As is well known, the basic process of screen printing is: using a screen, a net to make a stencil carrier, and producing an image on the carrier, and then forcing the ink to transfer through the opening of the image area and adhere to the printing by means of the pressure of the squeegee. Things. This process is not difficult to understand, especially the screen printing of color blocks, it should be said that there has been a wealth of experience.
However, the screen printing of such color blocks is increasingly unable to meet the demand for the fine screen printing market, especially the demand for the halftone screen printing market.
Because halftone screen printing can be used in many fields, such as advertising paintings, textile printing, T-shirts, ceramic glass printing, ceramic decal printing, CD printing, and the like. Half-tone screen printing can even be used in unexpected areas such as surface decoration of aerospace, aerospace and electrical products.
In recent years, the screen printing industry has generated a great interest in performing color halftone reproduction on different substrates. The ability of silk screen printing to perform color reproduction on substrates of different shapes and different materials has been recognized by many graphic designers, advertising manufacturers, packers and printers, and has received increasing attention. Its market is very rich. Competitiveness.
At present, the half-tone screen and brush technology in China can be used not only for small-format screen printing, but also for half-tone screen printing of large-scale outdoor advertising, showing screen printing-specific functions, such as: for printing bus stop signs. Screen printing of subway advertisements and outdoor advertisements has gradually become popular, and the application field is expanding. Therefore, halftone screen printing is also attracting Textiles, plastics, glass, metal screen printers and large-scale advertising and process equipment manufacturers. They have conducted research and explorations in terms of process, technology and materials. There are also many fine-printing half-tone printing products available.
However, it is not easy to master the process of half-tone screen printing, because when you look deep into the halftone screen printing process, you will find that the process itself is much more complicated than expected. There are many variables in the entire halftone screen printing process, and each variable factor affects the quality of the final web product.
Halftone screen printing should be considered! Division title: In short, what is the final product? What printing materials are printed on? What kind of ink is used? Take a few color printing? Specifically speaking, in the platemaking, such as the determination of the manuscript, the requirements for the positive figure, the selection of the screen, the determination of the stretching tension, the quality requirements for the template, and the requirements and control of the exposure, such as in screen printing The requirements and control of the squeegee, the control of the stencil variation, the control of the ink transfer amount, and the influence of the printing material on the accuracy show the prevention of static electricity, the order of the halftone screening, and the registration requirements. This article analyzes and discusses the factors that influence the quality of the above halftone network, such as causing the attention of screen printers and improving the quality of the halftone network.
1 What is halftone screen printing
1.1 What is halftone
There are many ways to express levels in printing. There are two common methods: one is continuous halo staining and hierarchical expression; the other is halftone hierarchical expression.
The image of the reflection original, from the highlights to the shades of the shades of tone, is formed continuously and uninterruptedly from deep to the money or from the money to the deep uniform density and is called continuous tone. For example, the colorless shade diagram baseplate without the net, the black and white photographs of the bottom edition and the drafts and photographs are continuously adjusted. Regardless of whether the image of the negative or positive image is from the highlight to the shadow, the shades of the image are represented by halftones, which are called halftones.
1.2 Screen Printing Halftone Level Representation
The representation of the halftone gradation is to divide the continuous tinting tone into different lines of thick, slender, short, or small dots of varying sizes. There are three main methods of general expression:
The first is the line representation, which is the high, medium, and low tone levels of the manuscript. It is expressed in terms of thickness, density, and length. The lines are thick and dense, and the lines are thin and sparse. The deficiency of this method of expression is that it is relatively rough, and it does not express the continuous tone levels of the bridges of the picture. Moreover, it can only appear in black and white or monochrome, there is no color change, and the rich colors of the manuscript can not be reflected by overlapping sets of colors.
The second is the AM representation. The shades of the original are represented by dots of different sizes and regularly arranged.
The third is the FM network representation. This method is rather special, with some irregularly arranged fine points to express the level of color, dense performance of dark and deep levels, point evacuation performance light and bright level.
Screen printing, in addition to the field color block patterns, text, lines, are halftone dot size, reproduction shades of gray tone level, instead of the original continuous blooming color, to complete the copy of the original image.
What is commonly used now is the amplitude modulation point. This kind of dot is the most basic unit that constitutes an image on a screen printing plate. It is medium. The actual points that have been arranged in equal and unequal areas. Dots are the basis of screen printing and copying process. The correct transmission of screens in screen printing and printing is the most basic requirement. In screen printing, the dots play the following roles:
(l) The task of presenting hue, brightness, and saturation is imposed on the printing effect.
(2) During the printing process. Is the basic element of image transfer.
(3) In color synthesis is the organizer of image color, gradation, and outline.
As we all know, the halftone screen printing graphic is done by the dot. After coating the sensitized film, printing plate, and other series of treatments on the screen, the dots are made into the image part, and the remaining part of the image part except the screen dots penetrates the mesh and seals the ink.
In this sense, half-tone screen printing limit 1 is used for dot printing. Then, why can the outlets realistically reproduce the continuous leveling on the manuscript? This is because once the manuscript image is screened, the manuscript image is divided into countless meshes of different sizes, that is, the image is converted into halftone image information after continuous image transfer. When the color is synthesized, since the dots of different sizes are printed at different angles or close together, the ink on the dots selectively absorbs and reflects the light under the action of light. The reflected part of the light passes through the light. Space mixing, acting on human eyes (colored nerves), creating illusions in people's eyes, looks like continuous tone. In fact, the space occupied by each dot on screen printing products is equal. The difference in color tone seen by people is due to the fact that the size of the space occupied by each dot is not returned, and the shade of shade is It is determined by the reflected light intensity of the dot space.
2 Requirements for originals in halftone screen printing
The main goal of half-tone screen printing is to control the ink deposition, so that the amount of printing ink is extremely accurate, and people seem to feel that the brightness, darkness, and subtle levels of the image colors can faithfully reproduce the originals. In the operation, this effect must be consistent between the printed sheet and the printed sheet. Any change in the process will result in the difference between the color and the gradation of the image, and the variable factors must be strictly controlled throughout the entire process. Only print qualified products. However, to control the entire process, the original must first be controlled and selected. The original is the basis.
Originals are provided by customers, and some are also called originals. Strictly speaking, only original works can be called originals, while a Chinese painting is original. Color reversal films taken with originals, black and white or color photos cannot be called originals but are called manuscripts.
The form, color, and structure of the manuscript are very different and can be clearly categorized.
2.1 According to the type of manuscript
(1) Photographic originals - color reversal film (natural color film), color copy positive film (color positive film copied with color negative film), color photos, and black-and-white photos.
(2) Original artwork - Chinese painting, gouache, watercolors, prints, and pencil drawings.
(3) The second manuscript—generally refers to a color reversal film or color photo that is a copy of an original artwork.
(4) Printed manuscripts—refers to the use of prints as manuscripts.
(5) Line manuscript - refers to the black and white line surface and the manuscript consisting of the pattern field, artistic characters, and text.
2.2 According to the light irradiation
It can be divided into two categories: transmissive and reflective.
(l) Transmission. The original is transparent. When the color is separated, the light source shines on the back of the original and the transmitted light is used for color separation.
(2) Reflection draft. In color separation, the light source illuminates the front surface of the original and is a manuscript that uses the reflected light of the original for color separation. Reflection drafts include original paintings, color photos, black-and-white photos, and brushwork.
The quality of the color separation is best with the original. The contrast of this type of manuscript is small, generally only about 1.4, and the bright density is 0.1-0.3. Accompany tune density 1.5 to 1.7.
Color photographic paper is a kind of color multi-layer photosensitive material, and its structure and coloring principle are similar to those of reversal film. The color photo image is enlarged and printed on the color photo paper by the color negative film, so the light and dark contrast is intense and the color is vivid and real. It is only the National East Reflection original, but the contrast of the reversal film contrasts strongly, and because it is a color negative film copy or enlargement, the level is subject to loss, the color has color cast, it is appropriate to make the original large or reduced copy.
2.3 Applicable and non-applicable originals.
The manuscript is the basis for screen printing and copying. The quality of the manuscript directly relates to the quality of the plate making and printing products. Therefore, when manuscripts and process design are performed, the original manuscript submitted by the customer must first be carefully examined and confirmed to determine whether or not the screen printing is complied with. Platemaking requirements.
2.3.1 Manuscripts for Screen Printing
Applicable manuscripts are often referred to as qualified manuscripts, that is, in accordance with the requirements of the screen printing process for making a master plate, and it is not necessary to make a manuscript that can be copied by processing correction. Its standards are: 1 image, good clarity; 1 fine particles, clean and clean the map; 3 moderate contrast, high and low profile levels; 4 correct color, bright colors, color balance; 3 to 4 times; 5 originals such as reflections and drawings must be flat and free from damage and dirt.
2.3.2 Manuscripts for Web Elf
Non-applicable originals, ie originals that do not meet the copying requirements. Although this type of manuscript can be copied, it requires a lot of processing adjustments and corrections, and the final copying effect is also unsatisfactory. Such as: 1 image is false and false, there are double shadows, poor clarity; 1 coarse grain, surface pollution, dirty spots, more roads; 3 contrast is too large, too stressed or too thin tone; 4 series color, color Chen ! Clearance ratio of 5 to more than 10 borrowed.
2.3.3 Cannot Copy Originals
Some manuscripts cannot be copied and should be returned. Such as: 1 image is serious and false, the outline level is unclear; 1 particles are too rough, borrow rate is too large; 3 graphics serious wrinkle, pollution. The main part of the image has obvious dirt spots, roads, molds, etc.; 4 serious color cast, the tone is completely distorted.
In short, whether it is a physical manuscript or an artwork, or a positive edition, these manuscripts determine the quality of future prints. Therefore, the most important thing is that the printer should be able to check and identify the quality of the manuscript, even if it is provided by the user. It is also necessary to correctly identify the quality of the manuscript. Why are you not satisfied with the manuscript? What are the defects and deficiencies in the manuscript? These must be given to the user in advance so that they know the consequences of these defects. If the manuscript was received without prior explanation, it would be too late to say it was rejected by the customer when handing over the screen print. The screen printer was responsible for this.
However, the screen printing of such color blocks is increasingly unable to meet the demand for the fine screen printing market, especially the demand for the halftone screen printing market.
Because halftone screen printing can be used in many fields, such as advertising paintings, textile printing, T-shirts, ceramic glass printing, ceramic decal printing, CD printing, and the like. Half-tone screen printing can even be used in unexpected areas such as surface decoration of aerospace, aerospace and electrical products.
In recent years, the screen printing industry has generated a great interest in performing color halftone reproduction on different substrates. The ability of silk screen printing to perform color reproduction on substrates of different shapes and different materials has been recognized by many graphic designers, advertising manufacturers, packers and printers, and has received increasing attention. Its market is very rich. Competitiveness.
At present, the half-tone screen and brush technology in China can be used not only for small-format screen printing, but also for half-tone screen printing of large-scale outdoor advertising, showing screen printing-specific functions, such as: for printing bus stop signs. Screen printing of subway advertisements and outdoor advertisements has gradually become popular, and the application field is expanding. Therefore, halftone screen printing is also attracting Textiles, plastics, glass, metal screen printers and large-scale advertising and process equipment manufacturers. They have conducted research and explorations in terms of process, technology and materials. There are also many fine-printing half-tone printing products available.
However, it is not easy to master the process of half-tone screen printing, because when you look deep into the halftone screen printing process, you will find that the process itself is much more complicated than expected. There are many variables in the entire halftone screen printing process, and each variable factor affects the quality of the final web product.
Halftone screen printing should be considered! Division title: In short, what is the final product? What printing materials are printed on? What kind of ink is used? Take a few color printing? Specifically speaking, in the platemaking, such as the determination of the manuscript, the requirements for the positive figure, the selection of the screen, the determination of the stretching tension, the quality requirements for the template, and the requirements and control of the exposure, such as in screen printing The requirements and control of the squeegee, the control of the stencil variation, the control of the ink transfer amount, and the influence of the printing material on the accuracy show the prevention of static electricity, the order of the halftone screening, and the registration requirements. This article analyzes and discusses the factors that influence the quality of the above halftone network, such as causing the attention of screen printers and improving the quality of the halftone network.
1 What is halftone screen printing
1.1 What is halftone
There are many ways to express levels in printing. There are two common methods: one is continuous halo staining and hierarchical expression; the other is halftone hierarchical expression.
The image of the reflection original, from the highlights to the shades of the shades of tone, is formed continuously and uninterruptedly from deep to the money or from the money to the deep uniform density and is called continuous tone. For example, the colorless shade diagram baseplate without the net, the black and white photographs of the bottom edition and the drafts and photographs are continuously adjusted. Regardless of whether the image of the negative or positive image is from the highlight to the shadow, the shades of the image are represented by halftones, which are called halftones.
1.2 Screen Printing Halftone Level Representation
The representation of the halftone gradation is to divide the continuous tinting tone into different lines of thick, slender, short, or small dots of varying sizes. There are three main methods of general expression:
The first is the line representation, which is the high, medium, and low tone levels of the manuscript. It is expressed in terms of thickness, density, and length. The lines are thick and dense, and the lines are thin and sparse. The deficiency of this method of expression is that it is relatively rough, and it does not express the continuous tone levels of the bridges of the picture. Moreover, it can only appear in black and white or monochrome, there is no color change, and the rich colors of the manuscript can not be reflected by overlapping sets of colors.
The second is the AM representation. The shades of the original are represented by dots of different sizes and regularly arranged.
The third is the FM network representation. This method is rather special, with some irregularly arranged fine points to express the level of color, dense performance of dark and deep levels, point evacuation performance light and bright level.
Screen printing, in addition to the field color block patterns, text, lines, are halftone dot size, reproduction shades of gray tone level, instead of the original continuous blooming color, to complete the copy of the original image.
What is commonly used now is the amplitude modulation point. This kind of dot is the most basic unit that constitutes an image on a screen printing plate. It is medium. The actual points that have been arranged in equal and unequal areas. Dots are the basis of screen printing and copying process. The correct transmission of screens in screen printing and printing is the most basic requirement. In screen printing, the dots play the following roles:
(l) The task of presenting hue, brightness, and saturation is imposed on the printing effect.
(2) During the printing process. Is the basic element of image transfer.
(3) In color synthesis is the organizer of image color, gradation, and outline.
As we all know, the halftone screen printing graphic is done by the dot. After coating the sensitized film, printing plate, and other series of treatments on the screen, the dots are made into the image part, and the remaining part of the image part except the screen dots penetrates the mesh and seals the ink.
In this sense, half-tone screen printing limit 1 is used for dot printing. Then, why can the outlets realistically reproduce the continuous leveling on the manuscript? This is because once the manuscript image is screened, the manuscript image is divided into countless meshes of different sizes, that is, the image is converted into halftone image information after continuous image transfer. When the color is synthesized, since the dots of different sizes are printed at different angles or close together, the ink on the dots selectively absorbs and reflects the light under the action of light. The reflected part of the light passes through the light. Space mixing, acting on human eyes (colored nerves), creating illusions in people's eyes, looks like continuous tone. In fact, the space occupied by each dot on screen printing products is equal. The difference in color tone seen by people is due to the fact that the size of the space occupied by each dot is not returned, and the shade of shade is It is determined by the reflected light intensity of the dot space.
2 Requirements for originals in halftone screen printing
The main goal of half-tone screen printing is to control the ink deposition, so that the amount of printing ink is extremely accurate, and people seem to feel that the brightness, darkness, and subtle levels of the image colors can faithfully reproduce the originals. In the operation, this effect must be consistent between the printed sheet and the printed sheet. Any change in the process will result in the difference between the color and the gradation of the image, and the variable factors must be strictly controlled throughout the entire process. Only print qualified products. However, to control the entire process, the original must first be controlled and selected. The original is the basis.
Originals are provided by customers, and some are also called originals. Strictly speaking, only original works can be called originals, while a Chinese painting is original. Color reversal films taken with originals, black and white or color photos cannot be called originals but are called manuscripts.
The form, color, and structure of the manuscript are very different and can be clearly categorized.
2.1 According to the type of manuscript
(1) Photographic originals - color reversal film (natural color film), color copy positive film (color positive film copied with color negative film), color photos, and black-and-white photos.
(2) Original artwork - Chinese painting, gouache, watercolors, prints, and pencil drawings.
(3) The second manuscript—generally refers to a color reversal film or color photo that is a copy of an original artwork.
(4) Printed manuscripts—refers to the use of prints as manuscripts.
(5) Line manuscript - refers to the black and white line surface and the manuscript consisting of the pattern field, artistic characters, and text.
2.2 According to the light irradiation
It can be divided into two categories: transmissive and reflective.
(l) Transmission. The original is transparent. When the color is separated, the light source shines on the back of the original and the transmitted light is used for color separation.
(2) Reflection draft. In color separation, the light source illuminates the front surface of the original and is a manuscript that uses the reflected light of the original for color separation. Reflection drafts include original paintings, color photos, black-and-white photos, and brushwork.
The quality of the color separation is best with the original. The contrast of this type of manuscript is small, generally only about 1.4, and the bright density is 0.1-0.3. Accompany tune density 1.5 to 1.7.
Color photographic paper is a kind of color multi-layer photosensitive material, and its structure and coloring principle are similar to those of reversal film. The color photo image is enlarged and printed on the color photo paper by the color negative film, so the light and dark contrast is intense and the color is vivid and real. It is only the National East Reflection original, but the contrast of the reversal film contrasts strongly, and because it is a color negative film copy or enlargement, the level is subject to loss, the color has color cast, it is appropriate to make the original large or reduced copy.
2.3 Applicable and non-applicable originals.
The manuscript is the basis for screen printing and copying. The quality of the manuscript directly relates to the quality of the plate making and printing products. Therefore, when manuscripts and process design are performed, the original manuscript submitted by the customer must first be carefully examined and confirmed to determine whether or not the screen printing is complied with. Platemaking requirements.
2.3.1 Manuscripts for Screen Printing
Applicable manuscripts are often referred to as qualified manuscripts, that is, in accordance with the requirements of the screen printing process for making a master plate, and it is not necessary to make a manuscript that can be copied by processing correction. Its standards are: 1 image, good clarity; 1 fine particles, clean and clean the map; 3 moderate contrast, high and low profile levels; 4 correct color, bright colors, color balance; 3 to 4 times; 5 originals such as reflections and drawings must be flat and free from damage and dirt.
2.3.2 Manuscripts for Web Elf
Non-applicable originals, ie originals that do not meet the copying requirements. Although this type of manuscript can be copied, it requires a lot of processing adjustments and corrections, and the final copying effect is also unsatisfactory. Such as: 1 image is false and false, there are double shadows, poor clarity; 1 coarse grain, surface pollution, dirty spots, more roads; 3 contrast is too large, too stressed or too thin tone; 4 series color, color Chen ! Clearance ratio of 5 to more than 10 borrowed.
2.3.3 Cannot Copy Originals
Some manuscripts cannot be copied and should be returned. Such as: 1 image is serious and false, the outline level is unclear; 1 particles are too rough, borrow rate is too large; 3 graphics serious wrinkle, pollution. The main part of the image has obvious dirt spots, roads, molds, etc.; 4 serious color cast, the tone is completely distorted.
In short, whether it is a physical manuscript or an artwork, or a positive edition, these manuscripts determine the quality of future prints. Therefore, the most important thing is that the printer should be able to check and identify the quality of the manuscript, even if it is provided by the user. It is also necessary to correctly identify the quality of the manuscript. Why are you not satisfied with the manuscript? What are the defects and deficiencies in the manuscript? These must be given to the user in advance so that they know the consequences of these defects. If the manuscript was received without prior explanation, it would be too late to say it was rejected by the customer when handing over the screen print. The screen printer was responsible for this.
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