如何去除FLEX LINECHART 线条阴影

<?xml version="1.0"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
verticalAlign="middle"
backgroundColor="white">
<mx:LineChart id="lineChart"
showDataTips="true"
dataProvider="{dp}"
width="50%"
height="50%"
seriesFilters="[]">

<mx:backgroundElements>
<mx:GridLines horizontalTickAligned="true" verticalTickAligned="true">
<mx:horizontalFill>
<mx:SolidColor color="haloBlue" alpha="0.2" />
</mx:horizontalFill>
<mx:horizontalAlternateFill>
<mx:SolidColor color="haloSilver" alpha="0.2" />
</mx:horizontalAlternateFill>

or

<mx:LineChart id="lineChart"
showDataTips="true"
dataProvider="{dp}"
width="100%"
height="100%">

<!-- series filters -->
<mx:seriesFilters>
<mx:Array />
</mx:seriesFilters>

<!-- . . . -->

</mx:LineChart>