Self-aligned aperture masks having high definition apertures

Abstract

Self-aligned aperture masks are produced using a positive-acting photoresist ( 18 ) which is developed with a liquid developer. The apertures ( 30 ) of the mask have lower levels of inter-aperture variability than masks produced using mechanical transfer of toner particles (FIGS. 4 - 5 and 7 - 8 ), both for the apertures of a given mask and between masks.

What is claimed is:  
     
         1 . A method for making an aperture mask for a screen comprising: 
 (a) providing a substrate having a first side and a second side, the first side having an array of lenses associated therewith;    (b) applying a positive-acting photoresist to the second side of the substrate, said photoresist comprising at least one pigment dispersed in a photosensitive matrix which, upon exposure to actinic radiation, becomes soluble in a developer solution, said at least one pigment absorbing light in the visible range;    (c) exposing the positive-acting photoresist by passing actinic radiation through the array of lenses to form an exposure pattern in the positive-acting photoresist, said exposure pattern being a function of the optical properties of the lenses; and    (d) developing the positive-acting photoresist using the developer solution to remove photoresist which has been exposed to the actinic radiation and thus form apertures in the photoresist which will transmit visible light to a greater extent than regions of the photoresist that have not been exposed to the actinic radiation.    
     
     
         2 . The method of  claim 1  wherein the array of lenses is an array of microlenses.  
     
     
         3 . The method of  claim 2  wherein the array of microlenses is formed in the first side of the substrate.  
     
     
         4 . The method of  claim 3  wherein the substrate comprises a first layer and a second layer and the array of microlenses is formed by embossing the first layer of the substrate.  
     
     
         5 . The method of  claim 4  wherein the first layer is a photocurable resin.  
     
     
         6 . The method of  claim 2  wherein the array of microlenses is applied to the first side of the substrate.  
     
     
         7 . The method of  claim 6  wherein the array of microlenses is applied to the first side of the substrate using an adhesive.  
     
     
         8 . The method of  claim 6  wherein the array of microlenses is molded onto the first side of the substrate.  
     
     
         9 . The method of  claim 1  wherein the at least one pigment comprises pigment particles having a mean diameter below 500 nanometers.  
     
     
         10 . The method of  claim 1  wherein the at least one pigment comprises carbon black particles.  
     
     
         11 . The method of  claim 1  wherein the photosensitive matrix comprises the reaction product of a resin and a diazo oxide.  
     
     
         12 . The method of  claim 1  wherein the actinic radiation is UV radiation.  
     
     
         13 . The method of  claim 1  wherein the actinic radiation has a spatial distribution corresponding to the spatial distribution of visible light which will pass through the lenses during use of the screen.  
     
     
         14 . The method of  claim 1  wherein the developer solution is an aqueous solution having a pH of 9 or higher.  
     
     
         15 . The method of  claim 1  wherein the apertures have at least one cross-sectional dimension of less than 100 microns.  
     
     
         16 . The method of  claim 1  wherein the apertures have at least one cross-sectional dimension of less than 50 microns.  
     
     
         17 . The method of  claim 1  wherein the apertures have a low level of inter-aperture variability.  
     
     
         18 . Apparatus comprising: 
 (a) a substrate having a first side and a second side;    (b) an array of lenses associated with the first side of the substrate; and    (c) an aperture mask on the second side of the substrate comprising: 
 (i) a pigmented polymer layer comprising at least one pigment dispersed substantially uniformly throughout the layer, said pigment absorbing visible light, said pigmented polymer layer being either an unexposed positive-acting photoresist or an exposed, but not developed, positive-acting photoresist; and  
 (ii) a plurality of apertures which pass through the pigmented polymer layer, the locations of the apertures being based on the optical properties of the array of lenses;  
 wherein the apertures transmit visible light to a greater extent than the pigmented polymer layer.  
   
     
     
         19 . The apparatus of  claim 18  wherein the array of lenses is an array of microlenses.  
     
     
         20 . The apparatus of  claim 19  wherein the substrate comprises a first layer and a second layer with the array of microlenses being formed in the first layer.  
     
     
         21 . The apparatus of  claim 20  wherein the first layer is a photocurable resin.  
     
     
         22 . The apparatus of  claim 19  further comprising an adhesive layer between the array of microlenses and the first side of the substrate.  
     
     
         23 . The apparatus of  claim 18  wherein the at least one pigment comprises particles having a mean diameter below 500 nanometers.  
     
     
         24 . The apparatus of  claim 18  wherein the at least one pigment comprises carbon black particles.  
     
     
         25 . The apparatus of  claim 18  wherein the pigmented polymer layer comprises the reaction product of a resin and a diazo oxide.  
     
     
         26 . The apparatus of  claim 18  wherein the apertures have at least one cross-sectional dimension of less than 100 microns.  
     
     
         27 . The apparatus of  claim 18  wherein the apertures have at least one cross-sectional dimension of less than 50 microns.  
     
     
         28 . The apparatus of  claim 18  wherein the apertures have a low level of inter-aperture variability.  
     
     
         29 . The apparatus of  claim 18  wherein the aperture mask further comprises a non-pigmented polymer layer which is either an unexposed positive-acting photoresist or an exposed, but not developed, positive-acting photoresist, said non-pigmented polymer layer being closer to the second side of the substrate than the pigmented polymer layer.  
     
     
         30 . The apparatus of  claim 29  further comprising an adhesive layer between the non-pigmented polymer layer and the second side of the substrate.  
     
     
         31 . The apparatus of  claim 18  further comprising an adhesive layer between the pigmented polymer layer and the second side of the substrate.  
     
     
         32 . A rear projection television comprising the apparatus of claim  18 .