Chinese printing industry has long known as offset lithography, in fact, derived from but indirect printing lithographic printing press, the plates stamped, not directly contact and the paper transfer of ink is printed, instead of using a blanket installed transfer media of the stamped ink on the blanket cylinder, as the middle, the stamped ink on the printed version of Access, and then transfer (write) the above paper was printed media, so the blanket in offset printing press to play a very important role, and therefore does not call the layout lithography, renamed its indirect printing blanket media called the offset, but a very small number of Toppan Printing must be done indirect printing on rigid materials surface, but also use the blanket to transfer printed The pattern is still known as the offset is not known.

Before the 1960s, all blanket use of natural rubber auxiliary materials to undertake stamped transfer blanket surface, but after the 1950s, due to the natural plant linseed oil for petrochemical mordant ink to replace the original natural rubber is clearly already Wu Nai live petrochemical solvents and resin intrusion produce abnormal Run swelling bulge phenomenon, in the 1960s, the blanket surface, have the use of synthetic rubber, and it gets the ink roller, the material of the water roll switch to synthetic rubber, DuPont invested over one billion U.S. dollars complete the study of synthetic rubber, from World War II, only 10 years circumstances. So far the blanket is all solid, no air bubbles in the sponge compressed structure, the pressure generated due to the printer speed high and rapidly rising. A very divergent theories, the first school at the time that the plates and the pressure roller (in addition to the printed paper) are rigid, so the rubber surface of the roller should be boosted, making the diameter greater than two hard roller diameter, can maintain the same diameter in the operation, but found that in 1937 Miller Miller presses, hardware drum embossed circle detour length is a fixed length of the diameter × π, but the rubber roller soft surface rolling circle is equal to diameter × π plus flexibility and pressure coefficient means that the blanket cylinder, even in the equivalent diameter, and the printing plate cylinder, the pressure tube embossing, the rotation length is greater than two hard rollers, tube diameter of the Act is deliberately increased by the compression of the rubber tube , so the length of the rubber roller to go the long, fast run, such as blankets and plates unnecessary friction, so the switch to the plate cylinder pad above the gear Festival Week 0.1 ~ 0.15mm extent, while the rubber drum pad and The blanket section of weeks the same height, same speed, surface embossing and stamped ink transfer in order to keep the imprint, This is called rolling length method of drum pad height practice has been continued until today. But was also found on the blanket cylinder blanket, in the imprint of the plate cylinder, the forward and backward raised to offset the pressure, the effect of this flange is like rubber ink roller, tighten with a wire The wire will certainly not into the rubber, while trapped under the rubber to muster on both sides of this effect is the same as mentioned earlier, the pressure of the flange.

Stamped and outlets to solve the flange sometimes drag marks, Diego shadow phenomenon, rubber plant in the manufacture of blankets, the blanket surface of the bottom four layers of interwoven textile yarn layer, in the second and third between layers, like a sandwich sponge layer folder into a layer of bubbles, the hardness of the surface rubber layer slightly increase to compensate for the sponge layer softening of the role of depression, but the sponge layer exist independently of each bubble can greater support for resistance to compression and decompression in order to provide a better rebound in force. If the bubble hole is overflowing through the air, the sponge layer compression linked to the contrary decompression support is also very weak, only the rubber structure of the elastic force in a weak rebound. Closed concatenation sponge bubble layer is very important, will it be possible to provide support and recovery of the stretch. This layer is an average of about 0.4mm sponge cushion layer, it provides a blanket pressure by India, directly to the sponge cushion layer to obtain the downward compression of space, do not have the forward and backward diversion flange, resulting in unnecessary motility, quality of images from the plate to avoid printing smear Diego Shadow. Achieve compression will not scroll through the length of the elastomer, the blanket pad height is necessary to heightening to maintain the idea of ​​approaching the same path method. Itself to provide additional flexibility, it can not do the traditional blanket perfectly inelastic in turn cushion blanket, plastic sheet lining the bottom of the blanket or hard mount, called the effect of the hard-liners, because of the cushion layer has provide additional flexibility.

Later, there are manufacturers blanket cushion sponge layer down one layer, close by the way between the third and fourth layer of the drum body, There is also a Move cushion layer under the rubber chemical surface, directly attached to the blanket surface below, to provide greater flexibility absorb pressure. But after the year 2005, but developed an extra-thick layer of cushion blanket, bubbles sponge layer to absorb the printing pressure increased to the extent of 0.8 ~ 1.4mm by 0.4mm, in particular, the total thickness of 2.4mm blanket before can accommodate up to 1.4mm bubble sponge layer, it can significantly reduce the printing pressure, while increasing the plate cylinder and blanket cylinder, and even the blanket cylinder and printing paper, contact and transfer the ink time. But does not produce the excess pressure peak, meaning to touch pieces of widening of the entire contact, but the pressure is much smaller and smooth, for the role of the mainframe printing tissue paper tail fan effect is very small and will not have the benefits of paper tail misregistration Otherwise, like the wide 1450mm above the large flat printer, printing paper under pressure, especially 80g/m2 following tissue compression, the cumulative paper tail upheld, 1.6, 1.7 times as much than 1000mm, while the unable to register and good dot reproduction.

Corrugated printing blankets flexible blanket embossed ribs patterned corrugated streak, but also corrugated peak pressure, even pressure to the collapse of the peak pressure and corrugated, whereas none of the corrugated peak support floating beneath the central sheet of paper, because of the blanket is not enough soft touch rate is not long enough pressure to transfer the image less than the strips of ribs pattern is more obvious, so the extra-thick layer of cushion blanket for giant flat printer, as well as corrugated more uniform compression and development.