JP4535692B2 - Chemically tempered glass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a chemically tempered glass, particularly a chemically tempered glass useful in fields such as electronic materials used for touch panels and the like, automobiles and buildings, and a method for producing the same.
[0002]
[Prior art]
From the viewpoints of resource and energy savings and changes in social needs, tempered glass is becoming thinner and the degree of strengthening is increasing. Since the production of glass having a plate thickness of 3 mm or less, particularly 2 mm or less is difficult with the commonly used air-cooling strengthening method, the chemical strengthening method is often used for glass of 2 mm or less. In addition, chemically tempered glass generally has an advantage that it can obtain higher strength than tempered glass obtained by air cooling.
[0003]
The reason why chemical tempered glass is widely accepted in the market is that, in addition to the above-mentioned strengthening and strengthening properties of thin glass, it can be cut even under certain conditions. In air-cooled tempered glass, if cracks are introduced in an attempt to cut, they break apart and cannot be cut.
[0004]
This is because, for example, as shown in FIG. 5 (see Non-Patent Document 1), the chemically tempered glass and the air-cooled tempered (physical tempered) glass have greatly different stress patterns formed inside the glass. Since the air-cooled tempered glass uses the temperature difference and the viscous flow between the glass surface layer and the inner layer, the outline of the stress pattern has a shape approximated by a quadratic curve, for example. In contrast, chemically tempered glass, for example, uses ion exchange on the surface layer, and strictly depends on Fick's diffusion law, but is often approximated by a straight line. When trying to obtain a predetermined surface compressive stress value with air-cooled tempered glass, the tensile stress in the inner layer inevitably increases. Since glass breakage depends on the tensile stress of this inner layer, it leads to a fragmentation phenomenon under a large tensile stress. On the other hand, in the case of chemically strengthened glass, even if the compressive stress value is increased, the tensile stress value of the inner layer is not so increased under normal conditions. The tensile stress value of chemically strengthened glass is largely a function of the surface compressive stress value and the compressive stress layer thickness.
[0005]
That is, both the air-cooled tempered glass and the chemically tempered glass have high breaking strength as glass. On the other hand, in the case of air-cooled tempered glass, it was impossible to cut, and in the case of chemically tempered glass, there was a problem that it was difficult to cut even though it could be cut.
[0006]
In addition, various methods are considered as a manufacturing method of chemically strengthened glass. For example, a method of replacing atoms of small ionic radius with atoms of large ionic radius, a method of replacing atoms of large ionic radius with atoms of small ionic radius using the viscous flow of glass, a method of utilizing difference in thermal expansion coefficient, There are many methods such as a method of crystallizing crystals and a method of combining the above methods. In general, many methods of replacing atoms with small ionic radii with soda-lime glass are used, and among them, many chemically strengthened glass is manufactured by the so-called immersion method, which is immersed in a chemical strengthening treatment tank. Has been. That is, a compressive stress layer is formed on the surface layer by immersing glass in a high-temperature chemical strengthening treatment solution, such as a potassium nitrate solution, and replacing sodium ions in the glass with potassium ions in potassium nitrate. In addition, as the chemical strengthening treatment liquid when the glass contains lithium, sodium nitrate or a mixed salt of sodium nitrate and potassium nitrate is frequently used.
[0007]
From the viewpoint of known technology, for example, the use of cut glass as chemical strengthening (see, for example, Patent Document 1) is a technique for measuring surface stress, which is an important factor in cutting conditions (see, for example, Patent Document 2). Is disclosed. Steps related to chemical strengthening of hard disk drives 1) Preheating in a preheating tank (heating to 380 to 500 ° C. over about 0.5 to 2 hours)
2) Chemical strengthening treatment with molten salt solution of potassium nitrate or sodium nitrate (about 0.5-6 hours)
3) Cooling in a blast cooling tank (forced cooling to a room temperature where the in-plane temperature difference is within 5 ° C. and below the melting point of the molten salt solution with cooling air of 5 to 25 m ³ / min)
Is also described in detail (for example, see Patent Document 3).
[0008]
[Patent Document 1]
JP 2002-160932 A [Patent Document 2]
Japanese Patent Publication No.59-37451 [Patent Document 3]
JP 2000-344550 A [Non-Patent Document 1]
HMGarfinkel et al., The Glass Industry, 50 (1969), p. 76.
[0009]
[Problems to be solved by the invention]
Chemically tempered glass can be cut. However, even though it is possible to cut, this cutting is a very difficult technology, which is the main cause of yield reduction during production, and even after it has become a product, there is a problem of destruction due to cutting failure etc. Yes.
[0010]
For example, in a chemically strengthened thin glass used for a touch panel or the like, an attempt is made to increase productivity by taking a plurality of sheets from a large chemically strengthened glass. However, when scribing with a wheel chip type cutting machine, there are many problems that it is not divided along the scribe line at the time of division, but separated from the scribe line. For this reason, there are many cases where the merit of using multiple results is different from the original plan. In addition, there is a problem that a panel using a scribed chemically strengthened glass breaks even when it is smaller than an assumed load after being put on the market.
[0011]
Thus, in reality, it cannot be said that the cutting of chemically strengthened glass is technically established.
[0012]
That is, in Japanese Patent Application Laid-Open No. 2002-160932, it is described that the cut glass is used for chemical strengthening, but the method for cutting chemically strengthened glass is not described. Moreover, although the technique of Japanese Examined Patent Publication No. 59-37451 can know the measurement technique of the surface stress, it does not show the technique that leads to the cutting of the glass. Furthermore, the chemical strengthening method disclosed in Japanese Patent Application Laid-Open No. 2000-344550 is a case where a hard disk drive having a diameter of 60 to 100 mm is chemically strengthened, and there is no mention of cutting ability.
[0013]
[Means for Solving the Problems]
The present invention compresses two types of stress patterns, a stress pattern A closer to the glass surface and a stress pattern B on the glass inner layer side, in a chemically strengthened glass in which a compressive stress layer is formed on the glass surface layer by ion exchange. When the stress pattern A and the stress pattern B are approximated by a linear function in the stress layer, the stress pattern A and the stress pattern B have different slopes, and the surface stress value obtained from the stress pattern A And a temporary surface stress value obtained from a line obtained by extending the compressive stress pattern B to the glass surface is a chemically tempered glass having a ratio of 0.8 to 0.95 .
[0016]
Furthermore, the above chemically strengthened glass has a compressive stress layer thickness of 2 μm or more and 15 μm or less by the stress pattern A.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a chemically tempered glass in which a compressive stress layer is formed on a glass surface layer by ion exchange. The compressive stress layer comprises two types of compressive stress pattern A closer to the glass surface and compressive stress pattern B on the inner glass layer side. Is a chemically strengthened glass. In order to improve the cutting property of glass, it is useful to have two types of stress patterns in the glass. By having two types of stress patterns, it is possible to obtain a chemically tempered glass that is easily cut while having a predetermined compressive stress layer thickness. In other words, it is not a chemically strengthened glass with a stress pattern that depends on Fick's law in the past, but it does not depend on Fick's law alone, especially the stress generated near the surface is expressed in another functional form. It is chemically strengthened glass.
[0018]
When the stress pattern A and the stress pattern B are approximated by a linear function, the stress pattern A and the stress pattern B are the above chemically strengthened glasses having different inclinations. The conventional chemically strengthened glass having no other stress pattern, that is, only one kind of conventional chemically strengthened glass has a problem that it has a large fracture strength but is difficult to cut. On the other hand, if it is attempted to cut easily, the breaking strength is reduced.
[0019]
Furthermore, the surface stress value calculated | required from the stress pattern A is chemically strengthened glass used as a value smaller than the temporary surface stress value calculated | required from the line which extended the stress pattern B to the glass surface. If the value is large, it becomes difficult to cut.
[0020]
Furthermore, the ratio between the surface stress value obtained from the stress pattern A and the provisional surface stress value obtained from a line obtained by extending the compression stress pattern B to the glass surface is 0.8 or more and 0.95 or less. It is chemically strengthened glass. The ratio with the temporary surface stress value calculated | required from the line which extended the stress pattern B to the glass surface is 0.8-0.95. If it is less than 0.8, the surface compressive stress is reduced, and the strength of the glass is substantially reduced. On the other hand, if it exceeds 0.95, the cutting ability is lowered. Desirably, it is 0.85 or more and 0.93 or less.
[0021]
In this case, depending on conditions, the inclination of the stress pattern A may be opposite to that of the stress pattern B as shown in FIG. That is, in the conventional chemically strengthened glass, the surface compressive stress is always larger than the stress value of the inner layer, but in the chemically strengthened glass of the present invention, the stress value of the portion entering the inner layer is slightly larger than the value of the surface compressive stress. May be indicated. Naturally, a chemically strengthened glass having such a stress pattern also falls within the scope of the present invention.
[0022]
Furthermore, the compressive stress layer thickness by the stress pattern A is 2 μm or more and 15 μm or less. If the compressive stress layer thickness due to the stress pattern A is smaller than 2 μm, the effect on the cutting property will be reduced, and if the compressive stress layer thickness due to the stress pattern A exceeds 15 μm, the fracture strength will be substantially reduced due to the properties of the chemically strengthened glass. Because. 3 μm or more and 9 μm or less are preferable.
[0023]
In addition, in order to perform the production management of chemically strengthened glass easily, the stress pattern in the chemically strengthened glass has been described as a first order approximation. However, strictly speaking, there are naturally cases where the stress pattern cannot be approximated by a linear function. This is because, as described above, ion exchange basically follows Fick's diffusion law, and since the diffusion law is not a linear function, strictly speaking, it is necessary to deviate from the approximate straight line. In addition, the stress generation in the glass is affected by many factors such as temperature distribution, deformation, and plate thickness in addition to ion exchange. If linear approximation is not possible or difficult to approximate in this way, the principle should be returned to whether the generated stress pattern can be represented by one function or requires two or more functions. Here, a multi-order function of third or higher order is not used for approximation. For the approximation, a function having one pole or no pole is used. When approximated using such a function, a conventional chemically strengthened glass can be represented by one function. On the other hand, when it is necessary to use two or more functions, the chemically tempered glass of the present invention is obtained. In addition, as a region considering functional approximation, it should be a compressive stress region. This is because the cutability and fracture strength of glass depend on the compressive stress value, and in the region where the tensile stress starts to become a constant value, the stress generation may become unstable, which may cause an error in the determination. is there.
[0024]
The thickness of the compressive stress layer and the compressive stress value of the chemically strengthened glass are not simple because they are greatly influenced by the processing temperature and processing time during chemical strengthening, as well as the selection of the processing liquid and its active properties. Moreover, it varies depending on the ion exchange status and crystallization status in the glass. However, it is possible to obtain chemically tempered glass that maintains the fracture strength at a practical level and has improved cutability. Hereinafter, based on an Example, it demonstrates concretely.
[0025]
【Example】
Example 1
A 0.7mm thick soda-lime float glass is immersed in molten potassium nitrate at 460 ° C for 10 hours and subjected to ion exchange treatment. Then, the chemically tempered glass is moved to a cooling bath set at 510 ° C. Hold for 60 minutes. Thereafter, the glass was cooled at a usual cooling rate (about 10 ° C./min) to obtain a predetermined chemically strengthened glass. The stress pattern of this glass is shown in FIG. In the figure, C indicates compressive stress, and T indicates tensile stress. Thus, it is a chemically strengthened glass having the characteristics that the compressive stress layer has two types of compressive stress pattern A closer to the glass surface and compressive stress pattern B on the inner side of the glass. This stress pattern shows the result of cutting and polishing chemically strengthened glass and observing it using a Babinet compensator and an optical microscope. The ratio between the surface stress value obtained from the stress pattern A and the provisional surface stress value obtained from the line obtained by extending the compressive stress pattern B to the glass surface was 0.93. The compressive stress layer thickness by the stress pattern A was 4 μm.
[0026]
When this chemically strengthened glass was subjected to a scribe (load weight: 2 kg) and a split test in accordance with a general cutting operation using a commercially available carbide wheel tip, it could be cut without any problem.
[0027]
(Example 2)
A first soda-lime float glass having a thickness of 0.55 mm was immersed in a molten salt of potassium nitrate at 470 ° C. for 4 hours to perform a first ion exchange treatment, and then immersed at 510 ° C. for 20 minutes to perform a second ion exchange treatment. After that, the glass was cooled at a cooling rate (about 10 ° C./min) that was normally used to obtain a predetermined chemically strengthened glass. The stress pattern of this glass is shown in FIG. The ratio between the surface stress value obtained from the stress pattern A and the provisional surface stress value obtained from the line obtained by extending the compressive stress pattern B to the glass surface was 0.89. The compressive stress layer thickness by the stress pattern A was 5 μm.
[0028]
When this chemically strengthened glass was subjected to a scribe (load weight: 2 kg) and a split test in accordance with a general cutting operation using a commercially available carbide wheel tip, it could be cut without any problem.
[0029]
(Comparative Example 1)
A soda-lime float glass with a thickness of 0.7 mm is immersed in a molten salt of potassium nitrate at 460 ° C. for 10 hours. After ion exchange treatment, the chemically strengthened glass is moved to a cooling bath set at 380 ° C. The product was cooled at a cooling rate of about 10 ° C./min to obtain a predetermined chemically strengthened glass product. The stress pattern of this glass is shown in FIG. Thus, it has one type of stress pattern. The ratio between the surface stress value obtained from the stress pattern A and the provisional surface stress value obtained from the line obtained by extending the compressive stress pattern B to the glass surface was naturally 1.0. The compressive stress layer thickness (stress patterns A and B) was 33 μm.
[0030]
When this chemically strengthened glass was subjected to a scribing (load weight: 2 kg) and a splitting test in accordance with a general cutting operation using a commercially available carbide wheel tip, slip was remarkable. Therefore, when the cutting pressure was increased (final load weight: 7 kg), a lot of linear glass powder was generated from the scribe line and could not be used as a chemically strengthened glass product. In addition, there were places where it was impossible to divide along the scribe line, that is, where it was off the cutting line.
[0031]
(Comparative Example 2) A soda-lime float glass having a thickness of 0.7 mm was immersed in a molten salt of potassium nitrate at 460 ° C. for 10 hours, subjected to ion exchange treatment, and then the chemically strengthened glass was moved to a cooling bath set at 410 ° C. In addition, it was held for 60 minutes. Thereafter, the glass was cooled at a usual cooling rate (about 10 ° C./min) to obtain a predetermined chemically strengthened glass. The stress pattern of this glass is shown in FIG. The ratio between the surface stress value obtained from the stress pattern A and the provisional surface stress value obtained from the line obtained by extending the compressive stress pattern B to the glass surface was 0.7. The compressive stress layer thickness by the stress pattern A was 17 μm.
[0032]
When this chemically strengthened glass was subjected to a scribe (load weight: 2 kg) and a split test according to a general cutting operation using a commercially available carbide wheel tip, slip was remarkable. Therefore, when the load weight was examined as 5 kg, this chemically strengthened glass was broken.
[0033]
As shown from the above results, chemically tempered glass that can be easily cut was obtained by adding the process of the present invention after the ion exchange process.
[0034]
【The invention's effect】
Up to now, it has become possible to stably cut chemically strengthened glass, which has been considered difficult.
[Brief description of the drawings]
1 is a schematic diagram of a stress pattern shown in Example 1. FIG.
2 is a schematic diagram of a stress pattern shown in Example 2. FIG.
3 is a schematic diagram of a stress pattern shown in Comparative Example 1. FIG.
4 is a schematic diagram of a stress pattern shown in Comparative Example 2. FIG.
FIG. 5 is a schematic diagram showing stress patterns of chemically tempered glass and air-cooled (physical) tempered glass.
6 is a schematic diagram showing a special example of a stress pattern A. FIG.
[Explanation of symbols]
1 Surface of chemically strengthened glass 2 Stress pattern B
3 Stress pattern A
4 Extension line d of stress pattern B Surface compressive stress layer thickness σ Surface compressive stress value σ Surface compressive stress value estimated from _B stress pattern B C Compressive stress T Tensile stress

Claims (2)

In chemically strengthened glass in which a compressive stress layer is formed on the glass surface layer by ion exchange, two types of stress patterns, stress pattern A closer to the glass surface and stress pattern B on the inner glass layer side, are contained in the compressive stress layer. When the stress pattern A and the stress pattern B are approximated by linear functions, the stress pattern A and the stress pattern B have different slopes, and the surface stress value obtained from the stress pattern A and the compressive stress A chemically tempered glass, characterized in that the ratio of the pattern B to a temporary surface stress value obtained from a line obtained by extending the pattern B to the glass surface is 0.8 or more and 0.95 or less. The chemically strengthened glass according to claim 1, wherein the compressive stress layer thickness by the stress pattern A is 2 μm or more and 15 μm or less.

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