Set Attribut Read Only dengan background abu-abu

{   
   border:false,
   margin: '5px 0px 0px 5px',
   items: [{
    xtype      : 'fieldcontainer',    
    items: [{     
      xtype      : 'textfield',
      width: 75,
      id         : 'batch_des',
      name       : 'batch_des',
      allowBlank : true,
      readOnly : true,
            fieldStyle  :'background-image:none;background-color:#BDBDBD', 
    }]
   }]
  }