Abstract A shadow mask is initially prepared with apertures dimensioned for printing a latent image of the pattern of apertures onto the faceplate of a color picture tube and, after this has been accomplished, the mask is re-etched to enlarge the apertures to a desired size in a final size relationship from aperture to aperture. An improvement in the re-etch process is achieved by enlarging the apertures of the shadow mask by differentially applying a suitable etchant thereto such that more etchant is applied to a second set of apertures susceptible to enlargement at a slower rate than to a first set of apertures susceptible to enlargement at a faster rate whereby the apertures are enlarged without disrupting the pattern. An apparatus for use with such process is also provided.
A method in accordance with claim 1 where said etchant is differentially applied to said mask such that more of said etchant is applied to said second set of apertures than to said first set of apertures by first applying said etchant to said second set of apertures to thereby render said second set of apertures larger than said first set, and thereafter applying said etchant to all of said apertures.
Claim 2
Dependent Claim
37 words
A method in accordance with claim 2 where said etchant is first applied to said second set of apertures by spraying said etchant onto said mask while shielding said first set of apertures from said etchant spray.
Claim 3
Dependent Claim
40 words
A method in accordance with claim 1 where more of said etchant is applied to said second set of apertures than to said first set by spraying said etchant onto said mask while partially shielding said first set of apertures.
Claim 4
Dependent Claim
30 words
A method in accordance with claim 1 where said etchant is applied to said mask by spraying said etchant onto said mask in a substantially normal direction to said mask.
Claim 5
Dependent Claim
25 words
A method in accordance with claim 5 where said etchant is sprayed onto said mask by a rotating array of a plurality of spray nozzles.