WO2015069513A1 - Encre hydrochromique durcissable sous l'effet d'une énergie - Google Patents

Encre hydrochromique durcissable sous l'effet d'une énergie Download PDF

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Publication number
WO2015069513A1
WO2015069513A1 PCT/US2014/062834 US2014062834W WO2015069513A1 WO 2015069513 A1 WO2015069513 A1 WO 2015069513A1 US 2014062834 W US2014062834 W US 2014062834W WO 2015069513 A1 WO2015069513 A1 WO 2015069513A1
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Prior art keywords
coating
ink
water
hydrochromic
substrate
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PCT/US2014/062834
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English (en)
Inventor
Philip Wilkinson
Stewart Kessel
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Sun Chemical Corporation
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Publication of WO2015069513A1 publication Critical patent/WO2015069513A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
    • C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/50—Sympathetic, colour changing or similar inks

Definitions

  • the present invention describes hydrochromic inks and coatings that are energy curable, allowing for near instantaneous cure, and thus allowing much faster
  • the inks and coatings of the present invention have good adhesion to a range of substrates for which the prior art hydrochromic inks and coatings are normally unsuitable.
  • the present invention relates to the formulation of hydrochromic inks and coatings which may be cured by exposure to UV light (or other means of energy cure) and which preferably adhere to commonly used plastic self-adhesive label substrates.
  • the ink or coating when printed and fully cured, becomes opaque such that it will preferably mask a previously printed image or legend. However, when water is applied to the cured coating it becomes translucent, allowing the underlying image or legend to be seen.
  • Hydrochromic coatings are currently used on a limited number of products to produce interesting effects. Examples include umbrellas, billboard advertisements, children's toys, and textiles.
  • the prior art teaches us that it is possible to produce a coating that will be opaque in its dry state, such that it will mask an underlying image or legend, but largely transparent or translucent when moistened with a liquid, e.g. water, allowing said underlying image or legend to become visible.
  • such coatings generally consist of a water-based binder and a porous extender pigment or combination of porous pigments - that is, pigments which have multiple micropores or cavities within their structure, and which are capable of absorbing liquids and gases.
  • Said pigments should have a refractive index of between 1.3-1.8. When coated and dried, these pigments reflect most of the incident light due to air filling the cavities within them, and are opaque. When subsequently moistened with a liquid, usually water, the cavities fill with the liquid, significantly altering the refractive index, allowing the incident light to be transmitted, and the coating to become transparent or translucent.
  • a liquid usually water
  • Other similar coatings are well known within the art to use solvent-based binders. Coatings as mentioned above are necessarily very highly pigmented in order to obtain the highest possible opacity in the dried coating film. This consequently limits the amount of binder possible in their formulation. This in turn can limit the adhesive properties of the coating and reduce the scope of end uses.
  • Such water-based and solvent-based coatings also tend to perform poorly on press, particularly during stoppages, and can be adversely affected by ambient climatic conditions.
  • the coatings also dry relatively slowly unless some form of heat is applied. These points tend to restrict their use to processes using sheet fed techniques and to a limited range of substrates.
  • the present invention provides a novel hydrochromic energy curable ink or coating comprising:
  • the hydrochromic energy curable ink or coating may further comprise:
  • the hydrochromic inks and coatings of the invention further comprise an activating agent.
  • the activating agents are preferably hygroscopic.
  • Such activating agents include polyvinyl pyrrolidone (PVP), polyvinyl pyrrolidone/vinyl acetate copolymers, polyvinyl alcohols, and polyvinyl copolymers.
  • the hydrochromic inks and coatings of the invention further comprise a colorant.
  • the hydrochromic inks and coatings of the invention further comprise a thermochromic pigment or slurry.
  • the hydrochromic inks and pigments of the invention are suitable for printing by screen printing (flatbed, rotary, cylinder), flexographic printing, gravure printing, lithographic printing, and roller coating.
  • the present invention provides a method for printing, comprising: a) printing the hydrochromic ink or coating onto a substrate;
  • the present invention provides a method of creating a hydrochromic print, comprising:
  • the printed substrate is subjected to heat or air-drying after energy curing.
  • the inks and coatings of the present invention preferably dry to an opacity equivalent to commercially available opaque coatings, but transition to a translucent film if the surface is moistened with a liquid, e.g. water.
  • the coatings naturally have a white appearance, but may be colored by the addition of colorants and/or effect pigments, e.g. pigments, dyes and thermochromic pigments or slurries.
  • Said inks and coatings also preferably exhibit acceptable adhesion to substrates beyond the scope of the prior art, thus widening the field of use of such effect coatings.
  • the coating may be applied by screen, flexographic, gravure, or any other suitable printing or coating method.
  • the inks and coatings of the present invention are screen printing inks.
  • inks and coatings are used interchangeably throughout this disclosure, and it is understood that the present invention is drawn to both inks and coatings.
  • film when used in reference to the inks and coatings, is understood to be the cured inks and coatings.
  • compositions of the present invention relate to their use as a special effects ink, i.e. an ink that changes appearance on application of water and is thus "hydrochromic.”
  • the coating is preferably visually opaque when printed and cured, but preferably becomes translucent in contact with a liquid, e.g. water. When the coating becomes dry again, it preferably returns to its opaque state.
  • the coating may be printed to mask a previously printed design or message, which is revealed when the print is moistened. Coatings of this nature are alternatively described as "wet and reveal.”
  • the hydrochromic effect is produced by the inclusion of materials whose refractive index is significantly altered as they absorb moisture. These materials have to be carefully balanced in the coating to give suitable levels of opacity and transparency while still maintaining acceptable printing characteristics.
  • the technology determines that the printed product preferably be opaque white when dry, and clear translucent when wet. However, the product may be tinted with pigments, preferably transparent pigments or dyes, to give an opaque dry color that becomes translucent when wet.
  • the product may furthermore be tinted with thermochromic pigments or slurries to give additional color changes if warm or cold water is applied to the film.
  • Thermochromic pigments or slurries contain complex particles of dye and waxes, which melt and dissociate within specific temperature ranges, consequently changing in color. This process is generally reversible as the temperature lowers or raises.
  • hydrochromic thermochromic coatings include, but are not limited to, Chromazone thermochromic dispersions and pigments (supplied by TMC Hallcrest), Thermasoft or Thermasharp slurries (Sun Chemical), or Thermasolve pigments (Sun Chemical).
  • Such coatings may include thermochromic materials such as those mentioned which are variously colored and transition at a variety of different temperatures.
  • the Chromazone thermochromics used may be black, blue, magenta, green, orange, red, purple, brown, or turquoise; and transition at approximately -10°C, 15°C, 31°C, 47°C, and 69°C.
  • the Thermasoft, Thermasharp, and Thermasolve materials may be orange, blue, black, magenta, red or green, and transition between 7°C and 10°C (cold), between 13°C and 16°C (cellar temperature), between 16°C and 20°C (room temperature), between 24°C and 29°C (touch temperature), between 39°C and 42°C (warm), and between 51 °C and 56°C (hot).
  • Suitable colorants include, but are not limited to, organic or inorganic pigments and dyes.
  • the dyes include but are not limited to azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, combinations thereof and the like.
  • Organic pigments may be one pigment or a combination of pigments, such as for instance Pigment Yellow Numbers 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188; Pigment Red Numbers 2, 22, 23, 48: 1, 48:2, 52, 52: 1, 53, 57: 1, 112, 122, 166, 170, 184, 202, 266, 269; Pigment Orange Numbers 5, 16, 34, 36; Pigment Blue Numbers 15, 15:3, 15:4; Pigment Violet Numbers 3, 23, 27; and/or Pigment Green Number 7, and the like.
  • Pigment Yellow Numbers 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188 Pigment Red Numbers 2, 22, 23, 48: 1, 48:2, 52, 52: 1, 53, 57: 1, 112, 122, 166, 170, 184, 202, 266, 269
  • Pigment Orange Numbers 5, 16, 34, 36 Pigment Blue Numbers 15, 15:3, 15:4
  • Pigment Violet Numbers 3, 23, 27 and/
  • Inorganic pigments may be one of the following non-limiting pigments: iron oxides, titanium dioxides, chromium oxides, ferric ammonium ferrocyanides, ferric oxide blacks, Pigment Black Number 7 and/or Pigment White Numbers 6 and 7, and the like. Other organic and inorganic pigments and dyes can also be employed, as well as combinations that achieve the colors desired. [0024] As with most coating compositions, additives may be incorporated to enhance various properties.
  • a partial list of such additives includes, but is not limited to, adhesion promoters, light stabilizers, de-gassing additives, flow promoters, defoamers, antioxidants, UV stabilizers, surfactants, dispersants, plasticizers, rheological additives, waxes, silicones, etc.
  • UV coatings also generally contain a minimal amount of volatile material, enabling better pigment wetting and adhesive properties in the dried film and also allowing for the reduction of potentially toxic materials into the waste stream.
  • a water dilutable UV curable oligomer such as, for example, epoxy, polyester, or preferably a urethane acrylate oligomer
  • a water-miscible solvent such as, for example, 1-methoxy 2-propanol, 1-ethoxy 2- propanol, 1-methoxy 2-propyl acetate, or methoxy propoxy propanol;
  • a reactive water miscible monomer such as for example polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, ethoxylated bisphenol-A diacrylate, N- vinyl pyrrolidone, acryloyl morpholine, N-hydroxyethyl acrylamide, or ethoxylated trimethylolpropane triacrylate, and similar materials;
  • water preferably deionized water
  • porous hydrochromic materials such as, for example, sodium aluminum silicate, alumina trihydrate, micronized amorphous silica gel and combinations thereof;
  • thermochromic pigments or slurries optionally, one or more thermochromic pigments or slurries.
  • the coating advantageously dries under exposure to actinic radiation, preferably ultraviolet radiation.
  • the coating may also include a proportion of an activating agent, such as, for example, polyvinyl pyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate
  • the activating agent is preferably hygroscopic, and effectively pulls water into the coating, causing it to become transparent more quickly.
  • humectant materials such as glycerol, butyl glycol, propylene glycol, hexylene glycol, glycerin and other materials, such as those available from Lubrizol and Tego Chemie, may also be beneficial to control moisture content.
  • the nature of the coating enables much faster processing than coatings based on the prior art, potentially widening the scope of use of the hydrochromic effect inks to products such as labels, which are generally produced at faster print speeds.
  • the present invention uses the terms "energy curable” (EC) and "UV-curable”, but it is understood that the present invention is drawn to inks and coatings that can be cured by any recognized form of actinic radiation known in the art. This includes but is not limited to, ultraviolet (typically medium pressure mercury lamps, but also LED, HUV, etc.), electron beam, infrared, etc. and combinations thereof.
  • colorants preferably transparent colorants
  • the hydrochromic coating can be used to assist in the masking effect when the coating is dry but it should be remembered that this color will remain visible when the coating is moistened.
  • thermochromic pigment or slurry with an approximately room temperature transition, to the coating can impart a threefold change in appearance, e.g. in the dry state it will be visually opaque; if wetted with cold water the coating becomes transparent but remains tinted; if wetted with warm water the coating loses both color and opacity.
  • the hydrochromic effect is achieved by the incorporation of specific materials from within a group generally known as extender pigments. These pigments have a porous structure and a refractive index preferably between 1.3-1.8, more preferably 1.4-1.7.
  • the refractive index range is of importance in the hydrochromic performance. If it were lower than water (1.33), there would be minimal difference between the wet and dry refractive index and the coating would remain transparent or translucent. If the refractive index were too high, all incident light would be reflected, thus the coating would be opaque whether or not it was wet or dry. In the dry state, the pores are filled with air, which has a refractive index of around 1.0.
  • the difference in refractive indices between the pigment and air causes any incident light to be deflected. If there are sufficient particles within the ink, nearly all incident light will be reflected and the coating will appear opaque. Conversely, when wetted, the air in the pores is replaced with, for example, water. As water has a refractive index closer to that of the pigment (1.33) there is less deflection of incident light and it can pass virtually straight through the coating film. This causes the coating to appear transparent or translucent.
  • UV curing inks and coatings have been used for a number of years in high speed label printing due to the near immediate drying. This makes them suitable for reel-to-reel processes commonly applied within the label making industry.
  • one object of the present invention is to provide a UV curing hydrochromic ink that would be the ideal product to increase the flexibility of use of this effect.
  • UV coatings dry virtually instantaneously on exposure to sufficient UV light energy, and are therefore suited to fast running coating equipment, for example reel to reel label printing machines. They are also known to adhere to a wide range of substrate materials, which are beyond the scope of the prior art hydrochromic inks and coatings. There were, however, several obstacles to overcome.
  • Standard UV systems are within the scope of the present invention but are not the most preferred as they tend to wet the extender pigments extremely well, and, once cured, tend to seal the pores of the pigment.
  • the coating may remain permanently opaque if air is trapped in the pores, or, as is usually the case, permanently translucent if the UV medium has permeated the particles.
  • One way to overcome this is to overload with extender but this may increase the structure and viscosity of the coating making it difficult to print, particularly on high-speed presses or coaters.
  • UV curable binders available within the art which are water miscible and it was hypothesized that the use of these would assist in producing a satisfactory hydrochromic product.
  • this ink tended to be too thixotropic, causing possible printing problems, and if reduced with monomer or water, there was great difficulty in driving the water from the printed coating. This meant that the coating didn't fully dry quickly enough, causing smearing, or took several minutes to develop its opacity.
  • the coating was also difficult to rewet because the UV cured media tends to seal some of the pores of the pigment and is impervious to water.
  • an object of the present invention was to produce a binder which had a manageable rheology, and sufficient wetting power to bind the amount of pigment required, without destroying the hydrochromic effect.
  • the binder would also preferably exhibit good adhesion to various potential substrates.
  • liquid e.g. water
  • UV monomers such as acryloyl morpholine (ACMO) or tri- propylene glycol diacrylate (TPGDA) are effective in reducing the viscosity of the oligomer, but because they are cross linkable during curing, they tend to seal the pigment particles, nullifying the hydrochromic effect.
  • Aromatic and aliphatic hydrocarbon solvents may be an option, but there are drawbacks in this approach. For example, fast drying solvents with low flash points are unsuitable as they would be considered an unacceptable hazard during the printing/curing process. Slow drying solvents would themselves be retained in the ink film after curing, and their vapor may also build in the energy curing apparatus giving rise to fire and other hazards.
  • Compatibility with other liquid components may be an issue, and odor may be unacceptable.
  • a combination of technologies may be the best approach, i.e. a water miscible monomer, a water miscible solvent and water.
  • the monomer acts as a diluent in the bulk coating, but crosslinks during the curing process to form part of the binding agent.
  • Water acts as the hydrochromic enabling agent, but is fully removed (or nearly fully removed) from the dried film.
  • the formulation includes a specific solvent which is miscible with all the other components, particularly the water, and preferably has a mid to low range flash point of about 20-80°C, but is not highly volatile. This solvent should preferably mix with the water and assist in its removal from the dried film.
  • Acryloyl morpholine is preferred as the water miscible monomer in the binder because it is water miscible and also exhibits good adhesion properties (aka "keying") to a variety of substrates, particularly plastics.
  • Methoxy propanol is a preferred solvent because it mixes readily with water, has a flash point which is neither too low nor too high (20-80°C), and is compatible with all the other components of the coating. If the flash point of the solvent is too high, it would remain too long in the coating film. If the flash point of the solvent is too low, it could give rise to flammability or even press stability issues.
  • This combination was surprisingly effective in producing a coating which dried instantaneously when subjected to energy cure; gave an extremely smooth and opaque film when dry; transitioned rapidly to near complete transparency when moistened; and reverted back to opaque upon drying.
  • a dried film of the coating on label substrate such as self- adhesive top-coated polyethylene, had surprisingly good adhesion and durability as compared to both water-based and solvent-based printed examples of the prior art. This adhesion and durability is vital if the coating is to be used for more demanding applications above and beyond the minimal requirements of novelty applications.
  • Coatings of the present invention also exhibited no apparent effect on the inherent, required properties of the substrate, i.e.
  • the binder medium is essential to the printing and adhesion properties of the present invention and comprises one or more UV curable resins, one or more diluent monomers, a water miscible solvent, deionized water, and, preferably, one or more photoinitiators.
  • Suitable water soluble/dilutable UV curable resins or combination of such resins are functionalized with chemical groups to enable crosslinking by UV light.
  • Preferred resins include urethanes, epoxy, polyester, polyether, polyvinyl alcohols, hydroxyalkyl derivatives of cellulose etc.
  • Water dilutable urethane acrylate oligomers such as CN9245 (Sartomer), Solmer SU550, Solmer SU560 (Soltech Ltd), Ebecryl 2002, and Ebecryl 2003 (Allnex) are preferred.
  • the binder would preferably contain 2-70%, more preferably 15-60%, but most preferably 20-50% of this resin.
  • Suitable diluent monomers which are reactive or cross linkable in the presence of UV light to assist with the control of the viscosity of the UV curable resin mentioned above are preferred. It is preferable that this diluent monomer be miscible with water.
  • Materials such as polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, ethoxylated bisphenol-A diacrylate, N-vinyl pyrrolidone, acryloyl morpholine, N-hydroxyethyl acrylamide, or ethoxylated trimethylolpropane triacrylate, and similar materials are preferred examples of such diluent monomers.
  • the binder would preferably contain 0-40%, more preferably 0-20%, but most preferably 5-15% of this diluent monomer as necessary to control viscosity.
  • a solvent which is miscible with water and evaporates readily with minimal heat application is preferred, such as methoxy propanol, ethoxy propanol, methoxy propyl acetate or methoxy propoxy propanol.
  • a preferred amount of 0-40%, more preferably 5-25%, but most preferably 10-20% of this solvent may be included in the binder to combine with the water and assist in removing it from the printed ink film. Said solvent is helpful for the efficient removal of water from the film during the curing process.
  • Water preferably deionized water, would preferably be present in the binder at 0- 70%; more preferably 15-50%>; and most preferably 15-40%.
  • the water controls the viscosity of the binder and also assists in producing the hydrochromic effect by combining with the specific extender pigments in the wet ink film.
  • the water in effect fills the voids in the extender pigment preventing the functionalized UV resin mentioned above from penetrating the particles. Once removed from the dried film, it leaves the pigment particles free to accept further water or air as required to produce the hydrochromic effect.
  • a photoinitiator or blend of photoinitiators to initiate the curing of the coating composition is preferably included.
  • photoinitiators including, but not restricted to, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (Irgacure TPO from BASF), bis(2,4,6,-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819 from BASF), bis(2,6- dimethoxybenzyl)-2,4,4-trimethylpentyl phosphine oxide, 2,4,6- trimethylbenzoylphenylphosphinate (Irgacure TPO-L from BASF), 2-benzyl-2- dimethylamino-l-(4-morpholinphenyl) butan-l -one (Irgacure 369 from BASF), 1 - hydroxycyclohexy
  • Non yellowing photoinitiators such as 2,4,6-trimethylbenzoyl diphenyl phosphine oxide and 2,4,6- trimethylbenzoylphenylphosphinate would be preferred in the white hydrochromic compositions where yellowing may be an issue.
  • the one or more photoinitiators are present in an amount of 0.5-5%. In another embodiment, the one or more photoinitiators are present in an amount of 1.5-5%.
  • a highly hygroscopic material such as polyvinyl pyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate copolymers, polyvinyl alcohols, or polyvinyl copolymers may be included, preferably at 0-25%; more preferably 0-15%; and most preferably 0-5%, in the binder as a moisture scavenger to speed up the transition from opaque to clear.
  • PVP polyvinyl pyrrolidone
  • PVAVC polyvinyl pyrrolidone/vinyl acetate copolymers
  • polyvinyl alcohols polyvinyl alcohols
  • polyvinyl copolymers preferably at 0-25%; more preferably 0-15%; and most preferably 0-5%, in the binder as a moisture scavenger to speed up the transition from opaque to clear.
  • the extender pigments, or in effect hydrochromic materials are preferably blended together to give the optimal opacity and transparency, and may preferably comprise 5-60%; more preferably 5-50%, or most preferably 10-40%) of the coating composition.
  • the hydrochromic materials may be taken from, but are not restricted to, a group of small particle size silica, silicates, barite powder, precipitated barium sulphate, barium carbonate, precipitated calcium carbonate, gypsum, clay, magnesium silicate, aluminum oxide, magnesium carbonate, etc., and combinations thereof.
  • the discrete particles may be of a porous nature, and/or be hydrophilic, and preferably represent a significant proportion of such particles.
  • Deionized water may be added to the coating to control viscosity/structure and to facilitate efficient printing.
  • the present invention may contain a colorant, preferably a transparent colored pigment, which will give an opaque color when dry, but a transparent color when wetted.
  • a colorant preferably a transparent colored pigment, which will give an opaque color when dry, but a transparent color when wetted.
  • the present invention may also contain a thermochromic pigment or slurry, which will preferably give an opaque color when dry, a transparent color when wetted with warm or cold water, or no color when wetted with warm or cold water.
  • the drying process was important in developing the properties of the coating.
  • conventional water-based UV inks it is essential that any residual water be driven off before UV curing, otherwise it can remain trapped in the ink film.
  • the water in the coating helps the pores in the pigment to remain open until the ink is cured.
  • the high pigment loading in the coating enables the water to subsequently escape.
  • the coating is preferably UV cured immediately or very soon after printing. It can then optionally be exposed to hot air drying or left to air dry to remove the last traces of moisture. Cool or hot air drying before UV curing is not preferred as it can cause loss of adhesion and compromised resistance properties.
  • the water and any solvent typically escape upwards out of the coating film.
  • the coatings of the present invention were applied using flat bed, sheet-fed screen printing. However, it is envisaged that the coating may also be applied by reel to reel screen printing, flexographic printing, gravure printing, or any other process capable of applying sufficient coating weight as required by the end-use application, and capable of applying sufficient UV energy to the coating surface as a drying operation.
  • the present invention enables coatings preferably having a dry film transmission density of 0.35 or higher measured on a Gretag D200-1 1 transmission densitometer, which is equivalent to similar prints of opaque white inks containing pigments such as titanium dioxide.
  • a liquid e.g. water
  • the same coating when wetted with a liquid, e.g. water, having a transmission density of between 0.00-0.15.
  • the water-based ink from Matsui measured 0.35 when fully dry and 0.05 when wetted.
  • the solvent-based ink from Sun Chemical measured 0.35 when fully dry and 0.10 when wetted.
  • the present invention preferably shows acceptable adhesion to paper, board and a variety of plastics substrates, including, but not restricted to, PVC, polyester, and top-coated polyethylene self-adhesive label material.
  • Solvent-based inks also have excellent hydrochromic properties. They also are comparatively slow drying and lack versatility of adhesion. Due to their high pigment loading they also can tend to dry on the press during stoppages.
  • 100% reactive UV energy curable inks are a possible embodiment of the present invention (see Example 6B). However, they are not the most preferred as they tend to wet the pigments too well to work optimally as hydrochromic effect coatings. They can be made to give a hydrochromic effect by having a high pigment to binder ratio but this may lead to increased viscosity and poor rheology, consequently making them difficult to print, especially on fast web-based presses.
  • 100% reactive it is understood that the main film forming materials (e.g.
  • oligomers, monomers, photoinitiators, etc. are 100% reactive (or nearly 100% reactive).
  • non-reactive materials e.g. additives, pigments, etc.
  • additives, pigments, etc. may also be incorporated into these inks and coatings.
  • UV coatings containing water, but without solvent are a possible embodiment of the present invention (see Example 7). These offer similar properties to 100% reactive UV coatings, but with improved rheology for better printability, with perhaps better dry opacity. However, they are not the most preferred embodiment of the present invention as they can take longer to fully dry due to slow release of the water content.
  • a water reducible UV curable binder was produced by combining water dilutable urethane acrylate oligomer (Ebecryl 2003 from Cytec) (29.5%), with a cross linkable monomer (acrylol morpholine) (12%), adding a water miscible solvent (methoxy propanol) (17.5%o), de-ionized water (36.5%), and a photoinitiator (2,4,6- trimethylbenzoylphenylphosphinate (TPO-L)) (4.5%). The mixture was stirred on a disc impellor mixer until homogenous. The viscosity of the binder resin was measured at 40 poise on an REL cone and plate viscometer at 25°C. Exam ple 1 UV Binder
  • Example 2 The formulation for Example 2 was as follows:
  • Example 2 Coating was then screen printed through a 43 threads per cm polyester mesh or equivalent to mask a screen, offset lithographic, or flexographic image previously printed on a self-adhesive top-coated polyethylene label, the coating then being cured by exposure to UV light. Subsequent wetting of the image with water revealed the underlying offset lithographic or flexographic image.
  • Example 2 By the addition of 5%> of a water miscible and UV curable colored toner to Example 2 above, a coating was produced which was colored and opaque when printed and dried as explained above, but was colored and transparent when wetted with water. As the untinted coating is essentially white when fully dried, the addition of toner produced a pale tint of the toner color when dried. When wetted, however, the color appeared stronger, but transparent, allowing the underlying legend to be read.
  • the formulation of the toner in this example was as follows:
  • thermochromic pigment specifically Thermasolve Magenta Touch from Sun Chemical
  • Thermasolve Magenta Touch is a thermochromic spray dried pigment which transitions from colored to clear at between 24 and 29°C (just below body temperature - hence "touch"). If wetted with warm water above 30°C (in the experiment the water was approximately 40°C from a hot tap) the coating became colorless and transparent.
  • Example 4 was produced by adding the pigment to the coating while stirring on a simple disc impellor mixer and continuing to stir until fully dispersed.
  • a coating was produced according to the following formula by high speed stirring on a disc mixer.
  • Example 5 printed well through a 43 threads per cm mesh and achieved good opacity very quickly on UV curing. This coating wetted more readily with water than Example 2 and gave an excellent hydrochromic effect with no marking where the water was applied.
  • Example 5 shows the advantage of using polyvinyl pyrrolidone as a hygroscopic additive.
  • Example 6 Hydrochromic Coating based on 100% UV Reactive Film Forming Materials
  • Example 6B was extremely high in viscosity and consequently difficult to print even through a 43 threads/cm screen mesh. Thinning with additional monomer such as TPGDA and or HDDA improved printing, but further reduced the hydrochromic effect. For these reasons, Example 6B is a possible embodiment within the scope of the present invention, but is not the most preferred inventive embodiment.
  • a water reducible UV coating was made according to the following formulation by blending the first four liquid items on a disc mixer and then slowly adding the hydrochromic powdered materials while stirring, easing the viscosity occasionally with the remaining deionized water.
  • Example 7 coating was printed through a 43 threads/cm screen mesh and cured at approximately 300 mJ/cm2 through a UV rig. Initially it remained transparent, but after a period of 3-5 minutes it started to develop opacity. An application of heat from a hot air blower assisted in developing acceptable opacity. Adhesion to paper, board and plastic substrates was good and the transition from opaque to clear on application of water was rapid as was the reversion to opaque on drying. This coating would be more suited to sheet-fed printing/coating, whereas the preferred option from examples 2, 3, 4, and 5 are printable on reel to reel machines. See Table 1 for general for properties.
  • the hydrochromic ink composition from Example 2 was printed onto top coated polyethylene self-adhesive label substrate using a Saurressig gravure color proofer CP.90/60 at the following etch depths and screen rulings: 32 ⁇ at 100 lines /cm; 35 ⁇ at 80 lines/cm; 40 ⁇ at 70 lines/cm; and 54 ⁇ at 60 lines/cm.
  • the prints were UV cured and dried as previously outlined above. The prints exhibited good adhesion and hydrochromic transition.
  • Example 2 The coating of Example 2 was also applied using an RK flatbed laboratory gravure coater onto board and top coated polyethylene label substrate.
  • the printed composition exhibited good adhesion and hydrochromic transition.
  • a black and white test card specifically a Leneta chart
  • Drying speed- The water and solvent based inks were printed onto coated board and timed until a finger dab no longer left an impression in the ink film.
  • the 100% reactive UV ink print was passed through the UV curing unit and assessed on exit.
  • the water-based UV ink print was also passed through the UV curing unit but then assessed by finger dab until fully dry. Each system was assessed and ranked for relative drying time which would influence expected press speeds.
  • the water-based coatings showed some damage and removal; the solvent-based coating showed severe damage and some removal; the Example 2 coatings of the present invention showed no damage at all.
  • the water-based coatings could be removed but with some difficulty; the solvent- based coating could be easily removed; the Example 2 coatings of the present invention could not be removed without extreme difficulty.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)
  • Paints Or Removers (AREA)

Abstract

La présente invention concerne la formulation d'encres hydrochromiques et de revêtements pouvant être durcis par exposition à une lumière UV, et qui de préférence adhèrent à des substrats d'étiquettes auto-adhésives plastiques couramment utilisés. L'encre ou le revêtement, quand il est imprimé et entièrement durci, devient opaque, de sorte qu'il va préférentiellement masquer une image ou une légende préalablement imprimée. Cependant, quand de l'eau est appliquée au revêtement durci, il devient translucide, ce qui permet de voir l'image ou la légende sous-jacente.
PCT/US2014/062834 2013-11-08 2014-10-29 Encre hydrochromique durcissable sous l'effet d'une énergie WO2015069513A1 (fr)

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US61/901,516 2013-11-08

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2552813A (en) * 2016-08-10 2018-02-14 Univ Oxford Innovation Ltd Wet surface indication
EP4286177A1 (fr) 2022-05-31 2023-12-06 BIC Violex Single Member S.A. Substrat de dessin
US20240083163A1 (en) * 2021-08-11 2024-03-14 Koenig & Bauer Ag Method for ink control in a printing press

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4452610A (en) * 1981-08-07 1984-06-05 Imperial Chemical Industries Plc Modified liquid hydrocarbons
US6416853B1 (en) * 1998-01-09 2002-07-09 The Pilot Ink Co., Ltd. Color-change laminates and toy sets with the use thereof
US20060229412A1 (en) * 2005-04-12 2006-10-12 Mikhail Laksin Water based energy curable hybrid systems with improved properties

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4452610A (en) * 1981-08-07 1984-06-05 Imperial Chemical Industries Plc Modified liquid hydrocarbons
US6416853B1 (en) * 1998-01-09 2002-07-09 The Pilot Ink Co., Ltd. Color-change laminates and toy sets with the use thereof
US20060229412A1 (en) * 2005-04-12 2006-10-12 Mikhail Laksin Water based energy curable hybrid systems with improved properties

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2552813A (en) * 2016-08-10 2018-02-14 Univ Oxford Innovation Ltd Wet surface indication
US10964236B2 (en) 2016-08-10 2021-03-30 Oxford University Innovation Limited Wet surface indication
US20240083163A1 (en) * 2021-08-11 2024-03-14 Koenig & Bauer Ag Method for ink control in a printing press
US11932004B1 (en) * 2021-08-11 2024-03-19 Koenig & Bauer Ag Method for ink control in a printing press
EP4286177A1 (fr) 2022-05-31 2023-12-06 BIC Violex Single Member S.A. Substrat de dessin

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