Analysis of Laser Hologram Label Molding Problems

Laser holography technology uses the basic laws of scattering, reflection, transmission, diffraction, interference, and absorption generated by the interaction of light and matter to obtain a special visual effect. The laser hologram label is a label that combines the three functions of anti-counterfeiting, display promotion and beautification made by applying laser holographic anti-counterfeiting technology. Laser holographic labels are colorful in the sun. When the light is dark, they are "without being exposed, and if not," they give people a fantastic feeling and unique artistic charm.

In recent years, with the rapid development of holographic anti-counterfeiting technology, laser holographic labels can not only exhibit three-dimensional three-dimensional effects, but also make a series of changes in the image with changes in the viewing angle, and the effects thereof are not achievable by ordinary printing methods, and thus are extensive. Applied to celebrity portraits, home appliances, medicines, foods, health products, cosmetics, securities, cards, and handicrafts, the emergence of molding technology has enabled the realization of low-cost, high-volume laser holographic labels.

This article discusses the issues related to the molding of laser holograms.

Types of laser hologram labels

There are many kinds of laser holographic labels, and here are the three commonly used ones.

1. Laser holographic self-adhesive type

This type of label is very convenient to use and can be completely glued to other locations when it is removed from one location. Because it can be used repeatedly, it loses its anti-counterfeiting effect, so its application range is limited.

2. Laser holographic tamper-proof type

Also known as a type of laser holographic label, which is characterized by: When the label is removed from the package, the pattern on the label is not complete, can not be used again, can not be imitation, and thus played a very good anti-counterfeiting effect, make up the self-adhesive Laser holographic labels cannot be counterfeit-proof. At present, the defence-type laser holographic label has been widely used and is the most promising one in the field of laser holographic labels.

3. Laser holographic hot stamping type

It is a laser holographic label that is tightly and completely adhered to the packaged object, and is integrated with it, and cannot be peeled off. If the label is applied at a reasonable position, it can exert a good anti-counterfeiting effect, and its application is also more.

In addition, the laser hologram label can also be encrypted to improve the technical content of the laser hologram label. Currently used encryption methods are: low-frequency lithography, laser reading, optical micro-shrinking, random interference fringes, Moiré fringe method, etc. Some of these encryption methods are difficult to identify, can play a very good anti-counterfeiting effect.

Laser holographic label molding process

The process of molding and copying the laser holographic label is to heat the holographic nickel plate (the nickel plate contains the embossed hologram) to a certain temperature, and press it with a certain pressure on the holographic material, and transfer the fine embossed interference fringes on the holographic nickel plate to The surface of the holographic material is printed on the surface of the holographic material. After being cooled and set, the surface of the holographic material forms the same stripes as the holographic nickel plate. These stripes are the embossed holograms. The imprinted holographic material is covered with a film, coated with a pressure-sensitive adhesive, and compounded with an appropriate backing paper to form a laser holographic label with a backing paper, which is then die-cut by a die-cutting machine to eliminate waste. Laser holograms were made. The production process flow of different material molded laser holographic labels is as follows.

Transparent PET (or Aluminized PET)→Electroforming Platemaking→Molding→Coating→Composite→Die Cutting→Finished Product

Transparent PVC (or Aluminized PVC)→Electroforming Plate Making→Molding→Transfer Film→Hot Stamping Transfer→Finished Product

OPP Holographic Base Film → Molding → Cooling → Winding → Die Cutting → Finished Product

Molding precautions

1. Material selection

Embossed holographic labels use more materials, including: polyester (PET), polyvinyl chloride (PVC), OPP holographic base film, etc., of which polyester, polyvinyl chloride are both transparent, but also aluminum plating. In production, materials of different types and thicknesses should be selected in conjunction with specific process conditions. In general, the following issues should be noted when selecting materials.

(1) Basic principles

The quality of holographic materials directly affects the quality of products. The basic principle is to choose materials with uniform thickness, good tensile strength, stable performance and low softening point. In addition, due to cost constraints, the level of holographic labels should also be considered, so that the selected materials match the grade of the product. High-quality products can use good-quality holographic materials, and vice versa. Holographic materials that are in direct contact with goods (especially foods, medicines, etc.) should also meet relevant hygiene standards.

(2) Requirements for material properties

The properties of transparent PVC and PET materials are to be satisfied: they have good wear resistance and corrosion resistance, and have good chemical stability; high flatness, uniform thickness, no watermarks, scratches, stains; good transparency, holographic layer The transmission rate reached more than 90%.

The performance of aluminum-plated PVC and PET materials must meet the following requirements: The aluminum-plated reflective layer is dense, firm, and has no defects such as blisters.

The properties of the OPP holographic base film must satisfy: uniform thickness, high gloss, low haze, good heat sealability, certain surface tension, and vacuum aluminum plating.

(3) Appearance and Thickness Requirements for Roll Materials

Both ends of the reel holographic material should be tight and tight, and the winding should be neat and tidy. There should be no "burst ribs" and uniform rewinding so that it will not run away when the film is conveyed. Roll holographic material should be suitable for rolling processing methods, generally require the thickness of the film is 0.06 ~ 0.10mm.

(4) Requirements for roll cores

Since the roll hologram material is wound around the core, the straightness and concentricity of the core are required to be high. If the straightness and concentricity errors of the core are large and the eccentricity of the reel is serious, then the embossed holographic pattern is difficult to die-cut (difficult to register), and sometimes it cannot be die-cut.

2. Material storage

Holographic materials should be stored in a dust-free, dry, ventilated, sun-protected place. Holographic materials contain static electricity and are prone to dust, so they must be protected against dust. Under the influence of sunlight, ultraviolet rays and heat, the molecular structure of PVC materials will change, so the storage environment should be protected from light and ventilation.

3. Molding method selection

Large-scale production of holographic markings generally uses a wide-width molding press, which is stamped in a circular press. Circular pressure is a continuous production method. It not only has high production efficiency, but also can produce large-area holographic markings. The characteristics of this production method are as follows.

(1) When the pressure is applied, the two press rolls are in line contact with each other, and the applied pressure is small. Under the same pressure, the width of the press roll is large, and large-area hologram labels can be produced. The holographic nickel plate has a long service life.

(2) Overprinting patterns and die-cut patterns have high overlay accuracy.

(3) Rolling speed is fast (up to 160m/min) and the production efficiency is high.

4. Production process control points

(1) Requirements for Molded Nickel Plates

1 Molded nickel plates should have high quality images, which is the most basic requirement.

2 The thickness of the molded nickel plate should be uniform. Due to the thin thickness of the holographic material, such as the non-uniform thickness of the nickel plate, defects such as blurred and unsatisfied individual images appear after molding. Molded nickel plate thickness error should be controlled within 0.001mm.

3 Molded nickel plate must have sufficient hardness, no cracks, no stress. The general Vickers microhardness should be maintained at 230 ~ 280N/mm2. Because the hologram is designed to apply a certain pressure to the embossing roller and mold the interference fringes, if the hardness of the embossed nickel plate is not enough, there is internal stress, the nickel plate will be deformed or damaged during the embossing process, and the embossed image quality is light. Decreased, nickel plate life shortened, while the nickel version can not be used.

4 The front of the nickel plate should be bright and white, no pinholes, no blisters, no imprints, and the reverse should be flat and free of distortion. In particular, hydrogen bubbles are formed on the surface of the nickel plate. If bubbles do not escape in time, pinholes will be formed. Products molded from such nickel plates are likely to be scrapped.

(2) Surface treatment of transparent plastic film

It is through the pretreatment or chemical coating method to coat the surface of the plastic film with a layer of 1 ~ 3μm thick coating, this layer of coating is the carrier of the holographic image.

(3) Imposition and loading

1 make up. There are two commonly used methods: one is to make a good version when electroforming; the other is to piece together a holographic nickel plate on the worktable. When imposition, attention should be paid to the arrangement of the pattern and the convenience of die-cutting and waste-discharging. The height of the template fixed on the same roller should be the same.

2 installed version. The foreign matter between the molding roller and the stencil should be removed when loading the plate, and the stencil should be installed in the center of the molding machine as far as possible to make the molding pressure uniform and reduce the wear caused by the unbalanced force of the machine part for a long time.

(4) Temperature setting

Under constant pressure, according to different heating temperature, thermoplastic materials are generally divided into four different states: glassy, ​​highly elastic, plastic and viscous. For a rigid PVC film, the embrittlement temperature Tg=55°C, the softening temperature Tm=70°C, and the degradation temperature Td=150°C. When the hologram label is duplicated, the PVC film should be in a plastic state, that is, above the softening point temperature of the PVC film and below the degradation temperature, that is, in the range of 70 to 150° C., the film is best formed. For PET, the heating temperature should also be controlled between the softening temperature and the degradation temperature. Because of its high plasticity temperature, the temperature and pressure required for molding are also higher.

(5) Synchronization and tension adjustment

After the moulding starts, the automatic adjustment device can be used to adjust the moulding synchronization in small increments and also to be constantly adjusted during the production process. In the molding process, changes in film roll diameter and factors such as speed increase, deceleration, start-up, and braking all cause changes in the tension of the holographic web, so the tension must be adjusted at any time. The size of the tension is neat, non-slip, and no fold.

(6) Molding pressure and speed control

The setting of the molding pressure should comprehensively consider the molding temperature, the type of holographic material, or the softening point of the coating layer and the case of the stencil. The pressure is too high, the template is easily damaged, or the holographic material is crushed; the pressure is too low and the molded image is unclear and incomplete. For the round press method, the initial pressure of the two sides of the pressure roller is generally about 0.08 MPa. After the molding is started, the pressure of the pressure roller is gradually increased to 0.30 to 0.50 MPa. Molding speed can be comprehensively adjusted according to impression quality, machine performance, etc. Wide format presses typically have speeds of 50 to 100 meters per minute. In actual production, these parameters can be adjusted according to the quality of the molded image.

(7) Covered film

In order to protect the laser holographic image, it is generally necessary to cover the surface of the holographic image with a packaging machine with a thickness of about 0.4 μm and a transparent film of 'target=_blank'.
(8) Molding workshop environment

Molding workshop must be required