JP3988209B2 - Alkali-free glass and liquid crystal display panel - Google Patents

Description

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【発明の効果】
本発明によるガラスは、フロート法による成形が可能である。また、ＢＨＦによる白濁が生じにくく、耐酸性に優れ、耐熱性が高く、低い熱膨張係数を有するのでディスプレイ用基板、フォトマスク基板として適する。特に、密度が非常に小さいので、大型のＴＦＴタイプのディスプレイ基板等に好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-alkali glass suitable for various displays and photomask substrate glass, which can be float-molded substantially without containing an alkali metal oxide, and a liquid crystal display panel using the same.
[0002]
[Prior art]
Conventionally, various display substrate glasses, particularly those in which a metal or oxide thin film is formed on the surface, require the following characteristics.
[0003]
(1) When an alkali metal oxide is contained, the alkali metal ions diffuse into the thin film and deteriorate the film characteristics.
(2) Since it is exposed to a high temperature in the thin film formation process, it has a high strain point in order to minimize the deformation caused by glass deformation and glass structural stabilization.
(3) Sufficient chemical durability against various chemicals used for semiconductor formation. In particular, it has durability against buffered hydrofluoric acid (BHF) mainly composed of hydrofluoric acid, ammonium fluoride, etc. for etching SiO _x and SiN _x .
(4) There are no defects (bubbles, striae, inclusions, pits, scratches, etc.) inside and on the surface.
[0004]
Conventionally, Corning Code 7059 glass has been widely used as substrate glass for various displays and photomasks. However, there was a point insufficient shown below as a de I spray on the glass.
[0005]
(1) Since the strain point is as low as 593 ° C., pre-heat treatment for reducing glass shrinkage 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 transparent conductive film (ITO, etc.) is large, and the eluate recrystallizes during the display manufacturing process, which makes it difficult to manufacture the display.
[0006]
In addition to the above requirements, the following two points have been newly demanded in recent years as the display becomes larger.
(1) The density of the cord 7059 glass is 2.76 g / cc, and a glass with a low density is required to further reduce the weight.
(2) The above-described code 7059 glass has a thermal expansion coefficient of 46 × 10 ⁻⁷ / ° C., and in order to increase the temperature raising / lowering speed during production of the display and increase the production efficiency, a glass having a smaller thermal expansion coefficient is required.
[0007]
Regarding B ₂ O ₃ , JP-A-1-160844 discloses B ₂ O ₃ containing 20 to 23 cations, but the amount of B ₂ O ₃ is large and the strain point is not sufficiently high. JP 61-281041 to 0.1 to 4% by weight of B ₂ O ₃ is from 0.1 to 5 mol% of B ₂ O ₃ is in JP-A 4-175242, the Japanese Patent Laid-Open 4-325435 B 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.
[0008]
Regarding BaO, JP-A-4-325434 contains 10 to 20% by weight of BaO, JP-A 63-74935 uses 10 to 22% by weight of BaO, and JP-A 59-169953 uses 15 to 40% by weight of BaO. Although what is contained is disclosed, the BaO content is large, the thermal expansion coefficient is large, and the density is also large.
[0009]
Regarding MgO, JP-A 61-132536 includes 6.5 to 12% by weight of MgO, JP-A 59-116147 includes 5 to 15% by weight of MgO, JP-A 60-71540 includes 5 to 5% of MgO. 17% by weight, and JP-A-60-42246 discloses a composition containing 10 to 25 mol% of MgO, but a glass containing a large amount of MgO tends to cause phase separation.
[0010]
Regarding CaO, JP-A-63-176332 has 11 to 25% by weight of CaO, JP-A-58-32038 has 7 to 20% by mole of CaO, and JP-A-2-133334 has 8 to 15% by weight of CaO. JP-A-3-174336 discloses 7-12% by weight of CaO, JP-A-6-40739 contains 10-12% by weight of CaO, and JP-A-5-201744 contains at least 18 cations of CaO. However, when CaO is contained in a large amount, the thermal expansion coefficient tends to increase.
[0011]
With respect to Al ₂ O _3, chemicals to 22.5 to 35 wt% of Al ₂ O ₃ in JP 61-236631, although those containing discloses, Al ₂ O ₃ amount is large such as hydrochloric acid There are many elutions.
[0012]
Regarding P ₂ O ₅ , JP-A-61-261232 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.
[0013]
[Problems to be solved by the invention]
Glasses having a strain point of 640 ° C. or higher and a relatively small thermal expansion coefficient are described in JP-A-4-160030 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 thermal expansion coefficient, and it has not completely met the demands of the era of increasing the size.
[0014]
The object of the present invention is to solve the above-mentioned drawbacks, have a strain point of 650 ° C. or higher, a small coefficient of thermal expansion and density, no white turbidity due to BHF, excellent durability to chemicals such as hydrochloric acid, melting and molding It is an object of the present invention to provide an alkali-free glass that is easy to float and can be float formed.
[0015]
[Means for Solving the Problems]
The present invention has a strain point of 650 ° C. or higher, and is substantially expressed in terms of weight%, SiO ₂ : 58.4 to 66.0%, Al ₂ O ₃ : 15.3 to 22.0%, B ₂ O ₃ : 5.0 to 12.0%, MgO: 3.9 to 6.5%, CaO: 0.9 to 7.0%, SrO: 4.0 to 12.5%, MgO + CaO + SrO: 9.0 ˜18.0%, substantially free of PbO, As ₂ O ₃ , Sb ₂ O ₃ and BaO, a density of less than 2.55 g / cc, and a thermal expansion coefficient of 40 × 10 ⁻⁷ The temperature at which the viscosity becomes 10 ² poise is less than 1670 ° C., and the weight loss per unit area after immersion in 0.1 N HCl at 90 ° C. for 20 hours is 0.3 mg / cm It is an alkali-free glass that is ² or less.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The alkali-free glass of the present invention contains substantially no alkali metal oxide (for example, Na ₂ O, K ₂ O, etc.). Specifically, the total amount of alkali metal oxide is 0.5% by weight or less, more preferably 0.2% by weight or less.
[0017]
The reason for limiting the composition range of each component as described above will be described.
If the content of SiO ₂ is too small, the strain point cannot be sufficiently increased, the chemical durability is deteriorated, and the thermal expansion coefficient is increased. Preferably it is 59.0 weight% or more. When too much, meltability will fall and devitrification temperature will rise. Preferably it is 65.0 weight% or less, More preferably, it is 62.7 weight% or less.
[0018]
Al ₂ O ₃ suppresses the phase separation of the glass, lowers the thermal expansion coefficient, and increases the strain point. If the content is too small, this effect does not appear. Preferably it is 15.3% by weight or more. When too much, the meltability of glass will worsen. Preferably it is 21.1 weight% or less.
[0019]
B ₂ O ₃ prevents white turbidity from being generated by BHF, and can achieve a reduction in thermal expansion coefficient and density without increasing the viscosity at high temperatures. When the content is too small, the BHF property is deteriorated. Preferably it is 5.2 weight% or more. If the amount is too large, the acid resistance is deteriorated and the strain point is lowered. Preferably it is 10.2 weight% or less.
[0020]
MgO is not essential among alkaline earth metal oxides because it has a low coefficient of thermal expansion and does not lower the strain point, but it can be contained. When the content is too large, white turbidity due to BHF or phase separation of glass tends to occur. Preferably it is 6.0 weight% or less.
[0021]
CaO can improve the meltability of the glass by containing. On the other hand, if too large, the coefficient of thermal expansion is increased, and the devitrification temperature is increased. Preferably it is 6.6 weight% or less.
[0022]
SrO is essential because it suppresses the phase separation of glass and is a relatively useful component against white turbidity due to BHF. Preferably it is 4.6 weight% or more. When there is too much the content, a thermal expansion coefficient will increase. Preferably it is 12.1 weight% or less.
[0023]
BaO is a component having an effect of suppressing phase separation of glass, improving meltability, and suppressing devitrification temperature. However, when the content is too large, the density increases and the thermal expansion coefficient tends to increase. From the viewpoint of a smaller density and a smaller thermal expansion coefficient, it is not contained in excess of (ie substantially) the amount contained as an impurity.
[0024]
MgO + CaO + SrO makes melting difficult if the total amount is too small.
Preferably it is 10.9 weight% or more. If it is too much, the density increases. Preferably it is 17.4 weight% or less.
[0025]
In recent years, polysilicon type TFTs have been proposed and used for those using amorphous silicon type TFTs that have already been commercialized as liquid crystal display devices. Polysilicon type TFT (1) Since the mobility of the transistor can be increased, the control time per pixel is shortened and the high definition of the LCD can be achieved. (2) A driving IC is provided around the screen. While there is an advantage that it can be mounted, a strong heat treatment (for example, 500 to 600 ° C. × several hours) is required in the manufacturing process.
[0026]
At such a high temperature, impurities in the glass diffuse into the TFT, increasing the leakage current, deteriorating the TFT characteristics, and making it difficult to produce a high-definition TFT. The most problematic of such impurities is phosphorus. When forming TFTs on a glass substrate, phosphorus diffuses into the TFTs by heat treatment, which may increase leakage current and deteriorate TFT characteristics. Therefore, in the present invention, phosphorus is 20 ppm or less in terms of atomic (cation) weight. It is preferable that
[0027]
In addition to the above components, the glass of the present invention can contain ZnO, SO ₃ , F, and Cl in a total amount of 5 mol% or less in order to improve the meltability, clarity, and moldability of the glass.
In addition, when PbO, As ₂ O ₃ or Sb ₂ O ₃ is contained, a lot of man-hours are required for the processing of the glass cullet.
[0028]
Thus, the composition of the glass of a preferred embodiment in the present invention is, for example, substantially in terms of% by weight, SiO ₂ : 59.0 to 62.7%, Al ₂ O ₃ : 15.3 to 21.1%, B ₂ O ₃ : 5.2 to 10.2%, MgO: 3.9 to 6.0%, CaO: 0.9 to 6.6%, SrO: 4.6 to 12.5%, MgO + CaO + SrO: 10.9 It consists of ˜17.4%.
[0029]
The glass of the present invention has a strain point of 650 ° C. or higher. The coefficient of thermal expansion is less than 40 × 10 ⁻⁷ / ° C., and particularly preferably 30 × 10 ⁻⁷ / ° C. or more and less than 40 × 10 ⁻⁷ / ° C. The density is less than 2.55 g / cc, preferably less than 2.50 g / cc.
[0030]
In addition, the glass of the present invention is suitable for float molding because the molding temperature (temperature at which the viscosity becomes 10 ⁴ poise) in the molding by the float method is not lower than the devitrification temperature.
[0031]
The glass of the present invention can be produced, for example, by the following method. That is, normally used raw materials for each component are blended so as to become target components, which are continuously charged into a melting furnace and heated to 1500 to 1600 ° C. for melting. The molten glass is formed into a predetermined plate thickness by a float method, and is cut after slow cooling. The glass plate thus obtained is used as at least one of a pair of substrates forming a cell of a liquid crystal display.
[0032]
【Example】
The raw material of each component was prepared so that it might become a target composition, and it melted at the temperature of 1500-1600 degreeC using the platinum crucible. In melting, the glass was homogenized by stirring with a platinum stirrer. Subsequently, the molten glass was poured out, formed into a plate shape, and then slowly cooled.
[0033]
Tables 1 to 4 show the glass composition, thermal expansion coefficient, high temperature viscosity, devitrification temperature, strain point, density, acid resistance, and BHF resistance thus obtained. Tables 5 to 8 convert the compositions of Tables 1 to 4 into mol%. Examples 23-27 are Examples, Examples 1-22 and Examples 28-34 are comparative examples. In particular, in Examples 28 to 32, the phosphorus content (atomic weight ppm) and the leakage current indicating the TFT characteristics are shown together.
[0034]
The coefficient of thermal expansion is shown in units of 10 ⁻⁷ / ° C., the high temperature viscosity is shown in terms of the viscosity (unit: ° C.) of 10 ² and 10 ⁴ poise, the devitrification temperature and strain point are shown in units of ° C. Is expressed in units of g / cc. The strain point (unit: ° C.) was measured according to JIS R3103.
[0035]
The acid resistance is shown by the weight loss per unit area (unit: mg / cm ² ) after immersion in 0.1 N HCl at 90 ° C. for 20 hours. The acid resistance is 0.3 mg / cm ² or less, and particularly preferably 0.2 mg / cm ² or less.
[0036]
BHF resistance is a unit area after immersion for 20 minutes at 25 ° C. in a NH ₄ F / HF mixed solution (a solution in which a 40 wt% NH ₄ F aqueous solution and a 50 wt% HF aqueous solution are mixed at a volume ratio of 9: 1). The weight loss per unit (unit: mg / cm ² ). The BHF resistance is preferably 0.7 mg / cm ² or less, particularly preferably 0.6 mg / cm ² or less.
[0037]
For the leakage current, a polysilicon type TFT having an electrode length of 10 μm was formed on a glass substrate, and the leakage current (unit: pA) was measured when the gate voltage was −5 V, the source voltage was 0 V, and the drain voltage was +10 V. . The leakage current is preferably about 50 pA or less.
[0038]
The glasses of Examples 23 to 27 have a low coefficient of thermal expansion of 30 × 10 ⁻⁷ to 40 × 10 ⁻⁷ / ° C., a high strain point of 650 ° C. or higher, and are sufficiently resistant to heat treatment at high temperatures. It is done. The density is also less than 2.55 g / cc, much less than 2.76 g / cc of the conventional Corning Code 7059 glass. In terms of chemical characteristics, BHF hardly causes white turbidity and has excellent acid resistance. The temperature corresponding to 10 ² poise, which is a standard for melting, is relatively low and melting is easy, and the temperature corresponding to 10 ⁴ poise, which is a standard for moldability, is higher than the devitrification temperature. It seems that there is no trouble such as generating.
[0039]
On the other hand, Examples 33 and 34, which are compositions outside the scope of the present invention, have a large coefficient of thermal expansion and a relatively high density. In Example 32, the phosphorus content is large and the leakage current is large.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
[Table 3]

[0043]
[Table 4]

[0044]
[Table 5]

[0045]
[Table 6]

[0046]
[Table 7]

[0047]
[Table 8]

[0048]
【The invention's effect】
The glass according to the present invention can be formed by a float process. Further, white turbidity due to BHF hardly occurs, the acid resistance is excellent, the heat resistance is high, and the coefficient of thermal expansion is low, so that it is suitable as a display substrate or a photomask substrate. In particular, since the density is very low, it is suitable for a large TFT type display substrate.

Claims (3)

A is the strain point of 650 ° C. or higher, substantially in weight _{percentages, SiO 2: 58.4~66.0%, Al} 2 O 3: 15.3~22.0%, B 2 O 3: 5 .0~12.0%, MgO: 3.9~6.5%, CaO: 0.9 ~7.0%, SrO: 4.0~12.5%, MgO + CaO + SrO: 9.0~18.0 %, PbO, As ₂ O ₃ , Sb ₂ O ₃ and BaO are substantially not contained, the density is less than 2.55 g / cc, and the thermal expansion coefficient is less than 40 × 10 ⁻⁷ / ° C. Yes, the temperature at which the viscosity becomes 10 ² poise is 1670 ° C. or less, and the weight loss per unit area after immersion in 0.1 N HCl at 90 ° C. for 20 hours is 0.3 mg / cm ² or less. Alkali-free glass.   The alkali-free glass according to claim 1, wherein the phosphorus content is 20 ppm or less in terms of atomic weight.   The liquid crystal display panel using the alkali free glass of Claim 1 or 2 as at least one board | substrate of a pair of board | substrate which forms a cell.