highlighting displays to much

[aowen]

i am using solr 4.3.1 and want to highlight complete sentences if possible or 
at least not cut up words. it it finds something the hole field is displayed 
instead of only 180 chars

the field is:
<fieldType name="text_de" class="solr.TextField" positionIncrementGap="100">
<field name="plain_text" type="text_de" indexed="true" stored="true" default="" 
/>      

solrconfig setting for highlighting:
       <str name="hl">true</str>
       <str name="hl.fl">plain_text title description</str>
       <str name="hl.simple.pre">&lt;b&gt;</str>
       <str name="hl.simple.post">&lt;/b&gt;</str>
       <str name="hl.snippets">5</str>
           <str name="hl.fragsize">180</str>
           <str name="hl.fragmenter">regex</str>
           <str name="hl.regex.slop">0.2</str>
           <str name="hl.regex.pattern">\w[^\.!\?]{20,160}</str>