JP3438445B2 - Metal vapor discharge lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor discharge lamp, and more particularly to a protective film formed on the inner surface of an arc tube thereof and a method for selecting a material for the protective film.

[0002]

2. Description of the Related Art In recent years, in order to improve color rendering properties and luminous efficiency of a metal vapor discharge lamp, a metal halide lamp to which one kind or a combination of several kinds of metal halides is added as a light emitting material is used.

Since the arc tube of the metal halide lamp becomes high in temperature during lighting, the luminous material (metal halide) enclosed with the arc tube reacts with the passage of time and the arc tube is discolored or the arc tube. There is a drawback in that the devitrification phenomenon or the like occurs due to the crystallization of the material, the light transmittance of the arc tube is lowered, the strength of the arc tube is lowered, and the lamp life is shortened. Further, the metal ions of the metal halide are dissolved in the arc tube and disappear from the light emitting space, and halogen is left behind in the light emitting space with the passage of time. This leads to an increase in the starting voltage and the discharge sustaining voltage, which also has the drawback of shortening the lamp life.

In order to solve these problems, there has been proposed a metal vapor discharge lamp in which the inner surface of the arc tube is coated. For example, one provided with an oxynitride glass layer after ammonia treatment (Japanese Patent Laid-Open No. 4-33724).
No. 1, etc.), those using silicon nitride (Si ₃ N ₄ ) (JP-A-51-36788, JP-A-56-22).
041, JP-A-51-120076, etc.). Also, a fused silica arc tube provided with a metal silicate coating (see Japanese Patent Laid-Open No. Hei 6-162999, etc.)
There is.

[0005]

However, in spite of the proposal of the above-mentioned coating, the luminescent metal portion of the inclusion in the inclusion is lost due to diffusion or reaction, and the free halogen in the arc tube is correspondingly lost. As for the problem of deposits, it has not been put to practical use because an appropriate solution has not been found so far.

For example, in the above-mentioned example in which the metal silicate is used as the protective film (see Japanese Patent Application Laid-Open No. Hei 6-162999), the specific composition of the metal silicate is not limited, and the devitrification phenomenon is completely suppressed. I can't. Further, since the crystal structure of the protective film is amorphous, there remains a problem that it is chemically unstable in a high temperature atmosphere.

The present invention has been made in view of the above drawbacks,
It is an object of the present invention to provide a metal vapor discharge lamp that is chemically stable, prevents the reaction between the light emitting tube and the light emitting substance, reduces the light transmittance, and has a small increase in the starting voltage.

[0008]

According to a first aspect of the present invention, there is provided an arc tube made of a metal oxide (eg, quartz glass, high silicate glass, translucent ceramics, or a crystalline nonmetallic inorganic material such as single crystal alumina). A thin film made of the same material as the reaction product of the luminescent metal and the arc tube generated at the time of lighting is formed on the inner surface as a protective film.

[0009] Then, the invention of claim 1, when selecting the protective film for preventing reaction between the luminescent tube material and the metal halide in the metal vapor discharge lamp, the metal of the arc tube material and the metal halide This is based on the finding that the determination can be made using a two-component system phase diagram (temperature-composition diagram).

That is, in order to make a composite material by the reaction of a two-component system, the composition ratio must be determined. The two-component materials in this case are A and B. From the two-component system phase diagram of A and B, it is necessary to find out the composition ratio which is the most stable and produces the pure compound AB without the excess of one component. That is, it is outside the mixture region such as AB + A or AB + B. Further, a compound that satisfies the above conditions and that can maximize the molar amount of the arc tube material is used as the protective film.

The reason for this is that in a general reaction in an arc tube, a certain small amount of the luminescent substance reacts with the arc tube having a large area, so that a compound having the largest molar amount of the arc tube material component is formed. It is a natural result. The inventors have identified the characterization of these composites from X-ray diffraction patterns. Thus, the composition of the protective film can be determined when selecting the material of the arc tube and the luminescent substance.

According to the second aspect of the present invention, when the arc tube material and the light emitting substance are limited to quartz glass and a rare earth metal halide, the composition ratio of the complex oxide which reacts at the time of lighting and is generated is SiO2: R2O3 = 2. 1 (R is a rare earth metal), and the composition limited to the above is used as a protective film.

According to a third aspect of the present invention, when the arc tube material and the light emitting material are limited to polycrystalline alumina and a rare earth metal halide, the composition ratio of the complex oxides that react during lighting and are generated is Al2O3. : R2O3 = 11: 1 (R is La) Al2O3: R2O3 = 1: 1 (R is Nd, Sm, Eu,
Gd, Sc) Al2O3: R2O3 = 5: 5 (R is Dy, Ho, Y, E
r, Tm, Yb, Lu), and the composition defined above was used as a protective film.

The invention of claim 5 is characterized in that the protective film has crystallinity in order to chemically stabilize the protective film.

In the present invention, when the light-emitting metal is sealed in the arc tube of the plurality, to prepare a reaction product of each of the luminescent metal and the arc tube material, even if the mixtures thereof and the protective film
Yes .

In the present invention, when the light-emitting metal is sealed in the arc tube of the plurality of the reaction product of the highest luminescent metal reactivity with the arc tube material may be a protective layer.

[0017]

[Function] There are crystalline non-metal inorganic materials such as quartz glass, high silicate glass, translucent ceramics and single crystal alumina as arc tube materials. A metal vapor discharge lamp using these materials for arc tube was turned on. In this case, since the arc tube becomes hot, the reaction between the arc tube and the luminescent metal occurs as described above.

This reaction will be described in more detail taking the case of using quartz glass as the material of the arc tube as an example. Recently, in order to improve the color rendering and the luminous efficiency of the lamp, a rare earth metal halide is often used as a light emitting substance.

When quartz glass is used for the arc tube and a rare earth metal halide is used as the light emitting material, the following reactions occur in the plasma being discharged.

MX → M + X (where M: rare earth metal, X: halogen) In the discharge space, the rare earth metal and halogen are dissociated and exist. This rare earth metal reacts with quartz glass to cause a reaction of the following formula: M + SiO ₂ → aM ₂ O ₃ · bSiO ₂ + cSiO (where a, b, and c are molar coefficients) Rare earth oxide and SiO ₂ composite oxide To make. on the other hand,
SiO generated simultaneously with this reaction is unstable, exists as a gas, and is recrystallized and exists as SiO _{2 on} the surface of the quartz glass. These complex oxides and recrystallization appear as a devitrification phenomenon, which causes a decrease in light transmittance and a decrease in the luminous flux of the lamp.

Further, by the reaction of the rare earth metal and quartz,
Since the rare earth metal ions in the arc tube decrease, the amount of free halogen remaining in the above formula increases in the arc tube, which causes deterioration of life such as increase in starting voltage.

In order to prevent the reaction of the rare earth metal ion with the tube wall, the reaction of the above equation should not proceed to the right. That is,
By forming a protective film of complex oxide aM ₂ O ₃ · bSiO _{2 on} the inner surface of the arc tube, the reaction to the right in the equation can be suppressed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an arc tube according to the present invention. A protective film 2 described later is formed on the inner surface of the arc tube 1. In the manufacturing method, after forming a protective film on the inner surface of the arc tube material (tube material), the tube material is cut into a predetermined length, and electrodes are sealed at both ends thereof. After that, the inside of the pipe is evacuated through the exhaust pipe 3, and then a filling substance such as a luminescent substance is filled.

In FIG. 1, 4 and 5 are main electrodes, and 6
Is an electrode for starting assistance, and these electrodes 4, 5, 6 are
They are sealed to the arc tube 1 via molybdenum foils 7, 8 and 9, respectively. In addition, each molybdenum foil 7,8,
Reference numeral 9 is electrically connected to an external circuit via lead wires 10, 11, and 12.

Next, the protective film 2 will be described in detail based on examples. (Example 1) A quartz glass used as the light emitting tube material, will be described as an example the case of using NdI ₃ as a metal halide phosphor.

Usually, as the lighting time increases, the amount of reaction of Nd ions, which is a light emitting metal, with quartz glass on the inner surface of the quartz glass without a protective film increases, and SiO ₂ and N
It has already been mentioned that a complex oxide of d ₂ O ₃ is formed.
Therefore, in order to determine the composition ratio of the composite oxide which is the product, the compound was identified by X-ray diffraction. As a result, the product was found to be 2SiO ₂ .Nd ₂ O ₃ . Therefore, 2SiO ₂ · Nd as a protective film
By forming a film of ₂ O ₃ on the inner surface of the arc tube, it becomes possible to prevent the devitrification phenomenon.

As a method for forming a film of 2SiO ₂ .Nd ₂ O ₃ on the inner surface of the arc tube, a sol-gel method using a metal alkoxide was used. First, in order to produce a composite oxide having the above composition ratio, Si (OC ₂ H ₅ ) ₄ solution and N
The d (OC ₂ H ₅ ) ₃ solution was mixed at a ratio of 2: 1 (molar ratio), and applied on the inner surface of the arc tube material by the dipping method, and 1
After natural drying for 2 hours, calcination is performed at 800 ° C for 1 hour, then 2S
An iO ₂ · Nd ₂ O ₃ film was formed. The thickness of the composite oxide film was about 1 μm. Furthermore, in order to improve the film quality, 11
The temperature was raised to 00 ° C and re-baking was performed.

In this way, the electrodes 4 and 5 are sealed at both ends of the arc tube material on which the protective film 2 is formed, to manufacture the arc tube 1.
After the inside of the arc tube 1 was evacuated, NdI ₃ was used as a filling substance.
A metal halide lamp of input 250W type, in which 10 mg of mercury, 40 mg of mercury and 30 Torr of Ar gas were enclosed,
The luminous flux maintenance factor after lighting for 6000 hours with a 250 W ballast was 80%. On the other hand, in the case of the lamp without the protective film (same enclosure, same size), the luminous flux maintenance factor after lighting for 6000 hours was 45%.

Next, the starting voltage was measured and compared. As a result, all the lamps immediately after production were lit in the range of 140 to 150 V, but the starting voltage after 6000 hours of lighting was:
The lamp without the protective film required 200 V or more, whereas the lamp of Example 1 was able to start at 165 V.

Example 2 The same effect as in Example 1 was obtained when quartz glass was used as the arc tube material and FeI ₂ was used as the metal halide.

In this case as well, by lighting, SiO ₂ and FeO
The complex oxide of
It was found iO is a ₂ · 2FeO. Therefore, as in Example 1, SiO ₂ .2FeO was applied as a protective film and fired similarly to manufacture a lamp having a protective film.

An input 250 W type metal halide lamp in which 10 mg of FeI ₂ , 40 mg of mercury and 30 Torr of Ar gas were enclosed as an encapsulating substance was produced, and the luminous flux maintenance factor after lighting for 6000 hours with a 250 W ballast was 82%. there were. On the other hand, in the case of the lamp without the protective film (same enclosure, same size), the luminous flux maintenance factor after lighting for 6000 hours was 48%.

Next, as a result of measuring the starting voltage, it was found that the lamp according to Example 2 could be started at 175 V or less, whereas the lamp without the protective film had a starting voltage of 20.
0V or more was required.

Example 3 FIG. 2 shows the arc tube material used in Example 1 and the oxides of the light emitting metal, that is, SiO ₂ and Nd _2.
It is a two-component system phase diagram (temperature-composition diagram) of O ₃ . The compositions capable of forming pure binary compounds from this phase diagram are composition a, composition b, composition c.

Here, the composition c is the same as the protective film prepared in Example 1, but the other two compositions a and b have not been tested. Therefore, the same arc tube material as that of the lamp of Example 1 and the same enclosure, and the same metal alkoxide solution for forming the protective film are also the same.
Compositions a and b were prepared by changing the mixing molar ratio as described below.

Si (OC ₂ H ₅ ) ₄ : Nd (OC ₂ H ₅ ) ₃ = 1: 1 (molar ratio) Si (OC ₂ H ₅ ) ₄ : Nd (OC ₂ H ₅ ) ₃ = 3: 2 ( (Molar ratio) Then, as in the other examples, dip coating was performed on the inner surface of the arc tube using the above mixed alkoxide solution, followed by firing to form a protective film. Here, the composition of the formed protective film is equivalent to each mixing ratio, that is, S
An iO ₂ · Nd ₂ O ₃ film and a 3SiO ₂ · 2Nd ₂ O ₃ film could be formed.

As a result of the same test as the other examples, 60
The characteristics of the protective film of composition a after lighting for 00 hours are as follows: luminous flux maintenance factor 65%, starting voltage 175 V, protective film of composition b: luminous flux maintenance factor 70%, starting voltage 170 V, protection of composition c It was slightly worse than the film (Example 1).
From this, it is understood that the composition c is preferably used in order to obtain a film that is most suitable as a protective film, that is, a film in which the reaction between the luminescent metal and the arc tube does not proceed.

The inventors have found from this result that the composition of the protective film can be determined from the binary phase diagram if the material of the arc tube and the encapsulating metal are determined. That is, from the binary phase diagram shown in FIG. 2, a method for selecting a composition having a composition ratio that gives a pure two-phase compound and having the maximum molar amount of the arc tube material as the protective film material.

(Embodiment 4) In this embodiment, when quartz glass is used as the material of the arc tube and a rare earth metal halide is used as the sealing metal, all devitrified substances generated in the arc tube are 2: 1.
It shows that it becomes a metal silicate. For example, Dy will be described as an example.

When DyI ₃ is used as a luminescent substance, when a lamp without a protective film is turned on, 2SiO ₂ · Dy ₂ O
Devitrified matter of ₃ (confirmed by X-ray diffraction) was generated. This is a two-component system phase diagram of Dy ₂ O ₃ and SiO ₂ as shown in FIG. 3, when determined in the same manner as in the composition ratio as in Example 3, 2SiO ₂
• Dy ₂ O ₃ applies to this.

Also, with other rare earth metal halides, a 2: 1 composite oxide was generated in the arc tube, as in the case of DyI ₃ .

Therefore, as in the other examples, a lamp having a protective film of the same composition as the devitrified material provided on the inner surface of the arc tube was prototyped and a lighting test was performed. As a result, the life characteristics of all the lamps were improved. did.

(Embodiment 5) In this embodiment, when polycrystalline alumina is used as the material of the arc tube and a rare earth metal halide is used as the filling metal, the devitrification substance generated in the arc tube is a kind of rare earth metal halide. It depends, in the case of LaI _3, in the case of _{11Al 2 O 3 · La 2 O} 3 NdI 3, in the case of _{Al 2 O 3 · Nd 2 O} 3 SmI 3, Al 2 O 3 · Sm 2 O 3 EuI 3 for, if the _{Al 2 O 3 · Eu 2 O} 3 GdI 3, in the case of _{Al 2 O 3 · Gd 2 O} 3 ScI 3, when the _{Al 2 O 3 · Sc 2 O} 3 DyI 3 is 5Al _{In the case of 2} O ₃ · 3Dy ₂ O ₃ HoI ₃ , 5Al ₂ O ₃ · 3Ho ₂ O ₃ YI _{3 in} the case of 5Al ₂ O ₃ · 3Y ₂ O ₃ ErI ₃ 5Al ₂ O ₃ · 3Er _In the case of ₂ O ₃ TmI ₃ , 5Al ₂ O ₃ · 3Tm ₂ O ₃ YbI _{3 in} the case of 5Al ₂ O ₃ · 3Y For the b ₂ O ₃ LuI _3, it was confirmed by X-ray diffraction to be a _{5Al 2 O 3 · 3Lu 2 O} 3. This is consistent with the selection method of the protective film according to the two-component phase diagram in Example 3.

As an example, LaI ₃ and Nd are used as luminescent materials.
Lamps using I ₃ and DyI ₃ were produced,
At this time, the metal alkoxide solution for forming the protective film was used with the mixed molar ratio changed as follows.

Al (OC ₂ H ₅ ) ₃ : La (OC ₂ H ₅ ) ₃ = 11: 1 (molar ratio) Al (OC ₂ H ₅ ) ₃ : Nd (OC ₂ H ₅ ) ₃ = 1: 1 ( Molar ratio) Al (OC ₂ H ₅ ) ₃ : Dy (OC ₂ H ₅ ) ₃ = 5: 3 (molar ratio) As in the other examples, the inner surface of the arc tube was dip-coated with the above mixed alkoxide solution. After that, firing was performed to form a protective film. Here, the composition of the formed protective film is equivalent to each mixing ratio, that is, 11Al ₂ O ₃
・ La ₂ O ₃ , Al ₂ O ₃・ Nd ₂ O ₃ , 5 Al ₂ O ₃
-A protective film of 3Dy ₂ O ₃ could be formed.

A lamp having the same specifications as in Example 1 was manufactured and subjected to the same test. As a result, the characteristics after lighting for 6000 hours were La.
In a lamp using I ₃ as a luminescent substance, the luminous flux maintenance factor is 80%,
Starting voltage 160 V, the lamps which are light-emitting substance NdI _3, the luminous flux maintenance factor of 75%, the starting voltage 162V, the lamps which are light-emitting substance DyI _3, the luminous flux maintenance factor of 82% was starting voltage 165V.

On the other hand, as a comparative example, as in Example 3,
As a result of the same test using the composition ratio of the protective film different from that described above, both the luminous flux maintenance factor and the starting voltage were slightly deteriorated.

(Sixth Embodiment) A point different from the other embodiments is that the protective film has crystallinity in order to chemically stabilize the protective film according to the first to fifth embodiments. .

For example, taking a lamp having the same specifications as in Example 1, 2SiO ₂ .Nd ₂ O ₃ is applied to the inner surface of an arc tube made of quartz glass by the dip coating method,
The same process was carried out until the baking was carried out at 0 ° C. for 1 hour, and thereafter, the baking was further carried out at 1250 ° C. for 1 hour to give the protective film crystallinity. For this film, an even stronger crystalline peak was confirmed by X-ray diffraction as compared with the protective film in Example 1.

A lamp having the same specifications as in Example 1 was manufactured and a lighting test was carried out. As a result, the luminous flux maintenance factor after lighting for 6000 hours was 9
The starting voltage was 0%, and the starting voltage was 160 V or less after lighting for 6000 hours. Thus, good results were obtained even when compared with the lamp of Example 1.

It is needless to say that the present invention is not limited to Examples 1 to 6 described above. For example, when a plurality of light emitting metals are enclosed in the light emitting tube, each light emitting metal and light emitting tube material are used. Reaction mixture may be formed on the inner surface of the arc tube as a protective film, or a reaction product with a luminescent metal having the highest reactivity with the arc tube material may be formed as a protective film. You may.

[0052]

As described above, according to the present invention, a thin film made of the same material as the devitrification product (the reaction product of the luminescent metal and the arc tube generated during lighting) is formed on the inner surface of the arc tube as a protective film. As a result, it is possible to provide a metal vapor discharge lamp that is chemically stable, prevents the reaction between the light emitting tube and the light emitting substance, reduces the light transmittance, and hardly increases the starting voltage.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an arc tube according to the present invention.

Fig. 2 Phase diagram of binary system of Nd ₂ O ₃ and SiO ₂ (Temperature-
It is a composition diagram).

FIG. 3 is a phase diagram of a binary system of Dy ₂ O ₃ and SiO ₂ (temperature-
It is a composition diagram).

[Explanation of symbols]

1 arc tube 2 protective film 3 exhaust pipe 4, 5 Main electrode 6 Starting aid electrode 7,8,9 Molybdenum foil 10, 11, 12 Introductory line

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takuma Hashimoto Takuma 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. 72) Inventor Eisuke Sugimoto 191 of 1015 Ajima, Niihama-shi, Ehime (56) Reference JP-A-6-162999 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 61 / 35

Claims (4)

(57) [Claims] 1. A metal vapor discharge lamp in which a metal halide is enclosed as a light emitting substance in an arc tube made of a metal oxide.
And the material used for the inner surface of the arc tube.
Phase diagram of binary system consisting of oxide of luminescent metal
(Degree-composition diagram), a set in which a pure two-phase compound is obtained
Composition that maximizes the molar amount of the arc tube material in the composition ratio
A metal vapor discharge lamp characterized in that a protective film to be a thin film is formed by using this composition as a material . 2. In a metal vapor discharge lamp in which a rare earth metal halide is enclosed as a light emitting material in an arc tube made of quartz glass, the composition ratio of the components of the protective film formed on the inner surface of the arc tube is SiO2: R2O3 = 2. 1 (R is a rare earth metal) is a metal vapor discharge lamp. 3. In a metal vapor discharge lamp in which a rare earth metal halide is enclosed as a light emitting substance in an arc tube made of polycrystalline alumina or single crystal alumina, the composition ratio of the components of the protective film formed on the inner surface of the arc tube is set. Al2O3: R2O3 = 11: 1 (R is La) Al2O3: R2O3 = 1: 1 (R is Nd, Sm, Eu,
Gd, Sc) Al2O3: R2O3 = 5: 5 (R is Dy, Ho, Y, E
r, Tm, Yb, Lu) is a metal vapor discharge lamp. 4. The metal vapor discharge lamp according to claim 1, wherein the protective film has crystallinity.