Nano-processing technology for non-absorbent material printing
Source: "Hua Printing Technology Newsletter" Issue 67 Speaker: Lai Dongyang, Deputy General Manager of Guanghui International Co., Ltd.
In the field of special printing, plastic materials to be printed cannot be printed directly. Surface treatment is required to polarize and roughen the surface of the material to be printed, so that the ink can be smoothly attached to the surface. Although the surface modification technology It has been around for a few years, but its application breadth and scale have grown significantly in the last 10 years. Most of this growth is due to the rapid and reliable development and spread of surface property treatment technology. These methods include chemistry, photochemistry and high-energy physics to improve the polymer surface. Chemical methods include reactions such as halogenation, addition, etching, and oxidation. Photochemical methods include surface reactions such as oxidative and non-oxidative degradation, halogenation and photografting. Physical methods include corona discharge, plasma, electron and ion beam treatment, etc. This article will introduce corona treatment, ultraviolet treatment and ion plasma treatment.
? Corona treatment
The principle of corona treatment is to use electrostatic discharge (electrostatic discharge) to improve the coating adhesion of plastic films, and solve the adhesion problems caused by the printing of polypropylene or polyethylene films. In addition, the moisture and high solids radiation cumable ink (high solids radiation cumable ink) produced on the surface of the film will increase the surface energy. For example, polyvinyl chloride and polyester belong to this type of film. The general pre-treatment of the film includes: burning treatment, corona treatment or coating operation to improve adhesion.
The corona treatment system includes: a generator, a high voltage transformer and a processing machine. The processing machine is basically a capacitor, and the processed material is placed between the electrodes so that The voltage is gradually increased until the purpose of corona treatment is achieved. Therefore, corona treatment can increase surface oxidation and promote the breaking of chemical bonds to cause more hydroxyl groups, carbonyl bonds and hydrogen peroxide Key, the surface of the film will change to roughen, which reduces surface contamination.
The plastic film is usually placed between rollers and treated with a bipolar substance and separated from the electrode surface by a few centimeters through the electrode. Corona treatment decreases with time, and its influencing factors include: elevated temperature and humidity. In addition, there are additives to reduce surface energy and improve slip after coating. Therefore, corona The treatment needs to avoid the generation of rabbit lumps and the increase of surface energy to affect the unwinding and winding.
Corona treatment is used for various changes of the film and related reports. The applicable range is polypropylene and low surface energy plastics. When the air interval is increased to 5omm, the voltage is 5600OKHz. In this way, the corona discharge can be controlled.
? UV treatment
Ultraviolet treatment is generally applicable to the combustion treatment of polypropylene buffers produced by the automotive industry. The treatment method is divided into two stages: first, the buffer is sprayed with a primer to form a layer of 3 ~ 5um Film. The primer is mainly benzophenone or chlorinated polymer. Its purpose is to add to the surface to improve the properties of polypropylene. Therefore, the primer is evenly applied to the plastic to prevent ultraviolet radiation. Therefore, It is suitable for the painting work of buffer.
? Ionic slurry treatment
Recently, ion plasma treatment methods have received great attention, and their methods can improve the adhesion of plastic film surfaces and improve their physical properties, such as wear resistance and gas permeability. The ion plasma method is to generate an ion plasma using a voltage in a cold or non-equilibrium low pressure vacuum chamber. The cold ion plasma is generally used in the electronics industry, for example: The resistance cover of the circuit melting and shielding photons also has the function of cleaning the contact surface, so that insulating coatings can be applied. This kind of equipment is quite expensive compared with pre-treatment equipment, so the scope of application of this method is limited, and its advantage is that the project is clean (clean), and only a few volatile organic compounds (VOCs) are generated. However, this method can promote extremely high surface energy and reactivity on the surface of the plastic film. In addition, it also has a regeneration function. This method can also provide good bonding and synthesis in electronic applications. Compound (potting compound).
Ionic slurry treatment method is widely used in plastic surface treatment, and the generation of ion slurry is accomplished by using the components and electrons between each other, or placing the electrons on the circumference and the components located in the central part, AC ions are usually using microwave or electrical frequency The airflow entering the vacuum chamber must be maintained at 50 ~ 100cm3 per minute. The depth of the surface treated by this method is about 0.02μm. Before this method, the surface dirt must be removed, usually the plastic surface is subject to electronic, The impact of positive ions and photons, as well as the type, pressure and power of the ion slurry, the factors are as follows:
The organic contaminants present on the surface of the joints will be destroyed by the ion plasma method, which will cause vapor phenomenon.
Because the ionic slurry breaks the chemical bond, an ablation phenomenon occurs and small molecules are generated on the surface of the plastic. This phenomenon is because the crystalline state of the semi-crystalline state and the non-crystalline plastic is easier to remove, thus changing the surface state.
The ion plasma treatment method can break the plastic surface link and ablate the surface molecules,
And new chemical groups have been created, for example: the polar functional groups (such as hydrogen groups) of ion plasma containing oxygen molecules can increase the surface energy.
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