Silver paste with adjustable color on the back of sintered glass, method and automotive glass

Abstract

This invention relates to a silver paste with adjustable backside color after sintering, a method thereof, and automotive glass. By mass percentage, it comprises the following components: 50%–75% conductive silver powder, 2%–8% glass powder, and 25%–45% organic carrier. The glass powder is a borosilicate system containing alkali metal oxides. By adjusting the mass percentage content of the alkali metal oxides in the glass powder, the diffusion rate and depth of silver ions in the float glass matrix are adjusted, thereby achieving control over the color development of the backside of the sintered glass. This invention significantly improves the controllability, uniformity, and stability of the backside color of the glass, effectively eliminating color differences and meeting the stringent aesthetic requirements of high-end automotive glass, while maintaining the excellent conductivity and adhesion of the silver paste.

Description

Technical Field

[0001] This invention relates to the technical field of materials for silver lines used in automotive front and rear windshield defrosters, specifically to a silver paste with adjustable color on the back of sintered glass, a method thereof, and automotive glass. Background Technology

[0002] In the automotive glass manufacturing industry, silver paste is a key material for rear windshield defrosting lines and antenna printing. Its post-sintering performance must simultaneously meet core indicators such as conductivity, adhesion, and weather resistance. However, a serious drawback of existing technologies has long existed: when silver paste is printed onto the tin side of float glass (i.e., the surface in contact with molten tin during the forming process) and undergoes a high-temperature sintering process, uncontrollable color development occurs in the corresponding area on the back side of the glass (i.e., the air side), typically manifesting as mixed hues such as yellow, brown, or red. More importantly, the depth and specific hue of this color development fluctuate significantly across different production batches or process conditions, resulting in poor consistency in the appearance of automotive glass and making it difficult to meet the stringent visual quality requirements of high-end models.

[0003] To improve the aforementioned color development issues, existing technologies mainly employ two approaches: one is to add transition metal oxides (such as oxides of molybdenum, manganese, and chromium) or inorganic colorants to the silver paste, attempting to cover the substrate color by deepening the color of the paste surface, resulting in a dark gray or black appearance after sintering; the other is to introduce metal compounds such as chromium and tin as reducing agents, aiming to inhibit the migration and diffusion of silver ions into the glass interior. However, in practice, it has been proven that the first method cannot block the color development mechanism of the glass itself, and the underlying yellow / brown hues will still show through the dark paste layer; the second method, due to the rigid requirements of the silver paste's conductivity and adhesion, requires insufficient reducing agent addition, and can only slightly reduce the degree of color development, failing to achieve precise color control.

[0004] Therefore, the industry urgently needs an innovative solution that can achieve precise control of color development from the source of silver ion diffusion dynamics, in order to completely solve the problems of uncontrollable color on the back of the glass and batch color difference. Summary of the Invention

[0005] To address the problems in the prior art, the purpose of this invention is to provide a silver paste with adjustable color on the back of sintered glass, a method thereof, and automotive glass.

[0006] The silver paste for automotive glass with adjustable back color after sintering, provided by the present invention, is composed of the following components by mass percentage: 50%–75% conductive silver powder, 2%–8% glass powder, and 25%–45% organic carrier; The glass powder is a borosilicate system containing alkali metal oxides; By adjusting the mass percentage content of the alkali metal oxide in the glass powder, the diffusion rate and depth of silver ions in the float glass matrix can be adjusted, thereby achieving the adjustment of the color development degree on the back of the sintered glass.

[0007] Preferably, the basic composition of the glass powder includes Bi2O3, SiO2, B2O3, ZnO, Al2O3, and Na2O and / or K2O; The alkali metal oxide contains at least one of Na2O and K2O.

[0008] Preferably, the glass powder comprises at least one of highly reactive glass powder and low-reactive glass powder. The total content of Na2O and K2O in the highly active glass powder is 5wt% to 15wt%, and the softening point is 500℃ to 600℃. The total content of Na2O and K2O in the low-activity glass powder is 0wt% to 5wt%, and the softening point is 550℃ to 650℃.

[0009] Preferably, by changing the blending ratio of the high-activity glass powder and the low-activity glass powder in the silver paste, the color of the back of the sintered glass can be continuously adjusted between light yellow and brownish-red.

[0010] When the high-activity glass powder content is less than 30%, the back of the sintered glass is light yellow; when the high-activity glass powder content is 30-50%, the back of the sintered glass is brownish-yellow; and when the high-activity glass powder content is greater than 50%, the back of the sintered glass is brownish-red.

[0011] Preferably, the mass percentage content range of each component of the glass powder is: Bi2O360%~70%, B2O310%~15%, ZnO8%~12%, SiO27%~15%, Al2O32%~4%, Na2O0%~6%, K2O1%~6%.

[0012] Preferably, the conductive silver powder is in the form of flakes or spheres, with a particle size ranging from 1.0 μm to 10.0 μm and a specific surface area of ​​0.5 m². 2 / g~2.0m 2 / g, tap density ≥3.5g / cm³ 3 ; The particle size of the glass powder is controlled to be 1.0 μm to 5.0 μm, and D90 ≤ 8 μm.

[0013] Preferably, the organic carrier is composed of an adhesive resin and an organic solvent, and the solid content of the organic carrier is 15wt% to 25wt%. The adhesive resin is selected from at least one of ethyl cellulose and acrylic resin; The organic solvent is selected from at least one of terpineol and butyl carbitol acetate.

[0014] The method for preparing the sintered, color-adjustable silver paste for automotive glass provided by the present invention includes the following steps: Step S1: Glass powder preparation. Glass raw materials are prepared according to the target alkali metal content, melted at 1400℃~1550℃ for 2h~4h, quenched in water, crushed, and ball-milled until the median diameter D50 is 1.0μm~3.0μm. Step S2: Slurry mixing. The conductive silver powder and the selected type of glass powder are added to the organic carrier and stirred at a speed of 800 rpm to 1500 rpm for 30 min to 60 min to obtain a mixed slurry. Step S3: Dispersion grinding. The mixed slurry is ground 5 to 10 times by a three-roll mill. During the grinding process, the gap between the rollers is gradually reduced to 5 μm to 10 μm. Finally, it is filtered through a 400-600 mesh sieve to obtain the silver paste.

[0015] The method for adjusting the back color of float glass provided by the present invention uses the silver paste, which is printed onto the tin surface of the float glass and sintered under a tempering process at 650℃±50℃. During the sintering process, by changing the content of alkali metal oxides in the glass powder of the silver paste, the exchange reaction between the silver ions released by the silver paste and the sodium ions on the surface of the float glass, as well as the diffusion depth of the silver ions, are controlled to regulate the size of the generated silver colloidal particles, thereby achieving color control of the back of the glass from light yellow to brownish-red.

[0016] The automotive glass provided by the present invention includes a float glass substrate and conductive defrosting lines and / or antennas attached to the surface of the float glass substrate, wherein the conductive defrosting lines and / or antennas are made by printing and sintering the silver paste.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention, through glass powder formulation design, enables continuous color control from light yellow, golden yellow, brownish yellow to dark brown, meeting the matching needs of different glass base colors. The colorant exists in the glass network in ionic form, exhibiting excellent chemical stability and UV aging resistance. While achieving color control, the core properties of the silver paste, such as adhesion, conductivity, and scratch resistance, remain unaffected and can even be improved by optimizing the softening point of the glass powder. The silver paste of this invention can be directly applied to the printing and sintering processes of existing defogging silver lines without the need for additional equipment or procedures. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram illustrating the color change of glass powder in an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0020] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0022] The technical solutions of the present invention and how they solve the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0023] In-depth analysis reveals that the root cause of the failure of existing solutions lies in their failure to address the fundamental mechanism of the color development phenomenon. During the sintering process of the tin surface of float glass, silver ions (Ag) released from the silver paste... + It will react with alkali metal ions (such as Na) in the glass surface. + An ion exchange reaction occurs, and the silver ions diffuse inward through the glass network structure. These diffused silver ions are reduced under specific temperature and reducing conditions, forming nanoscale silver colloidal particles. These colloidal particles selectively absorb specific wavelengths of visible light through surface plasmon resonance, directly causing characteristic color development on the back of the glass. The specific hue of the color development depends on the size and distribution density of the silver colloidal particles, while the particle growth state is determined by the diffusion depth and reduction rate of the silver ions. Existing technologies, whether employing color masking or local diffusion inhibition, are all passive strategies and fail to actively regulate the ion exchange environment to intervene in the nucleation and growth kinetics of the silver colloidal particles, resulting in color development results that remain random and uncontrollable.

[0024] This invention provides a silver paste with adjustable color on the back of sintered automotive glass. The core inventive concept lies in: based on the high-temperature sintering process of the silver paste on the tin surface of float glass, silver ions (Ag)... + ) and alkali metal ions (mainly Na) in the glass surface layer + The silver undergoes ion exchange and diffuses into the glass interior, subsequently being reduced to form nano-silver colloidal particles. These particles, due to surface plasmon resonance, produce a characteristic color on the back of the glass. This mechanism is achieved by precisely controlling the content of alkali metal oxides (Na₂O and / or K₂O) in the glass powder within the silver paste, thus actively controlling the Ag content. + The diffusion rate and depth in the float glass matrix are controlled, thereby regulating the size and distribution density of the silver colloidal particles, ultimately achieving continuous, stable, and controllable adjustment of different hues on the back of the glass, ranging from light yellow to brownish-red.

[0025] The silver paste of this invention comprises, by mass percentage, 50%–75% conductive silver powder, 2%–8% glass powder, and 25%–45% organic carrier. If the conductive silver powder content is below 50%, the resistivity of the conductive layer increases after sintering, making it difficult to meet the conductivity requirements for automotive defrosting and antennas; if it is above 75%, the paste viscosity is too high, resulting in poor printability. When the glass powder content is below 2%, its regulatory effect on ion exchange is weak, and the color adjustment effect is not obvious; when it is above 8%, excessive glass phase may lead to decreased silver layer adhesion or deteriorated conductivity.

[0026] The glass powder is a borosilicate system, whose basic components include Bi₂O₃, SiO₂, B₂O₃, ZnO, Al₂O₃, and Na₂O and / or K₂O. Bi₂O₃, as the main network former, lowers the glass softening point and improves its wettability to silver; B₂O₃ and SiO₂ constitute the network framework; ZnO and Al₂O₃ regulate the glass's chemical stability and coefficient of thermal expansion; Na₂O and K₂O are key functional components used to regulate Ag₂ content. + / Na + The activity of the exchange reaction.

[0027] Based on the different total alkali metal oxide contents, this invention classifies glass powder into the following two categories: Highly reactive glass powder with a total alkali metal oxide (Na₂O + K₂O) content of ≥5wt% and ≤15wt% and a softening point of 500℃~600℃. This type of glass powder can significantly accelerate Ag sintering. + With glass surface Na + The exchange rate promotes Ag + Diffusion into the depth of the glass helps to form larger silver colloidal particles, giving the back of the glass a darker hue (such as brown or reddish-brown).

[0028] Low-activity glass powder has a total alkali metal oxide (Na₂O + K₂O) content greater than 0 wt% and less than 5 wt%, with a softening point of 550℃~650℃. This type of glass powder inhibits ion exchange reactions and limits Ag⁻ content. + The diffusion depth limits the growth of silver colloidal particles, resulting in smaller or lower-density colloidal particles, giving the back of the glass a lighter hue (such as a light yellow).

[0029] By blending high-activity and low-activity glass powders in different mass ratios, the color of the back of the sintered glass can be continuously and repeatedly precisely controlled between light yellow and brownish-red.

[0030] In a preferred embodiment, the mass percentage range of each component of the glass powder is: Bi2O3 60%~70%, B2O3 10%~15%, ZnO 8%~12%, SiO2 7%~15%, Al2O3 2%~4%, Na2O 0%~6%, K2O 1%~6%.

[0031] The conductive silver powder is in the form of flakes or spheres, with a particle size ranging from 1.0 μm to 10.0 μm and a specific surface area of ​​0.5 m². 2 / g~2.0 m 2 / g, tap density ≥3.5 g / cm³ 3 Selecting silver powder within this parameter range can yield good sintering density and conductive network.

[0032] The organic carrier is composed of an adhesive resin and an organic solvent, with a solid content of 15 wt% to 25 wt%. The adhesive resin is selected from at least one of ethyl cellulose and acrylic resin, preferably ethyl cellulose; the organic solvent is selected from at least one of terpineol and butyl carbitol acetate, preferably terpineol. The organic carrier provides a dispersion medium and printability for silver powder and glass powder, and completely volatilizes or decomposes during sintering.

[0033] A typical preparation method of the silver paste of the present invention includes the following steps: For glass powder preparation, accurately weigh each glass raw material (Bi2O3, SiO2, B2O3, ZnO, Al2O3, Na2CO3 or Na2O, K2CO3 or K2O, etc.) according to the target alkali metal content, mix them evenly, and place them in a platinum or corundum crucible. Melt them at 1400℃~1550℃ for 2h~4h. Water quench the molten glass to obtain glass fragments, crush them, and then wet ball mill them in a planetary ball mill until the median diameter D50 is 1.0μm~3.0μm and D90 ≤8μm. Dry them for later use.

[0034] For slurry mixing, weigh conductive silver powder and selected type and proportion of glass powder according to the formula ratio, add them to the organic carrier, and mechanically stir at a speed of 800 rpm to 1500 rpm for 30 min to 60 min to obtain a preliminarily dispersed mixed slurry.

[0035] The mixture is then dispersed and ground in a three-roll mill, with 5 to 10 passes. During the grinding process, the gap between the rollers is gradually reduced to 5 μm to 10 μm. The ground slurry is then filtered through a 400-600 mesh sieve to remove large particles and impurities, yielding the finished silver paste.

[0036] The prepared silver paste is screen-printed onto the tin side of the float glass (the surface in contact with molten tin during the forming process) to form defrost lines or antenna patterns. It is then sintered in a tempering furnace at 650℃±50℃, with the holding time synchronized with the glass tempering process (usually 2–5 minutes). After sintering, it is cooled in the furnace to obtain automotive glass with controllable back color.

[0037] In the following examples, the conductive silver powder used is spherical silver powder with an average particle size D50 of 5.0 μm and a specific surface area of ​​1.2 m². 2 / g, tap density 3.8 g / cm³ 3The organic carrier was a 20 wt% solids solution of ethyl resin (STD-100) dissolved in terpineol. The glass powder particle size was controlled to be D50 = 2.0 μm and D90 = 6.5 μm. All examples and comparative examples used the same printing, drying (120°C × 10 min), and sintering processes (650°C × 3 min).

[0038] Example 1

[0039] The glass powder used has the following composition by mass percentage: Bi₂O₃ 62%, B₂O₃ 11%, ZnO 9%, SiO₂ 9%, Al₂O₃ 3%, Na₂O 4%, K₂O 2% (total Na₂O + K₂O content = 6wt%). Its softening point is approximately 540℃.

[0040] Silver paste formula: 65% conductive silver powder, 5% glass powder, and 30% organic carrier.

[0041] After sintering, the back of the glass is a uniform brownish-red color with a color difference value ΔE < 1.5 (relative to the standard plate). The resistivity of the silver layer is 2.8 mΩ·cm, and the adhesion is 100% with no peeling.

[0042] Example 2

[0043] The glass powder used has the following composition by mass percentage: Bi₂O₃ 66%, B₂O₃ 13%, ZnO 10%, SiO₂ 7%, Al₂O₃ 3%, Na₂O 0.5%, K₂O 0.5% (total Na₂O + K₂O content = 1.0 wt%). Its softening point is approximately 620℃.

[0044] Silver paste formula: 65% conductive silver powder, 5% glass powder, and 30% organic carrier.

[0045] After sintering, the back of the glass is a uniform light yellow color. The resistivity of the silver layer is 2.7 mΩ·cm, and the adhesion is 100% with no peeling.

[0046] Example 3

[0047] The high-activity glass powder from Example 1 and the low-activity glass powder from Example 2 were compounded at a mass ratio of 1:1, with the total glass powder accounting for 5% of the silver paste.

[0048] Silver paste formula: 65% conductive silver powder, 5% composite glass powder, and 30% organic carrier.

[0049] After sintering, the back of the glass is uniformly golden yellow (between light yellow and brownish-red). The silver layer has a resistivity of 2.8 mΩ·cm and 100% adhesion with no peeling.

[0050] Example 4

[0051] The same highly active glass powder as in Example 1 was used, but the glass powder content in the silver paste formulation was adjusted to 2%.

[0052] Silver paste formula: 70% conductive silver powder, 2% glass powder, and 28% organic carrier.

[0053] After sintering, the back of the glass was light brown, with a significantly lower color depth than in Example 1. The resistivity of the silver layer was 2.6 mΩ·cm, and the adhesion was 100% with no peeling.

[0054] Example 5

[0055] The same low-activity glass powder and formulation as in Example 2 were used, but the conductive silver powder was replaced with spherical silver powder with D50=2.0 μm.

[0056] After sintering, the back of the glass remained light yellow, essentially the same as in Example 2. The silver layer resistivity was 2.9 mΩ·cm, and adhesion was 100% with no peeling.

[0057] Comparative Example 1 The glass powder composition does not include Na2O and K2O, and the remaining components are the same as in Example 2: Bi2O3 67%, B2O3 13%, ZnO 10%, SiO2 7%, Al2O3 3%.

[0058] The silver paste formulation and preparation process are the same as in Example 2.

[0059] After sintering, the back of the glass appears bright yellow, but the adhesion between the silver layer and the glass substrate decreases to 85% (cross-cut test).

[0060] Comparative Example 2 The total Na2O+K2O content in the glass powder is 18% (Na2O 10%, K2O 8%), and the remaining components are adjusted proportionally.

[0061] The silver paste formulation and preparation process are the same as in Example 1.

[0062] After sintering, the back of the glass turned a deep reddish-brown, but the color uniformity deteriorated, with obvious local spots appearing. Furthermore, the resistivity of the silver layer increased to 4.5 mΩ·cm, and the adhesion decreased to 90%. This indicates that when the alkali metal content exceeded the preferred range, the ion exchange reaction became too vigorous, leading to uncontrolled diffusion.

[0063] The test results of the above embodiments and comparative examples are summarized and compared as follows.

[0064] Regarding color control, Example 1 used highly active glass powder with a total Na2O+K2O content of 6wt%, resulting in a uniform brownish-red back surface after sintering; Example 2 used low-active glass powder with a total content of 1wt%, resulting in a uniform light yellow back surface; Example 3 combined the two in a 1:1 ratio, resulting in a mid-tone golden yellow back surface; Example 4 reduced the amount of highly active glass powder to 2%, resulting in a light brown back surface, indicating that the color depth can be further fine-tuned by adjusting the glass powder content; Example 5 changed the form of silver powder, resulting in the same color as Example 2, indicating that the color is mainly determined by the glass powder. Comparative Example 1 used glass powder without alkali metal oxides, resulting in a bright yellow color, but the adhesion decreased to 85%; Comparative Example 2 used glass powder with an alkali metal content as high as 18%, resulting in a deep reddish-brown back surface with obvious spots, an increase in resistivity to 4.5 mΩ·cm, and a decrease in adhesion to 90%.

[0065] Regarding electrical conductivity, the resistivity of Examples 1 to 5 remained stable between 2.6 and 2.9 mΩ·cm, significantly better than the 4.5 mΩ·cm of Comparative Example 2. Regarding adhesion, Examples 1 to 5 achieved 100% adhesion without peeling using the cross-cut adhesion test, while Comparative Example 1 only achieved 85%, and Comparative Example 2 achieved 90%. Regarding color uniformity, Examples 1 to 5 exhibited uniformity, while Comparative Example 2 showed localized color spots.

[0066] The above results fully demonstrate that, through the technical solution of the present invention, it is possible to achieve precise, uniform, and stable control of the back color of float glass within the range of light yellow to brownish-red while maintaining excellent conductivity and adhesion.

[0067] In this embodiment of the invention, by adjusting the content of alkali metal oxides (Na2O+K2O) in the glass powder of the silver paste (0wt%~15wt%) and the compounding ratio of high / low activity glass powder, the back color of the float glass tin surface after sintering can be continuously, stably and controllably adjusted within a wide color gamut of light yellow, golden yellow and brownish red, with a color difference value ΔE<2.0, which completely solves the problem of uncontrollable color and large batch color difference of traditional silver paste.

[0068] While achieving color control, the resistivity of the conductive layer after silver paste sintering is stable at ≤3.0 mΩ·cm, the cross-cut adhesion is 100% with no peeling, and the resistance to organic solvents and acids is normal, meeting the stringent reliability requirements of automotive glass defrosting and antenna systems.

[0069] This invention eliminates the need for additional colorants or silver ion reducing agents, avoiding the risks of decreased conductivity, deteriorated adhesion, or environmental hazards associated with adding external components in traditional methods. All control is achieved through the intrinsic composition of the glass powder. It can be directly applied to existing automotive glass tempering production lines without altering printing, drying, or sintering equipment or process parameters, facilitating industrial-scale promotion. The coloring mechanism originates from the silver colloidal particles within the glass, rather than a surface coating, thus exhibiting excellent resistance to UV aging, acids and alkalis, and temperature shock. After 200 temperature shock cycles from -40℃ to 85℃, there is no significant change in color or conductivity.

[0070] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0071] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A silver paste for automotive glass with adjustable color on the back of the sintered glass, characterized in that, By mass percentage, it consists of the following components: 50%–75% conductive silver powder, 2%–8% glass powder, and 25%–45% organic carrier; The glass powder is a borosilicate system containing alkali metal oxides; By adjusting the mass percentage content of the alkali metal oxide in the glass powder, the diffusion rate and depth of silver ions in the float glass matrix can be adjusted, thereby achieving the adjustment of the color development degree on the back of the sintered glass.

2. The silver paste according to claim 1, characterized in that, The basic composition of the glass powder includes Bi2O3, SiO2, B2O3, ZnO, Al2O3, and Na2O and / or K2O; The alkali metal oxide contains at least one of Na2O and K2O.

3. The silver paste according to claim 1 or 2, characterized in that, The glass powder includes at least one of high-activity glass powder and low-activity glass powder: The total content of Na2O and K2O in the highly active glass powder is 5wt% to 15wt%, and the softening point is 500℃ to 600℃. The total content of Na2O and K2O in the low-activity glass powder is 0wt% to 5wt%, and the softening point is 550℃ to 650℃.

4. The silver paste according to claim 3, characterized in that, By changing the blending ratio of the high-activity glass powder and the low-activity glass powder in the silver paste, the color of the back of the sintered glass can be continuously adjusted between light yellow and brownish-red.

5. The silver paste according to claim 2, characterized in that, The mass percentage content range of each component of the glass powder is as follows: Bi2O360%~70%, B2O310%~15%, ZnO8%~12%, SiO27%~15%, Al2O32%~4%, Na2O0%~6%, K2O1%~6%.

6. The silver paste according to claim 1, characterized in that, The conductive silver powder is in the form of flakes or spheres, with a particle size ranging from 1.0 μm to 10.0 μm and a specific surface area of ​​0.5 m². 2 / g~2.0m 2 / g, tap density ≥3.5g / cm³ 3 ; The particle size of the glass powder is controlled to be 1.0 μm to 5.0 μm, and D90 ≤ 8 μm.

7. The silver paste according to claim 1, characterized in that, The organic carrier is composed of an adhesive resin and an organic solvent, and the solid content of the organic carrier is 15wt% to 25wt%. The adhesive resin is selected from at least one of ethyl cellulose and acrylic resin; The organic solvent is selected from at least one of terpineol and butyl carbitol acetate.

8. A method for preparing a sintered silver paste with adjustable back color for automotive glass as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step S1: Glass powder preparation. Glass raw materials are prepared according to the target alkali metal content, melted at 1400℃~1550℃ for 2h~4h, quenched in water, crushed, and ball-milled until the median diameter D50 is 1.0μm~3.0μm. Step S2: Slurry mixing. The conductive silver powder and the selected type of glass powder are added to the organic carrier and stirred at a speed of 800 rpm to 1500 rpm for 30 min to 60 min to obtain a mixed slurry. Step S3: Dispersion grinding. The mixed slurry is ground 5 to 10 times by a three-roll mill. During the grinding process, the gap between the rollers is gradually reduced to 5 μm to 10 μm. Finally, it is filtered through a 400-600 mesh sieve to obtain the silver paste.

9. A method for adjusting the color of the back side of float glass, characterized in that, Using any one of claims 1 to 7, the silver paste is printed onto the tin surface of float glass and sintered under a tempering process at 650℃±50℃. During the sintering process, by changing the content of alkali metal oxides in the glass powder of the silver paste, the exchange reaction between the silver ions released by the silver paste and the sodium ions on the surface of the float glass, as well as the diffusion depth of the silver ions, are controlled to regulate the size of the generated silver colloidal particles, thereby achieving color control of the back of the glass from light yellow to brownish-red.

10. An automotive glass, characterized in that, It includes a float glass substrate and a conductive defrosting line and / or antenna attached to the surface of the float glass substrate, the conductive defrosting line and / or antenna being made by printing and sintering the silver paste of any one of claims 1 to 7.

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