FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules  2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION: A METHOD OF EMBOSSING ROLLERS USING LASER BEAM

2. APPLICANT:
(A) NAME : SHILP GRAVURES LIMITED
(B) NATIONALITY : INDIAN
(C) ADDRESS : 778/6 Pramukh Industrial Estate 
Sola Santej Road  Village Rakanpur 
Tal. Kalol
Dist. Gandhinagar
3. PREMABLE TO THE DESCRIPTION
PROVISIONAL
The following specification describes the invention. þ COMPLETE
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 a method for embossing the surface of rollers for creating a fine or coarse texture on varied thin  flat  malleable or semi-fluid materials such as paper board  tissue paper  plastic film  metal foil  leather  textile fabric  nonwoven  glass etc.  in continuous or sheet form. More particularly  the present invention relates to a method for embossing roller by projecting laser beam on the roller surface.
Back ground and prior art of the invention
Method of embossing rollers by creating a fine texture or image on its surface is critical in the industry. Conventionally  several methods such as manual methods  mechanical methods and photochemical methods have been used for embossing the rollers. In manual method  engravers use a sharp steel tool called a graver or burin to carve the metallic surface of the rollers. In mechanical method  small tools or mills are used to form specific depth impression on the metal cylindrical rollers by pressing tools with pressure. In photochemical method  the cylindrical roller surface to be embossed is coated with a photo resist materials and such photo resist coated surface is exposed to a controlled UV light source through a litho film having image. This transfers the image from the litho film to the resist coated surface. The cylindrical roller surface with said image is then developed and the unexposed resist coated areas are then stripped away leaving the bare metal to be etched. However  due to failure of transferring the precise desired image and other eco-unfriendly results  a method of embossing the rollers by digitally transferring the image by utilizing direct and indirect laser means has been introduced. In direct method  the image from the workstation is sent to the laser engraver where the image is projected by the beam of very strong laser power and the metal from design area is directly sublimed due to high wattage laser beam to the required depth. Whereas  in indirect method of laser embossing  the roller is coated with photo resist and the digital image data of predetermined pattern from the workstation is sent to the laser engraver where the digital data is projected by beam of laser which exposes the photo resist. This leaves the pattern that is identical to the digital image pattern on the resist coated roller surface. The roller is then subjected to developing and unexposed resist area is stripped away leaving the bare metal which is subjected to etching.
The EP 0850702 also discloses a method for manufacturing engraved rolling roll by utilizing indirect laser beam. The method comprising the steps of forming a resin layer on the surface of a roll  forming a pattern by projecting the laser beam to the resin layer and engraving the pattern on the surface of the roll to a predetermined depth by a corrosive solution and finally washing the engraved surface using weak basic solution.
Even though the aforesaid European patent solves the problem of eco-unfriendly resulting at the end of the embossing process  by utilizing indirect laser technology  still it leaves the scope of providing accurate and precise embossed pattern texture by achieving desired depth and relief of the pattern design at the micron level on the surface of the roller.
Object of the invention
The main object of the present invention is to provide effective steps in a method for embossing the rollers to achieve accurate and precise embossed pattern of texture design on the surface of the rollers by utilizing indirect laser beam technology.
Another object of this invention is to provide different steps in a method for embossing the rollers to achieve the desired depth and relief of multi level embossed design at the micron level.
Yet another object of the invention is to provide different user friendly steps in a method for embossing rollers.
Summary of the Invention
The present invention discloses a method for embossing of surface of the metallic rollers by projecting laser beam by means of indirect laser technology. According to the present invention primarily the roller is fabricated as per the engineering drawing then it is subjected to the step of degreasing using electrolytic method. On the surface of the degreased roller black etching resistant ink is evenly coated to a predetermined thickness  for example scores of micrometer. After the completion of said coating  the ink coated surface is exposed to the laser engraving means for digitally transferring a predetermined texture to be embossed from the CAD (Computer Aided Design) system to the surface of the roller by ablating the said ink and then the roller is further subjected to etching with acid in which the remaining black ink coating on the roller surface is removed using a solvent. The aforesaid steps are repeated multiple times to achieve the predetermined depth and relief of the said predetermined texture.
Detailed description of the drawings
Fig. 1 is the flowchart of different steps involved in the method of embossing surface of the roller.
Hereinafter  exemplary steps of the present invention will be described with reference to the accompanying flow chart. In the following description of the present invention  a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.
Detailed description of the invention:
The present invention discloses a method of embossing metallic roller by projecting a laser beam on the surface of said roller to digitally transfer a predetermined pattern of a fine or coarse texture design on the surface of said roller to a predetermined depth and relief precisely and accurately. As directed in Fig. 1  in the said method of embossing the roller  primarily a metallic roller to be embossed is fabricated as per the engineering drawing to produce properly finished and dynamically balanced roller surface. In consequence to said fabrication  the roller surface is subjected to thorough cleaning using water along with a degreaser or using a methanol or a mild sulphuric acid  solvent to make the surface of the roller free of rust  dust and oil. On the degreased surface of the roller  a black etching resistant ink is then uniformly coated to a predetermined thickness of micrometer range by using a spray coating machine to ensure uniform coating thickness throughout the surface.
After the completion of said uniform ink coating  a predetermined pattern of the fine or coarse texture design is digitally transferred from the CAD system to the ink coated surface of the roller by projecting laser beam to transfer texture to the roller surface by ablating said ink coated on the roller surface. The said predetermined pattern of texture design is created by using digital graphic file in the said CAD system using Artpro and Photoshop applications in multiple layers and which is then transferred to the laser engraving machine. The design created in the digital graphic file of CAD system comprises Linework elements  Halftone elements and continuous tone elements. From the laser engraving machine the said pattern is digitally transferred to the ink coated metallic surface as explained earlier. The selected wavelength of said laser beam is 1064 nm. Since laser beam of 1064 nm is used  the embossing method does not react to visible light. Therefore  the work for exposing the black ink coated surface of the roller against the laser beam need not to be carried out in a safe lighting room.
Once  the black ink coated surface is ablated in the texture area by means of exposing the surface by the laser beam  an etching step is carried out using spray etching machine so that areas exposed to the laser beam or the ablated areas are eroded. The said etching step is being carried out by means of said spray etching machine with temperature controlled mild chromic acid or ferric chloride acid or mild nitric acid having controlled baume. The etching machine has bidirectional as well as varied speed rotation. In consequence to the roller surface that being undergone the etching step  the etched surface is now subjected to the decoating step in which the remaining blank ink coated layer of the roller surface is cleaned using acetone solvent. The aforesaid steps from coating step to etching step have been repeated multiple times  in which each time slightly modified data of the texture design from different layers is used to achieve a predetermined accurate depth and relief of embossed design precisely. Once the predetermined depth and relief is achieved the laser engraved surface of the roller with decoated black ink is subjected to carry out the surface finishing and chrome plating. Various methods including wire brush finishing  flap wheel finishing and belt finishing are adopted to get better finishing of the embossed design on the roller surface. Once the surface finishing of the roller is completed the roller surface is subjected to chrome plating in which a hard chrome plating layer is formed on the said surface and then said roller surface is subjected for polishing to get precise embossed surface of the roller.
While  the invention has been described with respect to the given embodiment  it will be appreciated that many variations  modifications and other applications of the invention may be made. However  it is to be expressly understood that such modifications and adaptations are within the scope of the present invention  as set forth in the following claims.

We Claim 
1. A Method of Embossing Rollers using Laser Beam comprising following steps:
a) fabricating a roller to be embossed;
b) degreasing the surface of said roller;
c) uniformly coating black etching resistant ink of predetermined thickness on the roller surface;
d) digitally transferring predetermined pattern of desired texture design from the CAD (Computer Aided Design) system on the black ink coated roller surface by ablating said black ink by laser means ;
e) etching the laser ablated region of the roller surface with acid for eroding said region;
f) decoating the black ink coated layer of the roller surface using a solvent;
g) finishing the decoated roller surface;
h) chrome plating and polishing the roller surface that went on from the finishing step  as mentioned in step g).
2. The Method of Embossing Rollers using Laser Beam as claimed in claim 1  wherein the steps c) to e) have been repeated multiple times to achieve a predetermined depth and relief of embossed design precisely on the roller surface.
3. The Method of Embossing Rollers using Laser Beam as claimed in claim 1  wherein the step c) is carried out by means of spray coating machine.
4. The Method of Embossing Rollers using Laser Beam as claimed in claim 1  wherein step e) is carried out by means of spray etching machine with temperature controlled acid.
5. The Method of Embossing Rollers using Laser Beam as claimed in claim 1  wherein step g) is carried out by means of brush finishing  flap wheel finishing and belt finishing.
6. The Method of Embossing Rollers using Laser Beam as claimed in claim 1  wherein during step h) a hard chrome plating layer is formed on the roller surface in consequence to step g) and then said roller surface is subjected for polishing.

Dated this on 24th April  2012