DESC:FORM 2

THE PATENTS ACT, 1970

(39 of 1970)

&

THE PATENT RULES, 2003

COMPLETE SPECIFICATION

[See Section 10 and Rule 13]

TITLE:

“PRINTING FLEXIBLE ELECTROCHROMIC DISPLAY WITH HIGH MOLECULAR WEIGHT ELECTROLYTE AND THE PROCESS OF FORMULATING THE SAME”

APPLICANT:

MANIPAL TECHNOLOGIES LTD.
A company under Indian Companies Act, 1956 having address at
Press corner, Manipal-576104
Karnataka

PREAMBLE TO THE DESCRIPTION:

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to printed flexible electrochromic display and the process of formulating thereof, using high molecular weight electrolyte. The high molecular weight organic electrolyte Poly (dially dimethyl ammonium) chloride (abbreviated as PDADMAC) utilized in the invention has molecular weight (Mw) in the range of 4, 00,000- 5, 00,000 g/mole for specifically enhancing the contrast ratio of the printed flexible electrochromic display.

BACKGROUND OF THE INVENTION
Chromic materials have a property of changing colour. The colour change is reversibly stimulated on exposure to different stimuli such as pH, light, heat, or electricity. The materials which change colour reversibly when stimulated by electricity are said to exhibit electrochromism. Materials showing such a property are called as electrochromic materials. However, for the electrochromic materials to exhibit electrochromism reversibly, the material has to be embedded or sandwiched or fabricated into device with suitable architecture or structure.
The overall redox reaction leading to change in colour of electrochromic material Poly (3, 4-ethylenedioxythiophene)-poly (styrenesulfonate) henceforth abbreviated as PEDOT PSS with burst of electric charges can be summarized according to the following equation:
PEDOT PSS+ + e- ? PEDOT PSS
(Colour less) (Blue Colour)

As mentioned earlier, the basic principle of working an electrochromic device is to perceive a reversible colour change in a material by stimulus of electricity. These materials are capable of changing colour due to oxidation and a reduction reaction which in-turn is stimulated by electricity (low current and voltage). Overall the oxidation and reduction of an electrochromic material can be perceived by stimulating through electricity, if the same material is fabricated in device architecture as shown above. The PEDOT PSS in the context of present work is colourless in the oxidized or neutral state and dark blue or navy blue when stimulated or reduced. The stimulated or reduced PEDOT PSS would become colourless on cutting off electricity. This entire process can be reversed a number of times. This electrochemical phenomenon can be used to make displays that can be used for commercial advertising.
The architecture to perceive electrochromic display by printing is shown in the Figure 1. In the device architecture, the electrochromic layer (containing the electrochromic material) is coupled to ionic storage layer (dielectric) and solid/liquid electrolyte consecutively. These electrochromic layer, ionic storage layer and solid/liquid electrolyte layer are sandwiched between two electrodes (one of the two electrodes being transparent). The advantage of using PEDOT PSS as electrochromic material is that it can itself serve as a transparent conductive electrode. Silver is being used as a second rear electrode. The reversible electrochromism or redox reaction of PEDOT PSS, as per the equation is initiated by charging and discharging the device with an applied external potential typically in the range of 1.0 - 3.0 V.
The entire device architecture as shown in the figure 1 can be used for screen printing method, based on a flexible and transparent PET substrate. It is necessary that the transparency of the substrate is more than 95%. All other layers as mentioned above electrochromic layer (PEDOT PSS), ionic storage layer and solid/liquid electrolyte layer PDADMAC are sandwiched between two electrodes transparent PET substrate and silver.
In PCT/EP2012/069769 a display device, displaying sharper images. The invention solves an inherent problem when desiring to create sharp images or symbols by this or vertical type of displays originates from the fact that ions must be mobile in both the electrolyte and in the electrochromic material itself in order to give rise to the colour change. So, initially the colour change will be seen only at the area of the electrochromic material which is covered by electrolyte. However, the ions will migrate both vertically and laterally in the electrochromic material, and thus also outside of the electrolyte covered area. This migration of the ions results in a blurring of the switched area, and thus also of the displayed symbol.
A part of the solution is formulating a new electrolyte, a composition comprising cations have a molecular weight lower than 1, 000 g/mole. The cations of the electrolyte composition have a molecular weight (Mw) between 10, 000 and 1, 00, 000 g/mole and more preferably between 20, 000 and 75, 000 g/mole.
However, there is a technological gap that such printed flexible electrochromic display utilizes PDADMAC polymer electrolyte below Mw 1, 00,000 g/mole. Although the solution provided by the most relevant prior provides a sharper image, but it has been found the images created in the cited prior art had low contrast ratio.
The quality of an electrochromic device depends on many parameters including the contrast ratio, switching rate, and cycle life. High contrast ratio is preferred for all commercial display devices.
There are technological barriers for exhibiting high contrast ratio of such printed flexible electrochromic display, including optimization for the process of formulating such printed flexible electrochromic display with high molecular weight PDADMAC polymer electrolyte in the range of 1, 00, 000-4, 00, 000 g/mole.

OBJECT OF THE INVENTION
The main object of the invention is to provide to a printed flexible electrochromic display with solid or liquid electrolyte such as Poly (diallydimethyl ammonium) chloride (PDADMAC) having a high molecular weight (Mw) in the range of 1,00,000-4,00,000 g/mole for enhancing the high contrast ratio of the display.
Yet another object of the invention is to use high molecular weight polymer in the range of 1, 00, 000- 4, 00,000 g/mole for enhancing the contrast ratio of the printed flexible electrochromic display.
Yet another object of the invention is to provide screen printing methodology for printed flexible electrochromic display comprising of preparing an electrochromic layer (PEDOT PSS); preparing an ionic storage layer; preparing an solid/liquid electrolyte layer (PDADMAC); sandwiching these layers between two electrodes, transparent PET substrate (with at least 95% transparency) and silver, and further optimising parameters for using a high molecular weight PDADMAC in the range of 1, 00,000-4, 00,000 g/mole for enhancing the contrast ratio of the display.
Yet another object of the present invention is to optimize the screen printing methodology, for enhancing the contrast ratio of the printed flexible electrochromic display, using the high molecular weight polymer in the range of 1, 00,000-4, 00,000 g/mole.
Yet another object of the present invention is to specifically optimize the drying parameters of screen printing methodology, for enhancing the contrast ratio of the printed flexible electrochromic display, using the high molecular weight polymer in the range of 1, 00,000-4, 00,000 g/mole.
Yet another object of the present invention is to optimise ink formulation, which is normally made by dispersing functional material in a vehicle/carrier fluid.
Yet another object of the present invention is to optimise formulation of each functional material to be deposited on the PET surface by dispersed it in a suitable vehicle, to be used as a screen printable ink.
Yet another object of the present invention is to optimise selection of the PET substrate (or a combination of vehicle), to determine the qualities of an ink and to differentiate one type of ink from the other.
Yet another object of the invention is to sandwich the electrochromic material into suitable device architecture and optimizes the same for a large area A4 size display.

SUMMARY OF THE INVENTION
The present invention relates to printed flexible electrochromic display and the process of formulating thereof. The present invention providing the printed flexible electrochromic display utilizing high molecular weight electrolyte.
The printed flexible electrochromic display in the architecture of the display, the electrochromic layer is coupled to ionic storage layer (dielectric) and solid or liquid electrolyte layer consecutively. These three layers are sandwiched between two electrodes (one of the two electrodes being transparent). Silver is being used as a second rear electrode. The reversible electrochromism or redox reaction of PEDOT PSS {Poly (3, 4-ethylenedioxythiophene)-poly (styrenesulfonate)} is initiated by charging and discharging the device with an applied external potential typically in the range of 1.0 - 3.0 V wherein high molecular weight organic electrolyte comprising of solid/liquid electrolyte, Poly (diallydimethyl ammonium) chloride (abbreviated as PDADMAC) having a high molecular weight (Mw) in the range of 1, 00, 000-2, 00, 000 g/mole for enhancing the contrast ratio of the display.
A printed flexible electrochromic display comprising of an electrochromic layer (PEDOT PSS); an ionic storage layer; solid/liquid electrolyte layer (PDADMAC); and two electrodes having transparent PET substrate and a silver, sandwiching the other layers; wherein, PDADMAC is having molecular weight in the range of 4, 00, 000-5, 00, 000 g/mole; electrolyte ink is optimized by mixing 3 – 7% PDADMAC in 35 – 40 % water and homogenizing the solution by stirring for approximately 30 mins at 100 RPM; adding 20 – 30% TiO2 with the average particle diameter > 2µm; further adding 15 – 20 % of heat curable Resin and stirring again at 1000-1500 RPM; and adding 20-25% of defoamer and stirring for at least 1 hr; customizing transparent PET substrate by insulating sheet of Poly ethylene terephthalate; depositing electrically conductive and electrochromically active layer of PEDOT PSS by screen printing in a mesh of 305 TPI; drying the PEDOT PSS layer at 100 0C for 30 mins; depositing a thick paste of dielectric material over PEDOT PSS by screen printing in a mesh of 230 TPI; exposing under UV for 30 mins; adding a layer of the electrolyte ink by screen printing in a mesh of 175 TPI; drying the electrolyte at 100 0C for 30 mins; and depositing using screen printing in a mesh of 305 TPI was dried at 100 0C; and effectively enhancing the contrast ratio of the printed flexible electrochromic display.
A screen printing method for printed flexible electrochromic display, comprising of preparing an electrochromic layer (PEDOT PSS); preparing an ionic storage layer; preparing an solid/liquid electrolyte layer (PDADMAC); and sandwiching these layers between two electrodes, transparent PET substrate (with at least 95% transparency) and silver; wherein, optimising electrolyte ink and customizing transparent PET substrate for utilizing high molecular weight PDADMAC in the range of 4,00,000-5,00,000 g/mole provides enhanced contrast ratio of the display.

BRIEF DESCRIPTION OF THE DRAWINGS
A complete understanding of the system and method of the present invention may be obtained by reference to the following drawings:
FIG. 1 is a flow chart of the process of formulation of the printed flexible electrochromic display; and
FIG. 2 provides the comprehensive information on all the materials components or materials used formulation of the printed flexible electrochromic display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.
In an embodiment of the present invention, the invention provides a printed flexible electrochromic display. The present invention providing the printed flexible electrochromic display utilizing high molecular weight electrolyte. The present invention utilizes Poly (diallydimethyl ammonium) chloride (abbreviated as PDADMAC) with molecular weight in the range of 1, 00,000 – 3, 00,000 g/mole for printing a flexible electrochromic display.
In another embodiment of the present invention, the printed flexible electrochromic display comprises of an electrochromic layer, ionic storage layer (dielectric) and solid/liquid electrolyte layer consecutively.
In yet another embodiment of the present invention the electrochromic layer is coupled to ionic storage layer (dielectric).
In yet another embodiment of the present invention these three layers are sandwiched between two electrodes (one of the two electrodes being transparent). Silver is being used as a second rear electrode. The reversible electrochromism or redox reaction of PEDOT PSS is initiated by charging and discharging the device with an applied external potential typically in the range of 1.0 - 3.0 V wherein high molecular weight organic electrolyte comprising of solid/liquid electrolyte, namely PDADMAC, having a high molecular weight in between 1, 00,000-2, 00,000 g/mole is utilized for enhancing the contrast ratio of the display.
A printed flexible electrochromic display comprising of an electrochromic layer (PEDOT PSS); an ionic storage layer; solid/liquid electrolyte layer (PDADMAC); and two electrodes having transparent PET substrate and a silver, sandwiching the other layers; wherein, PDADMAC is having molecular weight in the range of 4, 00,000-5, 00,000 g/mole; electrolyte ink is optimized by mixing 3 – 7% PDADMAC in 35 – 40 % water and homogenizing the solution by stirring for approximately 30 mins at 100 RPM; adding 20 – 30% TiO2 with the average particle diameter > 2µm; further adding 15 – 20 % of heat curable Resin and stirring again at 1000-1500 RPM; and adding 20-25% of defoamer and stirring for at least 1 hr; customizing transparent PET substrate by insulating sheet of Poly ethylene terephthalate; depositing electrically conductive and electrochromically active layer of PEDOT PSS by screen printing in a mesh of 305 TPI; drying the PEDOT PSS layer at 100 0C for 30 mins; depositing a thick paste of dielectric material over PEDOT PSS by screen printing in a mesh of 230 TPI; exposing under UV for 30 mins; adding a layer of the electrolyte ink by screen printing in a mesh of 175 TPI; drying the electrolyte at 100 0C for 30 mins; and depositing using screen printing in a mesh of 305 TPI was dried at 100 0C; and effectively enhancing the contrast ratio of the printed flexible electrochromic display.
A screen printing method for printed flexible electrochromic display, comprising of preparing an electrochromic layer (PEDOT PSS); preparing an ionic storage layer; preparing an solid/liquid electrolyte layer (PDADMAC); and sandwiching these layers between two electrodes, transparent PET substrate (with at least 95% transparency) and silver; wherein, optimising Electrolyte Ink and customizing transparent PET substrate for utilizing high molecular weight PDADMAC in the range of 4,00,000-5,00,000 g/mole provides enhanced contrast ratio of the display.
The invention optimises the drying time, after printing each layer; usually drying is done at 80 - 90 0C for 15-20 minutes.
Further, the invention optimises ink formulation, which is normally made by dispersing functional material in a vehicle/carrier fluid. Similarly, optimises formulation for each of functional material to be deposited on the PET surface by dispersing them in a suitable vehicle to be used in form of the screen printable ink.
The invention provides electrolyte comprising of 5% PDADMAC, 38% Water, 25% TiO2, 17% Resin and 15 % defoamer.
Accordingly, the invention optimises selection of the PET substrate (or a combination of vehicle) is of prime importance, since it is the PET substrate that largely determines the working qualities of an ink and differentiates one type of ink from the other.
As illustrated in FIG. 1, the process of formulation of the printed flexible electrochromic display provides a printed flexible electrochromic display comprising of an electrochromic layer (PEDOT PSS); ionic storage layer; and solid/liquid electrolyte layer (PDADMAC) wherein these layer are sandwiched between two electrodes, transparent PET substrate (with at least 95% transparency) and silver.
In yet another embodiment of the current invention the Ink Formulation comprising steps of
Electrolyte Ink Formulation
The electrolyte PDADMAC was obtained commercially from Sigma Aldrich. Different molecular weight ranges of the same were also obtained from Sigma Aldrich. PDADMAC was taken in the range of 3 – 7% in the formulation and mixed with 35 – 40 % water in a 500 ml steel container. The solution was homogenized by stirring for 30 minutes at 100 RPM in a stirrer and 20 – 30% TiO2 was added. TiO2 was obtained from Otto chemicals with the average particle diameter > 2µm. To this was added 15 – 20 % of heat curable Resin obtained commercially from Kamson chemicals Pvt ltd. The resulting mixture was stirred with an overhead stirrer at a speed of 1000-1500 RPM. While stirring 20-25% of de-foamer obtained commercially from BASF chemicals was added. Entire mixture was finally stirred for 1 hr with the overhead stirrer. The resulting final formulation was taken for screen printing the device architecture. The same procedure was followed for different PDADMAC electrolytes of varying molecular weights.
Device Fabrication with MW of 400000 - 500000
An insulating sheet of Poly ethylene terephthalate (PET, Hanita coatings) of100µm thick from was cut into a 10 cm X 10 cm dimensions. Over which electrically conductive and electrochromically active layer of PEDOT PSS was deposited by screen printing in a mesh of 305 TPI (Threads per inches) using squeegee. After drying the PEDOT PSS layer at 100 0C for 30 mins, it was ensured of desired conductivity between the diagonals of the square. The conductivity was measured using a standard FLUKE-179 EJKCT multimeter and must be in range of 100 – 200 ohms/Sq. Following this a thick paste of dielectric material (chemically containing Barium Titanate) was deposited over PEDOT PSS by screen printing in a mesh of 230 TPI using squeegee. After complete under UV for 30 mins it was ensured that dielectric layer had covered entirely the PEDOT PSS. Over these two layers the electrolyte ink (PDADMAC of molecular weight in 400000 - 500000) was deposited by screen printing in a mesh of 175 TPI using squeegee. After drying the electrolyte at 100 0C for 30 mins it was ensured that it had covered the entire dielectric layer printed prior. Over which the fourth layer of silver ink was deposited using screen printing in a mesh of 305 TPI using squeegee. The deposited layer was dried at 100 0C and ensured that complete drying to give conductivity of 10 – 30 ohms between the diagonals. The completed device had two electrodes i.e. PEDOT PSS and Silver, both of which were connected with an external power supply of battery of 1.5 -3V DC to observe the colour change in the PEDOT PSS layer from colourless to Blue.
PEDOT PSS
PEDOT PSS was obtained commercially from Clevious SV3 as ready in screen print format. This was used as such without any further modifications.
Dielectric Ink
UV curable dielectric material was obtained commercially from Creative Compounds as ready to screen print format. This was used as such without any further modifications.

Silver Ink
Silver Ink was commercially obtained from Advanced Electronic Materials Inc. as ready to screen print format.
Table 1 provides the comprehensive information on all the materials components/materials used:
S. No. Material Chemical Content Source (Commercial/
Indigenous) Method of Printing Mesh Size Ink Formulation Method of making formulation
1 PET Poly ethylene terephthalate Commercial from
Hanita coatings Used as substrate for printing N/A Obtained as Screen printable ink from commercial source N/A
2 PEDOT PSS Screen printable paste which contains 50-60 % of Pedot and rest contains additives and binders Commercial from

Clevious SV3 Germany Screen printing 196 Obtained as Screen printable ink from commercial source N/A
3 Dielectric UV curable dielectric Commercial from

Creative Compounds Screen printing 305 Obtained as Screen printable ink from commercial source N/A
4 Electrolyte PDADMAC
(Poly di allyl di methyl ammonium chloride)
Mw of
100000 - 200000 Commercial from

Sigma Aldrich
Screen printing 156 5% PDADMAC+ 38% Water+TiO2 25% + 17% Resin + 15 % defoamer All the materials grinding except defoamer ,before printing defoamer is added to the solution
5 Ag- EA-510 Commercial from

Advanced Electronic Materials Inc. Screen printing 305 Obtained as Screen printable ink from commercial source
6 Battery Commercially available 3V battery Commercial from

Duracell

Table 2 provides the comparative Contrast Ratio Recorded for different MW of PDADMAC Electrolyte:
Contrast Ratio Recorded for different MW of PDADMAC Electrolyte
S. NO MW Range Trails Contrast Ratio(w.r.t L A B values)
1. > 1,00,000 10 8.5
2. 20 8.35
3. 30 8.13

1. 1,00,000 - 2,00,000 10 14.27
2. 20 14.45
3. 30 15.22

1. 400,000 – 5, 00,000 10 21.54
2. 20 19.87
3. 30 19.92

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. The invention is defined by the claims.

,CLAIMS:
CLAIMS
We Claim:
1. A printed flexible electrochromic display comprising of
a) an electrochromic layer (PEDOT PSS);
b) an ionic storage layer;
c) a solid/liquid electrolyte layer (PDADMAC) having an electrolyte ink; and
d) at least two electrodes having a transparent PET electrode and a silver electrode, sandwiching the other layers;
wherein,
said PDADMAC is having molecular weight in the range of 4, 00,000-5, 00,000 g/mole;
said electrolyte ink is optimized by mixing 3 – 7% of the PDADMAC in 35 – 40 % water and homogenizing the solution by stirring for approximately 30 mins at 100 RPM; adding 20 – 30% TiO2 with the average particle diameter > 2µm; further adding 15 – 20 % of heat curable resin and stirring again at 1000-1500 RPM; and adding 20-25% of a defoamer and stirring for at least 1 hr;
said transparent PET electrode is customized by insulating sheet of Poly ethylene terephthalate; depositing electrically conductive and electrochromically active layer of said PEDOT PSS by screen printing in a mesh of 305 TPI; drying the PEDOT PSS layer at 100 0C for 30 mins; depositing a thick paste of dielectric material over the PEDOT PSS by screen printing in a mesh of 230 TPI; exposing under UV for 30 mins; adding a layer of the electrolyte ink by screen printing in a mesh of 175 TPI; drying the electrolyte at 100 0C for 30 mins; and depositing using screen printing in a mesh of 305 TPI was dried at 100 0C; and
said PDADMAC effectively enhancing the contrast ratio of the printed flexible electrochromic display.
2. The printed flexible electrochromic display as claimed in claim 1, wherein PET electrode is at least 95% transparent.
3. The printed flexible electrochromic display as claimed in claim 1, wherein the insulating sheet of Poly ethylene terephthalate (PET, Hanita coatings) of 100 µm thick from was cut into a 10 cm X 10 cm dimensions.
4. The printed flexible electrochromic display as claimed in claim 1, wherein thick paste of dielectric material contains Barium Titanate.
5. A screen printing method for printed flexible electrochromic display, comprising steps of
a) preparing an electrochromic layer (PEDOT PSS);
b) preparing an ionic storage layer;
c) preparing a solid/liquid electrolyte layer (PDADMAC) having an electrolyte ink; and
d) sandwiching these said layers between two electrodes, transparent PET electrode and silver electrode;
wherein,
optimising said electrolyte ink and customizing said transparent PET substrate for utilizing high molecular weight PDADMAC in the range of 4, 00,000-5, 00,000 g/mole provides enhanced contrast ratio of the display.
6. The screen printing method for printed flexible electrochromic display as claimed in claim 5, wherein said electrolyte ink is optimized by mixing 3 – 7% of said PDADMAC in 35 – 40 % water and homogenizing the solution by stirring for approximately 30 mins at 100 RPM; adding 20 – 30% TiO2 with the average particle diameter > 2µm; further adding 15 – 20 % of heat curable resin and stirring again at 1000-1500 RPM; and adding 20-25% of a defoamer and stirring for at least 1 hr.
7. The screen printing method for printed flexible electrochromic display as claimed in claim 5, wherein customizing said transparent PET electrode by insulating sheet of Poly ethylene terephthalate; depositing electrically conductive and electrochromically active layer of said PEDOT PSS by screen printing in a mesh of 305 TPI; drying the PEDOT PSS layer at 100 0C for 30 mins; depositing a thick paste of dielectric material over the PEDOT PSS by screen printing in a mesh of 230 TPI; exposing under UV for 30 mins; adding a layer of the electrolyte ink by screen printing in a mesh of 175 TPI; drying the electrolyte at 100 0C for 30 mins; and depositing using screen printing in a mesh of 305 TPI was dried at 100 0C.

Dated this 28th day of March, 2016