The possible issues lies in default index.css in cordova. Check if the body element has style defined for "text-transform:uppercase".
Atleast that was the issue for me, after removing this from body element in default index.css if you are using in your application, may help you as well.
For me I was using gurmukhi/punjabi fonts, and after the above line removal from index.css it just worked like charm with below css definiitions only
Example :
.demo {
font-family: anmol
}
@font-face {
font-family: anmol;
src: url(../fonts/anmol.ttf);
}