JP4250208B2 - Non-alkali glass and liquid crystal display panel for display substrates - Google Patents

Description

【００４６】
【表２】

【００４７】
【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、ＴＦＴ特性に悪影響を与えにくいので、、ＴＦＴタイプのディスプレイ基板等に好適である。
【００４８】[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 forming process, it has a high strain point in order to minimize the deformation caused by the glass deformation and the 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, BaO is large and the thermal expansion coefficient is 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, since a large amount of CaO is contained, 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]
A glass having a thermal expansion coefficient of 30 to 45 × 10 ⁻⁷ / ° C. and a density of 2.70 g / cc or less at 640 ° C. or higher is disclosed in JP-A-6-263473. However, when a glass prepared by batch-mixing, melting and molding this glass according to a conventional method is applied to a high-definition polysilicon type TFT, a transistor having sufficiently good characteristics may not be obtained.
[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 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.
[0016]
[Means for Solving the Problems]
The present invention is essentially by _{mol%, SiO 2: 60~72%, Al} 2 O 3: 9~14%, B 2 O 3: less than 5~10%, MgO: 1~5%, CaO: It is composed of 0 to 1.5%, SrO: 1 to 7%, BaO: 1 to 5%, MgO + CaO + SrO + BaO: 7 to 18%, does not substantially contain phosphorus, has a strain point of 640 ° C. or higher, and a density of 2. It is a non-alkali glass for display substrates that is 70 g / cc or less.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The antlerous 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]
Next, 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 72 mol%, the meltability decreases and the devitrification temperature increases. A more preferable range is 66 to 70 mol%.
[0020]
Al ₂ O ₃ suppresses the phase separation of the glass, lowers the thermal expansion coefficient, and increases the strain point .
[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. When the content is less than 5 mol%, the BHF property is deteriorated, and when it is 10 mol% or more, the acid resistance is deteriorated. A more preferable range is 6 to 9 mol%.
[0022]
MgO is not an essential component, but among alkaline earth metal oxides, it can be contained because it has a low coefficient of thermal expansion and does not lower the strain point. If the content exceeds 5 mol%, white turbidity due to BHF or phase separation of glass tends to occur. The range in this invention is 1-5 mol%.
[0023]
Although CaO is not an essential component, it can improve the meltability of glass by containing CaO. If the content exceeds 2.5 mol%, the characteristics of the high-definition polysilicon TFT may be deteriorated.
[0024]
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 not short, and high definition of the LCD is possible. (2) Driving ICs are 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. 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.
[0025]
The most problematic of such impurities is phosphorus in limestone used as a raw material for 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 using a high-purity raw material with a small amount of phosphorus impurities can be considered, but it is disadvantageous in terms of cost.
[0026]
In the present invention, since the CaO content is 1.5 mol% or less, the TFT characteristics are not deteriorated, and a glass substrate having excellent characteristics for a liquid crystal display panel can be obtained. CaO range of not more than 1.5 mol%, particularly preferably not substantially contained.
[0027]
SrO suppresses the phase separation of glass and is a relatively useful component against white turbidity due to BHF, so it is contained in an amount of 1 mol% or more. If the content exceeds 7 mol%, the thermal expansion coefficient increases. A more preferable range is 2 to 7 mol%.
[0028]
BaO is essential in the present invention because it has effects of suppressing glass phase separation, improving meltability, and suppressing devitrification temperature. If the content exceeds 5 mol%, the thermal expansion coefficient increases, and chemical durability such as acid resistance also deteriorates.
[0029]
MgO + CaO + SrO + BaO makes melting difficult if the total amount is less than 7 mol%. If it exceeds 18 mol%, the density increases. A more preferable range is 9 to 16 mol%.
[0030]
In the present invention, phosphorus because it may deteriorate the TFT characteristics, have a substantially contained.
[0031]
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.
[0032]
In addition, when PbO, As ₂ O ₃ and Sb ₂ O ₃ are included, a lot of man-hours are required for the treatment of glass cullet, so it is preferable not to include them except for those inevitably mixed as impurities.
[0033]
Thus, the composition of the preferred glass of the present invention, essentially by _{mol%, SiO 2: 66~70%, Al} 2 O 3: 9~14%, B 2 O 3: 6~9%, MgO: It consists of 1 to 5%, SrO: 2 to 7 %, BaO: 1 to 5%, MgO + SrO + BaO: 9 to 16%, and substantially does not contain phosphorus and CaO.
[0034]
The glass of the present invention has a strain point of 640 ° C. or higher . Preferably it is 650 degreeC or more. The thermal expansion coefficient is preferably 30 × 10 ⁻⁷ / ° C. to 45 × 10 ⁻⁷ / ° C., more preferably 30 × 10 ⁻⁷ / ° C. to 40 × 10 ⁻⁷ / ° C. Furthermore, the density is 2.70 g / cc or less . Preferably it is 2.65 g / cc or less.
[0035]
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.
[0036]
【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.
[0037]
Tables 1 and 2 show the glass composition, thermal expansion coefficient, high temperature viscosity, devitrification temperature, strain point, density, acid resistance, BHF resistance, and leakage current (TFT characteristics) thus obtained. Examples 1 , 5, and 7 are examples, and examples 2 to 4, example 6, and examples 8 to 13 are comparative examples.
[0038]
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 is shown in units of ° C., and the density is in units of units. Indicated in g / cc. The strain point (unit: ° C.) was measured according to JIS R3103.
[0039]
The acid resistance was shown as a 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, particularly 0.2 mg / cm ² or less.
[0040]
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 0.6 mg / cm ² or less.
[0041]
TFT characteristics were measured for Examples 1, 2, and 10-12. That is, 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 several pA or less.
[0042]
The glasses of Examples 1 to 10 have a low coefficient of thermal expansion of 30 to 40 × 10 ⁻⁷ / ° C., a high strain point of 630 ° C. or higher, and can sufficiently withstand heat treatment at high temperatures. The density is also less than 2.70 g / cc, 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.
[0043]
Furthermore, with respect to TFT characteristics, the leakage current is less than 10 pA, and it can sufficiently withstand the recent high integration of TFTs.
[0044]
On the other hand, Examples 11 to 13 have a leakage current of about a dozen to several tens pA, and may become a problem as TFTs are highly integrated.
[0045]
[Table 1]

[0046]
[Table 2]

[0047]
【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 it does not adversely affect the TFT characteristics, it is suitable for a TFT type display substrate.
[0048]

Claims (9)

Essentially by _{mol%, SiO 2: 60~72%, Al} 2 O 3: 9~14%, B 2 O 3: less than 5~10%, MgO: 1~5%, CaO: 0~1. 5%, SrO: 1 to 7%, BaO: 1 to 5%, MgO + CaO + SrO + BaO: 7 to 18% , substantially not containing phosphorus, strain point of 640 ° C. or higher, density of 2.70 g / cc or lower Alkali-free glass for display substrates . The alkali-free glass for a display substrate according to claim 1, substantially free of PbO, As ₂ O ₃ and Sb ₂ O ₃ . 90 ° C. 0.1N claim 1 or 2 display substrate for alkali-free glass according to weight loss per unit area after immersion for 20 hours in HCl is 0.3 mg / cm ² less. 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 The alkali-free glass for a display substrate according to any one of claims 1 to 3 , wherein is 0.7 mg / cm ² or less. Essentially by _{mol%, SiO 2: 66~70%, Al} 2 O 3: 9~14%, B 2 O 3: 6~9%, MgO: 1~5%, SrO: 2~7%, BaO: 1~5%, MgO + SrO + BaO: made 9-16%, phosphorus and CaO substantially containing non claim 1 display substrate for alkali-free glass according to any one of 4. The alkali-free glass for a display substrate according to any one of claims 1 to 5 , wherein the strain point is 650 ° C or higher. Thermal expansion coefficient of ^{30 × 10 -7 / ℃ ~40 ×} 10 -7 / ℃ at which claims 1-6 non-alkali glass for a display substrate according to any one of. Liquid crystal display panel used as at least one substrate of the pair of substrates forming the cell display alkali-free glass substrate according to any one of claims 1-7. A glass plate made of non-alkali glass for a display substrate according to any one of claims 1 to 7 a glass sheet by a float method.