JP2010116306A - Glass composition for illumination and fluorescent lamp envelope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass composition for illumination which is provided with an excellent ultraviolet shielding property to prevent degradation in a resin member in a liquid crystal display and has high transmittance even when not using Al<SB>2</SB>O<SB>3</SB>nor Sb<SB>2</SB>O<SB>3</SB>as essential components and to provide a fluorescent lamp envelope. <P>SOLUTION: The glass composition of illumination contains by mass, 55-75% SiO<SB>2</SB>, 0-10% Al<SB>2</SB>O<SB>3</SB>, 11-25% B<SB>2</SB>O<SB>3</SB>, 1.1-10% MgO, 0-10% CaO, 0-15% SrO+BaO+ZnO, 1.5-5% TiO<SB>2</SB>, 0-5% Na<SB>2</SB>O, 0-10 K<SB>2</SB>O, 3-15% Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O, <0.2% Sb<SB>2</SB>O<SB>3</SB>, <0.1% As<SB>2</SB>O<SB>3</SB>and 0.001-0.05% Fe<SB>2</SB>O<SB>3</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination glass composition, and more particularly to an illumination glass composition for producing a fluorescent lamp envelope used as a backlight source of a liquid crystal display element.

  Since the liquid crystal display panel does not self-emit, an illumination device such as a backlight is required. The illuminating device is called a backlight unit, and concentrates the light on a lamp as a light source, a reflector that reflects light emitted backward from the lamp to the front, a diffusion plate that uniformly averages the light, and a liquid crystal opening. And a lens sheet that reflects the others. The reflector, diffuser, and lens are made of resin. Specifically, the fluorescent lamp is placed directly under the liquid crystal display panel, the reflector plate emits light to the panel side, and the diffuser plate makes this light uniform light, and the fluorescent lamp is placed on the liquid crystal display panel side. There is an edge type illumination device that is installed on the side, guides light from the reflection plate to the light guide plate, and emits light to the liquid crystal display panel side through the diffusion plate. The direct type liquid crystal display device is suitable for a large liquid crystal display panel such as a TV, and the edge type liquid crystal display device is widely used in personal computers (PCs) because it can be thinned.

  As a fluorescent lamp used as a light source, a cold cathode fluorescent lamp is generally used (for example, Patent Document 1). The cold cathode fluorescent lamp is manufactured using an electrode such as kovar, tungsten, molybdenum, sealing beads for sealing the electrode, and a borosilicate glass outer tube coated with a phosphor on the inner surface. In addition, fluorescent lamps called external electrode lamps (for example, Patent Document 2) in which electrodes are formed on the outer tube surface have begun to be used. The light emission principle of these lamps is the same as that of general hot cathode lamps, and the mercury gas enclosed by the discharge between the electrodes is excited and applied to the inner wall surface of the outer tube by ultraviolet rays emitted from the excited gas. The phosphor emits visible light.

  The lifetime of the backlight unit is represented by the time when it becomes half of the initial luminous flux. The cause of light beam deterioration is not only the fluorescent lamp of the light source, but also the reflectance and transmittance deteriorate due to coloring due to deterioration of the resin reflecting plate that efficiently reflects the light and the diffusion plate that diffuses the light. Is caused. The deterioration of these resin materials is mainly caused by ultraviolet rays generated inside the lamp leaking out of the tube. In particular, since it is used for a long time in a TV application, the influence of leakage of ultraviolet rays (313 nm or the like) on a longer wavelength side, which does not cause a problem in a PC application with a relatively short life, cannot be ignored.

Therefore, it has been studied to use a borosilicate glass having a high ultraviolet shielding property by adding a large amount of TiO ₂ to the outer tube of a fluorescent lamp that requires a long life. For example, Patent Document 3 discloses an outer tube glass material for a fluorescent lamp that is provided with ultraviolet shielding properties using TiO ₂ .
JP-A-6-111784 JP 2005-93422 A JP 2005-320225 A

When the content of TiO _{2 in} the borosilicate glass is increased, the coloring of Fe ₂ O ₃ , Cr ₂ O _{3 and the} like contained in the glass as an impurity component is increased, the transmission of visible light is reduced, and the glass is markedly colored. When used as an outer casing for illumination, the light emitted from the visible light illumination lamp cannot be efficiently transmitted to the outside due to the coloring of the glass, resulting in a decrease in brightness of the illumination lamp. Further, as a backlight light source for liquid crystal, the transmission of specific visible light is hindered, thereby causing problems such as changing the color of an image obtained by the liquid crystal display device.

Therefore, Patent Document 3 discloses that the glass contains As ₂ O ₃ or Sb ₂ O ₃ as a method for preventing coloring of the borosilicate glass. However, As ₂ O ₃ and Sb ₂ O ₃ are desired not to be used from the viewpoint of the environment, and the current situation is that the restriction on the amount of use is proceeding in some environmental regulations.

An object of the present invention is to provide an excellent ultraviolet shielding property that does not deteriorate a resin member in a liquid crystal display device, and to achieve high transmittance without using As ₂ O ₃ and Sb ₂ O ₃ as essential components. It is an object to provide a glass composition for lighting and a sheath for a fluorescent lamp.

As a result of repeating various studies, the inventors have made borosilicate glass containing a high amount of TiO ₂ contain a certain amount or more of MgO without using a large amount of As ₂ O ₃ or Sb ₂ O _3. It discovered that coloring of glass could be suppressed. Furthermore, it has been found that if an appropriate amount of CaO is contained in a borosilicate glass containing a high amount of TiO ₂ , the ultraviolet absorption edge can be shifted to the longer wavelength side to improve the ultraviolet shielding property of 313 nm.

In other words, lighting glass composition of the present invention, _SiO 2 55 to _75% in mass _{percentage, Al 2 O 3 0~10%,} B 2 O 3 11~25%, MgO 1.1~10%, CaO 0 _{~10%, SrO + BaO + 0~15} % ZnO, TiO 2 1.5~5%, Na 2 O 0~5%, K 2 O 0~10%, Li 2 O + Na 2 O + K 2 O 3~15%, Sb 2 O ₃ Less than 0.2%, As ₂ O ₃ less than 0.1%, Fe ₂ O ₃ 0.001 to 0.05%.

  It is preferable that the glass composition for illumination of this invention contains 0.1 mass% or more of CaO.

According to the above configuration, it is possible to improve the ultraviolet shielding property of 313 nm by shifting the ultraviolet absorption edge to the long wavelength side. As a result, the TiO ₂ content can be reduced and glass coloring can be further suppressed.

  The lighting glass composition of the present invention is preferably for a fluorescent lamp. The fluorescent lamp includes a hot cathode type (HCFL), a cold cathode type (CCFL), and an external electrode type (EEFL). In the present invention, all types of fluorescent lamps are targeted. In particular, CCFL and EEFL which are widely used as backlight light sources of liquid crystal display elements are preferable.

  According to the said structure, the effect of this invention can be enjoyed exactly.

  The envelope for a fluorescent lamp of the present invention is characterized by comprising the above-mentioned lighting glass composition. Here, the “outer container” is a member for forming an internal space (discharge space) of the fluorescent lamp, and a tube-shaped one is generally widely used. In recent years, however, various types of fluorescent lamps have been studied. For example, in a flat type fluorescent lamp, an outer container having a box shape or the like is used. In the present invention, all of these forms are collectively referred to as an “outer container”.

  The envelope for a fluorescent lamp of the present invention is preferably used as an envelope for a fluorescent lamp for a backlight of a liquid crystal display device.

  According to the said structure, the effect of this invention can be enjoyed exactly.

Since the lighting glass composition of the present invention contains a high amount of TiO ₂ , it is possible to shield ultraviolet rays (313 nm or the like) on the longer wavelength side. Therefore, even when it is used for a long time like a backlight light source of a liquid crystal TV, it is possible to effectively prevent deterioration of the fluorescent lamp peripheral material.

Moreover, since it contains a predetermined amount of MgO, it is possible to prevent the glass from being colored by impurities even if it contains a large amount of TiO ₂ . For this reason, it is possible to minimize the use of environmentally undesirable components such as As ₂ O ₃ and Sb ₂ O ₃ .

  Therefore, it is suitable as a material constituting the outer casing of the fluorescent lamp for backlight of the liquid crystal display device.

  Hereinafter, the reason why the composition of the lighting glass composition of the present invention is limited as described above will be described. In the following description, “%” means “% by mass” unless otherwise specified.

SiO ₂ is a main component necessary for constituting a glass skeleton, and its content is 55 to 75%, preferably 60 to 75%. If SiO ₂ is 75% or less, it does not take a long time to melt the silica raw material, and the viscosity of the glass does not become too high. For this reason, for example, in glass tube production, it can be melted without difficulty and the molding temperature does not become too high, so that it can be produced easily. In addition, energy consumption can be kept low. On the other hand, if SiO ₂ is 55% or more, cracks are less likely to occur, so that it has sufficient strength as an illuminating glass and can sufficiently withstand use as a fluorescent lamp envelope. If SiO ₂ is 60% or more, it can have sufficient strength against the lengthening of the fluorescent lamp accompanying the enlargement of the liquid crystal television.

Al ₂ O ₃ has an effect of making it difficult for phase separation that easily occurs in borosilicate glass. This effect improves the weather resistance of the glass, suppresses alkali elution from the glass, and facilitates long-term storage and use of the glass tube. On the other hand, it is a component that increases the viscosity of the glass, increases the temperature of glass melting and glass forming, and increases energy consumption. The content of Al ₂ O ₃ is 0 to 10%, preferably 0 to 5%. If Al ₂ O ₃ is 10% or less, it becomes easy to melt glass industrially. Further, if Al ₂ O ₃ is 5% or less, energy consumption in glass production is reduced, which is preferable from the viewpoint of the environment.

B ₂ O ₃ is a component necessary for improving the meltability and adjusting the viscosity, and its content is 11 to 25%, preferably 11 to 23%. When B ₂ O ₃ is 25% or less, a homogeneous glass with little evaporation from the glass melt can be obtained. The phase separation that can occur in borosilicate glass is a phenomenon in which the glass phase separates at a certain temperature range and loses the homogeneity of the glass, and is caused by the coloration of blue or white or the precipitation of crystals from the separated glass phase. The glass becomes cloudy. If B ₂ O ₃ is 25% or less, the phase separation is suppressed and the glass does not become cloudy. On the other hand, if B ₂ O ₃ is 11% or more, the viscosity is sufficiently low, and it is easy to obtain a tube glass with good dimensional accuracy.

MgO is an important component in the present invention and an essential component. Coloring components such as Fe ₂ O ₃ and Cr ₂ O ₃ are present in the borosilicate glass as impurities. However, if the content of TiO ₂ is large, these colors the glass. MgO has the effect of suppressing this impurity coloring, and can prevent a decrease in transmittance in the visible light region. Moreover, it is a component that aids the melting of the glass and facilitates the melting of the glass. It also has the effect of improving weather resistance. On the other hand, it is a component that promotes the phase separation of glass, and if contained in a large amount, there is a possibility of deteriorating productivity in glass production. The content of MgO is 1.1% or more, preferably 1.3% or more, more preferably 2% or more. The upper limit is 10% or less, preferably 5% or less. If the MgO content is 10% or less, the glass can be molded into various shapes without causing phase separation, and if it is 5% or less, stable production is not caused by phase separation even during mass production. Production can be done. On the other hand, if it is 1.1% or more, it is possible to obtain a visible light transmittance that can be sufficiently used practically. Further, when the content of impurities is 1.3% or more, particularly 2% or more, even when impurity components such as Fe ₂ O ₃ and Cr ₂ O ₃ increase, glass coloring is sufficiently suppressed and a decrease in transmittance in visible light is prevented. It becomes possible to do.

The impurity coloring suppression effect by MgO depends on the TiO ₂ content. When the amount of TiO ₂ is small, a small amount of MgO is effective, but when the amount of TiO ₂ is large, a large amount of MgO is required. However, even if the amount of MgO increases more than necessary, an effect commensurate with the amount added cannot be obtained. Therefore, it is preferable that MgO / TiO ₂ is adjusted to the range of 0.3 to 2.5 in mass ratio.

In the borosilicate glass containing TiO ₂ , CaO is a component that remarkably improves the ultraviolet shielding effect by TiO ₂ and suppresses glass coloring due to impurity components such as Fe ₂ O ₃ and Cr ₂ O _3, and is in the visible light range. It is a component which prevents the transmittance | permeability fall. Moreover, it is a component which helps the melting property of glass, and makes glass melting | dissolving easy. It also has the effect of improving weather resistance. On the other hand, CaO is a component that promotes the phase separation of glass. Moreover, when CaO is contained in a large amount, CaO-containing crystals are likely to precipitate, which becomes a factor that deteriorates productivity in glass production. CaO is not an essential component but is preferably contained in an amount of 0.1% or more, particularly 0.5% or more, and the upper limit is 10% or less, preferably 5% or less. When CaO is 0.1% or more, an effect of enhancing the ultraviolet shielding effect of TiO ₂ or preventing glass coloring appears. Since the above effect becomes remarkable when is 0.5% or more, it is possible to reduce the TiO ₂ content, as a result, it becomes possible to further suppress the glass coloration. On the other hand, if the CaO content is 10% or less, phase separation does not occur, and glass can be formed into various shapes without precipitating crystals. If it is 5% or less, phase separation is possible even during mass production. Thus, stable production can be performed without causing production failure due to crystal precipitation.

SrO, BaO, and ZnO are components that remarkably improve the ultraviolet shielding effect of TiO _{2 in} borosilicate glass. Moreover, it is a component which suppresses the phase separation of glass, and has an effect of suppressing a decrease in productivity due to phase separation in glass production. On the other hand, since these components are heavy in density, they are separated from other low-density components when the glass is melted, which may deteriorate the homogeneity of the glass. In addition, crystals containing these components and the SiO ₂ component are likely to precipitate. The total content of SrO, BaO, and ZnO is 0 to 15%, preferably 0 to 10%. When the total amount of SrO, BaO, and ZnO is 15% or less, it becomes possible to obtain a homogeneous glass, and a glass having no heterogeneous parts such as striae or crystal precipitation can be stably produced. When it is 10% or less, striae and crystal precipitation do not occur even during mass production, and production can be performed stably. In addition, it is preferable that content of SrO, BaO, and ZnO is all 0-5%, especially 0-4%.

TiO ₂ is an important component in the present invention and is an essential component. TiO ₂ is a component that absorbs in the ultraviolet region and gives the glass an ultraviolet shielding effect. Furthermore, it is a component that provides an effect (short wavelength ultraviolet discoloration resistance) of preventing the glass from being discolored by exposure to short wavelength ultraviolet rays. On the other hand, when a large amount of TiO ₂ is contained, impurity coloring is promoted. Furthermore, there is a possibility that a TiO ₂ -based crystal having a needle-like or plate-like unique shape is easily generated or the phase separation tendency is increased, thereby reducing productivity. The content of TiO ₂ is 1.5% or more, preferably 2% or more, and the upper limit is 5% or less, preferably 4.5% or less, more preferably 3% or less. When the content of TiO ₂ is 5% or less, coloring of the glass can be suppressed to such an extent that it can be used by adding MgO or the like. If it is 4.5% or less, it becomes possible to produce glass without producing TiO ₂ -based crystals or phase separation. If it is 3% or less, mass production can be carried out stably without causing the above problems. On the other hand, if the content is 1.5% or more, a sufficient ultraviolet shielding effect can be obtained, and discoloration of the resin member used in the liquid crystal display device due to ultraviolet rays can be effectively suppressed. Further, discoloration due to short wavelength ultraviolet rays can be prevented, and the glass does not discolor even when used for a long time as a light source of a liquid crystal display device. If TiO ₂ is 2% or more, a sufficient ultraviolet shielding effect can be obtained even when the glass tube is used with a thin glass tube as a fluorescent lamp used in various types of liquid crystal display devices. .

_Li 2 O is an alkali metal oxides _{(R 2 O), Na 2} O, and _{K 2} O, to lower the viscosity of glass to facilitate glass melting, is a component that easily obtained homogeneous glass. Further, since the viscosity of the glass can be reduced, it is possible to operate at a low temperature, and it is possible to reduce energy consumption in melting and glass forming. It is also a component for adjusting the thermal expansion coefficient and viscosity. On the other hand, it is a component that deteriorates the weather resistance of the glass, increases the elution of alkali from the glass, and generates precipitates on the glass surface. Therefore, when these components are large, it becomes difficult to store and use them for a long time. The total content of alkali metal oxides is 3 to 15%, preferably 3 to 10%. If the total amount of these components is 15% or less, practically sufficient weather resistance can be obtained. In addition, since the coefficient of thermal expansion does not become too large, the thermal expansion of the glass beads that seal each metal when used in an envelope of a fluorescent lamp in which Kovar metal, tungsten metal, molybdenum metal, etc. are used as electrodes. It is easy to fit with the coefficient. If the total amount of these components is 10% or less, it becomes easy to match the thermal expansion coefficient of the glass beads to be sealed with tungsten metal or tungsten metal. On the other hand, if the total amount of these components is 3% or more, melting of the glass becomes easy and the viscosity does not become too high, so that energy consumption in melting and glass forming can be reduced.

Na ₂ O can be contained up to 5% in order to improve the meltability, expansion characteristics, viscosity characteristics and the like. When Na ₂ O is 5% or less, practically sufficient weather resistance can be secured, and the glass can be sufficiently endured for long-term storage.

K ₂ O can be contained up to 10% in order to improve the meltability, expansion characteristics, viscosity characteristics and the like. When K ₂ O is 10% or less, practically sufficient weather resistance can be secured, and the glass can withstand long-term storage.

Li ₂ O is a component that can be added up to 5%. However, when Li ₂ O is added to the borosilicate glass, it is easy to cause phase separation of the glass. Therefore, it is not always necessary to contain it as long as predetermined characteristics can be obtained by using other alkali components.

Sb ₂ O ₃ and As ₂ O ₃ are used as fining components and are components that improve the foam quality of glass. Also a component to suppress coloration of borosilicate glass where TiO ₂ is high content. On the other hand, in recent years, it is a component that is being regulated by the laws and regulations to limit the amount of use because it harms the environment. Further, if these components are contained in a large amount in the glass, the glass is blackened or a TiO ₂ -based crystal is generated during the heat treatment in the post-processing. Therefore, in the present invention, it is desirable that the amount of these components used be as small as possible. Specifically, Sb ₂ O ₃ is less than 0.2%, preferably less than 0.15%, and As ₂ O ₃ is 0.1%. Less than, preferably less than 0.05%.

Fe ₂ O ₃ is a component inevitably mixed as an impurity in the raw material and recycled cullet. It is a component whose content should be controlled because it is a component that significantly accelerates the coloring of glass and lowers the transmittance of visible light. If the content of Fe ₂ O ₃ is less than 0.001%, especially not contained at all, impurity coloring can be effectively suppressed even if a large amount of TiO ₂ is contained, but the cost is very high. It is not practical. On the other hand, if it exceeds 0.03%, especially 0.05%, it is difficult to prevent impurity coloring even if MgO, CaO, or the like is added.

The value of (Li ₂ O + Na ₂ O + K ₂ O) / SiO ₂ is an index for adjusting the thermal expansion coefficient of glass. If this value is in the range of 0.04 to less than 0.10, it becomes easy to obtain a thermal expansion coefficient (30 to 45 × 10 ⁻⁷ / ° C. at 30 to 380 ° C.) consistent with tungsten metal. If it exists in the range of 0.27, it will become easy to obtain the thermal expansion coefficient (46-58 * 10 < ^-7 > / (degreeC) at 30-380 degreeC) matched with a kovar metal and molybdenum metal.

The lighting glass composition of the present invention can contain various components in addition to the above components. For example, La ₂ O ₃ , Nb ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , WO ₃ , SnO ₂ , SO ₃ , Cr ₂ O ₃ , Eu ₂ O ₃ , Cl ₂ etc. as optional components or as impurity components May be included.

La ₂ O ₃ is a component that improves the ultraviolet shielding effect of TiO ₂ . On the other hand, it is a component that greatly promotes impurity coloring. The content of La ₂ O ₃ is desirably 3% or less.

Nb ₂ O ₅ is a component that improves the ultraviolet shielding effect of TiO ₂ . On the other hand, it is a component that greatly promotes impurity coloring. The content of Nb ₂ O ₅ is desirably 3% or less.

ZrO ₂ is a component that suppresses impurity coloring. On the other hand, it is a component that increases the viscosity of glass and hinders glass melting and glass forming. The content of ZrO ₂ is desirably 5% or less.

Y ₂ O ₃ is a component that improves the ultraviolet shielding effect of TiO ₂ and is also a component that suppresses impurity coloring. On the other hand, it is a component that inhibits melting during glass melting. The content of Y ₂ O ₃ is desirably 5% or less.

WO ₃ is a component having an ultraviolet shielding effect similar to TiO ₂ . On the other hand, when it is contained in a large amount in borosilicate glass, it is a component that promotes phase separation of glass. The content of WO ₃ is desirably 5% or less.

SnO ₂ is a component that works as a refining agent at the time of melting the glass and improves the bubble quality of the glass. On the other hand, it is a component that colors glass, and is a component that is blackened during glass thermal processing. The SnO ₂ content is desirably 3% or less.

SO ₃ , when contained in an appropriate amount, is a component that works as a clarifier when the glass is melted and improves the bubble quality of the glass. On the other hand, when it is contained in a large amount, the SO ₂ gas cannot be completely removed from the glass, but rather deteriorates the foam quality. The content of SO ₃ is desirably 1% or less.

Cr ₂ O ₃ is a component inevitably mixed as an impurity in the raw material and recycled cullet. It is a component whose content should be controlled because it is a component that significantly accelerates the coloring of glass and lowers the transmittance of visible light. The content of Cr ₂ O ₃ is desirably 0.01% or less.

Eu ₂ O ₃ is a component of the phosphor, and is a component mixed into the glass as an impurity when the fluorescent lamp is recycled. It is a component whose content should be controlled because it is a component that significantly accelerates the coloring of glass and lowers the transmittance of visible light. The content of Eu ₂ O ₃ is desirably 0.01% or less.

Cl ₂ is a component that works as a fining agent and improves the bubble quality of the glass. On the other hand, if it is contained in a large amount, chloride crystals will precipitate on the glass during glass thermal processing, and the glass will become cloudy. The Cl ₂ content is desirably 1% or less.

The glass composition for illumination of the present invention desirably has a spectral transmittance at a wavelength of 400 nm of 82% or more at a glass thickness of 4 mm. In a borosilicate glass, when a large amount of TiO ₂ is contained, impurities are colored remarkably. Absorption of the transmittance of Fe ions exists at a wavelength of 350 to 550 nm, and the decrease in the transmittance in this wavelength region causes the coloring of the glass. Since a decrease in transmittance leads to a decrease in lamp brightness, it is desirable that the glass is not colored. The degree of impurity coloring can be evaluated by spectral transmittance at a wavelength of 400 nm. The spectral transmittance at a wavelength of 400 nm can be increased by methods such as increasing the content of MgO, decreasing the content of TiO ₂ , and reducing the amount of impurities that cause coloring.

The glass composition for illumination of the present invention desirably has a spectral transmittance at a wavelength of 313 nm of 30% or less at a glass thickness of 0.3 mm. The lifetime of the backlight unit is also caused by deterioration in reflectance and transmittance due to coloring due to deterioration of a resin-made reflecting plate that efficiently reflects the light and a diffusion plate that diffuses the light. The deterioration of these resin materials is caused by leakage of ultraviolet rays generated inside the lamp to the outside of the tube. For this reason, it is desired that the glass used for the backlight has a high ultraviolet shielding property. The ultraviolet shielding property can be evaluated by the transmittance at a wavelength of 313 nm. The spectral transmittance at a wavelength of 313 nm can be lowered by a method such as increasing the content of TiO ₂ or increasing the content of CaO.

In the lighting glass composition of the present invention, it is desirable that the change in spectral transmittance at a wavelength of 400 nm before and after ultraviolet irradiation is 5% or less at a glass thickness of 0.3 mm. When the borosilicate glass is irradiated with ultraviolet rays, particularly short wavelength ultraviolet rays, the glass itself changes color. Discoloration of glass due to ultraviolet rays occurs mainly due to a decrease in transmittance at wavelengths of 300 nm to 650 nm. Since a decrease in transmittance leads to a decrease in lamp brightness, it is desirable that no glass discoloration occurs. The short wavelength ultraviolet discoloration resistance can be evaluated by a change in spectral transmittance at a wavelength of 400 nm before and after irradiation with short wavelength ultraviolet rays. The ultraviolet rays are irradiated by a low-pressure mercury lamp having a plate glass having a thickness of 0.3 mm and mirror-polished on both sides and a quartz glass outer tube of 40 W. For 60 minutes (irradiation distance 25 mm). Further, the amount of change in spectral transmittance at a wavelength of 400 nm before and after ultraviolet irradiation can be reduced by a method such as increasing the content of TiO ₂ or adding Nb ₂ O ₅ and WO ₃ as essential components.

As for the glass composition for illumination of this invention, it is desirable for the phase separation temperature of glass to be 1000 degrees C or less. It is known that borosilicate glass tends to cause phase separation. If crystals are deposited (devitrified) in the phase-separated portion, it becomes a cause in the glass production and the productivity is lowered. On the other hand, if the temperature at which phase separation occurs is high, the working temperature in glass production becomes narrow and mass productivity is impaired. Further, when glass that has been devitrified due to phase separation is used as an outer container, the transmittance of the glass is low, so that the lamp becomes defective. For this reason, it is desired that the glass is less likely to cause phase separation. The phase separation tendency of glass can be evaluated by the phase separation temperature. It can be said that the higher the temperature, the easier the phase separation. The phase separation temperature of the glass can be lowered by a method such as increasing the content of Al ₂ O ₃ or decreasing the content of B ₂ O ₃ , MgO, CaO, TiO ₂ , or Li ₂ O.

Lighting glass composition of the present invention, it is desirable that the precipitation temperature of the TiO ₂ type crystal is 1000 ° C. or less. When a large amount of TiO ₂ is contained in the borosilicate glass, a TiO ₂ -based crystal may be generated. The precipitation of TiO ₂ -based crystals causes defects in glass production and decreases productivity. On the other hand, if the temperature at which the TiO ₂ -based crystals are precipitated is high, the working temperature in glass production becomes narrow and mass productivity is impaired. Further, when glass on which TiO ₂ -based crystals are deposited is used as an outer container, the glass has a low transmittance, which makes the lamp unsatisfactory. For this reason, it is desired that the glass is a glass in which TiO ₂ -based crystals are difficult to precipitate. Precipitation tendency of TiO ₂ based crystal can be evaluated by the precipitation temperature of the TiO ₂ type crystal, the higher the temperature is higher TiO ₂ based crystal can be said to easily precipitate. Incidentally precipitation temperature of the TiO ₂ type crystal can be reduced by a method such reducing the content of TiO _2.

The lighting glass composition of the present invention is desired to have a thermal expansion coefficient of 30 to 58 × 10 ⁻⁷ / ° C. at 30 to 380 ° C. When used for a fluorescent lamp having an electrode inside, a rod-shaped electrode is inserted into a glass sealing bead, and the glass sealing bead is heated and softened to be fused and integrated with the electrode to produce an electrode member. The electrode member produced in this way is inserted from both ends of the tubular mantle container, heat-processed, and the mantle container and the electrode member are fused and sealed. The glass sealing bead has a coefficient of thermal expansion compatible with the electrode material. For the outer container, glass having a thermal expansion coefficient compatible with the glass sealing beads is used. In general, the glass sealing bead and the outer container are made of the same glass material. For this reason, when the electrode material is tungsten metal, molybdenum metal or Kovar metal, the lighting glass composition of the present invention constituting the outer casing is thermally expanded at 30 to 380 ° C. so as to be compatible with these metals. It is desirable to adjust the coefficient to 30 to 58 × 10 ⁻⁷ / ° C.

  In the fluorescent lamp, the glass sealing bead and the outer container may not be made of the same material. In this case, since the outer container does not directly contact the rod-shaped electrode, it is not necessary to match the expansion characteristics with the electrode material. In particular, when Kovar metal is selected as the electrode material, it is useful to make the glass sealing beads and the outer container different from each other because the degree of freedom in designing the composition of the outer container glass can be increased. In other words, since the elongation characteristics with respect to temperature change abruptly for Kovar metal, the glass for sealing beads needs to have the same expansion change as Kovar metal. However, the lighting glass composition of the present invention constituting the outer container does not need to undergo the same expansion change as that of Kovar metal, and only needs to be compatible with the expansion characteristics of the glass for sealing beads.

Further, in the case of a so-called external electrode fluorescent lamp having no electrode inside, there is no restriction on the thermal expansion coefficient with respect to the jacket glass. For example, the thermal expansion coefficient at 30 to 380 ° C. is in the range of 30 to 100 × 10 ⁻⁷ / ° C. I just need it.

  The fluorescent lamp envelope of the present invention has the above composition. Since the composition and characteristics of the glass composition constituting the outer container are as described above, description thereof is omitted here.

  Next, a method for producing a fluorescent lamp envelope according to the present invention will be described. Here, the production of a tubular outer container (outer tube) will be described as an example, but the present invention is not limited to this.

  First, raw materials are prepared so as to be glass having the above characteristics, and melted at 1400 to 1650 ° C. Next, the molten glass is formed into a tubular shape by a tube drawing method such as the Danner method, the down draw method, or the up draw method. Subsequently, the tubular glass is cut into a predetermined size, and post-processed as necessary to obtain a tubular outer container.

  The fluorescent lamp envelope obtained in this way is used, for example, for the production of a backlight fluorescent lamp for a liquid crystal display element.

  Hereinafter, the present invention will be described based on examples.

  Tables 1 and 2 show examples of the present invention (sample Nos. 1 to 10), and Table 3 shows comparative examples (samples No. 11 to 19), respectively.

  First, after preparing a glass raw material so that it might become a target composition, it melt | dissolved at 1550 degreeC for 5 hours using the platinum crucible. As the raw material, natural minerals, oxides, carbonates, sulfates and the like can be used, and the raw material may be prepared in consideration of the analytical value of the raw material, and the type of raw material is not limited. After melting, the melt was formed into a predetermined shape and processed to prepare each glass sample, which was used for each evaluation. The results are shown in Tables 4-6.

  As is apparent from the table, No. 1 as an example of the present invention. Each of the samples 1 to 10 has a 400 nm transmittance of 82% or more, and the coloring of the glass is sufficiently suppressed. Moreover, all the transmittance | permeability of wavelength 313nm is 30% or less, and hardly transmits harmful ultraviolet rays. Further, the decrease in the transmittance of 400 nm due to ultraviolet irradiation was 0%, and it had very high ultraviolet discoloration resistance.

On the other hand, No. which is a comparative example. Eleven samples had a 313 nm transmittance value exceeding 30%. Comparative Example No. Twelve samples had a coefficient of thermal expansion of 80 × 10 ⁻⁷ / ° C. No. Thirteen samples had a transmittance value at 400 nm of 82% or less. No. Sample 14 had poor phase separation and also had a high TiO ₂ crystal precipitation temperature. No. Fifteen samples had a transmittance value at 400 nm of 82% or less. Sample No. From 16 to 19, it can be seen that the _Fe 2 _{O 3} can not be obtained impurity coloration prevention effect by MgO or too little too large.

  The coloration of the glass was evaluated by measuring the transmittance at 400 nm. Specifically, a plate sample of 25 mm × 30 mm was cut out from each glass sample, polished to a thickness of 4 mm, and further, both surfaces were optically mirror-polished. Using the UV-3100PC spectrophotometer manufactured by SHIMADZU, the processed sample was measured for transmittance at wavelengths of 200 nm to 800 nm including a visible light region of wavelengths of 380 nm to 780 nm. A value at a wavelength of 400 nm was read from the measurement data.

  The ultraviolet shielding property was evaluated by measuring the transmittance at 313 nm. Specifically, a plate sample of 25 mm × 30 mm was cut out from each glass sample, polished to a thickness of 0.3 mm, and both surfaces were optically polished. The processed sample was read at a wavelength of 313 nm using a UV-3100PC spectrophotometer manufactured by SHIMADZU.

  Ultraviolet discoloration resistance was evaluated by measuring transmittance before and after ultraviolet irradiation at 400 nm. Specifically, a plate sample of 25 mm × 30 mm was cut out from each glass sample, polished to a thickness of 0.3 mm, and both surfaces were optically polished. Using the UV-3100PC spectrophotometer manufactured by SHIMADZU, the processed sample was read for the transmittance value at a wavelength of 400 nm. Then, after irradiating the sample with ultraviolet light having a main wavelength of 185 nm, 254 nm, 313 nm, and 364 nm for 60 minutes at an irradiation distance of 25 mm using a 25 W low-pressure mercury lamp, the transmittance value at a wavelength of 400 nm is read again, and the wavelength before and after the ultraviolet irradiation. A transmission difference of 400 nm was calculated.

  For the thermal expansion coefficient, an average linear thermal expansion coefficient at 30 to 380 ° C. was measured using a thermal expansion coefficient measuring device manufactured by MAC SCIENCE.

  The phase separation was evaluated by measuring the phase separation temperature. Specifically, glass is cut out from each glass sample, placed in a heat-resistant boat-shaped container of 120 mm × 1.2 cm × 1 cm, about 90% of the container capacity, and heated in an electric furnace at 1250 ° C. for 2 hours. The glass was melted and placed in a temperature-gradient furnace having a temperature gradient of 800 ° C. to 1100 ° C. and kept for 48 hours. After the sample was taken out of the temperature gradient furnace, the phase separation temperature was evaluated by visually observing the glass and comparing temperature data obtained by measuring the temperature of the phase-divided and clouded region in advance.

The precipitation temperature of the TiO ₂ crystal was evaluated by a method similar to the evaluation of phase separation. Specifically, glass is cut out from each glass sample, placed in a heat-resistant boat-shaped container of 120 mm × 1.2 cm × 1 cm, about 90% of the container capacity, and heated in an electric furnace at 1250 ° C. for 2 hours. The glass was melted and placed in a temperature-graded furnace having a temperature gradient of 800 ° C. to 1100 ° C. and kept for 48 hours. After removing the sample from the temperature gradient furnace, the glass is peeled from the heat-resistant boat, the peeled surface is observed with a polarizing microscope, and the highest temperature point where the TiO ₂ crystal is deposited is compared with the temperature data measured in advance. Was used to evaluate the TiO ₂ crystal precipitation temperature.

Claims (5)

_SiO 2 55 to _75% in mass _{percentage, Al 2 O 3 0~10%,} B 2 O 3 11~25%, MgO 1.1~10%, CaO 0~10%, SrO + BaO + 0~15% ZnO, TiO 2 _{1.5~5%, Na 2 O 0~5%} , K 2 O 0~10%, Li 2 O + Na 2 O + K 2 O 3~15%, Sb 2 O 3 less than _0.2%, As _{2 O} 3 0 less than _.1%, lighting glass composition characterized by a Fe ₂ O 3 0.001~0.05%.   The glass composition for illumination according to claim 1, comprising 0.1% by mass or more of CaO.   The lighting glass composition according to claim 1, wherein the lighting glass composition is used for a fluorescent lamp.   An outer casing for a fluorescent lamp having the composition according to any one of claims 1 to 3.   5. The fluorescent lamp envelope according to claim 4, wherein the fluorescent lamp envelope is used as a fluorescent lamp envelope for a liquid crystal display device.