Industry knowledge

Preliminary study on thermal CTP technology

Nov 06, 2018 Leave a message

Preliminary study on thermal CTP technology

We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.

For more information please visit 

http://www.joyful-printing.com.   ENG only    

http://www.joyful-printing.net 

http://www.joyful-printing.org

email: info@joyful-printing.net


The so-called CTP is the abbreviation of CTPlate, CTPress, CTProof, CTPaper/Print and CTcP. The CTP that is often said in the printing industry is from computer to plate (CTPlate). It is a computer that digitizes the original image and text, and combines it with the proof and proof. It directly images the plate and then develops it. Wait for a post-treatment process or post-treatment to make a plate. CTP technology can be divided into photosensitive CTP technology (visible light, violet laser, UV light) and thermal CTP technology. The following focuses on thermal CTP technology.


First, thermal CTP technology classification


Thermal CTP technology can be divided into the following categories according to the plate:

(1) Thermal ablation type; (2) Thermally crosslinked plate (preheating type, negative type); (3) Thermal decomposition type plate (preheat-free type, positive type); (4) Heat transfer Plate; (5) thermally induced phase change plate.


Second, the principle of thermal CTP technology imaging


Thermal CTP mainly uses thermal imaging technology to change the state of the material after the plate material absorbs heat, thereby changing the material properties.


(1) Thermal ablation type

1. Composition of the plate

This plate consists of a silicone oil repellent layer, a photothermal conversion layer (absorbance layer), an oleophilic layer and a plate base (see Figure 1).


2. Imaging principle

The main function of the light-to-heat conversion layer is to absorb the light energy emitted by the infrared laser and effectively convert the absorbed light energy into heat energy, so that the temperature of the plate surface rises to reach the vaporization temperature level. The photothermal conversion layer in the light region is vaporized by the thermal energy, and the silicone oil repellent layer at the corresponding position is removed by the vaporization of the photothermal conversion layer under the action of heat, so that the lower lipophilic layer is exposed to become the ink receiving plate. The part of the text; the photothermal conversion layer of the unexposed light region did not vaporize, and the silicone oil repellent layer at the corresponding position did not change, forming a blank portion of the printing plate (Fig. 2).


3. Edition

The plate base of such a plate can be either a metal plate base (such as an aluminum base) or a flexible polymer base (such as a polyester base), and has a relatively wide adaptability. This plate is suitable for on-machine plate-making systems because it can be printed after laser imaging.

Although this type of plate is also a direct plate that does not require post-treatment, it is necessary to take necessary measures for the sewage treatment to generate ablation vapor and debris during the imaging process, otherwise it will cause pollution to the imaging optics and the environment.


(2) Thermal cross-linking plates (preheating type, negative type)

1. Composition of the plate

The thermally crosslinked plate is composed of a heat sensitive coating and a hydrophilic plate. The heat-sensitive coating is generally composed of an (alkali) water-soluble film-forming resin (phenolic resin), a heat-sensitive crosslinking agent, and an infrared dye; the hydrophilic substrate can use the same aluminum plate as the conventional PS plate (Fig. 3). .


2. Imaging principle

The function of the infrared dye is to effectively absorb the light energy of the infrared laser and convert the absorbed light energy into heat energy, so that the temperature of the heat-sensitive coating layer can reach the reaction temperature of the heat-sensitive crosslinking agent; The reaction with the film-forming resin under the action of temperature forms a spatial network structure, so that the heat-sensitive coating loses water (alkali) solubility. Due to the effect of space cross-linking, the heat-sensitive coating of the light-receiving region undergoes cross-linking reaction in the action of heat. The film-forming resin changes from a small molecule to a macromolecule, from a linear molecule to a network molecule, and has no alkali solubility. After the development treatment, the pattern remains as a lipophilic image portion; the heat-sensitive coating layer in the light region is not cross-linked, has alkali solubility, is dissolved during development treatment, and reveals a hydrophilic substrate to become a pro The blank part of the water (Figure 4).


3. Preheat treatment

In order to further improve the effect of thermal cross-linking, some plates are often pre-heat treated after exposure to further deepen the thermal cross-linking effect (also an increase mechanism for increasing sensitivity). This type of plate is called a thermally crosslinked plate that requires preheating. The graphic area of the heat-cross-linking plate is composed of space-crosslinked polymer resin, so these plates usually have very high mechanical strength and printing durability, and can generally print hundreds of thousands of marks, which is very suitable for long-distance printing. Market (Figure 5).


(3) Thermal decomposition type plate (pre-heat treatment, positive type)

1. Composition of the plate

The thermally decomposed plate is composed of a heat sensitive coating and a hydrophilic plate. The heat-sensitive coating layer is generally composed of a film-forming resin insoluble in water (alkali) and an infrared dye; the hydrophilic plate group may be an aluminum plate base.


2. Imaging principle

The function of the infrared dye is to effectively absorb the light energy of the infrared laser and convert the absorbed light energy into heat energy, so that the temperature of the heat-sensitive coating layer can be decomposed by weakening the chemical bond connection of the film-forming resin on the surface of the plate material, thereby making the heat sensitive The coating has water (alkali) solubility. The heat-sensitive coating in the light region is decomposed by the action of heat, has alkali solubility, is dissolved during development treatment, and reveals that the hydrophilic plate becomes a hydrophilic blank portion; the heat-sensitive coating of the light region is not visible. The decomposition reaction occurs, and it does not have alkali solubility. After the development treatment, it remains in the image portion of the plate which becomes lipophilic (Fig. 6).


(4) Thermal transfer plate

1. Composition of the plate

The heat transfer direct plate is composed of a ribbon and an image receiving substrate. The ribbon is composed of a heat-resistant polymer base and a heat-sensitive layer (hot wax layer). The hot wax layer is composed of a low-melting polymer material and an infrared dye; the image-bearing substrate itself has good hydrophilicity (such as an aluminum plate). The main function is to accept the hot wax layer transferred by the ribbon and to construct a hydrophilic non-printing surface.


2. Imaging principle

When the image is in close contact with the image receiving substrate, the infrared dye in the light region absorbs the infrared laser light energy and converts it into heat energy, so that the temperature of the heat sensitive layer rises and the polymer of the hot wax layer melts, thereby melting the heat. The wax layer is transferred to the image receiving substrate to form a lipophilic image portion; the infrared dye that does not see the light region does not absorb the infrared laser light energy, the hot wax layer does not melt, and the image substrate does not receive the hot wax layer polymer material. A hydrophilic blank portion is formed. In order to improve the mechanical strength of the image area, it is often necessary to cure the hot wax layer transferred on the surface of the image receiving substrate at a higher temperature to crosslink the hot wax layer to form a spatial network structure. Although such a plate does not require post-development processing, the separate ribbon and the image receiving substrate may cause inconvenience in use and control, increasing the variable factor (Fig. 7).


(5) Thermally induced phase change plates

1. Composition of the plate

The plate is composed of a heat sensitive coating and a support substrate. The heat-sensitive coating has sufficient hydrophilicity (oil) and can be converted into lipophilic (water) under the action of thermal energy to become a graphic (blank) part.


2. Imaging principle

See the heat-sensitive coating (hydrophilic) in the light region, the infrared laser light energy is converted into heat energy, and the hydrophilic heat-sensitive coating layer undergoes physical and chemical reaction under the action of heat, becoming lipophilic and becoming a lipophilic graphic part; The heat-sensitive coating (hydrophilic) in the light region was not observed, and no physical and chemical reaction occurred, and it remained hydrophilic and became a blank portion. The plate base of this plate is only the support of the heat-sensitive coating, and does not participate in the final printing, so there is no affinity requirement, and it may be a polymer base or a metal plate.


(6) Free processing technology

Thermal ablation, heat transfer, and thermal induced phase change in thermal technology do not require subsequent chemical treatment processes, and can be printed on the machine, and thermal transfer and thermal induced phase transitions do not generate ablation debris and vapor during laser imaging. Fog, etc., saves time and saves investment in post-processing equipment and potion consumption.


Third, thermal CTP features


(1) Advantages of thermal CTP technology

1. High quality

(1.1) By using digital plate imaging technology, it is possible to obtain a clearer and sharper dot than the analog plate imaging technology (CTF). The shape and size of the dot are tighter and finer, and can produce 1% to 99% under the 300 lpi screen number. The dot, the dot diameter can be as small as a few microns, the edge is very straight, and the surface is very flat, which optimizes ink delivery.

(1.2) A more accurate plate registration can be achieved.

(1.3) There is no problem of post-exposure treatment caused by dust, film edge, etc.

(1.4) FM network points can be used. FM screening plays an important role in improving the quality of printed matter and improving the effect of ink. FM screening can produce higher density, smoother levels, more stable mesh tone, and affect the machine's dot gain; FM screen is not easy to form moiré, so you can use more ink to print. The collection of small dots has a longer side length than a large dot. The accumulation of ink on the edge of the dot will exceed the edge, so the FM screening increases the gain of the dot than the AM.

(1.5) Reproduce a larger tonal range (can reproduce better brightness and dark tone details).

(1.6) Smaller dot gain and thicker printing ink layer.


2. High aging

1 shorten the time of printing preparation through digital workflow; 2 there is no revision, dirty process; 3 faster digital calibration through digital settings; 4 shorter ink matching time (ink preset); 5 higher Reality (shorter delivery time).


3. Low cost

1 Using digital workflow can save material, manpower and working time; 2 saving film and film development, fixing syrup and punching machine investment; 3 fewer waste pages, reducing ink, dampening solution and paper consumption; 4 Reduced standby time due to manual revision or printing process, improved utilization of printing equipment and post-press equipment; 5 helps to achieve digital workflow for management, prepress, printing and postpress processes (CIP3/ CIP4) makes the entire workflow faster and more efficient.


4. High resistance to printing

Thermal plates are not easily worn and last for a long time. After baking, the printing durability can reach 1 million to 2 million impressions.


(2) Insufficient thermal CTP

Thermal imaging technology also has shortcomings, and the overall price is higher. First, the price of thermal plate is higher. The price of thermal plate on the market is higher than that of visible image, which is more expensive than the traditional offset PS plate. The second is the energy required to expose the thermal plate than the exposure of visible plate. The need is bigger; the third is that the price of the thermal system is relatively high.


All in all, thermal imaging technology has been around for many years, and the maturity and stability of thermal CTP technology has been recognized by the industry. Although the thermal CTP market is relatively stable, there are many variables, and there are many trends in the market for thermal CTP and violet laser CTP.

Send Inquiry