JP7102984B2 - Manufacturing method of 3D cover glass - Google Patents

Description

The present invention relates to a three-dimensionally shaped cover glass (3D cover glass) for an image display device used for mobile devices such as mobile phones, smartphones, and tablet terminals, and in-vehicle displays such as CIDs (Center Information Display) and clusters. Regarding the manufacturing method.

In order to improve the design of mobile devices such as mobile phones, smartphones, and tablet terminals, the application of a 3D cover glass as shown in FIG. 1 to an image display device used in a mobile device is being studied. FIG. 1 is a diagram showing a configuration example of the 3D cover glass 100, in which the central portion 110 is a flat surface and the peripheral portion 120 is a three-dimensional curved surface.

The cover glass of the image display device is chemically strengthened because it is required to have a certain strength in addition to being thinned, but the 3D cover glass having a three-dimensional curved surface at the periphery has a problem of warpage due to the chemical strengthening treatment. Become. 2 (a) and 2 (b) are schematic cross-sectional views showing the occurrence of warpage due to the chemical strengthening treatment of the 3D cover glass, FIG. 2 (a) is before the chemical strengthening treatment, and FIG. 2 (b) is a chemical strengthening treatment. It is sectional drawing which showed the state of occurrence of the warp by the chemical strengthening treatment of the 3D cover glass after the treatment. In this case, as shown in FIG. 2A, for example, the central portion is flat before the chemical strengthening treatment, whereas as shown in FIG. 2B, the central portion is convex after the chemical strengthening treatment. Warpage occurs in the shape.
Patent Document 1 proposes a method for correcting the warp of the 3D cover glass due to the chemically strengthened treatment generated in this way.

Special Table 2016-524582

Patent Document 1 proposes to use a mold in which the warp caused by the chemical strengthening treatment is simulated by using a computer and the result is inverted. However, in this case, if a plurality of molds having the same shape are produced, the shape of each mold will inevitably vary, so that the shape of the 3D cover glass formed for each mold may also vary.
In addition, when the warp of chemical strengthening is reflected in the shape of the mold, it becomes necessary to process the part corresponding to the flat part of the 3D cover glass into a three-dimensional curved surface, which makes the mold processing difficult, and is particularly called backlash. There is a risk that a step will occur and the processing accuracy will be inferior. Then, this step is transferred to the surface of the 3D cover glass, which causes an appearance defect and may impair the quality of the 3D cover glass.

In order to solve the above problems, an object of the present invention is to provide a method for producing a 3D cover glass capable of correcting the warp of the glass due to the chemical strengthening treatment without impairing the quality of the glass.

In order to achieve the above-mentioned object, the flat glass material is heated to a transition temperature Tg [° C.] or higher, and a pair of molds consisting of a convex mold and a concave mold is used to cover at least a part of the peripheral portion of the glass material. A glass forming step including a heating step of giving bending in the thickness direction and a cooling step of cooling the glass material to a temperature lower than the transition temperature Tg [° C.] of the glass material after the heating step.
After the glass molding step, the glass material is chemically strengthened, and the glass material is chemically strengthened.
In the cooling step, the control temperature of the concave shape facing the first main surface of the glass material corresponding to the convex side formed by the bending is set to the control temperature T1 [° C.], and the concave side formed by the bending. When the control temperature of the convex shape facing the second main surface of the glass material corresponding to is the control temperature T2 [° C.], at least one of the control temperature T2 [° C.] and the control temperature T1 [° C.] Is set to the transition temperature Tg [° C.] or less of the glass material, the temperature T2 [° C.] is larger than the temperature T1 [° C.], and the temperature difference between the control temperature T2 [° C.] and the control temperature T1 [° C.] (T2-T1) Provided is a method for producing a 3D cover glass, which comprises a procedure for holding [° C.] at 10 [° C.] or higher.

Further, in the method for manufacturing a 3D cover glass, the glass molding step includes a procedure of press molding using the pair of molds, and the temperature difference (T2-T1) [° C.] is controlled to control the temperature difference (T2-T1) [° C.] of the glass material. When the temperature of the first main surface is T3 [° C.] and the temperature of the second main surface of the glass material is T4 [° C.], the temperature T3 [° C.] and the temperature T4 [° C.] are transferred to the glass material. In the temperature range from the temperature Tg [° C.] to the strain point Ts [° C.] of the glass material, the temperature T4 [° C.] is larger than the temperature T3 [° C.], and the temperature T4 [° C.] and the temperature T3 It is preferable to include a procedure for maintaining the temperature difference (T4-T3) [° C.] from [° C.] at 0.3 [° C.] or higher.

Further, in the method for manufacturing a 3D cover glass, it is preferable that the pair of molds are made of a material having a thermal conductivity of 50 [W / (m · K)] or more.

In the method for producing a 3D cover glass of the present invention, the cooling step is the cooling rate of the first main surface of the glass material indicated by the change in the temperature T3 [° C.] per unit time, and the temperature per unit time. It is preferable that the cooling rate of the second main surface of the glass material indicated by the change of T4 [° C.] satisfies 0.1 [° C./Sec] or more and 10.0 [° C./Sec] or less.

Further, in the method for producing a 3D cover glass, in the cooling step, the temperature T4 [° C.] is higher than the temperature T3 [° C.], and the glass material is indicated by a change in the temperature T3 [° C.] per unit time. It is preferable that the cooling rate of the first main surface of the glass material is faster than the cooling rate of the first main surface of the glass material indicated by the change in the temperature T4 [° C.] per unit time.

Further, in the method for producing a 3D cover glass, it is preferable that the glass material has a minimum viscosity of 10 ¹¹ [Pa · s] or less in the heating step.

Further, in the method for producing a 3D cover glass, it is preferable that the glass material has a minimum viscosity of ^107.5 [Pa · s] or more in the heating step.

Further, in the method for producing a 3D cover glass, the glass material is preferably aluminosilicate glass.

Further, in the method for producing a 3D cover glass, the glass material may be lithium aluminosilicate glass.

Further, in the method for manufacturing a 3D cover glass, it is preferable that the heating step gives bending in the thickness direction over the entire circumference of the peripheral portion of the glass material.

Further, in the method for manufacturing a 3D cover glass, it is preferable that the pair of molds have a structure in which they are fitted by a ring mold.

Further, in the method for manufacturing a 3D cover glass, in the cooling step, the pair of gold is formed from a temperature at which both the temperature T3 [° C.] and the temperature T4 [° C.] are equal to or lower than the strain point Ts [° C.] of the glass material. It is preferable that the cooling time until the mold temperatures become the same is within 10 [minutes].

Further, in the method for producing a 3D cover glass, it is preferable that the maximum value of the press pressure in the glass molding step is 0.05 [MPa] or more.

Further, in the method for producing a 3D cover glass, it is preferable that the maximum value of the press pressure in the glass molding step is 1.0 [MPa] or less.

In the method for producing a 3D cover glass of the present invention, the warp of the glass due to the chemical strengthening treatment can be corrected without impairing the quality.

FIG. 1 is a diagram showing a configuration example of a 3D cover glass. 2 (a) and 2 (b) are schematic cross-sectional views showing the state of warpage of the 3D cover glass due to the chemical strengthening treatment, FIG. 2 (a) is before the chemical strengthening treatment, and FIG. 2 (b) is chemical. It shows after the strengthening treatment. FIG. 3 is a diagram showing a configuration example of a pair of dies used in the glass molding process. 4 (a) to 4 (d) are diagrams for explaining the state of the glass material in the heating step and the cooling step of the present manufacturing method. FIG. 5 is a schematic view of the molding apparatus in the embodiment. FIG. 6A shows the changes in the control temperatures T1 [° C.] and T2 [° C.] and the temperature difference (T2-T1) [° C.] in Example 1. FIG. 6B shows the changes in the temperatures T3 [° C.] and T4 [° C.] and the temperature difference (T4-T3) [° C.] in Example 1. FIG. 6C shows a change in the cooling rate at the temperature T3 [° C.], a change in the cooling rate at the temperature T4 [° C.], and a cooling rate at the temperature T4 [° C.] and a cooling rate at the temperature T3 [° C.] in Example 1. It shows the change of the difference with. FIG. 7A shows the changes in the control temperatures T1 [° C.] and T2 [° C.] and the temperature difference (T2-T1 [° C.]) in Example 2. FIG. 7B shows the changes in the temperatures T3 [° C.] and T4 [° C.] and the temperature difference (T4-T3) [° C.] in Example 2. FIG. 7C shows a change in the cooling rate at the temperature T3 [° C.], a change in the cooling rate at the temperature T4 [° C.], and a cooling rate at the temperature T4 [° C.] and a cooling rate at the temperature T3 [° C.] in Example 2. It shows the change of the difference with. FIG. 8A shows the changes in the control temperatures T1 [° C.] and T2 [° C.] and the temperature difference (T2-T1) [° C.] in Comparative Example 1. FIG. 8B shows the changes in the temperatures T3 [° C.] and T4 [° C.] and the temperature difference (T4-T3) [° C.] in Comparative Example 1. FIG. 8C shows a change in the cooling rate at the temperature T3 [° C.], a change in the cooling rate at the temperature T4 [° C.], and a cooling rate at the temperature T4 [° C.] and a cooling rate at the temperature T3 [° C.] in Comparative Example 1. It shows the change of the difference with. FIG. 9 is a graph showing the relationship between the temperature difference (T2-T1) [° C.] in the cooling step in the examples and the amount of warpage. FIG. 10 is a diagram comparing the cross-sectional shapes of the 3D cover glass obtained in Example 1 before and after the chemical strengthening treatment. FIG. 11 is a diagram comparing the cross-sectional shapes of the 3D cover glass obtained in Comparative Example 1 before and after the chemical strengthening treatment.

Hereinafter, the present invention will be described with reference to the drawings.
In the method for producing a 3D cover glass according to an embodiment of the present invention (hereinafter referred to as "the method for producing the present 3D cover glass" or "the present manufacturing method"), a flat glass material is heated to a transition temperature Tg [° C.] or higher. Then, a heating step of bending at least a part of the peripheral portion of the glass material in the thickness direction by using a pair of molds consisting of a convex mold and a concave mold is included. The glass molding step includes a cooling step of cooling the glass material to a temperature lower than the transition temperature Tg [° C.] of the glass material after the heating step, and a chemical strengthening treatment step of chemically strengthening the glass material after the glass molding step. ..

FIG. 3 is a diagram showing a configuration example of a pair of dies used in the glass molding process. The mold 20 shown in FIG. 3 is a pair of molds of a convex mold 21 and a concave mold 22, and the convex mold 21 and the concave mold 22 have a flat central portion 211 and 221 and are tertiary to at least a part of peripheral portions 212 and 222. It has an original curved surface. The shape of the pair of molds used in the glass molding step is not limited to this, and can be appropriately selected according to the shape of the 3D cover glass to be manufactured. For example, in a 3D cover glass having a substantially rectangular outer edge in a plan view, when manufacturing a 3D cover glass in which only the long side portion of the peripheral portion of the outer edge is a three-dimensional curved surface, the peripheral portion of the convex shape and the concave shape is manufactured. Of these, only a part (long side part) may form a three-dimensional curved surface. Further, when manufacturing a 3D cover glass in which the peripheral portion 120 has a three-dimensional curved surface over the entire circumference like the 3D cover glass 100 shown in FIG. 1, the convex and concave shapes are on the front side and the back side in FIG. It forms a three-dimensional curved surface including the peripheral part.

Further, the mold used in the glass forming step may further have a ring mold, and may include a structure in which the ring mold is fitted into a convex mold and a concave mold. In this case, for example, by fitting the convex and concave molds and then fitting the ring mold to cover the convex and concave fitting portions, it is possible to suppress the intrusion of foreign matter from the fitting portions. The quality of the 3D cover glass to be manufactured can be improved.

4 (a) to 4 (d) are diagrams illustrating a heating step and a cooling step of the present manufacturing method.
FIG. 4A shows the heating process of the present manufacturing method. By arranging the flat glass material 10 in the gap between the convex 21 and the concave 22 and heating the glass material 10 to a transition temperature of Tg [° C.] or higher. The peripheral part of the glass material is bent in the thickness direction.
In the heating step of this manufacturing method, it is preferable to press-mold the glass material 10 using a pair of dies 20 composed of a convex die 21 and a concave die 22. When the glass material is press-molded, the maximum value of the press pressure is preferably 0.05 [MPa] or more, more preferably 0.1 [MPa] or more in order to form the glass material into a desired shape. Further, in order to mold the glass material without causing cracks, the maximum value of the press pressure is preferably 1.0 [MPa] or less, more preferably 0.6 [MPa] or less.

Further, in the heating step of this manufacturing method, if at least a part of the peripheral portion of the glass material can be bent in the thickness direction by using a pair of molds consisting of a convex mold and a concave mold, molding other than press molding is performed. The method may be used, for example, vacuum molding or blow molding may be used.

In the heating step and the cooling step of the present manufacturing method, the temperatures of the convex 21 and the concave 22 facing the glass material 10 are controlled.
In the present manufacturing method, the main surface of the glass material 10 corresponding to the convex surface side formed by bending is designated as the first main surface 10a, and the glass corresponding to the back surface side with respect to the first main surface 10a, that is, the concave surface formed by bending. The main surface of the material 10 is the second main surface 10b. Then, the control temperature of the concave mold 22 on the side facing the first main surface 10a of the glass material 10 is set to the control temperature T1 [° C.], and the control temperature T2 [of the convex mold 21 facing the second main surface 10b of the glass material 10 is set. ℃]. In the heating step of the present manufacturing method shown in FIG. 4A, the control temperature T1 [° C.] of the concave mold 22 and the control temperature T2 [° C.] of the convex mold 21 are higher than the transition temperature Tg [° C.] of the glass material 10. The temperature may be high, and Tg + 50 [° C.] or higher is preferable, and Tg + 65 [° C.] or higher is more preferable. This is a condition for accurately molding the glass material. The control temperature T1 [° C.] of the concave type 22 and the control temperature T2 [° C.] of the convex type 21 are preferably Tg + 130 [° C.] or less, and more preferably Tg + 100 [° C.] or less. This is a condition for reducing the transfer of foreign matter and tool marks from the convex 21 and the concave 22 to the glass material 10. The transition temperature Tg [° C.] of the glass material 10 shown in FIG. 4 is a temperature at which the viscosity coefficient of the glass is 10 ¹² [Pa · s].
In FIG. 4A, since the control temperature T1 [° C.] of the concave mold 22 and the control temperature T2 [° C.] of the convex mold 21 are higher than the transition temperature Tg [° C.], the temperature of the glass material 10 is also the transition temperature Tg [° C.]. ], The stress relaxation time of the glass material 10 is short, and the glass material 10 is almost a viscous body and can be regarded as stress-free.

FIG. 4B shows the cooling process of this manufacturing method. In the cooling step of the present manufacturing method, at least one of the control temperature T1 [° C.] of the concave mold 22 and the control temperature T2 [° C.] of the convex mold 21 is controlled so as to be equal to or less than the glass transition temperature Tg [° C.] of the glass material 10. It is preferable that the temperature T2 [° C.] is larger than the control temperature T1 [° C.] and the temperature difference (T2-T1) [° C.] is maintained at 10 [° C.] or higher. In the cooling step of the present manufacturing method shown in FIG. 4B, for example, the control temperature T2 [° C.] of the convex type 21 is set to the same temperature as Tg [° C.], and the control temperature T1 [° C.] of the concave type 22 is set to the transition temperature Tg. The temperature may be lower than [° C.], and in this case, T1 is preferably Tg-10 [° C.] or less, and more preferably Tg-20 [° C.] or less. Further, T1 is preferably Tg-200 [° C.] or higher, and more preferably Tg-100 [° C.] or higher.
In the cooling step of FIG. 4B, at least one of the convex 21 and the concave 22 was changed from the state of FIG. 4A in which the control temperature of the convex 21 and the concave 22 was equal to or higher than the transition temperature Tg [° C.]. Since the control temperature (T1 [° C.] and / or T2 [° C.]) of the above changes to a state below the transition temperature Tg [° C.], at a certain moment, at least a part of the glass material 10, that is, the temperature T4 described later. [° C.] is the transition temperature Tg [° C.] or higher, and the temperature T3 described later is the transition temperature Tg [° C.] or lower. At that moment, the stress relaxation time is short as in FIG. 4A, and the glass material 10 can be regarded as almost stress-free.
Further, the temperature difference (T2-T1) [° C.] is more preferably 20 [° C.] or more. In this case, the lower limit of the temperature difference (T4-T3) [° C.] described later can be easily satisfied. The temperature difference (T2-T1) [° C.] is preferably 200 [° C.] or less, and more preferably 100 [° C.] or less. This is because it is preferable to independently control the temperatures of the concave and convex shapes that are in contact with each other across the glass after pressing.

FIG. 4C schematically shows a state when the glass material is cooled to room temperature. When the temperature of the glass material 10 is equal to or lower than the transition temperature Tg [° C.], the temperature difference (T2-T1) [° C.] between the control temperature T2 [° C.] of the convex type 21 and the control temperature T1 [° C.] of the concave type 22 is 10 [° C.]. When the glass material 10 is cooled to a transition temperature of Tg [° C.] or lower while being held at ° C.] or higher, a difference in shrinkage amount in the plate thickness direction occurs and a moment force in the arrow direction is generated, as shown in FIG. 4 (c). do. Actually, since it is restrained (fixed) by the mold 20, stress is generated in the glass material. As a result, the glass material 10 taken out from the mold has a warped shape as schematically shown in FIG. 4D due to the moment force, and the warpage due to the chemical strengthening treatment shown in FIG. 2B can be corrected.

In the cooling step of this manufacturing method, the temperature [° C.] of the first main surface 10a of the glass material 10 and the temperature [° C.] of the second main surface 10b are controlled by controlling the temperature difference (T2-T1) [° C.]. It is preferable that the temperature difference [° C.] satisfies the conditions described below.
Here, when the temperature of the first main surface 10a of the glass material 10 is T3 [° C.] and the temperature of the second main surface 10b of the glass material 10 is T4 [° C.], the temperature T3 [° C.] and the temperature T4 [° C.]. ] Is the temperature T4 [° C.] in the temperature range from the transition temperature Tg [° C.] of the glass material to the strain point Ts (the temperature at which the viscosity coefficient of the glass becomes 10 ^13.5 [Pa · s]) [° C.]. ] And the temperature T3 [° C.], it is preferable to keep the temperature difference (T4-T3) [° C.] at 0.3 [° C.] or more in order to obtain a shape corrected for deformation due to the chemical strengthening treatment.

The temperature T4 [° C.] is usually higher than the temperature T3 [° C.]. Therefore, suitable warpage of glass can be generated by keeping the temperature difference (T4-T3) [° C.] in the above temperature range at 0.3 [° C.] or more. This is to make a transition from the viscous region to the elastic region with a temperature difference in the plate thickness direction, and by doing so, in the process of eliminating the temperature difference in the glass plate thickness direction in the subsequent cooling. The warp of the glass can be controlled by the difference in heat shrinkage. Further, the temperature difference (T4-T3) [° C.] is more preferably maintained at 0.5 [° C.] or higher, and further preferably 1.0 [° C.] or higher in the above temperature range. Further, the temperature difference (T4-T3) [° C.] is preferably maintained at 100 [° C.] or less, and more preferably 50 [° C.] or less in the above temperature range. This is because the occurrence of glass breakage can be suppressed by setting the temperature difference (T4-T3) [° C.] to 100 [° C.] or less in the above temperature range.

In the cooling step of this manufacturing method, the temperature difference (T2-T1) [° C.] in the pair of molds 20 controls the temperature difference (T4-T3) [° C.] in the plate thickness direction of the glass material 10. The mold 20 is preferably made of a material having high thermal conductivity. Specifically, the mold 20 is preferably made of a material having a thermal conductivity of 50 [W / (m · K)] or more, and specific examples of the material satisfying the above include carbon, cemented carbide, and copper. Be done.

In the cooling step of this production method, the temperature T3 [° C.] and the temperature T4 [° C.] per unit time in the temperature range from the transition temperature Tg [° C.] of the glass material to the strain point Ts [° C.] of the glass material. The cooling rate of the first main surface of the glass material indicated by the change of the temperature T3 [° C.] and the cooling rate of the second main surface of the glass material indicated by the change of the temperature T4 [° C.] per unit time are 0. Satisfying 1 to 10.0 [° C./Sec] is preferable for improving productivity. Further, under the condition of T4 [° C.]> T3 [° C.], the cooling rate of the first main surface of the glass material indicated by the change in the temperature T3 [° C.] per unit time is the temperature T4 [° C.] per unit time. It is more preferable that the cooling rate is faster than the cooling rate of the second main surface of the glass material indicated by the change in.

In the cooling step of this manufacturing method, the temperatures of the pair of molds become the same after both the temperature T3 [° C.] and the temperature T4 [° C.] reach the temperature equal to or lower than the strain point Ts [° C.] of the glass material. It is preferable that the cooling time is within 10 [minutes] because the productivity is improved. However, if the above cooling time is too short, the glass material may be cracked. Therefore, the cooling time is preferably 30 [seconds] or more.

In this production method, the glass material used for the 3D cover glass is preferable from the viewpoint of moldability as long as the minimum viscosity in the heating step is 10 ¹¹ [Pa · s] or less. If the minimum viscosity in the heating process exceeds 10 ¹¹ [Pa · s], the glass material may crack in the heating process. The glass material used for the 3D cover glass is more preferably 10 ¹⁰ [Pa · s] or less, and further preferably 10 10 [Pa · s] or less, when the minimum viscosity in the heating step is 10 ^10.5 [Pa · s] or less. This is because it is easy to improve the shape accuracy of the 3D cover glass by bringing the peripheral portion of the three-dimensional curved surface into close contact with the mold. Further, the glass material used for the 3D cover glass preferably has a viscosity of 10 ^7.5 [Pa · s] or more in the heating step from the viewpoint of the appearance quality of the 3D cover glass, and more preferably 10 ^8.0 [Pa · s] or more. It is preferable, and 10 ^8.5 [Pa · s] or more is more preferable. A glass material having such a viscosity can suppress appearance defects that occur on the surface of the glass material in the heating step.

In this manufacturing method, the glass material after the glass molding process is chemically strengthened. Therefore, the glass material used for manufacturing the 3D cover glass is required to be a material that can be chemically strengthened. In the chemical strengthening treatment, alkali metal ions (typically Li ions and Na ions) having a small ion radius on the glass surface are converted into alkali ions (typically Li ions and Na ions) having a larger ion radius by ion exchange at a temperature below the transition temperature Tg [° C.]. It is exchanged for K ion). By such ion exchange, a compressive stress layer is formed on the surface of the glass to improve the strength.

Examples of glass that can be chemically strengthened include colorless and transparent amorphous glass, as well as glass plates made of crystallized glass, colored glass, and the like. More specifically, as the glass material, for example, non-alkali glass, soda lime glass, soda lime silicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, and borosilicate glass can be used. Aluminosilicate glass and lithium aluminosilicate glass are preferable because even if the thickness is thin, a large stress is easily applied by the strengthening treatment and a high-strength glass can be obtained even if the thickness is thin. As the chemical strengthening treatment, a method of immersing the glass in the molten salt or a method of applying the molten salt in the form of a paste or powder to the glass can be used, but usually, the glass is placed in the molten salt containing an alkali metal. It is done by immersing.

A more specific glass composition is a composition expressed in mol%, which contains 50 to 80% SiO ₂ , 0.1 to 25% Al ₂ O ₃ , 3 to 30% Li ₂ O + Na ₂ O + K ₂ O, and so on. Examples thereof include glass containing 0 to 25% of MgO, 0 to 25% of CaO and 0 to 5% of ZrO ₂ , but are not particularly limited. More specifically, the following glass composition can be mentioned. For example, "containing 0 to 25% of MgO" means that MgO may be contained up to 25%, although it is not essential. The glass of (i) is contained in the soda lime silicate glass, the glasses of (ii) and (iii) are contained in the aluminosilicate glass, and the glass of (v) is contained in the lithium aluminosilicate glass.
(I) Composition expressed in mol%, composition expressed in mol%, SiO ₂ 63 to 73%, Al ₂ O ₃ 0.1 to 5.2%, Na ₂ O 10 to 16%, A glass containing 0 to 1.5% K ₂ O, 0 to 5.0% Li ₂ O, 5 to 13% Mg O, and 4 to 10% Ca O.
(Ii) The composition expressed in mol% is 40 to 74% for SiO ₂ , 1 to 10% for Al ₂ O ₃ , 6 to 14% for Na ₂ O, 3 to 11% for K ₂ O, and Li ₂ O. 0 to 5.0%, MgO 2 to 15%, CaO 0 to 6% and ZrO ₂ 0 to 5%, the total content of SiO ₂ and Al ₂ O ₃ is 75% or less, Na A glass having a total content of ₂ O and K ₂ O of 12 to 25% and a total content of MgO and CaO of 7 to 15%.
The composition expressed in (iii) mol% is 68 to 80% for SiO ₂ , 4 to 10% for Al ₂ O ₃ , 5 to 15% for Na ₂ O, 0 to 1% for K ₂ O, and Li ₂ O. A glass containing 0 to 5.0% of MgO, 4 to 15% of MgO, and 0-1% of ZrO ₂ .
The composition expressed in (iv) mol% is 67 to 75% for SiO ₂ , 0 to 4% for Al ₂ O ₃ , 7 to 15% for Na ₂ O, 1 to 9% for K ₂ O, and Li ₂ O. 0 to 5.0%, MgO 6 to 14% and ZrO ₂ 0 to 1.5%, the total content of SiO ₂ and Al ₂ O ₃ is 71 to 75%, Na ₂ O and K. A glass in which the total content of ₂ O is 12 to 20%, and when CaO is contained, the content is less than 1%.
(V) The composition expressed in molar% is 56 to 73% for SiO ₂ , 10 to 24% for Al ₂ O ₃ , 0 to 6% for B ₂ O ₃ , 0 to 6% for P ₂ O ₅ , and Li. ₂ O is 2 to 7%, Na ₂ O is 3 to 11%, K ₂ O is 0 to 5%, MgO is 0 to 8%, CaO is 0 to 2%, SrO is 0 to 5%, and BaO is 0. A glass containing ~ 5%, ZnO 0-5%, TiO ₂ 0-2%, and ZrO ₂ 0-4%.

The 3D cover glass manufactured by this manufacturing method can be further applied to a target that satisfies the following conditions.

The thickness of the 3D cover glass is preferably 0.3 mm or more and 2.0 mm or less. If the plate thickness is less than 0.3 mm, it is difficult to obtain a temperature difference in the plate thickness direction of the glass material in the cooling process, and it is difficult to obtain a shape corrected for deformation due to the chemical strengthening treatment. If the plate thickness exceeds 2.0 mm, the deformation due to the chemical strengthening treatment is small, so that it is not highly necessary to correct the deformation due to the chemical strengthening treatment.

Further, the 3D cover glass preferably has a diagonal size of 50 mm or more and 1000 mm or less in a plan view. If the diagonal size is less than 50 mm, the deformation due to the chemical strengthening treatment is small, so that the appropriateness is not sufficient as a method for correcting by using the deformation due to the chemical strengthening treatment. Further, if the diagonal size is more than 1000 mm, it is difficult to cool the in-plane uniformly, and the deformation mode by the chemical strengthening treatment may be different from the deformation mode by the present manufacturing method, which makes control difficult. There is. Further, as the 3D cover glass, a substantially rectangular one including one having rounded corners is preferably used in a plan view, and even in this case, the diagonal size is preferably 50 mm or more and 1000 mm or less.

Further, the 3D cover glass preferably has a minimum radius of curvature R of a three-dimensional curved surface at a peripheral portion of 0.1 mm or more and 20 mm or less. When the minimum radius of curvature R is less than 0.1 mm, its controllability is difficult, and when the minimum radius of curvature R is more than 20 mm, its suitability as a method for correction using deformation by chemical strengthening treatment is not sufficient. Because there isn't.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Examples 1 and 2, Comparative Example 1)
In the present examples (1 and 2), the convex control temperature T2 [° C.] in the heating step and the concave control temperature T1 [° C.] are controlled at the same temperature, and the convex control temperature T2 [° C.] in the cooling step is controlled. ] And the concave control temperature T1 [° C.] and the temperature difference (T2-T1) [° C.] were changed to carry out the glass molding step. Then, the amount of warpage when taken out from the mold was evaluated by the following procedure. Specifically, as shown in FIG. 3, a convex shape 21 and a concave shape 22 in which the central portions 211 and 221 are flat and the peripheral portions 212 and 222 are three-dimensional curved shapes over the entire circumference are shown in FIG. As described above, the 3D cover glass 100 in which the central portion 110 is a flat surface and the peripheral portion 120 is a three-dimensional curved surface is manufactured and evaluated. As a comparative example, the amount of warpage under the condition (= 0 [° C.]) in which the temperature difference (T2-T1) [° C.] in the cooling step was not given was also evaluated.

First, using a molding apparatus manufactured by DTK (model number: DTK-DGP-3D12S), a glass material DT-STAR manufactured by Asahi Glass Co., Ltd. (plate thickness 0.5 [mm], transition temperature Tg = 547 [° C.], Strain point Ts = 501 [° C.]) was formed. A schematic view of the molding apparatus is shown in FIG. The molding device is divided into 4 zones of preheating 1 to 4, 3 zones of Press 1 to 3, and 4 zones of cooling 1 to 4, for a total of 11 zones. The glass was formed by controlling the temperature of the die and the pressing pressure by pressing. Here, the five zones of preheating 1 to 4 and Press 1 correspond to the heating step, and Press 2 and subsequent zones correspond to the cooling step. Specifically, at the Press1 position of FIG. 5 of the molding apparatus, the control temperature T1 [° C.] and the control temperature T2 [° C.] have a viscosity coefficient of 10 ^9.5 [Pa. It was molded so that the maximum value of the press pressure was 0.55 [MPa] at the temperature of [s]. After that, at the Press 2 position and the Press 3 position of FIG. 5 of the molding apparatus, the glass material is pressed with the maximum value of the press pressure of 0.5 [MPa], and a temperature difference (T2-T1) [° C.] is applied to cool the glass material. did. Here, the staying time per zone was 90 [seconds].

The dimensions of the mold used are (vertical) about 180 [mm] x (horizontal) about 120 [mm] x (height) about 30 [mm], and the volumes of the convex mold 21 and the concave mold 22 are the same (volume). The ratio was 1: 1), and a concave mold 22 was used as the lower mold and a convex mold 21 was used as the upper mold. As the material of the mold, carbon having a thermal conductivity of 104.4 [W / (m · K)] was used. The size of the molded 3D cover glass in a plan view is about 150 [mm] × 80 [mm], the four corners are substantially rectangular with curved shapes, and the minimum radius of curvature R of the three-dimensional curved surface at the peripheral portion 120 is 5 [ It was about mm].

Here, the viscosity coefficient of the glass is 10 ^9.5 [Pa. The temperature was controlled to be s] (630 [° C.]). Then, the control temperature T1 [° C.] of the concave mold 22 and the control temperature T2 [° C.] of the convex mold 21 in the cooling step of each embodiment were changed to form a 3D cover glass under the following conditions. The cooling time is 100 [° C.] at which the temperature of the convex type 21 and the temperature of the concave type 22 are the same from the temperature at which both the control temperature T1 [° C.] and the control temperature T2 [° C.] are Ts [° C.] or less. ] Is shown. In the comparative example, the temperature difference (T2-T1) [° C.] in the cooling step was not given.

Further, the temperature T3 [° C.] of the first main surface of the glass material and the temperature T4 [° C.] of the second main surface of the glass material are based on the control temperature T1 [° C.] and the control temperature T2 [° C.], respectively. , Dassault Systèmes Co., Ltd. calculated by heat conduction analysis of general-purpose analysis software ABAQUS. Specifically, the contact heat transfer coefficient between the convex / concave heater plate and the convex / concave type was experimentally set to 1000 [W / (m ² · K)], and the contact heat between the convex / concave type and the glass was experimentally set. The transfer coefficient was determined to be 300 [W / (m ² · K)], and these were used as the thermal boundary conditions for the simulation. The thermal properties of the glass are carbon type heat using a thermal conductivity of 1.2 [W / (m · K)], a specific heat of 1340 [J / (kg · K)], and a density of 2500 [kg / m ³ ]. As the physical properties, a thermal conductivity of 104.4 [W / (m · K)], a specific heat of 710 [J / (kg · K)], and a density of 1800 [kg / m ³ ] were used. The cooling rates at the temperature T3 [° C.] and the temperature T4 [° C.] are both calculated results obtained by dividing by the time required for cooling from Tg (= 547 ° C.) to Ts (= 501 ° C.). Further, the temperature difference (T4-T3) [° C.] between the temperature T4 [° C.] and the temperature T3 [° C.] is the temperature from Tg (= 547 ° C.) to Ts (= 501 ° C.). The minimum value of the difference.

FIG. 6 shows the temperature change profile in Example 1. Specifically, FIG. 6 (a) shows a change in the control temperature T1 [° C.], a control temperature T2 [° C.], and a change in the temperature difference (T2-T1) [° C.]. Changes in temperature T3 [° C.], temperature T4 [° C.], and temperature difference (T4-T3) [° C.] are shown. FIG. 6 (c) shows changes in the cooling rate at temperature T3 [° C.] and temperature T4. The change in the cooling rate at [° C.] and the change in the difference between the cooling rate at temperature T4 [° C.] and the cooling rate at temperature T3 [° C.] are shown.

FIG. 7 shows the temperature change profile in Example 2. Specifically, FIG. 7 (a) shows changes in the control temperature T1 [° C.], control temperature T2 [° C.], and changes in the temperature difference (T2-T1) [° C.], and FIG. 7 (b) shows changes in the temperature difference (T2-T1) [° C.]. Changes in temperature T3 [° C.], temperature T4 [° C.], and temperature difference (T4-T3) [° C.] are shown. FIG. 7 (c) shows changes in the cooling rate at temperature T3 [° C.] and temperature T4. The change in the cooling rate at [° C.] and the change in the difference between the cooling rate at temperature T4 [° C.] and the cooling rate at temperature T3 [° C.] are shown.

FIG. 8 shows the temperature change profile in Comparative Example 1. Specifically, FIG. 8A shows a change in the control temperature T1 [° C.], a control temperature T2 [° C.], and a change in the temperature difference (T2-T1) [° C.]. FIG. Changes in temperature T3 [° C.], temperature T4 [° C.], and temperature difference (T4-T3) [° C.] are shown. FIG. 8 (c) shows changes in the cooling rate at temperature T3 [° C.] and temperature T4. The change in the cooling rate at [° C.] and the change in the difference between the cooling rate at temperature T4 [° C.] and the cooling rate at temperature T3 [° C.] are shown.

The shape of the flat portion 110 of the 3D cover glass 100 using the 3D measuring machine ATOS (model number: ATOS Triple scan III) manufactured by GOM with respect to the molded 3D cover glasses of Examples 1 and 2 and Comparative Example 1. Was measured. Then, the deviation between the plane and the measurement result when the measurement result and the plane were best-fitted was calculated, and the difference between the maximum value and the minimum value of the deviation was converted into the warp amount. The result is shown in FIG.

As shown in FIG. 9, in the case of Comparative Example 1 in which the temperature difference (T2-T1) [° C.] was 0 [° C.], the amount of warpage when taken out from the mold was 0 [μm]. In the case of Examples 1 and 2 in which the temperature difference (T2-T1) [° C.] was positive, the amount of warpage when taken out from the mold showed a positive value (having a convex portion on the convex surface). When the central portion of the glass material was warped in the concave direction when viewed from the convex surface when taken out from the mold, the expected warp amount was set to a positive value.

(Example 3)
In this example, the 3D cover glass obtained in Example 1 and Comparative Example 1 was subjected to a chemical strengthening treatment, and the shape change before and after the chemical strengthening treatment was evaluated by the following procedure.
First, the 3D cover glass obtained in Example 1 and Comparative Example 1 was heated to 450 [° C.] and immersed in melted potassium nitrate salt for 2 hours for ion exchange treatment. Then, the 3D cover glass was pulled up from the molten salt and slowly cooled to room temperature in 1 hour to perform a chemical strengthening treatment. Further, this 3D cover glass was immersed in an alkaline solution (trade name: Sunwash TL-75, manufactured by Lion) for 4 hours and subjected to alkaline treatment to obtain a 3D cover glass after chemical strengthening treatment.

The shape change before and after the chemical strengthening treatment was also measured using the above-mentioned three-dimensional measuring machine.
FIG. 10 is a diagram showing a shape change of the 3D cover glass obtained in Example 1 in the Z-axis direction when viewed from the long-axis direction. In FIG. 9, the central portion of the 3D cover glass that is warped downward is shown upward, but as shown in FIG. 10, it was confirmed that the deformation due to the chemical strengthening treatment was corrected in advance. At this time, the surface shape of the central portion (134 [mm] × 64 [mm]) of the 3D cover glass before the chemical strengthening treatment of Example 1 had a PV value of 0.464 [mm] and a flatness of 0. The surface shape after the chemical strengthening treatment was 0.267 [mm] in PV value and 0.048 [mm] in flatness, whereas it was 159 [mm]. The amount of deformation before and after the chemical strengthening treatment was 0.237 [mm] on the entire surface and 0.237 [mm] on the flat central portion.

FIG. 11 is a diagram showing a shape change of the 3D cover glass obtained in Comparative Example 1 in the Z-axis direction when viewed from the long-axis direction. In FIG. 9, the central portion of the 3D cover glass in which the warp is generated downward is shown upward, and as shown in FIG. 11, it can be confirmed that the deformation is increased by the chemical strengthening treatment. At this time, the surface shape of the central portion (134 [mm] × 64 [mm]) of the 3D cover glass before the chemical strengthening treatment of Comparative Example 1 had a PV value of 0.150 [mm] and a flatness of 0. Whereas the surface shape after the chemical strengthening treatment was 110 [mm], the PV value was 0.313 [mm] and the flatness was 0.280 [mm]. The amount of deformation before and after the chemical strengthening treatment was 0.257 [mm] on the entire surface and 0.231 [mm] on the flat central portion. From the above, the flatness after chemical strengthening of Comparative Example 1 is 0.280 [mm], whereas the flatness after chemical strengthening of Example 1 is 0.048 [mm], and according to the present invention, the flatness is excellent. A 3D cover glass was obtained.

10: Glass material 10a: First main surface 10b: Second main surface 20: Mold 21: Convex type 211: Central part 212: Peripheral part 22: Concave type 221: Central part 222: Peripheral part 100: 3D cover glass 110: Central part 120: Peripheral part

Claims (17)

Heating in which a flat glass material is heated to a transition temperature of Tg [° C.] or higher, and at least a part of the peripheral portion of the glass material is bent in the thickness direction using a pair of molds consisting of a convex mold and a concave mold. A glass molding step comprising a step and a cooling step of cooling the glass material to a temperature lower than the transition temperature Tg [° C.] after the heating step.
After the glass molding step, the glass material is chemically strengthened, and the glass material is chemically strengthened.
In the cooling step, the control temperature of the concave shape facing the first main surface of the glass material corresponding to the convex side formed by the bending is set to the control temperature T1 [° C.], and the concave side formed by the bending. When the control temperature of the convex shape facing the second main surface of the glass material corresponding to is the control temperature T2 [° C.], at least one of the control temperature T2 [° C.] and the control temperature T1 [° C.] Is set to be equal to or lower than the transition temperature Tg [° C.] of the glass material, the control temperature T2 [° C.] is larger than the control temperature T1 [° C.], and the temperature difference between the control temperature T2 and the control temperature T1 [° C.] T2-T1) A method for producing a 3D cover glass, which comprises a procedure for maintaining [° C.] at 10 [° C.] or higher. The glass molding step includes a procedure of press molding using the pair of molds, and the temperature of the first main surface of the glass material is set to T3 [° C.] by controlling the temperature difference (T2-T1) [° C.]. ], And when the temperature T4 [° C.] of the second main surface of the glass material is set, the temperature T3 [° C.] and the temperature T4 [° C.] are derived from the transition temperature Tg [° C.] of the glass material. In the temperature range up to the strain point Ts [° C.], the temperature T4 [° C.] is larger than the temperature T3, and the temperature difference between the temperature T4 [° C.] and the temperature T3 [° C.] (T4-T3) [ The method for producing a 3D cover glass according to claim 1, further comprising a procedure for maintaining [° C.] at 0.3 [° C.] or higher. The method for producing a 3D cover glass according to claim 1 or 2, wherein the pair of molds is made of a material having a thermal conductivity of 50 [W / (m · K)] or more. The cooling step is the cooling rate of the first main surface of the glass material indicated by the change in the temperature T3 [° C.] per unit time, and the glass indicated by the change in the temperature T4 [° C.] per unit time. The method for producing a 3D cover glass according to claim 2 , wherein the cooling rate of the second main surface of the material satisfies 0.1 [° C./Sec] or more and 10.0 [° C./Sec] or less. In the cooling step, the temperature T4 is higher than the temperature T3, and the cooling rate of the first main surface of the glass material indicated by the change in the temperature T3 [° C.] per unit time is the temperature per unit time. The method for producing a 3D cover glass according to claim 4, which is faster than the cooling rate of the second main surface of the glass material indicated by the change in T4 [° C.]. The method for producing a 3D cover glass according to any one of claims 1 to 5, wherein the glass material has a minimum viscosity of 10 ¹¹ [Pa · s] or less in the heating step. The method for producing a 3D cover glass according to any one of claims 1 to 6, wherein the glass material has a minimum viscosity of 10 ^7.5 [Pa · s] or more in the heating step. The method for producing a 3D cover glass according to any one of claims 1 to 7, wherein the glass material is aluminosilicate glass. The method for producing a 3D cover glass according to any one of claims 1 to 7, wherein the glass material is lithium aluminosilicate glass. The method for producing a 3D cover glass according to any one of claims 1 to 9, wherein the heating step gives bending in the thickness direction over the entire circumference of the peripheral portion of the glass material. The method for manufacturing a 3D cover glass according to any one of claims 1 to 10, wherein the pair of molds has a structure fitted by a ring mold. In the cooling step, both the temperature T3 [° C.] and the temperature T4 [° C.] are cooled from a temperature equal to or lower than the strain point Ts [° C.] of the glass material until the temperature of the pair of molds becomes the same. The method for producing a 3D cover glass according to claim 2, 4 or 5 , wherein the time is within 10 [minutes]. The method for producing a 3D cover glass according to any one of claims 2 to 12, wherein in the glass molding step, the maximum value of the press pressure is 0.05 [MPa] or more. The method for producing a 3D cover glass according to claim 13, wherein in the glass molding step, the maximum value of the press pressure is 1.0 [MPa] or less. The method for producing a 3D cover glass according to any one of claims 1 to 14, wherein in the cooling step, the temperature difference (T2-T1) [° C.] is 50 [° C.] or more. The method for producing a 3D cover glass according to any one of claims 1 to 15, wherein in the cooling step, the time for holding the temperature difference (T2-T1) is 90 [seconds] or more. The 3D cover glass according to any one of claims 1 to 16, wherein in the heating step, the control temperature T1 [° C.] and the control temperature T2 [° C.] are equal to or higher than the transition temperature Tg + 50 [° C.] of the glass material. Manufacturing method.

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