<form name="newCarrierForm">
<td><input  ng-model="vm.newCarrier.Arrival" ng-pattern="vm.timeRegExp" ng-trim="false" ng-required/></td>
<td><button type="button" ng-disabled="newCarrierForm.$invalid"
                            class=" btn btn-success" ng-click="vm.add()" >Add</button></td>
 </form>

vm.timeRegExp = /^((0[0-9]|1[0-9]|2[0-3]):[0-5][0-9])$/;