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Thread: Anti-reflective coating processes

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    Anti-reflective coating processes

    In my investigation of various laboratories one of the things that comes up is the process used for AR coatings, with many well respected labs using some version of dip coatings for their house AR's. I can find some good articles discussing the pros and cons of spin vs dip coatings. As I have been using Zeiss products for the last several years I am more familiar with their use of electron vapor deposition process for their coatings, but can't seem to find anything comparing this method to the spin or dip processes. Can someone with more insight into these methods explain the differences/pros/cons of the varying methods?

    Also, do you know which process is used for the bigger name coatings like Crizal/Super Hi Vision/EX3/Seiko Surpass or Extreme/DuraVision/Purecoat.......

    Thanks

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    Bad address email on file OptiBoard Gold Supporter Sean's Avatar
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    Wave Anti -reflective coatings comparison.

    EBPVD (Electron-Beam Physical Vapor Deposition) is used to deposit anti-reflective thin films. Ingots from the different materials to deposit are placed in a low pressure reactor to be evaporated. The atomic vapor condense on the substrates, placed above the source, to form the coating. Ion etching and heating are useful to promote adhesion and to obtain dense films. A quartz cristal microbalance is often necessary to control the thickness during the process.

    Then comes the question of organic or inorganic anti-reflective's.The least expensive for this type would be vacum disposition.And organics are usually spin coated.

    Also,
    the sol-gel method can be used to prepare anti-reflective coatings.The dip coating method is generally used as the deposition method,where the substrate is immersed and withdrawn at a controlled speed.There are several advantages of using dip coating. It is possible to build an experimental set up for this process. Furthermore, both sides are coated at the same time, and there are no particular substrate size limitations. The only thing i'm really not to sure about is
    the amount of light reflected by a dip or spin coating. In case of vacuum deposition one can almost come close to <1% . I hope this was somewhat helpful ..............with out being to long winded.



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    Quote Originally Posted by NVEYEDR View Post
    In my investigation of various laboratories one of the things that comes up is the process used for AR coatings, with many well respected labs using some version of dip coatings for their house AR's. I can find some good articles discussing the pros and cons of spin vs dip coatings. As I have been using Zeiss products for the last several years I am more familiar with their use of electron vapor deposition process for their coatings, but can't seem to find anything comparing this method to the spin or dip processes. Can someone with more insight into these methods explain the differences/pros/cons of the varying methods?

    Also, do you know which process is used for the bigger name coatings like Crizal/Super Hi Vision/EX3/Seiko Surpass or Extreme/DuraVision/Purecoat.......

    Thanks
    Pretty sure you are confusing thin film coating, such as AR, Mirror, and Band Pass coating, which is applied via physical vapor deposition, vacuum sputtering, or sol-gel.

    With hard coating, which is normally polymer based, and is normally applied via a dip or spin process with a UV or IR curing process.

    There are PVD hard coatings, but they are on the more expensive side for now, and inferior to their dip/spin coated counter parts in terms of durability.


    As far as I know/have seen, all premium AR coatings use a dip applied hard coat.

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    Ghost in the OptiMachine Quince's Avatar
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    One major difference our office sees is the effect of substrate matching. Hoya (possibly Seiko in the future? since they merged) uses a process that bonds the AR (hi vision, EX3, recharge) to the actual lens material so it is not just a top layer coating. They change the chemical make-up of the coatings depending on the lens material to make the best bond. This keeps down flaking, crazing, and other defects that AR can be subject too. Way less warranties with this process, though it is more time consuming.
    Have I told you today how much I hate poly?

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    Quote Originally Posted by Quince View Post
    One major difference our office sees is the effect of substrate matching. Hoya (possibly Seiko in the future? since they merged) uses a process that bonds the AR (hi vision, EX3, recharge) to the actual lens material so it is not just a top layer coating. They change the chemical make-up of the coatings depending on the lens material to make the best bond. This keeps down flaking, crazing, and other defects that AR can be subject too. Way less warranties with this process, though it is more time consuming.
    Interesting. I thought the benefit of index matching the hard coats to the substrate was the lack of newtonian rings visible (the weird rainbow rings that turn up on high index lenses with AR) I didn't realize it actually increased durability.

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    @Tallboy - You sound about right to me. Usually the index matching helps with the Newton's rings (Shameless plug: OPT Magazine article on exactly this). Problem with trying to index match is often the higher index coatings are harder/more expensive to get. They also tend to be less scratch-resistant, since the material itself isn't as robust as the lower index materials.

    From what we've noticed, the index matching isn't what's responsible for the reduction in crazing. Usually what does it is the dip coating process applies the coat more evenly on the lens, regardless of the index of the coating when compared to the lens. Spin coating tends to be less even across the surface of the lens (we're talking microns here, so not a lot, but enough). Since spin coating is less even, it expands less evenly when it gets warmer (like on the dash of a car). The uneven expansion then causes the AR coating on top to crack/craze.
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    Ghost in the OptiMachine Quince's Avatar
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    I don't have proof of durability other than less coming back to us for warranties. I may have grouped the crazing in with flaking issues... I know it definitely makes a difference for the latter though!
    Have I told you today how much I hate poly?

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    Ml43, I probably am as I really don't know as much about it as I wish I did which is why I am fortunate to have found this board. So the production methods all start off with some version of dip or spin (dip preferred?) for the hard coat and then the AR can be a separate process (vacuum/vapor/sol-gel). Does the Sol-gel method allow you to do both hard coat and AR at the same time? Or are the lenses dipped in one solution, then the next and so on, to build the "stacks"? From what has been explained to me, the vapor is done by ionizing different materials in order to build the stack, true? Is one method generally considered better out of vacuum/vapor/sol-gel or are they just different ways to skin a cat? Pros and cons to the methods? Thanks.

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