Radiation imagery chemistry: process – composition – or product th – Transfer procedure between image and image layer – image... – Imagewise heating – element or image receiving layers...
Reexamination Certificate
2001-11-20
2004-07-20
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Transfer procedure between image and image layer, image...
Imagewise heating, element or image receiving layers...
C430S200000, C430S270100, C430S273100
Reexamination Certificate
active
06764803
ABSTRACT:
The invention relates to a laser transfer film for durable inscription on components made from a backing layer, where on the underside of the backing layer there is an adhesion layer with pigmented boundary layer.
Technical labeling is one of the methods used for the identification marking of components on vehicles, on machinery, and on electrical and electronic devices, examples being model-identification plates, labels for process control, and guarantee batches and test batches.
Increasing importance is being attached to identification marking by means of laser labels or printed or coated metal plates, specifically in the automotive industry, in particular for high-quality markings. This method is used to place information and advice, such as tire pressure or fuel type, on a very wide variety of components in the automobile for its subsequent user. A laser label may also be used to convey important production data within upstream stages of manufacture.
For this use, the label may be inscribed with a bar code. A suitable reading device gives an assembly team the opportunity of using the bar code for read-off of information concerning model, color, and special equipment, directly on the manufacturing line. Labels are used on the vehicle not only for this standard information but also for the placing of sensitive security data, such as chassis number and identification numbers. In the event of theft or an accident, this information is very important for tracing of a vehicle and of stages in manufacture.
The label material used therefore has to be highly counterfeit-proof, in order to prevent any attempt at manipulation. It has to be impossible to remove the label intact from the base to which it adheres.
Additional security is achieved by using highly breakable material in combination with high adhesive strengths. The adhesive strength of the material on the adhesion base is very significant. It is a decisive factor for resistance to any attempt at manipulation by removal.
Besides the standard material, there are modified labels intended to eliminate any possibility of imitating the material by using other safety features, such as embossments, holograms, or a lasting UV impression (footprint).
There are widely used high-performance controllable lasers for introducing markings, such as inscriptions, codings, and the like, using a burning process. Some of the requirements placed upon the material to receive the inscription, or used for the inscription process, are:
It has to be capable of rapid inscription.
A high degree of spatial resolution capability has to be achieved.
It has to be very simple to use.
The decomposition products have to be non-corrosive.
For particular cases moreover, additional properties are demanded:
The markings produced by applying the laser have to have sufficient contrast to be capable of being read without error even under unfavorable conditions and over large distances.
Heat resistance has to be high, for example extending above 200° C.
Good resistance to weathering, water, and solvents is desirable.
Complete separation of labels from the substrate is possible using sharp, flat blades. The bond between adhesive mass and substrate exhibits particular weaknesses on plastics substrates, such as polyethylene or polypropylene.
Despite increased adhesive strength on metallic or coated substrates, it is also possible here to remove part of the labels without irreversible damage, by using specific tools. A specific tool with a blade can be passed under the label at a shallow angle. Careful cutting movements can lift an edge, producing what is known as a grab site. This method creates a point of attack, which facilitates release.
If printing, rather than a laser label, is used to apply the inscriptions to the component, third parties can easily remove the inscription by washing or scratching. Simple rubbing of the inscribed article on a second article, for example a packing, is also often sufficient to reduce the clarity of the individual letters or numerals.
It is an object of the invention to provide a laser transfer film which permits rapid and precise inscription of any desired component, and which meets the abovementioned demand for improved security against counterfeiting, and which cannot be removed intact, even with the aid of a cutter, and which besides this in particular also has high contrast, high capability for resolution, high heat resistance, and good ease of use.
This object is achieved by means of a laser transfer film as described in the main claim. The subclaims provide particularly advantageous embodiments of the subject-matter of the invention, and also the use of the same.
The invention therefore provides a laser transfer film for durable inscription on components made from at least one backing layer, where on at least part of the underside of the backing layer there is an adhesion layer, wherein a pigment layer which comprises at least one laser-sensitive pigment has been applied to at least part of the adhesion layer and/or backing layer.
It is preferable that the matrix of the layer comprising the laser-sensitive pigments is likewise composed of the adhesive of the adhesion layer, so that the first adhesion layer and the pigment layer form a single homogeneous layer. The pigments have their distribution only in the periphery of the homogeneous layer, and specifically on the side facing away from the backing layer, and in particular in a narrow region of the homogeneous layer, and they therefore form a type of boundary layer.
For further improvement of the adhesion properties of the laser transfer film on the component to receive an inscription, there is preferably a second adhesive layer applied to the pigment layer comprising the laser-sensitive pigment.
A particular manner of application of the second adhesive layer is that of dots or screen print, or, where appropriate, an edge print, the result being that the transfer film can be adhesive-bonded to the substrate in any desired manner.
The thicknesses of the individual layers are preferably selected from the following ranges:
Backing layer
12 &mgr;m-240 &mgr;m, particularly 25 &mgr;m-100 &mgr;m
(preferably PET)
Adhesive mass
5 &mgr;m-45 &mgr;m, particularly 10 &mgr;m-25 &mgr;m
(preferably acrylate)
Pigment layer
1 &mgr;m-10 &mgr;m, particularly 2 &mgr;m-5&mgr;m
The films intended for use according to the invention have to be transparent and/or translucent, and at least designed in such a way as to prevent any absorption of the laser beam, which would cause serious damage to the same. In particular, it is desirable that the backing material absorbs no light within the wavelength range from 530 to 1064 nm.
According to the invention, the backing materials used preferably comprise films which, in another outstanding embodiment of the invention, are transparent, in particularly monoaxially or biaxially stretched films based on polyolefins, i.e. films based on stretched polyethylene or on stretched copolymers, comprising ethylene and/or polypropylene units, and, where appropriate, also PVC films, films based on vinyl polymers, on polyamides, on polyester, on polyacetals, or on polycarbonates. PET films in particular have outstanding suitability as backing.
According to the invention, the backing film used also comprise films based on stretched polyethylene or on stretched copolymers comprising ethylene and/or polypropylene units.
Monoaxially stretched polypropylene has a high tensile stress at break and low longitudinal strain. Monoaxially stretched films based on polypropylene are preferred for producing the labels of the invention.
For the last transfer films of the invention, particular preference is given to single-layer biaxially or monoaxially stretched films and multilayer biaxial or monoaxial films based on polypropylene which have a sufficiently strong bond between the layers, since delamination of the layers during use is disadvantageous.
Films based on rigid PVC or films based on plasticized PVC may be used for producing laser transfer films.
For the laser transfe
Koops Arne
Reiter Sven
Norris McLaughlin & Marcus PA
Schilling Richard L.
tesa AG
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