Application of non-diazonium naphthoquinone type positive PS plate (1)

I. Foreword

From the 1930s, the German company Carlyle invented the naphthoquinone-based positive PS version. Now, this version has been successfully applied for nearly 70 years. It has become a medium with a long history and cross century. So far, the photosensitive composition of the positive-acting PS plate used in the world has almost always been a system in which a diazonaphthoquinone sulfonic acid ester is a photoactive compound as a solvent-blocking agent. Especially in China, it is the only photosensitive composition of the positive graph PS (Yonegihiko Yonezawa: Introduction to the PS version, Japan Printing Society Publishing Department, 1993). Although there are many researches on the photosensitive composition of positive PS plates, for example, in the 1960s and the 1970s, people had studied the photosensitizing composition system of poly-o-phthalaldehyde positive PS plate; in 1980s, IBM invented the chemical amplification resistance. After the agent, he tried to transplant it into the production of the positive PS plate, but because these systems were either too expensive due to raw materials, the resulting photosensitive composition cost was too high, or because the plate making process became more complicated, plus the resulting The comprehensive performance of the plate is not better than that of the original diazonaphthalene-type PS plate, so in addition to its popularization and application in photoresists, it has not been popularized and applied in the positive PS plate. However, by the 1990s, the principles and design ideas of chemically amplified resists have been promoted in thermal CTP plates.

In 1990, Dennis et al. of 3M Company disclosed a patent for a photo-resist composition using a photo-active ester compound of diphenylacetic acid as a photosensitive composition of a PS plate. However, the photoactive compound (PAC) as a solvent has the following disadvantages: First, the compound itself is a low-viscosity liquid, and is easily dissolved in many organic solvents, especially in printing ink solvents. The PS printing plate coated with it as a photosensitive composition has a very low printing resistance; another major drawback is that the storage stability of this compound is poor, and it is found to be automatically decomposed into diphenylacetic acid after being stored at room temperature for several weeks. So even though they applied for a patent, they never saw a commercial PS version.

In recent years, in order to meet the needs of users for high-sensitivity plates, especially for CTcP platesetters' requirements for high-sensitivity plates, Agfa has introduced P-51 and P-61 high-sensitivity positive-charged PS plates, KPG launched. Virage type positive PS version, Fuji company launched VQ type positive figure PS version, and some companies are also actively researching and developing. Most of these new plates are non-diazonium naphthoquinones.

Recently, we learned from the basic principle of acid-base amplification at room temperature in chemically amplified resists. Through ingenious synthesis and formulation design, we developed a new type of non-diazonium naphthoquinone-based positive photosensitive composition for PS, which is used to coat The sensitivity, resistance, contrast, development latitude and other properties of the positive PS plate are higher than those of the traditional diazo naphthoquinone positive PS plate, which has good industrialization and commercialization prospects. .

Second, the basic principle of the new non-diazonium naphthoquinone positive photosensitive composition of PS version

As mentioned earlier, its basic principle is based on chemically amplified resists, and in particular, the basic principle of the near-normal catalytic acid amplification at room temperature. In the photosensitive composition, the photoactive compound used, ie, the solvent-blocking agent, is a novolac resin or a linear polymer having a carboxyl group linked thereto, and a keto or acetal protecting group is used to dissolve the alkali-soluble phenolic hydroxyl group. The carboxyl group is protected as a solvent for the photosensitive composition, and a photosensitive composition is formed by blending the film-forming linear phenol resin and the photoacid generator. When the photosensitive layer of the PS plate is exposed through the film, the acid generated by the light-receiving portion decomposes to generate acid, and the resulting acid can immediately remove the protective group at room temperature, releasing the phenolic hydroxyl group or carboxyl group, and blocking the photoactive compound. Dissolve into solubilized solution and develop with alkaline developer to obtain positive image. Photoactive compounds from the dissolution of solution into the principle of solubility.

Third, the performance characteristics of the new type of non-diazonium naphthoquinone positive PS version

High sensitivity

The previously used diazo naphthoquinone positive PS plate has a low sensitivity, and the general imaging exposure is 200 to 400 mJ/cm 2 . The VPS version of Fuji Film Co., Ltd. and the YPS version of the second Film Factory of Lucky Films Group are listed in the high-sensitivity diazonaphthalene-type positive chart PS version, and the image exposure is 100 to 150 mJ/cm2. The imaging exposures of the new non-naphthoquinonediazide positive PS plates developed by us were below 50mJ/cm2, and some were as low as 10mJ/cm2. Compared with the diazo-naphthoquinone positive PS version, the sensitivity has been improved a lot. This not only meets the requirements of users of the printing press and other high-sensitivity PS printing plates, but also satisfies the high sensitivity of the CTcP platesetter system to the plate material. The request.

2. Good resolution and dot reproduction

The resolution of traditional diazo-naphthoquinone positive PS plates is excellent, and this system is at the same level as the diazo-naphthoquinone positive PS plate. If the aluminum substrate has an Ra value of about 0.5, an Rh value of 2 to 4 μm, and an anodized film of 2 to 4 g/m 2 , a photo-sensitive layer of about 2 g/m 2 is coated on the aluminum substrate, and its resolution is Can be greater than 250 lines / inch, the minimum resolution of the line up to 6μm, can clearly reproduce 2% to 98% of the network. If the exposure and development conditions are well-controlled, dots of 1% to 99% can be reproduced.

3. High contrast (large γ value)

For a positive resist and a positive photosensitive composition for PS, it is theoretically preferable that the larger the value of γ, the smaller the number of transitions is, the better it is if it is detected by grayscale exposure and development. If the exposure is developed with a gray step scale with a step density of 0.15, under the most suitable exposure and development conditions, the number of transition segments obtained from a normal diazo naphthoquinone positive PS plate is 4 to 5 segments. This range, contrasting PS version of the transition section up to 6 or more. Fujifilm's VPS version is quite good, with only 2 to 3 transitions. The number of transitions refers to the number of segments (4 segments) between the highest segment of the number of wash segments (eg, 3 segments) and the highest segment (eg, 7 segments) where very slight resolution occurs. This evaluation method is basically the same as the number of transitions observed after inking. Some people use the difference between the highest number of discoloration and the highest number of washings as the number of transitions, which tends to produce large deviations. Because the PS version is now commonly used in color or subtractive color technology. In this case, the number of discoloration segments observed is large. In fact, the discoloration does not always occur in the defilming, and there is still good ink absorption. After the ink is applied, the ink is masked by the ink. Therefore, the number of observed transitions will be higher than the actual number. Less. The number of transitions in the new system we have developed is generally below 3, and in some cases it is 1 or 0.

4. Weak alkali development, large development latitude

Developing with weak bases is a major advantage of diazonaphthalene-type PS plates. Our new positive-acting PS plates can be developed with diazo naphthoquinone-based PS plate developers. Fujifilm's VPS version has a very large development latitude. It can quickly display images in DP-4 with a dilution ratio of 1:4, such as prolonging the development time, and also in 1:10 developing solutions. Can develop a clear image. The YPS version of the Lokkai Group's second film factory also has similar features, and it can be developed in a 1:5 to 1:12 dilution with its compatible positive-acting PS plate developer. Newer plates can be developed with this developer. The dilution ratio can be chosen from 1:3 to 1:6. It is planned to further improve the development latitude. Such a large development latitude can effectively prolong the service life of the developer and reduce the waste pollution caused by the waste developer. There is still a certain gap between the general PS version in China and the aforementioned latitude. There is also a feature of this new type of material: when developed at a proper development concentration and temperature for a certain period of time, the development time is lengthened, and only the transition is washed out. The number of washed-out segments remains unchanged, and thus a transitional segment of 1 segment or 0 segment can be obtained.

(to be continued)