DESC:FIELD
The present disclosure relates to UV curable ink compositions and a process for preparation thereof.
DEFINITIONS
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.
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.
BACKGROUND
In screen printing, an ink which forms an image is supported on a mesh stretched across a frame. The ink is forced through the openings in the mesh and onto the substrate by the action of squeegee which is drawn across the mesh. Once the ink has been transferred to the substrate it must dry within a reasonable amount of time which is dependent on the application. Inks suitable for application to a substrate using screen printing typically have a viscosity in the range of 0.1 Pas to 10 Pas (1 poise to 100 poise) at 25 ºC, when measured under shear conditions encountered during the printing process.
The ink used for screen printing can be dried using different drying processes, such as, evaporation, and ultraviolet radiation. Screen printing inks dried by evaporation usually contain a large proportion of a mobile liquid vehicle or solvent and cannot be handled after printing until the inks have dried, either by evaporation of the solvent or its absorption into the substrate. The drying process is often slow and in many cases (for example, when printing on to a heat-sensitive substrate, such as, paper) cannot be accelerated.
Screen printing inks that are dried by exposure to ultraviolet radiation contain unsaturated organic compounds, termed monomers or oligomers, which polymerize by irradiation, typically UV radiation, in the presence of a photoinitiator. Drying ink by exposure to UV is more rapid than evaporation of solvent at moderate temperatures. However, it is difficult to formulate inks which polymerize by irradiation and at the same time also provide printed images having both scratch and chemical resistance and high flexibility.
The high ink deposit that is provided by screen printing provides high colour strength and opacity. However, unless the degree of crosslinking that occurs during the curing process during the UV radiation is controlled, films having very low flexibility are obtained. As the thickness of the ink film increases, the UV light penetrating the film decreases in intensity, resulting in a film which is cured at the surface, but is essentially uncured at the substrate/coating interface. The resulting stresses within the ink deposit tend to show as a wrinkling on the surface, which is easily detached, leaving fluid ink below.
In order to minimize the stress in curing of thick ink deposits, the coating should be formulated to cure throughout the thickness at a relatively uniform rate as opposed to curing at the surface. The film thickness can be controlled to some extent by mesh selection but even with the finest possible meshes, the film weight deposited is still 5 microns. The high film weight produced makes it difficult to get the required flexibility whilst retaining the chemical and scratch resistance properties.
Therefore, there is felt a need to provide an ink composition that overcomes the drawbacks mentioned herein above.

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.
Another object of the present disclosure is to provide a UV curable ink composition.
Yet another object of the present disclosure is to provide a UV curable ink composition for printing on graphic touch panels 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 homogenized dispersion of a solid media and a liquid media. 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 % with respect to the total weight of ink composition, wherein the acrylates comprise polyester urethane acrylate, epoxy acrylate, and urethane acrylate; stabilizer in the range of 0.5 wt % to 1.5 wt % with respect to the total weight of the ink composition; and additive in the range of 1.5 wt % to 3 wt % with respect to the total weight of the ink composition.
The solid media includes photoinitiator in the range of 5 wt % to 10 wt % with respect to the total weight of the ink composition; matting agent in the range of 1 wt % to 2 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.
Typically, the liquid media are in the range of 80 wt% to 92 wt% of the ink composition and the solid media is in the range of 8 wt% to 20 wt% of the ink composition. The particle size of the solid media in the ink composition is less than 5 micron.
Further, the present disclosure relates to a process for preparing a UV curable ink composition. The process comprises the steps of admixing solid media which includes a photoinitiator, matting agent, 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, 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 the present disclosure, the inclusion of lactones and acetates in the ink composition, in combination with the acrylates, preferably urethane acrylates and epoxy acrylates and photoinitiators, allows the final dry film thickness to be controlled and results in improved film flexibility.
In one aspect of the present disclosure, there is provided a UV curable ink composition. The UV curable ink composition comprises a solid media and a liquid media. Typically, the liquid media are in the range of 80 wt% to 92 wt% of the ink composition and the solid media is in the range of 8 wt% to 20 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; 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, epoxy acrylate, and urethane acrylate; stabilizer in the range of 0.5 wt % to 1.5 wt % with respect to the total weight of the ink composition; and additive in the range of 1.5 wt % to 3 wt % with respect to the total weight of the ink composition.
The solid media includes photoinitiator in the range of 5 wt% to 10 wt% with respect to the total weight of the ink composition; matting agent in the range of 1 wt% to 2 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 5 microns.
One of the major factors to be considered when selecting the acetate(s) and lactone(s) as solvent 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 they 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 solvent includes 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 odour. 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, lactone(s) 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. The 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. However, use of higher functional acrylates may lead to the formation of undesirable brittle films. Hence the use of epoxy acrylates along with urethane acrylates allows the film to be rigid and flexible as well. The ratio of the epoxy acrylate to urethane acrylate is in the range of 2:1 to 1:2.
In one embodiment of the present disclosure, the acrylates are oligomers with free radical polymerizable groups.
In one embodiment, the ratio of the polyester to the urethane in the polyester urethane acrylates is 1:4.
Typically, the 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, urethane backbone, or 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 an exemplary embodiment the acrylates are polyester urethane acrylates, epoxy acrylates and urethane acrylates used in the ink composition.
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 matting agent can be selected from the group consisting synthetic barium sulphate (trade name “Blanc fixe micro”) and fumed silica (aerosil). The major global producers of fumed silica are Evonik (who sells it under the name “Aerosil”).
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.
The ink composition of the present disclosure includes one or more photoinitiators. Typically, the photoinitiator can be any suitable free radical photoinitiator known in the art can be used including, but 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, benzyl dimethylketal, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide or mixtures thereof. These photoinitiators are known and are 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), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone available under the trade name “UV cure 907”.
In accordance with one embodiment of the present disclosure, the ink composition includes a coloring agent. The colouring 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 colouring agent may be either dissolved or dispersed in the solvent of the ink composition. In one embodiment, the colouring agent is a dispersible pigment known in the art and is commercially available under the trade-names Paliotol (available from BASF), Cinquasia, and Irgalite (both available from Ciba Speciality Chemicals, Hostaperm and Sudarshan chemicals). The pigment can be of any required colour, 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. Whereas in case of the ink composition of the present disclosure further includes one or more metallic pigments. Further, 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 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; matting agent, 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 oC to 40 oC to obtain a resultant mixture. The resultant mixture is filtered to obtain the ink composition comprising homogenized dispersion, wherein the particle size of said solid media is 5 microns 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.
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 acrylates 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 ink composition which is devoid of coloring agent (transparent or colorless) in accordance with the present disclosure can be used as a varnish. In one embodiment, the colourless 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 colourless 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 colourless ink of the present disclosure and hence reduces the deleterious effect on the appearance of the metallic print.
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 (Colour: Black Smoke) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
Genomer 4215- Aliphatic Polyester Urethane Acrylate 37.00
CN 104 – Epoxy Acrylate 15.00
Gamma Butryl Lactone 13.4
Butyl Cellosolve Acetate 10.1
Tripropylene glycol diacrylate 7.8
Di functional Aliphatic Urethane Oligomer 7.00
Genorad16 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
Carbon Black HAF N 330 0.8
Blanc Fixe Micro 0.70
Aerosil 0.4
Total 100

Example-2: An ink composition (Colour: Black Smoke) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
CN 104 Epoxy Acrylate 15.00
CN9007- Difunctional Aliphatic Urethane Acrylate 37.70
Tripropylene Glycol Diacrylate 10.00
Gamma Butryl Lactone 14.00
Butyl cellosolve Acetate 10.00
Genorad 16 0.40
Tegorad 2200N 0.5
Tegorad 2500 0.5
Solid media:
Carbon Black HAF N 330 0.8
Blanc Fixe Micro 0.70
Aerosil 0.4
Irgacure 184D 3.0
Darocure 1173 4.0
UVcure 907 3.0
Total 100

Example-3: An ink composition (Colour: Black) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
CN 104 Epoxy Acrylate 18.00
CN 964 A85 Urethane Acrylate 34.7
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:
Carbon Black HAF N 330 0.8
Blanc Fixe b Micro 0.70
Aerosil 0.4
Irgacure 184D 3.0
Darocure 1173 4.0
UVcure 907 3.0
Total 100

Example -4: An ink composition (Colour: Black Diffuser) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
Genomer 4215- Aliphatic Polyester Urethane Acrylate 35.00
CN 104 – Epoxy Acrylate 16.10
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
Carbon Black HAF N 330 0.8
Acematt OK 412 2.00
Total 100

Example -5: An ink composition (Colour: Black Diffuser) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
CN9007- Difunctional Aliphatic Urethane Acrylate 32.00
CN 104 – Epoxy Acrylate 16.10
Gamma Butryl Lactone 13.4
Butyl Cellosolve Acetate 10.1
Tripropylene glycol diacrylate 7.8
Di functional Aliphatic Urethane Oligomer 10.00
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
Carbon Black HAF N 330 0.8
Acematt OK 412 2.00
Total 100

Example -6: An ink composition (Transparent/colorless) in accordance with the present disclosure was prepared by combining the following components:
Description Quantity (g)
Liquid media:
CN 964 A85 Urethane Acrylate 32.00
CN 104 – Epoxy Acrylate 16.10
Gamma Butryl Lactone 13.4
Butyl Cellosolve Acetate 10.1
Tripropylene glycol diacrylate 7.8
Di functional Aliphatic Urethane Oligomer 10.8
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
Acematt OK 412 2.00
Total 100

The viscosity was measured for the ink compositions of examples 1 to 6 at 25 ºC using Rotothinner and was found to be 25 poise.
Experiment-1: Screen printing was done on a polycarbonate substrate using the ink composition of the disclosure
The ink composition of examples 1 to 6 were screen printed on polycarbonate substrate (0.5 mm) 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 conveyor 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 ink composition of examples 1-6 exhibited satisfactory adhesion on the polycarbonate substrates. There were no pinholes observed on the printed surface.
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 for printing on graphic touch panels, that has high flexibility, and is environment friendly with reduced processing time.
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:1. A UV curable ink composition comprising a homogenized dispersion of:
a) solid media including
i. photoinitiator in the range of 5 wt% to 10 wt% with respect to the total weight of the ink composition;
ii. matting agent in the range of 1 wt % to 2 wt % with respect to the total weight of the ink composition; and
iii. 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, epoxy acrylate and urethane acrylate;
iv. stabilizer in the range of 0.5 wt% to 1.5 wt% with respect to the total weight of the ink composition; and
v. 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 92 wt% of the 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 8 wt% to 20 wt% of the 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 selected from silicon acrylate, and silicone polyether acrylate; and said matting agent is selected from synthetic barium sulphate and fumed silica
8. 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.
9. 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, wherein the ratio of said epoxy acrylate to said urethane acrylate is in the range of 2:1 to 1:2.
10. A process for preparing a UV curable ink composition, said process comprising:
a) admixing
i. solid media including photoinitiator, matting agent, and optionally a coloring agent, having particle size greater than or equal to 100 micron; with
ii. liquid media including lactone(s), acetate(s), acrylates, stabilizer and additive to obtain an admixture;
b) milling said admixture, preferably in a triple roll mill, at a temperature in the range of 20 to 40 oC 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.