Standard UV systems compared to LED UV sestems

Discussion in 'UV' started by Griznarf, Mar 6, 2011.

  1. Griznarf

    Griznarf Senior Member

    Joined:
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    Messages:
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    Location:
    Ontario, Canada
    I have been asked by one of my customers if it is possible to convert their press to LED UV instead of conventional UV lamps. Has anyone used the new LED UV systems and how does it compare to the conventional UV systems? What are the pro's and con's?
    I have done some research and this is what I have come up with;
    Conventional UV;
    High power consumption
    High heat output
    Wider range of UV light 200 - 400nm wavelength
    High press speeds
    Requires external cooling, air or water.
    Lamp life about 1000 hours
    Wide range of ink's, varnish's and coating's
    Creates ozone
    Hazardous light output, must be shielded
    Must protect wiring, seals etc.

    LED UV:
    Less power consumption
    Less heat output
    Narrow wavelength 395 nm +/- 5%
    Press speeds - unknown
    No external cooling required
    Lamp life 20000 -50000 hours
    Limited ink's, varnish and coating's
    No ozone
    Less hazardous light output

    Is conventional UV more forgiving than LED UV?
    How much of a cost savings is there to the LED UV system if you have to purchase specialized inks for the LED UV costing as much as 20% more than conventional inks?
    Which do you like better, conventional UV or LED UV?
     
  2. manccoo

    manccoo New Member

    Joined:
    Mar 2011
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    Location:
    Germany
    Hello Griznarf,

    It is a lot of hype in the market about LED-UV like low power consumption, cold UV, long life time, less hazardous radiation, no ozone plus further benefits and features compared to conventional UV-systems.

    LED-UV units are a longer time in the market and in use for different applications. Firstly mainly used for stationary applications like to fix components in the medical or electronic industry with an UV adhesive. This is still a main application. Today LED-UV systems will be used for curing inks in the printing industry as well. For example, the Japanese sheet-fed printing press manufacturer Ryobi introduced a LED-UV system at the DRUPA 2008 in a sheet-fed offset press. In the meantime are a lot of articles published in printing magazines about this technology following by presentations and discussions on conferences and events.

    What is the current status? You made some research and found most of the main features and differences of both technolodies (LED and conventional). Here are my comments to what you have found:

    Less power consumption of LED-UV. This is only correct in the first view if you compare a LED-UV system using LED UV-inks with a conventional UV-system using standard UV inks. A LED-UV-system is currently less efficient compared to a conventional UV-system. The intensity is also less. Further it operates with a very small wavelength range with peaks at 375, 385, 395 and 405 nm (these wavelength mainly used at the moment). Therefore LED-UV need special UV-inks. UV-inks with photoinitiators absorbing in the emitted wavelength range of the LED´s and with a high reactivity due to the low efficiency and intensity. These inks are also curable with conventional UV-systems. Tests showed that these inks can be cured with only one conventional UV-module with low power (max. 80 W/cm or less) at 15.000 sheets per hour in a sheetfed press (4/5 colors) without any problems. The total energy consumption of this unit is lower than with a LED-UV system. Komori introduced a low power conventional UV-unit from their Japanese supplier "Eye Graphics" for high reactive inks (like LED-UV inks) at the IPEX 2010. They named it H-UV (Hybrid UV). It is just a low power UV-module without generating ozone. The only new part is the high reactive UV-ink. The UV-technology is available since many years. Also other press manufacturers like manroland from their supplier "Eltosch" have such a low power UV-system available. They call it LEC (Low Energy Curing).

    A further problem of the LED-units are their low intensity. The units/modules have to be very near to the substrate surface (approx. 15 mm) to cure the inks. Due to this you cannot use them for packaging printing in sheetfed presses. The sheets are to strong and will touch the units. It is also a problem for food packaging due to the high amount of photoinitiators in the ink.
    Coatings are not really available (just first developments). In sheetfed presses are only installations above a cylinder possible and not in the delivery/extended delivery because of the high distance to the substrate.

    LED-UV is without IR and therefore no heat radiation. On the other hand heat increases the reactivity of UV-inks and therefore the curing efficiency. Heat is only not welcome if it disturbs the process and quality like a bad register when printing on plastics or heats up machine parts.

    LED UV-units need also an external cooling. They are in general water cooled. What they do not need is air cooling. Conventional UV-systems can be air cooled only or air and water cooled (water cooling for the housing and the shutter and air cooling for the UV-lamp).

    LED-UV does not produce ozone. If you use ozone free UV-lamps in a convenional UV-system you also do not produce any ozone. If you use high reactive LED-inks you can use ozone free doped lamps with a main output in the wavelength range of the LED-inks. Normally ozone free UV-lamps cutt off some short wave UV, however for LED inks not needed.

    LED lifetime is in the range of 20.000 hours. A UV-lamp between 1.000 and 1.500 hours. Lets assume only 1.000 hours. So you need 20 UV-lamps to reach the 20.000 hours lifetime of the LED. This is only the half truth. The important information is that the exchange of 20 UV-lamps is much cheaper than one exchange of the LED´s. The most expensive parts in a LED-UV system are the LED arrays.

    The price of an LED UV-system is higher as for a conventional UV-system. If we use only one low power conventional UV-module with LED inks than the price is very high compared to a conventional UV-system.

    Advantages of LED-UV systems are also that they need no start-up time and shutters. Further is a format size switching possible. The monitoring of single LED´s is very difficult.

    Finally I would like to state that LED-UV technology has already discovered some markets and applications. The efficiency and the output is not high enough for high speed applications. The necessary investment is still very high. The energy saving is not low comparing with a conventional UV-system if you cure LED-inks with conventional UV. Special inks (high eactive UV-inks) are necessary. High reactive UV-coatings are just at the beginning and in general not really available.
    However, LED-UV technology is a future technology and will get its market share. The speed this will happen depends on developments in the semiconductor industry and the price decrease. Both technologies (LED and conventional) will have their applications and markets.

    My general recommendation at the moment is to invest in a conventional UV-system, especially for the packaging market. If respective high reactive inks available for your application with the requested properties you can use them also with your conventional UV-system. You can use only one UV-module and cure it with very low energy consumption. This is the better strategy, also if you want to use UV coatings.

    I hope that my explanations give a little overview about both technologies and the current status.
     
  3. tbeusch

    tbeusch New Member

    Joined:
    Oct 2013
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    Location:
    South Florida
    Hello Manccoo,
    Your comments were very interesting, however they are now over 2 years old.
    In your opinion, where is LED UV now?
     
  4. UVLED

    UVLED New Member

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    Jan 2014
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    Location:
    sc
    uvledforums UV LED Printers

    For an updated directory of UV LED Printers in the market, this site has a nice compilation of UV LED Printer OEMs, brands, and models:

    www.uvledforums.com

    The page has a convenient listing of uv-led printers, including pricing, instruction manuals, and other end users of the UV printer information.

     

  5. Ade

    Ade Member

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    Dec 2013
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    Hi

    Question I have how do you determine the drying of these systems testing I have undertaken shows the sheets to be touch dry but not fully cured it certainly wouldn't be accepted as fully cured in a UV shop, so if it is say "soft cured" is it cured or not?
     
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