Are printing techniques trade secrets? I'm wondering what type of printer, foil, cardboard, etc., is required to print holographic cards of the sort you might see in Magic or Yu-Gi-Oh. I can find nothing about this online, and I'm wondering how the companies themselves source the industrial printing equipment.
They are not trade secrets, but some technical information may be limited online because these companies only communicate with serious clients.
For metallic effects the printer prints white and 4-color ink on top of a board with foil layer. Areas with white behind the color will be opaque and not have holographic effect. Different holographic effects are created based on the type of foil layer. If you look for "holographic special effect foil" you can see foils come with different patterns and rainbow/color effects.
Here is an example of a company that works with holographic foil. You can see they use a lot of technical jargon and you have to reach out to them to learn the details of their capabilities. http://www.crownrollleaf.com/foils_holographic_patterns.html
Looking at holographic Pokemon cards, they use certain patterned foils (dots or stars) that may be custom made for them by their manufacturer.
This is only a partial answer.
The core technology originated out of 3M. I'm not sure their Laminates & Security Features page describes the "actual" technology used in the cards, but this is an application of that technology.
3M developed the first holographic driver's licenses etc.
For many years WOTC used the Belgian company Carta Mundi for the physical production of the cards. It is probably also why WOTC's headquarters in Europe, Middle East, and Africa is still in Belgium. Eventually, WOTC chose not to have all its production done with one company. The United States Playing Card Corporation (USPC), Shepard Poorman, Quebecor, and Yaquinto are all now confirmed WOTC printers.
Foil cards have an extra foil layer on the card that highlights certain parts of the artwork over others. A print coating - a very thin, clear protective finish - is applied over the top of all printed materials.
Konami manufacturers the Yugioh cards themselves of the TCG's printing the following is said, but for the life of me I cannot get details about their foiling process.
North America is the main distribution region for the Trading Card Game, including the countries of Canada and the United States with English, French and Spanish prints being officially distributed and legal for tournament play. Although all other TCG prints are legal as well.
Cards are printed in the United States and from there distributed to the region, Canada gets French cards from either a main print in the United States or from Europe when necessary. Spanish cards can be officially requested by stores and distributors for sale inside the territory, but this is rarely done, and this causes the Spanish print to be not as expensive as the English one, and this happens to the French print as well.
The main reason to be separated from the rest of the Americas is the legality of promotional cards. Many such promotional cards however easily reach the Latin America and the Caribbean region, mostly Mexico, despite being illegal until officially reprinted in those regions. Following the discontinuation of the Shonen Jump promotional cards, there were considerably fewer differences in card legality between the regions.
JapanThe Pokémon Card Laboratory (PCL), located in Japan, is the designer of new cards and the ultimate authority on any matter relating to the Pokémon Trading Card Game.