JP2007186404A - Glass for illumination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass for illumination capable of screening ultraviolet light of long wave length such as 313 nm and hardly causing the crystallization of TiO<SB>2</SB>series or phase separation. <P>SOLUTION: The glass for illumination contains, by mass, 50-75% SiO<SB>2</SB>, 12-25% B<SB>2</SB>O<SB>3</SB>, 0-<3.2% Al<SB>2</SB>O<SB>3</SB>, 0-<0.5% Li<SB>2</SB>O, 0-7% Na<SB>2</SB>O, 3-15% K<SB>2</SB>O, 6-15% Li<SB>2</SB>O+Na<SB>2</SB>O+K<SB>2</SB>O, 0-3.2% Al<SB>2</SB>O<SB>3</SB>+Li<SB>2</SB>O, 0-20% BaO, 0-15% ZnO, 2.5-4.9% TiO<SB>2</SB>and 0-5% As<SB>2</SB>O<SB>3</SB>+Sb<SB>2</SB>O<SB>3</SB>and has 45-58×10<SP>-7</SP>/°C coefficient of thermal expansion at 30-380°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination glass, and more particularly to an illumination glass 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 the light is concentrated on a lamp as a light source, a reflecting plate that reflects light emitted backward from the lamp to the front surface, a diffusion plate that uniformly averages the light, and a liquid crystal opening. It consists of a lens sheet that reflects the others. The reflector, diffuser, and lens are made of resin. Specifically, a fluorescent lamp is placed directly under the liquid crystal panel, a reflector is used to emit light toward the panel, and this is used as a uniform light with a diffuser, and the fluorescent lamp is placed behind the liquid crystal panel. There is an edge-type illumination device that is installed in the projector and guides the light from the reflection plate to the light guide plate and emits the light to the liquid crystal panel side through the diffusion plate. The direct type liquid crystal display device is suitable for a large-sized 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 or molybdenum, sealing beads for sealing the electrode, and a borosilicate glass outer tube having a phosphor coated 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 caused by the 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.

In view of this, it has been considered that the outer tube of a fluorescent lamp requiring a long life is made of borosilicate glass having ultraviolet shielding properties. For example, Patent Documents 3 to 5 disclose fluorescent lamp envelope glass materials that are provided with ultraviolet shielding properties using TiO ₂ .
JP-A-6-111784 JP 2005-93422 A Patent 3575114 JP 2002-68775 A JP 2005-41768 A

In order to increase the ultraviolet absorption ability on the long wavelength side such as 313 nm, it is effective to contain a large amount of TiO ₂ .

However, glass containing a large amount of TiO ₂ tends to form crystals mainly composed of TiO ₂ when it comes into contact with a refractory during glass tube forming. When crystals are formed in the glass, the roundness of the glass tube deteriorates, and the phosphor cannot be uniformly applied, resulting in unevenness in lamp brightness. In addition, since the periphery of the crystal portion is recessed, when the crystal precipitation portion overlaps with the sealing portion, a gap may be generated in the sealing portion to cause a slow leak, and the lamp may not be lit.

Further, when the TiO ₂ content increases, the phase separation tendency of the glass becomes stronger. Therefore, in the sintering process of the phosphor applied in the glass tube, a phenomenon that the glass is phase-divided and the transmittance is deteriorated easily occurs. When such a phenomenon occurs, the resulting lamp becomes dark.

An object of the present invention is to provide a glass for illumination that can shield ultraviolet rays on a long wavelength side such as 313 nm, and that hardly causes TiO ₂ -based crystals or phase separation.

The lighting glass of the present invention is, by mass percentage, SiO ₂ 50 to 75%, B ₂ O ₃ 12 to 25%, Al ₂ O ₃ 0 to less than 3.2%, Li ₂ O 0 to less than 0.5%. , Na ₂ O 0-7%, K ₂ O 3-15%, Li ₂ O + Na ₂ O + K ₂ O 6-15%, Al ₂ O ₃ + Li ₂ O 0-3.2%, BaO 0-20%, ZnO 0 to 15%, TiO ₂ 2.5 to 4.9%, As ₂ O ₃ + Sb ₂ O ₃ 0 to 5%, and the thermal expansion coefficient at 30 to 380 ° C. is 45 to 58 × 10 ⁻⁷ / ° C. It is characterized by being.

  The envelope for a fluorescent lamp of the present invention is characterized by comprising the above-mentioned lighting glass.

The lighting glass of the present invention has a necessary ultraviolet shielding capability at 313 nm, and does not deteriorate the constituent resin members of the backlight unit. Further, since the amount of precipitated TiO ₂ crystals is extremely small, it is possible to manufacture a mantle tube with high dimensional accuracy and high sealing reliability. Moreover, since the phase separation is weak, the lamp does not darken. Therefore, it is suitable as an outer tube material of a fluorescent lamp, particularly as an outer tube material of a small-diameter fluorescent lamp used for a light source of an illuminating device of a liquid crystal display element premised on long-term use such as a TV application.

  Further, if the mantle tube made of the glass is used, a fluorescent lamp having high luminance and almost no luminance deterioration can be produced. Therefore, it is suitable as an outer tube of a fluorescent lamp for a backlight unit of a device used for a long period of time, such as a TV application.

The lighting glass of the present invention is made of borosilicate glass having high mechanical strength. In the case of producing a cold-cathode fluorescent lamp envelope using Kovar or molybdenum as an electrode, the thermal expansion coefficient at 30 to 380 ° C. is preferably adjusted to a range of 45 to 58 × 10 ⁻⁷ / ° C.

Further, by containing a large amount of TiO ₂ , it is possible to effectively shield 313 nm ultraviolet rays. In addition, in the present invention, the contents of Al ₂ O ₃ and Li ₂ O are limited in order to prevent precipitation of TiO ₂ crystals caused by containing a large amount of TiO ₂ and an increase in phase separation tendency. . More specifically, the lower the content of Al ₂ O ₃ , the less TiO ₂ -based crystals are deposited when the glass comes into contact with the refractory. Moreover, the smaller the Li ₂ O content, the weaker the phase separation tendency of the glass. Moreover, when the glass is phase-separated, crystals are likely to precipitate. However, if the Li ₂ O content is decreased to weaken the phase separation tendency, the precipitation of TiO ₂ -based crystals can be further suppressed.

If only the content of Al ₂ O ₃ is reduced without reducing the content of Li ₂ O, the viscosity of the glass is lowered, making it difficult to obtain viscosity characteristics equivalent to those of conventional products. Moreover, when only the content of Li ₂ O is reduced without reducing the content of Al ₂ O ₃ , the viscosity of the glass increases and it becomes difficult to obtain viscosity characteristics equivalent to those of conventional products. Therefore, if both are reduced at the same time, the above effect can be obtained without changing the viscosity characteristics. However, if the content of TiO ₂ becomes too large, it becomes difficult to suppress precipitation of TiO ₂ -based crystals and an increase in phase separation tendency even if the contents of Al ₂ O ₃ and Li ₂ O are limited. The preferred contents of Al ₂ O ₃ , Li ₂ O and TiO ₂ are shown below.

The ratio of Al ₂ O ₃ and Li ₂ O and TiO ₂ are in mass percentage, Al less than _{2 O 3 0~3.2%, Li 2} O less than _{0~0.5%, Al 2 O 3 +} Li 2 O 0 ~3.2%, TiO ₂ 2.5~4.9%, preferably Al ₂ O ₃ is 0~3%, Li ₂ O is _{0~0.4%, Al 2 O 3 +} Li 2 O is 0 3%, TiO ₂ is from 2.5 to 4.2%.

  The reason why the composition of the lighting glass of the present invention is limited as described above will be described below.

SiO ₂ is a main component necessary for constituting a glass skeleton, and its content is 50% or more, preferably 55% or more, and more preferably 58% or more. Moreover, it is 75% or less, Preferably it is 72% or less, More preferably, it is 69% or less. If SiO ₂ is 75% or less, it does not take a long time to melt the silica raw material. If it is 72% or less, SiO ₂ crystals hardly occur in the glass. Further, if it is 69% or less, it is possible to effectively suppress the deterioration of dimensional accuracy caused by partial viscosity inhomogeneity. On the other hand, when SiO ₂ is 50% or more, excellent weather resistance can be obtained due to a synergistic effect with TiO ₂ . If it is 55% or more, a stable glass can be obtained because crystals are hardly generated. Most preferred is 58% or more.

B ₂ O ₃ is a component that is contained in a relatively large amount for improving the meltability, adjusting the viscosity, improving the weather resistance, and adjusting the expansion coefficient. Its content is 12% or more, preferably 15% or more, and its upper limit is 25% or less, preferably 22% or less. When the B ₂ O ₃ content is 25% or less, since the evaporation from the glass melt is small, a uniform glass can be obtained. Further, if it is 22% or less, the glass component is less evaporated even during the thermal processing during the lamp manufacturing process, so that the processing becomes easy. On the other hand, if B ₂ O ₃ is 12% or more, the viscosity is sufficiently low, and it is easy to obtain a tube glass with good dimensional accuracy. If it is 15% or more, since melting becomes easier, it is suitable for mass production.

Al ₂ O ₃ is a component that reinforces the network of the cut glass by containing an alkali component and remarkably improves the devitrification property of the glass at the time of melting. On the other hand, in order to inhibit the melting of TiO ₂ into the glass, TiO ₂ -based crystals are easily generated. Moreover, it is a component which raises the viscosity of glass. The content of Al ₂ O ₃ is less than 3.2%, preferably 3% or less, more preferably 2.5% or less. If Al ₂ O ₃ is less than 3.2%, TiO ₂ -based crystals are hardly formed, and if it is 3% or less, it is more preferable. If it is 2.5% or less, the viscosity becomes sufficiently low and it becomes easy to obtain a tube glass with good dimensional accuracy. In addition, TiO ₂ -based crystals are difficult to appear even at low temperatures. Al ₂ O ₃ is not an essential component, but is preferably contained in an amount of 0.1% or more in order to produce homogeneous glass or perform stable molding.

Alkali metal oxides (R ₂ O) a is Li ₂ O, Na ₂ O, and K ₂ O has an effect of adjusting the thermal expansion coefficient and viscosity and an excellent glass of dimension properties to enhance the meltability Make it easier to get. On the other hand, the weather resistance of glass is deteriorated. For example, it reacts with carbon dioxide gas or water in the air to form a product, which causes foreign matter on the glass surface. For this reason, it is necessary to manage the alkali content within an appropriate range.

Li ₂ O has an effect of promoting phase separation in addition to the above in a borosilicate glass containing a large amount of TiO ₂ . In addition, it is also a component that facilitates the formation of TiO ₂ -based crystals by phase separation. The content of Li ₂ O is limited to less than 0.5%, preferably 0.4% or less, more preferably 0.3% or less. If Li ₂ O is less than 0.5%, phase separation is unlikely to occur and the lamp is unlikely to become dark. Further, it is preferably 0.3% or less in order to make it difficult to produce TiO ₂ -based crystals. If predetermined characteristics such as meltability, expansion characteristics, and viscosity characteristics can be obtained by using other alkali components, Li ₂ O is not necessarily contained. Moreover, the viscosity adjustment required with the decrease in the amount of Al ₂ O ₃ can be effectively performed by reducing the amount of Li ₂ O.

Na ₂ O is an optional component and can be contained at 7% or less, preferably 5% or less. If Na ₂ O is 7% or less, practically sufficient weather resistance can be secured, and tube forming is facilitated. If it is 5% or less, the thermal expansion coefficient is adapted to the thermal expansion coefficient of Kovar or molybdenum. It becomes easy. In addition, when 2 or more types of alkali metal oxides are contained for the purpose of obtaining an alkali mixing effect, the content of Na ₂ O is preferably 0.1% or more.

K ₂ O is preferably contained in an amount of 3% or more, particularly 5% or more. The upper limit is preferably 15% or less, particularly preferably 11% or less. If K ₂ O is 15% or less, the thermal expansion coefficient can be easily matched with Kovar or molybdenum, and if it is 11% or less, sufficiently high weather resistance can be maintained.

  The total content of alkali metal oxides is 6% or more, preferably 7% or more. The upper limit is 15% or less, preferably 12% or less. If the total amount of these components is 15% or less, the coefficient of thermal expansion will not be too high, and it will be easy to match with that of encapsulated metal such as Kovar. If it is 12% or less, sufficiently high weather resistance can be maintained, so that foreign matter generation and the like can be prevented. On the other hand, if the total amount of these components is 6% or more, the coefficient of thermal expansion does not become too small, and it becomes easy to match that of Kovar or molybdenum. If it is 7% or more, vitrification becomes easier and a homogeneous glass is easily obtained.

In order to improve the electrical resistance due to the alkali mixing effect, it is desired to contain two or more kinds of alkali metal oxides. Among the alkali metal oxides, the electric resistance at 150 ° C. tends to be increased as the content of K ₂ O increases. This is because the ion radius of K ⁺ is larger than that of other alkali ions and is difficult to move in the glass. For this reason, it is desirable to contain the K ₂ O content in the largest amount among the alkali metal oxides.

Since Al ₂ O ₃ and Li ₂ O are components that precipitate TiO ₂ -based crystals or enhance phase separation, the total content is 3.2% or less, preferably 3% or less, particularly It is desirable to limit it to 2.9% or less, more preferably 2.5% or less. The lower limit is preferably 0.1% or more, particularly 0.5% or more. When the total amount of these components is 3.2% or less, there is an effect of preventing TiO ₂ -based crystal precipitation. However, considering mass productivity, it is desirable to limit the molding temperature to 2.9% or less because a lower molding temperature is required, and to limit it to 2.5% or less if possible for improving reliability. Moreover, if it is 0.1% or more, the effect of a meltability improvement will be recognized. If it contains 0.5% or more, it is easy to melt and the production efficiency is improved.

  BaO is a component that lowers the melting point and suppresses the phase separation of the glass to stabilize it. BaO is an optional component and can be contained in an amount of 20% or less, preferably 8% or less. If BaO is 20% or less, the precipitation tendency of crystals containing BaO as a main component is reduced. If it is 8% or less, a glass with better dimensional accuracy can be obtained, which is preferable.

  ZnO is a component that helps the glass melt. Moreover, it has the effect of maintaining the transparency of glass by preventing phase separation and improving stability. It also has the effect of reducing the viscosity of the glass. On the other hand, since ZnO itself is volatile, it is preferably 15% or less, particularly 3% or less.

TiO ₂ is known to have absorption in the ultraviolet region, and is a component that absorbs ultraviolet light and gives a shielding effect to glass. Further, it is a component that imparts short wavelength ultraviolet discoloration resistance to glass. Moreover, there exists an effect which raises the weather resistance of glass, or improves an elastic modulus and raises an intensity | strength. On the other hand, when the content is increased, TiO ₂ -based crystals are likely to be formed, and the phase separation is strongly promoted. The content of TiO ₂ is 2.5% or more, preferably 3.1% or more, more preferably 3.6% or more, and further preferably 3.8% or more. The upper limit is 4.9% or less, preferably 4.4% or less, and more preferably 4.2% or less. The thickness of the glass jacket tube used at present is 0.3 mm, which is the thinnest except for special applications due to strength. The required ultraviolet shielding ability is about 25% or less at 313 nm with an ultraviolet transmittance of 0.3 mm considering the absorption of the phosphor. When TiO ₂ is 2.5% or more, 313 nm ultraviolet rays can be shielded when the glass thickness is large. If the glass thickness is 3.1% or more, the glass thickness is about 0.5 mm, and if it is 3.6% or more, the glass tube has a glass thickness of about 0.3 mm to obtain a sufficient shielding property of 313 nm ultraviolet rays. Can do. On the other hand, if it is 4.9% or less, production is possible while producing TiO ₂ -based crystals. If it is 4.4% or less, it becomes more difficult to produce crystals, which is suitable for mass production. Furthermore, in order to increase the mass production efficiency by lowering the molding temperature and to improve the reliability at the time of sealing, it is necessary that almost no TiO ₂ crystal is generated. In order to facilitate this, it is recommended to limit it to 4.2% or less.

As ₂ O ₃ and Sb ₂ O ₃ are components that give a fining effect. Further, when TiO ₂ is contained in a large amount, impurity coloring due to Fe ₂ O ₃ tends to occur, but As will be described later, As ₂ O ₃ and Sb ₂ O ₃ have an effect of preventing this coloring. These components are contained in a total amount of 5% or less, preferably 1% or less. If the total amount exceeds 5%, there is a disadvantage that the glass becomes black during heating during glass processing. In order to obtain the above-described effect, it is preferable to contain at least one of them. Further, the total content is preferably 0.0001% or more, particularly 0.001% or more, 0.01% or more, and further preferably 0.1% or more.

As ₂ O ₃ is an optional component, but when added, it is preferably 0.0001% or more, more preferably 0.001% or more. The upper limit is preferably 1% or less, particularly 0.1% or less, more preferably 0.05% or less, and most preferably 0.01% or less. If the content of As ₂ O ₃ is 0.0001% or more, the above-mentioned effect starts to appear, but it is desirable that the content is 0.001% or more. On the other hand, if the amount is too large, a reduction tendency may occur depending on glass melting conditions. In consideration of the environment, the smaller the content, the better.

Sb ₂ O ₃ is an optional component as well as As ₂ O ₃ . Although Sb ₂ O ₃ is less effective than As ₂ O ₃ , it has a feature that the burden on the environment is small. Sb ₂ O ₃ is preferably contained in an amount of 0.0001% or more, particularly 0.001% or more, and more preferably 0.01% or more. Further, it is desirably 5% or less, particularly 3% or less. If Sb ₂ O ₃ is 0.0001% or more, the effect starts to appear, but 0.001% or more, particularly 0.01% or more, is preferable because there is a margin in fining power in mass production. . If Sb ₂ O ₃ is contained in a large amount in the glass, blackening due to reduction tends to occur during lamp processing. However, if Sb ₂ O ₃ is 5% or less, blackening is difficult to occur, and if it is 3% or less, more stable glass processing is possible.

The lighting glass of the present invention can contain various components in addition to the above components. For example, MgO, CaO, SrO, Nb ₂ O ₅ , WO ₃ , ZrO ₂ , Ta ₂ O ₅ , SnO ₂ , CeO ₂ , SO ₃ , Fe ₂ O ₃ , Cl _{2 and the} like may be contained.

  MgO and CaO are components that help the glass melt. Both MgO and CaO are optional components, and can be contained at 10% or less, preferably 5% or less, respectively. If each component is 10% or less, the crystal tendency becomes small. If it is 5% or less, a glass excellent in dimensional accuracy can be obtained, which is preferable.

  SrO, like BaO, is a component that lowers the melting point and suppresses the phase separation of the glass to stabilize it. SrO is an optional component and can be contained in an amount of 20% or less, preferably 8% or less. If SrO is 20% or less, the precipitation tendency of crystals containing SrO as a main component is reduced. If it is 8% or less, a glass with better dimensional accuracy can be obtained, which is preferable.

Nb ₂ O ₅ is a component that enhances the ultraviolet shielding effect on the long wavelength side of TiO ₂ . Further, by absorbing ultraviolet rays, it contributes to prevention of short wavelength ultraviolet discoloration of glass. In order to acquire the said effect, it is desirable to contain 0.005% or more. Note that Nb ₂ O ₅ tends to promote phase separation and tends to affect the luminance and color tone of the lamp, so it should be avoided to use a large amount. Therefore, the Nb ₂ O ₅ content is preferably 10% or less, particularly 7% or less.

WO ₃ is a component having an ultraviolet absorption effect, and contributes to prevention of short wavelength ultraviolet discoloration of glass by absorbing ultraviolet rays. In order to acquire the said effect, it is desirable to contain 0.005% or more. Since WO ₃ tends to absorb visible light and easily affects the luminance and color tone of the lamp, it should be avoided to use a large amount. Therefore, the content of WO ₃ is preferably 10% or less, particularly 7% or less.

ZrO ₂ improves the weather resistance of the glass while increasing the viscosity of the glass, and can be contained up to 9%, preferably up to 6%. When the amount of ZrO ₂ increases, the viscosity of the glass increases and bubbles tend to remain. Further, crystals tend to be formed in the glass and tube drawing tends to be difficult, but if it is 9% or less, tube glass that can be used for fluorescent lamp applications can be stably formed. If it is 6% or less, the tendency of crystal precipitation decreases, and a glass with better dimensional accuracy can be easily obtained. On the other hand, ZrO ₂ may be mixed by 0.001% or more from glass raw materials or refractories, but the above effect can be expected if the total amount of ZrO ₂ including these is 0.002% or more.

Ta ₂ O ₅ has an effect of preventing short wavelength ultraviolet discoloration, and can be contained up to 10%, preferably up to 6%. If it is 10% or less, it is difficult to precipitate crystals, and a glass tube excellent in dimensional accuracy can be obtained. If it is 6% or less, the tendency to crystallize becomes small, and a glass with better dimensional accuracy can be obtained.

SnO ₂ is effective as a fining agent. In order to obtain a clarification effect, it is desirable to contain 0.0001% or more. If SnO ₂ is contained in a large amount, crystals are precipitated in the glass, but if it is 5% or less, no crystal is produced, and if it is 3% or less, more stable melting is possible.

CeO ₂ has a clarification effect as well as As ₂ O ₃ . The content is preferably 3% or less, particularly 0.2% or less, more preferably 0.05% or less, and most preferably 0.01% or less. If CeO ₂ is 3% or less, there is no possibility of forming crystals in the glass. However, since coexistence with TiO ₂ tends to cause yellow coloring, it is desirable to limit the amount used as much as possible. In addition, in order to acquire the said effect, it is desirable to contain 0.0001% or more.

A compound that generates SO ₃ has a clarification effect as well as As ₂ O ₃ , but SO ₃ itself has a disadvantage that it easily causes bubbles. The SO ₃ in the glass is not only a glass raw material (sulfate raw materials and impurities such as sodium nitrate (Na ₂ SO ₄ )), but also SO ₂ gas in the combustion atmosphere at the time of melting the glass dissolves in the glass melt. Incorporated into the glass composition. In order to obtain the same effect as As ₂ O ₃ , the glass raw material may be added so that SO ₃ in the glass (glass product) is 0.0001% or more, particularly 0.0005% or more. However, in order to prevent the generation of a large amount of bubbles, SO ₃ in the glass (glass product) is 0.2% or less, particularly 0.1% or less, further 0.05% or less, and optimally 0.8. It is desirable to adjust so that it may become 01% or less. In addition, as a means for reducing SO ₃ taken from other than the glass raw material, the SO ₃ partial pressure in the melting atmosphere, the adjustment of the melting temperature, the use of other clarifiers, bubbling and the like may be performed. It is also important to select and manage the fuel used for glass melting.

Fe ₂ O ₃ is preferably 0.05% or less, particularly 0.02% or less, and more preferably 0.01% or less. If the content of Fe ₂ O ₃ is 0.05% or less, it is possible to avoid a situation in which the glass is markedly colored. If it is 0.02% or less, coloring is difficult even in a composition system containing a large amount of TiO ₂ . If it is 0.01% or less, it becomes very difficult to color. Since Fe ₂ O ₃ is easily mixed as an impurity, the content thereof must be strictly controlled including the impurity. Further, it is extremely expensive and technically difficult to completely remove Fe ₂ O ₃ from the glass composition. Therefore, it is realistic that the lower limit of Fe ₂ O ₃ is 0.001% or more including impurities.

Since Fe ²⁺ ions have a broad absorption from a part of the visible range to the infrared range, they themselves cause coloring. In addition, Fe ²⁺ ions can be used as an index for managing coloring due to Fe ³⁺ ions having a low coordination number. That is, if the glass is more oxidized state, so that the number of Fe ³⁺ is present as Fe ³⁺ in high coordination number having no absorption in the visible region. When a large amount of Fe ³⁺ having a high coordination number is present, a strong light absorption occurs only in the ultraviolet region, and the glass has no absorption in the visible region. In other words, the glass transmittance curve has a sharp absorption edge in the ultraviolet region, and a colorless and transparent glass can be obtained. On the other hand, when there is much Fe ^<2+> , while it will cause coloring itself, Fe3 ⁺ of a low coordination number will increase in proportion to the amount of Fe ^{<2+ >} , and coloring will be shown. Therefore, in order to obtain a sufficiently colorless and transparent borosilicate glass, and the oxidation state reduces the proportion of Fe ³⁺ of Fe ²⁺ and low coordination number as much as possible, the proportion of Fe ³⁺ in high coordination number It is desirable to increase as much as possible.

In order to bring the glass into an oxidized state, it is possible to use an oxidizing agent, eliminate organic substances and metallic iron mixed in the glass raw material, perform oxygen bubbling, and manage the oxygen partial pressure in the molten atmosphere. For example, As ₂ O ₃ and Sb ₂ O ₃ added in the present invention have such an effect.

Cl ₂ is an optional component. Cl ₂ has an effect as a fining agent, and when it is desired to obtain the effect, the residual amount in the glass (glass product) is preferably expressed as Cl ₂ and is 0.001% or more. From the viewpoint of maintaining the working environment, Cl ₂ is preferably 0.5% or less.

Moreover, the glass for illumination of this invention has a thermal expansion coefficient in 45-58 * 10 < ^-7 > / degreeC in 30-380 degreeC. Usually, the sealing bead for sealing the electrode (introduction metal) of the fluorescent lamp is made of glass of the same material as the outer tube. Therefore, the outer tube needs to have a thermal expansion coefficient compatible with Kovar (thermal expansion coefficient 58 × 10 ⁻⁷ / ° C.) and molybdenum (thermal expansion coefficient 52 × 10 ⁻⁷ / ° C.) which are electrode materials. If the thermal expansion coefficient is in the above range, Kovar or molybdenum can be used as the electrode material. Needless to say, it can also be used as an outer tube of an external electrode lamp having no electrode inside.

  In addition to the above, characteristics such as a glass annealing point suitable for Kovar (when Kovar is used as an electrode), a sufficiently high glass softening point, and no glass coloring due to ultraviolet rays are required.

  Specifically, Kovar has a Curie point near 450 ° C. and the expansion changes abruptly. Therefore, in order to match the expansion with this, the glass strain point is preferably near 460 ° C. The glass softening point is preferably about 700 ° C. or higher so that the glass tube is not deformed when the phosphor is baked. Furthermore, it is desirable not to change color by short wavelength ultraviolet rays (253.7 nm, 185 nm, etc.) so that the luminance of the lamp does not decrease.

  Next, the outer tube for the fluorescent lamp of the present invention will be described.

First, raw materials are prepared and melted so as to be a glass having the composition of the glass for illumination. 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. It is desirable to adopt the Danner method from the viewpoint of mass productivity. When the Danner method is adopted, the glass and the refractory are in contact with each other for a long time as compared with other methods, so that TiO ₂ -based crystals tend to precipitate. Therefore, it can be said that the merit of employing the glass composition is great.

  In addition, it is desirable that the cooling rate after glass is formed into a tubular shape by the Danner method or the like is faster than that of conventional glass.

The reason is that the glass can be colored by reducing the glass by quenching after forming into a tubular shape. In other words, the glass being melted is colorless and transparent, but when the region from about 800 ° C. to about 500 ° C. is cooled slowly, it becomes easy to color. The reason why coloring is reduced by rapid cooling is considered as follows. This phenomenon is considered to occur because the distance between the cation (Fe, Ti) and the ligand (O) varies depending on the cooling rate. The melting glass has a large inter-ion distance because the ions constituting the glass can freely move. As the cooling decreases, the distance between ions becomes smaller, which affects the mutual bonding and coordination. The slower the cooling rate, the smaller the inter-ion distance, affecting each other. If the cooling rate is high, the glass is solidified in a state close to that of the glass being melted, so that the distance between ions becomes large and the mutual influence becomes small. If the distance between ions becomes narrow, Ti ions will affect the coordination state of Fe ³⁺ ions, and it will be colored as if it were in a coordination state that approximated the low coordination number state.

  Subsequently, the tubular glass is cut into a predetermined size and post-processed as necessary, whereby the outer tube for the fluorescent lamp of the present invention can be obtained.

  The outer tube for the fluorescent lamp of the present invention thus obtained is colorless and transparent, and can effectively shield ultraviolet rays of 313 nm or less. Furthermore, it has excellent short wavelength ultraviolet discoloration resistance.

Further, since the outer tube of the present invention is made of glass having the above composition, the precipitation of TiO ₂ crystals is small. Specifically, it is desirable that the number of TiO ₂ -based crystals existing on the inner surface of the tube is 10/100 cm ² or less, particularly 1/100 cm ² or less. A TiO ₂ -based crystal is a crystal containing TiO ₂ as a crystal component.

  This fluorescent lamp outer tube is used for manufacturing a fluorescent lamp for backlight of a liquid crystal display element, for example.

  Hereinafter, the present invention will be described based on examples. The table | surface has shown the Example (sample No. 1-5, 12-14) and comparative example (sample No. 6-11) of this invention.

  Each sample was prepared as follows.

First, a glass raw material was prepared so as to have the composition shown in the table, and then melted at 1550 ° C. for 8 hours using a platinum crucible. Next, the glass melt was formed into a predetermined shape and processed, and then subjected to each evaluation. The content of Fe ₂ O ₃ in the table is the amount of impurities mixed from the raw material. The SO ₃ content is the amount of contamination from the raw materials and / or combustion atmosphere. The content of Fe ₂ O ₃ indicates a value determined by fluorescent X-ray after glass sample preparation. SO ₃ indicates a value obtained by chemical analysis.

  As glass materials, stone powder, alumina, boric acid, lithium carbonate, sodium carbonate, potassium carbonate, potassium nitrate, barium carbonate, zinc oxide, titanium oxide, antimony oxide, niobium pentoxide, tungsten oxide, zircon, cerium oxide, sodium sulfate are used. It was. Note that the type of raw material is not limited to this, and may be appropriately selected in consideration of the redox state of the glass, the water content, and the like. Moreover, the component shown by a composition is a conversion value and is not limited to the description oxide valence.

As is apparent from Table 1, No. 1 as an example of the present invention. Since the samples 1 to 5 and 12 to 14 have a low temperature for generating TiO ₂ crystals, glass tubes can be formed with high accuracy. Further, when the obtained glass tube is hermetically sealed, there is no fear that a gap is generated and a slow leak is generated.

  The thermal expansion coefficient was obtained with a thermal expansion measuring device.

  The strain point was determined according to ASTM C336.

  The softening point was determined according to ASTM C338.

The crystal precipitation temperature at the platinum interface (the precipitation temperature of TiO ₂ -based crystals) is as follows. Glass is put in a platinum boat (15 cm long and narrow container) and the whole is heated at 1250 ° C. for 2 hours. (The sample obtained by cooling at 850 to 1050 ° C. for 70 hours was cooled and taken out, and the bottom surface that was in contact with platinum was observed with a 50 × deflection microscope, and the temperature corresponding to the highest portion of the crystal detected. It was confirmed by EPMA analysis that crystals precipitated at the platinum interface were TiO ₂ -based crystals.

  Next, an outer tube for a fluorescent lamp was manufactured using glass having the same composition as the glass sample.

First, the raw materials prepared so as to become the glass equivalent to each sample (composition of Table 1) were melted at 1600 ° C. in a refractory kiln. Thereafter, the glass melt was supplied to a dunner forming apparatus, formed into a tube, and cut to obtain an outer tube having an outer diameter of 4 mm, a wall thickness of 0.3 mm, and a length of 1600 mm. Note that an alumina silicate refractory sleeve containing about 60% Al ₂ O ₃ was used for the danna device.

The obtained outer tube sample was evaluated for the ultraviolet shielding property of 313 nm, the amount of TiO ₂ crystal on the inner surface of the tube, the phase separation, the coloring degree, and the short wavelength ultraviolet discoloration resistance. The results are shown in the table.

As a result of the evaluation, each sample as an example of the present invention has an ultraviolet shielding ability at 313 nm. It was also confirmed that the amount of precipitated TiO ₂ crystals was extremely small. In addition, since the phase separation is weak and it is difficult to discolor with short-wave ultraviolet light, it is possible to manufacture a fluorescent lamp with high luminance and low luminance.

  As for the 313 nm ultraviolet shielding property, a sample was prepared by halving a tube glass having an outer diameter of 4 mm and a thickness of 0.3 mm, and then the spectral transmittance at a wavelength of 313 nm was measured. The wavelength of 313 nm is a mercury emission line.

The amount of TiO ₂ -based crystals deposited was evaluated by observing the inner surface of the glass tube with a 10-fold magnifier and observing the number, and converting it to the unit tube glass surface area (100 cm ² ).

  For phase separation, a tube glass having a length of 100 mm was heated for 10 minutes at 700 ° C., which is the phosphor firing temperature, and then observed by the same method as the coloring degree. "," When the cloudiness occurs also in the tube glass thickness direction is "x".

  The degree of coloring was evaluated as follows. First, a tube glass having a length of 500 mm was suspended vertically while penetrating black paper, and then irradiated with uniform white light having no directivity from the lower end, and the color tone of the upper end surface of the tube glass was observed. In comparison with the same glass glass for backlight BFK manufactured by Nippon Electric Glass Co., Ltd., which was evaluated in the same manner, if the color tone was clearly equal to or higher, “◯” was given.

  The short wavelength ultraviolet discoloration resistance was evaluated by the difference in transmittance in the visible range before and after irradiation with short wavelength ultraviolet rays. 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 irradiation with short wavelength ultraviolet rays showed 80% was measured. Further, the sample was irradiated with short wavelength ultraviolet rays having a main wavelength of 253.7 nm (other wavelengths of 185 nm, 313 nm, and 365 nm) for 60 minutes (irradiation distance: 25 mm) with a 40 W quartz glass low-pressure mercury lamp, and the transmittance was 80% before irradiation. When the transmittance at a wavelength indicated by was measured again, a case where the decrease in transmittance due to irradiation with short-wave ultraviolet rays was 0.3% or less in consideration of measurement error was evaluated as “◯”.

  The lighting glass and the outer tube of the present invention are used for a cold cathode fluorescent lamp having electrodes such as kovar and molybdenum. In addition, it can be used for an external electrode lamp in which an electrode is formed on the surface of the outer container. Furthermore, the lighting glass of the present invention can be used as an outer container of a box-type or flat-type fluorescent lamp.

Claims (8)

By mass _{percentage, SiO 2 50~75%, B 2} O 3 12~25%, Al less than _{2 O 3 0~3.2%, Li 2} O less than 0~0.5%, Na ₂ O 0~7% , K ₂ O 3-15%, Li ₂ O + Na ₂ O + K ₂ O 6-15%, Al ₂ O ₃ + Li ₂ O 0-3.2%, BaO 0-20%, ZnO 0-15%, TiO ₂ 2 .5 to 4.9%, As ₂ O ₃ + Sb ₂ O ₃ 0 to 5%, and the thermal expansion coefficient at 30 to 380 ° C. is 45 to 58 × 10 ⁻⁷ / ° C. Glass. In percent by mass, lighting glass according to claim 1, wherein the Al ₂ O ₃ is 0-3%. The lighting glass according to claim 1, wherein Li ₂ O is 0 to 0.4% by mass percentage. In percent by mass, either lighting glass according to claim 1, wherein the TiO ₂ is 2.5 to 4.2%. By mass percentage, Al ₂ O ₃ is 0 to 3%, Li ₂ O is 0 to 0.4%, Al ₂ O ₃ + Li ₂ O 0 to 3%, TiO ₂ is 2.5 to 4.2%. The lighting glass according to claim 1.   The illumination glass according to claim 1, wherein the illumination glass is used as an outer tube of a fluorescent lamp.   An outer tube for a fluorescent lamp, comprising the glass according to any one of claims 1 to 6. The outer tube for a fluorescent lamp according to claim 7, wherein the number of TiO ₂ crystals existing on the inner surface of the tube is 10/100 cm ² or less.