UV inks - applications

UV inks - applications Features of using ultraviolet-curing paints

If we talk about ultraviolet-curing paints, then they have special substances that react to ultraviolet-type radiation and therefore dry out in the air.

Such a paint and varnish material is used for various types of printing, for example, flex, offset, screen-type, and also for reproducing raster-type graphics.

It can be applied to any kind of surfaces - plastic, paper, polyethylene, and both in a thin and thick layer.

General information

During printing, it is imperative to use ultraviolet lamps, which help to fix the paint applied to the surface of the products. Certain ink materials that are UV-cured are toxic and should never be printed on grocery packaging.

But when they dry, they will not emit solvents into the environment, unlike solvent-type compositions. But when using lamps, ozone is released, which can be toxic if its concentration in the air is very high.

Features of paints and varnishes

UV-curing paints and varnishes differ from simple, basic compositions on solvents, the ability to dry out and "set" almost instantly.

Here are other features of UV-curing coloring materials:

  • Structure rigidity.
  • More sticky and viscous.

  • Resistant to moisture.
  • Does not wear off as quickly as solvent-type paints.
  • Freezes (that is, dries up) only under the influence of ultraviolet radiation.

UV curable ink contains:

Please note that the colorant is nothing more than a curing polymer powder that heats up, starts to melt and forms a strong film on plastic, paper or even wood.

An interesting feature of UV-cured paints and varnishes is that the layer will fix faster on a snow-white building material, and much slower on a dark one, because a light background only repels ultraviolet radiation, but black absorbs.

Curing methods

The final stage in obtaining a layer of paints and varnishes will be drying. Dispersed media during drying of paints and powder varnishes is air. The film will turn out because polymer solid particles in the composition of the material begin to form a strong bond, and first they melt and then solidify. The coloring composition heats up to +115 degrees and hardens in a few minutes.

Sources of UV light

For UV-curing inks, the drying and curing process should be optimized, and this will directly depend on the choice of the UV emitter.

The following devices can be sources of ultraviolet light:

  • Mercury lamps.
  • LED, electrodeless or quartz emitters.
  • Xenon or fluorescent lighting devices
  • LED UV drying lamps.

The main rule when choosing a curing paint coating for a machine will be the radiation frequency of the device must necessarily coincide with the absorption frequency of the photoinitiator, which will be responsible for the optimal dose of UV rays, as well as the ability of coloring materials to enter into chemical reactions.

A wide range of lamps can be used to cure powder paint materials, but they have major disadvantages:

  • Toxicity.
  • Energy consumption.

Please note that all of the above devices, when heated, begin to emit a lot of ozone into the air, and it is known to have a negative effect on human health.

Qualitative characteristics of the coating

Polymers that cure in the composition of paints and varnishes during the drying process are capable of forming a strong film. The thickness of the layer will not affect the quality of the result.

The paint and varnish material will lie flat, will not spread beyond the contours of the image,

and will be evenly distributed. The following factors will affect the quality:

  • Color composition, which includes thinner, pigments, resins, photoinitiator, synergist and fillers.
  • Surface to be machined.
  • The conditions under which the staining will be performed.
  • Radiation dose
  • A type of ultraviolet device.

  • Distance between lamps and from the source of radiation to the substrate itself.

The paint coating will be resistant to moisture, durable, will not fade under the influence of sunlight, other types of radiation, and therefore even full-fledged images that are applied using ultraviolet curable paints will be of high quality.

Advantages and disadvantages of ultraviolet curing technology

The ultraviolet curing method is completely environmentally friendly. The rest of the advantages of modern technology are as follows:

  • A short time period for drying paints and varnishes.
  • High degree of productivity.

  • Economical as it does not take long to dry the finished product.
  • Use in parts, for example, painting a particular area of ​​the surface.
  • Reapplication of paint residue or even dripped paint / varnish.
  • Application in a thin layer is sufficient for high quality finished products.
  • Stability and strength of the painted surface.

  • Low level of explosive hazard.
  • Safety for human health.

But take into account the fact that UV-curing paints, or rather technology as a whole, have certain disadvantages:

  • automatic lines only pay off with a large production volume.
  • The cost of paints and varnishes is higher than similar folic or solvent ones.
  • If non-planar surfaces are to be painted, drying will take much longer.

  • To obtain a high quality, the curing process should be slowed down.

Moreover, if defects of the layer appear on the painted surface, for example, drops, smudges, then they are most often irreparable. On the market of paints and varnishes, there are several types of coloring compounds that dry out under the influence of ultraviolet rays.

Specificity of paintwork materials UV-curing

Acrylic, water-borne, and also polyester-type varnishes and paints that are cured by ultraviolet radiation are used in printing shops ..

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Acrylic

These types of paints literally dry out in a few minutes and are distinguished by a high degree of reactivity, and still have almost 100% dry residue. The composition contains an ultraviolet hardener, and the strength and hardness of the resulting layer make it possible to use materials when painting parquet-type coatings. They are completely environmentally friendly, and during drying, they practically do not emit evaporation. But in contact with open skin, they are ways of causing harm, and therefore work with acrylic paints and varnishes should be carried out in a respirator, gloves and glasses.

Due to its high viscosity, acrylic paints and varnishes cannot be sprayed on.

Polyester

Such varnishes and paints are inexpensive, but blowing is required for perfect drying. They cure when exposed to a huge amount of ultraviolet lamps. They are suitable for spray application and the layers of paint material tend to turn yellow when cured with UV light.

Water-borne

The characteristics of such materials are as follows:

  • High quality.

  • Environmentally friendly.
  • Security.

Please note that water-borne paints and varnishes do not turn yellow, but are still suitable for spraying. When dry, they form durable pigment layers of high quality.They are completely harmless when in contact with open areas of the skin.

They are also much more expensive. Than polyester and acrylic products and require convection drying.

For you, we have prepared a comparison table for polyester, acrylic and water-borne UV paints.

Name Degree of reactivity Environmental friendliness of the product Price Disadvantages

Acrylic

High

Not capable of emitting vapors, and also harmful when in contact with skin

Medium

Do not spray

Polyester

Low

Eco-friendly

Medium

Start turn yellow when dry, and for complete curing it is required to go through the blowing stage, as well as the tunnel

Water-borne

High

Eco-friendly, no harm in contact with the skin

High

Special convective drying is required

UV inks in printing

UV curing technique and it is used for almost all types of printing:

  • UV inks - applications Flexo printing.
  • Screen printing of all types.

  • Silk-screen printing.
  • Offset printing (roll and sheet)
  • Polygraphy.
  • Large format, for inkjet printers.

Due to the unique properties of the coloring materials, it begins to cure almost instantly, and printing with ultraviolet inks can be performed on various materials - plastic, paper, wood, plastic and film. If you print on non-absorbent materials such as polyethylene films, the surface tension should be checked, as adhesion problems of the ink layer with plastic or film can become a time bomb.

The flaws will be visible later, and it will no longer be possible to correct the flaws, and therefore the tension is checked with special ink or even test pencils.

When printing, the following climate conditions must be observed:

  • The temperature should be from +19 to +25 degrees.
  • Humidity level (acceptable) from 50 to 60%.

Please note that the light from fluorescent lamps, as well as the sun's ray, should in no case fall on the typewriter, as well as cans with coloring material. For protection on windows, yellow filters and lamps with safe white and yellow spectrum should be used.

Finished products can be coated with UV varnishes, which will protect the product and create special effects such as matt or glossy surfaces. UV varnishing is considered a safe, environmentally friendly and cost effective technology.In general, varnishes and paints that are cured by means of ultraviolet radiation are very popular in the Moscow printing shop, so even when printing on the most capricious materials, the results will be excellent.

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