DESC:FIELD
The present disclosure relates to UV curable ink compositions and a process for preparation thereof.
DEFINITIONS AND ACRONYM FULL FORMS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Decal: The term “decal” sometimes called as “transfers” is a plastic, cloth, paper or ceramic substrate having a pattern or image printed on it, which can be moved to another surface upon contact, usually with the aid of heat or water. A decal is a substrate that has a design, pattern or image on it which is meant to be transferred to another surface.
Actinic radiation: The term “actinic radiation” refers to the component of solar radiation that consists mainly of ultraviolet radiation, which is capable of stimulating photochemical and photo biological effects.
Radiation-curable material: The term “radiation-curable material” refers to a material that polymerizes or crosslinks when exposed to radiation, commonly ultraviolet light, in the presence of a photoinitiator.
Water slide decals (or slip decals): The term “water slide decals” refers to water-mounted decals to bond the decal transferred to a surface. A water-based adhesive layer can be added to the decal to create a stronger bond or may be placed between layers of lacquer to create a durable decal transfer.
VOC: herein means Volatile Organic Compound/s

BACKGROUND
A decal or transfer is a plastic, cloth, paper or ceramic substrate having a pattern or image printed on it, which can be moved to another surface upon contact, usually with the aid of heat or water.
Typically, decal comprises a plurality of layers, namely, a face-stock made up of paper or film as the top layer, with the printing done on the operative top surface of the face-stock; an adhesive layer which is applied to the operative bottom of the face-stock; a silicone or release coating layer; and a paper or film liner as the bottom layer.
There are different types of decals, such as, water-slide or water-dip, vinyl peel-and-stick, and the like. The water-slide (or water-dip) decal is screen-printed on a layer of water-soluble adhesive on a water-resistant paper, which is first dipped in water prior to its application. On contacting the conventional decals with water, the glue is loosened and the decal can be removed from its backing.
Conventionally the preparation of decals is very complicated due to the fact that multiple layers of color inks are to be applied on the substrate. After each layer of application, the ink layer on the substrate is allowed to dry naturally by racking, otherwise it will cause tackiness of the print. Further, the ink layer of the film needs to be dried for a time period of about 8 hours to 25 hours in a moisture controlled and temperature controlled environment. Hence, it is observed that decals preparation may take almost 3 to 5 days for completion. Further, every time during racking and drying, there is a chance that the print may gather dust/contaminants, thereby making it necessary to provide a dust free environment for the racking.
Therefore, there is felt a need for an ink composition which does not require the decal to be racked, does not require a temperature and moisture controlled environment for racking or drying, can be directly used on the substrate within few hours, which speeds up the decal manufacturing process and also reduces the environmental burden of solvents or volatiles.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a UV curable ink composition.
Another object of the present disclosure is to provide a UV curable ink composition for making of decals having high flexibility, environment friendliness, and which can be manufactured in relatively less time.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to UV curable ink compositions. The UV curable ink composition comprises homogenous dispersion of a solid media in the range of 10 wt % to 20 wt % and a liquid media in the range of 80 wt % to 90 wt % of the ink composition.
The liquid media includes lactone(s) in the range of 10 wt % to 15 wt% with respect to the total weight of the ink composition; acetate(s) in the range of 10 wt % to 12 wt % with respect to the total weight of the ink composition; and acrylates in the range of 60 wt % to 70 wt % with respect to the total weight of ink composition, wherein the acrylates comprise polyester urethane acrylate, and urethane acrylate; a stabilizer in the range of 0.5 wt % to 1.5 wt % with respect to the total weight of the ink composition; and an additive in the range of 1.5 wt % to 3 wt % with respect to the total weight of the ink composition. The solid media include a photoinitiator in the range of 5 wt % to 10 wt % with respect to the total weight of the ink composition; and optionally a coloring agent in the range of 1 wt % to 15 wt % with respect to the total weight of the ink composition. The particle size of the solid media in the ink composition is less than or equal to 5 micron.
In accordance with the present disclosure, the photoinitiator is at least one selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (UV cure 907). The stabilizer is glycerol propoxylate (1PO/OH) triacrylate, and the additive is at least one selected from silicon acrylate, and silicone polyether acrylate. Typically, the ratio of polyester to urethane in the polyester urethane acrylate is 1:4.
Further, a process for preparing a UV curable ink composition is disclosed. The process comprises the steps of admixing solid media which includes a photoinitiator, and optionally a coloring agent, wherein the solid media has a particle size greater than or equal to 100 micron; with liquid media which includes lactone(s), acetate(s), acrylates, a stabilizer, and an additive to obtain an admixture; milling the admixture at a temperature in the range of 20 ?C to 40 ?C, preferably in a triple roll mill, to obtain a resultant mixture; and filtering the resultant mixture to obtain an ink composition comprising homogenized dispersion, wherein the particle size of the solid media is 5 micron or less.
DETAILED DESCRIPTION
In accordance with an aspect of the present disclosure, there is provided a UV curable ink composition. The UV curable ink composition comprises homogenous dispersion of a solid media in the range of 10 wt % to 20 wt % and a liquid media in the range of 80 wt % to 90 wt % of the ink composition.
More specifically, the liquid media includes lactone(s) in the range of 10 wt % to 15 wt% with respect to the total weight of the ink composition; acetate(s) in the range of 10 wt % to 12 wt % with respect to the total weight of the ink composition; acrylates in the range of 60 wt % to wt 70 wt % with respect to the total weight of ink composition, wherein the acrylates comprise polyester urethane acrylate, and urethane acrylate; a stabilizer in the range of 0.5 wt % to 1.5 wt % with respect to the total weight of the ink composition; and an additive in the range of 1.5 wt % to 3 wt % with respect to the total weight of the ink composition.
Further, the solid media includes a photoinitiator in the range of 5 wt % to 10 wt % with respect to the total weight of the ink composition; and optionally a coloring agent in the range of 1 wt % to 15 wt % with respect to the total weight of the ink composition. The particle size of the solid media in the ink composition is less than or equal to 5 micron.
The liquid media includes lactone(s), acetate(s), and acrylates, wherein the acrylates comprise a polyester urethane acrylate and a urethane acrylate, a stabilizer, and an additive. The solid media includes a photoinitiator, and optionally a coloring agent. The particle size of the solid media in the ink composition is less than or equal to 5 micron.
The inclusion of lactone(s), and acetate(s) in the ink composition of the present disclosure, in combination with the acrylate(s), particularly the urethane acrylates and the photoinitiator, allows the final dry film thickness to be controlled and results in improved film flexibility. Use of the ink composition of the present disclosure enables production of films with high flexibility.
One of the major factors to be considered when selecting the acetate(s) and lactone(s) as solvents to be used in the ink composition of the present disclosure is the resulting volatility of the ink composition. The volatility of the ink composition is critical because of the ‘open’ nature of the screen printing process, which freely allows evaporation. There is a large amount of wet ink that is being processed (e.g. being spread over the screen, forced through the screen, applied to the substrate) on or above the substrate. Therefore, the ink should not be so volatile that the ink undesirably thickens during the printing process, nor should it clog or block the printing screen (also due to thickening or solidifying in the holes in the mesh), if the print process is temporarily stopped. Thus, the inks need to be ‘screen stable’. A good indicator therefore, for making screen stable inks is the selection of solvents with lower volatilities. N-butyl acetate having an evaporation rate of 100 is used as the reference standard for volatile solvents and solvents having an evaporation rate in the range of 5 to 70 can be used in the present disclosure. The selection of the solvent is also dependent on the printing environment, for instance, when the printing is carried out in a hot country; solvents that are less volatile are selected, i.e., having a lower evaporation rate number. Other important factor in selecting the solvents include the compatibility of the solvents with the acrylates (oligomers and/or substrate) used and health and safety considerations. In one embodiment, the solvents (acetate and lactone) have low toxicity and/or a low odor. Typically, the solvents that have been given Volatile Organic Compound (VOC) exempt status by the United States Environmental Protection Agency or European Council are used in the ink composition of the present disclosure.
In accordance with the present disclosure, lactones are found to improve the adhesion of the inks to the substrates. The acrylates used as a radiation-curable oligomer in the ink composition of the present disclosure cures the ink composition on exposure to radiation, in the presence of the photoinitiator to form a cross-linked, solid film. The resulting film has good adhesion to different substrates. Acrylates that are compatible with the remaining ink components and are capable of curing to form a cross-linked, solid film can be used in the ink composition of the present disclosure. In an embodiment of the present disclosure, the acrylates used in the ink composition comprises a urethane backbone, such as, urethane (meth) acrylate oligomers, which have excellent adhesion and elongation properties. Di-, tri-, or even higher functional urethane acrylates can be used in the ink composition of the present disclosure.
Typically, curing of the ink composition is carried out by actinic radiation/UV radiation.
Typically, the acrylates that are used in the ink composition of the present disclosure comprise a backbone, for example a polyester backbone, a urethane backbone, or a polyether backbone, and one or more radiation polymerizable groups. The polymerizable group can be any group that is capable of polymerizing upon exposure to radiation. In one embodiment of the present disclosure, the acrylates polymerize by free radical polymerization.
In one embodiment of the present disclosure, the acrylates are oligomers with free radical polymerizable groups.
In accordance with the present disclosure, the stabilizer can be glycerol propoxylate (1PO/OH) triacrylate, which is marketed under the trade name “Genorad 16” (company Rahn AG). The stabilizer used in the ink composition maintains the shelf life of the ink composition.
In accordance with the present disclosure, the additives can be selected from the group consisting of silicon acrylate which is marketed under trade name “Tegorad 2200N”, silicone polyether acrylate which is marketed under trade name “Tegorad 2500”, and the like.
Typically, the ink composition of the present disclosure includes one or more photoinitiators. The photoinitiator can be any suitable free radical photoinitiator known in the art can be used which includes, but are not limited to, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-benzyl-2-dimethylamino-(4-morpholinophenyl)butan-1-one, iso propyl thioxanthone, benzil dimethylketal, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide or mixtures thereof. These photoinitiators are known and commercially available. For example, 1-hydroxycyclohexyl phenyl ketone is commercially available under the trade name “Irgacure” and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one is commercially available under the trade name “Darocur” (from Ciba), 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (commercially available under the trade name of “UV cure 907”).
In accordance with one embodiment of the present disclosure, the ink composition includes a coloring agent. The coloring agent can be a dye or a pigment or a combination thereof. In accordance with another embodiment of the present disclosure, the ink composition is devoid of coloring agent. The ink composition devoid of the coloring agent is colorless or transparent and can be used as an overcoat, which protects the underlying layers.
The coloring agent may be either dissolved or dispersed in the solvent of the ink composition. In one embodiment, the coloring agent is a dispersible pigment known in the art and is commercially available under the trade-name Paliotol (available from BASF), Cinquasia, and Irgalite (both available from Ciba Speciality Chemicals, Hostaperm and Sudarshan chemicals). The pigment can be of any required color, such as, Carbon black HAFN330 CI No 77266, Mogal L, Lemon Yellow 1240 CI No 77603, Simular Fast Yellow, Lemon Chrome CI No 77600, Middle Chrome, Cromopthal Yellow 8GN CI No 20037, Scarlet Chrome 1475 CI No 77605, Cromopthal Reb BRN CI No 20735, Cromopthal Scarlet RN CI No 20730, Sudarshan Pink 2190 CI No 73915, Fast Pink DB – CI 146, Beta Blue 2680 CI No 74160, Sudarshan Green 2724 CI-17 CI No 74260, Prime Rose Chrome 1011 CI No 77603, Hostaperm Orange GR, Printex 45, Sudarshan Yellow 162 CI – 17, Novaperm Yellow HR-1D CI No 21108, Hostaperm Violet RL021N CI No 51319, Sudaperm Orange 2915 CI-36 CI No 11780, Carmine Red BB10, Novaperm Red F5RK – IN, Novaperm Yellow HR70 CI No 211808, Bismuth Vandate 6615B, Cromopthal Yellow 8GN, Cromopthal Red BT CI No 20735, Silberline E2945, Aluminium Paste SS3500, Aluminium Paste Tt 77, and the like. Mixtures of pigments can be used in the ink composition of the present disclosure. Pigments, such as, cyan: phthalocyanine pigments such as Phthalocyanine blue 15.4.; Yellow: azo pigments such as Pigment yellow 120, Pigment yellow 151 and Pigment yellow 155; Magenta: quinacridone pigments, such as Pigment violet 19 or mixed crystal quinacridones such as Cromophtal Jet magenta 2BC and Cinquasia RT-355D; and Black: carbon black pigments such as Pigment black 7, can be used in the ink composition of the present disclosure.
Conventional solvent-based metallic pigments can produce very bright metallic effects. The metallic pigments are in the form of flakes or platelets and these are randomly oriented in the un-dried liquid ink. In case of solvent-containing inks, the flakes can align parallel to the print surface as the ink film thickness reduces due to solvent loss during the drying process. The alignment of the metallic pigment flakes parallel with the print surface results in good reflectivity and metallic lustre. However, the films produced can often have very poor rub properties, which mean that the pigment can be easily removed from the print surface. Further, the UV cured metallic pigments generally have better rub properties, but are often dull in appearance because the metallic pigment flakes do not have time to align during the rapid UV curing process.
The ink composition of the present disclosure further includes one or more metallic pigments. The ink composition of the present disclosure containing the metallic pigments is dried in two stages. During the solvent evaporation step, the metallic flakes have time to align, allowing a bright metallic effect to be produced in the final image. However, the UV curing stage yields a rub-resistant film and hence overcomes the problems associated with the conventional solvent-based metallic inks.
Typically, the ink composition of the present disclosure has a viscosity in the range of 0.1 Pas to 10 Pas (1 poise to 100 poise) at 25 ºC. The viscosity can be determined using a Rotothinner which operates with a fixed spindle and fixed speed.
In another aspect of the present disclosure, there is provided a process for preparing the ink composition. The process comprises the step of admixing solid media, including photoinitiator; and optionally a coloring agent, having particle size greater than or equal to 100 microns with liquid media including lactone(s), acetate(s),acrylates, stabilizer, and additive, to obtain an admixture. The admixture is milled at a temperature in the range of 20 ?C to 40 ?C, preferably in a triple roll mill, to obtain a resultant mixture. The resultant mixture is filtered to obtain the ink composition comprising homogenized dispersion, wherein the particle size of the solid media is 5 micron or less.
The mixing can be done in a high-speed water-cooled stirrer, and milling can be done in a horizontal bead-mill and milling on triple roll mills, preferably triple roll mill.
The ink composition devoid of coloring agent (transparent or colorless) in accordance with the present disclosure can be used as a varnish. In one embodiment, the colorless ink can be used as a varnish for a conventional solvent-based metallic effect ink. Metallic effect prints can be protected with known UV curable varnishes but the high film weight produced when these materials are jetted, which dulls or reduces the metallic lustre of the prints and is deleterious to their appearance. The presence of a relatively large proportion of volatile solvent in the colorless inks of the present disclosure allows a low film weight to be deposited. Conventional UV varnish produces 10 µm to 15 µm film over the surface of the print. However, the film can be reduced to 2 µm to 3 µm using the colorless ink of the present disclosure and hence reduces the deleterious effect on the appearance of the metallic print.
Conventional solvent-based screen printing inks dry solely by solvent evaporation without any crosslinking or polymerization taking place and hence, the film produced has limited chemical resistance properties. In the known art in order to improve resistance of prints to common solvents, such as, alcohols and petrol, binder materials that have limited solubility in these solvents are added to the ink. The binder is typically in solid form at 25 °C so that a solid printed film is produced when solvent is evaporated from the ink. Binders, like vinyl chloride copolymer resins generally have poor solubility in all but the strongest of solvents, such as, cyclohexanone, which is classified as “harmful” and has a strong odour. In order to solubilize the binder, these solvents are generally added to the conventional ink.
Whereas, the ink composition of the present disclosure includes radiation-curable material that cures as the ink dries and therefore does not require a binder in the ink in order to provide a printed film having improved solvent resistance and hence the ink composition of the present disclosure is free from harmful binders and is comparatively safe.
The present disclosure is further described in light of the following laboratory scale experiments/examples which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments/examples can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
Example-1: An ink composition (Color: Red) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
Genomer 4215- Aliphatic Polyester Urethane Acrylate 47.1
Gamma Butryl Lactone 13.4
Butyl Cellosolve Acetate 10.1
Tripropylene glycol diacrylate 7.8
Di functional Aliphatic Urethane Oligomer 7.00
Genorad 16 0.6
Tegorad 2200N 0.5
Tegorad 2500 0.5
Solid media:
UV Cure 907 1.8
Irgacure 184D 1.8
Darocure 1173 2.6
Cromophtal Red BRN 7.00
Total 100
Example 2: An ink composition (Color: Blue) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
CN 910 A70- Di-functional Urethane Acrylate Oligomer 10.00
CN9007- Difunctional Aliphatic Urethane Acrylate 34.6
Tripropylene Glycol Diacrylate 10.00
Gamma Butryl Lactone 14.00
Butyl cellosolve Acetate 10.00
Genorad 16 0.4
Tegorad 2200N 0.5
Tegorad 2500 0.5
Solid media:
Beta Blue 2680 10.0
Irgacure 184D 3.0
Darocure 1173 4.0
UVcure 907 3.0
Total 100
Example 3: An ink composition (Colorless/transparent) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid Media:
CN 910 A70- Di functional Urethane Acrylate Oligomer 10.00
CN9007- Difunctional Aliphatic Urethane Acrylate 44.6
Tripropylene Glycol Diacrylate 10.00
Gamma Butryl Lactone 14.00
Butyl cellosolve Acetate 10.00
Genorad 16 0.4
Tegorad 2200N 0.5
Tegorad 2500 0.5
Solid Media:
Irgacure 184D 3.0
Darocure 1173 4.0
UVcure 907 3.0
Total 100

Example 4: An under base was prepared in accordance with the present disclosure by combining the following components:
Description Quantity (g)
Liquid Media:
Genomer 4215- Aliphatic Polyester Urethane Acrylate 28.2
Gamma Butryl Lactone 14.00
Butyl Cellosolve Acetate 10.00
Polyurethane Beads 15
Tripropylene glycol diacrylate 11.00
Di functional Aliphatic Urethane Oligomer 14.00
Genorad 16 0.6
Tegorad 2200N 0.5
Tegorad 2500 0.5
Solid Media:
UV Cure 907 1.8
Irgacure 184D 1.8
Darocure 1173 2.6
Total 100
The viscosity was measured for the ink compositions of examples 1 to 4 at 25 ºC using Rotothinner and was found to be 25 ± 2 poise.
Experiment-1: Screen printing of the ink composition of the present disclosure as a Decal
The underbase of example 4 was screen printed onto a water slide transfer Decal using a 140 PW screen. The wet film was oven dried for 3 minutes at 60 ºC before being UV cured by passing the print through a conveyorised drier running at 10 m/min. The drier was fitted with one 80 W/cm2 medium pressure mercury lamp, to obtain a cured print.
The cured print was then printed with the ink composition of example 1 and dried for 3 minutes at 60 ºC before being UV cured by passing the print through a conveyorised drier running at 10 m/min. The drier was fitted with one 80 W/cm2 medium pressure mercury lamp, to obtain a dried colored print.
The dried colored print was then overprinted with a peelable varnish YR-5900 and air dried. After air drying of the peelable varnish YR-5900, the print was immersed in water to separate the transfer paper from the print, which was then applied on a helmet and water was dried out from the print. After the print was dried completely, the peelable varnish YR-5900 was peeled off. The decal so obtained was found to exhibit good adhesion to a helmet. The decal also exhibited enhanced gloss and high flexibility.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a UV curable ink composition which has high flexibility, is environment friendly with reduced processing time as compared to the conventional ink composition.
The foregoing description of the specific embodiments fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values ten percent higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:We Claim:
1. A UV curable ink composition comprising a homogenized dispersion of:
a) solid media including
i. a photoinitiator in the range of 5 wt % to 10 wt % with respect to the total weight of the ink composition; and
ii. optionally, a coloring agent in the range of 1 wt % to 15 wt % with respect to the total weight of the ink composition,
b) liquid media including
i. lactone(s) in the range of 10 wt % to 15 wt% with respect to the total weight of the ink composition;
ii. acetate(s) in the range of 10 wt % to 12 wt % with respect to the total weight of the ink composition;
iii. acrylates in the range of 60 wt % to 70 wt % with respect to the total weight of the ink composition, wherein the acrylates comprise polyester urethane acrylate, and urethane acrylate;
iv. a stabilizer in the range of 0.5 wt % to 1.5 wt % with respect to the total weight of the ink composition; and
v. an additive in the range of 1.5 wt % to 3 wt % with respect to the total weight of the ink composition.
2. The UV curable ink composition as claimed in claim 1, wherein said liquid media is in the range of 80 wt% to 90 wt% of total weight of the ink composition.
3. The UV curable ink composition as claimed in claim 1, wherein said solid media is in the range of 10 wt% to 20 wt% of total weight of the ink composition.
4. The UV curable ink composition as claimed in claim 1, wherein the particle size of said solid media is 5 micron or less.
5. The UV curable ink composition as claimed in claim 1, wherein said photoinitiator is selected from 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone.
6. The UV curable ink composition as claimed in claim 1, wherein said stabilizer is glycerol propoxylate (1PO/OH) triacrylate.
7. The UV curable ink composition as claimed in claim 1, wherein said additive is at least one selected from silicon acrylate, and silicone polyether acrylate.
8. The UV curable ink composition as claimed in claim 1, wherein the ratio of polyester to urethane in said polyester urethane acrylate is 1:4.
9. The UV curable ink composition as claimed in claim 1 has a viscosity in the range of 0.1 Pas to 10 Pas at 25 ºC.
10. A process for preparing a UV curable ink composition, said process comprising:
a) admixing
i. solid media which includes a photoinitiator, and optionally a coloring agent, wherein the solid media is having a particle size greater than or equal to 100 micron; with
ii. liquid media which includes lactone(s), acetate(s),acrylates, a stabilizer, and an additive to obtain an admixture;
b) milling said admixture at a temperature in the range of 20 ?C to 40 ?C, preferably in a triple roll mill, to obtain a resultant mixture; and
c) filtering said resultant mixture to obtain the ink composition comprising a homogenized dispersion, wherein the particle size of said solid media is 5 micron or less.