UV inkjet printing technology application (4)

In order to meet the requirements of the UV lamp device described above, the following design principles are very important.

Irradiation device

In order to achieve a UV illumination that is both compact and high-intensity, the light valve diameter and reflector design are important. When the same energy is input into the light valve, the finer the diameter, the higher the energy density per unit volume. As a result, the number of photons output per unit area per unit area increases, thereby increasing the illumination illuminance.

About 70% of the UV-irradiated energy received by the substrate is obtained via a reflector. For this reason, the shape of the reflector and the UV reflection coefficient become important factors. In order to obtain high-intensity UV illumination, the shape of the reflector is preferably elliptical. It is important to place the lighted lamp valve at one focus of the ellipse and the irradiated substrate should be placed at another focus of the ellipse.

Furthermore, the reflection efficiency of the reflector is also related to the surface finish of the reflector, and the illuminance efficiency of the spectral band required for curing will change, so it is also very important. When it is desired to suppress the influence of the thermal energy to the irradiated substrate, a dichroic-reflective reflector that absorbs from the long wavelength region to the infrared region but reflects only the ultraviolet region should be used.

Since 70% of the UV energy reaches the substrate via the reflector, once the surface of the reflector is covered with dust and the like, illumination illumination decreases, so the key design is to ensure that the reflector is clean.

Luminescence spectrum and stability

UV light lamp valve has a variety of characteristics of the light band, so it is necessary to choose the best light valve for UV curing ink.

The UV curing lamp device is divided into an electrode lamp device that applies a high voltage to a filament of a light emitting lamp valve to make it emit light, and an electrodeless lamp device that does not have a filament in a light emitting lamp valve and emits light by absorbing microwaves. Lights. The experiment proved that the electrodeless lamp has stable output and spectrum because it has no filament.

Power device

The use of solid-state switch engine technology constitutes a high-voltage circuit power supply device, its power supply parts not only to achieve a compact, lightweight, power saving, but also to achieve a stable light output and variable adjustment, and then in a short time to complete the lamp ON/OFF control, so there is no need to set the shutter. According to this, in addition to curing the ink, it is possible to suppress the influence of the lamp on the inkjet printing mechanism. Figure 6 shows the ON/OFF output characteristics.

Lamp design

With fixed print heads or mobile print heads, the UV lamp design requirements are different. In the case of a fixed print head, it is possible to further compact the used UV lamp fixture and increase the illuminance output.

Figure 7 (see next page) is a lamp unit that was recently developed by Fusion UV and mounted on a mobile printhead printer. The lamp device is an electrodeless lamp with a luminous valve length of 1 inch. The microwave source is not at the light source but at the power source. Therefore, the size of the light source is only 8.6 x 8.6 x 4.6 cm. It is very compact, weighs only 200g, and has an illuminance of 1200mW/cm2.