Post-processing process for thin glass substrate

Abstract

The present invention provides a post-processing process for thin glass substrates. Compared with the prior art, the present invention pre-tempers the thin glass substrates to make their surface stress values ​​and stress layer depths smaller than general values, thereby ensuring that the glass substrate products have better toughness than untempered products. At the same time, after fine grinding of one side, no obvious warping will occur, so that the other side can be surface-treated to make the compressive stresses on both sides the same, avoiding the risk of warping. Finally, a second tempering treatment can be performed to ensure that the repaired thin glass substrate has good chemical strength and other properties while also having a good appearance. In addition, the process breakage rate is significantly reduced compared to traditional processes. Furthermore, the present invention directly bonds the thin glass substrate to a viscosity-reducing film material to grind and repair surface defects on the ultra-thin glass substrate, greatly improving production efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a post-processing process for a thin glass substrate. Background Art

[0002] With the development of the display industry, electronic display products are gradually moving towards lighter, thinner, and more flexible foldable designs. Major device manufacturers, such as Samsung, release at least one foldable flagship phone annually. These foldable phones typically use transparent polyimide (CPI) film or ultra-thin glass (UTG) as the outer substrate. UTG substrates offer advantages over CPI, such as better heat resistance, fewer creases, and a longer lifespan. However, they also suffer from issues such as low yield and high cost.

[0003] The high production cost of UTG substrates has always been a major factor in their manufacturing process yield. Surface scratches, a key factor impacting UTG substrate yield, are primarily caused by micro-scratches amplified during the etching process and contact with hard objects during the process. Because UTG products are extremely thin, typically under 30μm thick, traditional polishing processes result in nearly 100% fragmentation. Consequently, there is currently no effective repair method that can significantly improve yield.

[0004] The current common method for repairing scratches on UTG substrates is to attach the UTG substrate to the glass backplane through an adhesive layer, so that it changes from a "thin substrate" with a thickness of 30μm to a "thick glass" with a thickness of more than 1mm (its thickness mainly depends on the thickness of the backplane), and then perform surface treatments such as polishing on it to repair scratches and other defects on the UTG substrate. However, since the UTG substrate itself is relatively thin, there is still a risk of fragmentation when it is attached to the backplane (which can be made of glass, PVC, etc., without limitation) through an adhesive layer. After the polishing repair is completed, there is also a high risk of fragmentation when the UTG substrate is removed from the thick backplane, which has become a pain point and difficulty in the surface treatment process of the UTG substrate. If the product is first tempered (traditional tempering methods and conditions, CS value reaches 400MPa, DOL reaches more than 10μm) and then polished, after polishing one side, due to uneven stress on both sides of the product, the ultra-thin glass substrate will warp, affecting the product quality and the warping of the other side. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a post-processing process for thin glass substrates, which can repair the appearance of thin glass substrates while reducing the product breakage rate, improve the appearance of thin glass substrate products, and increase the yield of thin glass substrate products, thereby reducing their production costs.

[0006] The present invention provides a post-processing process for a thin glass substrate, comprising the following steps:

[0007] S1) subjecting the thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2;

[0008] S2) attaching one side of the thin glass substrate after the primary tempering treatment to a backplane via an adhesive layer to obtain a thin glass substrate bonded to the backplane;

[0009] S3) finely grinding the surface of the thin glass substrate bonded to the backplane, and then separating the backplane to obtain a thin glass substrate after one side is processed;

[0010] S4) attaching the treated one side of the thin glass substrate to a back plate via an adhesive layer, then finely grinding the other side, and then separating the back plate to obtain a double-sided treated thin glass substrate;

[0011] S5) performing a second tempering treatment on the double-sided treated thin glass substrate to obtain a repaired thin glass substrate.

[0012] Preferably, the thin glass substrate is an ultra-thin glass substrate; the thickness of the thin glass substrate is 25-50 μm.

[0013] Preferably, the temperature of the first tempering treatment is 350° C. to 370° C.; and the time of the first tempering treatment is 0.5 to 2 hours.

[0014] Preferably, the surface compressive stress of the thin glass substrate after the one-time tempering treatment is 100-150 MPa; the stress layer depth of the thin glass substrate after the one-time tempering treatment is 10-13 μm.

[0015] Preferably, the adhesive layer in step S2) and the adhesive layer in step S4) are viscosity-reducing adhesive layers.

[0016] Preferably, the fine grinding in step S3) is sweeping and / or polishing, and the grinding amount is 0 to 3 μm;

[0017] The fine grinding in step S4) is sweeping and / or polishing, and the grinding amount is 0 to 3 μm.

[0018] Preferably, the tempering liquid of the second tempering treatment comprises 90-100 wt % of potassium nitrate and 0-10 wt % of sodium nitrate.

[0019] Preferably, the temperature of the second tempering treatment is greater than or equal to 400° C.; and the time of the second tempering treatment is greater than or equal to 10 minutes.

[0020] Preferably, the surface compressive stress of the repaired thin glass substrate is greater than or equal to 400 MPa; and the stress layer depth of the repaired thin glass substrate is greater than or equal to 10 μm.

[0021] The present invention also provides a post-processing process for a thin glass substrate, comprising the following steps:

[0022] A1) subjecting the thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2;

[0023] A2) attaching one side of the thin glass substrate after the primary tempering treatment to a thin glass substrate bonded with ...

[0024] A3) finely grinding the surface of the thin glass substrate bonded with the viscosity-reducing film, and then separating the viscosity-reducing film to obtain a thin glass substrate with one side treated;

[0025] A4) attaching the treated side of the thin glass substrate to a viscosity-reducing film, then finely grinding the other side, and then separating the backplane to obtain a double-sided treated thin glass substrate;

[0026] A5) performing a second tempering treatment on the double-sided treated thin glass substrate to obtain a repaired thin glass substrate.

[0027] The present invention provides a post-processing process for a thin glass substrate, comprising the following steps: S1) subjecting the thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2; S2) attaching one side of the thin glass substrate after the first tempering treatment to a backplane via an adhesive layer to obtain a thin glass substrate bonded to the backplane; S3) finely grinding the surface of the thin glass substrate bonded to the backplane, and then separating the backplane to obtain a thin glass substrate after one side is treated; S4) attaching the treated one side of the thin glass substrate after the one side is treated to the backplane via an adhesive layer, and then finely grinding the other side, and then separating the backplane to obtain a thin glass substrate after double-side treatment; S5) subjecting the thin glass substrate after the double-side treatment to a second tempering treatment to obtain a repaired thin glass substrate. Compared with the prior art, the present invention pre-tempers thin glass substrates to reduce their surface stress and stress layer depth compared to typical values, ensuring that the glass substrate products have better toughness than untempered products. Furthermore, after fine grinding on one side, no noticeable warping occurs, allowing the other side to be surface-treated to equalize the compressive stress on both sides, thus avoiding the risk of warping. Finally, a second tempering treatment ensures that the repaired thin glass substrates have excellent chemical strength and other properties while maintaining a good appearance. Furthermore, the process breakage rate is significantly reduced compared to traditional processes.

[0028] Furthermore, the present invention directly bonds the thin glass substrate to the viscosity-reducing film material to grind and repair surface defects on the ultra-thin glass substrate, thereby greatly improving production efficiency. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The present invention provides a post-processing process for a thin glass substrate, comprising the following steps: S1) subjecting the thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2; S2) attaching one side of the thin glass substrate after the first tempering treatment to a backplane via an adhesive layer to obtain a thin glass substrate bonded to the backplane; S3) finely grinding the surface of the thin glass substrate bonded to the backplane, and then separating the backplane to obtain a thin glass substrate after one side is treated; S4) attaching the treated one side of the thin glass substrate after the one side is treated to the backplane via an adhesive layer, and then finely grinding the other side, and then separating the backplane to obtain a thin glass substrate after double-side treatment; S5) subjecting the thin glass substrate after the double-side treatment to a second tempering treatment to obtain a repaired thin glass substrate.

[0031] The present invention has no particular limitation on the sources of all raw materials, and any commercially available raw materials may be used.

[0032] In the present invention, the thin glass substrate is preferably an ultra-thin glass substrate; the thickness of the thin glass substrate is preferably 25 to 50 μm, more preferably about 30 μm, but is not completely limited to about 30 μm; the thickness of 30 μm mainly depends on the fact that the thickness of the UTG substrate used in general folding screen mobile phones is 30 μm. If the product is too thick (such as above 50 μm), it can generally be directly scanned through equipment improvements. The present invention focuses on improving the surface repair process of UTG substrates with a thickness of less than 30 μm. Of course, it is also applicable to UTG substrates with a relatively thick thickness (such as above 50 μm).

[0033] According to the present invention, the thin glass substrate is preferably cut first; the cutting size mainly determines the shape of the thin glass substrate, and its outer size is determined by product requirements and is generally 160*70mm, but is not limited to this fixed size and can be larger or smaller, so the size is not fixed; the cutting method includes but is not limited to laser cutting and can also be wheel cutting, and laser cutting is generally preferred.

[0034] The cut thin glass substrate is subjected to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment. The nitrate melt includes potassium nitrate and sodium nitrate. The mass ratio of potassium nitrate to sodium nitrate is 6:4 to 8:2. If the sodium nitrate concentration is too high, the ion exchange rate is very slow. If the sodium nitrate concentration is too low, the strengthening layer on the surface of the tempered product is difficult to control. Further preferably, the mass ratio of potassium nitrate to sodium nitrate is 7:3. The concentration of the first tempering treatment is preferably 350° C. to 370° C. The melting point of potassium nitrate is 334° C., and the boiling point of sodium nitrate is 380° C. If the temperature is too low, potassium nitrate cannot reach a molten state. If the tempering temperature is too high, sodium nitrate will boil and volatilize. The time of the first tempering treatment is preferably 0.5 to 2 hours. The surface compressive stress (CS value) of the thin glass substrate after the first tempering treatment is 100 to 150 MPa. The depth of stress layer (DOL) of the thin glass substrate after the first tempering treatment is 10 to 13 μm.

[0035] One side of the thin glass substrate after the first tempering treatment is attached to the backplane via an adhesive layer to obtain a thin glass substrate bonded to the backplane; after the first tempering treatment, the hardness and toughness of the thin glass substrate are improved, so its breakage rate is significantly reduced during the bonding process; the adhesive layer is preferably a viscosity-reducing adhesive layer; the viscosity-reducing adhesive layer includes but is not limited to a UV viscosity-reducing adhesive layer or a high-temperature viscosity-reducing adhesive layer, which has good adhesion to the thin glass substrate and the backplane and can lose adhesion to the thin glass substrate and the backplane under specific conditions; the backplane includes but is not limited to a glass backplane, a PVC backplane, etc.; the thickness of the backplane determines the thickness of the thin glass substrate bonded to the backplane, and the thickness of the thin glass substrate bonded to the backplane is generally greater than 1 mm.

[0036] The surface of the thin glass substrate bonded to the backplane is finely ground; scratches, water ripples and other defects on the surface can be removed by fine grinding; the method of fine grinding preferably includes but is not limited to physical grinding methods such as sweeping and / or polishing; the grinding amount of the fine grinding is preferably 0 to 3 μm; the surface compressive stress (CS value) of the glass substrate after traditional chemical strengthening treatment can generally reach more than 500 MPa, and the depth of the stress layer (DOL) is generally 7 μm. If it is physically ground (single-sided grinding), the surface compressive stress (CS value) of one side will be reduced, resulting in high surface compressive stress on one side of the UTG substrate and low surface compressive stress on the other side, which will cause the product to have a larger bending deformation, causing the product to warp poorly, and it is difficult to perform surface treatment and grinding repair on the other side. In the post-processing process provided by the present invention, after the thin glass substrate undergoes chemical strengthening in the above-mentioned first tempering treatment, the compressive stress value of the product surface is 100-150 MPa. After being attached to the backplane and finely ground, the stress value difference between the two sides of the substrate generally does not exceed 30 MPa. The deformation amount is generally controllable and does not affect the processing of subsequent steps.

[0037] After fine grinding, it is preferably cleaned, and then the backsheet is separated to obtain a thin glass substrate with one side treated. The method for separating the backsheet is selected based on the type of adhesive layer. The viscosity-reducing adhesive can lose its adhesion to the thin glass substrate and the backsheet under specific conditions, thereby separating the finely ground thin glass substrate from the backsheet. If the adhesive is UV-reducing adhesive, it is subjected to UV treatment to lose its adhesion to the adhesive layer, thereby separating the finely ground thin glass substrate from the backsheet. If the adhesive is high-temperature-reducing adhesive, it is heated (which may be, but is not limited to, oven baking or water bath heating) to lose its adhesion to the adhesive layer, thereby separating the finely ground thin glass substrate from the backsheet. Because the hardness and toughness of the thin glass substrate are improved after the first tempering treatment, the fragmentation rate during the separation process (which requires a certain amount of external force to separate the thin glass substrate from the backsheet and involves a certain amount of manual operation) is significantly reduced compared to the traditional separation method (i.e., separating the approximately 30μm UTG substrate that has not undergone the first tempering), and the fragmentation rate is reduced from 10% to below 1%.

[0038] The treated side of the thin glass substrate is attached to a backing plate via an adhesive layer, and the other side is finely ground. The backing plate is then separated to obtain a double-sided treated thin glass substrate. The adhesive layer, backing plate, fine grinding, and backing plate separation steps are the same as those described above and are not repeated here. This fine grinding achieves surface repair while ensuring that the compressive stress on both sides of the double-sided treated thin glass substrate is equalized, thus reducing the risk of warping.

[0039] The double-sided treated thin glass substrate is subjected to a second tempering treatment. In the present invention, the double-sided treated thin glass substrate is preferably cleaned before the second tempering treatment. The tempering liquid for the second tempering treatment is a potassium nitrate melt with a high concentration, preferably comprising 90-100 wt% potassium nitrate and 0-10 wt% sodium nitrate. The temperature for the second tempering treatment is preferably greater than or equal to 400° C. The duration of the second tempering treatment is preferably greater than or equal to 10 minutes, more preferably 10-20 minutes, and even more preferably 10-15 minutes.

[0040] After the second tempering treatment, it is preferably cleaned to remove residual salt or dirt on the surface to obtain a repaired thin glass substrate; the surface compressive stress of the repaired thin glass substrate is preferably greater than or equal to 400 MPa; the stress layer depth of the repaired thin glass substrate is preferably greater than or equal to 10 μm.

[0041] The present invention pre-tempers the thin glass substrate to reduce its surface stress and stress layer depth compared to typical values, ensuring that the glass substrate product has better toughness than untempered products. Furthermore, after fine grinding on one side, no noticeable warping occurs, allowing the other side to be surface treated to equalize the compressive stress on both sides, thereby avoiding the risk of warping. Finally, a second tempering treatment ensures that the repaired thin glass substrate has excellent chemical strength and other properties while maintaining a good appearance. Furthermore, the process breakage rate is significantly reduced compared to traditional processes.

[0042] The present invention also provides another post-processing process for a thin glass substrate, comprising the following steps: A1) subjecting the thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2; A2) attaching one side of the thin glass substrate after the first tempering treatment to a viscosity-reducing film material to obtain a thin glass substrate attached to the viscosity-reducing film material; A3) finely grinding the surface of the thin glass substrate attached to the viscosity-reducing film material, and then separating the viscosity-reducing film material to obtain a thin glass substrate after one side is treated; A4) attaching the treated one side of the thin glass substrate after the one side is treated to a viscosity-reducing film material, and then finely grinding the other side, and then separating the back plate to obtain a thin glass substrate after double-side treatment; A5) subjecting the thin glass substrate after the double-side treatment to a second tempering treatment to obtain a repaired thin glass substrate.

[0043] The remaining operations in steps A1) to A5) are the same as steps S1) to S5), except that the thin glass substrate is directly bonded to the anti-viscosity film for fine grinding; the anti-viscosity film includes but is not limited to UV anti-viscosity film or high-temperature anti-viscosity film; the thickness of the anti-viscosity film is preferably greater than or equal to 0.1 mm, more preferably greater than or equal to 0.2 mm.

[0044] The present invention directly adheres a thin glass substrate to a viscosity-reducing mold material to grind and repair surface defects on the ultra-thin glass substrate, thereby greatly improving production efficiency.

[0045] The present invention also provides a repaired thin glass substrate obtained by the post-processing process of the above-mentioned thin glass substrate; the surface compressive stress of the repaired thin glass substrate is preferably greater than or equal to 400 MPa; the stress layer depth of the repaired thin glass substrate is preferably greater than or equal to 10 μm.

[0046] In order to further illustrate the present invention, a post-processing process of a thin glass substrate provided by the present invention is described in detail below with reference to embodiments.

[0047] The reagents used in the following examples are all commercially available.

[0048] Example 1

[0049] 1.1 Cutting: The UTG substrate that has been thinned to a thickness of 30 μm is cut into a target size of 160*70 mm using a laser.

[0050] 1.2 One-time tempering: Tempering is carried out by chemical strengthening, that is, the product is immersed in a mixed solution of molten potassium nitrate and sodium nitrate (the mass ratio of potassium nitrate to sodium nitrate is 7:3), the tempering temperature is 360°C, the tempering time is 1 hour, and the UTG substrate after one tempering is obtained.

[0051] 1.3 Lamination: The tempered UTG substrate was attached to a 1 mm thick glass back panel through a UV adhesive layer (Suzhou Silitong Technology Co., Ltd., model: SLT-621).

[0052] 1.4 Surface repair: Use sweeping method to finely grind the product surface to remove scratches, water ripples and other defects on the surface. The single-side grinding amount is 1um.

[0053] 1.5 Separation: Clean the surface-treated UTG substrate together with the backboard, and then use UV to make the adhesive layer lose its stickiness to separate the UTG substrate from the backboard.

[0054] 1.6 After one side of the UTG substrate is dissociated, steps 3, 4, and 5 are repeated on the other side of the UTG substrate to repair the surface of the other side of the UTG substrate and obtain a double-sided treated UTG substrate.

[0055] 1.7 Secondary tempering: The UTG substrate after double-sided treatment is cleaned and tempered. The secondary tempering liquid uses potassium nitrate melt, the tempering temperature is 400℃, and the tempering time is 10 minutes. The UTG substrate after secondary tempering is then cleaned to remove residual salt or dirt on its surface to obtain a repaired thin glass substrate.

[0056] The glass surface stress meter was used to test the UTG substrate obtained in 1.2 after the first tempering, and the results are shown in Table 1.

[0057] The double-sided treated UTG substrate obtained in 1.6 was tested using a glass surface stress meter, and the results are shown in Table 1.

[0058] Examples 2 to 3 and Comparative Examples 1 to 4

[0059] Post-treatment was performed according to the method of Example 1, except that the mass ratio of potassium nitrate to sodium nitrate used in the first tempering was different, as shown in Table 1, wherein the warpage should be less than 1 mm.

[0060] Table 1 Tempering treatment conditions and test results of UTG substrate after treatment

[0061]

[0062]

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A post-processing process for a thin glass substrate, characterized in that: The following steps are involved: S1) subjecting a thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2; the surface compressive stress of the thin glass substrate after the first tempering treatment is 100 to 150 MPa; and the stress layer depth of the thin glass substrate after the first tempering treatment is 10 to 13 μm; S2) attaching one side of the thin glass substrate after the primary tempering treatment to a backplane via an adhesive layer to obtain a thin glass substrate bonded to the backplane; S3) finely grinding the surface of the thin glass substrate bonded to the backplane, and then separating the backplane to obtain a thin glass substrate after one side is processed; S4) attaching the treated one side of the thin glass substrate to a back plate via an adhesive layer, then finely grinding the other side, and then separating the back plate to obtain a double-sided treated thin glass substrate; S5) performing a second tempering treatment on the double-sided treated thin glass substrate to obtain a repaired thin glass substrate; The tempering liquid of the second tempering treatment includes 90-100wt% potassium nitrate and 0-10wt% sodium nitrate; the surface compressive stress of the repaired thin glass substrate is greater than or equal to 400MPa; the stress layer depth of the repaired thin glass substrate is greater than or equal to 10μm.

2. The post-processing process according to claim 1, characterized in that: The thin glass substrate is an ultra-thin glass substrate; the thickness of the thin glass substrate is 25-50 μm.

3. The post-processing process according to claim 1, characterized in that: The temperature of the first tempering treatment is 350° C. to 370° C.; and the time of the first tempering treatment is 0.5 to 2 hours.

4. The post-processing process according to claim 1, characterized in that: The adhesive layer in step S2) and the adhesive layer in step S4) are adhesive-reducing adhesive layers.

5. The post-processing process according to claim 1, characterized in that: The fine grinding in step S3) is sweeping and / or polishing, and the grinding amount is 0 to 3 μm; The fine grinding in step S4) is sweeping and / or polishing, and the grinding amount is 0 to 3 μm.

6. The post-processing process according to claim 1, characterized in that: The temperature of the second tempering treatment is greater than or equal to 400° C.; and the time of the second tempering treatment is greater than or equal to 10 minutes.

7. A post-processing process for a thin glass substrate, characterized in that: The following steps are involved: A1) subjecting a thin glass substrate to a first tempering treatment in a nitrate melt to obtain a thin glass substrate after the first tempering treatment; the nitrate melt comprises potassium nitrate and sodium nitrate; the mass ratio of the potassium nitrate to the sodium nitrate is 6:4 to 8:2; the surface compressive stress of the thin glass substrate after the first tempering treatment is 100 to 150 MPa; and the stress layer depth of the thin glass substrate after the first tempering treatment is 10 to 13 μm; A2) attaching one side of the thin glass substrate after the primary tempering treatment to a thin glass substrate bonded with ... A3) finely grinding the surface of the thin glass substrate bonded with the viscosity-reducing film, and then separating the viscosity-reducing film to obtain a thin glass substrate with one side treated; A4) attaching the treated side of the thin glass substrate to a viscosity-reducing film, then finely grinding the other side, and then separating the backplane to obtain a double-sided treated thin glass substrate; A5) subjecting the double-sided treated thin glass substrate to a second tempering treatment to obtain a repaired thin glass substrate; The tempering liquid of the second tempering treatment includes 90-100wt% potassium nitrate and 0-10wt% sodium nitrate; the surface compressive stress of the repaired thin glass substrate is greater than or equal to 400MPa; the stress layer depth of the repaired thin glass substrate is greater than or equal to 10μm.

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