JP2005310416A - Short arc type mercury lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a short arc type mercury lamp capable of preventing deterioration of an ultraviolet reflective film and reflecting ultraviolet rays certainly, even if the temperature of the reflective film becomes high during lighting, excellent in emission efficiency, and having higher luminance. <P>SOLUTION: This short arc type mercury lamp has an arc tube 1 made of quartz glass wherein a pair of electrodes 3, 4 are arranged, and mercury ≥0.20 mg/mm<SP>3</SP>is put and sealed. On the surface of the arc tube 1, an ultraviolet reflective film 5 is formed whose main body is principal tetragonal system crystal structures of zirconium oxide. Moreover, while this short arc type mercury lamp is lighted, the temperature of its arc tube 1 becomes 900°C or higher. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a short arc type mercury lamp used for a backlight of a projector device such as a liquid crystal display device or a DLP (digital light processor) using a DMD (digital mirror device).

  In general, a light source unit used in a liquid crystal projector device or the like is required to illuminate an image with a uniform and sufficient color rendering property on a rectangular screen. Short arc mercury lamps with metal halides enclosed are used.

  Such short arc type mercury lamps have a broad emission spectrum ranging from the ultraviolet region to the infrared region, but the wavelength used when actually illuminating an image is the visible region, and the remaining ultraviolet region and infrared region. The light in the area is not used for illumination.

On the other hand, recently, there has been a demand for a lamp with higher brightness by increasing the luminous efficiency of the lamp. An ultraviolet reflecting film is formed on the surface of the arc tube, and ultraviolet rays emitted from the arc are put into the arc tube by the ultraviolet reflecting film. In return, the mercury energy is increased to increase the luminous efficiency of the lamp and increase the brightness.
Such a technique is described in JP2003-242930A.

This ultraviolet reflective film is a film in which SiO ₂ and Ta ₂ O ₅ are alternately laminated. This ultraviolet reflective film in which SiO ₂ and Ta ₂ O ₅ are alternately laminated has low heat resistance, the film deteriorates due to heat, and has become a practical problem in a lamp in which the temperature of the arc tube is 900 ° C. or higher. .

Further, an ultraviolet reflecting film using zirconium oxide having a different film forming material is known.
Such a technique is described in JP-A-6-267504.
However, even when zirconium oxide is used, there is a problem that microcracks are formed in the film during lamp operation, the film becomes cloudy, light is scattered, and the light utilization rate is lowered.

In pursuit of the cause of such a phenomenon, it was found that the crystal transformation that changes the crystal structure of the zirconium oxide film occurs when the temperature of the arc tube becomes high.
That is, even if it is a single-layer film of zirconium oxide or an interference film in which SiO ₂ and ZrO ₂ are alternately laminated, the crystal structure of zirconium oxide is a monoclinic crystal structure, and the arc tube It has been found that when the temperature continues at a high temperature of 900 ° C. or higher, the volume changes and the film is cracked.
JP 2003-242930 A JP-A-6-267504

  The present invention has been made based on the above circumstances, and even when the UV reflective film is turned on at a high temperature, the film can be reliably reflected without deterioration, and the luminous efficiency is excellent. The object is to provide a high-intensity short arc mercury lamp.

The short arc type high-pressure mercury lamp according to claim 1 is a discharge lamp having a quartz glass arc tube in which a pair of electrodes are arranged and 0.20 mg / mm ³ or more of mercury is enclosed. An ultraviolet reflecting film mainly comprising a tetragonal crystal structure of zirconium oxide is formed on the surface of the arc tube.

  The short arc type mercury lamp according to claim 2 is the short arc type mercury lamp according to claim 1, and in particular, the temperature of the arc tube is 900 ° C. or more during lighting. To do.

  According to the short arc type mercury lamp of the present invention, even if the ultraviolet reflective film becomes high temperature during lighting, the film can be surely reflected without deteriorating, and light is emitted by returning the ultraviolet ray to the arc in the arc tube. High efficiency and higher brightness can be achieved.

The short arc type high pressure mercury lamp of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram of a short arc type high-pressure mercury lamp of the present invention.
The short arc type high-pressure mercury lamp has an arc tube 1 made of quartz glass and a sealing tube 2 formed extending on both sides of the arc tube 1. Electrodes 3 and 4 are disposed, and mercury of 0.20 mg / mm ³ or more is sealed, and a part of the electrodes 3 and 4 is sealed in the sealing tube 2.
An ultraviolet reflecting film 5 is formed on the outer surface of the arc tube 1.

Ultraviolet reflection film 5, zirconium oxide in the high refractive index layer (ZrO _2), a film formed by alternately laminating silicon oxide (SiO ₂₎ in the low refractive index layer.
The specific specification of the ultraviolet reflecting film is that the high refractive index layer is H and the low refractive index layer is L, and the optical film thicknesses (nd) of the high refractive index layer H and the low refractive index layer L are 89.4 nm, respectively. The minimum peak value of reflectance is 550 nm.

In the ultraviolet reflecting film 5, the high refractive index layer H and the low refractive index layer L are as shown in the following design, and one stack is 0.65 (H / 2 × L × H / 2). This is a combination of 8 stacks.
The ultraviolet reflecting film 5 is mainly composed of a tetragonal crystal structure.

Data showing the reflection characteristics of the ultraviolet reflecting film is shown in FIG. In FIG. 2, the horizontal axis represents wavelength (nm), and the vertical axis represents reflectance.
As can be seen from FIG. 2, the ultraviolet reflecting film of the short arc type mercury lamp of the present invention reflects ultraviolet light having a wavelength of 320 nm to 400 nm at a rate of 80% or more, and light from the visible light to the infrared region of 420 nm or more. It can be seen that the film reflects only 10% or less, reliably reflects ultraviolet rays, and transmits visible light.

Next, the crystal structure of the ultraviolet reflecting film of the short arc type mercury lamp of the present invention will be described.
Ultraviolet reflection film, a zirconium oxide in the high refractive index layer H (ZrO _2), a film formed by alternately laminating a low refractive index layer L on silicon oxide (SiO _2), the high refractive index layer H and the low refractive index layer L Is a combination of eight stacks each having a stack of 0.65 (H / 2 × L × H / 2), and the optical film thickness (nd of the high refractive index layer H and low refractive index layer L) ) Is 89.4 nm, and the minimum reflectance peak value is 550 nm.

  The ultraviolet reflective film 5 is one in which a high refractive index layer and a low refractive index layer are alternately laminated by a sputtering vapor deposition method, the target of the high refractive index layer is Zr, and the target of the low refractive index layer is Si. .

Then, each target is arranged in a reaction vessel, and while introducing Ar as a discharge gas and O ₂ as a reaction gas, a pulse voltage is alternately applied to each target, whereby a multilayer ultraviolet ray of ZrO ₂ —SiO ₂ is applied. A reflective film is formed.

At this time, when the low refractive index layer SiO _{2 of} the ultraviolet reflecting film is generated, Ar is fixed and introduced as a discharge gas at 50 sccm, and O ₂ is fixed and introduced as a reactive gas at 40 sccm, and when the high refractive index layer ZrO _{2 is} generated. A lamp in which Ar is fixed as a discharge gas and introduced at 50 sccm, and O ₂ is introduced as a reaction gas by changing between ₂₀ to 60 sccm, and an ultraviolet reflecting film having a different crystal structure is formed on the outer surface of the arc tube 5 were prepared, and an experiment was conducted to examine the difference in the crystal structure and the state of the ultraviolet reflective film after lighting for 1000 hours.

The difference in crystal structure is that when the amount of O ₂ that is a reaction gas is reduced during the formation of a high refractive index layer, the crystal structure of zirconium oxide (ZrO ₂ ) is mainly a tetragonal crystal structure. When the amount of O ₂ introduced as a gas is increased, the crystal structure of zirconium oxide (ZrO ₂ ) is mainly a monoclinic crystal structure. By changing the amount of introduced O ₂ as a reaction gas, zirconium oxide ( It changes the crystal structure of ZrO ₂ ).

Further, as a method for examining the crystal structure of zirconium oxide (ZrO ₂ ) constituting the ultraviolet reflecting film, X-ray diffraction of the ultraviolet reflecting film was performed.
In X-ray diffraction, the peak value in which the crystal structure of zirconium oxide (ZrO ₂ ) is a tetragonal system and the peak value in a monoclinic system are known in advance, and the peak values generated by the respective crystal structures are added together. The larger peak value is mainly composed of crystal structure.

FIG. 3 shows the result of X-ray diffraction of the ultraviolet reflecting film of the lamp 2 shown in FIG. 4 shown below. The peak in FIG. 3 is the crystal structure of the tetragonal crystal structure of zirconium oxide (ZrO ₂ ). Yes, the peak of ○ is the peak value of the monoclinic crystal structure of zirconium oxide (ZrO ₂ ). Obviously, this ultraviolet reflective film has a combined value (intensity value) of the peak value of ● It can be seen that this ultraviolet reflective film has a tetragonal crystal structure in the crystal structure of zirconium oxide (ZrO ₂ ).

Figure 4 is a summary of five lamp manufacturing method performed to be different crystal structure of the above zirconium oxide (ZrO _2), and X-ray diffraction intensity ratio of the crystal structure of zirconium oxide (ZrO _2), It is experiment explanatory drawing which described the state of the ultraviolet reflective film after lighting for 1000 hours.

The short arc type mercury lamp shown in FIG. 4 is a lamp having the following specifications, and only the ultraviolet reflecting film is different.
Arc tube: Quartz glass enclosure: 0.25 mg / mm ³ mercury and halogen rating with respect to arc tube volume: 250 W
Arc tube temperature at lighting: 930 ° C

In FIG. 4, in the lamp 1, the lamp 2 and the lamp 3, the X-ray diffraction intensity of zirconium oxide (ZrO ₂ ) in the ultraviolet reflecting film has a tetragonal intensity value larger than the monoclinic intensity value. It can be seen that the ultraviolet reflective films of lamp 1, lamp 2, and lamp 3 have a tetragonal crystal structure as the crystal structure of zirconium oxide.
On the contrary, in the lamps 4 and 5, the X-ray diffraction intensity of zirconium oxide (ZrO ₂ ) in the ultraviolet reflecting film has a tetragonal intensity value smaller than the monoclinic intensity value. In the ultraviolet reflecting film of the lamp 5, it can be seen that the crystal structure of zirconium oxide is a monoclinic crystal structure.

In addition, as shown in FIG. 4, the ultraviolet reflective films of lamp 1, lamp 2, and lamp 3 have a tetragonal crystal structure of zirconium oxide, so that the ultraviolet reflective film is cracked or clouded even when the lamp is turned on for 1000 hours. In this case, 0.20 mg / mm ³ or more of mercury is enclosed in the arc tube, and the arc tube has a temperature of 900 ° C. in order to evaporate all of the enclosed mercury. Even when the temperature is higher than the above, it is not deteriorated by the heat of the ultraviolet reflection film, and the ultraviolet rays can be reliably returned to the arc in the arc tube, resulting in a lamp with excellent luminous efficiency and higher brightness.

It is explanatory drawing of the short arc type high pressure mercury lamp of this invention. It is data explanatory drawing which shows the reflective characteristic of the ultraviolet reflective film of the short arc type high pressure mercury lamp of this invention. The X-ray-diffraction result of a ultraviolet reflective film is shown. It is experiment data explanatory drawing.

Explanation of symbols

1 arc tube 2 sealing tube 3 electrode 4 electrode 5 UV reflective film

Claims (2)

In a discharge lamp having an arc tube made of quartz glass in which a pair of electrodes are arranged and 0.20 mg / mm ³ or more of mercury is enclosed,
A short arc mercury lamp characterized in that an ultraviolet reflecting film mainly composed of a tetragonal crystal structure of zirconium oxide is formed on the surface of the arc tube. 2. The short arc type mercury lamp according to claim 1, wherein the temperature of the arc tube is 900 [deg.] C. or higher during lighting.

Images