Flexo plate material characteristics and process

First, the sticker material

The flexo roller is a circular smooth rigid body. The back of the flexographic plate (which can be bent into a curved surface) is required to firmly hold the plate in accordance with the prescribed position on the surface of the fixed cylinder, and cannot be displaced in the entire printing process. Run version). To achieve this goal, there must be a reliable link between the two. As an intermediate medium, this link body is generally referred to as a sticker material, that is, a double-sided adhesive tape (also called a double-sided adhesive lining) that is usually heard. It is a pressure sensitive adhesive material.

Bonding materials are not unfamiliar and can be found everywhere in production and life. Stamp glue, white glue used for binding books are all bonding materials. With the development of the synthetic polymer industry and the improvement of the chemical industry, the bonding material has become a novel material fertilizer and has attracted wide attention. It has also been widely used in the printing industry.

1. Adhesive technology as follows

(1) Different types of materials can be well bonded together. For example, lead alloys and steels, lead alloys and aluminum, aluminum alloys and copper-zinc plates and aluminum, copper and zinc plates and aluminum, copper and zinc plates and fiberboards, aluminum and steel, aluminum and aluminum.

(2) Bonding is lighter than mechanical connection such as riveting, welding, and clamping, and the method is simple and convenient.

(3) The stress of the adhesive is evenly distributed on the entire adhesive surface, especially for large areas, especially for large-area printing plate bonding, and since the high stress concentration is avoided, the bonding strength is improved.

(4) Bonding makes the surface of the printing plate easy to be smooth and flat, and can completely adhere the printing plate to the circular arc surface of the drum.

(5) Bonding has the advantages of simple process, convenient operation, energy saving, cost reduction, and labor intensity reduction. The bonding operation does not require a high level of expertise.

(6) The bonding process also has some shortcomings, mainly due to a large number of influencing factors, it is difficult to control, and the detection method is not perfect. There is no quick and reliable method for detecting its quality, and it is difficult to predict the possible problems. All these need to be improved and improved.

2. Printing plate, roll with the surface characteristics.

Macroscopically, there is no obvious difference between the surface and the interior of the printing plate and cylinder, but it is actually not the same. The surface of the printing plate and drum is exposed to air, contaminated, and forms an oxide film with oxygen. Therefore, the surface of the printing plate and the drum is usually composed of a gas adsorption layer, a dust pollution layer, an oxide layer, and the like. Even freshly processed surfaces are not always absolutely clean, and they may reach saturation pollution after five hours.

The surface of the printing plate and the roller is not smooth and therefore the two surfaces are in contact with each other and no adhesion can occur. If a binder with good fluidity, permeability, and ability to absorb gas adsorbed on the surface is chosen, the adhesive will be applied to the surfaces of the two and the surface will be in point contact with each other. The solid surface will be sticky. The surface contact of the mixture replaces and absorbs the adsorbed gas on the surface, and the adhesive can also penetrate into the micropores on the surface, so that a strong interaction force between the adhesive and the surface molecules is generated. After the above process is completed, the bonding between the printing plate and the bottom tray is realized. As shown in Figure 6-8.

It is generally believed that the process of bonding can be divided into two stages:

The first segment is liquid bonded. The molecules diffuse toward the surface of the drum by means of Brownian motion and gradually approach the surface of the drum. The pressure action facilitates the contact of the adhesive molecules and their chain links with the roller surface.

The second stage is the generation of adsorption. When the distance between the molecules of the binder and the drum surface is close to 10A, the electrostatic force of the physical force starts to act and increases to a maximum as the distance decreases further.

These two processes cannot be divided. It can be seen that the contact between the adhesive and the surface of the adherend is the key to the bonding effect. With the adhesive, it is possible to bond the printing plate and the bottom tray with a single press.

Pressure-sensitive double-sided adhesive tape consists of three parts: substrate, adhesive, and release agent (also called release agent).

Substrate paper, cloth, plastic film, metal, rubber film, glass fiber, foam and various composite materials. Commonly used are fibrous web substrates. It is characterized by easy coating of adhesives, double-sided bonding, and easy adhesion.

There are many kinds of adhesives, such as synthetic resin adhesives are rubber, cellulose, polyacrylates, polyethylene resin tackifiers are rosin, rosin ester, hydrogenated rosin, polyterpene resin, various Shiqi resin, xylene resin, epoxy resin, phenolic resin and so on.

Plasticizers include phthalates, chlorinated paraffins or other oils and fats.

In addition, there are anti-aging agents, stabilizers, cross-linking agents, colorants and fillers.

Strippers usually use silanes or other specially formulated treatments. Figure 6-9 shows the structure of the double-sided pressure-sensitive adhesive tape.

In general, double-sided adhesive tape is coated with a pressure-sensitive adhesive on a substrate and then rolled into a tube, which is then torn apart. The higher the strength of the pressure-sensitive adhesive, the more difficult it is to tear open. Therefore, it is necessary to use a release agent to improve its peeling performance. For double-sided pressure-sensitive adhesive tapes, it is necessary to sandwich the release tape material (that is, both sides are coated with a peeling material). .

(to be continued)