JPH09169539A - 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 has >=640 deg.C strain point and consists essentially of, by mol, 60-73% SiO2 , 5-16% Al2 O3 , 5-12% B2 O3 and 7-18%, in total, of 0-6% MgO, 0-9% CaO, 1-9% SrO and 0 to <1% BaO. It is preferable that this glass does not practically contain PbO, As2 O3 and Sb2 O3 and has <=20ppm by atomic wt. of P content, <2.60g/cc density and <40×10<-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 suitable for use as a substrate glass for various displays and photomasks, which does not substantially contain an alkali metal oxide and which can be float-molded, and a liquid crystal display panel using the same. .

[0002]

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

(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 deformation of glass and shrinkage accompanying stabilization of glass structure. (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 (bubbles, striae, inclusions, pits, scratches, etc.) on the 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 a material containing 15 to 40% by weight of BaO, it has a large amount of BaO, a large coefficient of thermal expansion, and a high density.

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;
No. 744 discloses one containing CaO in an amount of 18 cation% or more, but when CaO is contained in a large amount, the thermal expansion coefficient 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 strain point is 640 ° C.
As described above, glass having a relatively small coefficient of thermal expansion is disclosed in
-160030 and JP-A-6-263473. However, since this glass requires a considerable amount of BaO, it is difficult to achieve both a low density and a low coefficient of thermal expansion, and it has not completely met the demand of the era of larger size.

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 small 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, the strain point is 640.
℃ or more, in terms of mol% substantially SiO ₂ : 6
_{0~73%, Al 2 O 3:} 5~16%, B 2 O 3: 5~
12%, MgO: 0-6%, CaO: 0-9%, Sr
O: 1 to 9%, BaO: 0 to less than 1%, MgO + CaO
+ SrO + BaO: A non-alkali glass composed of 7 to 18%.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali-free glass of the present invention does not substantially contain an alkali metal oxide (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.

The reason for limiting the composition range of each component 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 73 mol%, the meltability is lowered and the devitrification temperature is increased. Preferably, 66-
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. It is preferably 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 exceeds 12 mol%, the acid resistance becomes poor and the strain point becomes low. Preferably, it is 6 to 9.5 mol%.

Among the alkaline earth metal oxides, MgO has a low coefficient of thermal expansion and does not lower the strain point, so MgO can be contained, although it is not essential. Its content is 6
If it exceeds mol%, turbidity due to BHF and phase separation of glass are likely to occur. It is preferably 1 to 5 mol%.

CaO is not essential, but its inclusion can improve the meltability of the glass. On the other hand, if it exceeds 9 mol%, the coefficient of thermal expansion will be increased and the devitrification temperature will be increased.
It is preferably 1 to 6 mol%.

Since SrO suppresses the phase separation of the glass and is a relatively useful component against clouding due to BHF, it is contained at least 1 mol%. If the content exceeds 9 mol%, the expansion coefficient increases. It is preferably 2 to 8 mol%.

BaO is a component that has the effect of suppressing the phase separation of glass, improving the meltability, and suppressing the devitrification temperature. However, if the content is 1 mol% or more, the density becomes large, and the coefficient of thermal expansion tends to increase. From the viewpoint of smaller density and a smaller coefficient of thermal expansion, 0.
It is preferably 5 mol% or less, and more preferably substantially not contained except the amount contained as an impurity.

MgO + CaO + SrO + BaO makes melting difficult if the total amount thereof is less than 7 mol%. If it exceeds 18 mol%, the density tends to be high. It is preferably 9 to 16 mol%.

In recent years, a polysilicon type TFT has been proposed and used in comparison with 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 can be shortened and the LCD can be made finer. (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, impurities in the glass diffuse into the TFT, increasing the leak current, degrading the TFT characteristics, and making it difficult to manufacture a high-definition TFT. The most problematic of these impurities is phosphorus. When forming a TFT on a glass substrate, phosphorus diffuses into the TFT due to heat treatment, which may increase the leak current and deteriorate the TFT characteristics. Therefore, in the present invention, phosphorus is not more than 20 ppm in atomic (cation) weight display. It is preferred that

In addition to the above-mentioned components, the glass of the present invention contains ZnO, SO in order to improve the meltability, clarity and formability 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 or Sb ₂ O
_{If 3} is included, a lot of man-hours are required for the treatment of the glass cullet, so it is preferable not to include it except those which are inevitably mixed as impurities.

Thus, the composition of the glass of the preferred embodiment in the present invention is substantially SiO ₂ : 66 in terms of mol%.
_{~70%, Al 2 O 3:} 9~14%, B 2 O 3: 6~
9.5%, MgO: 1-5%, CaO: 1-6%, Sr
O: 2 to 8%, MgO + CaO + SrO: 9 to 16%, and does not substantially contain BaO.

The glass of the present invention has a strain point of 640 ° C. or higher. Further, the strain point is preferably 650 ° C. or higher. The thermal expansion coefficient, preferably less than 40 × 10 ^-7 / ℃, in ^{particular, 40 × 30 × 10 -7 /} ℃ or higher
It is preferably less than 10 ^-7 / ° C. The density is preferably less than 2.60 g / cc, more preferably less than 2.55 g / cc, and most preferably less than 2.50 g / cc.

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. The glass plate thus obtained is used as at least one of a pair of substrates forming cells of a liquid crystal display.

[0034]

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 to 4 show the glass compositions thus obtained, the coefficient of thermal expansion, the high temperature viscosity, the devitrification temperature, the strain point, the density, and
It exhibited acid resistance and BHF resistance. Examples 1 to 25, Examples 28 to 3
1 is an example, and examples 26, 27 and 32 are comparative examples.
In particular, in Examples 28 to 32, the phosphorus content (atomic weight pp
m) and the leak current showing the TFT characteristics are also shown.

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 and the strain point are in the unit: ° C. The density is shown in units of g / cc. Strain point (unit: ° C) is JI
Measured according to SR3103.

The acid resistance is 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 0.3mg / cm
Preferably ² or less, particularly preferably 0.2 mg / cm ² or less.

The BHF resistance is as follows: NH ₄ F / HF mixed solution (40
(A liquid obtained by mixing a 9 wt% aqueous NH ₄ F solution and a 50 wt% HF aqueous solution at a volume ratio of 9: 1) at 25 ° C. for 20 minutes, and the weight loss per unit area (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 leak current is obtained by forming a polysilicon type TFT having an electrode length of 10 μm on a glass substrate, a gate voltage of −5 V, a source voltage of 0 V and a drain voltage of +10.
The leakage current (unit: pA) at V was measured.
The leakage current is preferably about 50 pA or less.

The glasses of Examples 1 to 25 and Examples 28 to 31 have a low coefficient of thermal expansion of 30 × 10 ⁻⁷ to 40 × 10 ⁻⁷ / ° C. and a high strain point of 640 ° C. or higher. Can withstand heat treatment at high temperature. Density is less than 2.60 g / cc and 2.76 g / of conventional Corning Code 7059 glass
Much smaller than cc. Regarding chemical properties, BHF
Therefore, cloudiness is less likely to occur and acid resistance is also excellent. 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.

On the other hand, Example 2 having a composition outside the scope of the present invention
6, Example 27 has a large coefficient of thermal expansion and a relatively large density.
In Example 32, the phosphorus content was large, and the leakage current was large.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

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. Especially, since the density is very small, large TF
It is suitable for a T type display substrate or the like.

Claims (9)

[Claims] 1. A strain point of 640 ° C. or higher, substantially in terms of mol%, SiO ₂ : 60 to 73%, Al ₂ O ₃ : 5
_{~16%, B 2 O 3:} 5~12%, MgO: 0~6%,
CaO: 0-9%, SrO: 1-9%, BaO: 0-1
%, MgO + CaO + SrO + BaO: 7-18%
Alkali-free glass consisting of. 2. The alkali-free glass according to claim 1, which is substantially free of PbO, As ₂ O ₃ and Sb ₂ O ₃ . 3. The alkali-free glass according to claim 1, which has a density of less than 2.60 g / cc. 4. The alkali-free glass according to claim 1, which has a coefficient of thermal expansion of less than 40 × 10 ⁻⁷ / ° C. 5. A phosphorus content of 20 ppm by atomic weight.
The alkali-free glass according to claim 1, which is as follows. 6. Substantially in terms of mol%, SiO ₂ : 66-
_{70%, Al 2 O 3:} 9~14%, B 2 O 3: 6~9.
5%, MgO: 1-5%, CaO: 1-6%, SrO:
2-8%, MgO + CaO + SrO: 9-16%, BaO is not contained substantially, The alkali-free glass in any one of Claims 1-5. 7. The alkali-free glass according to claim 1, which has a strain point of 650 ° C. or higher. 8. The alkali-free glass according to claim 1, which has a density of less than 2.55 g / cc. 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.