T-shirt printing prepress technology (2)

Second, making a draft

The manuscript can also be called a black and white manuscript, a color separation manuscript, a negative plate, and so on. Its main function is to make sensitized prints. Therefore, the manuscript must be drawn on a light-transmissive substrate. The image is light-impermeable ink (black or red), the light transmission of the substrate and the shading of the ink layer. Density is a key indicator of the quality of the manuscript. The production of the manuscript draft mainly adopts methods such as manual drawing, manual or mechanical engraving, photocopying, laser photocopying, printer drafting, etc., but there are also methods for producing plain manuscripts after translucent treatment (such as oil). .

1. Separation

There are two main types of color separation: spot color separation and primary color separation.

Spot color separation refers to using any specially prepared color as a printing color alone, and such several spot colors are subjected to color printing to form a color image. Five sets of color printing and twelve sets of color printing, which we usually talk about, refer to the overprinting of five spot colors or twelve spot colors to form color image printing products. However, the number of spot colors is not equal to the number of colors in the image, because spot colors can also be overprinted, so five spot colors can also print six or even seven colors and eight colors. Spot color printing is mainly used for color printing. Its reflection of natural scenes can only be simulated rather than reduced. This is the biggest difference from the original color printing. However, with the development of screen printing technology and the development of new types of ink, special color screen printing has risen rapidly in recent years. Especially in the printing of T-shirts, the most advanced T-shirt printing pattern in the world is currently the most advanced T-shirt printing technology. It is not the original color printing but the spot color screen printing, that is, the color special screen printing on the black T-shirt.

The primary color separation refers to the decomposition of the natural color image into three primary colors (magenta, cyan, and yellow) for the purpose of reducing the object image by performing the three-primary color price adjustment printing. Any color in the natural world is composed of three primary colors, so theoretically speaking, it is possible to print realistically restored images using the cyan, magenta, yellow, and three color plates, but due to various factors, the three primary color prints are difficult to achieve. This point. Therefore, four-color printing is usually used in printing practice, namely three primary colors plus black. In recent years, in order to restore the colors more vividly in the world, six-color printing and seven-color printing have been developed on the basis of four-color printing. The principle is to combine the colors of orange, purple, and green on a four-color basis. Separated to achieve high fidelity by reducing grayscale in printing. In order to differentiate from spot color printing, we usually refer to the original color printing (which can be understood as reducing color printing) by performing the color separation of natural color patterns by optical or digital technology. It is related to optics and color science. The concept of primary colors (only three primary colors) is different.

It is worth mentioning here that primary color printing and spot color printing are not incompatible. In the international community, the latest development of color printing is the combination of primary colors and spot colors for primary color printing, which has played both the strengths of both, complement each other, and has a more advanced printing effect, belonging to fine print. This has also been given permission to play in T-shirt printing. The author once saw a U.S.-made T-shirt with a total of 12 colors. In addition to the four primary colors, there are eight sets of spot colors. In addition to gold and silver and other colors, there are foam printing and crystal pulp printing. It's amazing not only that it has a strong sense of three-dimensionality, but also that it shines in a particular part.

Professional T-shirt designers usually design according to the principle of spot color or primary color. After obtaining such a design draft, they can perform color separation according to their requirements. However, there are also non-spotted designers or customers who only provide originals such as various pictures or drawings and require them to be printed on T-shirts. In this situation, we must communicate with designers and customers: First of all, we must understand their creative intentions and what kind of effect they want to express. Is it better to use spot-color printing or primary color printing to achieve this effect? Even the original color printing? At this time, it is necessary to provide them with T-shirts with different printing methods so that they can understand and select them. Secondly, they should tell them about the production cost of spot color printing and primary color printing so that they can make decisions based on their investment plans.

2. Separation of manuscripts

Separation of manuscripts is used to produce the corresponding separation screens. One of its quality requirements is that the light transmission performance of the substrate is good, the second is the high shading density of the image, and the third is the alignment accuracy between the dichroic sheets, and the edges of the image lines are clean and tidy, and the outlets are full and clear.

(1) Multi-color separations The positioning of cross-sections is generally based on crosshairs, but it is often easy to reverse the separations during the printing process, or to make mistakes on the front and back, or to turn the graphics upside down. We use left-rights. Right oblique method to position the crosshairs, that is, the left is +, the right is x, so that eliminate errors.
(2) Red tear film can be replaced with red self-adhesive paper because it is expensive and not easily available. As long as the red self-adhesive paste only on the PVC film (on the original or linework), you can use a carving knife to draw. Since the transparency of the red self-adhesive paper is far less than that of the red tear film, the light of the lighting drawing table should be brighter. In this way, you can achieve low prices, good shading effect, and clean lines, not afraid of water, even more wonderful is to modify the convenience - as long as the re-engraving can be removed, and red tearing can not be re-engraved, ink painting Only minor changes can be made.
(3) If the two printing plate patterns are not connected or overprinted, consider drawing two color drafts on one film, printing two plates at the time of printing, and closing the B pattern and B plate of the A plate. A pattern. It is even possible to burn a plate, add an ink strip between AB patterns, and print two colors at once.

3. Manual production

Manual drafting is the most basic traditional method, mainly manual drawing and manual drafting.
Hand-made drafting tools mainly include: light drawing table (OA table), drawing ink pen, drawing compass, triangle board, curve board, knife, steel ruler, drawing PVC film, PCV film ink, red tear film, red Self-adhesive paper and so on.

The shirts are hand-made. First, there must be a light drawing table. The light source is usually a fluorescent lamp. If an incandescent lamp is used, a frosted glass or a layer of copy paper under the glass should be used so that the light is soft and does not hurt the eyes. If you need to trace at home or in a temporary place, the emergency method is to put a square stool on the ground. Put a piece of glass on the four stool legs and put a table lamp below. Then you can use it.

Drawing ink pen, more use of needle pen, pen head diameter of 0.2 ~ 1.3mm. To prevent the tip of the pen, insert a piece of hollow cotton (or sponge, etc.) into a bottle, add half a bottle of water, and insert the pen into the bottle when the drawing pen is disabled. This will stop the tip of the pen from plugging.

Steel rulers are used to make red tear film and self-adhesive paper. When drawing with a triangular plate, curved plate, etc., the bevel face should be face down to prevent the ink from being dragged by the ruler edge.

The general drawing ink can not be used to draw the diaphragm, because of its slow drying, poor fastness, and the water-soluble rainy day. The drawing of PVC film is best to use special ink film drawing ink. If you cannot buy it at one time, you can use it instead of ink, but you need to press it for concentration. When using a large area of ​​ink in Adelaide's ink, be careful not to overcoat the ink layer to avoid cracking.

Be sure to wash your hands with soap before hand-drawing, as the grease on your hands will affect the ink painting.

According to the paste used and overprint order to draw. Printing paste has hiding power, so the graphic contact lines of each color draft can be overprinted, and even light color draft can be used as the base color of dark color graphics. For example, if the fabric is darker in color, it may be considered to be a white background. The sequence of the draft of the color printing of the glue printing is the opposite of the printing process. That is, first draw the dark draft, then the light color draft, and finally the white draft.

The water slurry is mainly used for printing white T-shirts, and is a transparent printing material. Therefore, the overprinting of the contact lines between each color draft is 1 to 2 mm. If there are too many overprints, the composite color of the two-color overprinting tends to occur. The order of drawing is to first draw a color draft (usually black) with outlines, and then draw the light from the light to the dark, based on the diaphragm.

The color separation sheet of the foam printing plate should leave room for the swelling of the foamed foam, with a high bubble of about 1 to 2 mm and a low bubble of about 0.5 to 1.0 mm.

The basic requirement for hand-painted (engraved) manuscripts is that the lines are smooth, smooth, smooth, and the drafted ink drafts generally must be repaired with a guillotine knife, especially at the sharp corners.

4. Computer digital production

With the development of computer technology and production, computer digital design and drafting and drafting have become quite popular in China. Compared with manual drafting and photo-making, it has the advantages of higher quality, faster speed, more convenient production, and lower cost, in particular, the quality of color separation and screening is much higher than manual and The level of photovoltaic production has become a widely used production method.

A series of work such as designing, color separation, screening, and filming of T-shirt designs on a computer must be completed by operating professional graphic design software and publishing software. General-purpose software such as Adobe L IIustrator, photoshop, CoreIDraw, etc. is mainly used for the design and production of image texts, but it will be more convenient if domestic professional screen printing publishing software such as Wenyuange, Mengtai, etc. are used.

The program for digitizing a t-shirt pattern by a computer is generally: graphic input-design editing-output effect color draft-separation-screening-setting screening angle-output. If you go to a professional to produce, be sure to tell some technical requirements: First, the intention of separation. Is the primary color separation or spot color separation or special primary color separation, etc., must make the production staff clear. Second, screening. The printing of T-shirt printing is generally less than 60 lines. The limitation of the number of screening lines depends on the production characteristics of the printing materials, the fabric texture and the color and other factors. Paste printing is usually not suitable for screen printing. Under special circumstances, screen printing technology is used. The number of screen lines should be below 40 lines. The number of screens for water paste printing is generally about 50 lines. The number of screens for hot melt ink can be selected between 35 and 60 lines. If the fabric is darker, 35 to 45 lines can be used to increase the hiding power of ink. The number of lines of foam ink and crystal ink should be thicker. Should not be fine, the number of lines playing white should be thicker than the number of lines of other colors. Due to the non-blocking characteristics of the hot melt ink, screens of 70 to 80 lines can also be used. T-shirt printing dot pattern usually uses oval, circular dot. Third, the angle of T-shirt screening is generally 15" intervals, usually starting from 5". Every 20' starts the seventh color of the screening angle (still 15'). Fourth, in particular, the production staff should be brought to the attention of Yang Yang film that Yang positive image, which is different from the usual printed draft.

The main methods of output are:

(1) The printer is drawing. Ink-jet printers, laser printers, and wax-jet printers can all be used. The cost of laser printers is higher but the cost of use is lower. The cost of ink-jet printers is low, but the cost of ink is high. Wax-jet printers (also called dry printers) ) The cost of acquisition costs is high. In terms of the quality of the drawn film, the wax-jet printer is the best, the laser printer is also good, and the inkjet printer is poor.
(2) Engraving machine engraving. That is, a computer cutting plotter is used to engrave the pattern on red (black) self-adhesive paper and then affixed on the PVC film. However, the precision of the engraving machine is not as good as that of the printer, and can only be used for printing where the color registration requires less precision.
(3) laser phototypesetting. Laser photocopying is the method of making the highest quality film. Only because the laser photocopying equipment is quite expensive, only the platemaking center with a certain scale will be configured, so generally the edited software is sent to the plate making center for filming. The price is higher than the printer picture, but the quality is much better.