Embodiment
Optical anti-counterfeit element according to the present invention and its preparation method are described in detail below in conjunction with accompanying drawing.
As shown in Figure 1, optical anti-counterfeit element according to one embodiment of the present invention comprises base material 3, described base material 3 comprises the first surface 31 and the 2nd surface 32, and the part region on described first surface 31 is sub-wavelength micro relief profile, part region is plane surface structure. Described sub-wavelength micro relief profile and plane surface structure region are all sequentially laminated with first medium layer 101, second dielectric layer 102 and the 3rd medium layer 103, thus form the interference structure 10 being positioned at sub-wavelength micro relief profile region and the interference structure 20 being positioned at plane surface structure region respectively. Wherein, the coordinate z in Fig. 1 represents vertical direction, and coordinate x represents horizontal direction.
The three layers of medium layer structure being made up of first medium layer 101, second dielectric layer 102 and the 3rd medium layer 103 have Fabry-Perot cavity filter structure, the white light of incidence is had selective action by it, outgoing light only comprises the light of some wave band, forms specific color; But when incident angle changes, the light path corresponded changes, and interferes wave band to change, causes the color presented also to change, thus presents light and become effect thereupon.
When three layers of medium layer light structure changes according to the present invention and sub-wavelength micro relief profile being combined, interference and diffraction acting in conjunction, it is possible to obtain its all band, this kind of effect is relevant to the incident angle of light, and the same one light that obtains becomes effect. So just obtain two kinds of light change effects by once steaming light-plated structure changes. When after the feature cycle suitably selecting sub-wavelength micro relief profile and medium layer parameter, homochromy asynchronous phenomenon can be realized, namely, under a viewing angle, the micro-embossment region of sub-wavelength is different from the reflection/transmission spectrum in the plane region without the micro-embossment of sub-wavelength but color is identical or close; When viewing angle changes, it is different that both light become effect, and the light that experience is different separately becomes process, produces difference. This will be described in detail in conjunction with concrete parameter hereinafter.
The intensity of Maxwell Equation for Calculating Electric and magnetic fields vector through each layer and each interface and phase change can be utilized, and consider final condition, obtain each medium layer and phase differential that light is produced by each interface and strength variation parameter, thus realize the parameter designing according to three layers of medium layer coating structure in the optical anti-counterfeit element of the present invention. When specifically calculating, each for medium layer interface can be thought of as virtual equivalent interface, obtain full detail, particularly intensity that light propagates in the coating variation relation with wavelength by the feature matrix of calculation combination admittance and rete, i.e. the reflection spectrum of coating. Finally by the color coordinates in CIE color space that reflection spectrum and tristimulus values function are carried out integration acquisition coating.
Sub-wavelength micro relief profile according to the present invention has multiple parameters, such as cycle, groove depth, grooved etc., when by sub-wavelength micro relief profile and three layers of medium layer textural association, also need the parameters such as each layer thickness in consideration three layers of medium layer coating, material specific refractory power. During specific design, rigorous coupled wave method (RCW), time-domain finite difference method (FDTD) isovector diffraction theory need to be utilized, in conjunction with Boundary Condition for Solving maxwell equation group. Vector Diffraction Theory press of Zhejiang University publishes, " micro-optic and system " that Yang Guoguang writes has detailed discussion. When designing according to the structural parameter of the optical anti-counterfeit element of the present invention, can from basic theories, particular case according to problem and to be realized optical signature design algorithm, program calculation, finally determine each side design variable, the groove depth of such as embossment structure, grooved, dutycycle and x direction or/and characteristic dimension on y direction, according to the number of plies of the coating of the present invention and each layer thickness, metallic substance, dielectric material, substrate material etc. Then according to optics vector theory, program according to the final condition of sub-wavelength multilayered structure coating structure: calculate according to initial structure parameter; According to calculation result optimum structural parameter; Carry out calculating, optimizing according to the parameter after optimization again, until reaching satisfied result.
According to, in a preferred embodiment of the present invention, the specific refractory power of first medium layer 101 and the 3rd medium layer 103 is more than or equal to 1.7, and its material is selected from such as ZnS, TiN, TiO2��TiO��Ti2O3��Ti3O5��Ta2O5��Nb2O5��CeO2��Bi2O3��Cr2O3��Fe2O3Deng in any materials or combination, and, the thickness of first medium layer 101 and the 3rd medium layer 103 can be 10nm to 300nm, it is preferable to 50nm to 200nm. The specific refractory power of second dielectric layer 102 is less than 1.7, and its material is selected from such as SiO2��MgF2��Na3AlO6��Al2O3In any materials or combination, and the thickness of second dielectric layer 102 can be 50nm to 1000nm, it is preferable to 100nm to 500nm.
According to, in a preferred embodiment of the present invention, described sub-wavelength micro relief profile can be dimension grating and a direction-agile. And, the cycle of described sub-wavelength micro relief profile is also variable, and wherein, the cycle of described sub-wavelength micro relief profile on x direction and/or y direction can be 50nm to 500nm, it is preferable to 200nm to 400nm. In addition, the groove depth of described sub-wavelength micro relief profile is also variable, and wherein, described groove depth is positioned at the scope of 10nm to 500nm, it is preferable that be positioned at the scope of 50nm to 200nm. The grooved of described sub-wavelength micro relief profile is also variable, and such as, described grooved can be at least one in sinusoidal, rectangle, zig-zag.
Provide some concrete structural parameter below and further describe the optical anti-counterfeit element according to the present invention.
Such as, sub-wavelength micro relief profile is one-dimensional sinusoidal grating, and its feature cycle is 340nm, and ditch groove depth is 180nm; First medium layer 101 is TiN, thickness is 50nm, and second dielectric layer 102 is Al2O3, thickness be 180nm, the 3rd medium layer 103 is TiO2, thickness be 70nm. Fig. 2 give in this case the interference structure 10 of optical anti-counterfeit element according to the present invention and the face tristimulus coordinates of interference structure 20 along with the changing conditions of viewing angle. It can be seen that when the first viewing angle is 0 ��, the color coordinates of interference structure 10 is (-3.2,67.8), presents yellow; The color coordinates of interference structure 20 is (2.4,78.1), also presents yellow, and both aberration �� E are 13.2, and for the vision of people, both colors are identical. When the 2nd viewing angle is 40 ��, the color coordinates of interference structure 10 is (1.9 ,-47.9), presents blueness; The color coordinates of interference structure 20 is (-24.4,63.9), presents green, and both have significant difference at color. Visible, when the first viewing angle is 0 ��, when namely vertically observing sub-wavelength this two regions of the smooth surface tissue of micro relief profile regional peace, their color is substantially identical; Along with the increase of viewing angle, the color distinction in two regions becomes big, becomes two kinds of significantly different tones. Like this, by the suitable design in plate-making, the smooth surf zone of sub-wavelength micro relief profile regional peace being coated with sub-wave length grating can be made to form word, the pattern of certain sense, when observation is faced in realization, word, pattern are hidden in background, the optical anti-counterfeiting effect that during oblique view, word, pattern manifest. When the color in the smooth surface tissue region of sub-wavelength micro relief profile regional peace is evaluated, adopt CIELAB chrominance space. CIELAB (CIELab) chrominance space is the even color space that International Commission on Illumination in 1976 is recommended, the GB792-87 that China in 1987 issues using LAB space as national standard. The industries such as current Color Scheme and duplication are in color correction, calculating and DTP system, and CIELAB space is commonly used. Wherein+a represents red, and-a represents green, and+b represents yellow, and-b represents blue, and L represents brightness. Table 1 provide interference structure in this example 10 and interference structure 20 0 �� with L, a, b parameter under 40 �� of viewing angles, sets forth the difference �� E between both colors, wherein �� E utilizes following formula to obtain:
��E=((L-L��)2+(a-a��)2+(b-b��)2)1/2
The CIELab coordinate of interference structure 10 and interference structure 20 under the different viewing angle of table 1
Preferably, it is possible to obtain distinct colors match condition by adjusting the parameters such as the material of the parameters such as the grooved of sub-wavelength micro relief profile, cycle, groove depth and each medium layer, thickness. Such as, sub-wavelength micro relief profile is one-dimensional sinusoidal grating, and its feature cycle is 280nm, and ditch groove depth is 150nm; First medium layer 101 is TiO2, thickness be 55nm, second dielectric layer 102 is Al2O3, thickness be 270nm, the 3rd medium layer 103 is TiO2, thickness be 85nm, when the first viewing angle is 0 ��, interference structure 10 and interference structure 20 all present green; When the 2nd viewing angle is 20 ��, interference structure 10 presents purple, and interference structure 20 presents cyan, and both have significant difference at color. Or sub-wavelength micro relief profile is one-dimensional sinusoidal grating, its feature cycle is 250nm, and ditch groove depth is 80nm; First medium layer 101 is TiO2, thickness be 100nm, second dielectric layer 102 is Al2O3, thickness be 210nm, the 3rd medium layer 103 is TiO2, thickness be 100nm, then when the first viewing angle is 0 ��, interference structure 10 and interference structure 20 all present blueness; When the 2nd viewing angle is 20 ��, interference structure 10 presents purple, and interference structure 20 presents orange, and both have significant difference at color.
Fig. 3 gives the interference structure 10 of the optical anti-counterfeit element according to the present invention and the tristimulus coordinates of interference structure 20 changing conditions along with viewing angle, wherein, sub-wavelength micro relief profile is one-dimensional sinusoidal grating, and its feature cycle is 340m, and ditch groove depth is 130nm; First medium layer 101 is TiO2, thickness be 100nm, second dielectric layer 102 is Na3AlF6, thickness be 250nm, the 3rd medium layer 103 is ZnS, thickness is 40nm. It can be seen that when the first viewing angle is 0 ��, the color coordinates of interference structure 10 is (3.7,46.0), presents yellow; The color coordinates of interference structure 20 is (-44.2 ,-19.1), presents blue-greenish colour, and both aberration �� E are 82.2, and color has obvious difference. When the 2nd viewing angle is 20 ��, the color coordinates of interference structure 10 is (-32.3 ,-36.6), presents blueness; The color coordinates of interference structure 20 is (-9.2 ,-38.8), also presents blueness, and both aberration �� E are 23.4, and color is close, and people's eye can not tell obvious difference. When viewing angle continues to increase to 40 ��, both aberration �� E are increased to again 110.2, and color distinction between the two becomes big again. Visible, when the first viewing angle is 0 ��, when namely vertically observing two regions, the color distinction in two regions is relatively big, is two kinds of different tones; Along with the increase of viewing angle, two field color are all to blueness change, and when reaching 20 ��, both are blueness at color, form identical color; After viewing angle continues increase, both change again at color, notable difference occur. Table 2 provides L, a, b parameter under different viewing angle of interference structure 10 and interference structure 20 in this case. Therefore, by suitable design, it is possible to realize picture and text and hide again to the process manifested from appearing to viewing angle.
L, a, b parameter of interference structure 10 and interference structure 20 under the different viewing angle of table 2
Certainly, in order to form the pattern such as word, mark, can also have engraved structure 5 according to the optical anti-counterfeit element of one embodiment of the present invention. As shown in Figure 4, having first area 1 and the 2nd region 2 on the first surface 31 of the base material 3 of this optical anti-counterfeit element, wherein first area 1 is sub-wavelength micro relief profile, and it is coated with interference structure 10; 2nd region 2 is plane surface structure, and it is coated with interference structure 20, and wherein, interference structure 10 and interference structure 20 can adopt above-mentioned various structures. 2nd surface 32 of base material 3 is optionally coated with or prints absorption layer 4(such as, Hei Mo or other colored absorption type coating), thus form void region 5, wherein can by suitably selecting so that void region 5 forms word, mark, pattern. Like this, when observing from the first surface 31, interference structure 10 and 20 on coating absorption layer 4 only reflection spectrum, present bright, to be easy to identification color, interference structure 10 and 20 on void region 5 presents vitreous state, when being particularly attached on the carriers such as paper, mainly present the color of the carriers such as paper. Especially, when observing under the viewing angle presenting same color at interference structure 10 and interference structure 20, a kind of picture and text effect can be increased by void region 5, promote the vision capture power of this Security element, strengthen antifalse effect. Like this, when taking reflection view mode, transmitted ray is absorbed by absorption layer 4, adds strong man's eye to the identification of reflection light, strengthens the vision effect of the optical anti-counterfeit element according to the present invention.
Fig. 5 gives an enforcement mode again of the optical anti-counterfeit element according to the present invention. wherein the first surface 31 of base material 3 is at least coated with two kinds of orthogonal sub-wave length gratings in direction, and described sub-wave length grating is coated with multilayered medium layer coating structure as above, thus form interference structure 10, interference structure 20 and interference structure 30, wherein interference structure 10, interference structure 30 cover on two kinds of orthogonal sub-wave length gratings respectively, and interference structure 20 is positioned on flat surfaces. by the parameter of the parameter and coating structure that suitably regulate sub-wave length grating, it is possible to obtain following effect: when vertically observing, interference structure 10, interference structure 20 are identical with the color of interference structure 30, during certain angle oblique view, interference structure 10 color keeps color constant, interference structure 20 change from the color of interference structure 30 and the color that obtains after changing different, now 90 �� rotate this optical anti-counterfeit element, and interference structure 10 and interference structure 30 occur color to exchange, the color of interference structure 20 under still keeping this angle original color constant. hide when utilizing this feature can realize vertically observing, the optical signature that when tilting and rotate, picture and text manifest. exemplarily, such as, sub-wavelength micro relief profile is one-dimensional sinusoidal grating, its feature cycle is 340nm, ditch groove depth is 130nm, first surface 31 of base material 3 has orthogonal two sub-wave length grating regions, thus form interference structure 10, interference structure 20 and interference structure 30, wherein interference structure 10, interference structure 30 covers on two kinds of orthogonal sub-wave length gratings respectively, interference structure 20 is positioned on flat surfaces, and described sub-wave length grating is coated with multilayered medium layer coating structure as above, wherein first medium layer 101 is TiN, thickness is 50nm, second dielectric layer 102 is Al2O3, thickness be 180nm, the 3rd medium layer 103 is TiO2, thickness be 70nm. Then when the first viewing angle is 0 ��, interference structure 10, interference structure 20 are yellow with the color of interference structure 30; When tilting this optical anti-counterfeit element and make the 2nd viewing angle be 40 ��, interference structure 10 color turns into blueness, and interference structure 20 turns into green, and interference structure 30 color keeps yellow constant; When rotating this optical anti-counterfeit element 90 �� under this angle of inclination, interference structure 20 color is still green, and interference structure 10 color turns into blueness, and interference structure 30 color turns into yellow, it is achieved the color swap of interference structure 10 and interference structure 30.
Should be understood that, Fig. 4 and Fig. 5 is only example, in fact, according to actual needs, the parameters of sub-wavelength micro relief profile, arrangement mode can be optimized, combine, and cover corresponding medium layer thereon, and combine with hollow out and form high false proof optical anti-counterfeit element.
Preferably, above-mentioned base material 3 can be transparent or non-transparent, coloured or colourless film. Can be such as poly terephthalic acid diol ester, polyvinyl chloride, polyethylene, polycarbonate, polypropylene, metal, glass and paper etc., and its thickness can be 5 microns to 500 microns, it is preferable to 10 microns to 100 microns.
In one embodiment according to the present invention, when adopting translumination observation mode, base material 3 can be left intact or be coated with the coating of transparent/translucent, so that light passes through.
In addition, it should be understood that color-match herein to refer to that color reaches to a certain degree similar, not meaning color must be completely identical.
In addition, opened window safety line can be made into according to the optical anti-counterfeit element of the present invention, paste bar, paste the product forms such as mark. Applying on product in order to convenient, one side or the two sides of this optical anti-counterfeit element scribble assembly glue, to be attached on carrier by the technique such as thermoprint or stickup. And, can be applied to according to the optical anti-counterfeit element of the present invention on the contour safety of banknote, card and high-grade goods or high value-added product.
As shown in Figure 6, the present invention also provides a kind of method preparing optical anti-counterfeit element, and the method comprises:
S61, offer base material, described base material comprises the first surface and the 2nd surface;
S62, form sub-wavelength micro relief profile on the first surface so that the part region on described first surface is described sub-wavelength micro relief profile, part region is plane surface structure;
Wherein, described sub-wavelength micro relief profile can be formed by the mode that double laser beams interferes exposure, laser scribing exposure or electron beam directly to be carved, or carries out batch duplicating by the mode of ultraviolet cast, mold pressing, nano impression. Such as, sub-wavelength micro relief profile can make mother matrix by methods such as holographic interferometric method, laser scribing technology, electron beam lithographies, makes working version by electroforming process, is transferred on base material by production technique such as mold pressing, UV duplications.
S63, on the smooth surface tissue region of sub-wavelength micro relief profile regional peace, form first medium layer simultaneously;
S64, on described first medium layer, form second dielectric layer simultaneously;
S65, in described second dielectric layer, form the 3rd medium layer simultaneously.
Wherein, described first medium layer, described second dielectric layer and described 3rd medium layer can be formed by the mode of the physical vapor depositions such as thermal evaporation, electron beam evaporation, magnetron sputtering or chemical vapour deposition.
In sum, medium layer structure according to the present invention can be formed by an evaporate process, and position and the characteristic dimension that micro-nano technology technique can control sub-wavelength micro relief profile on micron even Nano grade such as directly carve by laser scribing or electron beam, so, optical anti-counterfeit element according to the present invention not only increases anti-counterfeiting performance, and reduce technology difficulty, save cost.
It is to be understood that only describe the optical anti-counterfeit element according to the present invention with reference to preferred implementation above, but it will be appreciated by persons skilled in the art that, under the prerequisite not deviating from the spirit and scope of the present invention, it is possible to the present invention is made various changes and modifications.