JPH0569259B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is mainly used in discharge lamps that strongly emit green light with a wavelength of 535 nm, and is capable of blocking ultraviolet rays without reducing the transmittance of green light. The present invention relates to quartz for arc tubes.

[Prior art and its problems]

Many discharge lamps, such as xenon lamps, mercury lamps, and metal halide lamps, emit ultraviolet light with a wavelength of 340 nm or less. Ideally, the emitted ultraviolet rays should normally not be emitted, except when actively utilized. In other words, ultraviolet rays are undesirable because they react with oxygen in the air to produce harmful ozone and act directly on human skin, and therefore are particularly harmful to lamps that are lit in environments where humans interact. , it is required that no ultraviolet radiation be emitted.

By the way, for example, a metal halide lamp containing a water source, thallium, and halogen has a wavelength of 535 nm.
The emission wavelength peaks at the green light of Since the lights are turned on at 340nm, it is necessary to prevent them from emitting ultraviolet rays with a wavelength of 340nm or less.

Generally, the technology to prevent the emission of ultraviolet rays is carried out by coating or doping a substance that does not transmit ultraviolet rays on the surface or inside of the quartz glass that forms the _arc tube. _2nd place is known. As you can see from the name, quartz tubes doped with TiO ₂ are ozone-less tubes, the wavelength is
Although it blocks light of 220 nm or less and prevents the formation of ozone, it does not sufficiently cut out ultraviolet rays with wavelengths of 220 nm or more and passes through. That point
CeO ₂ can block ultraviolet rays with a wavelength of 340 nm or less, so it is an effective substance for blocking all ultraviolet rays. Therefore, arc tubes made of quartz doped with CeO ₂ are used for discharge lamps that do not transmit ultraviolet rays with a wavelength of 340 nm or less, but CeO ₂ has a high melting point of 2600°C, and it is difficult to disperse it uniformly inside the quartz. ,
When producing quartz, it is necessary to heat it to extremely high temperatures.
There are many technical and economic difficulties.

For this reason, there is a need for an arc tube that is easy to manufacture and can block all ultraviolet rays. However, it is necessary that the output of green light around 535 nm is not reduced by the arc tube.

[Purpose of the invention]

Therefore, the present invention is easy to manufacture and has a wavelength
The purpose of the present invention is to provide quartz for arc tubes that does not reduce the transmittance of green light around 535 nm and blocks ultraviolet rays with a wavelength of 340 nm or less.

[Structure and operation of the invention]

The quartz for arc tubes of the present invention is produced by coating the outer and/or inner walls of an arc tube made of quartz glass with a cerium alkoxide solution and firing the resulting CeO ₂ layer having a thickness of 0.25 to 0.35 μm or 0.40 μm. It is characterized by being ~0.49 μm.

That is, by using the cerium alcoholate solution, a uniform Ce layer is formed on the outer wall and/or inner wall of the arc tube. Therefore, by firing, the CeO ₂ layer is formed in a layered manner without being unevenly distributed.
Moreover, the thickness of the formed CeO ₂ layer is 0.25~
By setting it to 0.35 μm or 0.40 to 0.49 μm,
It is possible to obtain quartz for arc tubes that can sufficiently block ultraviolet rays without increasing the film thickness unnecessarily and does not reduce the transmittance of green light having a wavelength of around 535 nm.

〔Example〕

The present invention will be specifically described below based on embodiments shown in the drawings.

Figure 1 shows how the thickness of the _CeO2 layer formed on the quartz surface affects the spectral transmittance. The thickness of the quartz used was 3 mm.
The CeO ₂ layer is applied to the quartz surface using a method such as depping using a cerium alcoholate solution with a Ce content of 5% in terms of CeO ₂ , and after natural drying, the
Dry at °C. Then, this scanning is repeated until a CeO ₂ film of a predetermined thickness is coated, and then 500
It is obtained by firing at a temperature of at least 100°C, preferably at least 800°C, for about 10 minutes. In this way, compared to the conventional method of uniformly dispersing a substance that does not transmit ultraviolet light inside quartz, CeO ₂
layers can be formed.

In FIG. 1, A shows the case where the CeO ₂ layer is not formed, B, C, D show the case where the film thickness d of the CeO ₂ layer is 0.1 μm, 0.25 μm, 0, . Spectral transmittance at 45 μm is shown. As is clear from this,
If no _CeO2 layer is formed, the wavelength is
Shows 95% transmittance at wavelengths above 250nm.
Even at 200nm, 50% is transmitted. On the other hand, when _two CeO layers were formed, the transmittance in the ultraviolet region was significantly reduced. However, _CeO2
If the film thickness d of the layer is insufficient, the ability to block ultraviolet rays will be considerably reduced. That is, d=0.1μm
In this case, the transmittance at a wavelength of 340 nm is 65%, and about 10% is transmitted even at a wavelength of 300 nm or less. Therefore, in order to satisfy the performance of blocking ultraviolet rays, the film thickness must be such that the transmittance at wavelengths of 340 nm or less is 3% or less, that is, d = 0.25μ.
It is necessary to form _two CeO layers of m or more. However, as can be understood from this figure, when _two CeO layers are formed, the transmittance in the visible light region decreases slightly, and the peak of the transmitted wavelength shifts depending on the thickness of the formed film. That is, depending on the thickness of the formed film, the transmittance at wavelengths around 535 nm decreases, and when an arc tube with this characteristic is used, the output of green light decreases.

Therefore, we investigated how the transmittance at a wavelength of 535 nm changes when the thickness d of the CeO ₂ layer formed on quartz is changed. The results are shown in FIG. As is clear from this, d = 0.25μm or more, which can cut out ultraviolet rays with a wavelength of 340nm or less,
In the CeO ₂ layer, the transmittance at a wavelength of 535 nm at d = 0.3 μm is 85%, once reaching a peak, and when the film thickness d is increased further, the transmittance decreases once. However, as the film thickness d is further increased, the transmittance increases again and reaches its peak again at 85% at d=0.45 μm. Therefore, the film thickness d of the CeO ₂ layer to be formed is preferably around 0.3 μm or 0.45 μm, but since the practically required transmittance is 75%, in order to achieve this, the film thickness d from 0.25
It may be 0.35 μm or 0.40 to 0.49 μm. Note that when d=0.40 to 0.49 μm, the process of increasing the film thickness increases, but since the transmittance of ultraviolet rays can be reduced to zero, it is effective when it is necessary to completely cut out ultraviolet rays.

In this way, the thickness of _{the two} CeO layers to be formed is set to 0.25~
By setting it to 0.35 μm or 0.40 to 0.49 μm,
It is possible to obtain a maximum value of the transmission wavelength near 535 nm, and it is also possible to obtain quartz for arc tubes that does not transmit ultraviolet rays having a wavelength of 340 nm or less.
Therefore, if this quartz for arc tubes is used, for example, in the arc tube of a metal halide lamp filled with mercury, thallium, and halogen, it is possible to suppress the decrease of green light with a wavelength of around 535 nm as much as possible, and emit ultraviolet rays with a wavelength of 340 nm or less. It can be used as a fishing light that emits a strong green light without adversely affecting fishing crew members.

〔Effect of the invention〕

As explained above, in the present invention, a cerium alcoholate solution is applied to the outer wall and/or inner wall of an arc tube made of quartz glass and fired, and the thickness of the CeO ₂ layer thus formed is 0.25 to 0.35 μm.
Or, because it is characterized by a diameter of 0.40 to 0.49 μm, it can be easily manufactured, has the highest transmittance for green light with a wavelength of around 535 nm, and is for use in arc tubes that cut out ultraviolet rays with a wavelength of 340 nm or less. It is possible to use quartz.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between wavelength and spectral transmittance, and Figure 2 is a diagram of the relationship between wavelength and spectral transmittance.
A diagram showing the relationship between the thickness of the CeO ₂ layer and the transmittance at a wavelength of 535 nm.

Claims (1)

[Claims] 1. A cerium alcoholate solution is applied to the outer wall and/or inner wall of an arc tube made of quartz glass and fired, and the thickness of the CeO ₂ layer thus formed is 0.25 to 0.35 μm or 0.40 to 0.49 μm. Characteristics of quartz for arc tubes.