New micro corrugated paper printing
The corrugated board is first processed into corrugated paper, and then the surface and the intermediate corrugated layer are bonded from both sides with an adhesive, so that the middle layer of the cardboard has a hollow structure, which has high strength, stiffness, pressure and burst strength. Wait. Due to its special properties, it is now widely used in the packaging of products.
In recent years, especially in Europe and the United States, ultra-thin and ultra-strong micro-corrugated cardboard has quietly occupied more and more corrugated board market, because it has good physical properties and printing performance of corrugated board and thick cardboard. Compared with traditional thick cardboard, it has the characteristics of good strength, strong cushioning force, good elasticity, material saving, light weight and good printing effect. Compared with traditional corrugated cardboard, micro corrugated cardboard has the characteristics of small size, high stiffness, compact structure, firm and flat, light and thin material, good compression resistance, and direct printing by offset printing machine. The direct printing on the printing press and the printing process on the offset press can only be printed first, which simplifies the process, shortens the production cycle and improves the production efficiency.
Commonly used micro corrugated cardboards are F-type (0.75mm), G-type (0.5mm), N-type (0.46mm), O-type (0.3mm), etc., all of which are three-layered, namely, facial paper, enamel paper and bottom paper. . At the same time, the micro corrugated cardboard also has the following characteristics: (1) high strength, can enhance the protection function of the product, 40% higher than the strength of the thick cardboard; (2) light weight, 40% lighter than the thick cardboard, lighter than the corrugated cardboard %; (3) The surface is smooth, the pattern is exquisite, the color is bright, and the visual effect is strong.
1. Offset principle and its requirements for corrugated board printing
Currently, corrugated board printing is commonly used in flexographic printing, gravure printing, and offset printing. Among them, flexographic printing is the most commonly used, but the printing accuracy is not very high. Generally, only some low-grade rough cardboard boxes can be printed, and gravure printing and offset printing are pre-printing processes, that is, printing the facial paper first and then proceeding. The bonding treatment, although achieving good quality, is complicated in process and high in cost. Therefore, offset printing directly on corrugated board is a new process pursued by the packaging and printing industry. The current KBA Rapida 105 and Manroland 700, 900 can be directly offset on micro corrugated cardboard, and the printing quality can reach a very high level.
Offset printing is a natural law that makes oil and water immiscible. On the printing plate on almost the same plane, the image part only absorbs the ink, the blank part only absorbs water, and the ink is transferred to the substrate through the blanket. . Offset printing is the most widely used and most mature printing method due to its high image restoration and color reproduction capabilities. At present, it accounts for more than 50% of all printing in China, mainly based on paper printing. In recent years, with the rapid development of packaging printing, flexographic printing and gravure printing and screen printing have made great progress, and the development momentum and proportion of offset printing have declined.
At present, the offset printing process will regain its vitality due to the breakthrough in offset printing directly on micro corrugated paper. In the field of traditional fiberboard boxes, such as alcohol, small appliances, footwear, hardware tools, microelectronics, computer software, counter sales, fast food, etc., offset printing has begun with its better printing quality. Traditional thick corrugated cardboard competes for the market.
However, dampening solution should be used in offset printing (the dampening solution is mainly to keep the blank part of the printing plate clean and the main component of the dampening solution is water), which makes the offset printing process complicated. The mixing of ink and water will produce ink emulsification, which will cause deformation and strength of the paperboard to change, and the color, viscosity and drying performance of the ink will be affected. Therefore, the control of ink balance becomes very critical. If the amount of water is too large, the ink will be excessively emulsified, the drying will be slow, and the color will become lighter. In particular, the corrugated cardboard will absorb more water and the compressive strength and surface strength will be lowered, and even the printing pressure cannot be withstood and collapsed. The size of the paperboard becomes large, which makes the deformation of the paper and the paper inconsistent, which makes the printing suitability worse. Therefore, the water quantity control of the direct offset printing of the corrugated board is stricter than that of the ordinary paper printing. If the amount of ink is too large, problems such as dot enlargement, leveling, and dirtying may occur. Therefore, the ink balance must be controlled during the printing process, especially the amount of water.
Direct offset printing on corrugated board requires less light pressure than plain paper. Since the middle corrugated corrugated board is empty, if the pressure is too large, there will be failures such as dot enlargement and leveling, and at the same time, a "washing board" phenomenon will occur, and crushing will occur in serious cases. Therefore, the control of pressure should be more precise.
Due to the special structure and special requirements of corrugated board, this type of offset printing machine generally adopts a special blanket with good compressibility and certain hardness, so that the compression deformation of the blanket can be used to compensate for the different compression resistance of the corrugated board surface. Performance and deformation performance to improve print quality.
2. The effect of offset printing on corrugated board printing
(1) Effect on the strength of corrugated board
The enormous pressure of offset printing will reduce the compressive strength of corrugated board; the use of dampening solution will reduce the surface strength and compressive strength of the board due to water absorption.
(2) "washing board" phenomenon
The washboard phenomenon is the most common quality problem in corrugated board printing. This phenomenon may occur if the pressure and ink volume are not well controlled during printing.
(3) Ink imbalance
The biggest influence on the quality of offset printing is the balance of ink and water, especially the excessive amount of water has a greater impact on the micro corrugated board.
(4) dampening solution acidity and alkalinity
Too strong acidity will slow the drying and corrode the printing plate; if the acidity is too weak, it will not form an effective hydrophilic protective layer in the blank portion of the printing plate.
(5) Performance of the blanket
The performance of the blanket includes surface properties and compression set properties. Surface properties are the guarantee for absorbing inks and transferring inks, while compression set properties are the basis for obtaining high quality images on corrugated board.
Direct offset printing of micro corrugated cardboard is a brand-new printing process that achieves a high level of printing and printing quality. It is basically comparable to the quality of paper printing. It will become a high-grade corrugated carton and carton. The preferred paperboard for packaging can bring huge economic benefits to packaging and printing enterprises. It is one of the main directions for the development of offset printing in the future, which is the light that has been re-ignited for the development of offset printing.