Net-knot-free double-sided press-fit screen printing plate and preparation method thereof

Abstract

The invention belongs to a net-knot-free screen printing plate, and particularly relates to a net-knot-free double-sided press-fit screen printing plate and a preparation method thereof. A protective film is pressed on the S surface of the screen printing plate, a graphic film is pressed on the P surface of the screen printing plate, a grid line groove is formed in the graphic film according to a grid line graph, a material storage groove is formed in the protective film according to the grid line graph, the grid line groove is aligned with the center line of the material storage groove, and the width of a groove opening of the material storage groove is larger than that of the grid line groove. Compared with the prior art, the technical scheme provided by the invention has the following outstanding technical effects: (1) the protective layer is additionally arranged on the S surface, so that the friction of a scraper blade is effectively resisted, and the breakage rate of a silk screen at a lower cutter position of the S surface is obviously reduced from over 2 percent to below 0.5 percent; the smoothness of printing paste is remarkably improved, S-face laser grooving is achieved, the problem that paste permeation is blocked is thoroughly solved, the printing process is stable, the service life of the screen printing plate is prolonged by 30%, the efficiency of printed products is improved by 0.01%, and the screen replacing frequency and the production cost are reduced.

Description

Technical Field

[0001] This invention pertains to knotless screen printing, specifically relating to a knotless double-sided laminated screen printing and its preparation method. Background Technology

[0002] Currently, with the increasing maturity of solar power generation technology, the requirements for screen printing plates used in the fabrication of solar cells (such as crystalline silicon solar cells) are becoming increasingly stringent. The future trend in screen printing plate design is towards higher mesh counts, finer wire diameters, and narrower linewidths. Conventional screen printing plates, due to the presence of knots, are prone to problems such as broken grids and incomplete printing when producing ultra-fine linewidth grids, making it difficult to guarantee the quality of the grid lines. Therefore, knot-free screen printing plates have emerged.

[0003] like Figure 1 As shown, the screenless printing plate has a frame 11, a polyester screen 12 disposed within the frame 11, and a silk screen 13 disposed inside the polyester screen 12. A pattern area 14 is formed inside the silk screen 13. One side of the silk screen 13 is the S side (printing contact surface, in direct contact with the ink and squeegee), and the other side is the P side (non-printing contact surface, in contact with the printing platform). In the prior art, a PI (polyimide) film is laminated onto the P side. The PI film is laser-grooved according to the printing grid pattern. In use, the screen is placed on the object to be printed, such as on a silicon wafer. Then, the ink or ink is scraped from the pattern area of ​​the S side of the screen through the grooves on the silk screen 13 and the PI film on the P side, so that the grid pattern is formed on the object to be printed.

[0004] During the printing process, the breakage rate of the S-side lower blade position screen 13 exceeds 2%. The outer side of the graphic area on the mesh is very prone to cracking and damage. Furthermore, due to repeated friction from the squeegee, the current screen lifespan is only 350,000 cycles. Increasing the lifespan could significantly reduce the production cost of solar cells. Additionally, as the grid lines become finer and the mesh count of the screen increases, the resistance to ink penetration through the screen increases. Currently, due to poor ink penetration, the risk of "grid breakage" during printing exceeds 15%. Summary of the Invention

[0005] This invention provides a knotless double-sided pressed screen and its preparation method to solve the technical problems of short service life and poor slurry penetration of current knotless screens.

[0006] To solve the above technical problems, the present invention provides a knotless double-sided pressed screen, wherein a protective film is pressed onto the S side of the screen and a graphic film is pressed onto the P side of the screen. The graphic film has grid grooves formed according to the grid pattern, and the protective film has a storage groove formed according to the grid pattern. The center lines of the grid groove and the storage groove are aligned, and the width of the opening of the storage groove is greater than the width of the grid groove.

[0007] Adding a protective film to the S-side has several advantages. First, it reduces frictional wear on the screen. Second, because of the added film, even if the pattern film is damaged and leaks slurry, as long as the damage is outside the storage tank area, the screen can continue to be used, unlike existing screen structures that require direct scrapping. Third, compared to the current method of directly scraping the screen surface with a squeegee, the slurry is further squeezed into the storage tank. With the same squeegee force, the slurry receives greater pressure, and the slurry can also stay briefly in the storage tank, further facilitating targeted penetration of the slurry.

[0008] Optionally, the width of the storage tank opening is greater than 200 micrometers, and the distance between parallel storage tank boundary lines is greater than 200 micrometers.

[0009] If the groove width is too small, it will not help the slurry to penetrate effectively and may even have the opposite effect. However, if the groove is too wide, the distance between the boundary lines of the storage tank will be too small, that is, the membrane connecting the storage tanks will be too narrow. In this case, the membrane will be too weak to provide the desired scratch protection.

[0010] Optionally, when the grid line spacing is 700-1000 micrometers, the width of the storage tank opening is 350-450 micrometers.

[0011] Optionally, the wire diameter of the mesh is 9-11 micrometers and the wire spacing is 40-50 micrometers.

[0012] Optionally, the protective film covers the mesh and extends outwards by a blank area, the width of which is greater than 5 micrometers.

[0013] Optionally, the protective film is a PI film, and the patterned film is a PI film or a PET (polyester) film.

[0014] Optionally, the protective film has a thickness of 12-15 micrometers, a temperature resistance of 260°C or higher, and a tensile strength of ≥150MPa.

[0015] Optionally, the protective film has at least two positioning structures, and the graphic film has corresponding positioning structures.

[0016] The present invention also provides a method for preparing the above-mentioned knotless double-sided pressed screen, wherein the protective film and the graphic film are pressed and bonded to the screen once or twice by a double-sided synchronous presser, and there is a temperature difference between the upper and lower pressing blocks during the pressing process.

[0017] The temperature difference during lamination can ensure the flatness of the film bonding.

[0018] Optionally, when the protective film is a PI film and the graphic film is a PET film, they are laminated together with the screen in one step using a laminating machine; when both the protective film and the graphic film are PI films, they are laminated together with the screen in two steps.

[0019] Different materials for the upper and lower films can accommodate the temperature difference between the upper and lower pressure blocks, ensuring stable bonding of both films. When the upper and lower films are made of the same material, the temperature difference between the two pressing processes can ensure stable bonding of the upper and lower films, reducing the delamination rate to below 1%.

[0020] Optionally, the temperature of the upper pressing block is 210°C and the temperature of the lower pressing block is 150°C.

[0021] Optionally, a single pressing step includes:

[0022] 1) The protective film, screen mesh, and graphic film are stacked from top to bottom and simultaneously pressed together in a laminating machine to form a single unit;

[0023] 2) According to the grid line design drawing, grid line grooves are formed on the graphic film using a laser;

[0024] 3) According to the grid line design drawing, a storage tank is opened on the protective film by laser.

[0025] After double-sided synchronous bonding, a narrower grid groove is first opened. Even if the protective film is damaged by laser cutting, the damaged part can be removed when a wider storage groove is opened.

[0026] Optionally, the two pressing steps include:

[0027] 1) First, press the protective film and the screen mesh together on the press machine, with the protective film close to the lower pressing block;

[0028] 2) According to the grid line design drawing, a storage tank is opened on the protective film using a laser;

[0029] 3) Press the graphic film and the screen onto the press machine, with the graphic film close to the lower pressing block;

[0030] 4) According to the grid line design drawing, grid line grooves are opened on the graphic film by laser.

[0031] During the two-stage lamination process, the protective film needs to be laminated and grooved first. This allows for the subsequent lamination and grooving of the pattern film, which requires higher precision, to be carried out. This minimizes the impact of lamination and grooving on the precision of the pattern film and grid grooves.

[0032] Compared with the prior art, the technical solution provided by the present invention has the following outstanding technical effects:

[0033] 1) The addition of a protective layer on the S-side effectively resists scraper friction, significantly reducing the wire mesh breakage rate at the lower cutting position on the S-side from over 2% to below 0.5%;

[0034] 2) The smoothness of the printing paste is significantly improved. The S-side laser grooving completely solves the problem of paste penetration obstruction and ensures the stability of the printing process.

[0035] 3) The lifespan of the screen is increased by 30% (from 350,000 times to 500,000 times), the efficiency of printing products is increased by 0.01%, and the frequency of screen replacement and production costs are reduced. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a meshless screen in the prior art;

[0037] Figure 2 This is a cross-sectional view of a specific embodiment of the knotless double-sided laminated screen plate of the present invention;

[0038] Figure 3 This is a schematic diagram of a specific embodiment of the knotless double-sided laminated screen printing plate S-side of the present invention;

[0039] Figure 4 This is a schematic diagram of a specific embodiment of the knotless double-sided laminated screen printing plate P-side of the present invention.

[0040] The figure shows

[0041] 11-Frame, 12-Polyester mesh, 13-Wire mesh, 14-Graphic area;

[0042] 20 - Screen printing plate, 30 - Protective film, 40 - Graphic film, 50 - Grid groove, 60 - Storage tank, 70 - Positioning mark. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation and positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] like Figure 2-4 As shown, the knotless double-sided pressed screen of the present invention includes a frame 11, a polyester mesh 12 disposed within the frame 11, and a wire mesh 13 disposed inside the polyester mesh 12. A protective film 30 is pressed onto the S-side of the screen 10, and a patterned film 40 is pressed onto the P-side. The patterned film 40 has grid grooves 50 formed according to the grid pattern, and the protective film 30 has storage troughs 60 formed according to the grid pattern. The center lines of the grid grooves 50 and the storage troughs 60 are aligned, and the width of the storage trough 50 opening is greater than the width of the grid grooves 50. The protective film 30 is a PI film, and the patterned film 40 can be a PI film or a PET film. The protective film 30 has a thickness of 12-15 micrometers, a temperature resistance of over 260℃, a tensile strength ≥150 MPa, a wire diameter of 9-11 micrometers, and a wire spacing of 40-50 micrometers.

[0047] In this embodiment, the spacing L1 between the grid lines is 700-1000 micrometers, the width of the grid line groove 50 is 5-10 micrometers, and the width H of the storage tank 50 is set to 400 micrometers. That is, when the grid line spacing L1 is 700 micrometers, the distance L2 between the boundary lines of two adjacent parallel storage tanks 50 is 700-400=300 micrometers.

[0048] See also Figure 3 The protective film 30 covers the wire mesh and extends outwards by a blank area, the width of which is more than 5 millimeters.

[0049] See also Figure 3 and Figure 4 The protective film 30 and the graphic film 40 are respectively set with four cross-shaped positioning marks 70 at the four corners by laser, which establishes the coordinate system of the grooved pattern before grooving. In this way, after both sides are grooved, the positional deviation of the positioning marks 70 on both sides can be used to know the relative positional deviation of the center line of the grid groove 50 and the storage tank 60, so as to facilitate the adjustment of the laser grooving position.

[0050] Example 1: One-time pressing

[0051] The production of reinforced knotless screen printing plates is achieved through a five-step core process: "mesh pretreatment → double-sided material bonding → synchronous pressing → laser grooving → shaping and inspection". The specific solution is as follows:

[0052] 1) Mesh pretreatment: Commercially available tungsten steel knotless mesh (wire diameter 9-11um, knotless area line width 40-50um) is selected, and conventional mesh is stretched and laminated to obtain a conventional uncoated mesh. Then, the surface oil and metal debris are removed by ultrasonic cleaning machine (power 500W, time 10 minutes). A soft cleaning basket is used to avoid scratching the mesh. After cleaning, it is dried at a constant temperature of 60℃ for 30 minutes to ensure that the surface is free of impurities and to ensure the adhesion of the lamination.

[0053] 2) Double-sided material lamination: The S side (printing contact surface) is laminated with a commercially available polyimide (PI) film (thickness 12-15um, temperature resistance above 260℃, tensile strength ≥150MPa), with a 5mm blank area reserved at the edge (for local damage repair); the P side (non-printing contact surface) is laminated with a commercially available polyester wear-resistant layer (thickness 8-10um, surface hardness 2H, coefficient of friction ≤0.2), ensuring that both sides of the material completely cover the effective printing area of ​​the screen 13 and are aligned with the edge of the tungsten carbide mesh (screen).

[0054] 3) Double-sided synchronous pressing: Use a commercially available double-sided synchronous pressing machine (such as model HT-P200). The upper pressing block corresponds to the S-side PI film, i.e., protective film 30 (temperature 210℃, matching the softening characteristics of the PI film), and the lower pressing block corresponds to the P-side polyester film, i.e., graphic film 40 (temperature 150℃, to avoid excessive softening of the polyester layer); set the overall pressure to 4-6MPa (for the high hardness of tungsten carbide mesh, to ensure tight adhesion of the pressed layers without bubbles), and the pressing time to 15-20 minutes; after pressing, air cool for 5 minutes to room temperature to prevent delamination between the tungsten carbide mesh and the pressed layer due to the difference in thermal expansion coefficients;

[0055] 4) Laser grooving: Using an ultraviolet laser machine (power 40-50W, wavelength 355nm), first, positioning marks 70 are made on the P-side graphic film 40, and then grid grooves 50 are made. The grooving width is determined according to the grid line width. In this embodiment, it is 3-10 micrometers. The grooving speed is 80-100mm / s, and the burrs on the edge of the groove are ≤1um. It is also precisely aligned with the 40-50um line width of the tungsten carbide mesh (deviation ≤2um). Then, positioning marks 70 are made on the S-side protective film 30, and then storage grooves 60 are made. The grooving width is 400um (to adapt to the 700-1000um graphic line spacing in the market, ensuring that the slurry evenly covers the line area). The grooving speed is 80-100mm / s. The burrs on the edge of the groove are ≤1um, and it is precisely aligned with the 40-50um line width of the tungsten carbide mesh (wire mesh) (deviation ≤2um).

[0056] 5) Finalization test: The screen 20 is placed in a 210℃ constant temperature heating plate and heated for 50 minutes to increase film adhesion; the thickness of the protective film 30 / graphic film 40 is measured by a thickness gauge (error ≤1um), and the groove size (width error ≤5um, depth error ≤1um) and mesh line width (40-50um, error ≤2um) are observed by an optical microscope; finally, the service life of the screen 20 is increased from the traditional 350,000 times to 500,000 times.

[0057] Example 2: Two-stage pressing

[0058] 1) Mesh pretreatment: Commercially available tungsten steel knotless mesh (wire diameter 9-11um, knotless area line width 40-50um) is selected, and conventional mesh is stretched and laminated to obtain a conventional uncoated mesh. Then, the surface oil and metal debris are removed by ultrasonic cleaning machine (power 500W, time 10 minutes). A soft cleaning basket is used to avoid scratching the mesh. After cleaning, it is dried at a constant temperature of 60℃ for 30 minutes to ensure that the surface is free of impurities and to ensure the adhesion of the lamination.

[0059] 2) One-time lamination: The S side (printing contact surface) is laminated with a commercially available polyimide (PI) film (thickness 12-15um, temperature resistance above 260℃, tensile strength ≥150MPa), completely covering the effective printing area of ​​the mesh, and aligned with the edge of the tungsten carbide mesh (screen), with a 5mm blank area reserved at the edge (for local damage repair).

[0060] 3) S-side grooving: Using an ultraviolet laser machine (power 40-50W, wavelength 355nm), positioning marks 70 are made on the S-side PI film, followed by a liquid storage tank 60. The grooving width is 400um (to match the 700-1000um graphic line spacing in the market, ensuring that the slurry evenly covers the line area), and the grooving speed is 80-100mm / s. The burrs on the edge of the groove are ≤1um, and it is precisely aligned with the 40-50um line width of the tungsten carbide mesh (deviation ≤2um).

[0061] 4) Secondary lamination: The P side (non-printing contact surface) is laminated with a commercially available polyimide (PI) film (thickness 12-15um, temperature resistance above 260℃, tensile strength ≥150MPa), which completely covers the effective printing area of ​​the mesh and is aligned with the edge of the tungsten carbide mesh (screen).

[0062] 5) P-side grooving: Using an ultraviolet laser machine (power 40-50W, wavelength 355nm), positioning marks 70 are made on the P-side PI film, and then patterned grooves 50 are made. The groove width is determined according to the grid line width. In this embodiment, it is 3-10 micrometers. The grooving speed is 80-100mm / s. The burrs on the edge of the groove are ≤1um, and it is precisely aligned with the tungsten carbide mesh (wire mesh) with a line width of 40-50um (deviation ≤2um).

[0063] 6) Finalization test: Place the screen 20 into a 210℃ constant temperature heating plate and heat for 50 minutes to increase the adhesion of the double film; use a thickness gauge to detect the PI film thickness (error ≤1um), and use an optical microscope to observe the groove size (width error ≤5um, depth error ≤1um) and mesh line width (40-50um, error ≤2um); finally, the service life of the screen 20 is increased from the traditional 350,000 times to 500,000 times.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A knot-free double-sided compression screen, characterized in that, The protection film is attached to the screen S, and the pattern film is attached to the screen P, the pattern film is provided with a grid line groove according to the grid line pattern, the protection film is provided with a storage groove according to the grid line pattern, the grid line groove and the storage groove are in center line alignment, and the storage groove has a slot width greater than the grid line groove width.

2. The knot-free double-sided press-coated screen printing plate according to claim 1, wherein, The slot width of the storage groove is greater than 200 microns, and the distance between the parallel storage groove boundary lines is greater than 200 microns.

3. The knot-free double-sided press-coated screen printing plate according to claim 2, wherein, When the grid line spacing is 700-1000 microns, the slot width of the storage groove is 350-450 microns.

4. The knot-free double-sided press-coated screen printing plate according to claim 1, wherein, The protection film covers the screen and extends a blank area, and the width of the blank area is greater than 5 microns.

5. The knot-free double-sided press-coated screen printing plate according to claim 1, wherein, The protection film is a PI film, and the pattern film is a PI film or a PET film.

6. The knot-free double-sided press-coated screen printing plate according to claim 1, wherein, The protection film is provided with at least two positioning structures, and the pattern film is provided with corresponding positioning structures.

7. The method of claim 1-6, wherein the method is characterized by, The protection film and the pattern film are attached to the screen by one or two times of pressing by a double-sided synchronous pressing machine, and there is a temperature difference between the upper pressing block and the lower pressing block during pressing.

8. The preparation method according to claim 7, characterized in that, When the protection film is a PI film and the pattern film is a PET film, the protection film and the pattern film are attached to the screen by one time of pressing by a pressing machine; when the protection film and the pattern film are both PI films, the protection film and the pattern film are attached to the screen by two times of pressing.

9. The preparation method according to claim 7, characterized in that, The temperature of the upper pressing block is 210°C, and the temperature of the lower pressing block is 150°C.

10. The preparation method of claim 7, wherein, The one-time pressing step comprises: 1) the protection film, the screen and the pattern film are stacked from top to bottom, and are synchronously pressed in the pressing machine to be attached to each other; 2) a grid line groove is formed on the pattern film according to the grid line design by laser; 3) a storage groove is formed on the protection film according to the grid line design by laser; The two-time pressing step comprises: 1) the protection film and the screen are pressed in the pressing machine, and the protection film is close to the lower pressing block; 2) a storage groove is formed on the protection film according to the grid line design by laser; 3) the pattern film and the screen are pressed in the pressing machine, and the pattern film is close to the lower pressing block; 4) a grid line groove is formed on the pattern film according to the grid line design by laser.

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