Metal Packaging Knowledge Encyclopedia

1. What is an outlet?
Dots are the most basic units that make up prints and prints. They are real points with regular centers with different centers and equal areas. During the printing process, the dots reproduce the original layer and color by changing the area or amount of ink. The correct delivery of outlets among various processes is the most basic requirement for platemaking and printing, thereby ensuring the copying effect of printed materials on originals.
2. What is a screen?
The tool for photographing originals having different gradations on a photosensitive material as a screen pattern consisting of large and small dots is called a screen, which is also referred to as a screen or a screen version.
3. What kind of screen? What are their respective characteristics?
The commonly used screens are glass screens and contact screens. Glass screen is composed of two special optical glass, according to the specified number of lines, after meticulously portrayed lines and chemical processing, become equal to the thickness of black and white parallel lines, vertical glue made. Screens vary in size, both rectangular and round. The circular screen is suitable for color plate making, and the rectangular screen is suitable for shooting monochrome manuscripts. The contact screens can be divided into two categories: gray contact screens and magenta contact screens. Gray contact screens are formed by black and white staggered hierarchical points, with a variety of basic density ranges to suit the needs of direct screen color separation and copying positive images. The magenta touch screen is a magenta screen with a high density in the middle and a gradually fading edge. It is only suitable for direct screen color separation of black-and-white manuscripts, and positive copying by continuous tone printing. It cannot be used for color manuscripts. Separation. The contact screen has various dot shapes, such as: round, chain, diamond, square, double dot, and the like. Among them, the enlargement rate of the midtone dot screen of the diamond dot screen is lower than that of other dot dot screens, which can guarantee the softness of the middle tone of the picture, and is suitable for copying manuscripts based on characters.
4. What is the screen number?
The number of lines in a screen refers to the number of one-way parallel lines per inch (or per centimeter) on the screen. The commonly used screen lines are 24, 30, 32, 40, 48, 54, 60, 70, 80 lines/cm or 60, 75, 80, 100, 120, 133, 150, 175, 200 lines/inch. . The screens of different specifications have different numbers of lines, and thus the number and size of the dots in the unit area are different. The larger the number of general screen lines, the finer the network cable, the richer the performance level.
5. What is the cable angle?
The network line angle refers to the angle between the reference line and the mesh line (the line connecting the diagonals of the dot network is the mesh line) and is used to indicate the arrangement direction of the dots. There are two selection methods for the baseline: one is to use the horizontal line as the baseline, and the horizontal line is turned counterclockwise to form the screen angle; the other is to use the vertical line as the baseline, clockwise from the vertical line To the mesh line, form the network line angle. The dots on the printing screen are vertical intersecting lattices. In the same state (position), the screen has two mesh lines, generally less than 90 degrees from the screen angle. But this is not applicable to the chain-shaped screen because the chain-shaped screen uses the long diagonal of the screen as the mesh line. It has only one mesh line, so the chain-shaped screen will appear with more than 90o. The angle indicates the angle of the screen. The choice of screen angle is an important issue in the printing plate making. The first principle of selection is to make the directionality of the outlets as unobservable as possible; the second is to pay attention not to produce a moire when collocated with the multi-color printing plate. In general, monochrome printing requires only one kind of network cable angle, and often uses 45o; two-color printing requires two kinds of network cable angles, and the difference between them is preferably 30o.
6. What is screening?
Screening is to divide a continuously adjusted original image into halftone dots with the same blackness and different areas. There are two ways to add screens. One is to use a touch screen to screen and the other is to add an electronic screen. There are two ways of contact screen screening: indirect screening and direct screening. Indirect screening is the first to make a continuous tone picture, and then add a network to create a dot positive picture; direct screening is to add a screen together when the manuscript is separated, to create a negative dot network, and then copy it into a dot positive picture. Electronic screening is the use of laser electron dot generators to form dots, that is, a grid is divided into smaller sub-grids.
7. Why do prints use dots to represent colors and layers?
There are two common ways to represent the picture hierarchy: one is continuous halo staining and hierarchical expression, even if the hue, the level continuously and continuously changes from deep to shallow or from light to dark, and the other is the halftone level expression. That is, the continuous halo staining is divided into thick, short, and different lines or small dots of varying sizes. In addition to print, text, and lines, prints are printed with halftone halftones to replace the hue that is continuously blooming on the original. This completes the copying of the original image.
The ability to faithfully reproduce the continuous layering of the manuscript on the web is because the manuscript image is divided into countless unequal dots as soon as the original image is screened, and continuous tone image information is converted into halftone dot image information. In the color synthesis, dots of different sizes are superimposed or closely spaced at different angles. Under the irradiation of light, the ink on the dot selectively absorbs and reflects light. The part of the reflected light is mixed in the space and acts on the human eye. It is the illusion of the human eye, and the print looks like a continuous tone image. . The difference in hue seen by people is caused by the difference in the area of ​​space occupied by each dot, and the depth of hue is determined by the intensity of reflection of light at each dot.
8. How to measure or identify the number of outlets?
There are two ways to measure or identify the dots: One is to measure the integral density of dots with a densitometer.
Then it is converted into a percentage of the dot area; another method is to use a magnifying glass to visually measure the ratio of the dot area to the space area to estimate the dot number. For example, the diameter of the blank area between the two dots is equal to the sum of the diameters of the three dots is 1 point; the diameter of the blank area between the two dots is equal to the sum of the diameter of the two dots is 2 points; between the two dots The diameter of the blank area is equal to the sum of the diameters of the 1.5 dots being 3 points; the diameter of the blank area between the two dots is equal to the sum of the diameter of the 1.25 dots is 4 points; the diameter of the blank area between the two dots is equal to 1 The diameter of each dot is 50% (the dot area is equal to the blank area). The six-point and four-point points are exactly the opposite, that is, the diameter of the dot is equal to the sum of the diameters of 1.25 blank dots; the seven-point dot is opposite to the three-point dot, that is, the diameter of the dot is equal to the sum of the diameters of 1.5 blank dots; 8 dots and 2 dots In contrast, the diameter of the dot is equal to the sum of the diameters of the two blank dots; the nine-point dot is opposite to the one-point dot, that is, the diameter of the dot is equal to the sum of the diameters of the three blank dots. Compared with the above two methods, the former is more scientific and accurate, and the latter is a commonly used method based on experience in daily work, and the error is relatively large.
9. What is network expansion?
Dot enlargement is a kind of dot size change phenomenon that occurs during the process of plate making and printing. It makes the actual dot area larger than the expected dot area. The process of the phenomenon of network expansion is divided into two categories, which are the network expansion in the process of plate making and the expansion of the printing process. The dot gain in the process of plate making mainly exists in the two processes of film output and printing. The main factor affecting the dot enlargement during the output of the film is the optical nonlinear effect of the photo-composing machine. There are more factors affecting the dot enlargement during the printing process. It can be compensated by controlling the process parameters. In the printing process, under the influence of printing pressure, the ink must be expanded around the dot. At the same time, due to the compressive deformation of the liner, relative slipping occurs between the plate and the blanket, and between the blanket and the substrate. The result of this slippage is that the percentage of dots on the substrate is larger than the percentage of the original Internet site, that is, the dots on the printed matter have expanded.