Security devices and methods of manufacture thereof

A security device, comprising:

• a surface relief structure formed of one or more cured material(s) on a substantially flat substrate, the surface relief structure defining a primary set of relief elements at a first scale and a secondary set of relief elements at a second scale which is smaller than the first, the primary set of relief elements including a plurality of raised protrusions spaced by recesses and the secondary set of relief elements being disposed on a top of at least one of the raised protrusions and/or in at least one of the recesses,
• wherein the security device exhibits an image, and wherein elements of the image are provided solely by the surface relief structure,
• wherein the secondary set of relief elements define tactile structures, and wherein a tactility level of the tactile structures is configured to vary across the surface relief structure in a manner dependent on features of a corresponding part of the image, and
• wherein a height and/or width of the raised protrusions of the primary set of relief elements varies across the surface relief structure.

A method of manufacturing a security device, comprising forming a surface relief structure on a substantially flat substrate from one or more curable material(s) and curing the material(s), wherein the surface relief structure is formed by:

• providing a casting tool having a relief structure defined in a surface thereof, the relief structure corresponding to the surface relief structure;
• applying the one or more curable material(s) to the substrate and/or to the relief structure of the casting tool;
• bringing the substrate and the casting tool together, to thereby form the curable material(s) in a manner that conforms to the relief structure and curing the curable material(s) such that the surface relief structure formed of the cured material(s) is retained on the substrate;
• wherein the surface relief structure defines a primary set of relief elements at a first scale and a secondary set of relief elements at a second scale which is smaller than the first, the primary set of relief elements including a plurality of raised protrusions spaced by recesses and the secondary set of relief elements being disposed on a top of at least one of the raised protrusions and/or in at least one of the recesses,
• wherein the security device exhibits an image, and wherein elements of the image are provided solely by the surface relief structure,
• wherein the recesses between the raised protrusions comprise a base layer of the cured material(s), or comprise a base layer of a different cured material, whereby the plurality of raised protrusions of the primary set of relief elements are joined by the base layer, the base layer having a lower height than the raised protrusions of the primary set of relief elements, and
• wherein a height and/or width of the raised protrusions of the primary set of relief elements varies across the surface relief structure.

A security device, comprising:

• a surface relief structure formed of one or more cured material(s) on a substantially flat substrate, the surface relief structure defining a primary set of relief elements at a first scale and a secondary set of relief elements at a second scale which is smaller than the first, the primary set of relief elements including a plurality of raised protrusions spaced by recesses and the secondary set of relief elements being disposed on a top of at least one of the raised protrusions and/or in at least one of the recesses,
• wherein the security device exhibits an image, and wherein elements of the image are provided solely by the surface relief structure,
• wherein the recesses between the raised protrusions comprise a base layer of the cured material(s), or comprise a base layer of a different cured material, whereby the plurality of raised protrusions of the primary set of relief elements are joined by the base layer, the base layer having a lower height than the raised protrusions of the primary set of relief elements,
• wherein the secondary set of relief elements define tactile structure(s), and
• wherein in at least one region of the surface relief structure the tactile structures have an asymmetrical arrangement whereby a tactility level in a first direction differs from the tactility level in a second direction.

A security device, comprising:

• a surface relief structure formed of one or more cured material(s) on a substantially flat substrate, the surface relief structure defining a primary set of relief elements at a first scale and a secondary set of relief elements at a second scale which is smaller than the first, the primary set of relief elements including a plurality of raised protrusions spaced by recesses and the secondary set of relief elements being disposed on a top of at least one of the raised protrusions and/or in at least one of the recesses,
• wherein the security device exhibits an image, and wherein elements of the image are provided solely by the surface relief structure,
• wherein the secondary set of relief elements define tactile structures, and wherein a tactility level of the tactile structures is configured to vary across the surface relief structure in a manner dependent on features of a corresponding part of the image,
• wherein the secondary set of relief elements define tactile structure(s), and
• wherein in at least one region of the surface relief structure the tactile structures have an asymmetrical arrangement whereby a tactility level in a first direction differs from the tactility level in a second direction.