JP2001348245A - Reinforced glass, method for manufacturing the same and glass for display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide reinforced glass having high bending strength and thick stress-strained layer, glass for a display consisting of the reinforced glass, and particularly to provide a glass panel for a cathode ray tube and a cathode ray tube. SOLUTION: The reinforced glass is prepared by chemically reinforcing a physically reinforced base glass at the temperature lower than the strain point of the base glass. The reinforced glass has a stress-strained layer of >=250 μm thickness and >=300 MPa bending strength. The glass for a display consists of the aforementioned reinforced glass. The glass panel for a cathode ray tube consists of the glass for a display and the cathode ray tube has the aforementioned glass panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tempered glass, a method for producing the same, a glass for a display, a glass panel for a cathode ray tube, a cathode ray tube, and a method for producing the same. More specifically, the present invention produces a tempered glass having high bending strength and a thick stress-strain layer, which is suitably used for window glass, glass for display, glass for memory disk, glass panel for cathode ray tube, and the like. The present invention relates to a method, a glass for display and a glass panel for a cathode ray tube comprising the tempered glass, a cathode ray tube provided with the glass panel, and a method for producing the same.

[0002]

2. Description of the Related Art As a method for strengthening glass, a physical strengthening method and a chemical strengthening method are known. The physical strengthening method is a method of obtaining a compressive stress layer on the surface by creating a temperature difference between the glass surface and the inside by increasing the cooling rate from a temperature near the annealing point to a temperature near the strain point. The flexural strength of tempered glass obtained by this method is generally 200
Mpa, the thickness of the strained layer is several hundred μm or more. Wind cooling and liquid cooling are one of the physical reinforcement methods. However, the tempered glass obtained by such a physical tempering method, although a thick strained layer is obtained, high bending strength cannot be obtained, the surface hardness is not high, the tempered state largely depends on the sheet thickness, complex There are drawbacks such as being unsuitable for glass of various shapes.

On the other hand, the chemical strengthening method is a method of subjecting a glass surface to a chemical treatment to obtain a compressive stress layer on the surface. For example, a method is known in which a glass containing lithium or sodium is immersed in a molten salt containing sodium or potassium, and ions are exchanged to push in ions having an ion radius larger than that of the glass originally present, thereby obtaining a compressive stress layer. ing. The bending strength of the tempered glass obtained by this method is generally 300 to 700 MPa, and the thickness of the strained layer is 10 to 200 μm.

However, the glass obtained by such a chemical strengthening method has high bending strength,
There is a disadvantage that the thickness of the strained layer is small and weak against scratches.
The thickness of the strained layer of chemically strengthened glass greatly depends on the composition, and is several hundred μm in the case of aluminosilicate glass having high ion exchange efficiency, but is 10 to 30 μm in the case of general soda lime glass. . For this reason, it has been considered that a chemically strained glass cannot obtain a thick strained layer in window glass, display glass panel, and cathode ray tube glass panel using soda lime glass, for example.

For example, a physically strengthened glass panel is used for a flat CRT that has recently appeared. The glass panel of a flat cathode ray tube requires high strength to receive the atmosphere in a plane with a vacuum inside. However, the bending strength of this physically strengthened glass panel is 100 to 200 MPa, that is, about twice that of untempered glass. A 36-inch glass panel is required to have a thickness of about 20 mm.

Examples of chemically strengthening this CRT glass panel are disclosed in, for example, JP-A-1-31932 and JP-A-29-293.
No. 04067. These publications include C
When the RT glass was immersed in a potassium nitrate molten salt at 400 to 450 ° C. for 1 to 10 hours, a stress-strain layer of 10 to 50 μm was obtained. However, if the thickness of the stress-strain layer is 50
If it is less than or equal to μm, the CRT may be damaged by external impact during the manufacturing process or during use as a product,
Scratches penetrated the stress-strained layer and the glass was sometimes broken.

Conventionally, a glass having a stress-strain layer of 100 μm or more and a bending strength of 500 MPa or more is disclosed in, for example, Japanese Patent No. 2878
No. 37134, the composition range was limited. In particular, it is known that by containing a large amount of Al ₂ O ₃ , the ion exchange efficiency is improved and a thick stress-strain layer is obtained. However, the liquidus temperature of the glass increases, so that the glass tends to be devitrified. In many cases, glass production became difficult. In many cases, it is difficult to satisfy properties such as thermal expansion coefficient and chemical durability. Therefore, there has been a demand for a strengthening method that can be applied to glass having a wide composition range without largely depending on the composition.

[0008] Further, although many compositions have been disclosed for glass for plasma displays and CRTs, not only the glass itself, but also a stress-strained layer of 100 μm or more and a bending of 300 MPa or more by physical strengthening or chemical strengthening alone. The strength could not be compatible.

[0009]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a glass material having a high bending strength and a large stress strain even if the glass has a composition in which a thick stress-strain layer cannot be obtained by conventional chemical strengthening. While providing a tempered glass provided with a layer,
It is an object of the present invention to provide a glass for a display made of the tempered glass, particularly a glass panel for a cathode ray tube and a cathode ray tube provided with the glass panel for a cathode ray tube.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors physically strengthened the base glass and further chemically strengthened the base glass at a temperature lower than the strain point of the base glass. It has been found that the object can be achieved by the tempered glass obtained as described above, and the present invention has been completed based on this finding.

That is, the present invention provides (1) a tempered glass obtained by chemically strengthening a base glass obtained by physically strengthening the base glass at a temperature lower than a strain point of the base glass, and (2) a stress-strained layer having a thickness of 250 μm or more. And (3) a glass for a display comprising the tempered glass of the above (1) or (2), and (4) a glass for a display of the above (3). A glass panel for a cathode ray tube, which is made of glass;
(5) A cathode ray tube comprising the glass panel of (4), (6) After physically strengthening the base glass containing an alkali metal, at a temperature lower than the strain point of the base glass, A method for producing a tempered glass characterized by chemical tempering, and (7) an X-ray absorption coefficient of 28 / cm
A method for manufacturing a cathode ray tube, comprising: using the above base glass, using a tempered glass produced by the method of (6) above as a glass panel, and heating and integrating the glass panel and a funnel by frit sealing. Is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The tempered glass of the present invention has an extremely small dependence on the glass composition and has both a thick stress-strain layer and a high bending strength. It is a desirable condition that the base glass used in the present invention contains at least one of Li and Na. First, in order to obtain a strong stress-strain layer (compression stress layer) by ion exchange, mobile ions in the glass must be replaced with ions having a larger ionic radius. From the viewpoint of efficiency and cost, substitution of Li and Na and substitution of Na and K are effective. Also,
In addition to the ease of ion exchange or chemical strengthening,
Glass containing an appropriate amount of Li and / or Na has a measurable coefficient of thermal expansion to some extent and a low annealing point and strain point, so that physical strengthening can be performed efficiently.
Therefore, the preferable content of Li and / or Na is 5 to 20% by weight in total.

The tempered glass of the present invention is obtained by physically strengthening the base glass and then chemically strengthening the same. The method of physically strengthening the glass may be a conventionally used method. That is, the glass heated to a temperature equal to or higher than the annealing point of the glass and lower than the softening point is brought into contact with a low-temperature gas, liquid, or solid to create a temperature difference between the glass surface and the inside. When the temperature of the glass is cooled to near the strain point, the temperature difference becomes a strain and remains in the glass. This is stress strain. The stress-strain formed during the cooling process of the glass serves as a stress-strain layer (compression stress layer), and has a function of improving the bending strength of the glass. However, since an extreme cooling temperature difference leads to breakage of the glass, it has been put to practical use at a cooling rate within a range that does not cause breakage. The thickness of the strained layer obtained by this physical strengthening is about 1/6 of the plate thickness, but the bending strength is practically up to about 200 MPa.

For the chemical strengthening, a conventionally used method can be used, but it is essential to perform the treatment at a temperature lower than the strain point of the glass. This is why chemical strengthening is performed after physical strengthening. When processed at a temperature above the strain point,
The strained layer formed by physical strengthening is relaxed and disappears. Specifically, the glass is immersed in a molten salt maintained at a temperature lower than the strain point of the glass, held for a predetermined time, and then taken out and washed. The composition of the molten salt is selected according to the composition of the glass, but in the case of Li-containing glass, a salt containing Na ions, and in the case of Na-containing glass, it is more efficient to use a salt containing K ions, It is advantageous.

The molten salt may be a single molten salt or a mixed molten salt. As the type of salt, nitrate having a low melting point is preferable, but since nitrate has a low decomposition temperature,
A carbonate, a sulfate, or the like is used as appropriate. A suitable treatment temperature is 350 to 550 ° C. for nitrates. The immersion time depends on the processing temperature, but is preferably within 24 hours, particularly preferably within 4 hours, from the viewpoint of productivity.

The steps of physical strengthening and chemical strengthening may be independent steps or may be continuous steps.
For example, the glass is heated to a temperature between the annealing point and the softening point, and then quickly immersed in a molten salt maintained at a temperature below the strain point. At this time, a temperature difference occurs between the glass surface and the inside, and a stress-strain layer is formed. When immersed in the molten salt for a predetermined time as it is, ion exchange occurs between the glass surface and the molten salt, and a compressive stress layer due to chemical strengthening is added.

Whether chemical strengthening is achieved can be determined by examining the distribution of metal ions contained in the vicinity of the glass surface.
The depth distribution of a metal ion having a larger ionic radius (eg, an alkali metal ion) and a metal ion having a smaller ionic radius (eg, an alkali metal ion) are examined. (Density of metal ions having a larger ionic radius) / (density of metal ions having a smaller ionic radius) is closer to the surface than to a deep portion of the glass (for example, a portion having a depth of half the thickness of the glass). If the bending strength is within the range of the present invention, it can be understood that chemical strengthening by ion exchange has been performed.

When used for a glass panel for a cathode ray tube, in the present invention, although the restrictions on the composition of the glass are relatively moderate as described above, from the viewpoint of being suitable for chemical strengthening performed after physical strengthening, the following is shown. Base glass 1 and base glass 2 are preferably used.

First, the base glass 1 will be described. This base glass 1 is made of SiO ₂ , Al ₂ O ₃ , Li ₂ O, Na
₂ O, SrO, with including TiO _2, ZrO ₂ and CeO _2, wherein the MgO and / or CaO, Li ₂ O content is 5 to 20 mol%, the content of SrO is 3 to 15 mol% and ZrO ₂ is a glass having a content of 0.1 to 5 mol%.

Among them, SiO ₂ , Al ₂ O ₃ , Na
The content of ₂ O, TiO ₂ , MgO and CaO is mol%
_{In, SiO 2 40~70%, Al 2} O 3 0.1~15
_{%, Na 2 O 0.1~10%,} 0~15% MgO,
A CaO 0 to 15% and TiO ₂ 0.1 to 15%, and _{SiO 2 + Al 2 O 3 +} Li 2 O + Na 2 O + S
Glass having a total content of rO + TiO ₂ + ZrO ₂ + MgO + CaO + CeO ₂ of 85% or more is more preferable.

The base glass 1 is composed of BaO, ZnO, La ₂ O ₃ , Cs ₂ O, P ₂ O ₅ , B ₂
One or more glass components selected from O ₃ , Y ₂ O ₃ , Nb ₂ O ₅ , Sb ₂ O ₃ , SnO ₂ , K ₂ O and F,
It may be contained in a total amount of 15 mol% or less.

The base glass 1 comprises, in addition to the above glass components, one or more glass components selected from the group consisting of Ni, Co, Fe, Mn, V, Cu and Cr in a total amount of 1%.
It can be contained in a ratio of not more than mol%.

In the base glass 1, SiO ₂ is a basic component of the glass, and if it is less than 40 mol%, the devitrification resistance and the chemical durability deteriorate. Conversely, if it exceeds 70 mol%, melting becomes difficult. Therefore, the content of SiO ₂ is 40-70.
It is limited to mol%. Preferably it is 45-60 mol%, More preferably, it is 50-55 mol%.

Al ₂ O ₃ is a component which improves the devitrification resistance, chemical durability and ion exchange efficiency of glass.
Less than 0.1 mol% has no effect. Conversely, 15 mol%
If it exceeds 300, the devitrification resistance deteriorates. Accordingly the content of Al ₂ O ₃ is limited to 0.1 to 15 mol%. Al ₂
Since O ₃ is also a component that lowers the X-ray absorption coefficient, it is preferably 1 to 10 mol%, more preferably 1 to 5 mol%.

Li ₂ O is a component for chemically strengthening the glass by being ion-exchanged mainly with Na ions in the ion exchange treatment bath at the surface layer of the glass, but if less than 5 mol%, it has no effect. If it exceeds 20 mol%, the devitrification resistance and the chemical durability decrease. Thus the Li ₂ O content is limited to 5 to 20 mole%. Since Li ₂ O is also a component that lowers the X-ray absorption coefficient, it is preferably 7-1.
8 mol%, more preferably 10 to 15 mol%.

Na ₂ O is a component for chemically strengthening the glass and preventing browning by being ion-exchanged mainly with K ions in the ion exchange treatment bath at the glass surface layer. If the amount is less than 0.1 mol%, the effect is not obtained.
If it exceeds mol%, the devitrification resistance and the chemical durability decrease.
Thus the Na ₂ O content is limited to 0.1 to 10 mol%. Since Na ₂ O is also a component that lowers the X-ray absorption coefficient, the content is preferably 1 to 5 mol%.

MgO is a component for improving the Young's modulus of the glass, and can be contained in the range of 0 to 15 mol%. If it exceeds 15 mol%, the X-ray absorption coefficient decreases.
Therefore, the content of MgO is limited to 0 to 15 mol%. The preferred content is 5 to 10 mol%.

CaO is a component for improving the X-ray absorption coefficient and Young's modulus of glass, and can be contained in the range of 0 to 15 mol%. If it exceeds 15 mol%, the liquidus temperature rises. Therefore, the content of CaO is limited to 0 to 15 mol%. The preferred content is 5 to 10 mol%.

SrO is a component that plays an important role in the glass of the present invention. SrO is a component that has a remarkable effect of increasing the X-ray absorption coefficient, but it has been found that the addition of SrO does not significantly lower the Young's modulus or bending strength.
If it is less than 3 mol%, the X-ray absorption coefficient is less than 28,
If it exceeds 5 mol%, the devitrification resistance will decrease. Therefore S
The rO content is limited to 3 to 15 mol%. The preferred content is 5 to 13 mol%.

BaO, which is an optional component, is a component that improves the X-ray absorption coefficient of glass, and therefore can be contained. However, BaO has the effect of increasing the X-ray absorption coefficient,
The content of BaO is preferably from 0 to 5 mol% because it is about half of rO and is a component that lowers the Young's modulus.

Although ZnO, which is an optional component, has a large effect of increasing the X-ray absorption coefficient, it reduces the flexural strength and Young's modulus, so that it is preferably less than 5 mol%.

TiO ₂ is a component that improves the Young's modulus and X-ray absorption coefficient of glass and prevents coloring by X-rays.
Less than 0.1 mol% has no effect. Conversely, 15 mol%
If it exceeds, the devitrification resistance decreases. Therefore the content of TiO ₂ is limited to 0.1 to 15 mol%. TiO
₂ absorbs a short wavelength region of the transmitted light of the glass and is easily colored, so that the preferable content is 0.1 to 5 mol%.

ZrO _{2 is} also one of the components that play an important role in the glass of the present invention. ZrO ₂ is a component that improves the Young's modulus, X-ray absorption coefficient and bending strength of glass. Less than 0.1 mol% has no effect.
Conversely, if it exceeds 6 mol%, unmelted glass tends to be generated. Therefore the content of ZrO ₂ is limited to 0.1 to 5 mol%. The preferred content is 1 to 3 mol%.

CeO ₂ is a component that prevents coloring (browning) due to X-rays. The preferred content is 0.01
１1 mol%. K ₂ O, which is an optional component, can be contained in the base glass to prevent coloring (browning) due to X-rays. The preferred content is 0 to 5 mol%.

In addition, La ₂ O ₃ , Cs ₂ O, P ₂ O ₅ , B ₂
One or more of O ₃ , Y ₂ O ₃ , Nb ₂ O ₅ , Sb ₂ O ₃ , SnO _2, F and the like may be used to improve melting property, clarification, improvement of devitrification resistance, and viscosity of glass. , Adjustment of thermal expansion coefficient and X-ray absorption coefficient, adjustment of Young's modulus, adjustment of ion exchange rate, prevention of solarization, prevention of browning, etc. can do. Further, Ni, Co, F
One or more of e, Mn, V, Cu and Cr can be appropriately added for the purpose of adjusting the transmittance of the glass.

The base glass 1 does not substantially contain PbO. This is because the use of PbO is environmentally unfavorable, and PbO is a component that deteriorates chemical strengthening and a component that lowers Young's modulus.

In the base glass 1, a more preferable composition 1 is that, as a glass component, SiO ₂ 50 to 60% Al ₂ O ₃ 1 to 5% Li ₂ O 10 to 20% Na ₂ O 0.1 a composition comprising a _{~ 8% CeO 2 0.01~ 1%} MgO 1~10% CaO 1~10% SrO 5~10% TiO 2 0.1~ 5% ZrO 2 1~ 5%.

The advantage of the composition 1 is that, in the above composition range in which SiO ₂ is large and TiO ₂ is small, the Young's modulus is 95%.
A glass having GPa or more, a bending strength of 400 MPa or more, and excellent devitrification resistance can be obtained, and the X-ray absorption coefficient can be increased as the content of SrO increases.

Further, in the base glass 1, a more preferable composition 2 is that, as a glass component, SiO ₂ 40 to 50% Al ₂ O ₃ 1 to 5% Li ₂ O 7 to 15% Na ₂ O 0 0.1 to 8% CeO ₂ 0.01 to 1% MgO 1 to 10% CaO 1 to 10% MgO + CaO 10 to 30% SrO 5 to 15% TiO ₂ 5 to 15% ZrO ₂ 1 to 5% .

The advantage of composition 2 is that, in the above composition range where TiO ₂ is large, a Young's modulus of 100 GPa or more and a bending strength of 400 MPa or more can be obtained, and the X-ray absorption coefficient increases as the content of SrO increases. Is what you can do. The feature of the composition range 1 is that devitrification resistance and ease of molding are superior to the composition range 2 described above. The feature of the composition range 2 is that the Young's modulus is larger than the composition range 1.

Further, the glass of the more preferable composition 1 and the composition 2 in the above-mentioned base glass 1 has a glass surface after chemical strengthening having a Knub hardness of usually 600 GPa or more (particularly 650 GPa or more). Because the Nueve hardness is large,
Chemical strengthening not only prevents the growth of surface flaws, but also makes deep flaws less likely to occur.

The method for producing the base glass 1 is not particularly limited, and a conventionally used method can be used. For example, oxides, hydroxides, carbonates, nitrates, chlorides, sulfides, and the like are appropriately used as glass raw materials, weighed to have a desired composition, and mixed to obtain a mixed raw material. This is put in a heat-resistant crucible, melted at a temperature of about 1300 to 1500 ° C., stirred and clarified to obtain a homogeneous molten glass. The glass is then cast into a forming frame to form a glass block, form a sheet, or a cathode ray tube (CRT)
Press forming into shape. Transfer to a heated furnace near the annealing point of the glass and cool to room temperature. The glass block obtained by slow cooling is subjected to slicing, polishing, etc., the sheet-formed glass is subjected to cutting, polishing, hot bending and the like as necessary, and the press-formed glass is also subjected to polishing as necessary. You.

Next, the base glass 2 will be described. The base glass 2 has SiO ₂ and Al as essential components.
Containing ₂ O ₃ , alkali metal oxides, SrO, ZrO ₂ , and TiO ₂ or CeO _2, or both, and optionally containing BaO and Sb ₂ O ₃ ;
Is 5 to 20% by weight, and the total content of the above essential components and optional components is 90% by weight or more.

The content of Al ₂ O ₃ is desirably 0.1 to 20% by weight, since a thick stress-strain layer can be obtained by chemical strengthening.
% By weight or less, more preferably 5 to 20% by weight.
Is more desirable.

In the base glass 2, a more preferred glass composition is as follows:
With Li ₂ O 0-3%, Na ₂ O 4-20% and K
Together containing _{2 O1~10%,} the SiO _2, ZrO _2,
The content of TiO ₂ , CeO ₂ , BaO and Sb ₂ O ₃ is
In _{weight%, SiO 2 40~70%, ZrO} 2 1~7
_{%, TiO 2 0.1~1%, CeO} 2 0.1~1%,
BaO 0 to 15% and Sb ₂ O ₃ 0 to 1%.

The base glass 2 desirably does not substantially contain lead from the viewpoint of preventing coloring due to X-ray irradiation.
Here, it means that it does not contain lead, apart from impurities which do not substantially contain lead. Lead is a component that is not environmentally preferable, and also deteriorates chemical strengthening and lowers Young's modulus.

The base glass 2 is made of MgO, CaO, Zn
O, La ₂ O ₃ , P ₂ O ₅ , B ₂ O ₃ , SnO ₂ , NiO, C
At least one component selected from o ₂ O ₃ , Cr ₂ O ₃ and F can be contained in a proportion of 10% by weight or less. In the base glass 2, SiO ₂ is a basic component of the glass.
Devitrification resistance deteriorates. Conversely, if it exceeds 70% by weight, melting becomes difficult. Therefore, the content of SiO ₂ is 40-70.
% By weight. Preferably it is 55 to 65% by weight.

Al ₂ O ₃ is the most important component for improving the devitrification resistance, chemical durability and ion exchange rate of glass. If the content is less than 0.1% by weight, it tends to stall, and it takes time to perform a process for obtaining a thick stress-strain layer. Conversely, if it exceeds 20% by weight, the devitrification resistance will deteriorate. Therefore, the content of Al ₂ O ₃ is preferably more than 0.1% by weight and not more than 20% by weight.
In order to form a stress-strain layer having a thickness of not less than m, the content of Al ₂ O ₃ is preferably 5 to 20% by weight, and 4.0% by weight.
More preferably, it is more preferably not more than 20% by weight,
More preferred is 10 to 15% by weight.

As the alkali metal oxide contained in the base glass, Na ₂ O and K ₂ O, or Li ₂ O and Na ₂
O and K ₂ O are preferred. Li ₂ O is not an essential component, but is a component for improving the melting property of the glass. A component for chemically strengthening the glass by being mainly ion-exchanged with Na ions in the ion exchange treatment bath at the glass surface layer. Therefore, the ion exchange efficiency can be improved by the addition. However, when the content exceeds 3% by weight, the devitrification resistance and the chemical durability are reduced, and the viscosity of the glass is reduced, so that glass molding becomes difficult. Therefore Li
The content of ₂ O is preferably 0 to 3% by weight, more preferably 0 to 1% by weight.

Na ₂ O is a component for improving the melting property of the glass, and is a component for chemically strengthening the glass by being mainly ion-exchanged with K ions in the ion exchange bath at the surface layer of the glass. . If the amount is less than 4% by weight, the effect is poor, and if it exceeds 20% by weight, the devitrification resistance and the chemical durability decrease. Therefore, the content of Na ₂ O is preferably 4 to 20% by weight, more preferably 5 to 10% by weight.

K ₂ O is a component that improves the melting property of the glass and prevents coloring of the glass due to X-ray irradiation. Less than 1% by weight has no effect. Conversely, 10% by weight
If it exceeds, the ion exchange rate decreases. Therefore K ₂
The content of O is preferably from 1 to 10% by weight, more preferably from 5 to 10% by weight.

SrO has a great effect of improving the X-ray absorption coefficient and is an important component for improving the melting property of glass. Further, it is a component that can contain a relatively large amount of Al ₂ O ₃ having a function of promoting ion exchange. If the SrO content is less than 5% by weight, the X-ray absorption coefficient does not reach 28 / cm, and if it exceeds 20% by weight, the liquidus temperature rises. Therefore, the content of SrO is 5
Preferably, the content is set to 20 to 20% by weight, and more preferably, the content is 8 to 15% by weight.

Although BaO is not an essential component, it is a component that improves the X-ray absorption coefficient and improves the melting property of the glass. Although the effect of improving the X-ray absorption coefficient is smaller than that of SrO, BaO is preferably used because it is inexpensive. it can. When BaO exceeds 15% by weight, the ion exchange efficiency decreases. Therefore Ba
The content of O is preferably from 0 to 15% by weight, more preferably from 5 to 12% by weight.

ZrO ₂ is an important component for increasing the X-ray absorption coefficient and improving the chemical durability, devitrification resistance and ion exchange efficiency of glass. ZrO ₂ content of 1
If the amount is less than 7% by weight, the effect is not obtained. Therefore the content of ZrO ₂ is preferably set to 1 to 7 wt%, and more preferred content is 2-5 wt%.

TiO ₂ is a component for preventing glass from being colored by X-ray irradiation. If the amount is less than 0.1% by weight, the effect is not obtained. On the contrary, if the amount exceeds 1% by weight, coloring of the glass becomes large. Therefore, the content of TiO ₂ is preferably set to 0.1 to 1% by weight. CeO ₂ is a component that prevents glass from being colored by X-ray irradiation. If the amount is less than 0.1% by weight, the effect is not obtained. On the other hand, if the amount is more than 1% by weight, the glass is likely to be colored yellow. Therefore, the content of CeO ₂ is 0.1 to
It is preferably 1% by weight.

Although MgO, CaO and ZnO are not essential components, they can be contained because they are components for improving the melting property of glass. The preferred content is 0 to 4% by weight. Sb ₂ O ₃ is not an essential component, but is preferably used as a fining agent. The content of Sb ₂ O ₃ is preferably 0 to 1 wt%.

In addition, La ₂ O ₃ , P ₂ O ₅ , B ₂ O ₃ , Sn
O ₂ , NiO, Co ₂ O ₃ , Cr ₂ O ₃ and F are improved in fusibility, fining, adjustment of thermal expansion coefficient and X-ray absorption coefficient,
It can be used as appropriate for the purpose of adjusting the ion exchange rate, preventing solarization, adjusting the transmittance, and the like.

The method for producing the base glass 2 is not particularly limited, and a conventionally used method can be used. For example, oxides, hydroxides, carbonates, nitrates, chlorides, sulfides, and the like are appropriately used as glass raw materials, weighed to have a desired composition, and mixed to obtain a mixed raw material. This is put in a heat-resistant crucible, melted at a temperature of about 1400 to 1500 ° C., stirred and clarified to obtain a homogeneous molten glass. Next, the glass is cast into a forming frame to form a glass block, and then transferred to a furnace heated near the annealing point of the glass, and cooled to room temperature. The glass block obtained by slow cooling is subjected to cutting, polishing and the like.

Both the base glass 1 and the base glass 2 are excellent in chemical strengthening and X-ray absorption properties, but not limited to such a base glass, and a general glass such as soda lime glass may be used as the base glass. Can be used as

The tempered glass of the present invention can be produced by physically strengthening the above-described base glass containing an alkali metal and then chemically strengthening the base glass at a temperature lower than the strain point of the base glass. The tempered glass of the present invention has a thickness of 250 μm by physically strengthening the base glass having a specific glass composition and then chemically strengthening the glass.
Or more, preferably 300 μm or more, more preferably 4 μm or more.
It has a stress-strain layer of at least 00 μm and a bending strength of 30
0 MPa or more, preferably 350 MPa or more, more preferably 400 MPa or more, and an X-ray absorption coefficient of 28 / cm
It can be more than that.

The thickness of the stress-strain layer can be determined by a Babinet correction method using a precision strain meter or a method using a polarizing microscope. For the Babinet correction method using a precision strain meter, a commercially available measuring device may be used. In the method using a polarizing microscope, first, a glass sample is cut perpendicularly to the ion-exchange surface, the cross section is polished thinly to a thickness of 0.5 mm or less, and polarized light is incident perpendicularly to the polished surface with a polarizing microscope. Observe with crossed Nicols. In the chemically strengthened glass, a stress-strain layer is formed in the vicinity of the surface, so that the thickness of the strain layer can be measured by measuring the distance from the surface to the portion where the brightness or color is changing.

The difference between chemically strengthened glass and physically strengthened glass can be understood by examining the distribution of metal ions contained near the surface of the glass panel. Specifically, the depth distributions of a metal ion having a larger ionic radius (eg, an alkali metal ion) and a metal ion having a smaller ionic radius (eg, an alkali metal ion) are examined. (The density of metal ions having a larger ionic radius) / (the density of metal ions having a smaller ionic radius) is closer to the surface than to a deep portion of the glass (for example, a portion having a depth of half the thickness of the glass). Is bigger. Therefore, in the tempered glass of the present invention, although a stress-strain layer formed by chemical strengthening is found relatively close to the surface, and a stress-strain layer is formed relatively deep, No metal ion distribution characteristic of reinforcement is observed.

The present invention also provides a tempered glass having a stress-strain layer having a thickness of 250 μm or more and having a bending strength of 300 MPa or more, preferably a X-ray absorption coefficient of 28 / cm or more. Things.

The tempered glass of the present invention has a bending strength of 300
When it is at least MPa, the thickness of the stress-strain layer is at least 250 μm, preferably at least 300 μm, particularly preferably at least 4 μm.
It is not less than 00 μm. When the bending strength is 350 MPa or more, the thickness of the stress-strain layer is 250 μm or more, preferably 300 μm or more, and particularly preferably 400 μm or more.
μm or more. Even when the bending strength is 400 MPa or more, the thickness of the stress-strain layer is 250 μm or more, preferably 300 μm or more, particularly preferably 400 μm or more.

Further, a display glass comprising the tempered glass of the present invention described above, a glass panel for a cathode ray tube comprising the display glass, a cathode ray tube provided with the glass panel, and a mother glass having an X-ray absorption coefficient of 28 / cm or more. Another object of the present invention is to provide a method for manufacturing a cathode ray tube by using a material glass, forming a tempered glass produced by the above-described method into a glass panel, and heating and integrating the glass panel and a funnel by frit sealing.

[0066]

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

The thickness and flexural strength of the stress-strain layer of the obtained tempered glass were measured according to the following methods. (1) Thickness of stress-strain layer The cross section of the test piece was polished and measured with a polarizing microscope. (2) Bending strength 65 × 10 × 1 mm test piece according to JIS R160
The measurement was carried out according to the three-point bending test of 1.

Example 1 A soda-lime glass having a thickness of 5 mm was heated to about 700 ° C., cooled to 500 ° C. with an air jet blown from a nozzle having a cooling capacity of 500 W / m ² · ° C., and gradually cooled from 500 ° C. to room temperature. Cooled down. Next, the glass was immersed in a molten salt of potassium nitrate kept at 450 ° C., kept for 4 hours, taken out, cooled to room temperature, and washed. The thickness and bending strength of the stress-strained layer of the obtained glass were measured, and the results are shown in Table 1. In addition, the sample processed only by air-cooling strengthening with the glass of the same composition, and the sample processed only by chemical strengthening were measured similarly. Table 1 shows the results.

[0069]

[Table 1]

The composition of the soda-lime glass is as follows in terms of% by weight. SiO ₂ 71.2% Al ₂ O ₃ 1.5% Na ₂ O 13.1% K ₂ O 0.9% MgO 4.1% CaO 8.9%

Example 2 CRT glass having a thickness of 8 mm was heated at about 700 ° C., and then immersed in a molten salt of potassium nitrate kept at 420 ° C. After keeping it for 4 hours, it was taken out, cooled to room temperature, and washed. The thickness and bending strength of the stress-strain layer of the obtained glass were measured. Table 2 shows the results. In addition,
Samples treated with the same composition of glass only by physical strengthening and samples treated only by chemical strengthening were measured in the same manner. Table 2 shows the results.

[0072]

[Table 2]

The composition of the glass for CRT is as follows in terms of% by weight. _{SiO 2 60.6% Al 2 O 3} 1.0% Na 2 O 6.6% K 2 O 8.6% MgO 0.3% CaO 0.4% SrO 10.4% BaO 9.0% TiO 2 0.5% ZrO ₂ 2.1% CeO ₂ 0.2% Sb ₂ O ₃ 0.3%

Example 3 A glass for CRT having a thickness of 8 mm was heated to about 700 ° C., and then the glass was immersed in a molten salt of sodium nitrate (40% by weight) and potassium nitrate (60% by weight) maintained at 400 ° C. did. After keeping it for 4 hours, it was taken out, cooled to room temperature, and washed. The thickness and bending strength of the stress-strain layer of the obtained glass were measured. Table 3 shows the results. In addition, the sample processed only by physical strengthening with the glass of the same composition, and the sample processed only by chemical strengthening were measured similarly. Table 3 shows the results.

[0075]

[Table 3]

The composition of the glass for CRT is as follows in terms of mol%. _{SiO 2 62.0% Al 2 O 3} 2.0% Li 2 O 13.0% Na 2 O 1.0% MgO 4.0% CaO 6.8% SrO 5.0% TiO 2 2.0% ZrO ₂ 4.0% CeO ₂ 0.1% Sb ₂ O ₃ 0.1% NiO 0.05% Co ₂ O ₃ 0.01%

Example 4 A glass for CRT having a thickness of 8 mm was heated to about 700 ° C., and then the glass was immersed in a molten salt of potassium nitrate kept at 400 ° C. After keeping it for 4 hours, it was taken out, cooled to room temperature, and washed. The thickness and bending strength of the obtained stress-strained layer were measured. Table 4 shows the results. In addition, the sample processed only by physical strengthening with the glass of the same composition, and the sample processed only by chemical strengthening were measured similarly. Table 4 shows the results.

[0078]

[Table 4]

The composition of CRT glass is as follows in terms of% by weight. SiO ₂ 47.5% Al ₂ O ₃ 15.5% Na ₂ O 10.5% K ₂ O 5.0% SrO 9.5% BaO 6.5% TiO ₂ 0.5% ZrO ₂ 4.5% CeO ₂ 0.3% Sb ₂ O ₃ 0.2%

The tempered glass obtained in each of the above examples was heated and integrated with a funnel and a frit seal to obtain a cathode ray tube. The heating is desirably performed at a temperature lower than the strain point of the glass so that the stress of the stress-strain layer is not relaxed. Thus, a cathode ray tube having a glass panel having a stress-strained layer having a thickness of 250 μm or more and a bending strength of 300 MPa or more can be obtained.

[0081]

According to the present invention, even in a glass having a composition in which it was conventionally difficult to achieve both a thick stress-strain layer and high bending strength, it is easy to form a tempered glass having a thick stress-strain layer and high bending strength. Can be obtained. The tempered glass of the present invention is particularly suitably used for a glass panel for a display.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01J 29/86 H01J 29/86 Z F Term (Reference) 4G015 CA04 CB01 CB03 4G059 AA07 AA08 AB01 AB11 HB03 HB13 HB14 HB15 HB23 4G062 AA03 AA04 AA18 BB01 BB03 DA05 DA06 DA07 DB03 DB04 DC01 DD01 DE01 DF01 EA01 EA04 EB03 EB04 EC02 EC03 ED02 ED03 EE02 EE03 EF01 EF03 EF04 EG01 EG03 FA01 FA10 FB01 FC01 F01 FG01 FC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM12 MM25 MM27 NN14 NN33 5C032 AA04 BB03

Claims (13)

[Claims] 1. A tempered glass obtained by chemically strengthening a base glass which is physically strengthened at a temperature lower than a strain point of the base glass. 2. The tempered glass according to claim 1, which has a stress-strain layer having a thickness of 250 μm or more and a bending strength of 300 MPa or more. 3. The tempered glass according to claim 1, wherein the base glass is a glass containing Li ₂ O and / or Na ₂ O and having a strain point of 450 ° C. or higher. 4. Li ₂ O and / or Li ₂ O contained in the base glass.
4. The tempered glass according to claim 3, wherein the amount of Na ₂ O is 5 to 20% by weight. 5. The base glass is made of SiO ₂ , Al ₂ O ₃ , L
i ₂ O, Na ₂ O, SrO, TiO ₂ , ZrO ₂ and Ce
Together containing O _2, wherein the MgO and / or CaO, Li content of ₂ O 5 to 20 mol%, the content of content of 3 to 15 mol% and ZrO ₂ of SrO 0.1 to
The tempered glass according to claim 1, 2 or 3, which is 5 mol%. 6. The base glass contains SiO.sub.2 as an essential component.
₂ , Al ₂ O ₃ , alkali metal oxide, SrO, ZrO ₂ ,
And TiO ₂ or CeO ₂ or both,
Including BaO and Sb ₂ O ₃ as optional components,
4. The tempered glass according to claim 1, wherein the content of SrO is 5 to 20% by weight, and the total content of the essential components and the optional components is 90% by weight or more. 7. A tempered glass having a stress-strain layer having a thickness of 250 μm or more and a bending strength of 300 MPa or more. 8. The tempered glass according to claim 1, which has an X-ray absorption coefficient of 28 / cm or more. 9. A display glass comprising the tempered glass according to claim 1. Description: 10. A glass panel for a cathode ray tube, comprising the glass for a display according to claim 9. 11. A cathode ray tube comprising the glass panel according to claim 10. 12. A method for producing a tempered glass, comprising physically strengthening a base glass containing an alkali metal, and further chemically strengthening the base glass at a temperature lower than a strain point of the base glass. 13. A tempered glass produced by the method according to claim 12, wherein a base glass having an X-ray absorption coefficient of 28 / cm or more is used as a glass panel, and the glass panel and a funnel are heated by a frit seal. A method for manufacturing a cathode ray tube, characterized by being integrated.