JPH09169538A - Alkali-free glass and liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an alkali-free glass having a high strain point, a low coefft. of thermal expansion and low density, not getting cloudy under buffered hydrofluoric acid, excellent in chemical resistance, easy to melt and mold and capable of float forming by adopting a specified glass compsn. SOLUTION: This alkali-free glass consists essentially of, by mol, 60-72% SiO2 , 5-16% Al2 O3 , 5 to <10% B2 O3 and 7-18%, in total, of 0-6% MgO, 0-2.5% CaO, 1-9% SrO and 1-5% BaO. It is preferable that this glass does not practically contain P, PbO, As2 O3 and Sb2 O3 and has >=640 deg.C strain point and 30×10<-7> -45×10<-7> / deg.C coefft. of thermal expansion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-alkali glass which is suitable as a substrate glass for various displays and photomasks and which can be float-formed without substantially containing an alkali metal oxide, and a liquid crystal display panel using the same. .

[0002]

2. Description of the Related Art Conventionally, substrate glass for various displays,
In particular, the following characteristics are required for a metal or oxide thin film formed on the surface.

(1) When an alkali metal oxide is contained,
Alkali metal ions diffuse into the thin film, deteriorating the film characteristics. (2) Since it is exposed to a high temperature in the thin film forming step, it has a high strain point in order to minimize the contraction due to the deformation of the glass and the structural stabilization of the glass. (3) Having sufficient chemical durability against various chemicals used for semiconductor formation. In particular, durability against buffered hydrofluoric acid (BHF) containing hydrofluoric acid, ammonium fluoride, or the like as a main component for etching SiO _x or SiN _x . (4) No defects (foam, striae, inclusions, pits, scratches, etc.) inside and on the surface.

Conventionally, Corning Code 7059 glass has been widely used as a substrate glass for various displays and photomasks. However, this glass had the following inadequate points for display use.

(1) Since the strain point is as low as 593 ° C., a pre-heat treatment for reducing the shrinkage of glass in the display manufacturing process must be performed before the process. (2) The amount of elution into hydrochloric acid or the like used for etching a metal electrode or a transparent conductive film (ITO or the like) is large, and the eluted material is recrystallized during the display manufacturing process, so that it is difficult to manufacture the display.

[0006] In addition to the above requirements, in recent years, the following two points have been newly required as the size of the display increases.

(1) The code 7059 glass has a density of 2.76 g / cc, and it is necessary to have a low density in order to further reduce the weight. (2) The code 7059 glass has a thermal expansion coefficient of 46 ×
It is 10 ⁻⁷ / ° C., and a material having a smaller thermal expansion coefficient is required in order to increase the rate of temperature rise and fall during display production and increase production efficiency.

Regarding B ₂ O ₃ , Japanese Patent Laid-Open No. 1-16081
Although the 44 discloses those containing B ₂ O ₃ 20 to 23 cationic%, B ₂ O ₃ amount is large and the strain point not sufficiently high. 0.1-4% by weight of B ₂ O ₃ is in JP 61-281041, in JP 4-175242 B ₂ O
₃ to 0.1 to 5 mol%, and JP-A-4-325435 discloses B
The ₂ O ₃ 0 to 3% by weight, although those containing discloses, is not sufficient resistance to the amount of B ₂ O ₃ is less BHF.

Regarding BaO, JP-A-4-32543
No. 4 contains 10 to 20% by weight of BaO.
No. 35, 10 to 22% by weight of BaO.
Although 9953 discloses that it contains 15 to 40% by weight of BaO, it contains a large amount of BaO and has a large coefficient of thermal expansion.

Regarding MgO, Japanese Patent Application Laid-Open No. 61-1325
No. 36 contains 6.5 to 12% by weight of MgO.
No. 16147 contains 5 to 15% by weight of MgO.
71540 contains 5-17% by weight of MgO.
No. 42246 discloses a material containing 10 to 25 mol% of MgO, but a glass containing a large amount of MgO tends to cause phase separation.

Regarding CaO, JP-A-63-1763
No. 32 contains 11 to 25% by weight of CaO.
No. 038 contains 7 to 20 mol% of CaO.
334 contains 8 to 15% by weight of CaO.
336 contains 7 to 12% by weight of CaO.
39, 10 to 12% by weight of CaO;
Although 744 discloses that CaO is contained in an amount of 18 cation% or more, it contains a large amount of CaO, so that the coefficient of thermal expansion tends to increase.

Regarding Al ₂ O ₃ , Japanese Patent Laid-Open No. 61-23
22.5 to 35 wt% of Al ₂ O ₃ in 6631, although those containing discloses, Al ₂ O ₃ amount is large elution into chemicals to hydrochloric acid is large.

Regarding P ₂ O _5, there is disclosed in JP-A-61-261.
232 and JP-A-63-11543 disclose those containing P ₂ O ₅ , but this is not preferable because it deteriorates the semiconductor characteristics of the thin film.

[0014]

The coefficient of thermal expansion is 30 to 45 × 10 ⁻⁷ / ° C. and the density is 2.7 at 640 ° C. or higher.
Glasses of 0 g / cc or less are disclosed in JP-A-6-263473. However, this glass is
When glass prepared by batch mixing, melting and molding is applied to a high definition polysilicon type TFT, a transistor having sufficiently good characteristics may not be obtained in some cases.

The object of the present invention is to solve the above-mentioned drawbacks, to have a strain point of 640 ° C. or higher, a small coefficient of thermal expansion and a low density, to prevent clouding due to BHF, and to have excellent durability to chemicals such as hydrochloric acid, An object of the present invention is to provide an alkali-free glass which can be easily melted and formed and can be float-formed.

[0016]

According to the present invention, SiO ₂ : 60-72% and Al ₂ O ₃ : 5-substantially in terms of mol%.
16%, B ₂ O _3: less than 5~10%, MgO: 0~6
%, CaO: 0 to 2.5%, SrO: 1 to 9%, Ba
O: 1-5%, MgO + CaO + SrO + BaO: 7-
It is a non-alkali glass consisting of 18%.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali-free glass of the present invention is substantially free of alkali metal oxides (eg, Na ₂ O, K ₂ O, etc.). Specifically, the total amount of alkali metal oxides is 0.5% by weight or less, more preferably 0.2% by weight or less.
% By weight or less.

Next, the reason why the composition range of each component is limited as described above will be described.

When the content of SiO ₂ is less than 60% by mole, the strain point cannot be sufficiently raised, the chemical durability is deteriorated, and the thermal expansion coefficient is increased. If it exceeds 72 mol%, the meltability will decrease and the devitrification temperature will rise. A more preferable range is 66 to 70 mol%.

Al ₂ O ₃ suppresses the phase separation of glass, lowers the coefficient of thermal expansion, and raises the strain point. Its content is 5 mol%
If it is less than 10%, this effect does not appear, and if it exceeds 16 mol%, the meltability of the glass is deteriorated. A more preferable range is 9 to 14 mol%.

B ₂ O ₃ can prevent the occurrence of white turbidity due to BHF and can achieve a reduction in the coefficient of thermal expansion and the density without increasing the viscosity at high temperature. If the content is less than 5 mol%, BHF
If the amount is 10 mol% or more, the acid resistance becomes poor. A more preferable range is 6 to 9 mol%.

Although MgO is not an essential component, it can be contained among the alkaline earth metal oxides because it has a low coefficient of thermal expansion and does not lower the strain point. If the content exceeds 6 mol%, whitening due to BHF and phase separation of glass are likely to occur. A more preferable range is 1 to 5 mol%.

Although CaO is not an essential component, its inclusion can improve the meltability of the glass. If its content exceeds 2.5 mol%, the characteristics of the high definition polysilicon TFT may be deteriorated.

In recent years, a polysilicon type TFT has been proposed and used in contrast to a liquid crystal display device using an amorphous silicon type TFT which has already been commercialized. Polysilicon type TFT
(1) The mobility of the transistor can be increased, so that the control time per pixel is not short, the definition of the LCD can be increased, and (2) the driving IC can be mounted around the screen. However, strong heat treatment (for example, 500 to 600 ° C. × several hours) is required in the manufacturing process. At such a high temperature, the impurities in the glass become TF.
There is a possibility that diffusion to T increases the leak current, deteriorates the TFT characteristics, and makes it difficult to manufacture a high-definition TFT.

The most problematic of such impurities is phosphorus in limestone used as a raw material of CaO. Therefore, it is desirable that phosphorus is not substantially contained in the alkali-free glass of the present invention. In order to reduce phosphorus in the glass, a method of using a high-purity raw material containing few phosphorus impurities can be considered, but it is disadvantageous in terms of cost.

In the present invention, the content of CaO is set to 2.5 mol% or less, so that the TFT characteristics are not deteriorated and a glass substrate having excellent characteristics for a liquid crystal display panel can be obtained. The more preferable range of CaO is 1.5 mol% or less, and particularly preferably, it is substantially not contained.

Since SrO suppresses the phase separation of the glass and is a relatively useful component against white turbidity due to BHF, 1 mol%
It is contained above. If the content exceeds 9 mol%, the coefficient of thermal expansion increases. A more preferable range is 2 to 8 mol%.

BaO is essential in the present invention because it has the effects of suppressing the phase separation of glass, improving the meltability, and suppressing the devitrification temperature. If the content exceeds 5 mol%, the coefficient of thermal expansion increases and the chemical durability such as acid resistance deteriorates.

MgO + CaO + SrO + BaO makes the melting difficult if the total amount thereof is less than 7 mol%. If it exceeds 18 mol%, the density tends to be high. More preferable range is 9 to 1.
6 mol%.

In the present invention, since phosphorus may deteriorate TFT characteristics, it is preferable that phosphorus is not substantially contained.

In addition to the above-mentioned components, the glass of the present invention contains ZnO and SO in order to improve the melting property, clarity and moldability of the glass.
₃ , F and Cl can be added in a total amount of 5 mol% or less.

Further, PbO, As ₂ O ₃ and Sb ₂ O ₃
Since it requires a lot of man-hours to process the glass cullet, it is preferable not to include it except those which are unavoidably mixed as impurities.

Thus, the more preferred glass composition of the present invention is substantially SiO ₂ : 66-70 in mole percent.
%, Al ₂ O ₃ : 9-14%, B ₂ O ₃ : 6-9%, M
gO: 1-5%, SrO: 2-8%, BaO: 1-5
%, MgO + SrO + BaO: 9 to 16%, and does not substantially contain phosphorus and CaO.

The glass of the present invention preferably has a strain point of 640 ° C. or higher, more preferably 650 ° C. or higher. Further, the coefficient of thermal expansion is 30 × 10 ⁻⁷ / ° C. to 45 × 10.
^-7 / ° C is preferable, more preferably 30 x 1
It is 0 ⁻⁷ / ° C. to 40 × 10 ⁻⁷ / ° C. Furthermore, the density 2.
It is preferably 70 g / cc or less, and more preferably 2.65 g / cc or less.

The glass of the present invention can be manufactured, for example, by the following method. That is, the raw materials for each of the commonly used components are blended so as to be the target components, which are continuously charged into a melting furnace and heated to 1500 to 1600 ° C. to melt.
This molten glass is formed into a predetermined thickness by a float method, and then cooled and cut.

[0036]

EXAMPLES The raw materials of the respective components were prepared so as to have a target composition, and were melted at a temperature of 1500 to 1600 ° C. using a platinum crucible. Upon melting, the glass was homogenized by stirring using a platinum stirrer. Next, the molten glass was poured out, formed into a plate, and then gradually cooled.

Tables 1 and 2 show the glass compositions thus obtained, thermal expansion coefficient, high temperature viscosity, devitrification temperature, strain point, density, acid resistance, BHF resistance and leak current (TFT characteristics).
Examples 1 to 10 are examples, and Examples 11 to 13 are comparative examples.

The coefficient of thermal expansion is shown in the unit: 10 ^-7 / ° C., the high temperature viscosity is shown in the temperature at which the viscosity becomes 10 ² and 10 ⁴ poise (the unit: ° C.), the devitrification temperature is shown in the unit: ° C., and the density is Indicates the unit: g / cc. Strain point (unit: ° C) is JIS R
3103 was measured.

The acid resistance was indicated by the amount of weight loss per unit area after dipping in 0.1N HCl at 90 ° C. for 20 hours (unit: mg / cm ² ). Acid resistance is 0.3 mg / c
It is preferably m ² or less, particularly 0.2 mg / cm ² or less.

The BHF resistance is as follows: NH ₄ F / HF mixed liquid (40
Amount of weight reduction per unit area after immersion for 20 minutes at 25 ° C. in a solution in which a weight% NH ₄ F aqueous solution and a 50 weight% HF aqueous solution were mixed at a volume ratio of 9: 1 (unit: mg / cm ² ). Indicated by. The BHF resistance is preferably 0.7 mg / cm ² or less, and particularly preferably 0.6 mg / cm ² or less.

The TFT characteristics were measured for Examples 1, 2, 10-12. That is, a polysilicon type TFT having an electrode length of 10 μm is formed on a glass substrate, a gate voltage is −5 V, a source voltage is 0 V, and a drain voltage is +10.
The leakage current (unit: pA) at V was measured.
The leak current is preferably about several pA or less.

The glasses of Examples 1 to 10 have a coefficient of thermal expansion of 30.
It shows a low value of up to 40 × 10 ⁻⁷ / ° C. and a high strain point of 630 ° C. or higher, and can withstand heat treatment at high temperatures.
The density is also less than 2.70 g / cc and less than 2.76 g / cc of the conventional Corning Code 7059 glass. Regarding chemical properties, BHF hardly causes cloudiness and is excellent in acid resistance. The temperature corresponding to 10 ² poise, which is a guideline for melting, is relatively low, and melting is easy. The relationship between the temperature corresponding to 10 ⁴ poise, which is a guideline for moldability, and the devitrification temperature is good. It is considered that there is no trouble such as generation.

Further, regarding the TFT characteristics, the leak current is less than 10 pA, and it can sufficiently withstand the recent high integration of TFTs.

On the other hand, in Examples 11 to 13, the leak current is about ten to several tens of pA, which may cause a problem as the TFT is highly integrated.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

The glass according to the present invention can be formed by the float method. In addition, BHF is less likely to be clouded, has excellent acid resistance, has high heat resistance, and has a low coefficient of thermal expansion, so that it is suitable as a display substrate or a photomask substrate. In particular, it is less likely to adversely affect the TFT characteristics, and is therefore suitable for a TFT type display substrate or the like.

[0048]

Claims (9)

[Claims] 1. Substantially in terms of mol%, SiO ₂ : 60-
_{72%, Al 2 O 3:} 5~16%, B 2 O 3: 5~10
%, MgO: 0 to 6%, CaO: 0 to 2.5%, S
rO: 1-9%, BaO: 1-5%, MgO + CaO +
SrO + BaO: 7-18% non-alkali glass. 2. The alkali-free glass according to claim 1, which is substantially free of phosphorus. 3. The alkali-free glass according to claim 1, which is substantially free of PbO, As ₂ O ₃ and Sb ₂ O ₃ . 4. The alkali-free glass according to claim 1, which has a strain point of 640 ° C. or higher. 5. A coefficient of thermal expansion of 30 × 10 ⁻⁷ / ° C. to 45 × 1
The alkali-free glass according to claim 1, which has a temperature of 0 ^-7 / ° C. 6. Substantially in terms of mol%, SiO ₂ : 66-
_{70%, Al 2 O 3:} 9~14%, B 2 O 3: 6~9
%, MgO: 1-5%, SrO: 2-8%, BaO: 1
.About.5%, MgO + SrO + BaO: 9-16%, and substantially not containing phosphorus and CaO.
One of the alkali-free glass. 7. The alkali-free glass according to claim 1, which has a strain point of 650 ° C. or higher. 8. The coefficient of thermal expansion is 30 × 10 ⁻⁷ / ° C. to 40 × 1.
The alkali-free glass according to claim 1, which has a temperature of 0 ^-7 / ° C. 9. A liquid crystal display panel using the alkali-free glass according to claim 1 as at least one of a pair of substrates forming a cell.