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 
        showDataTips="true"
        dataProvider="{dp}"
        width="100%"
        height="100%">

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

    <!-- . . . -->

</mx:LineChart>