envelope of a small-diameter fluorescent lamp that is lit for a long time, in particular, a small-diameter fluorescent lamp that serves as a light source of an illumination device for a liquid crystal display element.

In addition, since the thin fluorescent lamp of the present invention has an envelope made of borosilicate glass having high mechanical strength and heat resistance and low dielectric loss, the diameter can be further reduced. Moreover, since the envelope has a linear thermal expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C. and is consistent with Kovar, which is an introduced metal, there is no possibility of causing slow leaks or cracks. Moreover, since the envelope has excellent solarization resistance, ultraviolet coloring is unlikely to occur even when it is lit for a long time. Therefore, it is particularly suitable as a small-diameter fluorescent lamp serving as a light source for a liquid crystal display element illumination device.

  Embodiments of the present invention will be described below. In addition, the following description shows an example of this invention and is not limited to this.

  The envelope for a small fluorescent lamp of the present invention is manufactured as follows.

First, a glass raw material is prepared so as to have a desired composition. For example SiO ₂ 55 to 73% by weight _{percent, B 2 O 3 10~25%,} Al 2 O 3 1~10%, Li 2 O + Na 2 O + K 2 O 4~16%, ZrO 2 0~5%, Sb 2 Prepare a composition of 0.1 to 4% O ₃ . Next, the prepared glass raw material is put into a glass melting kiln, melted at 1500 to 1650 ° C. to be vitrified, and then formed into a tubular shape using a tube drawing method such as a dunner method or a down draw method, to a predetermined length Disconnect. At this time, it may be directly molded so as to have a desired outer diameter and thickness, or after a parent pipe having a large outer diameter and thickness is produced, it may be thinned by a redraw method. Thus, the small diameter of this invention comprised with the tubular glass which consists of a borosilicate glass whose linear expansion coefficient is 43-55 * 10 < ^-7 > / (degreeC), outer diameter 5.2mm or less, and wall thickness 0.6mm or less. A fluorescent lamp envelope is obtained. In addition, you may give the process of forming a reduced diameter part in the both ends of a tubular glass as needed.

  Next, the thin fluorescent lamp of the present invention will be described.

  The small fluorescent lamp of the present invention uses the envelope produced as described above, and is sealed in a state where the introduction metal made of Kovar is inserted at both ends of the envelope, A gas such as mercury or xenon is sealed inside, and the inner wall surface of the envelope has a configuration in which a phosphor is applied. When a voltage is applied, a discharge occurs between the electrodes at the tip of each introduced metal, and a gas such as mercury or xenon enclosed by the discharge is excited, and the inner wall surface of the envelope is irradiated with ultraviolet rays emitted from the excited gas. The phosphor emits visible light.

  Such a small-diameter fluorescent lamp is used by being incorporated in an illumination device for a liquid crystal display element.

  Hereinafter, the linear expansion coefficient and the ultraviolet solarization resistance of the envelope for the small fluorescent lamp of the present invention will be evaluated.

  Table 1 shows examples (sample Nos. 1 to 3) and comparative examples (samples No. 4 and 5) of the borosilicate glass constituting the envelope of the present invention.

  No. shown in the table. Each sample of 1-5 was prepared as follows.

  First, glass raw 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 1 to 3 has a linear expansion coefficient of 45.3 to 49.2 × 10 ⁻⁷ / ° C., which is close to that of Kovar, and the transmittance decrease due to ultraviolet irradiation is 1.0% or less. Therefore, it can be understood that it has high ultraviolet solarization resistance.

On the other hand, a comparative example No. Samples 4 and 5 have a linear expansion coefficient in the range of 43 to 55 × 10 ⁻⁷ / ° C. that can be sealed with Kovar, but do not contain Sb ₂ O _3, and therefore, transmittance by ultraviolet irradiation. The decrease in UV 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, a sample was obtained by mirror-polishing both surfaces of a 1 mm thick plate glass. 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)

In weight _{percent, SiO 2 55~73%, B 2} O 3 10~25%, Al 2 O 3 1~10%, Li 2 O + Na 2 O + K 2 O 4~16%, ZrO 2 0~5%, Sb 2 Outside composed of 0.1 to 4% O ₃ and a borosilicate glass having a linear expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C. (excluding 43 × 10 ⁻⁷ / ° C.) at 30 to 380 ° C. An envelope for a small fluorescent lamp, characterized by being made of tubular glass having a diameter of 5.2 mm or less and a wall thickness of 0.6 mm or less. Li ₂ O is 0~4%, Na ₂ O is 0~4.3%, K ₂ O is thin fluorescent lamp envelope of claim 1, characterized in that 0 to 15%. Claim borosilicate glass, further SrO, BaO, CaO, MgO, ZnO, characterized in that it comprises one or more selected from _{P 2 O 5, As 2 O} 3, SO 3, F 2, Cl 2 1 Or 2 small diameter fluorescent lamp envelopes. The envelope for a thin fluorescent lamp according to any one of claims 1 to 3 , wherein the envelope is used for a thin fluorescent lamp serving as a light source of an illumination device for a liquid crystal display element. In weight _{percent, SiO 2 55~73%, B 2} O 3 10~25%, Al 2 O 3 1~10%, Li 2 O + Na 2 O + K 2 O 4~16%, ZrO 2 0~5%, Sb 2 Glass so as to be a borosilicate glass containing 0.1 to 4% of O _{3 and having a} linear expansion coefficient of 43 to 55 × 10 ⁻⁷ / ° C. (excluding 43 × 10 ⁻⁷ / ° C.) at 30 to 380 ° C. A method for manufacturing an envelope for a small-diameter fluorescent lamp, wherein raw materials are prepared, put into a melting furnace, vitrified, and then formed into a tubular shape. 6. The method for manufacturing an envelope for a small-diameter fluorescent lamp according to claim 5 , wherein the envelope is formed into a tubular glass having an outer diameter of 5.2 mm or less and a wall thickness of 0.6 mm or less. 7. The method for producing an envelope for a small fluorescent lamp according to claim 5 or 6 , wherein the envelope is formed by tube drawing. Li ₂ O is 0 to 4% Na ₂ O is 0 to 4.3%, either outside for small diameter fluorescent lamp of claim 5 to 7 K ₂ O is characterized by a 0-15% A method for manufacturing an envelope. Claim borosilicate glass, further SrO, BaO, CaO, MgO, ZnO, characterized in that it comprises one or more selected from _{P 2 O 5, As 2 O} 3, SO 3, F 2, Cl 2 5 The manufacturing method of the envelope for thin fluorescent lamps in any one of -8. A thin fluorescent lamp using Koval as an introduction metal, wherein the envelope for a thin fluorescent lamp according to any one of claims 1 to 4 is used as an envelope. A thin fluorescent lamp using Kovar as an introduction metal, wherein the envelope is a thin fluorescent lamp envelope manufactured by the method according to any one of claims 5 to 9. Diameter fluorescent lamp. Claim 1 0 or 1 1 of the small diameter fluorescent lamp, characterized in that it is used as a light source of a lighting device of a liquid crystal display device.