Why won't OnCollisionEnter work here (C#)

I’m obviously an idjut & missing something very basic…

I have a Camera colliding with an invisible Plane to trigger a GUI event
Plane has collider (even a rigid body though I doubt I need)
My Camera also has a Box Collider on it just to make sure

Why won’t my OnCollisionEnter script won’t work?

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;

public class triggerGUI : MonoBehaviour {

	public GameObject toAppear;
	public GameObject toDisappear;


	void OnCollisionEnter (Collision camera ) {
				Debug.Log ("Collide");
						toDisappear.SetActive (true);
						toAppear.SetActive (false);
		}
}

Thanks Y’all

~be

Thank you Baste
it is working!!
Here is the script:

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;

public class triggerGUI : MonoBehaviour {


	public GameObject toAppear;
	public GameObject toDisappear;

	void OnTriggerEnter(Collider camera) {
		Debug.Log ("Collide");
						toDisappear.SetActive (false);
						toAppear.SetActive (true);

		}
}