JP2013189320A - Method for increasing strength of glass substrate - Google Patents

Abstract

The present invention provides a method for increasing the strength of a glass substrate, wherein the glass substrate is less likely to warp and / or deform.
A method of increasing the strength of a glass substrate, comprising: (a) preparing a glass substrate having a first surface and a second surface facing each other; and (b) providing the first surface and the first surface. (2) Evaluating the ease of alkali metal removal on the surface of (2), (c) Based on (b), the ease of alkali metal removal on the first surface and the second surface is substantially equivalent. As described above, a plasma treatment is performed on the first surface and / or the second surface of the glass substrate, and (d) a chemical strengthening treatment is performed on the glass substrate after the (c). Method.
[Selection] Figure 3

Description

  The present invention relates to a glass substrate used for a display device or the like.

  In general, a glass substrate is widely used in display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic EL (Electroluminescent) display (OELD). Recently, a glass substrate with a thin plate thickness has been demanded in order to meet demands for further thinning and weight reduction of display devices.

  In general, the strength of a glass substrate decreases as the plate thickness decreases. Therefore, in order to actually apply a thin glass substrate to a display device or the like, it is necessary to improve the strength of the glass substrate. For this reason, it has been proposed to perform a chemical strengthening process on a glass substrate (Patent Document 1).

Japanese Patent Publication No. 5-3420

  By performing the chemical strengthening process on the glass substrate, the strength of the glass substrate can be increased even if the plate thickness is thin.

  However, when a chemical strengthening process is performed on the glass substrate, warping and / or deformation may occur in the finally obtained glass substrate. This is considered to be due to a minute difference in chemical properties between the two surfaces (front and back) of the glass substrate. For example, the two surfaces of the glass substrate are not always subjected to the same history. For example, in the process of manufacturing the glass substrate, the respective surfaces may receive different histories. In such a case, when the glass substrate is chemically strengthened, the glass substrate is warped and / or deformed due to a difference in chemical properties between the two surfaces.

  When it is assumed that the glass substrate is used for a display device, such warpage and / or deformation of the glass substrate is not preferable because it leads to distortion of an image emitted from the display panel side. Further, when such warpage and / or deformation occurs, it becomes necessary to repair the warpage and / or deformation by polishing the glass substrate, and extra cost and time are required.

  In particular, glass substrates for display devices tend to become larger and thinner, and such warpage and / or deformation problems are expected to become more prominent in the future.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a method for increasing the strength of a glass substrate, which is less likely to warp and / or deform the glass substrate. To do.

In the present invention,
A method for increasing the strength of a glass substrate,
(A) preparing a glass substrate having a first surface and a second surface facing each other;
(B) Evaluating the ease of alkali metal removal on the first surface and the second surface,
(C) Based on (b), the first surface of the glass substrate and / or the first surface and / or the second surface so that the ease of alkali metal removal on the second surface is substantially equal. Alternatively, plasma treatment is performed on the second surface,
(D) After (c), a method is provided in which a chemical strengthening treatment is performed on the glass substrate.

Here, in the method according to the invention:
In the first surface, when the alkali metal is easy to escape compared to the second surface,
(C)
The first surface may be irradiated with + (plus) ion plasma and / or the second surface may be irradiated with − (minus) ion plasma.

In the method according to the invention,
(B)
(B1) An evaluation film not containing the alkali metal is installed on the first surface, and the evaluation film is installed on the second surface,
(B2) heat treating the glass substrate;
(B3) The measurement may be performed by measuring the amount of the alkali metal contained in the evaluation film.

  In this case, the evaluation film may be a conductive oxide.

In the method according to the invention,
The heat treatment in (b2) may be performed in the range of 100 ° C. to 600 ° C. for 10 minutes to 1 hour.

In the method according to the invention,
The (b3) may be performed by continuously measuring the amount of the alkali metal while dry-etching the evaluation film by the SIMS method.

  In the method according to the present invention, the alkali metal may be sodium (Na).

  In the method according to the present invention, the glass substrate may be a glass substrate manufactured by a float process.

  In the method according to the present invention, the glass substrate may have a thickness in the range of 0.4 mm to 3 mm.

  In the method according to the present invention, the glass substrate may be for a display device of 32 inches or more.

  In the present invention, it is possible to provide a method for increasing the strength of a glass substrate, which is less likely to warp and / or deform the glass substrate.

It is the side view which showed typically the conventional glass substrate after carrying out a chemical strengthening process. It is the side view which showed typically the glass substrate by this invention after performing a chemical strengthening process. It is the flowchart which showed roughly an example of the method of raising the intensity | strength of the glass substrate by this invention.

  The present invention will be described below.

  As described above, conventionally, in order to increase the strength of a glass substrate having a thin plate thickness, it has been studied to apply a chemical strengthening treatment to the glass substrate.

  Here, “chemical strengthening treatment (method)” means that a glass substrate is immersed in a molten salt containing an alkali metal, and an alkali metal (ion) having a small atomic diameter present on the outermost surface of the glass substrate is dissolved in the molten salt. Is a generic term for technologies that replace alkali metals (ions) with large atomic diameters. In the “chemical strengthening treatment (method)”, an alkali metal (ion) having an atomic diameter larger than that of the original atom is arranged on the surface of the treated glass substrate. For this reason, compressive stress can be given to the surface of a glass substrate, and the intensity | strength (especially crack strength) of a glass substrate improves by this.

  For example, when the glass substrate contains sodium (Na), this sodium is replaced with, for example, potassium (Ka) by the chemical strengthening treatment. Alternatively, for example, when the glass substrate contains lithium (Li), this lithium may be replaced with, for example, sodium (Na) and / or potassium (Ka) by chemical strengthening treatment.

  Thus, by performing a chemical strengthening process with respect to a glass substrate, even if plate | board thickness is thin, the intensity | strength of a glass substrate can be raised.

  However, when a chemical strengthening process is performed on the glass substrate, the glass substrate finally obtained may be warped and / or deformed as shown in FIG.

  FIG. 1 is a schematic side view of a glass substrate 10 after a conventional chemical strengthening treatment. The glass substrate 10 has a first surface 12A and a second surface 12B that face each other. Further, the glass substrate 10 had a substantially flat shape without warping until immediately before the chemical strengthening treatment. However, after the chemical strengthening treatment, the glass substrate 10 is warped such that the first surface 12A becomes a convex surface and the second surface 12B becomes a concave surface.

  At present, the cause of such warpage and / or deformation in the glass substrate 10 after the chemical strengthening treatment is not clear, but the chemicals of the two surfaces 12A and 12B of the glass substrate 10 before the chemical strengthening treatment are not clear. It is considered that minute differences in properties are caused by such warpage and / or deformation.

  For example, in the process of manufacturing the glass substrate 10, when the surfaces 12 </ b> A and 12 </ b> B receive different histories, the warp as shown in FIG. 1 may occur.

  In particular, a glass substrate manufactured by a so-called float method is in a state where only one surface is in contact with a molten tin (Sn) layer during manufacturing. Therefore, depending on the presence or absence of contact with the molten tin layer, there may be a fine difference in chemical properties between both surfaces 12A and 12B. For example, when tin remains on the surface side that has been in contact with the molten tin layer, such a surface side is expected to become a surface on which alkali metal is more difficult to escape during the chemical strengthening treatment. This is because the residual tin suppresses the alkali metal of the glass substrate from escaping to the molten salt side. Further, for example, the alkali metal concentration itself may be higher on the surface side of the glass substrate that is in contact with the molten tin layer.

  According to this consideration, in FIG. 1, the second surface 12B side (that is, the concave surface) is a surface in contact with tin, that is, the surface 12B is compared with the surface 12A during the chemical strengthening treatment. It is expected that the alkali metal is difficult to escape to the molten salt side.

  In addition, the curvature and / or deformation | transformation of the glass substrate in the case of a chemical strengthening process are not restricted to the glass substrate manufactured by the float glass process, A curvature and / or deformation | transformation may also arise also in the glass substrate manufactured by the fusion method.

  Such warpage and / or deformation of the glass substrate 10 is not preferable when it is assumed that the glass substrate 10 is used for a display device. This is because an image output from the display device is distorted by the glass substrate 10 and there is a high risk that an appropriate image cannot be obtained. Further, when such warpage and / or deformation occurs, it becomes necessary to repair the warpage and / or deformation by polishing the glass substrate, and extra cost and time are required.

  In particular, glass substrates for display devices tend to become larger and thinner, and such warpage and / or deformation problems are expected to become more prominent in the future.

  On the other hand, in this invention, even if it implements a chemical strengthening process to the glass substrate with thin thickness, the curvature and / or deformation | transformation of a glass substrate can be suppressed significantly.

  In FIG. 2, the typical side view of the glass substrate 100 after carrying out the chemical strengthening process by the method of this invention is shown. Even after the glass substrate 100 is chemically strengthened, the first surface 112A and the second surface 112B remain substantially flat, and the glass substrate 100 is not warped and / or deformed. unacceptable.

  Thus, in the present invention, a glass substrate in which warpage and / or deformation is significantly suppressed after the chemical strengthening treatment can be obtained. Therefore, in the method according to the present invention, a chemically strengthened glass substrate can be applied as it is to a large display device (for example, a display device of 32 inches or more) or a thin display device.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  FIG. 3 shows an example of a method for increasing the strength of the glass substrate according to the present invention.

As shown in FIG. 3, the method of the present invention
(A) preparing a glass substrate having a first surface and a second surface facing each other (step S110);
(B) a step (step S120) of evaluating ease of alkali metal removal on the first surface and the second surface;
(C) Based on the step of (b), the first surface of the glass substrate is such that the ease of alkali metal removal on the first surface and the second surface is substantially equal. And / or performing a plasma treatment on the second surface (step S130);
(D) After the step (c), performing a chemical strengthening process on the glass substrate (step S140);
Have

  Hereinafter, each step will be described.

(Step S110)
First, a glass substrate 100 having a first surface 112A and a second surface 112B facing each other is prepared. The composition of the glass substrate 100 is not particularly limited as long as it contains an alkali metal, and the glass substrate 100 may be, for example, a soda lime glass substrate.

Glass substrate 100 is, for example, in terms of oxide, 60 mol% 80 mol% of _SiO 2, 0.5mol% _~7mol% of _{Al 2 O 3, 3mol% ~10mol} % of MgO, 6mol% ~9mol% of CaO, 0 to 5 mol% of SrO, have 0～4Mol% of BaO, _ZrO 2 of 0~2mol%, 4mol% ~13mol% of _Na 2 O, and the composition of 0.1mol% ~7mol% of _{K 2} O Also good.

  The thickness of the glass substrate 100 is not particularly limited, but the effect of the present invention is relatively reduced with a thick glass substrate. In addition, if the plate thickness is too thin, there is a high risk of the glass substrate being damaged during the chemical strengthening treatment. The thickness of the glass substrate 100 may be, for example, in the range of 0.4 mm to 3 mm, and particularly in the range of 0.7 to 2 mm.

  The glass substrate 100 may be manufactured by a float process or may be manufactured by a fusion process.

  Note that the end surface of the glass substrate 100 may be chamfered.

(Step S120)
Next, on the first surface 112 </ b> A and the second surface 112 </ b> B of the glass substrate 100, the difference in ease of removal of the alkali metal to be evaluated, that is, the alkali metal (for example, Na) substituted in the chemical strengthening treatment is evaluated. The

This evaluation is performed by the following method, for example. In the following description, for the sake of simplicity, sodium (Na) will be described as an example of an alkali metal to be evaluated for ease of removal:
(I) A first evaluation film that does not contain sodium is formed on the first surface 112A of the glass substrate 100. In addition, a second evaluation film that does not contain sodium is formed on the second surface 112 </ b> B of the glass substrate 100.

  Here, the first and second evaluation films need to be films of the same material and thickness formed under the same conditions. Otherwise, the comparative evaluation of the first and second evaluation films cannot be performed in the subsequent steps.

  The method for forming the evaluation film is not particularly limited, and the evaluation film may be a general method such as vapor deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering, or spin coating. The film may be formed by a typical film forming technique.

  Further, the evaluation film may be made of any material as long as it does not contain sodium (that is, the element to be measured). However, an evaluation film containing only an element having an atomic diameter smaller than that of sodium is not preferable. This is because in the subsequent heat treatment step (sodium diffusion step), it may be difficult to sufficiently diffuse sodium into the evaluation film in a realistic time. The evaluation film is preferably a conductive film, and more preferably an oxide. The evaluation film may be indium tin oxide, for example.

  The thickness of the evaluation film is not particularly limited. The thickness of the evaluation film may be, for example, in the range of 50 nm to 200 nm.

  (Ii) Next, the glass substrate 100 is heat-treated. This heat treatment is performed in order to diffuse sodium present in the respective surfaces 112A and 112B into the respective evaluation films.

  The heat treatment conditions are appropriately determined depending on the concentration of sodium contained in the glass substrate 100 and the like. That is, this heat treatment is performed under the condition that sodium present on both surfaces 112A and 112B moves into the respective evaluation films.

  The temperature of the heat treatment may be in the range of 100 ° C. to 600 ° C., for example. Moreover, the time of heat processing may be the range of 10 minutes-1 hour, for example. The atmosphere of the heat treatment is not particularly limited, but is preferably an air atmosphere from the viewpoint of the configuration of the apparatus and the ease of processing. In this case, the first and second evaluation films are preferably made of oxide.

  (Iii) Next, the amount of sodium contained in the first and second evaluation films is measured.

  Measurement of the amount of sodium in the evaluation film may be performed using a general analyzer. For example, the amount of sodium in the evaluation film may be quantified from the sodium count obtained by dry-etching the evaluation film in the thickness direction using a SIMS (Secondary Ion Mass Spectroscopy) apparatus. Alternatively, a sodium profile may be obtained by obtaining a profile in the depth direction of sodium in the evaluation film by an EPMA (Electron Probe Micro Analyzer) analyzer or the like and integrating this region.

  From the obtained results, it is determined which surface of the first and second surfaces 112A and 112B is easy for sodium to escape, and its degree.

(Step S130)
Next, plasma treatment is performed on the first surface 112A and / or the second surface 112B of the glass substrate 100 based on the result obtained in step S120 described above.

  Here, the “plasma treatment” is a treatment of irradiating the first surface 112A and / or the second surface 112B of the glass substrate 100 with plasma having a relatively small power that does not damage the surface. say. The “plasma treatment” is performed in order to “balance” (equalize) the ease of removal of sodium on the first surface 112A of the glass substrate 100 and the ease of removal of sodium on the second surface 112B.

  For example, in the result of step S120 described above, when it is confirmed that the first surface 112A of the glass substrate 100 is in a state in which sodium is more easily removed than the second surface 112B, the first surface “Plasma treatment” with + (plus) ions is performed on 112A. In this case, since the first surface 112A is irradiated with plasma having the same polarity (plus) as sodium ions, sodium in the vicinity of the first surface 112A moves to the inner side of the glass substrate 100. Alternatively, “plasma treatment” with − (minus) ions may be performed on the second surface 112 </ b> B of the glass substrate 100. In this case, sodium ions having a polarity (negative) opposite to that of the plasma move in the vicinity of the second surface 112B. Therefore, it becomes possible to “balance” the ease of removal of sodium on both surfaces by plasma irradiation.

  In addition, after the plasma treatment, the above-described step (step S120) may be performed again to confirm that the ease of removal of sodium on both surfaces 112A and 112B has been balanced. If the ease of removal of sodium on both surfaces 112A and 112B has not yet been balanced, the plasma treatment may be performed again. In this case, by repeating (Step S120) to (Step S130), the ease of removal of sodium on both surfaces 112A and 112B is made substantially equal.

The conditions for the plasma treatment are not particularly limited. In the plasma treatment, for example, a gas such as Ar (argon), N ₂ (nitrogen), or O ₂ (oxygen) is used in a vacuum chamber whose ultimate vacuum is in the range of 1 × 10 ⁻³ Pa to 1 × 10 ⁻⁵ Pa. Thus, the discharge vacuum degree may be set in a range of 1 × 10 ⁻¹ Pa to ¹ × 10 ⁻³ Pa. Moreover, the power of the plasma (RF) to be used is, for example, a discharge voltage of 100 W to 1000 W, and such plasma is irradiated to both surfaces 112A and 112B of the glass substrate 100 in a range of 1 minute to 1 hour. Also good.

(Step S140)
Next, a chemical strengthening process is performed on the glass substrate 100 in which the ease of removal of sodium on both surfaces 112A and 112B is “balanced”.

  In this state, since the ease of removal of sodium on both surfaces 112A and 112B is “balanced”, the amount of substitution of alkali metal ions (for example, potassium ions) on both surfaces caused by the chemical strengthening treatment is almost equal. . Therefore, the substitution reaction proceeds only on one surface (or vice versa), and the glass substrate 100 is suppressed from being warped or deformed after the chemical strengthening treatment. As a result, a glass substrate 100 can be obtained in which both surfaces 112A and 112B remain substantially flat as shown in FIG.

  In the above description, in step S120, the difference in the ease of removal of the alkali metal (sodium) to be evaluated on the first and second surfaces 112A and 112B of the glass substrate 100 is evaluated, and in the subsequent step S130, The method of the present invention has been described with reference to “balancing” this as an example. However, in step S120, the concentration of alkali metal (for example, sodium) is evaluated on the first and second surfaces 112A and 112B of the glass substrate 100 instead of the ease of removal of the alkali metal (sodium). May be. In this case, the conditions of the subsequent plasma treatment are determined based on the difference in the concentration of alkali metal (for example, sodium) on both surfaces 112A and 112B. And after the plasma treatment, the concentration of alkali metal (eg, sodium) on both surfaces 112A and 112B is “balanced”.

  The filter substrate according to the present invention can be applied to FPD devices such as liquid crystal displays, plasma displays, organic EL displays, and mobile displays.

DESCRIPTION OF SYMBOLS 10 Conventional glass substrate 12A 1st surface 12B 2nd surface 100 Glass substrate 112A 1st surface 112B 2nd surface

Claims (10)

A method for increasing the strength of a glass substrate,
(A) preparing a glass substrate having a first surface and a second surface facing each other;
(B) Evaluating the ease of alkali metal removal on the first surface and the second surface,
(C) Based on (b), the first surface of the glass substrate and / or the first surface and / or the second surface so that the ease of alkali metal removal on the second surface is substantially equal. Alternatively, plasma treatment is performed on the second surface,
(D) After (c), a chemical strengthening treatment is performed on the glass substrate.
Method. In the first surface, when the alkali metal is easy to escape compared to the second surface,
(C)
The first surface is irradiated with plasma of + (plus) ions, and / or the second surface is irradiated with plasma of-(minus) ions. The method according to 1. (B)
(B1) An evaluation film not containing the alkali metal is installed on the first surface, and the evaluation film is installed on the second surface,
(B2) heat treating the glass substrate;
(B3) The method according to claim 1 or 2, wherein the method is carried out by measuring the amount of the alkali metal contained in the evaluation film.   The method according to claim 3, wherein the evaluation film is a conductive oxide.   The method according to claim 3 or 4, wherein the heat treatment in (b2) is performed in a range of 100 ° C to 600 ° C for 10 minutes to 1 hour.   The step (b3) is performed by continuously measuring the amount of the alkali metal while dry-etching the evaluation film by a SIMS method. The method described in 1.   The method according to claim 1, wherein the alkali metal is sodium (Na).   The method according to claim 1, wherein the glass substrate is a glass substrate manufactured by a float process.   The method according to claim 1, wherein the glass substrate has a thickness in a range of 0.4 mm to 3 mm.   10. The method according to claim 1, wherein the glass substrate is for a display device having a size of 32 inches or more.

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