A. The mesh number of the screen: it determines the fineness of the print graphic, determines the stable tension value of the stretch net, and also determines the ink volume (volume) at the time of printing. In the color dot printing, it also determines whether the graphic text will The size of the moiré and its moiré. The unit is several filaments (or a number of cells) per centimeter length or per inch length;
B. Diameter of the wire: it affects the tension of the stretch net and the width of the opening of the wire mesh, that is, under the same mesh number and the same weaving method, the diameter of the filament wire is smaller than the tension of the thick wire diameter wire mesh. With a large opening width, the amount of ink is also large. Therefore, the use of the same mesh and the use of different wire diameter of the same weaving method of the screen, you can change the depth of color printing graphics to achieve the purpose of printing graphics hue;
C. The concept of silk screen ink volume: Determine the ink thickness (volume) obtained on the substrate. In color dot printing, it affects the depth of color and the reduction of hue and the size of hue, etc. It is also the basis for calculating the amount of ink required for each batch of prints;
D. Tension: The tension of a screen is determined by the mesh size of the screen, the diameter of the screen, and the weaving method. Whether the tension is reasonable or not determines the service life and screen printing quality of the web. The size of the tension, when not printed (static), determines the distance between the web and the substrate, called the web distance. The high tension is inevitably adjusted at a low screen pitch, and the positional accuracy of the resulting image and text is high. Therefore, the retina should reach the optimal tension before printing. During the whole process of printing, the tension of the reticulation plate is stable, and the stable tension must be ensured by the best network distance, so as to ensure the printing quality and service life of the reticulation plate. The best tension here is that when the net is stretched, the net is left with a certain amount of elasticity. This elastic margin ensures that in the whole process of screen printing, when the scraper (squeegee) scratches the screen template, the screen template can immediately shoot off the substrate. Otherwise, the number of sheets cannot be printed, and the tension of the screen template is reduced. From the elastic deformation to the deformation of the elasticity, the tension value is changed and the original tension value is changed. In the printing of the optical disc, there will be problems such as streak marks, patches, and different shades of color. At the same time, it is necessary to set the static screen pitch of the screen under the optimal tension of the stretching net, that is, during the entire printing process, the screen will always be able to stabilize the rebound distance, so as to ensure the quality and life of the film transmission. . If the tension value of the stretch net is optimal, and the static net pitch setting is unreasonable, if the net pitch is low, the scraper, the screen, and the substrate cannot contact one line, at this time, the web film rebounds during the printing process. If it is not timely, it is prone to problems such as dirty images, ghosting, and deformation. If you set the static network distance higher than the optimal network distance? The best tension of the reticule is then destroyed, especially in the printing dynamics, the tension of the retina subjected to the scraping pressure of the scraper will be very large, and the net will produce a super-extending stretch. In the initial stage, no poor printing was found. Only the scraping pressure of the squeegee was increased to complete the graphic transfer. However, as the printing continues, the wire is repeatedly stretched and fatigued. This will inevitably result in screen printing. The tension on the gradually smaller. With the continuous increase in the number of prints, there will be quality problems such as misalignment and hue deviation. When the net distance is so large that the mesh can no longer be stretched, the screen life ends, and the screen collapses.
Therefore, disc four-color printing requires screen printing under high tension and low screen distance. Therefore, the tension of the stretch net and the setting of the static mesh distance before printing are very important. Under unreasonable network distance, you must not arbitrarily pursue excessive tension from the characteristics of the screen, even if other fine screen printing is also the case, otherwise it is counterproductive. From this point of view, the high tensile strength and low elongation properties of the silk screen brands selected for CD-ROM screen printing are particularly important.
E. The color of the screen: The screen printing of the optical disc, retina production of the vast majority of the choice of spectral wavelength of 330 ~ 400nm sensitivity of the direct method photoresist and capillary photosensitive film. Therefore, the omentum plates are made of yellow or lemon yellow PET mesh. This is because the yellow spectral wavelength is 550~600nm, so the screen plate with the yellow screen is used to reverse (or fold) the screen to the photosensitive film layer which does not need to be exposed during the printing process. The wavelength is far away from the photosensitive wavelength of the photo-sensitive film (peak position 365mm), and the haze phenomenon of the photochemical adhesive reaction rarely occurs on the photosensitive adhesive film layer that does not require exposure, and the transparent part of the photographic film is still maintained during the printing. More than 99% of the sensitive light is irradiated on the photosensitive film of the image and text, so that the image point on the film is consistent with that of the photographic film. Therefore, the use of yellow light between the printing plate for lighting, in the printing process does not affect the photosensitive film, compared with the red light, people under the yellow light is not easy to fatigue, and at the same time when the printing plate to see clearly, and The human eye feels comfortable.
F. Screen printing should be made of monofilament or plain weave. Mesh version: Because the mesh of the plain weave mesh is one-up, one-weave, two-up, two-down, or two-under-twist. Compared with the net, the area of ​​the node between the warp and weft yarns of the plain weave mesh is twice or one time smaller than that of the diagonal weave. Therefore, when the plain weave mesh is made into the omentum printing, the ink is smooth and the ink can be extremely fast on the optical disc. Leveling. Therefore, it is not easy for ink traces to appear on the ink, and high-profile dots are not easily lost, which is advantageous for the printing of fine graphic texts on optical discs.
2. Frame:
Optical disk printing plates require large tension and high flatness. Therefore, the screen frames used on optical disks are mostly sandblasted plates with thickness of 3mm, length and width of 320*320mm, 320*280mm, and 320*260mm. Made of zinc steel frame. Therefore, the disc screen printing net frame generally does not warp under high tension, but in order to ensure the screen printing quality, the flatness of the frame should be tested before stretching. During the inspection, the feeler gauge shall be placed on the platform. The gap between any corner of the frame and the platform shall not exceed 0.5 mm, and the flatness of the frame surface shall be inspected. In this way, the surface of the frame can be adhered tightly to the screen. In the screen printing process, under the scraping pressure of the scraper, it is ensured that the screen and the frame do not debond. The tension of the screen is guaranteed to be stable, and the four-color printing of the graphic frame can be guaranteed accurately. If the old mesh frame is used to make the omentum version, the residual adhesive remaining on the surface of the frame should be completely removed before it can be used, otherwise the residual adhesive net is not removed after the net is stretched, the screen and the net Box is not close. The sticky mesh is not firm, causing degumming, affecting the tension of the screen plate, losing the tension when severe, and making the screen premature.
3. Stretching:
According to the requirements of the reticles, the four-color dot-printed omentum must be consistent with four:
A. The frame size is the same, and the elongation of the mesh when printed is the same.
B. The direction of the cutting (paste) of the screen on the frame is the same, ie, the orientation of the frame on the frame is made by the warp or weft orientation of the screen. This is because the screen is woven. The process was decided.
C. The tension settings of the four sets of color reticles are the same, because the tension is the same size, the size of the frame is the same, the position of the graphic and text on the screen is the same, the elongation of the screen is the same, and the position of the graphic in the screen printing The graphic size is the same, and the set is accurate.
D. Set the static net distance reasonable and consistent, because when the distance between the four-color retina version and the disc is the same, the tension between the screen is equal, then the screen printing process must be the same pressure. Under the control of the above four identical conditions, the overlap of screen dots in the silk screen or the position of the parallel dots is accurate, the color shift is small, and the color reproduction is good.
Therefore, the reticulated stretch nets of printed optical discs often have four-color screens placed on the same stretch net, and four, eight, twelve, etc. are completed at the same time. And in the frame on the latitude and longitude orientation mark, according to the direction of the positioning hole in the frame and the screen weaving line 6-10 degrees angled arrangement, and then glued firmly, until the glue is completely dry and then remove the screen. But it must be placed for 24 hours to allow the mesh to change further, so as to reach the final stable state of tension before applying photosensitized adhesive to make graphics.
Stretch net equipment is recommended to use a spiral stretching machine to adjust the tension, it is recommended not to use a lever to adjust the stretching tension. Because the tension of the optical film of the optical disk is generally stable at about 18N/cm-20N/cm, when the actual tension is stretched, the tension of about 1.2 times of 20N/cm must be stretched.
Therefore, when the wire mesh is raised or pulled under high tension, it must not be fed to the screen, but it should be slow, even, and vibration-free to lift the tension of the wire mesh so that the screen can reach the set tension value. Spiral stretching machine can meet the above requirements. The lever-type stretching machine adjusts the tension of the screen and the gear rolls on the rack. The pitch of the rolling is limited by the ratcheting movement, so it is an indirect type and stretches the screen under vibration. When the screen is under high tension and the tension is almost close to the limit tension, if the tension of the screen is raised under vibration, this is a destructive stretching of the impact of the mesh, and as a result, the screen is pulled and the net is stretched. The rate has dropped and I hope to draw attention when stretching!
Due to the weaving process of the screen, after the screen is knitted, the mesh of the screen must be fixed at the same size and close to a square. Therefore, the screen must be heat-set. In the heat setting process, the warp stretch of the screen is larger than the stretch in the weft direction. Therefore, according to this production process of the screen, when stretching the net, the tension in the upward direction should be first pulled to half of the required tension, and then the tension in the weft direction should be pulled to the full tension of the reticles, and Every 5 to 10 minutes, 3 to 5 times under the supervision of a tensiometer again adjust the tension of the screen in the warp and weft direction, until the request can be adhered to the net. After the adhesive net is completely dry, the screen plate is removed, and the plate is placed for at least 24 hours. This kind of stretch net is beneficial to the even tension of the screen plate, and the tension and size are stable during use, the nesting is accurate, and the service life of the screen template is prolonged.
Source: Silkscreen World