Violet laser and thermal laser competing for CTP equipment

Not long ago, the fierce debate over computer-to-plate (CTP) technology was whether to purchase an external drum plate machine or an internal drum plate machine. And a few years later we are faced with the coexistence of these two technologies, and both are viable options.

Manufacturers of CTPs are increasingly concerned about the needs of small and medium sized printers, and there is an increasing discussion of emerging violet laser technologies and what they mean for printers. Some companies that produce multiple types of platesetters, such as Agfa, Barco, Krause, and others, are now also equipped with violet-emitting laser heads in their devices. The new argument that followed appeared: Is it a violet laser or a thermal laser?

Purple laser imaging technology Many questions are raised about the application of violet laser technology in CTP systems: What are the costs compared to thermal imaging systems? What is the expected life of violet lasers? What is the imaging quality? Who will provide the plates with violet lasers? Problems such as this one must be considered by anyone who wants to invest a lot of money in the CTP system.

Purple laser diodes are used not only in the printing industry, but also in other fields, even on the next generation of ultra-high-quality DVD devices. Although the use of violet laser diodes in many fields is expected to reduce its price, there is still a large amount of information about what the price of it will be for the total price of the platesetter. For some small printers, if the price of the platesetter drops by $10,000 to $20,000, it is possible to decide whether to purchase a CTP. The only retailer of purple laser diodes is a Japanese company, Nichia ().

The emission spectrum of the violet laser is in the range of 391-420 nm, and the resulting laser spot size is very small, so the resolution of the imaging is very high, and the desired gray level can still be obtained when screens are screened with high screens. The current lifespan of violet laser diodes is 3000 hours. Mainly related to the working time of the diode and the exposure range on the plate. For example, it takes 3 minutes to expose a 30 x 40-inch plate, and 20 plates per hour can be exposed. According to this algorithm, a diode can expose a total of 60,000 plates, and its lifetime expires (assuming all media sizes are 30×40).

The CTP system using violet laser diodes can be operated in a yellow safety light environment. This is undoubtedly a good news for those who deal with visible light under the red security light. The use of violet lasers eliminates the need for preheating and does not require baking after imaging. This is particularly useful for small print or medium-sized printing companies that do not have a lot of space for operations. At present, Agfa is the sole supplier of Lithostar Ultra-V for violet laser printing. The printing rate of this type of plate is 350,000 sheets (as with other printing plates, this data will change with the printing environment, paper, and ink), and the reproducibility of dots when performing 250 lpi screening is 2%-98. %. CitiPlate is also developing a more powerful violet laser diode Aqua-LHP, which will be another option. Mitsubishi Chemicals and Fujifilm will also launch corresponding violet laser plates in the coming months.

Thermal laser technology Thermal laser technology has been used for many years. Many well-known manufacturers, such as Heidelberg, Sai Angel (production drum type), Cycbolic Science (production drum type), have adopted a large number of thermal imaging platesetters. The spectral emission range of thermal laser heads is 830-1064 nm, and some devices claim that their imaging resolution can reach 4000 dpi. The life of thermal laser is more than 5,000 hours. It's time to turn on, not necessarily on the plate. For example, a thermal plate-making machine works 1 shift 8 hours a day, works 260 days a year, and its service life is at least 2.5 years.

The CTP system with a thermal laser head can be operated under the light room. Depending on the amount of printing required, plates can be preheated or baked, or baked at all. Unbaked plates have print rates ranging from 100,000 to 150,000. The preheating of the plate prior to exposure can be increased to 250,000 impressions, while the image can be increased to 1,000,000 impressions or more after baking. Bakeplates require an oven - this requires sufficient space for installation. A device for developing the baked version is 22 feet long. In addition, the electric power required for baking is also very large and cannot be ignored. The temperature of the test box can reach 500oF. Therefore, a set of devices should be used to discharge this energy. Agfa, Fuji, Kodak Polaroid, Presstek, and others can provide hard thermal plates. With the participation of a large number of manufacturers, the competition has become more intense and the prices of plates have been declining.

The reason why the thermal technology was given so much attention at drupa in 1995 was because people saw the prospect of not needing imaging media. PDI and Presstek recently introduced plates that do not require development or simplified development. Products from Kodak Polaroid are also in Phase II testing. This is still the biggest advantage of thermal imaging under visible light. This is what the industry people are relentlessly pursuing - no plate is beneficial to the environment and operators. No development means no chemical change process, reduced costs, and reduced downtime due to cleaning and maintenance. In recent years, operators will choose from more types of non-developed plates.

Perhaps laser technology used on CTP systems is the driving force behind its continued advancement. The development of thermal laser technology is relatively slow, and UV laser technology continues to develop. The trend is to continuously increase the exposure speed, resolution, and diode lifetime and reduce costs. The efforts of CTP producers will give customers more choices. Computer direct platemaking is no longer the choice of large companies - the constant innovation of the platesetters and plates is for small and medium-sized printers.

Polyester Plates Are Widely Accepted Most of the previous articles and discussions related to CTP have focused on the advantages of metal plates. In fact, polyester plates have gradually been accepted by the industry. 20 years ago, the material was easily deformed and stretched, which made it difficult to position the printing plate. Now it is no longer a problem.

Agfa, Mitsubishi and Presstek have all developed new types of polyester plates that are more durable and have higher image quality. Their durability has also increased (up to 20,000 sheets), and they can maintain a better number of screens (up to 175 lpi). Positioning problems in the printing process have also been improved. In the past, polyester plates could only be used for products with a single color or less strict registration. Now, polyester plates can be used to print fine four-color products.

Polyester plates have received constant attention and acceptance, especially in small-scale printing companies. There are many reasons. First, the cost is only a small part of the metal plates, and there is no need to purchase plate-making machines, which can be used on existing photocopying devices. Imaging. This reduces costs for those who do not want to invest immediately in the platesetter or who have not yet determined that the technology will contribute to the market. At the same time, the polyester plate fits well into the short-run market. Surveys have shown that the volume of short-run printing is on the rise, and small-scale printing does not need to face the printing rate required by large companies.