Mirror image surfaces for décor applications

EP 2 871 062 A1
Production method of recording material, and recording material
Seiko Epson Corporation

This extensive patent (84 pages) is, like the following one, concerned with the production of a glossy or mirror-finished surface, however in this context it is applied to the production of hard surfaced décor panels and similar articles. The method can be used as an alternative to metallic plating or foil stamping and is beneficial in that it can be applied to a curved surface, and also that patterning and gradation in the metal tone can be achieved.

May-15In essence, two UV curable layers are sequentially printed on the substrate surface. The first layer is cured prior to printing the second layer so that it creates a regular dimpled texture with a surface roughness of 3 to100 μm; the metal-powder-containing upper layer has a planarising effect. Thus the time elapsing between the landing of any drop and curing is critical. In the case of the first layer (2), it is cured within a second of printing while a longer time (5-60 seconds) can elapse between deposition and cure of the top layer (3). The elapsed time can have significant influence on the appearance of the printed material.

While the substrate 1 can be more or less anything and may be absorbing or non-absorbing, a non-absorbing polyester-based substrate for which the contact angle of the ink droplets is at least 10 degrees is preferred and plastics such as PET are particularly suitable.

The first layer is formed from an ink comprising 50-88% of at least one monomer with an alicyclic structure, as this gives good adhesion to the polymer substrate. If at least some (15-75%) of this content is a monofunctional monomer with a heteroatom in the alicyclic structure, such as tris (2-(meth)acryloxyethyl) isocyanurate, then curing shrinkage can be minimised and furthermore, the long term jetting stability is good. The remainder of the monomer content need not have an alicyclic structure and can enhance some aspects of the film, for example inclusion of 2-(vinyloxyethoxy) ethyl acrylic acid improves the cure speed while inclusion of phenoxyethyl acrylate gives rise to a relatively flexible film. Inclusion of a colourant or metal powder in this layer can influence the colour tone or the opacity of the finished article.

The second, and metallic ink, will be deposited at a volume of 80 to 200% of the deposition volume of the first ink, in order to ensure full coverage and a glossy mirror finish. The greater print to cure interval also enables a smooth surface. More or less any metal powder (31) can be dispersed in this ink at a content up to 10% w/w. Ideally, the powder is formed by CVD and subsequently pulverised to give a flake structure which may additionally take the form of curved flakes for additional effects. The thickness of the flakes is preferably in the 20 to 80 nm range while the diameter is between 500 nm to 3 μm. Treatment of the flakes with a fluorinated compound, such as a silane, disperses the particles in the ink and enhances its storage stability, as well as improving the abrasion resistance and gloss of the printed film. In common with the first ink, the bulk of this ink is also made up of alicyclic monomers which will result in good inter-film adhesion, while the inclusion of minor quantities of other monomers will improve dispersion stability of the metal flakes, enhance cure rate and endow the final article with specific properties such as hardness and flexibility.

Seiko-Epson’s drum-based label press with UV inks

US 2013/0127962 A1 
Image recording device, image recording method 
Seiko Epson Corporation

This is a design for a web-based printer using UV-curable inks.  Epson is concerned that as well as exposing the web to UV light, a lot of heat is also generated by curing systems.  As the temperature of the substrate will rise much more where ink has been printed due to better absorbtion, the substrate can experience distortion and wrinkling.  This can also lead to uneven glossiness of the image, and changes in the texture and even the colours printed.  Substrates including paper, PET, PP and the like are considered.

May13

The solution is to use a drum-based system with a cooling mechanism.  The substrate is fed from roll 20 and through rollers 31.  At the other side the web is taken up on roll 40.  Rollers 32 draw the web through the system, with rollers 31 also driven to adjust the tension around the drum.  As the web passes around the drum the image is printed by heads 51 with pinning of the image using UV-lamps 61.  A more powerful UV source 62 fully cures the image.

There is a further ink jet head 52 that can jet transparent ink on the substrate to adjust the gloss levels of the image or overall.  This ink is cured by UV source 63.

Heat is removed from the system by fan 81 which blows cool air on the region of the drum not covered by the web.

The patent applications cover other topics such as web tension, and moving the printheads away from the drum when the web tension is being adjusted.

Improved head and UV lamp layout

US 2012/0287214 A1
Image forming apparatus
Seiko Epson Corporation

One of the problems with printers using UV-curable inks is that the curing systems must be placed relatively close to the printheads.  However if stray UV-light reaches the ink in the nozzles it can cure the ink at the meniscus and stop the printhead from working.  Most of the light that can reach the printhead is reflected from the substrate, so the standard technique is to space the printhead and curing system as far apart as is practical and insert an optical trap in between.  An optical trap is normally a component with multiple walls painted black to intersect and absorb as much light as possible.

Nov12

The solution here is to angle both the lamps and printheads towards the paper feed directions as shown in the figure.  This reduces the reflected light and removes the need for the optical traps.  This enables the printheads to be mounted closer together.  When printing and curing multiple colours, the closer together the printheads are together the better the registration between colours is likely to be.