Q Academy

A successful AR coating lab needs to provide a good quality product to its customers. In order to do so, the lab must conform to well established practices and procedures. It is the purpose of this document to provide an overview of the best practices for your lab.

NOTE: This document is an overview. Detailed step-by-step best practices are equipment/process specific.

Topics Covered

  • Personnel
  • Lab Environment
  • Job Preparation
  • Initial Inspection and Hand Cleaning
  • Ultrasonic Cleaning
  • Backside Hardcoating
  • Dip Hardcoating and Cure
  • Degassing
  • Fixturing
  • AR Coating
  • Flip/Final Inspection (Unloading)
  • Bead Blasting
  • Quality Assurance
  • Know Your Systems and Processes

Personnel

Well-trained and well-instructed staff is essential. Each phase of lens handling and processing depends on personnel following best practices repeatably and consistently.

Materials and Equipment

The following items should always be worn in the AR lab, so should be available and readily accessible to the staff:

  • Powder/lint-free gloves
  • Lab coats (laundered regularly)
  • Disposable masks
  • Eye protection
  • Disposable show covers (or sticky mats at each entrance)

NOTE: Making these practices A HABIT will help reduce chances of coating failure associated with lens handling and processing.

Lab Environment

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In order to help ensure repeatable, consistent results, the environment in the lab needs to be maintained and monitored.

Environmental Specifications

  • Relative Humidity = 45% ±5%
  • Temperature = 70° ±2°F
  • Air Quality = Class 100,000

Periodic Monitoring

  • Log the temperature and humidity periodically. Take action if environment is not to spec/function.

Weekly Cleaning

  • Every week, the entire room should be wiped down with damp, lint-free wipes.

Every Shift

  • Every shift, the following housekeeping tasks should be done and documented:
    • Wipe down inside of oven with clean/damp, lint-free wipes and 99% pure isopropyl alcohol (IPA)
    • Wipe down horizontal surfaces with clean/damp, lint-free wipes and IPA (99%)
    • Sweep and mop floor
    • Log DI water quality

Job Preparation

Separate Jobs

Separate jobs into two groups and place in separate areas:

  • Sensitive lenses, including:
    • Hi index
    • Transitions
    • Glass
    • Thin center thickness
    • Knife-edge
    • Wafer
    • Polaroid
  • All other lenses

NOTE: Generally, lenses over 1.60 index and/or with special properties will need to skip the first ultrasonic tank.

Special Instructions

  1. Take note of any special instructions written on the job data sheet/envelopes and separate if necessary. Examples are:
    1. Backside-only coating
    2. Match coating
    3. Strip
    4. Recoat
  2. Remove lenses from their tray/envelope and make a trace pattern on the sheet/envelope.
  3. Place lenses on top of the sheet/envelope.
  4. Glass lenses need to be processed differently than others.

Initial Inspection and Hand Cleaning

Initial inspection is critical, as it is the only time defects can be identified as not originating in the AR lab.

Materials and Equipment

  • Black background
  • Inspection lamp
  • Lint-free cloth
  • IPA (99%)
  • Progressive mark remover
  • Lens cleaning solution (1 gal DI water + ½ tsp Dawn dishwashing detergent)
  • Ultrasonic cleaning fixtures

Hand Cleaning

  1. Hand clean each lens with good attention to detail. The ultrasonic cleaning system will not remove all defects, so all of the following must be removed by hand:
    1. Smudges
    2. Streaks
    3. Dust
    4. Specks
    5. Coatings
    6. Films
  2. If there are ink marks or factory progressive marks on the lens, remove them with a non-acetone ink remover.
  3. Use cleaning solution and a lint-free cloth to remove all contaminants from the lens.
  4. Rinse the lens using DI water, then dry it.
  5. After cleaning, inspect each lens for scratches and defects using the inspection lamp against the black background.
  6. Mark any defects on the trace pattern on the sheet/envelope.
  7. Once the lens is clean, place it in the ultrasonic lens fixture/basket.
    1. On the envelop or job ticket, note which position and which basket the job is in.
    2. Keep the two groups (Sensitive, Other) separate.
  8. Run all Polycarbonate jobs on standard recipe; run CR-39 and Hi Index material-specific recipes. Always run problematic lenses (Transitions, Trivex, some Hi Index) through material-specific recipes.
    1. NOTE: In some cases, it will be required to completely strip sensitive jobs prior to dip coating.
  9. Once the ultrasonic basket is full, it is ready to be put in the ultrasonic cleaning unit.

REMEMBER: AR coatings highlight any and all defects on the lens prior to coating.

Ultrasonic Cleaning

Materials and Equipment

  • Ultrasonic cleaning system
  • Ultrasonic cleaning fixtures
  • Ultrasonic cleaning detergents
  • DI water (18-12 mega ohm)
  • pH test strips

Ultrasonic Considerations

  1. Ultrasonic cleaning systems require systematic scheduled cleaning and maintenance in order to produce repeatable results.
  2. Prepare your ultrasonic cleaning system per the manual.
  3. The amount of detergent used in soap tanks is determined by tank size and detergent used.
  4. Detergents have a shelf life. Do not use old detergents.
  5. Be sure to pour the correct amount of detergent into each tank using a clean container.
  6. After each 8-hour shift, drain soap tanks, then refill with fresh detergents.
  7. When placing the basket in the ultrasonic unit, make sure to skip the first bath as required for the sensitive group of lenses and special instruction lenses (strip and recoats).
  8. Be certain that all the lenses remain securely in their fixtures as the lenses move through the cleaning system.
  9. When the lenses complete the ultrasonic cycle, immediately transfer them to the degas oven.
  10. Test pH of soap tanks weekly. Do not allow DI water quality to drop below 12 mega ohms.

NOTE: Generally, time in each tank is 4 minutes.

Backside Hardcoating

Hardcoating is the foundation on which the rest of the AR coating is built. Bad hardcoating equals bad AR coating, so adhering to good hardcoating practices and procedures is essential for high quality AR coatings.

Materials and Equipment

  • Black background
  • Inspection lamp
  • Backside hardcoating system
  • Backside hardcoat solutions (use Quantum-tested materials)
  • Spectrophotometer
  • UV dosimeter
  • Tachometer

Backside Hardcoating Considerations

  1. Lenses must be clean before applying hardcoating; inspect carefully.
  2. Hardcoating systems require systematic scheduled cleaning and maintenance in order to produce repeatable results.
  3. Hardcoat solution has a pot/shelf life. Change it out per provided specifications.
  4. Backside hardcoating systems have two variables which can affect the performance of the hardcoating:
    1. Thickness
    2. Curing
  5. Hardcoating thickness needs to be between 3-5 microns (ref. manufacturer’s spec).
    1. Thickness is controlled by hardcoating viscosity and the the spindle speed of the backside hardcoating system.
    2. If the hardcoating is too thin, it will crack.
    3. If the hardcoating is too thick, it will not cure properly.
    4. Use a spectrophotometer to measure thickness.
  6. Curing is controlled by the UV lamp and cure time in the backside hardcoater.
    1. Over-cured hardcoating looks yellow.
    2. Under-cured hardcoating looks clear and feels dry.
    3. Under-cured hardcoating will have less scratch resistance and poor adhesion.
    4. Use a UV dosimeter to check the UV lamp.
    5. Use a tachometer to check spindle speed.

Dip Hardcoating and Cure

As stated earlier, hardcoating is the foundation on which the rest of the AR coating is laid. A high quality thermally-cured dip hardcoat provides the best scratch resistance and most durable foundation for AR coatings.

Materials and Equipment

  • Black background
  • Inspection lamp
  • Dip hardcoating system
  • Dip hardcoating fixtures
  • Dip primer (use Quantum-tested material)
  • Dip hardcoating (use Quantum-tested material)
  • Solvents
  • Percentage of solids management kit
  • DI water (18-12 mega ohm)
  • pH strips
  • Spectrophotometer
  • Cure oven

Dip Hardcoating Considerations

  1. Lenses must be clean before applying hardcoating; inspect carefully.
  2. Hardcoating systems require systematic scheduled cleaning and maintenance in order to produce repeatable results.
  3. Primer and hardcoat solutions have a pot/shelf life.
    1. Change filters, primer, and hardcoating out according to provided specifications.
  4. Dip hardcoating systems two variables which affect the performance of hardcoating:
    1. Thickness
    2. Curing
  5. Hardcoating thickness needs to be between 3-5 microns (ref. manufacturer’s spec).
    1. Thickness is controlled by:
      1. Solutions percent of solids (viscosity) — primer, hardcoat
      2. Extraction or drain speed of the dip hardcoating system
    2. If the hardcoating is too thin, it will crack.
    3. If the hardcoating is too thick, it will not cure properly.
  6. Check and control percent of solids of primer and hardcoating daily. For Quantum products, these should be:
    1. Primer: 4-5%
    2. Hardcoat: 21-24%
  7. Use a spectrophotometer to measure thickness.
  8. Dip hardcoating systems partially cure hardcoating thermally using temperature and time.
  9. Final cure of dip hardcoatings is done in an oven (ref. manufacturer’s spec).
    1. Cure temperature is 110°C.
    2. Cure time is 3 hours.
    3. Over-cured hardcoating looks yellow.
    4. Under-cured hardcoating looks clear and feels fry.
    5. Under-cured hardcoating will have less scratch resistance and poor adhesion.
  10. Test pH of soap tank weekly.
  11. Do not allow DI water quality to drop below 12 mega ohms.

Degassing

Degassing is done after the lenses have been through an ultrasonic cleaning system or dip hard coater in order to remove all traces of water, as any water in/on the lenses will cause adhesion failure of the AR coating.

Materials and Equipment

  • Oven
  • Oven trays/racks

Degassing Considerations

  1. Degas temperature is 55°C
  2. Degas time:
    1. Optimal degas time is 2 hours.
    2. Minimum degas time is 1 hour.
    3. If batching, cure times may vary.
  3. Holding (overnight) temperature is 40°C.
  4. If lenses have been in the degas/holding oven for more than 24 hours, run them through the ultrasonic wash/degas cycle again.

Fixturing

Materials and Equipment

  • Flow booth
  • Black background
  • Inspection lamp
  • Lint-free swabs
  • Anti-static gun
  • AR lens rings
  • Ring spreader
  • Sectors
  • Sector stand

Fixturing Considerations

  1. When fixturing lenses, always work in the flow booth to lessen the possibility of airborne contaminates getting on the lenses.
  2. Before fixturing each lens, use the anti-static gun to remove any statically charged particles from both sides of the lens.
  3. Inspect the lens for contamination and defects using the inspection lamp and black background.
  4. Carefully remove any particles or defects which would cause the lens to be rejected, using lint-free swabs.
  5. Use a sector stand to support a sector.
  6. Note the sector stand to support a sector.
  7. Using a ring spreader to load each lens carefully into the AR lens ring, checking to ensure it is held firmly/evenly.
  8. When the lens is firmly/evenly fixtured, place the ring into the previously noted hole in the sector, concave side down, to coat the backside first.
  9. When a sector is full, load it into the dome, making sure to note which position the sector is in.
  10. Do not leave any sector holes empty. Use a scrap lens or a lens ring covered with aluminum foil to fill the hole.
  11. Continue loading additional sectors full of lenses ore use blank sectors in the dome until it is full.
  12. Store full sectors under flow hood or in degas oven.
  13. If full sectors will not be processed for more than 1 hour, store in degas oven.

AR Coating

Materials and Equipment

  • AR coating system
  • Evaporation materials
  • Quartz crystals
  • Crucible liners
  • Sample lenses

AR Coating Considerations

  1. NEVER apply AR coatings to lenses that have not been hardcoated.
  2. AR coating systems require systematic scheduled cleaning and maintenance in order to produce repeatable results.
  3. Run leak rate and pumping speed tests monthly.
  4. Remove shields, clean chamber, and bake out weekly.
  5. Clean/rebuild e-gun emitter and i-gun according to hours used.
  6. Clean 1/3 of the shields and crucible liners every 4 runs.
  7. Include a witness sample lens in each run to test/ensure system performance. This will be used for Quality Assurance (Section 5).
  8. Load Recipe.
  9. Charge crucible.
    1. Adhesion material: Stir in pocket every run; replace every 8 runs.
    2. Low index material: Remove top crust, then “top off” every run.
    3. Hi index pill: Replace pill every run.
    4. Hydrophobic cup: Replace every run.
  10. Quartz crystal: Replace and verify frequency every run.
  11. Shutter: Replace with clean every run.
  12. E-gun: Clean with Scotch Brite and vacuum cleaner between each run.

NOTE: A run = door close to door open.

Flip/Final Inspection (Unloading)

Materials and Equipment

  • Flow booth
  • Black background
  • Inspection lamp
  • Lint-free cloth/swabs
  • Anti-static gun
  • Sector stand
  • Sample lenses

Flip/Final Inspection (Unloading) Considerations

  1. When the AR coating system is finished coating and the door opens, carefully unload each sector from the dome.
  2. Place it into the sector stand in the flow booth, being sure to note sector position in dome as it relates to position in stand.
  3. When flipping the lenses in the sector, remove each AR ring from sector hole and blow off the lens.
  4. Using the inspection lamp and black background, inspect each lens for debris and defects.
  5. Carefully remove any particles or defects which would cause a problem with the AR coating.
  6. Place lens back into sector hole with the side needing to be coated (convex) facing down. Repeat steps in AR Coating Considerations section.
  7. To unload fully coated lenses, remove each AR ring from sector hole and remove the lens from the AR ring.
  8. Perform final inspection on each lens using an inspection lamp and black background.
  9. Inspection consists of holding the lens up to the lamp in two positions:
    1. Looking through the lens into the light to reveal any particles, scratches and defects.
    2. Looking at the reflection of the light bouncing off the lens (flaring) to reveal coating voids and crazing.
  10. Compare AR color to sample lenses.
    1. If lens passes final inspection, place it into the proper job tray or envelope and forward to finishing department.
    2. If lens does not pass final inspection, forward to supervisor for review.

Bead Blasting

Materials and Equipment

  • Bead blaster
  • Disposable mask
  • Blast media
  • Blow-off nozzle
  • Acetone
  • Lint-free wipes

Bead Blasting Considerations

  1. Maximum compressed air pressure = 60 psi.
  2. Blast both sides of shields to prevent warping.
  3. Always blow off and then wipe down with acetone all parts that have been blasted before putting them in the chamber.
  4. In order to perform as designed, blasters require regular cleaning and maintenance.
  5. Repair leaks, clean filters and replace media regularly.
  6. Only AR chamber parts should go into the bead blaster.
    1. Never blast oily or greasy parts in the bead blaster.
    2. The media will become contaminated, which will later contaminate your chamber parts, possibly causing failure in your AR coatings.

Equipment Monitoring

  1. Create/use logs/charts to clearly and accurately record:
    1. Maintenance tasks: daily, weekly and monthly tasks.
    2. Systems alarms as they occur. Include alarm number/description, date and time.
  2. User charts and alarm log to generate a daily report.
  3. Review logs/charts and reports in order to identify problems before they can adversely affect production.

Quality Assurance

Materials and Equipment

  • Thermal shock (salt water boil) test kit
  • Test chemicals
  • DI water (18-12 mega ohm)
  • Spectrophotometer

Quality Assurance Considerations

  1. Perform QA daily.
  2. When performing QA tests, use -2.00 CR-39 hardcoated lenses for baseline.
  3. Label test lenses clearly.
  4. Do not perform thermal shock tests on lenses that do not have a hydrophobic coating.
  5. Use a Sharpie marker as a quick check of hydrophobic performance.
    1. If a lens has a good hydrophobic on it, the ink will bead up.
  6. When inspecting lenses for color:
    1. Be aware that several parameters have an effect on color, such as:
      1. Light source
      2. Angle between lens and eye
      3. Lens geometry
      4. Index of primer/hardcoating/lens material
      5. AR/mirror coating
  7. Quantum provides QA support for customers.
    1. Call to sign up for Quantum’s QA program (888.214.7932).
    2. Go to qtmi.net for more information.

Know Your Systems and Processes

  1. Read your user manuals and data sheets carefully. Make use of the instructions and explanations in them.
  2. The knowledge of safe, continuous, high-quality, trouble-free production depends primarily on the degree of your understanding of, and the willingness of you and your staff, to comply with best practices.
  3. Please do not hesitate to contact Quantum with any questions.