Danke an [Johannes][1] für die Antwort. Es hat prima funktioniert. Einfach textwidth **textwidth** mit columnwidth **columnwidth** ersetzen. Hier dann der fertige Zitatblockquelltext:
\thispagestyle{empty}% for cropping
\usepackage{microtype}
\usepackage{tikz}
\usetikzlibrary{backgrounds}%background
\thispagestyle{empty}
\makeatletter
\tikzset{%
fancy quotes/.style={
text width=\fq@width pt,
align=justify,
inner sep=1em,
anchor=north west,
minimum width=\columnwidth,
},
fancy quotes width/.initial={.8\columnwidth},
fancy quotes marks/.style={
scale=8,
text=white,
inner sep=0pt,
},
fancy quotes opening/.style={
fancy quotes marks,
},
fancy quotes closing/.style={
fancy quotes marks,
},
fancy quotes background/.style={
show background rectangle,
inner frame xsep=0pt,
background rectangle/.style={
fill=gray!25,
rounded corners,
},
}
}
\newenvironment{fancyquotes}[1][]{%
\noindent
\tikzpicture[fancy quotes background]
\node[fancy quotes opening,anchor=north west] (fq@ul) at (0,0) {``};
\tikz@scan@one@point\pgfutil@firstofone(fq@ul.east)
\pgfmathsetmacro{\fq@width}{\columnwidth - 2*\pgf@x}
\node[fancy quotes,#1] (fq@txt) at (fq@ul.north west) \bgroup}
{\egroup;
\node[overlay,fancy quotes closing,anchor=east] at (fq@txt.south east) {''};
\endtikzpicture}
\makeatother
[1]: http://texwelt.de/wissen/benutzer/14/johannes
