Conventional inspection in the production process of the positive PS plate
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In recent years, China's PS version technology has developed rapidly and production has continued to grow. The prosperity of the market will inevitably bring fierce market competition. If the PS version of the manufacturer wants to occupy a stable market share, it must ensure the quality and reputation of its products. Therefore, it is of vital importance to ensure the quality of the products in the PS version production process. Therefore, PS version quality control is achieved by some of the following routine tests.
Raw material testing
The positive PS plate consists of a photosensitive layer and an aluminum plate base. The raw materials commonly used in PS production plants can be refined into four aspects around these two parts:
1) various raw materials required for the preparation of the photosensitive liquid;
2) Various raw materials required for a series of processes for the aluminum plate base to meet the printing requirements;
3) The aluminum plate base required for the positive PS plate support;
4) The water quality of the production water for the PS version.
In order to stabilize the quality of the products, before purchasing the raw materials, the 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 for their main technical indicators.
1. Analysis and detection of various raw materials required for photosensitive liquid
The positive PS plate photosensitive liquid is mainly composed of a photosensitive resin, a film-forming resin, a dye, a solvent and other auxiliary agents.
1) Determination of the properties of 2.1.5-sulfonyl chloride
2.1.5-sulfonyl chloride is an orange-yellow crystal for the synthesis of a photosensitive resin.
1 Determination of melting point. The melting point of a solid substance refers to the temperature at which the substance reaches equilibrium at atmospheric pressure and solid state and liquid state. Very pure substance under a barometric pressure, the change between solid and liquid states is very sharp, from the initial melting to the full melting temperature does not change more than 1 ° C; if impurities, the melting point decreases, the melting point range is broadened. Therefore, the purity of the compound can be judged by measuring the melting point.
2 Determination of 2.1.5-sulfonyl chloride content. The content of 2.1.5-sulfonyl chloride has a great influence on the photosensitivity of the photosensitive resin. At present, the purity of 2.1.5-sulfonyl chloride produced by various manufacturers is higher, and the content is above 98%. However, in order to synthesize a stable photosensitive resin, the content of 2.1.5-sulfonyl chloride should be measured. The easiest and most accurate way to detect the 2.1.5-sulfonyl chloride content is to use an ultraviolet spectrophotometer to determine the domestic UV spectrophotometer.
3 Determination of the ultraviolet absorption spectrum. The maximum absorption wavelength of 2.1.5-sulfonyl chloride can be determined by an ultraviolet spectrophotometer.
2) Determination of film-forming resin
The film-forming resin is mainly a linear phenol resin and is a polymer compound.
1 Determination of molecular weight and molecular weight distribution. The polymer compound is composed of many molecules of different sizes, and the different molecules occupy different proportions. The width and width of the molecular weight distribution have 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 phenol resin can be easily and accurately determined by gel permeation chromatography (GPC).
2 Determination of viscosity. The viscosity of the film-forming resin can be measured by a rotary 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 addition to a small number of PS manufacturers in the country to prepare a photosensitive liquid with a mixture of ethylene glycol monoethyl ether, methyl ethyl ketone, esters, etc., most manufacturers only use ethylene glycol monoethyl ether as a solvent. However, whether using a multi-component solvent or a one-component solvent, the solvent content of the solvent must be determined using a Karl Fischer automatic titrator.
2. Analysis of the basis processing technology
The positive process PS version of the base processing process is:
Aluminum coil unwinding → alkaline washing → electrolysis → oxidation → hydrophilization
1) Alkali wash
Remove the grease and natural oxide film on the surface of the aluminum plate.
2) Electrolysis
A sand mesh is formed on the surface of the aluminum plate to increase the surface area to improve the hydrophilicity of the non-image area and the adhesion of the aluminum plate to the photosensitive layer.
3) Oxidation
A solid AI2O3 film is formed on the electrolytic aluminum plate to improve the wear resistance, corrosion resistance and stability of the printing plate.
4) Hydrophilic treatment
The adsorption of the AI2O3 film on the photosensitive layer is lowered, the hydrophilicity of the non-image area is improved, and the solubility of AI2O3 and Al in the developing solution is lowered.
The content of inorganic acids and inorganic bases in the raw materials used in the PS version of the base treatment process was determined by a volumetric analysis method. When measuring the sodium hydroxide content, since the industrial sodium hydroxide contains a small amount of sodium carbonate, the sodium carbonate should be first converted into a cesium carbonate precipitate and then analyzed.
3. Qualitative and quantitative analysis of trace elements in aluminum
The aluminum plate base usually contains a small amount of trace elements. The qualitative and quantitative detection of trace elements can be determined by atomic absorption spectrometry. The atomic absorption analysis method has the characteristics of high sensitivity, good repeatability, simple and fast operation, but the price of the instrument. Higher, manufacturers can regularly go to the physical and chemical testing center for testing.
4.PS version of production water analysis and testing
In the PS plate production process requires a large amount of water, preferably deionized water, because the cations and anions in the water will have a certain impact on the PS plate, such as halogen ions can corrode the oxide film to produce small holes.
Deionized water can be prepared by ion exchange method. The conductivity can be measured by conductivity meter. Each manufacturer can determine the conductivity value according to the quality requirements of its own production water and conduct regular measurement.
Product quality control testing
To evaluate the quality of a product, in addition to some of the properties of the product itself, it must also have good repeatability and stability. Manufacturers should have a strict set of corporate standard data to control the quality of the product.
1. Detecting the concentration of solution for solution treatment
The detection of the solution concentration used in the plate-based treatment process is mostly carried out by on-line detection, and the concentration of each solution used in the plate-based treatment process is periodically quantitatively tested in the production process to achieve the specified index. At the same time, it is necessary to detect the content of Al3+ in the oil, electrolyte and oxidizing solution. Concentration testing can be done with simple, fast acid-base titration analysis, and companies with good conditions can install on-line detectors. At present, the accuracy of the domestically produced PS version of the online testing instrument is not too high, and is only used as a reference. The actual online automatic detection instrument adopts electrochemical analysis method, which is to determine the content of each substance by using the quantitative relationship between chemical composition and voltage, current, conductance, etc. in the process of chemical energy and electric energy conversion.
2. Detect the intrinsic quality of the product
1) Edition performance testing
1 surface roughness. The surface roughness is measured by a surface roughness tester, and is generally evaluated by technical parameters such as Ra, Rz, and Sm, wherein
Ra - the arithmetic mean of the absolute value of the contour offset within the length of the sample;
Rz - the sum of the average of the five largest contour peak heights within the sampling length and the average of the five largest contour valley depths;
Sm - the average of the spacing of the microscopic irregularities within the length of the sample.
The density D of the contour peak can be calculated by Sm:
D = L / Sm , where L is the sample length.
2 oxide film. The merits of evaluating the oxide film mainly depend on the integrity and compactness of the oxide film, the crystal structure and thickness of the oxide film.
a. Inspection of integrity and compactness
The integrity and compactness of the oxide film are detected by a copper sulfate solution. Under acidic conditions, copper ions undergo a displacement reaction with aluminum and do not react with AI2O3. When there is an exposed aluminum base or an oxide film loose in the detection area, the copper ions in the copper sulfate solution undergo a displacement reaction with the aluminum at the defect, and at the same time, a gas is released, and a black spot can be observed at the defect of the oxide film. presence.
b. AI2O3 crystal shape detection
When the crystal structure of AI2O3 is observed by an electron microscope, the crystal form state can be detected, and if the lattice defects are small, the oxide film is excellent.
c. Determination of oxide film thickness
The thickness of the PS plate oxide film has a great influence on the 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 image PS plate chemical industry standard, HG/T2694 Measured by the method specified in -95".
2) Photographic layer physical and chemical properties testing
1 Determination of the thickness of the photosensitive layer. The thickness of the photosensitive layer has an influence on the lipophilicity, photosensitivity, resolution, printing durability and development effect of the image, and the thickness thereof must be strictly controlled within a certain range. The thickness of the photosensitive layer is expressed by the mass per unit area of the photosensitive layer (g/m2), and is measured in accordance with the method specified in "Industrial Type PS Chemical Industry Standard, HG/T2694-95".
2 photosensitive layer resistance to alkali retention film properties. The anti-alkali film retention property of the photosensitive layer has a great influence on the resolution and printing durability of the plate. The alkali resistance mainly refers to the solubility of the photosensitive layer in the developer, and is expressed by the alkali-resistant film retention rate. The alkali-resistant film retention ratio is the ratio (W2/W1) of the weight per unit area of the photosensitive layer (W1) to the weight W2 of the remaining photosensitive layer after immersion in an alkaline solution. The performance of the alkali-resistant film corresponding to different exposure amounts of the PS plate can be detected, and the difference in the photosensitive characteristics of the positive-working PS plate can be better expressed.
3) Detection of photographic performance
Sensitivity detection of the positive PS plate photosensitive layer includes items such as sensitivity, resolution, gamma, and background color of the PS plate.
1 sensitivity. Sensitivity refers to the sensitivity of the photosensitive material to light, that is, the speed of light, and the sensitivity of the PS plate is expressed by the amount of exposure. The smaller the exposure amount required to reach a certain density (the light energy absorbed by the photosensitive material), the higher the sensitivity; the more the required exposure amount, the lower the sensitivity.
2 resolution. Resolution refers to the ability of the photosensitive layer to distinguish the fine layer of the original after exposure to a certain amount of exposure.
3PS version of the gamma. The gamma is an important parameter of the PS plate. The gamma is large, the exposure transition area is small, and the image edge density loss is small. The image is clear, the dot reduction and resolution are good, the exposure latitude is large, and the printing durability is high. Photosensitive detection is generally measured by contact with a continuous adjustment step and a signal strip in contact with the PS plate, and after development.
4 layout background. The background color (D0) of the layout is measured by a reflection densitometer. Under normal conditions, D0 ≤ 0.03.
3. Detection of the surface gas guide layer
Nowadays, the domestically produced PS plate has increased the matte gas guiding layer, thereby improving the dot reduction and reducing the pumping time. In order to ensure the stability of the coating, it is necessary to detect the quality of the matting agent per unit area and the pumping time. When pumping, use the dot film and the PS plate to contact the pumping, and observe the time required for vacuuming.
Finished product appearance inspection
The last process of PS plate production is apparent inspection, mainly looking at the uniformity of surface coating of PS plate, whether the layout is flat, with or without creases, blisters, white spots and dirty spots. According to the grade requirements, the packaging is classified and then shipped.