Color printing, proofing (on)

Color platemaking is the former process of color reproduction and is the basis for color reproduction. Color platemaking mainly includes color separation (including electronic color separation and computer color separation), imposition (including manual imposition and computer imposition), and copy (copy large picture negatives that have been put together into full-version positive picture color separation sheets). , Shai Ban (the positive image separation color plate to the PS version), proofing and other major processes. The factors that affect the quality of the final product are extremely complex, and the variable factors in the color platemaking process are also numerous, including manuscripts, environmental conditions, raw materials, equipment conditions, process conditions, operator quality, and quality management levels. As a principle of color platemaking standardization, the first is to stabilize all kinds of variable factors as much as possible; the second is to start from the post-process to provide a normative basis for the pre-process.
Here we analyze the specification requirements for printing and proofing.
one. Specification of the printing process requirements 1, environmental conditions - room temperature: 20 °C -25 °C, daily monitoring.
- Clean: Clean the environment daily.
——Power network quality: Regulators are required when the power grid fluctuates by more than ±10% of the rated voltage.
- Water Quality: In the case of poor water quality, it is recommended to use distilled water to prepare the developer.
2. Raw material requirements - The brand and model of the fixed PS version. When changing models and batch numbers, the PS plate should be routinely tested to confirm the quality of the PS plate or modify the process parameters.
- Through the use of instructions, confirm the PS version of the light source spectrum, intensity, exposure time, development kits and the general requirements for developing conditions, so as not to appear raw materials and equipment and process conditions do not match the situation.
——Confirm that the date of manufacture, storage period and storage conditions of PS plates and kits should be within the normal range and requirements.
3. The original (positive image) requirements - film base density ≤ 0.08 (film base should not be too much overlap).
- (Field density) ≥ 3.00, preferably above 3.50.
- The dots and lines are clear and true.
——The position of the picture and text is correct, the size is suitable, the film is consistent, and the layout is clean.
4. Equipment requirements - the spectrum of the printing machine is suitable (350 ~ 450nm), the light intensity is more than 3000 W (usually an iodized zinc lamp), the light intensity is stable, the printing plate surface is uniformly irradiated (non-uniformity ≤ 15%), vacuum pumping The gas system is normal (the rated vacuum can be reached during operation).
——The glass surface of the printing machine is clean and free of dust, spots, fingerprints, and scratches. Clean it several times a day.
- The temperature, speed, replenishment, and agitation systems of the PS plate processor are normal; the processor is cleaned periodically (for example, weekly) and the mother liquor is replaced.
5. Process conditions - print control strip: The test strip is mainly used to determine the correct exposure time and evaluation of the PS version of the exposure, the quality of the development. The test strips consist of continuous ash grading scales (with a density difference of 0.15 to 0.16 per level) and with fine dots (Yang because of 0.5%, 1%, 2%, 3%, 4%, 5%; and 95%, 90 %, 97%, 90%, 99%, 99.5%) and thin straight lines (such as black or white lines having a width of 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, etc.).
- Printing process requirements: After fixing the PS plate development conditions (temperature, speed, concentration), according to the different exposure time on the PS plate with continuous ash scale and measurement and control strips for printing (gray scale and measurement bar The thickness of the underlying white film base should be the same as the actual original.) Finally select the appropriate exposure time that meets the following requirements:
· For Proof PS version (new version):
After printing and development, corresponding to O.50 ~ 0.60 density ash steps, it should have just emerged latent image (just inked); the transition level is 3 to 4 steps. 1% small outlet Qi, 99% outlets do not paste.
·For proofing PS version (recycled version):
With the above specifications, but require 2% of small outlets, 98% outlets do not paste.
· For printing PS version (new edition):
After printing and development, corresponding to 0.80 to 0.90 density ash steps, the latent image should have just emerged; the transition level is 3 to 4 steps. 2% of small outlets Qi, 98% outlets do not paste (printed version of the printing version is longer than the proofing version, is to make the printing version of the network, especially the intermediate tone point than the proofing version is slightly reduced, to make up for printing pressure than the proofing caused by too large Errors caused by dot gains).
· PS plate development temperature, speed, concentration (supplemented amount) should be referenced according to the use of kit requirements, one case should not be constantly changing, if you need to change, you should promptly check the quality of the plate after development.
· Whether baking (printing plate) is required or not is determined by the resistance force. The temperature and time of baking should be within the specified range.
• Whether or not the printing plate of the PS plate is protected after printing is developed depends on the printing time after printing. Keep drying time as short as possible. The proofing version is not glued in principle.
· PS version should be almost complete, no curling, lotus leaf phenomenon. (To be continued)