The cold light sheet is related to the working voltage and frequency, temperature, humidity and other factors, especially the frequency and humidity have the greatest impact on it, almost inversely proportional to the frequency, so the higher the working frequency, the faster the aging. In consideration of brightness and service life, the working voltage frequency is generally 400 ~ 1000Hz.
In addition to normal brightness attenuation, the cold light sheet (EL) also shows black spots and black spots during breakdown, which are mainly caused by improper materials or screen printing defects.
Low power consumption: generally, the capacitance value of El chip is not more than 0.4nf/cm2, and the current density is not more than 0.2ma/cm2 under the driving condition of 110V 400Hz. It can be adjusted according to the requirements of product brightness and driving circuit.
Low noise: in the use of mobile phones, the noise generated by El lights and driving circuits must be very
Small can't affect normal cell phone calls. Although the source of noise is complex, it can be avoided by proper driver circuit design.
Proper brightness: providing a certain brightness is the main role of EL lamps, but it is not that the higher the brightness, the better.
Aging performance test: generally, under the condition of 60 ¡æ temperature and 95% relative humidity aging, 100V / 400Hz driving operation is required, with half life of not less than 200 hours and no breakdown, black spot and other phenomena.
3¡¢ Brief introduction of cold light film making and selection of main raw materials
1. It is made by the thick film method of screen printing, and the working environment needs to have a dust-free purification workshop of more than 300000 levels.
Preparation of substrate: A. ITO substrate is made of ITO (indium tin oxide) evaporated on the surface of PET polyester film as the transparent front electrode of El photo plate; B. organic conductive paste is printed on special film as conductive substrate instead of normal ITO (screen printing of 120t-140t can be used).
Luminescent layer printing: luminescent powder and binder (organic polymer) are mixed into luminescent paste suitable for screen printing. The luminescent paste is printed on ITO substrate with a thickness of 30-40 ¦Ì m (60t-100t screen printing can be used).
Insulating layer printing: the barium titanate powder and binder (organic polymer) are mixed into insulating paste suitable for screen printing, and the insulating paste is printed on the light-emitting layer with a thickness of about 20-30 ¦Ì m (60t-100t screen printing can be used). Back electrode printing: the conductive silver paste is printed on the insulating layer to act as the back electrode, with a thickness of 8-12 ¦Ì m (80t-100t screen printing can be used).
Protective layer printing: UV curable ink is printed on the back electrode to play the role of insulation and protection (screen printing of 120t-140t can be used). Illuminated front graphic printing.
Assembly: ¡ð 1 cutting; ¡ð 2 sticking electrode; ¡ð 3 superplasticization (single side or double side); ¡ð 4 finished product detection; ¡ð 5 packaging.
2. The main raw materials for making EL film are ITO film or organic conductive paste, luminous powder, barium powder and organic adhesive (carrier).
Several problems in the production of El and their solutions. a. Printing defects are prone to black spots or breakdown. --------Check the screen, must be clean and smooth B, adhesion is not good, delamination phenomenon. ---------Select materials with good matching
c. Uneven printing will cause uneven light. --------The printing force should be kept constant. D. ITO conductive surface should be reversed. --------The accuracy of measuring resistance E and alignment. --------Use positioning hole to cross position F. keep materials properly.
---------Mark the surplus materials, and do not mix them together. G. there is bubble when printing conductive paste.
---------The screen should be clean, and there should be no dirt on the printed substrate. It is better to choose a screen with a high mesh number.