T E C H NICA L FIE L D OF INV E NTIO N

[001] The present invention relates to writing surfaces, and particularly to a polymeric writing surface or media. The embodiments of the present invention relates to a reusable paper material and method of fabricating the same.

BAC K G R OU ND O F INV E NT ION

[002] Paper has been a crucial writing surface for recording and disseminating information. From its invention in China to diffusion to India and rest of the world, paper replaced almost all writing surfaces those existed prior to it, and made the writing and maintaining written records far easier than any of its predecessors. Despite their impact on advancing human intellect and progress, their negative impact on environment cannot be understated, given that all paper comes from cutti ng of trees. It is a common knowledge that it takes about 12 trees to make one ton of 100 percent non- recycled newsprint It would take more than half a tree to make 10 reams of 100 percent, non- recycled 20- lb. copier paper. One tree makes about 16 reams of copy paper, or about 8000 sheets. In other words, one ream (500 sheets) uses 6 percent of a tree. As one can visualise, a large number of trees are cut every day to make paper that satisfies the global demand for paper. Moreover, the manufacturing of paper is also an energy intensive process that requires large quantity of water. The paper is recyclable but process of recycling involves disintegration, decolouration, de-inking of fibres in paper to make a new sheet of paper. This process involves cost that prohibits largescale recycling. Furthermore, the quality of recycled paper too fails to meet the required standard for many applications.

[003] Conventionally, paper includes randomly oriented fibres that render such surfaces rough and porous. Such surfaces are also hydrophilic so that when a drop of ink is dispersed on them, it wets the surface of the paper completely so that the colloidal particles that form the ink go into the pores of the paper and accomplish the act of writi ng. M oreover, the topographi cal and chemi cal property of the paper is controlled in a manner such that the ink spreads more along the thick direction into the paper, than in the horizontal direction; and thus, leading to very high resolution of the writi ng or printing. The disadvantage of such large extent of wetting is that the ink particles no longer remain accessible for removal or de- wetting by any simple process and the paper essentially forfeits its reusability.

[004] US 8203583 discloses an ink-free rewritable media that is imaged via a UV produced image in combination with a uniform heat source. The combination produces photochromic change i n the paper. CN 103434309 discloses a reusable water rewritable paper using water hydrochromic that change their molecular configuration or conformation causing change in colour in presence of water. W 02015032327 discloses a reusable water writing paper using oxazoline water- induced colour changing dye as the chromogenic component which changes its colour upon contacting water so as to display characters and/or patterns, and the colour returns when the water dries so as to cause the displayed characters and/or patterns to disappear. CN2628572 Y discloses a reusable water writing paper havi ng a paper base, a carbon black layer and a white spray i ng layer.

[005] Several attempts have been made to make the paper reusable with washing or wiping methods, which mostly involve making ink that gets vanished when exposed to either light or water. Y et, due to chemistry of the paper as explained previously, wiping off such inch always entails a palpable damage to the surface of paper. T here has not been any maj or attempt to make a paper I i ke material that can be reused, ever since paper was first invented.

[006] A ccordi ngly, there remai ns a need for devel opment of a writi ng surface or media that enables deletion of ink without complicated processes and by simple action of wiping or washing, and thus enabling reuse of same paper with same quality.

[007] The value additions and above mentioned shortcomings, disadvantages and problems are addressed herein, as detailed below.

O BJ E CT OF INV E NT ION

[008] The primary object of the present invention is to provide a writing surface or media that enables deletion of ink without complicated processes and by simple action of wiping or washing, and thus enabling reuse of same paper with same quality. [009] Another object of the present invention is to provide a writing media or surface wherein an ink can be easily removed by simply wiping with a wet cloth.

[0010] Y et another object of the present invention is to provide a writing surface or media that is made up of polymeric porous surface.

[0011] Y et another object of the present invention is to provide a writing media or surface that is partially hydrophilic in nature with a unique roughness pattern comprising nanostructures and microstructures.

[0012] Y et another object of the present invention is to provide a method of fabrication or synthesizing the reusable writing surface or media or paper.

[0013] Y et another object of the present invention is to provide a process for generati ng roughness patterns having length scales varying from tens of nanometers to tens micrometers by casting against porous and/ or rough templates havi ng controlled pore dimensions and pore morphology.

[0014] Y et another object of the present invention is to provide a writi ng and / or printing media or surface having porous surface with optimum three-dimensional structure and dimension so that particles remain weakly adhered to it and can be easi ly removed when ri nsed with water, or wi ped with a wet cl oth.

[0015] These and other objects and advantages of the embodiments herein wi ll become readily apparent from the following detailed description taken in conj uncti on with the accompanyi ng drawi ngs.

SU M MA RY O F INV E NT IO N

[0016] The various embodiments of the present invention provide a reusable writing surface or media and a method of fabricating the same. The writing or surface or media comprises a paper material having a plurality of randomly placed polymeric structures forming varied templates on the surface of the paper material. The plurality of polymeric structures are nanostructures and microstructures varying in diameter from 15 nm to ~150 ι m and height of 5 nm to 27i m

[0017] According to another embodiment of the present invention, a method of fabricating a reusable writing surface or media is provided. The method comprises preparing a rough polymeric template (101). The polymeric template is prepared by using a polymer, a cross-linking agent, a promoter, a redox initiator and optionally a precipitator. Further, a polymeric film is casted on the polymeric template (102). A sheet of paper is placed on the polymeric film while a cross- linking of a polymeric materials takes place (103) in the polymeric film and polymeric template. The sheet of paper is peeled off from the polymeric template ( 104) . T he peel ed sheet of paper i s dri ed ( 105) .

[0018] According to an embodiment of the present invention, the step of preparing the polymeric template comprises preparing a pre-polymer solution by mixing the polymer, the cross-linking agent the promoter, the redox initiator and optionally the precipitator. The pre-polymer solution is poured on a tray, and the pre- pol y mer sol uti on i s dri ed at a predetermi ned temperature of 35°-40° C .

[0019] According to an embodiment of the present i nvention, the polymer is 2- hydroxyethyl methacryl ate ( H E M A ) .

[0020] According to an embodiment of the present invention, the cross-linking agent is Ethylene glycol dimethacrylate (EG DMA).

[0021] According to an embodiment of the present invention, the promoter is T etramethyl ethyl enediami ne (T E M E D).

[0022] According to an embodiment of the present invention, the redox initiator is Ammonium Per Sulfate (A PS).

[0023] According to an embodiment of the present invention, the precipitator is sodi um chl oh de or cal ci um chl oh de.

[0024] According to another embodiment of the present invention, the step of preparing the polymeric template comprises dissolving an agarose gel in Tris/Borate/E DTA (T BE) buffer solution to form an agarose gel solution. The agarose gel solution is kept at a predetermined temperature of 90eC-100°C for atleast 4 minutes. The hot agarose gel is poured on a tray or dish and the agarose gel solution is cooled down for atleast 2 hours.

[0025] According to an embodiment of the present invention, the step of casting the polymeric film on the polymeric template comprises pouring a film formi ng material on a polymeric template forming a layer of thickness of 100-500 ι m The film forming material may be silicone, polyurethane but not excluding others.

[0026] According to an embodiment of the present invention, the peeled sheet of paper comprises a plurality of randomly placed polymeric structures formi ng varied templates on the surface of the paper. The plurality of polymeric structures are nanostructures and mi crostructures varying in diameter from 15 nm to 150 1 m and a height of 5 nm to 50 ι m It is worth mentioning here that these ranges are not restrictive.

[0027] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the followi ng descriptions, while indicati ng preferred embodiments and numerous specific details thereof, are given by way of illustration and not of I i mitation. Many changes and modificati ons may be made withi n the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

B RIE F DE SC RIPT ION OF D RAWINGS

[0028] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0029] FIG . 1 is a flow chart showing the various steps involved in the method of fabricating a reusable writing surface or media, according to an embodiment of the present invention.

[0030] FIG . 2 is an image of roughness pattern of typical polymeric papers, wherein (a-d) show the optical profilometer images of different random surfaces of the reusable polymeric writing surface or media, according to an embodi ment of the present i nventi on.

[0031] FIG . 3 shows the surface patterns of the li ne drawn using the ball point pen on the polymeric writing surface or media, according to an embodiment of the present invention.

[0032] F I G . 4 shows surface patterns of the I i ne drawn usi ng the bal I poi nt pen on the polymeric writing surface or media, wherein images (a) to (c) correspond to following different pens: Cello gripper 0.5, Cello pinpoint X S and Rorito L i qui fast respectively, accordi ng to an embodi ment of the present i nventi on.

[0033] FIG . 5 illustrates laser printing on conventional paper and reusable polymeric surface, according to an embodiment of the present invention. [0034] FIG . 6 shows that root mean square (rms) roughness of surface remains nearly unaltered over several cycles of writing with a ball pen and wiping the ink off the paper using a wet cloth and drying in atmospheric condition, according to an embodiment of the present invention.

[0035] F I G . 7 shows the opti cal prof i I ometer i mages of surfaces correspond! ng to FIG. 6, according to an embodiment of the present invention.

[0036] FIG . 8 il lustrates inkjet printing on convention paper and reusable polymeric surface, according to an embodiment herein.

[0037] FIG . 9 il lustrates wettability of Ink-jet printer's ink on A4 size paper and polymeric paper, wherein (a-e) shows wettability on A4 size paper and (f-j) shows wettability on rough polymeric paper, according to an embodiment of the present invention.

[0038] FIG . 10 shows the equi librium advancing contact angle that a typical ink of inkjet printer forms on polymeric paper of different roughness, according to an embodi ment of the present i nventi on.

DE TAIL E D DE SC RIPT ION O F E M BO DIM E NTS

[0039] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. The embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical, electronic and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0040] The various embodiments of the present invention provide a writing surface or media that can be used again and agai n. T he writing surface or media enables deletion of ink without any complicated processes and by simple action of wiping or washing, and thus enabling the reuse of same material with same quality. T he writing media is a polymeric writing media or surface. The writing media or surface, as disclosed herein, allows ink of a commonly used ball pen or other such pens, and other commonly used inks, and that from laser jet printers to produce delible impressions, which can then be wiped off gently with a wet cloth or other such equipment. T he polymeric surface of the present embodiment may be used for multi ple cycles of writing and wiping without any damage to the surface. In an embodiment, the polymer media or surface has control led topography enabling it to be easily washed, dried and reused.

[0041] The present invention provides a novel reusable writing surface or material or media on which it is possible to write using a ball pen and to print using a laser jet and an inkjet printer. The paper, disclosed in the present invention, allows the ink to be removed by simple process without the surface physical and chemical features getting altered to any measurable extent and the cleaned surface allows it be re- used for writi ng and pri nti ng over many cycl es.

[0042] According to an embodiment of the present invention, the reusable writing surface or media, comprises a paper material having a plurality of randomly placed polymeric structures forming varied templates on the surface of the paper material. The plurality of polymeric structures are nanostructures and mi crostructures varying in diameter from 15 nm to -150 ι m and height of 5 nm to 50i m.

[0043] FIG . 1 is a flow chart showing the various steps involved in the method of fabricating a reusable writing surface or media, according to an embodiment of the present invention. The method comprises preparing a polymeric template (101). The polymeric template is prepared by using a polymer, a cross-linking agent, a promoter, a redox initiator and optionally a precipitator. Further, a polymeric film is casted on the polymeric template (102). A sheet of paper is placed on the polymeric film while a cross-linking of a polymeric materials takes place (103) in the polymeric film and polymeric template. The sheet of paper is peeled off from the polymeric template (104). T he peeled sheet of paper is dried (105).

[0044] According to an embodiment of the present invention, the step of preparing the polymeric template comprises preparing a pre-polymer solution by mixing the polymer, the cross-linking agent the promoter, the redox initiator and optionally the precipitator. The pre-polymer solution is poured on a tray, and the pre-polymer solution is dried at a predetermined temperature of 35°-40° C.

[0045] According to an embodiment of the present i nvention, the polymer is 2- hydroxyethyl methacryl ate ( H E M A ) . [0046] According to an embodiment of the present invention, the cross-linking agent is Ethylene glycol dimethacrylate (EG DMA).

[0047] According to an embodiment of the present invention, the promoter is T etramethyl ethyl enediami ne (T E M E D).

[0048] A ccordi ng to an embodi ment of the present i nventi on, the redox i ni ti ator i s Ammonium Per Sulfate (A PS).

[0049] According to an embodiment of the present invention, the precipitator is sodi um chl oh de or cal ci um chl oh de.

[0050] According to another embodiment of the present invention, the step of preparing the polymeric template comprises dissolving an agarose gel in Tris/Borate/E DTA (T BE) buffer solution to form an agarose gel solution. The agarose gel solution is kept at a predetermined temperature of 90eC-100°C for at I east 4 mi nutes. T he hot agarose gel is poured on a tray or dish and the agarose gel solution is cooled down for at least 2 hours.

[0051] According to an embodiment of the present invention, the step of casting the polymeric film on the polymeric template comprises pouring a si I i cone/poly urethane material on the polymeric template forming a layer of thickness of 50-500 1 m.

[0052] According to an embodiment of the present invention, the peeled sheet of paper comprises a plurality of randomly placed polymeric structures forming varied templates on the surface of the paper. The plurality of polymeric structures are nanostructures and mi crostructures varying in diameter from 15 nm to 150 1 m and a height of 5 nm to 50 1 m. EX PE RIM E NTA L DETAILS

[0053] The present invention makes use of an environmentally benign polymeric material that has not been used earlier for writi ng or printing because of small frictional resistance that it exerts to sliding of a ball pen and because of its limited wettability by the ink. However, the present invention has made the use of this material suitable for writing and printing by roughening its surface which enhances both frictional characteristics of the surface and its wettability. So when a ball pen is slide past its surface, ink from the pen gets dispensed on ίζ the ink from different sources, e.g. ball pen, laser-jet can spread on it albeit to a limited extent and the ink can be easily removed by simple rinsing or wiping it with a wet cloth. The paper can be subjected to many such cycles of writing/printing - cleaning and rewriting without any loss of reusability. Thus, the invention opens up the possibility of reducing the usage of conventional paper which is expected to di mi ni sh the envi ronmental i mpact of usi ng paper.

[0054] Preparation of template using H E MA: In order to prepare the template, the pre-polymer solution (herein called liquid A) of 2-hydroxyethyl methacrylate (H E MA) in water was crosslinked with Ethylene glycol di methacrylate (EG DMA) as cross-li nker (1%-5% by weight of monomer), T E ME D as a promoter (1% -5% by weight of monomer), ammonium per sulfate (A PS) as a redox initiator (0.5%-1.0% by weight of monomer). In order to precipitate the non-aqueous phase sodium chloride (5.0%-8.0% by weight of water) was used as the precipitant. The monomer-to-water weight ratio was maintained such that the final product contains 70%-98% by weight of water. The prepolymer solution mixed with al I the reagents at desi red weight rati o was poured on a tray ( made of glass/A I uminium/steel/acrylic sheet), placed horizontally and was allowed to crosslink. The quantity of the pre-polymer solution was such that after crosslinking 5-10 mm gel thickness is achieved. Following crosslinking, the excess water in gel was drained out and fresh water was added to it for dissolvi ng any crystallized salt from the pores of the gel. This process was repeated 2-3 times. Following which, the gel layer was allowed to dry out in a hot atmosphere of 35°-40° C to the extent that 20%-90% of the initial water content of the gel was removed. In particular, the pores on the gel surface opened up while also remaining visi bly wet This surface was used as template for making the polymeric paper.

[0055] Preparation of template using Agarose: In order to prepare agarose gel template, 5X Tris/Borate/E DTA (T BE) buffer was first prepared by mixing in 20 mL of 0.5M E DTA solution (pH 8.3), 27.5 gm of boric acid, 54 gm of tris base and 980 mL of water. Prepared sol uti on was kept i n i ncubator shaker at 25eC unti I the constituents completely dissolved into the liquid. Desired amount of agarose was taken i n a glass beaker and 5X T B E buffer was added to it such that the f i nal agarose content in the solution was 0.5 to 4% w/w. The resulting solution was placed inside a microwave oven maintained at ~90eC-100°C for 4 minutes within which the solution turned transparent Makeup water was added to keep the volume of the sol ution constant. It was stirred for another 2 minutes at that temperature and the hot solution was then poured inside a petridish or a tray The sol uti on was al I owed to cool down and crossl i nk for 2 hours.

[0056] Casting of polymeric film on porous template: The templates prepared in the above methods were found to have pores, the size of which varied from tens of nm to tens of microns. Silicone/polyurethane material of different types (herein called liquid B), e.g. Dow Corning commercial product Sylgard 184 (mixed with the curing agent in 10:1 w/w ratio), TSE-3455T from Momentive (two components mixed as per the instruction of the manufacturer) were used for polymeric precursor material for casting their film on such porous templates. The liquid B was poured on the template while driving a doctor's blade over it to achieve thickness of 100-500 1 m

[0057] C uring of the precursor /cross linkable liquid: The film of liquid B is then crossl inked at room temperature for 2-3 hours during which it cures partially. A backing material which is usually a sheet of paper is then placed on the top surface of the partially cured layer which is then completely crossli nked in another 2-3 hours.

[0058] Separation of the crossli nked elastomeric layer from gel surface: The crosslinked layer along with the backing layer is gently peeled off the template. Flakes of the gel template normally remain adhered to this layer which is removed by wiping its surface off using a wet cloth. The surface is then dried in open atmosphere.

[0059] C haracterizing the polymeric paper: The polymeric paper was characterized by its roughness. In the experiments, surface area of a paper was scanned at different locations using an optical profilometer to obtain the corresponding rms (root mean square) roughness. The average value of the rms roughness data was generated from several such measurements. FIG . 2 is an image of roughness pattern of typical polymeric papers, wherein (a-d) show the optical profilometer images of different random surfaces of the reusable polymeric writing surface or media, according to an embodiment of the present invention. With respect to FIG . 2, different patterns or templates of randomly rough surfaces of the writing material can be seen. These are the polymeric microstructures and the nanostructures. The polymeric surface is partially hydrophobic and with roughness patterns as shown in the FIG . 2.

[0060] The sequence of optical micrographs demonstrates the effect of surface roughness of polymeric paper on quality of writing when a typical ball is used for this purpose. A li ne was drawn on polymeric paper of root mean square (rms) roughness varying from 10 nm to 1.6 ι m and was examined under optical microscope. FIG . 3 shows the surface patterns of the li ne drawn usi ng the ball point pen on the polymeric writing surface or media, according to an embodi ment of the present i nvention. With respect to FIG . 3, the line was fully disintegrated into tiny droplets on a smooth surface with rms roughness 10 nm but became less disintegrated as roughness was increased. The sharpness of i mage was found to maximize at an intermediate roughness of 0.75-0.93 ι m

[0061] The sequence of optical micrographs captured at two different magnifications show the effect of ball pen size on ability to write on a typical polymeric paper. Here a paper of root mean square (rms) roughness of 1.6 ι m was used for writing with ball pens. FIG . 4 shows surface patterns of the line drawn using the ball point pen on the polymeric writing surface or media, wherein images (a) to (c) correspond to following different pens: Cello gripper 0.5, Cello pinpoint X S and Rorito Liquifast respectively, according to an embodiment of the present invention. With respect to FIG . 4, the images clearly show that ball pen C el I o gri pper 0.5 generates sharpest and conti nuous I i ne.

[0062] According to the present invention, the polymeric paper or media can be used for laser pri nting over several cycles. Whereas, on conventional paper, laser printing can be done only once, on a reusable polymeric paper, laser printing can be done multi pi e ti mes, i .e. the pri nted i mage on paper can be wi ped off with wet cloth and dried in atmospheric condition and reused again for printing. FIG . 5 illustrates laser printing on conventional paper and reusable polymeric surface, according to an embodiment of the present invention. With respect to FIG . 5, the series of images show that the quality of the printed image does not diminish over repeated cycles. A polymeric paper of rms roughness 0.15 ι m was used for demonstrati ng the reusabil ity of the paper.

[0063] FIG. 6 shows that root mean square (rms) roughness of surface remains nearly unaltered over several cycles of writing with a ball pen and wiping the ink off the paper using a wet cloth and drying in atmospheric condition, according to an embodiment of the present invention. In order to obtain the rms roughness of these papers, 800 μιη x 800 μιη area was scanned.

[0064] F I G . 7 shows the opti cal prof i I ometer i mages of surfaces correspondi ng to F I G . 6, accordi ng to an embodi ment of the present i nventi on.

[0065] FIG . 8 il lustrates inkjet printing on convention paper and reusable polymeric surface, according to an embodiment herein. With respect to FIG . 8, the rough polymeric paper can be used for inkjet printing over several cycles. In each cycle, the printed i mage on paper is cleaned with wet cloth and dried in atmospheric condition. A polymeric paper of rms roughness of 0.15 ι m was used in these experiments.

[0066] FIG . 9 il lustrates wettabil ity of Ink-jet printer's ink on A4 size paper and polymeric paper, wherein (a-e) shows wettability on A4 size paper and (f-j) shows wettability on rough polymeric paper, according to an embodiment of the present invention. FIG . 9(a-e) shows that ink completely spreads/absorbs on the fibrous network of A4 Size paper. On the other hand, ink disintegrates into tiny drops on polymeric surface as shown in FIG . 9(f-j ). This shows the printing ability of the polymeric paper & that can be further enhanced by tuning the roughness of the polymeric paper. The rms roughness of papers as shown in figure (e) and (i) are 5.67 1 m and 1.33 1 m respectively.

[0067] FIG . 10 shows the equi librium advancing contact angle that a typical ink of inkjet printer forms on polymeric paper of different roughness, according to an embodiment of the present invention. The angle varies from 31 degrees to 51 degrees.

A) A DVA NTAG E S OF INV E NTIO N

[0068] The present invention provides a reusable paper wherein the ink can be removed by simple wiping off with a wet cloth. The paper is used for several cycles which reduces the cost of making the paper. The paper is reusable without any loss of quality over several cycles. The roughness patterns of the paper can be opti mized for drawing continuous yet sharp li ne of ink on the paper, very much similar to conventional paper. The paper allows almost all types of conventional inks to be used for writing without requiring any specially prepared ink material. The ink can be easily removed without any need of sophisticated equipment. Thus, the reusable paper does not require any special skill/equi pment to be adopted for writi ng and rewriti ng. It is possi bl e to draw also conti nuous I i ne usi ng conducting ink, which can be important for generating electronic circuit on flexible substrates and in reversible manner. It will allow also easy recovery of materials used for making the circuit after its use.

[0069] It i s to be understood that the phraseol ogy or termi nol ogy empl oyed herei n is for the purpose of description and not of l imitation. T herefore, 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 claims presented in the complete specification or non-provisional application.