JP3901757B2 - Alkali-free glass, liquid crystal display panel and glass plate - Google Patents

Description

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【表３】

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【表４】

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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, this glass has the following inadequate points for display.
[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.
[0007]
(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.
[0008]
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.
[0009]
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.
[0010]
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.
[0011]
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.
[0012]
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.
[0013]
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.
[0014]
[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 coefficient of thermal expansion, and it has not completely met the demands of the era of increasing the size.
[0015]
The object of the present invention is to solve the above-mentioned drawbacks, have a strain point of 640 ° C. or higher, a small thermal expansion coefficient and density, no white turbidity due to BHF, excellent durability against chemicals such as hydrochloric acid, and melting / 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.
[0016]
[Means for Solving the Problems]
In the present invention, the strain point is 640 ° C. or higher, and substantially in terms of mol%, SiO ₂ : 65 to 70%, Al ₂ O ₃ : 9 to 16%, B ₂ O ₃ : 6 to 12%, MgO: 0~6%, CaO: 0~7 %, SrO: 1~9%, MgO + CaO + SrO: made 7-18%, is substantially free of BaO, density is der less than 2.60 g / cc And the weight loss per unit area after immersion in 0.1N HCl at 90 ° C. for 20 hours is 0.3 mg / cm ^2. It is a Der Ru non-alkali glass below.
[0017]
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.
[0018]
The reason for limiting the composition range of each component as described above will be described.
[0019]
When the content of SiO ₂ is less than 60% mol, the strain point cannot be sufficiently increased, the chemical durability is deteriorated, and the thermal expansion coefficient is increased. If it exceeds 70 mol%, the meltability is lowered and the devitrification temperature is raised. Preferably, it is 66-70 mol%.
[0020]
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 less than 5 mol%, this effect does not appear, and if it exceeds 16 mol%, the meltability of the glass deteriorates. Preferably, it is 9-14 mol%.
[0021]
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. If the content is less than 5 mol%, the BHF property is deteriorated, and if it exceeds 12 mol%, the acid resistance is deteriorated and the strain point is lowered. Preferably, it is 6-9.5 mol%.
[0022]
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. If the content exceeds 6 mol%, white turbidity due to BHF or phase separation of glass tends to occur. Preferably, it is 1-5 mol%.
[0023]
Although CaO is not essential, the melting property of glass can be improved by containing CaO. On the other hand, if it exceeds 7 mol%, the coefficient of thermal expansion is increased and the devitrification temperature is increased. Preferably, it is 1-6 mol%.
[0024]
Since SrO suppresses the phase separation of glass and is a relatively useful component against white turbidity due to BHF, it is contained at least 1 mol%. If the content exceeds 9 mol%, the expansion coefficient increases. Preferably, it is 2-8 mol%.
[0025]
BaO is in terms of good Ri density to reduce the small thermal expansion coefficient, has a substantially contain except the amount contained as an impurity.
[0026]
MgO + CaO + Sr 2 O makes melting difficult if the total amount is less than 7 mol%. If it exceeds 18 mol%, the density increases. Preferably, it is 9-16 mol%.
[0027]
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.
[0028]
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
[0029]
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.
[0030]
Further, when PbO, As ₂ O ₃ or Sb ₂ O ₃ is contained, it takes a lot of man-hours for the processing of glass cullet, so it is preferable not to include it except for those inevitably mixed as impurities.
[0031]
Thus, the composition of the glass of a preferred embodiment in the present invention is substantially SiO ₂ : 66 to 70%, Al ₂ O ₃ : 9 to 14%, B ₂ O ₃ : 6 to 9.5% in terms of mol%, It consists of MgO: 1 to 5%, CaO: 1 to 6%, SrO: 2 to 8%, MgO + CaO + SrO: 9 to 16%, and does not substantially contain BaO.
[0032]
The glass of the present invention has a strain point of 640 ° C. or higher. Moreover, it is preferable that a strain point is 650 degreeC or more. The thermal expansion coefficient is preferably less than 40 × 10 ⁻⁷ / ° C., and particularly preferably 30 × 10 ⁻⁷ / ° C. or more and less than 40 × 10 ⁻⁷ / ° C. The density, 2.60 g / cc less der is, more preferably less than 2.55 g / cc, and most preferably less than 2.50 g / cc.
[0033]
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.
[0034]
【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.
[0035]
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. Example 1 to 5 Example 7, Example 9, Example 10, Example 12-19, Example 28 to 31 Examples, Example 6, Example 8, Example 11, Example 2 0-27, Example 32 is a comparative example. In particular, in Examples 28 to 32, the phosphorus content (atomic weight ppm) and the leakage current indicating the TFT characteristics are shown together.
[0036]
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.
[0037]
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 preferably 0.3 mg / cm ² or less, and particularly preferably 0.2 mg / cm ² or less.
[0038]
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.
[0039]
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.
[0040]
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 strain point of a high value of 640 ° C. or higher. Can withstand the heat treatment. The density is also less than 2.60 g / cc, much less than 2.76 g / cc of 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. The relationship between the temperature corresponding to 10 ⁴ poise, which is a standard for moldability, and the devitrification temperature is good, and devitrification occurs during molding. There seems to be no trouble such as generating.
[0041]
On the other hand, Examples 26 and 27, 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.
[0042]
[Table 1]

[0043]
[Table 2]

[0044]
[Table 3]

[0045]
[Table 4]

[0046]
【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 (10)

A is the strain point of 640 ° C. or higher, substantially by _{mol%, SiO 2: 65~70%, Al} 2 O 3: 9~16%, B 2 O 3: 6~12%, MgO: 0~ 6%, CaO: 0~7%, SrO: 1~9%, MgO + CaO + SrO: made 7-18%, is substantially free of BaO, density is Ri der less than 2.60 g / cc, and 90 The weight loss per unit area after immersion in 0.1N HCl at 20 ° C. for 20 hours is 0.3 mg / cm ² The following Der Ru alkali-free glass. PbO, alkali-free glass according to claim 1 which contains substantially no As ₂ O ₃ and Sb ₂ O _3. The alkali-free glass according to claim 1 or 2, wherein the content of B ₂ O ₃ is 6 to 9.5 mol%. The alkali-free glass according to any one of claims 1 to 3, which has a thermal expansion coefficient of less than 40 x ^10-7 / ° C.   The alkali-free glass according to any one of claims 1 to 4, wherein the phosphorus content is 20 ppm or less in terms of atomic weight.   The alkali-free glass according to any one of claims 1 to 5, wherein the content of CaO is 1 to 6 mol%. Essentially by _{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 to 8%, MgO + CaO + SrO: 9 to 16%, and contains substantially no BaO. 6. The alkali-free glass according to claim 1, 2, 4 or 5. Weight reduction per unit area after immersion in NH ₄ F / HF mixture (40% by weight NH ₄ F aqueous solution and 50% by weight HF aqueous solution mixed at a volume ratio of 9: 1) at 25 ° C. for 20 minutes alkali-free glass according to any one of claims 1 to 7 but is 0.7 mg / cm ² or less. The liquid crystal display panel which used the alkali free glass in any one of Claims 1-8 as at least one board | substrate of a pair of board | substrate which forms a cell. The glass plate which consists of an alkali free glass in any one of Claims 1-8 , Comprising: The glass plate shape | molded by the float glass process.