Copper-coating is one of the most important technique in DCEL

it can affects some significant properties of DCEL

such as forming process

lifetime and so on. Studies about this process are limited to technology conditions

its chemical reaction process has not yet been mentioned. This paper deals with some rules in copper-coating chemical reaction process for CaS:Ce and ZnS:Mn

Cu phosphors.Under normal conditions

the amount of coated copper on CaS:Ce or ZnS:Mn

Cu is seldom affected by concentration of copper

and it is gradually saturated with reaction time. This saturating amount relates to chemical properties and specific surface area of phosphor.Copper-coated amount increases with temperature in the function

W

=

Ae

-B/T

. The relationship between velocity constant of copper-coating reaction and temperature is in accordance with the Arrhenius’s empirical formula.The copper-coating reaction can be distinguished in three different stages

these are the extremely rapid reaction in the initial stage

then the rapid reaction in the second stage

and the slow reaction in the final stage. It is suggested that the three different stages related to different suface defects of CaS or ZnS. Crystal edge on suface of polycrystal particles is a area of the highest chemical activity

so it can be considered that the reaction will firstly take place in this area. In the second stage the reaction may take place in crystal plane.The reaction in the final stage may take place in crystal boundary near the surface of particles. The chemical activity on these three kinds of area decreases in their given order

and which is in accordance with the reaction velocity of the three stages.Analysis of copper-coated amount on CaS:Ce in three different stages shows that the CaS particle will be coated one molecular layer of Cu

x

S in the initial stage then 1-2

5 molecular layers in the second stage

and 2.5-3.5 molecular layers in the final stage

if We assumed that Cu

x

S grows homogeneously on the particle surface. But in fact Cu

x

S can not be grow in this way

its distribution relates to three different stages

so the variation of conductivity of phosphors also relates to three different stages or different surface defects. In the initial stage the conductive Cu

x

S grows tnainly on the crystal edge

therefore a reticulated conductive phase will be formed and the conductivity is very low

for this net is not complete enough. In the second stage

this net will be expanded and cover all of the surface

and therefore the conductivity sharply increases with copper-coated amount. In the final stage conductive phase will be formed mainly on the crystal boundary near the partical surface

and it only gives small contribution to the conductivity

therefore it tends not to increase again.