JP2003112942A - Glass substrate for field emission type display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate which satisfies the characteristics required for a field emission type display. SOLUTION: The glass substrate for a field emission type display substantially contains neither an alkali component nor PbO and has >=550 deg.C strain point, >=68 GPa Young's modulus and >=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 Field emission displays have many advantages such as thinness and light weight, low power consumption, clear display, and full-color display. Therefore, they are becoming more and more popular as display devices in the future.

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

By the way, in the field emission display, an electron beam emitted from an emitter is applied to a phosphor to emit light to display an image, but when an alkaline component is contained in a glass substrate, an electron is emitted. Alkali ions diffuse into the emitter, causing deterioration of the electron source. Therefore, it is required for the glass substrate to reduce the content of the alkaline component.

In addition, in the field emission type display, the inside of the panel is kept in a vacuum in order to maintain the electron beam emission characteristics for a long period of time. However, if the inside of the panel is kept in the vacuum, the glass substrate bends and the cell Since the gap may not be uniform and the image may be uneven or the panel may be damaged, the cell gap is maintained by interposing a support spacer at regular intervals between the front and rear glass substrates. Measures to take are taken. These spacers are installed between pixels. However, if the number of spacers is large, it is difficult to achieve high definition. Therefore, it is preferable that the number of spacers is small. Therefore, the glass substrate is required to be less likely to bend.

Further, in the field emission display, when the electron beam hits the phosphor to display an image, X-rays are generated inside the panel. Due to X-rays, the glass may be colored and the image projected may be difficult to see. In addition, there is a possibility that X-rays may leak outside the panel and adversely affect the human body. Therefore, the glass substrate for a field emission display is required not to be colored by X-rays and to have a high X-ray shielding ability.

Further, various kinds of films such as transparent electrodes and insulating films and emitters are formed on the surface of this type of glass substrate.
Moreover, various circuits and patterns are formed by photolithography etching (photoetching). Since various heat treatments and chemical treatments are performed in these film forming and photoetching steps, the glass substrate is also required to have heat resistance and chemical resistance.

[0008]

However, the glass substrate for plasma display and the glass substrate for liquid crystal display, which are conventionally known as glass substrates for displays, have a low X-ray absorption coefficient, and X-rays leak to the outside of the panel. Therefore, there is a possibility that a problem may occur that adversely affects the human body. Further, with respect to the glass substrate for plasma display, since the glass contains a large amount of the alkaline component, the alkaline component diffuses into the emitter, causing deterioration of the electron source.

As described above, since the existing glass substrate has not been developed for field emission display applications, none of the glass substrates satisfy all the characteristics required for the field emission display.

An object of the present invention is to provide a glass substrate which satisfies all the properties required for a field emission display.

[0011]

The glass substrate for a field emission display according to the present invention is substantially composed of an alkaline component and P.
It is characterized by not containing bO, having a strain point of 550 ° C. or higher, a Young's modulus of 68 GPa or higher, and an X-ray absorption coefficient of 125 cm ⁻¹ or higher at a wavelength of 1.5Å.

The glass substrate for field emission display of the present invention is a SiO ₂ —Al ₂ O ₃ —RO type glass (R
O is MgO, CaO, SrO, or BaO), and does not substantially contain an alkaline component and PbO,
O, SrO, and BaO are contained as essential components, and by mass percentage, Al ₂ O ₃ 2.1 to 30%, CaO + SrO + B.
aO is 20 to 45%.

[0013]

The glass substrate for a field emission display of the present invention contains substantially no alkali component, so that the electron source can be prevented from deteriorating.

The glass substrate of the present invention is 68 GPa.
Since it has a Young's modulus of (preferably 74 GPa) or more, even if the inside of the panel is held in vacuum, the glass substrate is unlikely to be deformed, and the number of spacers can be reduced. In order to set the Young's modulus of the glass substrate to 68 GPa or more, in the case of SiO ₂ —Al ₂ O ₃ —RO glass, for example, CaO, SrO, and BaO are essential components,
The total amount of these components should be 20 to 45%. When the total amount of these components is 20% or more, it is easy to obtain a Young's modulus of 68 GPa or more. However, if the total content of these components is more than 45%, the glass is devitrified or the coefficient of thermal expansion is increased, so that the glass substrate is easily broken in the heat treatment step. A preferred range is 21 to 44%.

Further, it does not contain PbO and contains CaO and Sr.
By including O and BaO in a total amount of 20% or more, the X-ray absorption coefficient at a wavelength of 1.5 Å can be 125 cm ^-1 or more without coloring the glass by X-rays. It can be shielded within the panel.

Further, since the glass substrate of the present invention has a strain point of 550 ° C. or higher, shrinkage does not occur in the heat treatment process for manufacturing a field emission display. In order to set the strain point of glass to 550 ° C. or higher, SiO ₂ —Al ₂ O ₃ —
In the case of RO type glass, for example, Al ₂ O ₃ may be contained at 2.1% or more. When the content of Al ₂ O ₃ is 2.1% or more, it becomes easy to obtain a strain point of 550 ° C. or more. However, if the content exceeds 30%, it becomes difficult to melt.

In the present invention, the coefficient of thermal expansion of glass is 40.
It is desirable to set it to 70 × 10 ⁻⁷ / ° C. If the coefficient of thermal expansion is 40 × 10 ^-7 / ° C (preferably 45 × 10 ^-7 / ° C) or more, two glass substrates can be frit-sealed well, and the inside of the panel is kept in vacuum for a long period of time. Therefore, the electron beam emission characteristics can be maintained. Also, 7
If it is 0 × 10 ⁻⁷ / ° C. or less (preferably 59 × 10 ⁻⁷ / ° C.) or less, cracking of the glass substrate in the heat treatment step can be suppressed. The coefficient of thermal expansion of glass is 40 to 70 ×
To obtain 10 ⁻⁷ / ° C., SiO ₂ —Al ₂ O ₃ —RO
In the case of a system glass, for example, CaO, SrO, and BaO may be contained in a total amount of 20 to 45%.

In the present invention, the liquidus viscosity of glass is 10
It is desirable to set it to ^4.0 dPa · s or more. The reason is that it is possible to mass-produce inexpensively by 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.

Specific ranges of the glass composition satisfying the above-mentioned required characteristics are shown below.

The composition range is substantially free of an alkali component and PbO, and in terms of mass percentage, SiO _{2 is} 40 to 40.
80%, Al ₂ O ₃ 2.1-30%, B ₂ O ₃ 0-20
%, MgO 0-10%, CaO 0.1-30%, S
rO 1-30%, BaO 1-30%, ZnO 0-1
0%, ZrO ₂ 0-10%, CeO ₂ 0-5%, Ca
O + SrO + BaO 20 to 45%.

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

SiO ₂ is a component which 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 heat resistance. If the content is 2.1% or more, the strain point of the glass increases and the heat resistance improves. Al ₂
When the content of O ₃ is large, the melting temperature tends to be high, but when the content is 30% or less, the melting of the glass is easy. The preferred range is 2.5 to 20%, more preferably 4 to 18%.

B ₂ O ₃ is a component which 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 raises the Young's modulus of the glass and lowers the high temperature viscosity to improve the meltability of the glass. When the content of MgO is large, the glass is significantly devitrified or the chemical durability is lowered. However, when the content is 10% or less, the glass is melted without devitrification or the chemical durability is lowered. The sex can be improved. The preferable range is 0 to 5%, and more preferably 0 to 3%.

CaO has the effects of increasing the Young's modulus of the glass and lowering the high temperature viscosity, and improving the meltability of the glass. When the content is 0.1% or more, the Young's modulus of glass can be increased. When the content of CaO is large, the glass tends to devitrify and the chemical durability tends to decrease, though not to the extent of MgO. However, when the content of CaO is 30% or less, the glass devitrification and the chemical durability decrease. The meltability of the glass can be improved without causing it. The preferred range is 1 to 25%, more preferably 2 to 20%.

SrO and BaO are components that increase the Young's modulus of the glass, increase the X-ray absorption coefficient, and improve the chemical durability and devitrification resistance of the glass. When the content is 1% or more, the Young's modulus of the glass can be increased and the X-ray absorption coefficient of the glass can be increased. When the content is high, the meltability tends to deteriorate, but when the content is 30% or less, the above effect can be obtained without deteriorating the meltability.
A preferable range is 1 to 25%, and a more preferable range is 2 to 25%.

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%.

Alkali components such as Li ₂ O, Na ₂ O and K ₂ O should not be introduced because they shorten the life of the electron source.

When PbO is contained in the glass, the glass is markedly colored by X-rays generated inside the panel, and therefore should not be incorporated.

In the present invention, in addition to the above-mentioned components, other components may be added within a range that does not impair the characteristics. For example, As ₂ O ₃ or 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.

[0034]

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

Tables 1 to 3 show examples of the present invention (Sample No.
1 to 10) and comparative examples (Sample Nos. 11 and 12). Sample No. 12 shows soda glass.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

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 melted at 1550 ° C. for 24 hours using a platinum pot. After that, the molten glass is poured onto a carbon plate to form a plate shape, gradually cooled, and then double-sided polished to a plate thickness of 2 mm, and the obtained plate glass is cut into a size of 200 mm square. This produced a glass sample.

For each of the samples thus prepared,
Density, strain point, thermal expansion coefficient, Young's modulus, X-ray absorption coefficient, X
The amount of line coloring, HCl resistance, buffered hydrofluoric acid resistance, and liquidus viscosity were evaluated. The results are shown in the table.

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. It is preferably 600 ° C. or higher.

The coefficient of thermal expansion is the average coefficient of thermal expansion measured at 30 to 380 ° C. using a dilatometer.

The Young's modulus is measured by a bending resonance method by cutting a piece cut out to 20 × 40 × 2 mm. The larger this value is, the more the deformation is less likely to occur even if the inside of the panel is evacuated. It is preferably at least 72 GPa.

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 mass% hydrochloric acid aqueous solution kept at 80 ° C. for 3 hours and then visually observing the surface state of each sample. 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.

Regarding the liquidus viscosity, each sample had 3
It was crushed to a size of 00 to 500 μm, put in a platinum boat, transferred to a temperature gradient furnace of 1000 to 1250 ° C., and kept for 24 hours. Then, the glass was taken out from the platinum boat and observed with a polarization microscope to determine the temperature at which crystals began to precipitate, and the viscosity of the glass corresponding to that temperature was taken as the liquidus viscosity. The value of liquidus viscosity greater is easily molded, it is preferable in particular is 10 ^{4. 0} dPa · s or more.

As is apparent from the table, the sample No. 1-No. Each sample of 10 has a strain point of 645 ° C. or higher and a thermal expansion coefficient of 46.5 to 59.0 × 10 ⁻⁷ / ° C.
Therefore, the heat resistance is excellent and frit sealing can be performed well. Further, since the Young's modulus is as large as 72 GPa or more, even if the inside of the panel is evacuated, the glass substrate is not deformed. Further, since it does not contain PbO, the X-ray coloring amount is as low as 35% or less, and the X-ray absorption coefficient is as high as 127 cm ^-1 or more, so that X-rays generated inside the panel can be shielded. It had good HCl resistance, buffered hydrofluoric acid resistance, and chemical resistance.
Further, the liquidus viscosity is 10 ^4.0 dPa · s or more, and it can be mass-produced inexpensively by using a method such as a float method, an overflow method, a downdraw method, and a rollout method.

On the other hand, the sample No. 11
Had a low X-ray absorption coefficient of 68 cm ⁻¹ . In addition, the sample No. No. 12 contains an alkaline component and may deteriorate the electron source. Also, the X-ray absorption coefficient is 56c.
It was as low as m ^-1 .

[0052]

As described above, the glass substrate for a field emission display of the present invention is unlikely to cause heat shrinkage or crack in the process of manufacturing the field emission display. In addition, deterioration of the electron source of the field emission display and coloring and leakage due to X-rays do not occur. Further, even if the number of spacers is reduced, it is difficult to bend, so that high definition is possible.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01J 29/86 H01J 29/86 ZF term (reference) 4G062 AA01 BB01 BB06 DA05 DA06 DA07 DB03 DB04 DC01 DC02 DC03 DC04 DD01 DE01 DE02 DE03 DF01 EA01 EB01 EC01 ED01 ED02 ED03 EE02 EE03 EE04 EF03 EF04 EG03 EG04 FA01 FA10 FB01 FC01 FC02 FC03 FD01 FE01 FE02 FE03 GH01 HG01 H01 GB01 H01 GB01 H01 GB01 H01 GB01 H01 GB01 H01 GB01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 FL01 H01 01 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ06 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM27 NN14 5C032 AA07 BB03 BB15

Claims (5)

[Claims] 1. A substantially free of alkali component and PbO, a strain point of 550 ° C. or higher, and a Young's modulus of 68 GP.
A glass substrate for a field emission display, which is a or more and has an X-ray absorption coefficient of 125 cm ^-1 or more at a wavelength of 1.5Å. 2. The glass substrate for a field emission display according to claim 1, which has an average coefficient of thermal expansion of 40 to 70 × 10 ⁻⁷ / ° C. up to 30 to 380 ° C. 3. A SiO ₂ —Al ₂ O ₃ —RO glass (R
O is MgO, CaO, SrO, or BaO), and does not substantially contain an alkaline component and PbO,
O, SrO, and BaO are contained as essential components, and by mass percentage, Al ₂ O ₃ 2.1 to 30%, CaO + SrO + Ba.
O: 20 to 45% A glass substrate for a field emission display, which is characterized in that: 4. SiO ₂ 40 to 80 in terms of mass percentage.
%, Al ₂ O ₃ 2.1 to 30%, B ₂ O ₃ 0 to 20%,
MgO 0-10%, CaO 0.1-30%, SrO
1-30%, BaO 1-30%, ZnO 0-10
%, ZrO ₂ 0-10%, CeO ₂ 0-5%, CaO +
20-45% of SrO + BaO, The glass substrate for field emission displays in any one of Claims 1-3 characterized by the above-mentioned. 5. The glass substrate for a field emission display according to claim 1, which has a liquidus viscosity of 10 ^4.0 dPa · s or more.