Thick film getter paste compositions with pre-hydrated desiccant for use in atmosphere control

Abstract

The invention is directed to a screen-printable getter composition comprising: (a) glass frit; and (b) pre-hydrated desiccant material; dispersed in (c) organic medium. The present invention further relates to a getter composition utilizing low-softening temperature glasses comprising, based on weight %, 1-50% SiO 2 , 0-80% B 2 O 3 , 0-90% Bi 2 O 3 , 0-90% PbO, 0-90% P 2 O 5 , 0-60% Li 2 O, 0-30% Al 2 O 3 , 0-10% K 2 O, 0-10% Na 2 O, and 0-30% MO where M is selected from Ba, Sr, Ca, Zn, Cu, Mg and mixtures thereof. The glasses described herein may contain several other oxide constituents that can substitute glass network-forming elements or modify glass structure. The desiccant material is pre-hydrated to reach its saturation level of moisture absorption. The process of pre-hydration can be done by exposing the desiccant in a normal temperature/humidity environment of for example, 25° C. and 50-60% RH. for 24 to 48 hours or up to the time when weight gain (due to moisture absorption) stops increasing. An accelerated hydration process in a chamber with higher than normal humidity level (i.e. 50% Relative Humidity) is also applicable to shorten the time of exposure to fully hydrate the desiccant material.

1 . A screen-printable getter composition comprising: 
 a) glass frit; and    b) desiccant material; dispersed in    c) organic medium.    wherein the desiccant material is fully hydrated prior to its use in the preparation of the getter composition.    
     
     
         2 . The composition of  claim 1  wherein said desiccant material is hydrated by exposing said material in an ordinary paste production environment to reach pseudo steady state weight gain due to the moisture absorption.  
     
     
         3 . The composition of  claim 1  wherein said desiccant is hydrated by exposing the material in a controlled temperature and humidity environment to reach pseudo steady state weight gain due to the moisture absorption.  
     
     
         4 . The composition of  claim 1  wherein said organic medium is comprised of organic polymeric binder and volatile organic solvent.  
     
     
         5 . The composition of  claim 1  wherein said organic polymeric binder is selected from the group comprising ethyl cellulose, ethyl hydroxyethy cellulose, wood rosin, mixtures of ethyl cellulose and phenolic resins, polymethacrylates of lower alcohols, monobutyl ether of ethylene glycol monoacetate, and mixtures thereof.  
     
     
         6 . The composition of  claim 1  wherein said volatile organic solvent is selected from the group comprising ethyl acetate, terpene, kerosene, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol, high boiling alcohols, alcohol esters, and mixture thereof.  
     
     
         7 . The composition of  claim 1  comprising 5 to 55 weight percent glass frit, based on total composition.  
     
     
         8 . The composition of  claim 1  comprising 5 to 65 weight percent of said desiccant material, based on total composition.  
     
     
         9 . The composition of  claim 1  comprising 30 to 55 weight percent of said organic medium, based on total composition.  
     
     
         10 . The composition of  claim 1  wherein said glass frit comprises: 1-50% SiO2, 0-80% B2O3, 0-90% Bi2O3, 0-90% PbO, 0-90% P2O5, 0-60% Li2O, 0-30% Al2O3, 0-10% K2O, 0-10% Na2O, and 0-30% MO where M is selected from Ba, Sr, Ca, Zn, Mg and mixtures thereof.  
     
     
         11 . A method of moisture control comprising: 
 a) providing the getter composition of  claim 1;     b) applying said getter composition to a device; and    c) processing said getter composition and device to volatilize the absorbed moisture in the desiccant material and organic polymeric binder and sinter the glass frit with the desiccant.    
     
     
         12 . The method of  claim 11  further comprising sealing said device.  
     
     
         13 . A device made by the method of  claim 12 .  
     
     
         14 . The device of  claim 13  wherein said device is selected from a light emitting diode device, electroluminescent device, field emission display device, surface emission display device, plasma display panel device, cathode ray tube device, and liquid crystal display device.