阅读说明：本技术 一种无碱基板玻璃及其减薄方法 (Alkali-free substrate glass and thinning method thereof ) 是由 王答成 兰静 曾召 孔令歆 郭静 于 2021-09-28 设计创作，主要内容包括：一种无碱基板玻璃,以质量百分数计,包括58.9％～62.5％的SiO-(2),14.2％～18.4％的Al-(2)O-(3),4.3％～13.7％的B-(2)O-(3),1.4％～1.9％的MgO、4.1％～7.6％的CaO、1.0％～2.1％的SrO、0～8.3％的BaO,和0.1％～0.2％的SnO-(2)。其减薄方法包括以下步骤,将上述无碱基板玻璃浸入氢氟酸、冰醋酸表面活性剂以及余量的水组成的化学侵蚀液中,使无碱基板玻璃减薄至0.4mm～0.5mm,将该无碱基板玻璃取出,超声清洗烘干；然后置于磨抛机的研磨盘上,机械抛光,使所述无碱基板玻璃减薄至0.3mm～0.35mm,得到柔性基板玻璃。该无碱基板玻璃成分合理,制得无碱玻璃的比模量值适中,使玻璃具有较好的柔韧性,其减薄方法操作便捷,通过化学刻蚀减薄以及机械抛光减薄两种方式的结合,对本发明中得到的厚度为0.7mm的无碱基板玻璃进行减薄,得到表面光滑,具备可弯曲性能的柔性基板玻璃。(Alkali-free substrate glass comprises 58.9-62.5% of SiO in percentage by mass 2 14.2 to 18.4 percent of Al 2 O 3 4.3 to 13.7 percent of B 2 O 3 1.4 to 1.9 percent of MgO, 4.1 to 7.6 percent of CaO, 1.0 to 2.1 percent of SrO, 0 to 8.3 percent of BaO and 0.1 to 0.2 percent of SnO 2 . The thinning method comprises soaking the alkali-free substrate glass in chemical etching solution composed of hydrofluoric acid, glacial acetic acid surfactant and water to thin the glass to 0.4-0.5 mm, taking out the glass, and processingCleaning and drying by sound; and then placing the glass on a grinding disc of a grinding and polishing machine, and mechanically polishing to thin the alkali-free substrate glass to 0.3-0.35 mm to obtain the flexible substrate glass. The alkali-free substrate glass has reasonable components, the specific modulus value of the prepared alkali-free glass is moderate, the glass has better flexibility, the thinning method is convenient and fast to operate, and the alkali-free substrate glass with the thickness of 0.7mm obtained in the invention is thinned by combining the chemical etching thinning mode and the mechanical polishing thinning mode to obtain the flexible substrate glass with smooth surface and bendable performance.)

1. The alkali-free substrate glass is characterized by comprising the following components in percentage by mass: 58.9 to 62.5 percent of SiO₂14.2 to 18.4 percent of Al₂O₃4.3 to 13.7 percent of B₂O₃1.4 to 1.9 percent of MgO, 4.1 to 7.6 percent of CaO, 1.0 to 2.1 percent of SrO, 0 to 8.3 percent of BaO and 0.1 to 0.2 percent of% SnO₂。

2. The alkali-free substrate glass according to claim 1, wherein the total mass percentage of MgO, CaO, SrO and BaO is 9.4 to 16.4%.

3. A method for thinning alkali-free substrate glass is characterized by comprising the following steps,

s1: immersing the alkali-free substrate glass of any one of claims 1 to 2 in a chemical etching solution for 10 to 30min to thin the alkali-free substrate glass to a first thickness, taking out the alkali-free substrate glass, ultrasonically cleaning the alkali-free substrate glass with alcohol and pure water, and drying the alkali-free substrate glass; the first thickness is 0.4 mm-0.5 mm; the chemical etching liquid comprises 25-35% of hydrofluoric acid, 10-15% of glacial acetic acid, 3-5% of surfactant and the balance of water by mass concentration;

s2: placing the glass sheet subjected to chemical etching thinning in the step S1 on a grinding disc of a grinding and polishing machine, and performing mechanical polishing for 20-60 min to thin the alkali-free substrate glass to a second thickness to obtain flexible substrate glass; the second thickness is 0.3 mm-0.35 mm.

4. The method of claim 3, wherein the surfactant comprises at least one of sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

5. The method for thinning the alkali-free substrate glass according to claim 3, wherein a plurality of grooves are arranged on a grinding disc of the grinding and polishing machine, and the grooves are communicated with each other; the bottom of the groove is provided with a hole for connecting vacuum equipment; when grinding and polishing are carried out, the glass to be treated completely covers the groove; the depth of the groove is 5 mm-10 mm.

6. The method of claim 3, further comprising repeating the step S1 at least 1 time after the step S1 to thin the alkali-free substrate glass to a first thickness.

7. The method of claim 3, wherein the step S2 is followed by repeating the steps S1 and S2 at least 1 time to thin the alkali-free substrate glass to a second thickness.

8. The method for thinning the alkali-free substrate glass according to claim 3, wherein the specific modulus of the thinned alkali-free glass is 30-31 GPa/(g/cm)³) An elastic modulus of 71 to 77GPa, and a coefficient of thermal expansion of 36 x 10 within a temperature range of 30 to 380 DEG C^-7℃～37×10^-7/℃。

Technical Field

The invention belongs to the field of manufacturing of bendable substrate glass, and relates to alkali-free substrate glass and a preparation method thereof.

Background

With the improvement of living standard, people's requirements for electronic display devices are developing towards the direction of lightness, thinness, intellectualization and flexibility, and especially in recent years, electronic wearable devices with higher heat, bendable smart phones and curved surface display technologies with stronger reality endow the ultrathin glass based on electronic display with new flexible performance requirements. In terms of flexible display products, the display screens thereof can be classified into four types, that is, a flexible display having a paper image quality, a flexible display having a micro-bending characteristic, a foldable display, and a rollable flexible display. The latter two types of flexible displays require very high flexibility for the glass used, while the former two types of flexible displays require the glass used to have microbending properties.

At present, the thickness of the mainstream substrate glass in the market is 0.5-0.7 mm, the thickness is thick, the brittleness is large, and the substrate glass is not suitable for being applied to a bendable flexible display. Therefore, the substrate glass with a relatively thick thickness is generally required to be thinned, common thinning methods include chemical etching thinning and mechanical polishing thinning, the existing substrate glass is time-consuming to polish and grind due to high surface hardness, and therefore chemical etching thinning is mostly adopted, namely, chemical etching liquid is sprayed through a spraying device to thin the glass, but the method can cause uneven etching on the surface of the glass, so that the surface of the glass is not smooth, and the product performance is influenced.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides alkali-free substrate glass and a thinning method thereof, the alkali-free substrate glass has a reasonable formula and moderate hardness, is easy for chemical etching thinning and mechanical polishing thinning, and can obtain bendable glass with smooth surface and good flexibility after thinning.

The invention is realized by the following technical scheme:

the alkali-free substrate glass comprises the following components in percentage by mass: 58.9 to 62.5 percent of SiO₂14.2 to 18.4 percent of Al₂O₃4.3 to 13.7 percent of B₂O₃1.4 to 1.9 percent of MgO, 4.1 to 7.6 percent of CaO, 1.0 to 2.1 percent of SrO, 0 to 8.3 percent of BaO and 0.1 to 0.2 percent of SnO₂。

Preferably, the total mass percentage of the MgO, CaO, SrO and BaO is 9.4-16.4%.

A thinning method of alkali-free substrate glass comprises the following steps,

s1: immersing any alkali-free substrate glass in a chemical etching solution for 10-30 min to thin the alkali-free substrate glass to a first thickness, taking out the alkali-free substrate glass, performing ultrasonic cleaning by using alcohol and pure water, and drying; the first thickness is 0.4 mm-0.5 mm; the chemical etching liquid comprises 25-35% of hydrofluoric acid, 10-15% of glacial acetic acid, 3-5% of surfactant and the balance of water.

S2: placing the glass sheet subjected to chemical etching thinning in the step S1 on a grinding disc of a grinding and polishing machine, and performing mechanical polishing for 20-60 min to thin the alkali-free substrate glass to a second thickness to obtain flexible substrate glass; the second thickness is 0.3 mm-0.35 mm.

Preferably, the surfactant comprises at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

Preferably, a plurality of grooves are arranged on a grinding disc of the grinding and polishing machine, and the grooves are communicated with one another; the bottom of the groove is provided with a hole for connecting vacuum equipment; when grinding and polishing are carried out, the glass to be treated completely covers the groove; the depth of the groove is 5 mm-10 mm.

Preferably, the step S1 is followed by repeating the step S1 at least 1 time to thin the alkali-free substrate glass to a first thickness.

Preferably, the step S2 is followed by repeating the steps S1 and S2 at least 1 time to thin the alkali-free substrate glass to a second thickness.

Preferably, the specific modulus of the thinned alkali-free glass is 30-31 GPa/(g/cm)³) An elastic modulus of 71 to 77GPa, and a coefficient of thermal expansion of 36 x 10 within a temperature range of 30 to 380 DEG C^-7℃～37×10^-7/℃。

Compared with the prior art, the invention has the following beneficial technical effects:

the invention provides alkali-free substrate glass which comprises 58.9-62.5 mass percent of SiO₂14.2 to 18.4 percent of Al₂O₃4.3 to 13.7 percent of B₂O₃1.4 to 1.9 percent of MgO, 4.1 to 7.6 percent of CaO, 1.0 to 2.1 percent of SrO, 0 to 8.3 percent of BaO and 0.1 to 0.2 percent of SnO₂。SiO₂Is a network former in glass, which is based on silicon-oxygen tetrahedron [ SiO ]₄]The structure of (a) forms an irregular continuous network to form a glass skeleton. SiO 2₂The thermal expansion coefficient of the glass can be reduced, the strain point of the glass can be improved, and the dimensional change of the glass caused by heat treatment in the using process can be prevented. But SiO₂When the content is too high, the high-temperature viscosity of the glass increases, and the glass is easily melted to cause defects such as bubbles and the like to affect the glass matrix, so that SiO in the present invention₂The mass percentage of the glass is controlled to be 58.9-62.5%, so that the glass has lower thermal expansion coefficient and easy molding temperature, and the defects of bubbles and the like caused by too high viscosity of the glass liquid can not be generated; al (Al)₂O₃Is an intermediate oxide, and when the glass has insufficient oxygen atoms, the coordination state of aluminum is aluminum oxygen octahedron [ AlO ]₆]At network gaps; when there are excess oxygen atoms in the glass, the coordination state of aluminum is alundum [ AlO₄]Enter into the glassThe structure plays the effect of mending the net, increases the stability of glass, reduces the coefficient of thermal expansion. However, Al₂O₃When the content is too large, the glass is easily devitrified. Thus, Al in the invention₂O₃The mass percentage of the glass is controlled to be 14.2-18.4%, thus avoiding the crystallization temperature of the glass from rising and also considering the high thermal stability of the glass. B is₂O₃It is a shaping agent and has the function of fluxing in glass and is made of boron-oxygen triangle (BO)₃]And boron-oxygen tetrahedron [ BO₄]Is a structural unit with silicon-oxygen tetrahedron [ SiO ]₄]Jointly form a network structure; b is₂O₃Can reduce the viscosity of the glass at high temperature and play a role in fluxing. If B is₂O₃If the content is too small, the fluxing action is not remarkable, and if the content is too large, the thermal stability of the glass is lowered, so that B in the present invention₂O₃The mass percentage of the glass is controlled to be 4.3-13.7%, which not only plays a role of fluxing, but also does not influence the thermal stability of the glass. Suitably increase B₂O₃The content of (A) can ensure that the hardness of the glass is moderate, and the glass is easy to mechanically polish; the alkaline earth metal oxides MgO, CaO, SrO and BaO belong to the network external oxides, and metal cations can freely move in molten glass at high temperature, so that oxygen atoms can be polarized to break the original glass network, thereby reducing the viscosity of the glass. At low temperature, the metal cations can enable smaller atomic groups to be aggregated, so that the low-temperature viscosity of the glass liquid is increased. Therefore, the alkaline earth metal oxide plays the roles of reducing viscosity at high temperature and assisting molding at low temperature. For alkaline earth metal oxides, the density and thermal expansion coefficient of the glass increase with increasing ionic radius. When the content of CaO in the glass is too large, the glass fritting property is shortened, the glass is not favorable for forming, the glass crystallization tendency is increased, the glass crystallization tendency can be reduced by using MgO to replace part of CaO, and the fritting property is adjusted, so that the glass is favorable for forming. Although SrO and BaO increase the strain point of the glass, the ionic radius is large, and when the content is too large, the density and the thermal expansion coefficient of the glass are greatly increased, and the thermal stability of the glass is reduced. Therefore, based on the theory, the weight percentage of MgO is controlled to be 1.4-1.9%, and the weight percentage of CaO is controlled to be4.1-7.6 percent of SrO, 1-2.1 percent of BaO and 0-8.3 percent of BaO; SnO₂Is a raw material which is used as a fining agent to replace poisonous arsenic oxide, is beneficial to discharging bubbles in the glass melting process, but easily forms stones when the content is excessive, so the SnO in the invention₂The mass percentage content of the components is controlled to be 0.1-0.2%. Through the adjustment of the content of the components, the specific modulus value of the prepared alkali-free glass is moderate, namely, the glass has better flexibility.

Furthermore, the total mass percentage of MgO, CaO, SrO and BaO is 9.4-16.4%, so that the glass has more excellent flexibility.

The invention also provides a thinning method of the alkali-free substrate glass, which is convenient to operate, and the alkali-free substrate glass with the thickness of 0.7mm obtained in the invention is thinned by combining two modes of chemical etching thinning and mechanical polishing thinning to obtain the flexible substrate glass with smooth surface and bendable performance. The thickness of the alkali-free glass can reach 0.4 mm-0.5 mm through chemical etching, and the thickness of the glass reaches 0.3 mm-0.35 mm through mechanical polishing, so that the thickness of the glass is effectively reduced, the glass can be bent, and the alkali-free glass has good flexibility and meets the use requirement.

Furthermore, the anionic surfactants of sodium dodecyl sulfate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate are used as additives, a hydrophilic anionic layer can be formed on the surface of the glass, the wettability of the glass is improved, the contact surface of a chemical etching agent and the glass is increased, and the chemical etching effect is improved.

Furthermore, in the mechanical polishing and thinning process, the grinding disc is provided with a plurality of grooves which are communicated with each other, and the depth of each groove is 5-10 mm. When grinding and polishing, the substrate glass completely covers the groove and is adsorbed on the grinding disc through vacuum, and the vacuum pressure is adjusted according to the difference of the glass thickness to prevent the glass from being broken due to too large suction force.

Furthermore, the chemical etching process can be repeated, and the chemical etching is effectively utilized, so that the thickness of the glass can quickly reach the required first thickness.

Further, the chemical etching and the mechanical polishing can be repeated for a plurality of times until the required second thickness is reached, so as to improve the efficiency of the mechanical polishing.

Furthermore, the specific modulus of the thinned alkali-free glass is 30-31 GPa/(g/cm)³) An elastic modulus of 71 to 77GPa, and a coefficient of thermal expansion of 36 x 10 within a temperature range of 30 to 380 DEG C^-7℃～37×10^-7V. C. Has good flexibility and operability, and has wider application range.

Drawings

FIG. 1 is a schematic view of a grinding disc of the polishing machine of the present invention;

FIG. 2 shows the process of making alkali-free glass and thinning the same in accordance with the present invention.

In the figure: a groove 1, a hole 2 and glass 3 to be polished.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The invention prepares the alkali-free substrate glass by the following method:

(1) the weight of each raw material is calculated according to the oxide proportion and accurately weighed.

(2) The weighed batch materials are uniformly mixed in a mixer, poured into a platinum crucible, placed into a high-temperature experimental furnace, heated to 1000 ℃ at the speed of 10 ℃/min, kept for 30min, heated to 1350 ℃ at the speed of 5 ℃/min, kept for 1h, heated to 1650 ℃ at the speed of 5 ℃/min, kept for 4h, poured into a preheated mold to form block glass with regular shape, placed into an annealing furnace heated to 720 ℃, cooled to 400 ℃ at the speed of 0.5 ℃/min, and cooled to room temperature at the speed of 2 ℃/min.

(3) The annealed glass block was cut into 0.7mm thin pieces on a wire cutter, and the 0.7mm thin glass pieces were subjected to ultrasonic cleaning using alcohol and pure water in this order, followed by drying in an oven at 105 ℃ to obtain alkali-free substrate glass having a thickness of 0.7 mm.

In the mechanical polishing and thinning process, the glass is placed on a grinding disc of a grinding and polishing machine for grinding and polishing treatment, and the specific process is as follows: as shown in figure 1, a plurality of grooves 1 with the depth of 5 mm-10 mm are arranged on the grinding disc, the grooves 1 are communicated with each other, and holes 2 are also arranged in the grooves and are used for connecting vacuum-pumping equipment. When grinding and polishing, the glass 3 to be ground and polished is arranged at the upper part of the groove 1 and completely covers the groove, the vacuumizing equipment is started, the vacuum pressure is adjusted according to the thickness of the glass, the glass is prevented from being broken due to too large suction force, and the glass 3 to be ground and polished is adsorbed on the grinding disc through the vacuum effect. The groove 1 comprises a plurality of horizontal rectangular groove bodies and a plurality of vertical rectangular groove bodies, and the horizontal groove bodies and the vertical groove bodies are communicated and intersected. The groove has two symmetry axes perpendicular to each other. The hole 2 is arranged at the intersection of the two axes of symmetry. The stress uniformity of all parts of the glass in the grinding and polishing process can be ensured, and the glass is prevented from being broken. In this embodiment, the number of horizontal grooves is 4, and the number of vertical grooves is 1.

Example 1

The alkali-free substrate glass comprises the following components in percentage by mass: 60.4% SiO₂17.1% of Al₂O₃12.8% of B₂O₃1.4% MgO, 6.7% CaO, 1.2% SrO, 0% BaO, and 0.1% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 25% by mass of hydrofluoric acid, 10% by mass of glacial acetic acid, and 3% by mass of sodium dodecylsulfate to erode for 30min, and the alkali-free substrate glass was taken out, cleaned with alcohol and pure water by ultrasound, and then measured for thickness by a micrometer screw until the thickness of the glass sheet reached 0.5 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 60min, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.35mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 31.1 GPa/(g/cm)³) The elastic modulus is 74GPa, and the thermal expansion coefficient in the range of 30-380 ℃ is 36.8 multiplied by 10^-7The density is 2.38g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 2

The alkali-free substrate glass comprises the following components in percentage by mass: 61.2% SiO₂18.4% of Al₂O₃10.3% of B₂O₃1.4% MgO, 7.5% CaO, 1.0% SrO, 0% BaO, and 0.2% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 27% by mass of hydrofluoric acid, 11.5% by mass of glacial acetic acid, and 3.2% by mass of sodium lauryl sulfate to erode for 28.5min, the alkali-free substrate glass was taken out, subjected to ultrasonic cleaning with alcohol and pure water, and then the step S1 was repeated 1 time, and the thickness was measured with a micrometer screw until the thickness of the glass sheet reached 0.45 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 50min, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.35mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30.8 GPa/(g/cm)³) The elastic modulus is 73GPa, and the thermal expansion coefficient in the range of 30-380 ℃ is 36.5 multiplied by 10^-7The density is 2.37g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 3

Alkali-free substrate glassThe composite material comprises the following components in percentage by mass: 60.8% SiO₂18.3% of Al₂O₃4.3% of B₂O₃1.9% MgO, 4.1% CaO, 2.1% SrO, 8.3% BaO, and 0.2% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 26.8% by mass of hydrofluoric acid, 12% by mass of glacial acetic acid, and 3.8% by mass of sodium dodecylbenzenesulfonate to erode for 27min, and the alkali-free substrate glass was taken out, subjected to ultrasonic cleaning with alcohol and pure water, and then subjected to thickness measurement with a micrometer screw until the thickness of the glass sheet reached 0.44 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 45min, repeating the step S1 and the step S2 once, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.35mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30.2 GPa/(g/cm)³) The elastic modulus is 76.7GPa, and the thermal expansion coefficient in the range of 30-380 ℃ is 36.3 multiplied by 10^-7The density is 2.54g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 4

The alkali-free substrate glass comprises the following components in percentage by mass: 59.2% SiO₂17.1% of Al₂O₃13.2% of B₂O₃1.5% MgO, 7.5% CaO, 1.0% SrO, 0.4% BaO, and 0.1% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 28.2% by mass of hydrofluoric acid, 12.5% by mass of glacial acetic acid, 4.4% by mass of sodium dodecylsulfate and sodium dodecylsulfate to erode for 25min, the alkali-free substrate glass was taken out, subjected to ultrasonic cleaning with alcohol and pure water, and then subjected to thickness measurement with a micrometer screw until the thickness of the glass sheet reached 0.45 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 40min, repeating the step S1 and the step S2 once, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.33mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30 GPa/(g/cm)³) An elastic modulus of 71.1GPa, and a thermal expansion coefficient of 36.4 x 10 within the range of 30-380 DEG C^-7The density is 2.39g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 5

The alkali-free substrate glass comprises the following components in percentage by mass: 58.9% SiO₂17.1% of Al₂O₃13.7% of B₂O₃1.4% MgO, 7.5% CaO, 1.1% SrO, 0.2% BaO, and 0.1% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 33.5% by mass of hydrofluoric acid, 13.6% by mass of glacial acetic acid, 4.8% by mass of sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate to erode for 20min, the alkali-free substrate glass was taken out, and after ultrasonic cleaning and baking were performed with alcohol and pure water, the step S1 was repeated 1 time, and the thickness was measured with a micrometer screw until the thickness of the glass sheet reached 0.42 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 40min, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.34mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30.1 GPa/(g/cm)³) An elastic modulus of 71.9GPa, and a thermal expansion coefficient of 37.1 × 10 within the range of 30-380 deg.C^-7The density is 2.39g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 6

The alkali-free substrate glass comprises the following components in percentage by mass: 60.7% SiO₂17.1% of Al₂O₃12.7% of B₂O₃1.4% MgO, 6.7% CaO, 1.1% SrO, 0.2% BaO, and 0.1% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 34% by mass of hydrofluoric acid, 14% by mass of glacial acetic acid, 4.8% by mass of sodium dodecylsulfonate and sodium dodecylbenzenesulfonate to erode for 15min, the alkali-free substrate glass was taken out, subjected to ultrasonic cleaning with alcohol and pure water, and then subjected to thickness measurement with a micrometer screw until the thickness of the glass sheet reached 0.42 mm.

S2: mechanical polishing and thinning: and (5) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 40min, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.3mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30.5 GPa/(g/cm)³) The modulus of elasticity is 72.5GPa,a thermal expansion coefficient of 36.7 x 10 in the range of 30 to 380 DEG C^-7The density is 2.38g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

Example 7

The alkali-free substrate glass comprises the following components in percentage by mass: 62.5% SiO₂14.2% of Al₂O₃12.8% of B₂O₃1.4% MgO, 7.6% CaO, 1.2% SrO, 0.2% BaO, and 0.1% SnO₂。

The alkali-free substrate glass with the thickness of 0.7mm is prepared by the preparation method of the alkali-free substrate glass.

A thinning method of alkali-free substrate glass comprises the following steps of thinning the alkali-free substrate glass,

s1: and (3) chemical etching and thinning: the alkali-free substrate glass in this example was immersed in a chemical etching solution containing 35% by mass of hydrofluoric acid, 15% by mass of glacial acetic acid, and 5% by mass of sodium dodecylsulfate to erode for 10min, and the alkali-free substrate glass was taken out, ultrasonically cleaned with alcohol and pure water, and then measured for thickness by a micrometer screw until the thickness of the glass sheet reached 0.4 mm.

S2: mechanical polishing and thinning: and (3) placing the glass sheet subjected to chemical etching and thinning in the step S1 on a grinding disc of a grinding and polishing machine, mechanically polishing for 20min, repeating the step S1 and the step S2 once, and testing the thickness of the glass sheet by using a micrometer screw until the thickness of the glass sheet reaches 0.3mm to obtain the flexible substrate glass.

The specific modulus of the thinned alkali-free glass is 30.8 GPa/(g/cm)³) The elastic modulus is 73.2GPa, and the thermal expansion coefficient in the range of 30-380 ℃ is 36.9 multiplied by 10^-7The density is 2.38g/cm at DEG C³. The raw material amounts and product properties are shown in Table 1.

The invention provides alkali-free substrate glass suitable for chemical etching thinning and a thinning method thereof, and simple equipment is adopted to carry out chemical etching thinning and mechanical polishing thinning on the substrate glass to obtain transparent bendable substrate glass with a smooth surface, and the bendable substrate glass is suitable for being applied to a flexible display with micro-bending characteristics. As shown in fig. 2, specifically, the following steps are performed:

(1) weighing the raw materials according to the mixture ratio, wherein the mass percentage of each raw material comprises: 58.9 to 62.5 percent of SiO₂14.2 to 18.4 percent of Al₂O₃4.3 to 13.7 percent of B₂O₃1.4 to 1.9 percent of MgO, 4.1 to 7.6 percent of CaO, 1.0 to 2.1 percent of SrO, 0 to 8.3 percent of BaO and 0.1 to 0.2 percent of SnO₂。

(2) The weighed batch materials are uniformly mixed, heated, melted and insulated in a platinum crucible, poured into a preheated mold to form block glass with a regular shape, and slowly cooled in an annealing furnace for fine annealing.

(3) The annealed glass block was cut into sheets on a wire cutter, and the glass sheets were subjected to ultrasonic cleaning using alcohol and pure water in this order, followed by drying in an oven.

(4) And chemically etching and thinning the dried glass sheet in an etching solution, taking out the glass sheet every 30min, cleaning and drying, and measuring the thickness by using a micrometer caliper until the thickness of the glass sheet reaches a certain target value.

(5) And then, placing the etched and thinned clean glass sheet on a grinding and polishing machine for grinding, polishing and thinning, and testing the thickness of the glass sheet by using a micrometer screw every 1h until the thickness of the glass sheet reaches a target value.

Table 1 examples 1-7 of the present invention are the glass components and the properties of the glass sheets produced, respectively.