Basic knowledge: CTP classification (1)

1, CTP classification

At present, according to different classification methods, CTP systems have different classifications.

(1) According to the working mode of the computer-to-plate system, the CTP plate-making machine mainly includes four types: inner drum type, outer drum type, platform type, and curve type. The curve type is rarely used. The following briefly introduces the features of the first three CTP systems.

The external drum CTP system is suitable for thermal plates and is suitable for large format. Due to the large amount of energy required for the thermal printing plate, the light source must have a large power, while using multiple laser heads. However, the size of the plate suitable for this type of CTP system is small, the rotation speed of the drum is not high, and the plate changing speed is relatively slow. Kodak and NetScreen have products with this type of exposure.

The inner drum CTP system is not suitable for large format output plates. However, this type of CTP system has a faster scanning speed and higher accuracy. At the same time, due to the use of a single-beam laser head, the price is relatively cheap, and the plate change is also simpler and more convenient than the external drum CTP system. It can simultaneously support a variety of punching specifications. Both ECCO and ECRM have mature products using such exposure methods. .

The platform CTP system also uses a single-beam laser head, which has a relatively inexpensive price. At the same time, this kind of system has a simple mechanical structure, stable operation, and high scanning speed, but it has a large area and is not suitable for large format printing plate output. Such representatives mainly include Barco's CTP system.

(2) According to the exposure light source, the light sources mainly used in the CTP system include gas lasers, solid-state lasers, and semiconductor lasers. The two types of CTP systems that currently exist on the market are violet laser CTP and thermal CTP.

The imaging technology of the violet laser plate making system is recognized as a durable, high-reliability technology. The CTP equipment made by combining the imaging technology with the violet laser technology has gradually gained recognition from the market in the past few years. Its characteristics are: Low purchase costs, low operating costs, and high operating speeds.

The advantage of the thermal technology is that the image quality is good, and the image hierarchy can be well restored for negative and positive images. However, thermal CTP has a high cost for small-format printing and is not competitive in the field of thermal newspapers, but there is a relatively large market in the field of commercial printing with high-precision copying requirements.

(3) According to the degree of automation, the CTP system can be divided into: manual stand-alone, semi-automatic, fully automatic, and hybrid (CTF-computer to film and CTP-computer to plate).

(4) From the aspect of the fixing method of printing plate on the drum, it can be divided into: full adsorption type and middle adsorption, and two types of card holders are fixed at the end and end. There is no limit to the size of the plate for full adsorption, and the size of the plate for the clip type must be fixed.

(5) From the aspect of application, it can be divided into commercial CTP system and newspaper CTP system.

2, CTP plate classification

At present, there are mainly three types of CTP plates that dominate the market: silver salt type, photopolymerization type, and thermal type (thermal imaging type). Below we mainly look at the characteristics of these several kinds of plates and their advantages and disadvantages.

Three types of media performance comparison

Types of

silver salt

Light Poly

Together heat Sensitive

Laser wavelength:

532nm

405nm

830nm

Light source energy:

<5mw

>30mw

40w

Media sensitivity:

μJ/cm2

mJ/cm2

J/cm2

Plate speed:

>180 sheets /h

<80 sheets /h

<30 sheets /h

Network reproduction:

2%-98%

2%-98%

1%-99%

Adaptation:

Newspaper industry

Business , Newspaper

business

Silver salt type CTP plates mainly include silver salt diffusion transfer plates and silver plates and PS plate plates.

The silver salt diffusion transfer plate is mainly composed of a base plate, a silver salt emulsion layer and a physical development core layer. It uses diffusion transfer imaging technology. The principle is the silver salt version exposed by laser scanning. In a developing solution containing a silver halide solvent, Ag+ complexes with the silver halide solvent and diffuses to the image receiving layer, catalyzing the physical development of the core. Under the effect of reduction into metal silver,

Deposited on the body surface to form a silver image. After the development is completed, the surface of the silver halide emulsion layer is removed by washing to expose the hydrophilic sand and image areas in the non-image area, and is selectively adsorbed on the surface of the deposited silver by a long-chain fatty molecule with a mercapto group in the sensory fat solution. Make the image area oleophilic. As a result, the deposited silver image begins to accept the ink and repel the water, while the non-image part (without silver deposition) still repels the ink, thereby achieving the purpose of direct computer platemaking.

The composite plate of silver salt and PS plate is mainly composed of a high-sensitivity silver salt emulsion layer and a PS plate with a wide color sensing range. A presensitized photosensitive polymer layer, an adhesive layer, and a silver halide emulsion layer were sequentially coated on the roughened and anodized aluminum substrates. The principle of imaging is to first expose the silver salt layer with a laser to form a graphic silver image on the resin layer, so that in the second exposure, the underlying photosensitive layer can be protected from light. After one development, the non-exposed parts of the emulsion layer are dissolved and then exposed twice, that is, the entire plate is exposed with UV light. Since the image and image layer blocks the light, the UV light only exposes the photo-degradable photosensitive resin layer that is not the image portion, and the second-developed and double-exposed resin layer is dissolved to expose the aluminum oxide substrate. Finally, the silver image layer can be treated with a solid solution.

Characteristics of Silver Salt CTP Plate

(1) Silver salt type CTP plate has high sensitivity, which can reach 1 ~ 3μJ/cm2, that is, the use of low output power, low energy, low intensity laser can also achieve high speed plate output. Moreover, the silver salt type CTP plate has a fast photospeed and is the fastest plate material in the CTP plate.

(2) The silver salt type CTP plate has a wide range of applications. The red laser, green laser, and violet laser systems can be used. The rinsing methods and post-treatment processes are the same as the traditional methods, and different manufacturers' CTP plates are used for chemical solutions. The formula is compatible.

(3) The silver salt type CTP plate has the characteristics of high resolution, wide spectral response and good dot reproducibility. The number of screen lines can reach 300 lines/inch, and dot coverage can reach 1% to 99%. Plate quality Excellent, resistant to print force up to 250,000 prints, more suitable for large print and high quality printing.

(4) As the silver salt type CTP plate adopts expensive silver as the raw material, the production cost is increased to a certain extent, and the silver salt type CTP plate material cannot be operated under the light room, and it brings certain preservation to the plate material. Limitations.