The positive inspection in the production process of positive chart PS plate

In recent years, China's PS plate technology has developed rapidly and its output has continued to grow. The prosperity of the market will inevitably bring about fierce market competition. If PS manufacturers want to have a stable market share, they must ensure the quality and reputation of their products. Therefore, it is of utmost importance to ensure good product quality in the production of PS plates. Therefore, the quality control of the PS plate must be achieved through the following routine tests.

Raw material testing

The positive PS version consists of a photosensitive layer and an aluminum plate base. The raw materials commonly used in the PS plate production plant can be divided into four parts around these two parts:
1) Various raw materials needed for preparing photosensitive liquid;
2) In order to meet the printing requirements, various raw materials required for a series of process treatment of aluminum base are processed;
3) aluminum plate base for the positive PS plate support;
4) The water quality of the production water for the positive PS version.
In order to stabilize the product quality, before purchasing raw materials, various technical performance indicators of the required materials shall be submitted to the raw material suppliers according to the production requirements; the purchased raw materials must be analyzed and tested on its main technical indicators.
1. The analysis and detection of various raw materials needed for the photosensitive liquid The positive photosensitive solution of PS version mainly consists of photosensitive resin, film-forming resin, dye, solvent and other auxiliary agents.
1) Determination of 2.1.5-sulfonyl chloride properties 2.1.5-sulfonyl chloride is orange-yellow crystals, used for the synthesis of photosensitive resins.
1 Determine the melting point. The melting point of a solid substance refers to the temperature at which the substance is at equilibrium at equilibrium with the liquid state. Very pure substances are very sensitive to changes between solid and liquid states at atmospheric pressure. They do not vary by more than 1°C from the initial melting point to the total melting temperature. If impurities are contained, the melting point decreases and the melting point range widens. Therefore, the melting point can be determined to determine the purity of the compound.
2 Determination of 2.1.5-sulfonyl chloride content. The content of 2.1.5-sulfonyl chloride has a great influence on the photosensitive properties of the photosensitive resin. The purity of 2.1.5-sulfonyl chloride produced by various manufacturers is now higher than 98%. However, in order to synthesize a stable photosensitive resin, the content of 2.1.5-sulfonyl chloride should be determined. The most simple and accurate way to detect the content of 2.1.5-sulfonyl chloride is to use a UV spectrophotometer and a domestic UV spectrophotometer.
3 Determination of UV absorption spectra. Ultraviolet spectrophotometer can be used to determine the maximum absorption wavelength of 2.1.5-sulfonyl chloride.
2) Determination of film-forming resin The film-forming resin is mainly a novolak resin and is a high molecular compound.
1 Determine the molecular weight and molecular weight distribution. The polymer compound is composed of many molecules of different sizes, and the shares of different molecules are different. The width of the molecular weight distribution has a great influence on the sensitivity and resolution. The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution of the phenolic resin can be conveniently and accurately determined by gel permeation chromatography (GPC).
2 Determine the viscosity. The viscosity of the film-forming resin can be measured with a rotational viscometer.
In addition to the above two tests, the melting point of the resin needs to be measured.
3) Determination of Solvent Moisture Content In China, except for a few PS plate manufacturers that use a mixed solvent of ethylene glycol monoethyl ether, butanone, and esters to prepare photosensitive solutions, most manufacturers use only ethylene glycol ether alone as a solvent. However, whether using a multi-component solvent or a single-component solvent, the water content of the solvent must be determined using Karl Fischer Autotitrator.
2. Plate base treatment process analysis The positive figure PS plate base treatment process flow is:
Aluminum coil unwinding → caustic washing → electrolysis → oxidation → hydrophilic treatment 1) Alkali washing Remove grease and natural oxide film on the surface of aluminum plate.
2) Electrolysis A sand grain is formed on the surface of the aluminum plate to increase the surface area so as to increase the hydrophilicity of the non-image area and the adhesion between the aluminum plate and the photosensitive layer.
3) Oxidation A solid AI2O3 film is formed on the aluminum plate after electrolysis to improve the wear resistance, corrosion resistance and stability of the plate.
4) Hydrophilic treatment Reduces the adsorption of the AI2O3 film to the photosensitive layer, improves the hydrophilicity of the non-image area, and reduces the solubility of AI2O3 and Al in the developer.
The content of inorganic acids and inorganic bases in the raw materials used in the PS plate base treatment process was determined by volumetric analysis. When measuring the sodium hydroxide content, since sodium hydroxide for industrial use contains a small amount of sodium carbonate, sodium carbonate should first be converted to barium carbonate precipitation and then analyzed.
3. Qualitative and quantitative analysis of aluminum-based trace elements Detection of aluminum traces usually contains a small amount of trace elements, qualitative and quantitative detection of trace elements can be measured by atomic absorption spectrometry, atomic absorption analysis method with high sensitivity, good repeatability, The operation is simple and fast, but the price of the instrument is relatively high. Manufacturers can regularly go to physical and chemical testing centers for testing.
4. PS version of the production of water analysis and testing in the PS plate production process requires a lot of water, it is best to use deionized water, because the water of the cations and anions will have a certain impact on the PS version, such as halogen ions can oxidize the oxide film and Produce holes.
Deionized water can be prepared by ion exchange. The water quality can be measured by a conductivity meter. Each manufacturer can set the corresponding conductivity value according to the quality requirements of its own production water, and conduct regular measurements.

Product quality control testing

To evaluate the quality of a product, in addition to the properties of the product itself, it must also have good repeatability and stability. Manufacturers should have a set of strict enterprise standard data to control the quality of products.
1. Detecting Solution Concentration for Plate Base Treatment The concentration of the solution used in the plate base treatment process mostly uses on-line detection. During the production process, the concentration of various solutions used in the plate base treatment process is quantitatively tested to achieve the specified index. At the same time, the content of Al3+ in the oil, electrolyte and oxidizing solution should also be measured. Concentration testing can be done with a simple, fast acid-base titration assay. Enterprises with good conditions can install an online detector. At present, the accuracy of the PS version of on-line detection instruments produced in China is not too high, and it is only used as a reference. The actual online automatic detection instrument adopts electrochemical analysis method, which uses the quantitative relationship between chemical composition and voltage, current, conductance, etc. to determine the content of each substance in the process of chemical energy and electric energy conversion.
2. Inspect the product's intrinsic quality 1) Plate base performance testing 1 Surface roughness. The surface roughness is measured by a surface roughness tester, which is generally assessed by technical parameters such as Ra, Rz, Sm, etc.
Ra - the arithmetic average of the absolute values ​​of the profile offset within the sampling length;
Rz - the sum of the average of the five largest peak heights in the sample length and the average of the five largest valley depths;
Sm - The average of the intervals of the profile micro-nonplanarities over the length of the sample.
The density D of the profile peak can be calculated by Sm:
D=L/Sm, where L is the sampling length.
2 oxide film. The evaluation of the quality of the oxide film mainly depends on the integrity and density of the oxide film, the crystal structure and the thickness of the oxide film.
a. Detection of Integrity and Density The integrity and density of the oxide film were measured using a copper sulfate solution. Under acidic conditions, the copper ion will react with aluminum instead of reacting with AI2O3. When the exposed aluminum or oxide film is loose within the test area, the copper ion in the copper sulfate solution will react with the aluminum at the defect, and the gas will be released. Black spots can be observed at the defects of the oxide film. exist.
b. Inspection of AI2O3 crystal state The observation of the AI2O3 crystal structure by the electron microscope can detect the crystal state of the AI2O3 crystal, and the oxide film is of high quality with few lattice defects.
c. Determination of oxide film thickness The thickness of the PS plate oxide film has a great influence on printing performance. The thickness of the PS plate oxide film is expressed by the mass of Al2O3 per unit area (g/m2), according to the positive PS version. Chemical Industry Standards, Determination of Methods as Specified in HG/T 2694-95.
2) The physicochemical properties of the photosensitive layer 1 Determination of the thickness of the photosensitive layer. The thickness of the photosensitive layer affects the graphic's oleophilicity, photosensitivity, resolution, print resistance, and developing effect, and its thickness must be strictly controlled within a certain range. The thickness of the photosensitive layer is expressed in terms of the mass per unit area of ​​the photosensitive layer (g/m2), and is measured in accordance with the method specified in the "Pattern Type PS Standard Edition Chemical Industry Standard, HG/T 2694-95".
2 photosensitive layer anti-alkali retention membrane properties. The anti-alkali retention property of the photosensitive layer has a great influence on the resolution and the printing resistance of the plate. Alkalinity mainly refers to the degree of dissolution of the photosensitive layer in the developer, and is expressed by the alkali-retaining film rate. The alkali-retention film ratio is the ratio of the weight per unit area of ​​the photosensitive layer (W1) to the weight W2 of the remaining photosensitive layer after soaking in an alkaline solution (W2/W1). Detecting the anti-alkali retention performance corresponding to different exposures of the PS plate can better show the difference in the photosensitivity of the positive PS plate.
3) Sensitometric detection Positive photosensitivity of the photosensitive layer of the PS plate includes determination of the sensitivity, resolution, gamma, and background of the PS plate.
1 sensitivity. Sensitivity refers to the sensitivity of the photosensitive material to light, ie, the speed of light, and the sensitivity of the PS plate is expressed in terms of the amount of light exposure. The smaller the exposure required to reach a certain density (light energy absorbed by the photosensitive material), the higher the sensitivity; the more exposure required, the lower the sensitivity.
2 resolution. Resolving power refers to the ability of the photosensitive layer to distinguish the fine level of the original after exposure with a certain amount of exposure.
3PS version gamma. The gamma is an important parameter of the PS version. The contrast coefficient is large, the exposure transition area is small, and the image edge density loss is small, the image is clear, the dot reproducibility and resolution are good, and the exposure latitude is large, and the printing force is high. Photosensitive detection is generally used continuous adjustment