JP2001348248A - Glass for cathode ray tube, method for manufacturing the same and glass panel for cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide glass for a cathode ray tube having a thick stress-strained layer, high strength and high absorption coefficient of X rays, and to provide a glass panel for a cathode ray tube and a cathode ray tube consisting of the aforementioned glass. SOLUTION: The glass for a cathode ray tube is prepared by chemically reinforcing a mother glass containing SiO2, Al2O3, alkali metal oxides, SrO and ZrO2 as the essential components and has >4 wt.% and <=20 wt.% Al2O3 content and 5 to 20 wt.% SrO content. The glass panel for a cathode ray tube is produced from the aforementioned glass for a cathode ray tube, and the cathode ray tube has the glass panel for a cathode ray tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass for a cathode ray tube, a method for producing the same, a glass panel for a cathode ray tube, and a cathode ray tube. More specifically, the present invention has a thick stress-strain layer obtained by chemically strengthening a base glass having a specific composition, and has a high strength and a high X-ray absorption coefficient. The present invention relates to a glass, a method for efficiently producing the glass, a glass panel for a cathode ray tube made of the glass, and a cathode ray tube provided with the glass panel.

[0002]

2. Description of the Related Art In recent years, flat-panel cathode ray tubes have been
Since the inside vacuum and the outside atmospheric pressure must be supported by a flat glass panel on the outside, a method of increasing the thickness of the panel or using physically strengthened glass has been adopted. For example, Japanese Patent No. 2904067 discloses a CRT panel formed of a physically reinforced glass panel.

However, the bending strength of physically strengthened glass is generally set to 100 to 200 MPa. This physically strengthened glass is made by rapidly cooling the base glass from near the softening point to near the strain point, thereby creating a temperature difference between the inside and the surface of the glass and forming a compressive stress layer on the glass surface. It has the merit that a stress-strain layer of about 1/6 of the above can be obtained, but it is not suitable for thin glass that does not easily create a temperature difference between the glass surface and the inside, or glass with a complicated shape that cannot obtain a uniform temperature distribution. There are drawbacks. CRT
In general, the glass panel for use has a complicated shape in which a junction with a skirt (frame) -shaped funnel is provided outside a plane portion from which an image is transferred. In particular, the outside of the image display unit is flat, but the inside has a curvature due to the scanning of the electron gun. For this reason, uniform cooling is difficult, and in the case of large-sized CRTs, which have become mainstream in recent years, if the cooling fails, the glass is broken and the cooling rate cannot be increased. Therefore, the bending strength is often 100 to 150 MPa. 100
With a glass having a bending strength of about 150 MPa, the thickness of the glass must be increased in order to receive the pressure difference between the inside and the outside of the CRT, which causes the glass to be thick and heavy.

On the other hand, Japanese Patent No. 2940467 also discloses a method of chemically strengthening a glass panel for CRT. However, as concluded therein, it has been considered that this chemical strengthening does not provide a sufficient stress-strain layer, and is not suitable as a glass for CRT. When the stress-strain layer is thin, CR
If a scratch is caused by an external impact received during the manufacturing process of T or during use as a product, the scratch may penetrate the stress-strained layer and break the glass.

Further, Japanese Patent No. 2837134 discloses a chemically strengthened glass having a high ion exchange efficiency. The glass described in this publication has a stress-strain layer of 200 μm or more and a bending strength of 800 MPa or more. However, the glass described in this publication has a low X-ray absorption coefficient,
X-ray absorption coefficient 28 /, which is the standard for CRT glass panels
cm. Specifically,
The glass composition described in this publication does not require any component other than ZrO ₂ to increase the X-ray absorption coefficient. For example, even if this ZrO ₂ is contained at a maximum amount of 15% by weight,
The X-ray absorption coefficient is about 25 / cm. Moreover, ZrO
₂ is a component that is hardly melted in glass.

As described above, a glass satisfying all of the stress-strain layer of 100 μm or more, the high bending strength of 300 MPa or more, and the X-ray absorption coefficient of 28 / cm or more has not been found yet. Was. Therefore, the CRT glass panel has to be thick and heavy, and for example, the TV receiver has become very heavy. Specifically, 36
The thickness of the inch CRT panel was about 20 mm, and the panel weight alone was about 40 kg.

[0007]

SUMMARY OF THE INVENTION Under such circumstances, the present invention uses a base glass capable of forming a stress-strained layer to a deep layer of glass by ion exchange, and uses the base glass as a chemical. It is an object of the present invention to provide a glass for a cathode ray tube which is strengthened and has a high strength and a high X-ray absorption coefficient, and to provide a glass panel for a cathode ray tube comprising the glass, and a cathode ray tube provided with the glass panel. is there.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a glass obtained by chemically strengthening a base glass having a specific glass composition has achieved the object. They have found that this can be achieved, and have completed the present invention based on this finding.

That is, the present invention provides (1) SiO ₂ , Al ₂ O ₃ , alkali metal oxide, SrO
And includes ZrO _2, and Al ₂ O ₃ content more 20 wt% or less than 4% by weight of the content of SrO 5 to 2
A cathode ray tube glass obtained by chemically strengthening a base material glass of 0% by weight; (2) a cathode ray tube glass panel comprising the above cathode ray tube glass; and (3) a cathode ray tube comprising the above cathode ray tube glass panel. And (4) a method for producing glass for a cathode ray tube by chemically strengthening a base glass, comprising, as essential components, SiO ₂ , Al ₂ O ₃ , an alkali metal oxide, SrO and ZrO ₂ , and
When the content of l ₂ O ₃ is more than 4% by weight and not more than 20% by weight,
A base glass having a SrO content of 5 to 20% by weight
It is intended to provide a method for producing glass for a cathode ray tube, comprising a step of performing ion exchange and chemical strengthening in a treatment bath containing an alkali metal ion heated to 350 to 550 ° C.

[0010]

In DETAILED DESCRIPTION OF THE INVENTION The present invention, thick stress-strain layer, high strength and high in order to obtain the cathode ray tube glass of X-ray absorption coefficient, Al ₂ O ₃ and chemically relatively more containing matrix glass SrO Strengthen. In conventional CRT glass, A
It was thought that when l ₂ O ₃ was contained in an amount of more than 4% by weight, the X-ray absorption coefficient was lowered and the meltability was deteriorated. However, in the present invention, this problem was solved by adding an appropriate amount of SrO.

Al_TwoO_ThreeBy increasing the content of
Increases the efficiency of chemical strengthening and is advantageous for forming thick stress-strain layers
It is. SrO does not reduce the solubility of glass
Al _TwoO_ThreeIt is a component to increase the content of
Is a component for improving the X-ray absorption characteristics of glass.
You. Therefore, the present invention has excellent X-ray absorption characteristics.
And suitable for chemical strengthening as glass for cathode ray tubes
Necessary conditions can be satisfied at once.

The base glass used in the present invention contains, as essential components, SiO ₂ , Al ₂ O ₃ , alkali metal oxide, Sr
It contains O and ZrO ₂ , and preferably further contains TiO ₂ and / or CeO ₂ as essential components, and also contains BaO and Sb ₂ O ₃ as optional components. By containing either TiO ₂ or CeO ₂ , glass coloring at the time of X-ray irradiation can be reduced, but from the viewpoint of preventing coloring, both TiO ₂ and CeO ₂ are used in the present invention. It is preferable to use a base material glass containing.

Hereinafter, the composition range of the base glass will be described. SiO ₂ is a basic component of glass. If it is less than 40% by weight, chemical durability and devitrification resistance may be deteriorated. If it exceeds 70% by weight, melting tends to be difficult. Therefore, the content of SiO ₂ is preferably from 40 to 70% by weight, more preferably from 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 4% by weight, the ion exchange rate is low, and a long time is required for processing for obtaining a thick stress-strain layer. Conversely, if it exceeds 20% by weight, the devitrification resistance will deteriorate. Therefore, Al ₂
Although the content of O ₃ is limited to more than 4% by weight and not more than 20% by weight, in order to form a thick stress-strained layer, for example, a stress-strained layer having a depth of 100 μm or more, the Al ₂ O ₃ content must be 5 ~
The content is preferably 20% by weight, more preferably 6 to
It is 20% by weight, more preferably 10 to 15% by weight.

The alkali metal oxide contained in the base glass is preferably Na ₂ O and K ₂ O, or Li ₂ O and Na ₂ O and K ₂ O. Although Li ₂ O is not an essential component, it is a component for improving the melting property of the glass, and is used for chemically strengthening the glass by being mainly ion-exchanged with Na ions in an ion exchange treatment bath at the glass surface layer. Since it is a component, the ion exchange efficiency can be improved by adding it. But 3
If the content is more than 10% by weight, the devitrification resistance and the chemical durability are reduced, and the viscosity of the glass is reduced, so that the glass molding becomes difficult. Therefore, the content of Li ₂ O is preferably set to 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 ion-exchanged mainly with K ions in the ion exchange treatment bath at the glass surface layer. . 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
The content of ₂ O is preferably 1 to 10% by weight,
More preferably, it is 5 to 10% by weight.

SrO has a large 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 limited to 5 to 20% by weight, preferably 8 to 15% by weight.

BaO is not an essential component, but is a component that improves the X-ray absorption coefficient and improves the melting property of glass. Although the effect of improving the X-ray absorption coefficient is smaller than that of SrO, it can be preferably used because it is inexpensive. When BaO exceeds 15% by weight, the ion exchange efficiency decreases. Therefore B
The content of aO is preferably 0 to 15% by weight,
A more preferred content is 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. Accordingly, 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 0.1 to 1% by weight.
It is preferable that

CeO ₂ is a component for preventing the glass from being colored by X-ray irradiation. However, if it is less than 0.1% by weight, it has no effect, and if it exceeds 1% by weight, the glass tends to be colored yellow. Therefore, the content of CeO ₂ is preferably 0.1 to 1% by weight. Sb ₂ O ₃ is not an essential component, but is used as a fining agent. The content of Sb ₂ O ₃ is 0 to 1% by weight
It is.

In the base glass used in the present invention, the total content of the above essential components and optional components is preferably at least 90% by weight. Further, in addition to the above components, MgO,
_{CaO, ZnO, La 2 O 3} , P 2 O 5, B 2 O 3, Sn
At least one selected from the group consisting of O ₂ , NiO, Co ₂ O ₃ , Cr ₂ O ₃ and F is used to improve melting properties, clarify, adjust the thermal expansion coefficient and X-ray absorption coefficient, adjust the ion exchange rate, For the purpose of preventing solarization, adjusting transmittance, etc.
It can be used in a proportion of 0% by weight or less. Among them, MgO, CaO, and ZnO are components for improving the melting property of glass, and the preferred content is 0 to 4% by weight.

It is desirable that the base glass does not substantially contain lead which is a component for coloring the glass by X-ray irradiation. The term "substantially free" means that the base glass does not contain lead, apart from impurities. The base glass contains a relatively large amount of Al ₂ O ₃ in the composition system of the present invention, and thus has a high glass transition temperature of 550 ° C. or more, as compared with conventional chemically strengthened glass for cathode ray tubes.
Therefore, the strain point becomes high, and even if heating is performed in a frit seal or the like at the time of assembling the cathode ray tube, the stress-strain layer is not easily relaxed. Therefore, it is possible to prevent the strength from decreasing even after assembling the cathode ray tube. Further, since the glass transition temperature is as high as 550 ° C. or more, it is advantageous when a glass panel is manufactured by cutting from a sheet glass.

The method for producing the base glass used in the present invention 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.

The glass for a cathode ray tube of the present invention is obtained by chemically strengthening a base glass having the above-mentioned composition, and its production method is not particularly limited. The desired glass for a cathode ray tube can be manufactured.

In the method of the present invention, the base glass having the above-mentioned composition is chemically strengthened. This chemical strengthening is performed by a conventionally used method, that is, a treatment including an alkali metal ion heated to 350 to 550 ° C. A method of performing ion exchange in a bath is used. Specifically, the base glass is immersed in a molten salt maintained at a temperature lower than the strain point of the glass, and is 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. In the case of a glass containing Na, it is efficient to use a salt containing a K ion, and in the case of a glass containing Li, a salt containing a Na ion is used efficiently. It may be a single molten salt or a mixed molten salt. As for the kind of the salt, a nitrate having a low melting point is preferable. However, since the nitrate has a low decomposition temperature, a carbonate, a sulfate or the like is appropriately used. In the case of nitrate, the treatment temperature is preferably 350 to 550 ° C.

Although the immersion time depends on the processing temperature, it is preferably within 24 hours, particularly preferably within 4 hours, from the viewpoint of productivity. As described above, by chemically strengthening the base glass, the depth of the stress-strained layer can be made 100 μm or more and the bending strength can be made 300 MPa or more. The glass for a cathode ray tube of the present invention can be obtained.

The thickness of the stress-strain layer can be determined by a Babinet correction method using a precision strain meter, a method using a polarizing microscope, or the like. 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. The thickness of the strained layer can be measured by measuring the distance from the surface to the portion where the brightness or color is changing. The present invention also provides a glass panel for a cathode ray tube comprising the glass for a cathode ray tube of the present invention, particularly a glass panel for a cathode ray tube used for a flat-type cathode ray tube, and a cathode ray tube provided with the glass panel for a cathode ray tube.

[0030]

Next, 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 to 6 and Comparative Examples Raw materials such as oxides, hydroxides, carbonates, nitrates, chlorides and sulfates were weighed and mixed so as to have the composition shown in Table 1 and mixed with platinum. Put in a crucible, heat to 1400 ° C, melt,
After stirring, homogenizing and clarifying, the mixture was poured into a mold.
After the glass was solidified, it was transferred to an electric furnace heated near the annealing point of the glass, and gradually cooled to room temperature.

The obtained glass block was polished on both sides to produce a plate glass of 65 × 10 × 1 mm. Then, KNO ₃ single salt or K kept at 380-450 ° C.
The glass sample was immersed in a mixed salt of NO ₃ and NaNO ₃ for a predetermined time to perform ion exchange, and then washed. Table 1 shows the glass composition and various measurement data.

The X-ray absorption coefficient is obtained by applying X-rays having a wavelength of 0.06 nm to the sheet glass produced, measuring the transmitted dose at a position 50 mm away from the opposite surface of the glass, and calculating the absorption coefficient. The thickness of the stress-strain layer was measured by polishing a cross section of the ion-exchanged sample and using a polarizing microscope. The bending strength of the ion-exchanged 65 × 10 × 1 mm sample was measured according to JIS.
-Measured according to the three-point bending test of R1601.

[0034]

[Table 1]

(Note) 1) A: SiO ₂ , Al ₂ O ₃ , Li ₂ O, Na ₂ O, K
The total content of ₂ O, SrO, BaO, TiO ₂ , ZrO ₂ , CeO ₂ and Sb ₂ O ₃ is shown.

As can be seen from Table 1, in each of the examples, chemically strengthened glass having a stress-strained layer having a thickness (depth) of 100 μm or more and a bending strength of 300 MPa or more was obtained. The linear absorption coefficients are all 28
/ Cm or more, and can be sufficiently used as glass for a cathode ray tube, particularly as a glass panel.

The glass for a cathode ray tube obtained in these examples was used as a glass panel for a flat cathode ray tube, and was heated and integrated with a funnel and a frit seal to obtain a 36-inch flat cathode ray tube. Then, it was confirmed that the glass panel did not bend due to a pressure difference between the inside and outside of the cathode ray tube, and the image was not distorted. It was also confirmed that the glass panel was not colored (browning) by X-ray irradiation.

[0038]

According to the present invention, a base glass capable of forming a stress-strained layer to a deep layer of the glass by ion exchange is used, and the base glass is chemically strengthened to form a glass for a cathode ray tube. A glass for a cathode ray tube having high strength and a high X-ray absorption coefficient can be provided. Further, since the above glass is used for the glass panel for a cathode ray tube, a glass panel for a cathode ray tube having high strength and a high X-ray absorption coefficient can be provided. Further, the cathode ray tube provided with the above glass panel can provide a relatively lightweight cathode ray tube without lowering the strength and X-ray absorption characteristics. Further, according to the manufacturing method of the present invention, high strength and high X
A glass for a cathode ray tube having a linear absorption coefficient can be efficiently produced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 29/86 H01J 29/86 Z F Term (Reference) 4G059 AA07 AC16 HB03 HB13 HB14 HB23 4G062 AA03 BB01 DA05 DA06 DB03 DB04 DC01 DC02 DC03 DD01 DD02 DD03 DE01 DE02 DE03 DF01 EA01 EA02 EA03 EB03 EB04 EC03 ED01 ED02 ED03 EE01 EE02 EE03 EF03 EF04 EG01 EG02 EG03 GB01 FA01 F01 F01 F01 F01 F01 F01 F01 F01 F01 FF01 GC01 GD01 GE01 GE02 GE03 HH01 HH03 HH05 HH07 HH08 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM25 NN14 NN33 5C032 AA02 BB03

Claims (10)

[Claims] 1. An essential component comprising SiO ₂ , Al ₂ O ₃ ,
Chemical strengthening of a base glass containing an alkali metal oxide, SrO and ZrO _2, having an Al ₂ O ₃ content of more than 4 wt% to 20 wt% and a SrO content of 5 to 20 wt% Glass for cathode ray tubes. 2. The base glass further comprises, as an essential component,
_2. The cathode ray according to claim 1, which contains TiO ₂ and / or CeO ₂ , contains BaO and Sb ₂ O ₃ as optional components, and has a total content of essential components and optional components of 90% by weight or more. Glass for tubes. 3. The base glass is an alkali metal oxide.
And Li_TwoO 0-3% by weight, Na_TwoO 4-20% by weight
And K_TwoO 1 to 10% by weight and SiO_Twoof
Content of 40-70% by weight, ZrO_TwoContent of 1 to 7
Wt%, TiO _TwoContent of 0.1 to 1% by weight, CeO_Two
Is 0.1-1% by weight, and the content of BaO is 0-1.
5% by weight and Sb_TwoO_ThreeWith a content of 0 to 1% by weight
The glass for a cathode ray tube according to claim 2, which is: 4. The base material glass is made of MgO, CaO, Zn.
O, La ₂ O ₃ , P ₂ O ₅ , B ₂ O ₃ , SnO ₂ , NiO, C
The glass for a cathode ray tube according to any one of claims 1 to 3, wherein at least one selected from o ₂ O ₃ , Cr ₂ O ₃ and F is contained in a proportion of 10% by weight or less. 5. The glass transition temperature of the base glass is 550 ° C.
The glass for a cathode ray tube according to any one of claims 1 to 4, which is the above. 6. The glass for a cathode ray tube according to claim 1, wherein the depth of the stress-strain layer formed by chemical strengthening is 100 μm or more. 7. The glass for a cathode ray tube according to claim 1, which has a bending strength of 300 MPa or more. 8. A glass panel for a cathode ray tube comprising the glass for a cathode ray tube according to any one of claims 1 to 7. 9. A cathode ray tube comprising the glass panel for a cathode ray tube according to claim 8. 10. A method for producing a glass for cathode ray tube matrix glass by chemical strengthening, as essential components, wherein SiO _2, Al ₂ O _3, alkali metal oxides, SrO, and ZrO _2, and Al ₂ O _The base glass having a content of ₃ of more than 4% by weight and not more than 20% by weight and a SrO content of 5 to 20% by weight
A method for producing glass for a cathode ray tube, comprising a step of performing ion exchange in a treatment bath containing an alkali metal ion heated to 50 ° C. to chemically strengthen.