Navigation in Ionic 2

Hi,
i am tring to navigate to another page, and on click the new page pops in bat the first page still exist on the view.
MY CODE:
import {Page, NavController} from 'ionic/ionic';
import {SignupPage} from '../signup/signup';
/*
Generated class for the WelcomePage page.

See http://ionicframework.com/docs/v2/components/#navigation for more info on
Ionic pages and navigation.
*/
@Page({
templateUrl: 'build/pages/welcome/welcome.html',
})
export class WelcomePage {
constructor(nav: NavController) {
this.nav = nav;
}
goToPage(){
this.nav.push(SignupPage);
};
}

i get on click tow page content + back button on the same page