As a crucial post-printing process,thermal lamination film lamination significantly enhances the glossiness, wear resistance and weather resistance of printed materials, and is widely used in fields such as books and picture albums, packaging gift boxes, and poster promotional items. The inspection of laminated samples serves as the "last line of defense" for controlling the final product quality, directly determining whether the product meets the delivery standards. During the inspection, both the appearance presentation, performance compliance and process compatibility need to be taken into account. The following is a detailed analysis of the inspection key points from five core dimensions.
I. Appearance Quality
Appearance is a fundamental indicator of effect and directly affects the visual effect of the product. It can be evaluated from three aspects: gloss, flatness, and cleanliness.
(1) Gloss is divided into matte and glossy. Observe whether the haze or gloss of the film after lamination is uniform from different angles.
(2) Flatness: Check if there are problems such as bubbles or lifting on the bonding surface. If so, adjust factors such as lamination temperature and pressure and test again.
(3) Cleanliness: Inspect the film surface or the adhesive layer of the film for any impurities. This can be done by touch or using a magnifying glass.
II. Adhesion of Laminating Film
Adhesion refers to the bonding strength between the thermal lamination film and the substrate, which directly determines whether the coated layer will fall off or delaminate during the subsequent use of the product. When inspecting, two commonly used methods, namely the "tape test" and the "cross-cut test", can be adopted.
The tape test method is convenient and fast, and is suitable for products with general adhesion requirements: Select a regular tape, stick it on the surface of the film coating, press it flat to ensure complete adhesion, then hold one corner and quickly tear off the tape at a 180° angle. Observe the residue of the tape and the ink on the film coating layer. If there is no residue or only a little residue, it indicates that the adhesion of the film coating is strong. Multiple tests can be conducted in different areas.
(2) The cross-hatch test method is suitable for high-end products with high adhesion requirements and requires the use of a cross-hatch tester. On the printed matter, use the cross-hatch tester to select squares with appropriate spacing, apply the test tape and then remove it, and observe the residue.
In addition, the adhesion can be assisted in judgment through the "bending test": repeatedly bend the sample 180° multiple times and observe whether the coating layer cracks or peels off at the bending point. If there is no abnormality after bending more than five times, it indicates that the adhesion is good.
III. Edge Quality
The edge treatment quality after lamination is often overlooked, but it directly affects the subsequent processing and safety of use of the product. Three key points need to be focused on: edge neatness, glue overflow, and the range of lamination.
IV. Durability
Durability is an important indicator for evaluating the service life of printed materials. It is necessary to test their durability by simulating the factors in the usage scenarios (friction, light exposure, cold and hot temperatures, and changes in temperature and humidity).
The abrasion resistance test can be conducted by the "friction test method": Use standard friction cloth, nails, knives, etc. to scrape back and forth on the surface of the film-coated several times, and observe whether there is a decrease in luster, ink wear, and exposure of the base material on the surface.
The impact of light on printed materials can be tested by exposing them to direct sunlight or using an ultraviolet aging test chamber. After 24 hours, observe whether the film surface shows signs of yellowing or fading.
(3) For the cold and heat, temperature and humidity adaptability test, the samples can be placed in a test chamber and exposed to a high-temperature and high-humidity environment (such as 40℃ and 85% relative humidity) for 48 hours. After taking them out, observe whether there are any issues such as wrinkling or peeling of the film layer, or deformation of the base material. This ensures that the product can maintain stable performance in various geographical locations and seasons.
V. Degree of Reproduction of Printed Graphics and Texts
If the process parameters are different or inappropriate during the lamination process, it may cause problems such as distortion and blurring of the printed graphics and text. It is necessary to compare the samples before and after lamination to check the degree of graphic and text restoration.
