Laser holographic label cutting technology

The requirements of the laser holographic die-cut labels for the nickel plated version are as follows:

1 Molded nickel plates should have high quality images.

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 has enough 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 silver, no pinholes, no sand holes, no imprints, and the negative side 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.

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.

Imposition and loading

1 Imposition. 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. 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.

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.

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.

Molding pressure, 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.

Lamination

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'.

Molding workshop environment

Molding workshops must be dust-free, free of impurities, and suitable humidity. The holographic material will generate a large amount of static electricity in the process of processing, and have strong adsorption power to dust impurities. If the dust and impurities fall on the holographic material, the quality of the molding will be seriously affected. At the same time, the molding machine is operated under high temperature and high pressure, dust impurities can easily enter the operating position of the machine and reduce the running accuracy of the machine.

Machine maintenance and maintenance

Molding presses are high-precision equipment. After a long period of operation, the accuracy will be reduced, and inspection and maintenance should be performed frequently. When replacing the components of the molding press, accessories should be made of high-quality parts and ensure the accuracy of the installation.

Common Molding Quality Problems

During the molding process of the holographic label, due to the influence of the precision of the molding press, the processing technology, the quality of the nickel plate, the heating temperature, the holographic material, and the environmental conditions, some quality problems may occur. Common quality problems and their solutions are as follows.

(1) The hologram pattern is partially blurred or incomplete

Solution: Check whether the thickness of the nickel plate is uniform, whether the pressure is too small, whether the temperature is too low, and whether the machine's degree of rigidity and precision are reduced.

(2) The hologram pattern is dull

Solution: Check if the heating temperature is too low, if the mold pressure drops, and if the nickel plate wears out.

(3) White hologram pattern

Solution: Check if the molding speed is too slow and the molding temperature is too high.

(4) Holographic Film Sticking

Solution: This is due to the fact that the hot pressing temperature is higher than the degradation temperature, the viscosity of the coating increases, and sticking is caused and the film is wound around the hologram embossing roller. At this point the hot press temperature should be reduced.

(5) The holographic pattern is a clear, blurred piece

Solution: Check whether the temperature distribution of the preheating device is even and whether the stencil is deformed or worn.

(6) The holographic film has "burst" in the longitudinal direction

Solution: Reduce the holographic film tension.

(7) Wrinkles in the holographic film

Solution: Increase the unwinding tension or winding tension until the creases are eliminated.

(8) Inconsistent elasticity on both sides of the holographic film, poor flatness

Solution: Increase the tension.

Keywords: die-cut/label/laser hologram