WO2012164412A1

WO2012164412A1 - Raised inkjet printing

Info

Publication number: WO2012164412A1
Application number: PCT/IB2012/052066
Authority: WO
Inventors: Eli Grinberg; Kobi Bar; Guy ALON
Original assignee: Scodix Ltd.
Priority date: 2011-06-01
Filing date: 2012-04-25
Publication date: 2012-12-06

Abstract

An ink for raised inkjet printing comprising: a UV curable basis and a silicone-based additive.

Description

RAISED INKJET PRINTING

FIELD OF INVENTION

The present invention relates generally to printing technologies and more particularly to systems, articles, and methods for raised inkjet printing.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority from and is related to U.S. Provisional Patent Application Serial Number 61/491,992, filed 1 June 2011, this U.S. Provisional Patent Application incorporated by reference in its entirety herein.

BACKGROUND

An inkjet printer creates an image by propelling variable-sized droplets of ink onto substrates. The conventional inkjet printing technology is unable to generate raised printing effectively and efficiently. The traditional screen printing and embossing process is a complicated, time-consuming, and expensive. Screen printing generally utilizes a woven mesh to support an ink-blocking stencil. The attached stencil forms open areas of mesh that transfer ink or other printable materials, which can be pressed through the mesh as a sharp-edged image onto a substrate. A roller or squeegee is moved across the screen stencil, forcing or pumping ink past the threads of the woven mesh in the open areas.

Embossing is typically accomplished by applying heat and pressure with male and female dies that fit together and squeeze the fibers of the substrate placed between the dies. The combination of pressure and heat raises the level of the image higher than the substrate, while "ironing" it to make it smooth. The screen printing requires preparation and maintenance of multiple screen meshes and stencils for different designs. The embossing process requires design and manufacture of molds. These processes increase complexity, incur extra cost, and slow down the printing process. The screen meshes, stencils, and molds are generally configured for a particular print task and cannot be reused for different print tasks. In addition, the screen printing and embossing process allows only one-side printing. Accordingly, an improved technology for generating raised printing is desirable. SUMMARY

According to a first aspect of the present invention there is provided an ink for raised inkjet printing comprising: a UV curable basis and a silicone-based additive.

The silicone-based additive may be about 0.1-0.5% of the ink by weight.

The basis may be based on acryl photo polymer.

Viscosity of the ink before curing may be about 8-20 cps at 70°C.

Surface tension of the ink may be about 25-30 dyne/cm.

According to a second aspect of the present invention there is provided a method of raised inkjet printing, comprising:

a. providing an ink comprising a UV curable basis and a silicone-based additive;

b. using an inkjet printer to apply a first layer of said ink onto a substrate; and c. curing said printed ink using UV radiation. The method may additionally comprise, following said step (b): using said inkjet printer to apply a second layer of said ink onto said substrate.

The method may additionally comprise, following said step (c):

using said inkjet printer to apply a second layer of said ink onto said substrate; and

curing said printed ink using UV radiation.

The cured ink may have a gloss level over 90 Gloss Unit (GU), according to ASTM Standard D2457 and ASTM Standard D523.

The first layer may have thickness of over 15 microns.

DETAILED DESCRIPTION

In one aspect, the invention provides a composition of an ink for raised inkjet printing. Table 1 below illustrates some characteristics of an ink according to some embodiments.

Table 1. Characteristics of an ink according to some embodiments. Referring to Table 1 , an ink in some embodiments according to one aspect of the invention comprises at least a basis and an additive. The basis is preferably UV curable. One example of such UV curable basis is based on acryl photo polymer. The additive is preferably silicone-based. Silicones (a.k.a. polymerized siloxanes or polysiloxanes) are mixed inorganic-organic polymers with the chemical formula [R2SiO]n, where R is an organic group such as methyl, ethyl, or phenyl. These materials form an inorganic silicon-oxygen backbone (•••-Si-O-Si-O-Si-Ο-···) with organic side groups attached to the silicon atoms. Sometimes, other chemical elements can be added to silicone as well. By varying the -Si-O- chain lengths, modifying side chain groups, and cross-linking, silicone can be synthesized with a wide variety of forms (e.g., oil, grease, rubber, resin, etc.) and compositions. The variations listed above can help to improve compatibility and change characteristics of the silicone. For example, silicone with more dimethyl groups generally has lower surface tension. In another example, a polyether chain, composed of ethylene oxide (EO) and/or propylene oxide (PO) units, can help generate polarity. In one embodiment, the silicone additive is about 0.1-0.5% of the ink by weight.

Table 2 below illustrates some characteristics of the basis within the ink of Table 1.

Table 2. Characteristics of a basis within an ink according to some embodiments. In some embodiments, the ink and the silicone additive can be mixed together by blades with various shapes and speeds for various durations. The silicone additive in the ink helps to control certain characteristics of the ink (e.g., reducing surface tension). In one embodiment, the viscosity of the ink before curing is in the range of 8-20 centipoises (cps) at a temperature of 70 °C (1 cps equals to 1 millipascal-second (mPa-s)); the surface tension of the ink before curing is in the range of 25-30 dyne/cm (1 dyne/cm equals to 0.001 N/m). Higher percentage of silicone additive can usually lead to lower surface tension.

Ink in some embodiments can in some situations be applied to substrates via ink- jet nozzles. Existing inkjet equipments and technologies can be utilized to apply such ink without needing extensive modification. U.S. Patent Applicant Publication

2010/0212821 and PCT Patent Application Publication WO 2009/047757 describe, among other things, overprinting equipments, systems, processes, and methods. Both of the above two applications are incorporated by reference herein in their entirety. After the ink is applied, a UV light is preferably used to cure the ink and the ink components therewithin. When it is cured, the ink preferably has a gloss level over 90 Gloss Unit (GU), according to ASTM Standard D2457 and ASTM Standard D523. In one embodiment, a layer thickness of over 15 microns can be achieved in one single printing pass.

In addition, ink may be applied to substrates by, for example, making multiple passes of the ink-jet nozzles over the substrate and preferably depositing ink on portions of the substrate previously printed. This allows for building up of further raised inkjet printing on the substrate. This may be accomplished either by applying the further ink deposit after the previous ink has been cured or partially cured, or by applying the further ink deposit over the previous uncured ink, depending on circumstances and desired effects.

Unlike the traditional screen printing and embossing process, inkjet printing using the ink in some embodiments according to the invention can be utilized in double-sided printing. In addition, since pre- manufactured screens, stencils, and molds are no longer needed, the printing process can be digitalized to reduce cost and increase productivity; and variable data printing technologies can also be used to allow variable printing on each page. Moreover, the ink in some embodiments according to the invention can be applied in multiple layers, with or without curing between jetting.

Having thus described at least one aspect of the invention, various alternations, modifications and improvements will readily occur to those skilled in the art. Such alternations, modifications and improvements are intended to be within the scope and spirit of the invention. The molecules and/or chemical components cited in the present document are not restrictive, but are illustrative of molecules, monomers, or polymers that have or exhibit identical or similar characteristics, properties, or functions. Other embodiments are within the scope and spirit of the appended claims. Accordingly, the foregoing description is by way of example only and is not intended as limiting.

Claims

WHAT IS CLAIMED IS:

1. An ink for raised inkjet printing comprising:

a UV curable basis; and

a silicone-based additive.

2. The ink in claim 1, wherein the silicone-based additive is about 0.1-0.5% of the ink by weight.

3. The ink in claim 1, wherein the basis is based on acryl photo polymer.

4. The ink in claim 2, wherein viscosity of the ink before curing is about 8-20 cps at 70°C.

5. The ink in claim 2, wherein surface tension of the ink is about 25-30 dyne/cm.

6. A method of raised inkjet printing, comprising:

b. using an inkjet printer to apply a first layer of said ink onto a substrate; and c. curing said printed ink using UV radiation.

7. The method of claim 6, additionally comprising, following said step (b):

using said inkjet printer to apply a second layer of said ink onto said substrate.

The method of claim 6, additionally comprising, following said step (c):

using said inkjet printer to apply a second layer of said ink onto said substrate; curing said printed ink using UV radiation.

9. The method of claim 6, wherein said cured ink has a gloss level over 90 Gloss Unit (GU), according to ASTM Standard D2457 and ASTM Standard D523.

10. The method of claim 6, wherein said first layer has thickness of over 15 microns.