Preparation method of photosensitive resist ink and metal grid line

Abstract

The invention provides photosensitive resist ink and a preparation method for a metal grid line in a photovoltaic cell. The photosensitive resist ink comprises the following raw materials: (A) acrylic copolymer resin; (B) a photopolymerizable compound; (C) a photoinitiator; the content of vinyl in every 100 grams of solid of the photosensitive resist ink is 0.2 to 0.5 mole; the molecular weight of the acrylic copolymer resin is 50,000-50,000. The photosensitive resist ink provided by the invention has good sensitivity, resolution and electroplating performance, so that a resist pattern with smaller residual foot size can be formed, and the photosensitive resist ink shows good comprehensive performance in the application of photovoltaic cells and has excellent application prospects.

Description

Technical Field

[0001] The present application relates to the technical field of printed circuit board manufacturing, and in particular to a photosensitive resist ink and a method for preparing a metal grid line in a photovoltaic cell. Background Art

[0002] Photovoltaic cells usually conduct current by printing silver paste on both sides of the cell and curing it at high temperature to form grid electrodes. Screen printing conductive silver paste is the current mainstream technology. However, the high consumption of silver paste and high cost are one of the pain points that restrict the acceleration of the industrialization of N-type batteries such as HJT. The industry urgently needs to innovate metallization processes to achieve cost reduction and efficiency improvement. One way is to use copper instead of silver powder to reduce the amount of silver powder used, such as electroplating copper technology.

[0003] The photovoltaic copper electroplating process mainly includes seed layer deposition, patterning, electroplating and post-processing. First, a transparent conductive film (TCO) is deposited on the surface of the heterojunction cell. Then, a metal seed layer is deposited using PVD equipment. A photosensitive resin layer is coated on the surface of the seed layer. After drying, selective illumination causes the photosensitive material in the position where copper plating is not required to undergo a chemical reaction, while the photosensitive material in the position where copper plating is required remains unchanged. Next, the unmodified photosensitive material is removed by development to form a patterned mask. Then, electroplating is performed to deposit copper on the seed layer exposed in the circuit pattern area. Then, a protective layer is made on the copper surface, the mask is peeled off, and finally, the seed layer is flash-etched to remove the surface and surface treatment is performed to obtain a copper gate electrode.

[0004] When making copper conductor patterns, the ideal pattern of the exposed electroplating area cross section is a rectangle or a right trapezoid, so as to form a gate line with an upper edge width less than or equal to the lower edge width. If the cross section of the resist is an inverted trapezoid, the cross section of the copper deposited in the plating process is an inverted trapezoid shape with a wide top and a narrow bottom, which affects the photoelectric conversion efficiency of the cell.

[0005] In addition, in the development process, the bottom of the side wall near the exposure part is prone to incomplete development and residual feet (or residual glue), which in turn affects the adhesion between the coating and the seed layer, making the conductive performance of the gate line formed by electroplating worse. Therefore, it is necessary to develop a photosensitive resist composition that can form a resist pattern with higher resolution and smaller residual feet. Chinese application CN116449650A discloses a resist for photovoltaic cells, using photosensitive resin, photopolymerization monomer, initiator, auxiliary agent, and solid particles with a particle size of 0.1-2 microns to achieve a gate line with a positive trapezoidal cross section of electroplated copper. However, the invention does not involve sensitivity and resolution, and the invention uses solid particles of 0.1-2 microns, which have a large particle size. During development, these solid particles enter the developer, and during development spraying, the particles hit the surface of the cell, which may cause scratches on the surface of the cell, so it is difficult to meet application requirements. Summary of the invention

[0006] The first purpose of the present application is to provide a photosensitive resist ink that can form a resist pattern with higher resolution and smaller residual foot size, so as to improve the application performance of the existing photosensitive resist ink.

[0007] The photosensitive resist ink provided in the present application comprises the following raw materials: (A) acrylic copolymer resin; (B) a photopolymerizable compound; (C) photoinitiator; The photosensitive resist ink has a vinyl content of 0.2-0.5 mol, preferably 0.2-0.44 mol, per 100 g solid content; and / or the acrylic copolymer resin has a molecular weight of 10,000-50,000, preferably 10,000-40,000.

[0008] By adopting the above technical solution, from the perspective of improving light radiation sensitivity and cross-sectional morphology, the content of vinyl is 0.2 mol or more per 100 grams of the total composition (i.e., photosensitive resist ink) after deducting the solvent component. From the perspective of solidified product stripping, the content of vinyl is 0.5 mol, especially 0.44 mol or less per 100 grams of the total composition after deducting the solvent component. The present application reasonably controls the content of vinyl in the photosensitive resist ink, which can effectively improve the efficiency and pattern quality of the photolithography process, especially the accuracy (such as resolution and imaging quality) and film-forming properties (film quality and physical and chemical properties).

[0009] From the perspective of improving resolution and reducing residual feet, the weight average molecular weight of the acrylic copolymer resin should be 50,000 or less; from the perspective of avoiding the cross-sectional shape of the resist to form a regular trapezoid, the weight average molecular weight of the acrylic copolymer resin is preferably 10,000 or more; the weight average molecular weight of the alkali-soluble resin is more preferably 10,000 to 40,000. By selecting an acrylic copolymer resin in a specific molecular weight range, the present application can further optimize the photosensitivity, imaging resolution, stability, and adhesion to the substrate of the ink.

[0010] The raw materials of the photosensitive resist ink provided in the present application preferably further include (D) an ultraviolet absorber, and the (D) ultraviolet absorber has absorptivity to light with a wavelength of 300 to 450 nm.

[0011] (D) The ultraviolet absorber may be any ultraviolet absorber as long as it absorbs light with a wavelength of 300 to 450 nm. It may be an inorganic ultraviolet absorber or an organic ultraviolet absorber, or a combination of an organic and an inorganic ultraviolet absorber may be used.

[0012] As the inorganic ultraviolet absorber, one or more of carbon black (Tianjin Jindadi Chemical, SM100), nano cerium oxide (Zhiti Nanomicro, ZT-Ce01), nano zinc oxide (Beijing Dekedaojin Technology, DK-ZnO-15), and nano titanium oxide (Beijing Dekedaojin Technology, DK405) can be selected, and carbon black and nano zinc oxide are particularly preferred.

[0013] As the organic ultraviolet absorber, one or more of benzophenone derivatives, benzoate derivatives, benzotriazole derivatives, triazine derivatives or benzoxazine compounds may be selected.

[0014] As the benzophenone derivative, it can be selected from 2,2'-hydroxy-4-methoxybenzophenone (Nanjing Milan Chemical, BP-8), 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (Nanjing Milan Chemical, BP-6), 2,2',4,4'-tetrahydroxybenzophenone (Nanjing Milan Chemical, BP-2), etc. As the benzoate derivative, it can be selected from diethylaminohydroxybenzoyl hexyl benzoate (Nanjing Milan Chemical, UV-A PLUS), 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester (Nanjing Milan Chemical, UV-2908). As the benzotriazole derivative, it can be selected from 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Nanjing Milan Chemical, UV-P), 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole (Nanjing Milan Chemical, UV-234), 2-(-hydroxy-3-tert-butyl-5"-methylphenyl)-5-chlorobenzotriazole (Nanjing Milan Chemical, UV-326), 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole (Nanjing Milan Chemical, UV-327), 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole (Nanjing Milan Chemical, UV-328), 2,2'-methylenebis[6- (2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] (Nanjing Milan Chemical, UV-360), etc. As the triazine derivative, it can be selected from 2-[4-[2-hydroxy-3-tridecyloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and 2-[4-[2-hydroxy-3-dodecyloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine mixture (Nanjing Milan Chemical, UV-400), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-[(2-ethylhexyl) [oxy]-2-hydroxypropoxyphenol (Nanjing Milan Chemical, UV-405), etc. As benzoxazines, 2,2'-(1,4-phenylene)bis-4H-3,1-benzoxazin-4-one (Nanjing Milan Chemical, UV-3638) can be selected.

[0015] Particularly preferably, the organic ultraviolet absorber can be selected from one or more of 2,2',4,4'-tetrahydroxybenzophenone (Nanjing Milan Chemical, BP-2), 2-(-hydroxy-3-tert-butyl-5"-methylphenyl)-5-chlorobenzotriazole (Nanjing Milan Chemical, UV-326) and diethylaminohydroxybenzoyl hexyl benzoate (Nanjing Milan Chemical, UV-A PLUS), preferably one or two.

[0016] (D) UV absorber can be used alone or in combination of two or more. The amount of (D) UV absorber is preferably 0.04 to 5.1 parts by weight relative to 100 parts by weight of the total amount of the (A) component, the (B) component and the (C) component; more preferably 1 to 3.9 parts by weight, such as 0.1 to 1.9 parts by weight (excluding the maximum value of this range, the same below), 1.9 to 2.5 parts by weight, 2.5 to 3.9 parts by weight, 3.9 to 5.1 parts by weight, etc. The specific ideal amount is 0.1 parts by weight, 1.9 parts by weight, 2.5 parts by weight, 3.9 parts by weight, 5.1 parts by weight, etc.

[0017] From the perspective of deep curing property, which is beneficial for forming a cured product with an inverted trapezoidal cross-sectional morphology, the amount of (D) ultraviolet absorber is preferably greater than 0.04 parts by weight, and from the perspective of photosensitivity, the amount of (D) ultraviolet absorber is less than 5 parts by weight.

[0018] When a specific addition range of (D) UV absorber is introduced into the resin system, through exposure, the (D) UV absorber absorbs UV light within a specific wavelength range. Along the thickness direction of the resist layer, the closer to the bottom of the resist (the side of the cell seed layer), the more UV light is absorbed, thereby forming a curing degree gradient; the bottom side of the resist layer is slightly less cured than the surface side of the resist layer. During development, the bottom side of the resist layer is more easily corroded by the developer, and finally a groove formed by the resist layer is formed. The width of the upper side of the groove is smaller than the width of the lower side of the groove. During electroplating, a grid line with a right trapezoidal cross-section is finally formed.

[0019] The photosensitive resist ink provided in the present application has a refractive index higher than 1.48 at 20° C. and a wavelength of 589.3 mm.

[0020] The mechanism of the refraction angle is still unclear, but from the analysis of experimental results, it is speculated as follows: In the photosensitive resist ink, the control of the refractive index is not only related to the accuracy and efficiency of the photolithography process, but also affects the quality of the final graphics. Although the light source of the exposure equipment is parallel light, the exposure light cannot be completely parallel and still has a certain degree of divergence angle. This makes the incident light of the photosensitive resist composition not completely perpendicular to the resist coating when it is exposed, and still has a certain incident angle. When the light is transmitted in the resist coating with a higher refractive index, it has a smaller refraction angle. Therefore, the light is transmitted in the resist layer closer to being perpendicular to the resist layer, and thus has better resolution.

[0021] In the photosensitive resist ink provided in the present application, the acrylic copolymer resin as component (A) preferably comprises at least one copolymer unit having the structural formulae (I), (II) and (III).

[0022]

[0023] Wherein, R1, R3, and R5 are each independently selected from any one of a hydrogen atom or a methyl group, and R2, R4, and R6 are each independently selected from any one of a hydrogen atom, an alkyl group, an alkoxy group, an aryl group or a substituted aryl group, a hydroxyl group, or a halogen atom; Preferably, the amount of the copolymer units represented by formula (I), (II) and (III) preferably accounts for 1 to 75% of the (A) acrylic copolymer resin, and more preferably 5 to 70%.

[0024] As another technical solution of the present application, (A) acrylic copolymer resin comprises a copolymer unit represented by structural formula (IV), and the copolymer unit can be used alone or in combination with copolymer units represented by formulas (I), (II), and (III).

[0025]

[0026] Wherein, R7 is a hydrogen atom or a methyl group; Preferably, the amount of the copolymerized units of the general structural formula (IV) is 10-30% by weight of the total weight of the acrylic copolymer resin (A), more preferably 10-25%.

[0027] In addition to the above-mentioned comonomers, the (A) acrylic copolymer resin may further contain other comonomers, which may be specifically selected from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tetrahydrofuran (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate.

[0028] More specifically, the acrylic copolymer resin of component (A) is selected from one or more of acrylic acid-phenoxyethyl acrylate-methyl methacrylate-ethyl acrylate, acrylic acid-styrene-benzyl methacrylate-methyl methacrylate, acrylic acid-benzyl methacrylate-methyl methacrylate-butyl acrylate, methacrylic acid-styrene-methyl methacrylate-ethyl acrylate, methacrylic acid-phenethoxyethyl acrylate-styrene-methyl methacrylate-ethyl acrylate, methacrylic acid-methyl methacrylate-ethyl acrylate, and methacrylic acid-styrene-methyl methacrylate-ethyl acrylate.

[0029] The preparation method of the acrylic copolymer resin described in the present application may adopt a well-known method, such as solution polymerization, bulk polymerization, suspension polymerization, etc., which is known to those skilled in the art and is not particularly limited in the present application.

[0030] From the perspective of improving resolution, reducing residual feet, and improving cross-sectional morphology, the weight average molecular weight of the acrylic copolymer resin (A) should be 50,000 or less. From the perspective of avoiding the cross-sectional shape of the resist to form a regular trapezoid, the weight average molecular weight of the acrylic copolymer resin (A) is preferably 10,000 or more, and the weight average molecular weight of the alkali-soluble copolymer resin (A) is more preferably 10,000 to 40,000.

[0031] Preferably, the weight amount of the acrylic copolymer resin (A) is preferably 49-69 parts by weight, preferably 49-64 parts by weight, more preferably 50-68 parts by weight, relative to 100 parts by weight of the total amount of the (A) component, the (B) component and the (C) component. The specific ideal amount is 49.7 parts by weight, 51.1 parts by weight, 53.2 parts by weight, 56.2 parts by weight, 57.3 parts by weight, 58.2 parts by weight, 63.1 parts by weight, etc.

[0032] In the photosensitive resist ink provided by the present application, the (B) photopolymerizable compound preferably comprises a (meth)acrylate compound having three or more vinyl groups in its molecular structure, and the compound can be selected from glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, tri(2-hydroxyethyl)isocyanuric acid triacrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated propoxylated trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated propoxylated pentaerythritol tri(meth)acrylate , ethoxylated propoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, ethoxylated dipentaerythritol tri(meth)acrylate, propoxylated dipentaerythritol tri(meth)acrylate, ethoxylated propoxylated dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol tetra(meth)acrylate, propoxylated dipentaerythritol tetra(meth)acrylate, ethoxylated propoxylated dipentaerythritol tetra(meth)acrylate One or more of dipentaerythritol penta(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, propoxylated dipentaerythritol penta(meth)acrylate, ethoxylated propoxylated dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, propoxylated dipentaerythritol hexa(meth)acrylate, and ethoxylated propoxylated dipentaerythritol hexa(meth)acrylate.

[0033] In certain specific embodiments provided in the present application, the (B) photopolymerizable compound may further contain a (meth)acrylate compound having one or more vinyl groups in other molecular structures, and such compound may be selected from one or more of lauryl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, phenoxyethyl (meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, ethoxylated propoxylated bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polyethylene glycol propylene glycol di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate.

[0034] More specifically, it is preferred that (B) the photopolymerizable compound is selected from one or more of tripropylene glycol diacrylate, 4 (ethoxy) bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate, especially one, two or three. The selection of the above-mentioned photopolymerizable compounds helps to ensure the photocuring speed of the ink (especially reflected in the adaptability and compatibility with the photoinitiator described in the present application), resolution (helps to reduce light scattering and improve imaging resolution), adhesion (mainly bonding with the resin substrate) and durability, etc., and more especially enables the resist ink to obtain good sensitivity and cross-sectional morphology.

[0035] From the perspective of improving light radiation sensitivity and cross-sectional morphology, it is preferred that the vinyl content is 0.20 mol or more per 100 g of the total solid content of the composition. From the perspective of the peelability of the cured product, it is preferred that the vinyl content is 0.44 mol or less per 100 g of the total composition after deducting the solvent component.

[0036] Preferably, the weight amount of the photopolymerizable compound (B) is 28 to 46 parts by weight, preferably 30 to 45 parts by weight, and further preferably 35 to 42 parts by weight, relative to 100 parts by weight of the total amount of the (A) component, the (B) component, and the (C) component. The specific ideal amount is 34.9 parts by weight, 35.5 parts by weight, 36.8 parts by weight, 38.9 parts by weight, 40.3 parts by weight, 40.9 parts by weight, 41.6 parts by weight, 44.7 parts by weight, etc.

[0037] The photosensitive resist ink provided in the present application, (C) the photoinitiator is a substance commonly used in the field of photocuring, such as one or more of benzoin ether, benzophenone and its derivatives, thioxanthone compounds, anthraquinone and its derivatives, acridine compounds, thioxanthone compounds, hexaarylbisimidazole compounds, pyrazoline compounds, and anthracene compounds (mixed in any proportion), preferably hexaarylbisimidazole compounds or acridine compounds.

[0038] More preferably, (C) the photoinitiator may be selected from: benzoin ether, benzophenone, thioxanthone, anthraquinone, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone, 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1 ,4-naphthoquinone, 9,10-phenanthrenequinone, 2,3-dimethylanthraquinone, 9-phenylacridine, 1,7-(9,9'-acridinyl)heptane, benzoin methyl ether, benzoin ethyl ether, benzoin phenyl ether, benzyl dimethyl ketal, benzoin dimethyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin phenyl ether, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, benzophenone, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), 4,4'-bis(diethylamino)benzophenone, Isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-tert-butylanthraquinone, N,N-dimethylethyl benzoate, dimethylaminoethyl benzoate, N,N-dimethylethanolamine, 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer One or more of oxadiazole dimer, 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole, 1-phenyl-3-(4-methoxyphenylvinyl)-5-(4-methoxyphenyl)-pyrazoline, phenyl-3-(4-isopropylphenylvinyl)-5-(4-isopropylphenyl)-pyrazoline, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dibutoxyanthracene, 9,10-bis(4-methoxyphenyl)-2-chloroanthracene.

[0039] The (C) photoinitiator is particularly preferably one or more of 9-phenylacridine, 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, tetraethyl Michler's ketone, dibutoxyanthracene and 1-phenyl-3-(4-methoxyphenylvinyl)-5-(4-methoxyphenyl)-pyrazoline, preferably one, two or three. The use of the above (C) photoinitiator helps to improve the photocuring speed (mainly based on the activity level of photoinitiator), imaging resolution, adhesion (mainly based on its interaction with the surface of the resin substrate during the photocuring process) and process adaptability. Based on the selection of the photoinitiator, especially when the light source emission wavelength is 355nm or 405nm, the photosensitivity of the resist can be effectively improved.

[0040] Preferably, relative to 100 parts by weight of the total amount of the (A) component, the (B) component and the (C) component, the (C) photoinitiator is added in an amount of 0.9 to 8.1 parts by weight, preferably 1.4 to 6.9 parts by weight, such as 1.4 to 1.6 parts by weight, 4.9 to 8.1 parts by weight, etc. The specific ideal amount is 1.4 parts by weight, 1.6 parts by weight, 4.9 parts by weight, 5.2 parts by weight, 5.6 parts by weight, 5.9 parts by weight, 6.9 parts by weight, 8.1 parts by weight, etc.

[0041] The photosensitive resist ink provided in the present application may be mixed with (F) other additives in addition to the above components.

[0042] As (F) other additives, there can be cited thermal inhibitors, silane coupling agents, plasticizers, flame retardants, antistatic agents, anti-aging agents, antibacterial and mildew-proof agents, defoamers, leveling agents, fillers, thickeners, adhesion-imparting agents, thixotropic agents, colorants, photoinitiators, sensitizers, curing accelerators, anti-sticking agents, surface treatment agents, dispersants, surface modifiers, stabilizers, phosphors, etc., and more commonly used ones include defoamers, leveling agents, colorants, dispersants, curing accelerators, etc. The specific selection is added by those skilled in the art according to actual needs, and this application does not make any special restrictions on this. Preferably, the other additives (F) used in this application include diamond green, 5-carboxybenzotriazole, defoamer-Japan Shin-Etsu KS-66 and leveling agent-Digo FLOW300, etc.

[0043] Regarding the amount of (F) other additives, the weight amount of other additives (F) is preferably 0.3 to 1 part by weight, more preferably 0.5 to 0.9 part by weight, relative to 100 parts by weight of the total amount of the (A) component, the (B) component and the (C) component. The specific ideal amount is, for example, 0.5 part by weight, 0.6 part by weight, 0.7 part by weight, 0.8 part by weight, 0.9 part by weight, etc.

[0044] The photosensitive resist ink provided in the present application can further add a diluting solvent for adjusting the viscosity as needed, that is, (G) solvent, which is selected from one or more of alcohols, ketones, ethers, aromatic hydrocarbons or ester solvents; specifically, it can be selected from: alcohols such as diethylene glycol, dipropylene glycol, butanol, diacetone alcohol; ketones such as butanone, cyclohexanone, isophorone, diisobutyl ketone, methyl butyl ketone; ethers such as ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, diethoxyethanol, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol methyl ether; aromatic hydrocarbons such as toluene, xylene, tetramethylbenzene; esters such as butyl acetate, butyl lactate, dipropylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate.

[0045] Particularly preferably, the (G) solvent is diisobutyl ketone and / or dipropylene glycol methyl ether.

[0046] More preferably, the amount of the (G) solvent is 55 to 175 parts by weight, and more preferably 58 to 166 parts by weight, based on 100 parts by weight of the total amount of the (A) component, the (B) component, and the (C) component.

[0047] The raw materials of the photosensitive resist ink of the present application also include (E) fumed silica, and the (E) fumed silica can be selected from various known products commonly used in the art, preferably Degussa A200. The main function of this component in the present application is to achieve thixotropy. When not in use, it basically does not affect the important properties of the resist layer such as photosensitivity, resolution, cross-sectional morphology, residual foot, and anti-plating properties; when added, it can make the glue liquid convenient to use sizing methods such as screen printing, and there is no special restriction on the model used.

[0048] Preferably, relative to 100 parts by weight of the total amount of the (A) component, the (B) component and the (C) component, the (E) fumed silica is preferably added in an amount of 0-5.1 parts by weight; more preferably 1.5-4 parts by weight, such as 1.5-2.7 parts by weight, 2.7-5.1 parts by weight, etc., and specific ideal amounts are 1.5 parts by weight, 1.6 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.7 parts by weight, 3.5 parts by weight, 3.8 parts by weight, 4.0 parts by weight, 5.1 parts by weight, etc.

[0049] As a preferred embodiment of the present application, the photosensitive resist ink comprises

[0050] (A) 50-68 parts by weight (preferably 50-60 parts by weight) of acrylic copolymer resin; (B) 28 to 44 parts by weight (preferably 30 to 38 parts by weight) of a photopolymerizable compound; (C) 2 to 6 parts by weight (preferably 4 to 6 parts by weight) of photoinitiator; (D) 0 to 5.1 parts by weight (preferably 0.05 to 2.2 parts by weight) of ultraviolet absorber; (E) 0-5.1 parts by weight (preferably 1.5-2 parts by weight) of fumed silica; (G) an appropriate amount of solvent (preferably 55 to 175 parts by weight, more preferably 110 to 120 parts by weight); Preferably, the resist ink has a vinyl content of 0.2 to 0.44 mol per 100 g solid composition, and the acrylic copolymer resin has a molecular weight of 10,000 to 50,000. More preferably, the ultraviolet absorber has absorptivity to light with a wavelength of 300 nm to 450 nm.

[0051] The photosensitive resist ink provided in the present application can be prepared by various known processes, preferably by the following method: fumed silica, solvent, etc. are put into a closed container, dispersed by a sand mill disperser, and then an initiator, an ultraviolet absorber, other auxiliary agents, and a photopolymerizable compound are added, and dispersed by a sand mill, and finally an acrylic copolymer resin is added, and dispersed evenly by a sand mill disperser.

[0052] The specific preparation conditions are known to those skilled in the art and are not particularly limited in this application.

[0053] The second object of the present application is to provide a method for preparing a metal grid line in a photovoltaic cell, wherein the aforementioned photosensitive resist ink is laminated on a seed conductor layer of a photovoltaic cell by screen printing, and then dried to obtain a photosensitive resist layer; An exposure step of selectively transmitting active light through the photosensitive resist layer to form a photocured portion; and a development step of removing the photosensitive resist layer outside the photocured portion to obtain a resist pattern on the photovoltaic cell; The photovoltaic cell sheet with the resist pattern is plated to form a metal grid line pattern; the photovoltaic cell sheet with the metal grid line pattern is stripped to obtain the metal grid line.

[0054] By adopting the above-mentioned technical scheme, the layer structure obtained by curing the aforementioned photosensitive resist ink in combination with the corresponding processing steps can form a metal grid line with a cross-sectional pattern of a "normal trapezoid", and the pattern has excellent expressiveness and high resolution, thereby ensuring that the photovoltaic cell has an excellent photoelectric conversion effect. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of this application clearer, the technical solution in this application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] The components involved in the embodiments and comparative examples provided in this application are as follows: A-1: Acrylic acid-phenoxyethyl acrylate-methyl methacrylate-ethyl acrylate = 10-5-70-15, weight average molecular weight: 39,200

[0057] A-2: Acrylic acid-styrene-benzyl methacrylate-methyl methacrylate = 25-50-20-5, weight average molecular weight: 11,000

[0058] A-3: Acrylic acid-benzyl methacrylate-methyl methacrylate-butyl acrylate = 14-15-60-11, weight average molecular weight: 31,500

[0059] A-4: Methacrylic acid-styrene-methyl methacrylate-ethyl acrylate = 19-35-36-10, weight average molecular weight: 23,300

[0060] A-5: Methacrylic acid-phenylethoxyethyl acrylate-styrene-methyl methacrylate-ethyl acrylate = 24-10-45-11-10, weight average molecular weight: 15,600

[0061] A-6: Methacrylic acid-methyl methacrylate-ethyl acrylate = 24-61-15, weight average molecular weight: 25,300

[0062] A-7: Methacrylic acid-styrene-methyl methacrylate-ethyl acrylate = 19-35-36-10, weight average molecular weight: 72,000

[0063] B-1: Tripropylene glycol diacrylate, Miramer M222

[0064] B-2: 4 (ethoxy) bisphenol A dimethacrylate, Miramer M241

[0065] B-3: Trimethylolpropane trimethacrylate, Sartomer SR350

[0066] B-4: Pentaerythritol tetraacrylate, Sartomer SR295

[0067] B-5: Dipentaerythritol pentaacrylate, Sartomer SR399

[0068] B-6: Dipentaerythritol hexaacrylate, Miramer M600

[0069] C-1: 9-phenylacridine, Changzhou Qiangli New Material TR-PAD-101

[0070] C-2: 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, Changzhou Qiangli New Materials TR-HABI-101

[0071] C-3: Tetraethyl Michler's ketone, Changzhou Qiangli New Material TR-EMK

[0072] C-4: Dibutoxyanthracene, Changzhou Qiangli New Material TR-PSS-303

[0073] C-5: 1-phenyl-3-(4-methoxyphenylvinyl)-5-(4-methoxyphenyl)-pyrazoline

[0074] D-1: Nano zinc oxide, Beijing Dekedaojin Technology, DK-ZnO-15

[0075] D-2: Carbon black, Tianjin Jindadi Chemical, SM100

[0076] D-3: 2,2',4,4'-Tetrahydroxybenzophenone, Nanjing Milan Chemical, BP-2

[0077] D-4: 2-(-Hydroxy-3-tert-butyl-5"-methylphenyl)-5-chlorobenzotriazole, Nanjing Milan Chemical, UV-326

[0078] D-5: Diethylamino Hydroxybenzoyl Hexyl Benzoate, Nanjing Milan Chemical, UV-A PLUS

[0079] F-1: Diamond Green

[0080] F-2: 5-Carboxybenzotriazole

[0081] F-3: Defoaming agent, Shin-Etsu KS-66

[0082] F-4: Leveling agent, Digo FLOW300

[0083] E-1: Fumed silica, Degussa A200

[0084] G-1: Diisobutyl Ketone

[0085] G-2: Dipropylene glycol methyl ether

[0086] The process of making the cell resist pattern using the ink of this application: The prepared photosensitive resist ink is screen-printed using a screen with a suitable mesh size. A layer of the photosensitive resist ink is screen-printed on the cell with the seed layer deposited thereon. The cell is then baked in an oven at 95°C for 5-10 minutes to obtain a coating with a thickness of 13-15 microns. The performance is then evaluated.

[0087] Development conditions: the developer is 1% sodium carbonate aqueous solution, the development temperature is 30°C, and the spray pressure is 1.5kg / cm2; Stripping conditions: Stripping liquid is 3% sodium hydroxide aqueous solution, stripping temperature is 50℃, spraying pressure is 1.5kg / cm2; Determination of minimum developing time: According to the above developing conditions, the unexposed resist layer is dissolved and removed, and the minimum time required for complete dissolution is taken as the minimum developing time.

[0088] Exposure: Adtec IP-6 (405nm) exposure machine was used for exposure, and stouffer 41-grid exposure ruler was used for exposure energy measurement;

Evaluation of sensitivity

[0089] A direct-drawing exposure machine (Adtec, Japan, trade name "IP-6") using a blue-violet laser diode with a wavelength of 405 nm as a light source was used to expose the photosensitive resin composition layer with an energy (exposure amount) of 20 to 70 mJ / cm² through a 41-step exposure scale.

[0090] After exposure, development was performed for twice the minimum development time to remove the unexposed portion. In this way, a cured film formed of the cured product of the photosensitive resin layer was formed on the copper surface of the substrate. The energy required when the number of residual steps of the exposure scale obtained as the cured film was 16 (unit: mj / cm 2 ), as a sensitivity evaluation method, the lower the required energy, the better the sensitivity.

[0091]

Resolution evaluation

[0092]

Evaluation of residual resist layer

[0093] The resist shape was evaluated by observing the portion of the resist pattern formed in the above-mentioned resolution evaluation where a groove with a mask gap (groove) width of 15 μm was formed. The bottom of the resist groove was observed at a magnification of 1000 times at an inclination angle of 55° along the groove direction using a scanning electron microscope (SEM), and the width of the residual foot was measured. The resist residual foot was evaluated according to the following criteria. That is, if the width of the residual foot is less than 1.0 μm, it is evaluated as "A", if it is greater than or equal to 1.0 μm and less than 2 μm, it is evaluated as "B", and if it is greater than or equal to 2 μm, it is evaluated as "C".

[0094]

Evaluation of resist cross-sectional morphology

[0095] The resist cross-sectional shape was evaluated by observing the portion of the resist pattern formed in the above-mentioned resolution evaluation where a groove with a mask gap (groove) width of 15 μm was formed. The resist shape was observed using a scanning electron microscope (SEM) at a magnification of 1000 times and an inclination angle of 55°, and the resist cross-sectional morphology was evaluated according to the following criteria. That is, if the groove shape formed by the resist is a cross-section with a narrow top and a wide bottom, that is, the upper edge width is smaller than the lower edge width, it is evaluated as "A", if the groove formed by the resist is a rectangular cross-section, or the shape is a cross-section with a narrow bottom and a wide top, that is, the upper edge width is greater than or equal to the lower edge width, and the difference is greater than or equal to 0 μm and less than 3 μm, it is evaluated as "B", if the groove shape formed by the resist is a cross-section with a narrow bottom and a wide top, that is, the upper edge width is larger than the lower edge width, and the difference is greater than or equal to 3.0 μm, it is evaluated as "C".

[0096]

Evaluation of anti-plating performance

[0097] Expose and develop using a photomask with Line / Space=400 / 15μm, immerse the cell in a pre-configured copper plating solution, with a current density of 2ASD and electroplating for 15 min. After washing, remove the cured film from the cell, and observe the appearance of the sample using a 500x high-resolution scanning electron microscope to see if there is any infiltration.

[0098] Examples 1-17 and Comparative Examples 1-4

[0099] The specific selection and relative weight dosage of each component in Examples 1-17 and Comparative Examples 1-4 and the performance evaluation results are shown in Table 1.

[0100] Table 1

[0101] By comparing Examples 1-17 with Comparative Examples 1-4, it can be found that Examples 1-17 all obtained photosensitive resist inks with relatively excellent key comprehensive properties such as refractive index, sensitivity, resolution, residual foot size, and electroplating performance. Among them, no ultraviolet absorber was added in Example 16, and its implementation results showed that the overall comprehensive performance of the corresponding resist was not greatly affected.

[0102] Comparative Examples 1 and 2 use different main resins (A6 and A7), and A7 uses a high molecular weight acrylic copolymer resin. As a result, the residual foot evaluation is significantly deviated, and the cross-sectional morphology also shows different degrees of deficiencies. Comparative Example 3 uses a vinyl content significantly lower than that of the present application, and the sensitivity and resolution of the resulting resist ink are significantly poor, the cross-sectional morphology of the resist is evaluated low, and plating occurs. Although Comparative Example 4 increases the vinyl content, the residual foot and cross-sectional morphology of the resist layer of the resulting resist ink are still not significantly improved.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A photosensitive resist ink, characterized in that: Its raw materials include: (A) acrylic copolymer resin; (B) a photopolymerizable compound; (C) photoinitiator; The photosensitive resist ink has a vinyl content of 0.2-0.5 mol, preferably 0.2-0.44 mol, per 100 g solid content; and / or the acrylic copolymer resin has a molecular weight of 10,000-50,000, preferably 10,000-40,000.

2. The photosensitive resist ink according to claim 1, characterized in that It also includes (D) an ultraviolet absorber, wherein the (D) ultraviolet absorber has absorptivity to light with a wavelength of 300 to 450 nm; Preferably, the (D) ultraviolet absorber is an inorganic ultraviolet absorber and / or an organic ultraviolet absorber; the inorganic ultraviolet absorber is selected from one or more of carbon black, nano-cerium oxide, nano-zinc oxide, and nano-titanium oxide; the organic ultraviolet absorber is selected from one or more of benzophenone derivatives, benzoate derivatives, benzotriazole derivatives, triazine derivatives, or benzoxazine compounds; Preferably, the amount of the (D) ultraviolet absorber is 0.04 to 5.1 parts by weight, preferably 1 to 3.9 parts by weight, based on 100 parts by weight of the total amount of the (A) component, the (B) component, and the (C) component.

3. The photosensitive resist ink according to any one of claims 1 or 2, characterized in that: The photosensitive resist ink has a refractive index higher than 1.48 at 20° C. and a wavelength of 589.3 nm.

4. The photosensitive resist ink according to any one of claims 1 to 3, characterized in that: The (A) acrylic copolymer resin comprises at least one copolymer unit having a structural formula as shown in formula (I), (II), or (III); Wherein, R1, R3, and R5 are each independently selected from any one of a hydrogen atom or a methyl group, and R2, R4, and R6 are each independently selected from any one of a hydrogen atom, an alkyl group, an alkoxy group, an aryl group or a substituted aryl group, a hydroxyl group, or a halogen atom; Preferably, the copolymer units represented by formula (I), (II) and (III) account for 1 to 75% of the (A) acrylic copolymer resin; Preferably, the (A) acrylic copolymer resin further comprises a copolymer unit represented by formula (IV), Wherein, R7 is a hydrogen atom or a methyl group; Preferably, the copolymer unit represented by formula (IV) accounts for 10-30% of the total weight of the (A) acrylic copolymer resin.

5. The photosensitive resist ink according to any one of claims 1 to 4, characterized in that: The (A) acrylic copolymer resin further comprises one or more comonomers selected from methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tetrahydrofuran (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate; The (A) acrylic copolymer resin is preferably added in an amount of 49 to 69 parts by weight, preferably 50 to 68 parts by weight, based on 100 parts by weight of the total amount of the (A) component, the (B) component, and the (C) component.

6. The photosensitive resist ink according to any one of claims 1 to 5, characterized in that: The (B) photopolymerizable compound comprises a (meth)acrylate compound having three or more vinyl groups in its molecular structure, and the (meth)acrylate compound having three or more vinyl groups in its molecular structure is preferably selected from glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanuric acid triacrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, Propane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated propoxylated trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated propoxylated pentaerythritol tri(meth)acrylate acrylate, ethoxylated propoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, ethoxylated dipentaerythritol tri(meth)acrylate, propoxylated dipentaerythritol tri(meth)acrylate, ethoxylated propoxylated dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol tetra(meth)acrylate, propoxylated dipentaerythritol tetra(meth)acrylate, ethoxylated propoxylated dipentaerythritol One or more of alcohol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, propoxylated dipentaerythritol penta(meth)acrylate, ethoxylated propoxylated dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, propoxylated dipentaerythritol hexa(meth)acrylate, and ethoxylated propoxylated dipentaerythritol hexa(meth)acrylate; The amount of the photopolymerizable compound (B) is preferably 28 to 46 parts by weight, more preferably 30 to 45 parts by weight, based on 100 parts by weight of the total amount of the components (A), (B) and (C).

7. The photosensitive resist ink according to any one of claims 1 to 6, characterized in that: The (C) photoinitiator is one or more of benzoin ether, benzophenone and its derivatives, thioxanthone compounds, anthraquinone and its derivatives, acridine compounds, thioxanthone compounds, hexaarylbisimidazole compounds, pyrazoline compounds, and anthracene compounds; preferably, hexaarylbisimidazole compounds or acridine compounds; More preferably, the photoinitiator (C) is selected from benzoin ether, benzophenone, thioxanthone, anthraquinone, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone, 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1 ,4-naphthoquinone, 9,10-phenanthrenequinone, 2,3-dimethylanthraquinone, 9-phenylacridine, 1,7-(9,9'-acridinyl)heptane, benzoin methyl ether, benzoin ethyl ether, benzoin phenyl ether, benzyl dimethyl ketal, benzoin dimethyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin phenyl ether, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, benzophenone, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), 4,4'-bis(diethylamino)benzophenone, Isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-tert-butylanthraquinone, N,N-dimethylethyl benzoate, dimethylaminoethyl benzoate, N,N-dimethylethanolamine, 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer One or more of oxadiazole dimer, 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole, 1-phenyl-3-(4-methoxyphenyl)-5-(4-methoxyphenyl)-pyrazoline, phenyl-3-(4-isopropylphenyl)-5-(4-isopropylphenyl)-pyrazoline, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dibutoxyanthracene, 9,10-bis(4-methoxyphenyl)-2-chloroanthracene; More preferably, the amount of the photoinitiator (C) is 0.9 to 8.1 parts by weight, preferably 1.4 to 6.9 parts by weight, based on 100 parts by weight of the total amount of the components (A), (B) and (C).

8. The photosensitive resist ink according to any one of claims 1 to 7, characterized in that: The raw material further includes (G) a solvent, wherein the (G) solvent is selected from one or more of alcohols, ketones, ethers, aromatic hydrocarbons or esters; Preferably, the ethers are selected from one or more of diethylene glycol, dipropylene glycol, butanol or diacetone alcohol; the ketones are selected from one or more of butanone, cyclohexanone, isophorone, diisobutyl ketone or methyl butyl ketone; the ethers are selected from one or more of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, diethoxyethanol, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether or tripropylene glycol methyl ether; the aromatic hydrocarbons are selected from one or more of toluene, xylene or tetramethylbenzene; the esters are selected from one or more of butyl acetate, butyl lactate, dipropylene glycol methyl ether acetate or diethylene glycol ethyl ether acetate; More preferably, the amount of the (G) solvent is 55 to 175 parts by weight, and more preferably 58 to 166 parts by weight, based on 100 parts by weight of the total amount of the (A) component, the (B) component, and the (C) component.

9. The photosensitive resist ink according to claim 8, characterized in that The raw materials also include (E) fumed silicon dioxide; The amount of (E) fumed silica is preferably 0 to 5.1 parts by weight, more preferably 1.5 to 4 parts by weight, based on 100 parts by weight of the total amount of the components (A), (B) and (C).

10. A method for preparing a metal grid line in a photovoltaic cell, characterized in that: include: The photosensitive resist ink according to any one of claims 1 to 9 is laminated on the seed conductor layer of the photovoltaic cell by screen printing, and then dried to obtain a photosensitive resist layer; An exposure step of selectively transmitting active light through the photosensitive resist layer to form a photocured portion; and a developing step of removing the photosensitive resist layer outside the photocured portion to obtain a resist pattern on the photovoltaic cell; The photovoltaic cell sheet with the resist pattern is plated to form a metal grid line pattern; and the photovoltaic cell sheet with the metal grid line pattern is stripped to obtain the metal grid line.

Images