J. of IEIJ Vol.88, No.5

The Abstracts of the Papers
J.Illum. Engng. Inst. Jpn. Vol. 88, 2004

No. 2 February
No. 5 May
No. 8A August
No. 11 November

The Characteristics of the Sealed Parts in Super High Pressure Mercury Discharge Lamps
Masahiko KASE, Yuichiro IWAMA and Toshiyuki SAWA

Super high pressure mercury discharge lamps have been used under conditions of more than 1MPa of internal pressure. They are usually used in exposure processes, such as PCBs patterning, as well as in LCDs and semiconductors. In addition, they must  be  secured for rupture, because of extreme internal pressure, thermal loads and so on, required by their use. Furthermore, ruptures may occur from the sealed parts in the lamps. Thus, it is necessary to examine the mechanical characteristics of the sealed parts. The objectives of this paper are to examine the sealed parts of the lamps to withstand under internal pressure experimental conditions and to calculate the stress distribution to predict the rupture potential using finite element calculations. We also conducted rupture tests of the lamps under static water pressure conditions. The lamps' stress distributions were observed in the rupture tests by using photoelasticity. As a result, we found the relationship between the shape of sealed parts and their rupture pressure. Ruptures were occurd where the boundaries of the sealed parts were joined by the silica glass and molybdenum foil were joined. We found that the rupture direction agreed with those obtained by FEM. Finally, it is important to note the relationship between the shapes of the sealed parts and their resistance to rupture while under internal pressure is important factor in developing an optimum design for the lamps.

KEYWORDS : super high pressure mercury discharge lamps, sealed parts, fracture under internal pressure, static water pressure test, calculating strain distribution , FEM calculations

Stress Analysis of Super High-pressure Mercury Discharge Lamp Bulbs under Thermal Loads
Masahiko KASE, Yuichiro IWAMA and Toshiyuki SAWA

Super high-pressure mercury discharge lamps have been used as a light source in photolithography. They are applied to manufacturing semiconductors, liquid crystal displays (LCD), printed circuit boards (PCB) and so on. It is well known that their working internal pressure is more than 1.0MPa and their temperature at bulb outer surface is more than 500°C. Therefore, it is essential to be examined whether their safety designs for fracture of the bulbs are enough or not. Because the bulb shapes have been designed empirically, research has yet been carried out on the optimal design of the lamps for preventing the bulb fracture, by using scientific methods such as  the theory of elasticity, finite element method and so on. In this study, the Finite Element Method (FEM) is applied to obtain the thermal stress of bulbs in operation, and the effects of the thermal stress on the bulb fracture is examined by comparing the obtained thermal stress with the critical stress of silica glass. As the result, we found that the obtained thermal stress of the bulb was much smaller than the stress, which was occurred under internal pressure at room temperature. In addition, it was observed that the thermal stress distributions in the lamps were varied by due to the restricted condition at the bulb ends. Thus, it can be concluded that designers for bulbs should pay a lot of attention how to fix the bulbs, because the stress in the bulbs increases by the restricted conditions and ruptures of the bulbs may occur due to the stress concentration.

Effect of the Highest Lightness on the Brightness Size of Recognized Visual Space of Illumination
Hideki YAMAGUCHI, Hiroyuki SHINODA and Mitsuo IKEDA

We have proposed a new estimation method for a perceived brightness of a room based on the concept of the recognized visual space of illumination, or RVSI. We use the term ‘brightness size’ of RVSI to express an observer’s perception of the intensity of illumination. We define the border luminance between surface color and unnatural surface color modes as the brightness size of RVSI. Our previous work1) showed that the border luminance was proportional to the illuminance of a room and that was equal to the luminance of the brightest object in the room. We measured the border luminance in two differently decorated rooms to test the effect of the highest lightness of object. One room was furnished with white walls and various lightness objects from black to white (environment N). The other was furnished with black walls and objects whose Munsell Value were 5 or less (environment L). Although the  illuminances of two rooms was the same, the border luminance in environment L was a half of that in environment N. Contrary to our previous result, the border luminance in environment L was higher than the luminance of the brightest object. We also compared the border luminance among three different positions where the local contrast and the local illuminance were different. The border luminance was almost constant regardless of the measuring position, suggesting that the local environments have little effect on the perceived brightness of a room.

Evaluation of Tungsten Cluster Radiation Dependent on Various Metal Halides
Ayumu SATO, Kazuyuki HOSAKA, Hiroki KUBO, Seishi SEKINE and Masashi OHKAWA

Tungsten cluster lamps are expected to yield high efficiency and excellent color rendering. However, a regenerative halogen cycle is required to form and maintain the small clusters within the microwave-excited high-pressure discharge. Metal halides play an important role in building the halogen cycle, but we still do not know how the metal halides affect the radiation characteristics of the tungsten clusters. We investigated the spectral radiant exitance, the luminous flux, and the color temperature of the tungsten cluster radiation in various metal halides, such as NaCl, KCl, CsCl, NaBr, KBr, CsBr, NaI and KI. The radiation from the tungsten clusters yielded a continuous spectrum with a maximum between 650 and 700 nm, although the spectra were dependent on the type of metal halide used. The luminous fluxes in the metal alkali bromides were twice as large as those in the metal alkali chlorides and iodides. Also, the luminous fluxes in the sodium halides were twice as large as those in the potassium halides, and four times as large as those in the cesium halides. From those results, we confirm that NaBr is suitable as a metal halide in tungsten cluster lamps.

KEYWORDS : cluster lamp, metal halide, tungsten, incandescent radiation, favorable color rendering property, high luminous efficacy

Energy Balance and Other Characteristics of Rare Gas Fluorescent Lamps for Image Illumination
Takafumi MIZOJIRI, Ryouta SONODA,Tetsu OKAMOTO and Masaki YOSHIOKA

A rare gas fluorescent lamp, which has a pair of external electrodes, is widely used as a means for image illumination in offices. However, few studies and reports have been conducted on this lamp. Thus, we examined its energy balance. What we found was that over 90% of the lamp input power changes into thermal energy. To improve the luminous efficacy, we developed a novel structure in which a pair of electrodes was used, one on an inner and the other on an outer surface of a lamp bulb. A comparison was done with a conventional bulb. At the same inverter conditions, the new lamp could be run at only 80% of the voltage of the conventional one. Consequently, the lamp input power increased about 6%, and the illuminance increased about 7%. No luminous efficacy improvement was observed.

KEYWORDS : rare gas fluorescent lamp of external electrodes type, rare gas fluorescent lamp of an internal and external electrodes type, image illumination, energy balance

Ca(Eu_1-xLa_x)₄Si₃O₁₃ Red Phosphor and its Application to Three -Band- Type White LEDs
Kenichi YAMADA, Masato OHTA and Tsunemasa TAGUCHI

To facilitate the application of three-band-type white LEDs, we developed a Ca(Eu_1-xLa_x)₄Si₃O₁₃ red phosphor that emits red light at a peak wavelength of 613 nm when it is excited by near-ultraviolet rays at a peak wavelength of 395 nm. The activator concentration dependence of the light conversion efficiency showed that the optimum composition of the red phosphor was at x=0.5 and that the conversion efficiency was 0.14. When a near-ultraviolet LED with an assumed external quantum efficiency of 0.40 was combined with Ca(Eu_0.5La_0.5)₄Si₃O₁₃ red phosphor and existing green and blue phosphors, the calculated luminous efficacy and general color rendering index of the resultant white LED were 21.6 lm/W and 83.9, respectively.

KEYWORDS : CaEu₄Si₃O₁₃, red-emitting phosphor, Eu³⁺ ion, near-ultraviolet, white LED, semiconductor lighting