1 Development of dry silver imaging technology
Since 1964, the United States 3M Corporation proposed for the first time the use of thermal imaging for the silver salt imaging technology. After the “Silver Silver†imaging technology, Kodak, Fuji, and other camera companies have conducted a large amount of basic research in this technology field until In 1995, 3M company marketized the technology and pioneered the medical image dry processing system.
In 1998, Kodak purchased 3M's dry silver imaging technology and began to launch DryView series of medical products, including the DryView laser imager and supporting infrared laser film. Fujifilm and Agfa also launched an output film in the next few years. Complementary imaging systems, including laser imagers, conform to the trend of digital medical imaging technology. In addition to being used primarily for medical imaging, dry silver materials are also used in microfilming and printing platemaking industries. There are currently a small number of patent applications for colored dry silver materials, but market products are rare.
2 Dry Silver Film Structure, Imaging Principles and Advantages
2.1 Structure
Unlike traditional silver halide film, dry silver film is a photographic material that is exposed by laser and imaged by thermal development. Its structure is mainly composed of a protective layer, a photosensitive layer, a bottom layer, and a support. If necessary, an anti-halation layer can also be applied.
Photographic imaging layer features: Photosensitive imaging layer is mainly composed of 4 parts:
(1) The main source of silver for image production - non-photosensitive organic silver salts such as silver behenate, silver stearate, and others.
(2) Reducing agent (usually includes developer).
(3) A small amount of silver halide that catalyzes the development of the imaging process.
(4) Hydrophilic or hydrophobic binders. Unlike the preparation of a conventional light-sensitive silver halide emulsion, the photosensitive imaging coating includes a developer, whereas in a conventional photographic system, the developer is a chemical processing liquid, and the film itself does not include a developer.
In addition, binders used in the preparation of dried silver emulsions exhibit diversity, such as gelatin, gelatin derivatives, polyvinyl alcohol, polyacetal substances, and various other polymers which can be used as binders, and silver halide photosensitive materials Only one kind of gelatin in the adhesive.
2.2 Imaging principle
The dry silver imaging process is a catalytic process. A small amount of silver halide in the dry silver material can form a catalytic center under the irradiation of low energy light, and any visible light, ultraviolet and infrared rays from 1 to 10 Erg can expose it. The non-photosensitive organic acid silver and the reducing agent are subjected to an oxidation-reduction reaction under heating to generate a permanent silver image, i.e., the image-forming silver is derived from a non-photosensitive organic acid silver.
We can see from the imaging principle of dry silver products that the main advantages of dry silver film include three aspects:
(1) Environmental protection: Chemical processing liquids are not required, and waste liquids and waste water are not generated, of course.
(2) Easy to use: No dark room operation required.
(3) In addition to the above advantages, the laser imager currently processing dry silver film has a small footprint, for example, Agfa.
The company's Drystar 2000 can be placed on the desktop.
3 Current Market Silver Film and Technical Progress
3.1 Product Technology Status
At present, the traditional camera companies Kodak, Fujifilm, and Agfa have monopolized the global dry silver imaging market and launched laser imagers and related consumables with different innovation systems.
In the same type of dry imaging system, Kodak's DryView system has maintained a leading position in technology and market. The system occupies more than 50% of the global market share. By October 2002, Kodak has installed 20,000 units worldwide. DryView laser imager.
In 2003, for the larger market demand in North America, Fujifilm's X-ray film factory in Greenwood City, Fuji, has begun production and sale of medical water-soluble dry silver film. Water-soluble dry silver film is more environmentally friendly than solvent-based film. The first factory in the United States to manufacture water-soluble medical dry silver films, and the products are exported to Canada and Mexico in addition to meeting the needs of North America.
3.2 From the patent point of view, technological progress, water-soluble dry silver material is the future direction of development
According to the carrier of the photosensitive imaging layer coating solution, dry silver film can be divided into two types of solvent-based and water-soluble products. Most of the dry silver films currently in use on the market are solvent-based products. Some of Kodak's, Fujifilm's, and Agfa's products are also solvent-based. Currently, only Fujifilm USA produces water-soluble dry silver films. The solvent-based products are not only harmful to the human body during the production process, but also have high costs. The water-based dry silver materials do not have similar problems. In the patents published by the USPTO in the first half of 2003, Kodak disclosed 14 patents for dry silver, of which 6 Water-soluble dry silver technology is involved. Fuji and other companies also have patent applications involving water-soluble dry silver materials. This marks that water-soluble dry silver materials have attracted the attention of developers and will become the future direction of development.
3.3 The contents of the latest dry silver imaging technology patents
In the first half of 2003, the dry silver technology patents disclosed by the USPTO were mainly related to medical film. The current dry silver film has not been perfected and improved in terms of photographic performance in terms of photographic performance. It mainly solves four problems:
(1) Development and application of new chemical sensitizers;
(2) reduce Dmin, increase Dmax;
(3) To reduce the fog of the dry silver material before and after the development;
(4) Improve the coating performance.
4 Status and Development Prospects of Dry Silver Imaging Products Market
A recent investigation report by Lyra Corporation of the United States pointed out that the consumption of medical dry film is due to the simple imaging of dry materials, the convenience of processing, the increasing number of global digital X-ray imaging equipment CR and DR, and the establishment of remote image information storage and communication systems. Will gradually exceed the traditional wet processing film, and with the continuous improvement of digital imaging technology, the medical imaging industry will eventually cancel the use of film, but in the next few years, as the social population tends to aging and people's health awareness The overall global consumption of medical film (including dry and wet) will also increase.
In recent years, in some developed countries, the consumption of wet film has been declining year by year, and dry film has received more and more attention from people. Its consumption has increased year after year. For example, currently more than a quarter of medical X-ray film consumed in North America is dry film, and nearly one-third of the film consumed in 2005 is expected to be dry film.
At present, the traditional wet film in developing countries is still the main product of medical film, but the image quality of dry film has been recognized by the hospital and is the development direction of medical film in the future. According to relevant data, in 2002, China's domestic ray film market capacity was 21 million square meters, and dry thermal film was about 1.4 million square meters.
From the technical characteristics of dry silver film and the current market application, the demand for dry silver film, especially medical dry silver materials, may increase year by year, and the market prospects are bright. However, since the advent of dry silver imaging technology and the marketization of products has been going on for more than 30 years, and in addition to film, dry laser imaging systems and software systems are also a very complex part of traditional silver imaging systems. Kodak, which is very strong in the field of photography technology, is also able to grow in the new imaging field by purchasing 3M's dry silver imaging technology. At present, there is a certain gap between us and Kodak, whether it is talent or technology. We should take Kodak as an example and accelerate the pace of product development through technical cooperation channels to meet market demand.
Author/Wang Rui
Source "Image Material"