The original poster is correct. Without the backlight layer lit, an LCD screen cannot display text or images; all we see is black, just like when your phone/laptop is off. As a professional screen manufacturer technician, I will provide a professional yet practical explanation from the perspectives of LCD structure and display principles.
Simply put, a complete LCD screen capable of displaying applications consists of two parts: a backlight and a panel. The panel is composed of an upper and lower glass substrate sandwiching a layer of liquid crystal. The upper glass substrate is called the color filter glass, and it has regularly distributed red, green, and blue color blocks separated by black blocks. This is the key to the color display of an LCD screen.
The TFT-array circuit board has circuit layers, a surrounding adhesive layer bonding the upper and lower glass substrates, and polarizers on the outer surfaces of the upper and lower glass substrates. The polarizers on the upper and lower substrates are orthogonal. Backlight light passing through the lower polarizer becomes polarized light with a single propagation direction. Without the intermediate liquid crystal layer, the backlight light cannot directly penetrate the upper and lower substrates to reach the human eye.
At this point, the liquid crystal begins its performance: due to the electrical characteristics of the liquid crystal, it will be twisted under the control of the microcircuit on the TFT circuit board, changing the propagation direction of polarized light. Different voltages control the liquid crystal to twist to different degrees, thereby controlling the amount of backlight transmitted. Each red, green and blue sub-pixel area can independently control the degree of liquid crystal deflection, thus enabling the synthesis of images of different colors.