Tsuyoshi Kano

Phosphor Materials for Cathode-Ray Tubes

Publisher Summary The cathode-ray tube (CRT) was invented by Karl Ferdinand Braun essentially for displaying electrical signals. This chapter discusses the basic luminescent processes.It describes the specific excitation processes occurring under electron bombardment. The chapter also examines the phosphor materials for specific applications along with the methods for the synthesis of phosphors. Furthermore, the chapter discusses screen fabrication techniques and describes phosphor screens with special properties. The processes involved in the aging of phosphors are also presented in the chapter. The chapter describes the methods for enhancing the image contrast of phosphor screens. It is noted that the highly advanced state of development of CRTs used for consumer, military, and industrial applications has largely been made possible by the advances in phosphor materials. However currently, the central issue remains the development of a blue phosphor that can substitute for ZnS:Ag, Al or ZnS:Ag, and Cl materials whose brightness saturation often presents a serious problem under high loading power. In this context, exploratory work on rare-earth phosphors as well as improving ZnS:Ag phosphors is necessary.

NaLnF4 : Yb3 + , Er3 + ( Ln : Y , Gd , La ) : Efficient Green‐Emitting Infrared‐Excited Phosphors

Hexagonal was found to be an efficient green‐emitting phosphor with infrared excitation. It was prepared by firing a mixture of and coprecipitated at 630°C in an argon atmosphere. The optimum firing condition of was revealed to lie in the region where (a) the decomposition reaction is complete, (b) liquid and hexagonal are coexistent, and (c) the phase transition of from hexagonal to cubic does not occur. When pumped by a Si‐doped diode, properly prepared is 4 ~ 5 times as bright as the commercially available .

Formation process of Y/sub 2/O/sub 2/S:Eu/sup 3/ in a preparation with flux

The formation process of a red emitting phosphor, Y/sub 2/O/sub 2/S:Eu/sup 3/ has been clarified in a reaction Y/sub 2/O/sub 3/ + Eu/sub 2/O/sub 3/ + Aux(S + Na/sub 2/CO/sub 3/ + K/sub 3/PO/sub 4/) ..-->.. Y/sub 2/O/sub 2/S:Eu/sup 3/ + flux Sulfuration of Y/sub 2/O/sub 3/ and Eu/sub 2/O/sub 3/ is completed at a firing temperature as low as 700/sup 0/C and at a firing period of 2h. Diffusion of Eu/sup 3/ follows the sulfuration, and grain growth begins when lattice disorder of Y/sub 2/O/sub 2/S decreases to a minimum at 1050 /sup 0/C. Larger particles are obtained when a part of Y/sub 2/O/sub 3/ is replaced with YPO/sub 4/.

Laser‐stimulable transparent CsI:Na film for a high quality x‐ray imaging sensor

Transparent films, which can be stimulated by laser beams after x‐ray irradiation, have been searched to improve the spatial resolution of digital x‐ray imaging sensors. As a result, evaporated CsI:Na films are found to be efficiently laser stimulable around 77 K. The modulation transfer function (MTF) of the film is evaluated using a scanning Ga1−xAlxAs semiconductor laser. The high MTF value (57% at 2 1p/mm), strong x‐ray absorption, and high stimulation efficiency of the film ensure a high quality sensor for digital radiography.

Satellite Lines Due to Ion-Pairs in the Luminescence Spectra of Y2O2S:Eu3+

In the luminescence spectra of the 5 D 0 → 7 F 1 transition of Y 2 O 2 S:Eu 3+ , satellite lines separated from the main lines by several cm -1 were observed. Under the excitation by 365 mµ radiation, the intensity of the main line increases linearly with the concentration of Eu 3+ , whereas that of the satellite lines increases as the 1.36 th power of the concentration. When Gd 3+ is codoped in Y 2 O 2 S:Eu 3+ keeping the concentration of Eu 3+ constant, the intensity of the satellite lines relative to the main line increases with the concentration of Gd 3+ . It is concluded that the satellite lines originate from the splitting and shift of the crystalline-field components resulting from a slight lattice distortion around a pair of Eu 3+ ions or that of an Eu 3+ ion and a Gd 3+ ion which occupy two nearest cation sites.

Cis-Trans Photoisomerization of Perinaphthothioindigo for Use as a Photo-Imaging Sensor Using Fluorescence under He-Ne Laser Excitation

An imaging sensor based on the cis/trans isomerization of thioindigoid dyes is proposed. A photo-image (~500 nm) is stored as a density distribution of the trans-form in the cis-form material, and read out as fluorescence (~700 nm) from the trans-form by scanning with He-Ne laser (633 nm) excitation. As the fluorescence decay time of perinaphthothioindigo is 1.8 ns, the sensor permits rapid read-out. For light exposure L from 10-4 to 10-1 J/cm2 at 500 nm, the fluorescence intensity under laser excitation varies as L0.8.

Preparation and properties of Y3Si2O8Cl; Ce phosphor

Abstract A new phosphor Y 3 Si 2 O 8 Cl; Ce was prepared by firing the mixture of Y 2 O 3 , CeF 3 , colloidal SiO 2 and NH 4 Cl in an argon atmosphere at around 1100°C. The luminescence properties, crystal structure and formation processes of the phosphor are presented and discussed.

Preparation and luminescence properties of Y2(WO4)3:Eu3+

A red-emitting Y2(WO4)3:Eu3+ phosphor (orthorhombic high temperature phase, anhydride) is prepared by two different methods: the firing of mixtures of constituent oxides and that of precipitates from aqueous solutions. After optimizing preparation conditions, the cathodoluminescence brightness reaches 56% that of Y2O2S:Eu3+, a commercial red phosphor for color TV. Formation of a high temperature phase below the reported transition temperature is noted in the fired precipitates. This phase occurrence is shown to depend on the treatment of the precipitates to be fired. Reflection difference measurement of Eu-doped and undoped samples assigns an excitation band of about 245 nm to the Eu-O charge transfer band. Different by-products in the two preparation methods are identified by measuring emission spectra under selective excitation. Reversible hydration—dehydration of the phosphor is demonstrated by successively measuring photoluminescence first in vacuum and then in air at various temperatures. No deterioration of luminescence efficiency is observed after repeating this reversible structural change.