The printing suitability of the blanket refers to the performance of the blanket that matches the printing materials and printing conditions and is suitable for printing operations. These properties can make the printed or printed information imprints transferred or imprinted by the blanket achieve certain quality requirements and reproduction effects in terms of uniform ink color, dot reproduction, graphic clarity, and accurate overprinting. For blankets, the printability is mainly reflected in the following aspects:
1. The ink absorption of the blanket: refers to the performance of the blanket to absorb ink on the surface under the action of printing pressure. The ink absorption of the blanket is the primary condition for the blanket to transfer the graphic information. The fineness of the blanket is good, the amount of ink on the surface of the graphic is sufficient, the quality and effect of the printing are good, and the converse is poor. The adsorption capacity of the blanket surface for ink depends on the surface condition and printing conditions of the blanket. The blanket needs to undergo fine grinding treatment during molding to form a certain amount of sand on the surface to produce a velvet surface state. This surface has Strong ink absorption. However, after the printing blanket is used for a period of time, when the surface is smooth and a bright film appears, the ability to absorb ink will decrease. At this time, the transfer rate of ink will also decrease as the amount of absorbed ink decreases. The ink will be insufficient, and the white background will appear. At this time, this bright film must be wiped off to ensure the original ink absorption performance of the blanket.
2. The ink transmission property of the blanket: refers to the performance of the blanket to transfer the ink on the surface of the blanket to the surface of the substrate under the action of printing pressure. The blanket needs not only good ink absorption, but also good ink transfer, so that the ink on the surface can be transferred to the surface of the paper to form a graphic imprint that meets the requirements of the printing and copying standards. If the ink transfer performance of the blanket is poor, the amount of ink transferred to the surface of the substrate is insufficient, which not only affects the color density of the printed matter, but also accumulates more ink on the surface of the blanket, causing printing problems such as paste printing.
3. Peelability of blanket: refers to the peeling performance of blanket and paper under the action of printing pressure. In actual use, the main factors that affect the peeling performance of the blanket are the chemical composition of the surface adhesive, the hardness and the smoothness and electrical properties of the surface, the physical properties of the ink, the surface state of the paper, and the size of the solid area on the printed matter Other factors also have a greater relationship. When the paper finishes a printing cycle and the paper peeled from the blanket during the peeling process, due to the high speed peeling, the paper will be subjected to a large peeling tension, which will often cause the paper to stretch or wrinkle and pull, which will cause serious peeling Breaking failure. This not only increases the scrap rate, but also causes paper wool and paper dust to accumulate on the blanket or on the printing plate, forming faults such as paste or pile.
4. The resilience of the blanket: It refers to the performance of whether the blanket can return to its original state instantly after removing the pressure from the printing operation. Also known as instant recovery. The transfer process of lithographic offset printing is to use the high elasticity of the rubber cloth to complete the transfer of the graphic imprint with the minimum pressure and friction coefficient, so as to achieve the print quality effect of clear graphics, full ink color and rich levels. If the elastic resilience of the blanket is poor, plastic deformation occurs and it cannot be restored to its original elastic state. The blanket and the plate cylinder and the impression cylinder cannot fully contact and maintain the original linear pressure. Instability of ink transfer, such as unevenness of ink color before and after.
5. Tensile deformability of the blanket: it refers to the deformation of the blanket under the action of tension. This deformation is manifested in three aspects: the length of the blanket increases in the direction of the force; the lateral dimension is shortened and the thickness is reduced. The thickness change caused by the stretch deformation of the blanket will affect the elasticity and hardness of the blanket. Therefore, in the operation of the blanket, it is not possible to tighten only at the trailing end of the blanket, but to apply pressure in sequence on the bite and trailing portions of the blanket, so that the blanket can be uniform on the roller The degree of tension, so as to ensure that the blanket does not move and change relative position during high-speed operation.
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