JP2003026442A - Glass substrate for field emission display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate for a field emission display less prone to cause coloring of glass by X-rays even when a high voltage is applied and further having high X-ray absorption capacity. SOLUTION: The glass substrate for the field emission display is characterized by practically containing no PbO and having >=125 cm<-1> X-ray absorption coefficient at 1.5 Å wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate for field emission display.

[0002]

2. Description of the Related Art A field emission display is thin and lightweight, has low power consumption, has a clear display, and can be easily miniaturized to realize a high-quality image. Since it has advantages, it tends to be more and more popular as a display device in the future.

In a field emission display, a front glass substrate on which transparent electrodes and phosphors are formed and a rear glass substrate on which cathode electrodes, gate electrodes, cold cathodes (emitters), insulating films, etc. are formed are opposed to each other. It is made by frit sealing the surroundings. Then, an electron beam emitted from the cold cathode is applied to the phosphor to cause it to emit light, thereby displaying an image.

Since various films such as transparent electrodes and insulating films and emitters are formed by heat treatment, photoetching, etc., the glass substrate is subjected to various heat treatments and chemical treatments.
Therefore, the glass substrate used for the field emission display is required to have the following characteristics. (1) High chemical resistance so that it is not deteriorated by various acids, alkalis and other chemicals used in the photo-etching process. (2) The glass substrate has a high strain point so that the glass substrate does not shrink due to heat in a thermal process such as film formation to cause a pattern shift.

Conventionally, as a substrate glass for field emission which satisfies such characteristics, soda glass or high strain point glass for plasma display or alkali-free glass for liquid crystal display is known.

[0006]

However, in the field emission display, since the braking X-rays are generated inside the panel when displaying an image, the glass substrate needs to have an X-ray absorbing ability.

However, since none of the above glasses was developed as a glass substrate for a field emission display, the X-ray absorbing ability is not considered in the first place. Therefore, when a high voltage is applied for the purpose of increasing the brightness and increasing the screen size, X-rays generated inside the panel may leak to the outside and adversely affect the human body.
Further, there is a possibility that X-ray coloring may occur.

The object of the present invention is to provide a high voltage,
It is an object of the present invention to provide a glass substrate for a field emission display, which is less likely to be colored by X-rays and has a high X-ray absorption ability.

[0009]

The glass substrate for field emission display of the present invention contains substantially no PbO,
The X-ray absorption coefficient at a wavelength of 1.5Å is 125 cm ^-1 or more.

[0010]

The glass substrate for a field emission display of the present invention has an X-ray absorption coefficient of 125 cm at a wavelength of 1.5Å.
^Since it is ^-1 or more, X-rays do not leak even if a high voltage is used.

In order to increase the X-ray absorption coefficient of glass,
Although it suffices to contain PbO in the glass, the use of PbO-containing glass causes a problem that the glass is colored by the X-rays generated when the image is displayed and the image displayed on the display becomes difficult to see. . The glass substrate of the present invention is made of glass that does not contain PbO and can suppress coloring of glass by X-rays. In order to obtain an X-ray absorption coefficient of 125 cm ⁻¹ or more at a wavelength of 1.5Å in a glass not containing PbO, for example, Sr
O and BaO may be contained in a total amount of 5 to 50%. 5%
If it is above, the X-ray absorption coefficient of 125 cm ^-1 or more is easily obtained, and further, the chemical durability and the devitrification resistance of the glass are improved. If it is 50% or less, there is no possibility of impairing the meltability of glass, which is preferable. The preferred range is 12-50%
And more preferably 15 to 50%.

The glass substrate of the present invention has a strain point of 50.
It is preferably 0 ° C or higher. When the strain point is 500 ° C. or higher, shrinkage does not occur in the heat process of manufacturing the field emission display.

Besides the X-ray absorption coefficient, the specific range of the glass composition satisfying the above-mentioned required characteristics is shown below.

The composition range is that PbO is not substantially contained, and the mass percentage is SiO ₂ 40 to 80%, Al ₂ O _{3
0~30%, B 2 O 3 0~20} %, MgO 0~10
%, CaO 0-30%, SrO 0-30%, BaO
_{0~30%, Li 2 O 0~20%} , Na 2 O 0~2
_{0%, K 2 O 0~20%} , 0~10% ZnO, Zr
O ₂ 0-10%, CeO ₂ 0-5%, SrO + BaO
5 to 50%.

The reason why the glass composition is limited as described above in the present invention is as follows.

SiO ₂ is a component that serves as a glass network former. When the content is 40% or more, the heat resistance and chemical durability of the glass are improved. SiO
_{If the number of 2} is large, the melting temperature of glass tends to increase, but
When the content is 80% or less, the melting temperature of the glass does not become too high and the glass is easily melted. The preferred range is 40-75
%, And more preferably 40 to 70%.

Al ₂ O ₃ is a component that raises the strain point of glass and enhances heat resistance. If the content of Al ₂ O ₃ increases, the melting temperature tends to increase, but if the content is 30% or less, the melting of the glass is easy. The preferred range is 0-2
It is 0%, and more preferably 0 to 18%.

B ₂ O ₃ is a component that acts as a flux and improves the meltability. When the content of B ₂ O ₃ increases, the strain point tends to decrease and the heat resistance tends to decrease, but if it is 20% or less,
The melting temperature can be lowered while keeping the strain point of the glass high. The preferred range is 0 to 18%, more preferably 0 to 15%.

MgO is a component that lowers the viscosity at high temperature and improves the meltability of glass. When the content of MgO is large, the glass tends to devitrify or the chemical durability tends to decrease. However, when the content is 10% or less, the glass does not devitrify or the chemical durability decreases and The meltability of the can be improved. The preferred range is 0 to 8%, and more preferred is 0 to 7%.

CaO, like MgO, has the effect of lowering the high temperature viscosity and improving the meltability of glass. When the content of CaO is large, the glass tends to devitrify or the chemical durability tends to decrease. However, when the content of CaO is 30% or less, the glass does not devitrify or the chemical durability deteriorates. The meltability of the can be improved. The preferred range is 0-2
It is 5%, more preferably 0 to 20%.

SrO is a component that enhances the X-ray absorption coefficient and improves the chemical durability and devitrification resistance of glass.
When the content of SrO increases, the meltability tends to deteriorate, but if the content is 30% or less, the X-ray absorption coefficient can be increased without deteriorating the meltability, and the chemical durability and resistance of glass can be improved. The devitrification can be improved. The preferred range is 0 to 25%, more preferably 2 to 25%.
Is.

Similar to SrO, BaO is a component that enhances the X-ray absorption coefficient and improves the chemical durability and devitrification resistance of glass. When BaO increases, the meltability tends to deteriorate, but if the content is 30% or less, the X-ray absorption coefficient is increased without deteriorating the meltability, and the chemical durability and resistance of glass are improved. The devitrification can be improved. The preferred range is 0 to 25%, and more preferred is 2.1 to 25%.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the viscosity of the glass and improve the meltability. When the amount of these alkali components is large, coloring due to X-rays tends to occur, or the strain point of the glass tends to decrease, resulting in a decrease in heat resistance. Can be improved and the meltability can be improved without lowering the heat resistance. The preferred range is 0 to 10%. Also, if the glass does not contain an alkaline component,
Since it is possible to remarkably suppress coloring due to X-rays, it is more preferable not to contain it.

ZnO is a component that lowers the high temperature viscosity and improves the meltability of glass without lowering the strain point.
When ZnO increases, the glass tends to devitrify, but if the content is 10% or less, the glass does not devitrify and the meltability can be improved. The preferable range is 0 to 8%, and more preferably 0 to 5%.

ZrO ₂ is a component that improves the chemical durability of glass. When the content of ZrO ₂ is large, particles such as zircon tend to be deposited in the glass, but if the content is 10% or less, the chemical durability of the glass can be improved without depositing the particles. The preferred range is 0
-8%, more preferably 0-6%.

CeO ₂ is a component that suppresses coloring of glass by X-rays. If the CeO ₂ content is large, the transmittance tends to decrease, but there is no problem if it is added up to 5%. The preferable range is 0.01 to 5%, and more preferably 0.1 to 5%.

If PbO is contained in the glass, it should not be incorporated because the glass is markedly colored by X-rays generated inside the panel.

Further, in the present invention, in addition to the above-mentioned components, other components may be added within a range not impairing the characteristics. For example, As ₂ O ₃ and Sb may be used as a fining agent.
₂ O ₃ , SnO ₂ , F ₂ , Cl ₂ , SO ₃ etc. up to 3% each,
In order to improve the chemical durability of glass, Nb ₂ O ₃ ,
It is possible to add Y ₂ O ₃ and La ₂ O _{3 up} to 5% and P ₂ O _{5 up} to 5% in order to enhance the devitrification resistance of the glass.

The glass substrate of the present invention can be mass-produced inexpensively by using a method such as a float method, an overflow method, or a roll-out method, which is known as a method for forming sheet glass.

[0030]

EXAMPLES The present invention will be described below based on examples.

Tables 1 to 5 show examples (Sample Nos. 1 to 16) of the present invention and comparative examples (Samples No. 17 to 19).

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

Each sample in the table was prepared as follows.

First, glass raw materials were prepared so as to have the composition shown in the table, and the mixture was heated at 1450 to 1600 ° C. for 4 hours using a platinum pot.
Melted ~ 24 hours. After that, the molten glass is poured onto a carbon plate to form a plate, and after gradually cooling, the plate thickness is 2 mm.
Both sides are polished so that
A glass sample was prepared by cutting into a size of mm square.

For each of the samples thus produced,
The X-ray absorption coefficient, X-ray coloring amount, HCl resistance, buffered hydrofluoric acid resistance, thermal expansion coefficient, density and strain point were evaluated. The results are shown in the table.

The X-ray absorption coefficient is obtained by calculating the absorption coefficient for a wavelength of 1.5Å based on the glass composition and the density.

Regarding the amount of X-ray coloring, the thickness of each sample was 2
After optically polishing both sides to a wavelength of 400 mm
The visible light transmittance at m was measured. Then, 1 X-ray generated from a Rh tube of 30 kv and 15 mA was applied to this sample.
Irradiate for 5 minutes. After that, the visible light transmittance at 400 nm was measured again, and the transmittance difference (ΔT%) before and after the X-ray irradiation was measured.
Was determined as the X-ray coloring amount. The larger the X-ray coloring amount, the more easily the brightness of the field emission display deteriorates.

The HCl resistance was evaluated by immersing each sample in a 10% by mass aqueous hydrochloric acid solution kept at 80 ° C. for 3 hours and then visually observing the surface conditions of the samples. The buffered hydrofluoric acid resistance was 38.7% by mass of ammonium fluoride, 1.6% by mass of which each sample was kept at 20 ° C.
After immersing in buffered hydrofluoric acid consisting of hydrofluoric acid for 10 minutes, the surface condition of these was visually observed and evaluated. ○ If the surface of the glass substrate does not change at all
The discolored one is indicated by x.

The coefficient of thermal expansion is a value obtained by measuring the average coefficient of thermal expansion at 30 to 380 ° C. using a dilatometer.

The density was measured by the well-known Archimedes method.

The strain point is measured according to the method of ASTM C336-71. The higher the value, the better the heat resistance.

As is apparent from the table, the sample No. 1-No. In each of the 16 samples, the content of SrO and BaO is 5% or more, so the X-ray absorption coefficient is 125 cm.
^-1 or higher, and because it does not contain PbO, X
The amount of line coloring was also 29% or less. In particular, No. 1 containing no CeO ₂ or containing no alkaline component. 1 to
The samples of Nos. 12, 15 and 16 had a low X-ray coloring amount of 27% or less. Furthermore, the HCl resistance and the buffered hydrofluoric acid resistance were good, the strain point was as high as 650 ° C. or higher, and there was no problem in heat resistance.

On the other hand, the sample No. which is a comparative example. 17
In Nos. 18 and 18, since the total amount of SrO and BaO was lower than 5%, the X-ray absorption coefficient was low at 57 cm ^-1 or less. Also,
Sample No. Since No. 19 contained PbO, the glass was markedly colored by X-ray irradiation.

[0048]

INDUSTRIAL APPLICABILITY As described above, the glass substrate for field emission display of the present invention has a high X-ray absorption coefficient and is less colored by X-rays, and is therefore suitable as a glass substrate used in the field emission display. is there.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C03C 3/089 C03C 3/089 3/091 3/091 3/093 3/093 3/095 3/095 H01J 29/86 H01J 29/86 Z 31/12 31/12 CF term (reference) 4G062 AA01 BB01 DA05 DA06 DB01 DB02 DB03 DB04 DC01 DC02 DC03 DC04 DD01 DD02 DD03 DE01 DE02 DE03 DF01 EA01 EA02 EA03 EA04 EA10 EB01 EB02 EB03 EB04 EC01 EC02 EC02 EC01 EC02 ED01 ED02 ED03 EE01 EE02 EE03 EE04 EF01 EF02 EF03 EF04 EG01 EG02 EG03 EG04 FA01 FA10 FB01 FC01 FC02 FC03 FD01 FE01 FE02 FE03 FF01 FG01 GB01 FR01 FF01 F01 F01 F01 F01 F01 F01 F02 F01 F02 F01 F02 F01 F02 F01 F01 F02 F01 F01 F02 F01 F01 F02 F01 F02 F01 F01 F01 F02 F01 F02 F01 F01 F01 F02 F01 F01 F01 F02 F01 F01 F01 F02 F01 F01 F01 F02 F01 F01 F02 F01 F02 F01 F01 F01 F01 F01 F01 F02 F01 F01 F01 F01 F01 F01 F01 F02 F01 F01 F01 F01 F01 F02 F01 F01 F01 F01 F01 F02 F01 F01 F01 F01 F01 F01 F01 F01 F02 F01 F01 F01 F02 F01 F01 F01 F02 F01 F01 F01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ06 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 NN14 5C032 AA01 BB20 5C036 EE19 EF01 EF06 EF09 EG02

Claims (6)

[Claims] 1. A glass substrate for a field emission display, which is substantially free of PbO and has an X-ray absorption coefficient at a wavelength of 1.5 liters of 125 cm ⁻¹ or more. 2. The glass substrate for a field emission display according to claim 1, wherein the strain point is 500 ° C. or higher. 3. The glass substrate for a field emission display according to claim 1, wherein SrO + BaO is 5 to 50%. 4. PbO is not substantially contained, and by mass percentage, SiO ₂ 40 to 80%, Al ₂ O ₃ 0 to 30%,
B ₂ O ₃ 0-20%, MgO 0-10%, CaO 0
-30%, SrO 0-30%, BaO 0-30%,
Li ₂ O 0-20%, Na ₂ O 0-20%, K ₂ O
0-20%, ZnO 0-10%, ZrO ₂ 0-10
%, CeO ₂ 0-5%, SrO + BaO 5-50%
The glass substrate for a field emission display according to any one of claims 1 to 3, wherein 5. The glass substrate for a field emission display according to claim 1, which does not substantially contain an alkali component. 6. A CeO ₂ content of 0.01 to 5 in terms of mass percentage.
% Of the glass substrate for a field emission display according to any one of claims 1 to 5.