JP2002293569A - Glass for electric lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass composition for a compact, fluorescent lamp electric lamp having a high luminance, without coloring by UV nor UV leakage out of a tube. SOLUTION: The glass composition has SiO2 -Al2 O3 -R2 O-R'O based composition, and a CeO2 content is 0.2-2 mass% and a SO3 content is 0-0.18 mass%. And after UV radiation, it has the following characteristics. (1) The Y value on the XYZ color specification system regulated in the JIS Z8701, for a wall thickness of 1 mm, is >=90.0%. (2) A light transmittance of 400 nm for a wall thickness of 1 mm, is >=88.0%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition for an electric lamp used for a fluorescent lamp, and more particularly to a glass composition for an electric lamp used for a compact fluorescent lamp.

[0002]

2. Description of the Related Art A fluorescent lamp utilizes ultraviolet light generated by an arc discharge to excite a fluorescent material applied to a glass tube wall, and utilizes visible light generated by the excitation.

[0003] Glass used for fluorescent lamps is roughly classified into a tubular bulb portion and a stem portion, and the bulb portion generally has a straight pipe or an annular shape obtained by thermally processing the straight pipe. However, recently, compact fluorescent lamps having a complicated shape such as a U-shaped tube and a twin tube connecting them have been developed for the purpose of increasing the efficiency and reducing the size of the lamp. At first, lead-containing glass with good workability was used for compact fluorescent lamps that required complex processing, but lead is an environmentally hazardous substance, so lead-free glass is currently being replaced. .

[0004]

It is known that a part of the ultraviolet light generated in the fluorescent lamp tube passes through the phosphor film and affects the glass tube. In particular, compact fluorescent lamps require higher power than ordinary fluorescent lamps,
The amount of ultraviolet irradiation per unit area becomes several times. As a result, the coloring of the glass due to the generation of colored ions and the coloring centers of the glass structural defect due to the ultraviolet energy becomes remarkable, causing a problem that the luminance of the fluorescent lamp deteriorates with time. Further, the amount of ultraviolet rays leaking out of the tube increases, and the resin cover for protecting the fluorescent lamp is discolored.

An object of the present invention is to provide a glass composition for an electric lamp which is capable of producing a high-intensity compact fluorescent lamp without coloring by ultraviolet rays or leakage of the ultraviolet rays to the outside of the tube.

[0006]

As a result of various experiments, the present inventors have found that the above object can be achieved by adding CeO ₂ and limiting the content of SO ₃ to 0.18% or less. And propose the present invention.

That is, the glass for electric lights of the present invention is made of SiO _{2
-Al 2 O 3 -R 2 O-} R'O has the composition system, the content of CeO ₂ is from 0.2 to 2 wt%, the content of SO ₃ is 0-0.
18% by mass, and has the following characteristics after irradiation with ultraviolet rays. (1) At a wall thickness of 1 mm, the Y value based on the XYZ color system specified in JIS Z8701 is 90.0% or more under a C standard light source. (2) At a thickness of 1 mm, the light transmittance at 400 nm is 88.0% or more.

In the present invention, the Y value and 400 nm
Has a dominant wavelength of 256 nm for a sample of 30 × 10 mm and a thickness of 1.0 ± 0.02 mm optically polished to such an extent that polishing scratches cannot be confirmed with an optical microscope having a 30-fold visual field. It is a value evaluated after irradiating with ultraviolet light at an illuminance of 7.5 mw / cm ² for 8 hours. The light transmittance at 400 nm was measured using a C standard light source with a spectrophotometer.
The transmittance in nm was determined, and the Y value was determined in the same manner as the transmittance in a measurement range of 200 to 800 nm.
It is calculated based on JIS Z8701.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted detailed investigations on the ultraviolet shielding ability of CeO ₂ and the optical deterioration phenomenon of glass due to ultraviolet rays, and have found interesting knowledge about SO ₃ contained in glass.

In general, it is known that CeO ₂ may be added to impart ultraviolet shielding ability to glass.
Further, by the addition of CeO ₂ , coloring due to ultraviolet irradiation is slightly suppressed. On the other hand, when CeO ₂ is added, 400 nm
The light transmittance in the vicinity is reduced and the glass becomes yellow, so-called initial coloring is likely to occur, and the brightness of the lamp is reduced. Therefore, there has been a problem that the luminance of the lamp is reduced when it is attempted to prevent the ultraviolet rays from leaking out of the tube or coloring by the ultraviolet rays.

However, it has been found by experiments of the present inventors that the transmittance characteristics of glass to which CeO ₂ is added are greatly affected by the presence of SO ₃ . That is, when the content of SO ₃ is limited to 0.18% by mass or less, the light transmittance near 400 nm is increased to prevent the initial coloring, and the coloring due to ultraviolet irradiation is significantly suppressed. This SO ₃
Glass materials (sulfate materials such as sodium sulfate (Na ₂ SO ₄ ) and impurities) and SO ₂ gas in the combustion atmosphere when the glass is melted are incorporated into the glass composition.

In the lamp glass of the present invention, CeO ₂
The contents of SO ₃ and SO ₃ are determined based on the above findings.

CeO ₂ has the function of imparting ultraviolet shielding ability to glass and, at the same time, having an SO ₃ content of not more than 0.18% by mass, and has a function of significantly suppressing coloring due to ultraviolet irradiation. It also functions as a fining agent. CeO ₂ is 0.2
% Or less, there is no effect, and if it exceeds 2%, coloring becomes remarkable, and it becomes difficult to obtain a high-luminance lamp. The preferred range of CeO ₂ is 0.3 to 1.2%, especially 0.1 to 0.2%.
4-1%.

The content of SO ₃ is limited to 0.18% by mass or less. SO ₃ is a component that promotes coloring of glass with CeO ₂ and is liable to cause ultraviolet coloring. The smaller the content, the better. For this reason, 0.15% or less,
In particular, the content is preferably 0.1% or less, and preferably not contained.

Further, the glass of the present invention has, after irradiation with ultraviolet light, (1) a Y value based on the XYZ color system specified in JIS Z8701 of 90.0% or more, and (2) a light transmittance at 400 nm at a thickness of 1 mm. Is 88.0% or more. By satisfying these characteristics, a lamp with high luminance can be manufactured.
The light transmittance at 400 nm is preferably 90.0% or more, particularly preferably 90.5% or more.
It is preferably at least 1.0%, particularly preferably at least 91.5%.

In addition to the above characteristics, the glass of the present invention has an ultraviolet absorption edge of 314 nm or more, especially 320 nm.
It is preferable that it is above. That is, the spectrum generated from the fluorescent lamp has a main peak near 258 nm, and there are some other sub-lines. Among them, the longest sub-line peak extends to the visible light region. Although it is difficult to sufficiently shield ultraviolet rays in a wavelength range longer than 258 nm with general lamp glass, these sub-lines hardly cause a problem in ordinary fluorescent lamps. However, in compact fluorescent lamps that emit a large amount of ultraviolet radiation,
In particular, the resin cover easily discolors due to the sub-line near 313 nm. Therefore, it is desired that the absorption edge of ultraviolet rays is on the longer wavelength side than 313 nm.

The glass of the present invention is made of SiO ₂ —Al ₂ O
Having a composition of ₃ -R ₂ O-R'O system. Here, R represents an alkali metal (Na, K, Li), and R ′ represents an alkaline earth metal (Ca, Mg, Sr, Ba). The composition of the glass is not particularly limited, but PbO and As ₂ O ₃ should be avoided for environmental reasons.

Next, other characteristics required for fluorescent lamp applications and glass compositions suitable for the characteristics will be described. Amalgam (H) reacts with mercury gas enclosed in the tube.
High chemical durability is required so as not to generate gNa). Specifically, the alkali elution measured by the method shown in JIS R3502 is 0.7 mg or less. When used for a stem, it must have a coefficient of thermal expansion of 90-100 × 10 ⁻⁷ / ° C. so that the expansion is compatible with the Dumet lead wire. When used for stems, the volume resistance is 10 ^-7 Ω
cm or higher. Glass melting is easy. For compact fluorescent lamp bulb applications, the working point (temperature corresponding to 10 ⁴ poise) must be 1010 ° C. or less in order to obtain high workability.

As a preferred composition example of a glass satisfying all of these requirements, SiO ₂ 60 to 8 in terms of mass% is used.
_{0%, Al 2 O 3 0.3~5} %, B 2 O 3 0~3%, N
a ₂ O 2 to 10%, K ₂ O 2 to 10%, Li ₂ O 0
3%, CaO 0-8%, MgO 0-8%, SrO
2 to 10%, BaO 2 to 12%, CeO ₂ 0.2 to
2%, can be exemplified SO ₃ from 0 to .18% of the glass.

The reasons for limiting the composition range of the glass as described above will be described below.

SiO ₂ is a component that forms the skeleton of glass. When the content of SiO ₂ is less than 60%, the formation of the glass skeleton becomes insufficient, and the mechanical strength is reduced. 8 SiO ₂
If it is more than 0%, the viscosity of the glass increases, and melt molding becomes difficult. The preferred range of SiO ₂ is 60 to 75%.

[0022] Al ₂ O ₃ is also a skeleton forming component, also improves the chemical durability, the effect of suppressing devitrification during glass molding. If the content of Al ₂ O ₃ is less than 0.3%, the effect is not obtained, and if it is more than 5%, melting and molding become difficult. The preferred range of Al ₂ O ₃ is 0.5 to 3%, especially 1 to 3%.
3%.

B ₂ O ₃ has the effect of improving chemical durability and reducing high temperature viscosity. However, B ₂ O ₃ is an environmentally hazardous substance, and it is desirable not to use it unless it is unavoidable. When the content of B ₂ O ₃ is more than 3%, the low-temperature viscosity of the glass increases, and the workability deteriorates. In addition, the coloring tendency of CeO ₂ is increased.

Alkali metal oxides such as Na ₂ O, K ₂ O, and Li ₂ O are components for adjusting the coefficient of thermal expansion and reducing the viscosity of glass to enhance workability. Na
By coexisting ₂ O and K ₂ O at a specific ratio, an effect of improving chemical durability and electrical insulation, called an alkali mixing effect, can be obtained. It is not preferable to add Li ₂ O in a large amount because of the high raw material cost, but the effect of adjusting the expansion is about twice as high as that of other alkali metal components.

When the content of Na ₂ O is less than 2%, the effect is not obtained. When the content is more than 10%, no alkali mixing effect is obtained, and the chemical durability is deteriorated. Na ₂ O content is preferably within a range of 4-8%.

When K ₂ O is less than 2%, the effect is not obtained. When K ₂ O is more than 10%, the alkali mixing effect is not obtained, and the chemical durability is deteriorated. The preferred range of K ₂ O is 4
~ 8%.

If the content of Li ₂ O exceeds 3%, the raw material cost becomes too high. In the case where the content is less than 0.3%, Na ₂ O or K ₂
A large amount of O must be contained, and the chemical durability tends to deteriorate. Li ₂ O The preferred range is 0.3 to 3
%, Especially 0.5 to 3%.

The total amount of the alkali metal oxides is 11 to 1
Preferably, it is 8%. If it is less than 11%, it will be difficult to obtain conformity of expansion with a dumet lead wire when used for a stem application. Further, the viscosity of the glass increases, and the workability tends to deteriorate. When the total amount of alkali metal oxides is 18
%, It becomes difficult to obtain consistency in expansion with a dumet lead wire when used for a stem application. Further, the chemical durability is deteriorated, and the generation of amalgam, which causes the luminance deterioration, is likely to occur. Note that a more preferable range of the total amount of the alkali metal oxide is 13.2 to 18%.

Alkaline earth metal oxides such as CaO, MgO, SrO and BaO are components for obtaining high electrical insulation and good workability. In particular, SrO and BaO having properties relatively close to PbO are mainly used. However, these components have strong reactivity with refractory bricks used at the time of glass melting or at the time of pipe forming, and cause reaction products. If it is desired to avoid generation of such products, a part of them may be replaced with CaO or MgO. Where C
Since aO tends to lower the light transmittance of glass when coexisting with CeO ₂ , it is desirable to minimize the addition of aO.

When CaO exceeds 8%, it causes devitrification during glass forming. By limiting CaO to 0.5% or less, higher light transmittance can be obtained.

If the content of MgO exceeds 8%, it causes devitrification at the time of molding the glass, and also increases the viscosity of the glass to deteriorate the workability. The preferred range of MgO is 2-6%.

If SrO is less than 2%, other alkaline earth metal oxides must be contained in a large amount in order to obtain high electrical insulation and good workability, but this tends to cause devitrification. If it exceeds 10%, SrO-based devitrified matter is generated, and the raw material cost is undesirably increased. Sr
The preferred range of O is 4 to 10%, particularly 4.2 to 8%.

If the content of BaO is less than 2%, a large amount of other alkaline earth metal oxide must be contained in order to obtain high electrical insulation and good workability, but this tends to cause devitrification. If it exceeds 12%, the reaction with the refractory (Al-based refractory) is remarkable, causing devitrification. The preferred range of BaO is 3 to 10%.

The alkaline earth metal oxide is 5 to 5 in total.
It is preferably 15%. If these combined amounts are less than 5%, it becomes difficult to obtain characteristics required for fluorescent lamp use, such as electric resistance. On the other hand, if it exceeds 15%, a devitrified substance or a reaction product is generated during molding of the glass, which may cause a product defect. A more preferable range of the total amount of the alkaline earth metal oxide is 6 to 13%.

In addition to the above components, it is possible to add a component for improving the light transmission characteristics such as a rare earth oxide, or a component having an effect of preventing ultraviolet coloring such as TiO ₂ and ZrO ₂ . Further, a Cl-based raw material such as NaCl may be added as a fining agent. In addition, Fe ₂ O ₃ is often included as an impurity. However, Fe is a colored ion and causes a reduction in transmittance. Therefore, the content of Fe is limited to 0.05% or less, particularly 0.03% or less. is important.

The glass for an electric lamp of the present invention is desirably melted in an oxidizing atmosphere.

That is, CeO ₂ which plays an important role in the glass of the present invention is in a redox equilibrium state of Ce ³⁺ ⇔ Ce ^{4+ in} the glass. Generally, Ce ³⁺ is 316 nm
In addition, Ce ⁴⁺ has a main absorption band around 243 nm, and both functions absorb ultraviolet rays on the long wavelength side to form an ultraviolet absorption edge of glass. Here, when the amount of Ce ³⁺ increases, the absorption edge of ultraviolet rays moves to the longer wavelength side, and the absorption band width increases. As a result, the visible region around 400 nm is absorbed, the glass becomes yellowish, and the transmittance decreases. This is the initial coloring by CeO ₂ , which causes a high-luminance fluorescent lamp to not be obtained. Therefore Ce ³⁺
It is important that Ce ⁴⁺ and Ce ⁴⁺ be present in an appropriate ratio.
Therefore, by melting the glass in an oxidizing atmosphere, C
e ⁴⁺ can be increased, absorption in the visible region around 400 nm can be suppressed, and initial coloring can be prevented.

As a method for melting in an oxidizing atmosphere, for example, an oxidizing agent (for example, sodium nitrate or potassium nitrate) may be added to a glass raw material batch so that the glass is oxidized when the glass is melted. The amount of the oxidizing agent to be added to the batch depends on the type of the oxidizing agent to be used.
About 3% by mass is preferable. The reason is that if it is 0.5% or less, a sufficient effect cannot be obtained, and if it exceeds 3%, only the raw material cost increases, and the effect hardly changes.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 Tables 1 and 2 show CeO ₂ and SO ₃
Example of the present invention (Sample Nos. 1 to 4) and Comparative Example (Nos.
7). FIG. 1 shows the relationship between CeO ₂ and SO ₃ with respect to ultraviolet coloring.

[0041]

[Table 1]

[0042]

[Table 2]

Each sample was prepared as follows.

First, glass raw materials were prepared so as to have the composition shown in the table. Further, the prepared raw material was stirred for 10 minutes with a mortar-type crushing and stirring machine called a raikai machine, to obtain a raw material batch of 300 g. The raw material used was shore sand (SiO ₂ fraction 9) having relatively few Fe impurities as the SiO ₂ raw material.
9.8 mass%), commercially available dolomite as MgO raw material and CaO raw material, cerium oxide for glass industry (CeO ₂ fraction of 99.8% or more) as CeO ₂ raw material, and other oxide raw materials are mainly suitable for mass production. Among the commonly used materials, the most inexpensive industrial glass materials were used. Sodium nitrate was used as an oxidizing agent.

Next, the raw material batch was placed in a platinum rhodium alloy crucible having a capacity of 300 cm ³ , and was placed in a box-type electric furnace for 1450 hours.
Melted at ~ 1500C for 4 hours. In addition, stirring was performed three times in total using a platinum stirring rod every 30 minutes after the start of melting.

Subsequently, the molten glass was poured out onto a carbon molded plate, placed in a box-type Kanthal annealing furnace maintained at 560 ° C., and cooled at an average cooling rate of 4 ° C./min. Further, a sample was prepared from the annealed glass block and used for evaluation. The results are shown in Tables 1 and 2. FIG. 1 also shows the change in the Y value before and after ultraviolet irradiation.

As a result, Sample No. containing 0.2% of SO ₃ was obtained. In Nos. 5 to 7, the initial Y value was low, and the decrease in the Y value due to ultraviolet irradiation was large. Sample No. without the SO ₃ contrast It was found that the samples Nos. 1 to 4 had a high initial Y value and hardly decreased the Y value. In other words, it is shown that if SO ₃ is reduced, glass having a high transmittance and hardly causing ultraviolet coloring can be obtained.

No. In the samples Nos. 5 to 7, the Y value tends to decrease as the CeO ₂ amount increases. In the samples Nos. 1 to 4, the initial Y value hardly changes even if the amount of CeO ₂ increases. This suggests that CeO ₂ can be added in a large amount in order to enhance the ultraviolet absorbing ability of the glass.

The coefficient of thermal expansion indicates an average coefficient of linear thermal expansion at 30 to 380 ° C., and was measured using a dilatometer. The softening point is a temperature indicating a viscosity of 10 ^7.6 dPa · s, and the working point is a temperature indicating a viscosity of 10 ⁴ dPa · s. The softening point was determined by a fiber pulling method and a platinum ball pulling method specified by ASTM, respectively. . The volume electric resistance was measured based on ASTM C657-78, and the resistance at 250 ° C. was logarithmically indicated. The alkali elution amount is measured based on JIS R-3502.

The Y value, the light transmittance at 400 nm, and the ultraviolet absorption edge were determined as follows. First, a sample having a size of 30 × 10 mm and a thickness of 1.0 ± 0.02 mm, which was optically polished to such an extent that polishing scratches could not be confirmed with an optical microscope having a 30 × visual field, was prepared. Next, using a C standard light source, the transmittance at 200 to 800 nm was measured with a spectrophotometer (UV3100PC manufactured by Shimadzu Corporation) to determine the transmittance at 400 nm and the ultraviolet absorption edge. The ultraviolet absorption edge was a wavelength at which the transmittance could be regarded as substantially 0% on the short wavelength side of the light transmittance curve. Further, from the transmittance measurement data, JIS Z8701 was used.
The Y value was calculated based on the XZY color system specified in (1). Subsequently, using a UV dry processor (manufactured by Oak Manufacturing Co., Ltd.), the sample was irradiated with ultraviolet light having a main wavelength of 256 nm at 7.5 nm.
After irradiating at an illuminance of mw / cm ² for 8 hours, the transmittance was measured again, and the Y value after ultraviolet irradiation and the transmittance at 400 nm were determined.

(Example 2) Tables 3 to 7 show other examples (samples Nos. 8 to 27) of the present invention, and Table 8 shows a comparative example (sample N).
o. 28) respectively.

Each sample was prepared according to Example 1.
evaluated.

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

[Table 5]

[0056]

[Table 6]

[0057]

[Table 7]

[0058]

[Table 8]

From the table, it can be seen that Sample No. which is an embodiment of the present invention was used.
In Nos. 8 to 27, the Y value after ultraviolet irradiation and the light transmittance at 400 nm were 90.9% or more and 88.7% or more, respectively, and the high transmittance was maintained even after ultraviolet irradiation.

[0060]

As described above, the lamp glass of the present invention can produce a compact fluorescent lamp with high brightness without coloring by ultraviolet rays or leakage of ultraviolet rays outside the tube. It is suitable as glass for electric lights. In this specification, the glass for a bulb of a compact fluorescent lamp has been mainly described. However, the glass of the present invention is not limited to this, and may be used for other lamps (for a fluorescent lamp of a backlight used for a liquid crystal display). Bulbs) and other lighting components (stems, exhaust pipes, etc.)
May be used.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in Y value before and after ultraviolet irradiation.

Continued on the front page F term (reference) 4G062 AA03 BB01 DA06 DB03 DC01 DD01 DE01 DF01 EA03 EB03 EC03 ED03 EE03 EF03 EG03 FA01 FA10 FB01 FC01 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL02 FL03 GA01 GA01 GB01 H01H HH11 HH13 HH14 HH15 HH16 HH17 HH18 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM24 NN13 5C043 AA04 AA06 CC09 CD10 DD01 EA09 EB15 EC11

Claims (2)

[Claims] 1. SiO._Two-Al_TwoO_Three-R_TwoO-R'O-based
Having the composition, CeO _TwoContent of 0.2 to 2% by mass, S
O_ThreeIs 0 to 0.18% by mass, and is irradiated with ultraviolet light.
An electric light glass having the following characteristics. (1) Specified in JIS Z8701 when the thickness is 1 mm
Y value based on the XYZ color system
90.0% or more. (2) When the thickness is 1 mm, the light transmittance at 400 nm is
88.0% or more. 2. The glass for an electric lamp according to claim 1, which is used as a glass tube for a compact fluorescent lamp.