Hello Pochi,
Your situation is "classic." I have responded to this same question in the Ask column, over and over to people whose loved ones refuse treatment.
Get one thing straight: you can't convince someone that he is ill if he lacks awareness that he has an illness. This lack of awareness, what is called anosognosia, is actually a symptom of the schizophrenia caused by a disturbance in the brain.
The sooner you reconcile that your job is NOT to "convince him he's sick" but to get him in treatment, the easier it will be for everyone involved.
I've answered at least five of these questions like yours, and I will tell you what I've told the others, and what I will tell the next person down the line: read the book, I Am Not Sick, I Don't Need Help by Xavier Amador, who has coached over ten thousand people in how to talk to their loved ones so that the person is persuaded to take meds.
The cornerstone of his philosophy is "Motivational Interviewing," and you use that to find out what the person's goals or dreams are, and build a relationship of trust so that when he talks to you about his hopes, you have the segue to suggest that taking meds would enable him to achieve what he wants in life.
His illness didn't come on overnight, and this situation won't be solved in a day.
So I urge you to read the Amador book, and as soon as possible, get it out of your head that your job is to convince your father he's sick. In his mind, he's not sick. This belief may never change and may persist throughout his life, yet even though he believes this, he will take the medication if you can show him it will get him what he wants.
Xavier Amador's brother, Henry, after many years of non-compliance, started taking the meds when Amador used the techniques outlined in the book I recommend. Yes, it seems unlikely, but people who lack the insight that they're ill will take the medication if they see a personal benefit. It's the old adage "What's In It For Me?" This is a big motivator.
Try it, let us know how it goes.
Best wishes,
cb