Magnetic plate for printing of optical effects
View Patent ↗This invention discloses a magnet for use as a printing plate or printing head that is used for aligning flakes or particles in a paint or ink. A composite sheet or block of magnetizable material is selectively magnetized so that a magnet is formed within the sheet or block that has a shape of a predetermined image, logo, or indica. Dies are used to magnetize the magnetizable material and preferably the does contact the material to be magnetized. A pre-magnetized sheet such as a refrigerator magnet may be re-magnetized differently so that a magnetic image is encoded therein for use as a printing plate. Preferably the printing plate is flexible so that it can be formed to a curved surface of a cylinder or drum for printing. Conveniently these flexible magnets can be changed for other designs and placed on the same drum for use in printing.
1. A method of forming a reusable magnetic printing plate comprising the steps of:
a) providing a monolithic sheet or block of magnetizable material;
b) providing a shaped magnetizing die having an outer surface in the form of an image, logo, or indicia;
c) disposing the outer surface of the shaped magnetizing die adjacent to a surface of the sheet or block of magnetizable material; and
d) applying a magnetic field through the shaped magnetizing die to form a magnet in a form corresponding to the image, logo, or indicia within the sheet or block of magnetizable material, wherein the magnetic field emanating from the outer surface of the shaped magnetizing die is in the form of the image, logo, or indicia and is substantially uniform in intensity and direction.
2. A method as defined in claim 1 , wherein step (c) includes the step of contacting the outer surface of the shaped magnetizing die with the surface of the sheet or block of magnetizable material.
3. A method as defined in claim 2 , wherein the outer surface of the shaped magnetizing die is non-planar, and wherein step (c) includes the step of contacting an outermost portion of the non-planar outer surface of the shaped magnetizing die with the surface of the sheet or block of magnetizable material.
4. A method as defined in claim 2 , wherein step (b) includes the step of providing a second shaped magnetizing die having an outer surface in the form of a mirror image of the image, logo, or indicia, and wherein step (c) includes the step of simultaneously contacting the outer surface of the second shaped magnetizing die with an opposite surface of the sheet or block of magnetizable material.
5. A method as defined in claim 1 , wherein the magnet formed within the sheet or block of magnetizable material provides a magnetic field in a form corresponding to the image, logo, or indicia.
6. A method as defined in claim 5 , wherein the magnet formed within the sheet or block of magnetizable material provides a magnetic field that will align field alignable flakes upon a substrate in a form corresponding to the image, logo, or indicia.
7. A method as defined in claim 1 , wherein the magnetic field emanating from the outer surface of the shaped magnetizing die is in a direction substantially perpendicular to the surface of the sheet or block of magnetizable material.
8. A method as defined in claim 1 , wherein the shaped magnetizing die consists of a monolithic body of a soft magnetic material.
9. A method as defined in claim 1 , further comprising the step of moving the sheet or block of magnetizable material relative to the shaped magnetizing die and subsequently repeating steps (c) and (d).
10. A method of forming a flexible magnetic printing plate comprising the steps of:
providing a magnetized sheet having more than 40% of magnetic field lines aligned in a same direction;
providing a shaped magnetizing die having a non-planar outer metal surface defining an image, logo, or indicia; and
contacting an outermost portion of the non-planar outer metal surface with a region of the magnetized sheet, while applying a magnetic field through the shaped magnetizing die and into the region of the magnetized sheet to change a magnetic field within the region, wherein the magnetic field emanating from the non-planar outer metal surface is in the form of the image, logo, or indicia and is substantially uniform in intensity and direction, and wherein the region is in a form corresponding to the image, logo, or indicia.