Reference / Paper · 1976
Ise's paper on its flat nine-digit tube for hand-held calculators: fabrication steps, 2.7 V AC filament, 24 V drive at 1/12 duty, brightness against duty, and a whole-tube power of 39.6 mW.
10.4: Flat Panel Multi-Digit Fluorescent Display Kentaro Kiyozumi, Mituru Masuda and Tadashi Nakamura Ise Electronics Corporation, Mie Pref., Japan Introduction The requirement for digital display to be used in electronic calculators, measuring instruments, and in other industrial purposes are emphasized in the re- duction of size and power consumption as well as in the flat panel configuration. The vacuum tube type fluorescent alpha-numerical display, which we call the 'ITRON' or rather the GREEN TUBE as is widely Inown in U.S., was initially developed in 1967 at Ise Hlectronics Corp. It is used popularly -in electronic calculators due to its legibility, low voltage and low power consumption. The "Flat Panel Itron', which will be described here, is a new outgrowth from the tubular concept to a thin panel construction with several outstanding improvements in manufacturing technology, namely the application of Thick Film Screen Printing on glass plate which constitutes a part of the display device enclosure. It is also featured by its improvement in power consumption resulting from the improvement in the alignment and configuration of the electrodes. Flat Type Multi-Digit Numeric Display Heretofore, multi-digit display devices were developed along a few paths, such as the tubular glass envelope type within which a multiple digits were en- closed, the metal envelope with window type, and the ceramic envelope with window type. The basic process of the new flat multi-digit display is in the application of thick film screen printing technology in making the luminous anode. Formerly, a flat ceramic was used as the substrate glass envelope. This was improved and simplified so that the anode was made of a flat glass substrate which was made to serve a part of the vacuum envelope. (1) Glass plate A remarkable point of glass flat type, Multi-digit display is the glass plate that constitutes a part of the vacuum sealed package. Figure 1 illustrates a brief construction of the glass plate. : (2) Processing of glass flat multi-digit numeric display Figure 2 explains the fabrication process of flat glass type multi-digit numeric display. (3) Characteristic of glass flat nine digit display Application of this particular display is mainly in the hand-held electronic calculator. Therefore power consumption among other characteristics is always the major subject to be discussed. Since the battery operated hand held calculator was dominated by nine digit displays, there was pre- dominant requirment for the nine multi-digit display device to have the least power consumption. To achieve this requirement it is necessary to reduce the filament power (Wf) and grid power (Wc). 130 @ SID 76 DIGEST In reducing the filament power (Wf), although it may be conceivable to use a thinner filament wire, it proves to be not economical from the point of productivity and reliability. The conventional tubes have two filament wire, and apparently the removal of one filament should re- sult in half the filament power. Nevertheless, this causes the electron distribution upon the anode to be extremely poor, hence non uniform brightness. on the segments. To overcome this defect, the number of filament was reduced without affecting its length while the anode dimmension was reduced to secure uniform electron distribution on all the segments. The character size was thus reduced to 3.7 x 1.7m. The configuration of the grid was also improved in consideration to achieve uniform brightness. Thus the total power consumption was bright down to 39.6 mW. Figure 3 shows a comparison of the characteristic between the present and new nine digit display. (4) Characteristic data of anew nine digit display device Figure 4: Filament voltage (Ef) vs filament current (if), plate current (ib), grid current (ic) and brightness (Ft-L). Brightness is in Ft-L. Figure 5: Plate voltage (eb) and grid voltage (ec) vs plate current (ib), grid current (ic), and brightness (Ft-L). Figure 6: Duty factor vs brightness: Conclusion Since the development of the vacum fluorescent display by Ise Electronics Corp. in 1967, this display became to be a major readout for use in various electronic calculators in Japan. It is also applied in various fields of digital instruments such as measuring and weighing equipments, clock computer terminals, taxi meters etc. The display to be made smaller and compact in size and diminished in power consumption so as to prolong the operating life for a given battery is still a continued demand. The flat panel display therefore, should be the solution to this requirment. Acknowledgments We wish to thank the members of Nippon Toki Corp., Nagoya Factory, for their assistance in preparing the glass plate with print. References (1) Electronics May 29, 1967 pp212 - 213 (2) Electronics April, 1969 pp 220 . painting & welding of Fluorescent glass plate >> nenanrnaia PP fiarent & getter -—o) seating -— Electric Conductor 2. / Insulated Layer face glass painting of with NESA soft glass Y Y d Electric Conductor 1. aintin etter vacuums checking aging i. nip < ere ‘a exhausting pin flashing ~————----= Glass Plate Fig. 1. Construction of Glass Plate Fig. 2. Fabrication Process of Flat Tube. Block Diagram _— ~ I(mAac) (FL) NO we ef lie lue leo € o oss es & | secmay 1° bietm ; Cc, WxixT xt 1 ¥) [Cm oie] Cy) a y =e Libr ay mye 200/- Plat l= 24Vj 7 5 EG (mn) { (mm) TYP [MA “de (us) aw )}{ mi ate vol. = PP, LY MAX] -|rvP INax hdc) Doom fina Grid vol.= 2% Vpp, Z _—T im a Duty Factor =1/12, typet2zx7.2] 5%2-43.0/22 [66 |24 11.0 |2.0/24 |1.5]3.0}3.cleo0|/i2| 40 |60 j26h12.3 Uu Pulse Width=40 ms £ (mAp-p) ayes eae on 2.7/12 [32.424 |0.4[0.8)24 Jo.5]0.sb2.a]200|yiz|ao leislsa |s.4 2 06 ~ 0.4 aU 5 NOTE: Qss ; out side scale Ecco : grid cut off voltage = 5 c cs : character scale L ’ brightness (fL) Go 3 EF : Filament volt , : a . Wf + Filament power Wooo anode power + grid power QO. eb + anode voltage wT : total power ib : anode current Wd : Watt ¢ digit ol. 1. ec : grid voltage 0 1.0 20 3.0 0 te grid current Filament Voltage (Ef) (Vac) Fig. 3. Charasteristic of Flat Tube Fig. 4, Brightness, Plate, Grid § Filament Current \ . v.s. Filament Voltage (FL) Filament vol. =2.7 Vac i =27 Vac i = Filament vol, ae (mAp-p). Pulse Width 40 Ms (FL) uty Factor = L 500+ Pulse Width =40Ms 410 400k (1) eb=ec = 15 Vp-p 300L as (2) » 4 = 20 « (ays) ee 300; (3) 8 «6 524 » hn rt wn (4) " «230 « L 33 @ 200; £200 655 & 200 raj x a 5 oi 0,4 2 u coc 100r ct 100; oo a 40.2 oly oo 4) 2) @) "10 15 20 v4s) 30. 0 20 . . ‘ (Vp-p) 15 1/10 1150 1/100 Plate Voltage(eb) , Grid Voltage(ec) Duty Factor Fig. 5. Brightness, Plate § Grid Current Fig. 6. Brightness v,s. Duty Factor v.s. Plate §& Grid Voltage SID 76 DIGEST @ 131