Guidelines for Processing Sensitized Screens

Guidelines for Processing Sensitized Screens

sensitized screen

The market continues to see rapid changes. The companies surviving the fray are flexible and move faster than their competitors. Everyone is trying to fabricate their next best product.

What if R&D had tools that allowed for many iterations of rapid prototyping? Companies can create products in the automotive, container, electronic, or medical industries. The freedom to change designs often grabs the attention away from competitors. Entrepreneurs can create pre-sales samples to close more deals. This article covers steps in processing a sensitized screen, emulsion, and image for printing. Read on to understand the process.

Sensitized Screens

Sensitized screens are a great tool for industries that change their designs often. Sensitized screens are covered in sensitized emulsions which are ready to be exposed with camera ready art or designs. They are ideal in industries that generate a lot of designs.

 

A sensitized screen consists of a screen covered with a base layer of emulsion. This layer contains a light-sensitive compound called a sensitizer. When exposed to ultraviolet (UV) light, the coating hardens.

 

MicroScreen screens come in light-tight sealed bags. This protects the emulsions from light as well as shifts in temperature. To ensure you use the right screen for the right project, the specifications are printed on the screen frames. We store the screens at 65°F (+–5°) with relative humidity below 50%. This is because high humidity can cause the emulsion to swell. Once you have the right screen, follow these steps for use:

  1. Mesh Prep

MicroScreen inspects all mesh to specification before shipping. This process makes sure you receive the best materials for your printing projects. The inspection includes

  • Wire diameter
  • Mesh opening
  • Weave thickness
  • Mesh count
  • Uniformity
  • And more

Many recommend mechanical abrasion of new mesh to increase the surface area to create a better mechanical bond with the ink. Reused mesh requires degreasing. It's best to check the product requirements before use based on the project needs.

  1. Activate Emulsion

Screen printing emulsion can run too thick. When this happens, room temperature water is used to thin the sensitizer. Then, the dissolved sensitizer is added to the emulsion. The liquid is stirred with a clean tool until it becomes a consistent color and then sits for an hour or more until the bubbles release.

 

If you prefer to avoid steps 2-4, MicroScreen has pre-sensitized emulsion screens as well as finished screens to meet your specifications.

  1. Apply Emulsion

There are a couple of methods for applying emulsion to the screen. The first method is to apply one coat of emulsion on the print side of the screen and another on the squeegee side. Make sure the screen is dry. The second method requires two coats on each side before drying. The key is to rotate the screen 180° after each coat. Once done, we must make sure the screen dries. An alternative to this second method requires two more coats on the print side of the screen. Screen drying time follows.

  1. Drying the Screen

The screen must dry in a horizontal position with the print side down. The drying must be in a dust-free environment at room temperature with less than 50% humidity. A filtered fan can speed up the process.

  1. Expose the Emulsion

Based on the emulsion and coating method used, the emulsion must be exposed to UV light. Exposure timetables are available to avoid the need for guesswork. The key is to factor in the distance the UV light is from the screen.

 

A step-wedge test helps find the best exposure. Here are some success indicators:

  • No outline of the positive image is visible if the exposure increases
  • The emulsion is hard on the squeegee side of the screen
  • A print test is at the proper resolution
  1. Clear the Emulsion

The most common troubleshooting requires cleaning the emulsion. Gently spray both sides of the screen with cold water, and then use a power sprayer on the print side of the screen until it's clear. Finally, use a gentle spray to rinse both sides until no soft emulsion remains on the squeegee side of the screen. There should not be any foam or bubbles, either. Unprinted paper stock helps blot up any excess water.

  1. Reclaim the Screen

To reclaim the screen for a different project, use a solvent designed for the ink used. Then, degrease the screen to remove any solvent residue. Finally, rinse the screen, dry it, and store it for future use.

Reuse Touchups

When you need to keep a screen over time, it's prudent to check the image for breaks, cracks, and fallout. If you need to fix a blockout section, add extra emulsion as a filler. When the screen requires a touchup, you can use extra emulsion in those areas and re-expose the screen to UV light. Just be careful to use the same volume of products to match the existing layer.

Sensitize Screen Emulsion and Image

Sensitized screens are useful in prototyping for a wide range of industries. MicroSreen provides high quality precision fabricated screens, including wire cloth with frames, covered screens, sensitized screens, and finished screens. Learn more about our screens here.


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