Transparent hologram anti-counterfeiting film
With the development of technology and the improvement of people's living standards, anti-counterfeiting technology is widely used in a variety of commodity circulation and has become a new industry. Due to the development of the commodity economy, more and more attention in China's anti-counterfeiting technology. The modern anti-counterfeiting technology involving physical, chemical, and other multi-discipline, including many new materials, optics, information technology. Actual use the most widely-reflective aluminized the combined holographic film security stickers early use of the diffraction effect of the high reflectance and the grating strips aluminizer prepared by combining laser holographic techniques. From the late 1980s onwards tip products began to be developed and applied, more than a decade with the modifications of knowledge and technology development, the security function has been gradually updated lost view of this situation, it is necessary to research and development of new high-tech technology to prepare hard to fake security products. Preparation of the total price of existing facilities and technology, to replace the aluminum film to high refractive transparent dielectric films, making transparent laser holographic anti-counterfeit film is a relatively simple and efficient way.
Aluminized thin film technology in order to replace the high-refractive index of the transparent dielectric film, generally using physical vapor bottom or sputtering a the ZnS high refractive index material, having good optical characteristics and security features, and is more applied similar ID card , passport and other important documents. But the deposition rate is very low, high production costs, it is difficult to promote to the modifications of the day-to-day consumer goods. Sol - gel method for the preparation of high refractive index material, coated with a chemical into a transparent film, with the same optical properties and the effect of security, and easy to process low production cost, but also applies to the needs of the large area of ??anti-counterfeiting products.
Transparent laser holographic security film allows an observer in the process of converting Perspective on the transparent plastic film (PET, OPP, etc.) to see significant holographic image, the required performance of the object with laser holography techniques shooting optical carving and means of electroforming hologram system to the metal nickel template. Holographic images in the form of the grating strips is retained on the high refractive index material of the pore size and porosity is adjustable, having a nanostructure of TiO2. The reproduction of the holographic image, and records the effect of the optical properties of the dielectric material of principal and interest, as well as the dielectric material and the base material optically matched metal stencil will determine the quality of the entire security article.
2, transparent laser holographic anti-counterfeiting film Features and Benefits
2.1 transparent laser holographic security film has the following characteristics: (1), good light transmission, does not affect the apparent image of forgery, change the angle can clearly see the security film, laser holographic anti-counterfeiting pattern. (2), laser holographic security information between the layer of nanoparticles to form a three-dimensional network embedded in the base film with good abrasion resistance. (3), the security film applied to the a disposable overall package, replacing the previous the aluminized labels manually paste cumbersome. It is suitable for a variety of products, packaging and identification cards, passports and other documents, securities, notes, and so the security of anti-counterfeiting. (4), the perspective of laser holographic security film film, nanomaterials coated film, with a low cost, suitable for mass production, and can be easily authenticity characteristics. (5) Super security identification, security film of the surface layer is a colorless and transparent substrate on per square centimeter (1 × 105 to 5 × 105) breathable permeable microporous combination of milky white pattern, rather than printing, overprint.
2.2 is advantageous in that: ? transparent holographic film is coated on the film substrate is a high refractive index of the organic resin film, so this can be used directly for plastic and surface processing, and to expand its application areas. (2) As the organic resin of the high refractive index that is cheaper than the inorganic dielectric, and thus greatly reduces the costs of materials of the holographic film, and a combination of organic resin with an organic film substrate more firmly. (3) coated on the organic thin film, the high refractive index of the organic resin is more dense than the inorganic dielectric formation, which can effectively reduce the scattering of light, and improve the efficiency of film reflector, so this the laser hologram pattern is formed by the transparent security film brighter clearer, in favor of consumers clearly identified.
3, TiO2 transparent thin-film technology
3.1, TiO2 Thin Films
The nanostructured TiO2 transparent film using the sol - gel process. Sol - gel is a good way to prepare new material at home and abroad this more than has been reported, and mature theories and models, but almost no reproduction holographic laser image applications. Reflected the mimeograph fringes of the holographic image is laser Weidiao previously prepared and copied to the metallic nickel plate, the grating strips of the molding machine will be copied again in the dedicated to the TiO2 film, to complete reproducing holographic image on the film. Holographic image optical phenomena and the role of nanostructures on TiO2 film. Sol - gel method for chemical coating, chemical coating process TiO2 thin films. By the sol - gel method may be a component of the material, ratio and the micro-structure of the particle skeleton, holes, etc. of the thin film formed regulated to obtain the desired characteristics, including optical adapt to the production of transparent laser holographic film characteristics. Of the TiO2 film production and affect the characteristics of the relevant factors described below.
Counterfeiting film is a double-layer structure (Figure 1) the base layer is a polypropylene film (BOPP), or win ester film (PET), the upper information layer, i.e., with the grating strips of TiO2 film. TiO2 thin films in two steps. The first step in the preparation of TiO2 solution selection of organic metal titanium alkoxide - butyl titanate as precursor, ethanol or ethyl solvent added catalyst. The Tetrabutoxide by hydrolysis and polycondensation reactions ultimately generate TiO2 film. The sol process can be conducted at room temperature. Uniform appropriate mixing of the sol reaction.
The TiO2 solution was uniformly applied to the substrate on the implementation of the second step of TiO2 solution process using a dedicated roll plating equipment, it was also known as the chemical coating, sol process is completed in this basic, roller plating apparatus used in this process is gravure textured coating equipment used in the printing and packaging industry. The Anilox on regularly distributed recessed holes formulated the good sol uniformly, through the contact with the depression of the rubber roller and extrusion, the sol was transferred to a plastic substrate. Gel process containing sol plastic film is fed 5-10m/min the drying tunnel, drying tunnel temperature 80-100 ° C film drying tunnel reserved for 1-3min. During this time, the process of TiO2 thin films basically completed.
Laser engraving prepared in advance holographic image, and copy it to the metal on the nickel version, known as the working template. Working template is installed in molding equipment dedicated version of roller, feed roller and pressure roller sol - gel prepared TiO2 film with a plastic base with feed through plate roller and pressure roller intersection. The the Feeding and speed through the intersection 10-20m/min, the press temperature of 80-100 ° C, pressure 2-4kg/cm2. Under the joint action of the plate roller and pressure roller, light stripes on the template is transferred to the film, the completion of the process of suppressing grating stripes, the hologram is immediately apparent in the film, and almost no impact on the transparency of the original plastic base. The main factors to affect the performance of the TiO2 transparent laser holographic film In addition to the the film first optical design and matching the structure and characteristics of the material.
3.2 nanostructured TiO2 Films
The nanostructured TiO2 Thin Films ie gel process in the coating film-forming and later in the baking process. TiO2 sol was uniformly coated on the base film, and then fed at a certain speed, and through the drying channel. Drying tunnel temperature must be controlled within a certain range. In known when the temperature can continue to complete the hydrolysis and polycondensation reaction so that the original does not respond adequately sol; continue volatiles due to temperature, and role of the solvent in the sol gel process begins. The results of the gel to form a nano-structure of the porous polymer network gel films. The coated amount of the sol determines the basic thickness of the film. Baking temperature and time to determine the degree of perfection of the gel reaction, the final form excellent film has a crucial impact.
Nanostructured TiO2 film, specific surface copy engraved with laser dermabrasion technology grating stripes, clearly reflects the hologram can be used as anti-counterfeit material. Optional butyl titanate as the precursor of the sol - gel, by controlling the water and the catalyst participating in the reaction, the structure of the films regulating particles, so that the refractive index of the film is maintained at 1.8; transmittance of more than 90%. Reproducing the effect of the holographic image, and the film of the optical matching related both to the film thickness of each of 1um and 10um appropriate. The grating depth of the sinusoidal grating and 100nm on the reproduction of the holographic image is also very important. Diffraction effect and the angle of incident light or viewing angle, when the incident light is greater than 60 ° diffraction effect is most obvious.
3.3 Optical Properties
The information layer is to be applied to the plastic film on the layer of sol - gel TiO2 film, having a porous network structure. The film by the skeleton and holes evenly distributed from the refractive index is determined by the porosity. When the size of the hole is much smaller than the wavelength of the incident light, the available zero-order effective medium theory to calculate the refractive index of this nano-porous film: here were the refractive index of the medium of film, skeleton, and the holes filled, Vp is the film within the porosity of the .
Sol - gel precursor is to determine the refractive index of the size of the premise. The catalyst on the film structure also has an important influence on the refractive index of the film is also impact. In addition, the optical thickness and refractive index of the film have a corresponding relationship, and at the same time by the gel when the heat treatment time and temperature and impact.
4 Application Examples
The transparent laser holographic security film can be used not only as a transparent security tag, makes laser holographic anti-counterfeiting technology and expansion to the overall mechanization of tobacco, alcohol, cosmetics, health care products, food, clothing and other goods anti-counterfeiting packaging and documents, securities, notes and a variety of smart magnetic cards and other anti-counterfeiting.
4.1 laser holographic image pseudo trademark
Stickers laser hologram anti-counterfeit trademark is very convenient to use, better adaptability labeling machinery, different smearing glue and other adhesives used in the production line does not appear stains, especially for the more high-end packaging issued The effect is more obvious. This trademark is currently also the largest amount. But it has a fatal flaw can be used repeatedly, can be peeled off from the next position is completely glued to another location, so that some criminals can take advantage of the old packaging and trademark counterfeiting, thus affecting the security effect. From a security point of view to consider that such a trademark should not be used as anti-counterfeit trademark. Trademarks of the development of the laser hologram anti-tamper type to make up for the shortcomings of the self-adhesive laser hologram anti-counterfeit trademark, it only once and, when peeled off from the packaging, on which the image has been distorted beyond recognition, and can not be used again. Many businesses in developing tamper-type laser hologram anti-counterfeit trademark, the trademark is the most promising in the field of packaging a security trademark. Stamping laser hologram security identification one simply can not be peeled off the laser security trademark, it can be securely completely adhered to the items to be packaged, with the packaging member is formed integrally. If you can reasonably choose the location of the adhesive, the effect of security will be better than the effect of the above two types of forgery. Laser hologram anti-counterfeit trademarks encryption viable greatly enhance the security effect. Encryption method used fuzzy image processing method, the the moire fringe Act feud Fourier transform spectrum method, password law. Use these encryption methods, which greatly improved the technical content of the laser hologram anti-counterfeit trademark, which caused the encryption method has high unrecognizable, is well positioned to achieve security purposes.
4.2 in cigarette packaging printing
Not aluminized transparent medium and multi-layer film series structure produced the transparent laser holographic anti-counterfeiting film, the overall effect is very good, clear and bright laser pattern, but also to ensure better transparency to meet the requirements of the market. Used more often on the cigarette packets two technologies transparent holographic transfer and transparent hot stamping technology. Laser holographic materials in its anti-counterfeiting, eye-catching and novel advantages has become the highlight of the modern cigarette packaging market.
The laser holographic security film material is organic film coating adhesive layer formed by vacuum aluminum deficiencies that the overall package of steamed aluminum opaque material, both can not be used for merchandise, and also can not be used the overall security of the documents, securities, notes and a variety of smart magnetic card, making its applications greatly restricted, use it at the same time as the security tag affixed only by hand by the anti-counterfeiting, and can not be mechanized, nanostructured TiO2 film essential materials of the new security film, has been widely used in the manufacture of transparent security film; the transparent laser holographic anti-counterfeiting membrane from the fundamental solution to the above inadequacies, and thus not only can be used as a transparent security marking, and makes the laser holographic anti-counterfeiting technology expanded to tobacco, alcohol, cosmetics, health care products, food, clothing and other goods the overall mechanization security packaging and forgery of documents, securities, notes and a variety of smart magnetic card, etc.. The technology has broad application prospects.