Thermal, Photopolymer and Silver-halogen Plates: Which is the Best for Your Business

The type of plate you choose, can impact your bottom-line.

The concept of Computer-to-Plate (CTP) technology is relatively easy  for those in the printing industry to understand, but the numerous nuances and wide variety of manufacturers often make it difficult for business owners and decision-makers to choose the best solution for their specific business needs.

One such distinction is the type of printing plate —the tool which transfers images onto a certain type of material to create the final product — that will meet your expectations.

Thermal plates are the most common among pre-press and printing operations. However,  like most solutions,  each technology — thermal, photopolymer and silver-halogen plates — has its pros and cons.

Here’s a look at those differences.

Thermal Plates

Thermal CTP has been a big hit in the United States and around the world. Thermal technology was introduced at DRUPA, the largest printing equipment exhibition in the world, held every four years in German. In 1995, the conference attracted over 385,000 visitors, 1,670 exhibitors from 44 countries and all of the big printing brands announced one or more thermal-related products.

Advantages

  • Offer the highest quality output when compared to the other two competing technologies
  • Depending on the type of paper, thermal printers don’t need ink or toner, only heat
  • Processing during daylight hours is possible so a safe light is not necessary
  • Improved print consistency across both the length of runs and repeat runs
  • Require little or no processing
  • Provide the largest section of plate options across a multitude of providers
  • Less impact to the environment
  • Can output longer runs, exceeding 1 million impressions (but requires baking); Unbaked run lengths vary from 100,000 to 500,000
  • A durable plate
  • Doesn’t cause overexposure
  • Outputs finer and sharper detail, accommodating over 200 lines per inch (LPI)
  • High process stability

 

Disadvantages

  • Some thermal plates need baking to achieve longer runs, requiring an additional step in the process, more labor resources and time
  • There are fewer plate choices in the no-bake category
  • Post-baking may damage plates by weakening the aluminum, cracking and requiring early replacement
  • Requires more time
  • Some printers cite substantial cost premiums
  • Thermal equipment is more complex than competing technologies
  • Maintenance costs can be higher
  • Plate imaging is slower

Photopolymer Plates

Photopolymer plates have experienced many changes over the years.

Louis Minsk, an employee of Eastman Kodak, patented the 1st  synthetic photopolymer plate in 1952. Time, Inc. introduced the 1st  photopolymer-based letterpress plate in 1957 for printing magazines Jump to 2002 when DuPont’s Cyrel Fast technology entered the market, eliminating the need  for solvents in plate processing and melting unexposed photopolymers. Photopolymer plates differ from other technologies by applying a light-sensitive coating to the surface of an aluminum plate, exposing it to light, causing the coating to harden in image areas and remain soluble in non-image areas.

Advantages

  • Coatings provide more durable and abrasion-resistant image areas
  • Produce longer print runs up to 250,000 impressions
  • Have been known to print runs of more than 1,000,000 impressions
  • Dye-sensitized photopolymers can be etched by lasers
  • Requires more energy for exposure

 

Disadvantages

  • Requires a chemical treatment after exposure to remove the coating in non-image areas
  • Cannot print as high of a resolution as silver-halide plates

Silver-halogen Plates

Also referred to as  silver-halide (silver salt) plates and silver-based violet plates, silver-halogen plates are used for offset printing and use a film- or metal-based plate coated with a silver-halide emulsion, similar to processing photo film. Silver halide is one of the chemical compounds which can form between the silver and halogen elements. This technology varies in that it transfers the image directly to the surface of the plate.

However, silver-halogen plates are less widely accepted in the industry and experts predict they will eventually become obsolete because they harm the environment more than other technologies. As a result, silver-halogen plates are being replaced with photopolymer plates (described above).

Advantages

  • Silver-halide plates can be etched using photographic negatives
  • Requires low laser energy for exposure
  • Lasts up to approximately 350,000 runs
  • Can print up to 450 LPI
  • The silver provides a faster emulsion and require less energy for exposures

 

Disadvantages

  • High sensitivity to blue light so developing and storing plates require a darkroom with a yellow-filtered light
  • Processing chemicals contain heavy metals — in particular, silver — which pollute the environment
  • The liquid waste produced contains metallic silver and classifies concentrations above 5 parts per million (PPM) as hazardous waste
  • Discharging any silver into a sewer is also regulated and must be treated a specific way, or sent to a special treatment plant
  • Relies on photosensitive materials which are more expensive than other technologies
  • Is not known for its durability
  • Requires specific ink
  • Unexpected failure during any step of the process will damage plates

Making the Choice

There are different ways printers can determine what plates the need for specific platesetters. The first step is to test the plates you may be considering on your platesetter and presses. Of course, this means purchasing various types of plates. Once you’ve determined a plate works, you need to consider direct cost — including plates and processing expenses — and indirect costs, such as purchasing a processing, or baking unit.

True in any industry, it pays to hire an expert for advice and equipment warranties. Platesetters.com is one such expert and has earned a  global reputation as the most dependable source for reconditioned prepress CTP equipment, parts and service. For a complimentary consultation about your imagesetters’ plate needs, call Platesetters.com at 888-380-7483.

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