Factors affecting the color difference of spot color in printing

專色印刷大量使用在畫冊印刷中，專色印刷的產品色彩鮮艷，減少網點疊印、網點變形，顏色穩定，專色印刷也容易產生色差，那么導致專色油墨產生色差的因素有哪些呢?

Spot color printing is widely used in album printing. The products of spot color printing have bright colors, reduce dot overprint and dot deformation, and the color is stable. Spot color printing is also easy to produce color difference. What are the factors leading to the color difference of spot color ink?

1.紙張對顏色的影響

1. Influence of paper on color

紙張對墨層顏色的影響主要體現在3個方面。

The influence of paper on the color of ink layer is mainly reflected in three aspects.

(1)紙張白度：白度不同(或帶有一定顏色)的紙張，對印刷墨層的顏色顯現有不同的影響。因此，在實際生產中應盡量選用白度相同的紙張印刷，以減小紙張白度對印刷顏色的影響。

(1) Paper whiteness: paper with different whiteness (or with a certain color) has different effects on the color display of the printing ink layer. Therefore, in actual production, paper with the same whiteness should be selected as far as possible to reduce the influence of paper whiteness on printing color.

(2)吸收性：同一種油墨在相同條件下印刷到吸收性不同的紙張上時，會有不同的印刷光澤。非涂料紙與涂料紙相比，黑色墨層會顯得灰、無光澤，并且彩色墨層會產生漂移，由青色墨和品紅色墨調配出的顏色表現更明顯。

(2) Absorbency: when the same ink is printed on paper with different absorbency under the same conditions, it will have different printing luster. Compared with coated paper, the black ink layer will appear gray and dull, and the color ink layer will drift. The color mixed by cyan ink and magenta ink is more obvious.

(3)光澤度與平滑度：印刷品的光澤度取決于紙張的光澤度與平滑度。印刷用紙的表面屬于半光澤表面，尤其是涂料紙。

(3) Gloss and smoothness: the gloss of printed matter depends on the gloss and smoothness of the paper. The surface of printing paper belongs to semi gloss surface, especially coating paper.

2.表面處理對顏色的影響

2. Effect of surface treatment on color

畫冊印刷產品的表面處理方式主要有覆膜、上光等。印品經過這些表面處理后，會有不同程度的色相變化和色密度變化。覆亮光膜、光油和UV油時，色密度增加;覆亞光膜、罩亞光油時，色密度降低。化學變化主要來自覆膜膠、UV底油、UV油內含有的多種溶劑，它們會使印刷墨層的顏色發生變化。

The surface treatment methods of album printing products mainly include film coating, polishing, etc. After these surface treatments, prints will have varying degrees of hue changes and color density changes. When covered with bright film, varnish and UV oil, the color density increases; When the matte and oil film are coated, the density decreases. The chemical changes mainly come from a variety of solvents contained in film covering glue, UV primer and UV oil, which will change the color of the printing ink layer.

3.撤淡劑對顏色的影響

3. Effect of desalting agent on color

撤淡劑是一種油膏狀的無色透明物質，在專色印刷中主要起沖淡顏色的作用。撤淡劑的加入量不同，對色相的影響也不同，尤其是藍色表現得明顯。

Diluent is a kind of colorless and transparent material in the form of ointment, which mainly plays the role of diluting color in spot color printing. The influence of different amount of diluent on hue is also different, especially blue.