The present invention relates to a screen printing system to achieve a high level of registration for multilayer pattern printing on transparent as well as opaque substrates. It consists of an optical light-assisted screen printing bed along with a micro-scale gridline for the perfect alignment of mask and successive printed line/pattern.
Background
Screen printing is a stencil-based printing technique in which the ink is transported to the substrate through the screen mesh made of porous silk, metal, or synthetic fibers etc. Mesh on the non-printing area is closed by photo-polymerized resin, whereas the remaining openings are left open for printing. This technique is being commercially used in printable electronics to print the circuit boards, antennas, and other devices on both rigid and flexible substrates.
Registration marks are normally being used in sheet to sheet as well as roll-to-roll multilayer printing. These marks can be of different sizes, shapes and can be transferred to the substrate by printing and perforating. Nevertheless, the precise alignment of these marks with the printing system substantially depends upon the user ability. To minimize the error, Clarence A. Lewis JR., invented a system and method for register mark recognition (US 2004O163562A1). It consists of a marking system with its image processing to recognize the location of the substrate. As their system also depends upon the registration mark and their relative alignment, there remains a chance of inaccurate registration on successive printing. In the proposed system, the substrate will be divided into micron level gridlines which will make the alignment very easy and more precise. Backlight will also act as a medium to register the substrate/ printed pattern with the printing system more accurately and precisely . It will also improve the yield of the automatic system by providing improved images.

Statement of the invention
Optical light-assisted micro gridline bed will provide better registration for multilayer screen printing. It consists of gridlines and optical light so that the user can preciously register a mask with a printed pattern and/or substrate.
Brief description of the drawings
There are two figures to describe the present innovation. Figure 1 shows the complete setup of screen printing. It shows the frame attached with masked mesh and the base. Figure 2 shows the transparent base with gridlines and optical light. The gridlines in the base will provide position coordinates to the printed pattern and/or substrate. To register the printed pattern with the mask, the printed substrate can be moved and matched with the mask using gridline and optical light.
Due to micron size space and line width of the gridlines it would be hard to match it with the mask. However, due to provision of the optical light arrangement just beneath the arrangement the probability of fine registration will be improved.
Detailed description of the drawings
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

FIG. 1 depicts building blocks of embodiments of the present invention; (100) represents the stencil of the screen printing setup which compromises the mesh which could be made up of polymer or metal attached with frame (wooden, metal). (101) represents the mask developed on the mesh with the help of emulsion coating or any patterned adhesive film. (102) represents the transparent glass which acts as a base for the substrate and printing. (103) represents the gridline mask which could be of any shape and size depending upon the requirement. (104) is the light source and acts as a medium to perform the alignment. (105) is the adapter to deliver controlled power to the light source.

FIG. 2 shows identification embodiments of the present invention; where a gridline pattern can be seen on the top of the glass and beneath that is the light source.
In a normal system, registration marks (‘+’, ‘-’ etc.) are being used to align the substrate and the printing system. But, this has limitations for use in the flexible substrate as improper tension can also cause misalignment despite the aligned registration mark. As per our knowledge, there is no such mechanism available where we can directly register the printed pattern.

The proposed system provides an ease to register multiple images with minimum error, as the system will directly register the printed pattern rather than the substrate. The propsed system can be understood in order to print a three layers of a squared size image. Due to poor registration the required printed circuit/image can not be achieved and may leads to poor functionality of the printed layer. Once a square has been printed, it will attain a specific position on the substrate and cannot be shifted. To print the second layer on the square, it should be ensured that it print exactly above the first printed layer. In order to do so, the operator can shift/move the substrate with first printed square below the mask and can properly match the registration with the help of gridlines and optical light to print the second layer exactly above the first one. Gridlines will direct the exact coordinates of the square and its registration with the mask with background optical light which enhances the matching. But, the luminence of the back light should be enough to get the clear vision of the gridline. In case the visibility is poor, the intensity of the light can be increased. In the case of a transparent and translucent substrate, the printed pattern can directly be registered. While, in the case of an opaque substrate, it can be registered with the mask from four corners using gridlines. The proposed system can also be adaptable in roll-to-roll printing by using camera and image processing (as described in US 2004O163562A1) with the added advantage of more precision registration using gridline mask and backlight.

CLAIMS:
We claim,
1. A system for registration of screen printing mask with substrate and printed layer comprises a box with a light source, and the top of the box is made of transparent material with gridline; the substrate is kept above the transparent material; and the mask is created on a stencil, which is translucent.
2. A system as claimed in claim 1, wherein the light source can be a plurality of; device can be the light source.
3. A system as claimed in claim 1, wherein light source can be a plurality of LEDs, OLEDs, bulb, and fluorescent tubes, etc.
4. A system as claimed in claim 1, wherein the transparent material can be glass, fiber, etc.
5. A system as claimed in claim 1, wherein the screen printing film can be made of cotton, silk, etc.
6. A system as claimed in claim 1, wherein the substrate can be made of any translucent material.
7. A system as claimed in claim 5, wherein the substrate can be made paper, cloth, polymer, etc.
8. A system as claimed in claim 7, wherein the alignment is made by observing the reference marks on screen printing film and the substrate with a light source in the background.
9. A system as claimed in claim 1, wherein the registration setup can be applied in both sheet to sheet and roll to roll printing process.
10. A system as claimed in claim 1, wherein the registration setup can be applied for both monolayer and multilayer printing.
11. A system as claimed in claim 1, wherein it can be used to print multilayer graphics as well as electronic devices.