Explore UV printing quality difference analysis (1)

Summary

As the island's printing production methods, inks, and technologies are changing with each passing day, and then taking into account the future trend of environmental protection, it is necessary to consider high-speed, high-quality, and non-pollution on the printing press. Therefore, this article is aimed at UV inks. In addition to inks, this article also discusses the interrelationship between printing presses and dryers to find out the most appropriate quality assessment of the printing process.

Preface

With the advancement of printing technology, the printing quality is gradually becoming faster. However, in the process of speeding up, some problems occur, such as drying. UV inks have better drying conditions than other conventional inks, so they can be printed in a wide range of materials and UV inks can be used in various formats. In view of this, UV inks will occupy a large seat in various inks in future printing trends. Because UV inks have a wide range of applications, the two types of layouts are discussed in view of the speed of rotation lithographs, the large amount of production, and the wide range of printed materials for screens. How to get the most suitable quality [Figure 1] must be analyzed with the cost, quality, and product value.

Figure 1

The origin of UV ink (UV ink)

First, the history of UV ink development

The idea of ​​using ultraviolet light to irradiate ink to make it completely dry and hard in just a few seconds was proposed in 1994. Until 1960 oil was successfully developed by a British company. UV inks were not initially appreciated because of the fast drying and solvent-free all-solid components that UV inks emphasize. At the time, there were no better conditions than other inks. However, UV inks are very popular on the screen. Because of the screen printing, its printing speed is not faster than that of other types of printing. Strictly speaking, the difference is large, and the printed ink film is particularly strong. Naturally, the time required is longer. The main reason is "solvent." This thing. And the disadvantages of the solvent in the screen, such as the ink plug the network can not be printed, only due to the relationship between the solvent evaporated in the mesh; ink is too hard to print and the ink is too thin and can not be printed, are caused by solvents . In short, the problems brought about by the "solvent" in the industry will be very nerve-racking. Therefore, the two major characteristics of UV ink to solve the problems plagued by screen printers, and the industry still think UV ink development is too slow.

Second, the characteristics of UV ink

[1] Simplicity and low inventory: New UV inks can be mixed with only the four basic colors to achieve the desired color, and the thickness of the printing ink film is thin, the amount of ink needed is reduced, it is very simple and therefore inventory can be reduced.

[2] Opacity Easy to control: The pigments or pigments can be added to the extension to achieve your desired brightness in a standard ratio.

[3] Color matching ability: The pigment added to the stretching group can be given an appropriate viscosity, hue and lightness, and can be provided with an extremely rich color, so long as two or more basic colors are mixed to obtain various desired colors.

[4] Ink saving: Since the composition contains no solvent, only one-third to one-half of the traditional one is needed, and the desired effect can be obtained with the ink volume.

[5] The ink roller and the printing plate are not blocked: Unirradiated ink, even if it can not be dried for at least 48 hours on the ink roller or printing plate, there is no need to worry about the crust on the roller or the plate is blocked .

[6] Provincial ink: Only three quarters to one-fifth of the traditional ink hot stove can be dry.

[7] Gloss: The gloss of UV inks is very good, and special treatment can also be used to achieve special effects.

Third, UV ink and traditional ink comparison

The biggest difference between UV inks and traditional inks is that it is a constituent molecule. It is an all-solid-state tissue form and contains no solvents. And its media, pigments, resins and other chemicals are different from traditional inks. Traditional inks contain solvents [40%–60%], which require the solvent to completely evaporate before leaving a dry film of ink that is made up of blending agents, pigments, and additives. UV ink pigments and resin systems, unlike conventional inks, do not have such high brightness and opacity.

Fourth, the advantages and disadvantages of UV ink

UV is a type of electromagnetic wave, and UV inks use UV radiation energy to achieve its drying effect. There are many types of UV dry-solid systems, but the principle is based on the chemical reactions caused by the sensitizer's absorption of high-intensity ultraviolet light [UV]. The sensitizer is a chemical product with special reaction ability, which can convert light energy into chemical energy and instant solidify different mixtures. But the most important point is that the energy of the UV light used is 600 times that of the home fluorescent lamp, so it will not dry immediately due to sunlight in the environment.

[1] Advantages

1. Volatile Organics: Most UV products contain little or no organic solvents.

2. To improve the quality of finished products: Through the crosslinked structure of polymers, not only is it highly tough [Toughness], but it is also anti-fouling [stainresistance] and anti-abrasion [abrasionresistance] And the characteristics of solvent resistance [Solventresistance].

3. Low energy demand: The energy consumed by a typical radiative solid-state production line requires only 25% of the energy required for drying with heat energy.

[2] Disadvantages

1. The "line of sight" type of dry solid: UV products usually only dry under UV irradiation. 2. Difficulties in dry solids containing pigment systems: UV has difficulty penetrating thicker and pigmented coatings. In general, only EB has a good effect. Recent research and development in chemical and light energy have improved the effect of UV on the product.

3, raw material prices are too high: the current high prices of raw materials is due to the market is small, coupled with high research costs, resulting in product unit prices higher than the traditional products. It should be noted here that UV products are 100% solids, unlike traditional inks, coatings and adhesives containing volatile solvents. 4, dry solid equipment [curingunit]: high cost of basic equipment investment prices.

5. Possible hazards of UV products: Most UV products can be considered skin irritants before they are dried. However, these products, due to their low volatility, can reduce such problems if they can maintain the habit of wearing skin care gloves and goggles during operation.

6, poor adhesion: In general, compared with traditional products, some materials, including steel and aluminum sheet poor adhesion, for chemical improvement and post-baking treatment [post-Baking] Can eliminate some of the problems of poor adhesion, but also reduce the stress caused by shrinkage in the dry process.

叁, Factors Affecting UV Printing Quality

The first step to consider before printing is design. The design should first think of ink, because any printed matter is the effect of ink on the solidified film of paper or other substrates.

First, the ink

[1] UV ink does not have a long shelf life: UV inks do not have a long shelf life because UV inks are prone to gelation and deterioration.

[2] UV ink ink film thickness, transparency: ink ink film thickness is too thick, it will also affect the speed of UV light irradiation, resulting in ink hardening is not easy. As for the transparency of the ink, the transparency of the UV ink is much faster than the opaque UV ink. In ink, the speed of UV light irradiation is not only faster, but also a more uniform relationship. For example, the color with the fastest hardening speed is blue in color four-color printing, followed by magenta and yellow. The black ink cures very slowly, and the hardest to harden is opaque white. Not only that, opaque whites tend to be yellow when exposed to UV light.

Second, printing machine

In terms of screen layout, the layout of the screen is different depending on the printed material. [Figure 2]

Figure II

The main topic discussed in this paper is screen printing lithography. Separate prepress and postpress for factors that may occur at the time of printing.

[1] Scraper

1. The hardness unit of the hardness blade face is generally measured with a hardness meter of JIS [Japanese Industrial Standards]. If the hardness of the blade surface is larger, the contact between the blade surface and the plate surface will be smaller, so it is suitable for those who print high, and the tangent line is sharper and smaller, and the printing ink is thinner. Conversely, the softer the blade surface, the larger the contact area, it is suitable for printing thick and rough, monotonous imprint pattern. The distinction is as follows: Extra soft 45 degrees to 55 degrees, soft 55 degrees to 65 degrees, medium 65 degrees to 75 degrees, and rigid 75 degrees to 85 degrees.

2. Width In simple terms, the width of the doctor blade must be greater than the width of the imprint and less than the width of the frame, so that the printing requirements can be achieved. However, in order to request quality, reduce the occurrence of imprint distortion, and consider the factors of the width of the doctor blade, there is still a basis for it. The positions of the width of the imprint and the width of the frame are discussed separately.

A. In terms of the frame position: Of course, the width of the scraper must be smaller than the frame in order to print. Ideally, the smaller the blade width is, the better, that is, the larger the distance between the left and right ends of the blade and the frame, the better, because in this state, the mesh can be in the process of squeegee printing. Soft contact with the printed material, the net cloth stretch is also smaller. On the contrary, when the distance between the scraper and the frame is too small, the net fabric is too rigid, resulting in an excessively large angle of the cloth at both ends of the scraper, resulting in a distorted shape, which is the main cause of the distortion of the print pattern. In general, for every 10 inch increase in the scraper, there is an error of 100 micron, and the width of the scraper is preferably not more than 50 percent of the frame size. If this is not possible, at least the ends of the scraper must be away from the frame. Distance must be 5 cm to ensure print quality.

B. In terms of imprinting positions: Generally, the width of the doctor blade must be greater than the width of the imprinting pattern by 2 to 10 cm. The reason why the width of the doctor blade is smaller, the better, must also be determined depending on the size of the imprint. In the event that a re-inking knife is used, the width of the ink-returning blade should be wider than the width of the printing squeegee, so that the ink overflowed at both ends of the printing squeegee can be completely transported back.

3, squeegee speed and angle The speed and angle of squeegee mainly affect the amount of ink reaching the printed object through the mesh. Squeegee printing speed is less penetrating and thin, slow printing speed is more ink and thicker. However, if the squeegee speed is too fast, the thickness of the ink is not enough, and the imprint may be unclear. When the squeegee is too slow, it may easily cause bleeding and the imprint may not be sharp enough. The general print speed is about 60 to 200 cm per second, depending on the conditions at the time. The angle of the squeegee also affects the amount of ink. When the angle is small, the amount of ink is large. When the angle is large, the amount of ink is small. The angle usually used is between 45 and 75 degrees. Scratching must pay attention to uniform speed requirements, and the angle must be the same before and after, it will not produce different shades of ink in the same print.

4, squeegee pressure: we must first understand a view