The ink absorption of paper is not only related to the degree of looseness and pore state of paper, but also related to the surface properties of paper fiber, the content of filler, pigment and rubber, the composition and characteristics of ink, printing mode, printing pressure and other factors. In actual printing, the absorption of ink by paper can be divided into two stages. The first stage is the moment when the printing press presses. Depending on the printing pressure, part of the ink transferred to the surface of the paper is pressed into the larger pores of the paper, that is, the whole ink (including the pigment in the ink) enters the pores of the paper. This process is generally called the pressure infiltration stage.
在這一階段,紙張對油墨的吸收主要取決于印刷壓力的大小、紙張的結構和油墨黏度等因素。如印刷壓力較大或紙張的結構疏松,紙張對油墨的吸收能力也會較強。一般來說,印刷結構疏松的紙張,如新聞紙、凸版紙等非涂料紙,印刷壓力應小一些,油墨黏度也應低一些。而印刷結構緊密的紙張,如涂料紙,印刷壓力可適當大一些,油墨黏度也可稍高一些。 第二階段是從紙張離開壓印區,直到油墨完全干燥為止,這一階段主要是依靠紙張的毛細管作用吸收油墨,稱為自由滲透階段。
At this stage, the absorption of ink by paper mainly depends on factors such as printing pressure, paper structure and ink viscosity. If the printing pressure is large or the structure of the paper is loose, the absorption capacity of the paper to the ink will also be strong. Generally speaking, for paper with loose printing structure, such as newsprint, relief paper and other non coating paper, the printing pressure should be lower and the ink viscosity should be lower. For paper with compact printing structure, such as coated paper, the printing pressure can be appropriately higher, and the ink viscosity can also be slightly higher. The second stage is to leave the embossing area from the paper until the ink is completely dry. This stage mainly depends on the capillary action of the paper to absorb the ink, which is called the free penetration stage.
在這個階段,連結料從油墨整體中分離出來,通過小孔隙和紙張纖維粗糙的表面,以相當慢的速度進入紙張內部。因而這個過程實際是連結料從油墨向紙張孔隙遷移的過程,因為連結料從油墨整體中分離出來,將會改變保留在紙面墨膜的結膜性質,墨跡的固著與干燥也要在這個過程中完成。
At this stage, the binder is separated from the ink as a whole and enters the interior of the paper at a rather slow speed through small pores and the rough surface of the paper fiber. Therefore, this process is actually the migration of the binder from the ink to the paper pores, because the separation of the binder from the ink as a whole will change the conjunctival properties of the ink film retained on the paper, and the fixation and drying of the ink should also be completed in this process.
在這個階段,紙張對油墨的吸收速率決定著印刷品的光澤度,以及是否會發生透印、粉化等現象。當油墨轉移到紙張上時,隨著時間的延長,低分子的連結料(溶劑)將開始向紙層內滲透,這樣紙面上油墨層中的溶劑含量就會下降,油墨黏性增大,墨層產生凝結。 紙張的吸墨性取決于紙張毛細管的數量和毛細管直徑的大小。紙張是一種多孔材料,紙張內部的纖維與纖維之間、纖維與填料之間以及顏料粒子之間都存在著許多大小不等的間隙,這些間隙就相當于許許多多的毛細管。
At this stage, the absorption rate of the paper to the ink determines the gloss of the printed matter, and whether there will be through printing, pulverization and so on. When the ink is transferred to the paper, with the extension of time, the low molecular binder (solvent) will begin to penetrate into the paper layer, so that the solvent content in the ink layer on the paper will decrease, the ink viscosity will increase, and the ink layer will condense. The ink absorption of paper depends on the number of paper capillaries and the diameter of capillaries. Paper is a porous material. There are many gaps of different sizes between fibers, between fibers and fillers and between pigment particles in the paper. These gaps are equivalent to many capillaries.
在這些毛細管的作用下,可以吸收油墨中的連結料,而且毛細管的直徑越粗,對油墨的吸收速度就越快,因此,紙張的孔隙結構決定了其對油墨的吸收性。 紙張越疏松,孔隙越大,吸墨性也越強。比如新聞紙比較疏松,具有較強的吸墨性,因此轉移在新聞紙上的油墨固著很快,有利于印刷速度的提高。
Under the action of these capillaries, the binder in the ink can be absorbed, and the thicker the diameter of the capillaries, the faster the absorption of the ink. Therefore, the pore structure of the paper determines its absorption of the ink. The looser the paper, the larger the pore, and the stronger the ink absorption. For example, newsprint is relatively loose and has strong ink absorption, so the ink transferred on newsprint is fixed quickly, which is conducive to the improvement of printing speed.
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