如何使得unity ui.image 获得循环纹理

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;


public class back_move_Screem : MonoBehaviour
{
    float scrollSpeed = 0.5f;
    
   public Material Back;
    void Start()
    {
        
        Back = GetComponent<Image>().material;
    }

    // Update is called once per frame
    void Update()
    {
        float offset = Time.time * scrollSpeed;
        Back.SetTextureOffset("_MainTex", new Vector2(-offset, -offset));
    }
}