| Summary: | 碩士 === 文化大學 === 造紙印刷研究所 === 83 === Screen Squeegee is a simple but quite important printing tool.
Young M. (1988) indicate there are 8 variances at least could
affect or control tone reproduction, hardness is one of those.
For line art, It''s not apparent that ink deposit influence on
solid ink density. But for halftone dot, Total tine density
affects by IFT(ink film thickness) and DDP (dot area
percentage) , so that It varies more than line art. For keeping
density constanting, to approach quality control goal. This
research studies how screen Squeegee Hardness influence on
screen printing tone reproduction qualities, tone items
including TTD (total tine density), tone reproduction curve, DG(
dot gain) and PC(print contrast).Dependent variable is Squeegee
Hardness, indepedent variable is TTD of 11 tone grades of gray
scale on print layout printed by screen press. We draw 31
sheets randomly from qualtied printed sheets preselected with
SPC(statistical process contral) to provide for raw data
measurement. 1 Squeegee hardness has significant influence on
TTD, DG and PC. 2 Squeegee hardness is negative relation with
TTD and DG, but is positive relation with PC. 3 Under different
Squeegee Hardness, plate-press curve show S-shape. It exists
quite difference from U-shape of ideal plate-press curves.
Research finds that hardness above 67.43o, curves vary
regularly, under 67.43o change irregularly. Squeegee Hardness
between 67.43o and 82.7o, plate-press curves downward with
hardness increase, but It shows a constant tendency. 4 Squeegee
Hardness between 67.43o and 82.7o, It''s TTD, DG and PC are is
variating constantly. It is suitable for Screen Printing .
Although hardness 93. 27o is best for tone quality but not for
other Printing requirement. 5 Finding that inter-active among
Squeegee 8 variances, DG Maximum point moves from 50% dot area
to 60% area with hardness increase and then fixes at 60% dot
area. 6 Best regression model is : y=b0+b1x1+b2x2+b3x3+b4x4
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