Ink classification and selection in inkjet printing process

Ink-jet printing (Ink-jet printing) is a topic that print designers are currently concerned about. It is a kind of digital printing design that uses digital data to store images and can arbitrarily change the output before output. , So it has the advantages of high speed, small amount of copy, easy combination, variable information printing design, low pollution, etc. Inkjet printing design expands the connotation of traditional printing design in terms of printing design format, diversification of printing ink and printing medium, and has formed a digital inkjet printing design, digital proofing, digital inkjet market and so on.

The inkjet printing design is a contactless, pressureless, and non-printing printing design technology. The earliest development was in 1878. By 1951, Siemens patented the technology of converting liquid ink into ink droplets. Ink problems, poor results, health products packaging, until 1960 only officially entered the practical stage. With the constant development and progress of technology, the market continues to expand, according to the United States I. TStrategies predicts that by 2009, the total revenue of the global inkjet market (including hardware, inkjet design media, and inks) will exceed $57 billion.

The color performance and high image quality of inkjet printing designs have satisfied most consumers, but the time for printing is still too slow, and the demand for paper is also high. Although there are many inkjet papers on the market , but the prices are high, it is difficult for general families and student populations to use universally, so let ink-jet technology can be widely applied to all kinds of paper, is now the most urgent need to develop technology, if it is to make special materials for special paper parity This is not easy, so developing a new ink composition is a straightforward and effective method.

The ink used in the ink jet printing design is a special ink with a moderate viscosity, and is nontoxic, stable, does not clog the nozzle, has good moisture retention, good jetting properties, and does not corrode the metal components of the head. At present, ink-jet inks are mostly dye-based inks, and the ink of the inkjet printing design machine must have enough surface tension to prevent the ink from spattering when ejected. In addition, the ink must be fast-drying to prevent haziness on the paper. Therefore, the ink itself is also one of the factors that affect the quality of the print design. In the printing design, choosing the right ink and adjusting the printing design parameters can get satisfactory printing products.

First, the composition of inkjet inks, types

Ink is a very important part of inkjet printing design. The development of inkjet ink also explains the development of inkjet printing design technology to some extent, because ink not only determines the quality of inkjet images, but also determines the ink. The shape of the drop and the reliability of the printed design system. Inkjet inks generally consist of colorants, binders, and additives. The ink binders can be water, oily materials, solvents, resins, etc. It determines the dynamic properties of the ink distribution, personalized crystal engraving; in ink-jet inks, binders account for 40% -90%. The colorant plays a role of color development in the ink, generally accounting for 1%-10%. The rest is called additive, which is mainly used to improve the ink viscosity, adhesion strength, thermal stability, light resistance and surface tension.

In general, there are many types of inks used in the inkjet printing design process, and there are many classification methods. At present, inks can generally be classified according to their different aspects. In general, inks are classified into water-based inks, oil-based inks, solvent-based inks, and thermosetting inks according to different linking materials.

1. Water-based ink

It is commonly used on apertured and non-coated substrates such as paperboard and paper, and is often used most often in the print design of direct mail products and other commercial printing designs. Can also be divided into pigment type and dye type, because the pigment is insoluble in water, it will precipitate, so the pigment particles to be ground very small, to be less than 30μm, will have a better spray printing effect, or use high resolution Can cause obstruction. The pigment's weather resistance, lightfastness, wash fastness, and fastness are all very good. The advantage of the dye is that there is no problem in solubility, and there are many types of colors, and the brightness is good, but the fastness is poor.

2. Oil-based ink

It is best suited for printing designs on perforated materials because it is dried by absorption. They are formulated with vegetable oils or mineral oils, which are particularly useful in the field of cardboard packaging; not suitable for use in enclosed office spaces because It will produce air pollution.

The colorants used can be divided into two types: pigment type and dye type. Oil-soluble type inks are characterized by fast drying, so they are more commonly used in the industry.

3. Solvent based ink

It is widely used, from signage printing design to bar code printing design to outdoor advertising. The use of this kind of ink has high economic efficiency, quick drying, and can be printed on a variety of materials, especially for the printing design of non-coating materials, such as ethylene. Base, screen, glass and paper.

4. UV/EB thermosetting ink

The ink is suitable for printing designs on a variety of soft and rigid substrates, such as corrugated cardboard and metal foils. UV/EB inks cure faster and have greater durability under UV light. Ideal for DOD applications such as retail display advertising, calling cards, credit cards and frequently used shopping cards.

In addition to the classification of the connection materials, in practice, there are some other classification methods: According to the color materials, divided into organic dye inks, polymeric dye inks and pigment inks; if used according to the ink The different drying mechanisms can be divided into volatile inks and polymeric inks. Aqueous and non-aqueous inks use water or other solvents as the binder. Drying is accomplished by the penetration and absorption of the ink by the substrate. If ordinary copy paper or flat paper is used, the ink and its binder are absorbed together by the substrate. This absorption will reduce the color density and sharpness of printed designs. Thermosetting ink means that the ink is a solid at room temperature. When it is ejected from a nozzle, it is a hot melt liquid and rapidly solidifies when it reaches the surface of the substrate. This rapid solidification feature prevents the ink from spreading or penetrating into the interior of the substrate. , to ensure the quality of print design.

Second, choose the right ink

1. Ink supplied by ink jet digital printing design machine manufacturer

In the actual production process, producers generally choose the ink provided by ink jet equipment providers. In fact, this has both advantages and disadvantages. Of course, different digital printing design opportunities use different technical methods, such as continuous inkjet (CIJ) and drop-on-demand (DOD). The two inks are not interchangeable, because the two technologies are completely different. The CIJ technology refers to the continuous generation of ink droplets to form an ink droplet stream, which is imaged through a deflection plate; and DOD technology, which is a digital signal generated on demand. Some ink droplets, rather than an ink stream, change the ink at will, causing ink mess. Therefore, in the production, the premise of the maximum effect of the printing design machine is to have a full understanding of the ink used, which needs to consider the influence of various factors.

2. Printing media and ink selection

For ink jet printing design, how to control the printing design effect on different printing media must analyze the performance of the printing material. Taking paper as an example, due to the thermodynamic interaction between paper and ink, the capillary action of the paper, and the spread of the ink chemical composition, etc., the absorption of ink components by the paper is caused, that is, the ink penetration. Among them, the capillary action of paper is the main cause of ink penetration. Because the paper itself is a porous water-permeable structure, the ink is easily diffused inside the paper. With the increasing development of the paper surface coating process, the different distribution of the ink inside the paper leads to different ink penetration effects. Therefore, the inkjet printing design paper requires a smooth surface with a certain degree of sizing. The ink sprayed on the surface is evaporated and dried, the dots are circular, the printed characters are clear, and the graphics are beautiful. The color ink jet printing design paper preferably has a very thin transparent coating on the surface, which not only absorbs ink quickly but also avoids light scattering.

Inkjet inks can be printed on a variety of substrates, which is a big advantage, advertising paper cups, such as fiber, wallpaper, glass, plastic, metal foil and plastic film, of course, can also be on various types of paper . Knowing which type of ink-jet technology is suitable is just one aspect of the problem. Also, is the substrate material coated or uncoated? Is the substrate material porous or non-porous? Printing materials absorb water or not absorb water? How is the effect of ink on the surface of the substrate? All of these will be related to the formulation of print design operations plans, increase production efficiency, and ultimately improve the return on investment.

3. Selection of dye inks and pigment inks

From a chemical point of view, the dyes are present in a single molecular state in the ink, while the pigments are composed of a floc that has numerous pigment molecules aggregated.

In general, the color performance or color gamut of dye inks is superior to pigment inks. When printing designs on relatively good substrates, the use of dye inks can achieve the same quality as silver salt photographs. However, dyestuff inks have poor stability, especially lightfastness, dark storage stability, moisture resistance, and water resistance. The reason is that individual dye molecules have very unstable chemical properties under light, moisture, and oxidation conditions. It is prone to chemical reactions that cause the printed design to fade. Unlike dyes, pigments in pigment inks exist in a state of flocculation in which numerous pigment molecules aggregate, and therefore their stability to the environment is better.

Dye inks are also very picky for print design media and often require specialized media support to implement. When designing printing on ordinary copy paper, because the copy paper is composed of criss-crossing paper fibers, the glue material is filled between them, and the hydrophilic dyes in the general dye ink account for a large proportion due to the hydrophilicity. The role of factors, dye ink is easy to penetrate along the paper fibers, resulting in the production of blooming on the ordinary copy paper, seriously affecting the final print design. In contrast, pigment inks are the opposite. Instead of the hydrophilic factors, a large number of water-repelling factors are used so that the ink does not penetrate into the deep layers along the fibers, but rather adheres to the surface of the paper.

According to the above advantages and disadvantages, we can know that the dye ink has strong performance, colorful, uniform, high brightness levels, easy to express color, so it is particularly suitable for indoor use; pigment ink stability and durability, suitable for outdoor use .

Third, choose the right ink

1. Ink supplied by ink jet digital printing design machine manufacturer

In the actual production process, producers generally choose the ink provided by ink jet equipment providers. In fact, this has both advantages and disadvantages. Of course, different digital printing design opportunities use different technical methods, such as continuous inkjet (CIJ) and drop-on-demand (DOD). The two inks are not interchangeable, because the two technologies are completely different. The CIJ technology refers to the continuous generation of ink droplets to form an ink droplet stream, which is imaged through a deflection plate; and DOD technology, which is a digital signal generated on demand. Some ink droplets, rather than an ink stream, change the ink at will, causing ink mess. Therefore, in the production, the premise of the maximum effect of the printing design machine is to have a full understanding of the ink used, which needs to consider the influence of various factors.

2. Printing media and ink selection

For ink jet printing design, how to control the printing design effect on different printing media must analyze the performance of the printing material. Taking paper as an example, due to the thermodynamic interaction between paper and ink, the capillary action of the paper, and the spread of the ink chemical composition, etc., the absorption of ink components by the paper is caused, that is, the ink penetration. Among them, the capillary action of paper is the main cause of ink penetration. Because the paper itself is a porous water-permeable structure, the ink is easily diffused inside the paper. With the increasing development of the paper surface coating process, the different distribution of the ink inside the paper leads to different ink penetration effects. Therefore, the inkjet printing design paper requires a smooth surface with a certain degree of sizing. The ink sprayed on the surface is evaporated and dried, the dots are circular, the printed characters are clear, and the graphics are beautiful. The color ink jet printing design paper preferably has a very thin transparent coating on the surface, which not only absorbs ink quickly but also avoids light scattering.

Inkjet inks can be printed on a variety of substrates, which is a big advantage, such as fiber, wallpaper, glass, plastic, metal foil and plastic film, of course, can also be on various types of paper. Knowing which type of ink-jet technology is suitable is just one aspect of the problem. Also, is the substrate material coated or uncoated? Is the substrate material porous or non-porous? Printing materials absorb water or not absorb water? How is the effect of ink on the surface of the substrate? All of these will be related to the formulation of print design operations plans, increase production efficiency, and ultimately improve the return on investment.

3. Selection of dye inks and pigment inks

From a chemical point of view, the dyes are present in a single molecular state in the ink, while the pigments are composed of a floc that has numerous pigment molecules aggregated.

In general, the color performance or color gamut of dye inks is superior to pigment inks. When printing designs on relatively good substrates, the use of dye inks can achieve the same quality as silver salt photographs. However, dyestuff inks have poor stability, especially lightfastness, dark storage stability, moisture resistance, and water resistance. The reason is that individual dye molecules have very unstable chemical properties under light, moisture, and oxidation conditions. It is prone to chemical reactions that cause the printed design to fade. Unlike dyes, pigments in pigment inks exist in a state of flocculation in which numerous pigment molecules aggregate, and therefore their stability to the environment is better.

Dye inks are also very picky for print design media and often require specialized media support to implement. When designing printing on ordinary copy paper, because the copy paper is composed of criss-crossing paper fibers, the glue material is filled between them, and the hydrophilic dyes in the general dye ink account for a large proportion due to the hydrophilicity. The role of factors, dye ink is easy to penetrate along the paper fibers, resulting in the production of blooming on the ordinary copy paper, seriously affecting the final print design. In contrast, pigment inks are the opposite. Instead of the hydrophilic factors, a large number of water-repelling factors are used so that the ink does not penetrate into the deep layers along the fibers, but rather adheres to the surface of the paper.

According to the respective advantages and disadvantages mentioned above, it can be known that the dye ink has strong performance, bright and uniform color, high brightness level, and easy to express color tone, so it is particularly suitable for indoor use; the stability and stability of the pigment ink.