About the production of spot color version

When receiving a manuscript from a customer, we often have a large background color similar to M80%, Y100%, and M40%, Y50% color blocks, in order to facilitate printing, improve the printability, and also to reduce The use of ink to reduce production costs, we often use the spot color version of the color printing, obviously in the processing of manuscripts, determine the plate making technology requirements, the M80%, Y100% of the large area color as a spot color on the ground, The M40% and Y50% color patches are set as spot colors and hang 50%. However, it is often impossible to achieve printing. M80% and Y100% of the large-area background color can easily meet the requirements. M40% and Y50% spot color blocks are difficult to catch up with the customer's signature. Experienced technicians generally require the plate maker to deepen the M40% and Y50% spot color blocks. In fact, this is a matter of the relationship of a layer of ink for several layers of ink. The embossed M40% and Y50% color patches are two layers of ink, while the spot color patches are a layer of ink, so it is not difficult to understand why 50% of the screens are The place needs to be deepened. This article will explore this issue from a geometric perspective. Please correct the deficiencies.

It is assumed that the dots of the electric carving are all regular pyramids, the bottom area is s, the height is h, and the volume is V.
The image on the paper or glue (hereinafter referred to as the paper) is determined by the combination of the grain size and the dot area. It is assumed that the magenta pigment has the xm ratio and the yellow ink has the xy coefficient.

Two-color imprinting, printing M80%, Y100% color, the amount of pigment corresponding to a single dot of the ink in the field is s Ã— xy, M80% corresponding to a single dot of the ink layer of the pigment is 80% s Ã— xm;
When the prints are red M40% and Y50%, the amount of pigment corresponding to a single dot of the red ink layer is 40%Ã—xm, and the amount of pigment corresponding to a single dot red ink layer is 50%sÃ—xy.

The gravure spot color version can meet the field hypothesis. The proportion coefficient of magenta pigment is xm1, and the yellow pigment ratio coefficient is xy1. When expressing M80%, Y100% colors,
Solid yellow corresponds to the amount of single dot ink layer pigment (sÃ—hÃ—xy1)/3=sÃ—xy(1)
The amount of M80% pigment corresponding to a single dot ink layer is (sÃ—hÃ—xm1)/3=80%sÃ—xm(2)
In print M40%, 50% color, assuming that the dot area is s1 and the dot depth is h1, it is not difficult to find from the figure below that the volume of the positive quadratic pyramid is V=(s1Ã—h)/3.
The amount of red ink layer pigment corresponding to a single dot is: (s1Ã—h1Ã—xm1)/3=40%sÃ—xm(3)
The amount of pigment corresponding to a single dot of the yellow ink layer is: (s1Ã—h1Ã—xy1)/3=50%sÃ—xy (4)
Substituting (1) into (4), (s1Ã—h1Ã—xy1)/3=50%Ã—(sÃ—hÃ—xy1)/3
S1Ã—h1=50%Ã—sÃ—h
S1=50%Ã—sÃ—h/h1(5)
Because: h/h1=(s)1/2/(s1)1/2
So (5) is: s1=50%Ã—sÃ—(s)1/2/(s1)1/2
(s1)3/2=50%Ã—(s)3/2
S1=(50%)2/3Ã—(s) (6)
Substituting equation (2) into equation (3) also yields equation (6).

From this we can conclude that in the case where the spot color version is used to express the effect of two-color imprint and the spot colors of M80% and Y100% are determined on the spot, the dot area corresponding to M40% and Y50% colors is (50%). ) 2/3 = 0.63, ie 63% of the nets, not 50%.

Using the spot color version to express the effect of a certain paper draft, when the spot color electric carving is adopted, if the percentage of the corresponding shallow dot network in the paper draft is n, then it is not difficult to introduce a spot color spot percentage of n2/3.
From this you can draw the following curves:

It can be seen that the number of nets will increase correspondingly when it is changed to spot color.

The following principles should be observed when determining the color change:

First, to determine the spot color when hanging in the field should be based on the color of the paper block color structure ratio to calculate the maximum number of dots in the paper is 100% of the color block structure, in order to determine the ink hue on the ground. For example, in the paper, there are colors M60, Y50, C30, M40, Y33, and C20. The color structure when M100 is calculated based on 60:50:30 is: M100, Y83, C50, then the actual ink hue For M100, Y83, C50.

Second, determine the number of spot colors in the paper. The above drafts have the following colors: M60, Y50, C30, and M40, Y33, and C20. From the above graph, it can be found that the nets are 71% and 54%, respectively.

Third, the maximum number of spot colors that can be linked to the spot can be either on-site or off-site, depending on the printability. For example, the above color block can also be linked to another type of network, the specific method is as follows: The M60, Y50, C30 color blocks and M40, Y33, C20 color blocks are converted into other color structures in proportion to make an Excel table as follows:

As can be seen from the table below, using the spot color version of the hanging net to achieve paper clips in the M60, Y50, C30, M40, Y33, C20 and other color blocks have many programs that can be hung up to 56% and 42%, 61% and 47%, 66% and 51%, 76% and 58%, 80% and 61%, 84%, 65%, etc., but the corresponding ink color changes accordingly. The best solution can be selected during process design. The most favorable printing solutions for ink saving are the above-mentioned 76% and 58%, 80% and 61%, 84% and 65% printing, which are easy to cause dot formation due to network consolidation and should be avoided as much as possible. Since the plate roll is susceptible to wear, the change in hue should also be avoided as much as possible.

In addition, for color blocks with disproportionate color structure, such as: M60, Y50, C30 color blocks, M40, Y53, C20 color blocks, in the special color setting, the unbalanced color Y53 can be decomposed into Y33 and Y20. In this case, the spot color can be linked to 61% and 47% of the net number, and the remaining yellow can be refilled with the three primary colors.

In practical work, based on various factors such as the printability of ink, the viscosity of the ink used, the angle of the equipment, the electric engraving type, and the angle of the electric engraving needle, the percentage of the dot of the spot color version should be appropriately changed. Under normal circumstances, there is a difference between warm and cool colors, and the percentage of deep-colored cold-tone hanging nets should be appropriately increased, while light-colored or warm-colored hanging nets should be slightly reduced. For the sake of accuracy, it is best to use a ladder ruler with different parameters on the printing roller according to the data made when doing color matching. The common color or desired color is printed with the spot color ink according to the normal process, and then it is made The color book serves as a reference to provide accurate basis for determining the number of linked networks.

Author: Liu Shaolan from: Kim Yu Henan Industrial Co., Ltd.