The hottest laser holographic anti-counterfeiting

2022-08-20
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Laser holographic anti-counterfeiting film points

in anti-counterfeiting technology, laser holographic anti-counterfeiting has played a very important role, but with the progress of science and technology, the traditional laser holographic anti-counterfeiting is far from meeting the needs of anti-counterfeiting. In order to meet the needs of users to the greatest extent and better meet the market requirements, we have developed a new perspective laser holographic anti-counterfeiting film. Because it is a perspective type, it does not cover the following information, and at the same time, it uses points as a reflection layer to improve its brightness. It is an anti-counterfeiting material with high anti-counterfeiting performance, especially suitable for 2. The operating procedures of electronic tensile testing machine are applicable to the anti-counterfeiting of some important certificates. For example, the anti-counterfeiting film is used on driving licenses in the United States and Indonesia, some documents in Japan, resident identity cards in Taiwan Province of China and some documents in the mainland. In the past, this kind of membrane was imported from the United States and required a lot of foreign exchange. This new material developed by us can not only replace imported products, but also save a lot of foreign exchange for the country, opening up a new field of laser holographic anti-counterfeiting applications. In this scientific research project, the production of dots is an extremely important and indispensable link. The development process and production method of the dot are discussed below

overview of the new perspective laser holographic anti-counterfeiting film

the new perspective laser holographic anti-counterfeiting film uses points as a local reflection layer, which can be observed on the same side. Its structure from the inside to the outside is point layer, information layer and PET polyester layer, as shown in Figure 1

pet polyester layer has high transparency, smooth surface and good wear resistance. It is an ideal material for anti-counterfeiting film substrate and the outermost layer of new laser holographic anti-counterfeiting film; The information layer is the carrier of laser holographic graphic information; The point layer is composed of vacuum aluminized layer. The vacuum aluminized layer has dense structure and high reflectivity. It is an ideal reflective layer, and the point is the basic unit of reflection. The diffraction light observed on the same side of the holographic pattern without a reflector is very little, and the efficiency is very low. Therefore, it can be said that point is not only the basic unit of reflection, but also the basic unit of graphic information. Without point, there is no new laser holographic anti-counterfeiting film. Because the friction coefficient of the organic material brake pad is higher (0.33~0.40) as the reflecting layer, it is possible to observe the certificate on the same side, which greatly simplifies the identification of the certificate

There are two methods of making points, which will be discussed separately below

exposure method dot

the principle of exposure method dot is to use the photosensitivity and corrosion resistance of diazo naphthoquinone sulfonate, Protect the aluminum layer covered with "since the modification in 2007, and let the aluminum layer in the blank part be corroded by the corrosive solution to generate points (see Figure 2).

1. Production process

(1) coating photosensitive adhesive

can be completed by using conventional coating equipment, which will not be repeated here.

(2) Exposure

irradiate with the most sensitive spectrum of diazo naphthoquinone sulfonate, as shown in Figure 3

due to the use of positive photosensitive adhesive, the part of the photosensitive adhesive covered by the black part (i.e. dot) of mask is not photosensitive, and the blank part is photosensitive and dissolved during development. Generally, the commonly used photosensitive adhesives are 2,1,5 diazo naphthoquinone sulfonate, 2,1,4 diazo naphthoquinone sulfonate and 1,2,4 diazo naphthoquinone sulfonate. Their reaction products can react with water to form indenoic acid and react with alkali (usually NaOH) to form a water-soluble compound -- sodium salt of indenoic acid compound

(3) development

the photosensitive gel product decomposed in the presence of light is hydrolyzed to form indenoic acid, and then reacts with oh- to form water-soluble sodium indenoic acid. In this way, the photosensitive glue covered by the mask point is retained because it is not photosensitive, forming a structure as shown in Figure 4

(4) cleaning

in order to prevent the developer from flowing into the next process, rinse the residual developer on the film with clean water

(5) non metallized

after development, the aluminum layer as a point needs to be covered by photosensitive glue, and the photosensitive glue in the blank part is cleaned during the development process. Therefore, when in contact with the corrosive solution, the aluminum layer of the blank part is corroded by the corrosive solution, and the point part is retained due to the protection of the photosensitive adhesive of the corrosive solution to form the structure shown in Figure 5

this process can be expressed by the ionic equation as follows:

2al + 6h- = 2al3+ + 3h2

(6) cleaning and drying to get the finished product

2. Experimental analysis

(1) photosensitive adhesive experiment

the experiment shows that the photosensitive speed of 2, 1, 5 diazonadione sulfonate and 2, 1, 4 diazonadione sulfonate is faster than that of 1, 2, 4 diazonadione sulfonate. In order to facilitate control, we use 1, 2, 4 diazonadione sulfonate

① experiment on the relationship between photosensitizer ratio and alkali resistance

experimental method: add different proportions of phenolic resin into photosensitizer as film-forming agent to carry out alkali resistance experiment, and get the data as shown in Table 1

since the concentration of NaOH developer we use is usually about 0.7% - 1.0%, the ratio of photosensitizer to film-forming resin should be 0.50 ∶ 1 ~ 0.62 ∶ 1. In the comparative experiment of different photosensitizer proportions, it is also found that when the photosensitive solution is used alone, the alkali resistance is very strong, but the film-forming property is poor, it is easy to embrittle, the development is quite difficult, and there is an uncorrupted aluminum layer around the point made; When a certain amount of film-forming agent (phenolic resin) is added, the alkali resistance decreases, but the film-forming ability and adhesion to the aluminum layer are greatly enhanced, and the development becomes relatively easy. The edges of the points made are clear and free of sundries. In the later pilot experiments, it was also shown that when the photosensitive dose was too small, the damage in the development process became smaller, and the spot became weak; When the photosensitizer content is too high, it becomes more difficult to develop and nonmetal, and there is an uncorroded aluminum layer around the point. So the proportion of photosensitizer must be moderate

② experiment on the relationship between photosensitizer content and photosensitive speed

experimental method: carry out the exposure experiment with the photosensitive layer containing different photosensitizers in 100ml photosensitizer (the exposure light source is 6kW air-cooled tritium lamp), and record the exposure time of the point with the same size as mask (see Table 2)

from the above data, the lower the photosensitizer content, the shorter the exposure time; The higher the photosensitizer content, the longer the exposure time. When the content is 3%, the point is easy to lose; When the content is 6%, it is very difficult to develop and nonmetal. Therefore, its content should be 4% - 5%

(2) light source selection experiment

we know that the photosensitive range of diazo naphthoquinone sulfonate is 350 ~ 460mm, so we should make clear the emission spectrum of the light source when selecting the light source. We choose two typical PS plate printing light sources - iodine gallium lamp and high-efficiency fast plate printing lamp

compared with the two light sources, although the power of high-efficiency and fast printing lamp is lower than that of gallium iodide lamp, most of its spectrum is concentrated in the photosensitive range of photosensitive glue, and the working temperature is low, so it is an ideal light source

(3) light source uniformity experiment

experimental method: use SB-30 908.8mm lamp tube, shine the high-efficiency and fast plate printing lamp on a black flannelette, and take 65cm in the middle of the lighting range × 65cm rectangle, use an illuminance meter to measure the ratio of the four corner illuminance value and the middle illuminance value of different lamp spacing, and get the data in Table 3. The curve can be drawn according to the data in Table 3 (see Figure 6)

as can be seen from Figure 6, when the lamp distance is not more than 60cm, it can ensure that the four corner illumination is very uniform within the effective area, so that the exposure can be uniform and very uniform points can be obtained. In other words, the maximum radius of the exposure drum can reach 60cm

(4) there is a certain difference between the exposure time experiment and the actual test value

SB-30 high-efficiency fast plate printing lamp is used, and the experiments of different exposure times are carried out according to the development time and temperature recommended by the photosensitive adhesive supplier. After development and non metallization, the point is reached. The point situation is shown in Table 4

gravure printing dot

the principle of gravure printing dot is to use corrosion-resistant ink to print dots on the aluminum layer through gravure printing, which plays the role of protecting the aluminum layer. The blank part is corroded because there is no ink protection. The process is shown in Figure 7

1. production process

(1) gravure printing

transfers the corrosion-resistant ink to the aluminum layer of the holographic film, and these inks are distributed on the aluminum layer in the form of dots, so as to achieve the purpose of protecting the aluminum layer

(2) non metallization

refer to the point making process of exposure method (5)

(3) cleaning and drying

refer to the point making process of exposure method (6)

3. Experimental analysis

scraping corrosion resistance test and spot test were carried out on the inks produced by different manufacturers, and comparative experiments were carried out to determine that the inks with good corrosion resistance and easy control of spot quality are gravure inks

gravure printing is an ideal method with fast dot making speed, short cycle, simple process, easy control, low cost and stable quality. However, in the production process, we should pay attention to the influence of air relative humidity and ink viscosity on the size of printing point and printability, and adjust the proportion and viscosity of ink diluent according to different seasons and relative humidity

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