How to display 20 2-digits numbers?
... i need to display 20 independent 2-digit numbers that are located in different places. ... I guess acceptable digit height can be in a range of 1 - 1.5 mm




It's not at all clear what you're trying to do here and how far apart these "different places" are (within 10s of mm of each other or on different continents) and I haven't seen 1.5 mm seven-segment displays since I peered into the TI30 calculator I purchased in 1977. 


  Well, after some thinking it became obvious that 7-segment displays would require enormous amount of pins or expensive driver ICs.




Figure 2. Seven segment displays typically require seven pins (one for each segment and, optionally, an extra one for the decimal point) + one pin for each digit. Source: Multiplexed seven-segment displays.

If the displays are in close proximity then you need seven pins + one per digit. (So the eight-digit display in the TI30 would require 16 pins to drive it.) If you haven't got that many pins you may need to look at shift registers or some other way of multiplexing at each display or group of displays.

See the linked article for a little more on the topic. Edit your question to clarify if this doesn't answer your question.